Effect of the heat input on microstructure and properties of submerged arc welded joint of 08Cr19MnNi3Cu2N stainless steel

SAW308L submerged arc welding wire and SJ601A submerged arc welding flux were selected to weld the 12 mm 08Cr19MnNi3Cu2N low nickel and high nitrogen austenitic stainless steel plates with three different welding heat input,and microstructure,tensile properties,microhardness and corrosion properties of the welded joints were studied.The results show that no defects are found in the three groups of welded joints,and the welded joints have better performance.The tensile strength of 08Cr19MnNi3Cu2N stainless steel welded joints with different heat input is slightly lower than that of the base metal,and fracture occurs in the weld zone,and the hardness of the weld zone is lower than that of the base metal.The weld microstructure of stainless steel welded joints with different heat input is composed of austenite+δferrite,and ferrite is uniformly distributed in austenite.With the increase of the welding heat input,the ferrite content in the weld zone decrease gradually,the grain size in the thermal affected zone increase gradually,and the impact toughness reduce.

Effects of Isothermal Aging on Microstructure and Mechanical Property of Low-Carbon RAFM Steel

In order to investigate the microstructure and mechanical property evolution of low-carbon reduced activation ferritic/martensitic(RAFM)steel during isothermal aging,the normalized and tempered specimens were aged at 600℃for 500,1000,and 3000 h,respectively.The microstructural evolution with aging time was analyzed,including the precipitation and growth of M23C6 and MX-type carbides as well as the formation of Laves phase.The results indicate that the coarsening of M23C6 is more obvious than that of MX with increase in aging time.During the long-term thermal exposure,the Fe2 W Laves phase precipitates adjacent to M23C6 along the prior austenite grain boundaries and packet boundaries.Lower carbon content can delay the precipitation of Laves phase compared to the steel containing higher carbon.In addition,the Laves phase precipitated along boundaries can provide the precipitation strengthening,slightly increasing the tensile strength of low-carbon RAFM steel after aging for 3000 h.

Improvement of High-Temperature Mechanical Properties of Low-Carbon RAFM Steel by MX Precipitates

To investigate the influence of tantalum content on high-temperature mechanical properties of low-carbon reduced acti- vation ferritic/martensitic （RAFM） steels, RAFM steels containing different tantalum contents （0 and 0.073%） were fabricated, and the tensile tests at room temperature and high temperature were performed, as well as the creep tests were conducted at 550 ~C with the applied stress of 180 and 220 MPa. It was found that 0.073% tantalum addition results in the increase in amount of stable carbonitrides （MX）, and the creep rupture time of the steel under 180 MPa is obviously increased. In addition, the increase in MX caused by tantalum addition also leads to the improvement of high-temperature tensile strength. The improvement of high-temperature mechanical properties of RAFM steels is primarily related to the evolution of precipitates.