Effect Of Cold Metal Transfer,Laser Cladding And Plasma Transferred Arc Welding On The Residual Stress Of Q235 Steel

The Q235 steel is the most widely used low carbon structural steel.It has many advantages,such as good plasticity and toughness,good weldability and cheap price.It is widely used in boilers,pressure vessels and mould manufacturing and other aspects.However,under high temperature conditions,the wear resistance and hardness of Q235 steel are insufficient.Therefore,it is very important to perform surface cladding on Q235 steel to improve its surface properties.However,due to non-uniform heat input during the cladding process,the weldment will generate a certain amount of residual stress.The residual stress will not only affect the strength,machining accuracy and service life of the weldments,but also produce cold cracks,resulting in quality accidents.Therefore,it is necessary to analyze and master the distribution of residual stress on the Q235 steel after cladding to improve the surface cladding technology and to ensure the safety of the welding parts.The heat treatment has an irreplaceable role in reducing or eliminating residual stress,and is one of the effective methods to prevent the excessive corrosion cracking of the welded parts.Therefore,it is of great engineering significance to formulate a suitable post-weld heat treatment scheme to provide reference for the elimination of the residual stress of Q235 steel with surface cladding of 316 L stainless steel.In this paper,the surface of Q235 steel was coated with 316 L stainless steel by cold metal transfer,laser cladding and plasma cladding.The residual stress of Q235 carbon steel welding specimens prepared by the three cladding methods was measured by blind-hole method.The distribution of welding residual stress and its characteristics were analyzed;and the influence of different post-weld heat treatment temperature on welding residual stress was also discussed.Research indicates:(1)The residual stresses of the Q235 steel after cold metal transfer,laser cladding and plasma transferred arc welding are all residual tensile stress in the heat affected zone.while the heat affected zone of the laser cladding specimen is less than cold metal transfer and plasma transferred arc welding;the laser cladding sample has the highest residual stress in the heat affected zone,followed by the cold metal transfer welding sample,and the smallest is the plasma transferred arc welding sample.(2)Cold metal transfer or laser cladding or plasma surfacing for Q235 carbon steel matrix has little effect on the final residual stress in the heat affected zone after welding.(3)Comparing the samples without post-weld heat treatment and post-weld heat treatment at 400°C×1h and 600°C×1h,it was found that the longitudinal residual stress and the transverse residual stress decreased significantly after post-weld heat treatment.And after the 600°C post-weld heat treatment,the decrease of residual stress of Q235 welding is even greater.