Recently, Xingtai steel successfully developed and produced cold heading steel containing Nb for high end for the first time. The successful production of this steel fills the blank of cold heading steel containing Nb and diversifies the structure of high-end cold heading steel in Xingtai Steel.

　　36MnB4 is a trademark of European standard. It belongs to typical middle carbon cold heading steel containing boron, which is mainly used to produce the rivets for new-energy vehicles. 36MnB4 also can replace the imported materials.This rivet not only requires high tensile strength, but also good toughness and formability after heat treatment. The toughness can be improved by adding Nb-base alloy refined grain to rivets. However, it is difficult to produce Nb containing steel slab which has strong crack sensitivity because it’s easy to occur cross cracks in its corner. The Technician of our company optimized the design of Nb content, selected ferroniobium, controlled nitrogen in LF refining, optimized second cooling technology and whole-course protected casting so that chemical component and surface quality of slab could meet customers’ requirements, which marks cold heading steel containing Nb for high end 36MnB4 was developed successfully at once.