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Blades ugly after heat treatment.
- Thread starter legato1
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you used a forge to heat treat?
- Joined
- Sep 23, 2006
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some pics would be good, along with a description of how you heat treated
- Joined
- Dec 2, 1999
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- 9,910
I believe you overheated the steel. A coal fire has the ability to ruin steel in a hurry. Maybe you could give some details of the forging process also?
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Can you grind through them? Has one broken or can you break it to see what the grain looks like? Try etching it and see what it looks like....
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- Sep 8, 2006
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im gonna post pics when its doen etching, but for now il tell about forging process, i dont really know any fancy terms, but i got it dull orange, the chart i have describes it as approximately 2350 the chart is from Wayne Goddard's book the wonder of knife making (after i made my rail spike knife my gf got it for me as a gift so i wasent completely in the dark) and beat it to shape after the first heat treat i quenched it in water and the point curled up cause i had it really thin so i cut it off and shortened the blade (about 1/2 inch) i hand rubbed it up to 400 and tried to heat treat it and now here we are.... i hope that is enough of an in-depth enough description of forging process...
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i didnt even think to check the chart to see if it was in the temp range suggested by the heat treating data book. it says 5160's range is from 1600-1700 the chart in goddards book says 1600 is dark orange, mabey i doomed my self... i just thought to get it hot and quench it... now i know for next time. im still curious what those rings are...
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- Dec 2, 1999
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- 9,910
The rings are blisters from quenching when the steel was way too hot. You should use a magnet to test the steel. As soon as the steel is nonmagnetic quench it, if you wait too long it will have grain growth and blisters which result in an inferior performance blade. Did you normalize the blade first?
Its all good for ya. Just learn from it and make another one. This is what we call "Fun". Welcome to Bladesmithing
Its all good for ya. Just learn from it and make another one. This is what we call "Fun". Welcome to Bladesmithing
- Joined
- Sep 8, 2006
- Messages
- 1,188
the quality of the pic is poor i know, but i couldent get it to see what i see. all those marks are "blisters" is this blade still useable? or should i just stop working on it and start another project? did the heat treat at least make it hard enough to use or did it just destroy the grain?
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- Dec 2, 1999
- Messages
- 9,910
I say toss it and make another one. Are you going to use a coal forge again? If so you will need somebody to walk you through it.
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- Nov 26, 2001
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- 1,375
From the pic I can barely see a blade-shaped thingy, not much help there.
Anyway, I use a coal forge to make my knives. I have two, one, larger, with an electric blower. The second, smaller, with a hand cranked one.
Although a coal forge temperature is not as easy to set and maintain as, for example, an electric kiln, actually it has many advantages over other types of forges . First it lets you control where you apply heat. You can do differential heating, for example.
Anyway, there are some things you can do to have better results.
1) If at all possible, do heat treating in the dark.
Or at least in the shadow.
Seeing clearly the color of the piece is paramount, even if you use a magnet.
A magnet is a helper, but doesn't substitute your skill in determining the temperature by color, and which parts of the manufact are at a proper heat.
Strong light will make you believe the manufact is much colder than it really is, making it very easy to overheat the piece and cause grain growth, over scaling, decarburization, and other bad stuff.
The darker, the better.
For tempering you'll need good light to see the oxidation colors, but for quenching light is your enemy.
2) Use fine coal.
If at all possible, try to use coal in small pieces, not larger than a thumbnail, perhaps. You can do a proper heat treat with larger pieces (the ones I use vary from egg-sized to cherry-sized) but it's more difficult to get uniform heat.
3) Use coke, if at all possible.
If you hase to use coal, by all means let it coke for a while before doing heat treating. Smoke and live flame are the bane of a proper heat treat, since they prevent you from seeing the piece and the colors, and can also put bad stuff (like sulphur) in the steel.
4) Us a gentle heat, and little air.
Don't turn the coals to a raging inferno. Turn on the heat without the blade in the coals, to make the whole mass as homogeneous as possible and build up some reserve of heat, then turn down the air drastically. Leave as little air as needed to have the coals burn at a constant, uniform orange heat.
I don't know your forge, but in mine a breath is all it needs. In doubt, too little is far better than too much. You may always cranck up the air if you don't reach critical, but if you burn the steel, the knife is trashed.
Put the knife in the coals so that it receives as uniform a heat as possible.
Slowly heat it up. Don't try to bring it to critical in a hurry.
You have to bring the steel to, say, 850 °C: strong heat will bring you there faster, but will also make it very easy to miss the point and overheat the blade. If your forge is at 850°, the blade will take time to get at that temp, but in the end it will get there, and you won't overheat the steel.
The ideal is to run slightly higher heat than necesary initially, and as the blade starts to glow, turn down the air and let pure radiated heat do the rest.
This is also why you need a dark room. By the time you see the glow in strong daylight, the blade will be far overheated.
5) Move the knife
Move the blade lengthwise, to avoid hot spots. You shouldn't have any hot spots if you followed properly what said at point 4), but move it all the same.
The ideal is to have a V shaped groove in the hot coals where the blade runs back and forth, back and forth, slowly.
6) Quench IMMEDIATELY.
When the blade reaches non mag, or the color you know is right, leave it in the coal some more to soak in more heat and get o the proper temp through all its thickness.
Use this time to plan your quench. The tank should already be there and ready since you first put the blade to the fire.
Now, plan how to grip the blade in the proper way with your tongs, how you want to dip it into the quench medium, if you want to dip it vertically or horizontally, only part or all of it, if you want to move it or keep it still, etc. Make a mental sequence.
