Effect Of Heat Treatment On Microstructure And Properties Of 0Cr13Ni5Mo/28Mn Welded Joints

Super martensitic stainless steels(SMSS)have been widely used as pipeline materials.It is developed on the basis of traditional martensitic stainless steel by redesigning the alloying syste i.e.reducing C content(<0.07%),strictly controlling Ni content(4%-6%)and Mo content(1.5%-2.5%).Compared with conventional stainless steels,SMSS exhibits a more excellent combination of strength and toughness,as well as good corrosion resistance.In addition,SMSS demonstrates advantages in overcoming the sulfur induced stress cracking sensitivity during the welding process as well as possessing better weldability,The study of super martensitic stainless steel was mostly focused on the exploration of the corrosion mechanism and inverter austenitic formation mechanism at present,while the research about welding between the super martensitic stainless steel dissimilar steel and the mechanical properties of welded joint was very little.The research subject is determined the content of inverter austenite under different tempering temperature by X-ray diffraction method first,and combined with microscopic metallographic observation and material testing means of hardness test and so on,to exploring the variation of 0Cr13Ni5Mo microstructure changes under different tempering temperature.For oil pipe 0Cr13Ni5Mo and 28Mn,using HS13/5L,the 0Cr13Ni5Mo/28Mn is carried out on dissimilar steel welding by manual tungsten argon arc welding,and the welded joint is carried out on different heat treatment process,combined with metallographic microstructure observation,scanning electron microscopy(SEM),and test of hardness,tensile properties,impact toughness,and so on,to explored the variation of the organization and performance.The results showed that:(1)the influence of tempering temperature on the content of inverter austenite which is produced in the tempering process of 0Cr13Ni5Mo.With the increasing of the tempering temperature,the content of inverter austenite is increased firstly and then reduced,and the the content of inverter austenite reached a peak at 650℃.(2)The width of martensite lath of 0Cr13Ni5Mo is gradually thinned with the increasing of the tempering temperature,and the degree of the refinement increases after 650℃.Tempering have effect on the hardness of material.The hardness is decreased firstly,and then rised with the increasing of the tempering temperature.(3)The martensite of 0Cr13Ni5Mo/28Mn dissimilar steel welding joint of 28Mn in side heat affected zone(HAZ)is carried out to be acicular,which is fine sorbite organization after tempering.The weld organization is lath martensite,and the side HAZ of 0Cr13Ni5Mo is not grow up,and the weld organization is thinned to some extent.(4)When the welded joint is quenched at 480°C by short-term and tempered,good impact toughness can be obtained in the fusion line of 28Mn,and the fracture of tensile specimen is to take place upon the parent metal of 28Mn.