Author Topic: Cast Master  (Read 480 times)

savarin

Re: Cast Master
« Reply #15 on: July 31, 2020, 07:23:53 PM »
I have found a tin can works for one only melt of aluminium and dont hold it in there once melted but dont use stainless containers, they dissolve.I use a simple sheet steel flare on the end to help with holding the flame that I replace as needed (when its burnt through) but once the kiln is hot (red) the flare isnt required.The burner is also placed in at an angle to swirl around the inside and I have a steel baffle to prevent the flame from impinging directly on the crucible.The clay graphite crucibles are very good albeit a tad expensive but in the long run well worth it.I think I need a couple of full days casting to convert all my ally and brass scrap into ingots to move to my new shed.

woodchucker

Re: Cast Master
« Reply #16 on: July 31, 2020, 08:13:17 PM »
they disolve?  I always used SS because I thought it was capable of higher temps... When I built waste oil heaters for friends I used Stainless because it lasted. I used regular oil burner, fire bricks, and SS in the burn area.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

savarin

Re: Cast Master
« Reply #17 on: July 31, 2020, 08:20:16 PM »
I tried to melt some ally in a stainless bowel, it dissolved a heap of holes right through.
The only saving grace was I turned off the gas and it solidified quick enough that I only lost about a cup.
Also it wasnt quite hot enough to totally liquify the complete mass and the resulting lump was virtually porosity free.
This led to experimenting with casting the ingots then re melting them just barely hot enough to pour which to date has produced very good solid casts with no pinholes or porisity.
I'm wondering if we all have different results due to the variety of burners and gas pressures.
« Last Edit: July 31, 2020, 08:21:50 PM by savarin »

PJB

Re: Cast Master
« Reply #18 on: July 31, 2020, 09:33:57 PM »
Ya  molten aluminum will dissolve bare steel/stainless steel rapidly.   You can do it but need to spray with a clay or talc mold wash as a barrier.
I make disposable furnace rakes for the guys in the foundry to skim slag and they last maybe a week.   
1991 Bridgeport Series I 2J-VS  9"x48"
1979 Clausing Colchester Bantam Mk2 11"x30"
1972 Harig Super 612
2015 Tormach PCNC-1100 Mill

"I wants what you gots!"

woodchucker

Re: Cast Master
« Reply #19 on: August 01, 2020, 11:05:10 AM »
Ya  molten aluminum will dissolve bare steel/stainless steel rapidly.   You can do it but need to spray with a clay or talc mold wash as a barrier.
I make disposable furnace rakes for the guys in the foundry to skim slag and they last maybe a week.


it's not just a thermal reaction then, since aluminum melts at a much lower temp than SS. There must be a chemical component in the reaction.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

PJB

Re: Cast Master
« Reply #20 on: August 02, 2020, 10:46:28 AM »
I remeber years ago when I naively used 304 SS tube for a stalk tube on an experimental miniature low pressure casting furnace I built.  That wasnt the only blunder either but it was pretty funny after one shot of blowing air we pulled the stalk out from the crucible and it was literally almost gone.   
ZYP makes a boron nitride refractory coating you can get in rattle cans but not sure how long it would work in a crucible application.   We use it more as a release/topcoating on permanent molds.   
1991 Bridgeport Series I 2J-VS  9"x48"
1979 Clausing Colchester Bantam Mk2 11"x30"
1972 Harig Super 612
2015 Tormach PCNC-1100 Mill

"I wants what you gots!"

savarin

Re: Cast Master
« Reply #21 on: August 02, 2020, 07:40:35 PM »
I've read about boron nitride as a release agent and protecting layer but didnt know it was available in rattle cans.
I must search for some.

woodchucker

Re: Cast Master
« Reply #22 on: August 02, 2020, 09:21:22 PM »
check welding stores for the boron nitride. it's used in welding too.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

PJB

Re: Cast Master
« Reply #23 on: August 03, 2020, 01:36:06 PM »
We resell it as an accessory item to our products.   $45 US a can.   
Not exactly inexpensive stuff.   Im sure its available cheaper we obviously mark it up.
Other thing to note is its more of a release coat than a base refractory material.   Aside from using a proper clay graphite or silicon carbide crucible, to coat a steel vessel I would look into more of a clay vermiculite material that provides a heavier/ insulating barrier.
Foseco and Pyrotech are a few mfgs
To get good adhesion the vessel needs to be sandblasted, roughened surface, preheated to 650-700ish F then sprayed.   
1991 Bridgeport Series I 2J-VS  9"x48"
1979 Clausing Colchester Bantam Mk2 11"x30"
1972 Harig Super 612
2015 Tormach PCNC-1100 Mill

"I wants what you gots!"

jpigg55

Re: Cast Master
« Reply #24 on: August 03, 2020, 01:43:28 PM »
We resell it as an accessory item to our products.   $45 US a can.   
Not exactly inexpensive stuff.   Im sure its available cheaper we obviously mark it up.

You weren't kidding. Just took a look on Amazon: https://www.amazon.com/Aerosol-Lubricoat-can-oz-High-Temperature/dp/B013X7D25G/ref=sr_1_2?crid=3P9IGS4BXBLW9&dchild=1&keywords=boron+nitride+mold+release+spray&qid=1596479957&sprefix=boron+nitride+m%2Caps%2C195&sr=8-2

There were cheaper options, but had less than stellar reviews.
SB 9A, Clausing 8520, Sanford MG 612

woodchucker

Re: Cast Master
« Reply #25 on: August 03, 2020, 05:28:16 PM »
I think mcmaster and grainger have boron nitride for less.

Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts