According to the complaint, filed 11 February, the Pittsburgh, Pa.-based producer threatened to discipline or fire workers if they called a strike or suggested that their working conditions would change for the worse if they did so. The complaint also accuses the company of casting aside tentative, local-level agreements that had been reached between the union and managers. 
 
The previous labor agreement between the two expired 30 June 2015. And in August, the company locked out the union after it let lapse a company-imposed deadline to accept what it called its last, best and final offer.
 
In a statement, the company denied the NLRB charges.
 
"ATI believes this is a legal work stoppage that resulted after a lack of progress in contract negotiations. We further believe that the allegations of the complaint are not supported by the facts or the law, and ATI will vigorously challenge the complaint through the appropriate legal process," the company said in a statement.
 
It added: "Since contract negotiations began, ATI and its employees and representatives have acted lawfully, reasonably and in good faith. We remain committed to successfully resolving the labor dispute and negotiating a fair and competitive labor agreement, which is critical to returning this business to sustainable profitability in the face of U.S. and global competition, and keeping great jobs at our plants today and into the future." 
 
The company has until 25 February to respond to the complaint. A hearing before an administrative law judge has been set for 23 May.
 
"The company has, since day one, engaged in a pattern of intimidation, manipulation and bad-faith bargaining in a blatant attempt to force hard-working people into accepting deep cuts in pay and benefits," USW International president Leo W. Gerard said in a statement.

"We are pleased to see that this complaint validates every significant charge the USW has made against ATI from the beginning," he said.