A method and apparatus for treating a workpiece such as a mold grid includes moving the workpiece laterally along a conveyor assembly into a furnace for heating in a carbon-rich atmosphere to form a heated workpiece. The heated workpiece is then received from the furnace onto the conveyor assembly in an enclosed vestibule whereupon it is clamped under pressure between an overhead mechanical press and the conveyor assembly to form a clamped assembly. The clamped assembly, including a portion of the conveyor, is then lowered into a quenching bath via an elevator assembly until the heated workpiece is quenched, whereupon the clamped assembly is raised out of the bath and the clamping force released. This clamping during quenching acts to maintain the workpiece in a planar orientation while reducing warpage during the quenching process.

A spring induction heater assembly is shown and described. The device has a quench tank incorporated into the design. A motor and drive mechanism provide rotation of a spring about one axis from a first position used for loading, to a second position for heat treatment with an induction coil and a third position where the spring is released dropped into a quench tank. Another rotational system is operational to rotate the spring on a spindle in the second or horizontal position while the spring is located between at least two legs of an induction coil. The induction coil provides even heating to the spring coils thereby providing desired changes to the material properties. The quench tank can have an automated system to remove the springs from the quench tank.

A spring induction heater assembly is shown and described. The device has a quench tank incorporated into the design. A motor and drive mechanism provide rotation of a spring about one axis from a first position used for loading, to a second position for heat treatment with an induction coil and a third position where the spring is released dropped into a quench tank. Another rotational system is operational to rotate the spring on a spindle in the second or horizontal position while the spring is located between at least two legs of an induction coil. The induction coil provides even heating to the spring coils thereby providing desired changes to the material properties. The quench tank can have an automated system to remove the springs from the quench tank.

The steel sheet of the present invention has a steel microstructure containing, in area fraction, martensite: from 20% to 100%, ferrite: from 0% to 80%, and another metal phase: 5% or less, and in which a ratio of a dislocation density in metal phases on a surface of the steel sheet to a dislocation density in the metal phases in a thicknesswise central portion of the steel sheet is from 30% to 80%. The maximum amount of warpage of the steel sheet when the steel sheet is sheared to a length of 1 m in a rolling direction is 15 mm or less.

The steel sheet of the present invention has a steel microstructure containing, in area fraction, martensite: 20% to 100%, ferrite: 0% to 80%, and another metal phase: 5% or less, in which, on a surface of the steel sheet, a ratio of dislocation density in metal phases at a widthwise edge of the steel sheet to dislocation density in the metal phases at a widthwise center of the steel sheet is 100% to 140%, and, at a thicknesswise center of the steel sheet, a ratio of dislocation density in the metal phases at the widthwise edge of the steel sheet to dislocation density in the metal phases at the widthwise center of the steel sheet is 100% to 140%. The maximum amount of warpage of the steel sheet when the steel sheet is sheared to a length of 1 m in a rolling direction is 15 mm or less.

The steel material according to the present disclosure has a chemical composition consisting of, in mass %, C: 0.20 to 0.35%, Si: 0.05 to 1.00%, Mn: 0.01 to 1.00%, P: 0.025% or less, S: 0.0100% or less, Al: 0.005 to 0.100%, Cr 0.25 to 0.80%, Mo: 0.20 to 2.00%, Ti: 0.002 to 0.050%, B: 0.0001 to 0.0050%, N: 0.0020 to 0.0100% and O: 0.0100% or less, with the balance being Fe and impurities, and satisfying Formula (1). A number density of precipitates having an equivalent circular diameter of 400 nm or more is 0.150 particles/μm.sup.2 or less. The yield strength is within a range of 655 to 965 MPa. A dislocation density ρ is 7.0×10.sup.14 m.sup.−2 or less.
5×Cr—Mo-2×(V+Ti)≤3.00  (1)

The multi-chamber heat treatment device includes intermediate conveyors connected together, each treatment conveyor of the intermediate conveyors is attached with a treater that applies predetermined heat treatment to a treatment object and conveys the treatment object to the treater, and each treater is either one of a main treater that applies main treatment to the treatment object, a preheater that applies preheating treatment to the treatment object before the main treatment, and a cooler that applies cooling treatment to the treatment object after the main treatment.

A device for heating and quenching a tubular member has a central axis. The device includes a first quenching ring, a second quenching ring axially spaced from the first quenching ring, and a heating ring axially positioned between the first quenching ring and the second quenching ring. Each quenching ring and the heating ring is configured to receive the tubular member. The heating ring is fixably coupled to the first quenching ring and the second quenching ring. The heating ring includes an induction coil configured to heat an annular target zone along the tubular member. The first quenching ring is configured to deliver a first quenching fluid to the target zone and a first annular heat affected zone along the tubular member, and the second quenching ring is configured to deliver a second quenching fluid to the target zone and a second annular heat affected zone along the tubular member.

A device for heating and quenching a tubular member has a central axis. The device includes a first quenching ring, a second quenching ring axially spaced from the first quenching ring, and a heating ring axially positioned between the first quenching ring and the second quenching ring. Each quenching ring and the heating ring is configured to receive the tubular member. The heating ring is fixably coupled to the first quenching ring and the second quenching ring. The heating ring includes an induction coil configured to heat an annular target zone along the tubular member. The first quenching ring is configured to deliver a first quenching fluid to the target zone and a first annular heat affected zone along the tubular member, and the second quenching ring is configured to deliver a second quenching fluid to the target zone and a second annular heat affected zone along the tubular member.

A cold rolled steel flat product for packaging made of a low carbon steel having a thickness of less than 0.49 mm and a method of making. The steel flat product has a martensite-free microstructure and represents a standard grade for packaging with tensile strengths from 300 to 550 MPa, which can be produced from a cold-rolled steel sheet with a carbon content from 0.01% to 0.1% by weight by inductive annealing of the steel sheet and subsequent water cooling for quenching the recrystallization-annealed steel sheet. To achieve flatness of 5 I-units or less, the induction annealed steel sheet is first primarily cooled in the manufacturing process to a take-off temperature at a rate of less than 1000 K/s, with the take-off temperature being below the transformation temperature of 723° C., and thereafter a secondary cooling by water cooling with a water temperature of less than 80° C. at a rate of more than 1000 K/s.