Method for producing seamless steel pipe for inflator of air bag

Abstract

The invention proposes a method for manufacturing a seamless steel pipe having high strength, high toughness, and high formability for an airbag. A method for manufacturing a seamless steel pipe comprising a process for manufacturing a raw material for steel pipe having a composition containing 0.01 to 0.10% of C, 0.5% or less of Si, 0.10 to 2.00% of Mn, more than 1.0% and 2.0% or less of Cr, and 0.5% or less of Mo to form the seamless steel pipe, a process for drawing the seamless steel pipe in cold working, and a quenching and tempering process for heating the seamless steel pipe to A c3 transformation point or more and 1050° C. or less and then quenching, then tempering at 450° C. or more and A c1 transformation point or less is proposed. A method for manufacturing a seamless steel pipe where the cold drawing process is replaced after the quenching and tempering process is proposed. The composition may further contain, in addition to the composition, one or two or more selected from 1.0% or less of Cu, 1.0% or less of Ni, 0.10% or less of Nb, 0.10% or less of V, 0.10% or less of Ti, and 0.005% or less of B.

1 . A method for manufacturing a seamless steel pipe having high strength, high toughness, and high formability for an airbag characterized by comprising, 
 a process for manufacturing a steel pipe having a composition containing 0.01 to 0.10% of C, 0.5% or less of Si, 0.10 to 2.00% of Mn, more than 1.0% and 2.0% or less of Cr, and 0.5% or less of Mo by mass to form the seamless steel pipe,    a quenching and tempering process for heating the seamless steel pipe to a temperature in a range of A c3  transformation point or more and 1050° C. or less and then quenching, then tempering at a temperature in a range of 450° C. or more and A c1  transformation point or less, and    a cold drawing process for drawing the seamless steel pipe in cold working.    
   
   
       2 . The method for manufacturing the seamless steel pipe having the high strength, high toughness, and high formability for the airbag in  claim 1 , wherein order of the cold drawing process and the quenching and tempering process is reversed.  
   
   
       3 . The method for manufacturing the seamless steel pipe having the high strength, high toughness, and high formability for the airbag according to  claim 1  and  2  characterized in that the composition further contains, at least one element selected from 1.0% or less of Cu, 1.0% or less of Ni, 0.10% or less of Nb, 0.10% or less of V, 0.10% or less of Ti, and 0.005% or less of B.  
   
   
       4 . The method for manufacturing the seamless steel pipe having the high strength, high toughness, and high formability for the airbag according to  claim 3  characterized in that the seamless steel pipe is subjected to normalizing, for heating to a temperature in a range from 850 to 1000° C. and then air cooling, instead of the quenching and tempering process.