O-1 vs W-1

One of my guilty pleasures is watching "Forged in Fire." While I wish they'd put a lot less energy into attempting to create drama & tension and more into teaching the craft, there's enough in there to keep it at least marginally interesting.
One thing, though - I have repeatedly seen them quenching W-1 steel in oil. While it gives that satisfying and dramatic plume of flame and smoke, I thought W-1 is supposed to be quenched in water.
So, what's the deal here? Obviously, I have no skills in this area, but why would they do that?
Just curious.
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On 5/28/2019 5:05 PM, rangerssuck wrote:

slow quench . Which leads me to a question for any knife makers hangin' out here . What kind of oil do you use ? I have a blade I forged that needs heat treat (4140 type AFAICT) . I also have a whole shitload of that same steel , so figuring out the proper heat treat will make a difference in what i use it for . BTW , one of the FIF guys lives here , I've met Shawn Ellis and he's a pretty nice guy . SHAAZZZAAAAMMMMM!
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On 5/28/2019 3:20 PM, Terry Coombs wrote:


One of the FIF guys lives here as well. He will remain nameless. He contacted me about cutting profile blanks for knives out of stock, but didn't seem to want to pay anything for it. Maybe I just misunderstood. LOL.
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On 28/05/2019 23:20, Terry Coombs wrote:


I made some replacement pipe cutter wheels from EN24T (4340 a low alloy steel common in the UK), similar to 4140, and treated them like carbon steel for quench and temper and when tested they crumbled as still brittle. When I looked up the heat treatment for the alloy online, took awhile, the quench may have been similar but the tempering for what I was aiming at was up around 500C + and held for a longer period than basic carbon steel so the temper temperature for the alloy was some 300C - 350C higher than a basic carbon steel for the same hardness. Does make me wonder when I watch FIF how they manage with unknown steels as the heat treatment requirements can vary widely depending on alloy composition.
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On Tuesday, May 28, 2019 at 6:56:02 PM UTC-4, David Billington wrote:

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So does that pretty much call the whole show "just a show?" Their "tests" s ubject the knives to some pretty harsh stuff - the Marines' KA-BAR replicas chopping away at a rifle barrel and still holding their edge (though one g ot a pretty good chunk busted out) - how could that and the other nasties t hey do work if the heat treat is all wrong?
Again, I wish they'd spend more time on the craft and less on the show. Som e of these guys are really talented, but it gets lost in the high drama the y are attempting to create.
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On 29/05/2019 14:07, rangerssuck wrote:


Likewise. I don't disagree that the tests are tough and real and the process of tempering is frequently mentioned on the show but I don't recall ever seeing a blade bulk tempered after quenching to bring the hardness of the whole blade down, especially the edge. All I can remember is them showing localised tempering of the back of the blade and tang to increase toughness of those areas. Regarding material maybe they just make sure the source materials are going to be simple carbon steels and so behave as expected. IIRC 5160 is used a number of times and having just looked up the tempering data for that it was given as being between 426C(800F) and 704C(1300F) so somewhat higher than a simple carbon steel.
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wrote:


Keep in mind that recommended tempering temperatures often are based on *expected uses* of the steel. If it's expected to be used for a straight razor, the tempering temperature will be low. If 4140, it's expected to be used in a structural application and it will need to be less brittle. If it's 5160, it's expected that it will be used for a spring, and it will need to be tough and even somewhat ductile at high stress levels.
And so on. d8-)
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The 5160 froe is intended to be driven by a wooden club (beetle) and thus could be tempered hard and possibly brittle. The instructor suggested a temperature that a toaster oven can reach, though I completed an old heat treating oven project to do it.
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On Wed, 29 May 2019 11:01:04 -0400, "Jim Wilkins"

There is quite a bit of variation in tempering recommendations, and in practice. It's a case of "use what works." But steel is versatile enough, and forgiving enough, that the "experts" often don't know what works best.
The major tool-steel companies do extensive testing and provide a wealth of information. But when you're using some hunk you got off of a scrap heap, good luck, and may the angels be with you. d8-)
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I forged and hardened a froe (shingle or kindling splitter) from 5160 and was advised to temper it at around 180-200C for half an hour or so, which gave a faint yellow color. A file barely scratches it. http://www.cashenblades.com/heattreatment.html
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On Wed, 29 May 2019 10:39:07 -0400, "Jim Wilkins"

That's a sort of all-purpose tempering temperature for most tools. It works for me. Longer is better. Up to 230C (450F) or so.
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Do you know a good non-destructive test for proper temper?
My bouncing-ball scleroscope reads low on thin or light stock like lathe bits, even when clamped in a heavy vise. It did read a heavy hammer head known to be RC58 correctly.
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On Wed, 29 May 2019 11:20:40 -0400, "Jim Wilkins"

No I don't. The question is, what is "proper" temper? For what application? The big tradeoffs are hardness, impact strengh (notched or unnotched?), elongation (ductility, more or less), and local hardness vs. toughness (a softer temper for the back of a knife blade or a saw blade). Then you get into fatigue strength, "timbre" (don't ask), thermal tolerance (high-speed steel) and more. I don't know of a multi-purpose non-destructive test. There may be one; I just don't know what it would be.

