Metallic tubular structure having improved collapse strength and method of producing the same
AssigneeSumitomo Metal Industries, Ltd.
InventorsKenichi Tanaka, Katsuyuki Tokimasa
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Abstract
Disclosed is a metallic tubular structure having an improved collapse strength characterized in that the tubular structure has a circumferential residual tensile stress left in the inner peripheral surface thereof, said residual stress ranging between 0 and 15 % of the yield stress of the tubular structure. The material of the structure may be any one selected from a group consisting of plain steel, alloy steel, stainless steel and Fe--Ni--Cr alloy. The tubular structure of the invention can suitably be used as pipes under severe condition such as in deep oil wells.
Claims11
A method of producing a metallic tubular structure having improved collapse strength, comprising applying two pairs of compression loads to two pairs of points on the outer surface of the tubular structure from opposite sides thereof, the two points of each pair of points being spaced apart from one another by an angle of 40-90 degrees measured from the longitudinal axis of the tubular structure, the magnitude of the loads being such that a circumferential residual tensile stress greater than zero and at most 15% of the yield stress of the material consistituting the tubular structure is developed in the inner peripheral surface of the tubular structure, said loads being repeatedly applied to different portions of the circumference of said tubular structure.
A method of producing a metallic tubular structure having improved collapse strength, comprising:
- disposing at least one ring having a diameter larger than the diameter of the tubular structure around the tubular structure;
- and
- applying a force to said ring so that a distributed load is applied to the tubular structure at different portions on the periphery thereof, the distributed load being of a magnitude such that a residual tensile stress in the circumferential direction having a magnitude greater than zero and at most 15% of the yield stress of the material constituting the tubular structure is generated in the inner peripheral surface thereof.
Dependencies are inferred from the claim text.