In metal cutting, do you judge the cutting temperature based on the cutting of steel? Generally speaking, it is reasonable for the iron chips cut from almost all steel materials to appear purple during normal dry cutting.
The change process of chip color is the process in which most of the work consumed in the cutting process is converted into cutting heat. It can also be regarded as the process of tool loss (sharp → passivation → severe passivation → scrap).
picture
What we usually call cutting temperature refers to the average temperature. During dry cutting, the temperature can rise from about 200 degrees Celsius to more than 500 degrees Celsius. The changes in the color of the iron chips include: silvery white → light yellow → dark yellow → crimson → dark blue →Blue →Blue-gray →Off-white →Purple-black.
Relying on changes in cutting color to reasonably determine cutting parameters is also a method commonly used by experienced technicians.
It is more reasonable when the cutting color is blue or bluish-purple; if it is silvery white or yellow, the efficiency is not fully utilized; if it is blue-gray, the cutting amount is too large; when using high-speed steel tools, it is appropriate to cut into silvery white and slightly yellow; if it is blue, it will be reduced. Small speed or feed.
The relationship between chip color and cutting temperature:
Silver white: about <200℃ or below
Light yellow: about 220℃
Dark blue: about 300℃
Light gray: about 400℃
Deep purple black: about >500℃
