Process control of intense stirring along a solidification front and adjustments in casting speeds during direct chill casting of 7xxx series alloys can decrease an ingot’s cracking susceptibility. Intense stirring control is used to reduce the thickness of the solidification front, promote agglomeration of hydrogen gas rejected at the solidification front, remove impurities rejected at the solidification front, and improve grain size. Intense stirring control is used to operate at faster casting speeds without risk of increasing the thickness of the solidification front. Optional reheating during casting to promote dispersoid formation is used to generate a high-strength zone of dispersoid-strengthened solidified metal in the outer periphery of the ingot, which can further decrease the ingot’s susceptibility to cracking.

A continuously casting method including arranging temperature measuring elements according to specified conditions, selecting as evaluation targets for temperatures of copper plates on a wide face of mold values measured by the temperature measuring elements arranged closer to a center in a width direction of a cast slab than short sides of the cast slab under continuous casting at levels of 50 mm or more lower in a slab withdrawal direction than a meniscus of a molten steel in a mold, and adjusting a casting condition such that a standard deviation of the values measured over the width direction of the copper plates on the wide face of mold at a same level in the slab withdrawal direction is 20° C. or lower.

A steel sheet having a specified chemical composition and a tensile strength of 1,320 MPa or more, and methods for producing the steel sheet. The steel sheet has a specified microstructure including martensite and bainite, the total area fraction of the martensite and the bainite being 95% or more and 100% or less, the balance being one or more selected from ferrite and retained austenite. The forumulae [% Ti]+[% Nb]>0.007 and [% Ti]×[% Nb].sup.2≤7.5×10.sup.−6 are satisfied in the chemical composition.

Disclosed is a light reduction method for continuous casting of a bloom plain-barrelled roll-roll combination. The method comprises: firstly obtaining three-dimensional temperature field profile, a two-phase region, solid-phase region thickness, and solid-phase fraction of a billet, determining positions of start and end rolls of the reduction, and setting a reduction amount of each tensioner roll according to the volume shrinkage of the billet; in an interval f.sub.s=0.9-1.0 of the solid-phase fraction of the billet, performing a heavy reduction working mode; and in an interval f.sub.s=0.25-0.80 of the solid-phase fraction of the billet, performing a light reduction working mode.

A method for casting longitudinal cast products including casting longitudinal cast products in a semi-continuous manner using a DC casting apparatus having a mold, wherein the mold has top and bottom openings and partially solidifies molten metal that enters into the mold via the top opening and outputs the cast product via the bottom opening, recording a thermal image of the cast product output via the bottom opening, determining at least three non-overlapping temperature ranges comprising a first, second and third, determining a peak temperature in the thermal image; comparing the peak temperature with the at least three temperature ranges; and performing operations depending on where the peak temperature falls within the at least three temperature ranges.

A continuously casting method including arranging temperature measuring elements according to specified conditions, selecting as evaluation targets for temperatures of copper plates on a wide face of mold values measured by the temperature measuring elements arranged closer to a center in a width direction of a cast slab than short sides of the cast slab under continuous casting at levels of 50 mm or more lower in a slab withdrawal direction than a meniscus of a molten steel in a mold, and adjusting a casting condition such that a standard deviation of the values measured over the width direction of the copper plates on the wide face of mold at a same level in the slab withdrawal direction is 20° C. or lower.

A method for casting longitudinal cast products including casting longitudinal cast products in a semi-continuous manner using a DC casting apparatus having a mold, wherein the mold has top and bottom openings and partially solidifies molten metal that enters into the mold via the top opening and outputs the cast product via the bottom opening, recording a thermal image of the cast product output via the bottom opening, determining at least three non-overlapping temperature ranges comprising a first, second and third, determining a peak temperature in the thermal image; comparing the peak temperature with the at least three temperature ranges; and performing operations depending on where the peak temperature falls within the at least three temperature ranges.

Disclosed is a light reduction method for continuous casting of a bloom plain-barrelled roll-roll combination. The method comprises: firstly obtaining three-dimensional temperature field profile, a two-phase region, solid-phase region thickness, and solid-phase fraction of a billet, determining positions of start and end rolls of the reduction, and setting a reduction amount of each tensioner roll according to the volume shrinkage of the billet; in an interval f.sub.s=0.9-1.0 of the solid-phase fraction of the billet, performing a heavy reduction working mode; and in an interval f.sub.s=0.25-0.80 of the solid-phase fraction of the billet, performing a light reduction working mode.

A system for detection of the level of a liquid metal within a crystallizer of a mold has a detection system. The detection system is based on a transmission of at least one signal transmitted toward a crystallizer having the liquid metal therein and a reception of a reflection of the transmitted signal. A first ultrasonic element transmits a ultrasonic elastic wave and a second ultrasonic element receives the ultrasonic elastic wave. A processor measures a time elapsed between transmission and reception and correlates the elapsed time relative to the level of liquid metal in the crystallizer.

Disclosed is a continuous casting ingot mold for metals, of the type made of an assembly of metal plates mounted against cooling devices configured to allow cooling of the metal plates by the circulation of a liquid coolant. Said ingot mold comprises an optical fiber with a diameter greater than 1.6 mm, having a plurality of fiber Bragg grating filters and extending in a wall of at least one of said plates in a direction that is not parallel to the axis of casting of the ingot mold.