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HAREDEN, MILD STEEL?

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Can Mild steel be hardened by quenching? I know the carbon content is very low, and if it does harden at all is it any significant amount. I know the processes would involve the carbon content and with such a low amount does it amount to anything. Not necessarily in blade making, just in general. I had this question posed to me.

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It's been my experience that mild steel doesn't harden enough to notice, no matter what I've quenched it in. I've noticed some difference in steels with .4% carbon and up, but nothing below that. However, THIS THREAD by Ariel Salaverria details a process of case hardening where he got RC 56 out of 1030 (I think it was 1030, anyway).

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Almost all metals can be work hardened to some extent if they are not too brittle to begin with.

I have no practical knowledge of the subject, just what I have read.

 

It can be case hardened, but this is only skin deep and will be worn away after the first few sharpenings.

 

For that matter, you can case harden it, cut it into pieces, then stack the pieces and fire-weld it together just like you would damascus. Basically do-it-yourself shear steel (Not for the timid or faint of heart, I suspect).

 

If the piece really needs to be hardened, spring steel would be a better choice.

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Mild(1018,1020)does surface- harden slightly in a brutal water quench.Even more considerably in a brew known as SuperQuench-a detergent based liquid.The hardness obtained is often enough for expediency in some blacksmithing process,such as a quick and dirty drift.

Edited by jake pogrebinsky

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And then there's good old A36 structural steel, which is usually what they sell you as mild steel these days. It can harden up enough to annoy you, but not enough to hold an edge.

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thanks for reply guys. Learning as I go here. I wasn't sure to what extent it did harden but I figured it couldn't be much, I told this and just wanted to be sure I didn't mispeak.

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When I've made hooks and the like out of mild, I've had several snap when I've tried to tweak them a little. After the first couple, I thought it was because I'd quenched but even one that I let air cool broke. That's not to say the steel would be good for knives, but it can get brittle. The steel yard I buy from sells both 1018 and A36 and I buy the 1018, for what it's worth.

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When I started with stock removal, I was making blades out of concrete saws. I had a sheet of 4x6x1/8 steel. I figured I was set for life. My buddy explained the whole mild steel/ case hardening thing to me. Dang!

 

I used the sheet of steel to build a gas forge. Mild steel is good for many things, even forging knives. Just don't make the knife from it.

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And then there's good old A36 structural steel, which is usually what they sell you as mild steel these days. It can harden up enough to annoy you, but not enough to hold an edge.

 

 

Oh yeah! It can surely annoy the fire out of you on occasion. I was cutting some 2 x 2 heavy wall A36 tubing in the course of building my mini hydraulic press. I got a little ways into the cut and got the steel heated up real good then had to interrupt the cut. Didn't get back to it until the steel had cooled. Must have air hardened because the rest of the cut was rugged. A36 also seems to have varying hardness in places because one section would cut like butter but another a few inches away was tough.

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That's one of the big problems with re-melt, there could be any kind of steel in there, melted in the quickest fashion and extruded. Structural steel only has to meet structural requirements. There is no requirement for the steel to be an even diffusion of alloys across the whole melt. I think that's the one big reason that some steels that would not normally be expected to perform like a clean spec'd bar will. It leads to all sorts of claims that are outside expectations.

 

Just goes to show that you have to treat each piece of iron or steel as an unknown. Until you know, that is.

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That's one of the big problems with re-melt, there could be any kind of steel in there, melted in the quickest fashion and extruded. Structural steel only has to meet structural requirements. There is no requirement for the steel to be an even diffusion of alloys across the whole melt. I think that's the one big reason that some steels that would not normally be expected to perform like a clean spec'd bar will. It leads to all sorts of claims that are outside expectations.

 

Just goes to show that you have to treat each piece of iron or steel as an unknown. Until you know, that is.

BING! This is the problem I've had with rebar, too. Some sections are soft as putty and another section a couple inches away won't cut for love or money.

