Abstract
When the SA-210 steel water-cooled pipes are under high temperature and high pressure, high pressure steam will generate an outward pressure on the inner wall of the pipes, which will cause the pipe to swell outward. If there is a small defect on the inner wall of the water-cooled tube, this defect will become a stress concentration point. The additional pressure acts on the stress concentration point to cause cracks, and after the cracks generated, lead to the cracks to expand at the same time. In the cracks, vapor will diffuse into the matrix along the cracks, occurring corrosion under the action of high temperature, which further accelerates crack growth. Eventually, it leads to water-cooled tube wall leakage.
Highlights
In recent years, the causes of the unit abnormal shutdown caused by the boiler are mainly concentrated on the heating wall leakage
Its chemical composition is simple, with the exception of high carbon and manganese content, the rest are similar to 20G, and its yield strength is about 20% higher than that of 20G, while its plasticity and toughness are comparable to 20G
2.1 Macro morphology analysis The water-cooled tube wall was cut along the longitudinal direction of the tube bundle and observed
Summary
The causes of the unit abnormal shutdown caused by the boiler are mainly concentrated on the heating wall leakage. It was found that there was a large area of leakage in the water-cooled wall pipe. The production process of the steel is simple and the hot and cold workability is good. Using it instead of 20G can reduce the wall thickness, reduce the amount of material used, and improve the heat transfer status of the boiler. Sampling was performed on the inner wall of the tube where the crack was obvious and the oxide skin did not fall off (point A in Figure 1), which was labeled as Sample 1.
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