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Surface Treatment Methods for Thick-wall Seamless Steel Pipes

The manufacturing standard of new thick-wall seamless steel pipe is relatively high. The quality of its surface requires various production factors to be different, and the proportions of various factors need to be developed according to detailed design plans. Good treatment should be carried out in terms of hot rolling, cold rolling, high temperature, and high pressure, and strict adherence to national requirements is necessary. The appearance of the product has a certain impact on the product quality, and surface defects will reduce the quality of seamless steel pipes. Therefore, the production manufacturers of thick-wall seamless steel pipes should continuously promote the manufacturing methods and strictly follow the industry standards in the manufacturing process.

The surface roughness of thick-wall seamless steel pipes is required in the standard. Generally, it cannot have application-harmful defects such as layering, scabs, and gaps. The allowable standard for shape deviation of thick-wall seamless steel pipes is also specified in the standard, generally including bending radius, edge width, edge thickness, angle, weight calculation formula, and requires that thick-wall seamless steel pipes cannot have obvious distortions.

Rusting of phosphating parts of thick-wall seamless steel pipes

Cause: High free acidity, high concentration of Fe2+ ions, insufficient phosphating time.

Solution: Adjust the acid ratio, replace the tank or use hydrogen peroxide treatment, and increase the processing time.

Uneven film and flow marks on thick-wall seamless steel pipes

Cause: Incomplete degreasing, slightly lower phosphating temperature, and thick-wall seamless steel pipe has a passivation layer.

Solution: Strengthen degreasing, increase temperature, and acid pickling passivation.

Blank spots on the film of thick-wall seamless steel pipes

Cause: Phosphating temperature is too low, thick-wall seamless steel pipes are hung too tightly or overlapped, and the acid ratio is too large.

Solution: Raise the temperature, increase the gap of the thick-wall seamless steel pipes, and adjust the acid ratio.

Grey hanging on thick-wall seamless steel pipes

Cause: Precipitates in the tank liquid, phosphating liquid is not rinsed clean, phosphating liquid C content is too high.

Solution: Remove the precipitates, acid pickling passivation and re-phosphating after cleaning, and adjust the phosphating liquid C amount.

Coarse crystalline structure on the film of thick-wall seamless steel pipes

Cause: Fe2+ cation content is too high, phosphating liquid C content is high, and temperature is too high.

Solution: Replace the tank liquid or use hydrogen peroxide to solve the problem, adjust the phosphating liquid C amount, and reduce the temperature.

The above is the corresponding metal surface treatment standard and detailed analysis of thick-wall seamless steel pipes. We should attach great importance to the quality of surface treatment for thick-wall seamless steel pipes and do a good job in surface quality. In this way, thick-wall seamless steel pipes will have more characteristics.

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