1095 heat treat failure

G

ggoose

Joined
Apr 30, 2014
Messages
139
Hello All,

A heat treat failure question if I may...I heat treated a knife made out of 1095 and after the quench gave it the file test which concerned me a bit, as it seemed to bite more that I though it should. Having no way to test it, I simply continued to finish it. Since then I purchased a Grizzly hardness tester and used the same ht procedure on a scrap of 1095 from the same bar as the knife. The results were disappointing: ~HRc 39.
My ht procedure was:

Kiln heat to 1475 degrees F and soak for 10 min (3/16 in 1095)
Quench in Parks#50 preheated to ~130F

I then scraped off any scale in a couple of spots and tested the hardness (softness :( ) on the Grizzly (which was calibrated correctly according to the 3 test blocks).

Any obvious (or otherwise) errors in my procedure?

As always, thank you for any input...
 
I typically use brine for 1095, there is a risk of cracking, but, gets the job done, maybe someone else will discuss parks 50.

To prevent this problem I cut some test pieces from the same steel and go through the ht process with the knife, you are right about the file test, when ht is proper you will not make a mark on the hardened 1095, also you can tap with a hammer and shatter the piece, or just throw it on the floor. I also send test pieces through the temper, to see how tough they get, pretty amazing, you should be able to hit a 1/8 piece as hard as you want with a hammer without breaking.
 
Hi .. I am glad this came up. I was having some problems from time to time with 1095. I was doing my heat treat very similar to you using Parks digital kiln and doing everything right , Or as right as I thought. I was getting readings of 43 right at the flattest spot as close as I could get where it would not be seen because of the handle.

Basically I had a batch of 1095 that I had bought and when I got these readings I stayed away from it since last year. About a month ago I decided to do a test coupon and it got hard as it should. So I decided to do another blade. After heat treat cleaned up the blade on the grinder and to the tester and there I was ..again at 40/43 . But I was holding this knife in my hand and I said. I know this blade is hard. I could just tell. So I cleaned up the blade some more and I found what had been happening to me all along. I was getting a auto hamon or a differentially hardened blade at the thickest spot I had been testing.

So all I did is I moved away from the center of my testing area. I could see the faint hamon are so I knew where the soft stuff was. And that's it. I was always testing the soft stuff. All the blades I tossed were actually hard but I just didn't know it ... well because I am still learning. So this was one of those learning moments for me. I really don't have any help at this . Just what I read on the forum and books . But a lot of this has to be learned from experience. I can only hope this is what is happening to you,
 
Hi Ggoose,

You mention 'scraping off' the scale before testing the hardness; this may not be enough. Your 10 minute soak has probably caused some decarburization of the surface of the steel, which will need to be ground off completely in order to get an accurate hardness reading.

Good luck!
 
Are you measuring soak time 10 minutes, AFTER the temp has recovered from opening the door ?

or from the time you closed the door.
 
Thank you for the input gentlemen...

Patrickknives said:
... you are right about the file test, when ht is proper you will not make a mark on the hardened 1095, also you can tap with a hammer and shatter the piece, or just throw it on the floor.
Click to expand...

I thought of this and in fact dropped the test piece on the floor...chipped the concrete a bit, but the steel was fine :(

Marko3 said:
...So all I did is I moved away from the center of my testing area. I could see the faint hamon are so I knew where the soft stuff was. And that's it. I was always testing the soft stuff.
Click to expand...

After reading this and Will Morrison's reply I went out and ground the test piece down to shiny steel and retested all over it. It did test a few points harder near the edges, likely because it cooled faster there, but even then only to HRc45. Perhaps if the test piece had a bevel it would yield different (harder) results. I'm stumped at the moment...
 
12345678910 said:
Are you measuring soak time 10 minutes, AFTER the temp has recovered from opening the door ?

or from the time you closed the door.
Click to expand...

Place the blade in cold kiln and close the door, initiate program to begin climb to target temp, reach target temp and hold for ten minutes, open door and remove blade, quench...is that what you mean?
 
