determining temperature with scale buildup on billet
determining temperature with scale buildup on billet
(OP)
We are using IR thermometers rated to 1650°C(3002°F) to measure billet temperature leaving a furnace to a forging press. The issue I am having is getting an accurate reading on materials that develop scale quickly upon leaving the furnace, mostly grades of steel(4340, 52100, M50..etc), other materials don't really have this issue ie your Inconels, Ti alloys, and stainless. Is there some way to account for the emmisivity drop between basemetal and the scale buildup. (note: I do not trust the emissivity settings on the IR thermometer)
JC
JC





RE: determining temperature with scale buildup on billet
I suspect your problem is more that the surface of the scale is actually cooler than the underlying steel and that is what is creating the problems. That you will not fix by the e-value, only by getting a clean surface to check or just accepting that your reading will be slightly lower than the actual value.
rp
RE: determining temperature with scale buildup on billet
the scale is coming out about 200°F lower than the furnace temperature, (2000°F-->1800°F) I'll have to do some trials but some grades seem to give larger scale "pieces" which throws the thermometer off more.
Thanks again,
JC
RE: determining temperature with scale buildup on billet
Maui
www.EngineeringMetallurgy.com
RE: determining temperature with scale buildup on billet
the tricky part is that the distance between the furnace and the press is about 0.5-2.0 seconds maybe a day when production is slowed this would be an option. do you have any additional information on these temple sticks?
JC
RE: determining temperature with scale buildup on billet
Would it be possible to have a small pocket (hohlraum) milled/machined/cast/whatever into a viewable end of the billet? The emissivity of a cavity approaches 1.0 (regardless of surface emissivity) for fairly reasonable depth-to-diameter ratios.
Past that, my only other suggestion would be to kiss the surface of the billet with an abrasive wheel (or sandblast jet) just before measuring.
RE: determining temperature with scale buildup on billet
RE: determining temperature with scale buildup on billet
I know they work pretty well at 1650, as we use one here in our shop for case hardening steel (via flame). The "temperature crayons" listed in McMaster are offered up to 2000 F.
RE: determining temperature with scale buildup on billet
rp
RE: determining temperature with scale buildup on billet
I think the tempilstiks are gonna be the way to go. thanks all.