S-7 and H-13

Hi all, I've been searching the web for info on S-7 and H-13, for hot work. I have a couple of basic questions from the information which I found on the net. I'm trying to get this stuff straight but sometimes we get conflicting answer. So...

Is this the correct process for making an S-7 hot work tool:

Heat to 2000-1700F and forge to shape. Air quench Grind cutting edges as appropriate

Now - do I temper this or use it as-is? Does the "shock resitances" of this steel allow me to use it un-tempered without it breaking? If temper, what's a good heat to temper to for hot work? What about if I were to use it for cold work - temper, no temper, ? Should we not care because it's going to get hot and re-temper itself anyway? Is the water-quench (from cool a hot tool) going to temper it harder then air quencing?

Would the proces for H-13 be exactly the same (except I'd never cool the tool in water)? Is the advantage of H-13 over S-7 that the H-13 is going to remain harder then the S-7 as it heats up from use?

If all my tools were going to have handles (such that hold a hot punch wouldn't be an issue, and thus no cooling in water), would H-13 be a better choice?

Thanks in advance for any and all information,


Reply to
don schad
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Looks good after reading my copy of ASM's "Tool Steels" by Roberts and Cary.

Mentioned that annealing in ashes/vermiculite etc is recommended before heat treating. Also that normalizing was not recommended.

If you want more details just say so (fixin to cook hamburgers;).

It's a "medium carbon" steel and to me that means you can get away with no tempering. "high carbon" gotta temper. "low carbon" can't harden.

That's why the carbon content range in "numbers" varies, the number isn't set alloying effects the carbon content's effect.

As quenched S7 is about 60hrc

200F ~= 59 300F ~= 58 400F ~= 56 500F ~= 54 600F ~= 53 700F ~= 52 800F ~= 52 900F ~= 51 1000F ~= 51 1100F ~= 50

It's not a straight line it curves one way then the other. :/ Above 100F it drops off like it means business. ;)

1200F ~= 33hrc

That's learned through "your use".

The surface will do that and if it's going to get above 1100F then obviously you need to switch away from S7.

..."water quench from cool a hot tool"? :/

Qualified no, if I'm quessing what you mean right. S7 can handle being cooled with water and the only way to effect it harder is to again get it high enough to "austenitize"(non-magnetic) and re-quench. Everything else except for work hardening softens the steel.

Maybe, what temperature are the parts you are going to be working?

H13 is lower carbon and higher alloying than S7 so it's stronger and more heat resistant but more expensive.

That was a quick reveiw I might have to back pedal on half that after getting into it farther, later. ;)

Haven't studied those in this much detail in years. :/

Alvin in AZ

Reply to

Damned if I know the "correct" way to go about it, but I can tell you how some farriers do it.

Farriers use lots of S-7 and a little bit of H-13 for pritchels. A pritchel is a specialized punch used to make nail holes in shoes. An ideal pritchel has a relatively thick shank, a very thin working end (roughly .0625" x .1875") and can punch cleanly through dull-red/black steel without leaving a slug or deforming the tool.

I'm not a big fan of air hardening steels, but S-7 is an ideal steel for pritchels because it "re-hardens" between shoes. I forge pritchel points at a bright red/dull yellow and don't hit it after it cools to a medium/dull red. When I get the point forged, I throw it on the shop floor and let it air quench. This lazy man's heat treatment yields an extremely useful tool in a very short time but I don't use 'em.

As to why I'm not a big fan of air hardening steels, I am in the habit of going to water to keep my stamps and pritchels cool when I forge shoes - I've been making shoes for a long time and old habits are hard to break. 20-odd years ago, I bought a pritchel forged from H-13. I went to water between nail holes a couple of times and the next time I hit it, the damn thing flew to pieces and a piece stuck in my fat belly. I sprung a serious leak and when I got the bleeding stopped, I decided right then and there I wasn't ready for tools made out of stuff I couldn't dunk in water between nail holes.

Reply to
Tom Stovall

Never cool or quench air hardening steel in water. The whole point of air hardening steels such as S7 and H13 is that their critical cooling rate (which makes them hard) is so slow that you can do it in air. If you cool in water, they will crack. The rate is so slow that they are almost impossible to anneal without the right equipment--plan ahead if you expect to do any machining!

Note that the forging temperature is quite a bit higher than with plain carbon steel. Not that I have a lot of experience with air hardening, but I try to not forge below an orange color.

I've added some stuff below from my archives.

Steve Smith

---------------------------------------------------------------------------------------------------------------------------------------- Here's some info from Dave Smucker:

Here is how I heat treat H-13 with a coal forge. (Don't quench H-13 in anything but STILL AIR -- NOT OIL and above all NOT WATER.)

