Pipe leak repair
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The heat exchange tubes of the economizer in coal chemical plants are made of 20# boiler steel, which is exposed to temperatures over 600 degrees Celsius. In addition, sulfur, hydrogen, and carbon monoxide can penetrate this material; the composition may also include chromium. What type of welding rod should be used to repair leaks in these pipes? I’ve tried 507, 317, and 422 rods, but none of them work – the surfaces don’t fuse together. I seek an explanation for this.
Try degassing first; use a temperature of 300 and maintain that temperature for 0.5 hours. Before welding, the oxide layer must be thoroughly polished to reveal the metallic luster. The main issue is the presence of scale
Carbon steel operating at such temperatures should have undergone decarburization. When steel is heated, the carbon in its surface layer reacts with oxygen, hydrogen, carbon dioxide, and water vapor present in the medium (or atmosphere), resulting in a decrease in the carbon concentration in that surface layer – a process known as decarburization. After quenching, decarburized steel exhibits reduced surface hardness, fatigue strength, and wear resistance; moreover, residual tensile stress forms on the surface, which can lead to the development of network-like cracks. Welding is no longer possible in this state.