Schedule
9–12 March 2025 • Hilton Orlando Lake Buena Vista at WDWl • Orlando, FL, USA
Sunday, 9 March 2025 | |
| 4–6 p.m. | Registration |
| 5–6 p.m. | Reception |
Monday, 10 March 2025 | |
| 7 a.m. | Breakfast and Registration |
| 8 a.m. | Introductions and Opening Remarks |
| Session Chairs: Grant Thomas, Cleveland-Cliffs Research and Innovation Center; Lawrence Cho, Colorado School of Mines | |
| 8:15 a.m. | Keynote: Forging the Future: Hot Stamping Innovation Trends for an Electrified Automotive World Paul Belanger, Gestamp Hot stamping innovations address the challenges of an electrified automotive industry, including managing higher impact loads in battery electric vehicles while reducing build time and complexity through part reduction. Sustainability is emphasized by using higher-strength steels to reduce vehicle weight, contributing to lower CO2 emissions. |
| 8:50 a.m. | Microstructure and Properties of B-Containing Press Hardening Steel Manufactured Using EAF-CSP Strategy Weiping Sun, Nucor Corp. This paper presents the achievements on developing and manufacturing B-containing press hardening steel (PHS) at Nucor Steel–Berkeley LLC using the highly energy-efficient electric arc furnace – compact steel production (EAF-CSP) process. The relevant EAF and CSP facility and steelmaking process as well as the corresponding sustainable benefits are first reviewed. Compared to conventional mills using blast furnaces (BF) and basic oxygen furnaces (BOF), steels produced by this strategy introduce significantly less CO2 emissions and use much less energy. This process also offers advantages such as shorter lead times and excellent thickness control. The hot press hardening processes applied on the coils are described, followed by testing and evaluation procedures. The mechanical property data and bendability performance are discussed. It is demonstrated that the properties are uniform from head to tail within a coil and consistent from coil-to-coil with different thicknesses. The microstructure reveals a fully martensitic structure with minimal surface decarburization. |
| 9:10 a.m. | Hydrogen Uptake Reduction Technology in Hot-Stamped Boron Martensitic Steels Through Functional Surface Coatings Hee-Gwon Shin, Hye-Jin Kim, Seung-Pill Jung, Dong-Yul Lee, and Joo-Sik Hyun, Hyundai Steel Co. Recently, hot stamping technology has been increasingly used in automotive structural parts with ultrahigh strength to meet the standards for both high fuel efficiency and crashworthiness. A common method of the hot stamping process is direct hot stamping, where a blank is heated in a furnace, transferred to a press, and subsequently formed and quenched in a cooled die. However, one concern regarding these martensitic steels, which are fabricated using the hot stamping process, is that they are highly vulnerable to hydrogen-delayed cracking caused by diffusible hydrogen flow through the surface reaction of the aluminum-silicon (Al-Si) coating in a furnace atmosphere. This is especially important for newly developed hot-stamped martensitic steels with 1800 MPa tensile strength, where understanding diffusible hydrogen behavior is crucial for their application in the automotive industry. This study focuses on the use of functional surface coatings as a method to reduce hydrogen uptake, aiming to identify effective solutions for preventing hydrogen-delayed cracking in hot-stamped boron martensitic steels. The authors conducted a 4-point bending test and thermal desorption spectroscopy (TDS) analysis after hydrogen charging by controlling the dew point of the furnace atmosphere during the hot stamping process. Additionally, coating analysis was performed using Fourier transform infrared (FT-IR) spectroscopy and field emission scanning electron microscopy (FE-SEM). The research found that a newly applied lubricant containing polyester groups reacts with moisture at high temperatures to form hydrogen bonds, thereby reducing hydrogen uptake. In contrast, existing lubricants and non-lubricant scenarios resulted in higher hydrogen uptake, leading to delayed cracking. As a result, surface control with metallic coating species and post-treatment processes improved the delayed fractures of hot-stamped boron steels. Ultimately, it is important that the design of chemical composition and functional surface treatment is considered essential to achieve both suitable performance and reasonable cost in hot press-formed parts. |
| 9:30 a.m. | Ultrahigh-Strength Tubular Components as Structural Reinforcement in New Generation of Vehicles Eliseo Hernandez-Duran, Cleveland-Cliffs Inc. This paper will review tubing applications utilized in the new generation of vehicles including EVs. Ultrahigh-strength martensitic steels will be introduced and subjected to various mechanical testing evaluations. Results are to be compared to current complex phase and dual-phase grades utilized in structural applications |
| 9:50 a.m. | Importance of Understanding Martensite Transformation for Product Development Ravi Ranjan, Tata Steel Jamshedpur Martensite is perhaps the most underappreciated phase among all the phases that exist in steels. It is a phase where strength can be greatly increased in the most economical way just by increasing the level of carbon. However, it suffers because it offers a very low elongation. Therefore, it is important to understand the martensite transformation in steel to discover the attributes that could help achieve higher elongation. In this work, a new approach to analyze the martensite transformation through dilatometer experiments is discussed. The dilatometer study revealed: (i) the importance of considering the effect of substitutional alloying elements in the determination of the lattice parameter of martensite and its impact on the advance analysis of the dilation curve, and (ii) the martensite transformation could be used to determine the lattice parameter coefficient directly from the dilation curve increasing the landscape of the application of dilatometer. The lattice parameter coefficient is generally determined through techniques, such as x-ray diffraction, transmission electron microscopy, etc., which are highly sample-sensitive. Based on the learning on phase transformations, a few heat treatments were performed on a few designed steels. It was observed that the as-quenched martensite offered strength in the range of 1500–1800 MPa with a total elongation of only 1–2%. A slight modification in the processing enhanced the elongation nearly four times to 7–8% with negligible impact on the strength. With further adjustment in the processing and a slight tweak in the alloy chemistry, the authors were able to further double the elongation to 14–15%. |
| 10:10 a.m. | Break |
| 10:40 a.m. | Development of Cold-Rolled Martensitic Steels for Improving the Hydrogen Embrittlement Resistance and Surface Flatness Bong June Park, Min Ho Jang, Seung-Pill Jung, Hye-Jin Kim, Seong Kyung Han, and Tae Woo Kwon, Hyundai Steel Co. The application of martensitic steel has been expanded for securing crashworthiness in the automotive industry. Martensitic steel generally has been produced by the water quenching and reheating process. This process has a rapid cooling rate to room temperature. Therefore, martensitic steel, which is produced by water quenching, has poor flatness of the strip due to rapid quenching and requires electrogalvanizing to increase corrosion resistance. In this work, the process for mass production of martensitic steel was designed for improving flatness and hydrogen embrittlement using by gas quenching. Because gas quenching has a lower cooling rate than water quenching, the quality of flatness was improved. However, the hardenability of steel is increased for obtaining martensite phase in gas quenching process. It is necessary to add the austenite stabilizers (Mn, Cr, etc.) to suppress the transformation from austenite to ferrite or bainite at moderate cooling rate in the gas quenching process. Based on the concepts, coated and uncoated martensitic steel sheets with a tensile strength above 1.5 GPa were produced in factory. The mechanical properties, flatness, surface quality and hydrogen embrittlement resistance of these sheets were satisfactory for applying as automotive parts. |
| 11:00 a.m. | Effect of Isothermal Holding Around the Martensite Finish Temperature on Properties of Martensitic Steels S.M. Topper, Emmanuel De Moor, John G. Speer, Colorado School of Mines; C. Suppan, voestalpine Stahl GmbH Martensitic steels provide high strength for anti-intrusion components. Various quench temperatures, quench rates and isothermal holding temperatures could potentially be employed in these steels. Initial quench temperatures around room temperature have been known to result in higher strength. In modified alloys, some fractions of austenite may also be maintained and enriched with C during isothermal holding and affect mechanical properties. Low-C alloys with Si and Cr additions were investigated in this study. Heat treatments involving austenitizing and controlled quenching with an isothermal hold around the martensite finish (Mf) temperature were conducted. The cooling rate and quench temperature were also varied. Tensile testing was implemented to identify changes in mechanical properties. The determination of retained austenite content and martensite content were conducted via magnetic saturation (MSAT) and x-ray diffraction (XRD), while microstructural analysis was conducted via electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) to help explain the observed tensile behaviors. |
| 11:20 a.m. | On Fracture Resistance of Ultrahigh-Strength Quench-Hardening Steels Jun Hu, Cleveland-Cliffs Inc. Ultrahigh-strength quench-hardening steels (UHS-QHSs) are being increasingly adopted in various modern vehicles to satisfy and balance the elevating safety and lightweighting needs. Nevertheless, due to the carbon-rich fresh martensitic microstructures after the quenching, these UHS-QHSs are born to have some fracture resistance limitations. Accordingly, a series of precedent works proposed a low-temperature-tempering technique and presented the effectively improved fracture resistance of a 22MnB5 steel grade. As a continued effort, this work will start from comparing the fracture resistance of two UHS-QHS grades at the as-quenched condition, and then investigate their improvements after the low-temperature-tempering (LTT) treatments. Additionally, inspired by the actual automotive paint-baking cycles, the effects of double LTT on the fracture resistance will also be investigated. Furthermore, a series of advanced mechanical testing will be presented, including the rate-dependent and the stress-state-dependent tests, to reveal the performance of these two steel grades with and without the LTT treatments in the practical crash scenarios. The ultimate objective of this work is to not only highlight the promising potential of UHS-QHS in automotive applications but also provide the corresponding references for future steel grade development. |
