In metal cutting processing, the cutting performance of tool materials directly affects production efficiency, the machining accuracy of parts and machined surface quality, tool consumption, and processing costs.
Correct selection of tool material is one of the important contents of tool design and selection, especially for the cutting of some difficult-to-machine materials, the selection of tool material is particularly important.
The development of tool materials promotes the progress of metal cutting to a certain extent.
The basic performance and classification of cutting tool materials
1. High hardness
The hardness of the cutting tool material must be higher than that of the material being processed, otherwise, the sharp geometry of the cutting tool cannot be maintained under high temperatures and pressure.
At present, the tool material with the worst cutting performance - is carbon tool steel, its hardness should be above 62HRC at room temperature; the hardness of high-speed steel is 63~70HRC; the hardness of cemented carbide is 89~93HRA.
Both HRC and HRA belong to Rockwell hardness. HRA hardness is generally used in the high-value range (>70). The effective range of HRC hardness value is 20~70. The hardness of 60~65 is equivalent to 81~83. 6HRA and Vickers hardness 687 ~830HRA.
2. Sufficient strength and toughness
The material of the cutting part of the tool has to bear a lot of cutting force and impact force when cutting.
For example, when turning 45 steel, when ap=4mm, f=0.5mm/r, the tool should bear a cutting force of about 4000N.
Therefore, the tool material must have sufficient strength and toughness.
Generally, the bending strength σbb of the tool material is used to indicate its strength.
The impact toughness ak0 is used to represent its toughness, which reflects the ability of tool materials to resist brittle fracture and chipping.
3. Good wear resistance and heat resistance
The wear resistance of a tool material refers to the ability to resist wear.
Generally speaking, the higher the hardness of the tool material, the better the wear resistance.
4. Good thermal conductivity
The thermal conductivity of the tool material is expressed by the thermal conductivity [unit: W/(m·K)].
High thermal conductivity means good thermal conductivity, and the heat generated during cutting is easily conducted out, thereby reducing the temperature of the cutting part and reducing tool wear.
In addition, tool materials with good thermal conductivity have enhanced thermal shock resistance and thermal crack resistance.
This performance is especially important for intermittent cutting with brittle tool materials, especially when processing parts with poor thermal conductivity.
5. Good craftsmanship
In order to facilitate manufacturing, tool materials are required to have good machinability, including forging, welding, cutting, heat treatment, grind ability, etc.
6. Good economy
The economy is one of the important indicators for evaluating new cutting tool materials, and it is also one of the main bases for correctly selecting cutting tool materials and reducing product costs.
Tool materials can be divided into five categories: tool steel, high-speed steel, cemented carbide, ceramics, and superhard materials.
At present, the most widely used are high-speed steel and cemented carbide.
According to statistics, my country's current high-speed steel consumption accounts for more than 60% of cutting tools, and cemented carbide accounts for more than 30%.
With the increase in the application of difficult-to-machine materials, the use of ceramic cutting tools and superhard cutting tool materials is increasing.
TAG:   PCD Tool Cutting tool