All-position gas shielded flux-cored wire downward semi-automatic welding method for long-distance pipeline

Abstract

The invention provides an all-position gas shielded flux-cored wire downward semi-automatic welding method for a long-distance pipeline. The all-position gas shielded flux-cored wire downward semi-automatic welding method comprises the steps of performing groove machining and alignment on the long-distance pipeline, and then welding the pipeline by adopting a multi-layer multi-pass welding manner, wherein tungsten inert gas welding is adopted for a root welding layer; gas shielded flux-cored wire downward semi-automatic welding is adopted for a hot welding layer, a filling welding layer and a cosmetic welding layer; pure CO2 is used as a shielding gas for gas shielded flux-cored wire downward semi-automatic welding; an alkaline flux-cored wire is used as a welding material; the welding direction is downward welding; direct current straight polarity is used; the welding current is 110-170A; the welding voltage is 16-20V; welding positions comprise straight sections and mountainous area sections; the diameter range of the long-distance pipeline is more than 300 mm; and the wall thickness range of the long-distance pipeline is more than 8 mm. The all-position gas shielded flux-cored wire downward semi-automatic welding method for the long-distance pipeline is capable of improving the welding efficiency and the welding seam toughness, and is suitable for all-position, all-terrain and multiple-groove-type long-distance pipeline welding.

Description

technical field [0001] The invention relates to the technical field of pipeline welding, in particular to a downward semi-automatic welding method for all positions of long-distance pipelines with gas-shielded flux-cored wires. Background technique [0002] With the continuous development of the petroleum industry, pipeline transportation of oil and gas has developed rapidly due to its safety, economy, efficiency, and environmental protection. The welding quality of pipelines is particularly important as the basis and basis for ensuring its safe operation. In the construction of long-distance pipelines, the welding process used in the on-site welding of pipelines has gradually moved from the traditional manual downward welding process to semi-automatic and fully automatic. However, due to the limitations of many factors such as terrain factors and economic costs, the development of fully automatic welding is relatively slow, and it can only be partially tested in pipeline pr...

AI Technical Summary

Problems solved by technology

[0005] However, regardless of self-shielded semi-automatic welding or gas-shielded semi-automatic welding, in order to ensure welding operability, acidic flux-cored wire with rutile as the main flux core component is used. Hydrogen, and there are more non-metallic inclusions remaining in the weld metal, resulting in unstable and low toughness of the weld, and a relatively large risk of cracking

Moreover, the acidic flux-cored wire can only be welded upwards in the way of DC reverse connection, using mixed gas as the shielding gas, the welding speed is slow, and the welding heat input is high, which will easily lead to a decrease in the impact toughness of the weld

Images