Effects of Cooling Conditions on Thermal Crack Initiation of Brittle Cutting Tools during Intermittent Cutting

Abstract:

It is well known that a series of cracks running perpendicular to the cutting edge are sometimes formed on the rake face of brittle cutting tools during intermittent cutting. The cutting tool is exposed to elevated temperatures during the periods of cutting and is cooled quickly during noncutting times. It has been suggested that repeated thermal shocks to the tool during intermittent cutting generate thermal fatigue and result in the observed thermal cracks. Recently, a high speed machining technique has attracted attention. The tool temperature during the period of cutting corresponds to the cutting speed. In addition, the cooling and lubricating conditions affect the tool temperature during noncutting times. The thermal shock applied to the tool increases with increasing cutting speed and cooling conditions. Therefore, to achieve high-speed cutting, the evaluation of the thermal shock and thermal crack resistance of the cutting tool is important. In this study, as a basis for improving the thermal shock resistance of brittle cutting tools during high-speed intermittent cutting from the viewpoint of cutting conditions, we focused on the cooling conditions of the cutting operation. An experimental study was conducted to examine the effects of noncutting time on thermal crack initiation. Thermal crack initiation was found to be restrained by reducing the noncutting time. In the turning experiments, when the noncutting time was less than 10 ms, thermal crack initiation was remarkably decreased even for a cutting speed of 500 m/min. In the milling operation, the number of cutting cycles before thermal crack initiation decreased with increasing cutting speed under conditions where the cutting speed was less than 500 m/min. However, when the cutting speed was greater than 600 m/min, thermal crack initiation was restrained. We applied the minimal quantity lubrication (MQL) coolant supply to the intermittent cutting operation. The experimental results showed that the MQL diminished tool wear compared with that under the dry cutting condition and inhibited thermal crack initiation compared with that under the wet cutting condition.

• Periodical: Key Engineering Materials (Volumes 656-657)
• Pages: 237-242
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.656-657.237
• Online since: July 2015
• Authors: Kenji Yamaguchi*, Tsuyoshi Fujita, Yasuo Kondo, Satoshi Sakamoto, Mitsugu Yamaguchi, Kazutake Uehara
• Keywords: Cemented Carbide, Cutting, Milling, Minimal Quantity Lubrication, Thermal Crack, Thermal Shock, Tool Failure

References

[1] H. Wu and J. E. Mayer, An Analysis of Thermal Cracking of Carbide Tools in Intermittent Cutting, J. Manuf. Sci. Eng. 101–2 (1979), 159–164.

DOI: 10.1115/1.3439489

[2] T. Sugita and I. Yamada, Thermal Cracks of Ceramic Face Milling Cutter (1st Report) Effects of Some Machining Conditions, J. of the JSPE, 30–8 (1964), 662–670. (in Japanese).

DOI: 10.2493/jjspe1933.30.662

[3] Y. Kakino, K. Nakamura, A. Fujiwara, and M. Hashitani, A Study on the Thermal Crack Resistivity of the Cutting Tool (2nd Report) Parameters Deciding Macroscopic Thermal Crack Resistivity, J. of the JSPE, 53–06 (1987), 934–939. (in Japanese).

DOI: 10.2493/jjspe.53.934

[4] H. Matsuoka, T. Ryu, T. Nakae, and T. Kodera, Fundamental Research on Thermal Cracks of Cemented Carbide Hob in Hobbing, J. of the JSME, 79–802 (2013), 2221–2232. (in Japanese).

DOI: 10.1299/kikaic.79.2221

[5] A. J. Oliveira and A. E. Diniz, Effect of Minimal Quantity of Lubricant (MQL) in High-speed Milling of AISI H13 hardened Steel with Carbide Tool, Proceedings of COBEM 2009, http: /www. abcm. org. br/pt/wp-content/anais/cobem/2009/pdf/COB09-0584. pdf.

[6] F. Obata and K. Yamaguchi, Thermal Shock Resistance Evaluations of Brittle Tools by CO2 Pulse Laser Beam Irradiation (Thermal Cracks in a Cemented Carbide Tool), J. of the JSME, 65–640 (1999), 4882–4889. (in Japanese).

DOI: 10.1299/kikaic.65.4882

[7] K. Yamaguchi and F. Obata, Thermal Shock Resistance Evaluations of Brittle Tools by CO2 Pulse Laser Beam Irradiation (Effects of Laser Beam Off Time on Thermal Crack Initiation), J. of the JSME, 68–665 (2002), 270–275. (in Japanese).

DOI: 10.1299/kikaic.68.270