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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making. |
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#1
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Damascus HT problems
Hopfully some of you Damascus makers can help me with a head scratcher I have.
I recently made up my 1st 1084/15N20 damascus billet. I was able to get 2 knife blanks from it and I attempted to HT 3 knives yesterday, the 2 damascus a 1084/wrought iron san-mai blade and two coupons of 1084/wrought iron as a control for normalization. I ran 3 normalizing cycles on the two damascus blades I made. 1600 degrees soak 10 min, cool to room temp. 1500 degrees soak 10 min, cool to room temp. 1450 degrees soak 10 min, cool to room temp. The first coupon was removed and broke shortly past 1500 degrees as control. The second coupon was ran trough all 2 norm cycles. Heated to 1500, soaked for 5 min, quenched in parks 50. The grain was checked against the control piece and showed grain reduction and was almost as fine grained as when i get it from NJSB. Then I ran the 3 blades through my HT program for 1084. 1500 soak 5 min, quench in parks 50 temp 50-70 degrees Blade is let to cool and both sides sanded with 400 grit trizact belt to shiny steel and then checked on my Rockwell hardness tester, and a file. My normal as quenched RC for 1084 when running this HT program (minus normalization as most of my blades are stock removal) is around 63RC. Both blades seemed to skate a file on its face, but I was able to get the file to dig in when the corner was used. I put them under my Rockwell tester they both read on average 56RC with 5 tests on each blade. I couldn't run any tests on the san mai as it was clad in wrought iorn. My Rockwell tester is running about .5 off of my calibration blocks so i know its not the tester. These are the first damascus blades i have attempted to HT. If anyone could shed some light on what i did wrong and what i could do to save the blades i would be most appreciative. I have spent a lot of time on these blades and would really hate to Put them into my RIP box. I did a snap temper at 340 for an hour to remove any built up stresses while i try to sort out my problem. |
#2
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Shift the last two normalizing cycles down by 75°F., the grain should be finer than as received.
Lower your hardening temp from 1500°F to 1475°F or less, especially if you are doing the soak. Normal as-quenched hardness should be 65 HRC, but if HRC reading is being taken on any section that exceeds .186” it will be lower. There is a hidden variable here, there always is. If oven calibration is right, carbon solution should not be the problem with these alloys. Decarb is a strong possibility and a 400X belt may not be enough to eliminate it. Effective cooling from austenitzation temperature in the quench may be a factor. How far away from your oven is the quenchant? Parks #50 can be used at, or slightly above, room temperature but 50°F to 65°F is a bit low, I prefer 98°F to 108°F. Your snap temper is a full temper, you need to lower a snap temper to around 300°F. Once again there is a variable that is not being caught here but without working with you in your shop I can only guess at it. Last edited by Kevin R. Cashen; 01-14-2019 at 09:14 AM. |
Tags |
1084, 15n20, belt, billet, blade, blades, blanks, ca, damascus, degrees, fac, file, hidden, iron, knife, knives, made, makers, problem, quenched, steel, stock removal, temper |
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