MattBower

....who just came back from a year in Afghanistan. 1084/15n20 mosaic pattern weld by Chad Nichols. Whitetail crown handle with rosewood. Wrought iron buttcap and guard, etched and rust blued. (Well, the buttcap is cold blued. It was originally rust blued. Long story.) Cast coin silver medallion with copper spacer. Wood lined sheath with elk rawhide covering, sewn with artificial sinew.

I've been away from IFI for a while - can't really explain why - and I just want to say that it sure is great to see you back on the forum and back in the shop, Frosty!

I've had good results with Fluid Film for unpainted steel left outdoors. CarWell CP90 also looks very promising, but I haven't tried it yet. If you do cover the anvil, you need to allow it to breathe. A tight, waterproof cover will actually make things worse by trapping condensation.

Thanks. That's been bugging me for a long time.

Ah, somebody who actually understands this stuff! Great! We need more of those. (I'm certainly not one. I get by with what I've picked up from smarter people on the Internet.) If you wouldn't mind, can you explain what's meant by an "equilibrium phase" as opposed to a "metastable phase"?

I've heard some rumors to that effect before, but since practically every iron-carbon phase diagram I've ever seen shows A2 as a straight line at 1414 F (or 1418 F), I didn't follow up on them. But you got me researching, and I did find a table in a book called the Handbook of Induction Heating that shows the Curie temp of 1008 as 1414 F, and the Curie temp of 1060 as 1350 F. Very interesting. I'll have to ponder that a little; it could affect how we use the magnet to heat treat steels in a certain carbon range. Nevertheless.... No! That's not necessarily true! That's exactly what too many folks fail to understand about the magnet! Please look at the iron-carbon phase diagram at this link. Alloying elements may move some of the lines around a little bit -- up or down, left or right -- or may affect the precise shapes of their curves, but I believe the basics of this diagram apply to any common steel. Please note the line, A3, that begins on the Y axis and slopes downward to 0.83% carbon, the eutectoid point. (Other references will show the eutectoid at 0.77% or 0.84% C. And we're talking metallurgy textbooks! Where is it actually located? I'm not sure. I've even seen metallurgists admit they're not sure. For now let's stick with 0.83%.) At that point it changes names -- from A3 to Acm -- and slopes back upward as it moves to the right. Note the flat line, A1, at 1333 F -- that's the minimum temperature at which some austenite will form. And while we're at it, note the flat line, A2, at roughly 1415 F; that's your Curie point (but see above). Steel in the area above the curve constituted by A3 and Acm has formed all the austenite it can possibly form. Steel below Acm, but above A1, is a mixture of austenite and cementite (iron carbide). Steel below A3, but above A1, is a mixture of alpha-iron (basically pure iron) and austenite. In order to produce as much martensite as possible, we need to quench from a condition in which we have as much austenite as possible; that means quenching from above A3 or Acm, as applicable. Also note that while the Fe-C diagram shows you the necessary temperatures to achieve particular structures, there's also a certain time factor, especially when there are lots of alloying elements tied up in carbides along the grain boundaries of the steel, and we want to put them into solution. By exceeding the minimum temperature somewhat (not too much!) we can shorten the time for the conversion/alloy dissolution to take place, which is a good thing when we lack the precise equipment to allow us to soak the steel at a fixed temperature for 5, 10 or more minutes. Now, yes, the magnet can be very useful for helping us to judge A3/Acm within a certain carbon range: roughly (as Bob Nichols says in his heat treating blueprint) 50 to 95 points carbon. But note that the farther you get to the right or left of the eutectoid point, the higher Acm/A3 is, and the less useful the magnet becomes. Since this thread was about mild steel, note that down toward the bottom end of the curve the A3 line approaches -- and at very low carbon levels even exceeds -- 1600 degrees F. If you use the magnet to judge A3 for something like 1018, you're likely going to shortchange yourself on austenite and therefore martensite -- which you can't afford to do with a steel that won't make much austenite in the first place That's why I said to go hotter with the low carbon stuff. Also note an interesting fact about the eutectoid point: A1 and A3/Acm actually touch. There's no open area under the curve, in which you have mixed structures. Eutectoid steel kicks over to 100% austenite more or less immediately upon reaching A1/A3 -- and a magnet is a pretty darned good way to judge whether you're there. This is why 1084 has become very popular among bladesmiths with simple heat treating capabilities; you can heat treat it with simple methods and still get very good results. (And it's why the Steel Fairly delivered me some 1084 on Monday morning. ) That's certainly true; I should have specified that I was talking about relatively simple steels. But the highly alloyed stuff is totally unsuitable for primitive heat treating anyway.

All steels go non-magnetic at essentially the same temperature, the Curie point, which is right around 1415 to 1420 F, depending on your reference. (That's on the way up. On the way down, magnetism doesn't entirely return until the steel reaches a considerably lower temperature.) Non-magnetic is nothing more or less than a convenient way of estimating temperature if you don't have anything more precise; it really has nothing to do with whether the steel is ready to harden. For most medium/high carbon steels the recommended austenitizing temperature (the temp you quench from) is a good 100 degrees F hotter than non-magnetic, sometimes more. So no, it really isn't right to say that you "want to be as close to the magnetic point of your steel as possible before quenching." You generally want to be hotter than that. The instructions I've seen for Super Quench say to heat the steel to 1550, nearly 150 degrees hotter than non-magnetic, and quench from there. I still suspect you might get slightly more hardness from 1600, if you're using something like 1018.

