摘要
Abstract
Objective This study aims to investigate the welding thermal deformation mechanism of the outer tank wall plates of large-scale LNG double-metal full-containment tanks,which are made of S30408 austenitic stainless steel and prone to deformation during welding due to material properties,and to establish a comprehensive control technology system to mitigate deformation,thereby ensuring tank geometric accuracy and structural safety.Method In the second phase of the Datong LNG Peaking Regulating,Reserve and Distribution Center project,a 30 000 m3 double-metal full-containment LNG tank(outer shell:S30408 stainless steel)was used as an engineering case.By combining materials science theory with engineering practice,the influence of S30408's low thermal conductivity,high coefficient of linear expansion,and lack of phase transformation on welding deformation was analyzed.The construction technology based on the hydraulic lifting inverted erection method,the low-heat-input multi-layer and multi-pass welding procedure,the symmetrical segmented back-step welding sequence,as well as anti-deformation measures such as rigid fixing and reverse deformation was also described.The control effectiveness was verified by on-site measurement data.Result Control of welding parameters matching the characteristics of S30408(e.g.,welding heat input of 8-15 kJ/cm)effectively suppressed the width of the heat-affected zone and welding deformation.After application of the control technology system,the one-time welding qualification rate of the outer tank wall plate reached 98.9%,the ovality of the wall plate was controlled to≤35 mm(better than the D/200 requirement of 50 mm specified in API 620-2022),and the verticality deviation was≤28 mm.The differences in the core control factors for welding deformation between stainless steel outer tanks and carbon steel tanks were also clarified.Conclusion For the S30408 outer tank wall plate,welding deformation can be effectively controlled by adopting a low-heat-input welding process that matches the material characteristics,combined with refined construction organization and whole-process monitoring.This technology system ensures the construction quality of the full-containment tank and provides a technical reference for similar large-scale stainless steel storage tank projects.关键词
LNG全容储罐/S30408不锈钢/外罐壁板/焊接变形/低热输入焊接/倒装法Key words
LNG full containment tank/S30408 stainless steel/outer tank wall platewall plate/welding deformation/low heat input welding/top-down erection
