How hot tester

JTknives

JTknives

Joined
Jun 11, 2006
Messages
8,651
i am looking for a percise way to test the temp of a blade when pulled from the forge. i have seen the ir point and shoot type but it seams thay just go up to 1835F. what can i use?
 
This may sound dumb, but why would you need that? Are you just educating yourself on color and temps? Don't get me wrong, thats admirable, but you have to realize that if your wanting to use it as an indication of forging, quenching, normalizing or annealing temps, it won't work like you think. As soon as you pull a blade out of the forge, it is loosing heat, and unless your annealing container or quench tanks is inches from the forge, you'll miss your target temp by the time you get there, most of the time by a wide margin. Most everything you do concerning a blade and forging, you will have to compensate one direction or another for the heat loss or gain that takes place when performing given tasks. I'm not trying to be a butthead, its just that in my experience, this is something that a lot of newer bladesmiths fail to realize.

I think you might have more/better success getting a pyrometer for your forge. That way you will know the interior temp of the forge, and be better able to judge the type and intensity of correction you have to make for each given situation.
 
JT
The "how hot tester" is a pyrometer. If you google it you may find one that will work for you, but like you said most I've seen tend to end about there.
Matt
 
I was able to get a IR point and shoot off of ebay that measures to 2972 F. cost was just above 200.00
 
i have a pyrometer its just not very fast. i make knives in any weather and the color looks diffrent depending on weather. i need to train my eye so to speak. wont the thermocupple just messure flame temp. im just wanting to make shure im on target with my temp jugment.
 
If you have a sheath over the thermocouple, it should register the same temp as the blades in the forge. I often bring the forge to full soak (takes about 15 minutes) and shut it off to see what the meter reads with no flame at all. It drops a little bit quickly (due to the flame contact being gone), and then slowly cools down. Putting the blade and the probe in the same muffle (a pipe) will assure the temp reading is the same.

Ed's advise is dead on. It is the experience and feel that you want to get used to in forging. For HT, learn to make your equipment do what you want it to, and use those readings and times. !0 minutes at 1450 in your forge may be 5 minutes at 1500 in another's forge. It is the total effects and changes in the steel that you are shooting for, not any numbers written on paper. The numbers are in the books to tell you where and when the changes happen, it is up to your learning and experience to determine how those changes can be brought about using the equipment you have. This is why switching from steel to steel is not a good thing. Master a steel,learn to HT it right,refine and perfect that procedure to the max.

Stacy
 
Ed Caffrey said:
As soon as you pull a blade out of the forge, it is loosing heat, and unless your annealing container or quench tanks is inches from the forge, you'll miss your target temp by the time you get there, most of the time by a wide margin. Most everything you do concerning a blade and forging, you will have to compensate one direction or another for the heat loss or gain that takes place when performing given tasks. I'm not trying to be a butthead, its just that in my experience, this is something that a lot of newer bladesmiths fail to realize.
Click to expand...


Perhaps a metallurgist could correct me here but

But I've been under the impression that the exact temperature of the steel the instant it touches the quench medium isn't that critical, depending on the timing. The temperature it soaked at (at time at soak temp) are what is critical, but the few hundred degrees it may lose in the second or two out of the furnace are just part of the quench.

Or, to be more concise, so long as the cooling rates and temperatures are compatible with the Time Temperature Transition characteristics of the steel you're working with, the finished product is the same.

Here is a TTT chart for O1.

O1.jpg


http://www.navaching.com/forge/forge.gifs/O1.jpg

If, after a few seconds the blade has cooled in the air to 1,200 before going into quench, there is no difference than if it was into quench instantaneously from 1,500.

There would be a difference, however, if you tried to compensate by heating it to 1,700 so it would be 1,500 when it hit the oil. Your grain would be more coarse.



EDIT:
I misunderstood what he was getting at. I thought part of what he was saying was you'd need to compensate the heat on the blade so it would be a certain temperature as it went into the quench. Meaning the temperature of the steel going into the quench was what is important rather than the temperature it soaked at. Which is wrong, but it isn't what he meant. My bad.

(mental note, think twice before contradicting Mastersmiths)
 
I would think that would depend somewhat on the steel. 1095 and the like have a very short time period and those seconds could be critical. Now with O1, 5160 or 51200 that may be true. When I do 1095 I have the quench right under the door of my oven, but the next question is how fast does the piece air cool on its trip from oven to quench. The bigger pieces and thicker sections should lose heat faster. A pocket knife blade is going to cool way faster than a 12" bowie, even the tongs will suck out heat. Is this helping or hindering if I stay under the steels nose time. Hmmmm, Would it help to use light preheated tongs on those small thin blades? Am I being paranoid about this or not.
 
