Cast Aluminum

[Rusty55125]

I have a cast part with some machined surfaces. Is the act of machining the part, other than the obvious removal of material, weakening this area. Is there some kind of surface hardening that has taken place during the simple pour operation? I know there isn't much information but I am just looking for some opinions. Would I be better served by trying to make the part with no secondary machining operation?

Scott

 

[dwightdixon]

Simple casting does not impart special properties to the surface. Diecasting does give you a denser surface and more porus interior with poorer properties. Forged aluminum parts have the best properties.

 

[arunmrao]

Are your parts sand cast/die cast or investment cast? if they are sand cast and you have removed some material by machining you have infact improved the quality of your castings. as most of the suface defects have been removed by machining.

Machining does not make the casting inferior. How did you get such an idea? Die cast parts are inherently denser than sand cast. If you still desire to improve your product try hipping.

 

[Rusty55125]

I didn't think that this would be the case but just needed another opinion. Here is my reasoning. When the molten material makes contact with the colder mold surface, it may cause the material in direct contact to solidify faster than the core or center of the now new part. Is this enough of a different in cooling rates to cause a difference in mechanical properties in the metal from the surface to the core? Now by removing the harder surface material, am I decreasing the mechanical properties in a measurable way?
Anyway, that was my thought process
Scott

 

[swall]

Only true with aluminum die castings.