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Notes on Heat Treatment of Carbon Steel


Phil White

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  • 3 weeks later...

Hi Phil,

 

Great tutorial! I've only used O1 and silversteel for my cold chisels. After polishing I heat it up with a propane torch to an orange colour. Little sparks, dark ones, are having a ball on the tip, and then I quickly quench it in sunflower oil. The tempering is done in a small household oven, 2 hours at about 180-190 degrees Celcius. They're though.

 

cheers, Sjoerd

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  • 4 weeks later...

thank you for this extensive tutorial -- when I make tools I stay with high carbon material, some steels and especially stainless contain bismuth or tungsten which can hinder the hardening. My engraver meister (long ago) told me that the best color for hardening is cherry red (best seen when the lights are dim), anything close to orange may crack the piece. We used to swirl the hot iron in heavily used motor oil, such as crank case oil from big trucks or harley oil. Only harden the portion that will come in contact with the working material. As for tempering -- I sand and semi-polish the piece and rub it into an ivory soap bar (to keep scale from forming), then carefully hold a flame to about 2 inches from the tip of the tool (for chasing tools), watching the temperline crawl down the tool end -- when it is straw yellow I swirl it into oil or water. To test the proper temper you slightly run an old file over the hardened portion, it should glide across with a screech but not catching the metal. Graver tips are very thin and "burn" easily, you have to grind off the overheated part. If anything goes wrong and the tool is badly hardened or overheated in the tempering process, you need to heat up the whole piece evenly on a clay shard or a jeweler's soldering block and let it cool slowly, and then start over again.

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  • 1 month later...

Thanks for this, Phil.

 

Does anyone temper silver steel rod using an oven?

I've been making some small chisels/gravers with some success but am finding they chip out. I've been tempering at 190 degrees C for around an hour.

Guess I should try a slightly higher heat.

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Thanks for this, Phil.

 

Does anyone temper silver steel rod using an oven?

I've been making some small chisels/gravers with some success but am finding they chip out. I've been tempering at 190 degrees C for around an hour.

Guess I should try a slightly higher heat.

 

I've made several gravers and punches out of 01 drill rod (known as silver steel in Europe). I use a small kiln with a digital controller to do all my tempering. Seems a little more predictable than the color method. The color method is way too easy for me to overshoot the mark. I've been having success tempering at 425F (218C) for a little more than an hour.

 

I know several folks who use small toaster ovens (the little counter top kitchen ovens) for tempering, or even just the kitchen oven, just be sure to use an accurate thermometer, since the settings on the dial aren't at all accurate.

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I've made several gravers and punches out of 01 drill rod (known as silver steel in Europe). I use a small kiln with a digital controller to do all my tempering. Seems a little more predictable than the color method. The color method is way too easy for me to overshoot the mark. I've been having success tempering at 425F (218C) for a little more than an hour.

 

I know several folks who use small toaster ovens (the little counter top kitchen ovens) for tempering, or even just the kitchen oven, just be sure to use an accurate thermometer, since the settings on the dial aren't at all accurate.

 

 

Thanks, Tom.

Looks like I'll have to get a thermometer as I'm using a toaster oven at 230C for an hour but still getting chips.

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Like Phil, I have been tempering using the color method. The making of stamping tools was one of the first things I was taught. We used O1 steel drill rod. I recall watching a video many years ago on the making of a forged wood cutting axe. Hardening and tempering were done in a single process by quenching only the blade and then quickly removing the oxide by rubbing on a brick and then watching the tempering color creep from the residual heat of the body of the axe and then finally quenching to stop the process.

 

When using the Japanese tool blanks, we did not temper after hardening. The reason was not explained nor was it clear. Perhaps someone with more experience with the steel composition of the tool stock from Komokin has an explination.

 

A most humbling experience was to watch the coppersmiths from Santa Clara de Cobre in Mexico make a texturing hammer. They threw a coiled spring from a truck into their open forge and then pulled it straight while hot. They puched in the opening for the handle and then scored a section for the length of the hammer quenched it and broke it off. This left the rough texture on the face of the hammer. They whittled the handle from from broken broom handle attached it and immediately began using it to texture portions of the vase they were working on. The immediacy of the process was magical.

 

Phil, Your demo was very clear and helpful. Thanks, Fred

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Unable to find a suitable thermometer, and still having no luck with the toaster oven even on the highest heat (240c), I tried the colour method.

It seems I have success.

They are still hard enough to skate a file, but my chipping problems have stopped.

 

After fully quenching to cold, I cleaned the steel then held the Mapp torch flame close to the back of the tool held in vice grips. I let the very back turn to blue, backed off a little with the flame, then ran the heat further towards the tip, watching as the 'straw' colour worked its way towards the tip. When it reached, I quenched again. That seems to do the job.

 

Is this correct?

It's working, so I'm happy anyway.

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Hi Lee,

 

Welcome to the forum!

