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Charlie Meek

Water Quench Failure Question

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So I had my first blade fail in a water quench. I've done a few smaller blades with no problem but this was my first larger blade attempt. Bear in mind the grinds are rough. I thought I'd at least clean it up a bit so I could see the issues. I'm thinking it was a bit thin and that I overheated the tip area. My small gas forge needs to modified a bit for larger blades apparently. Could have been that my grind was off as well. May just be the knife gods teaching me a lesson. 1095 steel. Blade was coated with some off the shelf refractory cement. Room temperature from my spark bucket that's not been changed in a month. I attempted to do an interrupted 3 in and 1 out then back. It didn't ping right away. Happened during the second time in. Check it with a magnet and a high temperature heat gun and I could see the transformation happening so pretty sure I was at least close on the temp. I did only do two cycles of normalizing though.

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Edited by Charlie Meek

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Break it off clean and check the grain.

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my only question would be, why submit yourself to a quench process that has a high percentage chance of failure? If i did interrupted it would be from water to oil. I finally just broke down and got some Parks

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I've had successful water quenches with MUCH thinner edges, it's all about having the right temp and a really low manganese steel, lower carbon range helps too, I like 1075 and 1080 for water quenching.I closely watch the color and do a snap temper immediately after the quench followed by my normal tempering cycle.

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3 in and 1 out? Why not just quench and leave it quenched and reduce the stress on the steel? Am I missing something? If I'm not missing something then that would be my guess as to why it cracked, and also - oil is the way forward!

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I'll definitely snap that puppy and take a look. Honestly I just like the idea of water quenching. Heck I've got the time and the steel to make more blades so why not. Plus it's just more practice.

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Everything needs to be very close to perfect for water quenching. Grinds, finish, account for sori, clay. Takes time to find what works for you. Watch your temp closely, heat the water to 120-140 Fahrenheit (add some soap if you want), quench at the lowest heat possible. Cracks will happen, but at least for myself, I've had a very high success rate with decent hamons. Also, I ONLY water quench when I want an active hamon.

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If I was going to go back to water quenching, actually brine quenching, I'd experiment to see how long I needed to hold the blade in the brine and then take it out and allow to air cool and still achieve good hardness. The aim would be to beat the nose of the cooling curve but not cross the Ms or just do so by a little and then allow the steel to cool slowly through the Mf until it hardens fully. That way the stress of martensite formation is reduced.

 

Doug

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I had a hell of a time breaking a piece off. End up putting a piece of square tubing about 3' long and was able to get a pretty good break on the hardened portion which did snap after a bit. The clay coated side just bent a little sideways which I guess means I'd have had a pretty good blade if hadn't of cracked. Grain is real tight on the uncoated and gets looser towards the spine. I'm pretty sure I overtempter it and tip area was hotter. I'm assuming it pulled faster than the other sections and that's what tore it on the radius. I'm sure I can just reforge the rest of it or flux it and recycle the rest.

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I've done quite a few blades in 1095 with a brine quench chasing hamons. However, I always finish them in oil, so 3 or 4 seconds in brine, then immediately to oil. I also coat the blade with a super thin clay wash to prevent scaling, and I have been told that that is probably helping keep the blade in one piece during the brine quench. Additionally, internet lore tells us that a brine quench is supposedly more gentle than a water quench even though it is faster.

 

 

3 in and 1 out? Why not just quench and leave it quenched and reduce the stress on the steel? Am I missing something? If I'm not missing something then that would be my guess as to why it cracked, and also - oil is the way forward!

 

After you get past the nose in the heat treat curve, the carbon is frozen in place to create austenite, but the blade is still quite hot. It will change shape as it cools down, but the stress will be uneven because of the shape of the blade. Allowing this portion of the cooling to happen slower in oil is less stressful than doing it is water. (Once again according to internet lore)

Edited by Brian Dougherty

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Hey Charlie, you're braver than I am! I've done one water quench that didn't go so well at all. I had my grind pattern going edge to spine, just like yours. That was but one mistake among a few I made! For future water quench....

1. If you are set on water quenching 1095, use brine over straight water. It is a "faster" quench in the sense that the salt helps to break up the vapor jacket, allowing a better contact of water to blade...that is how I understand it. I would also do an interrupted quench as well. 3 seconds into brine, then immediately into oil until ambient temp. Then temper.

2. Canola oil at 130°F will harden 1095 in thin sections (under 1/8" spine, thin edge) pretty well, for future reference.

3. Have grind lines running horizontally (tip to ricasso) instead of perpendicular (spine to edge). The grind lines at a thin edge (especially an edge that is apexed) is a huge target for a crack to promulgate.

4. Looks like you put an edge on that blade before quenching. Am I seeing that right? Best to leave the edge ~0.030" or more. 0.020" bare minimum.

5. A thin clay slip along the edge, as Brian mentioned, helps in the way that salt does in water. Breaks up the vapor jacket.

 

A few notes, 1095 best hardening temp is 1475°F with a short 10 minute soak to allow the extra carbon in solution, if you have the ability to hold that temp in your gas forge. Normalizing needs only to be performed if the steel has been forged (and if it's heavily spheroidized...but most 1095 is fine spheroidized). Normalizing, by definition, is only done once. For 1095 that is 1600°F with an air cool. After normalizing, you can do a few "thermal cycles" to help "shrink" the aus grain, usually in descending heats with air cools, as in 1500°F, then 1450°F, then 1375°F, as an example.

 

If you will be making a lot of knives in 1095 or especially W2 in the future, one of the biggest bangs for the buck is a fast oil quench medium like Parks 50 or DT-48. These are formulated to simulate the speed of a water quench, without the risks. Best $$ I've spent for the shop. You won't look back.

 

Good luck on the next one! Let us know how it goes, if you would, and tell us what you changed for better success.

Edited by stuart davenport

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Hey! I've done a lot of water quenching in the past, and had relative success. I've done it with 1075 1084 1095, 1095/15n20 mix, and home made steel.

 

The best trick I have seen for getting no cracks is rounding your edge really nicely so there are no stress risers in the blade. Same for the spine. make sure that it is rounded enough you don't snag your fingers on it as you run them down the blade and then you should be set. As far as actual quenching I do y normalizations and then into water. I haven't noticed the temp of the water making a difference. I do an interrupted quench where I go into the water long enough for the edge to cool and begin transforming, then I leave the water to lessen the shock of the vapor jacket, and then back in for the rest of the cooling. The only cracks I've gotten lately have come from way overheated 1095.

 

I hope that helps some?

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Normalizing, by definition, is only done once.

 

No, by definition a normalization is any raising above critical then air cooling (this becomes an air quench for air hardening alloys). It is very wise to do at least 2 or 3 to refine the grain structure. No real benefit from doing it at temperatures below critical.

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