| 11:40 a.m. | Transformation and Evolution of Automotive Steels at Nucor Steel–Arkansas Igor Vieira, Nucor Corp. Nucor Corp. made a significant upgrade on facilities in Nucor Steel–Arkansas (NSAR) to transform its product mix, focusing on high-value-added products to support the automotive industry. This upgrade consisted of the construction of the Specialty Cold Mill Complex, which features cutting-edge technology, including a high-performance push pickling line, S6-high cold rolling mill, 4-high temper mill, batch annealing furnaces, and a continuous galvanizing line capable of producing first- and third-generation advanced high-strength steels (AHSS). Since its startup in 2019, these advanced capabilities have driven the product and application development efforts at NSAR. This paper describes the comprehensive product development journey at NSAR, from the production of surface-critical hot-rolled and pickled products to the latest advancements in galvanized and galvannealed advanced high-strength automotive steels. In addition, the presentation will provide an in-depth look at the evolution of NSAR's manufacturing capabilities and automotive product matrix with improved properties, which have enabled NSAR to meet the increasing demands from the automotive industry, positioning the company as a key player in the production of high-performance steel products. |
| 12:00 p.m. | Lunch |
| Session Chairs: Grant Thomas, Cleveland-Cliffs Research and Innovation Center; Lawrence Cho, Colorado School of Mines | |
| 1:00 p.m. | Carriages to Crash Energy Management: The History of Sheet Steels in the Automotive Industry James R. Fekete, JRF Technical Consulting LLC Today’s vehicles contain more steel than any other material, and one may think that it has always been so. But there was a time when the use of steel in a motor vehicle was just as exotic as carbon fiber is today, with similar issues of cost, manufacturability and durability. The engineering of early vehicles from the late 19th to the early 20th century was based on technology used for horse-drawn carriages, with wood as the predominant material of construction. The evolution of the motor vehicle from these early “horseless carriages” to the fast, safe, clean and steel-intensive vehicles of today is a fascinating story of innovation, persistence and technological development. This paper will weave together the concurrent developments of motor vehicle manufacturing technology, steel process technology, steel product development and the many external influencing factors impacting both steel and motor vehicle development. The presentation will first review the early days of the “horseless carriage,” including the materials and manufacturing technologies prevalent at the beginning of the motoring age. The development of steel manufacturing technologies like open hearth steelmaking and the continuous rolling will be discussed in parallel with the evolution of vehicle structure engineering to demonstrate how steel came to overcome wood and dominate the market. The impact of safety, emissions and efficiency regulation on the automotive industry will be discussed, along with the response of the steel industry, including the development of new alloys and applications technology to maintain steel’s position as a high-quality, cost-effective automotive material. A discussion of the impact of electrification and the continued development of advanced steel alloys will conclude the presentation and echo the audacious innovation of the early pioneers in steel and automotive engineering. |
| 1:20 p.m. | A New Design of Inner Rocker Panel for Improved Integration With Rocker Reinforcement Yu-Wei Wang, Cleveland-Cliffs Inc. A new design is proposed for an inner rocker panel with additions of recessed pockets that enable its joining with C-STAR rocker (side sill) reinforcement using laser welding. These pockets, approximately 2 in. x 3 in. in size, are strategically placed on the vertical wall of the inner rocker panel, providing a suitable platform for laser welding. These changes are localized and do not interfere with existing mating parts. Formability evaluations indicate that the new design can be successfully manufactured using either cold or hot stamping processes. Furthermore, this innovative inner rocker panel design can also be adapted for other steel reinforcements, including roll-formed panels. By replacing the current bolts and brackets joining method, this new design achieves reductions in both mass and cost for the reinforcement assembly. Additionally, its structure performance is shown to be superior to the existing design by computer-aided engineering (CAE) analysis. |
| 1:40 p.m. | Evaluation of Fatigue Properties of Advanced High-Strength Steels for Durability Analysis Youngseo Lee, Hakhoon Kim, Kyoungju Sohn, Jinhwa Jeon, Hyundai Steel Automotive chassis parts are critical elements directly involved in the vehicle driveline systems and are constantly subjected to harsh cyclic loading during operation. To meet the demand for lightweight vehicles aimed at enhancing fuel efficiency, contemporary industry favors stronger and thinner steels for the chassis parts. Reduced thickness, however, leads to reduced stiffness, lower natural frequency, and eventually may deteriorate the durability of the part itself or the whole assembly. Given the conservative approach required for designing chassis parts, an accurate evaluation of fatigue properties of the materials and a thorough verification of the durability through computer-aided engineering (CAE) should precede the development of high-performance automotive chassis parts using new advanced materials. This study explores the fatigue properties of advanced high-strength steels widely used in the chassis parts and investigates the parts’ durability via finite element analysis (FEA). Strain-controlled low cycle fatigue tests are conducted on steels of grade 590 MPa or higher. Test data are post-processed to obtain the parameters which the user should input into the FEA software. Durability analysis is performed, and the experimental and FEA results are compared to validate the fatigue properties. |
| 2:00 p.m. | Effect of Prestrain and Strain Path on the Retained Austenite Transformation and Fracture Behavior in Quenched and Partitioned Steels Brian Lin, ArcelorMittal The post-forming fracture behavior of two industrially produced quenched and partitioned steels was investigated as a function of prestrain and strain path. The microstructure of both steels consisted of ferrite, martensite, bainite and retained austenite, but of varying volume fractions to achieve 980 and 1180 MPa strength levels respectively. A Marciniak punch was used to prestrain panels for different strain paths. The remaining volume fraction of retained austenite after each prestrain was characterized by x-ray diffraction. Samples were extracted from the prestrained panels for VDA bend testing with digital image correlation to determine the maximum fracture strain at the bent surface. In both steels, it was found that the fracture strain was dependent on the remaining retained austenite after pre-straining and less on the strain path. Characterization of the prestrained samples was performed to further understand the role of microstructure in fracture behavior. It was observed that the 1180 MPa steel had a larger reduction in fracture strain for decreasing retained austenite volume fraction as compared to the 980 MPa steel. |
| 2:20 p.m. | Break |
| 2:50 p.m. | Effect of Si Content on Thermal Stability of Austenite in Low-Alloyed TRIP Steel (Bainite Transformation Behavior in Austemper of Medium-Si Steel) Fangyi Wang, JFE Steel Corp. Low-alloyed transformation-induced plasticity (TRIP) steel with high strength and ductility has been widely used in the automotive industry. Austempering is a heat treatment utilized to produce low-alloyed TRIP steel, and it is mainly discussed in high-Si steel since Si is considered beneficial to obtain enough retained austenite. However, the effect of Si content on thermal stability of austenite is unclear, especially in steel with lower Si content. The purpose of this study is to investigate the effect of Si content on transformation behaviors and thermal stability of austenite during austempering. Cold-rolled steel sheets with chemical compositions of Fe-0.2C-(0.5, 1.0, 1.5) Si-2.0Mn (mass%) were prepared for this study. Specimens were heat-treated by salt bath furnaces. Specimens were austenitized at 900℃ for 600s, and then rapidly cooled to various austempering temperatures of 400/450/500℃ above martensitic transformation start (Ms) temperature and isothermally held for various times (Austempering time, 0–3600s). After holding, specimens were water quenched to room temperature. Microstructures were examined by scanning electron microscope (SEM). Microstructures after 400℃ austempering were compared. In all steels, the decomposition of austenite between bainite laths was observed after different austempering times. Decomposition of austenite occurred at the beginning of bainite transformation in 0.5 Si steel, which was much faster than 1.0 Si steel and 1.5 Si steel. In the case of 400℃ austempering, the thermal stability of austenite increased with Si content. To find out the optimum austempering temperature for 0.5 Si steel, microstructures of 0.5 Si steel after 400/450/500℃ austempering were compared. Decomposition of austenite was postponed by increasing austempering temperature. Indicates that the optimum austempering temperature various with the Si content. This paper will discuss the mechanism from the perspective of Acm lines in the para-equilibrium condition. |
| 3:10 p.m. | Investigating the Microstructures and Mechanical Properties of As-Cast and Continuously Cast Advanced High-Strength Steels Nhu Hannah Ngo, Carnegie Mellon University Third-generation advanced high-strength steels (AHSS) exhibit increased strength and formability due to their chemical composition and precisely controlled thermomechanical processing. Reliable production of these steels requires understanding of the chemical composition effects on microstructure development during all steps of processing. This study focuses on comparing laboratory-cast ingots with continuously casted slabs containing 0.2 wt.% C, with varying Mn, Si and Al concentrations. Microstructural features and mechanical properties are investigated throughout the study. Results show that higher alloying addition increases the A3 transformation temperature and amount of ferrite. For as-cast microstructures, Si-containing steels have proeutectoid ferrite while the combined Si and Al alloys have primary ferrite. Steels alloyed with only Al have both primary and proeutectoid ferrite. Gleeble results show that ferrite does not affect the fracture path for all compositions. |
