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Main Boards => Hunting Knives and Crafters => Topic started by: razorback on February 17, 2011, 04:44:00 PM
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I have gained access to several potters kilns with a new job I just took. One is a small jewelery electric kiln that can go up to >2000 degrees. If I want to harden a blade (old file), what temp should I get the kiln to and how long should I leave the blade in there to get it to temp before quenching. I know that steel type and other variables are necessary for completely accurate information, so ballpark numbers are great. Anything to help will be appreciated.
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Most high quality files are 1095 steel. Look up the specs online for quenching temps and tempering temps. This should put you right on the money. If your hardeness level comes up weird then you either have really bad files ( Chinese steel ), or the file has 1.2% carbon which requires a longer soak time to go into saturation.
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Will leaving it soak longer hurt it if it is 1095. it is an american made nicholson file so should be decent steel. I'm hoping this works as it will give a much better hardening than my little hand blown charcoal forge.
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90% of Nicholson files are 1095 the rest are 1.2% carbon steels. A longer soak time at the proper temperature will not hurt the steel or its hardenability. Just don't go more than 20 degrees hotter than the soak temperature and you will be ok. When you overheat the steel you end up loosing carbon in the steel and growing grain size which is to be avoided at all costs.
One important note here is that you either need to use a thin clay wash that is dried on the steel prior to placement in the kiln, or use stainless steel pouches with a small amount of charcoal in them to protect the finish of the steel. The charcoal burns enough to eat up all the oxygen in the pouch. Kilns tend to cause excessive scale build up due to the oxidizing atmosphere in the kiln. Get the blade to the finish level you want. Get a thin clay wash dried on the blade. This makes it easy to get the finish you want on the blade once it is hardened and tempered.
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How thin a wash of clay and what type. These are kilns from a pottery workshop[, so a clay wash should not be difficult to get if it is not some special clay.
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As thin a wash as you can get is best. I like Rutland High Heat Mortar. Satanite works, finely ground or powdered clay soil or pottery clay will work. The key is to get it fully dried to the blade prior to starting the heating process for hardening and tempering. Rutlands sticks pretty well for me. You can also use it for creating a nice hamon in 1095.
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1095's soak temp is 1475 for a minimum of 5 minutes at that temp. I looked it up.
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In an electric kiln how long is it likely to take to get to that temp. i can control the kiln temp but am unsure of how long it will take to get the blade to that temp before I leave it to soak.