Rolled samples treating for microtensile test

[seep555]

Hello everyone,

I have to do a heat treatment (600C and 1000C for 24 hours) of rolled samples (1mm thickness, 40mm length) of austenitic stainless steel and I am not sure if it's ok if I just use argon atmosphere (24h is not very long in my opinion) or it's better if use a glass protection... What do you think?

 

[EdStainless]

You will get surface oxidation in Ar. It just isn't clean enough.
If you are going to pickle afterward then you are fine.
If there is minimal oxidation (maybe light yellow or straw color) than pickling will not roughen the surfaces much at all.
If you not pickling then you should work in dry hydrogen (and no nitrogen).

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P.E. Metallurgy, Plymouth Tube

 

[seep555]

It's not enough just to polish the sample a little after heat treatment?

 

[EdStainless]

The polishing will work harden the surface and not remove the oxide, it just breaks it up and re-embeds it.
Picking is much easier and will not risk damaging the samples.

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P.E. Metallurgy, Plymouth Tube

 

[seep555]

But when you measure the hardness you also have to polish the samples first, right?
And what exactly do you mean by picking?

 

[CoryPad]

seep,

Regarding polishing, usually tension test specimens are polished with dry abrasive cloths, which breaks up and re-embeds the oxide. Metallographic specimens polished for hardness testing use wet abrasives that remove the oxide from the specimen and carry the swarf away (usually down the drain).

Picking is supposed to be pickling.

 

[EdStainless]

Sorry, yes pickling.
I presumed that he was doing surface prep prior to anneal.
I don't see any reason that you couldn't just lap them after HT.
Do it wet, low loads, and very flat.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

I bet you are doing lab experiment since your samples are so small. 1000C/24h is a hom process for such small specimens? you will get very coarse grain size. I was wondering what would be your purpose.

Anyway, for small samples like that, I recommend using quartz to seal the samples with a torch (very easy process). you can vacuum then seal, or vacuum then fill with Ar2. Even there is some oxygen in the quartz tube, after it is consumed, no new source.