Edge quenching 1095, results and questions, (but more questions than results)

Lerch

Lerch

Well-Known Member
I finally got a chance to start work on a group of small 1095 blades i planned on edge quenching. This is 1/8" 1095 steel that i soaked at 1475deg for 5min and then edge quenched on a aluminum limiter plate in canola oil heated to 150deg.

I placed the blade tip down in the quenchant on the limiter plate and held it there for maybe 4sec and then rocked the rest of the cutting edge in to the quench and held there for about 4 sec, then back the tip down for another 4 count and then again back to the rest of the cutting edge down and then held until the blade was completely black heat.

here is a pic of the blade belt sanded to about 300grit and etched to try to show the hamon. Its a crappy pic i know but i am hoping you all can see the temper line, the distinct one that shows where the tip was placed down first and then a lighter temper line where the rest of the cutting edge was rocked back into the quench

photo-21.jpg


photo-22.jpg


My theory is that i am holding the blade stationary for to long and i would be better served to keep a constant rocking motion from the tip down to the back of the cutting edge to get the even temper line i am lookin for.

IF any one has any ideas please let me know

thanks
steve
 
Yes, I think that you have the problem identified. Put the point down and then immediately start rocking it to the edge and back. You shouldn't have to rock real fast but you need to get all the the steel where you're quenching cooled fairly quickly. I would keep rocking until you loose color in the spine area and then put it all in the quenchant. Let it cool to the touch and then temper. I think that if you tested the edge that it would be rather soft. You have less than one second to get the temperature of the steel from a little above 1300° to below about 1000° or you will cross the pearlite start line. You probably have good martensite up to the band at the point but the edge is a mixture of martensite and pearlite, maybe with a little upper bainite thrown in.

Doug
 
Lerch,

I've played with 1095 alot and it sure is alot of fun. I would suggest that the "rocking" type of edge quench is not the best method to use with 1095.

I'd go a step further than Doug and recommend that if you want to edge quench you go straight into the quench so your hamon will be at an angle from the top of the choil to maybe 1/2" back from the tip. My guess is that the rocking method will nearly always give you a mix of martinsite and pearlite on the back side of your edge.

That said IMHO the best method to get what your after would be to use clay and do a full quench. I'd use a compass to draw a line parallel to the edge on both sides roughly 1/2" away from the edge then coat the top with a thin layer of satanite or refractory cement like Rutlands.

-Josh
 
I'm with Josh,... just go straight in at an angle with one smooth motion.

However, if you are just looking for a plain quench line, you can skip the clay. Also, with canola there is no vapor jacket to speak of, and it should get around the pearlite nose in under a second, so any rocking or manual agitation would likely be of no use. About the only other thing you could try is using a slicing motion going in, but since there is no vapor jacket to defeat, it probably isn’t going to make a drastic difference. All of the studies on canola that I’ve seen are done without agitation of any kind. Once the back gets to a black heat, you can go ahead and put it under until it gets below the smoke point of the oil, then take it out, straighten it immediately if necessary, and go straight to the first temper while still warm to the touch.
 
Yes, 1300° is not a mistake. It is about where the Ar1 point will be which is different from the austinization temperature. The Ar1 point is where the phase change starts to take place for hypereutectic steels as the steel cools which is lower than than what is usually shown on the IT diagrams as the A1 point which is more of an average between the the Ar1 point and the Ac1 point, which is where the phase change starts as the steel heats. The actual temperature of these points also depend on the rate in temperature change as they cool or heat. A lot of people think that the blade has to get into the quenchant while the steel is still at the austinization temperature but you really have more time than that.. It actually needs to get into the quenchant before it crosses the the Ar1 point and then cross the pearlite start point. BTW the A1 points are also dependent on the alloy. When you are dealing with hypoeutectic steels the conversion starts at the A3 point.

Doug
 
Just to play it safe… it’s a good idea to keep the quench tank close to the furnace and get the blade into the medium without hesitation. A thin edge can air chill pretty darn fast.

Better safe than sorry.
 
