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Sumitomo Metals Develops new High Strength, Highly Corrosion-Resistant Alloy
12/12/2011 - Sumitomo Metal Industries, Ltd. has developed new martensitic stainless steel OCTG, SM17CRS-125 (referred to as Super 17Cr), which the company claims has best-in-class corrosion resistance and strength to meet increasing demand in ultra-deep well developments.
Sumitomo Metal Industries, Ltd. has developed new martensitic stainless steel oil country tubular goods (OCTG), SM17CRS-125 (referred to as Super 17Cr), which the company claims has best-in-class corrosion resistance and strength. This product will be used to meet increasing demand in ultra-deep well developments.
In recent years, development of wells that are more than 6000 meters deep has been increasing and the strength to withstand formation pressure and string weight as well as corrosion resistance are required for OCTG. In such an environment, 13Cr OCTG cannot be used because of stress corrosion cracking, Sumitomo Metals explained. Therefore, higher-grade duplex stainless steel OCTG has been used. But, it contains a large amount of expensive alloy elements such as nickel and molybdenum, and cold working is required to obtain the strength.
According to Sumitomo Metals, Super 17Cr steel has better corrosion resistance than 13Cr with leaner alloy content than duplex stainless steels without cold working. Sumitomo Metals has found that 17% chromium is optimal to ensure corrosion resistance required for ultra-deep CO2 containing wells.
With 17% chromium, the material structure cannot be single phase of hard martensite, but dual phase containing some soft ferrite. However, by optimizing other alloying elements, Sumitomo Metals achieved 125 ksi (861 MPa) grade, exceeding the general yield strength level of 13Cr, which is 80 to 110 ksi (551 to 758 MPa) grade without cold working process.
Super 17Cr steel was released at the ISO Committee concerning corrosion-resistant materials for OCTG and SPE workshop this September. Sumitomo Metals has started providing samples for customer qualification.