 

Sounds as though you have got the idea. I generally temper my engraving tools to a straw color. If you find that they still chip, you can re-heat it to a dark straw/brown color, without having to go through the hardening process again. Once you get used to hardening and tempering a couple of steels, for different purposes, you will find the process quite easy.

 

Glad my intro was of some use.

 

Phil

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  • 6 months later...
Any and all feedback is greatly appreciated.

 

great tutorial :rolleyes:

 

but there where a few points

including spark testing would probably be helpful

 

while there was reference to "cherry red" a lot, and the more technical metallurgical structures where omitted on purpose

there is a very simple test to see if the steel has been heated enough..... its no longer magnetic, often an easier description and test for someone just starting.

 

while forging wasnt covered all that much, when you are forging steel a normalizing process afterwards helps to relieve internal stresses. This has some bearing on steel applied for tools and a "normalizing" annealing step should be a recommended after forging.

 

the assertion that mild steel can't be hardened is maybe a little too absolute (never the less tool steel is obviously preferable)

 

finally there is no avoiding the need to match a steel and quench regimen if optimal results are the goal

 

when I "ballpark" a steel of unknown pedigree, I generally employ a heated oil quench

 

as linked above haphazardly, here in total

Fundamentals of Knife Forging, Starting from Zero

(one of the more lucid presentations Ive encountered)

 

I am by no means a master blacksmith, just a studious apprentice :rolleyes:

 

PS we also temper by color (oxy-acetylene), and watchmakers often temper small parts in sand or brass filings for more even heating, like the plate solution but with greater contact distribution

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I've made several gravers and punches out of 01 drill rod (known as silver steel in Europe).

 

Sorry Tom, had to correct this. O1 is known in britain for example as BO1. Silver steel is closest to W2 with an imperceptible bit of nickel thrown in I believe.

 

Regards

 

Hyllyn

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Thanks Chuck,

 

I like your color chart and graph. The ones that I have become used to dealing with are much more complex, and were left out of this tutorial for that reason. This tutorial was originally prepared as a slide presentation for a presentation that I gave many years ago at a conference on the conservation of industrial artifacts. The intention was to give people a general overview of the historical process of hardening and tempering carbon steel.

 

It's always interesting to see what others are doing. The reference to hardening mild steel is interesting. I suppose that it could be done, at least to some degree, but why?

 

Thanks again for your input.

 

Phil

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  • 4 months later...
Thank you all for your comments!

 

Karl,

 

I suppose that overheating for annealing could burn some carbon out, but since it is mostly locked into the crystal structure, this would take a lot of overheating. When I first started making tools, I was trying to make a small chisel for carving bone from a file. It worked at first,but I wasn't satisfied with the temper. I heated and reheated it several times, and eventually ruined it. I was likely removing carbon to the point where it would not harden properly any more. Kasenit (or Casenite) will only add carbon into the surface for a few thousandths of an inch.

 

Dick,

 

I did make the flintlock. The parts were made from rough bar stock by forging sawing and filing. No machinery was used, and no casting. All hand work. It took 3 1/2 weeks to make, 8 to 10 hours a day.

 

Ford,

 

Have you ever read the 11th century treatise on metal working by Theophilus "De Diversis Artibus", or the Various Arts? It is a wonderful account of medieval metalworking technology. Mostly good practical stuff, with a few wildly fantastic accounts for turning copper into gold, etc. He advocates, in several situations using the urine of a small red haired boy, and the blood of a red haired man, as a quenching medium.

 

These quenching mediums are actually sound advice for cooling the steel quickly, but not as quickly as water(although, I don't see the importance of the red hair, and don't advocate the use of bodily fluids)... Water will often cool tools too quickly, and it is sometimes preferable to slow it down a bit, particularly for delicate tools. I usually use oil for this purpose, particularly for small thin knives. This is something that I should add to the tutorial.

 

Any and all feedback is greatly appreciated.

 

Phil

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  • 6 months later...

Thanks Mike,

 

Recently I was thinking about this and other tool discussions on TCP as my woodturning teacher and I were considering tools and how we might adapt some for the tiny work (relative to the work of most turners) that I am working on while learning to use a lathe. Your posting on this topic and bringing it to the top of thie list is helpful. Thank you.

 

Janel

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Janel,

 

FYI, drill rod makes very good turning tools, especially small scrapers, and is readily available from most metal dealers, as well as from many hardware stores. You just have to find out wether or not it is meant to be quenched in oil or in water, the latter being most common. If you follow the sequence laid out for hardening and tempering you will have some excellent custom tools that will hold an edge well.

 

Mike,

 

Thanks for bringing this out again!

 

Phil

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Hi Janel,

 

Try ordering here: Brownells They sell small pieces, and also flat stock, which is ideal for turning tools. They also stock 1095 steel, which is excellent for making small carving knives. Both these steels are sold in the annealed state and can be shaped by grinding or filing (my preference) as is. When you are happy with the shape, the tool can be hardened and tempered.

 

Phil

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