Hot rolled steel having improved formability
AssigneeDofasco Inc.
InventorsMaria-Lynn Turi, Stephen Lynes
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Abstract
A method of producing hot rolled steel having improved formability and minimal silver formation comprises the addition of Titanium and Boron to the molten steel to combine with and remove the free nitrogen prior to rolling: Titanium is added so that the amount of nitrogen remaining after Ti addition is about 0.0005 wt % to about 0.0025 wt % and Boron is added to remove the balance of the nitrogen by forming BN.
Claims12
A method of producing a hot rolled steel sheet having a yield strength measured in a transverse direction of less than about 43 ksi, from molten steel, said sheet having increased formability and low slivering, the method comprising the steps of:
- a) measuring the total nitrogen concentration of the molten steel;
- b) adding a sufficient amount of Titanium to the molten steel to bind with a first portion of the total nitrogen to form TiN, thereby leaving a second portion of total nitrogen;
- c) adding a sufficient amount of Boron to the molten steel to bind with the second portion of the total nitrogen to form BN;
- and,
- d) hot rolling the steel.
A method of producing a low yield strength hot rolled steel sheet having a yield strength measured in a transverse direction of less than about 43 ksi, from molten steel, said steel sheet having increased formability and low slivering, the method comprising the steps of:
- a) measuring the total nitrogen concentration of the molten steel;
- b) adding sufficient amounts of Titanium and Boron to the molten steel in a proportion wherein the range of a stabilization ratio, SR corresponding to the relationship:
- (B/0.77+Ti/3.42)/Ntot
- is
- 0.7≦SR≦2
- where:
- Ntot is the total nitrogen as measured in wt %
- and the range of the Boron bound to nitrogen remaining after Ti addition, B×N* is
- 0 wt %2<B×N≦4.5×10−6 wt % 2;
- where:
- N*=Ntot−(Ti/3.42);
- and
- c) hot rolling the steel.
Dependencies are inferred from the claim text.