View Full Version : Quenchant temperature...


chrisinbeav
04-04-2005, 09:15 PM
The past couple days I've been working on my first big bowie. I had all the bevels perfectly ground. The blade clay coated (5160 Steel). Now I know this steel won't show a hamon too much but I thought I would clay coat it just because of the size. Anyways, I heated it up in the forge and quenched it in oil and SNAP! Ah S**T! (Yeah there were a few explicatives) Yep the blade broke. Now normally I don't heat up my oil. I've never really had a problem with it.

My question is, should I have heated up the oil due to the size of the blade? I know this is recomened to do anyway, but should I really have made sure I did heat it up first because of the blade's size?

Or, here's another thought for the size of this blade should I have not ground the cutting edge so close? I cut it down to about 1/16 of an inch thick...

Chris Nilluka

Mark Van Loon
04-05-2005, 12:37 AM
oil seems to quench better at between 130-140 deg, if your blade broke all the way through like the picture shows i think you may have something else wrong also, was the blade forged? i take all my blades to 1/16 or less before the oil quench, so i doubt that was it. did you bring the blade up to temp slowly or very fast? ive had problems in the past bringing my blades up to temp too fast.

chrisinbeav
04-05-2005, 12:45 AM
No the blade didn't break all the way through. Once it cracked in 2 spots I intentionally broke it. The big crack is where the blade broke at.

When I am hardening blades I try to put them in my forge when the forge is cold that way the blade heats up along with the forge. Plus it saves a little on gas. I'm guessing it's mostly just due to the quenchant temp. I'm guessing the oil was probably only about 70 degrees at best...(I should have known better :( )

Chris Nilluka

TexasJack
04-05-2005, 12:54 AM
You don't mention normalizing the blade. If you didn't, I would suspect that far more than the temperature of the quenchant. (60 degrees difference out of 1900 is only about 3%.)

Burke
04-05-2005, 01:46 AM
You don't mention normalizing the blade. If you didn't, I would suspect that far more than the temperature of the quenchant. (60 degrees difference out of 1900 is only about 3%.)

TJ is correct. Heating oil will make it cool faster than leaving it cold. So not heating the oil would not be the reason that the blade cracked. I suspect that there is some very large grain in the steel of your blade or that you got it too hot before quenching. Do you have a thermal couple in your forge? How hot was it? 5160 will show a nice hamon. If you want a wavy line you have to exaggerate{sp?} the waves Or you still get a straight line.

Bill

mete
04-05-2005, 09:24 AM
Lack of normalizing, decarburization,overheating.

cactusforge
04-05-2005, 10:43 AM
Was this virgin steel or a spring leaf? I have had this happen when using springs. Also did you overheat when forging, did you normalize? I don't like to go below 1/8" when forging the bevel that way when I get to the cutting edge I have good steel. Of course I heat treat right after forging that way I avoid a lot of problems like cracking, warping and doing the grinding twice. Gib

Kevin R. Cashen
04-05-2005, 12:04 PM
Please forgive me if your experience negates my suggestion, but you image is giving me some very strong clues. Do you see the heavy bubbling, streaking/marbling effect on the portion that was exposed? To my eye this is highly indicative of over-heating (or exposure to EXTREME oxidizing atmospheres). It should be very difficult to crack a blade in oil without very high austenitizing temperatures. 5160 in particular, being loaded with proeutectoid ferrite and lathe martensite, should be quite resistant to such failure.


Take you oil to 150F. and heat the blade no higher than 1550F. and you should achieve much success with full hardness (around 62HRC for that alloy).

chrisinbeav
04-05-2005, 12:04 PM
Okay...

First off this blade was not forged. It was all done via stock removal with virgin steel. I guess there's another problem... I did not normalize this one either after I was done grinding. The temperature I am going by the non-magnetic properties. I'm testing it till I just reach non-magnetic then put it back in the forge for about 5 more seconds then quench. I usually have pretty good results with that technique.

Another thing I want to do, since I am not using a termocouple in my forge and I am judging the temps via magnetic properties, I want to start hardening my blades at night. That way I can see the steel colors better.

Chris Nilluka

Ed Caffrey
04-05-2005, 08:26 PM
I have to agree with Kevin.......if that photo is true to life, there isn't much doubt that the blade was WAY overheated, for WAY too long. Don't get down on it though...I had a bunch that looked like that during my first year of knifemaking....at that time I just figured that you got it just as hot as you could, and then quench it in something as cold as you could!

chrisinbeav
04-05-2005, 09:06 PM
I have to agree with Kevin.......if that photo is true to life,


Actually no... Originally after I quenched it there were just two big cracks in it. If you follow the break line, at first the break is perpendicular to the edge, then turns and runs parallel, then turns again and goes perpendicular again. Well it's at that last turn were one of the original cracks stopped. I was just so PO'd that I just smacked it once on the ground and broke it the rest of the way. (boy did it break easily!)

See here's the deal, I know I screwed up, and I now know a few other things I need to do next time. I just got in a hurry and tried to speed things up a bit. I was going to try and have this knife done for the Eugene knife show this coming weekend. Well ultimately I paid the price for not doing it right. So, now I have another blade started, and this one I am going to do right. Fortunately I already have the guard, spacers, and some of the handle made. I'll just make sure I take my time on the blade and not skip any steps :o .

Chris Nilluka

TOM BUCHANAN
04-07-2005, 08:42 PM
hang in there, chris.it's just a dumb piece of steel.YOUR'E the one with the brains.