Large-diameter steel pipe
inner wall anticorrosion
1. Before processing all steel pipes, the steel plate on the inner wall side of the large-diameter steel pipe shall be de-rusted until the metal is exposed to metallic luster (whitening). It should meet the sa2.5 standard required in GB8923-88 of "Steel Surface Corrosion Grade and Rust Removal Grade Before Painting".
2. The steel after de-rusting should be processed immediately (to prevent secondary rusting). After the processing is completed, 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 use GZ-2 gray new polymer in time Anti-corrosion paint (high-build type) is used as a primer twice, and the top coat is painted with sky blue paint twice so that the total thickness of the paint film reaches 250-300μm.
3. The primer should be finished before the pipe fittings leave the factory, and the top coat should be painted before the pipe installation. All pipe fittings should not be painted within 200mm of both ends (installation welds) and should be painted after the pipe fittings are installed.
4. You only need to use a brush when applying the primer, and the spraying method is not allowed. The spraying method can be used for the top coat.
5. Ventilation conditions should be provided in the painting site to prevent the metal surface from getting wet, and the site should not have strong winds, dust, hot sun exposure, and other bad weather, (such as high temperature > 70 ℃, or too low < + 5 ℃ rainy days, etc.) Do not carry out painting work, it is best to paint at 10°C-25°C, and the relative humidity is 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 useful methods to reduce the deformation of precision messy molds. The reasons for the deformation of precision and messy molds are often messy, but we only need to grasp the rules of deformation, analyze the causes of its occurrence, and use special methods to prevent the deformation of the mold, which can be reduced and controlled.