The inclusions evolution behavior in the continuous casting slab, rolled plates, and simulated welding samples of EH36 steels with and without Zr addition has been systematically investigated. The inclusions in plain ...The inclusions evolution behavior in the continuous casting slab, rolled plates, and simulated welding samples of EH36 steels with and without Zr addition has been systematically investigated. The inclusions in plain EH36 steel are almost composed of Al-Ca-S-O（-Mn） and undergo negligible changes during the whole process. With Zr addition, a large amount of individually fine MnS precipitates and Zr-containing inclusions are generated. In the rolled EH36-Zr sample, Zr-containing complex inclusions are effective to promote the nucleation of acicular ferrite on the surface, which are hardly found in the simulated welding sample of EH36-Zr steel due to the segregation of soluble Ti and Zr on the grain boundary.展开更多
镁处理可以大幅提高船板钢的大线能量焊接性。钢中加入镁一方面可以实现夹杂物的细化,提高了夹杂物对IAF诱发的概率;另一方面镁可以增强钢中第二相粒子的高温稳定性,有效抑制了大线能量输入下HAZ原奥氏体晶粒的粗化。其中钢中第二相粒...镁处理可以大幅提高船板钢的大线能量焊接性。钢中加入镁一方面可以实现夹杂物的细化,提高了夹杂物对IAF诱发的概率;另一方面镁可以增强钢中第二相粒子的高温稳定性,有效抑制了大线能量输入下HAZ原奥氏体晶粒的粗化。其中钢中第二相粒子稳定的钉扎作用是镁氧化物冶金作用实现的关键,但相关领域的研究,特别是镁对钉扎粒子的影响机制还有待进一步深入。为此从不同焊接线能量的热模拟试验出发,系统分析了焊接线能量对钉扎粒子构成的影响,并结合粒子析出和MgO生成热力学、化合物晶体学关系和钢中元素的扩散行为等进行分析和讨论,以期确定镁对钢中钉扎粒子的影响机制。研究结果表明,对于镁处理船体钢,当焊接线能量超过200 k J/cm时,钢中的钉扎粒子会出现部分解钉失效的现象。而随着焊接线能量的增大,HAZ中的钉扎粒子尺寸经历了先减小后增大的变化过程,并且焊接线能量越大,大尺寸的TiN粒子越多。此时的钉扎粒子多为以TiN-MgO-Al_(2)O_(3)为基体、表层附着部分含Nb C的复合粒子。粒子析出热力学、MgO生成热力学、粒子析出错配度关系和钢中元素扩散系数分析结果表明,由于MgO生成和TiN析出的温度区间较为接近,且两者为共格析出,在长时间的高温作用下会生成MgO-TiN复合析出物,使钢中第二相粒子的高温稳定性大幅增强。基于焊接热模拟试验和理论分析结果可以看出,钢液经过镁处理后,在连铸和大线能量焊接过程中均有可能生成高温稳定的MgO-TiN-Al_(2)O_(3)复合粒子。但对于试验钢,钢中MgO的量远低于TiN析出量,TiN的溶解势必会影响钢中第二相粒子的钉扎效果,因此,提高钢中镁含量是提高镁处理船体钢大线能量焊接性的关键。展开更多
Fused CaF_(2)-TiO_(2) fluxes have been designed,prepared,and applied in the flux cored wires to join EH36 shipbuilding steels under high heat input electro-gas welding.Ensuing microstructural evolution in the weld met...Fused CaF_(2)-TiO_(2) fluxes have been designed,prepared,and applied in the flux cored wires to join EH36 shipbuilding steels under high heat input electro-gas welding.Ensuing microstructural evolution in the weld metals subjected to varied CaF_(2)-TiO_(2) flux cored wires has been fully documented.It has been demonstrated that as the content of TiO2 in the fused fluxes increases,columnar grain size increases,and major constituents in the weld metal change from lath bainite,to granular bainite,and then to acicular ferrite.Such phenomena are elucidated via salient chemical reactions involving oxygen pickup and concurrent titanium transfer.展开更多
Fused ternary CaF_(2)–SiO_(2)–MnO fluxes have been manufactured and applied to join EH36 shipbuilding steel under high heat input submerged arc welding.Five fluxes have been designed to clarify the effect of MnO con...Fused ternary CaF_(2)–SiO_(2)–MnO fluxes have been manufactured and applied to join EH36 shipbuilding steel under high heat input submerged arc welding.Five fluxes have been designed to clarify the effect of MnO content in CaF_(2)–SiO_(2)–MnO flux on the impact toughness of the weld metal,with the added amount of MnO from 10 to 50 wt.%at the expense of CaF_(2).With the increase in MnO content,the Charpy impact energy increases first and then decreases,experiencing a maximum value at 30 wt.%MnO.Microstructure of the weld metals has also been studied to account for impact toughness variations.It has been demonstrated that the highest acicular ferrite volume fraction in the weld metal is achieved at 30 wt.%MnO,which is concurrent to the maximum value of Charpy impact energy.It is believed that the Mn and O content variations in the weld metal contribute synergistically to such an interesting phenomenon.展开更多
