The primary national standard for gray iron castings in my country is **GB/T 9439 "Grey Iron Castings,"** which clearly specifies grades, mechanical properties, chemical composition ranges, and technical requirements. Common grades include HT150, HT200, HT250, HT300, and HT350; they differ mainly in tensile strength and suitability for specific operating conditions, serving as the fundamental basis for material selection during design.
Regarding dimensions and precision, gray iron castings typically adhere to **GB/T 6414 "Castings-System of Dimensional Tolerances and Machining Allowances."** This standard defines dimensional tolerance grades and machining allowance ranges for various casting methods, controlling the relationship between casting accuracy and subsequent machining, and ensuring assembly quality.
For quality inspection and defect control, relevant standards for non-destructive testing (NDT) and general acceptance criteria-such as those for ultrasonic testing, magnetic particle testing, and visual quality assessment-are also referenced. Manufacturers often establish stricter internal acceptance standards based on the product's intended use to ensure a dense internal microstructure and controlled defect rates.
Gray iron castings may also be subject to more specific industry or enterprise standards-such as specialized specifications for machine tools, automotive components, or pressure vessels. These standards often build upon the GB/T framework by imposing higher requirements for strength, surface quality, and reliability to meet safety and service life demands under specific operating conditions.