The GB/T 7216-2023 standard specifies the methods and requirements for the metallographic inspection of gray cast iron, including the detailed process of sample preparation, inspection items, rating diagrams, result representation and test reports. This standard is suitable for evaluating the microstructure of gray cast iron to ensure that its mass meets specific microstructure requirements. The sample preparation process needs to avoid the casting surface, and prepare the metallographic sample according to the provisions of GB/T 13298 to prevent tissue changes, graphite flaking and graphite trailing. The surface of the sample needs to be kept smooth and clean, and there should be no coarse scratches to ensure accurate metallographic inspection results.