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Hardness / temper designations

Hardness / temper designations

(OP)
We have some copper strip material that has been specified as "1/4 hard", but some people here think that it in fact is "1/2 hard", and thus we need a longer anneal time.

I'm not familiar with the designations '1/4 hard' and '1/2 hard'.  Can someone explain to me what these mean?

Thanks!

RE: Hardness / temper designations

It depends on the section area reduction percentage of the strip when it is rolled to its final thickness from a previous initial thickness.

RE: Hardness / temper designations

(OP)
So soft strip is rolled to either a 1/4 or 1/2 reduction, thus cold-working the material?  Hmm, I'm under the impression that the material underwent a temper after being rolled. I suppose I should just call the manufacturer... however it's not my project, yet.

RE: Hardness / temper designations

What is your material designation? For example, Copper, UNS 18100, Cold Worked (40% reduction) Strip which is aged and solution treated.  Also, check www.matweb.com for an endless list of material designations.

Best Regards,

Heckler
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Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

RE: Hardness / temper designations

bschroet,

Be careful with the word temper, as it differs depending on the context.  Tempering can mean heating to modify the microstructure, such as the operation performed after quenching of a hardenable steel.  Temper is also used to refer to the state of strength/rolling of metals that have been rolled into strip.  Temper rolling of steel usually refers to rolling that is performed after annealing to remove the effect of discontinuous yielding (cause of Luders lines) and improve shape characteristics (flatness, camber, etc.).  It can also be applied to cold rolled materials like steel or copper, with the increased rolling (and subsequent strain hardening) indicating an increased "temper" of the material.  Beyond the 1/4 hard, 1/2 hard descriptions one encounters "spring" tempers.  Obviously this is not a desirable situation, but that is how the industry has evolved...

RE: Hardness / temper designations

(OP)
So the word "temper" can indicate either a heat treatment or cold-work?  That is wacky.

So does a "quarter-hard" or "half-hard" copper material refer to the amount of cold-work during rolling, or does it refer to the degree of annealing after rolling?

I have studied metals extensively in the past, however mainly in an academic setting so I'm still unfamiliar with many industry terms and designations.

Thanks!

RE: Hardness / temper designations

I've usually seen these designations on beryllium-copper alloys.  Is that what it is?  Depending on the alloy and shape it can be hard "H", 1/2H, 1/4H or even 3/4H.  There can also be a "T" added for "heat-treat", like 1/2HT.  Obvioiusly the yield and tensile strengths go up with the hardness designation.  Sometimes they come as A for "solution annealed" or even AT for heat treat from the annealed condition.

These alloys are either solution hardened, or precipitation hardened (aging), or both.  Some of the alloying agents either come out of solution or go into solution when heated for several hours to give the desired properties.  Depending on temperatures and quenching methods, you get the various "hards".

Don
Kansas City



RE: Hardness / temper designations

(OP)
Thanks for all your help.  It sounds like the designations are very material specific, which i suppose makes sense because different treatments have totally different effects on different materials.  

Ok, but at least I don't feel like an idiot anymore for not knowing exactly what 1/2 and 1/4 means.  

RE: Hardness / temper designations

1/4-Hard and 1/2-Hard do not indicate cold workings of 25 & 50%, respectively.

Rather, these terms are relative to the maximum hardness achievable by cold working, i.e., Full Hard or simply Hard beyond which fractures appear in the edges.  Although, there are higher hardnesses than Hard:

For rolled Cu & brass sheet,
1/4-hard ~ 10.9 % reduction in thickness;
1/2-hard ~ 20.7 % reduction in thickness;
3/4-hard ~ 29.4 % reduction in thickness;
Hard ~ 37.1 % reduction in thickness;
Extra hard ~ 50.1 % reduction in thickness;
Spring ~ 60.5 % reduction in thickness;
[several more spring grades exist].

From Metals Handbook, vol. 2, ...Non-Ferrous (9th edn.), p. 248.

A more complete listing is given pp. 248-251 of same, and the current official list is in ASTM B601, 'Standard Classification for Temper Designations for Copper and Copper Alloys—Wrought and Cast.'

Note that there are combinations of cold work, partial stress relief, annealed tempers dependent upon grain size, solutionized, precipitation-hardened & quenched hardened tempers for Cu & Cu-based alloys.

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