Explain hardness of stainless steel to me?

[antknee]

I have some stainless steel 316 that is 0.2mm thick. From one supplier it is quite flexible and from another quite rigid. From what I can gather there are hardness scales that are full hard, half hard.

If the hardness is lets say 27ksi yield strength for the annealed non hard condition what would half hard and full hard be?

Is there a simple way of identifying what hardness stainless steel I have?

Thanks,

Ant.

[Gordon]

Hi Ant

to the Surface Engineering Forum.

316 is an austenitic stainless steel, it can not be hardened by heat treatment, but can be hardened by cold work i.e. rolling.

The temper in this case is a grading; soft, 1/4 hard, 1/2 hard, full hard etc is to indicate the level of stiffness, hardness or strength imparted by cold working or softening by annealing.

Some info taken from 316 tube supplier:

316 Temper--Tensile-----Yield--------Min. Elongation--Rockwell
---------------Strength---Strength----in 2" (%)---------Hardness
---------------ksi----------ksi

Annealed-----100 max.---30-50------35----------------B 95 max.
Half Hard------110-140----70-110----15----------------B 95-C 26
Full Hard------140 min. ---110 min.---- 6---------------C 24 min.

Some info I suspect of manufacturers own interpretation of tempers for austenitic stainless steels.

Temper-------Hardness-----UTS/kpsi
Soft-----------87 HRB--------75
1/4 hard------25-30 HRC----125
1/2 hard------30-35 HRC----150
3/4 hard------35-40 HRC----175
Full hard------185 HRC-------185
Extra hard-----45 HRC ------200

Quote:Is there a simple way of identifying what hardness stainless steel I have?

Hardness testing, in your case a very light load vickers hardness test. A qualitative comparative test could be a simple bend test to see at what angle permanent deformation starts to occur.

[antknee]

Hi Gordon,

That was a very thorough and complete answer, thank you!

I have just deformed one of my parts and they seem to go to less than 45 degrees before going out of shape, I wouldn't say the thickness 0.2mm (quite thin) has any affect on that, so at a guess they are full hard. This makes sense because I asked for 0.2mm 'rigid' without understanding the hardness.

From the other supplier I got what is 0.2mm soft I'd say, it was a shim in a can and can double over on itself without any difficult.

Do you know of a good supplier of stainless steel parts that are laser cut? Most laser cutting companies seem to want 0.5mm or above in thickness and I only need up to 0.3mm. I got the best ones, simple discs from a laser drilling company, but the price was north of what I was hoping. I got the soft stainless steel which is uncut from stephens gaskets, I will phone them back to see if they do full hard stainless steel parts but I have a feeling you will know someone better. (I'm in the UK and thanks for the welcome)

Best regards,

Anthony.

[Gordon]

Hi Anthony

Quote:Do you know of a good supplier of stainless steel parts that are laser cut? Most laser cutting companies seem to want 0.5mm or above in thickness and I only need up to 0.3mm. I got the best ones, simple discs from a laser drilling company, but the price was north of what I was hoping. I got the soft stainless steel which is uncut from stephens gaskets, I will phone them back to see if they do full hard stainless steel parts but I have a feeling you will know someone better. (I'm in the UK and thanks for the welcome)

Sorry, I can't help on that one.

[antknee]

That's ok. Thanks.