Heat Transfer Coefficient of Zinc Phosphate Coating with Metal Soap during Cold Backward Extrusion

Abstract:

In cold forging, the temperature difference between the workpiece and the tool is small and thus deformation analysis is rarely coupled with thermal analysis. However, the friction coefficient of zinc phosphate coating with metal soap has a large temperature dependence. Consideration of the effects of workpiece and tool temperature change on the friction coefficient is thus expected to improve the analytical accuracy of cold forging. Thermally coupled cold forging analysis requires thermal conductivity, specific heat, heat transfer coefficient between the workpiece and the tool, in addition to the temperature dependence of flow stress and friction coefficient. The heat transfer coefficient between workpieces coated with zinc phosphate with metal soap and tools is investigated in this paper. Cold backward extrusion was performed with a 50% reduction of area, and the temperature history in the punch was measured with a thermocouple. The forging speed was 1, 3, and 10 spm. FEM analysis was performed to simulate the experiment by considering the temperature dependence of flow stress and friction coefficient. The heat transfer coefficient was estimated at 20 kW/(m2•°C) by comparing the experimental result and calibration curves.

• Periodical: Defect and Diffusion Forum (Volume 414)
• Pages: 139-145
• DOI: https://doi.org/10.4028/p-wev8oa
• Online since: February 2022
• Authors: Osamu Kada*, Zhi Gang Wang
• Keywords: Cold Forging, FEM Analysis, Flow Stress, Friction Coefficient, Heat Transfer Coefficient, Zinc Phosphate Coating

References

[1] H.-W. Raedt, F. Wilke, C.-S. Ernst, The lightweight forging initiative - Automotive lightweight design potential with forging, ATZ Worldwide, 116, 3(2014), 40-45.

DOI: 10.1007/s38311-014-0152-9

[2] S. Isogawa, I. Mori and Y. Tozawa, Determination of basic data for numerical simulation – Analysis of multi-stage warm forging sequence for austenitic stainless steel 1, J. Jpn. Soc. Technol. Plast., 38-436(1997), 480-485.

[3] O. Kada, T. Miki, M. Toda and K. Osakada, Calculation of isothermal flow stress by combination of FEM and simple compression test, CIRP Ann., 47(1998), 185-188.

DOI: 10.1016/s0007-8506(07)62814-5

[4] A. Yanagida, J. Liu and J. Yanagimoto, Flow curve determination for metal under dynamic recrystallization using inverse analysis, Mater. Trans., 44-11(2003), 2303-2310.

DOI: 10.2320/matertrans.44.2303

[5] S. L. Semiatin, E. W. Collings, V. E. Wood and T. Altan：Determination of the interface heat transfer coefficient for non-isothermal bulk-forming processes, Trans. ASME J Eng. Ind., 109-1(1987), 49-57.

DOI: 10.1115/1.3187094

[6] H. Saiki, A. Minami and H. Yagoura, An estimation method of thermal contact and cooling conditions in warm and hot forging die, J. Jpn. Soc. Technol. Plast., 30-336(1989), 51-56.

[7] W. Nshama, and J. Jeswiet, Evaluation of temperature and heat transfer conditions at the metal-forming interface, CIRP Ann., 44(1995), 201-204.

DOI: 10.1016/s0007-8506(07)62307-5

[8] O. Kada, Z. Wang, K. Miyanishi, H. Yanagi and Y. Nose, Evaluation of anti-galling ability of zinc phosphate coating by backward extrusion of cylindrical cup, J. Mater. Process. Technol., 285(2020), 116765.

DOI: 10.1016/j.jmatprotec.2020.116765

[9] Information on https://www.sentesoftware.co.uk/jmatpro.

[10] O. Kada and Z. Wang, Lubricating performance of residual zinc phosphate coating on forged specimen in Bowden-Leben sliding test, Key Eng. Mater. 767( 2018), 124-130.

DOI: 10.4028/www.scientific.net/kem.767.124

[11] Information on https://www.rkcinst.co.jp/technical_commentary/1339/.

[12] H. Abe, S. Tashiro and Y. Miyoshi, Investigation of model to evaluate the pyrolysis properties of zinc stearate, J. Atomic Energy Soc. Jpn., 6-1(2007), 10-21.

DOI: 10.3327/taesj.j05.028