中碳钢丝形变组织演变及其形成机制

Microstructure evolution and formation mechanism of medium carbon steel wire

为研究高强度中碳钢丝的生产工艺并探讨变形组织演变及其形成机制,以45钢直径6.5 mm盘条为原料,计算经不同道次拉拔钢丝的真应变,采用扫描电镜进行金相组织分析及背散射电子衍射(EBSD)取向分析,用定量金相法计算铁素体、珠光体体积分数及其真应变。结果表明,中碳钢丝拉拔过程中,随应变的不断增大,铁素体、珠光体并不是同步变形,先共析铁素体变形大于珠光体,横截面上先共析铁素体所占的比例在不断减小,导致应变不均匀,从而形成拉拔的微缺陷。通过伪共析处理工艺抑制先共析铁素体的析出,可提高中碳钢丝拉拔的强度极限,获得抗拉强度大于2 400 MPa的中碳钢制绳钢丝。

In order to research production technology of high strength medium carbon steel wire and probe the deformation microstructure evolution and its formation mechanism,taking 45 steel wire rod with diameter 6.5mm as material,the true strains of steel wire undergoing different pass drawn are calculated,adopting SEM to analyze microstructure and adopting EBSD to analyze grain orientation,using quantitative metallography to calculate volume fraction of ferrite and pearlite and their true strain,the results show that the ferrite and pearlite are not synchronization deformation as strain increase gradually during medium carbon steel wire drawing,the deformation of pre-eutectoid ferrite is more than that of pearlite,the proportion of pre-eutectoid ferrite decreases continuously in cross-section as the strain increasing,which causes inhomogeneous deformation and leads to microstructure defect.Adopting pseudo-eutectoid process to inhibit precipitation of pre-eutectoid ferrite can improve drawing strength limit of medium carbon steel,and the medium carbon steel wires for rope with more than 2400MPa tensile strength are produced.