1. Classification of carbon steel

Usually the carbon content, the quality of the steel or the use are classified.

1. Classification by carbon content According to the carbon content of steel, it can be divided into the following three categories.

Low carbon steel: wc<0.25%.

Medium carbon steel: 0.25%≤wc≤.

High carbon steel: wc>0.60%.

2. Classification according to the quality of steel According to the mass fraction of harmful impurities sulfur and phosphorus in steel, it can be divided into the following three categories.

a. Ordinary quality carbon steel. The content of S and P in steel is relatively high (ws≤0.050%, wp≤0.045%), which mainly include general-purpose carbon structural steel, carbon reinforced steel, and general carbon steel for railways.

b. High-quality carbon steel. The content of S and P in steel is low (ws≤0.035%, wp≤0.035%), mainly including high-quality carbon steel for mechanical structure, carbon steel for engineering structure, low-carbon structural steel for stamping sheet, carbon steel for welding rod, non-alloy Free-cutting structural steel, high-quality carbon cast steel, etc.

c. Special quality carbon steel. The content of S and P in steel is very low (ws≤0.20%, wp≤0.03%), mainly including carbon steel to ensure hardenability, carbon spring steel, carbon tool steel and hollow steel, special free-cutting steel, special welding rod Carbon steel, special carbon steel for railways, etc.

3. Classification by use of steel According to different uses of steel, it can be divided into the following three categories.

Carbon structural steel: This type of steel is mainly used to manufacture mechanical parts and engineering structures, and is generally low and medium carbon steel.

Carbon tool steel: This type of steel is mainly used to manufacture various cutting tools, measuring tools and molds, and is generally high-carbon steel.

Carbon cast steel: This type of steel is mainly used to make steel castings that have complex shapes and are difficult to form by forging.

2. the number of carbon steel

1. The number of carbon structural steel The grade of carbon structural steel is composed of four parts in sequence, which are the initials of Chinese pinyin representing the yield point of steel, the value of the yield point, the symbol of quality grade, and the symbol of deoxidation method. Among them, the quality grades are represented by the letters A, B, and E respectively: A grade S and P have the highest content and the lowest quality grade; E grade S and P have the lowest content and the highest quality grade. The deoxidation methods are represented by the Chinese pinyin letters F (rimmed steel), b (semi-stabilized steel), Z (stabilized steel), and TZ (specially stabilized steel). In the steel number, Z and TZ can be omitted.

2. The number of high-quality carbon structural steel The grade of high-quality carbon structural steel is represented by two digits, which represent the ten-thousandths of the average carbon mass fraction in the steel. If the manganese content in the steel is high, add the symbol "Mn" for manganese after the two digits. If it is boiling steel, add the symbol "F" after two digits.

For example: 45 means high-quality carbon structural steel with an average carbon mass fraction of 0.45%; 65Mn means carbon structural steel with an average carbon mass fraction of 0.65% and higher manganese content (wMn=0.9%~1.2%); 08F means The high-quality carbon structural steel with an average carbon mass fraction of 0.08% belongs to boiling steel.

3. The number of carbon tool steel The grade of carbon tool steel is indicated by adding one or two digits after the Chinese pinyin prefix "T" of "carbon". The number indicates the thousandth of the average carbon mass fraction in the steel, if It is a high-quality carbon tool steel, and then A is marked after the number.

For example, T8 steel represents a high-quality carbon tool steel with an average carbon mass fraction of 0.8%, and T10A represents a high-quality high-quality carbon tool steel with an average carbon mass fraction of 1.0%.

4. Numbering of cast carbon steel The grades of cast carbon steel used in engineering are represented by the Chinese pinyin prefix "ZG" of the word "cast steel" plus two sets of numbers. The first set of numbers indicates the minimum yield point, and the second set of numbers indicates the minimum tensile strength. Strength value. If "H" is marked at the end of the grade, it means that it is cast carbon steel for welded structure.

For example: ZG310-570 means cast steel with a minimum yield point of 310MPa and a minimum tensile strength of 570MPa.