Process for the production of a strip of a chromium stainless steel of a duplex structure having high strength and elongation as well as reduced plane antisotropy

Claim 2

A process for the production of a strip of a chromium stainless steel of a duplex structure, consisting essentially of ferrite and martensite, having high strength and elongation as well as reduced plane anisotropy and having a hardness of at least HV 200, which process comprises: a step of hot rolling a slab of a steel to provide a hot rolled strip, said steel comprising, by weight, from 10.0% to 20.0% of Cr, up to 0.15% of C, up to 0.12% of N, the (C+N) being not less than 0.02% but not more than 0.20%, up to 2.0% of Si, up to 1.0% of Mn and up to 0.6% of Ni, the balance being Fe and unavoidable impurities; a step of cold rolling the hot rolled strip to provide a cold rolled strip of a desired thickness; and a step of continuous final heat treatment in which the cold rolled strip is continuously passed through a heating zone where it is heated to a temperature ranging from the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite and maintained at that temperature for not longer than 10 minutes, and the heated strip is cooled at a cooling rate sufficient to transform the austenite to martensite.

Claim 3

The process in accordance with claim 1 wherein in said continuous heat treatment step the cold rolled strip is heated to a temperature ranging from at least 100° C. above the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite.

Claim 4

The process in accordance with claim 1 wherein in said continuous heat treatment step the cold rolled strip is heated to a temperature ranging from 900° C. to 1100° C. to form a two-phase of ferrite and austenite.

Claim 5

The process in accordance with claim 1 wherein in said steel employed consists essentially of, by weight,: up to 0.10% of C, up to 2.0% of Si, up to 1.0% of Mn, up to 0.040% of P, up to 0.030% of S, up to 0.60% of Ni, from 10.0% to 14.0% of Cr, up to 0.08% of N, the (C+N) being not less than 0.02% but not more than 0.12%, up to 0.02% of O, up to 0.20% of Al, up to 0.0050% of B, up to 2.5% of Mo, up to 0.10% of REM, and up to 0.20% of Y, the balance being Fe and unavoidable impurities.

Claim 6

The process in accordance with claim 1 wherein in said steel employed consists essentially of, by weight,: up to 0.15% of C, up to 2.0% of Si, up to 1.0% of Mn, up to 0.040% of P, up to 0.030% of S, up to 0.60% of Ni, more than 14.0% to 20.0% of Cr, up to 0.12% of N, the (C+N) being not less than 0.03% but not more than 0.20%, up to 0.02% of O, up to 0.20% of Al, up to 0.0050% of B, up to 2.5% of Mo, up to 0.10% of REM, and up to 0.20% of Y, the balance being Fe and unavoidable impurities.

Claim 7

A process for the production of a strip of a chromium stainless steel of a duplex structure, consisting essentially of ferrite and martensite, having high strength and elongation as well as reduced plane anisotropy and having a hardness of at least HV 200, which process comprises: a step of hot rolling a slab of a steel to provide a hot rolled strip, said steel consisting essentially of, by weight,: up to 0.10% of C, up to 2.0% of Si, up to 1.0% of Mn, up to 0.040% of P, up to 0.030% of S, up to 0.60% of Ni, from 10.0% to 14.0% of Cr, up to 0.08% of N, the (C+N) being not less than 0.02% but not more than 0.12%, up to 0.02% of O, up to 0.20% of Al, up to 0.0050% of B, up to 2.5% of Mo, up to 0.10% of REM, and up to 0.20% of Y, the balance being Fe and unavoidable impurities; at least two steps of cold rolling the hot rolled strip to provide a cold rolled strip of a desired thickness, including a step of intermediate annealing between the successive two cold rolling steps, said intermediate annealing comprising heating and maintaining the strip at a temperature to form a single phase of ferrite; and a step of continuous final heat treatment in which the cold rolled strip is continuously passed through a heating zone where it is heated to a temperature ranging from the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite and maintained at that temperature for not longer than 10 minutes, and the heated strip is cooled at a cooling rate sufficient to transform the austenite to martensite.