Those tests will tell you hardness, but with a grain of salt. Thickness of the piece; differential hardening *within* the piece; backing; etc. all require some interpretation.
I'm no expert on testing methods, but I enjoyed working for Mitutoyo years ago and learning from the experts there. My takeaway is that you have to know exactly *why* you're testing for some property, or combination of properties, because you can only test for one or two things at a time.
To me, it's part of what makes metalworking so interesting. And frustrating. <g>
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On 5/29/2019 8:07 AM, rangerssuck wrote:


I've ever watched and only because he's a friend of my neighbor the blacksmith . I do know that Shawn's knives are selling for some serious money . Pretty nice stuff , definitely worth what he's charging .
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wrote:


My go-to for carbon and alloy steels. This appears to be the same edition as my print copy issued by Bethlehem Steel ca. 1980. Some of the older editions are also available as scans online. The only real difference I've noticed is some editions include Rockwell in addition to Brinell hardnesses in the tempering graphs, which I sometimes find helpful.
https://www.akronsteeltreating.com/docs/default-source/default-document-library/ast-book.pdf?sfvrsn=0
I wouldn't expect 4140 to make a very good knife, not compared to tool steels anyway.
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Ned Simmons

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On 5/29/2019 1:19 PM, Ned Simmons wrote:


given several rounds varying from 2 1/4 to 3 3/8 diameter and all around 6 feet long . Any knives I make will be just for me , practice , whatever . Should I ever decide to make knives for sale , they will be made from new stock purchased for the purpose . Until then , I still have a couple hundred pounds of this stuff left to experiment with . I will say that it does forge nicely - once I got the heat up where it needed to be . The one piece I'm having problems with is big enough to really need a power hammer , my puny little arm isn't makin' much headway with a 4 pound hammer . When that piece is finally beat into shape it will be machined into the body of a screwless vise for my mill . In fact , the vise project is what induced me to buy an anvil and build a forge .
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On Tue, 28 May 2019 15:05:23 -0700 (PDT), rangerssuck

You may have gotten enough of the picture from the other posts, and I don't want to add confusion, but maybe a different description will flesh it out.
"Water hardening" and "oil hardening" are just names that refer to the necessary quench rates of different steels. It doesn't mean that you have to quench it in water or oil. In fact, you may need to quench thick oil-hardening in water, and thin water-hardening in oil.
The terms refer to the *quench rate* required for a *typical thickness* of each steel, to convert it to the hard, martensitic phase. A thin piece of W-1, like many knife blades, will be quenched with adequate speed in oil. Preferably, you don't quench it any faster than necessary, but you have to quench it quickly enough to get a complete, or near-complete, conversion of the austenetic phase to a martensitic (hard) phase. Plain carbon steels (W-1) require a faster rate than oil-hardening alloys, which, in turn, require a faster rate than A-1 air-hardening. The higher-alloy, slower-quenching steels don't get any harder. W-1 will get as hard as the others. But it may not harden as deep, if it's a thick piece.
You want a complete conversion with *maximum safety*. That means you want to minimize the chance of cracking. The thicker steel is, the more likely it is to crack from an excessive quench rate, both from differential thermal shrinkage and from something I'll explain below. Once you've reached the necessary quench rate, quenching it faster won't make it any harder -- or not enough harder to be worth the risk.
The hardness of the finished piece depends on the percentage of the steel that was converted to maretnsite. We'll put tempering aside for now -- that confuses the picture a bit. But be aware that the different steel phases (ferrite, austenite, martensite and the mixtures, like pearlite) have different densities. When you convert ferrite to austenite by heating it above its critical temperature, it expands from the heat. When you quench it, it shrinks. But, say, you've quenched a thick piece of W-1 in water, and the inner part of the piece doesn't quench quickly enough to get a high conversion to martensite. That's common. So now you have a martensitic outer, say 1/4 inch, and then the slower conversion of the inside returns it to ferrite. Ferrite is *denser than martensite*. That's the other thing that leads to cracking. So you have high stress where the outer, martensitic layer transitions to the inner ferritic layer. It will shear at the transition point, and it can be enough shear stress to crack the martensitic layer right off of the piece.
Hmm. I'm getting a little windy. <g> Steel is very complicated. I studied it for years when I was materials editor at _American Machinist_. It kept me busy. But you don't need all of that detail to get the baisic idea. If you need more explanation, let me know.
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On Wednesday, May 29, 2019 at 10:04:36 AM UTC-4, Ed Huntress wrote:

ey'd put a lot less energy into attempting to create drama & tension and mo re into teaching the craft, there's enough in there to keep it at least mar ginally interesting.

il. While it gives that satisfying and dramatic plume of flame and smoke, I thought W-1 is supposed to be quenched in water.

why would they do that?

"Steel is very complicated." An understatement of majestic proportions. It is just these complications that made me question the whole FIF thing in th e first place.
They never show any sort of tempering, just heat the piss out of it (for wh atever value of "it" they have chosen that day) and plunge it into oil and hope for the best. Then they slash a pig carcass, pound the blade through s teel plate, chop up bricks, bend the blade 40 degrees, and rarely have any of the blades sustain damage or fail the tests. Methinks there's a whole lo t they don't show.
Thanks to all you guys for your input. Especially Ed for an excellent level of detail. I will continue to watch FIF, but with a more relaxed hope of l earning stuff.
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On 29/05/2019 15:42, rangerssuck wrote:

Actually since I posted last I do remember a recent FIF episode on UK Freeview TV where towards the end of the show one of the guys making a sword at his home forge was shown quenching it and then placing it in a heat treatment oven for tempering but it seems very unusual to show that tempering step on the show.
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On Wed, 29 May 2019 07:42:13 -0700 (PDT), rangerssuck

If they start quenching in the blood of a virgin goat, you can safely discount their technical accuracy. d8-)
BTW, somebody asked about quenching oil. That one is easy -- buy quenching oil. A bucket of it will last a lifetime. Quench in used motor oil only if you wnat a surface mottled with hard and soft spots.
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