Free-cutting steel includes a specific composition, with an A value defined by a following formula (1) satisfying 4.0 or more and 20.0 or less, and remainder having Fe and an unavoidable impurity; and texture with 1000 or more sulfide particles with an equivalent circle diameter of less than 1 m per mm.sup.2, 500 or more sulfide particles with an equivalent circle diameter of 1 m or more and 5 m or less per mm.sup.2, and 1000 or more Pb particles with an equivalent circle diameter of 1 m or less per mm.sup.2, wherein
A value=(Mn+5Cr)/S(1) here, symbols of elements in the formula indicate contents (% by mass) of the elements.

Free-cutting steel includes a specific composition, with an A value defined by a following formula (1) satisfying 4.0 or more and 20.0 or less, and remainder having Fe and an unavoidable impurity; and texture with 1000 or more sulfide particles with an equivalent circle diameter of less than 1 m per mm.sup.2, 500 or more sulfide particles with an equivalent circle diameter of 1 m or more and 5 m or less per mm.sup.2, and 1000 or more Pb particles with an equivalent circle diameter of 1 m or less per mm.sup.2, wherein
A value=(Mn+5Cr)/S(1) here, symbols of elements in the formula indicate contents (% by mass) of the elements.

A method for heating at least one semi-finished metal products to be further laminated, via a heat exchanging device comprising a chamber containing solid particles, supporting means able to support semi-finished metal product and a gas injector, having the successive steps of: i. injecting a gas into said chamber so as to form a fluidized bed, ii. inserting at least one hot semi-finished metal product such that said at least one hot semi-finished metal product is able to transfer heat to said fluidized bed, iii. inserting said at least one semi-finished metal product to be further laminated such that said fluidized bed is able to transfer heat to said at least one semi-finished metal product to be further laminated, iv. taking out said at least one semi-finished metal product to be further laminated of said fluidized bed when the temperature of said at least one semi-finished metal product to be further laminated is less than 100 C. below the temperature of said fluidized bed.

A steel, particularly as steel sheet, having the following composition: 0.02-0.1% by weight of carbon; 0.01-0.1% by weight of silicon; 0.60-2.00% by weight of manganese; >0 and 0.01% by weight of aluminum; 0.01-0.30% by weight of copper; 0.01-0.60% by weight of nickel; 0.01-0.30% by weight of chromium; 0.005-0.050% by weight of niobium; 0.005-0.050% by weight of titanium; 0.0005-0.0050% by weight of sulfur; 0.001-0.005% by weight of calcium; 0.0050% by weight of oxygen; 0.010% by weight of nitrogen; 0.02% by weight of phosphorus; 0-0.0050% by weight of magnesium; 0-0.0060% by weight of Vanadium; 0-0.15% by weight of molybdenum; and balance: iron and production-related impurities, and a process for production and a method of processing the steel.

Disclosed is a skew rolling assembly suitable for large-size superalloy bars, including four rollers with completely identical shape and size, where the four rollers are all active rollers. In the production process, the four rollers play a role in promoting the forward flow of blank metal in a rolling direction, thus avoiding a rolling jamming phenomenon caused by the obstruction of guide plates to the forward flow of the blank in the rolling process of the prior art. The providing of the four rollers improves the rolling speed and increases the degree of deformation. Disclosed is a skew rolling method suitable for large-size superalloy bars. By utilizing the skew rolling assembly suitable for the large-size superalloy bars, and utilizing four rotating active rollers for the skew-rolling forming of bars, the rolling speed is improved, the problem that the cooperative rolling of two rollers and guide plates in the prior art is prone to the phenomenon of rolling jamming is avoided, the forming quality is guaranteed, the rolling production efficiency is improved, and the degree of deformation is increased.

This hot-rolled steel sheet has a predetermined chemical composition, and in a case where the thickness is denoted by t, the metallographic structure at a t/4 position from the surface contains one or both of tempered martensite and lower bainite at a volume percentage of 90% or more, the tensile strength is 980 MPa or more, and the average Ni concentration on the surface is 7.0% or more.

This hot-rolled steel sheet has a predetermined chemical composition, and in a case where the thickness is denoted by t, the metallographic structure at a t/4 position from the surface contains one or both of tempered martensite and lower bainite at a volume percentage of 90% or more, the tensile strength is 980 MPa or more, and the average Ni concentration on the surface is 7.0% or more.

The billet rolling mill comprises two rolls for shaping a blank, each shaping roll being provided with at least one rolling tool and being rotated about an axis of rotation by a drive motor, and a manipulator subassembly for moving the blank with respect to the shaping rolls. The manipulator subassembly comprises a clamp gripping the blank and a carriage moving the clamp at least along a direction of rolling of the blank. The manipulator subassembly comprises a linear motor moving the carriage along the direction of rolling. The direction of rolling is perpendicular to the axis of rotation of the rolling tool. The linear motor is configured for accelerating the blank and selectively exerting on the blank, either a tensile force, to extract the blank from a gap defined between the rolling tools, or a braking force, to limit a speed of ejection of the blank.

The billet rolling mill comprises two rolls for shaping a blank, each shaping roll being provided with at least one rolling tool and being rotated about an axis of rotation by a drive motor, and a manipulator subassembly for moving the blank with respect to the shaping rolls. The manipulator subassembly comprises a clamp gripping the blank and a carriage moving the clamp at least along a direction of rolling of the blank. The manipulator subassembly comprises a linear motor moving the carriage along the direction of rolling. The direction of rolling is perpendicular to the axis of rotation of the rolling tool. The linear motor is configured for accelerating the blank and selectively exerting on the blank, either a tensile force, to extract the blank from a gap defined between the rolling tools, or a braking force, to limit a speed of ejection of the blank.

The present disclosure relates to an extremely thick steel material for a flange having excellent strength and low-temperature impact toughness, and a method of manufacturing the same.