Introduction to the Naming Convention of Heat-Resistant Steels in China
Heat-resistant steel is a kind of steel which has excellent high-temperature performance and can be used in hot-working conditions, such as high-pressure vessels, petrochemical industry, aerospace industry and so on. Heat-resistant steel in China is recognized and specified by the naming conventions of its respective grades. In order to ensure consistency and dependability when ordering heat-resistant steel from different suppliers, it is important to understand the make-up of heat-resistant steel grade names and abbreviations in China.
A General Description about Naming System of Heat-Resistant Steel in China
The general system for the naming of heat-resistant steel grades in China consists of four parts. The first part is the alloy type, the second part is the mass fraction of carbon, the third part is the strength level, the fourth part is the additional alloy elements.
The alloy type is represented by the first letter of its name. For example, “8” stands for heat-resistant steel; “5” stands for creep-resistant steel; and “3” stands for corrosion-resistant steel.
The mass fraction of carbon is represented by the second and third digits in the grade name. The mass fraction of carbon is calculated in hundredths. For instance, 23 7 denotes the mass fraction of carbon is 0.23, 43 4 means the mass fraction is 0.43.
The strength level refers to the stress1 and creep2 strength of the steel after the aging treatment. It is represented by the last digits in the grade name. Higher strength level of steel can achieve higher stress3 and creep4 strength after heat treatment. In general, 2 represents the minimum strength level and 6 represents the highest strength level.
The additional alloy elements refer to the other alloy elements besides carbon which are added to improve the mechanical properties of the steel. It can be represented by symbols. For example, Mn represents manganese, Cr represents chromium, Mo represents molybdenum, Si represents silicon, Cu represents copper and so on.
Examples of Nomenclature for Different Grades of Heat-Resistant Steel
In order to further illustrate the naming system of heat-resistant steel grade in China, here are several examples of grade name and grade composition.
Grade 8 23 7 is a type of heat-resistant steel with a mass fraction of carbon at 0.23 and a strength level after aging treatment of 7.
Grade 5 43 4 is a type of creep-resistant steel with a mass fraction of carbon at 0.43 and a strength level after aging treatment of 4.
Grade 3 23 4 Mn 1 Cr 1 is a type of corrosion-resistant steel with a mass fraction of carbon at 0.23, a strength level after aging treatment of 4 and additional alloy elements of manganese and chromium in 1 mass fraction.
Conclusion
The naming system for heat-resistant steel grades in China can clearly identify different grades of heat-resistant steel and helps engineers to select the most suitable heat-resistant steel for their application. Understanding this naming system is of great importance for commercial negotiations since each grade of heat-resistant steel has corresponding US, European and Japanese grade names which are used internationally.
1 Stress: A force that acts on a material object and changes its shape or internal structure
2 Creep: A type of plastic deformation caused by a sustained load
3 Stress: A measure of the internal force that an object can withstand
4 Creep: A measure of the deformation caused by a sustained load on a material object
