First, the classification of alloy steel
The so-called alloy steel is to add some alloying elements on the basis of carbon steel, such as Si, mn, w, v, ti, CR, ni, mo, etc., to improve the strength, toughness, hardenability, weldability and other properties of steel. Alloy steel is divided into low alloy steel (alloying elements less than 5%), medium alloy steel (alloying elements are 5%-10%), and high alloy steel (alloying elements are greater than 10%).
In industrial production and life, alloy steel will be used in specific industries, so it is also very important to divide it by use. For example, wind power steel, which has been very popular in recent years, is specially tailored for the wind power industry. Alloy steel is divided into three major plates according to its use, first, alloy structural steel, second, alloy tool steel, and third, special performance steel.
1. Alloy structural steel is divided into low-alloy high-strength structural steel, carburizing steel, free-cutting steel, quenched and tempered steel, spring steel, and rolling bearing steel according to its use.
Second, the material and classification of tools
There are many types of tool materials, and the commonly used materials are tool steel, cemented carbide, ceramics and superhard materials.
1. Carbon tool steel
Carbon tool steel refers to high-quality high-carbon steel with a mass fraction of 0.65%~1.35% carbon. The grades used for knives are generally T10A and T12A. Hardness at room temperature is 60~64HRC. When the cutting edge is heated to 200~250°C, its hardness and wear resistance will decrease rapidly, resulting in the loss of cutting performance. Carbon tool steels are mostly used to make low-speed hand tools, such as files, hand saw blades, etc.
2. Alloy tool steel
In order to improve the properties of carbon tool steel, an appropriate amount of alloying elements such as manganese, chromium, tungsten, silicon and vanadium are often added to it, thus forming an alloy tool steel. Commonly used grades are 9SICR, GCRL5, Crwmn, etc. Compared with carbon tool steel, alloy tool steel has similar hardness after heat treatment, while the heat resistance and wear resistance are slightly higher, and the heat treatment performance is also better. However, compared with high-speed steel, the cutting speed and service life of alloy tool steel are far inferior to high-speed steel, so its application is greatly limited. Therefore, alloy tool steel is generally only used to replace carbon tool steel as some low-speed, manual tools, such as hand taps, manual reamers, round teeth, thread rolling boards, etc.
3. High-speed steel
High-speed steel is a kind of high-alloy tool steel containing more alloying elements such as tungsten, aluminum, chromium, vanadium, etc. The main advantages of high-speed steel are that it has high hardness, strength and wear resistance, and has good heat resistance and hardenability, and its allowable cutting speed is more than twice that of carbon tool steel and alloy tool steel. The cutting edge of high-speed steel is sharp after grinding, so it is also called "edge steel" and "white steel". High-speed steel is a tool material with good comprehensive performance and a wide range of applications, which is commonly used to manufacture tools with complex structures, such as forming turning tools, milling cutters, drills, and reamers. Broaches, gear cutters, etc.
According to its different uses and properties, high-speed steel can be divided into ordinary high-speed steel and high-performance high-speed steel, and according to its different chemical composition, it can be divided into tungsten high-speed steel and tungsten-molybdenum high-speed steel.