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Hardening mild steel??


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Hi everybody. I am making some butcher dies for my home made guillotine fuller. I know that a tool steel would be better, but all I have at the moment is some mild steel to do the job. It is 3/4 inch thick so I thought maybe if I heated to a dull red or until de-magnetized then dunked it that maybe it would harded somewhat. What are your thoughts about this? Thank you for your responses. Mike.:rolleyes:

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I dont think that will do much to harden them, here is an old method that works for me, is non toxic, and should be easily available to anyone.


To surface harden mild steel.

Take a spoonful of wholemeal flour, add two spoonfuls of salt, add a little water and make into a smooth paste.

Heat the end of the item to be hardened until the paste will stick to it, when you have the item coated where you want it, heat the area to a bright red heat and plunge the item into cold clean soft water. The coated area will be appreciably harder.

Good luck with it,

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But if the metal under the thin skin that you surface hardened cannot support the impact, the surface will collapse into the core just like it wasn't hardened at all. If it is low carbon steel as you say, you need to heat it much hotter than non-magnetic. Quenching from non-magnetic is only good for high carbon steels. Water quench it from a high red but don't temper it. It won't harden much but it might do better than you think.

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Here is a method I use with good results. I use hard coal in my forge which is high in carbon. Carbon will migrate from the higher source to a lower source at the proper temperature. I first heat the metal to a bright red and sprinkle on borax. Immediately place it back into the fire and bring it up to a yellow heat just under welding sparking heat. Quench it in water and keep moving it around until it is cool. The borax adds a bit of boron to the metal in addition to the carbon being pulled from the coal. I don't know if this works with soft coal since I only ever used hard coal. I made my on touch mark and hardened it this way and it has held up for over 2 years. Using a guillotine will probably require you to re-treat it from time to time if you see it starting to show some deformity. I have also had good results making chisels and center punches using this process. Good luck.

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Do a search on this website for "Super Quench". Brine will harden most A36 pretty well, (it is is close to Robb Gunter' original lye/water/surfactant mix, which is no longer recommended due to the dangers of handling and use). In fact, I replace broken post vise springs with A36 versions by hardening in brine but no temper - makes great springs that don't break.

A36 is about 30 points of carbon so it's at the lower level of common spring steels.

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I have made many dies for my gillotine tool out of mild steel. I just quenched them in iced salt water they are fine for working hot iron. The only problem I had was the ends mushrooming from being hammered. The working ends of the dies are still as good as the day I made them

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Butcher dies usually fail by deforming, not abrasion. Thus, the case hardening would be expected to be less effective for them. I saw a great case hardening demo done on a mild steel bottom tool for shaping. The shape tends to wear away because of scale. Abrasion resistance really helps here.

For my butcher dies, I use poor man's hardsurfacing. I am too afraid to daub with hardsurfacing rod. Plus it is too expensive. Instead, I use HSLA rod to weld a bit of junk rail clip. These things have at least 60 points of carbon all the way through, and they possess a little bit of red hardness. I make sure the piece is small enough that it is blue temper after the welding is complete (thus skipping pre and post heat).

Never had one fail, but I did hear of somebody having a problem. Not the weld, but the rail clip shattered. No injury. Unlike what I was doing, this failed piece had some forging done on it. I did post-mortem and found internal cracks. I suspect that either the cracks were introduced by forging too cold or it was already cracked from use. You saves yo' money and yo' take yo' chances. ;)

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I have noticed that when I was making hooks out of mild steel if you heat it to an orange and dunk it till cool it hardens enough you can kill a drill bit with it. As for guillotine material the hammered end always mushrooms but that's not a big deal if you make the guillotine "blade" long enough that the mushroomed part doesn't bind the sliding action. I've considered taking some tool steel and plating the ends with it. Shape the plate and weld it to the mild steel in the wear areas. Haven't had enough problems with the mild steel to go that far though.

Best of luck to you

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I think I heard somewhere that the best you could get with superquenching mild steel is about a Rockwell 42. I have seen chisles made out of mild steel that were superquenched and not tempered then used to cut the parent metal.

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A lot of the cutting ability of a chisel is the geometry of the chisel and the hardness of what you're cutting. Annealed mild steel can be cut by a mild steel chisel just fine, but dont expect to cut any tool steel with it.

In addition, non-magnetic is still too low of a temperature for even tool steels. Non magnetic, or the curie point, is 1414, you need to reach the fully austenitic state before quenching your steel to get fully hard. AC1 (where austenite starts to form) at the lowest temperature is around 1333, but AC2 / Acm where the steel is fully austenitic is higher than that for almost every steel. The exception is the eutectoid steel (.83 carbon) where the Acm point is the lowest of any steel, and non-magnetic is a sufficient test, but this is the only steel this works effectively with. The addition of further alloying elements will increase the soak time at Acm that you need in order to reach fully austenitic to fully harden a steel. O1 for example needs a soak time of around 15 minutes for all the elements to go fully into solution. You will end up with fine pearlite mixed in with austenite if you just go to non magnetic, and you will never get fully hardened.

Martensite, the crystaline form of steel that makes steel hard, can ONLY be formed from austenite, so if you don't get fully austenitic, you cant get fully hardened.

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Do not understand why not make it simple and get a piece of right steel and make a GOOD TOOL
THE SUPPERQUENCHED steel will never hold high temp the moment u''ll use the tool the quenched miled steel will be SOFT again because it is not heat withstanding steel !!!
GET a piece of good steel and you get a good tool that will last longer and save lots of time and frustration!!!
Hofi

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Something that I have found to work fairly well, if you can weld of course, is to hard face the surface you are going to be using. But if you can't weld, then I would recommend case hardening it just as John B said. But if it's just going to be part of a guillotine tool, I don't think that you will need it so much but, yes, tool steel is preferred.

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I would think if you only intend to use the tool a small amount then use whot u got but if your expecting this tool to do work for you and last find a piece of tool grade steel any old tools or springs around I have tools made from mild for short runs but the more it works the more it neads to be tough (you only get whot you pay for)

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If there is one lesson learned from the senior blacksmiths I've met, it is that exceptional work results from the application of mastered technique, but to no lesser degree the manipulation of finely crafted tools. I would have to agree with HOFI, invest in a piece of suitable alloy steel -- s7(air hardening with great impact toughness) is a good choice for example -- then make a die that will last a lifetime and will butcher a keen edge predictably each time you use it. Good luck!:)

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xxxx xxxx
What a jump, going from mild to H13, H13 is what we used to call Hot Die, we still use it for punches to punch the eyes on rail spike hammers, blob punching in a die through about 80mm of 4140 at 1100deg in one go using a 250KG hammer. H13 holds up fairly well but my blokes insist on cooling the punches in water which ultimately stuffs them. We normally get about 20 to 25 hammers punched before the punch is RS. If you are using H13 it will be important to get the heat treatment right, and be careful of your heat when and if you forge it, as I remember it can be fairly easy to burn.
Good luck
Phil

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