Elmax heat treating issues

R

rjfm1972

Joined
Jan 13, 2013
Messages
221
Has anyone had issues with getting Elmax to harden? I have tried several times with several methods, and I think I have just trashed 8 blades and about 20 hours of hand sanding. I give up. Here's what I've tried....
First attempt: Ramped up to 1500 and let it sit there for 15 minutes, then ramped up to 1975 and held for 30 minutes. Blades were foil wrapped. Pulled out and immediately put between a couple of 1" thick aluminum plates and blew compressed air on them until cool enough to handle. Removed foil and lowered them in acetone/dry ice bath for 4 hours. Removed from subzero bath and put them on aluminum plates until they came to room temp, then placed them back in the evenheat oven at 500 for 2 hours. Removed and put on aluminum plates until room temp again. Put back in cryo for 4 hours, removed, let them warm back to room temp, then back to temper for another 2 hours at 500. Went to run an RC55 file across them, and it dug right in. Ground away some metal on the handle, tested again, dug right in. Took my softest test file, rc40, and still scratched it. It didn't harden at all.
Second attempt: Ramped up to 1980, then put one of the blades that I already attempted to harden, and one fresh one. Both foil wrapped. After 20 minutes at temp, I bumped the heat up to 2100 for 15 minutes. Pulled out of the oven and dropped them into oil (still in foil), swirling around to cool them as fast as possible, then pulled them out and finished them between the aluminum plates while blowing compressed air between them. Pulled them out of the foil and ran the 55 file across them. Both scratched no problem. Ran the 40 file across them, and they still scratched. Again, they didn't harden. Took one in a vise and it bent about 20 degrees then it snapped. I have NEVER had any steel bend at all immediately after quench without it snapping right away, let alone bending 20 degrees.
3rd attempt: took the blade that was fresh from the second attempt, and threw it in at 2100 for 15 minutes without foil. At this point I just wanted to get it to harden at all, regardless of decarb. I pulled it out and dropped it directly in oil and cooled it almost completely in a fast quench oil. I then put it in a cold bucket of water, wiped the oil off and took it to the belt sander to get down to fresh metal. Guess what? It didn't harden at all, scratched by the 40 file.

Now, only days ago I hardened some CPM S35VN blades using the same protocol as the first attempt on the elmax, minus the cryo. I had them tested on an actual rockwell tester after my RC55 testing file couldn't scratch them and my RC60 file could barely scratch them. And guess what? They tested right at RC 59-60. So...... Did I get some bad steel here? Or is there something I don't know or that I am missing?????
 
According to the guy from B-U that I talked to a Blade a couple of years ago, dry ice does not get cold enough for Elmax. it also may required faster quench. Have you tried slow oil?
 
Elmax-Typical.gif
 
The guy from B-U said it requires LN, so that may mean 95C. My recollection form the chart they had at Blade was that it needs a minimum of -120F. I specifically asked hi if dry ice got cold enough and he said no. I am not sure than any commonly use blade steel actually needs 3-4 hours unless you are trying to form those strange little eta (?) carbides. IIRC, Roman Landes says that the conversion of RA is almost instantaneous once you hit the proper temperature. B-U and others say that Elmax is almost a totally different steel when you get up around 61-62 and has like 75-80% of the abrasion resistance of the crazy streets like M390 or CPM90V without the cost or some of the quirks.
Lo/Rez said:
I was reading on Alpha Knife Supply that it needs a minimum of -95F for 3-4 hours.
Click to expand...
 
I think it would be hard to do 3-4 hours with dry ice unless you added some during the process. I've only done it once in a cooler with denatured alcohol and got maybe 2 hours out of it. Maybe I was doing it wrong?
 
I remember reading on another forum that Elmax had can on it as it comes from BU that needs to be removed first.

It might be what is causing the problems during heat treat.

Found the discussion.

UDDEHOLM said:
Gentlemen, this is the Deal with the can:

Ben is correct, we use a 304 stainless can for the stainless powders, in order to protect the steel surface from oxidation during the forging, rolling and subsequent soft annealing processes. It is possible to produce ELMAX with a carbon steel can, but then you will end up with a bad quality surface, with an uneven and unpredictable oxide layer on top and a decarb layer below, which would require a larger machining allowance than with the stainless can. Like Chuck says, this is expected to be removed during manufacturing and recommended machining allowance is 0,008" (0,2 mm) per side for plate thicknesses above 0,12" (3 mm)and 0,004" (0,1 mm) per side for plates below 0,12".

