Construction preparation before large-diameter steel pipe welding:
1. Organize relevant operators, familiarize themselves with construction drawings and procedures, formulate welding procedures, and compile welding operation instructions.
2. Welders should be trained in corresponding projects and have operating qualification certificates for corresponding projects.
3. Check whether the roundness and misalignment of the arriving steel pipes meet the relevant technical requirements.
4. Check the surface of metal pipe sections for defects such as scars, cracks, severe corrosion, etc.
5. Before installing large-diameter steel pipes, the pipe sections should be measured and numbered one by one. It is advisable to use pipe sections with small diameter differences for butt welding.
6. When welding in windy, rainy, or snowy weather, there is a windproof, rainproof, and snowproof shed.
7. Before welding, the welder should clarify the requirements and welding measures.

Anti-corrosion of the inner wall of large-diameter steel pipe:
1. Before processing all steel pipes, the steel plate on one side of the inner wall of the large-diameter steel pipe must be de-rusted until the metal shows metallic luster (whitening). It should meet the sa2.5 level standard required in GB8923-88 "Steel Surface Rust Level and Rust Removal Level before Painting".
2. The steel after rust removal should be processed immediately (to prevent secondary rust). After processing is completed, use a clean rag to wipe away the remaining rust powder on the inner wall of the pipe (if secondary rust is found, perform secondary rust removal to ensure painting), and use GZ-2 gray new polymers promptly Apply two coats of anti-corrosion paint (thick build type) as the primer, and two coats of sky blue paint as the topcoat, so that the total thickness of the paint film reaches 250-300 μm on both bases and sides.
3. The primer should be completed before the pipe fittings leave the factory, and the topcoat should be applied before the pipes are installed. Paint should not be painted within 200mm of both ends of all pipe fittings (installation welds), and should be painted after the pipe fittings are installed.
4. When applying primer, only use a brush and do not use spraying. The topcoat can be applied by spraying.
5. The painting site should have adequate ventilation conditions to prevent the metal surface from getting wet. The site is not allowed to have strong winds, flying dust, scorching sun exposure, and other adverse weather conditions (such as temperatures that are too high >70℃, or too low <+5℃, rainy days, etc.) Painting work is not allowed. It is best to paint at a temperature of 10℃-25℃ and a relative humidity below 70%.

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