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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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anneal or not?
Having read some posts on other threads..I thought I would ask a question about annealing.
Is it necessary to anneal? If you anneal, should you anneal before normalising or after?. Should you anneal or normalise just before hardening? I would be interested to hear what you guys have to say. Thanks. __________________ Kevin Davey |
#2
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Don't know if its right or wrong, but here is what I have been doing with 52100-
I anneal so I can drill it and file it for the guard. I mostly do hidden or mortise tangs. I need the tang to be fairly soft. I anneal after thermal cycling to avoid any air hardening. What I do is not a full anneal. Being careful not to get up to critical, I get the blade to around 1200 degrees and stick it in vermiculite for a couple hours. I will normally do this twice, and sometimes a third time. Bill |
#3
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I have found it to be time well spent if I anneal before I profile the billet. I do 3 normalizing cycles before the HT.
__________________ Ken (wwjd) http://www.wacoknives.com "One Nation Under God" |
#4
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Thats interesting.
I predominately use 52100, and I am not using an annealing process. I do what I think is a thorough normalisation immediately after the forging process and before grinding. The steel seems soft enough and I can also file it pretty easy as well. If annealing is just being used to make the steel as soft as possible, then I dont think I am going to gain anything in my shop........but I am curious if its a benefit to grain size or not and helps create a better end product?........ __________________ Kevin Davey |
#5
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There is annealing [100F above critical, slow cool ] ,subcritical anneal [hardened and tempered about 1200F ] both should give spheroidized structure for maximum softness. If you don't need the softness then normalizing will be fine .There is no point in annealing and normalizing.
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#6
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I do not have an RC tester, here at my shop. There is one at the local VOTEk college. I have ordered same steel from different purveyors and then RC tested the steel, very different RC. In some instances as much as 35 points. This has varied quite abit with different types of steels and the same steel, but a different order. Grinding belts are the biggest day to day expense for me, so I would prefer the steel to be as soft as possible. In a lab or text book setting I would think the steel would be the same day in and day out. In the real world this is not possible, considering all the recycling that is being done. I do not think a proper anneal on steel does any harm to the structure and is beneficial in the long run. I anneal before I grind and do normalizing cycles before HT. Do or don't, that is completely up to each individual, but I think I will continue to do so, belts keep going up.
__________________ Ken (wwjd) http://www.wacoknives.com "One Nation Under God" |
#7
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Normalize to refine grain and even out all the havoc that you inflicted in the forging process. Anneal to soften and relieve stress in preparation for machining. If you plan on milling or drilling you will really need to anneal, unless you have an unlimited supply of bits. For this reason you will obviously need to anneal before the grinding and machining operations, which would be a good idea anyhow since annealing tends to be a decarburizing operation and you will want to remove that low carb skin.
Some steels can throw a curve ball at you. Hypoeutectoids, any steel with less than .83% (depending on the charts) carbon, can be normalized or lamellar anealed and then drilled with no problem. Steel with greater than .83%C will appear soft from these operations and will rockwell out as dead soft as well, but will then allow you to drill part way through before burning up every bit you own. These steels will have excess carbides that will tend to pool up and form very hard little packets in what appears to be completely annealed steel. This is where the hardening and then subcritical anneal that mete mentioned comes in handy. The hardening operation will break up those packets and scatter them evenly throughout in the form of little spheres, and then the next heat will soften the hardened steel around them. When machining, those little spheres will just get ripped out of the surrounding soft material and offer no resistance at all. |
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blade, forging, knife |
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