first blade broke in quench

kile

kile

Joined
Mar 19, 1999
Messages
620
I was getting tired of finishing up all the stainless blades I have around the shop, so I decided to start one from scratch today, profiled it, drilled it, ground the bevels, normalized 7 times. Then I got stupid. I have seen a lot of blades with amazing temper lines on them lately, so I decided I was going to try for a really nice one. I decided to quench my 1084 blade in water. I finished it up to 220 grit, and decided to use my regular water bucket that I use for dunking blades in when I am grinding them. It is full of lots of steel and micarta dust, as well as some liquid soap so that nothing floats. I quenched the blade, pulled it out, polished it up real quick with a cork belt, and then as I was letting the oven warm up, I decided to etch it to make sure it hardened properly, I put it in some warm vinegar because I was to lazy to run out to the shop and get the ferric chloride, anyway I waited about 15 minutes, came back and check the blade and there was a big crack in it it started at the edge and then branched out so that it was basically "T" shaped. My question is if I had tempered it sooner is there a chance it wouldn't have cracked? If it didn't crack would there still be a weak spot in the blade at that point after tempering, or would everything be ok after the blade was tempered?
Just thought I would share this with everybody, I have quenched several 1084 blades in oil and never had anything warp or crack or anything. I think I will go back to the oil quench.
P.S. is there any performance advantage to the water quench?
Thanks,
Kyle Fuglesten
 
I commend you on your courage. I'm not nearly brave enough to try a water quench.
This is strictly my opinion, but, I'm thinking that crack started in the quench and just became visible in the etch. Water is just too fast a quench.

I'm sorry to hear that the blade broke on you.:(


All the best,
Mike U.
 
You can quench in water and in wayer that is not heated. Room temp is fine. I believe the biggest critical items are: an even heat, a straight plunge into the water and don't swirl. The soap may also contributed by being a quicker quench. I use plain water.

I use to have many problem using water as a quench, my blades warped and cracked and so on. I use a rosebud on my torch and heat the blade very evenly, edge on (meaning I aim at the edge)of course you have to go on the sides occasionly but evenly. Water quenches will produce awesome temperlines, you just have to practice.
 
I watched a maker that I visited quench some S5 or S7 tool steel in water. He heated it just past non-magnetic then edge quenched it in room tempature water in a pan that had about 1/2" of standing water in it.

The trick that he used was you dip tip first and rock the edge back. Then remove the knife entirely from the quench, dip and rock, dip and rock. He did it 4 times, each time the knife was a little cooler, but it still boiled the water each time it touched it.
I did not get to see how he did his HT on his knives, but I thought the tempering was cool.

I looked at some of his completed knifes and alot of them had 4 distinct temper lines very close to each other.

Although he used a different steel it might work on what you are doing.
 
I have read that soap in the water makes a big difference in the speed of the quench. The soap makes the water tension breaking point much lower so that steam doesn't form a, somewhat, protective envelope around the blade. Because of this the water is able to get to the blade easier and therefore cool it much faster. Hope that made some sense.
 
I usually use 5160 or O1 and austemper with salt but play a lot with 10XX steels and water quenching. I have cracked a bunch, some on purpose some by accident.

Try using warm water and forget the soap and stuff. Quench edge first and only hold the blade under until it stops vibrating...about 3 seconds and then pull it out for 3 seconds and then plung it again until its just warm. Don't let it get to water temperature and don't fool around looking and etching and stuff after it is hardened. Get it into a temper oven or a salt bath *right now* 'cause most of the stuff I have seen crack on me cracks about 3 to 5 minutes after the quench is over. If they crack in the quench they make a distinctive ping sound and you'll know it cracked on you more than likely.

Don't get the steel too hot before the quench as 1450-1475 is hot enough for 1084 when using water. And remember to interrupt the quench after 3 seconds and don't swirl or move the blade at all in the quench.

My 2 cents.

Brian
 
thanks for the advice Brian. I still have two questions though, besides getting a more distinct temper line does water quenching make a better blade as far as performance goes? If I would have tempered right away, would the stress have been releived completely, or would the blade have been week at the point it cracked at even if I tempered it in time?
Thanks,
Kyle Fuglesten
 
Kyle, I don't find increased performance in water hardened blades. I don't find increased performance in differentially hardened blades unless they are really long (swords) but really the water thing is all about the hamon. Through hardened 1084 when properly hardened and tempered is an awesome thing....toughness and edge holding are excellent.

As far as the cracking goes it depends on when it happened. If it did crack in the quench you need to reduce the temp. of the blade at quench and warm your water...slow the quench down. Also, was the blade normalized a couple of times? Normalizing reduces the hardenability and will help prevent cracks when quenching. If you hear it go "ping" when quenching then that is one thing...if it seemed OK for a few minutes and then cracked while you were out in the garage or looking at the hardening line or fooling around and not getting it into the temper ASAP then that is another.

For me, if they are gonna crack in the quench they just go on ahead and do it! And it goes 'ping" and I know it's all over. But if I interrupt the quench and it comes out OK, it may still crack as the Martensite coninues to "set up" just after the quench. Water quenched steel is highly stressed after quenching and the steel is screaming from the stress. Don't mess around...get it into the temper immediatly...like less than 60 seconds after a successful quench in water.

Temper lines are cool to look at but I'm not convinced that they mean anything special or that they make the blade tougher or better in the performance department. I find austempered O1 or 5160 to be about as tough as it gets but then again I am less concerned with edge holding or pretty stuff and mostly into the blades ability to be used and abused and still survive.

Experiment with water and steel and see what works for you...I have even quenched 5160 in water without cracks...it can be done.

Brian
 
Water quenching is a tricky business. We use brine (saturated salt solution). We also warm it up to just below boiling. We have done few experiments with edge-quenching like this, but even with a full qeunch, warping and cracking are real concerns. We have on educated opinion that 10xx series quenches successfully in oil, and we have had some success with this, but blades do not always come out fully hard. Good idea might be to reserve some grinding for after heat treat to reduce stress zones and provide for a thicker piece going into the oven.
 
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