高強度鋼の冷間据込みにおける荷重および平面度の簡易予測

―凸面工具による荷重低減と高平面精度化―

抄録

Recently, the simple upsetting of high-strength steel has often been performed without heating and lubrication at a high compression ratio to improve the environment by sustainable manufacture and a productive automobile. Under these severe conditions, the extremely high pressure causes the tool to be elastically concaved. The shaped tool induces an increase in upsetting load and a decrease in the flatness of upset products. In this study, the convex tool with a small slope is investigated experimentally and analyzed by finite element method (FEM) to reduce the overload and improve the flatness. The obtained load (F_c = C₁CAY = C₁F_s) indicates a second correction factor C₁ for modifying the load F_s which is estimated by a conventional slab method as F_s = CAY, where the coefficient C is determined by friction coefficient and product height diameter ratio, and A and Y are the cross-sectional area and flow stress of the work, respectively. Additionally, the modified flatness α_t = C₂ (δ₀ - δ_R ) of the work is estimated by a combination of the elastic theory and FEM analysis, where the correction coefficient C₂ is determined by FEM analysis and δ₀ - δ_R is the elastic difference between the thickness δ₀ at the center and the thickness δ_R at the outer diameter of the work.