Follies in the Shop

[Sam Cade]

Sacrificed to the gods of heat treatment.

I thought that the shop oven that I've been using for tempering heated up quicker than it should have.

Ground out a rough knife-like object to give it a try.

Looks like the thermometer was off by about 200 degrees.

 

[Andrew Wyatt]

your photo is broke, dude.

 

[Deltaboy1984]

Ouch!!!!

 

[bldsmith]

Can't see a photo but I can feel your pain!! Happens from time to time.

 

[Sam Cade]

Odd. I can see it and it is hosted on THR.

http://www.thehighroad.org/attachment.php?attachmentid=196211&stc=1&d=1395004533

 

[Sam Cade]

I had to recalibrate the thermostat but everything seems to be copacetic now.

 

[Sam Cade]

Weird. VBB has eaten my picture it seems.

After renaming it, it allowed me to reupload.

Does this work?

 

[hso]

Yep

Did it fail in the furnace like that???

 

[Sam Cade]

That is the result of a single lateral load on fully through hardened (brine quenched) 1/8" 1095. It shattered like glass and blew chunks out along the fracture.

Failure to harden is annoying.
Failure to temper is dangerous.

As best as I can tell the oven fell out of calibration and wasn't getting hot enough to temper at all so I set up a worst case scenario and ground out a sacrificial knife like object to destroy.
My only clue that something wasn't right with the oven was an overly short pre-heat time that I could have easily missed if I hadn't been watching the clock.

 

[bldsmith]

Now I see them. Can you get a shot of the fracture? Would like to see the grain structure.

Had a similar thing happen to me. Caused by excessive grain growth.

 

[Sam Cade]

No prob.

Give me a few min.

 

[Sam Cade]

The missing chunk was toward the inside of the flexion.

It may be hard to discern from the marcos since the fracture is so ragged, but the grain structure is actually very fine and tight.

 

[bldsmith]

That looks like you have a pretty large grain structure to me. Especially if you quenched in brine.

Here is a picture of mine. O1 right out of the forge. No thermal cycles/normalizing



Here is a picture of the same blank after thermal cycling/normalizing



Here is after 3 normalizing and a low temp quench in motor oil.



Here is my take on your situation. Due to the tearing I see on your blade I feel you tempered the blade but as you stated it was on the low side. But with the larger grains it looks like the blade was either made from hot rolled as rolled and not annealed/normalized or the blade was over heated at some point in a forge and not normalized. I have found the normalizing really helps a great deal. However it can be over done. I usually normalize once at 1650, then once at 1500 then one at 1450. Then do the HT as normal. This really improves the performance of the blade. Even if you do not forge it is a good idea just to make sure it was done properly.

Just an opinion from what I have discovered.

Good luck

 

[Sam Cade]

That looks like you have a pretty large grain structure to me

Its surprisingly tight. The way that the fracture propagated mades it look coarser that what it actually is.

It was normalized once (just ran up to nonmagnetic, very scientific ). Remember, this was made to break and wasn't actually a knife. Just an experiment with worst case scenario heat treatment error so I didn't put much effort into it.

I've found that I've got to cycle at least twice to keep bad stuff from happening on quench with the brine, at least with this batch of steel.



1095 from NJSB btw.
.http://newjerseysteelbaron.com/shop/1095/

The first batch of 1095 that I got was from Admiral and it was just awful. and wouldn't consistently harden. Just loose mush no matter what I did with it. Now, I'm a noob at this, and I thought that *I* was screwing up the process somehow. Confidence crushed.
After 12 linear feet of frustration I took a bar over to a more seasoned acquaintance who proceeded to declare it "crap". Such a tremendous relief.

 

[bldsmith]

Aldo is the way to go with steel. His prices have risen a bit but as you mentioned it is worth the lack of frustration.

Few recommendations,

See if you can find a 5 gal pail of parks 50. Yes it is a bit expensive but much more forgiving than brine. If you want some I will be happy to send you an email of a source. About $150 plus shipping but when doing 1095, W1 or W2 it is the bomb. Also take your grind to 100 grit or finer. All those heavy scratches are going to cause stress risers and quenching in brine will propagate cracks.

I think if you do 2 normalizing cycles you might find your grain even finer. Then when you do a quench it should look like glass IF it happens to break. That is the optimum.

Keep at it. Hope you don't mind a few pointers, bit late to ask I know.

 

[Sam Cade]

All those heavy scratches are going to cause stress risers and quenching in brine will propagate cracks.

I know. Doing everything wrong was the point of the experiment.

This wasn't a knife that failed, it was a knife-like-object broken with a cheater bar.

 

[bldsmith]

You had to use a cheater bar to break that. Well I would call that a success. Keep it up.

 

[Sam Cade]

You had to use a cheater bar to break that.

Well probably didn't have to, but slipping a bar over it seemed like a good way to keep everything safe from flying chunks. Better than chucking it in a vise and hauling on it barehanded.

It popped at about 10 degrees FWIW, and the two breaks are from a single flex.