Q235 steel is a plain carbon structural steel which is widely used in China, Q235 material in Chinese standard GB/T 700 is divided into 4 quality grades: Q235A, Q235B, Q235C and Q235D; Density of this steel is 7.85 g/cm3, tensile strength is 370-500 MPa; yield strength is 235 MPa (data are for steel bar or steel plate diameter≤16mm). Since it's mild steel, it is used directly without heat treatment.