Microstructure And Mechanical Properties Of CMT + P Welding Process On New Martensitic Heat Resistant Steel G115

In this paper,the CMT+P welding process,microstructure and properties of G115steel were studied.Based on the process test and mechanical analysis,the CMT+P welding process of G115 steel was developed to solve the welding problem of G115steel.The main conclusions are drawn as follows.The influence of wire feeding speed,welding speed,shielding gas,CMT/P ratio,and welding torch swing on the weld formation of G115 steel plate surfacing was analyzed.In addition,the effect of groove gap,welding torch inclination,and welding torch swing on the weld formation of G115 steel thick plate was discussed.Eventually,the optimized welding process of G115 steel sheet was obtained,and the detailed welding parameters were shown:i)the Ar+2.5%CO₂ shielding gas,ii)the1:10/1:15/1:20 duty ratio in CMT/P method,iii)the 4.5～6 m/min wire feeding speed,iv)the 4.5～5.5 mm/s welding speed,v)the 1 mm swing amplitude of the welding torch,and vi)the 0.2 s left-to-right residence time of the welding torch,respectively.The optimized thick plate welding processes were shown:i)the 1.5 mm groove gap at the arc initiation,ii)the 5 degree to 15 degree welding torch angle,and iii)the swing bottom welding with swing parameter 1.2.By analyzing the effects of two kinds of welding materials（GER95 welding material and BYH15 welding material）on the microstructure and properties of G115steel welded joints,it can be found that the microstructure of the weld metal was two morphologies of equiaxed crystal and columnar crystal,and the precipitates in the joint was M₂₃C₆ in all cases.The number of precipitates in GER95 weld metal is four times that in BYH15 weld metal.The tensile strength of GER95 welded joint at room temperature and high temperature was similar to that of BYH15 welded joint.The impact energy of weld and HAZ in the BYH15 welded joint was better than that in the GER95 welded joint.The hardness of GER95 weld metal was higher than that of BYH15 weld metal.Conclusively,BYH15 welding material is superior to GER95welding material.By analyzing the effects of three welding heat inputs（5.1,7.1,8.9 k J/cm）on the microstructure and properties of G115 steel welded joints,it is found that the content of precipitates increases with the increase of welding heat input.With the increase of welding heat input,the room temperature tensile strength of the welded joint increases by 10%,and the high temperature tensile strength increases by 18%.But the impact energy of weld metal and HAZ increased first and then decreased sharply.The hardness of weld metal of welded joint gradually increases.