Described is a method of modifying material properties of a workpiece using a high-pressure-torsion apparatus, comprising a working axis, a first anvil, a second anvil, and an annular body, comprising a first conductive chiller, a second conductive chiller, and a heater, positioned between the first conductive chiller and the second conductive chiller along the working axis. The method comprises compressing the workpiece along a central axis of the workpiece and, simultaneously with compressing the workpiece alone the central axis, twisting the workpiece about the central axis. The method further comprises, while compressing the workpiece along the central axis and twisting the workpiece about the central axis, translating the annular body along the working axis of the high-pressure-torsion apparatus, collinear with the central axis of the workpiece, and heating the workpiece with the heater.

Steel according to one embodiment of the present invention has predetermined chemical components, wherein in a region where a distance r from the center of a cross-section perpendicular to the length direction satisfies 0.7Rr0.9R, structures include ferrite and bainite, the average fraction of the ferrite is in the range of 40 to 70% in terms of area ratio, the total average fraction of the structures other than the ferrite and the bainite is 0% or more and 3% or less on average, and the balance includes bainite; and the standard deviation of a ferrite fraction in the region is 4% or less.

Embodiments of an ultra-fine-grained, medium carbon steel are disclosed herein. In some embodiments, the ultra-fine grained steel can have high corrosion fatigue resistance, as well as high toughness and yield strength. The ultra-fine grained steels can be advantageous for use as sucker rods in oil wells having corrosive environments.

When a rod-shaped workpiece (W) having an outer peripheral surface with a circular cross section is inductively heated to a quenching temperature while being conveyed at a predetermined velocity along an axial direction of the rod-shaped workpiece (W), the rod-shaped workpiece (W) being currently conveyed is heated to a predetermined temperature equal to or lower than the quenching temperature by a first heating coil (2A), which is electrically connected to a first high-frequency power supply (3) and has a constant output. Then, the rod-shaped workpiece (W) being currently conveyed is heated so as to be maintained at the quenching temperature by a second heating coil (2B), which is electrically connected to a second high-frequency power supply (4) and has a constant output.

Provided is a method for manufacturing a magnetostrictive torque sensor shaft mounting a sensor portion of a magnetostrictive torque sensor. The method includes conducting heat treatment on a shaft material including chrome steel or chrome-molybdenum steel by carburizing, quenching and tempering, and conducting shot peening on the shaft material after the heat treatment at least on a position where the sensor portion is to be mounted. The shot peening is conducted by firing shot with a particle size of not less than 0.6 mm and a Rockwell hardness of not less than 60 at a jet pressure of not less than 0.4 MPa for a jet exposure time of not less than 2 minutes.

A forged component having a chemical composition including, by mass %, C: 0.30 to 0.45%, Si: 0.05 to 0.35%, Mn: 0.50 to 0.90%, P: 0.030 to 0.070%, S: 0.040 to 0.070%, Cr: 0.01 to 0.50%, Al: 0.001 to 0.050%, V: 0.25 to 0.35%, Ca: 0 to 0.0100%, N: 0.0150% or less, and the balance being Fe and unavoidable impurities, and satisfying formula 1. Metal structure is a ferrite pearlite structure, and a ferrite area ratio is 30% or more. Vickers hardness is in the range of 320 to 380 HV. 0.2% yield strength is 800 MPa or more. A Charpy V-notch impact value is in the range of 7 to 15 J/cm.sup.2.

A stud-weldable rebar and a method for making the rebar are disclosed. The rebar has a steel body with a weld end and a diameter that is substantially uniform along a length of the body. A tip portion at the weld end includes a hardened zone and a base portion is formed of the remaining steel body. The hardened zone has a hardness that is about 1.5-3.0 times greater than a hardness of the base portion. Induction hardening is used to form the hardened zone.

Provided is a coolant spray module system for a heat treatment metal product, comprising: a first coolant spray module (1A), wherein the first coolant spray module (1A) comprises a first module housing (10), a first module cover (20), and a first nozzle (30), wherein the first nozzle (30) is fixed between the first module housing (10) and the first module cover (20) by first nozzle fixing blocks (13) and second nozzle fixing blocks (23), wherein the coolant spray module system sprays the coolant onto the heat treatment metal product to quench and clean the heat treatment metal product.

A steel bar having yield strength of 700 MPa class, excellent yield ratio, and excellent uniform elongation property is provided. The steel bar includes bainite and ferrite included in a center of the steel bar and bainite accounts for 20 to 80% by volume.

A predetermined composition is had, when a C content is represented by (C %), in a case of (C %) being not less than 0.35% nor more than 0.65%, a volume fraction of pearlite is 64(C %)+52% or more, and in a case of (C %) being greater than 0.65% and 0.85% or less, the volume fraction of pearlite is not less than 94% nor more than 100%, and a structure of the other portion is composed of one or two of proeutectoid ferrite and bainite. Further, in a region to a depth of 1.0 mm from a surface, a volume fraction of pearlite block having an aspect ratio of 2.0 or more is not less than 70% nor more than 95%, and a volume fraction of pearlite having an angle between an axial direction and a lamellar direction on a cross section parallel to the axial direction of 40 or less is 60% or more with respect to all pearlite.