Am I using the right grade of steel

[twistedmetalman]

OK, I am trying to twist 2" thin wall square tubing but no matter what I've tried thus far the tubing collapses on me (usually at either end) before I can get a twist of any significance. I've tried packing the tube with sand and welding the ends closed, tried a pipe down the center, tried it cold (which would be my preferred method) and tried it hot with the same results.
Someone mentioned to me that I may not be using the right type of steel which may be causing the problem. Does square tube come in different grades and if so any advice on the type I should use or any other ideas on how to get the twists without it collapsing.

Beers,

 

[johnoder]

Think of a short piece of square tube and twisting it. The sides are each a web in a box beam system. The webs fail in a similar fashion to any webbed beam and this is due to shear.

The only way to prevent this is have webs closely supported or stiffened.

If you install solid "diaphragms" close enough together, you will have some control over what the webs will do.

It is easy to twist a solid square for the simple reason that the outer extremites (webs) are 100% supported.

John

 

[gwilson]

Have you thought of pouring the tubing full of lead and twisting it?This technique has been used to bend round tubing without collapsing it.I cannot guarantee this would work,and you might need a lot of lead.how long are the square tubes?

 

[twistedmetalman]

The tubing can be up to 5 feet long

 

[starbolin]

Yes square steel tube comes in different grades. A36, A513 and A500 grades are commonly stocked in different wall thicknesses including 0.065, 0.083 and 0.120 wall. A36 is also stocked in hot rolled and cold rolled.

starbolin

 

[gbent]

The filler material of choice for filling sections before bending is cerro-bend. There are several alloys all with very low melting points. The lowest is IIRC 158 degrees F. Used to make double wall water cooled boat headers, among other things.