Recycling 6061 - Thought chain

Ok.. I've studied on this for a while.
Everybody says (exaggeration) you can't cast 6061 it has to be wrought. If you try to cast it you get large crystals and poorly structured metal. One
article I read about casting 6061 seemed to indicate that rapid cooling of sand type castings by blasting away the sand with water jets retarded crystal growth. As near as I can tell wrought means formed by working or under higher pressure. I'm sure somebody can provide a better definition in context. I think forming under pressure might also retard crystal growth.
Now one of the pretty well known enemies of aluminum casting is the formation of aluminum oxides during the melting process, and of course oxides that have already formed. Rapid melting with a forced air foundry as opposed to a naturally aspirated foundry seems to reduce this dramatically. Surface area of the starting stock is also a factor so even with a forced air furnace machined chips might not be a good candidate.
So why not use a steel die (permanent mold) with a cylinder shaped casting sprue, and then when full place it on a press with a piston to apply pressure. Then liquid cool it while still under pressure. If the process proves possible its all achievable in the conditions of a home shop. Well a home shop capable of making steel dies anyway. I would think pressure would have to be regulated so that cooling contraction does not destroy the part. The simplest shop press might not be upto the job as somebody would have to stand there surround by steam pumping the jack. LOL.
The biggest issue I see is figuring out how to cap the vents when the die is full so that you don't spray molten metal around the shop when you apply pressure.
I don't even know if I should post this... Ah what the heck.
Flame on. (pun intended)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

https://www.kineticdiecasting.com/what-is-die-casting.html
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Uh, actually, I've posted the information here several times over the years that you can cast 6061. It's not great, but it's good.

I've never heard that, but that's essentially what you're doing with high-pressure die casting. The high pressure is to get better filling of a mold, and to reduce pinholes and porosity.
But die casting usually involves rapid cooling, as well -- the fastest you can achieve -- simply to improve production rates. Well-made die casting do have pretty good grain structure but, even if you use alloys made for diecasting, they're not exactly malleable.

You've just described cold-chamber die casting. d8-)

A common issue with conventional die casting. They use chill vents, sometimes made of beryllium copper, but more often machined right into the steel die itself.

No flames. It''s an interesting thought. You should look into die casting processes -- low pressure (BOP V8 of the early '60s, for example); high pressure (most die casting) cold chamber (used more often with magnesium, but also with aluminum in small-scale operations); and hot-chamber (most aluminum die casting).
There are a number of issues to consider, not the least of which is flash formation. With high pressure, it can be a big problem.
BTW, the thought of doing this at home gives me the chills. One of my old co-workers at _American Machinist_ described his first visit to a die-casting shop. "Now I know what it's like in hell," he said. d8-)
--
Ed Huntress

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 25/03/2019 16:45, Bob La Londe wrote:








Maybe do some research into the use of chills in sand casting. IIRC the old British Gardner Diesel engine had a sand cast aluminium crankcase and used numerous chills in critical places to unsure rapid cooling of critical areas for optimum strength. A mate works in engine design and he has mentioned that aluminium cylinder heads are often done by specialist casters as they have the knowledge to control the dendrite formation in the castings especially for critical parts of the cylinder head such as the head gasket face to get the maximum strength.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.