55SiCr盘条拉拔脆断分析

分析Φ6.5 mm 55SiCr盘条拉拔过程发生抽芯断裂的原因.采用热模拟试验测定断裂试样在不同冷却速度下的相变组织:当冷却速率不超过2℃/s时,其显微组织为索氏体、珠光体、少量铁素体；当冷却速率大于3C/s时,其显微组织为屈氏体、贝氏体、马氏体等异常组织.试验结果表明盘条的异常组织是产生拉拔脆断的主要原因.给出改进措...

Analysis of 55SiCr wire rod drawing brittle failure

To analyze the reason of loose core fracture of diameter 6.5 mm 55SiCr wire rod in the course of drawing. Adopting thermal modeling test to determine the phase transition microstructure of fracture samples at different cooling temperature： the microstructure is sorbite and pearlite and small ferrite as cooling speed is no more than 2 ℃/s; the microstructure is troostite, bainite and martensite abnormal structure as cooling speed is more than 3 ℃/s. Test results show that the abnormal structure is the cause for drawing brittle fracture. The improving measures are ： （ 1 ） to improve center segregation of cast billet by electromagnetic stirring for molten steel during solidification and by light pressing for sectional cast billet near last solidification region; （2） to optimize rolling control cooling program, after wire rod laying and air cooling then entering cosy, this time the temperature should be controlled at 650 -700 ℃. Adopting above two measures to produce diameter 6.5 mm wire rod, its microstructure is sorbite and pearlite and small discontinuous net ferrit, no fracture appear in the course of use of users, it can satisfy drawing requirements of consumers.