Start by heating you piece slowly, there is no hurry. Industrial heat treat includes a stress releif step -- that is why we heat slowly. Start on the outside of you fire and bring it into the center a little at a time up to about 1000 F -- Dark Red, in low light. Now go on heating up to above the critical temperature which for H-13 means to take it to 1850 F. This is a good Bright Orange heat, (Not yet a Bright Lemon which is 2000 -- 2050 and too hot) Again I assume in low light -- not outdoors in sunlight. Don't hurry here either -- let the temperature soak in, but don't get it too hot, keep turning you item over.

Now come the easy part. Set the item on a fire brick and let it air cool. This is a STILL AIR QUENCH -- a lot of smiths have trouble believing this is a quech but it is. Let it cool to 140 -- 150 F. (You can just hold your hand on it.)

Now temper by heating to 1000 F, the Dark Red, some call it Blood Red. Let air cool again, Repeat. (temper twice)

You are done. Clean up and put to work. It should be about Rockwell C 54.

------------------------------------------------------------------ Here's some info from Mike Linn:

I use a lot of H-13 for various hot (and cold) work tools. I think I'm the main supplier for the Alabama Forge Council. I get drops from a plastic

injection molding plant. All of the mold ejector pins are H-13. The pins come in 18" sections with a head similar to a thick nail head. They may only use 6" of the pin, and they would cut off and throw away the rest. I now have a box in the machine shop with my name on it for all scraps and old pins. I normally get a handful a week of pieces from 3/16" to 1 1/2" in diameter and 1 to 15" long. It varies depending on the repairs and rebuilds that week. I donate a lot of this material for our auctions and iron-in-the-hats.

I normally bring it to a medium to bright red for forging, then just air cool. You guys are making this stuff too complicated. When I first got this stuff we forged a chisel from a piece of 1/2 material, let it air cool, and proceeded to cut through a piece of 3/8th diamond plate, COLD, under a treadle hammer with no marking or dulling of the chisel. Pretty simple. I've never quenched in oil because I've never needed my tools to be harder than an air quench.

When making tools for hot work, especially when I'll be doing a lot of hot cutting or punching I make 2 identical tools. I'll use one while one is air cooling, and swap out when the one in use gets too hot. This system seems to work. If your working very hot metal, which you should be, The tool, especially if its thin in cross section will heat up rather quickly. So to keep the pace going, just have a spare tool ready to go.

Check the yellow pages for injection molding companies and talk a deal with the tooling shop manager or lead die man.

d> Hi all,

Reply to
Steve Smith

Others have answered your other questions better than I could. I have made various punches from H-13. I welded mild steel handles to them using 312 stainless steel filler rod with both O/A and TIG. I've only ever had one fail. It was re-welded and is still going.


Reply to
Ted Edwards

Needs to stop glowing before cooling with a water spray or oil? They made a big deal about it, in the book I was reading, how great S7 and H13 were at handling that sort of sudden heating and cooling treatment. But they were thinking of large tools?

What in the heck is the OP actually going to be using it for and how big of a tool?

"hey man, nice shot!" -Filter ;)

So which steel do you use instead? :)

Alvin in AZ (not worth a damn at shoeing horses)

Reply to

Thanks for everyones response...of course it raises as many questions as it answers. But I guess I would echo some of Alvin's questions/comments

- I was under the impression that S-7 could take a dunkin' w/o becoming too hard, and thus cracking. I was thinking of the "wack-wack-wack, dunk, wack-wack-wack, dunk" scenario where the tool isn't allowed to get all that hot, and certainly not red. I thought that was one of the big selling points of the S-7. It was my impression that the above wouldn't be a good idea with H-13 though. Hmmm...

I wondering if the "max rate of cooling before cracking" is known/published, and if we could use this? For example, would a rapid

200F to 70F dunk be okay while a 1000F to 70F dunk wouldn't? I guess the answer is to experiement a bit, but I don't really want to pick steel out of my gut if I can't avoid it...

So do you guys use a tool steel for your hot work which you dunk, and if so which one(s)? Or is dunking bad? Sound like we're going to have similar problems with all. I've been using coil spring and not bothering to harden/temper it. Or at least not in a controled way (see: wack-wack, dunk methodology). It has worked okay, but the tools don't last all that long, so I figured I'd take some time to make some good tools, and then take care of them.

Of course the idea of having multiple tools to work with while one is cooling is nice also. Also you don't cool the work with the dunked tool. Best though - it increases the liklihood that you'll be able to find at least ONE appropriate tool at any give time!



d> Hi all,

Reply to
don schad

The idea behind dunking is to keep regular tool steel from losing its hardness, which starts happening about 400F. It is not the correct method for high temp tool steel.

The main idea behind using a high temperature air hardening tool steel is that it stays hard at much higher temps. S7 doesn't lose significant hardenss until you get above 900F or so:

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What you do with a high temp tool steel is use it way past where you would normally dunk. Then you lay it down (not on a metal surface, it should be in air or on a brick) and let it cool. By the next heat it should be back to usable temperature. Replace dunking with cooling in air.

