STEEL PIPE FOR AIRBAG SYSTEM AND METHOD FOR ITS MANUFACTURE

A high strength steel pipe for an airbag system has a steel composition comprising C: 0.05 - 0.20 %, Si: 0.1 - 1.0 %, P: at most 0.025 %, S: at most 0.010 %, Cr: 0.05 - 1.0 %, Al: at most 0.10 %, at least one of Ti and Mn satisfying (1) Ti ≤ 0.02% and (2) 0.4% ≤ Mn + 40Ti ≤ 1.2%, and a remainder of Fe. The composition may further include one or more of (i) at least one of Mo: 0.05 - 0.50 %, Ni: 0.05 - 1.5 %, V: 0.01 - 0.2 %, and B: 0.0003 - 0.005 %, (ii) at least one of Cu: 0.05 - 0.5 % and Nb: 0.003 - 0.1 %, and (iii) at least one of Ca: 0.0003 - 0.01 %, Mg: 0.0003 - 0.01 %, and REM: 0.0003 - 0.01 %. The steel pipe can be manufactured by forming a pipe from the above-described steel composition to obtain prescribed dimensions, heating to at least the Actransformation point and quenching, and then tempering at the Actransformation point or below.