STEEL MATERIAL FOR COMPOSITE PRESSURE VESSEL LINER, STEEL PIPE OR TUBE FOR COMPOSITE PRESSURE VESSEL LINER, AND METHOD OF MANUFACTURING STEEL PIPE OR TUBE FOR COMPOSITE PRESSURE VESSEL LINER

摘要

Provided is a steel material for a composite pressure vessel liner whereby a liner having adequate strength and a high fatigue limit can be provided when the steel material is used as a raw material for manufacturing a composite pressure vessel liner, and which makes it possible to manufacture an inexpensive composite pressure vessel. A steel material for a composite pressure vessel liner, the steel material having a component composition containing, in terms of mass%, 0.10-0.60% C, 0.01-2.0% Si, 0.1-5.0% Mn, 0.0005-0.060% P, 0.0001-0.010% S, 0.0001-0.010% N, and 0.01-0.06% Al, the remainder comprising Fe and unavoidable impurities, and the steel material having a metallographic structure in which the average grain size of prior austenite grains is 20 µm or less, and the total area fraction of martensite and lower bainite is 90% or greater.