@Richard_Wallace referred to our steel chassis. Here’s what it looks like naked.
It’s 4130 tube from this list.
If you aren’t a welding team, this probably isn’t for you. I don’t think it can be riveted (citation needed). I’m not sure what your limitations are since you are outside the U.S. but, in my opinion, the 1x2 aluminum the is commonly used by most teams is the best bang for the buck.