Research On Field Welding Quality Of Rail In Cold Area

In the orbital field,one of the most representative achievements is seamless lines at the twentieth century,which can significantly improve the comfort and safety of the train.Most areas of China has long and cold winter,low temperature welding or temporary repair is inevitable.As the rail welded joint has undergone a special heat-machine process,different metallurgical changes with the mother is inevitably,so the joints are often the weak links,especially in cold areas,At low temperature environmental conditions usually use the traditional aluminum thermal welding joints.The impact of large heat dissipated will cause hardened martensite,heavy injury rate is high,a broken safety risk;the softening area of aluminum thermal welding joints is wide,easy to wear in the wheel under the action of the saddle-shaped wear disease,affecting the line ride comfort.It is very important to study the construction technology of high quality welding rail in cold area and maximize the strength and the long life of the welded joint at low temperature,which is of great significance to ensure the safety of the line and reduce the maintenance amount.The new YHGQ-1200 gas pressure welding car has a high degree of automation,welding and normalizing integration of the operation function,under low temperature welding and post-weld heat treatment,can improve the joint organization,grain refinement,improve joint toughness and wear.Now there is no scientific data to ensure that the technical life of the long-term safe service of the welding head.In this paper,orthogonal test method and physical metallurgical analysis method were used to test the welding rail at the low temperature of-10 ??10 ?,and the effects of different normalizing air cooling conditions and hardness of rail joints were studied.Microstructure change law,obtained a set of joint strength and toughness of the quality of low-temperature welding process.The results show that:(1)The operation parameters of YHGQ-1200 gas welding rail are used.The normalizing process parameters are:oxygen flow rate is 68.4 SLM,acetylene flow rate is 74.5SLM,heating time is 200s,air blows to low rail surface temperature At 500 ?,the blowing pressure of the normalizing process is 0.30MPa<P<0.50MPa,the cooling rate(T8/5)is 2 ?/s?4 ?/s,the resulting structure is fine pearlite,the organization performance is good,The joint effect of the best toughness.(2)The application of the process to the Qinghai-Tibet Plateau Railway,Harbin,Shenyang Railway and other cold areas,not only to meet the TB/T1632 "rail welding" standard requirements,and welding joint hardness and base metal,softened area is very narrow,Fine grain.The set of technology for the cold area of the seamless line from the source control broken rail,to reduce the saddle-shaped wear disease provides technical support,has a good application value.