Claim 8

A process for the production of a strip of a chromium stainless steel of a duplex structure, consisting essentially of ferrite and martensite, having high strength and elongation as well as reduced plane anisotropy and having a hardness of at least HV 200, which process comprises: a step of hot rolling a slab of a steel to provide a hot rolled strip, said steel consisting essentially of, by weight,: up to 0.10% of C, up to 2.0% of Si, up to 1.0% of Mn, up to 0.040% of P, up to 0.030% of S, up to 0.60% of Ni, from 10.0% to 14.0% of Cr, up to 0.08% of N, the (C+N) being not less than 0.02% but not more than 0.12%, up to 0.02% of O, up to 0.20% of Al, up to 0.0050% of B, up to 2.5% of Mo, up to 0.10% of REM, and up to 0.20% of Y, the balance being Fe and unavoidable impurities; at least two steps of cold rolling the hot rolled strip to provide a cold rolled strip of a desired thickness, including a step of intermediate annealing between the successive two cold rolling steps, said intermediate annealing comprising heating and maintaining the strip at a temperature to form a single phase of ferrite; and a step of continuous final heat treatment in which the cold rolled strip is continuously passed through a heating zone where it is heated to a temperature ranging from the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite and maintained at that temperature for not longer than 10 minutes, and the heated strip is cooled at a cooling rate sufficient to transform the austenite to martensite.

Claim 9

The process in accordance with claim 6 wherein in said continuous heat treatment step the cold rolled strip is heated to a temperature ranging from at least 100° C. above the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite.

Claim 10

The process in accordance with claim 6 wherein in said continuous heat treatment step the cold rolled strip is heated to a temperature ranging from 900° C. to 1100° C. to form a two-phase of ferrite and austenite.

Claim 11

A process for the production of a strip of a chromium stainless steel of a duplex structure, consisting essentially of ferrite and martensite, having high strength and elongation as well as reduced plane anisotropy and having a hardness of at least HV 200, which process comprises: a step of hot rolling a slab of a steel to provide a hot rolled strip, said steel consisting essentially of, by weight,: up to 0.15% of C, up to 2.0% of Si, up to 1.0% of Mn, up to 0.040% of P, up to 0.030% of S, up to 0.60% of Ni, more than 14.0% to 20.0% of Cr, up to 0.12% of N, the (C+N) being not less than 0.03% but not more than 0.20%, up to 0.02% of O, up to 0.20% of Al, up to 0.0050% of B, up to 2.5% of Mo, up to 0.10% of REM, and up to 0.20% of Y, the balance being Fe and unavoidable impurities; at least two steps of cold rolling the hot rolled strip to provide a cold rolled strip of a desired thickness, including a step of intermediate annealing between the successive two cold rolling steps, said intermediate annealing comprising heating and maintaining the strip at a temperature to form a single phase of ferrite; and a step of continuous final heat treatment in which the cold rolled strip is continuously passed through a heating zone where it is heated to a temperature ranging from the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite and maintained at that temperature for not longer than 10 minutes, and the heated strip is cooled at a cooling rate sufficient to transform the austenite to martensite.

Claim 12

A process for the production of a strip of a chromium stainless steel of a duplex structure, consisting essentially of ferrite and martensite, having high strength and elongation as well as reduced plane anisotropy and having a hardness of at least HV 200, which process comprises: a step of hot rolling a slab of a steel to provide a hot rolled strip, said steel consisting essentially of, by weight,: up to 0.15% of C, up to 2.0% of Si, up to 1.0% of Mn, up to 0.040% of P, up to 0.030% of S, up to 0.60% of Ni, more than 14.0% to 20.0% of Cr, up to 0.12% of N, the (C+N) being not less than 0.03% but not more than 0.20%, up to 0.02% of O, up to 0.20% of Al, up to 0.0050% of B, up to 2.5% of Mo, up to 0.10% of REM, and up to 0.20% of Y, the balance being Fe and unavoidable impurities; at least two steps of cold rolling the hot rolled strip to provide a cold rolled strip of a desired thickness, including a step of intermediate annealing between the successive two cold rolling steps, said intermediate annealing comprising heating and maintaining the strip at a temperature to form a single phase of ferrite; and a step of continuous final heat treatment in which the cold rolled strip is continuously passed through a heating zone where it is heated to a temperature ranging from the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite and maintained at that temperature for not longer than 10 minutes, and the heated strip is cooled at a cooling rate sufficient to transform the austenite to martensite.

Claim 13

The process in accordance with claim 9 wherein in said continuous heat treatment step the cold rolled strip is heated to a temperature ranging from at least 100° C. above the Ac1 point of the steel to 1100° C. to form a two-phase of ferrite and austenite.

Claim 14

The process in accordance with claim 9 wherein in said continuous heat treatment step the cold rolled strip is heated to a temperature ranging from 900° to 1100° C. to form a two-phase of ferrite and austenite.