SHEET STEEL FOR CONSTRUCTION PIPES OR TUBES, METHOD OF MANUFACTURE OF SHEET STEEL FOR CONSTRUCTION PIPES OR TUBES AND CONSTRUCTION PIPES AND TUBES

摘要

FIELD: metallurgy.;SUBSTANCE: invention relates to a sheet steel for a structural pipe product in the form of a tube or pipe. Sheet steel contains, wt%: C from 0.060 to 0.100; Si from 0.01 to 0.50; Mn from 1.50 to 2.50; Al 0.080 and less; Mo from 0.10 to 0.50; Ti from 0.005 to 0.025; Nb from 0.005 to 0.080; N from 0.001 to 0.010; O 0.0050 and less, P 0.010 and less, S 0.0010 and less, Fe and inevitable impurities are the rest. Ratio of Ti/N=2.5 and more to 4.0 and less, C_eq=C + Mn/6+ (Cu+Ni)/15 + (Cr+Mo+V)/5 (1), wherein C_eq=0.45 and more, X=(C+Mo/5)/C_eq (2), wherein X = less than 0.30 and Y=[Mo]+[Ti]+[Nb]+[V] (3), wherein Y=0.15 and more, each element symbol has a value of 0 in the absence of an element in the steel. Microstructure of the steel is formed from bainite and martensitic-austenitic component with a fraction of the surface area of less than 3.0 %, while the steel sheet has a tensile strength in the direction of rolling TS_L of 760 MPa and more, and TS_C – TS_L value of 30 MPa or less, expressed as an absolute value, where TS_C indicates the tensile strength in the direction orthogonal to the direction of rolling.;EFFECT: high strength in the direction of rolling and a slight difference between strength in the direction of rolling and strength in the direction perpendicular to the direction of rolling.;6 cl, 3 tbl