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  #1  
Old 05-10-2013, 05:32 PM
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twgray twgray is offline
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heat treat problems

Yesterday I did the heat treat on 3 blades in the previous post. Here is my process.....
Anneal at 1450 and let cool in the oven overnight.
Clean up the profile and do a preliminary bevel grind.
Stress relieve at 1250, hold for 20-30 minutes, then air cool.
Harden at 1525, hold for 20-30 minutes then quench in warm, agitated canola oil.
Temper at 350, twice, 2 hours each cycle.
When all was done my hrc's were 40-44. In fact, my blades that have yet to go through HT are harder than the knives I just heat treated. I've done this before, same steels, same process and hit 60-62. What am I doing wrong? BTW, it's sawmill steel that resembles L6, 3/32' thick.
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Old 05-11-2013, 07:34 AM
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Steve Randall Steve Randall is offline
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Tom that sucks. It all looks good to me ,I would do a normalizing cycle instead of just anneal especially if you had them cut out with a plasma cutter. That said the steel should get harder than 44 without any problem.
My next question ,have you used this particular batch of steel maybe its not L6. you can try quenching a test peace in water see if it gets hard. good luck.

Steve


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  #3  
Old 05-11-2013, 08:02 AM
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Ah, water quench a test piece. Now that's a good idea. Steve I'll try a normalizing cycle today. I figured annealing would make it all consistent. As to the batch, that might be the problem, but considering the needs of the sawmill it makes sense to me they would be using the same blades from the same providers. I'm not trying to cheap out, just enjoy taking advantage of local, recycled resources when I can.
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Old 05-11-2013, 07:24 PM
Ed Tipton Ed Tipton is offline
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twgray...Your techniques seem to be OK. If you have used steel from this source before...and had good luck with it...then I would feel somewhat confident about the results...but when it's all said and done...it's still mystery metal. Even assuming that the sawmill used the same provider, there is no gaurantee that his provider used the same type of steel.
This is just one more case that perfectly illuystrates why using mystery metal is ill advised. You may be able to get away with it...but this could be the time when the time and effort to make three blades is all a big waste. At least you have gained some experience grinding and forging.
At this point, trying the water quench is about all you can do. If it still fails to harden, then I'd just chalk it all up to experience and order some steel from Aldo or Kelly cupples.
Ordering the common knife steels from either of these guys is not expensive....and it takes the guessing out of the picture....and it also makes it easier for this forum to help you in the event of problems.
After all, if you aren't sure of what kind of steel you have then you can't expect us to know either. and without that critical piece of knowledge, help is hard to find.
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Old 05-12-2013, 07:47 AM
Barry Jones Barry Jones is offline
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Quote:
Originally Posted by twgray View Post
Harden at 1525, hold for 20-30 minutes then quench in warm, agitated canola oil.
Phillip quenches our PB&J blades (sawmill blade steel) in peanut oil. He does not warm it unless it's real cold outside and the oil has stiffened up.

Not sure if that is what your problem is, though.

You could send me one of your blade blanks so Phillip and I can try to heat treat it.


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Old 05-12-2013, 11:25 AM
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Thanks Barry. I'll clean one up, re-annealed yesterday after normalizing, and send it your way.
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Old 05-12-2013, 12:38 PM
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I check HRC at each tempering cycle; I've done the same steel and can vary from 30 minutes to one hour. I tripple quench 1095 and 52100 so that would require additional tempering. Are you checking to insure you attained proper martinsite before tempering.


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Old 05-13-2013, 09:36 PM
Doug Lester Doug Lester is offline
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Because you were using old saw mill blades it's a crap shoot to figure out the proper heat treat. Each saw mill blade could be of different steel and require different treatment. How do you know that they are all L6, by the way?

Even if they are L6 that can still give you a carbon content from 0.70% carbon, which is slightly hypoeutectic to 0.90% carbon which is pretty hypereutectic and won't heat treat the same. If it's more the 0.70% carbon type the 1525? would be good but the 20-30 minutes could be a little long. If the steel has more like 0.90% carbon the the temperature is too high and the soak time is too long, unless you are adding the kiln recovery time to that, and you could be getting a lot of retained austinite.

The tempering temperature seems to be a little low for a steel of 0.90% carbon but it might not be bad for something with 0.70% carbon.

My advice is that you stop using mystery metal unless you know the exact alloy of each blade and go to a known steel that will be pretty much the same batch to batch.

Doug


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  #9  
Old 07-18-2013, 12:08 PM
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Decaurburazation.....
I coated the blades with an alcohol and borax mixture before hardening cycle, and after tempering at 325 for 2 hours the hrc was 61.5, right on the money for what I'm doing.
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Old 07-18-2013, 07:56 PM
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Cool, glad you figured it out.
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  #11  
Old 07-23-2013, 08:20 AM
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Look here it has a vast amount of info on steels and the How To Do's for heating,quenching,and normalizing them.

http://hudson-metals.com/

Sam


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