车用高碳钢冷拔形变中的力学性能和组织演变分析

Analysis on mechanical properties and microstructure evolution for automotive high carbon steel in cold drawing

为提高汽车轮胎上冷拔高碳钢的力学强度与高韧性,通过拉伸力学、SEM、TEM和DSC等测试手段分析了不同应变与回火条件下得到的冷拔高碳钢组织结构与力学特性的改变规律,并表征了不同工艺条件下对应的组织结构与性能。研究结果表明:随着应变的增加,回火处理能达到的高碳钢拉伸强度提高比例逐渐减小;回火处理可以提高冷拔高碳钢强度,但会引起塑性的略微降低;经过175℃回火处理后,片状珠光体还是与拉拔方向持平行状态,渗碳体片层内生成了许多纳米级渗碳体颗粒;在150℃回火后,原位再结晶形成纳米颗粒与偏析C可以对位错产生较强的钉扎作用,显著提高高碳钢的变形抗力。应变为3.0时,高碳钢只形成了2个放热峰;应变为5.0时形成了3个放热峰。

In order to improve the mechanical strength and toughness of cold drawing high carbon steel on automobile tires, the changes of microstructure and mechanical properties of cold drawing high carbon steel obtained under different strain and tempering conditions were analyzed by tensile mechanics, SEM, TEM and DSC, and the corresponding microstructure and properties under different process conditions were characterized. The results show that with the increasing of strain, the proportion of tensile strength for high carbon steel increased by tempering is smaller, and the tempering treatment improves the strength of cold drawing high carbon steel to cause a slight reduction in plasticity. After tempering at 175 ℃, the lamellar pearlite is still in parallel with the drawing direction, and many nanoscale cementite particles are formed in the lamellar cementite. However, after tempering at 150 ℃, nanoparticles and segregation C formed by in-situ recrystallization can produce strong pinning effect on dislocations, and significantly improve the deformation resistance of high carbon steel. Thus, when the strain is 3.0, only two exothermic peaks are formed in high carbon steel, and when the strain is 5.0, three exothermic peaks are formed.