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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #1  
Old 10-09-2015, 10:02 AM
solvetek solvetek is offline
 
Join Date: Oct 2015
Posts: 7
O1 heat treat newbe

I am making a wood carving knife for myself and this is my first homemade knife.
I want a thin blade and will use 1/16 thick o1.
I know that 10x is better than o1 for beginners but I got a very good deal on the o1 and could not find 10x in 1/16.
The blade geometry is as follows: 1/16 thick, 1.5 inches long, 1/3 inch wide.
Heat treat process
1) heat with two propane torches, one on each side of the blade.
2) test with magnet until the blade is non-magnetic.
3) Once the blade is non-magnetic I will soak or continue to heat for 3 minutes trying to keep the same color.
4) after the 3 minute soak dunk straight into a glass of canola oil heated to 125 degrees.
5) after it cools bake in oven at 400 degrees for one hour
question:
1) should I put a dull edge on the blade before I heat treat, I have read that the blade edge should not be two thin?
2) i used this url to calculate soak time - is minutes correct correct http://htsteel.blogspot.com/p/heat-t...ool-steel.html
3) does the heat treat process I am using sound reasonable?
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  #2  
Old 10-09-2015, 11:14 AM
samuraistuart samuraistuart is offline
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You're right, 1084 especially is better for beginners, but I understand you need thinner stock than 1084 comes in. So PG O1 is OK for you to use, even as beginner.

With a blade that small (1/16"x1/3"x1 1/2"), I don't think you'll need two flames....just one. And probably no need for a "two brick forge" either, just use the flame as you were intending.

Pre heat treat your edge should be no thinner than 0.020".....especially with a bladed that thin.....I would just leave it full size and grind bevels afterwards. That's a small knife, and sandpaper with a hard backing will cut O1 well enough even hard.

Use dim or no light to get your eyes used to the colors at temperature. Use your magnet if you like. Just remember, non magnetic is not hot enough. Non magnetic is around 1414?F, and you need to be at 1475?F-1500?F. Once you reach 1500, O1 needs a soak, and I soak it in a kiln for at least 20 minutes. That is going to be very hard to do with a torch....but just try your best to not overshoot the heat, and keep the blade evenly heated at 1500 for at least 5 minutes. I recommend you check for decalescence as well....the shadow that moves across the blade at critical temp. This is better than the magnet, because the shadow will tell you exactly when you hit critical. Once the shadow moves across the blade, then hold it at that temp for at least 5 minutes.

130?F canola will work great with O1. Remember to agitate either vertically or forward/back...never side to side. Dunk in the oil for a slow 10 count, pull it out and with gloved hands you can straighten the blade if any warp forms when the temp is between 900?F and 400?F. Once the blade is straight, put back into oil until it reaches ambient.

Take blade out and check with file if it hardened. Remember that decarb may trick you into thinking it did not. So make sure you file thru any decarb layer before you think you failed!

Once you've verified that it is indeed hard, place into the oven at 400?F for at least one hour, twice. I do a water quench during tempers. Check the edge, if it's too chippy, back into temper at 425?F and check again.
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  #3  
Old 10-09-2015, 11:51 AM
Doug Lester Doug Lester is offline
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I'm not as optimistic as Stuart about you being able to use an open propane torch to heat treat the blade. I think that you will need a tin can or a two brick forge to concentrate the heat enough to do the job. Another thing that you could try is a acetylene torch with a rosebud tip. You've not chosen a steel that lends itself well to heat treating in a forge but it can be done. It would be easier if you could spot decalessance but you can try to soak the steel for 10-15 minutes at non-magnetic. You just don't want to let the steel get super hot. You might be better off by taking it up to non-magnetic and holding for 3-5 minutes before quenching just accepting that you are going to overheat the steel to a certain degree.

I would temper at 400? for two 2 hour cycles to try to convert any retained austinite to tempered martensite.

Doug


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  #4  
Old 10-10-2015, 11:04 AM
samuraistuart samuraistuart is offline
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A blade that is 1.5" long and only .3" wide and .063" thick? I would think one open propane flame would work fine. The flame itself is almost that big.
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  #5  
Old 10-10-2015, 11:28 AM
jmccustomknives jmccustomknives is offline
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I've heat treated blades up to 5" with a cutting torch, so he shouldn't have any problems.
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  #6  
Old 10-11-2015, 02:18 PM
samuraistuart samuraistuart is offline
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Maybe I should clarify my reply....

I wouldn't say, by any stretch of the imagination, that one "should" go about heat treating in this manner by using an open flame. Especially O1 steel. O1, as we know, "should" get a proper soak with tight temperature control.

We realize that not everyone has the equipment for the particular heat treat an alloy needs. Of course, 1084 is indeed a better steel for a simple heat treat set up like this. But if all one has is O1 steel and a torch, and the blade to be heat treated is about the size of a swiss army classic blade, it can be done.

