Surface finish help

Now I'll have to go out and check mine. I know they have a serial port on them to couple up to a computer to record readings.
But I'm willing to bet the batteries are dead in them right now....

 

If your wrong, you will have to dance in a G string with pasties on for Jason...

 

@ka_6772 Did you get a chance to pour yet Kevin?? Anxious to see how this one comes out.
Tried to order myself some fresh slurry yesterday so I can play, but they aren't shipping right now because its snowing....

 

Ever check the pH of your slurry??? Lol

 

Only clay graphite for me. How well does the sodium silicate stand up to metal contact?

Why use a hoist for such a small melt? - More of curiosity question here....whatever works.

Good buy. Wouldn't worry about crashing it. Takes a toll on the IFB over time but it's a long time and at $85....who cares?

Little too sporty for me when a push button makes possibility of shock go to zero......but we all decide what's safe enough.

I take it this is for measuring the melt temp. Seems fine to me. I use an 1/8" Inconel sheathed K-type inside a carbon gouging rod. It has an ceramic wool insulated stainless extension and I just stick it in through a hole in the lid so I lose no heat during measurement......I still shut off the power to the coils. The carbon sheath slows response time, but it's at 95% of reading within a minute. I get 100-200 dips per carbon sheath before they are consumed by O2. I've been using the same TC for years.

Best,
Kelly

 

Do you think that was because debris settled into those areas when washed or other reason? I cant tell from the pictures.

In a former life, I did a lot of work with gas separation processes including semi-permeable mebranes. There will be very modest benefit from the reduction of O2 but all semipermeable membranes are also very effective desiccators so removal of H20 is probably the biggest benefit by eliminating a source of H2 and reducing the H2 vapor pressure above the melt. This will bring more H2 out of solution in the melt. You might consider just using a crucible hat and only inert the area between the melt and the hat as opposed to the whole kiln. A small Inconel tube to introduce the Argon would be best but stainless or just carbon steel would due, though the latter would be consumed over time.

Crucible Hat and Degassing Lance Build

Bubbles can be aspirated air or H2 porosity, the latter being common. Aspiration are usually gross defects and H2 fine pocks on the upward facing surfaces. You might take a look at the lance in the above link. Earlier you had mentioned you degassed with Argon. If it is just a tube bubbling gas through the melt, you are probably doing more harm than good due to agitating the melt surface and resulting oxidation. My lance works well but it's a PITA to use. In addition to inerting the space above the melt while degassing, I built the crucible cap to prevent splashing or dripping aluminum on the heating elements which causes them to fail in short order. I was/am going to build a small rotary degassing lance like Palmer's.

It could be inserted and removed through a small hole much easier than my current lance. Mine would be much simpler and driven by a cordless drill with a rotary joint for the gas.

Rotary Degasser

Almost nothing is soluble in molten Aluminum except H2 and it's a bugger. I would pour cooler than you are. I pour at 1470F but I have to evaporate foam. I'd pour cooler than that in a sand casting and I would think you could pour even cooler in a heated shell mold. The amount of H2 soluble in Al is a strong function of temp and H2 partial pressure. I'd also tell you there is no benefit in melting rims into ingots before casting with them. Minimally heat the melt, flux if you must, degass, and pour. I've been using virgin A356 ingot without degassing and without issue. These are all finer points but matter depending on the quality of result you seek. I'd also tell you you are ahead of the game by using an electric furnace because you don't have to worry about introducing H2 through the tune of your burn, and more importantly, all of the water that comes along for the ride with combustion air.

-Keep up the good work.

Best,
Kelly

 

Are they just pressure swing adsorption molecular sieve systems?

No

Mercury Marine in Fon du lac, Wisconsin uses Vacuum/Pressure assisted lost foam casting where after pouring the flask under vacuum, they close a lid on the flask and pressurize to 150psi before solidification. They claim the post pressurization reduces/improves micro porosity 100-fold from 1% to .01% for low copper aluminum alloys (like 356)......so they also realized big improvements in elongation.

I think it would be relatively easy to make a pressurized flask for small castings. I've probably only had one part that it would have been worth it for the improved mechanical properties. I think you can probably get to where you want to be without it by being selective with casting stock and melt management.

Best,
Kelly

 

Sounds like garden variety PSA system to me. There are some zeolite molecular sieves that will do the job, but Carbon molecular sieves are much more energy efficient. Still likely to be a fraction of a percent of O2 depending on the draw being tapped from the column.

Best,
Kelly