Matters needing attention are summarized as follows: covered electrode should be dried, the welding speed should be fast, the current should be low, the interlayer temperature should be about 60 degrees, and the welding should be interrupted. In order to avoid intergranular corrosion, welding should be cooled immediately.
Specification for welding of stainless steel pipes
First, preparation before welding;
Welding groove preparation quality inspection, according to the requirements of groove size, precision and surface quality specified in construction drawings and welding process instructions, groove quality includes flatness, verticality and cleanliness.
1, check the groove machining dimensions (height, corner edge and blunt edge, etc.). ) and accuracy are
Whether it meets the requirements of relevant technical standards.
2, check the groove surface roughness and surface defects (gas cutting cracks, spots
Layer and slag inclusion) if the defect exceeds the allowable range of the standard, it should be repaired. If the surface roughness is not up to the standard, it can be polished with emery cloth.
3, check the groove surface cleaning quality. The surface of the groove and its two sides are at least 200mm.
Scope should be clean, no burr, slag, rust, oil, oxide film, paint and other harmful foreign bodies.
4. Non-destructive testing of groove surface. For welding process documents, the slope is specified.
Materials (such as CY-M steel, Fe-CY-N high temperature alloy steel, etc. ) The mouth surface that needs nondestructive testing (such as coloring) should be nondestructive tested, and defects such as cracks should be eliminated if found.
Second, assembly and spot welding inspection;
1, check whether the geometric dimensions and shapes after assembly meet the requirements of the drawings. ：
2. The assembly clearance is 1.5-2mm, and TIG welding is adopted for three-point tack welding.
Welds shall be located at 3 o'clock, 9 o'clock and 12, and the welding materials used shall be the same as those of weldments. The length of solder joint is 10- 15 mm, which requires penetration and no defects, and the offset is ≤1.5-2 mm.
3. Forced loading is not allowed during assembly, and the inner wall of the joint must be flush.
4. There shall be no air, slag inclusion, tungsten inclusion and cracks during spot welding.