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how do you prevent warping

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toek

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When heat treating thin blades.

Im thinking of stainless warping during heat treatment. Whats the thinnest you "dare" to grind befor heat treating? Any advice you can give on how not to warp.

The steel "we" tried was rwl-34 (CPM154, ats-34).
 

Marko Tsourkan

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Why do you need to pregrind deep hardening steel? Hardened steel is just a little bit harder to grind than unhardened, and grinding introduces stress in the steel and a possibility of warping during heat treating.

Pick the thickness that is close to the final thickness. Heat treat a blank in a full thickness, aluminum plate quench, temper and then grind. Do a cryo quench if you have a capability. Use good quality ceramic abrasives belts. They will remove metal efficiently while keeping it cool (you will need to dip your blank in a bucket of water periodically)

M
 

Mike Davis

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Why do you need to pregrind deep hardening steel? Hardened steel is just a little bit harder to grind than unhardened, and grinding introduces stress in the steel and a possibility of warping during heat treating.

Pick the thickness that is close to the final thickness. Heat treat a blank in a full thickness, aluminum plate quench, temper and then grind. Do a cryo quench if you have a capability. Use good quality ceramic abrasives belts. They will remove metal efficiently while keeping it cool (you will need to dip your blank in a bucket of water periodically)

M
+1
 

Eamon Burke

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Why do you need to pregrind deep hardening steel? Hardened steel is just a little bit harder to grind than unhardened, and grinding introduces stress in the steel and a possibility of warping during heat treating.

Pick the thickness that is close to the final thickness. Heat treat a blank in a full thickness, aluminum plate quench, temper and then grind. Do a cryo quench if you have a capability. Use good quality ceramic abrasives belts. They will remove metal efficiently while keeping it cool (you will need to dip your blank in a bucket of water periodically)

M
Marko, do you have any suggestions as to where one might find a wide variety of thin stock? It seems that the field and camp knife folks think that .15" is pretty thin.
 

toek

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Thanks Marko, do you know where i can get some more info about plate quenching?
 

jmforge

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Aldo has .103 stock in a lot of the steel he carries, which is like 3/32 with a little extra meat on it. On some of the CPM stuff, he has stock as thin as .062.
 

Marko Tsourkan

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Admiral steel has Sanvik variants in several thicknesses.

Aluminum plate quenching is basically using two thick aluminum plates (I use 1" thick) to cover the blank (one on the bottom, one on the top) for fast and efficient cooling. It helps a lot with keeping a blank straight. Search youtube or google to find more on the subject.

You can also try to straighten a warped blade using this method:
http://www.bladeforums.com/forums/showthread.php/838681-Straighten-During-The-Temper

M
 

toek

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Pick the thickness that is close to the final thickness. Heat treat a blank in a full thickness, aluminum plate quench, temper and then grind. Do a cryo quench if you have a capability. Use good quality ceramic abrasives belts. They will remove metal efficiently while keeping it cool (you will need to dip your blank in a bucket of water periodically)
Done a lot of reading tonight =), just to clarify HT -> plate quench, temper -> cryo quench? And if it still warps use the clamp temper method. If i get it i should interupt the tempering befor it reaches the right temp and tighten the clamps? then temper and then quench, perhaps in sub zero?
 

Marko Tsourkan

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Done a lot of reading tonight =), just to clarify HT -> plate quench, temper -> cryo quench? And if it still warps use the clamp temper method. If i get it i should interupt the tempering befor it reaches the right temp and tighten the clamps? then temper and then quench, perhaps in sub zero?
Always cryo before tempering. Are you going to try RWL-34 again? You might check their website for heat treatment temp recommendation of give them a phone call. Sometimes they specify how long to cryo quench.

It you don't pregrind, and you plate quench, you should have no problem with warping. If for some reason you do, you can over-clamp it during tempering to straighten the blank. A little bit of warping can be ground out as well.

M
 

toek

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The "plan" is to stick with RWL-34. I spoke with them a couple of days ago about forging the steel due to the size, they have 50mm standard i need 55 =/. Aperantly its quite sensitive about overheating but they say no problem with forging. They also recommend low temp HT with cryo for the steel to be less sensitive to corrosion but still quite hard.

Cryo seem to be done for 10min but at what stage should i plate quench? shall i HT then cryo im a bit confused now (as usual)

Thanks for your advice Marko
 

Marko Tsourkan

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This is a basic HT schedule for all steels (blanks are cut out of sheets, not forged. Shallow hardening steels need to be pre-ground on the edge, while deep hardening don't)

- Bring your blank to the temperature you are heat treating at (also called austenitising temperature)
- Soak at that temp for how long is required
- Quench (oil, water, plate, air-cool)
- Cryo
- Temper

For temperature and soaking time it is useful to read steel data sheets or talk to manufacturer. It is also useful to heat treat and measure hardness to see how close you are to the manufacturer's data. You might have to adjust temp on you oven, soaking time or both.

Since you are in Sweden, calling manufacturer and discussing heat treatment sounds like a logical step, especially if you are new to this.


M
 
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