Submerged arc welding (including submerged arc surfacing and electroslag surfacing, etc.) is a method in which the arc burns under the flux layer for welding. Its inherent advantages such as stable welding quality, high welding productivity, no arc light and little smoke make it the main welding method in the manufacture of important steel structures such as pressure vessels, pipe section manufacturing (mainly SSAW pipes and LSAW pipes), and box-shaped beams and columns.
Preparation before welding: submerged arc welding must be prepared before welding, including the groove processing of the weldment, the surface cleaning of the part to be welded, the assembly of the weldment, the cleaning of the welding wire surface, and the drying of the flux.
① Groove processing
Groove processing requirements should be followed to ensure that there is no incomplete penetration or slag inclusion at the root of the weld, and to reduce the amount of filler metal. Groove processing can use planer, mechanized or semi-mechanized gas cutting machine, carbon arc gouging, etc.
②Cleaning of parts to be welded
Steel pipe cleaning is mainly to remove rust, oil and moisture, and prevent the generation of pores. Generally, it is removed by sand blasting, shot blasting or manual removal, and if necessary, the parts to be welded are baked with flames. Before welding, the surface rust, scale, oil, etc. on the surface of the groove and the 20mm area on both sides of the groove and the parts to be welded should be cleaned.
③Assembly of weldments
When assembling the weldment, it is necessary to ensure that the gap is uniform, the height is flat, and the amount of misalignment is small. The length of the tack weld is generally greater than 30mm, and the quality of the tack weld is consistent with the quality requirements of the main weld. Use special tooling and fixtures when necessary.
For the assembly of straight seam steel pipes, arc-starting plates and lead-out plates should be installed at both ends of the weld, and cut off after welding. Its purpose is to obtain a weld section of normal size at the beginning and end of the welded joint, and to remove defects that tend to occur at the start and end of the arc.
④Cleaning of welding materials
The welding wire and flux used in submerged arc welding have a great influence on the composition, structure and properties of the weld metal. Therefore, the scale, rust and oil stains on the surface of the welding wire must be removed before welding. Pay attention to moisture-proof when storing flux, and dry it according to the specified temperature before use.
Preparation before welding: submerged arc welding must be prepared before welding, including the groove processing of the weldment, the surface cleaning of the part to be welded, the assembly of the weldment, the cleaning of the welding wire surface, and the drying of the flux.
① Groove processing
Groove processing requirements should be followed to ensure that there is no incomplete penetration or slag inclusion at the root of the weld, and to reduce the amount of filler metal. Groove processing can use planer, mechanized or semi-mechanized gas cutting machine, carbon arc gouging, etc.
②Cleaning of parts to be welded
Steel pipe cleaning is mainly to remove rust, oil and moisture, and prevent the generation of pores. Generally, it is removed by sand blasting, shot blasting or manual removal, and if necessary, the parts to be welded are baked with flames. Before welding, the surface rust, scale, oil, etc. on the surface of the groove and the 20mm area on both sides of the groove and the parts to be welded should be cleaned.
③Assembly of weldments
When assembling the weldment, it is necessary to ensure that the gap is uniform, the height is flat, and the amount of misalignment is small. The length of the tack weld is generally greater than 30mm, and the quality of the tack weld is consistent with the quality requirements of the main weld. Use special tooling and fixtures when necessary.
For the assembly of straight seam steel pipes, arc-starting plates and lead-out plates should be installed at both ends of the weld, and cut off after welding. Its purpose is to obtain a weld section of normal size at the beginning and end of the welded joint, and to remove defects that tend to occur at the start and end of the arc.
④Cleaning of welding materials
The welding wire and flux used in submerged arc welding have a great influence on the composition, structure and properties of the weld metal. Therefore, the scale, rust and oil stains on the surface of the welding wire must be removed before welding. Pay attention to moisture-proof when storing flux, and dry it according to the specified temperature before use.
