Provided are lean duplex stainless steel having a dual-phase structure of an austenite phase and a ferrite phase, and a method for producing the lean duplex stainless steel. The lean duplex stainless steel, as a ferrite-austenite stainless steel, has the preferred stacking fault energy (SFE) value of the austenite phase, expressed by the formula 2 below, of 19-37 and critical strain value range, within which the strain-induced martensite phases occurs, of 0.1−0.25. Formula 2: SFE=25.7+1.59×Ni/[K(Ni)−K(Ni)×V(γ)+V(γ)]+0.795×Cu/[K(Cu)−K(Cu)×V(γ)+V(γ)]−0.85×Cr/[K(Cr)−K(Cr)×V(γ)+V(γ)]+0.001×(Cr/[K(Cr)−K(Cr)×V(γ)+V(γ)]).sup.2+38.2×(N/[K(N)−K(N)×V(γ)+V(γ)]).sup.0.5−2.8×Si/[K(Si)−K(Si)×V(γ)+V(γ)]−1.34×Mn/[K(Mn)−K(Mn)×V(γ)+V(γ)]+0.06×(Mn/[K(Mn)−K(Mn)×V(γ)+V(γ)]).sup.2. Ni, Cu, Cr, N, Si and Mn indicate the overall content (wt. %) of the respective constituent element, and K(x) is the distribution index of respective constituent element (x) and is expressed by the formula 3 below, and V(γ) is the component ratio of austenite (in the 0.45-0.75 range). Formula 3: K(x)=[amount of element x in ferrite phase]/[amount of element x in austenite phase]

Provided are lean duplex stainless steel having a dual-phase structure of an austenite phase and a ferrite phase, and a method for producing the lean duplex stainless steel. The lean duplex stainless steel, as a ferrite-austenite stainless steel, has the preferred stacking fault energy (SFE) value of the austenite phase, expressed by the formula 2 below, of 19-37 and critical strain value range, within which the strain-induced martensite phases occurs, of 0.1−0.25. Formula 2: SFE=25.7+1.59×Ni/[K(Ni)−K(Ni)×V(γ)+V(γ)]+0.795×Cu/[K(Cu)−K(Cu)×V(γ)+V(γ)]−0.85×Cr/[K(Cr)−K(Cr)×V(γ)+V(γ)]+0.001×(Cr/[K(Cr)−K(Cr)×V(γ)+V(γ)]).sup.2+38.2×(N/[K(N)−K(N)×V(γ)+V(γ)]).sup.0.5−2.8×Si/[K(Si)−K(Si)×V(γ)+V(γ)]−1.34×Mn/[K(Mn)−K(Mn)×V(γ)+V(γ)]+0.06×(Mn/[K(Mn)−K(Mn)×V(γ)+V(γ)]).sup.2. Ni, Cu, Cr, N, Si and Mn indicate the overall content (wt. %) of the respective constituent element, and K(x) is the distribution index of respective constituent element (x) and is expressed by the formula 3 below, and V(γ) is the component ratio of austenite (in the 0.45-0.75 range). Formula 3: K(x)=[amount of element x in ferrite phase]/[amount of element x in austenite phase]

To achieve a substantially uniform microstructure across a continuously cast thin metal strip, it is beneficial to cool a width of the strip to a substantially constant temperature before further cooling the strip to reach any desired phase transformation temperature. Accordingly, methods of continuously casting a thin metal strip may include moving the thin strip to a cooling section, the cooling section having a plurality of coolant discharge ports configured to discharge a flow of coolant along the thin strip; initially sensing the temperature of the thin strip to determine a temperature distribution across the width of the thin strip, and producing a sensor signal corresponding to a sensed temperature at each of the first plurality of locations; and individually controlling the cooling across a width of the thin strip by way of the plurality coolant discharge ports in each zone of a first row using the determined temperature distribution.

