What is the allowable stress for ductile iron qt450?

Tensile strength σb (MPa): ≥450; Conditional yield strength σ0.2 (MPa): ≥250; Elongation δ (%): ≥10; Hardness: 160–210 HB. Microstructure: As-cast: graphite + ferrite (matrix structure) + pearlite; Normalized: graphite + more pearlite + ferrite, which results in higher overall mechanical properties, particularly improved plasticity and toughness. (2) The design pressure of pressure vessels made of malleable cast iron and ductile iron shall not exceed 1.6 Mpa, with the design temperature ranging from -10 to 350°C. For the strength design of the pressure-bearing elements in cast iron vessels, the allowable stress is determined as follows: for gray cast iron, it is the tensile strength at the design temperature divided by a safety factor of 10.0 ； Malleable cast iron and ductile cast iron are based on the tensile strength at the design temperature divided by a safety factor of 8.0. Article 42: For the strength design of the pressure-bearing components of steel cast pressure vessels, the allowable stress is determined as follows: when the operating temperature is below 300°C, it is the material’s tensile strength divided by a safety factor of 4.0. and multiplied by the casting coefficient, a value for which should not exceed 0.9 ； When the operating temperature is greater than 300°C, the value is obtained by dividing the yield strength of the material at that temperature by a safety factor of 1.5 and then multiplying by a casting coefficient; this coefficient shall not exceed 0.9.

In accordance with the provisions of TSG R0004, Safety Technical Inspection Regulations for Fixed Pressure Vessels

Ductile iron grades and mechanical properties of single-cast test pieces: QT450-10 – tensile strength σb/MPa ≥ 450, yield strength σ0.2/MPa ≥ 310, elongation δ(%) ≥ 10, hardness HBS 160–210; details can be found in TSG R0004, Safety Technical Regulations for Fixed Pressure Vessels