I see two things:
1) Parks #50 should be used at room temp. 130F is for other oils.
2) You have to grind the decarb off the blade to get any sort of accurate test. A file will often bite quite a bit along the edge....for the first four pf five file strokes. then it will skate like it was on glass as it hits the hard steel under the decarb. Same for testing the flats. I test the tang just off the ricasso. I grind a clean flat spot that gets below the decarb...and test there.

The only other thing that could be wrong would be if the temperatures you get are not what the oven is at. Have you checked to see if the TC and controller are accurate?
A simple test is to take a 4X4" piece of scarp steel and place it in the oven. Put a teaspoon full of rock salt on it. Turn the oven on and set it for 1485F. If the salt melts after 10 minutes at 1485F, then the temp is probably OK ( salt melts at 1474F). To check for overheating, do the same test with the controller set at 1465F. The salt should not melt. If both tests are good, your TC and PID are accurate to less than 1% error. If the tests don't work right, try again at +/-20F range. That is only 1.5% error.
 
Yes Stacy has it right about the parks for sure. Do not pre heat it. According to it literature it is only effective up to 120f.

Have you made a knife out of this bar before?? And did it harden as expected??
 
ggoose said:
Place the blade in cold kiln and close the door, initiate program to begin climb to target temp, reach target temp and hold for ten minutes, open door and remove blade, quench...is that what you mean?
Click to expand...

No, Bring kiln up to temp. Open door and put blade in. Close door and let the oven equalize/return to tgt temp. Begin the 10min timer. Then remove and quench.
 
Before you proceed any further. Cut a piece off the bar, Bring it up to temp and quench in either water or brine. It should get screaming hard. If you put it in the vise you should be able to hit it with a hammer and break it. If not you either got a bad bar of steel or someone mixed up your bar stock. Always check at least with a file. Yea I know it is not as good as an RC tester but will at least give you an idea. And make sure you get through the decarb.
 
I agree with Chuck. Do a test coupon before going any farther.

Turn the oven on and set to 1475F. When at temp, put in the coupon ( just a 2-4" piece of the steel) and let it come back up to 1475F. Time for 10 minutes, remove , and water quench. It should be really hard ( might even crack in the quench). It should not file at all. Put one end in a vise and hit it with a hammer. It should snap off with little resistance. Look at the grain. It should be fine and silver-gray. If all that is right, try again with a knife blade from the steel. If not, you will need to determine if it is the oven or the steel.
 
I re-tested another sample of the steel in question, this time with a water quench and a good post-quench grinding. I am getting consistent RHc 63.5! Also smacked the "coupon" in half with a hammer, which was not only therapeutic, but revealed a very fine grain and the silver-grey color you alluded to Stacy. Looks like it was pilot error with the preheating of the Parks. Thanks Stacy and Chuck for the test parameter suggestions, and everyone else for input. All is peaceful and orderly in my shop again... :)
 
ggoose said:
I re-tested another sample of the steel in question, this time with a water quench and a good post-quench grinding. I am getting consistent RHc 63.5! Also smacked the "coupon" in half with a hammer, which was not only therapeutic, but revealed a very fine grain and the silver-grey color you alluded to Stacy. Looks like it was pilot error with the preheating of the Parks. Thanks Stacy and Chuck for the test parameter suggestions, and everyone else for input. All is peaceful and orderly in my shop again... :)
Click to expand...

Try 10f increments up and down (I would go down first) and see what the Rc value out of quench is. You should be able to get Rc66 right out of quench. At least you know you are on the right track. :thumbup: Dial in this batch, and get the most out of it.
 
Willie71 said:
Try 10f increments up and down (I would go down first) and see what the Rc value out of quench is. You should be able to get Rc66 right out of quench. At least you know you are on the right track. :thumbup: Dial in this batch, and get the most out of it.
Click to expand...

I was curious what a good target might be...thank you
 
Great Day !!


ggoose said:
I re-tested another sample of the steel in question, this time with a water quench and a good post-quench grinding. I am getting consistent RHc 63.5! Also smacked the "coupon" in half with a hammer, which was not only therapeutic, but revealed a very fine grain and the silver-grey color you alluded to Stacy. Looks like it was pilot error with the preheating of the Parks. Thanks Stacy and Chuck for the test parameter suggestions, and everyone else for input. All is peaceful and orderly in my shop again... :)
Click to expand...
 
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