Partitioning method for pipe material, pipe material manufactured by the method, and gas generator

A gas generator for an airbag comprising:

• an elongated cylindrical tube comprising metal, the tube including a first closed end and second end;
• a partitioning plate which partitions an inside of the tube, in an axial direction, into
• a combustion chamber packed with gas generant which is burnable to generate high pressure gas, and
• a hollow cylindrical filter chamber fitted with a filter material;
• an igniter, fitted at the second end of the tube, that ignites and burns the gas generant in the combustion chamber;
• and
• a holder which closes the second end of the tube and holds the igniter,
• wherein the partitioning plate comprises a metal higher in hardness than that of the tube,
• wherein the tube includes a crimped portion on its peripheral face at locations adjacent to the partitioning plate,
• wherein plastic deformation of the crimped portion creates, on the inside face of the tube, a depressed portion which reduces a plate thickness of the tube such that the partitioning plate bites 0.1 mm or more into a wall of the tube from a peripheral edge face of the partitioning plate,
• wherein the partitioning plate has a first thickness portion and a second thickness portion, which is smaller in thickness than the first thickness portion and is a leading end of a portion that bites into the wall of the tube, and
• wherein the partitioning plate is tapered from the first thickness portion to the second thickness portion, so that the thickness of the partitioning plate decreases toward the second thickness portion.