How long do stainless steel welds last?

[DasKleineWunder]

Are they prone to fatigue, or some kind of breakage?

Is there a big difference between welds in Austenitic vs Ferritic stainless steel alloys?

 

[weldstan]

Your question is too open ended.
?1. Yes, include pitting corrosion, MIC, corrosion fatigue, stress corrosion cracking, crevice corrosion, thermal fatigue.
?2. Both yes and no.

 

[EdStainless]

Getting good solid, corrosion resistant welds in non-stabilized ferritic alloys is difficult.
The welds will always have slightly lower corrosion resistance than the base metal.
The strength and ductility of the welds in austenitic alloys is every bit as good as the base metal.

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Plymouth Tube

 

[moltenmetal]

Qualify Ed's comment by saying that the weldment and HAZ in an austenitic stainless steel CAN BE just as corrosion resistant as the base metal. I was going to say that it's possible to make the weldment itself more corrosion resistant than the parent metal, but that may not be a good idea in some services due to galvanic potential differences. The welds tend to be stronger than the parent metal though, as the filler metals are designed to resist cracking during cooling. Fatigue is an issue for analysis. Welds are inspected for defects which may enhance fatigue problems by producing locally high stresses.

 

[Duwe6]

Stainless welds are susceptable to Intergranular Chloride Stress Corrosion Cracking - IGSCC. Very "temperature vs. Cl2 concentration" dependant. We cracked out some cooling tubes that were 304, using 'city water' with a chloride concentration less than 10 ppm. But the temperature on the other side of the tube was 900°F and the inlet temperature was about 55°F. High tmeperature plus high stress rendered ≈4 ppm of chloride enough to cause severe IGSCC.

For 'normal' structural weldments, if the 'correct' filler is used, like moltenmetal wrote, the service life is measured in centuries.

 

[Ron]

Any elastic material is subject to fatigue....depends on the geometry, the stress level, the number of fatigue cycles and the SN curve for that particular material.

 

[tbuelna]

What about welding an austenitic stainless steel like 303Se? Would a 303Se welded structure have reasonable fatigue life?

 

[Duwe6]

303 s/s isn't considered 'weldable' - the sulphur that makes it easy to machine caused sulphide stringers at the welds, and it starts cracking immediately.

 

[btrueblood]

Or selenium in the case of 303Se. The same stringers cause low fatigue life for the 303 series, even in unwelded parts.