# Can you work hardened steel?



## heatherw (17 Sep 2015)

Hi everyone,

I've just bought a second hand rolling mill which was very cheap.....but the rollers aren't completely smooth, they seem to be slightly pitted, possibly from old rust. 
My question is, if I remove the rollers and take them to the steel workshop round the corner, would they be able to skim them to make them smooth again, or can you not work hardened steel? (Perhaps they harden it after working it? I don't know)


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## Dee J (17 Sep 2015)

There's hard and there's hard.... But something like this could be ground between centres. real issue would be - are they the same hardness right through, or would you risk grinding through the hard layer into a softer core?


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## DTR (17 Sep 2015)

Depends what kit they've got. A cylindrical grinder might do the job, if they've got one on that scale. Otherwise it might mean annealing, skimming then re hardening the rollers. 

Is the pitting really a problem?


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## Phil Pascoe (17 Sep 2015)

From my (limited) use of a mill, yes, the smallest flaw is a nuisance - you are transferring the mark from the roller to whatever you are rolling. (I assume this a jewellers type mill?). 
The manufacturers of mills must be few and far between - have you a makers name? If so, it might be worth asking them (if still extant).


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## woodpig (17 Sep 2015)

The right Lathe tool insert should be able to deal with it.


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## heatherw (17 Sep 2015)

Thanks everyone.
The mill seems to be an unusual one, I haven't been able to find spare rollers so far. At the moment the pitting doesn't bother me because I hammer the metal after it's been through the rollers, but I can envisage a time when I will want them to be completely smooth. 
Might just take it round to the guys and see what they say. It's a bit heavy to lug around though without thinking about it beforehand. I was assuming they'd put the rollers on a lathe.


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## CHJ (17 Sep 2015)

You are talking about hardening, how hard is the existing surface of the rollers?


1. Mild steel (easily marked with abrasive or file)
2. Case Hardened mild steel (hard surface but softer core)
3. Tool steel (hardened through and through)


2 & 3 may be difficult to determine but readily obvious when machining or trying to re-harden.

As for your question "can you work harden steel" as long as you qualify the type the answer is yes.

Hence why a nail or steel strip will fracture if you keep bending it to produce a fatigue fracture or a blunt drill ends up burning away its cutting edge because the metal has become harder than the drill because of work being done.

But all these effects and results vary considerably upon the steel alloy.

Hardening for your purposes in providing a hard surface involves either adding extra carbon to the surface of a softer a more resilient steel or heating and quenching higher carbon content steels. 

Would be very difficult to work harden a formed roller in common steels, it's more usual to have to heat treat them (anneal) to remove any stress forming work hardening during manufacture as a first step to proper heat hardening.


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## bugbear (18 Sep 2015)

heatherw":34t5yxcn said:


> can you not work hardened steel?



You can certainly grind it.

BugBear


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