The Research On The Welding Process Of Ultra-narrow Gap Of Dissimilar Steel Rail

With the development of seamless track,the favorable mechanical properties of the welding joint is a key factor for the rail quality.The running rail and guardrail are two kinds of common rails,and the materials mainly used are U71 Mn,NM400,et al.In order to meet the requirement of different applications in rails,resource saving and reducing production cost,many practical questions are emerged for the butt joint of dissimilar metal welding.The common joining method for rails are exothermic welding,arc welding,gas pressure welding,flash butt welding and et al.The main disadvantage of the above welding method,however,is relatively wide heat affected zone and large amount of melting of base metal,and thus most of these methods are not suitable for the welding of dissimilar steel rails.The ultra-narrow gap welding coupling with constricting arc with flux strips is a potential welding method for the joining of dissimilar steel rails due to low heat input,depressed melting quantity of base metal and narrow heat affected zone,et al.In this study,the welding of NM400 and Q235 steel using ultra-narrow gap welding coupling with constricting arc with flux strips were conducted to investigate the mechanical properties of welding joint.And a series of welding gun and auxiliary equipment of OTC robot platform suitable for rail welding are developed.The results of welding test show that the appearance of welding joint are favorable using developed equipment.Applicable former groove reserved size of ultra-narrow gap welding was acquired by the analysis of ultra-narrow-gap welding,and then obtaining the optimal welding procedure for the rail welding.The results are as follows:(1)The ultra-narrow gap welding equipment was developed for the butt joining of Different shape cross section.The equipment was mainly composed of enclosed block assisting weld forming,ultra-narrow gap welding gun,foundations controlling deformation and flux belt placement tool.(2)The weldability test of dissimilar steel by ultra-narrow gap welding which using aforementioned equipment are conducted.The optimal welding parameters and the variation laws of deformation are obtained.(3)The microstructure was analyzed and hardness test was applied for the welding joint microstructure of dissimilar steel rails.The results show that the welding zone are consist of ferrite and pearlite,and hardness of the welding joint was not lower than base metal.The heat affected zone are composed of tiny pearlite,and the hardness was higher than base metal.