While the thick growth of intermediate phase layers generally benefits the corrosion resistance of galvanized steels,it is unfavorable from the standpoints of mechanical integrity and economics.Thus,the influence of n...While the thick growth of intermediate phase layers generally benefits the corrosion resistance of galvanized steels,it is unfavorable from the standpoints of mechanical integrity and economics.Thus,the influence of nickel chloride-based fluxes and the typical zinc-ammonium chloride flux on galvanized coating thickness as well as coating morphology and composition is examined.The investigation of pretreated hot dip galvanized steel specimens for various durations has verified that nickel chloride fluxes influence the growth rate of the zeta interlayer.This results in the overall reduction of the coating thickness by as much as two times compared to those prepared with the conventional flux.Nickel from the fluxes gradually diffuses away from the substrate＇s surface,and hence the initial concentration of the nickel salts along with the hot dip duration needs to be controlled appropriately for effective use of nickel chloride-based fluxes in the galvanizing process.展开更多
Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5：4：1. Compared with con...Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5：4：1. Compared with conventional TIG welding, the penetration increases 164% by the action of the flux. Tensile test result indicates that the fracture strength of the mixed flux A-TIG weld bead is higher than base metal, and it increases along with the decrement of the welding current. The average extensibility of the weldment is beyond 100%, which means perfect ductility. MetaUographs elucidate that there exist lots of deep and evenly distributed dimples on the fiacture section of weld bead while on that of base metal there only exists a few shallow dimples and massive tearing ridge.展开更多
Stainless steel crude alloy recovery from direct smelting of low-grade chromite, nickel laterite and manganese ores was investigated. The mixed low-grade ores were directly smelted in an elevator furnace at smelting t...Stainless steel crude alloy recovery from direct smelting of low-grade chromite, nickel laterite and manganese ores was investigated. The mixed low-grade ores were directly smelted in an elevator furnace at smelting temperatures ranging from 1550 to 1600 ℃. Smelting experiments were conducted in a laboratory elevator furnace equipped with 8 U-shaped high- quality molybdenum disilicide heating elements. A low-grade coal was used as the reductant. Experimental results showed that the recovery of Fe, Cr, Ni, Mn and Si within the alloy increased from 34.22, 60.27, 57.14, 25.42 and 13.02% to 69.91, 99.26, 86.02, 60.8 and 34.21%, respectively, when the temperature was increased from 1550 to 1600 ℃. There was a general increase in the total recoveries of Fe, Cr, and Ni in the alloy with CaO addition increasing from 0.4 g up to 1.2 g. However, the recoveries of Mn and Si vividly decreased as the CaO contents were increased. In general, the recoveries of the metal contents of the crude alloy increase with the increase in the amount of manganese ore. Compared to the recoveries of Fe, Cr, and Ni when CaO was added, the recoveries of Fe, Cr and Ni were lower when manganese ore was used as an additive.展开更多
Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced crac...Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced cracking(HIC) but they are very expensive. In recent years, the developments of low hydrogen ferritic steel(LHF) consumables that contain no hygroscopic compounds are utilized for welding Q&T steels. Heat affected zone(HAZ) softening is another critical issue during welding of armour grade Q&T steels and it depends on the welding process employed and the weld thermal cycle. In this investigation an attempt has been made to study the influence of welding consumables and welding processes on metallurgical characteristics of armour grade Q&T steel joints by various metallurgical characterization procedures. Shielded metal arc welding(SMAW) and flux cored arc welding(FCAW) processes were used for making welds using ASS, LHF and HNS welding consumables. The joints fabricated by using LHF consumables offered lower degree of HAZ softening and there is no evidence of HIC in the joints fabricated using LHF consumables.展开更多
基金Item Sponsored by Iron and Steel Institute of Thailand(ISIT) for Research Funding(022/2552)
文摘While the thick growth of intermediate phase layers generally benefits the corrosion resistance of galvanized steels,it is unfavorable from the standpoints of mechanical integrity and economics.Thus,the influence of nickel chloride-based fluxes and the typical zinc-ammonium chloride flux on galvanized coating thickness as well as coating morphology and composition is examined.The investigation of pretreated hot dip galvanized steel specimens for various durations has verified that nickel chloride fluxes influence the growth rate of the zeta interlayer.This results in the overall reduction of the coating thickness by as much as two times compared to those prepared with the conventional flux.Nickel from the fluxes gradually diffuses away from the substrate＇s surface,and hence the initial concentration of the nickel salts along with the hot dip duration needs to be controlled appropriately for effective use of nickel chloride-based fluxes in the galvanizing process.
文摘Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5：4：1. Compared with conventional TIG welding, the penetration increases 164% by the action of the flux. Tensile test result indicates that the fracture strength of the mixed flux A-TIG weld bead is higher than base metal, and it increases along with the decrement of the welding current. The average extensibility of the weldment is beyond 100%, which means perfect ductility. MetaUographs elucidate that there exist lots of deep and evenly distributed dimples on the fiacture section of weld bead while on that of base metal there only exists a few shallow dimples and massive tearing ridge.
文摘Stainless steel crude alloy recovery from direct smelting of low-grade chromite, nickel laterite and manganese ores was investigated. The mixed low-grade ores were directly smelted in an elevator furnace at smelting temperatures ranging from 1550 to 1600 ℃. Smelting experiments were conducted in a laboratory elevator furnace equipped with 8 U-shaped high- quality molybdenum disilicide heating elements. A low-grade coal was used as the reductant. Experimental results showed that the recovery of Fe, Cr, Ni, Mn and Si within the alloy increased from 34.22, 60.27, 57.14, 25.42 and 13.02% to 69.91, 99.26, 86.02, 60.8 and 34.21%, respectively, when the temperature was increased from 1550 to 1600 ℃. There was a general increase in the total recoveries of Fe, Cr, and Ni in the alloy with CaO addition increasing from 0.4 g up to 1.2 g. However, the recoveries of Mn and Si vividly decreased as the CaO contents were increased. In general, the recoveries of the metal contents of the crude alloy increase with the increase in the amount of manganese ore. Compared to the recoveries of Fe, Cr, and Ni when CaO was added, the recoveries of Fe, Cr and Ni were lower when manganese ore was used as an additive.
基金Armament Research Board (ARMREB), New Delhi for funding this project work (Project no. MAA/03/ 41)
文摘Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced cracking(HIC) but they are very expensive. In recent years, the developments of low hydrogen ferritic steel(LHF) consumables that contain no hygroscopic compounds are utilized for welding Q&T steels. Heat affected zone(HAZ) softening is another critical issue during welding of armour grade Q&T steels and it depends on the welding process employed and the weld thermal cycle. In this investigation an attempt has been made to study the influence of welding consumables and welding processes on metallurgical characteristics of armour grade Q&T steel joints by various metallurgical characterization procedures. Shielded metal arc welding(SMAW) and flux cored arc welding(FCAW) processes were used for making welds using ASS, LHF and HNS welding consumables. The joints fabricated by using LHF consumables offered lower degree of HAZ softening and there is no evidence of HIC in the joints fabricated using LHF consumables.