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Some thoughts - on cutting A36. If you get the leading edge of the cut hotter than the transition temperature the quench you'll get from the surrounding cold metal is about as drastic a quench as you can get - faster than water or brine. Expect just about any steel with a little carbon to get hard.

 

Steel is not commonly extruded - extrusion is saved for complex shapes & tube as it's a fairly costly process. It's melted, often in an electric arc furnace from scrap, melt times and processing are such that the molten steel is pretty uniform, and then continuosly cast going from molten to solid, typically reheated and then rolled to the final cross section desired. There are uniformity requirements for steel across a piece and across a melt. For structural steel they're pretty broad. I'd suspect hardness variation as more the reult of uneven cooling of product - a lot of structural steel such as rebar doesn't have controlled cooling, so if it is capable of hardening some of a rolling will and some won't depending on the cooling conditions each piece experiences. If you want uniform properties, you need to control cool the material - adding cost to it's production which you'll need to pay for when you purchase the producct.

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A36 and 1018, the claim to fame for both is formability and machineability . Has anyone here ever tried doing anything with a steel called Hardox , or AR400 / AR500 ? I've been told ( by a welder ) it wouldn't make good blades , but in it's heat treated form I have bent the daylights out of it , it sprang right back ,,, and beat on a big hardened steel scrap bin with it , the dents and chipping were in the bin steel , no damage to the hard stuff . Just wondering ,

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Ken, it might be good for a large chopper or an axe, but toughness does not equal hardness, which allows a blade to get and keep an edge. That said, I haven't had any experience with AR400 or AR500. I was talking with my teacher the other day and we talked about how it is really a waste of time to try to get a piece of steel to do something it was never meant to do. That might be the easiest way to put it. (I hope I don't sound like a pompous ass)

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I don't have any idea what the rockwell might be on it , but it will smoke a new HSS drill bit . When I cut it I had to slow the blade waaay down otherwise a Lennox or Starrett band/blade would immediately wipe out on it . We used it for wear strips inside refuse trucks .

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Daaaaaaaamn. If it's used for wear strips, sounds like it is tough stuff ;)

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I don't have any idea what the rockwell might be on it , but it will smoke a new HSS drill bit . When I cut it I had to slow the blade waaay down otherwise a Lennox or Starrett band/blade would immediately wipe out on it . We used it for wear strips inside refuse trucks .

 

 

Do you know whats in it? Might be good stuff.

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It took some digging to find info on AR400 ateel. There are no ASTM or AISI chem ranges for the grade, so it's up to each mill to determine how they make it. There are a lot of trade names for it - one I ran across at www.fordsteel.com was Wearalloy 400. For that grade, they offer the chemistry of Carbon 0.12/0.16 %, Manganese 1.55 % max, Phosphorous 0.025 % max, sulfur 0.005 % max, silicon 0.35 to 0.55 %, Boron 0.0005 to 0.005 %, chromium 0.55 % max, nickel 0.35 % max, and molybdenum 0.55 % max. It's typically supplied as plate in the quenched and tempered form with a Brinell Hardness (BHN) of 388 to 430, roughly 41 to 46 Rockwell C.

 

For the 500 grade, they increase Carbon to 0.27 to 0.30 %, drop manganese to 0.95 % max, keep phosphorous, sulfur, boron, and nickel the same, increase silicon to 0.45 to 0.55 %, chrome to 0.75 % max, and molybdenum to 0.65 % max and claim a BHN range of 477 to 544, roughly 49 to 54 Rockwell C.

 

Though it's abrasion resistant, I'm not certain how well it would work for knives. Abrasion resistant doesn't necessarily equate to good edge keeping/holding ability - one of the abrasion resisitant steel's is known as 13% manganese, or Hadfield's steel - abrasion resisitant, and hardens as you try to cut it. It's austenitic at room temperature and isn't useful as a knife alloy - does work for "jail bar", as it will work harden as someone tryies to cut it with a hacksaw.

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