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
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) in th...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) 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 because of higher solubility for hydrogen in austenitic phase. The use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q&T steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic steel(LHF) consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. The use of ASS and LHF consumables will lead to distinct microstructures in their respective welds. This microstructural heterogeneity will have a drastic influence in the fatigue crack growth resistance of armour grade Q&T steel welds. Hence, in this investigation an attempt has been made to study the influence of welding consumables and welding processes on fatigue crack growth behaviour of armour grade Q&T Steel joints. Shielded metal arc welding(SMAW) and Flux cored arc welding(FCAW) were used for fabrication of joints using ASS and LHF consumables. The joints fabricated by SMAW process using LHF consumable exhibited superior fatigue crack growth resistance than all other joints.展开更多
以γ-Al_2O_3为载体,采用等体积浸渍法制备了4种不同镍钨质量比的Ni-W/γ-Al_2O_3催化剂,采用X射线衍射(XRD)、N2吸附-脱附、程序升温脱附(NH_3-TPD)和扫描电镜(SEM)等方法对催化剂物化性质进行表征,在30 m L固定床反应器上对小于360℃...以γ-Al_2O_3为载体,采用等体积浸渍法制备了4种不同镍钨质量比的Ni-W/γ-Al_2O_3催化剂,采用X射线衍射(XRD)、N2吸附-脱附、程序升温脱附(NH_3-TPD)和扫描电镜(SEM)等方法对催化剂物化性质进行表征,在30 m L固定床反应器上对小于360℃低温煤焦油馏分油进行加氢实验,筛选出加氢效果较好的催化剂,并考察了加氢工艺条件对加氢产物分布情况及杂原子脱除效果的影响。结果表明,高温不利于油品轻质化且会降低噻吩类有机含硫物的脱除速率,但是有利于脱除难脱除的多环含氮物;高压可以抑制裂化反应和脱氢反应,增加汽柴油的收率,同时有利于提高多环含氮物的加氢饱和反应速率,进而提高脱氮率;低空速下进行加氢反应有利于杂原子脱除和油品轻质化。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.
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) 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 because of higher solubility for hydrogen in austenitic phase. The use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q&T steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic steel(LHF) consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. The use of ASS and LHF consumables will lead to distinct microstructures in their respective welds. This microstructural heterogeneity will have a drastic influence in the fatigue crack growth resistance of armour grade Q&T steel welds. Hence, in this investigation an attempt has been made to study the influence of welding consumables and welding processes on fatigue crack growth behaviour of armour grade Q&T Steel joints. Shielded metal arc welding(SMAW) and Flux cored arc welding(FCAW) were used for fabrication of joints using ASS and LHF consumables. The joints fabricated by SMAW process using LHF consumable exhibited superior fatigue crack growth resistance than all other joints.
文摘以γ-Al_2O_3为载体,采用等体积浸渍法制备了4种不同镍钨质量比的Ni-W/γ-Al_2O_3催化剂,采用X射线衍射(XRD)、N2吸附-脱附、程序升温脱附(NH_3-TPD)和扫描电镜(SEM)等方法对催化剂物化性质进行表征,在30 m L固定床反应器上对小于360℃低温煤焦油馏分油进行加氢实验,筛选出加氢效果较好的催化剂,并考察了加氢工艺条件对加氢产物分布情况及杂原子脱除效果的影响。结果表明,高温不利于油品轻质化且会降低噻吩类有机含硫物的脱除速率,但是有利于脱除难脱除的多环含氮物;高压可以抑制裂化反应和脱氢反应,增加汽柴油的收率,同时有利于提高多环含氮物的加氢饱和反应速率,进而提高脱氮率;低空速下进行加氢反应有利于杂原子脱除和油品轻质化。
