采用传统闪光焊接780MPa级海洋软管铠装层用钢时，因接头高强度马氏体的氢陷阱特性及较差裂纹止裂性，导致接头易出现硫化物应力腐蚀开裂(SSCC)，而闪光焊调控接头冶金行为能力受限。预研表明，激光-MAG复合焊接该钢时，通过熔池中引入含Ti粒子可在接头中获得具有良好强韧性和抗SSCC性的针状铁素体(AF)，形成AF-马氏体复相组织，以调控氢陷阱分布及裂纹扩展。本项目提出将激光-MAG复合焊接用于该钢焊接，研究Ti粒子含量及工艺参数对组织性能影响，探明含Ti粒子及AF调控机制；研究接头裂纹扩展与微区材料特性对应关系，构建AF含量与抗SSCC性之间的关系；分析氢渗透和充氢应力腐蚀断裂行为，明确H原子-接头交互作用过程；研究氢扩散和裂纹扩展行为，提出最优Ti含量及焊接工艺参数。项目研究成果将揭示AF-马氏体复相组织抗SSCC机制，为实现高强度海洋软管铠装层用钢的高效优质焊接提供科学依据和技术方向。

The welded joint fabricated by traditional flash welding of armor layer steel with 780 MPa strength of flexible pipe suffers from sulfide stress corrosion cracking (SSCC) because of the hydrogen traps characterization and poor resistance to cracking of high strength martensite. However, the control ability of changing metallurgy behavior of flash welding is limited. The advanced study indicates that the acicular ferrite (AF) with excellent strength and toughness and resistance to SSCC is obtained through the Ti containing particles in pool when laser-MAG hydride welding is used. Then, the complex microstructure of AF and martensite is formed to control hydrogen trap distribution and cracking propagation. Therefore, this project proposes the assumption that laser-MAG hydride welding is used to weld armor layer steel. This project aims at the effect of Ti containing particle content and process parameter on microstructure and mechanical property and exploring the controlling mechanism of Ti containing particles and AF. This project studies the relative relationship of cracking propagation and micro-zone material characterization to building the relation between AF content and SSCC. The behavior of hydrogen permeation charged stress corrosion cracking is analyzed to clarify the interaction process of H atom and welded joint. This project also studies the behavior of hydrogen diffusion and cracking propagation. Furthermore, the optimal Ti content and welding process parameters are proposed. The research achievement of this project will reveal the SSCC mechanism of complex microstructure of AF and martensite. The project will also provide the scientific fundament and technology direction of the welding process with high efficiency and quality of armor layer steel flexible pipe.