ISO 185/JL/300 is a higher-tensile-strength gray cast iron that has a pearlitic matrix; it has a tensile strength of 300–400 MPa (44–58 ksi), when determined on test pieces machined from separately cast, 30 mm (1.2 in.) diameter test bars. It provides high strength while still maintaining good thermal conductivity compared with other types of cast iron. This grade approaches the maximum tensile strength attainable in gray cast iron. Applications therefore tend to be confined to those where thermal conductivity requirements in service preclude the use of one of the other higher-strength materials such as spheroidal graphite cast irons, which have inferior thermal properties. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on casting and heat treating. Filing Code: CI-82. Producer or source: International Organization for Standardization.