Anticorrosion of the inner wall of large-diameter steel pipes:
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, carry out secondary rust removal to ensure painting), and promptly use GZ-2 gray new polymer anti-corrosion paint (high build type) to brush twice as a primer, and use sky blue paint to brush twice, and the total thickness of the paint film to reach 250-300μm on both sides.
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 at both ends (installation welds) within 200mm should not be painted, and 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. There is no bad weather such as strong wind, dust, hot sun exposure, etc. (such as high temperature > 70 ℃, or low temperature < + 5 ℃ rainy day, etc.) No painting work is allowed. The best choice for painting is 10 ℃ - 25 ℃, 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.