| 摘要 |
A press forming method for a metal sheet is provided. The method is capable of improving a forming limit at which a crack appears in a metal sheet and being easily applied to a large press machine for mass production with a low cost, without correcting the shape of dies, such as a punch and an upper die, or changing the shape or material of a blank to a special shape or material. Dies, a surface roughness of which is an arithmetical mean roughness Ra of 7.5 µm or smaller, are used as a punch 10, an upper die 20, and a blank holder 30. Fluid with a kinematic viscosity of 500 mm 2 /s or lower (40°C) is used as a lubricant, and is supplied to a space between a metal sheet 100 and the blank holder 30, a space between the metal sheet 100 and the punch 10, and a space between the metal sheet 100 and the upper die 20. A die is detached from a workpiece in the middle of forming, and resuming the forming, thereby improving formability. |
