Ausforming and martensitic stainless steel

[awhicker84]

Hi all,

I wrote up a question earlier about specifying reduction ratio (or grain size) into a martensitic stainless steel forging spec. I really appreciate the feedback.

Now I have similar forging spec related question on the same material (410 Cond II):

I am reading about fatigue testing and have come across a paper, Landgraf 'Cyclic Deformation and Fatigue Behavior of Hardened Steels'. I understand that this paper is discussing low cycle fatigue in order to study the behavior of materials better than they can be understood with high cycle testing (which is the problem we are facing). However, the author keeps alluding to the idea that ausformed materials generally have better fatigue failure results than non-ausformed materials.

This report was written in 1968.

Is the standard in 2018 that all materials that undergo quench and temper receive ausforming? Maybe I'm not understanding the process correctly. I'd love to understand this more. Do I need to specify this on a forging spec? Is this a type of heat treatment that has nothing to do with stainless steels?

I'll continue reading...


Thanks much and cheers,

Andy

 

[Lyrl]

The report may have been referring to what is now called austempering?

Normal quench into a fluid of 100-200°F of a hardenable steel produces a crystal structure called martensite.

Austempering is when the quench fluid starts at 450-750°F and produces a crystal structure called bainite.

Bainite is slightly softer than martensite but has much better fatigue resistance.

Austempering requires specialized equipment that many commercial heat treaters do not own, it absolutely has to be specified if that is what you need.