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The Newbies Arena Are you new to knife making? Here is all the help you will need. |
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#1
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Heat treat
I just tried heat treating a small piece of 01 steel in my old forge. I got it hot enough that a magnet wouldn't stick. It was glowing yellowish orange. I quenched it in canola oil and it flamed up a good bit. I then tested it with a file and snapped the piece in half. It is definitely hard but I am wondering if it is too hard. Is there a way to tell by the color of the metal where it snapped? It was a strange greyish white color.
https://drive.google.com/file/d/0Bxh...w?usp=drivesdk https://drive.google.com/file/d/0Bxh...w?usp=drivesdk |
#2
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Everything looks good. Of course right now it's too hard for a knife, that's why you temper it to reduce hardness.
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#3
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Ok good to hear. I will soon move forward and treat my knife and temper it. Would it be acceptable to evenly heat my knife until nonmagnetic and then quench only half of the blade and tang making sure the tip is quenched? Afterwards I would temper in the oven
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#4
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Assuming you mean the lower or edge half of the blade that's called 'edge quenching' and it's quite common. There isn't much point in edge quenching on a small knife though unless you are trying to create a hamon. Done correctly, edge quenching can make a large blade that will take a lot of punishment without breaking. A small blade will never be used to do heavy chopping and edge quenching them is more likely to make a blade that will bend and stay bent ...
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#5
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Ok, I'll stick to quenching the whole blade. I remember reading something about tempering that said you should do the first temper within 10 minutes of the heat treat. Is this necessary and what does it accomplish?
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#6
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as ray said on a small blade I would quench the whole thing....then be carful not to drop it so it wont break and temper right away. What happens is when you harden that steel it is under a lot of stress when its hard like that. this is why your piece of steel broke easily. IF you leave it like that and don't temper right away the stress wil cause tiny lil stress fractures in the steel wich could weaken the steel and the knife could break later on. I have even heard of after hardening putting it on a table and not tempering right away when they came back it had broken itself in half all by itself from the stress in the steel. again this didn't happen to me but I have heard of it best to temper right away. I have never used O1 so best to talk to one of the other guys about what temperature to temper temp to high = soft steel temp to low = steel to hard..
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#7
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How fast you need to get your blade into a tempering oven is going to depend on a few other things, mainly how you quench the blade. If you quench in oil for about 6-8 seconds and then take the blade out to air cool to the martensite finish (Mf) point on a TT diagram then you will need more time than you would if you held the blade in the oil until it reduced to the temperature of the oil. We won't even get into air quenching steels at this point.
A basic rule of thumb is that you need to let the blade cool until you can comfortably hold it in your hand. This will allow the last remaining austenite that will change to martensite to do so. If you start your temper before the conversion is complete that austenite could convert to something like bainite. Doug __________________ If you're not making mistakes then you're not trying hard enough |
#8
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when I quench it would be best to keep it in the oil until it I am able to handle it and then move on to tempering it? It would be incorrect to wait a few hours after HT to do the temper correct?
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#9
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That's correct. Sometimes you might get away with waiting depending on the steel but I wouldn't bet on it. Don't wait, temper as soon as the steel can be handled without burning your hand....
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#10
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The idea behind doing an interrupted quench where you hold the blade in the oil for 6-8 seconds and then letting it cool in the air until it passes the Mf point is to reduce stress in the steel as it cools. Holding the blade in the quenchant until they are the same temperature is to speed up the cooling. I'm not going to get into a discussion as to which one's the best.
I will say that one maker posted that he was having trouble getting 1095 come out of the quenchant with the Rockwell hardness that he expected. His wife, who also made knives, advised him to allow the blade to sit another half hour and then test the blade. He did and the HRc did come up. Keep in mind he was dealing with 1095 not O-1 and that he had a Rockwell tester that he coulduse to tell that the 1095 had not fully hardened when he took it out of the quench tank and it gained hardness with an additional rest. Barring something unforeseen like this I would recommend that you have your tempering oven ready to go before you start hardening blades and that you get the blades into the oven just as soon as you can handle them with your bare hands. Doug __________________ If you're not making mistakes then you're not trying hard enough |
#11
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That's strange Doug, I've heard of 440C doing that. Mostly because they were working it wrong.
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#12
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With my limited knowledge of metallurgy I don't know why 1095 should resist slipping from a face centered cube to a body centered cube especially being that it's a shallow hardening steel but that is what he said. I wish that I could remember who said it so that we could check back with him. I could kind of get my head around it happening with 440C if the chromium is added a bit by substitution in the iron matrix and causing retained austenite.
Doug __________________ If you're not making mistakes then you're not trying hard enough |
#13
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I am going to heat treat and temper tonight. Should 375? be a good temp for the initial temper? I was thinking I can always do a little higher temp for the second temper. I made an aluminum foil dish and am going to put about 2" of sand in it and put the blade in the sand.
Last edited by gkyle840; 11-01-2016 at 05:24 PM. |
#14
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Here are a couple pics of the blade ready to be heat treated and tempered
https://drive.google.com/file/d/0Bxh...w?usp=drivesdk https://drive.google.com/file/d/0Bxh...w?usp=drivesdk |
#15
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Are we still talking about O1 blades? If so, 400 - 425 is more appropriate...
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Tags |
440c, back, blade, common, conversion, edge, file, forge, hamon, handle, harden, heat, heat treat, hot, knife, make, making, metal, quenched, small, steel, tang, temper, tiny, white |
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