Abstract: The production flowsheet of Φ35 mm bar of non-quenching-tempering steel C70S6 (/% ： 0.72C, 0.20Si, 0.58Mn, 0.015P，0.065S，0.12Cr，0.05Ni， 0.035V， 0.008Al) is 60 t UHP EAF-LF-VD-240 mm x240 mm bloom casting-rolling process. The analysis on structure, fracture and shearing technology of cracking bar during shearing process is carried out. It is obtained that the structure and hardness of cracking bar are no-obvious different to the non-cracking bar during shearing, and during shearing process by shearing stress action the shift of bar along horizontal plane occurs led to increasing the interval between flat cutter and round cutter, the deformation of bar shearing plane curving and deforming, finally causing crack at end of bar. With the measures including decreasing the interval between cutters from 0.5 mm to 0.3 mm, increasing clamping force from 3 t to 3.5 t and carried out spraying water on steel bar to enlarge coefficient of wear as installing cutters, the results of cutting 30 t steel C70S6 Φ35 mm bar products show that the rate of cutting cracking decreases to 0 from original 10% .

Key words: High Carbon Steel C70S6, Fracture Splitting Connecting Rod, Cutting Cracking, Structure, Improved Measure

摘要： Φ35mm C70S6非调质钢(/%:0.72C,0.20Si,0.58Mn,0.015P,0.065S,0.12Cr,0.05Ni,0.035V,0.008Al)生产流程为60 t UHP EAF-LF-VD-240 mm×240 mm方坯连铸-轧制。通过对剪切下料时开裂钢棒的组织、断口和剪切工艺进行分析,得出剪切过程开裂钢棒和未开裂钢棒组织、硬度无明显差别,因棒材在剪切过程受剪切力作用,出现水平方向移动,造成平刀和圆刀之间的间隙增大,使棒材剪切面弯曲变形,造成端部开裂。通过安装时将间隙由0.5 mm减少至0.3 mm,棒材夹持力由3 t增至3.5 t,对钢材进行淋水锈蚀处理以增大摩擦力等措施,剪切30 t Φ35mm C70S6钢材结果表明,剪切开裂率由原10%降为0。

关键词: C70S6高碳钢, 胀断连杆, 剪切开裂, 组织, 改进措施