Analysis of the Causes of Cracks in Stainless Steel Jacketed Kettle

### Analysis of Cracks in Stainless Steel Jacketed Kettles

Cracks in stainless steel jacketed kettles can occur due to several factors related to their manufacturing and welding processes. Here's an analysis of the causes, focusing on electric-heated jacketed kettles:

1. **Residual Stress from Cold-Forming**:

- The hemispherical head segments of the kettle are cold-formed during manufacturing without undergoing stress relief treatment. This results in significant residual stress within the segments.

2. **Welding Constraints**:

- During welding, the fixed dimensions of the segments and the constraints imposed by the welding process create tensile stress perpendicular to the weld seam and heat-affected zone. As the molten pool cools, the metal contracts, further exacerbating this stress.

3. **Welding Process and Sensitization**:

- Manual arc welding with A102 welding rods, used for 1Cr18Ni9TI stainless steel plates, introduces significant temperature gradients between the base metal, fusion zone, and heat-affected zone.

- This temperature variation causes sensitization heating of the stainless steel, leading to carbon diffusion to the intergranular boundaries.

- Chromium carbides (Cr23C6) precipitate at the grain boundaries, depleting the surrounding areas of chromium. This creates chromium-depleted zones, which are more susceptible to corrosion and cracking.

These factors collectively contribute to the formation of cracks in stainless steel jacketed kettles, particularly in the weld seams and heat-affected zones. Proper stress relief treatments and controlled welding processes can help mitigate these issues.