heat treating S7

[Rhrocker]

So, I've got a few lengths (36" x 5/8's" dia.) of S7, and am wanting to make up some leaf tooling as per Mark Aspery's books. Also want to start a set of "animal head chisels".
What's the advice for the heat treating and tempering?
Thanks in advance!
Robert

[dablacksmith]

s7 is a air hardening tool steel ... forge the working end and let air cool DONT QUENCH!!!and dont heat the hammer strikeing end (trust me from experience) ..it makes great hot tooling as it doesnt move even at dull red heat .. forge at yellow to orange heat .just remember NEVER QUENCH!

[ornametalsmith]

FWIW, the S7 that I have(1/2" round)....came with these instructions. Purchased via Jere at Valley Forge

Thyssen S7

Heat Treatment:
Hot forming - 2000-2050 F............furnace cool
Annealing - 1500-1550 F ..............furnace cool.....225 Max. BHN
Hardening - 1725-1750 F
Sections under 2 1/2"- air cooled
Sections OVER 2 1/2" - Oil quench

Tempering - Temper immediately after quench
Cold work tools -400-500 F- 54/57 Rc
Hot work applications - 900-1000 F- 50-53 Rc
Double tempering recommended

Applications:
pneumatic tools, hand and or blacksmith's chisels, snap dies, trimming tools, cold piercing punches, plastic moulding, shears.

[Rhrocker]

Good deal guys. Let's see though, Dablacksmith doesn't want me to get the back end of the tool hot, but Bills formula says to temper after quenching at 900 to 1000, so maybe I should disregard the notice about not getting the hammer end hot, so that I can temper the thing. Right? Wrong?

[Rich Hale]

I have used this method on a lot of tools and have taught alot of folk to do the same...give it a try:

Forge the working end to how you want it. Heat the whole piece to non magnet4ic and immediatly place in a bucket of vermiculite overnight.
The next day heat the working end to red or non magnetic and toss under the bench where it won't get stepped on. This will leave the end to be struck softer and should not chip shrapnel from itself or hammer face. A coal forge is ideal for this isolated heat.

You can also just cold work the working end by grinding etc. Then heat that end like above and by pass the annealing step.

[Rhrocker]

I have used this method on a lot of tools and have taught alot of folk to do the same...give it a try:

Forge the working end to how you want it. Heat the whole piece to non magnet4ic and immediatly place in a bucket of vermiculite overnight.
The next day heat the working end to red or non magnetic and toss under the bench where it won't get stepped on. This will leave the end to be struck softer and should not chip shrapnel from itself or hammer face. A coal forge is ideal for this isolated heat.

You can also just cold work the working end by grinding etc. Then heat that end like above and by pass the annealing step.

Thanks Rich, I'll add this to my list, and will probably try several of the methods. I especially like the last one of yours )
Robert

[thingmaker3]

Heat the whole piece to non magnet4ic and immediatly

That's a good plan for low-alloy and plain-carbon steels. The transition point of simple steels is very close to the non-magnetic "Curie point."

S-7 is a high alloy steel, with the Curie point not near the transition temperature. One needs another method of judging temperature - a tempil stick or a thermocouple or some such.

S-7 is not likely to anneal in vermiculite, as will low-alloy and plain-carbon steels.

[Bubba-san]

I have a big piece of S-7 I am going to use as anvil , It was a leftover piece from a company that sells anvils . Since its so big I would presume it needs an oil quench ? it weighs about 95 Lb and is shaped like traditional japanese anvil 5" wide 12 " long and 14" high .

[Steve Sells]

you got a 55 gal drum of oil laying around ?

[Rhrocker]

That's a good plan for low-alloy and plain-carbon steels. The transition point of simple steels is very close to the non-magnetic "Curie point."

S-7 is a high alloy steel, with the Curie point not near the transition temperature. One needs another method of judging temperature - a tempil stick or a thermocouple or some such.

S-7 is not likely to anneal in vermiculite, as will low-alloy and plain-carbon steels.

Thingmaker, thanks for your input! Can you expand on the annealing part though? I understand about needing the sticks or a thermocouple to accurately determine when the right temp is hit, and it's apparently not at the non-mag point. The statement you make about not being able to use vermiculite is where I'm stumped. Would another type of
medium work better, like wood ash, or are you saying that S7 can't be annealed with any of the "standard" type methods??

Thanks!
Robert

[Bubba-san]

you got a 55 gal drum of oil laying around ?

Hello steve , as a matter of fact I do have some Parks 50 in a 50 gallon drum , I guess just bring to crtical non magnetic and drop her in . Down her in the sticks , I have seen Tom Clark (Deceased)owner of ozarks school of blacksmithing . He would start a fire near the edge of his pond , get the anvil good and hot , when ready he would roll them into the pond !!! ouch I dont have the nerve to do that . But, apparently Tom had been doing that for 40 -50 years and he had the tecnique down .His anvils were quite good .

[Frank Turley]

Disclaimer. Some of my heat treatments and end usages may not be according to the book, because I'm in a small shop situation. Beware.

S7 is a high alloy steel, a little above 5%. Therefore, you can't always go by magnetic or non magnetic when heat treating.

S7 is delivered in the annealed state. I've forged S7 tools, and so far, have had success judging the heat temperatures by eye. A couple of items. There is a limited forging range. Do not forge below 1700ºF, which is a full, bright red, above the cherry red ranges. In other words, don't forge at cherry red and below.

I've never been able to follow the specific annealing instructions in my small shop. Ideally, from 1500-1550ºF, you're supposed to lose only 25ºF per hour down to 1,000ºF (dark red), and then air cool. My personal anneal is to bury the hot steel in a lime/woodash mixture until ambient temperature. The steel will not become as soft as a manufacturer's anneal. That is the reason in the above posts, that the suggestion is made not to forge the striking head of the tool. Simply leave it in the as shipped, annealed state.

