采用残余应力和力学性能测定、化学成分分析、断口扫描及金相检验等方法对铁路货车用L-B型组合式制动梁撑杆翼板产生裂纹的原因进行了分析。结果表明,由于焊前未预热且焊接工艺不规范,导致在焊缝处存在较大残余拉应力和不良显微组织;焊后又未采取必要措施消除上述缺陷;加上材质本身存在力学性能和化学成分不符合有关标准的要求,使该制动梁在运行中产生裂纹,最终导致失效。提出了改进措施。 The causes of cracks in the L-B composite brake beam spars were analyzed by residual stress and mechanical properties, chemical composition analysis, fracture scanning and metallographic examination. The results show that there is a large residual tensile stress and poor microstructure in the weld due to the non-preheating and the non-standard welding process. However, no necessary measures are taken to eliminate the above defects after welding. In addition, the mechanical properties And the chemical composition does not meet the requirements of the relevant standards, so that the brake beam cracks in the operation, and ultimately lead to failure. Put forward the improvement measures.