Can You Weld a Stainless Steel Flange to a Carbon Steel Pipe?

Can You Weld a Stainless Steel Flange to a Carbon Steel Pipe?

✅ Yes – and ASME B31.3 allows it.

Welding dissimilar metals such as a 304 stainless steel flange to an A106 Gr. B carbon steel pipe is a common yet critical challenge in piping fabrication.

🔍 Here are 5 key considerations to ensure success:

1. Code Compliance

ASME B31.3 permits dissimilar metal welds as long as the procedure is qualified according to ASME Section IX (WPS/PQR/WQTR).

2. Filler Metal Selection

Use:

ER309L for GTAW/MIG

E309L-16 for SMAW

For more critical or corrosive services, ERNiCr-3 (Inconel 82) offers superior resistance.

3. Welding Procedure

Preheat the carbon steel side (~100°C).

No preheat needed for stainless steel.

Avoid post-weld heat treatment unless absolutely required.

4. Corrosion Protection

Dissimilar welds are prone to galvanic corrosion. Effective methods include:

Installing insulating gaskets/sleeves

Coating the carbon steel portion

Applying a buttering layer of 309L on the carbon steel side

5. Qualified Personnel

Ensure welders and procedures are properly qualified under ASME IX for dissimilar metal joints.

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🔧 Bottom line:

Yes, 304 SS flanges can be welded to A106 Gr. B pipes as per ASME B31.3. Just make sure your welding procedures, filler selection, and corrosion mitigation measures are correct.