The ISO 7778 standard specifies the through thickness characteristics of steel and aims to evaluate the performance of steel products in different thickness directions. These characteristics are essential for the mechanical properties, corrosion resistance and processing adaptability of steel. The test methods and evaluation procedures are described in detail in the standard, which involves the testing of the microstructure, mechanical properties and other aspects of the steel in the through thickness direction. Through the evaluation of the through thickness characteristics, the performance of steel in practical applications can be better predicted, ensuring its Reliability and durability during manufacturing, processing and use. The standard is widely used in the fields of steel production, quality control and research and development.