高强度海洋工程用钢水下固相摩擦焊组织演变及韧化机制研究

Focusing on high strength marine steels and combining with currently advanced underwater friction hydro pillar processing(FHPP) technology, we investigate the application fundamental issues of welding metallurgical processes,microstructure evolution and thoughening technologies during the underwater solid-state friction welding processing:the features of friction thermal source and heat input for underwater solid-state friction welding processes, the varying laws of friction thermal-mechanical coupling processes and welding thermal cycles; the interactive and influencing rules among the thermal-palstic flowing in welds,the severely strain rates,the water forced cooling rates and deformative strengthening; the solid-state diffusive bonding mechanism between welds and base metal, the metallurgical features between friction interfaces and surfaces and the evolutive mechanism of welded defects; the representations of welds and heat affected zone inhomogeneous microstructures, the metallurgical features and evolutive laws of base metal and welded microstructures; the interactive laws among welding parameters, the alloying components of welds and base metals and heat treatment conditions; the evolutive laws of microhardness profiles, mechanical properties and fracture toughness in weld region, the cracking sensitivity of weld region and the fracture modes failure mechanism; the controlled and modified methods for the microstructures of weld region, the influences of inherent factors and mechanisms on the strength and toughness for underwater solid-state friction welded joints,and the metallurgical and technological methods of controlling and improving the strength and toughness of underwater solid-state friction welded joints. These resarches would provide the important foundation to establish the physical and metallurgical fundamental theory of underwater solid-state friction joining and processing, and effectively promote the industrical applications of the underwater solid-state friction welding technologies for the high strength steels used in marine engineering.

针对高强度海洋工程用钢结合目前先进水下等静压摩擦柱塞焊(FHPP)工艺过程,研究水下固相摩擦焊接冶金过程、组织演变及韧化的应用基础问题：水下固相摩擦焊过程中摩擦热源及热输入特征、摩擦热-力耦合过程及焊接热循环变化规律；焊缝热塑性流动、应变速率、水冷速率及形变强化之间相互影响机制；焊缝与母材固相扩散连接机制、界面冶金特征及焊接缺陷形成机制；焊缝区及热影响区非均质组织表征、焊缝与母材焊接组织冶金特征及演变规律；焊接工艺参数、焊缝及母材合金成分与热处理状态的相互影响规律；焊接区显微硬度、力学性能及断裂韧度的演变规律，焊接区裂纹敏感性、断裂模式及失效机制；焊接区微观组织改性与控制、影响水下固相摩擦焊接头强度和韧性的内在因素及机制、控制与改善焊接接头强韧性的冶金和工艺措施。研究结果为建立水下固相摩擦连接加工物理冶金基础理论、有效促进水下固相摩擦焊接技术在海洋工程中工业化应用提供重要基础。

针对高强度海洋工程用钢结合目前先进水下等静压摩擦柱塞焊(FHPP)工艺过程，研究水下固相摩擦焊接冶金过程、组织演变及韧化的应用基础问题：水下固相摩擦焊过程中摩擦热源及热输入特征、摩擦热-力耦合过程及焊接热循环变化规律；焊缝热塑性流动、应变速率、水冷速率及形变强化之间相互影响机制；焊缝与母材固相扩散连接机制、界面冶金特征及焊接缺陷形成机制；焊缝区及热影响区非均质组织表征、焊缝与母材焊接组织冶金特征及演变规律；焊接工艺参数、焊缝及母材合金成分与热处理状态的相互影响规律；焊接区显微硬度、力学性能及断裂韧度的演变规律，焊接区裂纹敏感性、断裂模式及失效机制；焊接区微观组织改性与控制、影响水下固相摩擦焊接头强度和韧性的内在因素及机制、控制与改善焊接接头强韧性的冶金和工艺措施。通过项目研究开发出国内最大功率的水下等静压摩擦柱塞焊(FHPP)装备及试验平台，在该平台上可实现摩擦柱塞焊、摩擦塞补焊机摩擦堆焊多种摩擦焊原理试验研究，针对海洋工程用高强钢获得FHPP焊接工艺窗口范围，积累大量FHPP焊缝区域组织特征、力学性能及断裂韧性原始数据并证实其焊接接头具有良好综合性能，提出的“开放式”、“半开放式”及“封闭式”摩擦焊工艺过程为评价摩擦焊接工艺原理的优势及局限性提供新概念。。研究结果为建立水下固相摩擦连接加工物理冶金基础理论、促进水下固相摩擦焊接技术在海洋工程中工业化应用提供重要基础。