deferentially heat treating O1 tool steel

Knifemaker87

Knifemaker87

Joined
Jan 2, 2006
Messages
1,073
hey question here....
on my first batch of heat treating knives in my new propane forge, i cracked all of the blades. not HUGE cracks but small one along the blade edge. now the blades were O1 tool steel, i clayed them with refractory cement and then qunched them in brine. am i pretty much doomed with the set up? or what can be fixed? should i change the quench to oil? should i not heat them as much? is O1 bad steel to diferentially treat? should i put more clay on? less?
my best batch of knives so far....gone. anyway i wont give up but some advice would be nice
thanks
~Chris
 
Brine is too fast for O1. Actually the "O" in O1 stands for "oil". Besides that I think you did everything right.
 
If you are grinding the edges too thin before hardening, you are adding to your fracturing problem. If you switch to oil it will be apparent if you are grinding to thin. Maybe no fractures but a rippled edge or warp.
The O-1 is a great steel. Deep hardening and rugged it will hold a fine edge.
It makes an excellent camp knife.
Pick up some W-2 if you want to use water.

Post a picture of one of the fractured blades if possible.

Fred
 
What Bruce said. Find another steel, if clay hardening is your goal. O1 is designed to get fully hard, really easily. There are much better choices for clay hardening. Pretty much any of the simple carbon steels work better than O1; like the 10xx series, W1, W2.
 
All the above,plus make sure that the temperature of the blade is what you want,not higher. One problem with "non-magnetic" is that 1800 is just as non-magnetic as the 1500 you want. Overheating is one of the main causes of poor blades and HT results.
Stacy
 
hey thanks for the info.
well i will try to oil cool...that was my next guess...but i hadnt thought a WHOLE lot about not girinding the knives down as much. i will do both of those things.
I have been buying my steel from McMaster Carr....do yal have a better resourse for 1095, 1075 and W1 & W2 steel? or other good hammon producing steel? thanks
heres the pic
IMG_0483.jpg


thanks
~chris
 
i dont have a temperature regulator on my forge...how can i assure that i have the right temperature? this is the first time i have used my new forge.
thanks
~Chris
 
Chris,

Looks way to thin on the edge from that angle. When you grind the edge that thin it makes it hard to control the temp in that part of the blade. The result is overheating, distortation and fracture when the blade is quenched.
Leaving a 1/16th plus on the edge will make heating the entire blade more uniform and easier to judge. Heat the spine first working towards the edge. Watch the heat move thru the blade. This will help you learn to judge the temp as it reaches non magnetic. Are you working on the inside of the forge or from the side. Having a set up that allows you to protect the edge and tip of the blade makes this process a lot easier.


Good luck, Fred
 
Chris,

From the looks of your forge you may have a bit too much of a direct flame for HT. It can be done but it will be difficult. You may want to try a secondary chamber. Get a 2 or 3 inch diameter pipe the length of your forge. Cap one end then put it into your forge and bring it up to temp. You can even throw a piece of charcoal into it to create a neutral atmosphere. Us e this chamber to heat the blade. If you can get a temp sensor all the better. They can be found cheap on ebay, thermocouple and controller for $60. If you do use the forge directly keep the flame off the blade if possible. Use a magnet to check for proper temp then quench your O-1 in warm oil. The more control you have in the HT the better.

Good Luck
Chuck
 
From that picture, it appears the flame is too direct/focused--more like a welding/brazing flame than a forge flame. It should be bushier, more dispersed and yellow-orange, for the most part (I realize you probably used a filter that took out some of the orange hues), but still, the fact that the flame has a 'cone' is enough to make the point, I think.

I would strongly suggest you revisit the burner design/applicaiton.
 
If you really want a hamon, then Don Hanson is selling W2. I bought 237 lbs of it.....so far:D Bad news is that it is in round bars, the smallest being 7/8ths in diameter. But in my limited experience with the W2, I have actually found it to be as forgiving if not more than 5160 and pretty much as easy to forge. Don says that the vanadium content helps limit grain growth unjlessyou REALLY torch the stuff badly. So buy some 7/8th round bar and build up some Popeye forearms pounding it down.:thumbup: You don't NEED a power hammer or press for 3/4 or 7/8ths.....you do for that 1 1/4 stuff:mad:
 
That forge will work for forging (you still have to watch overheating when forging) but might be problematic for HT. The single high intensity flame is like using a welding torch. It has a lot of heat,but all in one place. You want the heat diffused through out the chamber. The ways to have that happen are:
1) have multiple burners.
2) have the flames swirl around the chamber.
3) heat the chamber up to the desired temperature and hold it there with a lowered flame.
4) place the blade to the sides of the chamber and keep it moving.
5) have a temperature control to regulate the gas flow.