? I haven't played with quenching mild steel much, since if I want a hard tool I tend to use a steel with enough carbon to harden properly. But for most medium and high carbon steels you actually want well above (100+ degrees F) non-magnetic. And recommended austenitizing temperatures generally climb as carbon content falls. So if it were me, I'd probably quench mild steel from around 1600 F, maybe even a little more. Why would that be?

You're overcomplicating it. The amount of smoke your fire is producing pretty much tells you all you need to know. Build a coal fire. When it gets to the point that it's only giving off a little smoke around the edges, it's a coke fire -- the smoking area around the edges is where you still have come unconverted coal. As you run low on coke in the fire, you periodically rake some fresh coke from the mound around the edges. And as the mound gets low, you periodically refresh it with new coal, which converts to coke while you're working. This is all much simpler to do than to explain.

That's really cool, Grant.

And for the record: in the event that my advice conflicts with Grant's, you should always listen to Grant!

Frankly, I'm not at all sure O1 is the steel you want to use for this. Striking tools are usually medium carbon steels like 1045(ish), 4140, etc., which are inherently tough, or S-series shock resistant steels that specifically designed to be beaten on. O1 is around 1% carbon, which gives you very high maximum hardness but also a certain amount of brittleness. (And it's not an ideal steel for primitive heat treating methods, which probably also doesn't help you. You're liable to get carbon and alloying elements elements segregating on the grain boundaries, which promotes brittleness.) But if you must try to make it work with O1, temper them much hotter -- maybe dark blue to start with? Roughly straw color is suitable for knife edges, not striking tools. Grain size seems to be good, from what I can see.

Oh, for Pete's sake! Now the Google cache won't work? This is getting ridiculous. Here's what I was trying to link to:

What you have there is a baked-on oil finish, very much like the seasoning in a cast iron pan. It can work fairly well, but it isn't as durable as the finish I was trying to point you toward. The reason the link won't work is that the whole forum is down. Here's the Google cache: Black Oxide - Bladesmith's Forum Board Look at posts 9 and 11 by Brian Van Speybroeck.

Yes, O1 isn't an ideal steel for relatively primitive, backyard heat treating methods.

Whew! Dude, slow down and read some blueprints. Enthusiasm is wonderful, but by itself it'll end up costing you a lot of unnecessarily wasted time. There are dozens of approaches to rust bluing, but this is a very effective one: Black Oxide - Bladesmith's Forum Board The thing I particularly like about that method is that it doesn't involve really nasty chemicals such as nitric acid -- unlike many, many rust bluing recipes.

Blacksmithing Basics for the Homestead - Google Books

I also use a bull pin drift. (I find that a 1.25" bull pin driven not quite all the way in is about right.) I use moly-graphite lube based on Hofi's, and a decent sized sledge. Even with all that it takes me several heats.

I'd like to know what's up with the face. It's obviously been refinished. Why? Has someone tried to build it back up with hardfacing electrodes, and if so did they know what the **** they were doing? Or was it just ground down to make it look pretty -- in which case, how much of the original steel plate was ground away?

I guess you could try chopping the stuff up and selling the pieces to guys who want rail anvils but can't figure out where to get rail locally.

H.L. Mencken said, "Nobody ever went broke underestimating the intelligence of the American public." It's not just Americans. However, in many cases "it doesn't make sense" really should be, "it would make a lot more sense if I had all the relevant information."

I've never burnt steel in a propane forge, but I wouldn't go so far as to say it's impossible. I'm sure it can be done. OTOH, coal/coke does it quite easily. This isn't usually considered an explicit reason to use propane, AFAIK, but it can be a nice side effect. That said, I really like the very high temperature potential of coal forges. Overheating is actually more of a concern with higher carbon steel, as opposed to lower carbon.

I believe normal masonry mortars are based on Portland cement. Portland will not stand up to anything even close to forging temperatures. It sets by becoming chemically hydrated, when you heat it up you reverse that process. It can also spall violently as that water turns to steam, though this might not be as big a problem with a porous aggregate. This is why commercial castable refractories use things like calcium aluminate cements.

I remember that, Rich. I may be able to find it. Having copper actually alloyed with the steel is one thing; having once melted a tiny little bit of copper in the forge is something else entirely. Of course if you stick a penny in a joint you're trying to weld, it's going to be impossible. (You'll be in good shape to braze it, though!) But the idea that just because you once melted a penny in the forge, it somehow permanently contaminates every piece of metal you stick in the forge just doesn't make sense to me. Even if the penny and the iron are in the forge at the same time, as long as you're not rubbing molten copper or dirty clinker into the joint, I have trouble seeing how it can cause a problem. I'm convinced this is an old wive's tale and nothing more.

Thanks, Grant. You just dispelled a lot of misconceptions that I had about A36! Now I don't feel so bad about using it in stuff liked wrapped and welded hawks. (With a higher carbon bit, of course.) :)