[TheForge] Tempering and hardness

[Paul Novorolsky]

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