Simple ways to deal with these issues are:
The forge shown has a lot of open area at the ends,which is OK for forging,but not what you want in HT. Block off the back with a stack of fire bricks ,and close off a good part of the front with brick. Run the forge for 10-15 minutes ,until it gets up to temperature (the inside glowing) and cut back the flame to just maintain a good glow.Place a piece of 1/8" bar stock in the chamber and move from side to side,avoiding the center where the flame is.(BTW,To check the chamber temperature with a pyrometer,like one of those HF specials, shut off the flame and inset the probe.If the flame is on you will be reading the flame temp,not the chamber temp!) Allow the bar to come up to a slight glow. Check on a magnet.If it sticks,let it come up to more of a glow (turn up gas if needed). When it just stops being magnetic look at the color of the blade and the color of the chamber. If the blade looks reddish orange,and the chamber looks bright orange, the chamber is too hot. If they look about the same color the chamber is at about the right temp.Keep the bar in the chamber for two or three minutes,checking it with a magnet occasionally. If it stays non-magnetic, then the temperature is high enough. Now to find out if it is too high (without a pyrometer) take the bar out of the chamber and start checking it with the magnet. If it takes more than two or three seconds for it to become magnetic,it is too hot.Turn down the gas pressure.If your setup won't run at lower pressures,turn it off and on to control the temp. (That is what the solenoid valve does when using a controller to regulate to a set temp)
Once you have experimented with your forge to get the feel of how to control the chamber temp,you can HT a blade almost as well as with a Paragon oven.Getting a pyrometer will be a big help.They are less than $50 at HF,and work fine for this type of job. Remember that it is the chamber temp you want to determine,not the flame.When all is right,the way to know that the blade is ready for the quench,is that it is the same color as the chamber,and the color is even throughout the blade. If the edge or tip is bright yellow orange and the spine is dull red-orange you will not get the results you want.If you mount a permanent probe in the chamber,it will have to be a sheathed type K unit. Put it as far out of the flame as possible (up in the top corner).When it holds at the temp you want (say 1550) then the color of the probe is the color you want the blade to be.

AC Richards pipe trick is a good idea,too.Especially when used in combo with keeping the chamber temp down and regulated.
Stacy
 
wow...
this infrmation is almost to valuble to imagine. i have never seen another knifemaker work...so all of my work is self experimentation and what i read. this is really nice. Nice to hear from people who know what they are doing. heh...I'm only 19...so how much experience can you get? thanks a bunch
the only thing that i would note is that the picture of the forge doesnt relaly do it justice.. the flame isnt that focused. but i do get two hot spots (i have two burners)
where is it that i can get the pyrometer? what is HF?
thanks again
~Chris
 
Here is were I got my pyrometer, http://auberins.com/index.php?main_page=index&cPath=1

Look up on ebay for a type K thermocouple or ask the above link about them. It makes a world of difference. Also those hot spots can be problematic. Most knifemaker forges have offset burners to get a swirling flame it gives a more indirect heat. If you are looking for any books i recemmend Wayne Goddards 2 books, The Wonder of Knifemaking and The $50 knifeshop. These 2 books give the most information for the buck.. I recommend them to all my students.

Chuck

Chuck
 
HF is Harbor Freight. They sell Chinese tools and low price equipment. Some not so good,but much of it OK for the low price.A lot of makers use a HF metal cutting band saw.Ebay is a great source for type K thermocouples,PID controllers,and other Pyrometer supplies.A complete controller for your forge can be made for less than $100 (maybe half that) with Ebay parts.
Stacy
 
While I've never tried clay, I've found that edge quenching O1 does not give a good hamon, only method I've found for that is torch HTing with only heating the edge.
 
Chris, Thanks for asking, and Thanks for the responses from all the makers. I learn everytime I log onto BF
 
For getting rid of hot spots, the best thing is a round forge, with an offset burner to get the swirling motion going. You could use cast-able refractory to round off the corners in your square forge. Don't know if you can move the burner.
 
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