Ask a Basher #1

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Whilst I wouldn’t say I’m inundated with weird and wonderful requests and questions from all four corners of the internet, I would say that I do get more than my fair share.

There are questions sitting in the comments and in my inbox that are either worthy of an answer of even worthier of my/your/our contempt.

Keep them coming people and I’ll make sure they get the ‘appropriate response’.

Dear Sir,

I am a student studying in M.Sc. (Engg.) New Product Design.

I would like to know whether aluminium is costly or stainless steel is costly with respect to the quality and ability to produce sheet metal components (which determines manufacturig or processing cost) like PEPSI I mean cold drink tins..Kindly respond to the above question as early as possible.

Thanks and regards,

SANTOSH G DEVIHOSUR

Over to you………

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Paul Desveaux

I recently recovered my roof (asphalt shingles) and I was unable to find a local tinsmith who would help me with flashing for the square aluminium chimney on the roof. I proceeded to cut and shape the flashing but the saddle or the piece of flashing which sits at the top or back of the chimney is presenting a greater challenge and I believe that unless the two corners are extended by welding additional pieces/wings to it, it will not devert rain water and melting snow away from the chimney as it should. Is it that difficult to weld the thin/soft metal used for flashing? Is there a special tool needed or a particular solder required? From what the locals tell me, it would seem to be the case. Can you tell me more?

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Paul Woodhouse

When I had a spell selling these in the UK I never recall being asked for a 'true' 45 degree elbow. M/M, M/F, F/F threaded or weldable elbows with regards to either metal or plastic I do remember, but true I don't know.

Any help?

william mac phee

what is a true 45 degree elbow

colin

I have a hunch Santosh is in India. More bloody outsourcing.

Steve Sawford

"I believe only the USA has the capabilities to make aluminum. The rest of the world is stuck with aluminium."

Classic Danny :)

Absolutely splendid.

Danny Schaeffler, Engineering Quality Solutions

Multi-faceted question!
First and foremost, aluminium in general and stainless steels in general are both capable of producing high quality sheet metal components. The forming process/die process chosen impacts the overall cost as well, along with part design and raw material cost.

In the USA, the beverage can market is dominated by aluminum. (I believe only the USA has the capabilities to make aluminum. The rest of the world is stuck with aluminium.) The reason for this domination is that the aluminum industry did a much better marketing job than the steel industry. By having 100% of the cans made from the same aluminum grade, they can recycle cans with no problem. By contrast, there are cars with aluminum closure assemblies (like boot and bonnet [which are usually not on cars sold on this side of the pond]). The outer skin panel is made from one grade of aluminum (like 6111) while the underside unexposed inner panel is made from another grade (like 5182, if I remember the grade designation properly). When these assemblies are recycled, they need to be separated first and segregated. This is because the alloying elements of the 5xxx series are detrimental to the 6xxx series, and vice versa.
But I digress… we’ve established that there is a single aluminum grade used for beverage cans in the USA. You have undoubtedly noticed that these are smooth cylindrical sides. But other aluminum cans like that used for canned veggies have ridges along the edge. Why? It all has to do with the modulus of aluminum being 1/3 that of steel. In carbonated beverages, the internal pressure of the bubblies is enough to keep the can straight. Unless you have “wee beasties,” this is not the case for canned food. So you need the ridges for stiffness.

As for stainless steel, there are 2 primary series to consider - the 400 series (like 409 or 439 for example - used in auto exhaust systems, among other places) and the 300 series (like 304 or 316 - used in medical devices for example). The 300 series has inherently a greater formability than the 400 series. Why use 400-series then? Among other reasons, better high temperature properties. So for can-making, it's better to use the 300 series, right? I mean, for can making, isn't formability important? Of course it is, but I believe "cost" was mentioned in the question. The primary alloying element in 300-series stainless steels is nickel. Which seems to be daily increasing in price.

What about low carbon steels for your beverage can application? This was a popular choice in the USA until the steel industry gave the aluminum industry an opening here, and the aluminum industry capitalized on it. There is some public domain information at http://www.steel.org/AM/Template.cfm?Section=Cans_....

Sorry about the long answer, but I didn’t have the time to write a short one. (I love that quote!)

Best of luck!

Cheers,
Danny