I believe most panels are made from a low carbon sheet steel, 1008/1010 variety. Low cost, and easy to work with when stamping.
The mechanical properties make up how the metal behaves, and the process in which it's rolled also effect the material, for example "cold worked". Each time a metal is bent, it gets cold worked, and stiffens. Grain structure can also impact the strength of a metal.
Nickel content and Cromium are the most costly components of a carbon steel.
I would suspect that the low carbon steel has less Nickel content than 40 years ago as these costs have gone thru the roof.
Steel surcharges are common in the industry especially for Stainless Steel. Low Carbon Steel is also on the rise.