| 3:30 p.m. | Austenite Stabilization in Advanced High-Strength Steel Using Quench and Partitioning Technique Chiradeep Ghosh, Monojit Dutta, Tata Steel Ltd. The automotive market is undergoing a rapid change, with the future of mobility will be largely dominated by electric vehicles. The primary focus of the auto manufacturers will remain in reducing the car body weight with enhanced crash safety performance. All these will necessitate the usage of more and more third-generation advanced high-strength steel (AHSS). These steels enable low-cost strategies to vehicle lightweighting, guarantee vehicle crashworthiness and occupant protection while contributing to increase fuel efficiency. In line with this, an effort has been made to develop AHSS through stabilization of retained austenite in martensitic matrix in different low-alloyed compositions using the Quench and Partitioning (Q&P) technique. The alloys were initially processed through hot and cold rolling route. Finally, the cold-rolled samples were heat-treated using different Q&P treatments. A thorough investigation was carried out to ascertain the microstructural and mechanical property evaluations under different heat treatment conditions. The alloys have been designed in such a way that they can provide the required amount of hard phase (i.e., mainly martensite) for achieving the strength as well as the requisite fraction of retained austenite which enhances the TRIP effect to a certain extent during deformation. This has improved the ductility and the strain hardening exponent of the steel. |
| 3:50 p.m. | Influence of Initial Microstructure on the Evolution of Microstructure and Mechanical Properties of Galvanized Third-Generation Automotive Steel Feng Yang, Yun Han, Huaxiang Teng, Huasai Liu, Musheng Qiu, Yin Zou, Shuo Han, Cheng Zhang, Research Institute of Technology of Shougang Group Co. To mitigate fuel consumption and enhance automotive safety, the strength grades of car body parts are increasing while their shapes are becoming more intricate. In response to the challenges associated with forming intricate components, several leading steel manufacturers have sequentially developed a range of third-generation AHSS characterized by exceptional formability. Meanwhile, the Shougang R&D team investigated the influence of various initial microstructures on the mechanical properties of QP980+Z and devised a new process to enhance the formability of galvanized quenched and partitioned (Q&P) steel. When the initial microstructure consists of deformed ferrite and pearlite, the room temperature microstructure after annealing is primarily composed of equiaxed ferrite, martensite, bainite and a small amount of retained austenite (RA). The RA content ranges from 5% to 8%, with A80 values reaching up to 20%. In cases where the initial microstructure is undeformed martensite or annealed martensite, the resulting microstructure after annealing mainly comprises lath or fibrous ferrite, martensite, and RA. The measured RA content falls between 10–15%, with A80 reaching nearly 25%. Both the RA content and elongation are significantly enhanced when the initial microstructure is undeformed martensite. The increase in RA content and elongation is believed to be related to both the shape of reversed austenite and the enrichment of C atoms during partitioning process. After soaking the undeformed martensite in the two-phase region, the reversed austenite is mainly in the form of lath or fibrous with the size of about 300 nm, resulting in significantly improved stability compared with equiaxed reversed austenite. During the following Q&P process, the C concentration in austenite is further enriched, which is beneficial to obtaining more RA and higher elongation at room temperature. |
| 4:10 p.m. | Adjourn |
Tuesday, 11 March 2025 | |
| Session Chairs: Weiping Sun, Igor Vieira, Nucor Corp. | |
| 8:15 a.m. | Keynote: Innovation in Steelmaking to Automotive Design J.B. Chronister, Cleveland-Cliffs Inc. Over the past 20+ years, innovation in manufacturing has moved quickly in all areas of steel production. Much of this innovation has been driven by automotive OEM demands for more precise materials related to strength levels and formability. One consistent theme is that steel remains the material of choice for the majority of automotive parts and is positioned to remain for decades to come. |
| 8:50 a.m. | Modeling of Complex Transformation Products in Advanced Steels Matthias Militzer, University of British Columbia Advanced high-strength steels (AHSS) with complex multiphase microstructures are key materials for a wide range of automotive parts in modern vehicle designs. The different transformation products in these steels can include ferrite, bainite, martensite and retained austenite. Their fractions during processing of these steels must be carefully controlled to meet the property targets for automotive applications. Thus, microstructure-based process models are of critical significance to aid the development of optimized steel chemistries and robust processing paths. In addition to conventional phenomenological models, phase field modeling is a suitable technique to describe the evolution of morphologically complex microstructure components including the formation of bainite. A systematic phase field analysis will be presented to evaluate the role of elasticity and interface anisotropy on austenite decomposition into bainitic ferrite. Based on this analysis a phase transformation model is proposed to describe the formation of multiphase microstructures as a function of industrially relevant heat treatment paths. The model is benchmarked and validated with experimental data on austenite decomposition in transformation-induced plasticity (TRIP) and carbide-free bainite steels. The strength and limitations of the proposed modeling approach will be critically reviewed. |
| 9:10 a.m. | Hot Rolling and Microstructural Optimization Modeling for Enhanced Mechanical Properties of High-Strength Multiphase Steels Unai Mayo, Nerea Isasti, Pello Uranga, CEIT and University of Navarra-Tecnun; Brandon Hance, CBMM North America Inc.; Yanwen Wang, Sanjeev Sharma, Weiping Sun, Nucor Corp. A Nb-Ti-Mo microalloyed hot-rolled high-strength multiphase steel has been developed using energy-efficient and environmentally sustainable electric arc furnace–compact strip production (EAF-CSP) manufacture process to improve vehicle structural performance, safety and fuel efficiency. This study focuses on the hot rolling and microstructural optimization of this advanced steel grade, aiming at enhancing its mechanical properties through advanced microstructural characterization and hot rolling modeling techniques. Using scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD), a comprehensive microstructural characterization of hot-rolled coils was completed. This approach enabled precise quantification of grain size distributions, sub-structure definition as well as dislocation density. Additionally, transmission electron microscopy (TEM) was employed to analyze fine precipitates in coils, providing insights into precipitation strengthening mechanisms and their influence on the final mechanical properties. The microstructural evolution during hot rolling was modeled using MicroSim® software. This modeling allowed prediction of the microstructural evolution of austenite and the final homogeneity before transformation. To further understand the phase transformation kinetics, continuous cooling transformation (CCT) diagrams were constructed and validated using the PhasTranSim® model. These diagrams are crucial for optimizing cooling rates and achieving the desired microstructural phases. The relationship between microstructural features and mechanical properties was investigated, demonstrating how control of rolling parameters and cooling rates can enhance the strength of hot-rolled coils. The combined use of experimental techniques and modeling provided a robust framework for predicting and optimizing the properties of sustainable high-strength multiphase automotive steel. |
| 9:30 a.m. | Modeling of Hot Rolling Technologies in the Context of Developing New Steel Grades Eugene Nikitenko, United States Steel Corporation The importance of having accurate models of a hot strip mill cannot be overestimated. Such models allow for the successful development of new steel grades with specified properties and provide significant reduction in resource and time costs. Models give the opportunity to optimize the throughput while avoiding equipment overloading, to predict roll forces, torques, and power in the roughing and finishing stands, to calculate mechanical properties of hot bands coiled at various coiling temperatures with the alternative cooling strategies. Modeling must provide the adequate means to precisely simulate both the traditional integrated hot mills and thin casting–hot rolling technologies. Examples of such technologies can be compact strip production (CSP®), endless strip production (Arvedi ESP), and quality strip production technology (QSP®). Moreover, the availability of such models makes it possible to accelerate the testing of new steel grades through virtual trials. Virtual trials can save costs and time in the process of finalizing steel composition. The paper summarizes successful experiences of U. S. Steel in development such models and their usage. |
| 9:50 a.m. | Break |
