The Process And Quality Of 60N U76CrRE Steel Rail On Gas Pressure Welding

The 60N U76CrRE heat treated rare earth rail independently developed by Baotou Iron and Steel Group has higher strength(1280MPa level),which can better meet the needs of wear-resistant rail for heavy haul railway and mixed passenger and freight transportation lines,and has become a new kind of rail for railway lines in China.However,due to the improvement of strength level,whether the welding quality can meet the standard requirement becomes a bottleneck problem whether it can be applied to the transmission line.It is of great significance and engineering value to carry out research on air pressure welding parameters of 60N U76CrRE heat treatment rare earth steel rail to meet the requirements of TB/T1632"rail welding".In this paper,the"GPW-1200"gas pressure welding machine was used to carry out the60N U76CrRE heat treatment rail gas pressure welding process test.Through setting up multiple groups of welding processes,the performance of joints under different processes was tested and analyzed,and the optimized welding process parameters were obtained.The60N U76CrRE heat-treated rail joint welded by the optimized welding process has stable drop weight performance up to the standard,and the drop weight fracture meets the standard requirements without obvious defects;The average hardness of the joint is 348HB(H_J/H_P=0.91),the average hardness of the soft spot is 310HB(H_J1/H_P=0.81),the impact energy of the joint is 10.3J,the tensile strength is 1023MPa,and the elongation of the section is 10.5%;The microstructure of the joint is pearlite and a small amount of ferrite,and there is no other harmful structure.The grain size grade is above grade 7,which meets the requirements of TB/T1632"rail welding".In view of the obvious weakening phenomenon of softening zone in 60N U76CrRE heat-treated rail,this paper proposes a hardness measurement method using Leeb hardness tester and"refining measuring point spacing",and obtains the law of hardness and width of softening zone under different welding processes:increasing welding heating time will significantly increase the width of softening zone(77%?156%);Normalizing heat treatment can increase the hardness of softening zone(9%);The width of softening zone(24%?42%)can be effectively reduced by reducing the swing of air cooling and increasing the air pressure,but the hardness of softening zone is not significantly improved.