Underground cable and an analysis of rail rapid copper heat welding method to explore

( Industry news] Underground cables and the rail rapid copper heat welding method to analyze chenyl P in recent years, urban rail transit development blustery, drama stage, the current domestic more than 40 more than millions of people in megacities, already has more than 30 cities in the construction of the urban rapid rail or construction prophase work, report about 14 cities in urban rail transportation network planning scheme, is proposed to 55 route planning construction, about 1500 kilometers long. Data show that during the 'tenth five-year plan, China's subway construction investment is expected to 200 billion yuan. During the period of '11th five-year plan' in rail transit construction is expected to cities will also invest more than 2000 one hundred million yuan. The rapid development of rail transit, bring a rare opportunities for wire and cable industry, cable is studied and discussed with the rail welding, it is necessary. In the subway system, rail should not only bear the load of the vehicle directly, but also as backflow rail traction power supply system, is also a carrier of the resonant track circuit signal system. At present, Beijing, Shanghai, guangzhou, tianjin and wuhan subway power supply rail connection backflow line cable and signal cable connected to the rail mainly adopts copper heat welding method to fast, and abroad have been gradually with bolted method. Rapid copper heat welding method is one of the types of aluminium heat welding, the reflection mechanism for CuO + Al = Cu + AlO. Welder with cable sleeve, igniter, mold ( And clamp one) And flux. With rapid copper heat welding method and selects the country A and B domestic two welding flux welding and A cable with rail ( UMn kg/m) Joint of country B heat flux regulation before welding of rail to ℃, with insulation cover heat preservation after welding. On the welding joint microstructure observation, the microhardness and the analysis of fatigue test. Were selected by country A and country B welding flux of each A welded joint, the joint area along the middle transverse incision. Observation of incision, that cut copper parts delay fusion line appear more pores, accompanied by fusion flaw. This is due to the coefficient of thermal conductivity of copper and its alloy, linear expansion coefficient and the shrinkage rate is large, fast cooling after welding and make it easy to appear porosity and incomplete fusion flaw. According to railway rail welding repair experience, Suggestions for the length of the rail must be preheated before welding to ℃ above, heat preservation after welding; Also suggested that the subway track should choose construction when the environment temperature ℃ or so, in case the temperature difference and so on reasons, lead to the generation of stress in the rail. Rapid copper heat welding method in cables and the rail welding, for technology reason, on the rail lateral heat affected zone in high hardness martensite structure, lead to local regional rail embrittlement, prone to rail in the operation of the subway damage. The process, the complexity of the improved method takes the manpower and material resources. Nowadays, the railway qing-shen passenger bolted method is used to connect cables and rail. At present, the study is being conducted by the approach of the Beijing subway. Bolted method is the future development direction of underground cable connected to the rail.