Laser-MIG hybrid welding to aluminium alloy carbody shell for railway vehicles

摘要

Safety and reliability are absolute requirements fornrailcars, which are used by the public and carry a largennumber of people, and this necessitates that the chassis isnstrong, the measurements are precise, quality is consistentnand appearance is good. The material principally used forncarriages is metal, since it has the required strength andndurability for long-distance travel, is safe in the eventnof fire or impact and can be recycled, and welding isnone of the key production technologies. Conventionalnsteel has long been used, but increased requirementsnfor reductions in weight and for corrosion resistancenhas led to increasing use of aluminium alloys andnstainless steel and this has led in turn to the structuresnand production methods that make the best use of theirnproperties. Welding methods can be classified into a widenrange of techniques but the principal ones in use are arcnwelding and resistance spot welding, as appropriate fornthe materials and structures. Efforts are being made tonimprove the quality and productivity of these weldingnmethods and for the welding of aluminium alloy, anmaterial which has high rates of heat conductance andnthermal expansion, it is desirable to take the heat effectsnand thermal deformation of the base metal into account,nand to choose a welding method in which heat input isnconcentrated on the weldment and welding is completednquickly with a small heat input.nMethods that meet these requirements include lasernwelding and laser-MIG hybrid welding but the limitednoutput of lasers means that the field of application isnlimited to thin plates and small structures. With the recentndevelopment of high quality and high output lasers, thenfield has widened, and continues to widen, and successnin test applications has led to its current use for cars andnaeroplanes. Hybrid welding, another technique whichnmeets the requirement for low heat input and rapidity,nis used for aluminium alloy railcars.