[TheForge] Tempering and hardness

[Saint Phlip]

http://www.upmet.com/301-full-hard.shtml

"301 Full Hard differs from other forms of 301 offered by United
Performance Metals in that it has been hard cold rolled to its full
hard condition. This increases the metal's attractiveness for forming
and increases its fatigue life. In its full hard condition, type 301
stainless steel has a tensile strength of 185,000 PSI minimum, and a
minimum yield strength of 140,000 PSI. The combination of hardness and
toughness make it ideal for springs."



On Mon, Dec 5, 2011 at 11:25 PM, Bruce Freeman <freemab222 at gmail.com> wrote:
> I am no expert either, but I've also done some reading on these
> subjects.  You are correct about carbon steels and some alloy steels.
> You harden them (typically after annealing) by heating them to red and
> quenching rapidly.  You temper the glass-hard steel by heating to a
> much lower temperature (as indicated coincidentally by the temper
> colors) to reduce the hardness and increase the toughness. AFAIK,
> steel is the only material that can be hardened this way.
>
> Someone else on this forum will have to elaborate on the metallurgy.
>
> SS is steel in that it is mostly iron, but it has so much chromium and
> nickel (and other elements?) that its behavior can be quite different
> from carbon steel.  There are more than one kind of SS.  I understand
> some SS's can be hardened and tempered, but I'm not sure of that.
> IIRC, the 300-series can only be work-hardened.
>
> But if you weren't forging SS, then SS was pretty much irrelevant to
> the question. He might as well have spoken about copper or brass,
> which you anneal by heating to red and plunging into water, and harden
> by work-hardening (e.g., hammering or drawing through a die).  Try
> THAT with tool steel and see how "soft" it gets!
>
> The effect of hardening and tempering, along with grain growth, can be
> demonstrated fairly easily with a test piece, if you want to go to the
> trouble.  I would have told this know-it-all to go fire up a forge and
> try it himself if he didn't believe me.
>
> On Mon, Dec 5, 2011 at 9:59 PM, Paul Novorolsky <crosspein at sbcglobal.net> wrote:
>> During a public demonstration last weekend, I was explaining to someone
>> about hardening and tempering in pretty general terms. When I said that
>> tempering sacrifices some hardness for toughness, a spectator told me I
>> was wrong. He pretty much said "No it doesn't, tempering makes it harder".
>>
>> I disagreed assuming he had hardness and toughness confused, stating
>> that the heat treating charts for common steels show a reduction in
>> hardness at various tempering levels. He continued to tell me I was
>> wrong, because he had bought 100's of tons of "full hard stainless
>> steel" and asked how I explain that material. I told him I had no
>> knowledge of it, but tool steels will lose some hardness during
>> tempering. He repeated that I was wrong. At that point I was agitated,
>> and told him to do some research and he'll see that tempering does
>> result in loss of hardness, at which time his wife seemed annoyed with
>> him and dragged him out of our shop. (amusing in itself, as he was a big
>> man)
>>
>> While I could have handled that a little better, probably by asking for
>> a detailed explanation of the process used for "full hard stainless",
>> which I'm sure he had no clue.
>>
>> Anyway, I'm looking for more education. When I got home, I did some
>> research, but I'm still short on details. If I understood what I read,
>> "full hard stainless" is tempered, and then maybe cold rolled to work
>> harden back hardness. I'm not really looking for tremendous detail here,
>> just an explanation "in blacksmith terms" about what this stuff is.
>>
>> I also came across a statement in one search that popped up that said
>> that some alloys will become harder by tempering. Being an internet
>> source and therefore dubious in my eyes, I tried unsuccessfully to find
>> additional sources to provide some verification. (and then lost the link
>> that had that statement in the first place). So question 2 is "are there
>> steels that become harder by tempering?"
>>
>> It's been awhile since I read anything on metallurgy, and since I tend
>> to use macro processes for my heat treating, I tend to forget a lot of
>> the details, but I'm hoping there are a few bits of knowledge, or maybe
>> rumors to be had from the list. Any help?
>>
>> **Paul
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>
>
> --
> Bruce
> NJ
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-- 
Saint Phlip

So, you think your data is safe?
http://www.cnn.com/2010/OPINION/01/23/schneier.google.hacking/index.html?hpt=T2

Heat it up
Hit it hard
Repent as necessary.

Priorities:

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.I never wanted to see anybody die, but there are a few obituary
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