These hardness requirements ensure that the cutting tools can maintain sharpness during the cutting process, effectively cut the workpiece, resist wear, and extend their service life. In practical applications, it is necessary to select appropriate tool materials and hardness based on the workpiece material and cutting conditions.
Ⅰ. High hardness and wear resistance:
1. The hardness of the cutting part of the tool must be higher than that of the workpiece material to ensure effective cutting.
2. The higher the hardness of the tool material, the better its wear resistance, thereby extending the service life of the tool.
3. Specific requirements: The hardness of the tool material at room temperature should be above HRC62.
II. Relationship between hardness and wear resistance, strength, and toughness:
1. Cutting tool materials not only need high hardness, but also sufficient strength and toughness to withstand the pressure and impact during the cutting process, preventing edge chipping and breakage.
2. Strength is generally expressed by bending strength, and toughness is expressed by impact value.
III. Hardness Characteristics of Different Cutting Tool Materials:
1. High-speed steel: It has high thermal stability, strength and toughness, as well as certain hardness and wear resistance, and is suitable for processing non-ferrous metals and various metal materials.
2. Cemented carbide: It has very high hardness and wear resistance. Its cutting performance is better than that of high-speed steel, and its durability is several to dozens of times that of high-speed steel, but its impact toughness is relatively poor.
3. Coated inserts: Coated by CVD or PVD methods to further improve the durability of cemented carbide tools. The CVD coating material is TiC, and the PVD coating materials are TiN, TiAlN, and Ti(C,N).
4. CBN (Cubic Boron Nitride): Its hardness and thermal conductivity are second only to diamond. It has high thermal stability and good chemical stability, and is suitable for processing quenched steel, hard cast iron, etc.
5. PCD (Polycrystalline Diamond): When used as a cutting tool, it is sintered on a cemented carbide substrate and can perform precision machining on high-hardness materials such as cemented carbide and ceramics.
Ⅳ.Hardness Representation in the ISO Indexable Insert Material Classification Method:
1. Steel parts: P05, P25, P40. The smaller the number, the harder the blade, the better the wear resistance, but the poorer the impact resistance.
2. Stainless steel: M05, M25, M40, with a classification logic similar to that of steel parts.
3. Cast iron: K05, K25, K30, with a classification logic similar to that of steel parts.
