Study On Low-temperature Sensitivity Of Welded Joints Of HSLA Steel

By means of studying on KNM steel(15Cr2Mol) is applied to produce high strength steel,low alloy centrifugal compressor impeller, KMN steel is base of Cr, Mo alloy steel aschromium phase heat resistant steel, It has the high oxidation resistance and heat intensity, thiskind of steel also has good resistance to corrosion of hydrogen and sulfide, it is widely used inpetrochemical equipment manufacture and pipe installation. Studying on chromium phase ofheat resistant steel welding, for engineering quality, time limit for a project, benefit and so onall have a positive impact due to the widely used.In this paper, studying on the impact toughness of welded joint performance of KMNsteel under low temperature condition, making KMN steel could used under low temperatureapplications(-50℃), By choosing three different kinds of welding materials includingE9018-B3L-Ni, CHH407A, S9018-B3. Analyzing and comparing the mechanical properties ofwelded joint by tensile test, bending test, impact test, hardness test performance and so on, andanalyzing the influence of the microstructure of welding joint from the metallograph at thesame time. Choose the different tempering temperature due to considering the heat treatmentafter welding on the mechanical properties of welded joint, analyzing and comparing themechanical properties of welded joint, studying after welding heat treatment process on theproperties of welded joint by the tensile and impact properties tests.The test results showed that in the same heat treatment state and the same weldingparameters, through comparing the selected three kinds of welding rod of various mechanicalperformance data, the E9018-B3L-Ni electrode welding sample impact performance is best atlow temperature, the tensile and bending performance can satisfy the requirements of thematerial, CHH407A electrode low-temperature impact properties were greater than27J,tensile and bending properties meet the requirements. S9018-B3electrode tensile and bendingproperties meet the requirements, but the low temperature impact performance is unqualified,it cannot be used at low temperature condition. Because of the E9018B3L-Ni containing avariety of alloy elements, it have beneficial effects on the weld microstructure, showing goodlow-temperature impact performance. Under different tempering temperature, the mechanicalproperties of welded joint have change, with the increase of tempering temperature, the welding joint of yield strength and tensile strength decreased, while the impact toughnessincreased.Using the E9018-B3L-Ni and CHH407A electrode weld KMN steel can meet the use ofthe working condition of low temperature requirements at50℃.