Tempering: S30V vs. ats-34/154cm

Sando

Sando

Knife Maker
Joined
Jul 4, 2002
Messages
1,148
Face it, you can use basically the same austenitizing temp for S30V and ats-34/154cm. You can quench the same. S30V will get a point or 2 harder. (I'm not talking about your recipes, just looking at the data sheets.)

The interesting thing I've just noticed is that the CPM data sheet has 2 1 hour tempers for 154cm and 2 2 hour tempers for S30V.

Any ideas why they want longer tempers for S30V? Is this common to vanadium steels?

Steve
 
WAIT A MINUTE.

I found another data sheet at CPM that differs. This one has 2 hour tempers for 154CM!? and these numbers:

Austenitizing:

S30V 1950 as quenched oil/cryo = 63
cm154 1950 as quenched oil/cryo = 63

Temper

S30V 600 degrees 2 - TWO hour = 58.5
154cm 600 degress 2 - TWO hour = 60



154CM

S30V

Shorter Tempering Sheet for 154CM

OK, so this science has soo many variables, everything is a bit 'gooshy'

Steve
 
Yes it is, Steve. The data sheets on any given steel vary wildly from revision to revision, even from the same manufacturer, let alone the distributors. The only real way I've found to deal with it is to buy a good deal of steel at a time, and using their guidlines, figure out your own best HT schedule.
Temper for the longer time periods, it won't hurt the steel. It is a matter of the correct temperature and some minimum time, based on the steel composition and grain size.
I tend to use at least two and often three tempers on the SS's. You can always raise the temp 25-50 degrees on the second temper if it's still too hard and then do a third cycle, but you obviously can't regain lost hardness very easily. (There is a caveat here, and that is the fact that a lot of these steels have a secondary tempering hump in their hardness curve. I won't try and go there in this post.)
 
Heehee,
Steve, remember what I said earlier...Doesn't take a rocket scientist, but you can't be a dummy either....take lotsa notes :)
 
Thanks Fitzo, advice taken to heart. I'm gonna extend the tempering times - can't hurt. Also, I'm not getting the RC low enough. I suppose experimenting is in order.

Kit,

Ha! I took your advice! In the barn I have an old desk. BUF (Butt Ugly Furnace) is on top. In the drawer is a notebook and pencil. See I listen. All sorts of details, except when/where I bought the steel. I'm gonna add Fitzo's advice and keep track of my orders/batches and record which batch has what.

Great guys, now I have to worry about what lot the steel came from.

------------------------------------------------
FWIW yesterday I did 2 blades in the same cycle. One S30V and one ATS34. Same temps, same quench, same cryo. The S30V blade is 2 points higher.

So, even tho the datasheets are almost identical (to this point) the results vary. In fact S30V just seems to run higher.

-------------------------------------

Steve
 
Fitzo's right, the S30V is a bit more complex so other things are going on. The times should be considered minimum. Pick one steel, get one batch and work out the details for your shop.
 
There's one more caveat, here, too, Steve. When I had a long discussion with Paragon about temp control about 6 months back, we discussed precision at lower temp settings. The reply I received was somewhat surprising when they informed me that 100F imprecision or more at tempering setpoints is not uncommon. Their take on things was that the furnaces should be accurate at the high end of the range, and a bit non-plussed when I got pissed they told me the low end is anybody's guess.

There is an obvious reason why critical-controlled lab furnaces are $5000-12,000 and ours cost about a grand. Really wanna get upset, get an outboard probe and meter and set it through a peephole right next to where the blades lay in your furnace. This is why it's so important to work out the method for each steel. The temp you THINK you have may not be within a 100F or more right at the blade. :mad:

Once you work it out for your furnace, though, it works great until you don't realize the thermocouple has gone bad and lost accuracy, especially at higher temps like we use for hardening. The more one looks into it, the more attractive it is to turn these SOB's into flower planters and send the blanks to Paul. :(

I now use two meters and three probes and have grown quite dingy about temp control. But then, I was nuts to begin with....:D
 
Thanks guys!

Fitzo,

Actually I didn't even think of tempering in the furnace. The low temp is probably an issue with type K thermocouplers. They probably don't respond well at lower temps - chemistry problem I'm guessing.

I have a high-tech, tempering oven cleverly disguised as an old toaster oven for that.

Three probes!? This is starting to sound like shipping off blades isn't so bad!

Steve
 
I've gotta get out to some yard sales and get me a "good" tempering oven.:)

The three probes is just because I got a little weirder even than usual when I found out how inaccurate they were for tempering.

It's way too cool doing one's own HT to ever send out anything i could do here at home.
 
Steve, put an oven thermometer in the tempering oven and check it. If it looks good leave it there for a while to see how much the oven fluctuates as it cycles. I often use my Evenheat for tempering, especially for the second temper. I doubted it so I tested it with what I suggested above. It's okay if I allow the oven time enough to stabilize after reaching target temp. (after it says it reached target).

RL
 
Oh yeah Roger, I do.

I have a very nice themometer I use for bullet casting. That's how I know this oven holds such a nice consistent heat. The dial on 400 runs at 425. Funny thing is set it on 500 and you get about 600.

Also, I run the oven for a while before putting the blades in. Just to make sure the temp is stable.

Steve
 
For tempering, my kitchen stove oven holds a very even 400°F when set for 380°. I keep an oven thermometer in it to check. I do all tempers for two hours and triple temper.
 
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