A method of casting a metal ingot with a microstructure that facilitates further working, such as hot and cold rolling. The metal is cast in a direct chill casting mold, or the equivalent, that directs a spray of coolant liquid onto the outer surface of the ingot to achieve rapid cooling. The coolant is removed from the surface at a location where the emerging embryonic ingot is still not completely solid, such that the latent heat of solidification and the sensible heat of the molten core raises the temperature of the adjacent solid shell to a convergence temperature that is above a transition temperature for in-situ homogenization of the metal. A further conventional homogenization step is then not required. The invention also relates to the heat-treatment of such ingots prior to hot working.

A method of casting a metal ingot with a microstructure that facilitates further working, such as hot and cold rolling. The metal is cast in a direct chill casting mold, or the equivalent, that directs a spray of coolant liquid onto the outer surface of the ingot to achieve rapid cooling. The coolant is removed from the surface at a location where the emerging embryonic ingot is still not completely solid, such that the latent heat of solidification and the sensible heat of the molten core raises the temperature of the adjacent solid shell to a convergence temperature that is above a transition temperature for in-situ homogenization of the metal. A further conventional homogenization step is then not required. The invention also relates to the heat-treatment of such ingots prior to hot working.

A material-property-value estimating method of estimating a material-property-value of a target steel-strip product manufactured via at least one of a reheating process, a rolling process, and a cooling process, which are performed while a target material is being conveyed along a conveyance route, the material-property-value estimating method includes an estimating step of estimating a material-property-value of each of meshes dividing the target steel-strip product based on a measured value that has been measured once or more by a measuring device installed on the conveyance route, the measured value including at least a temperature of the target material; and a chemical composition per component of the target steel-strip product.

A material-property-value estimating method of estimating a material-property-value of a target steel-strip product manufactured via at least one of a reheating process, a rolling process, and a cooling process, which are performed while a target material is being conveyed along a conveyance route, the material-property-value estimating method includes an estimating step of estimating a material-property-value of each of meshes dividing the target steel-strip product based on a measured value that has been measured once or more by a measuring device installed on the conveyance route, the measured value including at least a temperature of the target material; and a chemical composition per component of the target steel-strip product.

In this cast strip manufacturing method, in a first step, one end side and another end side in a rotation axis direction of a pair of cooling drums are pressed with a first pressure in a direction in which the cooling drums come close to each other, in a second step, the one end side and the another end side in the rotation axis direction of the cooling drums are pressed with a second pressure, which is higher than the first pressure, in the direction in which the cooling drums come close to each other, and in a third step, pressure control is performed so that a total value of reaction forces on the one end side and the another end side in the rotation axis direction of the cooling drums is set to a predetermined value, and rotation axes of the cooling drums are held in parallel.

In this cast strip manufacturing method, in a first step, one end side and another end side in a rotation axis direction of a pair of cooling drums are pressed with a first pressure in a direction in which the cooling drums come close to each other, in a second step, the one end side and the another end side in the rotation axis direction of the cooling drums are pressed with a second pressure, which is higher than the first pressure, in the direction in which the cooling drums come close to each other, and in a third step, pressure control is performed so that a total value of reaction forces on the one end side and the another end side in the rotation axis direction of the cooling drums is set to a predetermined value, and rotation axes of the cooling drums are held in parallel.

Disclosed are an electromagnetic stirring device and a method for a secondary cooling zone during slab continuous casting. The device comprises an electromagnetic stirring device main body comprising a protection housing (3), a phase sequence control assembly, an iron core (4) and an electromagnetic coil (5) for carrying out variable-direction electromagnetic stirring on molten steel by means of three-phase current phase sequence transformation; an opening adjustment assembly comprising an air cylinder (7), a fixed base (8), a movable joint shaft (12) and a silicon steel sheet group insert (13) for adjusting online the opening degree of the closed annular iron core by means of a movable joint structure; and the secondary cooling assembly comprising a cooling water inlet (9) and a cooling water nozzle (10) for cooling the electromagnetic coil and spraying cooling water to a surface of a cast slab (1).