Steve Smith

d> Thanks for everyones response...of course it raises as many questions

Reply to
Steve Smith

Being the frugal (aka, "cheap") sort, I use whatever auto/truck coil springs are handy to forge stamps, pritchels, punches, creasers, and other tools going into hot iron. Cheap, readily available - and water coolable without subsequent shrapnel.

Reply to
Tom Stovall

Yeah what Steve said. ;)

They talk about water and oil misting and air blasting in the ASM book on the subject.

And I typed the wrong number early on it should have read above

1000F the hardness drops off to mush pretty quickly. (i'd left out a 0)

Yep H13 beats S7 in every way (by a little bit) except for price.

Multiple tools in S7 or H13 (or what ever you run across cheap;) would be the way to go.

The books tend to talk about intricate very expensive tooling, not hole punches. They only list punches as an after thought at the very end with the whole list of stuff it's used for.

H13's number one use (from what I pictured reading about it) is for zinc casting molds and the other uses that S7 can do for cheaper, are secondary as if it's an upgrade for S7 but only when you need to. And then it's only slightly better anyway.

I studied up on S7 and H13 somemore and will type out more details later. Remember tho I'm a book worm on this part never actually seen any S7 or H13 and knew it. :/

Alvin in AZ

Reply to

If you were to remove all my cheap parts there would be nothing left but dust. :/

While reading your post first thing popped into mind was some of the drift pin punches I have with what looks like a hunk of music wire stuffed into a softer hex-shaped body. They are as good as any.

Only difference was, I pictured a hunk of valve stem... :)

Think it'd work?

Alvin in AZ

Reply to

BEWARE, of putting "Valve Stems" in a forge or even heating them with a torch. Exhaust valves are often filled with Sodium and nasty reactions will occur when heated. I have been following this thread for a while and one thing no one mentioned is the habit of doing punching operations at the correct heat. If you are working mild steel get it HOT HOT like lemon yellow heat. Your effort is lessened and the punch will move very quickly through the material. The idea is the tool spends less time at temperature and is so less affected by the heat. I can punch through and back punch 1/2" plate in one heat using a handled (plain carbon) 3/8" punch and a 6 lb. hand sledge. I only need to cool the tool when I'm done. S-7 and H-13 are great but personally they are way more trouble than needed unless you are doing production on a power hammer. My advice is spend more time on learning good technique and save your bucks for coal or propane.

Glen G.

Reply to

Thanks for all the advice. I'll fool around with the stuff and see what works.

For those that are interested there is a guy selling various tool steel drops on ebay. Prices are a lot better then the online steel suppliers and you can make requests if you don't see what you are looking for.

No affiliation here.

Thanks aga> Hi all,

Reply to
don schad

Cool thanks. :) I don't hang out on ebay so wouldn't have known otherwise. Maybe I'll get some of that ellusive -F2- after all? :)

Alvin in AZ

Reply to

I though about mentioning them but was under the impression (from reading auto NGs) they are pretty rare animals anymore.

Also figured on a guy cutting them to size first thing. Hmmm... shouldn't have figured on that tho. :/ Since this is a blacksmithing newsgroup... first thing here I guess would be to hammer it to shape then cut?

Sounds good to me. :)

Alvin in AZ

Reply to

S7 and H13 are supposed to out perform plain carbon steels in that respect.

After reading GlenG's rant on plain carbon steels then re-reading the sections over the plain carbon steel (.60-.75% carbon) are still used by industry. Only when needed do they go to S7.

The one that shattered might have been something other than what it was supposed to be?

There are many types... S7 is a Cr type (class 510) H10,11,12,13 are a Cr/Mo type (class 520) H14,16,19,23 are a Cr/W type and (class 530) H20,21,22,24,25,26 are a W type (class 540) H15,41,42,43 are a Mo type (class 550)

Formulation wise class 540 and 550 look like half-carbon content HSS's.

They mention the W types being prone to shattering from rapid heating and cooling, they require a continuous cooling from internal circulation. That's thermal shock and they can't handle extreme impact shock loads either. But with the high number of them with an AISI/SAE letter+number designation they seem to be highly thought of by industry. :) I guess it's their "high hot hardness" ranking.

ASM studies them all and so have their own designation system, most tool steels aren't listed by AISI/SAE.

The published information I have is all comparitive. The discussion will automatically answer your questions if what you're seeking is a modification of what you are already doing. If this doesn't work for this reason... go to that. If this doesn't work for that reason... go to this.

If the common "cold cut" type punch is not working for you, determine why then the answer will be easy, after reading the discussion. One or more problems could be addressed at once too since it's pretty thorough. :)

Sounds like S7 is the way to go then?

For high production work only? Or if what you have isn't working?

Alvin in AZ

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