Microstructure And Properties Research Of Twip Steel Tig Welding Head

For the characteristics of Expandable Tubular Technology, successful designed and developed21Mn24Cr5Ni2A12Si-TWIP steel for Expandable Tubular Technology which has high strength, high plasticity and can resistance acid corrosion by using vacuums melting, hot rolling, cold rolling process. The research for microstructure and mechanical properties of TWIP steel’s welded joint has important application significance. In this paper, using parent material as the welding material, TIG of TWIP steel butt welding.Using OM, SEM, EDS, XRD analytical tools, combined with room temperature mechanical properties test and SCC test of electrochemical hydrogen charging of welded joints, has studied the changes of the micro-organizational structure, the formation mechanism of annealing twins and deformation twins of the21Mn24Cr5Ni2A12Si-TWIP steel welded joints before and after the solution treatment, also studied the affect of microstructure changes for welded joints mechanical properties; fracture mechanisms, and stress corrosion of welded joints in different electrochemical hydrogen charging state and the stress corrosion mechanism. The results show that:Welded joints and base metal both was single austenite, welded joints apparently has the characteristics of weld zone and heat affected zone. But there is huge difference mechanical properties and morphology between base metal and welded joints which has no heat treatment, indicating that both the performance is extremely not match, and the effect of the TWIP is not obvious. After solution heat treatment at1050℃, keep warm for30min, then water quenching, the welded joints produced the same large number of annealing twins and deformation twins as the base metal, the welded joints mechanical properties and morphology can be restored to the base metal. After the solution treatment of welded joints welded joints has obvious tendency to stress corrosion at the electrochemical hydrogen charging status. During0mA/cm2～100mA/cm2charge hydrogen range, stress corrosion sensitivity increases gradually with the increase of the hydrogen charging current density. But the welded joints still maintain good elongation, tensile fracture has dimple ductile fracture characteristics, TWIP effect has the ability to alleviate the stress corrosion cracking.