Patent ID: 8202469

Claim:
A method of manufacturing a hollow structural member using a substrate for hollow structural member production, in which the substrate has a surface on which a plastic deformation film is formed, and a plurality of recesses which open toward the surface and which store therein a gas for forming a plurality of hollows by expanding and drawing the plastic deformation film through discharging of the gas, the method comprising: (a) using a gas-permeable material in part of a material that constitutes the substrate for hollow structural member production; (b) encapsulating a high-pressure gas by injection in advance, under high-pressure conditions, into the gas-permeable material; (c) forming the plastic deformation film on the surface under reduced-pressure conditions; and (d) manufacturing the hollow structural member, while preventing the plastic deformation material from entering the recesses, by discharging the high-pressure gas that is encapsulated in the gas-permeable material into each of the recesses so that the plastic deformation film is expanded and drawn by the high-pressure gas into each of the recesses, wherein the high-pressure gas is injected into the gas-permeable material in (b) from a place other than the surface.