42CrMo钢表面单道激光宽带处理后熔凝层的残余应力

Residual Stress Analysis of the Remelting Zone on 42CrMo Steel Plate in Single-Pass Laser Wide-Band Treatment

基于有限元软件SYSWELD平台，建立激光熔凝三维有限元模型，编制宽带热源的FORTRAN子程序，采用不同的工艺参数对42CrMo钢表面的单道激光宽带熔凝区的组织和残余应力进行数值计算与分析。测定了激光熔凝表层的热循环曲线，利用扫描电镜（SEM）观察熔凝区相变。结果表明，工艺参数对熔凝区残余应力分布状态影响较大，激光线能量密度（PE）过高或过低，均影响熔凝层的表面成型质量；当激光束输出功率为3500W，扫描速率在600～1000mm／min时（即ρE=20．9～35．0J／mm^2），熔凝区可获得有利的残余压应力分布。42CrMo钢母材组织为铁素体＋珠光体，经激光处理后，熔凝区组织转变生成的马氏体相比例高达95％以上。

Based on SYSWELD finite element code, a three-dimensional finite element model for laser remelting process was created, the wide-band hear＇source model implemented by a FORTRAN subroutine was developed to simulate the single-pass laser wide band remelting process on 42CrMo steel, and predict residual stresses of the remelting zones with different technological parameters were estimated and analyzed. The thermal cycle was measured by temperature measuring equipment and phase transformation was observed by scanning electron microscopy （SEM）. The results showed that technological parameters has a great influence on the residual stress distribution of the remelting zone, the superficial processability of the laser remelting zone is bad whether the laser energy input density is too high or too low. The favorable residual compressive stress in the remelting zone can be achieved when the laser output power is 3500 W, the scanning rate is ranged from 600 mm/min to 1000 mm/min, that is, the energy input density is within 20.9 - 35.0 J/mm^2. After the processing, the initial ferrite-pearlite microstructure of the matrix is transformed to martensite phase with the proportion higher than 95 %.