A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed an...A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed and analyzed.The results show that the forming part includes four regions.The solidification zone solidifies as typical columnar crystals from a molten pool.The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100℃,and the typical columnar crystals in this zone are difficult to observe.The partial austenitizing zone forms from the completely austenite zone heated between Ac1(austenite transition temperature)and1100℃,which is mainly equiaxed grains.After several thermal cycles,the partial austenitizing zone transforms to the tempering zone,which consistes of fully equiaxed grains.From the solidification zone to the tempering zone,the average grain size decreases from 75 to20μm.The mechanical properties of HBMDPJ satisfies the requirement for the intended application.展开更多
A kind of self-protective flux cored wire has been developed for joining 960 MPa high strength steel. Weld metal containing different aluminium elements contents was obtained by changing the content of aluminum powder...A kind of self-protective flux cored wire has been developed for joining 960 MPa high strength steel. Weld metal containing different aluminium elements contents was obtained by changing the content of aluminum powder in the composition of the flux core. The strength and toughness of weld metal were tested by tensile test and impact test at different temperatures, and the influence mechanism of aluminium element on the microstructure and mechanical properties of weld metal was analyzed by means of metallographic microstructure observation and scanning electron microscope observation. The results show that aluminium element content on impact ductility of weld metal of 960 MPa high strength steel is great, but the influence on tensile strength and elongation of weld metal is little. With increasing aluminium element contents of weld metal, the impact energy of weld metal increases at first and then decreases, the best aluminium element content of weld metal is 0.2 wt.%. Aluminium oxide is easy to be formed in weld metal with low aluminium element contents, and the aluminium oxide can easily become nucleation particle for acicular ferrite. It is conducive to formation more acicular ferrite and will improve impact absorbing energy of weld metal. Aluminium nitride will easily formed in weld metal with high aluminium element content, and the coarse ferrite microstructure appears in weld metal and reduces impact energy of weld metal.展开更多
基金financially supported by the National Key R&D Program of China(No.2017YFB1103200)the Independent Innovation Research Fund Project of Huazhong University of Science and Technology(No.2018KFYXMPT002)。
文摘A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed and analyzed.The results show that the forming part includes four regions.The solidification zone solidifies as typical columnar crystals from a molten pool.The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100℃,and the typical columnar crystals in this zone are difficult to observe.The partial austenitizing zone forms from the completely austenite zone heated between Ac1(austenite transition temperature)and1100℃,which is mainly equiaxed grains.After several thermal cycles,the partial austenitizing zone transforms to the tempering zone,which consistes of fully equiaxed grains.From the solidification zone to the tempering zone,the average grain size decreases from 75 to20μm.The mechanical properties of HBMDPJ satisfies the requirement for the intended application.
基金Project was supported by the 2019 Scientific Research Foundation of Liaoning Provincial Education Department (Grant No. LJJF201902)Special Research Foundation of Liaoning Equipment Manufacture College of Vocational and Technology (Grant No.2018YYYJ-5)。
文摘A kind of self-protective flux cored wire has been developed for joining 960 MPa high strength steel. Weld metal containing different aluminium elements contents was obtained by changing the content of aluminum powder in the composition of the flux core. The strength and toughness of weld metal were tested by tensile test and impact test at different temperatures, and the influence mechanism of aluminium element on the microstructure and mechanical properties of weld metal was analyzed by means of metallographic microstructure observation and scanning electron microscope observation. The results show that aluminium element content on impact ductility of weld metal of 960 MPa high strength steel is great, but the influence on tensile strength and elongation of weld metal is little. With increasing aluminium element contents of weld metal, the impact energy of weld metal increases at first and then decreases, the best aluminium element content of weld metal is 0.2 wt.%. Aluminium oxide is easy to be formed in weld metal with low aluminium element contents, and the aluminium oxide can easily become nucleation particle for acicular ferrite. It is conducive to formation more acicular ferrite and will improve impact absorbing energy of weld metal. Aluminium nitride will easily formed in weld metal with high aluminium element content, and the coarse ferrite microstructure appears in weld metal and reduces impact energy of weld metal.
