Nova Patents
EP1568792B1

Hot-rolled steel sheet for high-strength electric-resistance welded pipe and method for manufacturing the same

Abstract

This record has no abstract on file.

EP1568792B1, drawing sheet 1
Sheet 1 of 15

Term

Term ended

Expired 15 February 2025, 1.6 years ago.

  1. Priority
  2. Filed
  3. Granted
  4. Expired
  5. Today

4 claims: 1 independent, 3 dependent

  1. 1
    A hot-rolled steel sheet for a high-strength electric-resistance welded pipe having sour-gas resistance and excellent weld toughness, consisting of:0.03% to 0.06% C;0.05% to 0.50% Si;0.5% to 1.5% Mn;0.010% or less P;0.0010% or less S;0.01% to 0.10% Al;0.01% to 0.10% Nb;0.001% to 0.025% Ti;0.001% to 0.005% Ca;0.003% or less O;0.005% or less N, at least one element selected from the group consisting of 0.01% to 0.10% V;0.01% to 0.50% Cu;0.01% to 0.50% Ni;and 0.01% to 0.50% Mo on the basis of mass, wherein C, Si, Mn, Cu, Ni, Mo, and V satisfy Px given by Relationship 1: Px = C + Si / 30 + Mn + Cu / 20 + Ni / 60 + Mo / 7 + V / 10 ≤ 0.17 Ca, O, and S satisfy Py given by Relationship 2: Py = Ca − 130 × Ca + 0.18 × O / 1.25 × S 1.2 ≤ Py ≤ 3.6 and further optionally comprising at least one element selected from the group consisting of less than 0.1% Cr;0.003% or less B;and 0.005% or less REM on the basis of mass, wherein the elements of C, Si, Mn, Cu, Cr, Ni, Mo, V, and B satisfy Relationship 3: where in Relationship 1,2 and 3 (M) indicates the content by mass percent of an element M the balance is Fe and incidental impurities;and the microstructure of the steel sheet is composed of 95% by volume or more bainitic ferrite and wherein the ratio of Nb precipitation in the steel sheet is from 30% to 70% by mass with respect to the total Nb content. Px = C + Si / 30 + Mn + Cu + Cr / 20 + Ni / 60 + Mo / 7 + V / 10 + B × 5 ≤ 0.17