Will an infrared thermometer work on molten lead?

[JimGnitecki]

I have a Lyman Mag 25 furnace with its own built-in temperature measuring and control system. But my s.s. alloying pot - a saucepan conscripted into this service - of course has no built-in thermometer. In my TIG welding, I use a digital infrared thermometer gun to check material temperature. It captures the temperature of an item by simply aiming at the item and pulling the trigger. So, I am wondering: if I aim the gun at a pot of molten Lead, will I get a usable reading? Or do I need to buy a "Lead casting thermometer"?

Jim G

 

[CoalCrackerAl]

A weld is much hotter than molten lead. I don't see why you cant use your thermometer for your pot.

 

[Atavar]

Do remember that surface reflectivity can throw an IR thermometer off. If possible do a sanity check with the Lyman furnace. You can also paint a patch of the outside of the pot below the normal level with flat high temp paint and use that for your target.

 

[theotherwaldo]

Mine can check the temperature of my lead pots - and my molds.

 

[JimGnitecki]

Mine can check the temperature of my lead pots - and my molds.

That's encouraging! Hopefully, mine will too!

Jim G

 

[BBarn]

It will likely show a temperature, but as mentioned it's accuracy depends on the material (emissivity). If you "calibrate" it with the Lyman furnace first, you can get a better idea of any readout "error" when measuring liquid lead. The temperature displayed will probably also vary with how reflective the surface is (shiny bright versus dull oxides on top). Probably more accurate with dull oxides top.

 

[JimGnitecki]

It will likely show a temperature, but as mentioned it's accuracy depends on tha material (emissivity). If you "calibrate" it with the Lyman furnace first, you can get a better idea of any readout "error" when measuring liquid lead. The temperature displayed will probably also vary with how reflective the surface is (shiny bright versus dull oxides on top). Probably more accurate with dull oxides top.

I suspect you are correct. I raed one of the Amazon reviews on a different brand but similar infrared gun. The buyer reported that it displayed only about half of the actual temperature of a hot metal he tried it on as a test.

I may have to buy the digital Lead temperature probe that Lyman sells as a standalone product for use with pots that don't have a built-in system. It's a bit costly here in Canada: about $70 CAN.

Jim G

 

[jmorris]

The one I got from granger a couple decades ago will not correctly measure the temperature of skimmed molten lead.

It doesn’t get much more shiny/metal, than molten lead. I use thermocouples myself.



If you hit your melt with it and it tells you it’s cool enough to touch, don’t believe it…

 

[mcb]

Get an infrared thermometer that allows for adjustment of the assumed emissivity of the target (varies between 0-1.0) and you can take accurate temperature measurements off shiny metals. I have one I use with my forge that allows the user to change this value. Most cheap infrared thermometers assume and emissivity of ~.95 but a shiny metal surface is much closer to 0.

 

[reddog81]

You don’t need a thermometer for casting. Paying attention to how quickly the sprue plate cools will give you better info than a thermometer. If you’re getting wrinkly bullets turn the temp up and/or cast faster.

 

[JimGnitecki]

You don’t need a thermometer for casting. Paying attention to how quickly the sprue plate cools will give you better info than a thermometer. If you’re getting wrinkly bullets turn the temp up and/or cast faster.

This is NOT for the casting process (I have a Lyman Mag 25 furnace with temperature control for that). This is for use with the s.s. pot that I will use to alloy Lead with differing Tin and Antimony content to make Lead alloy of appropriate Brinell hardness for different usages (My Pedersoli Sharps replica will need 500g bullets that are BHN = 12.5 or thereabouts for best accuracy with no leading. If I can't know and control the temperature in the pot, I can accidientally go too highwhich would (a) pull the Tin out of the Lead matrix and (b) create fumes that are toxic. I don't want to alloy without knowing the temperature at all times.

Jim G

 

[reddog81]

Raise the temp until it’s fluid and able to be stirred. Sometimes researching a topic too much makes it sound more difficult than it actually is.

 

[mcb]

If your experience it probably is pretty easy. You know what to looking for and can infer the correct temperatures from other factors but until you build up that experience a good temperature sensor can help a lot. Everyone told me I didn't need a temperature sensor to forge weld I could just tell it from a variety of other signs. I tried that many times and failed. I did not successfully forge weld until I had the sensor and new for sure I was at the right tempeture. Now that I have done it a few time with the aid of my infared temperature sensor I am becoming less and less reliant on that sensor and no doubt will be able to forge weld without it soon but I would have never gotten there without the sensor and/or a more experience blacksmith showing me direclty.

