Introduction to the GB Standard Designation System

Kivonat:

The group of Chinese (GB) standard specifications covers iron and carbon and alloy steel within different delivery conditions such as plates, strips, shits, bars, wires, castings, forgings etc. All character set standards that originate in the PRC have designations that begin with "GB". GB is an abbreviation of Guojia Biaozhun, meaning "national standard".

GB standards are the Chinese national standards issued by the Standardization Administration of China (SAC), the Chinese National Committee of the ISO and the IEC. All character set standards that originate in the PRC have designations that begin with "GB". GB is an abbreviation of Guojia Biaozhun, meaning "national standard". Recommended steel standards are prefixed "GB/T" (T from Chinese language ?? or tuijian, which translates as "recommended"). The remainder of the Standard designation is constructed from a numerical code which follows "GB" or "GB/T".

The group of Chinese (GB) standard specifications covers iron and carbon and alloy steel within different delivery conditions such as plates, strips, shits, bars, wires, castings, forgings etc.

The GB designations for non-alloy common steels and HSLA steels use the prefix letter Q, followed by the yield strength value (MPa). For example, Q235, Q345, Q390 denote non-alloy common steels and HSLA steels with a yield strength of 235, 345, and 390 MPa, respectively. Non-alloy structural steels and alloy structural steels are represented by numerical codes, which represent the average carbon content to a multiple of 100. For example, numeric code 45 shows a steel containing 0.45% C. Alloy elements in steel use the descriptive code with chemical symbols, followed by its average content. If the average content is less than 1.5%, it is indicated only with the chemical symbol, for example :

34CrNi3Mo containing 0.30–0.40% C, 0.70–1.10% Cr, 2.75–3.25% Ni, and 0.25–0.40% Mo.

Non-alloy tool steels are represented by the prefix letter T, followed by numeric codes, which represent the average carbon content to a multiple of 10. For example, T8 means the steel contains an average carbon content of about 0.80%. When the average carbon content is more than 1.0% in alloy tool steels, the steel grade would not indicate the carbon content in the standard designation. For example:

CrMn steel containing 1.30–1.50% C, 1.30–1.60% Cr, 0.45–0.75% Mn,
or
9Mn2V steel containing 0.85–0.95% C, 1.70–2.00% Mn, 0.10 to 0.25% V.

The descriptive method for the alloy element is the same in alloy structural steels.

Carbon content is not indicated in high-speed steels, and only uses the descriptive code with chemical symbols, followed by the alloy element content. For example:

Tungsten high speed steel 18-4-1 (T1) is represented by W18Cr4V

W–Mo high-speed steel 6-5-4-2 (M2) is represented by W6Mo5Cr4V2.

They are represented by a numeric code, which represents the carbon content to a multiple of ten, followed by the chemical symbols of the alloy elements with their content in stainless steels and heat-resistant steels, If the present alloys are microalloy elements the designation only shows the chemical symbols.

For example:

steel 9Cr18MoV contains 0.85–0.95% C, 17–19% Cr, 0.0–1.3% Mo, 0.07–0.12% V.

If the carbon content is less than 0.03 or 0.08%, 00 or 0 would be used for the steel designations, respectively, e.g. 00Cr18Ni10 and 0Cr13.

The following is a list of some National Standards of the People's Republic of China.


Click on the link to see a list of GB Standard List covering the following material categories:

  • Irons
  • Structural and Constructional Steels
  • Stainless Steels
  • Castings
  • Welding and Filler materials

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