Research on Rolling Wear and Damage Properties of Gas Pressure Welding Joint of U71Mn rail

The structure and properties of the Gas Pressure welding joint of U71Mn rail were studied. The MMS-2A wheel-rail rolling wear and contact fatigue testing machine was used to test the joint material and the parent material. The wear and damage characteristics of the joint and the parent material were studied. The results showed that the microstructure of the joint was pearlite, but the size of grain and the shape and size of cementite were different. The pearlite grain of the weld bead was smaller than that of the parent metal, and the shape of cementite was fine lamellar and fine granular, so the hardness and the plastic deformation ability were higher. At 1×10⁵ and 2×10⁵, the wear resistance was better than that of the parent material; at 3×10⁵, the wear loss of the weld bead was larger than that of the parent material, and the surface damage was more serious. On both sides of the weld, there were two areas (softened zones) which were composed of granular cementite and a small amount of lamellar cementite. The grain size and the thickness of the lamellar of cementite were not uniform, so the hardness was the lowest. Moreover, the wear, cracks and plastic deformation were aggravated.