The chemical composition of steel is one of the important factors related to the quality of steel and its final performance. It is also the main basis for formulating heat treatment systems for steel and even final products. Therefore, in the technical requirements section of steel standards, it serves as an important basis for production enterprises and customers to accept steel and its chemical composition. ① Melting composition of steel The chemical composition specified in general standards refers to the melting composition. It indicates the chemical composition during the mid-stage of pouring after steel smelting is completed. To ensure representativeness, analysis is conducted according to specified standard methods (GB/T223), and the results must comply with standardized chemical composition ranges, which also serve as a basis for customer acceptance. ② Finished product composition Finished product composition, also known as verification analysis composition, is obtained by drilling or planing samples from finished steel products according to specified methods (GB/T222) and analyzing them using standard methods (GB/T223). Due to uneven distribution (segregation) of alloy elements in steel during crystallization and subsequent plastic deformation, the finished product composition mainly serves for acceptance by using departments or quality inspection departments. Production enterprises generally do not conduct finished product analysis (except when requested by users), but they should ensure that finished product analysis complies with standard regulations. ③ Arbitration analysis When there are significant differences in results from two laboratories analyzing the same sample that exceed the allowable analytical error between them, or when there are differing opinions between production enterprises and using departments or between buyers and suppliers regarding finished product analysis of the same sample or batch of steel, a third-party authoritative unit with rich analytical experience can conduct re-analysis, which is referred to as arbitration analysis. The result of arbitration analysis serves as the final determination basis. | 