| 10:20 a.m. | Application of Rapid Induction Heating to Third-Generation Advanced High-Strength Steels Alec Williamson, Samuel Findley, David Ulrich, Colorado School of Mines; Matthew Merwin, Matthew McCosby, United States Steel Corporation; Malavikha Rajivmoorthy, Eliseo Hernandez-Duran, Cleveland-Cliffs Inc.; Robert Goldstein, Fluxtrol; Emmanuel De Moor, Lawrence Cho, Colorado School of Mines An important pathway to reduce carbon emissions and transition to more sustainable manufacturing practices in the steel industry is the electrification of reheating furnaces, e.g., utilizing induction heating technology. This study investigates the feasibility and benefits of induction heating to replace conventional gas-fired furnaces used for continuous annealing while enhancing the performance of advanced high-strength steels (AHSS) designed for automotive applications. The current investigation involves a comparative study of simulated induction annealing versus conventional continuous annealing, focusing on the effects on microstructure development and mechanical performance for third-generation AHSS grades. Two medium Mn (3 to 5 wt pct) steels designed for quenching and partitioning (Q&P) applications are being investigated for this study. The conventional Q&P cycles based on common continuous annealing practices and induction annealing cycles that are “industrially viable” through common inductor designs were designed, and the heat treatments were performed using a Gleeble thermomechanical simulator and dilatometry. The heat-treated microstructures were characterized using electron microscopy and the magnetization saturation method, highlighting that rapid induction heating stabilizes higher fractions of retained austenite compared to conventionally continuous-annealed microstructures, possibly due to microstructural refinement or local chemical heterogenies. Several technical challenges that currently hinder the widespread adoption of induction heating in steel processing are also reviewed, such as managing thermal gradients and achieving homogeneous microstructures. |
| 10:40 a.m. | Flash Annealing of Steel: Challenges and Technologies D. Barbier, Fives KEODS; J.P. Nauzin, Fives Steel Division The energy transition in the steel industry and related massive electrification is a key opportunity for adoption of new processes. In particular, flash annealing of flat-C steels is foreseen as a game changer leading to potential increased production rates and improved material properties, primarily achieved through grain refinement. The beneficial effect of flash annealing on the mechanical properties of either conventional or advanced high-strength steel grades have been studied the past decades. It has been shown that strong improvement of mechanical and ductility/forming properties can be achieved thanks to flash annealing, while limiting the alloying content. Some metallurgical uncertainties remain, mainly related to phased distribution and homogeneities. Most of these studies were performed at laboratory scale, as the technologies required for these treatments were not mature enough. Newly developed induction and quenching technologies make it possible to consider flash annealing and galvanizing at industrial scale. Induction technologies (transverse and longitudinal flux) allow rapid heating (~500°C/s) over a large temperature range as requested for the management of multiphase material containing substantial amount of austenite. Moreover, they allow efficient strip reheating in the case of complex annealing cycles such as quenching and partitioning (Q&P) concepts. Dry-H2 fast cooling and wet quenching cooling (up to –1,000°C/s) enable metallurgical control of all required phases as well as management of all requested product dimensional ranges and similar annealing cycles for single-alloy chemical concepts, whatever the strip thickness. This paper will review the metallurgical benefits of flash annealing, the related key technologies, requirements, and industrial line footprint. All these considerations will cover a large spectrum of steel grades, from conventional to third-generation advanced high-strength steels. |
| 1:00 a.m. | Bending Deformation Behavior of a TS 1180 MPa Grade Complex Phase Steel Rosa Kim, Joo-Yeon Moon, Seong Kyung Han, Tae Woo Kwon, Hyundai Steel This study presents a 1180 MPa grade complex phase (CP) steel with enhanced bending toughness and describes the characteristics of the developed steel with a focus on their microstructure and defect formation during a bending test. The developed CP steel demonstrates a high ultimate tensile strength (UTS) of 1223 MPa, and an excellent bending property with the 0.2 for 90º R/t value. This value represents excellent bending properties compared to conventional CP steels, which have R/t values ranging from 1.0 to 3.0. The improved bendability was achieved by optimizing the microstructure to minimize the hardness distribution. Analysis of deformation and fracture behavior during bending test shows that the superior bending toughness of the developed CP steel results from enhanced resistance of crack propagation provided by the tempered bainite and martensite. To ensure improved bendability, the martensite start temperature (Ms) should be set significantly higher than the finish quenching temperature, which is crucial for achieving optimal mechanical properties through proper heat treatment. |
| 11:20 a.m. | Formability Evaluation of 980MPa and 1180MPa Grades With Different Microstructures for Automotive Applications Vasant Pednekar, United States Steel Corporation Battery electric vehicles (BEV) have drastically changed automotive body-in-white (BIW) structures design. Intrusion protection for the battery is of primary importance in addition to energy absorption for battery-enclosed structures. GPa advanced high-strength steels (AHSS) including press-hardened steels (PHS), dual phase (DP), multiphase (MP), complex phase (CP), and third-generation steels serve this exact purpose by becoming the material of choice for design. Higher yield strength materials especially in 980/1180 MPa MP and CP category are chosen for part design over conventional low yield strength DP. An extensive study is conducted to compare and comprehend the typical mechanical properties and global and local formability performance differences among 980 DP, MP and CP grades. The evaluations are focused on the potential of using higher yield strength AHSS (MP/CP) to form 980 DP-type parts in terms of both global and local formability performances. |
| 11:40 a.m. | Cold-Forming Techniques for Curved Component of Ultrahigh-Strength Steel Satoshi Sumikawa, JFE Steel Corp. In order to reduce CO2 emissions, lightweight reduction of automobile bodies is required. The strength grade of the cold-formed steel used in structural components is increasing year by year, and ultrahigh-strength steel (UHSS) exceeding 1 GPa are widely applied to structural components. For further strengthening and expansion of application, cold-forming techniques of UHSS to overcome forming problems such as fractures, wrinkles and springback are necessary, especially in the forming of long curved components. In this study, the two new forming techniques for curved components using UHSS were developed. The forming technique for the suppression of fractures and wrinkles induces in-plane shear strain at side walls by twist deformation. It was found that the twist angle at side wall influences on the formability of the curved component, and optimum twist angle was determined in the computer-aided engineering (CAE) evaluation. The forming technique for the suppression of springback utilizes the stress reversal during two-step forming. This technique can reduce the stress at the flange, which is a cause of twist springback. The practicality of these two forming techniques was verified by the press-forming trials in the actual component scale. |
| 12:00 p.m. | Lunch |
| 1:00 p.m. | Influence of Stamping Temperature on Retained Austenite Evolution and In-Service Behavior for GI Fortiform 980 Hong Zhu, ArcelorMittal Global Research & Development In this study, a test procedure has been developed to characterize retained austenite volume fraction evolution vs. various prestrains at stamping temperatures (100°C) by hybrid MTS and ex situ x ray diffraction (XRD) for GI Fortiform® 980, a retained austenite–containing steel with 980 MPa tensile strength. In situ tensile tests at stamping temperatures with HEXRD were also performed to confirm the finding from ex situ tests. It was found that retained austenite as a function of prestrain was more stable at 1,000°C as compared to room temperature (20°C) from both the in situ and ex situ tests. Tensile strength at 100°C was 100 MPa lower as compared to the room temperature behavior. Reduction of area and fracture strain measured from an image-based approach are found to be higher at 1,000°C compared with room temperature due to the higher stability of retained austenite. These findings are crucial to design robust stamping process development for the part properties after stamping. |
| 1:20 p.m. | Resistance Spot Welding Technology for Ultrahigh-Strength Steel Sheet to Improve Both Liquid Metal Embrittlement Cracking Resistance and Joint Strength Shinsuke Komine, Tomomi Kanazawa, Reiko Endo, Chikaumi Sawanishi, Katsutoshi Takashima, JFE Steel Corp. The purpose of this study is to suppress liquid metal embrittlement (LME) cracking and improve joint strength, which are important issues in resistance spot welding. LME cracking and joint strength decline are especially remarkable in the resistance spot welding of ultrahigh-strength steels. The fundamental study on resistance spot welding technology to accomplish both LME cracking suppression and joint strength improvement was carried out in this study. As a concept of LME cracking suppression, the authors focused on raising the melting point of Zn coat. The pulsed current pattern was used as a method to raise the melting point of Zn coat. In the pulsed current pattern, no LME cracks were observed. In the corona bond, Fe concentration of Zn coat was increased. It suggests that the alloying reaction between Zn (Zn coat) and Fe (base metal) was accelerated by the pulsed current pattern and the melting point of the Zn coat was increased. In the joint strength evaluation of cross-tension strength (CTS), the fracture mode was changed from interface fracture (brittle fracture) to plug fracture (ductile fracture) and CTS was increased by the pulsed current pattern. In the pulsed current pattern, P segregation near the nugget edge was suppressed. It suggests that the toughness of the nugget edge was improved by the suppression of P segregation, which contributed to the CTS improvement in the pulsed current pattern. |
