I'm so frustrated I could kick a puppy.. Major HT issues... Help needed.

M

Mikmerk

Joined
Apr 23, 2016
Messages
15
Well, not really, I love my puppy. But I am frustrated.

I've just set up my evenheat kf 27. I am trying to HT some 1084 I got from Aldo. Here is a video of my initial attempt:

[video]https://youtu.be/oBE5BbijeAA[/video]

After the video I took the blank home and put it in my oven at 400 deg for 2 hours, twice. The next day I showed it to my machinist friend who had a file and hardness tester. Both indicated that my blade blank was very soft.. about 32 RC. I thought perhaps I had tempered it too far, but it turns out that my problem lies with the HT. No matter what I've tried, I simply cannot get the steel to harden.

I'm heating the blade blank to 1500 in the kiln. The blank is balanced on its spine on the floor of the kiln near the door (I don't have long tongs yet). I let it soak for 5 min to make sure it was evenly heated, then remove it with a pair of pliers and quench in canola oil preheated to 130deg. I agitate it back and forth until the bubbles stop then let it sit in the oil.

I'm borrowing a friends ancient hardness tester. It is consistently 3 RC soft on the calibration test blocks but it still gives me a ballpark RC on my blades.

My blades are registering low 30's to low 40's RC every time. I've tried several pieces of 1080, 5160, even a block of 1045. Always soft.

On A whim I quenched a blade blank and the block of 1045 in water and warped the crap out of the blank but it did get it full hardened. The 1080 was about 64 RC and the 1045 was 60. This was from 1500 deg. Of course now I'm doubting the RC reading.

I thought that perhaps I didn't have enough oil to dissipate the heat so I added an additional 2 gallons. It didn't seem to affect anything.

To make sure the steel was up to temp I increased the soak time to 20 min. Fail.

Worried that my kiln wasn't reading the correct temperature, I tried increasing the temp to 1550, then 1600, then 1700 before quenching. Didn't make a difference.

I thought perhaps the kiln wasn't heating evenly, so I tried pushing the steel further into the kiln instead of just by the door. NO difference except now I have no hair on my arm.

I tried quenching in used 10w30 motor oil. NO difference, still soft and now my shop stinks.

I wondered if perhaps the Hardness tester was off or I was using it wrong so I tried a file instead. It ate into the steel like it was annealed.

Before testing the hardness I'm grinding off all the scale down to shiny metal to avoid a bad reading. I've even cut deep with a file just in case only the surface was soft.

This is my first attempt to HT on my own. I've been experimenting for 3 days now. I've consulted with two knife maker friends to no avail.


I am doing something fundamentally wrong but I can't figure it out. I can't even tell what details I'm observing are important or relevant. In fact whatever I'm doing wrong is so stupid I managed to stump Tai Goo.

So I am throwing myself to the mercy of the Board; the person who posts a solution to my problem will receive a special prize...
 
That's strange you got that low of readings .. you didn't mention that you removed the decarb layer that you get when doing HT . So if you have not done that I would look at that as a first step . So sand that puppy up and you should get a better read on that . I am also pretty sure your kiln has a switch on the door that shuts the coils down every time you open it ..But to be safe assume it doesn't . Let us know how that goes.
 
Thanks for the Reply Marko..

Is the grey scale that flakes off the same as decarb? IF so I've been grinding it off to clean shiny metal before checking for hardness. I've run that blank though so many HT attempts today that the metal is starting to pit from all the scale coming off of it. Unfortunately my kiln did not come with an auto shutoff switch, though it is available for purchase. I probably should get it before I get electrocuted. hehe.
 
Your quench tank is too short. You need to slice/agitate the blade back&forth fairly fast at least 15 seconds. Thermal conductivity of oil is too low for that blade in static position (just dropped into the tank), thus that blade is probably highly pearlitic. Your test coupons quenched in water got over 60rc probably because the blade drop through enough water (top to bottom of tank) to avoid or only partially hit PN.
 
Thank you bluntcut. After the video I changed to a larger tank, about twice the size, and added in two more gallons of oil for a total of three, but I still had the same problem. I will try agitating faster in the larger tank.
 
Regarding decarb: there are a few discussions - including my own question - about the decarb layer. Example:
http://www.bladeforums.com/forums/showthread.php/1383808-decarb-layer?highlight=decarb

As such, my guess is that it may yet be hardened deeper below the layer you tested.

Suggestion:
Given a steel that has been heat-treated, leave one section 'raw', then grind different depths along the way, as much as 0.02".
Try testing the section that has been ground the deepest. If it is still testing as soft (<45 Rc), then yeah, something is weird and I have no idea.
 
Now that sounds like a possibility!... When I'm at the shop next I'm gonna grind down a good distance before testing.
 
good point PT DOC. maybe check it with a magnet with the oven set at critical temp. i just read an old bladesfourms post, saying non magnetic is around 1420F, and the temp at which it should be quenched is 1500F.
 
