Construction preparation and inner wall anticorrosion before welding of large-diameter steel pipe

Construction preparation before welding of large diameter steel pipe:
1. Organize relevant operators, be familiar with construction drawings and regulations, formulate welding procedures, and compile welding operation instructions.
2. Welders should be trained in corresponding projects and have operation qualification certificates for corresponding projects.
3. Check whether the roundness and misalignment of the incoming steel pipe meet the relevant technical requirements.
Fourth, check the surface of metal pipe joints for defects such as scars, cracks, and serious corrosion.
5. Before the installation of large-diameter steel pipes, the pipe joints should be measured and numbered one by one.
6. Welding in windy, rainy, and snowy weather There is a wind-proof, rain-proof, and snow-proof shed.
7. The welder needs to clarify the requirements and welding measures of the welder before welding.

Anti-corrosion of the inner wall of large-diameter steel pipe:
1. All steel pipes should be trusted on the steel plate on the inner wall of the large-diameter steel pipe before processing, and the metal should be exposed to metallic luster (whitening). It should meet the sa2.5 level standard required in the "rust grade and rust removal grade of steel surface before painting" GB8923-88.
2. The steel after derusting should be processed immediately (to prevent secondary rusting). After processing, use a clean rag to wipe the residual rust powder on the inner wall of the tube (if secondary rust is found, carry out secondary rust removal to ensure painting) and use GZ-2 gray new polymer in time. Two coats of anti-corrosion paint (high build type) are used as the primer, and two coats of sky blue paint are used for the topcoat so that the total thickness of the paint film can reach 250-300μm.
3. The primer should be finished before the pipe fittings leave the factory. The topcoat should be brushed before the pipe is installed. All pipe ends (installation welds) are not painted within 200mm, and the pipe should be installed before painting.
4. When applying primer, you only need to use a brush instead of the spraying method. The topcoat can be done by spraying method.
5. The ventilation conditions that the painting site should have, to avoid the metal surface being wet, and the site is prohibited from bad weather such as strong wind, dusty, scorching sun exposure, (such as the temperature is too high > 70 ℃, or too low < + 5 ℃ rainy days, etc.) No painting work is allowed, and the painting should be done at 10°C-25°C and the relative humidity is below 70%.

Reasonable tempering heat treatment process for large diameter steel pipe:
Correct heat treatment process operation and reasonable tempering heat treatment process are also useful methods to reduce the deformation of precision and messy molds. The reasons for the deformation of precision and messy molds are often messy, but we only need to master the deformation rules, analyze the reasons for their occurrence, and choose abnormal methods to avoid the deformation of the molds, which can be reduced and controlled.