The can material is rather soft and can be machined or ground off easily, with resulting guaranteed top quality material below. Nathan, thanks for your good comments on the machining.

Uddeholm has over 2000 people in the global sales organization, and I apologize for the apparent information gaps that can occur between the mill in Sweden and the respective markets. Some are more used to working with plate material and the knife business, others might have been focusing on the plastic injection moulding business, where pre machined flat and round bars of larger dimensions are being used. These do not contain can material.

Petter Damm - Director of product management and customer service - Uddeholm Sweden
Click to expand...
 
In case you guys missed it, regardless of the dry ice/acetone bath this steel did not harden at all. I should have gotten close to 60 rc with what I did without the cryo, and I am scratching it with a 40 rc file. I tried quench plates. And oil. And air.
 
I have heat treated a couple ELMAX blades with good and consistent results.
When I heat treat I will do at least 3 or 4 knives at the same time.
The only big difference I use is I skip the preheat step. I program my oven to the temp I want. At around 1500 I put the blades in and let them come to temp with the oven. I use this step as my preheat. My notes show a 15 minute soak at 2100 and then plate quench between 1" thick aluminum. This has given me a consistent 64+ out of quench. I then use Dry Ice and acetone for a cryo. Not sure if that is cold enough or not, but I just tested a knife I made for my wife from ELMAX and it tested at 62 Rc after 350 degree tempers. The knife was made about a year ago using the process I just described.

I am pretty sure though that if you are going to oil quench you need to get the blade out of the foil. The stainless wrap will prevent good heat transfer from blade to oil.
 
After reading your first post again I have some questions for you.
Where are you tempering? House oven, heat treat oven, or a toaster oven? Are you trusting your thermocouple for the 500 degree temp or do you have an extra thermometer in there monitoring temp. You temper could have been considerably hotter than your setting.
Have you successfully heat treated any other stainless or high alloyed blades.
Do you have any other blades of known hardness that you can use for comparison with your hardness files? The hardness files are not completely accurate and their use can be very subjective to the pressure applied to make them scratch. Yes, I have some and have used them to compare blades heat treated by Peters to blades I have heat treated.

I had really good luck the first time I heat treated S35VN, but it took me several attempts to dial in my heat treat for 10V.
 
Big Chris, I tempered them in the heat treat oven. And the second attempt was tested right after quench, before tempering at all. As I stated, I did heat treat S35VN and had the blades tested and they cam out exactly what they should have according to the data sheets I have read. Now for the good news....... I had one of the blades tested that I was scratching with the files on a rockwell tester, and it read 57-58. Why I can scratch it with the files and the S35vn won't, I don't know. I broke 3 of the blades to check the grain, and it's about the finest grain I have ever seen. So, maybe I just need to start tweaking the heat treat till I get it where I want with this oven (brand new Evenheat KF22.5). BTW, I also just got a 10 liter Dewar delivered today, and the local welding supply carries liquid nitrogen and is 5 minutes away, so no more dry ice and acetone for me. Thanks for everyone's replies. I have a few more elmax blades to try out, hope I can get it down. This stuff is way too expensive to waste.
 
I have to agree with Chris on the accuracy of the files. It would be wise to find a rockwell hardness tester to ensure accuracy of the heat treating results without having to run around and have a machine shop
do your testing. I would suggest shopping for a used handheld "Ames" tester which can be a reasonable option to the heavier bench models which can be found used but the shipping will eat up any savings.
I purchased a used Ames off the auction site and brought it to work to check the calibration against a certified Rockwell unit we have calibrated every six months and it was within .5 of a 60c scale test block.
These will pop up from time to time in the machinist's forums or you can check the auction site and pounce when one is in the budget...

You will appreciate that Liquid Nitrogen is cheap and will last quite a while if the plug is in good shape...remember its a Liquid that wants to turn to a Gas so it has to be allowed to vent off or you create an explosive
situation...:eek:
 
You must log in or register to reply here.
Back
Top