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High-Performance Blades Sharing ideas for getting the most out of our steel.

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  #1  
Old 05-10-2013, 11:11 AM
Any 22 Any 22 is offline
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Forging Question

Heres the background Im 63 still forging by hand using a whisper Momma & 6 lb hammer above a 100lb emmerson horseshoeing anvil . I use 1" bar stock of 52100 usually about 4" stick . Now I used to forge 2 knives back to back then 1 now here I am taking a break 1/2 way through 1 . Question does quality suffer if you rest during the forging would it suffer if it rested all night & got finished tommorrow? by resting I mean I heat to forging temp them drop into quench which I do several times during forging, this time taking a long break.. My theory is make the best one you can & needs to be better than the last one,or go to Walmart & get one. I try to follow mr. Fowlers forging and treating methods except I dont have a power hammer.
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Old 05-10-2013, 12:45 PM
Doug Lester Doug Lester is offline
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Number one, if you drop to about a 2-2.5 lb hammer you will be able to forge longer and with more control plus you will be less likely to give yourself tennis elbow.

Second 52100 is really not a good candidate for heat treating in a forge. It takes a long soak, at least 10 minutes at about 1450?-1475?. Higher than that and you can run into problems with grain growth and forming retained austinite. Can you heat treat 52100 in a gas forge? Yes, especially if you can spot decalesence and recalesence. Can you reliably heat treat 52100 in a gas forge? My opinion is that you cannot, nor will you be able to spot that you have a problem by just looking at the blade.

Multiple quenches, the way that you describe it has a chance to cause microscopic cracks in the 52100. By microscopic I mean that you might need a scanning electron microscope to see them. This problem is cause by plate martensite abutting against each other a causing a stress crack when quenched. This is a problem with high carbon steels that is recognized in the steel industry. I cannot say for certainty that the more you quench a steel like 52100 that you will get more of these cracks but I haven't found anything that says that you won't. I would not use Mr Fowler's triple quench method for that reason and, if you have a regulated heat treating oven as he does, there is not reason to do so. Austinize the steel at under 1485? for about 10 minutes in a controlled environment and quench once.

If you have to take a break with your blade partially forged, do at least one normalization cycle to relieve stress in the blade. If you austinize, quench and lay it aside until later you are asking to have the steel break from the stress between the atomic bonds in the iron crystal matrix of the steel. It's probably one of those things that you can get by with 100 times but on the 101st time you will come back to broken blades on your work bench.

Better steels for heat treating with a forge would be 5160, 9260, 1070, 1080, 1084, or other steels with around 60-85 points of carbon.

Doug


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Old 05-10-2013, 07:57 PM
Any 22 Any 22 is offline
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Thanks for the reply Doug . I use the 6 lb hammer to get from a 1x4 bar to a 1.5 x 1/4 x8 flat bar then i get progressively smaller with my hammers . As far as 52100 goes I personally just like the steel also like 5160 but when Im serious about makin a knife I use 52100 , that being said I dont professs to be a master smith but have had good luck with the working of this steel in my lil gas forge. Probably not Up there with Eds or yours but am learning. Dont have access to every convenience available so have to work with what I have. Using the magnet as a thermomemoter and a tripple quench heck I even temper in the kitchen oven I turn out a useable knife of which Ive never had one returned since I started using 52100. I dont do this for a living so cant justify some of the more expensive toys. Maybe ill just make a smaller knife . May GOD blees everyone thats helped me I learn something new everyday.
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Old 05-10-2013, 10:01 PM
Doug Lester Doug Lester is offline
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I like 52100 also and I have turned out a few blades from it. I've even done some modified austempering with it. I'm going to a simpler steel because there is no way that I am satisfied that I can harden 52100 correctly reliably and consistently.

When you get dealing with any steel that is up around 1% carbon you will run into problems with microscopic quench cracking due to the plate martensite bumping up on each other, as I have explained. As far as the retained austinite goes about all you can do is to make a test blade, noting exact temperatures and times, then sending it out to be sectioned and examined under a light and scanning electron microscopes. There is no way that you can look at a blade and judge how much retained austinite there is. There is no way for you to tell when you've corrected it.

Of course, you can assume that there is too much retained austinite and get yourself a tank of liquid nitrogen and convert the retained austinite to untempered martinsite. You might be able to do that in a bath of kerosene and dry ice but to be sure you need to use liquid nitrogen. The best thing that you can do with steels with up around 1% carbon is to use a regulated heat source, such as a heat treating oven or molten salt bath and keep to under 1485? for about 10 minutes from the time that the steel comes up to temperature. That way you will not cause the problem in the first place.

With the microscopic cracks in the hypereutictic steel, you can't stop it but you can reduce it. One, only quench once to harden. I have done things like quench the point when it was getting a lot hotter than the thicker parts and returning the blade to the forge to prevent grain growth in that area. The best way to do this with a hypereutectic steel like 52100 is to do that before the point is fully austinized. You can also reduce the effect of cracking like this by keep your grain size, thus crack size, down. Another thing would be to marquench to reduce stess in the steel that occurs when there is more than one iron crystal phase by getting it to switch phase as close to the same time as possible.

I really do like 52100. I think that it's a great knife steel. I just don't have the equipment to handle it at this time and I need a new roof more than I need to get a heat treating oven and have my garage rewired for 240 volts. So the best thing that I can do is choose a steel that I can handle with the equipment that I have on hand.

Doug


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  #5  
Old 05-11-2013, 08:03 AM
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Gary Mulkey Gary Mulkey is offline
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Quote:
Originally Posted by Any 22 View Post
Heres the background Im 63 still forging by hand using a whisper Momma & 6 lb hammer above a 100lb emmerson horseshoeing anvil . I use 1" bar stock of 52100 usually about 4" stick . Now I used to forge 2 knives back to back then 1 now here I am taking a break 1/2 way through 1 . Question does quality suffer if you rest during the forging would it suffer if it rested all night & got finished tommorrow? by resting I mean I heat to forging temp them drop into quench which I do several times during forging, this time taking a long break.. My theory is make the best one you can & needs to be better than the last one,or go to Walmart & get one. I try to follow mr. Fowlers forging and treating methods except I dont have a power hammer.

If you are worrying about doing the forging during different days then I don't believe that there is any problem with it as long as you normalize the piece before quitting for the day. This will relieve any stress in the steel. It may cause a little more loss to scale though so start with a piece that is a little oversize.

I guess that I am not understanding you completely when you say that you "drop then into quench several times during forging". If you are actually quenching the blade several times during forging then this isn't necessary nor advisable but maybe we aren't communicating.

Gary


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