Construction preparation before welding of large-diameter steel pipes and introduction to inner wall anti-corrosion

First, construction preparation before welding of large-diameter steel pipes:
1. Organize relevant operators, familiarize themselves with construction drawings and procedures, formulate welding processes, and prepare welding operation instructions.
2. Welders should be trained for corresponding projects and have operation qualifications for corresponding projects.
3. Check whether the roundness and misalignment of the steel pipes received meet the relevant technical requirements.
4. Check whether there are defects such as scars, cracks, and severe rust on the surface of metal pipe joints.
5. Before installing large-diameter steel pipes, pipe joints should be measured and numbered one by one, and pipe joints with small diameter differences should be selected for welding.
6. When welding in windy, rainy, and snowy weather, there should be windproof, rainproof, and snowproof sheds.
7. Before welding, make the welder clear about the requirements and welding measures.

Second, anti-corrosion of the inner wall of large-diameter steel pipes:
1. Before processing, all steel pipes should be rust-free on the steel plate on one side of the inner wall of the large-diameter steel pipe until the metal shows its metallic luster (whitening). It should meet the sa2.5 standard required by GB8923-88 “Surface Rust Level and Rust Removal Level of Steel before Painting”.
2. The steel after rust removal should be processed immediately (to prevent secondary rust). After processing, use a clean rag to wipe off the residual rust powder on the inner wall of the pipe (if secondary rust is found, perform secondary rust removal to ensure painting), and promptly use GZ-2 gray new polymer anti-corrosion coating (thick paste type) to apply two coats as primer, and use sky blue paint to apply two coats of topcoat, so that the total thickness of the paint film reaches 250-300μm on both the bottom and the surface.
3. Primer should be applied before pipes leave the factory, and topcoat should be applied before pipe installation. No paint should be applied within 200mm at both ends of all pipes (at the installation welds), and paint should be applied after the pipes are installed.
4. When applying primer, only a brush is needed, and spraying is not allowed. The topcoat can be applied by spraying.
5. The painting site should have good ventilation conditions to prevent the metal surface from getting wet. The site is prohibited from having bad weather such as strong winds, flying dust, and scorching sun (such as high temperature >70℃, or too low <+5℃ rainy days, etc.). Painting is not allowed. It is best to paint at 10℃-25℃ and relative humidity below 70%.

Third, reasonable tempering heat treatment process for large-diameter steel pipes:
Correct heat treatment process operation and reasonable tempering heat treatment process are also useful methods to reduce the deformation of precision messy molds. The causes of deformation of precision and complex molds are often complex, but as long as we understand the deformation rules, analyze the causes of its occurrence, and use special methods to prevent the deformation of the mold, it can be reduced and controlled.