AerMet100 ultra-high strength steel plates with a thickness of 2 mm were welded using a COz laser welding system. The influences of the welding process parameters on the morphology and microstructure of the welding jo...AerMet100 ultra-high strength steel plates with a thickness of 2 mm were welded using a COz laser welding system. The influences of the welding process parameters on the morphology and microstructure of the welding joints were investigated, and the mechanical property of the welding joints was analyzed. The experimental results showed that the fusion zone of welding joint mainly consisted of columnar grains and a fine dendrite substructure grew epitaxially from the matrix. With the other conditions remaining unchanged, a finer weld microstructure was along with the scanning speed increase. The solidification microstructure gradually transformed from cellular crystal into dendrite crystal and the spaces of dendrite secondary arms rose from the fusion line to the center of the fusion zone. In the fusion zone of the weld, the rapid cooling caused the formation of martensite, which led the microhardness of the fusion zone higher than that of the matrix and the heat affected zone. The tensile strength of the welding joints was tested as 1 700 MPa, which was about 87% of the matrix. However, the tensile strength of the welding joints without defects existed was tested as 1832 MPa, which was about 94% of the matrix.展开更多
The formation and control of sharp {100}〈021〉 texture in electrical steels were experimentally investigated and the main influencing factors were discussed. The steels of a base composition of Fe-3.2%Si with a certa...The formation and control of sharp {100}〈021〉 texture in electrical steels were experimentally investigated and the main influencing factors were discussed. The steels of a base composition of Fe-3.2%Si with a certain amount of carbon and manganese were employed to obtain {100}〈021〉 texture through one stage cold rolling and annealing. The results indicated that by careful control of the amount of alloying elements and the annealing temperature, a relatively sharp {100}〈021〉 texture in fairly thick sheets is obtained. After primary recrystallization, a weak component of {100}〈021〉 and strong component of （447） 〈18114〉 texture, which constitute ∑9 coincidence site lattice boundaries with a common 〈011〉 axis for 39° difference, are presented. This special grain boundary promotes the growth of {100}〈021〉 grains in addition to the lower surface energy of （100） grains during secondary recrystallization.展开更多
The microstructure evolution law and the structure of precipitates produced during the tempering of steel AerMet100 based on TEM observation and the calibration of diffraction spot were revealed.The electronic structu...The microstructure evolution law and the structure of precipitates produced during the tempering of steel AerMet100 based on TEM observation and the calibration of diffraction spot were revealed.The electronic structure and the stability of the MoxCr2-xC phase were calculated using the plane-wave pseudo-potential method on basis of density functional theory.TEM observations show that the precipitation phases Fe3C and Fe2-xCx(x=0.05～0.14) between martensite lath are produced at 425 and 480 ℃,respectively.The increase of tempering temperature or time can lead to the redissolution of both phases Fe3C and Fe2-xCx,and also lead to the precipitation of the phase Cr2C in martensite lath.The calculation results of formation energies and the density of state(DOS) demonstrate that in point of MoxCr2-xC structures formed during tempering,the early precipitation phase is Cr2C and finally later evolves into Mo2C phase with diffusing of incorporation of Mo atom into the Cr2C crystal cell,lattice,which can results in a energy decreases of the structure MoxCr2-xC phase with the increase of x.展开更多
According to the study of the microstructure and properties of X100 pipeline steel, the welding consumable-wire based on Mn-Ni-Mo-B-Ti alloy system was successfully designed and developed. The yield strength of the de...According to the study of the microstructure and properties of X100 pipeline steel, the welding consumable-wire based on Mn-Ni-Mo-B-Ti alloy system was successfully designed and developed. The yield strength of the deposited metal of the developed welding wire was 695 MPa, the tensile strength was 810 MPa, and Charpy impact energy was 92 J at negative 20 ℃ when matching with BSG-SJ101H1 sintered flux. The results of the weldability test for X100 pipeline steel which adopting this developed wire showed that the tensile strength of the weld was 827 MPa, 185 J of Charpy impact energy（ -10 ℃ ） , 97% of section of shear and the weld had good strength and toughness matching when the welding speed got to 1.7 m/min. The microstructure and fracture appearance of the weld were analyzed by using metallographic microscope, scanning electron microscope （SEM） and laser confocal microscope, the results indicated that the microstructure was mainly granular bainite in the weld metal, and the fracture was dimple with 200 - 300 μm depth presenting a typical ductile fracture characteristics. The test of welding wire with different content of Ni and Cr element indicated that Ni was better than Cr in improving the strength and toughness of weld metal.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51201087,51165038)the Project of Jiangxi Province of Education(No.GJJ13493)+1 种基金the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201306)the China Postdoctoral Science Foundation(No.2014M552485)
