The impact of Delta Ferrite on the workability of Martensitic SS 1

[john807]

Is there a curve or calculation that can quantify the effect delta ferrite has on the propensity of cracking during deformation working processes (riveting for example). I am reviewing report that states that a higher amount of delta ferrite indicates a higher propensity for material cracking during this type of processing, but I cannot find any indication of how this is quantified.

 

[mcguire]

I don't know if this has been quantified in a useful way. There may be hot ductility tests somewhere. Since martensitic steels are austenitic at hot working temperatures, the presence of more than 10% delta ferrite, which is much softer, poses a problem. Its morphology is a factor. Continuous is worse than isolated in an austenite matrix.
Normally in hot working austenite which stainless 10% ferrite is where things start to go bad.

 

[EdStainless]

What base material are you working with?
In austenitic stainless you usually need some ferrite for hot working or you will get cracking on cooling, but too much will kill you too.
mcguire hit it on the head though. Even if you could find working/cracking curves morphology would be the big variable.

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