1095 HT what happened question

firephil

Active Member
I have been quenching 1095 in olive oil with OK results, then I read 1095 benefits from a brine quench. So I took it to non magnetic and into the brine in less than 2 seconds. Held it in the quench for a 7 count. All 3 blades warped but not very bad. While they were above handwarm I sanded the scale and into a 450 oven for the draw. I thought about something shiny and forgot the blades so they were in the oven for 4 hours. After the temper I put one in the vise to try to bend out the warp and it snapped with minimal effort, the other 2 followed suit. So just what happened and what did I do wrong?
 
What do you mean by OK results with the olive oil? Was it hard but you felt like you could get it harder? What could have been happening when you quenched the 1095 in oil, the actual cooling curve passed through the nose of the ITT diagram which allowed some pearlite/upper bainite to form giving you a less hard but tougher blade. When you quenched in the brine, which is real agresive, you completely missed the nose and you had near 100% conversion to martinsite and that martinsite was of maximum carbon saturation. That made the steel a lot harder but less tough and more brittle. You might try putting the blade into the brine for 2-3 seconds then take it out and straighten before the steel cools enough to reach the Mf point.

Doug
 
What's the usual RC of a full hard 1095 blade tempered at 450? I get 60-61 with my 1080 and a 450 temper. Blade that hard is going to snap, especially if you only do one temper.
 
61-62 RC, according to my info... a bit harder than I like. Try 500 and see if that works better. How does the grain look at the break? You can learn a lot from a broken blade....
 
Pictures of the broken blades would be helpful. Where did they break exactly? Are you sure there wasn't already a crack or a fracture before you started bending the blades? Did you bend them hot or cold?
 
I tried to bend them cold after 2 tempers. Nice clean even break showing what I think would be fine grain. One broke on the blade and 1 on the handle. I'll try to load some pictures. I'm thinking I will now concentrate on o-1 steel and my question now is... is O1 the same fron any supplier or are there differences?
 
No need to give up on the steel at this point. Look up the post on bladeforums about straightening during the temper cycle. Basically you clamp the blade to a little past straight, then run it through the temper. Trying to bend them cold is going to be trouble more often than not.
 
Jason makes a good point. I have successfully cold straightened blades with a jig after tempering but only with very slight warps. Anything more than that and the blade snapped. I've even snapped blades doing what Jason advised The difference is something that you will have to learn by experience. Sometimes the best that can be done is to reaustinize the knife and straighten it hot then normalize to reduce the stress in the blade and repeat the heat treatment.

Doug
 
It probably had some micro cracks in it from the brine quench -- do not use the stuff on steel unless you want a lot of heartache.
 
A high carbon steel such as 1095 is pretty much going to form all plate martinsite when quenched and a high percentage of plate martinsite tends to form microscopic cracks. Water and brine are agressive quenchants and the temperature shock can cause these cracks to expand and cause the dreaded "tink". However, I've had 1095 that would only harden adiquately in brine. I think that most experienced knife makers do avoid water and brine but there are also those who like to use it and have better than average luck with it. I've even seen where some even use water or brine on steels like (shutter) 5160 and 52100. Personally, I go with what Wayne Goddard said in his books, oil is best but sometimes you might have to go to water or brine to get some shallow hardening steels to harden the way you want it.

Doug
 
I'm talking more from what I've heard than what I know - so take it for what it's worth. 1095 is a spring steel. When bent, after hardeneing, it's supposed to go back to where it started. Seems that flexing beyond that spring return point is just begging for trouble. I've had some success with straightening, but heating significantly (like about 1200F) - straightening - and then re-hardening and retempering. This involves a few problems. A 1200F knife is hard to handle, though I suspect it can be handled down to about 400F. Second, I have no idea why I picked 1200F. I wanted to get it past spring martensite and I arbitrarily grabbed that number, knowing that it would be more forgiving on the way down. Lastly, its a P.I.T.A. to get it right. Put a few bends in a coat hanger and try to straighten it. How'd that work out for you?

This is a frustrating subject for me, so I'm watching the thread closely.

Rob!
 
And the lesson is to make sure that the blade is straight and properly heat treated before putting a handle on the blade. It's not more than inconvient when you are dealing with an inexpensive wood handle and simple pin material, though it's a pain when you have hardware installed. If you are using some real fancy and expensive handle material like fossil bone or ivory you really don't want to find out that you have to take the handle appart to straighten or reheat treat the blade. I only had to take a couple of handles off to learn this lesson.

Doug
 
I guess that is the bright side to the mishap, besides learning all this stuff ya'll are posting. The rapid "sectioning" of the steel precluded any handle application.
 
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