Med ali,

Do you mean material composition?
You can find it on ASTM code
It's Pressure Vessel Plates, High-Strength, Low-Alloy Steel and the composition for A737, Gr C is below(First row is element, second is heat analysis, last one is Product analysis)

Carbon, max 0.22, 0.24
Manganese 1.15–1.50, 1.07–1.62
Phosphorus, max 0.025, 0.025
Sulfur, max 0.025, 0.025
Silicon 0.15–0.50, 0.10–0.55
Vanadium 0.04–0.11, 0.03–0.12
Columbium, max 0.05, 0.05
Nitrogen, max 0.03, 0.03