Paranoid, Who Me? Who said that? What are you looking at? Who Me?

The time from forge to quench is not an issue.The amount of heat loss in a second or two is nil.(It would take longer to measure it with an IR gun than to just quench it ,probably) The time that it takes to cool the blade from austinitizing temp to below the nose is critical. With 1095 you have about 1 second to get it from 1400F to 900F. A fast oil no warmer than 130F, water, or brine will do this. You could probably hold a 1450F blade out of the forge for several seconds before quench and still would have time to spare. It is the time it takes for the austenite to convert to martensite that you are concerned with.This time starts when the austenite drops to the conversion point (which is different on the way down than on the way up).You have about 100F to drop before you reach this point with a properly soaked blade. Once the conversion starts ,if you are too slow you get pearlite/bainite etc.

BTW, I would move the quench tank to the side of the forge to avoid a possible flash from the smoke igniting.
I think you had a typo:
The bigger sections and thicker pieces will lose heatslower not faster.
The tongs will pre-heat plenty just reaching in and picking up the blade.

Stacy (Quit looking at me, I know you can see me through the computer.)
 
Within the tolerances of 1095, there falls some that no matter how fast you quench it you can not avoid some pearlite. The "nose" goes all the way to the left side of the TTT graph, not possible to get under it. Even then, with the very high rate of quench required, that high rate of quench is not needed throughout the entire temperature range, but you do need to get under the nose. I believe, (though I'm not sure) that even with 1095, the "clock" doesn't start "ticking" immediately, you only need that rate of quench once you fall below a certain temperature. Perhaps Kevin or Mete could shed some light on this.

I expect that cold, or even warm tongs would be best in the handle or other noncritical area of the blade.
 
Stacy,

You beat me to it. I've got to start refreshing the window to see if somebody already said what I was gonna say before composing a response.

I will point out that I don't entirely agree with what you said about the blade staying that hot for very long. I believe that most of the blade stays that hot for plenty long, but I've observed the tip start to go dark (below critical, uh oh, better get a move on) within a few seconds. Depends on the surface area and thermal mass. That very tip sometimes has a bunch of the first, and not much of the second.
 
I think Ed Caffrey didn't exactly mean that you would screw up the quench by measuring the temp, but if you're trying to train your eye to temperature, the heat lost while doing the measurement will throw you off. If you want the IR meter to read 1500 on the blade after you pull it out, then the steel needs to be hotter than that inside the forge. So you can't tell what temp you're soaking at by what temp the blade is outside the forge environment, and you won't know how much the temp has dropped, or at what rate.
 
Yes I did mean the thicker piece would lose heat slower. I just walked in to read this before I go out and pull a blade from my oven. The quench is a couple feet under the door and it is an electric oven. I figured I was fine because all my stuff so far has came out ok. Just want to do as good as I can. Every little possible thing to make the blade better. Thanks you guys Jim
 
hardheart said:
I think Ed Caffrey didn't exactly mean that you would screw up the quench by measuring the temp, but if you're trying to train your eye to temperature, the heat lost while doing the measurement will throw you off. If you want the IR meter to read 1500 on the blade after you pull it out, then the steel needs to be hotter than that inside the forge. So you can't tell what temp you're soaking at by what temp the blade is outside the forge environment, and you won't know how much the temp has dropped, or at what rate.
Click to expand...


Yeah, I went back and re-read it. I misunderstood what he was getting at. I thought part of what he was saying was you'd need to compensate the heat on the blade so it would be a certain temperature as it went into the quench. Meaning the temperature of the steel going into the quench was what is important rather than the temperature it soaked at. Which is wrong, but it isn't what he meant. My bad.

(mental note, think twice before contradicting Mastersmiths)
 
The problems we face are the temperature ranges in which certain phases will form. If a person knows the times at certain temperatures quite well that different phases will form it is possible to cool slow, accelerate, slow down again, or even halt for a second or two, and still get a successful heat treat, however I wouldn't advise it. With hypo-eutectoids one needs to be very careful from Ar3 to Ar1 or you will precipitate ferrite and things will be soft. The real killer is the 1000F range where pearlite will rapidly form. For 1095 that has been properly austenitized the 1000F window will be under a second but still quite doable in knife size cross sections. But from 1475F to around 1200F you have around 2 seconds to start the cooling, once the cooling begins YOU ARE COMMITED as the race is on and you had better get it below 900F right now!

