Steel tube of high strength and high strength steel plate excellent in the ability of deformation and toughness at low temperature, and method of production of the steel sheet

摘要

Abstract invention patent: "tube of high strength steel having excellent ductility and toughness at low temperature, high strength steel sheet and method for producing steel plate.High strength steel tube excellent in ability to deformation and toughness at low temperature and the steel tube obtained by a steel plate base in the form of a tube being a soldier.In which the steel plate base contains, in mass%, C: 0010 to 0.080%, Si: 0.01 to 0.50%, Mn: 1.2 to 2.8%, s: 0.0001 to 00050%, Ti: 0003 to 0.030%, B: 0.0003 to 0.005%, N: 0010 to 0.008%,: 0.0001 to 0.10.080% one or more elements among Cr, Cu and Ni, P: limited to 50% or less, al: limited to 0.020% or lower, Mo: limited to 0.03% or less, a CEQ obtained by (expression 1) below 0.30 to 0.53 and a PCM obtained by (term 2) below 0.10 to 0.20, and a balance consisting of iron and unavoidable impurities.And a metallic structure of the steel sheet base contains 27 to 90% in ratio of area of polygonal ferrite and a hard phase composed of one or both of bainite and martensita as your balance.