As a kind of metal pipe, the stainless steel pipe has the characteristics of corrosion resistance, high temperature and high strength, most of which are used in the process pipeline of newly built and expanded petrochemical equipment. However, the biggest problem of this type of stainless steel welded pipe is the complete fusion welding problem of the base and the laminates. Therefore, to obtain the best welding effect, the following is the most correct welding method of stainless steel welded pipe.
Before welding, clean up the paint, dirt and oxide layer of the contact layer before welding, and prevent the impurity in the welding process from being decomposed into H2O and CO2 to affect the welding effect. Preheat the base and laminates of thestainless steel pipe before welding. Preheat the use of electric heating method. The center line is used as the benchmark, and the two sides are not less than three times the thickness of the wall, and not less than 50mm, and avoid overheating.
In the welding process, it is necessary to weld the composite layer before welding the base, and the sequence of the whole process is sealing layer, bottom welding, transition layer, filling layer and covering layer. The inner wall of the pipe shall be kept flush when the pipe is welded, and the inner wall shall not exceed 10% of the thickness of the pipe wall, and shall be less than 2mm. When welding, use multi-layer welding as far as possible, the joint of weld bead weld bead should be as wrong as possible, the weld bead is not too broad and too thick. In the process of soldering, the pipe must be filled with argon to ensure the weld quality. In the bottom welding position, the position of the inverted welding is used with the inner fillet, and the position of vertical welding and horizontal welding is used for welding.
Additional best even in the arc of groove, avoid in the arc welding parts, the arc place to ensure the weld penetration and fusion, to fill arc crater, near the end of welding, to reduce the argon gas flow rate, pressure to avoid overheating ambassador weld sag. Don’t contact with tungsten or the arc column of the arc, avoid damaging the stability of arc and forming the tungsten defect. The wire end shall not be withdrawn from the protected area to avoid the oxidation of the welding wire. In a way to control the temperature between under 150 ℃, on both sides of weld used in the construction of water cooling method, is to put a wet towel wrapped on both sides of the outside is 80 mm from the weld steel pipe, the weld as soon as possible to below 150℃.
After welding, carefully clean the surface of the stainless steel pipe pieces of welding slag, welding tumor spatter and various kinds of dirt, when necessary, the weld seams should be partially repaired. The residual stress should be eliminated after the heat treatment, the post-welding process should be carried out according to the design requirements, and the best use of the electric heating method in local heat treatment.
Source: China Stainless Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)