4Cr9Si2马氏体钢气门楔横轧工艺研究

摘要

The constitutive relationship of 4Cr9Si2 martensite refractory steel was obtained by isothermal compression,and the forming process of 4Cr9Si2 martensite refractory steel by cross-wedge rolling was simulated by means of DEFORM-3D software.The influence regularities of necking and internal defeats of process parameter were obtained.Rolling experiments were carried out to verify the correctness of the FEM simulation,and metallographic microstructure of rolled alloy was analyzed.The results show that with the increase of forming angel,decreasing transverse maximum stress and its duration time is accompanied by axial metal flow with a greater value than that of transverse metal flow and consequently lower the possibility of internal defects.Also,the value and duration time of transverse stress can be reduced by increasing stretching angle and thus lead to the lower possibility of internal defects.Besides,the decreasing forming angel and increasing stretching angel are associated with the reduced axis force Fz and as a result the probability of phenomenon about necking can be improved.The size of original austenitic grain is 11 μm in the central part of cross-section and the microstructure of valve is improved.%通过热模拟等温压缩实验,获得4Cr9Si2马氏体耐热钢的本构关系.借助DEFORM-3D有限元软件针对4Cr9Si2马氏体耐热钢楔横轧成形过程进行数值模拟,得到工艺参数对轧件缩颈和心部疏松的影响规律.通过轧制实验验证有限元模拟的正确性,对轧制后的轧件进行金相组织分析.研究结果表明:随着成形角增大,楔入段轴向金属流动速度大于横向金属流动速度,减小横向应力最大值和横向应力持续时间,使轧件心部缺陷产生可能性减小；随着展宽角增大,同样可以减小横向应力数值和横向应力持续时间,使轧件心部缺陷产生可能性减小；随着成形角减小和展宽角增大,减小轴向力F2,改善缩颈现象；其横截面中心原奥氏体晶粒尺寸为11μm,气门杆部微观组织得到改善.