Study On Solidification Cracking Susceptibility Of Stainless Steel Based On New Evaluation Theory During Welding

Solidification cracking is a common weld defect.It is still a major issue in stainless steel welding,which has not been well solved so far.The evaluation of solidification cracking susceptibility requires the specialized test methods.In this thesis,to study effect of different welding process parameters on solidification cracking susceptibility of stainless steel,and to evaluate solidification cracking susceptibility of different types of stainless steel,the transverse motion weldability test platform newly built was used.At the same time,to study effect of changes in alloy elements on solidification cracking susceptibility of stainless steel,and establish the relationship between alloy elements and solidification cracking susceptibility,the method of calculating solidification cracking susceptibility index was used.Effect of different welding process parameters on solidification cracking susceptibility of 304 stainless steel has been studied by changing welding speed and welding current.The test results indicated that under certain conditions,the higher welding speed,the lower the susceptibility to solidification cracking;the higher welding current,the higher the susceptibility to solidification cracking.When welding current and welding speed were changed simultaneously,on the one hand,an increase in welding speed reduced the susceptibility to solidification cracking,on the other hand,an increase in welding current increased the susceptibility to solidification cracking.And effect of simultaneously changing two parameters on the susceptibility to solidification cracking would consider whether they were cumulative effect or counteracting effect.Similarly,using this test,solidification cracking susceptibility of 304,310,410 stainless steel and dissimilar joint stainless steel were quantitatively evaluated under the same welding process conditions.The test results indicated that solidification cracking susceptibility of 304,310,and 410 stainless steels was ranked from high to low as follows:310 stainless steel>410stainless steel>304 stainless steel.During the overlap welding process of dissimilar stainless steel,the fusion of 410 stainless steel into 310 stainless steel reduced its solidification cracking susceptibility;melting 310 stainless steel into 410 stainless steel increased its.The feasibility and reliability of the transverse motion weldability test for evaluating the susceptibility of stainless steel welding solidification cracking were verified from the perspectives of process（welding current,welding speed）and metallurgy（different types of stainless steel）.Based on Pandat software,T-（fs）^1/2curves for 304,310,and 410 stainless steels were calculated.The maximum of|d T/d（fs）^1/2|near（fs）^1/2=0.98 was used as the criterion for solidification cracking susceptibility.Solidification cracking susceptibility of three types of stainless steel was evaluated,which showed a crack susceptibility ranking similar to that based on the test.And using this criterion,effect of changes in alloy elements on solidification cracking susceptibility was explored on the basis of 304 stainless steel.The results showed that when the equivalent ratio of chromium to nickel was between 1.5 and 2.1,the susceptibility to solidification cracking first decreased and then increased with the increase of its ratio.Around 1.8,the susceptibility to solidification cracking was the lowest.At the same time,when the chromium nickel equivalent ratio was the same,those with high chromium and nickel content also had high susceptibility to solidification cracking.A slight change in phosphorus content would have a significant impact on the susceptibility to solidification cracking.And the phosphorus content was almost linearly related to the susceptibility to solidification cracking,and as the phosphorus content increased,the susceptibility to solidification cracking became higher.