炭素鋼の熱間衝撃押出し
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概要
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The effects of extrusion ratio and punch velocity on the impact extrusion punch pressure of sevral kinds of carbon steels containing 0.02 to 0.52% carbon were investigated at the temperatures from 800℃ to 1200℃. The extrusion ratio R was varied from 2.4 to 19, and the punch velocity ν from 3.8 to 9.8m/sec, respectively. The results are summarized as follows. 1) The maximum extrusion punch pressure p_<max> changes discontinuously at the temperature of α-γ transformation, and above the temperature, it is related to the temperature T(°K) by the following equation, p_<max>=A′ln R. exp (B/T). Where the constant A′ decreases with carbon content, while B increases. The estimated punch pressure at the melting temperature T_m, which expresses resistance of viscocity of extrusion at R=2.3, becomes 26 kg/mm^2, irrespective to the carbon content. 2) The constant B gives the value of the activation energy of deformation ⊿H in the relationship B=⊿H/mk, where m is the parameter of stress dependence of the strain rate, and k the Boltzmann constant, respectively. The observed increases of B with the carbon content comes from the dependence of m on the carbon content. The value m changes from 10 to 5 due to the increase of the carbon content from 0.02 to 0.52%, which gives 32∿37kcal/mol as ⊿H. This result shows that the activation energy of deformation in the impact extrusion is fairly small compared with the energy of self diffusion of γ-iron, and it is suggested that the deformation mechanism operative in the impact extrusion differs from that for the static deformation. 3) The following empirical relationship in M.K.S. unit for the maximum impact extrusion punch pressure p_<max> (kg/mm^2) versus carbon content C% at different extrusion conditions are proposed, p_<max>=ν^<0.094>[20exp{(1/T-1/T_m)(3600×C%+1100))}In R+2exp{7590(1/T-1/T_m)}]+ρ/(2g)(Rv)^2×10^<-6>. The second term in the right hand side of the equation represents the inertia resistance associated with the high rate extrusion, where g is the gravity constant and ρ the density of steel.
- 社団法人日本鉄鋼協会の論文
- 1968-04-01