How to Judge the Cutting Temperature by the Color of Iron Chips?

In metal cutting, will you judge the cutting temperature according to the cutting of steel?

Generally speaking, in normal dry cutting, it is reasonable that almost all iron filings cut from steel appear purple.

The change process of chip color is the process that 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 → scrapping).

How to Judge The Cutting Temperature by The Color of Iron Chips

The cutting temperature we usually refer to refers to the average temperature.

During dry cutting, the temperature can rise from about 200 ℃ to more than 500 ℃.

The color changes of iron filings include: silver white → light yellow → dark yellow → crimson → dark blue → blue gray → gray white → purple black.

It is also a common method for experienced technicians to reasonably determine cutting parameters by the change of cutting color.

It is more reasonable when the cutting color is blue or blue purple;

If silver or yellow, the efficiency is not fully exerted;

If blue gray, the cutting amount is too large;

When using high-speed steel cutting tools, it is appropriate to cut them to silver white and yellowish.

If cutting them to blue, it is necessary to reduce the speed or feed.

Relationship between chip color and cutting temperature:

  • Silver White: about <200 ℃;
  • Light yellow: about 220 ℃;
  • Dark blue: about 300 ℃;
  • Light gray: about 400 ℃;
  • Dark purple black: about >500 ℃.

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