Submerged arc welding process has been simulated to investigate the molten pool features of EH36 shipbuilding steel.One case only involved the surface tension model,and another one involved both the surface tension mo...Submerged arc welding process has been simulated to investigate the molten pool features of EH36 shipbuilding steel.One case only involved the surface tension model,and another one involved both the surface tension model and the interface tension model.The role of interface tension during welding is revealed,and the evolution of molten pool morphology is understood by comparing the surface temperature distribution,surface tension and interface tension distribution,and the streamline of the molten pool for the two cases.When the interface tension model is disregarded,a flow conducive to the outward expansion is formed in the surface area of the molten pool,resulting in a small weld depth-to-width ratio.After applying the interface tension model,the expanding outward flow is restrained,which leads to a deep penetration morphology with a large weld depth-to-width ratio due to the inward flow governed by the Marangoni forces.The simulation results involving the interface tension model have been verified with satisfactory predictability.展开更多
文摘The inclusions evolution behavior in the continuous casting slab, rolled plates, and simulated welding samples of EH36 steels with and without Zr addition has been systematically investigated. The inclusions in plain EH36 steel are almost composed of Al-Ca-S-O（-Mn） and undergo negligible changes during the whole process. With Zr addition, a large amount of individually fine MnS precipitates and Zr-containing inclusions are generated. In the rolled EH36-Zr sample, Zr-containing complex inclusions are effective to promote the nucleation of acicular ferrite on the surface, which are hardly found in the simulated welding sample of EH36-Zr steel due to the segregation of soluble Ti and Zr on the grain boundary.
文摘镁处理可以大幅提高船板钢的大线能量焊接性。钢中加入镁一方面可以实现夹杂物的细化,提高了夹杂物对IAF诱发的概率;另一方面镁可以增强钢中第二相粒子的高温稳定性,有效抑制了大线能量输入下HAZ原奥氏体晶粒的粗化。其中钢中第二相粒子稳定的钉扎作用是镁氧化物冶金作用实现的关键,但相关领域的研究,特别是镁对钉扎粒子的影响机制还有待进一步深入。为此从不同焊接线能量的热模拟试验出发,系统分析了焊接线能量对钉扎粒子构成的影响,并结合粒子析出和MgO生成热力学、化合物晶体学关系和钢中元素的扩散行为等进行分析和讨论,以期确定镁对钢中钉扎粒子的影响机制。研究结果表明,对于镁处理船体钢,当焊接线能量超过200 k J/cm时,钢中的钉扎粒子会出现部分解钉失效的现象。而随着焊接线能量的增大,HAZ中的钉扎粒子尺寸经历了先减小后增大的变化过程,并且焊接线能量越大,大尺寸的TiN粒子越多。此时的钉扎粒子多为以TiN-MgO-Al_(2)O_(3)为基体、表层附着部分含Nb C的复合粒子。粒子析出热力学、MgO生成热力学、粒子析出错配度关系和钢中元素扩散系数分析结果表明,由于MgO生成和TiN析出的温度区间较为接近,且两者为共格析出,在长时间的高温作用下会生成MgO-TiN复合析出物,使钢中第二相粒子的高温稳定性大幅增强。基于焊接热模拟试验和理论分析结果可以看出,钢液经过镁处理后,在连铸和大线能量焊接过程中均有可能生成高温稳定的MgO-TiN-Al_(2)O_(3)复合粒子。但对于试验钢,钢中MgO的量远低于TiN析出量,TiN的溶解势必会影响钢中第二相粒子的钉扎效果,因此,提高钢中镁含量是提高镁处理船体钢大线能量焊接性的关键。
基金support from the National Natural Science Foundation of China (Grant Nos.U20A20277,52050410341,52011530180,and 52150610494)Royal Academy of Engineering (TSPC1070)+3 种基金ResearchFund for Central Universities (Grant Nos.N2025025 and N2125016)Regional Innovation Joint Fund of Liaoning Province (2020-YKLH-39)Open Projectof State Key Laboratoryof Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University (SKLASS 2020-09)the Science and Technology Commission of ShanghaiMunicipality (No.19DZ2270200).
