| 摘要 |
PROBLEM TO BE SOLVED: To economically produce a pressure hollow barrel body provided with formability as to the conical shape forming operation for the neck part of a cylinder, high resistance to stress corrosion and intergranular corrosion and ductile action at the time of a bursting test under the internal water pressure. SOLUTION: This method includes (a) a casting stage for a billet made of an AlZnMgCu alloy having a composition containing, by weight, 7.14% Zn, 1.67% Mg, 2.06% Cu, 0.04% Fe, 0.02% Si and 0.20% Cr, (b) a homogenizing stage in which the temperature of the metal is lower than the initial melting temperature, (c) a softening stage in which cooling is performed for 20 to 40 hr at 200 to 400 deg.C so as to control its hardness to <54 HB, (d) a cutting stage for the bloom, (e) a cold extruding stage for a vessel in which the starting temperature of the extrusion is <300 deg.C, (f) a conical shape forming stage for the vessel, (g) a solid solution stage for a time by which specific energy associated with an AED signal is controlled to <3 J/g, (h) a quenching stage with cooled water and (i) a tempering stage.
|
