Quenched and Tempered （Q＆T） steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking （HIC） an...Quenched and Tempered （Q＆T） steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking （HIC） and softening in the heat affected zone （HAZ） after welding. The use of austenitic stainless steel （ASS） consumables to weld the above steel was the only available remedy to avoid HIC because of higher solubility for hydrogen in austenitic phase. Recent studies revealed that low hydrogen ferritic （LHF） steel consumables can also be used to weld Q＆T steels, which can give very low hydrogen levels in the weld deposits and required resistance against cold cracking. Hence, in this investigation an attempt has been made to study the performance of armour grade Q＆T steel joints fabricated by flux cored arc welding with LHF steel consumables. Two different consumables namely （i） austenitic stainless steel and （ii） low hydrogen ferritic steel have been used to fabricate the joints by flux cored arc welding （FCAW） process. The joints fabricated by LHF consumable exhibited superior transverse tensile properties due to the presence of ferrite microstructure in weld metal. The joints fabricated by ASS consumable showed higher impact toughness due to the presence of austenitic phase in weld metal microstructure. The HAZ softening in coarse grain heat affected zone （CGHAZ） is less in the joints fabricated using LHF consumable due to the lower heat input involved during fabrication compared to the joints fabricated using ASS consumables.展开更多
Applying the extreme low-level γ-ray spectroscopic analysis the environmental neutron flux is measured using different moderator construction and environment through the reaction 197Au (n, γ) 198Au. The contribution...Applying the extreme low-level γ-ray spectroscopic analysis the environmental neutron flux is measured using different moderator construction and environment through the reaction 197Au (n, γ) 198Au. The contribution of thermal and resonance neutrons is separated using the cadmium difference technique, while fast neutrons are measured by the paraffin moderator. The results of altitude dependence of the neutron flux are discussed. The thermal neutron flux near the surface of sea water is less than its value at 100 cm over ground near sea water, while the value over the surfaces of fresh water is higher than that near the surface of sea water. Also the thermal neutron flux at 5 cm soil depth increases, then decreases to its original value at 10 cm depth and still constant until 25 cm, then decreases rapidly to reach 27% of its original value at 60 cm depth. The soil compositions, corresponding neutron temperatures and effective absorption cross sections of earth are the most effective factors on the equilibrium region of thermal neutrons in the ground.展开更多
Viscosity stability indexes of mold flux at high temperature and low temperature havebeen introduced and the effects of flux compositions on viscosity stability indexeshave been studied. Two mold fluxes have been deve...Viscosity stability indexes of mold flux at high temperature and low temperature havebeen introduced and the effects of flux compositions on viscosity stability indexeshave been studied. Two mold fluxes have been developed by analyzing the effects offlux viscosity stability on the process and the condition of continuous casting slab ofmedium carbon steel. The results show that the fluxes are suitable for the process.展开更多
In order to remove hydrogen and inclusions from A356 alloy melt, a low melting point glass flux, JDN Ⅱ, was developed. The results indicated that JDN Ⅱ flux has distinct effect of purification and protection on A356...In order to remove hydrogen and inclusions from A356 alloy melt, a low melting point glass flux, JDN Ⅱ, was developed. The results indicated that JDN Ⅱ flux has distinct effect of purification and protection on A356 alloy melt. When the dosage of the flux was 3%, the content of hydrogen in A356 melt was only 2.6?mL/kg at 857?℃ and 0.7?mL/kg even at 750?℃. In the meantime, the mechanical properties of the alloy increase greatly with the covering of 3% JDN Ⅱ flux. Compared with no flux, the tensile strength of A356 alloy increases by 9.42% and the elongation increases by 22%. The purification mechanism of JDN Ⅱ glass flux was discussed too.展开更多
基金New Delhi for funding this project work(Project No.MAA/03/41)
文摘Quenched and Tempered （Q＆T） steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking （HIC） and softening in the heat affected zone （HAZ） after welding. The use of austenitic stainless steel （ASS） consumables to weld the above steel was the only available remedy to avoid HIC because of higher solubility for hydrogen in austenitic phase. Recent studies revealed that low hydrogen ferritic （LHF） steel consumables can also be used to weld Q＆T steels, which can give very low hydrogen levels in the weld deposits and required resistance against cold cracking. Hence, in this investigation an attempt has been made to study the performance of armour grade Q＆T steel joints fabricated by flux cored arc welding with LHF steel consumables. Two different consumables namely （i） austenitic stainless steel and （ii） low hydrogen ferritic steel have been used to fabricate the joints by flux cored arc welding （FCAW） process. The joints fabricated by LHF consumable exhibited superior transverse tensile properties due to the presence of ferrite microstructure in weld metal. The joints fabricated by ASS consumable showed higher impact toughness due to the presence of austenitic phase in weld metal microstructure. The HAZ softening in coarse grain heat affected zone （CGHAZ） is less in the joints fabricated using LHF consumable due to the lower heat input involved during fabrication compared to the joints fabricated using ASS consumables.
文摘Applying the extreme low-level γ-ray spectroscopic analysis the environmental neutron flux is measured using different moderator construction and environment through the reaction 197Au (n, γ) 198Au. The contribution of thermal and resonance neutrons is separated using the cadmium difference technique, while fast neutrons are measured by the paraffin moderator. The results of altitude dependence of the neutron flux are discussed. The thermal neutron flux near the surface of sea water is less than its value at 100 cm over ground near sea water, while the value over the surfaces of fresh water is higher than that near the surface of sea water. Also the thermal neutron flux at 5 cm soil depth increases, then decreases to its original value at 10 cm depth and still constant until 25 cm, then decreases rapidly to reach 27% of its original value at 60 cm depth. The soil compositions, corresponding neutron temperatures and effective absorption cross sections of earth are the most effective factors on the equilibrium region of thermal neutrons in the ground.
文摘Viscosity stability indexes of mold flux at high temperature and low temperature havebeen introduced and the effects of flux compositions on viscosity stability indexeshave been studied. Two mold fluxes have been developed by analyzing the effects offlux viscosity stability on the process and the condition of continuous casting slab ofmedium carbon steel. The results show that the fluxes are suitable for the process.
文摘In order to remove hydrogen and inclusions from A356 alloy melt, a low melting point glass flux, JDN Ⅱ, was developed. The results indicated that JDN Ⅱ flux has distinct effect of purification and protection on A356 alloy melt. When the dosage of the flux was 3%, the content of hydrogen in A356 melt was only 2.6?mL/kg at 857?℃ and 0.7?mL/kg even at 750?℃. In the meantime, the mechanical properties of the alloy increase greatly with the covering of 3% JDN Ⅱ flux. Compared with no flux, the tensile strength of A356 alloy increases by 9.42% and the elongation increases by 22%. The purification mechanism of JDN Ⅱ glass flux was discussed too.