文摘Fused CaF_(2)-TiO_(2) fluxes have been designed,prepared,and applied in the flux cored wires to join EH36 shipbuilding steels under high heat input electro-gas welding.Ensuing microstructural evolution in the weld metals subjected to varied CaF_(2)-TiO_(2) flux cored wires has been fully documented.It has been demonstrated that as the content of TiO2 in the fused fluxes increases,columnar grain size increases,and major constituents in the weld metal change from lath bainite,to granular bainite,and then to acicular ferrite.Such phenomena are elucidated via salient chemical reactions involving oxygen pickup and concurrent titanium transfer.
基金The authors sincerely thank the State Key Laboratory of Refractories and Metallurgy(Grant No.G202206)National Natural Science Foundation of China(Grant Nos.U20A20277 and 52150610494)National Key Research and Development Program of China(Grant No.2022YFE0123300).
文摘Fused ternary CaF_(2)–SiO_(2)–MnO fluxes have been manufactured and applied to join EH36 shipbuilding steel under high heat input submerged arc welding.Five fluxes have been designed to clarify the effect of MnO content in CaF_(2)–SiO_(2)–MnO flux on the impact toughness of the weld metal,with the added amount of MnO from 10 to 50 wt.%at the expense of CaF_(2).With the increase in MnO content,the Charpy impact energy increases first and then decreases,experiencing a maximum value at 30 wt.%MnO.Microstructure of the weld metals has also been studied to account for impact toughness variations.It has been demonstrated that the highest acicular ferrite volume fraction in the weld metal is achieved at 30 wt.%MnO,which is concurrent to the maximum value of Charpy impact energy.It is believed that the Mn and O content variations in the weld metal contribute synergistically to such an interesting phenomenon.
基金The authors sincerely thank the National Natural Science Foundation of China(Grant Nos.U20A20277,52150610494,52104295,52011530180 and 52050410341)Research Fund for Central Universities(Grant Nos.N2125016 and N2025025)Young Elite Scientists Sponsorship Program by CAST(YESS)(Grant No.2021-2023QNRC001).
文摘Submerged arc welding process has been simulated to investigate the molten pool features of EH36 shipbuilding steel.One case only involved the surface tension model,and another one involved both the surface tension model and the interface tension model.The role of interface tension during welding is revealed,and the evolution of molten pool morphology is understood by comparing the surface temperature distribution,surface tension and interface tension distribution,and the streamline of the molten pool for the two cases.When the interface tension model is disregarded,a flow conducive to the outward expansion is formed in the surface area of the molten pool,resulting in a small weld depth-to-width ratio.After applying the interface tension model,the expanding outward flow is restrained,which leads to a deep penetration morphology with a large weld depth-to-width ratio due to the inward flow governed by the Marangoni forces.The simulation results involving the interface tension model have been verified with satisfactory predictability.
