How stupid can I get?

sharpeknives

sharpeknives

Joined
Jan 13, 2006
Messages
1,655
Due to a thread on 1095 I came to a great realization. About 5 years ago I came into a large amount of 1095. So I decided to master it. I read that I needed to quench at 1480 F in salt brine. So away I went. I just couldn't get good performance out of my blades.Then I found Parks 50. Still couldn't get my blades to hold an edge. Seemed too soft. So I started playing with temp and found that I got great performance at a 1550 F quenched in 130 F Parks 50 followed by 2 temper cycles at 450 F.
After reading todays post and the thoughts given by makers whom I respect I decided to do some testing. I quick ground some small blades and went to heat treating them. My best results were at 1550 F for the quench. A friend came by and he has a laser temp tester that goes to 3000 F. When we shot the blade at 1550F the laser read 1455F. We started checking temps on my oven I am dead on at 1100 but start spreading out above that. By the time my readout says 1450 I am actually at 1375. At 1550 I'm at 1455.
Anyway it breaks down to my oven is off calibration. To all those who I have given advise to I apologize. For 5 years my perspectives have been wrong. I feel like such an ass.
 
Your oven may be off, but it depends on his temp gun too.


His may be different than the ones I have used especially if he has a 3000F range

but in the manuals for the temp guns I read:

The laser is just a dot that helps point it and doesn't actually read anything.

The temp guns use Infra Red Emissivity to measure temp and the Emissivity of metals is different than other materials

.

there will be error
(possibly solved it you are pointing at the brick oven walls and not the blade.
Some models have adjustment for that


"Can you tell me the correct Emissivity setting for the material I am temping out?

The default E setting of 95E works for most applications.

The adjustable Emissivity setting for the PE2 allows you to “calibrate” the units to shoot proper temps in more esoteric circumstances. Unless you truly understand how and why adjusting the E setting works for your application, it is best to leave it set at the default of 95E. If it is accidentally misadjusted by your kids, your goofy buddy, or your cat, you most likely need to reset it back to 95E. You can find the steps on how to do that in your instructions, which are also available HERE .

But let’s say you DO need to adjust the E setting for your application, perhaps you are shooting a highly polished metal surface like aluminum, you can find various E settings listed at these two links:

http://www.infrared-thermography.com/material.htm

http://www.electro-optical.com/bb_rad/emissivity/matlemisivty.htm"



most have
Default settings .95

Steel polished is .85 ?
from this chart
http://www.infrared-thermography.com/material.htm
 
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We were shooting the blade outside the oven. About a foot from the door. It explained allot such as why my blades went non magnetic at around 1480 instead of 1414. I have another pid controler and thermocouple. I will hook them up tomorrow and see what I get. I think its the pid controler.
 
Couldn't your kiln have slowly gotten off over time as well? I thought I read that they will do that. The temp sensor starts to degrade. Could be that 5 years ago it was spot on at 1,550 and today it's off.
 
I experienced the very same conflicts with temps as you describe.
Your oven may quite well be accurate.
I have a high temp gun as well. Your oven will actually "stratify" temps from top to bottom of the oven unless you give the entire oven time to come up to temp.
Up by the thermocouple at the top of the oven where it reads the temp may be well over 100+ degrees warmer than on the floor of the oven where your blade sits.
I set my temps and wait a MINIMUM of 45 minutes for the ENTIRE oven to come up to temp before performing any procedures.
As well, about two years ago, I created a layer of 1" thick wrought iron on the floor of the oven. I let this come up to heat with the oven for a minimum of 45 minutes BEFORE performing any processes.
Now, when the readout says 1525 degrees, I open the door, shoot my blade with my laser, and guess what it reads?
1525.
 
Thanks for the input guys. There is so much to think about. I'll try the 45 min soak and take readings. I let my blades come up to temp with the oven. My oven is a 120 V. Takes about 45min to get up to temp. Will the long soak (45 min at temp )have any ill effects on the steel?
 
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You are the exact opposite of "stupid", you're doing your best to verify your procedures and results. Thank you!
 
this is the reason i have 3 probes in my oven. 1 to my pid and 2 more to a dual Omega controller. I do something similiar to Karl but use a hard fire brick as a heat absorber and stablizer now my temps stay within 5 degrees or less of my pid and i know its at the corect temp. There should also be a way for you so set a default overead on the temp. When i started checking mine it ws off by about 40 degress and my pid has a way to readjust the temp display to make it acurate
 
Andy at those temps the time will not have any serious negative effects on the steel. I would not let it come up to temp with the oven but make sure the oven is well heated. You might try using the thermal gun on the oven when it is at heat. This might tell you a lot also. The bottom of the oven might be a lot cooler than the top. This may be the difference you are experiencing. If you put in the stabilizing material (wrought iron or bricks) the mass will help even out the swings but it might take a while longer to bring it up to temp. You might try putting a thermocouple at the bottom of the oven and one at the top. When both are within 5-10f the oven has evened out and is ready for work. A friend of mine also has a 110v oven but he has to let it soak for over a hour before it stabilizes. It is great that you found the problem and are working it out. Good luck and keep us updated.

PS seems like you might be feeling a bit better. Nice to hear your out working.
 
The emmissivity setting to get accurate temp. reading from an IR thermometer is critical, and the correct setting actually varies depending on the amount of scale on the piece you are measuring. So your friend's IR thermometer may not be dead on either. The non-magnetic point is going to be your most reliable indicator for calibrating. I have 2 TC's in my oven for just this reason and have identified a bad TC this way before. It happens, which is why I have taken to calibrating my oven every other run or so.
 
I'm going to install my other pid controler and thermocouple at the bottom of the oven. I also have a temp guage (Needle type) I will slowly ramp up and see what my differences in temp are between the three and use non magnetic 1414 F. as my control point.
 
Hey, there's nothing wrong with the endless pursuit of perfection! Keep it up!
 
Seems like the real lesson here is in your commitment to striving for the result you desired in your heat treated blade. In spite of what your recipe called for as the proper temp, and in spite of what your thermal readout reported, you actually found the sweet spot anyway through thorough trialing and testing. Right on!
 
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