22万m^(3) LNG储罐铝吊顶焊接质量控制

Quality Control of Aluminum Ceilings Welding for LNG Storage Tanks

LNG储罐罐体吊顶铝板焊接容易出现变形、气孔、裂纹、未焊透等缺陷,尤其是第十三圈加强筋与吊顶底板的角焊缝处。针对22万m^(3) LNG储罐铝吊顶的设计结构,详细阐述了铝吊顶焊接过程质量控制要点:采用氩气保护的非熔化极气体保护焊,引弧、收弧应提前送气,收弧后继续送气,防止熔融金属氧化,同时避开在同一部位重复起弧;当焊接电流为160~170 A,焊接速度38~40 cm/min,填丝速度38~40 cm/min,保护气体流量20~25 L/min时,铝吊顶焊缝成形较好;搭接位置至少焊2道,采用分段退焊或对称焊接法,适当增加焊道两侧承重,以达到控制焊接变形的目的。并从“人、机、料、法、环”等方面对铝吊顶焊接质量控制措施进行了优化。

Defects such as deformation,porosity,cracks,incomplete penetration,etc.are easy to occur in the welding of aluminum plate on the ceiling of LNG storage tank.Especially the fillet weld between the thirteenth ring stiffener and the ceiling bottom plate.According to the design structure of the aluminum ceiling of 220000 m^(3) LNG storage tank,the key points of quality control in the welding process of the aluminum ceiling are elaborated in detail:using argon gas shielded metal arc welding,the gas should be supplied in advance when starting and closing the arc,and continue to supply gas after closing the arc to prevent the molten metal from oxidation and avoid repeated arc starting at the same time;When the welding current is 160~170 A and the welding speed is 38~40 cm/min.When the wire filling speed is 38~40 cm/min and the shielding gas flow rate is 20~25 L/min,the weld of aluminum ceiling is well formed.At least two passes shall be welded at the overlapping position,and the sectional withdrawal welding or symmetrical welding method shall be adopted,and the load bearing on both sides of the pass shall be appropriately increased to achieve the purpose of controlling welding deformation.The quality control measures of aluminum ceiling welding are optimized from the aspects of"man,machine,material,method and environment".