One of two things are likely to happen, tho. The blade ends up overheating because we're trying to soak it at a particular temp and it just gets too hot ......or it gets undersoaked because we're afraid it will get too hot, resulting in a blade that is basically 1084.

Not trying to discourage anyone, but just saying an open flame isn't the best way to treat O1 steel, especially for beginners.
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  #7  
Old 10-12-2015, 05:39 AM
solvetek solvetek is offline
 
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If o1 is under heated will it come out with the same properties as 1084? In other words is a improperly heat treated 01 blade as good as a properly heated 1084 blade in terms of holding a fine cutting edge?
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  #8  
Old 10-12-2015, 05:46 AM
jmccustomknives jmccustomknives is offline
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It's not an under heated thing, under heated it will not harden. No, without the proper soak time O-1 and steels like it will not see their full potential. It's performance will be diminished without the soak, that however doesn't mean it won't make a good knife.
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  #9  
Old 10-12-2015, 06:55 AM
solvetek solvetek is offline
 
Join Date: Oct 2015
Posts: 7
Quote:
Originally Posted by samuraistuart View Post
You're right, 1084 especially is better for beginners, but I understand you need thinner stock than 1084 comes in. So PG O1 is OK for you to use, even as beginner.

With a blade that small (1/16"x1/3"x1 1/2"), I don't think you'll need two flames....just one. And probably no need for a "two brick forge" either, just use the flame as you were intending.

Pre heat treat your edge should be no thinner than 0.020".....especially with a bladed that thin.....I would just leave it full size and grind bevels afterwards. That's a small knife, and sandpaper with a hard backing will cut O1 well enough even hard.

Use dim or no light to get your eyes used to the colors at temperature. Use your magnet if you like. Just remember, non magnetic is not hot enough. Non magnetic is around 1414?F, and you need to be at 1475?F-1500?F. Once you reach 1500, O1 needs a soak, and I soak it in a kiln for at least 20 minutes. That is going to be very hard to do with a torch....but just try your best to not overshoot the heat, and keep the blade evenly heated at 1500 for at least 5 minutes. I recommend you check for decalescence as well....the shadow that moves across the blade at critical temp. This is better than the magnet, because the shadow will tell you exactly when you hit critical. Once the shadow moves across the blade, then hold it at that temp for at least 5 minutes.

130?F canola will work great with O1. Remember to agitate either vertically or forward/back...never side to side. Dunk in the oil for a slow 10 count, pull it out and with gloved hands you can straighten the blade if any warp forms when the temp is between 900?F and 400?F. Once the blade is straight, put back into oil until it reaches ambient.

Take blade out and check with file if it hardened. Remember that decarb may trick you into thinking it did not. So make sure you file thru any decarb layer before you think you failed!

Once you've verified that it is indeed hard, place into the oven at 400?F for at least one hour, twice. I do a water quench during tempers. Check the edge, if it's too chippy, back into temper at 425?F and check again.
What is the benefit of tempering for 1 hour at 400 degrees two times as opposed to once and would 3 times be even better?
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  #10  
Old 10-12-2015, 02:56 PM
samuraistuart samuraistuart is offline
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I think all steels should receive at least two temper cycles. For me, tempering is a complicated subject, I don't even pretend to know exactly what is what and how is best. There are a few things that tempering does, and one cycle (even if it's for a few hours) may not get all the "jobs" done. Carbon steels are much simpler than stainless, obviously, and for that reason carbon steels don't usually need three tempers, two is usually enough. I think one hour per cycle is plenty of time to get the "jobs" done. And I recommend always at least two cycles, at least an hour each.

So what are these "jobs" that tempering does? Well, I can recall a few of them, but not sure exactly what order these things actually occur. The main thing that we understand is that the steel is relaxed from much of the stress it saw in the quench, and sitting there as untempered martensite it's pretty stressful! The second thing that tempering does is convert some of the left over "retained" austenite into fresh martensite. I "think" that happens during the first temper cycle. The second temper cycle will temper that freshly created martensite from the RA. Also, I believe there are some super small carbides that might be precipitated during the tempering cycle(s).

I try not to assume that my hardening was perfect, so the tempering charts I only use as a guideline. I start at a low temper, maybe 350?F, and check after that first cycle to see if the edge might be too chippy. If it is, and usually that is the case because my hardening procedure is down pat, then bump up the temp to 375?F and check. If it's a kitchen knife, I like to leave 'em hard, often not even exceeding 375?F. If the knife might see more abuse than a kitchen slicer, then 400?F is a good starting point. For O1, 400?F should put you in the 61HRC ballpark, if you reached max hardness out of the quench. If you don't reach max hardness from the quench, start with those lower tempering temps and check the edge (or try to re-harden the blade and see if you can reach 65 or so).

Last edited by samuraistuart; 10-12-2015 at 02:59 PM.
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1084, blade, blades, carving, degrees, edge, file, forge, grind, harden, heat, heat treat, homemade, hot, knife, make, making, o-1, simple, small, steel, temper, wood


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