Author Topic: Effects of casting on metal  (Read 184 times)

jpigg55

Effects of casting on metal
« on: February 17, 2020, 08:09:59 AM »
Does home casting change the properties of a metal ?
Specifically, I'm considering casting a piece out of 6061 aluminum. Buying stock in the required size is cost prohibitive along with the need to machine away a good portion of it.
I began to wonder if casting the piece and then machine it to dimension would be a more cost effective and easier way to go, but began to wonder if doing this would impact the strength of the aluminum way below the specifications of stock material.
SB 9A, Clausing 8520, Sanford MG 612

woodchucker

Re: Effects of casting on metal
« Reply #1 on: February 17, 2020, 08:58:54 AM »
From what I know 6061 does not cast well.
Watch videos online,  the best have been my ford boy, inmho.


He uses aluminum wheels he gets from the junk yard
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: Effects of casting on metal
« Reply #2 on: February 17, 2020, 05:11:55 PM »
Melting and casting will definitely lower the strength and hardness vs the wrought 6061 material.   More than likely you’ll end up with soft, gooey porous cheese.
I would try to find scrap cast AL parts to melt down. 
319 or 356  are what you want.

"I wants what you gots!"

savarin

Re: Effects of casting on metal
« Reply #3 on: February 17, 2020, 08:45:35 PM »
I use any ally I can find but love pistons and ally wheels.I have found that melting a load into ingots any old how to work well then use the ingots in a controlled melt, ie not too hot then pour when just liquid enough to give me a solid casting with no porosity.Depending upon how thick the part is will depend upon how large to make the sprue,  castings freeze from the outside in so a hard shell with possible shrink voids in the middle will happen unless you have a large feeder.
I have cast 3-4 inch dia bars in tin cans knowing this but as I had to  bore out the middle the voids  weren't a problem.
The casting will be way softer than the original material.
Check this post
https://www.machinistgazette.com/index.php?topic=197.0
« Last Edit: February 17, 2020, 08:50:19 PM by savarin »

jpigg55

Re: Effects of casting on metal
« Reply #4 on: February 18, 2020, 12:12:48 PM »
Thanks for the feedback.
Based on this, I did a little Googling and it seems the best sources for cast-able aluminum is from car parts like intake manifolds and pistons.
According to a YouTube video I watched, mixing pistons (A413 aluminum) with 6061 can work. Not sure of the mixture ratio though.

Any other recommendations of scrap sources of aluminum for casting ?
SB 9A, Clausing 8520, Sanford MG 612

PJB

Re: Effects of casting on metal
« Reply #5 on: February 18, 2020, 01:39:58 PM »
Alloy wheels.    They are usually low pressure cast and should be god for recasting. Maybe go to a boneyard and see if they negotiate a good price on a scrapped one with cosmetic damage.   Lot of weight for hopefully low$
"I wants what you gots!"

savarin

Re: Effects of casting on metal
« Reply #6 on: February 18, 2020, 06:04:13 PM »
The main problem with ally wheels is cutting them small enough to get in the crucible.
If you have room sling them on a fire to get hot enough to crumble but not melt.
I think thats called hot shortness but am not sure

PJB

Re: Effects of casting on metal
« Reply #7 on: February 18, 2020, 07:51:35 PM »
Agreed.  I was going to mention the issue of getting them cut up small enough.   Sawzall??   Sledgehammer
"I wants what you gots!"

woodchucker

Re: Effects of casting on metal
« Reply #8 on: February 18, 2020, 09:36:40 PM »
Agreed.  I was going to mention the issue of getting them cut up small enough.   Sawzall??   Sledgehammer


sawzall or watch this:
https://www.youtube.com/watch?v=QOkbl61Hsiw
was impressed.
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

Terrywerm

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Re: Effects of casting on metal
« Reply #9 on: February 22, 2020, 03:07:25 PM »

When I was in high school (a very long time ago) I derived great enjoyment and success casting aluminum. As mentioned, pistons, wheels, cast intake manifolds, and other aluminum castings were the scrap of choice, but aluminum extrusions from screen doors and the like worked very well also. We would mix the extrusions with the castings, using a ratio of about 75% cast to 25% extruded. We would usually pour into rammed up molds and pour the excess into ingot molds made from angle iron. If we were melting our own ingots for casting, we did not add any scrap to the melt, but if we came up short we would only add cast aluminum.


For breaking wheels we just cut them on the large bandsaw that we had in the shop. Never realized just how fortunate we were to have a nice saw like that!
Terry

Making chips with old machines!