Chemical composition and mechanical properties

(1) ordinary carbon structural steel

(2) high quality carbon structural steel

The quality carbon structural steel brand is expressed by carbon content + deoxidation method or chemical composition symbol + quality grade.

(3) special carbon structural steel

According to the special requirements and USES of some industries, the composition and properties of ordinary carbon structural steels are adjusted, and a series of special carbon structural steels are derived.

1) Marine carbon structural steel

In GB 712-2000 "structural system for ship hull", structural steel for ship hull is classified into general strength steel and high strength steel.Carbon structure is A general strength steel, it is divided into A, B, C, D four different quality grades.

The chemical composition and mechanical properties of Marine carbon structural steel are listed in table 7-2-6 and table 7-2-7 respectively.

2) carbon steel for boiler

There are two types of steel plates used for boiler compression components: carbon steel and low-alloy steel, among which there is only 20g carbon steel (g table boiler steel in steel number).

3) carbon steel for pressure vessels

There are many kinds of steel for pressure vessels, among which there is only 20R carbon steel (the R in steel number represents steel for pressure vessels).The chemical composition and mechanical properties are shown in table 7-2-10 and table 7-2-11.

There are only two types of carbon structural steels in the steel used for welding gas cylinders. Their chemical composition and mechanical properties are shown in tables 7-2-12 and 7-2-13.

5) carbon structural steel for Bridges

Bridge beam with a variety of steel, carbon structural steel only 16q (steel number q for the bridge of Chinese pinyin abbreviation).

(4) carbon steel castings for welding structure according to GB/T 7659 -- 1987, there are three kinds of carbon steel castings for cast-welding joint structure, and their chemical composition and mechanical properties are shown in tables 7-2-16 and 7-2-17.

In addition, the cast carbon steel used in general engineering, when its own defects often have to weld repair.The weldability of this kind of steel castings is not considered, so care must be taken when welding.