Chromium Carbide Precipitation at Grain Boundaries
Precipitation of chromium carbides in the sensitization temperature range, leading to local chromium depletion and increased susceptibility to intergranular corrosion.
When welding stainless steel, incorrect heat control can cause chromium to combine with carbon at the grain boundaries. This binds the chromium in the surroundings, and the steel loses its corrosion protection there – this is called chromium depletion. The result is intergranular corrosion, which in the worst case can lead to cracks. You can counteract this by keeping the heat input low and not leaving the heat in the workpiece for too long. The faster the cooling, the less time the carbides have to form. For thin sheets, cooling the part also helps. When welding thick sections, you should use a steel with low carbon content or a stabilized filler material.