High Strength Thick-Gauge Electric-Resistance Welded Steel Pipe Excellent in Hardenability, Hot Workability and Fatigue Strength and Method of Production of the Same

摘要

The present invention provides high strength thick-gauge electric-resistance welded steel pipe excellent in hardenability, hot workability, and fatigue strength and a method of production of the same, that is, thick-gauge electric-resistance welded steel pipe containing, by mass %, C: 0.25 to 0.4%, Si: 0.01 to 0.50%, Mn: 0.8 to 1.5%, P: 0.05% or less, S: 0.05% or less, Al: 0.05% or less, Ti: 0.005 to 0.05%, B: 0.0005 to 0.01%, N: 0.001 to 0.05%, and a balance of Fe and unavoidable impurities, having a critical cooling rate V_c expressed by equation 1 of less than 30° C./s, and having a ratio of thickness t and outside diameter D, t/D, of over 0.15 to 0.30 in range:; log Vc=2.94−0.75β  1where, β=2.7C+0.4Si+Mn