The present work attributes the role of boron on the high strength steel submerged arc weld using an undermatching filler wire.Mild steel filler wire was used for welding in constant machine parameters setting to eval...The present work attributes the role of boron on the high strength steel submerged arc weld using an undermatching filler wire.Mild steel filler wire was used for welding in constant machine parameters setting to evaluate the joint strength due to the enrichment of boron.To change the chemical composition of the weld metal,boron trioxide powder was blended with virgin flux in various proportions(2.5%−12.5%),which led to an increase in boron weight percentage in the range of 0−0.0065.The results show that weld metals(WM)optical micrographs depict the various types of ferrites,pearlites and secondary phases like martensite-austenite(M-A).Acicular ferrite content was influenced by the boron trioxide addition.Heat affected zone(HAZ)micrographs were not showing appreciable changes with oxide enrichment.Hardness and toughness of weld metals showed the mixed trend with B_(2)O_(3) enrichment whereas,small reduction in ultimate tensile strength(UTS)and yield strength(YS)was observed.展开更多
The influence of Ce on the solidification microstructures of M2 high speed steel was studied. The results show that Ce has the effect of alleviating the segregation of alloying elements such as W and Mo in high speed ...The influence of Ce on the solidification microstructures of M2 high speed steel was studied. The results show that Ce has the effect of alleviating the segregation of alloying elements such as W and Mo in high speed steel. With the addition of Ce, the amount of eutectic carbides is decreased and the flakes of the carbides are refined. Ce mainly segregates onto the interface between the eutectic carbide and austenite, and a Dart of Ce enters M2C carbide. Ce can also enhance the breaking and spheroidizing of the network eutectic carbides during high temperature heat treatment.展开更多
Microstructure of the deepest zone of high speed steel W6Mo5Cr4V2(M2)melt after laser fu-sion was found to be so fine as the ehill zone of a solidified ingot.When narrower chill zoneformed,the long columnar dendrites ...Microstructure of the deepest zone of high speed steel W6Mo5Cr4V2(M2)melt after laser fu-sion was found to be so fine as the ehill zone of a solidified ingot.When narrower chill zoneformed,the long columnar dendrites grow into the melt and then the fine equiaxed cellularstructure appears in upper melt region nearly surface.The substructure of cellular grains anddendrites was observed to consist of martensite and retained austenile,while the carbides asM_6C_■ Cr_7C_3 and MC distributed at their boundaries.It is believed that the highermicrohardness up to HV_(0.1)=865-960 of the laser fused structure of the alloy is due to the oc-currence of martensite.展开更多
Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated....Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 ℃, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 μm, shape factor is 0.83, and mean thickness of network carbide is 5.21 μm.展开更多
文摘The present work attributes the role of boron on the high strength steel submerged arc weld using an undermatching filler wire.Mild steel filler wire was used for welding in constant machine parameters setting to evaluate the joint strength due to the enrichment of boron.To change the chemical composition of the weld metal,boron trioxide powder was blended with virgin flux in various proportions(2.5%−12.5%),which led to an increase in boron weight percentage in the range of 0−0.0065.The results show that weld metals(WM)optical micrographs depict the various types of ferrites,pearlites and secondary phases like martensite-austenite(M-A).Acicular ferrite content was influenced by the boron trioxide addition.Heat affected zone(HAZ)micrographs were not showing appreciable changes with oxide enrichment.Hardness and toughness of weld metals showed the mixed trend with B_(2)O_(3) enrichment whereas,small reduction in ultimate tensile strength(UTS)and yield strength(YS)was observed.
文摘The influence of Ce on the solidification microstructures of M2 high speed steel was studied. The results show that Ce has the effect of alleviating the segregation of alloying elements such as W and Mo in high speed steel. With the addition of Ce, the amount of eutectic carbides is decreased and the flakes of the carbides are refined. Ce mainly segregates onto the interface between the eutectic carbide and austenite, and a Dart of Ce enters M2C carbide. Ce can also enhance the breaking and spheroidizing of the network eutectic carbides during high temperature heat treatment.
文摘Microstructure of the deepest zone of high speed steel W6Mo5Cr4V2(M2)melt after laser fu-sion was found to be so fine as the ehill zone of a solidified ingot.When narrower chill zoneformed,the long columnar dendrites grow into the melt and then the fine equiaxed cellularstructure appears in upper melt region nearly surface.The substructure of cellular grains anddendrites was observed to consist of martensite and retained austenile,while the carbides asM_6C_■ Cr_7C_3 and MC distributed at their boundaries.It is believed that the highermicrohardness up to HV_(0.1)=865-960 of the laser fused structure of the alloy is due to the oc-currence of martensite.
基金Funded by the Science Foundation of Beijing Jiaotong University (No.230-12)
文摘Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 ℃, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 μm, shape factor is 0.83, and mean thickness of network carbide is 5.21 μm.