| 1:40 p.m. | The Effects of Substrate Aluminum Content on Liquid Metal Embrittlement Susceptibility of Resistance Spot Welds in Galvanized Third-Generation Advanced High-Strength Steels J. Colburn, John G. Speer, J. Klemm-Toole, Colorado School of Mines In recent years, the automotive industry has sought to implement third-generation advanced high-strength steels (AHSS) in automotive bodies to further lightweight and increase the crashworthiness of vehicles. However, the phenomenon of liquid metal embrittlement (LME) in these Zn-coated steels during resistance spot welding (RSW) has hindered their implementation. In this work, the authors seek to understand how the substrate Al content affects the LME susceptibility of two quench and partitioned (Q&P) alloys containing equal silicon contents. Hot tension test results on 0.5 Si – 0.05 Al and 0.5 Si – 1.38 Al alloys show that the higher Al alloy exhibited less ductility and strain energy losses, indicating a reduction in LME susceptibility. Diffusion simulation results at 800°C suggest that Al enrichment occurs at the coating-substrate interface in the 1.38 Al alloy to a degree in which the beneficial Γ-Fe3Zn7 phase is stabilized at the expense of the deleterious liquid phase. An increase in substrate Al content also decreases the solubility and diffusivity of Zn in the substrate phases at 800°C, resulting in a decrease in the flux of Zn into the substrate. The flux of Zn into the substrate is further decreased by the presence of the Γ phase acting as a physical barrier to Zn diffusion in the 1.38 Al and leads to an overall decrease in solid-state, stress-assisted diffusion of Zn ahead of the LME crack tips. The embrittlement of the 1.38Al is, therefore, decreased as compared to the 0.05 Al alloy. RSW testing assessing the average cracking index was conducted on the two alloys to assess the applicability of the hot tension test and simulation results to actual spot-welding conditions. The results of this work are expected to provide insight into designing more LME-resistant third-generation AHSS for lightweight automotive applications. |
| 2:00 p.m. | Development of Spot-Welding Technology Applying Adaptive Control With Dynamic Selection From Multiheat Target Naoaki Munemura, JFE Steel Corp. The reduction of the nugget diameter is concerned when the sheet gap exists in the resistance spot welding of ultrahigh-strength steel. Adaptive control welding is examined as a technology to stabilize nugget formation, there have been few reports on its application to sheet gap. The adaptive control welding phenomenon in the presence of the sheet gap was examined using experimental and numerical analysis in this study. In addition, a new welding method to form a stable nugget diameter even in the presence of a sheet gap was investigated by selecting multiple target heat quantities. Welding and numerical analysis were conducted on 1180 MPa cold steel sheet under two conditions: no sheet gap and 2.5-mm sheet gap. The nugget diameter and the nugget thickness decreased with the increase of the sheet gap in the constant current welding. As a result of numerical analysis, it was confirmed that the contact area between the electrode and the steel sheet increased. On the other hand, when the conventional adaptive control welding was conducted, sputtering occurred in the 2.5-mm gap. This is because of the decrease of the required heat quantity along with the increase of the sheet gap, and this result suggested that the conventional adaptive control with the target heat quantity set without the sheet gap caused the excessive heat input. Therefore, multiple target heat values were set, and adaptive control welding was conducted. Consequently, a nugget diameter of 5√t can be ensured without sputtering up to a sheet gap of 3.0 mm. |
| 2:20 p.m. Break | |
| 2:50 p.m. | Formability Characteristics of Advanced High-Strength Low-Alloy Steels Hardy Mohrbacher, NiobelCon BV; Caio Pisano, Bernardo Barile, CBMM Europe Advanced cold-rolled high-strength low-alloy (HSLA) steels have been developed extending the range of available grades from 550 up to 800 MPa yield strength. The processing of such steels is possible using any of the widely established production facilities such as batch annealing, continuous annealing and hot-dip galvanizing. The strength relies on a partially recrystallized or fully recovered microstructure. Contributing strengthening mechanisms are grain size, solution strengthening and microalloy precipitation. Besides strength, formability is a key aspect for automotive applications. Based on tensile testing and respective elaborate data analysis, the strain hardening behavior could be related to the microstructural features. It became clear that even at the theoretical limit strength the n-value does not decrease to zero but settles on a minimum value of around 0.03. As expected from the Considère criterion, the uniform elongation is directly related to the n-value, which in turn is implicitly influenced by the level of precipitation strengthening. Advanced HSLA steels also expose pronounced Lüders deformation, which is shown to directly correlate with the magnitude of precipitation strengthening. The particular role of the precipitates is derived from digital image correlation (DIC) analysis. Regarding practical forming processes, the forming limit curve (FLD) of advanced HSLA steel has been synthesized and is compared to that of similar strong dual-phase steel. Furthermore, the local vs. global formability behavior was analyzed for both steels. It will be shown that advanced HSLA steels have an exceptionally high fracture strain. It can be tuned to an excellent balanced combination of global and local formability making it suitable for a large variety of different forming methods. |
| 3:10 p.m. | Metallurgical Strategies in the Production of Bake-Hardenable Steels Malavikha Rajivmoorthy, Cleveland-Cliffs Inc. Bake-hardenable steels are a class of steel grades that represent a good combination of strength and formability. The yield strength in these steels is increased by 10% or more during the paint baking process making them dent-resistant, and therefore ideal for applications like external body panels. They are typically ultralow-carbon steels, I-F partially stabilized when produced in a continuous annealing process such as hot-dip galvanizing. Carbon dissolved in ferrite, if too low, may not produce sufficient increase in yield strength, and if too high, may have less resistance to room temperature aging. Precise control of solute carbon is essential to produce an optimal bake-hard response, while avoiding the occurrence of any aging. In addition to composition, bake-hard response is also affected by process parameters such as soaking furnace temperature, and microstructural features such as grain size. This study aims to provide a comprehensive overview of production strategies for three different ultralow-carbon bake-hard grades — with varying content of microalloying additions (Ti, Nb, V) — in an effort to assess properties, performance and processing parameters. Bake hardenability of advanced high-strength steel grades are also discussed. |
| 3:30 p.m. | Enhancing Ultrahigh-Strength Low-Alloy Steels for Modern Automotive Applications: The Influence of Titanium on Recrystallization and Precipitation Behaviors Sang Hun Shin, Jong Myeong Kim, Hyundai Steel; Alexander Gramlich, RWTH Aachen University; Kwang Su Na, Tae Woo Kwon, Hyundai Steel As the automotive industry increasingly adopts minimalist designs, particularly in electric purpose-built vehicles (PBVs), the demand for materials that meet unique structural requirements is growing. Traditional dual-phase steels, valued for their balance of tensile strength and formability, have been widely used in automotive components such as crash boxes and pillars. However, their inherent phase hardness disparity can limit bending capabilities, which is crucial for modern vehicle designs emphasizing flat platform structures. In response, ultrahigh-strength low-alloy (UHSLA) steels are gaining attention due to their single-phase structure, which provides superior bending performance. Among the alloying elements in these steels, titanium is particularly effective in enhancing mechanical properties and cost-efficiency. This research examines the impact of varying titanium concentrations on the recrystallization behavior and precipitate formation in UHSLA steels. Through detailed analyses of recrystallization kinetics and microstructural evaluation, this work aims to understand how titanium influences these processes. This study seeks to inform the development of advanced steels tailored to the evolving needs of modern automotive applications. |
| 3:50 p.m. | Optimization of Global and Local Formability Properties Through Nb Microalloying Hardy Mohrbacher, NiobelCon BV; Brandon Hance, CBMM North America Inc. Automotive high-strength steels have specific microstructure-dependent forming characteristics. Global formability is generally associated with high uniform strain values which imply good drawability and stretch forming properties driven by pronounced work hardening. Local formability on the other hand is often measured by various fracture strain values — generally higher in single-phase steels. In this respect, the so-called “local/global formability map” concept has been established not only to provide a comprehensive methodology to characterize existing automotive steels but also to enable improvement strategies toward more balanced forming characteristics. Niobium (Nb) microalloying is a powerful tool to achieve both property improvement in general and property balance in particular. More than two decades of research has demonstrated that Nb-induced microstructural optimization is applicable to high-strength low-alloy (HSLA) steels, advanced high-strength steels (AHSS) (dual phase (DP), complex phase (CP), transformation-induced plasticity (TRIP), twinning-inducted plasticity (TWIP)) and press-hardened steels (PHS), and it has been realized in commercial production of such steels. This contribution details the underlying metallurgical and processing effects of Nb microalloying in automotive high-strength steels and highlights achieved global and local formability improvements. Respective optimization vectors are demonstrated through intrinsic formability mapping, where the possibilities and limitations are indicated. |
