Is there a fatigue factor when calculating cold vs hot rolled designs?

[theedudenator]

I am aware of some of the advantages in cold vs hot rolled products.

This is what I have:
1050 steel shaft, currently cold rolled and turned down to size, and threads added.

Possible savings in switching to a hot rolled product.

The UTS/YTS of the hot rolled product is less, but still within the endurance limit of the design.

Is there a quantitative factor I can use to show a difference between hot and cold rolled?

I would image the grain structure benefits of cold rolled would play a part? Or is this already realized in the higher mechanical properties.

 

[TVP]

Is this part induction hardened on the surface? If so cold-drawing the bar/wire prior to hardening does not significantly affect the fatigue properties. The fatigue strength of the threaded ends may be different, but it depends on the initial hot-rolled diameter, the amount of diameter reduction during cold-drawing, and how much of this is subsequently machined away. I doubt that the cold drawing is improving the fatigue strength much if the thread size is much less than 75% of the initial diameter.

 

[theedudenator]

There is no heat treatments to this part.
The bar is 1.25" dia and it has 1" threads that are cold rolled. Most of the bar is machined to 1.125" with a few transitions to less then 1"

I image my fatigue failure locations would be in one of these machined transitions as the threads are rolled.

So... any benefit to cold rolled material?

 

[EdStainless]

The only thing that I can think of is the uniformity of the microstructure. As long as you don't have variations in the grain size and mechanical properties I don't see why the hot finished bar would not work.
You may want to think about rolling the threads since you are giving up a bit of strength.

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[TVP]

I agree with Ed, there is very little benefit to using cold drawn steel in this application. The surface finish will be better with cold drawn bars, and the dimensional variation will be less, but your application is not really deriving much of a strength benefit unless the bar has been heavily drawn (say 20% or more).