弹簧钢60Si2Mn轻压下工艺调试及质量改进

PROCESS ADJUSTMENT AND QUALITY IMPROVEMENT OF SOFT REDUCTION FOR 60Si2Mn SPRING STEEL

分析了弹簧钢60Si2Mn(/%:0.58~0.62 C,1.65~1.85 Si,0.80~0.90 Mn,≤0.020 P,≤0.015 S)的210 mm×210 mm连铸方坯中心区域碳偏析和残余缩孔的原因,认为高碳钢在凝固过程中选分结晶和两相区铸坯长度较长,钢水无法补缩导致。利用现有连铸机7组拉矫机的轻压下功能,在不改变连铸工艺参数,保证弹簧钢60Si2Mn铸坯表面质量的前提下,通过模拟计算对铸坯凝固终点进行了理论研究。在此基础上,对不同拉矫机及不同压下量方案进行了优化试验,并分析了连铸方坯的低倍质量,找出了最优的轻压下工艺方案。结果表明:现有工艺装备条件下,采用5#拉矫机3 mm压下量、6#拉矫机5 mm压下量和7#拉矫机2 mm压下量的压下工艺,铸坯内部没有压下裂纹,能够控制残余缩孔在0.5级以下,中心碳偏析指数在1.04~1.10之间的比例达95%左右,实现了改善铸坯残余缩孔和中心碳偏析的目的,同时弹簧钢60Si2Mn采用轻压下工艺时单组拉矫机压下量不超过6 mm。

The reasons for carbon segregation and residual shrinkage in the central area of 210 mm×210 mm continuous casting billets of spring steel 60Si2Mn(/%:0.58~0.62 C,1.65~1.85 Si,0.80~0.90 Mn,≤0.020 P,≤0.015 S)were analyzed.It is believed that high carbon steel has longer casting billet length in the crystallization and two-phase regions during solidification,which is caused by the inability of molten steel to compensate for shrinkage.By utilizing the soft reduction function of seven sets of straightening machines in existing continuous casting machines,theoretical research was conducted on the solidification endpoint of spring steel 60Si2Mn billets through simulation calculations without changing the continuous casting process parameters and ensuring the surface quality of the billets.Based on this,optimization experiments were conducted on different straightening machines and different reduction schemes,and the low fold mass of continuous casting billets was analyzed to find the optimal soft reduction process scheme.The results showed that under the existing process equipment conditions,using the soft reduction of 3 mm reduction on the 5#straightening machine,5 mm on the 6#straightening machine,and 2 mm on the 7#straightening machine,there were no pressing cracks inside the casting billet,and the residual shrinkage cavity could be controlled below level 0.5.The proportion of central carbon segregation index between 1.04~1.10 was about 95%,achieving the goal of improving the residual shrinkage cavity and central carbon segregation of the casting billet.At the same time,when the spring steel 60Si2Mn was lightly pressed,the reduction of a single set of straightening machines did not exceed 6 mm.