Effect Of Controlled Rolling And Controlled Cooling On The Network Carbide Of The GCr15 Bearing Steel

Wire rod short flow production line in Northeast Special Steel Co., Ltd. Has multiple functions for steelmaking, refining, continuous casting and continuous rolling. The trial production started in September 2009. and the production officially began in April 1.2010. The main equipments of the rolling system include stepping beam type heating furnace (LOI Co., Ltd., Germany), continuous rolling mills (Danieli Co., Ltd., Italy), finishing mills and reducing sizing mills(Morgan Co., Ltd., USA). Since the production line was formally put into operation, the production of bearing steel has been unable to to meet the performance requirements of high-grade products due to the existence of unreasonable structure of the network carbide. Therefore, it has gradually become a technical problem for a long time.This paper investigated the effects of processing parameters of the key equipment on the morphology of carbide and properties of the bearing steel products. The beari ng steel mesh level was controlled by adjusting the slab reheating temperature, finish rolling temperature and spinning temperature in this study. The results are shown as f ollows:1 Heating temperature:the optimal heating temperature is 1180? for the 150 m 3 and 1200? for the 180 m3.After diffusion at high temperature, the reduction of ban ded segregation decreases the level of network, providing the basis for the following r olling and cooling.2 Final rolling temperature and spinning temperature:only lowering the finish roll ing temperature can decrease the level of network carbide, but cannot reach the standa rd requirements. The two aspects of controlled rolling and controlled cooling must be taken simultaneously to reduce the network carbide level. The optimal processing para meters are shown as follows:The temperature was760-830?at the beginning of the finishing rolling and red ucing and sizing rolling. The two cooling water should increase after rolling wire. The laying temperatureswere740?770? for the wires with the diameter of less than 10. 0mm and 750?790? for the wires with the diameter of more than 10.0mm. This p rocessing method inhibit the precipitation of carbide network and reduce the network c arbide level. The carbide network in productions produced by various specifications of the high line wire rod can reach less than 2.5 level requirements.The research suggests that, on the short process production line in the northeast special steel, optimizing the controlled rolling and controlled cooling process, the carbide network in bearing steel can reach 2.0 level. It is a good foundation for the future production of high speed wire rod with higher requirements of bearing steel.