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 heat treatment apparatus (1), including: a conveying device (10), which is configured to convey a rod-shaped workpiece (W) at a predetermined velocity along an axial direction of the workpiece (W); and a heating device (2) including a heating coil (3) configured to inductively heat the workpiece (W) being conveyed to a quenching temperature, wherein the heating coil (3) includes a first heating section (3A) and a second heating section (3B), which are coupled to each other in series along the axial direction of the workpiece (W), and is electrically connected to a single high-frequency power supply (4), and wherein a coil pitch (D2) of the second heating section (3B) arranged relatively on a front side in a conveying direction for the workpiece (W) is larger than a coil pitch (D1) of the first heating section (3A) arranged relatively on a rear side in the conveying direction.

A member (10), for bearing a load, including a load receiving portion (12) at which the load is applicable to the member. A strainable portion (14) is connected to the load receiving portion to be strained by the load. A datum (16a) is defined and an elongate portion (18) defines another datum (18a). The datums are arranged such that relative displacement therebetween indicates an amount by which the strainable portion is strained. The strainable portion defines the datum.

The present invention discloses a steel for bolts, which comprises the following chemical elements in percentage by mass in addition to Fe and inevitable impurities: C: 0.37 to 0.45%; Si: 0.01 to 0.08%; Mn: 0.45 to 0.80%; Cr: 0.90 to 1.30%; Mo: 0.20 to 0.45%; Ni: 0.10 to 0.30%; V: 0.15 to 0.30%; and Al: 0.015 to 0.035%. The present invention further discloses a method for manufacturing the steel for bolts, which comprises the following steps: (1) smelting; (2) casting; (3) rough rolling; (4) high-speed wire rolling; (5) Stelmor controlled cooling; and (6) heat treatment, wherein the holding temperature of spheroidizing heat treatment is 760 to 790? C. and the holding time is 4 to 12 h, followed by a slow cooling process after the holding with a cooling speed of lower than 40? C./h. The drawing area reduction rate of a coil rod is controlled to 5 to 30%. The heating temperature of quenching and tempering heat treatment is 850 to 950? C. The tempering temperature is 500 to 600? C. The steel for bolts disclosed in the present invention has a uniform structure and performance, has low production costs, and has high strength and good delayed fracture resistance.

A method for producing a threaded nut of a threaded drive, includes the following steps: a sleeve is produced from a steel sheet which is suitable for case-hardening; a rolling profile for a rolling contact with rolling bodies is molded on the inner circumference of the sleeve, said rolling profile being wound in a helical manner about the longitudinal axis of the sleeve; a flange is welded to the end face of the sleeve; the flange is provided with a welding surface on the flange end face facing away from the sleeve for welding to a machine part; the welding surface initially has a diffusion-inhibiting layer which inhibits the penetration of carbon; and the welding surface is exposed by removing the diffusion-inhibiting layer after case-hardening the threaded nut. A threaded nut produced according to the method can be part of a ball screw drive, the flange of which can be welded to a provided machine part by the user.

A method of heat treating a fastening member having a head portion, a shank portion, and a thread portion includes hardening the fastening member to a first hardness value. Hardening of the fastening member includes heating the fastening member at a first pre-set temperature value. The method also includes tempering the fastening member at a second pre-set temperature value to a second hardness value. The method further includes induction tempering the thread portion of the fastening member. Induction tempering of the thread portion includes heating the thread portion at a third pre-set temperature value to a third hardness value. The third hardness value of the thread portion is less than the second hardness value of the head portion and the shank portion.

The present invention relates to a ferritic stainless steel according to the present invention, containing, in mass %: 0.001%C0.020%, 0.05%Si0.50%, 0.1%Mn1.0%, 15.0%Cr25.0%, Mo<0.50%, 0.50%W5.00%, and 0.01%Nb0.50%, with a balance being Fe and unavoidable impurities, having a content (coarse Laves phase ratio) of coarse Laves phase having a diameter of 0.50 m or more being 0.1% or less, and having an average grain size being 30 m or more and 200 m or less.

A method of machining a screw is provided that is capable of preventing formation of a protruding section at a thread tip section. A thread is formed by cutting on a cylindrical body, and a surface of the thread is plastically deformed by rolling. Because of the cutting, a width between-side surfaces of a thread tip section is in a narrowed state as compared to a normal width. This width is narrowed toward a tip of the thread while a thread body section has a width expanded as compared to a normal width. Consequently, the side surfaces are formed to bulge by an excess thickness portion as compared to normal side surfaces. The rolling plastically deforms both side surfaces to cause the excess thickness portion to plastically flow toward the side surfaces.

A bolt is provided that has high strength and excellent hydrogen embrittlement resistance characteristics. A bolt according to an embodiment of the present invention consists of, in mass %, C: 0.32 to 0.39%, Si: 0.15% or less, Mn: 0.40 to 0.65%, P: 0.020% or less, S: 0.020% or less, Cr: 0.85 to 1.25%, Al: 0.005 to 0.060%, Ti: 0.010 to 0.050%, B: 0.0010 to 0.0030%, N: 0.0015 to 0.0080%, 0: 0.0015% or less, Mo: 0 to 0.05%, V: 0 to 0.05%, Cu: 0 to 0.50%, Ni: 0 to 0.30%, and Nb: 0 to 0.05%, with the balance being Fe and impurities. The bolt satisfies Formula (1) and Formula (2), and has a tensile strength of 1000 to 1300 MPa and satisfies Formula (3).

4.910C+Si+2Mn+Cr+4Mo+5V6.1 (1)

Mn/Cr0.55 (2)

[dissolved Cr]/Cr0.70 (3)

A hollow screw and related process of making is provided, wherein the hollow screw is formed from a generally circular corrosion resistant stainless steel disk cut from flat roll stock. The hollow screw includes a head and an elongated and hollow shaft having a wall thickness between about 0.2 to about 0.7 millimeters extending therefrom and defining a shank portion and a threaded portion having a plurality of threads thereon with a rotational drive mechanism configured to facilitate tightening via the threads. The process involves annealing to soften the stamped hollow screw, followed by thread rolling, and then age hardening the hollow screw. As such, the resultant hollow screw is relatively lightweight, about 50% the mass of a solid core screw made from the same material, with a sufficient thread strength to meet most aerospace applications and contributes to important aircraft fuel economy.