Due to the existence of cutting deformation in the cutting process (see the description of the three deformation zones in the metal cutting principle for details), the cutting force is generated, and most of the cutting force work (Q=FV) is consumed by the cutting heat, cutting heat according to the heat dissipation of the cutting area (mainly thermal conductivity and specific heat capacity two parameters) determines the level of the cutting temperature, such as cutting stainless steel, superalloy The cutting temperature will be much higher, and the cutting temperature of gray cast iron will be lower.
The most critical factor affecting the tool wear speed is the cutting temperature, the higher the cutting temperature, the faster the wear speed, each tool material has its own adaptation to the cutting temperature range, such as conventional coated carbide tools can withstand the maximum temperature of 800 to 900,CBN can withstand the appearance of 1300. If the cutting heat is large, the wear rate of the tool will inevitably accelerate. Of course, wear and tear is very complicated and involves many factors.
The factors that affect the life of the tool are the wear caused by mechanical action - the friction caused by the relative movement of the tool and the workpiece. Wear due to element diffusion - When cutting at high speed, carbon elements will spread from materials with high carbon content to materials with low carbon content. Wear caused by strong impact - in intermittent cutting, due to strong impact or brittle damage caused by frequent heating and rapid cooling. The wear caused by the thermal current in the cutting zone - under the action of the cutting heat, the tool and the chip, the tool and the workpiece contact area produce a high temperature, due to the difference in the material of the tool and the workpiece, it forms a thermocouple and generates a thermoelectric motive force, resulting in thermal current. Under the action of the thermal current, the carbon ion migrates, which will lead to the weakening of the tool material organization and the aggravation of the tool wear. Cutting speed, feed rate and cutting depth are the three elements of cutting parameters. Among them, the cutting speed has the greatest influence.