Aluminium grain?

[firebird]

Hi

At a recent steam fair I bought a block of aluminium, its bout 4 x 4 x 3. No particular reason for buying it but it was cheap so I had it. I noticed today that it has some markings on one face. Any body know what they mean??



Cheers

Rich

 

[substandard]

My mostly uneducated guess is that the aluminum was extruded. The markings show the direction the metal was extruded.

 

[raym 11]

my mostly uneducated question , does the direction of extrusion create a grain direction? If so does it affect machinability in any way?

Ray M

 

[substandard]

my mostly uneducated question , does the direction of extrusion create a grain direction? If so does it affect machinability in any way?

Ray M

I wish I could tell you the answer, but my knowledge of extruding metal is very limited. Hopefuly someone with more smarts will chime in, like Bogstandard.

 

[doc1955]

Yes grain direction does make a difference in strength and in amount of warping you will get.

 

[Noitoen]

I once saw a program where they were going to machine one of those metal swim suits and, after they poured a big cubic chunk of aluminium, they put it in a hydraulic press and "squeezed" it in the 3 axis, before they mounted on the CNC to machine. My thought was to eliminate any risk of porosity.

 

[doubletop]

Stew

So when are you starting your V8, machined from solid?

Pete

 

[Paul_C]

Can only imagine extruded aluminum swim trunks would be pretty uncomfortable. Here's a video of extruded scuba tanks.
XXhttp://www.liveleak.com/view?i=e04_1274556654

EDIT. Can't seem to post or link url to Liveleak on this board. So remove the XX from the link.

 

[Kermit]

As best I remember it. Cracks will grow fastest along the L axis. The one marked as the grain direction. Any stress, or load should be in line with the axis that is indicated with an arrow so all cracks will be along and have to propagate through the two shorter grain directions, giving a stronger part overall.

If you cut two long strips; one long in the grain direction and one long perpendicular to it. The one cut 'across' the grain would seperate along a grain line with much less force than one running with the grain.

This is in aluminum metal that has been rolled and reduced and has elongated mostly in one direction during the process.

That's all I've got. Some one will be along shortly to correct me.
Kermit

 

[firebird]

Hi

Thanks for the replies. I'm guessing that the grain will make little difference to the type of work we do then??

Pete, my names Rich not Stew stickpoke stickpoke stickpoke, unless you have posted to Stew in the wrong place then his name is Stew not Rich ;D ;D ;D Does that make sense ??? ??? ??? ???

Any way I'll wait till I can afford a top of the range CNC mill and lathe before I chew a V8 out of solid.

Cheers

Stew,

I mean Rich

 

[doubletop]

Doh!!

I'm in a bit of a stew. Hey my excuse is we are busy celebrating the Queens birthday out here in the colonies and maybe had one to many toasts with a fine Hawkes Bay Merlot.

Pete

 

[Lew_Merrick_PE]

At a recent steam fair I bought a block of aluminium, its bout 4 x 4 x 3. No particular reason for buying it but it was cheap so I had it. I noticed today that it has some markings on one face. Any body know what they mean??

All metals have "grain" somewhat analogous to wood's grain. The grains, formed during cooling, end up with "directional properties" such that the metal is stronger in the direction it was rolled -- this is the "long traverse" direction you would see if you looked into a detailed metal's strength reference (such as MIL-HDBK-5). Aluminum and some titanium alloys are affected by this more than others.

You can usually get a cleaner cut with less power (though you need really sensitive meters to prove this) cutting across the grain rather than along the grain. It's not something most people would notice (I did a study on this and other factors back when I was in college). If you are using hypersonic cutter speeds and very aggressive feeds, it actually is important. [Hey, I spent nearly five years working for the National Bureau of Standards way back when.]

Aerospace applications need to know the grain direction for any critically loaded part. That's why it is marked on your piece. The assumption that metals are homogeneous and isotropic is usually acceptable in most situations. They aren't in actual fact, but it is only certain applications where that distinction becomes important.

 

[firebird]

Hi Lew

Thanks for the info.

Cheers

Rich