Steel vs aluminum alloy strength in sheet material?

[julianf]

I have boxes made up in 1.5mm aluminium alloy. I'm fairly sure it's 1050 but not certain.

If I wanted to make the same box out of mild steel to match the strength of the alloy, how would I calculate the thickness to use?


I'm aware the job will be heavier, by a fair bit - what I'm trying to do is match strength rather than match weight.


At this point even an experienced comment is fine, rather than a massive mathematical sum!

Thank you

 

[DeBangis]

Haha! :smile: your last paragraph made me laugh.
Booked space, waiting for expert comments.

 

[hotponyshoes]

Depends what sort of "strength" you are looking for.

1050 sheet has less than half the tensile strength of mild steel sheet so 0.6mm steel would be ok in that regard

 

[wyn]

What do you mean by "strength"?

 

[julianf]

What do you mean by "strength"?

Again, im not so interested in the maths, but, in laymans terms -

"I have boxes made up in..."

So, the ability to retain "box" shape, when folded, under "general" environmental conditions.


Ie if someone slings it in the back of a van, to dent or not dent under about the same conditions.
Or, if someone puts somthing heavy in it, or on top of it, etc etc to deform under about the same conditions.


I was trying to avoid Young's modulus calculations but more of a generalisation so as not to get bogged down in specifics.

 

[voipio]

The weight difference between equivalent boxes made from ali and mild steel might not be as much as one would expect, based on density alone.

Taking cycle frames as an example, a typical steel cycle frame might weigh 4-5lbs, whilst a comparable aluminium alloy frame might be about 3lbs, making the steel equivalent about ~50% heavier than its ali counterpart. OK, we're comparing something like Reynolds 531 vs duralumin, so specialised alloys, rather than common or garden mild steel or pure aluminium, but you get the idea. Based on that weight difference, and the densities of the two materials, my simple calculation makes the steel thickness for "equivalence" to be about half that of the ali.

 

[wyn]

How about sticking with the aluminium but putting some "shape" into the flat surfaces with a bead roller.

 

[julianf]

In my instance -

A standard box in aluminium weighs 0.97kg
Changing that to mild steel it would be 2.8kg

So approximately 3x the weight.

Mild comes in "standardised" thicknesses, which i never actually know, but im guessing 0.8 may be one of them?

Ive just had a very brief look online -

0.8, 1.0, 1.2

Do you think i should go for 1.0 to be safe? Id like to reduce weight, but i do not want to compromise strength. Given the choice between the two, theres no point in having a rubbish item, no matter how light it is!

 

[julianf]

How about sticking with the aluminium but putting some "shape" into the flat surfaces with a bead roller.

Has to be ferrous. Arty acid stuff - wont work with alloy, and dont want to get into paints.

 

[Erie Fred]

Your moving your hands, but I'm not seeing anything....
Post some pix of the existing box please.

 

[julianf]

Your moving your hands, but I'm not seeing anything....
Post some pix of the existing box please.

I'll need to find some when I'm off the phone, but the existing stuff isn't quite the same design.

 

[Erie Fred]

I'll need to find some when I'm off the phone, but the existing stuff isn't quite the same design.

I have boxes made up in 1.5mm aluminium alloy. I'm fairly sure it's 1050 but not certain.

If I wanted to make the same box out of mild steel to match the strength of the alloy, how would I calculate the thickness to use?


I'm aware the job will be heavier, by a fair bit - what I'm trying to do is match strength rather than match weight.


At this point even an experienced comment is fine, rather than a massive mathematical sum!

Thank you

Your OP gave no dimensions other than thickness that i can find.
Until more information is posted (pictures are best) everything else is just speculation/conjecture.

 

[Gareth J]

Look around at some existing things with similar flat dimensions. Shelving units, filing cabinets, tool drawers etc.

See what feels like it'll perform the way you want. The properties of Ali and steel differ in other ways than just strength/weight so while you might find a 0.8mm steel box is "strong" enough, it might feel too tinny so decide to go with 1 or 1.2.

 

[julianf]

Your OP gave no dimensions other than thickness that i can find.
Until more information is posted (pictures are best) everything else is just speculation/conjecture.

This kind of thing, but probably 2x as long -

Maybe 40" or so long, by 7" by 3.5"

 

[Misterg]

the ability to retain "box" shape, when folded, under "general" environmental conditions.


Ie if someone slings it in the back of a van, to dent or not dent under about the same conditions.
Or, if someone puts somthing heavy in it, or on top of it, etc etc to deform under about the same conditions.

Your concerns may depend more on stiffness than strength.

I know you wanted to avoid Mr. Young, but [eta: bending] stiffness is proportional to Young’s modulus and thickness^3.

Youngs modulus for steel is ~3 x that for aluminium, so for something in sheet steel to feel as stiff as 1.5mm aluminium, it would need to be ~1mm thick (1.5/cube root of 3).

 

[julianf]

Nice, thank you - that was what i was after.