| 4:10 p.m. | High-Strength Hot-Rolled Steel Sheet With Improved Stretch Flangeability for Automotive Applications Madhawan Chandrawanshi, Sushil Kumar Giri, G. Senthil Kumar, Nigamananda Routray, Tuhin Chatterjee, Biswajit Ghosh, Tata Steel Ltd. Jamshedpur Hot-rolled steel sheets used for automotive applications, such as wheel disc, lower control arm and chassis parts, require a combination of improved stretch flangeability and very high strength. Stretch flangeability is measured in terms of hole expansion ratio (HER), which is an important product attribute to assess the local formability of the material. However, as the strength increases, the formability and HER of steel sheet deteriorates. The present work demonstrates the effect of chemical composition, hot rolling parameters, controlled cooling in runout table (ROT) and resulted microstructure on formability and HER of TS 590 MPa steel grades. Different chemical composition of TS 590 steels, such as Nb+Ti microalloyed, Ti-only microalloyed design is described in terms of microstructure and mechanical property. The developed hot-rolled steel grades have improved strength and HER combination as compared to dual phase/transformation-induced plasticity (DP/TRIP) or any conventional high-strength low-alloy (HSLA) steel. It was attributed to suppressed cementite precipitation at the grain boundaries, ferrite + bainite or bainitic ferrite microstructure through controlled cooling, and appropriate inclusion control during steelmaking, resulting in an excellent hole expansion ratio (HER > 100%). Formation and propagation of microcracks during hole expansion was suppressed by ferrite-bainite duplex microstructure due to reduced harness ratio between the ferrite matrix and second phase. It was also observed that formation of large textural colonies in Nb-added steel deteriorates the stretch flangeability. Reduction in void nucleating sites (inclusion, large TiN precipitate, cementite, etc.) results in improved HER. In the case of Ti-only microalloyed design, precipitation strengthening with nanometric homogeneously distributed precipitate in ferrite or low-carbon bainitic ferrite single-phase matrix can enhance strength and HER combination. |
| 4:30 p.m. | Adjourn |
Wednesday, 12 March 2025 | |
| Session Chairs: Ana Paula Domingos Cardoso, International Zinc Association; Stavros G. Fountoulakis, ArcelorMittal Global R&D – East Chicago; Shreyas Devanathan, Steel Dynamics Inc. — Flat Roll Group Southwest-Sinton Division | |
| 8:15 a.m. | Keynote: Developments and Outlook of Automotive Sheet Steels in China Li Wang, Baosteel Iron & Steel Co. Ltd. The output of China’s automobile industry has been ranked first in the world for 15 years, and new energy vehicles have developed rapidly. The changes in the structure of automobiles have an impact on materials; high strength with good formability and high corrosion resistance are still the main development directions of automotive sheet steels. In addition, low-carbon-emission automotive steel has also been in urgent demand in recent years. The high strengthening and low carbon emission of steel sheets also bring technical challenges to production, manufacturing and application, such as surface quality, stability of mechanical properties, hydrogen embrittlement, and welding performance. This paper will review some technological progress made by Baosteel in response to these challenges. Baosteel automotive steel sheet’s carbon-neutral routes and recent activities in developing low-carbon-emission automotive steel sheets through the electric arc furnace process are shared. |
| 8:50 a.m. | Evolution of Microstructure During Partitioning Associated With Galvanizing/Galvannealing of Advanced High-Strength Steels Sachin Kumar, Colorado School of Mines; Kyoung Min Kim, Ho Yong Um, Hyundai Steel; Emmanuel De Moor, John G. Speer, Colorado School of Mines Quenching and partitioning (Q&P) steel offers an excellent combination of strength and ductility, making it ideal for third-generation advanced high-strength steels (AHSS) used in automotive body parts. The Q&P process, particularly the partitioning stage, can be integrated within conventional Zn hot-dip coating cycles (e.g., galvanizing (GI)/galvannealing (GA)), leading to impressive mechanical performance and good corrosion resistance. However, higher partitioning temperatures during coating cycles, particularly GA, compared to an optimized continuous annealing Q&P process may increase cementite precipitation and austenite decomposition, potentially impacting mechanical properties. The scope of this work is to understand the evolution of microstructure, transformation behavior and kinetics of cementite precipitation in relation to partitioning temperature and time in GI/GA steels subjected to a prior quenching step below Ms (termed as GI/GA Q&P steels). The GI/GA Q&P cycles were simulated in a dilatometer using three conventional C-Mn steels containing Si, Al and Cr. As the GA process progressed at higher temperatures, the austenite fraction and its C content, along with the amount of transition carbides, formed during initial quenching or isothermal holding at the quenching temperature, decreased, while cementite precipitation increased. Dilatation data exhibited complex variations, indicating carbon rejection from martensite at the start of the GA step, cementite precipitation from martensite and/or austenite during the intermediate stage and austenite decomposition into ferrite and cementite during the later stage of GA. The kinetics of cementite precipitation was simulated using TC-PRISMA® to explain the experimental findings. Calculations demonstrated the thermodynamic feasibility of cementite precipitation from both martensite and remaining austenite during GI/GA. Cementite formation from C-enriched austenite resulted in a decrease in the C content of remaining austenite and thus it might decompose to ferrite and cementite, as observed experimentally. These findings can facilitate precise control of austenite volume fraction and its stability and would be a step forward for optimizing the partitioning stage. |
| 9:10 a.m. | Synchrotron Characterization and Mesoscale Crystal Plasticity Simulation of the Retained Austenite Transformation of Quenched and Partitioned Steels in a Bend Specimen Brian Lin, ArcelorMittal The transformation behavior of retained austenite is critical to the forming and performance of quenched and partitioned (Q&P) steels in automotive applications. Differences in the volume fraction of retained austenite transformed across a stamped part can dictate where failure occurs. Most studies have examined the transformation behavior in Q&P sheet steels predominantly in uniaxial tension and occasionally biaxial stretching, however little is known on the transformation behavior during bending, which is another major stamping process. In this investigation, the retained austenite profile through the thickness of a 90°bend specimen of a Q&P sheet was studied via high-energy x-ray diffraction performed at the Advanced Photon Source at Argonne National Laboratory. Differences in the volume fraction of retained austenite transformed were observed on the tension side of the neutral axis versus the compression side. These experimental results were used to further validate a mesoscale crystal plasticity finite element model developed to model the deformation and transformation kinetics in third-generation advanced high-strength steels. |
| 9:30 a.m. | Influence of Intercritical Austenitizing Temperature on 1000 MPa Tensile Strength Class Third-Generation Advanced High-Strength Steels Applied in the Automotive Industry Henrique Lacerda Eleuterio, Usiminas The application of third-generation advanced high-strength steels (AHSS) in the automotive industry has been steadily increasing, aiming to reduce environmental impact and to improve passenger safety. This steel class has an excellent combination of formability and high strength after forming, enabling a reduction of vehicle weight through the use of smaller thicknesses. Third-generation AHSS achieves its characteristics by forming a homogeneous bainitic/martensitic matrix with a high percentage of retained austenite (RA). The main heat treatment applied to obtain this microstructure is quenching and partitioning (Q&P), which has proven suitable for producing these steels. In this context, this study aimed to investigate the effect of intercritical austenitizing temperature in the Q&P process applied in a continuous annealing line. The investigation focused on the properties and microstructure evolution of a third-generation AHSS with tensile strength above 1000 MPa to understand its connection with the RA nucleation during the austenitizing heat treatment. The steel samples were heat treated in laboratory using a Gleeble thermomechanical simulator and characterized by scanning electron microscope with energy-dispersive spectroscopy (SEM/EBSD), and x ray diffraction (XRD). The intercritical heat treatment was found to be beneficial for promoting the homogeneity of microstructure morphology and mechanical properties, especially concerning a given RA fraction and elongation. Furthermore, higher elongation values were attributed to the influence of a higher ferrite fraction combined with the RA in the microstructure. |
| 9:50 a.m. | Influence of Hot Deformation Behavior on Development of Third-Generation Advanced High-Strength Steels M. Valdez-Vázquez, Universidad Autónoma de Nuevo León; O. García-Rincón, Ternium Mexico; L. Leduc-Lezama, MP. Guerrero-Mata, Universidad Autónoma de Nuevo León In the development of advanced high-strength behavior steels, the industry is looking for the best combination of ductility resistance and lightweighting. The relationship among these properties is important for the automotive industry because of its potential for carbon emissions reduction without safety compromises. Some of approaches to obtain such properties are, a) microstructural control to obtain different phases in the steel; b) chemical composition control to change the transformation curves; c) addition of microalloying elements to form carbides or carbonitrides; and d) grain refinement. In this context, single-pass compression tests were carried out to investigate the behavior of a microalloyed low-carbon steel with different deformation rates (0.1,1,10 s-1) under temperatures in the range of A3 + 50°C – A3 + 200°C. The steel flow stress curves obtained under different percentages of deformation, and the effects of various parameters are discussed in this work. Constitutive equations were developed and used to determine the conditions to promote dynamic recrystallization (DRX). These constitutive equations, together with stress relaxation tests and simulation via JMatPro, were then used to obtain precipitation-time-temperature diagrams. It is proposed that this information could be the key to the designing routes for thermomechanical processes, controlling the pinning of the precipitation to obtain a grain refinement that promote the increasing of mechanical properties up to 1 GPa. |
| 10:10 a.m. | Break |
| 10:40 a.m. | Keynote: Current Trends and Technical Challenges for Galvanized Automotive Steel Sheet Frank Goodwin, International Zinc Association This keynote lecture will address the current challenges being faced in the manufacture and automotive applications of zinc-coated galvanized steel sheet. Highlights of recent technical achievements relating to meeting these challenges will then be described. |
