Stainless suitable for home heat treat

J

John L

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Oct 28, 2004
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What would be the best stainless alloy to make knives from that are also heat treated at home in an HT oven...but lacking all the cryo and specialty treating? Not forging./..just grinding bar stock.
 
John,

I am just a hobbyist at knife making and I might not count. But my choice would be CPM S90V. Keeps a very sharp and durable edge.
But there are draw backs, you won't get a high polished blade. Your oven will need to operate at a high temperature and the steel will need to be wrapped in a high temp. stainless foil wrap. You need to cool it quickly. More grinding belts and time invested in the blade. The steel dust under the grinder on the floor will make you think about the cost of the wasted steel at your feet. And the vanadium carbides can make you wish you were grinding 440c. But done right, you will be pleased.

Jeff Pelz
 
This is for 440C I forgot who gave it to me.
: I forged my 440 blades down from two inch ball bearings. I ground them clean, then heated to non magnetic and quenched in 135 degree pre heated texaco type A quenching fluid, letting them cool down in the oil to room temp. I tested blades from one quench to 7 as I remember. Three quenches seemed to be the best bang for the buck. I tempered at 350 degrees they passed the edge flex test, two passes on the steel right and left. They did not cut as good as 5160 forged blades at that time. I did not try all the experiments possible or seek any laboratory assistance. It was fun at the time, and probably they could be taken further. I did not try any rust experiments so do not know if the 'stainless quality' was present.


We were at the annual Flint River Knife Club's annual picnic yesterday in Georgia and I was taking to some of the knifemakers there about oil quenching 440C. I told them how I did it and it only checked 50 on the Rockwell C scale. The general consciences was not to normalize and only quench once. They seem to think it needed to get to 2000 degrees at quench and the oil needed to be around 170 degrees. Temper twice at 350 degrees then thrown in the freezer overnight.
Hope it helps.
 
Mete will chime in here,I'm sure.Stainless steel is a bit more complicated than the average home treater is set up for.You will have to be able to exclude oxygen from the steel with a stainless wrap,and hold it at an accurately controlled temperature of around 2000F for a period of around 1/2 hour. Quench is in air usually.Most stainless benefits from some sort of cryo treatment, which adds another whole non-hobbyist level to the deal.In the end the results will be mediocre at best,poor most likely.Send it to a heat treater for $5 to $10 and have it done right.All that said,if you are determined to waste some expensive steel,stay away from the exotics like CPM S90V and the like.Use 440,154CM,and ATS34.Good old D2 is a good near-stainless steel,which you will have some results with treating yourself.
My question to those who want to do a half-a$$ed home job is - Why use stainless,if you are going to make a poor quality knife? Doesn't your knife deserve to be hardened right?
 
I agree with you bldsmth, I used D2 for almost all knives from the begining but even with this steel I am not satisfied with the results. No matter how much I try, the strenght and the hardness is not as expected. You have to buy some precision equipments, at least a pyrometer, K-Type thermocouple. This way you can adjust the temperatura more precise. For now, I cant afford these so I will stick to High carbon and low alloys. Lately I am getting satisfying results with my "silversteel" (Böhler K510 (DIN 115 CrV 3)) stock. I found a suplier for CPM S90V in Turkey, but before investing on this steel I will buy a pyrometer, hopefully after I finish these reed knives...
 
bladsmth said:
My question to those who want to do a half-a$$ed home job is - Why use stainless,if you are going to make a poor quality knife? Doesn't your knife deserve to be hardened right?
Click to expand...

Stacy, I have never sold a 440C blade that I had HT. Grasshoppa and myself were doing experiments with it and he made a knife for one of his cooking teachers to see how it held up in a restaurant environment. It came out to nice and the teacher doesn't use it, so much for that test. HEHEHE!!!
I plan on doing one for a shop knife just for the hell of it. :D :D
PS: Who you calling HalfA$$. HEHEHE!!!!! ;) :D
 
One posibility for cryo is to make up a batch of blades and use the dry ice/acetone cryo methoud. Dry ice and acetone will get down to -70 from what I under stand.

Me personaly I wouldn't consider stainless without cryo, just from my own testing.
 
for hardening/tempering stainless with cryo, how would a flask of Liquid Nitro work? It's no great deal to get a few litres of L.N in a chilly flask here, I know theres a place in town called liquid air that provides it as a by product of LOX manufacture.

Just what does Cryo actually require?
 
I would say any high alloy and most tool steels we would choose to use for our blade purposes will benefit substantially from cryo aging.

Kiwi, I just lower it in deliberately and quickly, so as to help avoid high/low temperature areas about the steel body, and let deep cryo minimum 10 hours. Before doing so though I snap temper about 325 F / 1 hour and many times high alloys I snap temper at only 300 F. A good school of teaching dictates gradually and uniformly lowering steel temperature to cryo. I and am sure many of us have not that capability.

RL
 
Since we are already drifting OT here.....Cryo has to be done immediatly after quench to get the benefit.If you wait until you have a batch to do,a lot of the good will be wasted.
 
If I'm not mistaken should not cryo be done after the first tempering? It seems to me that the possibilities of stress fracturing could be extemely high if placed in cryo right after quench.

Allen
 
You must do something right after the quench otherwise it's a very high risk of cracking .Two options -go directly to cryo with some small risk of cracking or - immediately snap temper 300-350F , then cryo .Once you have snap tempered you have relieved quench stresses so immediate cryo is not so critical.
 
John:
I use 440c, CPM-S30V, and ATS-34 and a lot of Double Stainless Damascus, And you can cryo with Dry Ice and 92% Alcohol and 99.5%
of my knives come out to be 58-60 RC. This is what works for me, somebody
else mite have other tricks that works for them.

Hope this helps.

Blademan3

James
 
I didn't go into the total "how to" on cryo.Yes you are best to do a snap temper,then cryo.This is done sort of as one process.Not an interrupted series of separate events.The point I was making is that quench-temper-cryo are part of the cooling/recrystallization process.Time is a factor in that equation.Many new makers think it is fine to harden and quench their blades and stack them up until they have a batch for the oven.The martensite/austentite mix is still changing until it is stabilized by tempering(and cryo).Later is not the same as immediately. - Stacy
 
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