正火热处理对钢轨焊接接头表面硬度的影响

Effect of Heat Treatment on Rail Surface Hardness of Welded Joints

钢轨焊接接头由于内部组织与母材不同,上道服役后会产生马鞍形磨耗,导致线路不平顺。我国铁路行业标准规定:接头焊后都必须采用正火热处理,达到提高接头组织强韧性,保证平顺性的目的。本文采用火焰正火方法,研究了现场闪光焊和气压焊焊接接头的表面硬度。结果表明:气压焊U75VG钢轨正火喷风冷却比焊态自然冷却接头硬度高,为308 HBW,硬度值波动范围也增大到4.4%,软化区宽度平均值减小到5.69 mm;气压焊U71MnG钢轨正火喷风冷却性能最好,接头硬度值为306 HBW,软化区宽度最窄,均值为1.55 mm,硬度波动范围为6.7%;闪光焊U75VG正火喷风冷却较焊态自然冷却接头硬度高,为320 HBW,硬度值波动范围提高到2.6%,软化区宽度平均值减小到3.89mm,焊缝处由于碳烧损,存在硬度值的下降。

Due to different internal microstructure and base material of rail welded joints, saddle-shaped abrasion produces on road after service, resulting in line irregularity. China＇s railway industry standards： the welding joints must adopt normalizing heat treatment, in order to improve the strength and toughness of the welded joint mierostructure to ensure smooth purpose. Using flame normalizing method, the surface hardness of pressure welding and flash welding was studied. The results show that： the hardness of U75VG pressure welding normalizing spray-cooled is higher than that of welded natural cooling, increased by 308 HBW, but the fluctuation range of hardness increases to 4.4%, the average width of the softening zone reduces to 5.69 ram. U71MnG pressure welding normalizing spray rail has the best air cooling performance, the welded joints have the highest hardness of 306HBW, the width of soften zone is the narrowest, mean of 1.55mm, and the hardness fluctuation range is 6.7%. The hardness of U75VG flash welding normalizing spray-cooled is higher than that of welded natural cooling, increased by 320HBW, the fluctuation range of hardness increases to 2.6% and the average width of softening reduces to 3.89 ram. the hardness of the welded joints decreases significantly due to the presence of carbon burning.