文摘AerMet100 ultra-high strength steel plates with a thickness of 2 mm were welded using a COz laser welding system. The influences of the welding process parameters on the morphology and microstructure of the welding joints were investigated, and the mechanical property of the welding joints was analyzed. The experimental results showed that the fusion zone of welding joint mainly consisted of columnar grains and a fine dendrite substructure grew epitaxially from the matrix. With the other conditions remaining unchanged, a finer weld microstructure was along with the scanning speed increase. The solidification microstructure gradually transformed from cellular crystal into dendrite crystal and the spaces of dendrite secondary arms rose from the fusion line to the center of the fusion zone. In the fusion zone of the weld, the rapid cooling caused the formation of martensite, which led the microhardness of the fusion zone higher than that of the matrix and the heat affected zone. The tensile strength of the welding joints was tested as 1 700 MPa, which was about 87% of the matrix. However, the tensile strength of the welding joints without defects existed was tested as 1832 MPa, which was about 94% of the matrix.
文摘The formation and control of sharp {100}〈021〉 texture in electrical steels were experimentally investigated and the main influencing factors were discussed. The steels of a base composition of Fe-3.2%Si with a certain amount of carbon and manganese were employed to obtain {100}〈021〉 texture through one stage cold rolling and annealing. The results indicated that by careful control of the amount of alloying elements and the annealing temperature, a relatively sharp {100}〈021〉 texture in fairly thick sheets is obtained. After primary recrystallization, a weak component of {100}〈021〉 and strong component of （447） 〈18114〉 texture, which constitute ∑9 coincidence site lattice boundaries with a common 〈011〉 axis for 39° difference, are presented. This special grain boundary promotes the growth of {100}〈021〉 grains in addition to the lower surface energy of （100） grains during secondary recrystallization.
文摘The microstructure evolution law and the structure of precipitates produced during the tempering of steel AerMet100 based on TEM observation and the calibration of diffraction spot were revealed.The electronic structure and the stability of the MoxCr2-xC phase were calculated using the plane-wave pseudo-potential method on basis of density functional theory.TEM observations show that the precipitation phases Fe3C and Fe2-xCx(x=0.05～0.14) between martensite lath are produced at 425 and 480 ℃,respectively.The increase of tempering temperature or time can lead to the redissolution of both phases Fe3C and Fe2-xCx,and also lead to the precipitation of the phase Cr2C in martensite lath.The calculation results of formation energies and the density of state(DOS) demonstrate that in point of MoxCr2-xC structures formed during tempering,the early precipitation phase is Cr2C and finally later evolves into Mo2C phase with diffusing of incorporation of Mo atom into the Cr2C crystal cell,lattice,which can results in a energy decreases of the structure MoxCr2-xC phase with the increase of x.
文摘According to the study of the microstructure and properties of X100 pipeline steel, the welding consumable-wire based on Mn-Ni-Mo-B-Ti alloy system was successfully designed and developed. The yield strength of the deposited metal of the developed welding wire was 695 MPa, the tensile strength was 810 MPa, and Charpy impact energy was 92 J at negative 20 ℃ when matching with BSG-SJ101H1 sintered flux. The results of the weldability test for X100 pipeline steel which adopting this developed wire showed that the tensile strength of the weld was 827 MPa, 185 J of Charpy impact energy（ -10 ℃ ） , 97% of section of shear and the weld had good strength and toughness matching when the welding speed got to 1.7 m/min. The microstructure and fracture appearance of the weld were analyzed by using metallographic microscope, scanning electron microscope （SEM） and laser confocal microscope, the results indicated that the microstructure was mainly granular bainite in the weld metal, and the fracture was dimple with 200 - 300 μm depth presenting a typical ductile fracture characteristics. The test of welding wire with different content of Ni and Cr element indicated that Ni was better than Cr in improving the strength and toughness of weld metal.