| 11:00 a.m. | The Influence of Coating Weight on the Properties of Zn-Mg-Al Coatings Produced by Continuous Galvanizing David Penney, Swansea University Galvanized metallic coatings are the last line of defense against corrosion of automobile panels and chassis. Traditional zinc hot-dip coatings have been the benchmark for decades owing to ease of manufacture, formability and corrosion resistance. However, demand to reduce vehicle weight has led to the introduction of Zn-Mg-Al (ZMA) coatings with reported superior corrosion resistance. This permits the use of lower coating weights without a deleterious effect on corrosion performance. This work examines the microstructural and corrosion performance of three coating weights (80, 200 and 310 g/m2) produced on a continuous galvanizing line with a chemistry of 1–2 wt.% Al, 1-2 wt.% Mg and remainder Zn. The 80 g/m2 exhibited 84% volume fraction of primary zinc phase compared to 74% primary on the 310 g/m2 coating, with corresponding changes in eutectic fractions. This microstructural change was attributed to the high pressure at the gas knives required to produce the lowest coating weight. It is proposed that rapid cooling in the knives causes nucleation of primary Zn leading to Al and Mg solute-rich liquid being removed. This was evidenced using ICP-OES analysis and showed a lower Al and Mg levels in the 80 g/m2 coating compared to the higher coating weights. Corrosion tests performed in 0.17 M NaCl showed cut edge corrosion was dominated by oxygen reduction on the steel leading to similar corrosion rates across all coatings. Surface corrosion testing using timelapse, DC electrochemistry and SVET showed 64% higher corrosion rates on the 80 g/m2, attributed to modifications in the microstructure caused by wiping. However, the 80 g/m2 coating exhibited greater anodic spreading on the surface, meaning there is potential for less through-coating penetration. This work demonstrates the importance of understanding mechanistic spatial and temporal corrosion activity on ZMA alloys and links microstructure to performance. |
| 11:20 a.m. | Atmospheric Corrosion Behavior of Automotive Cold-Rolled and Galvanized Steel Sheets Exposed in East and Southeast Asia Region Rinta Sato, JFE Steel Corp. This paper discusses the results of atmospheric exposure tests of several automotive body steel sheets, such as cold-rolled steel (CRS) and galvanized steel, demonstrated at exposure sites in Japan and Indonesia. In addition to bare (unpainted) panels, specimens simulating car bodies, painted panels with X-cut scribes, and spot-welded lapped panels were studied. Corrosion behaviors were analyzed using physical analysis techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The relationship between environmental factors, shape of specimens and the corrosion behavior will be discussed. |
| 11:40 a.m. | Designing New Metallic Coating Alloys for Synergistic Enhancement of Inhibitor Systems: A Study of the Corrosion Mechanisms of Zinc and Zinc-Calcium Alloys in the Presence of Chloride and Phosphate Ions James Sullivan, Swansea University An investigation was performed to assess the effect of 1 wt.% additions of Calcium to Zn (Zn-1Ca) on its corrosion performance in 0.17 M NaCl and with phosphate corrosion inhibitor additions, a favored chromate replacement technology for galvanized products. Zn-1Ca displayed uniformly dispersed intermetallic CaZn13 phases throughout the microstructure. Corrosion was assessed using DC electrochemistry, the scanning vibrating electrode technique (SVET) and in situ timelapse microscopy (TLM). Metal loss from 24-hour SVET experiments decreased by 56% for Zn-1Ca compared with Zn. TLM and SEM-EDS analysis revealed preferential attack of the CaZn13 phase. This was driven by the more negative reduction potential of Ca highlighted by a decrease in open circuit potential (OCP) for Zn-1Ca. Additionally, TLM showed a greater precipitation of corrosion products for Zn-1Ca occurring over cathodic regions of the microstructure. Linear polarization resistance (LPR) demonstrated a 2.5 times decreased corrosion rate for Zn-1Ca with a decreased cathodic current observed during cathodic polarization. It is postulated that preferential attack of Ca rich phases generated chemical conditions that facilitated precipitation of corrosion products at the cathode resulting in cathodic deactivation and a reduced corrosion rate. 1 x 103 mol.dm3 phosphate additions to 0.17 M NaCl decreased the corrosion rate of both Zn and Zn-1Ca. 24-hour SVET-derived metal loss decreased by 48% for Zn and 72% for Zn-1Ca. Inhibition was greater for Zn-1Ca where uniform precipitation of mixed metal phosphates produced anodic and cathodic inhibition. The increased pH enabled by Ca2+ released from uniformly distributed CaZn13 phases resulted in increased precipitation of insoluble metal phosphate films leading to both cathodic and anodic deactivation. It has been demonstrated that observing corrosion mechanisms at a microstructural level, in combination with electrochemical techniques, enables alloy systems to be designed providing tailored ion release and chemical conditions that can enhance the performance of inhibitors. |
| 12:00 p.m. | Lunch |
| 1:00 p.m. | The Influence of Al and Mg Content on the Microstructure and Corrosion Behavior of Hot-Dipped Galvanized Zn-Mg-Al Coatings Amar Dhoj Malla, Swansea University Among the commercially available continuous galvanized metallic coatings, Zn-Mg-Al provides superior corrosion protection due to its complex microstructure. Zn-Mg-Al coatings are used in a wide range of industries from white goods to automotive. In addition to excellent corrosion protection Zn-Mg-Al offers excellent scratch resistance, microhardness and galling behavior. Because of Zn-Mg-Al’s popularity and existing patents, each producer tends to develop their own bespoke coating composition and register them with their product name. Therefore, in Europe, Al content varies from 1–3.7 wt.% and Mg varies from 1–3 wt.% in the Zn-Mg-Al coatings. In this investigation, four different Zn-Mg-Al coatings were produced using a hot-dip process simulator. The Al and Mg content in the 1–3 wt.% range was systematically varied to assess the individual element contribution in changes to microstructure and corrosion behavior. Time-lapse microscopy, scanning vibrating electrode technique and potentiodynamic methods were used to study the surface corrosion behavior in pH 7 0.17 M NaCl solution. Investigation revealed that the microstructural phases and their surface distribution determine the anodic and cathodic behavior of the coating. Increasing Al and Mg from 1–3 wt.% leads to a better corrosion resistance of the coating, yet the enhancement was greater for Al compared to Mg. Concurrently increasing both Al and Mg to 3 wt.% once again increased the corrosion performance. However, it was greater than 3 wt.% Mg but was lower than 3 wt.% Al. This work helps to develop a fundamental understanding of each element’s effect, thus enabling informed decisions regarding the compositional design of coatings for new products and markets. |
| 1:35 p.m. | Advanced Stereoscopic Imaging for Precision Measurement in Post-Slit Automotive Steel David Kober, Global Gauge Corp. This paper introduces a cutting-edge solution for the precision measurement of post-slit automotive steel mults, employing advanced stereoscopic imaging technology. This technical discussion details the system’s design, operation and integration into existing slitting lines, highlighting its capability to maintain stringent width tolerances and enhance downstream processing efficiency. The Mult Width Gauge system incorporates two high-resolution cameras, strategically positioned to capture synchronized images of the moving steel strip. Through stereoscopic imaging, the system enables accurate, real-time width measurements along the entire length of the product, crucial for ensuring compliance with tight manufacturing tolerances. Key technical features include the system’s ability to provide continuous monitoring and immediate feedback, minimizing the occurrence of out-of-tolerance mults. The integration with slitting line control systems enables automated corrective actions, reducing reliance on manual measurements and enhancing operational efficiency. The presentation will cover the calibration procedures necessary for achieving optimal measurement accuracy, addressing potential environmental influences such as dust, vibrations, and lighting conditions. Additionally, the system’s data logging capabilities will be examined, demonstrating how comprehensive width measurement reports are generated for quality control and traceability purposes. By implementing the Mult Width Gauge, manufacturers can achieve significant improvements in material utilization, product consistency and overall production throughput. This paper aims to provide a detailed understanding of the technical aspects and benefits of the Mult Width Gauge, underscoring its role in advancing precision measurement in the flat-rolled metals industry and its applicability to the high standards required in automotive manufacturing. |
| 1:55 p.m. | Effect of Boron on Surface Oxidation Behavior and Phosphatability of High-Strength Cold-Rolled Steel Sheets S. Furuya, T. Chiba, K. Okai, D. Mizuno, JFE Steel Corp. Surface oxides consisting of Si and Mn formed on steel during the annealing process affect the phosphatability of cold-rolled steel sheets. Addition of B to the steel changes the formation behavior of these Si-Mn surface oxides. To understand the effect of B on the surface oxidation behavior and phosphatability of high-strength cold-rolled steel sheets, 0.001 wt.% B-added and B-free steels containing 0.6 wt.% Si and 2.0 wt.% Mn were studied. The specimens were annealed at 800℃ in a 5 vol% H2-N2 atmosphere with a dewpoint of –50℃. The surface oxides of the annealed samples were analyzed by glow discharge–optical emission spectrometry (GD-OES), Fourier transformed–infrared spectroscopy (FT-IR) and scanning electron microscopy–energy-dispersive x-ray (SEM-EDX). The annealed steel sheets were then subjected to zinc phosphate treatment, and the effect of the surface oxides on phosphatability was evaluated by SEM-EDX. As a result of a detailed analysis, coarse oxides (>1 μm) containing Si and Mn and film-like oxides containing Si were observed on the surface of the B-added steel before zinc phosphate treatment. In contrast, neither coarse oxides nor film-like oxides were formed on the surface of the B-free steel, but uniform formation of small oxides (≦300 nm) containing Si and Mn was observed. During annealing, the B contained in the steel segregated to the surface, which promoted coarsening of Si-Mn complex oxides and resulted in an increase in coverage by the film-like SiO2 between those oxides. After zinc phosphate treatment, zinc phosphate crystals had not formed over the whole surface of the B-added steel, but the surface of the B-free steel was completely covered with a zinc phosphate crystal coating. Based on these results, it was suggested that the film-like SiO2 that formed on the B-added steel inhibited the dissolution reaction during zinc phosphate treatment, and thereby caused defects in the zinc phosphate coating. |
