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Annealing and tempering steel

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Andrew Tinsley19/09/2021 12:08:59
1611 forum posts

I use a gas fired kiln for annealing and tempering steel. I currently use a themocouple for measuring temperature.

I would like to try a pyrometer for temperature measurement, There appears to be a plethora of cheapish pyrometers on the market (although most use a fixed emissivity) right up to hugely expensive professional gear.

Has anyone any experience or recommendations?


David George 120/09/2021 17:12:08
1871 forum posts
505 photos

Hi Andrew. I once made a gas fired furnace which used a pyrometer to check the temp but that was 40 years ago. Since then I have just made and controlled electric heaters and equipment which use thermocouples. There was a member called Oven Man on here and thought he may appear but not yet.


JohnF24/09/2021 09:55:41
1172 forum posts
193 photos

Andrew try putting pyrometer or temperature control in the search box there are some things that may be of interest. I find single words or 2 words in the search bring better results -- don't tell it too much !


Oven Man24/09/2021 11:47:29
185 forum posts
34 photos

My experience with optical pyrometers is using the commercial ones made by companies like Land Pyrometers. They are very expensive and probably well outside the budget of most hobby people. We only tended to use them for very high temperatures when using thermocouples would be a problem. If you are annealing and tempering then you are going to be at the low end of the operating range of an optical pyrometer. Yes you can get inexpensive ones that work at temperatures close to room temperature but I don't think these would be any good for temperatures up to 600 deg C.

Emissivity is a major consideration. Without correct calibration you could be way out. Base metal thermocouples do have their own problems but on a price performance ratio they are the best choice for temperatures up to 1000 deg C anf up to 1200 deg C for short term work.

The idea of using an optical pyrometer is nice, you can aim it at the work to get its temperature rather than just measuring the overall furnace temperature. Alternatively fasten a thermocouple to the work. You can create cascade control systems so that the furnace is itself is controlled off the work thermocouple but its probably getting a bit over complicated for the sorts of heat treatment we do.

My advice is stick with thermocouples, they are cheap, reliable and easily available.


Andrew Tinsley24/09/2021 14:36:51
1611 forum posts

Thanks everyone for your input, as I suspected, a radiation based pyrometer is not a realistic option as it is going to be very expensive.

I will stick with thermocouples.


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