The material of the cutting tool is the fundamental factor determining the cutting performance of the tool, which has a significant impact on machining efficiency, machining quality, machining cost, and tool durability. When using carbon tool steel as the tool material, the cutting speed is only about 10m per person/nln; At the beginning of the 20th century, high-speed steel cutting tool materials emerged, with cutting speeds increasing to tens of meters per minute; In the 1930s, hard alloys emerged, with cutting speeds increasing to over 100 to several hundred meters per minute; The emergence of ceramic cutting tools and superhard material cutting tools has increased the cutting speed to over 1000 meters per minute, and the development of processed materials has greatly promoted the development of tool materials.
A cutting tool material with excellent performance is the basic condition for ensuring efficient tool operation. The cutting part of the tool should meet the following basic requirements when working under strong friction, high pressure, and high temperature.
1) The hardness of cutting tool materials with high hardness and wear resistance must be higher than the hardness of the processed material in order to cut metal. This is a basic requirement for cutting tool materials, and the hardness of existing cutting tool materials is above 60HRC. The harder the tool material, the better its wear resistance. However, due to the complex cutting conditions, the wear resistance of the material also depends on its chemical composition and the stability of its metallographic structure.
2) Sufficient strength and impact toughness. Strength refers to the performance that should be possessed to resist the action of cutting force without causing the blade to break or the tool holder to break. Generally expressed in terms of flexural strength. Upper impact toughness refers to the ability of tool materials to ensure no blade breakage under intermittent cutting or working conditions with impact. Generally, the higher the hardness, the lower the impact toughness, and the more brittle the material. Hardness and toughness are a contradiction and a key factor that tool materials should overcome.
3) High heat resistance, also known as red hardness, is the main indicator for measuring the performance of cutting tool materials. It comprehensively reflects the ability of tool materials to maintain hardness, wear resistance, strength, oxidation resistance, adhesion resistance, and diffusion resistance at high temperatures.
4) In order to facilitate manufacturing, tool materials should have good processability, such as forging, heat treatment, and grinding performance, in terms of good craftsmanship and economy. Of course, economic considerations should be taken into account when manufacturing and selecting. Currently, the cost of superhard materials and coated tool materials is relatively high, but their service life is long. In mass production, the cost allocated to each part is actually reduced. Therefore, when selecting, it is necessary to consider comprehensively.
The commonly used tool materials include tool steel, high-speed steel, hard alloy, ceramics, and superhard tool materials. Currently, the most commonly used tools are high-speed steel and hard alloy. Table 6-2 shows the grades, properties, and uses of commonly used tool materials.
High speed steel is a type of high alloy tool steel that contains a significant amount of tungsten, chromium, vanadium, and other alloying elements, and has excellent comprehensive properties. Its strength and toughness are the highest among existing tool materials. The manufacturing process of high-speed steel is simple and easy to grind into sharp cutting edges; Forging and heat treatment have small deformation, and they still play a major role in the manufacturing of complex tools, such as Fried Dough Twists drills, taps, broaches, gear cutters and forming cutters.
