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
In general, the weld thermal cycle results in significant changes in microstructure and mechanical properties of the weld heat affected zone （ HAZ）. The microstructure, microhardness and low temperature impact tough...In general, the weld thermal cycle results in significant changes in microstructure and mechanical properties of the weld heat affected zone （ HAZ）. The microstructure, microhardness and low temperature impact toughness of HAZfor X100 pipeline steel were studied by means of welding thermal simulation. Influence of cooling time on the microstructure and properties in coarse-grained heat affected zone （CGHAZ） was investigated. The results illustrated that polygonal ferrite and a small amount of granular bainite were obtained when the cooling time ts/5 is larger than 1 500 s. Mainly granular bainite was formed when the cooling time t8/5 is in the range of 1500 s to 100 s. Bainite ferrite was observed when the cooling time is smaller than 60 s. Martensite appeared in the CGHAZ with the 20 s cooling time. The value of microhardness in the CGHAZ was higher than that of base metal （ BM） when the cooling time ts/s is smaller than 100 s. The CVN absorbed energy in the CGHAZ was higher than the value of BM when the cooling time t8/5 is smaller than 30 s.展开更多
The influence of the secondary thermal cycle on the microstructure of coarse grain heat-affected zone in an XIO0 pipeline steel was investigated by means of a thermal simulation technique and microscopic analysis meth...The influence of the secondary thermal cycle on the microstructure of coarse grain heat-affected zone in an XIO0 pipeline steel was investigated by means of a thermal simulation technique and microscopic analysis method. The property of coarse grain heat-affected zone was characterized by Charpy V-Notch impact properties testing. The results indicated that the experimental steel exhibited local brittleness of intercritically reheated coarse-grained heat-affected zone when the peak tempera- ture of secondary thermal cycle was in the range of two phases region （ ~ and 3/）. There were two main reasons for the local brittleness. The first was that the microstructures of intercritically reheated coarse-grained heat-affected zone were not fined although partial grain recrystallization occurred. The second was that M-A islands, which had the higher content, larger size and higher hardness, existed in intercritically reheated coarse-grained heat-affected zone.展开更多
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.
文摘In general, the weld thermal cycle results in significant changes in microstructure and mechanical properties of the weld heat affected zone （ HAZ）. The microstructure, microhardness and low temperature impact toughness of HAZfor X100 pipeline steel were studied by means of welding thermal simulation. Influence of cooling time on the microstructure and properties in coarse-grained heat affected zone （CGHAZ） was investigated. The results illustrated that polygonal ferrite and a small amount of granular bainite were obtained when the cooling time ts/5 is larger than 1 500 s. Mainly granular bainite was formed when the cooling time t8/5 is in the range of 1500 s to 100 s. Bainite ferrite was observed when the cooling time is smaller than 60 s. Martensite appeared in the CGHAZ with the 20 s cooling time. The value of microhardness in the CGHAZ was higher than that of base metal （ BM） when the cooling time ts/s is smaller than 100 s. The CVN absorbed energy in the CGHAZ was higher than the value of BM when the cooling time t8/5 is smaller than 30 s.
基金This work was supported by the National Natural Science Foundation of China（ No. 50874090）.
文摘The influence of the secondary thermal cycle on the microstructure of coarse grain heat-affected zone in an XIO0 pipeline steel was investigated by means of a thermal simulation technique and microscopic analysis method. The property of coarse grain heat-affected zone was characterized by Charpy V-Notch impact properties testing. The results indicated that the experimental steel exhibited local brittleness of intercritically reheated coarse-grained heat-affected zone when the peak tempera- ture of secondary thermal cycle was in the range of two phases region （ ~ and 3/）. There were two main reasons for the local brittleness. The first was that the microstructures of intercritically reheated coarse-grained heat-affected zone were not fined although partial grain recrystallization occurred. The second was that M-A islands, which had the higher content, larger size and higher hardness, existed in intercritically reheated coarse-grained heat-affected zone.
