Tube turns blue
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During a regular inspection of industrial steam pipelines, it was found that the pipes were blue. I don’t know why. Is the material damaged? The pipe material is A106 and the valve material is WC6. Please give me some advice.
Bluishing of pipes is usually caused by high-temperature oxidation, which can be caused by too high a temperature or too much oxygen inside the pipe. The pipe material is A106, a type of carbon steel pipe that is easily oxidized at high temperatures, so regular inspections are required to ensure the safety of the pipe. The valve material WC6 is a kind of chromium-molybdenum steel, which has good high temperature resistance. However, due to the oxidation problem inside the pipeline, it also needs regular inspection to ensure normal use. If there is serious damage in the pipeline, the pipeline needs to be replaced in time to avoid safety accidents. .
The design temperature of the pipe is more than 200 degrees, and carbon steel is allowed to be below 425 degrees.
It is difficult to find the cause. You can only make a rough judgment based on experience. Now that you have found a problem during inspection, you can suspect that the user unit is overheated and look at the user's reasons for rebuttal.
The unpainted areas of the steam pipes will be blue, no problem
Generally, when we open the pot, we bake the pot at high temperature to form a protective film on the surface of the pot. The blue color on the pipe weld joint is mostly caused by the welding heat treatment. The valve is chromium-molybdenum steel, so the weld joint should be heat treated. Check the heat treatment temperature. This temperature should be much higher than your designed working temperature of 200 degrees.
The welding of molybdenum steel and carbon steel uses carbon steel welding consumables. The pipe is not thick and does not require heat treatment.