When you are ready, remove the blade from the fire and quench it in a single, rapid move. DO NOT fall to the temptation of looking at the blade to see if it's the "proper color". You'll have already looked at it before, you put it back into the gentle fire, and now you know it's ready. You will only waste heat doing so. Out of the fire, an into the quench in one move is all.
Then, remove all oil, rinse, grind away scale and clean with acetone to remove any trace of grease and then temper immediately as fit.
Anyway, I use a coal forge to make my knives. I have two, one, larger, with an electric blower. The second, smaller, with a hand cranked one.
Although a coal forge temperature is not as easy to set and maintain as, for example, an electric kiln, actually it has many advantages over other types of forges . First it lets you control where you apply heat. You can do differential heating, for example.
Anyway, there are some things you can do to have better results.
1) If at all possible, do heat treating in the dark.
Or at least in the shadow.
Seeing clearly the color of the piece is paramount, even if you use a magnet.
A magnet is a helper, but doesn't substitute your skill in determining the temperature by color, and which parts of the manufact are at a proper heat.
Strong light will make you believe the manufact is much colder than it really is, making it very easy to overheat the piece and cause grain growth, over scaling, decarburization, and other bad stuff.
The darker, the better.
For tempering you'll need good light to see the oxidation colors, but for quenching light is your enemy.
2) Use fine coal.
If at all possible, try to use coal in small pieces, not larger than a thumbnail, perhaps. You can do a proper heat treat with larger pieces (the ones I use vary from egg-sized to cherry-sized) but it's more difficult to get uniform heat.
3) Use coke, if at all possible.
If you hase to use coal, by all means let it coke for a while before doing heat treating. Smoke and live flame are the bane of a proper heat treat, since they prevent you from seeing the piece and the colors, and can also put bad stuff (like sulphur) in the steel.
4) Us a gentle heat, and little air.
Don't turn the coals to a raging inferno. Turn on the heat without the blade in the coals, to make the whole mass as homogeneous as possible and build up some reserve of heat, then turn down the air drastically. Leave as little air as needed to have the coals burn at a constant, uniform orange heat.
I don't know your forge, but in mine a breath is all it needs. In doubt, too little is far better than too much. You may always cranck up the air if you don't reach critical, but if you burn the steel, the knife is trashed.
Put the knife in the coals so that it receives as uniform a heat as possible.
Slowly heat it up. Don't try to bring it to critical in a hurry.
You have to bring the steel to, say, 850 °C: strong heat will bring you there faster, but will also make it very easy to miss the point and overheat the blade. If your forge is at 850°, the blade will take time to get at that temp, but in the end it will get there, and you won't overheat the steel.
The ideal is to run slightly higher heat than necesary initially, and as the blade starts to glow, turn down the air and let pure radiated heat do the rest.
This is also why you need a dark room. By the time you see the glow in strong daylight, the blade will be far overheated.
5) Move the knife
Move the blade lengthwise, to avoid hot spots. You shouldn't have any hot spots if you followed properly what said at point 4), but move it all the same.
The ideal is to have a V shaped groove in the hot coals where the blade runs back and forth, back and forth, slowly.
6) Quench IMMEDIATELY.
When the blade reaches non mag, or the color you know is right, leave it in the coal some more to soak in more heat and get o the proper temp through all its thickness.
Use this time to plan your quench. The tank should already be there and ready since you first put the blade to the fire.
Now, plan how to grip the blade in the proper way with your tongs, how you want to dip it into the quench medium, if you want to dip it vertically or horizontally, only part or all of it, if you want to move it or keep it still, etc. Make a mental sequence.
When you are ready, remove the blade from the fire and quench it in a single, rapid move. DO NOT fall to the temptation of looking at the blade to see if it's the "proper color". You'll have already looked at it before, you put it back into the gentle fire, and now you know it's ready. You will only waste heat doing so. Out of the fire, an into the quench in one move is all.
Then, remove all oil, rinse, grind away scale and clean with acetone to remove any trace of grease and then temper immediately as fit.
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
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- Aug 20, 2004
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- 38,521
As I see that you are a student, I would suggest that you hook up with one of the several good smiths in the San Antonio area and make a visit to their shop. You will get a lot better idea of what is going on by seeing it done, and learning firsthand.
Stacy
Stacy
- Joined
- Nov 26, 2001
- Messages
- 1,375
It's not only possible to overheat it, but to burn it for good, or melt it.
A forced air coal forge can reach temperatures well over the burning point of steel.
Briquettes are not a good way to forge, though.
Charcoal is a good, clan fuel, and can give a good amount of heat, especially when crushed in small pieces (japanese smiths worked with charcoal forges for centuries). But nowadays is expensive and you have to burn a lot of it. Coal is better, but you have to coke it. Coke is best.
If possible, get Jim Hrisoulas books.
Best of all, have a professional teach you. You can learn more in a single day than in a year of reading.
A forced air coal forge can reach temperatures well over the burning point of steel.
Briquettes are not a good way to forge, though.
Charcoal is a good, clan fuel, and can give a good amount of heat, especially when crushed in small pieces (japanese smiths worked with charcoal forges for centuries). But nowadays is expensive and you have to burn a lot of it. Coal is better, but you have to coke it. Coke is best.
If possible, get Jim Hrisoulas books.
Best of all, have a professional teach you. You can learn more in a single day than in a year of reading.