Author Topic: bad crucible  (Read 194 times)

savarin

bad crucible
« on: December 27, 2018, 11:28:53 PM »
A couple of years ago when I first started casting aluminium I used a stainless steel bowl for a crucible and filled it with a mix of unknownium.
This was a bad idea as it developed pin holes and the liquid aluminium started leaking out.
I let it solidify and threw it to the back of the shed.
Yesterday I decided to cut it in half so it would fit in a graphite crucible for re melting and was astounded to see the inside, totally homogeneous and solid, no impurities visible by eye.
Maybe I should have turned it into a usable piece.

kvt85

Re: bad crucible
« Reply #1 on: December 28, 2018, 07:43:15 AM »
now you can make two parts,   Just a bit smaller.   
Ken in SA TX

Jet 10x24 and Taiwan 10x24
Enco 30 mill
Sherline Lath and mill

Jake Parker

Re: bad crucible
« Reply #2 on: December 28, 2018, 01:08:29 PM »
I have that problem, no matter how many times I cut it, its STILL too small!

savarin

Re: bad crucible
« Reply #3 on: December 28, 2018, 11:00:49 PM »
Thinking back I think I may have learnt a valuable lesson here.
Most of my castings have tiny black porosity inclusions but this one didnt.
It was cooled as soon as it was all melted, in other words it didnt stay in the furnace until I was sure every bit was molten.
I will experiment with my next cast and pour as soon as possible and see what happens.

kvt85

Re: bad crucible
« Reply #4 on: December 29, 2018, 10:42:01 AM »
Keep us informed,  anything to improve my pours will be welcome.   

Ken in SA TX

Jet 10x24 and Taiwan 10x24
Enco 30 mill
Sherline Lath and mill

Uglydog

Re: bad crucible
« Reply #5 on: January 02, 2019, 05:28:11 PM »
... It was cooled as soon as it was all melted, in other words it didnt stay in the furnace until I was sure every bit was molten.
I will experiment with my next cast and pour as soon as possible and see what happens.

I'm curious as to how you and others know when your aluminum is hot enough.
I was fortunate to have been gifted a thermometer appropriate to the task.
However, this is an interesting question!
I wonder if the HF and other inexpensive infrared thermometers would work.
We used one on the fire truck before we could actually afford a fire rated thermometer with all the necessary certs.
Worked just as well as the expensive one we now have...
Yes.... the new one also has additional bells & whistles but the temp part works just as well.

Daryl
MN

chips and more

Re: bad crucible
« Reply #6 on: January 02, 2019, 07:49:10 PM »
Sorry, I do not think the common non-contact IR temp guns will read that high a temp? And then there is the emissivity factor? Those temp guns are really good for comparing like for like surface temps. But not so much on a single surface with an unknown emissivity. Knowing that, they are still a great toy for the shop!

Edit: and I should have also mentioned that the field of view of the instrument should be filled when under test for a meaningful measurement.
« Last Edit: January 03, 2019, 01:36:48 PM by chips and more »

Terrywerm

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Re: bad crucible
« Reply #7 on: January 04, 2019, 09:19:39 AM »
I wonder if the HF and other inexpensive infrared thermometers would work.
We used one on the fire truck before we could actually afford a fire rated thermometer with all the necessary certs.
Worked just as well as the expensive one we now have...
Yes.... the new one also has additional bells & whistles but the temp part works just as well.

Daryl
MN

I just looked up the details on HF's website. The least expensive units only go up to 230 and 500 F, while their best unit only goes up to a few degrees past 1000 F. You might be able to find a unit somewhere that will work, but I have no idea on the cost.

A person might be able to make do with a pyrometer for a diesel engine. They typically measure up to 1600 F, more than enough to measure the temperature of the aluminum in your crucible. All you need is $200 and a 12VDC power supply. Mount the probe on a long handle so you can dip it in the melt. It wouldn't go high enough for brass, bronze, gold or silver,  and it would not give you a real accurate reading within a couple of degrees either, but it would give a good idea of where you are.
Terry

Making chips with old machines!

4GSR

Re: bad crucible
« Reply #8 on: January 04, 2019, 09:58:11 AM »
Go look up Omega.com.  they have pryometers and theromocouples long enough to submerge into your molten metal to tell you if it is at the right temperature.  Just be sure to get the correct one's, J or K I believe it is.  Been many years since I've worked with this stuff.

Ken
Ken

Jake Parker

Re: bad crucible
« Reply #9 on: January 04, 2019, 01:49:43 PM »
Myford boy on youtube built a pyrometer.
Check it out.
« Last Edit: January 05, 2019, 04:00:08 PM by Jake Parker »

chips and more

Re: bad crucible
« Reply #10 on: January 05, 2019, 01:32:31 PM »
Maybe you now have an excuse to buy a new toy for the shop? Like a thermal imager.