The plot thickens (or sickens)

Phillip Patton

Phillip Patton

Knifemaker / Craftsman / Service Provider
Joined
Jul 25, 2005
Messages
5,362
Some of you might remember awhile back I posted about some L-6 I was having some trouble with. To recap, what happened was some knives I made from it got somewhat hard, and very tough, but not as hard as it should.
Well, I think I've figured out what the problem is. It's not L-6. Probably. I just austenitized a piece of it at 1885 degrees for 10 minutes. I figure L-6 at that temp for that long would have some massive grain growth, right? I notched the piece beforehand, austenitized, dropped the piece out of the SS envelope and blew on it until it lost it's glow. (redneck forced air quench :D ) After it was cool, I broke it in half to see what the grain looks like. It wasn't exactly silky, but it wasn't bad either. Very hard though. (Not knowing what it is, I'm sure I didn't heat treat it right.)
I don't think it's L-6. Apparently, it's some high alloyed steel that will get somewhat hard when quenched at 1510, but not full hard. I'm going to temper one of the pieces at 900 degrees and see if it's still hard.
I'll call Crucible monday and see if we can figure out what they sent me.
 
thats what i'd do...... cause the champalloy that i got was a damn good steel..... even if you didn't soak it....a file would skate like crazy.... its a beautiful steel for a very tough knife... the only bad thing i found was that the scale likes to stick to it.... ....doesn't pop off that easy when forging...
-- just takes abit more wire brushing or a quick buzz on the grinder...

what you've got is definitely not L6....

how does it spark test...?
 
Greg Obach said:
thats what i'd do...... cause the champalloy that i got was a damn good steel..... even if you didn't soak it....a file would skate like crazy.... its a beautiful steel for a very tough knife... the only bad thing i found was that the scale likes to stick to it.... ....doesn't pop off that easy when forging...
-- just takes abit more wire brushing or a quick buzz on the grinder...

what you've got is definitely not L6....

how does it spark test...?
Click to expand...

The sparks look kind of like O1, but this stuff is definitely air hardening.
The piece I tempered at 900 is pretty soft now. Could be 440c, for all i know. I'm going to see if this stuff will rust...
I'm disappointed Crucible would be so careless. I guess I'll have to try again ordering Champalloy. It's a steel I'd like to get to know.
 
The Champalloy I recently ordered from them had L6 hand-written directly on the bars.

Here's a picture of it:

l6_bars.jpg
 
Thanks Wulf, that looks just like the stuff I got. That doesn't necessarily mean anything; other steels might have the same finish. I did call Crucible today, and they insist they sent me the right stuff. I'm willing to give them the benefit of the doubt, and assume for now that they did. I did find a partly disintegrated sticker on one of the pieces that has the last 7 letters of "Champalloy" on it.
It's possible my heat treat oven is off 100 degrees or so. That's the variable I'm going to check out next.
I just got through forging another test blade.
Wish I had a Rockwell tester...
 
Hi, Phillip,

Not saying this is your problem, but I found out my old Paragon needed a new thermocouple when several blades in a row didn't turn out satisfactory. My conversation with the company suggested that indeed they could keep reading as if all was ok, but actually be even more than a 100F off. The more cycles up toward the high end, the worse they get. For that reason I run a second probe nowadays, to make sure to get a match with what the furnace reads.

What I'm getting at is, if you think the thermocouple might be off, go ahead and replace it. They're cheap enough it is not worth a string of bad blades. :barf:
 
Thanks Fitzo. Glad to hear that's a possibility. I hope that's the problem. I'm going to check it before I use it anymore.
 
Phill

In addition to forging a test blade, just chop off a couple inches of bar stock and run you heat treat on it to see what kind of results you get, then compare this with the test blade. If the results are the same it eliminates your forging as a possible source of the problem and narrows it down to your heat treating equipment or the bar stock!

If you need a hardness test run, mail it to me.

Jim A.
 
Mike's suggestion of using two thermocouples is a very good one. I have had/seen several occasions at work where a bad thermocouple caused days of extra work. We use them to monitor the temperature of components in the electrical equipment that we develop.

Make sure that the thermocouple does not touch anything that is electrically "live" or any large piece of metal in your oven. A connection to an outside voltage (either AC or DC) will screw up the reading on your thermometer. A large piece of metal that is touching the thermocouple can act as a receiving antenna and inject a voltage into the input of your thermometer, screwing up the reading. To check for either of these conditions, turn on your thermometer first. It should read about room temperature. When you turn on your oven, an immediate jump in the reading means that you have a problem. If shutting off the oven makes the reading go back to room temperature, you definitely have one of these two problems.

Hope this helps.

Phil
 
I'm almost 100 % sure the problem is a bad thermocoupler. I just hardened a test blade ( I'll do some "coupons" too Jim) and I think it worked. I set the temp to 1600 and soaked for 5 minutes.
I had noticed in the past that the temp reading on the oven when at room temp did not match up with the thermometer on my wall. That should have caught my attention. Oh well.
I'll have a test blade and some samples for you Jim. :) Thanks again.
Thanks Phil. I have some type K wire. I'll rig up a thermocouple and see if I can figure out how to use my voltmeter to read the temp. I have the Omega temp hand book, but this electrical stuff is way over my head.
 
I have run some experiments lately using standalone Orton pyrometric cones as a tertiary "backup" indicator of temps in the furnace. These are little clay cones used in ceramics kilns. They slump over as a function of time at temp. I bought a range of them from a ceramics outfit and plan on including three of them per run in the future, bracketing the temp range I desire. One will puddle, one slump, and one should remain unaffected. They are comparatively dirt cheap and help assuage my paranoia about having unnoticed temp excursions.
 
fitzo said:
I have run some experiments lately using standalone Orton pyrometric cones as a tertiary "backup" indicator of temps in the furnace. These are little clay cones used in ceramics kilns. They slump over as a function of time at temp. I bought a range of them from a ceramics outfit and plan on including three of them per run in the future, bracketing the temp range I desire. One will puddle, one slump, and one should remain unaffected. They are comparatively dirt cheap and help assuage my paranoia about having unnoticed temp excursions.
Click to expand...


Good idea. I'll see if I can track some down...
 
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