Liner stainless steel compound steel pipe welding process
Publish Time: 2016-09-14 Origin: Site
Liner stainless steel compound steel pipe (304 + Q235B) is a new kind of composite pipe material, corrosion resistance, high temperature resistant, high extensibility, high strength etc., are widely used in the new construction and expansion of process pipeline of petrochemical plant.The pipe material the use of the biggest problem is that at the grass-roots level and composite layer of fusion welding problem completely.To get good welding effect, the correct welding method is:
1, welding preparation
Before welding will contact layer of paint, clean up dirt and oxide layer, so as to avoid the welding process impurities heat will decompose into H2O and CO2.
Even before welding to preheat at the grass-roots level and composite layer.Preheat the electrical heating method, with the center line of the counterpart as a benchmark, on both sides of the wall thickness is not less than three times, and not less than 50 mm, and prevent overheating.
2, the welding process
Welding compound layer first, then at the grass-roots level, flow, sealing, backing welding, the transition layer -- - filling layer cover surface.
1) pipe butt welding set pair, its inner wall should flush, the lining of the wrong side volume shoulds not be more than 10% of wall thickness, and should be 2 mm or less.
2) welding, should try to use multilayer welding, the welding layer of weld joint should be staggered, bead shoulds not be too wide too thick.
3) some solid welding tube must be filled with argon, to ensure the weld quality.Position of backing weld, overhead welding using the wire filling, vertical and flat position is welding with the external wire filling method.
4) should be in arc of groove, prohibited in the arc welding parts, arc should guarantee the weld penetration and fusion, should fill arc crater and when arc welding at the end, should reduce the argon gas flow, prevent pressure, ambassador weld sag.
5) level with tungsten wire cannot contact or directly into arc arc column area, to prevent the destruction of arc stability and produce tungsten inclusion defects, welding wire end not exit reserves, prevent the oxidation of the wire.
6) between temperature should be controlled under 150 ℃, the construction of the welding seam on both sides of the water cooling method, the wet towel wrapped in 80 mm on both sides of the outside steel pipe from weld, the weld has dropped below 150 ℃ as soon as possible.
3, after welding
After welding should be carefully clean up the welding slag on the surface of the weldment, flash splash and other debris and partial response to weld repair when necessary.To eliminate residual stress after welding, should be after heat treatment, welding processing should be carried out in accordance with the design requirements, local heat treatment, appropriate USES electric heating method.At the grass-roots level shall be in accordance with the requirements of basic material of welding post-processing choose heat treatment temperature, other parameters according to the stainless steel inner liner pipe total thickness (7 + / - 1.5) mm.