Sticking Thermocouple on Red Hot Steel Forging

Maybe it could be brazed on with a suitable high-temperature brazing metal? The person doing it could wear suitable insulating clothing like welder's gear. Just a guess.

Fine solution. Optical non contact digital pyrometer is routinely used by heat treaters to measure high temperatures of salt bath.

hi , thanks for the reply. Actually pyrometers cannot be used as our goal is to get a record of the temperature drop with time, while the material cools. We need the cooling curves , which is only possible if we log or record the temperature drop every second , so pyrometers cannot be used , .......

You might want to look around; some of them might be able spit out successive values to a computer or whatever. Furthermore, the cooling curve will be pretty smooth, so there is no need for overly frequent readings, anyway.

Optical pyrometers such as the disappearing filament type require human interpretation and can not provide data each second. Other types are almost instantaneous and will provide data at any rate you require. An infrared pyrometer attached to a lap top with charting software will solve your problem.

The link I gave you says:

"The Extech 42570 dual laser infrared thermometer has a USB interface which includes software for downloading data to a PC..."

It also is described as having an internal memory that will store 100 readings that can be later downloaded to the PC. My guess is that the software will allow instantaneous downloading and (probably) PC control to take readings at fixed time intervals -- but you'd have to verify that with the manufacturer.

From what you've said, this device (or one of the many other ones on the market) will fill your needs. But if not, you could consider my other post, #3, below.

Dear all , pyrometers surely are a great idea , but you know what....i cant put a pyrometer anywhere in the cooling zone or move it with the beam as the heat is enormous inside . also the beams are hung from hangers vertically and they move a lot and sometimes also collide with the immediate beams ...so pyrometers cannot give the accurate readings . i hope you understand....the only possibility i see is with the use of some type of adhesive which could instantly bind the thermocouple wire to the forging , so that we may record temperatures....any clue on this ??

The other option would be to attach the thermocouple to a piece of ceramic with a very low thermal conductivity, like firebrick, and then attach it to a pole that would be held against the side of the hot forging. So the thermocouple is held against the hot metal and only reads the metal's temperature. Something like this:

Not all that sure why you want to read these in this manner. But, if this is what you need, any good refractory supply house will have access to thermocouple wells that work is this manner. Most of us have gone to non contact measurements.

You might consider a device (like a gun) that fires a projectile containing a thermocouple that penetrates and imbeds itself in your hot target, or welds itself to the surface of your target. We have percussive welding techniques that do such things. It would work like a specialized stun gun.

You might consider attaching the thermocouple leads by capacitance discharge welding (similar to spot welding) before heating the workpiece. I have done this quite often in the past. Recently I attached 12 thermocouples on various parts of a stainless steel forging to record the heating and cooling cycles (up to 1100 deg C). The welds are easily broken when the work is moved so attach extra ones in case some fail. For more information Google "capacitance discharge thermocouple welding"

hi , thank you all for the suggestions .....does this capacitive discharge welding equipment welds on 1200 C hot steel piece also ??....

Fire clay, blue ram or ganister with a thermocouple embedded in it should adhere to the work piece. Blue ram is the one I'd go for, I've used it at 1800C but for something totally different. It's like Plasticine until heated to above 1000C

hi , i tried to search for blue ram on internet , it shows a kind of fish ???......help me with the exact word. also , i will need to use it to a piece already at 1200 C ,k will it stick to it at this high temp also ????

If you can drill a hole in your forging about 10 thermocouple diameters deep, then you will be creating a thermowell. All you need to do is to insert the thermocouple into the hole until it bottoms. The radial fit is not important because the thermocouple is fully immersed in the high temperature environment. This is the lowest cost method and more accurate than sticking the thermocouple to the surface with cement.

hi , do you think the drill will stand such high temp of 1200 c ??

I was thinking you might drill the hole before you heat the forging. If you must drill the hole in the forging while it is hot, consider using a carbide drill, or a laser.