SEAMLESS STEEL TUBE FOR AIRBAG ACCUMULATORS AND PROCESS FOR PRODUCTION THEREOF.

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A seamless steel tube for airbag accumulators which can be produced by normalizing heat treatment alone without quenching and tempering and has a tensile strength of 850MPa or above and burst resistance at -20°C. The seamless steel tube has a steel composition which contains by mass C : 0.08 to 0.20%, Si : 0.1 to 1.0%, Mn : 0.6 to 2.0%, P : 0.025% or below, S : 0.010% or below, Cr : 0.05 to 1.0%, Mo : 0.05 to 1.0%, Al : 0.002 to 0.10%, at least one member selected from among Ca : 0.0003 to 0.01%, Mg : 0.0003 to 0.01% and REM (rare earth elements) : 0.0003 to 0.01%, and at least one member selected form between Ti : 0.002 to 0.1% and Nb : 0.002 to 0.1% and has a Ceq value of 0.45 to 0.63 as defined by the formula (1) and a mixed metal structure of ferrite and bainite : Ceq = C + Si/24 + Mn/6 + (Cr+Mo)/5 + (Ni+Cu)/15... (1) wherein each symbol of element represents the content of the element in % by mass.