 

[jmorris]

I don't want to alloy without knowing the temperature at all times.

Then you need something in the pot at all times. If I didn’t trust a thermostat or needed one, these days, I’d just use a PID/thermocouple.

 

[JimGnitecki]

Then you need something in the pot at all times. If I didn’t trust a thermostat or needed one, these days, I’d just use a PID/thermocouple.

Are PID/Thermocouples available to buy or do you need to build one yourself? If available, where do you get them? Is that a better solution than the Lyman digital gauge with probe?

Jim G

 

[mcb]

Lots of digital readouts with enclosed thermocouples on amazon for a few dollars. Many of those would work for what your trying.

 

[jmorris]

Are PID/Thermocouples available to buy or do you need to build one yourself? If available, where do you get them? Is that a better solution than the Lyman digital gauge with probe?

Jim G

The SSR will switch he high current as thePID will tell it to.

 

[JimGnitecki]

The SSR will switch he high current as thePID will tell it to.

Hmm, at Amazon CANADA, that PID costs almost as much as the Lyman digital Lead thermometer, and one the reviewers tested the PID and said it overshoots a LOT. Looks like the Lyman solution might be the most practical solution, given it is designed for specifically this application and costs almost nothing more than the PID.

Jim G

 

[Blue68f100]

PID controllers can be tuned for the conditions. Most of the newer ones have a self tune feature. Which should get you close. I used PID controllers in my lab and tuned them all to have a max of 0.1F drift. Any more and it would show up on the pressure transducer. Doing R&D work requires a higher lever of controlling the environment.

 

[denton]

Controller On Ebay

This is close to what I use. You'll need one with a bit longer thermocouple. If you can't find the right kit, the stainless steel clad thermocouple should be under $5.

A Chinese PID should run less than $20. Mine came with a 40 amp solid state relay and a stainless steel jacketed thermocouple for under $20. I use it to control the temperature of an annealing liquid.

My pot only draws about 5-6 amps, so the solid state relay doesn't even need a heat sink.

 

[BushMaster-15]

One could verify an I F digital thermometer using a SS or other pot by swabbing Tempilaq on the outside of the pot . Seeing as You already own an I F thermometer : IF you didn't have an I F Thermometer ,then a PID/thermocouple would be the way to go .

Tempilaq Advanced is an accurate temperature indicating liquid that verifies the achievement of a specific temperature. It leaves a visible mark that dries fast prior to heating then liquefies at the stated temperature.

 

[hso]

will I get a usable readin

Gotta ask, why do you need to know take temp if the metal has melted? Melting points exist for pure lead (327.5 C), pure antimony (630.7 C), or the eutectic alloy (251.2 C). Other Pb-Sb alloys form a slush-like mixture of one solid metal within a liquid of the other metal. A eutectic alloy goes from a solid to a liquid (or vice-versa) at the eutectic alloy's melting temp without going through a slushy phase. So why take the temp?

 

[JimGnitecki]

Gotta ask, why do you need to know take temp if the metal has melted? Melting points exist for pure lead (327.5 C), pure antimony (630.7 C), or the eutectic alloy (251.2 C). Other Pb-Sb alloys form a slush-like mixture of one solid metal within a liquid of the other metal. A eutectic alloy goes from a solid to a liquid (or vice-versa) at the eutectic alloy's melting temp without going through a slushy phase. So why take the temp?

All the instructions I will try to follow give specific temperatures for different processes: alloying, fluxing, casting. Since I am not a chemist or metallurgist, I will follow the instructions without fully understanding the reasons for specific temperatures. One thing though that I want to do is minimize the temperatures used within reason, so as not to cause harm: e.g. letting the temperatures get high enough drive out the Tin, or to create unnecessary hazardous fumes. Basically, I want to be able to follow temperature instructions reasonably closely.

Jim G

 

[reddog81]

What temps drive out the tin and create harmful fumes?

 

[JimGnitecki]

What temps drive out the tin and create harmful fumes?

I cannot remember the temperatures at which the problems apparently begin, but if I follow the temperature instructions I was given for the various different processes and steps, I won't create temperatures high enough to create those problems. The idea is to raise the temperatures only enough to do what is needed, and not go past that.

Like I said, I am not a chemist or metallurgist, but I can follow specific instructions in a "recipe". I view this the way a person following a recipe does: I may not understand the chemical processes going on when baking or cooking food, but I know that if I get the temperatures too high bad things will happen!

Jim G