Do you measure metal temperature and how ?

Discussion in 'Foundry tools and flasks' started by metallab, Oct 31, 2020.

  1. 0maha

    0maha Copper

    I guess I should have been more clear. I'm planning on getting a piece of conduit just like you're using and more or less doing the same construction.

    I'm going to see if I can connect the wires from the thermocouple directly to the plug I got from Clay-King. Assuming I can get that sorted, I plan on working out some way of attaching the pyrometer unit to the end of the conduit.
     
  2. rocco

    rocco Silver

    BTW, thermocouple wires are always colour coded, on K-type thermocouples, the wires are red and yellow, it's a little counter-intuitive but the red wire is negative and the yellow wire is positive
     
  3. Petee716

    Petee716 Gold Banner Member

    If none of your kit instructions says which wire goes to which spade on the connector, just google k-type pyrometer and you'll easily find the info. I already had an attachment provision setup on my conduit as described previously, but HT1's method of just slitting the end of the conduit and hose-clamping it will work fine.
    I bought the $20 multimeter from harbor freight that has the k-type setting and outlet on it. It came with a little probe and connector so I just used that connector with a little of the provided wire and attached to the new probe leads.
    My old setup usually showed about 35C ambient so I know it was off. My new probe shows around 25 so. I'm in Buffalo, not Tucson.
    I try to creep up on my temp. Shooting for around 710C in aluminum, I preheat the tip till it shows around 550 and climbing. Then I shut off the furnace and dip the pyrometer. I try to get a feel for the rate of climb as the reading increases. I wait until the reading stops increasing and then bounces back a degree or two. If I've stopped at 690, I'll turn the furnace back on for 2 or 3 minutes and then pour. If it has gone over 700 and rising, I know I'm too hot and I'll remove the crucible and wait for it to cool down. It's easy to get fooled and overheat the metal. It takes awhile to finally get all melted, but once it does the temp shoots up fast.

    Pete
     
  4. HT1

    HT1 Silver Banner Member

    slit the end of the conduit with a hacksaw, and use a small hose clamp to hold the thermocouple into the conduit. QED

    V/r HT1
     
  5. 0maha

    0maha Copper

    I don't know if anyone is interested in this, and haven't even gotten everything together yet, so I don't know if I like this idea...but I put together a mounting bracket for the UT302A thermometer unit.

    The idea is to clamp it onto the end of the conduit, so the whole thing becomes a single assembly.

    I put this together in Fusion 360. The model is here: https://a360.co/3CQUve1

    It's not perfect, but it's close enough for now.

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  6. 0maha

    0maha Copper

    Got it put together. Much appreciation for the information I got here. This forum really is fantastic!

     
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  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Nice job on the build. After water immersion I’d recommend bringing that tc to temp in the furnace vent before sticking it into molten metal.

    Best,
    Kelly
     
    0maha likes this.
  8. Melterskelter

    Melterskelter Gold Banner Member

    Nice build and video. At 1000 feet elevation in Omaha water should boil at 211. A precision deviation of .5% for a TC is not bad at all. Given the TC read you ambient temp prior to immersion at 82, I assume it does compensate for cold junction temp.

    You may have folks lining up to buy the printed bracket!:)

    Denis
     
    0maha likes this.
  9. 0maha

    0maha Copper

    LOL! :):):)

    I'm not going into the bracket business! Hopefully others find the 3D model useful.

    FWIW, I didn't put much effort into refining it. The print I ended up using was just the second run from that file. Initially, I had some of the parameters a little large, and the thermometer had a loose fit. With the second one, I reduced those parameters and it's a tight fit.

    I should also mention that the nuts and bolts I used are 1/4"-20.
     
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  10. 0maha

    0maha Copper

    Just finished my first pour (Everdur) using the new pyrometer.

    Everything went as expected. With the foundry running, I hung the probe over the exhaust vent (the hose clamp proved handy...just hang it on the edge of the hole) until it got up to 2kF or so, then dunk it in. Plenty of reach with this design to get into the metal with the foundry running.

    The immediate lesson learned here is that I've been pouring at way too low of temperatures. I waited to test the temperature until I figured I was probably a little high. Then I'd let it cool down to casting temp.

    (I was targeting 2150F for this).

    Turns out not. My first measurement was barely 2kF.

    Took a while, but eventually got it up to the 2150 I wanted.

    I'm letting the flask cool right now. Really interested to see how this one comes out.

    Thanks again to everyone here with the ideas/design/etc on that. I think this is going to be a very useful tool!
     
  11. Zapins

    Zapins Gold Banner Member

    Great! Thats how I do it too. Overshoot then turn off flame and let it cool to 2,150 and pour. Works well. Post updates on casting quality!
     
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