Introduction
China has a unique system of numbering and coding a wide range of metallic materials, called Chinese Standard (GB) Metal Materials Numbering System (in Chinese “gong bu”). Generally, it is a four-digit designations for classifying and determining basic Metal materials.
The Purpose of the System
The purpose of this system is to provide a unified numbering system for all metal materials used in manufacturing across China. It facilitates the rapid regulation and cost estimation of industrial processes involving metal materials, particularly when raw materials are sourced from different manufacturers. In addition, it provides a common standard for the comparison between materials and their applications.
Structure of Numbering System
The structure of the GB numbering system can be broken down into four individual parts. The first part is the two-digit Prefix Code, which has been assigned to indicate the material category. The other three parts are the Suffix Code, Execution Standard, and Type Code. Together, the four components present the entire GB standard number of the material.
Prefix Code
The Prefix Code is the first two digits of a GB number, and it is referred to as the material group in GB. This code is allocated for indicating the general type of metallic material. For example, 05 indicates 5xxx series aluminium Alloy, 45 indicates 45Steel and so on.
Suffix Code
The Suffix Code, which is the third and fourth digits of the GB number, represents the particular series and the state of strain of the material. By adding suffix to the two-digit Prefix Code, it is possible to differentiate the material further and to indicate the chemistry and mechanical properties of the material.
Execution Standard
The Execution Standard, written as Y in the GB number, refers to the standard of execution and technology accepted by the Ministry of Metallurgic Industry. It has the same meaning as defined in Chinese National Standard, GB/T standard, or ISO standard for materials.
Type Code
The Type Code is an alphabetical code that represents the material grade, to differentiate each material from another, even when a material has the same Prefix Code and suffix.
Conclusion
The Chinese GB metal materials numbering system is a complete, unified coding system that is used to classify, determine and identify metallic materials across China. It is important to understand the structure and meanings of the four components so that the correct coding can be used to accurately specify the desired material.
