Using dynamic induction heating to inhibit martensite structure formed in heat-affected zone of U71Mn steel rail aftersurface welding

A dynamic induction heating method was used to inhibit the formation of martensite in heat-affected zone(HAZ) of U71 Mn steel rail after surface welding. The inhibition of martensite structure was characterized by optical microstructure analysis and microhardness testing. The experimental results showed that when the U71 Mn steel rail was welded in cold welding condition, cracks would form directly in the heat-affected zone, and the microstructure was martensite. With the increase of preheating and post-heating temperature, the amount of martensite reduced significantly. When the preheating temperature was 320℃ and post-heating temperature was 550℃, the martensite structure could be inhibited completely, and the heat-affected zone consisted of sorbite structure whose size was smaller than pearlite structure in the base metal. The microhardness of the heat-affected zone also distributed uniformly.