Pre-welding preparation of spiral welded pipe (also called as SSAW steel pipe): submerged arc welding must be prepared before welding, including the weld groove processing, to be welded parts of the surface cleaning, welding parts and welding wire surface cleaning, flux drying and so on.
1. Groove processing
Bevel processing requirements according to GB 986-1988 implementation, to ensure that the root of the weld does not appear not penetrated or slag, and reduce the amount of filler metal. The groove can be processed using planing machine, mechanized or semi-mechanized gas cutting machine, carbon arc gouging and so on.
2. Cleaning up the parts to be welded
Weldment cleaning is mainly to remove the corrosion, oil and water, to prevent the generation of stomata. Generally with sandblasting, shot peening method or manual removal, if necessary, with flame baking to be welded parts. Before welding should be groove and groove on both sides of the 20mm area and the surface to be welded parts of the rust, oxide, oil and other clean up.
3. Welding parts assembly
Assembly welding to ensure that the gap is uniform, high and low formation, the wrong amount of small, the length of the weld is generally greater than 30mm, and positioning the quality of the weld quality consistent with the main weld. If necessary, the use of special tooling, fixtures.
For the assembly of the straight seam weldment, the arc plate and the lead plate shall be fitted at both ends of the weld and shall be cut off after welding. The purpose is to obtain the weld section of the normal size at the beginning and the end of the welded joint, Can remove the arc and finish prone to defects.
4. Cleaning of welding materials
The welding wire and flux for submerged arc welding have a great influence on the composition, organization and performance of weld metal. So the welding must be removed before the surface of the wire oxide, rust and oil and so on. Flux preservation should pay attention to moisture, must be used before the required temperature drying stand.