Stainless steel can crack after welding due to a combination of thermal stress, poor welding technique, incorrect filler metal, or metallurgical changes during heating and cooling. These cracks often appear during or after the weld cools and are classified into a few types depending on when and how they form.
🔧 Common Causes of Cracking in Stainless Steel After Welding
1. Hot Cracking (Solidification Cracking)
- Occurs during cooling of the weld metal.
- Caused by:
- High sulfur or phosphorus content in the metal
- Improper filler metal selection
- High heat input or wide weld beads
- Most common in austenitic stainless steel like 304 or 316.
2. Cold Cracking (Delayed Cracking)
- Happens hours or even days later.
- Often due to hydrogen embrittlement or residual stress.
- Typically seen in martensitic or ferritic stainless steels.
3. Sensitization & Intergranular Cracking
- Caused when stainless steel is heated to 400–850°C, forming chromium carbides at grain boundaries.
- This reduces corrosion resistance and leads to cracking.
- Common in non-stabilized grades like 304.
4. Stress Corrosion Cracking (SCC)
- Long-term cracking due to residual stresses, chloride exposure, and poor heat treatment.
- Cracks grow over time in a corrosive environment.
5. Improper Joint Design or Fit-up
- Gaps, poor fit-up, or improper angles create excessive stress points.
- Combined with rapid cooling, this can initiate cracks.
✅ How to Prevent Cracking in Stainless Steel Welding
| Solution Area | What to Do |
|---|---|
| Filler Metal | Match alloy type (e.g., 308L, 316L, 309L for dissimilar metals) |
| Heat Control | Use low heat input, avoid excessive weaving |
| Shielding Gas | Use pure argon (TIG) or Ar-CO₂ mix (MIG) — avoid contamination |
| Clean Surface | Thoroughly clean base metal before welding to remove oil, rust, and contaminants |
| Post-Weld Cooling | Control cooling rate; avoid quenching; allow gradual cool down |
| Joint Prep | Ensure good alignment and appropriate gap spacing |
| Material Grade | Use low-carbon variants like 304L/316L to reduce sensitization |
🔍 Expert Tip:
To avoid intergranular cracking in austenitic SS, never hold the weld in the 450–850°C range for long, and always prefer L-grade (low-carbon) or stabilized grades like 321 or 347 for critical applications.
Would you like a weld failure checklist, or need help with a specific crack issue (like in railings, tanks, or kitchen structures)?