Free cutting structural steel (GB/T8731-1988)

Cold-worked steel (GB/T8731-1988) Introduction

Cold-worked steel refers to a type of steel that has been processed or worked at a low temperature, such as below the recrystallization temperature. The low temperature processing assists in creating desired shapes, hardness, strength, and texture. There are a variety of cold-worked steels, including cold rolled, cold drawn, and cold forged. This article will cover the cold-worked steel standards of GB/T8731-1988.

Definition of Cold-worked Steel according to GB/T8731-1988

GB/T8731-1988 provides a definition of cold-worked steel as follows: Cold-worked steel is a metal product obtained by mechanical deformation (cold working) of a hot-rolled metal, passing through a stage between solidifying and normalizing temperatures, after being worked at a temperature below the recrystallization temperature; nevertheless, it can also be defined as a metal product with a specifically produced structure, while having improved hardness, strength, and wear resistance.

Definitions of Steel Classes According to GB/T8731-1988

GB/T8731-1988 defines the different classes of cold-worked steel, which are categorized according to their intended use. The following table outlines the different classes of steel according to GB/T8731-1988:

Class 1: Structural steel

Class 2: High-strength structural steel

Class 3: Boiler and pressure vessel steel

Class 4: Plate steel

Class 5: High-strength low-alloy structural steel

Class 6: Basic building steel

Class 7: Mold and tool steel

Class 8: Stainless steel

Class 9: High alloy tool steel

Class 10: Spring steel

Class 11: Bridge steel

Class 12: Certain weldable steel

Class 13: Ship steel

Class 14: Automobile steel

Class 15: Nickel-chromium steel

Class 16: High manganese steel

Class 17: Bearing steel

Class 18: Electric steel

Class 19: Cold roll forming steel

Class 20: Heat-resistant steel

Mechanical Requirements According to GB/T8731-1988

GB/T8731-1988 outlines the mechanical requirements of cold-worked steel according to the different classes of steel. For instance, Class 4 plate steel needs to meet requirements including lower yield limit and upper yield limit, tensile strength, elongation, and hardness. GB/T8731-1988 also lists requirements for additional tests, including impact testing, notch toughness, and bend testing for Classes 10, 15, and 16.

Conclusion

GB/T8731-1988 sets the standards for cold-worked steel, ranging from its definition to the mechanical requirements for each of the different classes of steel. In conclusion, GB/T8731-1988 is a valuable resource for obtaining cold-worked steel with a desired structure, hardness, strength, and wear resistance.

GB/T8731-1988 is a Chinese national standard that provides technical requirements and test methods for the cutting of structural steels. Structural steels are steels used for manufacturing structures such as civil engineering and architecture. This standard does not cover special structures such as cars, ships, bridges, etc.

GB/T8731-1988 is divided into three parts. Part 1 stipulates the scope of the standard, the terms and definitions used, and the quality requirements for finished products. Part 2 stipulates the technical requirements for cutting structural steels, including the shape, size and authentication of the cutting region, finishing requirements and the equipment used. Part 3 provides the test methods and test procedures for the items specified in Part 2.

In addition to GB/T8731-1988, there are many other related standards, such as GB/T17505-1998, GB/T17550-1998 and GB/T22159-1996. The scope of these standards includes cutting, welding and heat treatment of structural steels. The requirements of these standards ensures that all products are uniform in quality and meet the same requirements for use.

GB/T8731-1988 is an important standard for cutting structural steels. This standard is not only beneficial for the uniformity and reliability of these products, but also for the development of the entire engineering and architectural industry.