i have enrolled myself to fabricate a car for a race. i have to fabricate a car's roll cage obeying their specs. those specs are as listed below

can use a material which s having a carbon content of 0.18% and its bending strength and stiffness should be more or less equal to 1018 steel

so pls. guide wat material can i use to fabricate a roll cage for ma car which s to going to participte n a racing.