NEED HELP Aluminum Extrusion Failure

[Hill05]

Hello,
We had a part fail in an odd way. The part is 6061 aluminum. The same company cast, Hot extrudes and machines. During our process a center core plug of the aluminum popped out. Being this was extruded from a billet, this is not supposed to happen. The company that makes the part has run a ground so to say, and does not understand how this happend.

Anyone have any expierene to this type of aluminum failure that can help?

 

[cngbrick]

A picture would help.

RT

 

[boslab]

Impossible to say without a photo, could be back end defect or a stop mark, was there black gunk in the fault ( aquadag) or white oxide ( inclusion) void in the billet filled with a clump of oxide, turns into a linear lamination
Mark

 

[john.k]

There are plenty of pics of extrusion defects in textbooks.

 

[Hill05]

The first image is what is is supposed to be. The second image is with the plug out. This is supposed to be one sold piece of cast billet then extruded . The 3rd pic is of the plug its self. The plug can be pushed out with some force by hand. The Flow Chart of companies Extruder=> Machine shop=> Molding.

 

[boslab]

Imho it’s back end defect, the ass end of the billot ( correctly used !) gets shoved through the die in a coaxial discontinuity, the black is dag or graphite grease
It looks that it was pushed through a port hole die, you can see some of the support web lines in there.
Send the bar back for replacement if I was you.
Mark

 

[Hill05]

Reading more into this, it look like it could be a transverse weld defect that didn't get removed.

 

[boslab]

That defect ( note that stop marks usually get cut out) can be even worse when the same die is running 2 chemistry’s, there should be a good length cut out and scrapped, it’s mixed chemistry to make it worse, some plants cheap out and run different alloy on one press run, not a good idea!
Mark

 

[surplusjohn]

I have seen in house billet casting for extrusion. Looked like a pile of random scrap poured through a filter that captures the pebbles and bottle caps.

 

[boslab]

Normally the Lauder filters are silica, after casting the log goes into the oven for homogenisation , then the log saw to make billot stock that fits the canister of the extrusion press, the stuff for aerospace sometimes gets stripped, a scarfing process the scrapes the billot through a hard stripper plate to get some surface crud off ( lots of extruders dont but the press is supposed to shear the back off before the next billot goes in, they often push the billot too far for throughput)
Mark