Effect of preheating before welding on the microstructure and properties of 40Cr steel pulse cold welding joint
In order to realize the high-performance repair of traction tie rods,the effect of local low-temperature preheating method before welding on the microstructure and properties of 40Cr quenched and tempered steel pulse cold surfacing joints was studied.The microstructure and properties of the weld repair joints under the conditions of preheating and non-preheating were compared and analyzed,and the improvement mechanism of the microstructure and properties of the joints by the low-temperature preheating process before welding was studied through metallographic,microhardness,tensile and lateral flexure tests.The results show that the struc-ture of the surfacing joint is similar to that of the joint at room temperature under the preheating condition,and the main difference is the formation of bainite in the coarse grain area of complete quenching.Compared with room temperature:after preheating,the high point of hardness of the coarse grain zone is reduced by 62 HV,and the hardness of the tempering zone is reduced by about 30 HV;The tensile strength of the overlay and heat-affected zone has been reduced by about 2％.By taking 100 ℃ preheating before welding,the strength of the 40Cr pulse cold welding joint is not affected,and only slightly decreased,but the hardness of the repair welding layer is improved,and the highest point is reduced to meet the requirements of the ISO 15614,which can be used to repair the local defects in the inner hole of the traction tie rod.
pulse cold welding40Crtowing tie rodmicrostructureproperties
万方数据