If you forge only the business end, you should anneal (the best way you can), harden, and temper only that end. On small tools, harden in air from the full, bright red (creeping into an orange heat). Use a rising heat; don't overheat and let it run backwards. When air cooling, place the tool upon a non reactive material such as a fire brick, a pile of coke, or a block of graphite.

When at room temperature, I sometimes use hot tools such as pritchels and hot chisels in the as-hardened state. The specs say, however, to temper hot tools to 1,000ºF or a little above. In tempering to that range, you are not chasing tempering colors down the length of the tool. Besides, the temper color rainbow stops at about 630ºF, so you're going to drop-kick the heat rainbow out the shop door. You simply soak the business end in the fire until it is a dark red incandescence and again, let it air cool.

S7 is versatile. You can temper for cold work tools, 400-500ºF, sometimes a little above.

When hardening pieces over 2.5 inches thick, you go to an oil quench, but you need a large volume of oil. I think you would want to wear protective clothing and face protection. My Jorgensen book says to quench down to a black heat (about 800ºF?). I assume you would then bring the piece out and air cool it from the black heat. If the piece is to be used as an anvil, I would temper at least to 500ºF.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[Rhrocker]

Thanks Grandaddy Frank! I guess we're working two senerios here, anvils and tools. Most of what I want to harden/temper will be punches, slitters, chisels, and the like. I h ave 6 feet of S7 from McCarr just for the purpose (couldn't find any H13 while flitting around finding tool steel). I also have 5160, which would probably be good, and 52100, plus W2 from Senior Hanson. I got the S7 in 5/8th's" hoping that I'd just have to work with the working end, and leave the hammer end alone. Looks like that part will work fine. I'll study your post some more and try and figure out how to HT and Temp the stuff without getting the other end to much involved. I use a gasser and not coal, so that's a disadvantage here where I need to spot heat. Right off the bat I'll be forging the top 1/3rd into various shapes, so I'll see what I can do to keep the bottom 2/3rd's cool. Just can't be that hard, folks have been using S7 for a long time so I'm thinking that all of the secrets are out in the open now.
Robert

[thingmaker3]

Thingmaker, thanks for your input! Can you expand on the annealing part though? I understand about needing the sticks or a thermocouple to accurately determine when the right temp is hit, and it's apparently not at the non-mag point. The statement you make about not being able to use vermiculite is where I'm stumped. Would another type of
medium work better, like wood ash, or are you saying that S7 can't be annealed with any of the "standard" type methods??

Thanks!
Robert

I apologize for being ambiguous. As Mr. Turley noted, for a full anneal the S-7 has to cool at a much much slower rate than low-alloy or plain carbon-steel. If you know anyone with a little kiln, they will be able to help you with annealing.

[SoCal Dave]

Frank: Once again you amaze me in your knowledge and willingness to share it with others. When you help one you help everyone looking for information. Thanks and keep it coming.
Your ex-student, Dave

[Rhrocker]

ThingmakerIII,
Thanks again, I have it straight now with all the info from this thread. Yes, I've had an
Evenheat kiln, 18" for years that I HT and Temper knives in. Never used it for annealing so I went and took a look and sure enough, I think I can ramp it up or down. I'll play with a piece and check it w/my Rockwell and see if I can get a differintial HT. Was thinking about putting clay (satanite) on the hammer end of the S7 like we do when bringing out (well, trying to bring out) a hamon in a knife. The clay should help keep the heat off of the hammer end for a while anyway.
Thanks again guys,
Robert

[thingmaker3]

Clay won't keep the heat off the S-7 any more than it keeps heat off tamahagane. The clay impedes cooling. I doubt it will impede cooling enough on S-7. Unless it takes more than 75 seconds to get down to 500F, you miss the bainite nose.

I would use the kiln to anneal, and I would HT by heating only one end. (Actually, that's not true. I would harden & temper the whole thing. Temper at 1-1.1 KF and the RC is only 47-51 with darn good impact resistance. And real good resistance to temper drawing.)

[Rhrocker]

Clay won't keep the heat off the S-7 any more than it keeps heat off tamahagane. The clay impedes cooling. I doubt it will impede cooling enough on S-7. Unless it takes more than 75 seconds to get down to 500F, you miss the bainite nose.

I would use the kiln to anneal, and I would HT by heating only one end. (Actually, that's not true. I would harden & temper the whole thing. Temper at 1-1.1 KF and the RC is only 47-51 with darn good impact resistance. And real good resistance to temper drawing.)

Humm...makes sense I guess. Something to think about.
Thanks TM3.
Robert

[Nakedanvil - Grant Sarver]

I HATE the common definition of "normalizing"; "heat to the critical temperature and air cool". For air hardening steels that's known as "quenching"! Every other process (except drawing) is defined by a specific cooling rate. Normalizing is actually somewhere between the required cooling rate for a full anneal and full hardening. In any event, almost any cooling rate will put it in better condition for hardening. If the object is to be able to drill the piece, it will usually require something closer the required rate for annealing.

I never advocate leaving the battering end untreated. This is often done to make the tool "safer". In my opinion, it does the opposite. The first thing that happens with a soft end is that it mushrooms. "I can just grind that off", you say? Well yeah, but the end is now work hardened. There is no more brittle, fracture prone condition than work hardened. Much better to quench both ends (or the whole tool) and draw the battering end to a "black red"

While I use some tools "as forged", I never advocate other do the same. I am aware of my final forging operation, but my "as forged" may be quite different than someone elses. Only specific processes can be conveyed reliably.

I'm with thingmaker 100% (as usual)