Patent ID: 6931906

Claim:
A process for reinforcing an end of a rectangular metal tube having inner and outer surfaces and first and second ends, the process comprising the steps of: a) providing a lower die having a first and second end and defining a cavity conforming to the outer surface of said tube; b) providing an upper die having an upper die cavity conforming to a required outer surface, after reinforcing, of said tube; c) placing said tube in said lower die cavity such that said tube first end extends out of said lower die cavity; d) providing means for preventing movement of said tube longitudinally with respect to said lower die cavity; e) providing a rectangular mandrel having a first and a second end, longitudinal corner radii, and being connectively fixed at said second end to said upper die, said mandrel being adapted to fit within said rectangular tube through said first end of said tube, and said second end of said mandrel having tapered, flared corners formed by decreasing said longitudinal corner radii; f) inserting said mandrel first end into the first end of said tube until said flared corners contact said tube inner surface; g) advancing said upper die under pressure until said closed, second end contacts said first end of said tube, thereby causing flared deformation of said first end of said tube; and h) moving said upper die under pressure until said upper die comes in close proximity to said first end of said lower die, thereby causing cold deformation of said first end of said tube, whereby a cold worked product with higher yield strength is produced.