Steel pipe for air bag inflator and method for production thereof

Abstract

A steel pipe for an air bag inflator which has a high strength of a tensile strength of 900 MPa or more, preferably 1000 MPa or more, together with high toughness, and exhibits good burst resistance wherein no cracks develop in a burst test at -40 DEG C or lower is produced by a method comprising providing a raw steel pipe containing, in mass %, 0.05 to 0.20 % of C, 0.1 to 1.0 % of Si, 0.025 % or lower of P, 0.010 % or lower of S, 0.05 to 1.45 % of Cr, 0.10 % or less of Al, 0.02 % or less of Ti, and one or both of Ti and Mn satisfying 0.4 = Mn + 40 X Ti = 1.2, rapidly cooling the raw steel pipe from a temperature of Ac1 transformation temperature or higher, tempering the resultant steel pipe at a temperature lower than Ac1 transformation temperature, subjecting the tempered steel pipe to a cold working wherein a reduction of area is 65 % or less, and then subjecting the worked steel pipe to a stress relief annealing at a temperature lower than Ac1 transformation temperature. The L/T ratio of X ray integral intensity ratios of {110} face measured in the cross section perpendicular to the axis direction (L) and the cross section perpendicular to the periphery direction (T) of the above steel pipe is 50 or lass.

Description

technical field [0001] The present invention relates to steel pipes for airbag inflators (steel pipes for airbag inflators) having both high strength such as a tensile strength of 900 MPa or more, preferably 1000 MPa or more, and a steel pipe for airbag inflators preferably at -40°C. There is no brittle fracture surface at -60°C, and no cracks develop in the static pressure rupture test under such low temperature conditions. Such good toughness and low temperature crack resistance. Background technique [0002] In order to increase the safety of the car, the airbag (air cushion) system installed on the driver's seat and the passenger's seat has become a standard configuration. Previous airbag systems used explosive chemicals to generate the gas used to deploy the airbag. However, other types of airbag systems that fill steel pipes called inflators (or air reservoirs) with high-pressure gas for airbag deployment have been developed and used widely in response to the need to ...

AI Technical Summary

Problems solved by technology

However, although the technologies described in the above-mentioned publications all intend to obtain high-strength and high-toughness steel pipes for air bags, the achieved tensile strength is 800 MPa or more and less than 900 MPa, or 900 MPa or more and less than 1000 MPa, and even the highest is 947 MPa. , but did not achieve high strength and excellent toughness above 1000MPa at the same time

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