Do you measure metal temperature and how ?

I had a conversation a few months ago with the guy who owns the company that makes the probes MIFCO sells. Good guy. Very helpful.

He painted a picture that there are three things that impact the life of the probe in applications like ours:

- The number of dips
- The amount of time in the metal for a given dip
- Whether or not you pre-heat the probe before dipping

He's got a customer who uses the same probes we do in a continuous, brass casting environment. That guy replaces his probes every other day. That's pretty hard core.

My specific question for him was this: Suppose I'm targeting 2200F, and I dip the probe and see 2160F. The furnace is still on, and the temp is still climbing. Am I better off just leaving it in the melt for the five or ten minutes (or whatever) as it gets up to temperature, or should I pull it and remeasure from scratch after a few minutes.

His advice was to pull and remeasure.

He was also very emphatic that pre-warming the probe in the furnace exhaust was essential to the long life of the probe. According to him, the thermal shock from dipping an ambient temperature probe into a 2000F melt is super hard on it.

Thought I'd pass that along...

 

How long did he say to leave it in the exhaust?

 

He didn't say exactly in terms of clock time. I told him my practice was to hang it over the edge and wait for it to read 2000F before plunging, and he approved.

 

Yup thats what I've always done too.

 

Besides preheat and non-continuous use, are there any other care and feeding tips for the Mifco thermocouples? Anything special about gas furnaces and melting aluminum?

 

guys this is great advice, the explanation is really simple , the temp is "taken" at the little "tit" at the very end of the probe, , that is the ONLY part you want to get exposed to heat, which is pretty much impossible in our application(Fuel fired crucible furnaces), the rest of the probe is pretty well protected, but not perfectly, the wires in the ceramic "insulators/protectors" are not well protected at all, and thus a weak point, that is why the longer 12 inch probes for $10 extra dollars are really a GREAT bargain. and why your entire Pyrometer needs to be handled quite gently , those wires get hot and jostled, they may break

V/r HT1

 

Not that I know of.

I think the bottom line for applications like what I think most of us are using is that if you follow those three guidelines, the probe should last a good long time. But it is still a consumable part that will not last forever. Depending on the particulars of your situation, having a spare on hand isn't a bad idea.

 

Expecting the mini-K ends for the Mifco and some graphite rods to protect my little stainless Amazon probe to come in today.

Is there a good way to remove dross from a stainless probe that was dipped in aluminum without a sheath?

 

AND...right on schedule I aborted a melt this morning because my thermocouple died.

 

Bummer. If you weren't a state and a half away I'd loan you mine...

The new mini-K's from Amazon are working. Hooked to a 12$ 4-inch SS probe the HF meter clocked an ice cube at -4 C.
I have yet to try the MIFCO.
When I am back at work next week I will make an adapter to assemble one of the graphite's over that 4" probe.

 

That's nice of you to say.

The good news is I checked the function of the lance before the melt had really started. Was just pre-warming on propane at that point. Able to abort things before I had any actual melt in the crucible.

And it gives me an opportunity to tighten up a few things in my process and equipment that I've been putting off.

 

Got my 'burger flippah' put together...most of the metal came off the probe with gas stove heat and a Stanley knife. The rest filed off pretty easily, enough to slide into the graphite sleeves and coupler they machined for me at work. Paddle end is about 4 inches in diameter plus a small laser-burned chart on the handle since I do not know any of these temps by heart yet.

 

pointing out the obvious
those are melting temperatures not pouring temperatures


V/r HT1

 

Thanks, true, it's worth mentioning for sure. I should find a different table and redo it.

"Proper pouring temperatures for a given metal vary with the casting size, design, and desired rate of pouring. For this reason, the pouring ranges given below should be taken as a general guide only:
Pouring-Temperature Range

In general, thin-walled castings are poured on the high side of the range and thick-walled castings on the low side."
Source: USN Foundry Manual 1958, page 142, with added Celsius conversions

 

I worked on my Mifco thermocouple today. The lead machinist at work made made me a .500" bore x 2" long x 1 end @ .700" or so OD coupler to clamp into a piece of old 1/2" EMT with a 'free' bend. There is a 10-24 set screw in the coupler to catch the probe. I am trying to decide to keep using the HF meter or get something just for the foundry. If I picked up a 2 channel one I could test them both (this one and the one make previously) at the same time.

 

to Jason
I use those, they are good tips, but not good for constant emersion.
I am currently using a Rex C100 process controller set to type K with a 10 foot shielded lead with an emersion tip. I melt aluminum and I like to get my temp from the center of the bath.
I am accurate plus or minus 1 degree at 1500F.