Deformation and densification laws of powder cold forging

Abstract

The deformation and densification laws of preform upsetting and closed-die forging were researched based on experimental results of cold forging of deoxidized Fe powder sintering porous material under different initial conditions such as friction factor, ratio between height and diameter and relative density. The fracture limit criterion for powder cold-forging upsetting and the limit strain curve were achieved. The effect of friction factor, ratio between height and diameter and relative density on fracture strain limitation was emphatically analyzed. The limit process parameter curves for the deformation of upsetting were also confirmed. Laws of deformation, densification and density distribution for closed-die forging of powder perform during cold-forging were further analyzed and discussed with the help of experimental phase analysis. As a result, this experiment established theoretical foundations for the design of preform and die as well as optimization of technological process parameters.

Keywords

powder cold-forging / fracture limit strain criterion / deformation law / densification mechanism

References

[1] Huang P. The Theory of Powder Metallurgy[M], 1982. Beijing: Metallurgical Industry Press. 361-385.

[2] Doraivelu S. M., Gegel H. L., Gunasekera J. S., . A New Yield Function for Compressible P/M Materials[J]. Int.J. of Mech. Set., 1984, 26(9): 527-535.

[3] Hua L., Zhao Z. Plastic Theory and Application of Sintering Material[J]. Journal of Mechanism Engineering, 1992, 28(4): 94-101.

[4] Zhao Z., Hua L., Wang H. The Forming and Densification of Sintered Powder Materials[J]. Int.J.Sci.of Sintering, 1987, 19(2): 65-80.

[5] Kim H. S., Won C. W., Chun B. S. Plastic Deformation of Porous Metal with an Initial Inhomogeneous Density Distribution[J]. Journal of Materials Processing Technology, 1998, 74: 213-237.

[6] Lippmann H., Iankov R. Mathematical Modeling of Sintering During Powder Forming Processes[J]. Int.J.Mech. Sci., 1997, 39(5): 585-596.

[7] Hua L., Zhao Z. Experimental Study on Filling Cavity Process of Powder Sintering Material[J]. Die and Mould Technology, 1999, 1: 22-24.

[8] Hua L., Qin S., Mao H., Zhao Y. The Plastic Deformation and Yield Criterion for Compressible Sintered Powder Material[J]. Journal of Plasticity Engineering, 2003, 10(6): 62-65.

[9] Lee P. W., Kuhn H. A. Fracture in Cold Upset Forming—a Criterion and Model[J]. Met. Trans., 1973, 4(4): 969-974.

[10] Zhang X., Li S., Wu A. Prediction of Defect During Cylindrical Upsetting of Porous Material by Finite Element Method[J]. Chinese Journal of Aeronautics, 1997, 18(4): 509-512.

[11] Zhang X., Peng Y., Ruan X. Prediction of Surface Crack During Cylindrical Upsetting of Porous Material by FEM[J]. Journal of Shanghai Jiao Tong University, 1998, 32(5): 14-17.