Quench heat for L6

L

LRB

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Feb 28, 2006
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What is the ideal quench heat for L6, and what is a good temper range. Thanks in advance for your help.
 
LRB,
In "Step-by-Step Knifemaking", David Boye says its heat treat between 1425 and 1550F and describes the color as an even, red glow. He recommends cutting several test strips of the steel, notching each piece, then heat to different shades of red up to bright orange yellow, quench then break at notch and see which pieces look the most refined... he describes the best visible texture to be "fine grey velvet".

I'll get around to doing that test thing one day...instead, I use a magnet to check mine when it starts to get that red look. Magnet don't stick, pull it out and quench in my ford tractor all mineral transmission oil. The same book lists 300f=63rc, 350f=62rc, 400f=61rc, 450f=60rc, 500f=58rc, 550f=57rc, 600f=56rc, 650f=55rc. Slowly and evenly bring the whole blade up to the desired temperature and color, which the author recommends as medium straw for a "nearly impossible to break blade". He also says to aneal the spine and guard areas, which is something that I haven't done yet and things still seem to be fine- (edge quenching instead of annealing).

I may have missed it in the book, but I didn't see where the author said what temperature HE tempers at, just the colors he looks for. I temper mine @450 until the steel turns medium straw color- between 25min and 45ish minutes depending on how thin/thick the blade is. For one reason or another, this steel seems to be more thickness sensitive than others, the first time I tempered it, I left it in the oven for an hour and found one thin blade to be a pretty redish color(vermillion), another convex blade was light straw near the spine- then dark straw further down and the edge was vermillion. The final blade in that batch was a very wide pig sticker type that was a uniform straw color throughout. So I re-heat treated the two smaller blades, tempered separately and started checking their colors every 5 minutes until they got to medium straw. I also edge quenched the second go around and it worked out well (been doing it ever since).

Hope this wasn't too wordy and was what you were looking for.
 
As a low alloy steel, I'd go for the magnet test as an accurate way of judging when L6 is ready for quenching. If you manage to control forge temperature, and keep it slightly above that temp, you could soak the piece for a while without having to worry for grain growth.
Quench in hydraulic fluid or thin oil like warmed 5w30 motor oil
This, I mean, with my backyard shop resources. A professional would probably do it with a thermostate and a salt bath... :)
 
The 1500 To 1550F numbers are the ones that I work off from, I think I get better results going on the lower end of that range. I would not go any lower than 1500F however, I have found L6 to be a bit persnickity about going entirely into solution at times. This will of course rely heavily upon your prior treatments, if you have it spheroidized (by yourself, or as it comes from the mill) you will need at least 8 minutes at temperature to get full hardness. If all you did was normalize, I feel sorry for your belts and other tools, but it will go into solution much quicker.

On the temper, what hardness range are you looking for? I temper from 400F to 440F depending upon the application. If you as-quenched hardness is less than 62hrc You will wnat to definitely keep it on the lower end.
 
Sometimes you have to adapt your materials to your resources.
Kevin has salt baths, thermostate and much more that allow him to do wonderful things with steel (I've read one of his articles where he explained how to quench in salts and correct warp while the steel converted into martensite that left me astonished like a caveman that thinks he's good at banging stones together seeing a rocket wooshing into the sky. :D
That's why I steer well clear of sophysticated alloys: I just don't have the technology to properly heat treat it.
I use a coal forge, and quench in hydraulic fluid, 5W30 motor oil, or 15 W 40 motor oil for a milder quench.
Coke and motor oil is all I can lay my hands on, and so keep to that level of technology. Plain carbon steel. No fancy alloys, no stainless. :rolleyes:

PS: Kevin, if you have some advice about how to heat treat L6 or similar alloys with a coal forge, magnet and motor oil (I stay consistent in grade and avoid mixes) I'm all ears (yuck!)
 
Thanks Mr. Cashen, and all others who gave input. I was asking for a friend. I don't use L6, and could find little on it's makeup or proper heat treat. My friend was not getting the heat up enough to give it a decent hardness apparantly. You have all been a great hel[p. Thanks again.
 
Alarion said:
...PS: Kevin, if you have some advice about how to heat treat L6 or similar alloys with a coal forge, magnet and motor oil (I stay consistent in grade and avoid mixes) I'm all ears (yuck!)
Click to expand...

The good thing about L6 is that quenching in just about anything is not a problem, the stuff will reach 61 HRC just cooling in air, as for the heating and holding, I am sure that one can get satisfactory results with the tools mentioned, since so many seem to really enjoy the knives made from it using those tools. It is just a matter of being obsesively thorough on my part, as long as there are a few percent left untapped it will haunt me. I have been squeezing those few extra points, and observing the effects for so long that not knowing the temperature within a couple of degrees and the time in minutes and seconds leaves me very unbalanced.
 
Shouldn't you give up steel for some time and just cook some apple pie? :foot: :p :D

Thanks for the tip. If I can get som L6 I will try it then!
 
I do, my wife is a good cook but I am the only one in the house that can make a good pie crust from scratch:o, normally I make blueberry though, apple just seems boring to me. However I have a different approach in cooking, my wife measures ingredients, uses exact times in the oven and adheres closely to recipes, I toss things in until it tastes right and often ignore portions of the recipe. Perhaps if I were selling my pies for $500 a pop I would do it differently but until then it is more fun to just wing it in the kitchen.
 
They probably wouldn't be as good if you did things differently. My father is a cook much like you. He tosses ingredients he feels are right together until it tastes good. And it usually tastes REAL good.
When he screws up, he screws up badly, though... I still remember some canapes...:barf: "Night of the living canapes" :eek: :D
My brother and me still make fun of him after 15 years... :rolleyes:

Ok, sorry, enought OT... back to L6...
I have to find some here in Italy.
 
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