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!
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
RE: Hardness / temper designations
RE: Hardness / temper designations
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Heckler
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RE: Hardness / temper designations
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
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
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
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
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.