Thanks guys

I will probably just go with a angled quench, i just dont know how i could get both the tip and the back edge of the blade cooled quickly enough rocking it,

thanks for the info guys, i will post some more results as i get a chance

thanks
steve
 
The only other thing I can think of is dropping the temperature of the oil to between 120-130. It’s a little safer and less likely to flair up. Dropping the temp., a little won’t have any noticeable effect on the viscosity or cooling characteristics of the canola.
 
Tai, no argument on keeping the quench tank close, especially with a shallow hardening steel like 1095. It's just that a lot of people, myself included, have thought that you have less than a second to get the steel from the forge to the quenchant while still at austinizing temperature when that less than one second is from a temperature, the A1 point, that is below the austinizing temperature by maybe 150-200°. If you watched the National Geographic production about the Ulfberht swords it was surprising how many steps Ric took from his forge to the quench tank. It was farther than I would have been comfortable with but it evidently worked.

Doug
 
I understand Doug. I'm hesitant to put an exact time limit on it due to variables like ambience temperature, amount of mass, edge thickness etc. The time you have to get it into the quenching medium can vary.

I think you are correct about the temps., terms and misconceptions though. No argument there.

I’m just saying why take any chances?
 
Last edited:
any suggestion on which one you all think would work better ? Edge quenched in heated canola oil or clay coated and full quenched in room temp Parks 50 ?? whick method do you all think would produce the best edge holding in a heat treated blade ?

thanks
steve
 
Lerch said:
any suggestion on which one you all think would work better ? Edge quenched in heated canola oil or clay coated and full quenched in room temp Parks 50 ?? whick method do you all think would produce the best edge holding in a heat treated blade ?

thanks
steve
Click to expand...

If it were me I would go for the optimum phase/microstructural condition at the edge and thus the clay with full immersion in the Parks #50, this will allow you to also agitate to assist the convective action by keeping fresh cooler quenchant in contact with the blade, vapor jacket concerns are but one benefit of proper agitation. With the edge quench you have perhaps 1/2" of oil to do the cooling action while a large mass of superheated steel is fighting it, with the clay method you have the full volume of your quench tank at your disposal. Occasionally I have to do a differentially hardened blade by request, I always use the clay if my mark is going on the knife. The only time I edge quench is when I teach the ABS intro courses because it makes it easier to bend a blade, but I personally don't like bent blades.
 
O.K. Doug. I can handle that. :)

Kevin, clay edge quenching vs. non-clay edge quenching, and the advantages or disadvantages of edge quenching in general might be a good topics for other threads.
 
Good point about the agitation Kevin.

However, in this scenario, (edge quenching 1095 without clay), manually moving the blade in the medium complicates things and can be harder to control. It will speed up the quench a little theoretically, but whether or not it’s necessary or of any advantage could depend on a number of variables. My personal opinion is that it’s not going to make a big difference in this particular case, small 1/8 inch 1095 blade in canola. Besides,… how much manual agitation can you do in under a second? By the time the edge of the blade gets from the surface of the medium to it’s final depth, in motion, it’s probably already around the pearlite nose or within a fraction of a second from it. That part happens real fast… virtually instantaneous while the blade is in motion for the most part. As I mentioned using a slicing motion or keeping the blade in motion may be worth a try, but harder to control and debatable whether or not the risk missing your mark, fumbling or bumping the quench tank is worth it.

If the quench is too fast, you also run a greater risk of the edge cracking. For whatever it's worth, I have heard of and seen a few pix of thin 1095 blades edge quenched in canola that cracked and even blew the edge clean out on one. I don't think it happens a lot but,... It's fast and questionable whether or not it needs to be sped up... The industrial lab studies I've read say it generally doesn’t need any cooling rate accelerators even for difficult to harden steels.
 
Last edited:
Doug Lester: The information you have posted is overwhelming to me. However this is the stuff I am looking for! Where does on start, as in book, to learn to follow and understand the charting infromation sometimes found with steel heat treating? Surely someone has a small book that will be perfect to educate a knife maker with the terms and science...
 
You must log in or register to reply here.
Back
Top