IR thermometer

[territorialmillworks]

Found an IR thermometer w/ 1800F @ at an affordable price. Could it be used for heat treating?

[LDW]

I bought one a couple years ago for the same reason. If you are doing small items like knives it is hard to get quick readings. If you use it and heat up something a little larger that does not cool as quickly you can use it to see what color you want to achieve. I played around with taking a large piece of metal and bring it up to non-magnetic and checked it with the thermometer and the temps jump around, but you can get an average temp pretty quick. If you can use it to learn how much the color shade increases to go about 100 degrees above critical it would probably be a good thing.

[clinton]

I found that they give a good reading on a dull surface, but on shiny surface they are way off, we discovered this while doing an anvil repair on Fewoods Peter Wright, we had temp sticks to compare the readings (when I say way off it was 200- 300 degrees off)

[BIGGUNDOCTOR]

The IR gun we had at the foundry needed to be calibrated for the emissivity of the metal that you were dealing with. We used it to check temps for casting. It was made by Raytek.

[son_of_bluegrass]

I would imagine somewhere there is a range for accuracy. It may be expressed as a percentage. If it says accurate to 1% and you are measuring 1500 degrees it could be 15 degrees off. If the accuracy is to 5% then it could be 75 degrees off at 1500.
Or it may give an accuracy of +/- X degrees.
There may be other limitations such as others have mentioned. Such as the need to calibrate occasionally. If you don't have a way to calibrate it, then you really don't know how far off it is.

ron

[Ric Furrer]

I would imagine somewhere there is a range for accuracy. It may be expressed as a percentage. If it says accurate to 1% and you are measuring 1500 degrees it could be 15 degrees off. If the accuracy is to 5% then it could be 75 degrees off at 1500.
Or it may give an accuracy of +/- X degrees.
There may be other limitations such as others have mentioned. Such as the need to calibrate occasionally. If you don't have a way to calibrate it, then you really don't know how far off it is.

ron

I have used two of the Ebay Chinese units for hot and liquid metal and returned them both. Measuring hot metal is not a simple thing, but if you wish to read the furnace wall then they are OK.
Like Big Gun says the emissivity needs to be calibrated...the factory was not able to help me dial in the $300 units from Ebay so I sent them back.
I have seen the $2,000 units work well, but they much have a different sensor or something.

Now I have a "K" type thermocouple and let the furnace settle on a temp for five minutes before I put in the blade...when the blade matches the color of the thermocouple then I soak a bit more and quench.

Ric

[David Ab]

You might want to call the manufacturer and talk with their techs about your intended use. The suggestions the other guys have given you are some of the same information I got from the Extech techs, about problems from the range of accuracy, and calibration which is expensive.

I ended up getting a digital thermometer with K probe, from Grainger. I think it was about $200. It's the cheapest one I could find that goes up to around 2600F.

One other option is learning to read the colors, which admittedly can be tricky, but if you are using a steel that gets non-magnetic at its austenitic temperature, which I think most do, the combination of color and non-magnetic could do it.

Kevin Cashen talks about how important it is to soak the metal at temperature for long enough. He said he soaked some 01 steel at something like 1550 degrees farenheit for hours, and then took photomicrographs of it, and the grain structure wasn't damaged at all because the steel never got hot enough to start decarburizing or growing big grains. Another master bladesmith told me that it's common for people to not soak metal long enough.

David

[ThomasPowers]

And studies by major steel companies have shown that piece often reach a constant interior temp in just minutes---they did the test by mounting thermocouple in large pieces of steel at different levels and then recording temps as the piece heated.

Of course where a 4" bar may need only a short while to come up to temp a knife sized piece of steel will not require a lot longer!

Where it makes a difference is ALLOY, some alloys need a soak at the proper temperature to dissolve carbides, others do not. Some alloys get very large grain growth fairly fast at elevated temperatures, others do not. Some alloys can refine grain through normalizations, others do not. Some alloys prifit from cryo-tempering, others do not.

People tend to make blanket statements based on what they use; which may turn out to be quite wrong for what other folks use. ALLOY drives properties, properties drive process!