CuZn39Pb3 vs Al 6082 - machinability

[Rdpere]

I did a quick calculation and Al 6082 is approximately five times cheaper than CuZn39Pb3 - per Volume!

But the question is - is it really so much easier to machine CuZn39Pb3 (compared to Al 6082) so that in the end it is cheaper to manufacture products from CuZn39Pb3 material?

For example, this coupling:


[URL unfurl="true"]https://www.merabell.com/image/cache/catalog/potrubni-system/fitinky/M0210-G1-1_4-G1-1_4-DN25-700x466fill.png[/url]

... what would be more cost efficient to use with this example, if there were yearly quantities of 20.000/year ?



Thank you in advance for any information!

 

[btrueblood]

Not sure how many aluminum threaded couplings you could sell; the material tends to have galvanic corrosion issues with things it is paired with, the threads are prone to galling.

Machining wise, yes, the brass will be easier to machine because cutting tools simply won't wear out during a production run of that volume, and can be made from HSS or other cheap tool steels. Aluminum, on the other hand, will always have an oxide coating (which is inherently abrasive) that will tend to dull edges, even on carbides.

 

[Rdpere]

But galvanic corrosion depends if the coupling would be paired with some metal ...
in my case it would be used to couple with a plastic object - so probably this is not an issue?

Also, here it says that 6082 has good machinability (probably still a lot worse than brass if i understand you correctly?) and it has a good corrosion resistance:
[URL unfurl="true"]https://www.metalsupermarkets.co.uk/7-things-to-consider-when-choosing-an-aluminium-grade/[/url]


It is also important that the product will have great surface treatment, so it looks neat - that is pretty important in this case (anodised or something similar if aluminium, nickeled if brass).

 

[EdStainless]

If material didn't matter wouldn't a free machining steel be lowest cost?
Material compatibility with the system is first consideration.
Then often available product forms are a major factor.
For this coupling you might justify spending 2 or 3 times as much to buy hollow hex vs solid bar because it would save so much machine time. Making ID holes is slow and expensive.

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P.E. Metallurgy, consulting work welcomed

 

[Rdpere]

I know that Steel is lot harder to machine compared to al/brass (especially for mass production), but wasnt sure about brass/aluminium.

Also, the price of Al6082 is in our country approximately 6.7$/kg and Brass is 10$/kg (cylindrical rough material).

I dont know the cost of a free machining steel though ...

Outer part is cylindrical for my aplication (approximately 30 mm), length approximately 40 mm, and the smallest through hole has to be 6 mm in diameter - it wont be hex.

 

[EdStainless]

Even though a free machining steel cuts well your Al will machine about twice as well.
But nowhere in the league of a leaded brass.
If a free machining steel (12L12) is 125, and wrought Al is 200, the leaded brass will be 300.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[btrueblood]

Talk to a machine shop that runs automated equipment (in the olden days Swiss Automatics or screw machines), and ask for a quote for 20000 units in either material. Those will be much firmer numbers than a bunch of bored engineers on the internet could give you.

We buy quite a lot of machined brass parts, because it has inherent corrosion resistance and durability. But...we also get the parts for not much more than the net material costs, if our order is large enough. In other words, we don't really pay for the machining - the vendor uses "lights out" machining on WW2 era screw machines. They source the 360 brass bars from a nearby foundry and get credit for returning them clean chips from the machining process. Aluminum chips aren't nearly as recyclable...though I think 6082 makes curls more than chips, which makes them even harder to process.

 

[Rdpere]

Aluminium would probably be anodised, so the corrosion wont be a problem. IF we choose aluminium.

You are right - that is the best way to find out about the price (the machine shops).
I just wanted to see another perspective of the issue, so im better informed