When processing spiral steel pipes, these should be avoided.

Release date:

2023-02-28

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Steel Pipe Knowledge

Spiral steel pipes play a crucial role in our daily lives. Below, we will examine the common defects associated with each heat‑treatment process used for spiral steel pipes.

Spiral steel pipes play a crucial role in our daily lives. Below, based on the heat‑treatment processes used for spiral steel pipes, we will outline the common defects associated with each process.

Defects arising during the heating process. For heat treatment, it is essential to select appropriate heating equipment and heating media. Common issues include surface oxidation caused by oxidizing atmospheres and overheating beyond specified process parameters. Such conditions can lead to excessively coarse austenite grains or even grain boundary melting, severely compromising both the surface appearance and internal quality of the component. Therefore, in practical applications, feasible corrective measures should be implemented based on a thorough analysis of these defects.

Defects that arise during the quenching of small-diameter helical tubes. After heating and austenitizing, the part is cooled to achieve the desired microstructure and mechanical properties. At this stage, the appropriate cooling medium must be selected based on the material and target hardness; ideally, it should provide rapid cooling at high temperatures and slow cooling at lower temperatures (around 300°C). Common cooling media include air, water, oils (mineral oil, vegetable oil, etc.), 5%–10% saline solutions, 5%–15% alkaline solutions, synthetic coolants, water‑quenched oil, water‑quenched nitrate salts, alkaline baths, nitrate salt baths, chloride salt baths, and others. These cooling media exhibit widely varying cooling characteristics, particularly in the case of saline solutions, alkaline solutions, oils, alkaline baths, nitrate salt baths, and chloride salt baths. If the performance of the cooling medium deteriorates due to aging or other factors, and this is not detected promptly, it can become a significant source of defects. Insufficient hardness, soft spots, quenching cracks, and distortion of quenched parts are among the most common heat‑treatment defects.

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