Investigation On Ductility Dip Cracking Susceptibility Of Deposited Metal With New Type 690 Nickel Alloy Strip By Electroslag Cladding

690 nickel-based alloy not only has good resistance to pitting corrosion and stress corrosion cracking,but also has good metallurgical stability and mechanical property.Therefore,690 welding materials have also been developed rapidly,which has been widely used on the main equipment including PWR steam generator and the reactor pressure vessel,etc.690 nickel-based alloy has poor weldability.690 alloy deposited metal is very susceptible to welding cracking.There are mainly solidification cracking and ductility-dip-cracking(DDC).The solidification cracking can be solved effectively by controlling the impurity elements such as sulfur and phosphor.DDC is a kind of high temperature solid state cracking,which often appears in nickel base alloy,austenitic stainless steel and other materials with single-phase structure of deposited metal.At present,domestic and foreign scholars have studied DDC,but it still appears in engineering application.This cracking has potential hazard to the stability of welding structure.So reducing the 690 alloy susceptibility to DDC is urgent.Researching DDC susceptibility of 690 nickel-based alloy has great significance to engineering applications.Based on the engineering requirement,this paper carried out studying on the DDC susceptibility of deposited metal with new type 690 nickel alloy strip.Through the high-temperature tensile test,the new type 690 alloy was studied,and the temperature range of plasticity reduction was determined.The DDC sensitivity of material was evaluated by section shrinkage rate.The STF test was used to further explore the susceptibility of the new type 690 alloy deposited metal,and the minimum critical strain value was used to evaluate the DDC susceptibility.By large thickness welding test,the DDC susceptibility was evaluated by the number of bending cracking.Experimental results show that the range of plasticity reduction temperature of the deposited metal with new type 690 nickel alloy is 800 ? to 1100 ?;According to the STF test,the DDC critical strain value is 4.3%,which is higher than 690-7A critical strain value.No cracking was found on the curved surface of bending test by large thickness welding.The tests show that the deposited metal with new type 690 nickel alloy has low susceptibility to the DDC.