In recent years, with the continuous expansion of pipeline installation projects, the gap of excellent welders is relatively large. In addition, the manual welder training cycle is long and the cost is high, and the use of automatic pipeline welding can reduce the number of welders, reduce construction costs, and the automatic welder training cycle is short, the technology is stable, and the influence of external factors is small.
Selection and introduction of pipeline prefabrication automatic welding process
(1) Automatic GMAW welding.
The arc heat of automatic GMAW welding is concentrated and the melting depth is relatively deep. And the welding efficiency is high, the welding deformation is small, and the weld metal with low hydrogen content can be obtained. However, the mechanical properties of welded joints with this process are slightly poor, and there are design documents that restrict the use of GMAW process.
(2) Submerged arc welding.
Submerged arc welding has high arc penetration capacity and welding wire deposition efficiency, and has the advantages of high weld quality, good working conditions and high production efficiency.
However, submerged arc welding can not be used in pipeline welding because of its limited role in pipeline welding.
(3) Automatic TIG welding.
TIG welding can weld almost all metals, good welding process performance, open arc, can observe arc and molten pool, and arc combustion stability, no splash, no slag and polishing after welding, beautiful weld shape; It can realize the all-position welding and is the ideal welding method to realize the forming of single side welding back.
But the welding depth of TIG welding is shallow, the melting speed is slow, and the welding productivity is low. Tungsten electrode current carrying capacity is limited, too large welding current will cause tungsten electrode melting and evaporation, its particles may enter the weld pool, resulting in weld metal pollution.
Through the comparison of the above welding methods, the process and mechanical properties of automatic TIG welding are better, and the process design concept of pipeline welding supports the use of TIG welding, so we choose automatic TIG welding for pipeline prefabrication. With the further maturity of technology, we will gradually study the automatic TIG welding base + submerged arc welding filler surface welding method for pipeline prefabrication.
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