first knife heat-treat...

B

bushcraftbasics

Joined
Sep 16, 2011
Messages
51
hey guys and gals...so i ground my first knife yesterday out of 1084, fired it in an old kiln that i rebuilt and i just had a few questions...

i used pyrometric cones to heat up to about 1500* and quenched in veggie oil heated up to 150*...

so what flaked off the steel into my oil during quench? did i lose carbon or what? is this knife shot? is my oil ruined?

the knife passed the file-test for hardness, the flat bastard slid right off like glass, so i then tempered at
300* for two hours...

every source seems to have conflicting info as far as heat-treat/tempering temps...i have heard to heat-treat anywhere from 1475-1625 depending on the source, and have heard to temper at 400* from most sources here, however a book that i have says 10XX steel has a hardness of Rc 60 as quenched, and if tempered at 300* will be at an RC 59

i think i am going to make the switch to o1 steel because i can get it local but i wanted to clear up some of these questions...my book also states that o1 will heat-treat at the same 1575* and should be quenched in oil (hench the "o") but will be much harder (Rc63) and should be tempered at about 400* to reach an RC60...

whattdya think? sorry for rambling, and thanks in advance!!

BB
 
I can't speak for everything, but your veggie oil should be around 120f. Also saying generally that 10xx steels HT the same isn't true, there's a huge difference between 1084 and 1095 for example. You'd do very well to read the stickies, particularly Kevin Cashen's "Working with three steels", which when done you'll have a much better understanding.

http://www.bladeforums.com/forums/threads/673173-Working-the-three-steel-types

The count will hopefully be along with his compilation of great info as well.
 
thanks for your response mgysgthath...ive read the stickies numerous times, and Mr. Cashen, albeit a true genius, gentleman and a scholar no doubt, while full of information has pretty much confused the crud outa me with all the - hyper-hypoeutectoid Ac1 perlite problematic leftover carbon spherodising austenite solutions...to put it simply "i aint no chemist"...just a guy who wants to get started making high-quality consistent knives out of simple steels...ie: when teaching a youngster to drive a car, you dont start with the intricities of the internal cumbustion engine...you tell em that the gas is the long skinny one on the right...you know what i mean?

thanks agian! :D
 
Oh I understand completely, it can make your head spin. But the important thing for now is you started with 1084 a Eutectoid (one of the simplest to HT) steel. That is the steel that pretty much everyone here will suggest you use. I would stick with that for now and refine your process. I'm not sure how hard 1084 will get in ideal conditions, I'm sure someone will chime in about that, but RC60 seems a bit low.
 
yeah I thought 60 sounded a little low myself... I guess it could be due to the fact that my information is from a blacksmith source rather than a knife maker... I wonder if you will get harder RC as quenched with a thinner material as opposed to a thicker material?
 
wow...so i just got off of kevin cashen's website...its like a newb knifemakers dream cookbook! THANK YOU KEVIN! clearly layed out in laymans terms are a list of steels and heat treatment instructions...why i havent found this before is beyond me...now to round out these temp. discrepancies...

can anyone tell me what the "scale" or whatever that sluffed off my blade during quench is? should that happen, is it normal? do i need to filter out my quenching oil?

thanks again guys
 
1084 at 1475-1500F and quenched in 120 canola should be fine. At 150F the oil is too hot, but the blade should still get hard. results may be less than optimal.
The stuff that fell off is the scale from where the oxygen in the air reacts with the steel during the HT. Nothing abnormal going on. After sanding/grinding the blade a few thousandth it will be all good. The scale is black iron oxide.
Temper should be at 400-450F for two hours, twice. That should be around Rc 58-59 in theory (actual hardness is unknown since your quench is non-exact).
Your 300F was too low, re-temper once more at 400F.
 
bladsmth said:
1084 at 1475-1500F and quenched in 120 canola should be fine. At 150F the oil is too hot, but the blade should still get hard. results may be less than optimal.
The stuff that fell off is the scale from where the oxygen in the air reacts with the steel during the HT. Nothing abnormal going on. After sanding/grinding the blade a few thousandth it will be all good. The scale is black iron oxide.
Temper should be at 400-450F for two hours, twice. That should be around Rc 58-59 in theory (actual hardness is unknown since your quench is non-exact).
Your 300F was too low, re-temper once more at 400F.
Click to expand...

thanks bladsmth...i will definately re-temper, that blade is super hard, still cant grab it with the file...as for getting closer to that 58-60 hardness, is there a better way to get a more exact quench? a better medium? im thinking about doing a few blades with slightly different HT formulas and taking em down to the steel yard to see if they can Rc test them for me...
 
Canola oil ( not just any veggie oil) will work for 1084, but a commercial quenchant is better. Parks AAA or any of the medium to faster speed oils will be fine. #50 is a tad faster than 1084 needs, but will work. Use at least a gallon, with two gallons or more being preferable if you do more than one blade or larger blades. The commercial oil will last for many years, but the vegetable oil will not. The quench tank needs to be big enough to allow for heat transfer, too. At least 3-4" on each side of the blade and an extra 4-6" in depth.

Good heat control is key to good results. Knowing as closely as possible what temperature the blade is ( and having the whole blade evenly heated) is key to getting optimal results. When using a forge for HT, a pyrometer is great, but with some practice a magnet and a good eye will do. A controlled HT oven is the best choice. A good kitchen oven will usually work fine for tempering ( but the HT oven will do it with closer tolerances). A toaster oven is not very well regulated, unless you modify it for PID control ( see the sitckys).

Keeping records of your HT regimen is necessary if you are going to experiment. It isn't always what you think that makes changes in results. Sometimes looking at all the factors turns up the culprit. That said, sticking with the tested and established methods and temperatures is the best way to get top notch results. Tens of thousands of hours using millions of dollars in equipment went into establishing and testing those procedures. It is highly doubtful you will stumble on a new and better hardening procedure for 1084.

A file will tell you the blade is hard, but it won't tell you how hard or if it is even martensite - yes, fine pearlite can skate a file. Good attention to the HT temps and procedures will get you good results. Having a few blades tested from time to time is fine, but the edge is what you are interested in, not the tang or ricasso where most tests are done. The real test comes in putting on an edge and cutting stuff.....lots of stuff. That will tell you if the temper is right and the edge is properly hardened. Cut paper, cardboard, wood, rope, do an edge flex test ( brass rod test), etc. After these tests, you will know if your HT methods are working.

You can take the knife right out of the temper oven, wrap the handle in tape, put an edge on, and test the edge. If it is too hard and chippy, re-temper at a higher temp ( about 25°F higher). If it is too soft, dull the edge and re-harden the blade with closer attention to the temps and times. Once the edge seems right, dull it a bit and then finish the knife.
 
You must log in or register to reply here.
Back
Top