| It can greatly reduce the production costs by using stainless steel and weather-resistant steel as the substrate of flat roof and roof side in a low-floor rail vehicle.And the heat input of arc brazing is small,it can strictly control the welding distortion,and the property of the base material after welding doesn’t basically change.It’s energy-efficient and high-efficiency to weld the seam between flat roof and roof side by arc brazing.The research on arc brazing of butt joint between SUS304 stainless steel sheet and Q355 GNHD weathering steel sheet was carried out in this paper.Focus on the butt joint of SUS304 stainless steel sheet and Q355 GNHD weathering steel sheet,the technology comparison process of manual MIG arc brazing was carried out.To select the good solid wire from CuAl8、CuAl8Ni2、CuSi3 and CuSn6.The results show that CuAl8 have good wettability and the tensile strength of joints are high when the welding process of them are sable,and the cost of filler metal made with CuAl8 is low.Then CuAl8 is selected as the final filler metals which use for manual MIG arc brazing of joint between stainless steel and weathering steel.MIG arc brazing of the stainless steel and weather-resistant steel using CuAl8 is carried out and the influence of welding current,gap value,misalignment amount and pre-welding cleaning condition on the joint properties and appearance of weld was studied.The results show that butt joint of SUS304 stainless steel sheet and Q355 GNHD weathering steel sheet is successfully received by manual MIG arc brazing.The tensile strength of joint can reach 339.58 MPa,strength coefficient of joint is 83.66%.The reasonable range of welding parameters are obtained: welding current is 60~70A,the range of gap is 0~0.5mm,the range of misalignment amount is 0~0.5mm,and the surface of base metal should be polished and cleaned by acetone before welding.To observe the microstructure of brazed joint and adopt methods of SEM and EDS to analyze the diffusion behavior of alloying elements in interface of brazed joint.The results show that small part of stainless steel and weathering steel is melted.As a result of element diffusion,the interface structure with a certain thickness is formed by unmelted base material and brazing metal.The interface structure which is made up by Fe based solid solution is formed by melted base material and brazing metal.The penetration crack which is found in the interface structure of SUS304 stainless steel and brazing metal extends along the austenite grain boundary,and the crack is caused by the penetration of Cu atom.The MIG arc brazing and MIG welding process were compared,the results show that both of seams welded by the methods of MIG arc brazing and MIG have good forming qualities.When compared with MIG arc brazing,the tensile strength of the joint welded by MIG improved 34.05%.The flexibility and fatigue performance of joint welded by MIG are better.And the deformation is smaller when welded by MIG arc brazing. |
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