Last edited:
I'm guessing it's not 1084 or the temp is not right. 1084 is pretty forgiving, so you shouldn't be having these difficulties. Next try, get the blade up to temp and see if a magnet will stick, if if does, your temp reading on the oven is wacked.
 
A friend suggested a good idea. I'm going to go heat a piece to non magnetic with a propane torch then quench. IF it hardens then I'll know something is up with the kiln. If it doesn't then I can guess the quench is bad or possibly the steel. I've wondered if the steel isn't 1084. I bought it from Aldo but then sent it to a laser cutting company to make the blank. Originally it was a big parang, but it broke while I was messing around so I cut the current smaller blade blank from that.

I have some other theories though thanks to you guys. I'm going to grind into it deep and take a hardness reading.
 
I watched your video. From the colour of the steel it looks like you might be in the right temperature range:

heat-treat-colors-copy.jpg


For sure your quenching technique needs changing. You want to have the blade slice back and forth through the water many times otherwise the blade will heat a small amount of oil to a very high temperature around it making an insulative layer and slow your quench. Don't drop it in the tank, hold on to it and move it around allowing it to slice through the quenchant rather than fan it with the flat of the blade. You can use tongs or just have a coat hanger through a hole in the tang.
 
Last edited:
Ok .. I am going to also suggest that the steel is either mislabeled .. I don't want to speak badly about the place that you bought from because I used to religiously use him for steel and I know he gets a lot of love around here but here goes. I have purchased steel numerous times from Aldo and could not get the steel hard no matter what I did , When it happened the first few times I chalked it up to inexperience after awhile I started using O1 and D2 a lot and it was easier to order all my material from one place . Something was wrong with the steel I was using . I know it was not me . I have heat treated many ...Many blades and never have I had a issue with anyone at least regarding hardness. So I blame distributor in my case and I wont buy much from them anymore because I cant trust them .. Sorry to the fans but I can heat treat as well as I need to be. I don't have time for voodoo magic to get that guys steel hard .

So I don't know what to tell you .. Cut another bar and grind it smooth ..Do the test with the torch and do a test in the kiln . Bump the kiln up to 1525 just for the sake of it and leave it in for 12 minutes but make sure your kiln has been at temp for 15 min before you set steel inside to rule out that problem . waiting for your results.
 
Take a piece of that steel and heat it up to your set temp and let it set/soak for 4-5 minutes AT TEMP.
Fill up a five gallon bucket with water.
Pull the austenized steel from the oven in instantly quench in the water and swirl it all around until cool.
Take it to an anvil/vise and break it.
It should break like glass.
If not either your steel or oven are wrong.
 
Aldo had some 1084 that was VERY spheroidized that wouldn't harden without normalization. Try 1700, 1600, 1500 with air cool to black in between, then 1500 and quench.


Sent from my iPhone using Tapatalk
 
Problem solving is several steps.

1. Decarb. Make sure you are through the decarb.

2. Verify kiln temps. Make sure the blade is at temp before quenching.

3. Make sure you have the right quenchant and enough of it. Also that the steel isn't cooling too much before quenching.

4. Normalize the steel, and thermal cycle it. Course spheroidizing must be broken up to get the carbon into solution.

5. Send a piece of the steel to the supplier to have them verify you have the right steel.
 
I've been reading this thread with much interest, after all, things are easy when everything works, its when they don't work that we're really able to learn something. While I've never done it in the past, I've heard from various sources that when dealing with 1080, 1084, or 1095 carbon steels that they should be normalized by the purchaser regardless of any claims made by the seller as to the metal already being normalized. I guess the logic is that at this point a person is starting with an absolute known condition of the steel assuming of course the carbon content is what you think it is. I hope this is on topic enough to get some responses to this question. Should we be normalizing first?
 
TonyRV2 said:
I've been reading this thread with much interest, after all, things are easy when everything works, its when they don't work that we're really able to learn something. While I've never done it in the past, I've heard from various sources that when dealing with 1080, 1084, or 1095 carbon steels that they should be normalized by the purchaser regardless of any claims made by the seller as to the metal already being normalized. I guess the logic is that at this point a person is starting with an absolute known condition of the steel assuming of course the carbon content is what you think it is. I hope this is on topic enough to get some responses to this question. Should we be normalizing first?
Click to expand...

I normalize all of the 10xx steels, 52100, W2, and 80crv2. The steels that don't need it are O1, 15n20, and hitachi steels, in my experience, although I have been normalizing the Blue I got from Aldo. I had one blade not harden properly. The supply from dictum didn't need it. Doing this leaves me assured the steel is in great condition when I heat treat, and my results are consistent.
 
You must log in or register to reply here.
Back
Top