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.

A hot-stamped article according to the present invention has a plating layer being attached to a single surface in an amount of 10 g/m.sup.2 or more and 90 g/m.sup.2 or less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and impurities on a surface of a base steel sheet having a predetermined chemical composition, in a surface layer region, a metallographic structure includes 80.0% or more of martensite and 8.0% or more of residual austenite in terms of area percentage, and the concentration of Ni in the surface layer region is 8 mass % or more.

A steel material for a low yield ratio, high-strength steel pipe having excellent low-temperature toughness according to an aspect of the present invention comprises, by weight %, 0.03-0.065% of C, 0.05-0.3% of Si, 1.7-2.2% of Mn, 0.01-0.04% of Al, 0.005-0.025% of Ti, 0.008% or less of N, 0.08-0.12% of Nb, 0.02% or less of P, 0.002% or less of S, 0.05-0.3% of Cr, 0.4-0.9% of Ni, 0.3-0.5% of Mo, 0.05-0.3% of Cu, 0.0005-0.006% of Ca, 0.001-0.04% of V, and the balance of Fe and inevitable impurities, wherein a number of deposits having an average diameter of 20 nm or less per unit area in a cross section of the steel material may be 6.5*10.sup.9/mm.sup.2 or greater.

Disclosed is a non-heat-treated steel that has low deformation resistance during cold forging in bolt head forming and excellent product yield, and that can be manufactured without the need to perform heat treatment for controlling strength variation. The disclosed steel has a chemical composition containing C: 0.18-0.24%, Si: 0.10-0.22%, Mn: 0.60-1.00%, Al: 0.010-0.050%, Cr: 0.65-0.95%, Ti: 0.010-0.050%, B: 0.0015-0.0050%, N: 0.0050-0.0100%, P: 0.025% or less inclusive of 0, S: 0.025% or less inclusive of 0, Cu: 0.20% or less inclusive of 0, and Ni: 0.30% or less inclusive of 0, in a range satisfying: 0.45≤C+Si/24+Mn/6+Ni/40+Cr/5≤0.60 and N≤0.519A1+0.292Ti, with the balance being Fe and inevitable impurities; and a microstructure in which bainite is present in an area ratio of 95% or more, where the microstructure contains prior austenite grains with a grain size number of 6 or more, and strength variation is 100 MPa or less.

A hot-stamped article according to the present invention has a plating layer being attached in an amount of 10 g/m.sup.2 or more and 90 g/m.sup.2 or less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and an impurity on a surface of a base steel sheet having a predetermined chemical composition, a surface layer region includes 90.0 % or more of martensite in terms of area percentage, and a concentration of Ni in a prior austenite grain boundary in the surface layer region is 5.5 mass % or more.

A steel sheet for hot stamping according to the present invention has a plating layer being attached in an amount of 10 g/m.sup.2 or more and 90 g/m.sup.2 or less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and impurities on a surface of a base steel sheet having a predetermined chemical composition, in a surface layer region, 15.0% or more of the crystal grains of one or two kinds of unauto-tempered martensite and lower bainite are included in terms of area percentage, and the average dislocation density is 4×10.sup.15 m/m.sup.3.

A machine component, made of steel or cast iron and having a circular hole that opens in a first surface, includes a plurality of first quench-hardened regions that include the first surface and are arranged apart from each other along a first circle surrounding the hole when viewed in a plane in a direction perpendicular to the first surface, and a base region that is a region other than the first quench-hardened regions.

A device and a method for continuous temperature gradient heat treatment of a rod-shaped material are disclosed. The furnace body of the device includes an upper heating zone and a lower heating zone inside, which are independently controlled in temperature by means of an upper heating power supply and a lower heating power supply. Moreover, both the upper heating zone and the lower heating zone are closed heating zones. The closed heat insulation plates could prevent heat loss and ensure precise temperature control of the upper heating zone and the lower heating zone. In the device, a vacuum pumping equipment is included; an annular radiation screen is configured between the upper heating zone and the lower heating zone, and the rod-shaped material is not in contact with the annular radiation screen. The rod-shaped material conducts one-dimensional heat transfer along the axial direction.

There are disclosed a heat treatment installation and a method of producing shaped components having at least two microstructural regions of different ductility or strength from semi-finished products of hardenable steel, using a continuous furnace which permits heating of the semi-finished products to a first temperature in a first region and permits heating of the semi-finished products to a second temperature, which differs from the first temperature, in a second region. The two regions are separated from one another by partition walls extending in the transport direction, and the continuous furnace includes a lifting-step chain conveyor as a transport device.

Embodiments are described herein of a bifurcated heat treatment apparatus and methods for localized heat treatment of a golf club hosel or golf club head. The heat treating method comprises a bifurcated process in which the golf club head is treated in the first heating unit via induction heating and then moved to the second heating unit for convection heating. Both steps are to localize the hosel heat treatment. The heat treatment apparatus may also include a cooling component, such as a heat sink, to ensure the body of the club head remains at the correct temperature during the second heating stage when the hosel is heated in isolation. The overall bifurcated method and apparatus of the localized heat treatment leads to a hosel or golf club head with at least two different hardness values to allow for manipulation of the material without cracking or fracturing.