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
Distribution of localized damage in shear band can’ t be predicted theoretically based on classical elastoplastic theory. The average damage variable in shear band was considered to be a non-local variable. Based on ...Distribution of localized damage in shear band can’ t be predicted theoretically based on classical elastoplastic theory. The average damage variable in shear band was considered to be a non-local variable. Based on non-local theory, an analytical expression for the localized damage in strain-softening region of shear band in the process of shear band propagation was presented using boundary condition and symmetry of local damage variable, etc. The results show that dynamic shear softening modulus, dynamic shear strength and shear elastic modulus influence the distribution of the localized damage in shear band. Internal length of ductile metal only governs the thickness of shear band. In the strain-softening region of shear band, the local damage variable along shear band’s tangential and normal directions is non-linear and highly non-uniform. The non-uniformities in the normal and tangential directions of shear band stem from the interactions and interplaying among microstructures and the non-uniform distribution of shear stress, respectively. At the tail of the strain-softening region, the maximum value of local damage variable reaches 1. This means that material at this position fractures completely. At the tip of shear band and upper as well as lower boundaries, no damage occurs. Local damage variable increases as dynamic shear softening modulus decreases or shear elastic modulus increases, leading to difficulty in identification or detection of damage for less ductile metal material at higher strain rates.展开更多
为解决6061-T6铝合金焊后热影响区软化导致力学性能下降的问题,基于焊接接头余高大变形强化过时效软化区的思想,采用双轧辊系统对6061-T6薄板铝合金直流双脉冲熔化极气体保护焊(DC double pulse metal inert gas welding,DP-MIG焊)接头...为解决6061-T6铝合金焊后热影响区软化导致力学性能下降的问题,基于焊接接头余高大变形强化过时效软化区的思想,采用双轧辊系统对6061-T6薄板铝合金直流双脉冲熔化极气体保护焊(DC double pulse metal inert gas welding,DP-MIG焊)接头进行同步双面轧制,并分析了焊轧复合成形接头组织与力学性能.结果表明,焊缝晶粒受到竖直方向的轧制力发生大塑性变形,内部气孔消失,焊缝区域变宽,邻近焊缝的热影响区受到来自焊缝的挤压力发生协同宏观变形,远离焊缝的过时效软化区组织受到来自焊缝处的压应力,从沿垂直焊缝方向产生部分协同形变强化;接头的硬度明显提升,过时效软化区的硬度由60~70 HV提升至80~90 HV,过时效软化区的拉伸性能也有所提升,当焊接速度为800 mm/min时,抗拉强度最佳可达到母材的83.6%,相较于焊接接头提升19.4%,进而实现了对过时效软化区的强化效果.展开更多
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.
基金Project(2004F052) supported by the Educational Department of Liaoning Province, China
文摘Distribution of localized damage in shear band can’ t be predicted theoretically based on classical elastoplastic theory. The average damage variable in shear band was considered to be a non-local variable. Based on non-local theory, an analytical expression for the localized damage in strain-softening region of shear band in the process of shear band propagation was presented using boundary condition and symmetry of local damage variable, etc. The results show that dynamic shear softening modulus, dynamic shear strength and shear elastic modulus influence the distribution of the localized damage in shear band. Internal length of ductile metal only governs the thickness of shear band. In the strain-softening region of shear band, the local damage variable along shear band’s tangential and normal directions is non-linear and highly non-uniform. The non-uniformities in the normal and tangential directions of shear band stem from the interactions and interplaying among microstructures and the non-uniform distribution of shear stress, respectively. At the tail of the strain-softening region, the maximum value of local damage variable reaches 1. This means that material at this position fractures completely. At the tip of shear band and upper as well as lower boundaries, no damage occurs. Local damage variable increases as dynamic shear softening modulus decreases or shear elastic modulus increases, leading to difficulty in identification or detection of damage for less ductile metal material at higher strain rates.
文摘为解决6061-T6铝合金焊后热影响区软化导致力学性能下降的问题,基于焊接接头余高大变形强化过时效软化区的思想,采用双轧辊系统对6061-T6薄板铝合金直流双脉冲熔化极气体保护焊(DC double pulse metal inert gas welding,DP-MIG焊)接头进行同步双面轧制,并分析了焊轧复合成形接头组织与力学性能.结果表明,焊缝晶粒受到竖直方向的轧制力发生大塑性变形,内部气孔消失,焊缝区域变宽,邻近焊缝的热影响区受到来自焊缝的挤压力发生协同宏观变形,远离焊缝的过时效软化区组织受到来自焊缝处的压应力,从沿垂直焊缝方向产生部分协同形变强化;接头的硬度明显提升,过时效软化区的硬度由60~70 HV提升至80~90 HV,过时效软化区的拉伸性能也有所提升,当焊接速度为800 mm/min时,抗拉强度最佳可达到母材的83.6%,相较于焊接接头提升19.4%,进而实现了对过时效软化区的强化效果.
