SUS321 Stainless Steel Welding Guide
SUS321 stainless steel (AISI 321 / EN 1.4541) is a titanium-stabilized austenitic stainless steel widely used in high-temperature equipment, pressure vessels, exhaust systems, heat exchangers, and welded structures that operate in the 450–850°C sensitization range.
Because welding is a critical fabrication step, understanding the correct welding methods, filler metals, heat input, and post-weld performance is essential to avoid carbide precipitation, intergranular corrosion, and cracking.
Is SUS321 easy to weld?
SUS321 contains titanium (Ti ≥ 5×C%). During welding, titanium preferentially forms titanium carbide (TiC) rather than chromium carbide. This prevents chromium depletion at the grain boundaries, thus reducing the risk of intergranular corrosion after welding. Post-weld annealing is not required for most applications, and it is suitable for continuous use environments up to 900°C.
SUS321 Chemical Composition Relevant to Welding
| Element | SUS321 (wt%) |
|---|---|
| C | ≤ 0.08 |
| Cr | 17.0–19.0 |
| Ni | 9.0–12.0 |
| Ti | ≥ 5 × C% |
| Mn | ≤ 2.0 |
| Si | ≤ 0.75 |
| P | ≤ 0.045 |
| S | ≤ 0.03 |
Recommended Welding Processes for SUS321
| Welding Process | Suitability | Typical Use |
|---|---|---|
| GTAW/TIG | ★★★★★ | Thin sheets, precision welding, pipe welding |
| GMAW/MIG | ★★★★☆ | Structural welding, general fabrication |
| SMAW/Stick | ★★★☆☆ | Field welding, repair jobs |
| FCAW | ★★★☆☆ | Thicker sections but less common |
What filler wire is best for welding SUS321?
For welding SUS321 stainless steel, the best filler wires are ER321 (titanium-stabilized) or ER347 (niobium-stabilized), as they match the base metal's stabilization, ensuring good high-temperature strength and corrosion resistance, with ER347 offering superior high-temp strength for severe applications.
| Base Metal | Recommended Filler | Reason |
|---|---|---|
| SUS321 | ER347 / E347 | Nb-stabilized filler prevents sensitization |
| SUS321 | ER308L | Acceptable for non-critical welds |
| SUS321 + Mild Steel | 309L | Dissimilar welding |
Why is ER347 filler recommended for SUS321 welding?
ER347 filler is recommended for welding SUS321 stainless steel because its niobium stabilizer prevents chromium carbide precipitation at high temperatures, preventing intergranular corrosion. This is crucial because SUS321 has a titanium stabilizer, and ER347 (which uses niobium) ensures the weld can withstand high-temperature service without becoming brittle.
Welding Parameters & Heat Input Guidelines
| Thickness (mm) | Process | Current (A) | Voltage (V) | Travel Speed (mm/s) | Notes |
|---|---|---|---|---|---|
| 1–3 mm | TIG | 40–90 | 10–14 | 2–6 | Low heat input to prevent distortion |
| 3–6 mm | TIG / MIG | 80–140 | 12–22 | 3–7 | Multi-pass recommended |
| 6–12 mm | MIG / SMAW | 120–220 | 20–26 | 4–9 | Preheat not required |
| >12 mm | MIG / FCAW | 180–280 | 22–30 | 5–10 | Consider back-purging |
Key Rule:Use slow cooling and moderate heat input to avoid titanium nitride/oxide inclusions.
Post-Weld Treatments
| Treatment | Required? | Reason |
|---|---|---|
| Post-Weld Annealing | Not required | Ti stabilization prevents sensitization |
| Pickling & Passivation | Recommended | Restores chromium oxide layer |
| Stress Relief | Only for critical high-temperature parts | Reduce residual stress |
What are common welding defects for 321 stainless steel?
Common welding defects for 321 stainless steel include cracks, porosity, slag inclusions, lack of fusion, and undercut. These defects compromise the weld's mechanical properties and corrosion resistance and can be caused by issues like improper cleaning, incorrect settings, excessive heat input, and contamination. Additionally, specific problems for 321 include heat tint, spatter, and post-weld stress corrosion cracking (SCC) in certain environments.
If you have any questions about welding SUS321 stainless steel, please feel free to contact me. Our team will be happy to provide you with support and assistance!
SUS321vs SUS304 & SUS316：Weldability
| Property | SUS321 | SUS304 | SUS316 |
|---|---|---|---|
| Weld-sensitization | ★★★★★ (Best) | ★★☆☆☆ | ★★★☆☆ |
| High-temp performance | ★★★★★ | ★★★☆☆ | ★★★★☆ |
| Chloride resistance | ★★☆☆☆ | ★★☆☆☆ | ★★★★★ |
| Recommended filler | ER347 | ER308L | ER316L |
Need SUS321 Stainless Steel Plates, Pipes, or Welded Components?
Gnee supplies SUS321 sheets, coils, pipes, bars, and welded components with:
EN 1.4541 / ASTM A240 / A312 compliance
Thickness 0.3–60 mm, width ** up to 2000 mm**
MTC 3.1 / SGS / BV certification
7–12 day delivery time
Cutting, bending, welding, machine processing services
