LNG用奥氏体不锈钢NBG-GTAW接头微观组织与力学性能

Microstructure and mechanical properties of NBG-GTAW joints of austenitic stainless steel for liquefied natural gas

  • 摘要:
    目的 为了提高大型液化天然气(LNG)建造项目中奥氏体不锈钢管焊接时钢管背面的保护效果,提出了一种采用背衬垫的工艺方案提高焊接生产效率。
    方法 文中针对设计服役温度为−196 ℃的ASTM A358 304L奥氏体不锈钢管,摒弃管内充盈惰性保护气体的钨极氩弧焊接(GTAW)工艺方案,采用在管道内壁粘贴玻璃纤维背衬带进行无背面保护气体GTAW(NBG-GTAW)周向环缝焊接试验,极大提高焊接生产效率。
    结果 视觉检测、无损探伤、微观组织、力学性能和铁素体含量的检测和分析结果表明,焊缝正面成形优良且余高合适,焊缝背面未产生氧化且熔透充分,未发现明显焊接缺陷;且焊接接头具有良好的抗拉强度、抗低温冲击韧性和抗晶间腐蚀能力,充分满足LNG项目的严苛要求。
    结论 NBG-GTAW工艺方案可广泛应用于在超低温环境服役的LNG建造项目中奥氏体不锈钢管的焊接。

     

    Abstract: Objective In order to improve back shielding effect of welding austenitic stainless steel pipe in large-scale liquefied natural gas project, a technology scheme using back liner is proposed to improve welding production efficiency. Methods In this paper, for ASTM A358 304L austenitic stainless steel pipe at a designed service temperature of −196 ℃, GTAW process scheme filled with inert shielding gas in the pipe is abandoned, and circumferential welding test of GTAW with no backing gas (NBG-GTAW) is carried out by pasting glass fiber weld backing tape on the inner wall of the pipe, which greatly improves welding production efficiency. Results The detection and analysis results of visual inspection, nondestructive testing, microstructure, mechanical properties and ferritic content show that morphology of welded joints is well and reinforcement height is appropriate, back of weld is not oxidized and penetration depth is sufficient, and no obvious welding defects is found. In addition, welded joints have good tensile strength, low temperature impact toughness and intergranular corrosion resistance, which fully meets the strict requirements of LNG projects. Conclusion NBG-GTAW process can be widely used for welding of austenitic stainless steel pipes in LNG construction projects servicing in ultra-low temperature environment.

     

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