A method for producing steel strip, in particular hot strip in the form of coiled coils or in the form of folded individual sheets, in which a steel melt is first produced, this is then formed into a strand in a continuous casting system, the strand is then fed into a heating unit and the heated strand is then rolled into hot strip in a subsequent rolling mill. The casting of the strand, the passage through the heating unit, and the rolling take place in a continuous process. To be able to produce hot-rolled steel strips in the most energy-efficient way possible and to make these strips available for further processing into high-quality cold-rolled and, if necessary, coated strips, the invention provides that, first of all, a steel melt is produced.

A method for producing steel strip, in particular hot strip in the form of coiled coils or in the form of folded individual sheets, in which a steel melt is first produced, this is then formed into a strand in a continuous casting system, the strand is then fed into a heating unit and the heated strand is then rolled into hot strip in a subsequent rolling mill. The casting of the strand, the passage through the heating unit, and the rolling take place in a continuous process. To be able to produce hot-rolled steel strips in the most energy-efficient way possible and to make these strips available for further processing into high-quality cold-rolled and, if necessary, coated strips, the invention provides that, first of all, a steel melt is produced.

A hot-rolled flat steel product having a thickness of <1.5 and consisting of, in % by mass, C: 0.04-0.23%, Si: 0.04 0.54%, Mn: 1.4-2.9%, Ti+V, wherein 0.005%<%Ti+%V<0.15%, and optionally one or more elements of Al, Cr, Mo, and B, where AI: 0.01-1.5%, 0.02<%Mo+%Cr<1.4%, and B: 0.0005-0.005%, and the remainder consisting of iron and inevitable impurities. The structure of the flat steel product consists of, in percent by area, in sum, 50-90% ferrite and bainite ferrite, 5-50% martensite, 2-15% residual austenite and <10% other structure elements. The flat steel product has a yield point Rp0.2>290 MPa, a tensile strength Rm>490 MPa and an elongation at break A80 where A80[%]=B−Rm/37 with 31<B<51. To at least one surface of the flat steel product, a Zn coating is applied by hot-dip coating. Also a method for producing a flat steel product of this kind.

A hot-rolled flat steel product having a thickness of <1.5 and consisting of, in % by mass, C: 0.04-0.23%, Si: 0.04 0.54%, Mn: 1.4-2.9%, Ti+V, wherein 0.005%<%Ti+%V<0.15%, and optionally one or more elements of Al, Cr, Mo, and B, where AI: 0.01-1.5%, 0.02<%Mo+%Cr<1.4%, and B: 0.0005-0.005%, and the remainder consisting of iron and inevitable impurities. The structure of the flat steel product consists of, in percent by area, in sum, 50-90% ferrite and bainite ferrite, 5-50% martensite, 2-15% residual austenite and <10% other structure elements. The flat steel product has a yield point Rp0.2>290 MPa, a tensile strength Rm>490 MPa and an elongation at break A80 where A80[%]=B−Rm/37 with 31<B<51. To at least one surface of the flat steel product, a Zn coating is applied by hot-dip coating. Also a method for producing a flat steel product of this kind.

An aspect of the present invention relates to a cold-rolled steel plate for hot forming, which is excellent in corrosion-resistance and spot-weldability, contains, by weight %, C: 0.1-0.4%, Si: 0.5-2.0%, Mn: 0.01-4.0%, Al:

0.001-0.4%, P: 0.001-0.05%, S: 0.0001-0.02%, Cr: 0.5% to less than 3.0%, N: 0.001-0.02%, and a balance of Fe and inevitable impurities, satisfying formula (1) below, and includes an Si amorphous oxidation layer continuously or discontinuously formed at a thickness of 1 nm-100 nm on the surface thereof. Formula (1): 1.4≤0.4*Cr+Si≤3.2 (wherein element symbols denote measurements of respective element contents by weight

An aspect of the present invention relates to a cold-rolled steel plate for hot forming, which is excellent in corrosion-resistance and spot-weldability, contains, by weight %, C: 0.1-0.4%, Si: 0.5-2.0%, Mn: 0.01-4.0%, Al:

0.001-0.4%, P: 0.001-0.05%, S: 0.0001-0.02%, Cr: 0.5% to less than 3.0%, N: 0.001-0.02%, and a balance of Fe and inevitable impurities, satisfying formula (1) below, and includes an Si amorphous oxidation layer continuously or discontinuously formed at a thickness of 1 nm-100 nm on the surface thereof. Formula (1): 1.4≤0.4*Cr+Si≤3.2 (wherein element symbols denote measurements of respective element contents by weight

The invention relates to a surface-hardened, rotationally symmetrical workpiece, to a hardening method and to a hardening apparatus. The proposed hardening apparatus comprises a machine frame on which two coaxially arranged rotary bearings designed to support a rotationally symmetrical workpiece are arranged, at least one rotary bearing being operatively connected to a drive device to generate rotation of the workpiece; and at lease one laser apparatus for generating focussed, high-energy radiation is arranged on said rotary bearing, said laser apparatus being movable in the axial direction, and the radiation being directed toward the workpiece.

The invention relates to a surface-hardened, rotationally symmetrical workpiece, to a hardening method and to a hardening apparatus. The proposed hardening apparatus comprises a machine frame on which two coaxially arranged rotary bearings designed to support a rotationally symmetrical workpiece are arranged, at least one rotary bearing being operatively connected to a drive device to generate rotation of the workpiece; and at lease one laser apparatus for generating focussed, high-energy radiation is arranged on said rotary bearing, said laser apparatus being movable in the axial direction, and the radiation being directed toward the workpiece.

A method is used to fabricate a hot-rolled steel having a yield strength greater than 550 MPa and an impact toughness of at least 27 J at a temperature of -40° F. In one embodiment, the yield strength is greater than 690 MPa. The method includes melting steel to create melted steel. The melted steel is poured into a mold. The metal steel is continuously cast into a steel slab. The steel slab is heated to maintain a predetermined temperature. The steel slab is rolled to reduce the thickness to a predetermined thickness to create a hot-rolled steel sheet.

A method is used to fabricate a hot-rolled steel having a yield strength greater than 550 MPa and an impact toughness of at least 27 J at a temperature of -40° F. In one embodiment, the yield strength is greater than 690 MPa. The method includes melting steel to create melted steel. The melted steel is poured into a mold. The metal steel is continuously cast into a steel slab. The steel slab is heated to maintain a predetermined temperature. The steel slab is rolled to reduce the thickness to a predetermined thickness to create a hot-rolled steel sheet.