Effect And Mechanism Research Of High Temperature Welding On Residual Stress Of 12Cr2Mo1R Steel Welding

Due to uneven heating and cooling,the weld joint and its near areas of welding base metal inevitably produce uneven plastic deformation resulting in the stress is remaining in welding base metal after the weldment cooling.The stress is called welding residual stress.The effect of welding residual stress on fatigue life,structure property and corrosion resistance of weldment is adverse.Due to welding seam uneven heating and cooling and the welding residual stress,fatigue life and stress corrosion resistance,and the organizational properties of metal is lower than the base metal,but more than the base metal welding residual stress,therefore the weldment fracture often occur in the weld seam.The new welding technology in this project experiments can effectively reduce the residual stress after welding,which has great economic and social benefits to prevention of accidents.The purpose of this project is to prove whether the new welding technology can effectively reduce the residual stress after welding in high temperature condition.This technology is the welding preheating to very high temperatures before welding,make uniform heat welding base metal,and then in preheating temperature to weld,after welding make the weldment at room temperature natural cooling.The theory of this welding technology is to reduce the temperature difference of the welding joint temperature field and the welding residual stress by high temperature preheating and high temperature welding.In this experiment two pieces of 12Cr2Mo1R steel plates were preheated and high temperature welding at800 ? and 900 ?respectively.The residual stress value of the specimen was measured by the small diameter blind hole method,and was compared with the value at normal temperature.And then a series of test have been researched:corrosion test,metallographic test,fatigue test and so on.The changing situation of welding residual stress,corrosion rate,metallographic structure and fatigue life have been analyzed comparatively between high temperature welding and room temperature welding.