| 2:15 p.m. | Development of a New On-Line Sensor for Steel Surface Contamination David Egner, Sarclad Sarclad and CRM Group have successfully developed a new on-line sensor for steel strip contamination. The system utilizes laser-induced breakdown spectroscopy to give a continuous and real-time assessment of the contamination levels post-cleaning on a typical steel strip galvanizing line. Critically, this is the first system available that can distinguish between surface carbon and iron fines contamination with quantitative data. This will enable the highest product quality alongside optimized core cleaning section parameters to give the greatest process efficiency. This paper describes the technology used, its advantages and performance in industrial trials, whilst also addressing the practical considerations of implementing the technology in the commercial industrial environment. |
| 2:35 p.m. | Break |
| 3:05 p.m. | The Defect Detection Technique of Surface Inspection Systems With Texture Analyses Using Gabor Filters Mitsutoshi Kemmochi, JFE Steel Corp. Surface inspection of steel products is very important for quality assurance. Galvanized steel sheets and galvannealed steel sheets are mainly used for automobiles and usually need strict surface quality. Therefore, automatic in-line surface inspection systems have already been installed in sheet production lines such as continuous galvanizing lines. The systems use multiple light sources and cameras to highlight luminance differences in images of normal and defective surfaces. However, some kinds of surface defects are difficult to detect by conventional surface inspection systems because the differences on inspection images can be very subtle, so human inspection is still required. In this study, the authors propose a technique to detect surface defects on steel sheet products by texture analysis using Gabor filters considering defect orientation. In this technique, texture features are extracted by a group of Gabor filters with multiple scales and orientations. By statistically analyzing the extracted texture features, the defects are detected as pixels with statistically abnormal texture features. Abnormality of texture features is evaluated by Mahalanobis distance. Moreover, sub-band decomposition adapted to defect orientation is introduced in Gabor filtering to improve sensitivity to linear defects, which are common in steel sheet products and elongated in the longitudinal direction of steel sheet. The proposed technique enables detection of detects with low signal-to-noise ratio on inspection images, which are difficult to detect by conventional methods. As a result of applying the technique to the surface inspection system on a continuous galvanized line for galvanized steel, it is confirmed that a specific kind of defect is able to be detected and this technique will enhance the surface quality of products. |
| 3:25 p.m. | Effect of Selenium on the Machinability of Special Steels Denise Correa de Oliveira, Gerdau Special Steels Machining is one of the most common operations in the automotive industry. Some of the steel grades used in this process typically contain lead, which acts as a natural lubricant to ensure good machinability. However, lead can have negative effects on health and the environment. As a result, other elements such as selenium, which also provide good lubricating properties, are becoming increasingly attractive to the auto industry. In an effort to provide environmentally responsible solutions and respond to increasing global restrictions on the use of lead, Gerdau has been developing alternative grades that offer good machining performance. This study presents one of these solutions, focusing on the addition of selenium. The influence of varying chemical compositions and heat treatments on the microstructure and machinability of SAE 8620 steel was investigated, comparing a base grade, alternative grades, and a lead-containing grade. Conditions examined included as-rolled and heat-treated. The cutting tests involved semifinish turning under flood conditions on a CNC lathe, using an uncoated cemented carbide tool at two distinct cutting speeds. The depth of cut and feed rate were maintained at 1 mm and 0.2 mm/rev, respectively. Tool life, cutting forces and chip formation were recorded during the tests. Additionally, the worn tool surfaces were analyzed using a scanning electron microscope (SEM). The findings revealed that the combination of chemical composition, heat treatment and cutting speed had a significant impact on cutting forces and the machinability of the grades. |
| 3:45 p.m. | Bake Hardening of Advanced High-Strength Automotive Steels Hany Khalifa, EZZ Steel Dual phase (DP) steels compromise a combination of tensile properties as low yield strength and high tensile strength, which make them distinctive amongst advanced high-strength steel grades (AHSS). Moreover, it demonstrates great work hardening rates in the early phase of tensile testing in addition to a significant bake hardening (BH) prospective. Thermomechanical-controlled processing (TMCP) offers a cost-effective method for manufacturing direct hot-rolled DP steel. In this technique, alloy design, rolling schedule and cooling pattern has a major effect on the microstructure and mechanical properties of the produced steel. The current study delivers comprehensive outputs of replication of hot rolling mill by TMCP to develop new grades of DP steel that possess enhanced mechanical properties and bake hardenability. This is achieved by different alloying concepts along with optimization of the thermomechanical-controlled rolling parameters. Moreover, this study offers a detailed investigation of the local aging and BH behavior of DP steel with enhanced properties for the automotive industry. |
| 4:05 p.m. | Development of Ultrahigh-Strength Complex Phase Steels With Enhanced Ductility Huasai Liu, Feng Yang, Musheng Qiu, Huaxiang Teng, Yun Han , Research Institute of Technology of Shougang Group Co.,. and Beijing Key Laboratory of Green Recyclable Process for Iron & Steel Production Technology In recent years, ultrahigh-strength steels are used more and more in the automotive industry to reduce the weight of body-in-white, such as dual phase (DP), complex phase (CP) and dual phase with high ductility (DH) steels. In these kinds of steels, DP steel and DH steel have higher tensile strength and good formability in most cases. But for some components, bending and flanging are needed during the cold-forming process. However, DP and DH steels have a poor stretch flangeability which will not meet the requirements of the OEMs. For CP steel, due to its complex microstructure with bainite, martensite and ferrite, it has a higher stretch flangeability but poor formability compared with DP and DH steels. The newly developed ultrahigh-strength CP steel with retained austenite embedded in bainitic ferrite and martensite matrix has a higher elongation than traditional CP steel, which attracts OEMs’ attention. In this research, ultrahigh-strength complex steels with enhanced ductility with a minimum tensile strength of 980 MPa are studied. Different annealing parameters are adopted to adjust the content of the retained austenite and mechanical properties of the steels, and the hole expansion test is also conducted to evaluate the flangeabiliy of the annealed steels. After the lab simulation, the suitable annealing parameter is adopted for the industrial production of the ultrahigh-strength CP steel with enhanced ductility. |
| 4:25 p.m. | Effect of Batch Annealing Parameters on Mechanical Properties and Microstructure of a Cold-Rolled Dual-Phase Steel Zhen Li, Quanli Wang, Jian Gong, Beijing Shougang Co. Ltd.; Chunqian Xie, Libin Liu, Shougang Research Institute of Technology; Pengyu Wen, Hao Chen, Tsinghua University Fuel economy and, thereby, weight reduction are extremely important factors for the automotive industry. The development of lightweight vehicles with high safety has been accomplished through the use of high-strength steels, like multiphase steels. Because of the unique properties of low yield strength, high tensile strength, continuous yielding, and good uniform elongation, dual phase (DP) steels have become an excellent new class of high-strength low-alloy steels used for lightweight vehicles. These steels are usually produced by annealing low-carbon cold-rolled sheets in an intercritical temperature range to produce the ferrite-austenite mixture followed by rapid cooling to transform austenite into martensite. There is now a broad consensus that the excellent mechanical properties of low-alloy DP steels such as low elastic limit, continuous yielding and high strain hardening rate are developed as a consequence of austenite to martensite phase transformation, which involves volume expansion inducing plastic deformation into adjacent ferrite grains, and therefore creating a high density of unpinned geometrically necessary dislocations within ferrite causing a higher work hardening effect of ferrite. Several investigations have revealed induced geometrically necessary dislocations pile up at ferrite-martensite interfaces and so the special strain hardening behavior of DP steels is in part the result of this phenomenon. The effect of batch annealing parameters on the microstructure and properties of DP980 steel was studied by tensile testing, optical microscopy and transmission electron microscopy (TEM). With an increase in the batch temperature and time, the yield strength increases, and the hole expansion rate increases 100%. During the batch annealing process, the carbon atoms diffused into dislocations to form Cottrell atmosphere pinning dislocations, and excess carbon atoms formed carbon clusters or low-temperature carbide pinning dislocations. In addition, a lot of fine cementite formed in the ferrite base. It is well known that the large amount of small-size precipitates will produce strong strengthening to the ferrite and finally strengthen the steel. With the increase of tempering temperature, the boundary of the martensite lath bundle gradually disappeared and fine cementite gradually also formed in the martensite, resulting in yield strength and hole expansion rate increase. |
| 4:45 p.m. | Closing Remarks |
| 4:50 p.m. | Conference Adjourn |