There is a version of 1095 modified that does indeed offer no opportunity to miss the pearlite nose but it is not the same stuff we are all familiar with. If folks are working with a hypereutectoid, and particularly an alloyed one, please don’t trip over yourselves running to the quench. Have the quench near at hand and relax while getting the stele into the quench in a smooth and methodical manner, you will be fine as the air will not pull so much heat out in the time it takes to get it to the quench to worry about it. Once under the surface cool as you can to below 900F and as evenly as you can to 450F. There is where the blade will begin to harden, and if you made no other phases on the way down, you will get complete martensite. From 400F to 100F things should be as even and gentle as possible in a continuous cool. It can be slower but it should be continuous, or you may have to contend with austenite that gets too comfortable at lower temperatures.

A lot of things happen as iron/carbon/alloy systems cool from austenite and it is nowhere near as simple as just cooling things as fast as you can, but getting it back to room temperature as efficiently and simply as possible is the safer way to err.
 
I love this website!

Kevin, I have been working on trying to improve my heat treat consistency over the last several months for O-1. I've been using a home-built digital kiln, heating to 1200 for several minutes to get everything to the same temperature, raising the temperature to 1475 for a 10 minutes soak, and then edge quenching in 130 degree oil. Following initial quench, I leave the full blade in the oil until the oil stops eddying around it. I then go straight to a rinse in hot flowing water and straight into a preheated 400 degree oven for tempering.

From 400F to 100F things should be as even and gentle as possible in a continuous cool.
Click to expand...

I pull the blade from the oil when it's just cool enough to touch without burning. I'm not sure where the temp is at this time, but it's somewhat above the oil temp. Should I leave the blade in the oil until cooler to achieve a more even cooling to 100 degrees? And should I avoid the hot water rinse to avoid further shocking the steel for a more gentle process?

Anyone have any suggestions to better my heat treating?

Thanks for a good thread!

--nathan
 
Would it be a dumb idea to get a dark, steel box so that colours are always the same?
 
silver_pilate said:
I love this website!

Kevin, I have been working on trying to improve my heat treat consistency over the last several months for O-1...

...Anyone have any suggestions to better my heat treating?

Thanks for a good thread!

--nathan
Click to expand...

Nathan I personally am not into edge quenching at all, so you are one your own there, except to say that I don't see any gains in ductility, that other folks would like, when using O1. The spine of that blade will not go entirely pearlitic on O1 and you will have a mixed microstructure with a hodge podge of upper bainite (not good at all) some martensite and perhaps some fine pearlite. This would result in a lack luster hamon, and lowered impact toughness while no strength from hardness. Fully hardening the blade and then drawing the spine back softer would definitely produce a superior blade to an edge quench with O1.

As for the rest, I am not certain if the presoak would be necessary for O1, particularly something as simple in shape as a blade. I can only cover the quenching from the perspective of a full quench. In the quench you either do 1 of two things, cool all the way to the temp of the oil and then temper as soon as possible, or marquench it. If the blade is below 130F. you are good to go on the temper, if you have continually cooled all the way to that temp I would only rinse with warm water before tempering if you have distortion or cracking concerns. Another method would be to attempt to interrupt the quench at around 400F (do not heat the oil any hotter than 150F unless it is designed to do martempering), and allow it to air cool. Allow it to cool however, don't get creative with messing around with the cooling rate, just let it do its thing. If done right you should be able to take it all the way to room temperature and not worry about shocking the steel with a rinse. I like to rinse my marquenched blades in cold water before tempering.

A dark box is an all right idea but a bit more than necessary, in my opinion. I think it is best to just have subdued lighting in the shop that is consistent all the time- a window that pours sunlight into the area in the afternoon that was dark in the morning can be disastrous. Keep the lighting dim and the same and practice learning the colors there and you will be all right.

The IR thermometer idea is great fro learning the colors but for actual heat treating I agree with Ed Caffrey that it is one too many things to fumble with while trying to quench for it to be worth the trouble. Time doesn't bother me as much for the phase changes but instead the decarb and scaling. Better to have the inside of your heat source at the temperature that you want and then equalize the blade to it. Then when it is time to quench all you need to worry about is properly dunking that blade.
 
Great advice. I'll switch over to a full quench followed by drawing the spine.

The only reason I go to 1200 and pause for a bit is to allow everything to equalize out as I am starting the kiln from room temperature, not to improve anything in the heat treat other than control. As the heat increases, I want to be as accurate as possible, and my PID has a bit of trouble controlling the overshoot. This way I can do it slowly and incrementally from 1200 without overshooting my upper temp.

When performing an interrupted quench, how do you judge the temperature of the blade so you know when, approximately, to pull it out of the oil (ie, 400F)?

I know I've read posts on marquenching, but since my memory is not what it used to be and we don't have the search function (I know...I'll eventually start paying :D) are you seeing an improvment in interrupting the quench vs. cooling all the way to the oil temperature?

Thanks again!

--nathan
 
You must log in or register to reply here.
Back
Top