Research On JYH21CT Ferritic Stainless Steel Welding And Weld Grains Refinement

In recent years, with the global nickel tight supply, ferritic stainless steel which is lowor free nickel has attached more importance by the researchers both at home and abroad,and is widely used in the fields of automobile, boiler, heat exchanger, catering equipment.Compared to the austenitic stainless steel, the ferritic stainless steel has advantages of lowcost, small thermal expansion rate, good ability to resist high temperature oxidation,pitting corrosion, and crevice corrosion, but it also prone to appear some problems in thewelding process, such as welding joint embrittlement, the decline of corrosion resistance,heavily grow up of weld grain, etc.Focus on the coarse grains in the ferritic stainless steel welding process, this paperdoes research in JYH21CT plank welding with TIG welding method, explores the effect ofthree different technological measures of grain refining(A-TIG welding, adding Ni powder,micro alloying) and their principles. And on this basis to further we developed the specialflux of grain refining for JYH21CT ferritic stainless steel welding, the follow-up testsconfirmed its effect.The results indicate that: these three technological measures(A-TIG welding, addingNi powder, micro alloying) can effectively refining ferritic stainless steel weld grain, butthe principles are different. A-TIG welding method can adopt smaller welding heat inputand obtain the same weld depth because of the advantage of active flux can increase thedepth of weld, and the smaller the heat input is, the less obvious the weld grain grow up;Ni changes the composition of welding pool and then brings changes to the process ofphase change and recrystallization of the weld pool metal, dividing the weld grains intoaustenitic organization which is much smaller; the principle of refining weld grains by themicro alloying process is the metal elements, such as Ti, Zr, combining with the C,N in theliquid molten pool to form stable high melting point compounds, which act as the nuclearshaping particles and promote the process of heterogeneous nucleation in the weld metal.Furthermore, we developed the special flux of grain refining which is comprised ofactivate flux A, Ni, Titanium iron, Zr for JYH21CT ferritic stainless steel welding, it can not only refine the grain size to the level of base metal, but also improve the weld’smechanical properties and intergranular corrosion resistant ability.