Disclosed is a shot ball having excellent strength and wear resistance. The shot ball according to an embodiment of the present disclosure includes, by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 1.0% to 8.0% of chrome (Cr), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe), and other unavoidable impurities.

Disclosed is a shot ball having excellent strength and wear resistance. The shot ball according to an embodiment of the present disclosure includes, by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 1.0% to 8.0% of chrome (Cr), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe), and other unavoidable impurities.

A workpiece conveyance jig, which is formed of a threaded shaft made of a ceramic, includes an inner member, which is formed of a solid shaft having a constant diameter, and is configured to receive a rotational driving force, and an outer member, which has a hollow shaft-like shape, has a helical protrusion, and is mounted on an outer periphery of the inner member so as to be rotatable integrally with the inner member. The outer member includes a plurality of cylindrical bodies arranged in a row in an axial direction of the workpiece conveyance jig, and has a convex and concave fitting portion formed between two adjacent ones of the plurality of cylindrical bodies, which is configured to engage the two adjacent cylindrical bodies with each other in a direction of rotation of the inner member.

A workpiece conveyance jig, which is formed of a threaded shaft made of a ceramic, includes an inner member, which is formed of a solid shaft having a constant diameter, and is configured to receive a rotational driving force, and an outer member, which has a hollow shaft-like shape, has a helical protrusion, and is mounted on an outer periphery of the inner member so as to be rotatable integrally with the inner member. The outer member includes a plurality of cylindrical bodies arranged in a row in an axial direction of the workpiece conveyance jig, and has a convex and concave fitting portion formed between two adjacent ones of the plurality of cylindrical bodies, which is configured to engage the two adjacent cylindrical bodies with each other in a direction of rotation of the inner member.

A bearing part is composed of a chromium molybdenum steel, and includes a raceway surface or a rolling contact surface. A precipitated compound composed of at least one of a carbide, a nitride, and a carbonitride exist in the raceway surface or the rolling contact surface. An area ratio of the precipitated compound in the raceway surface or the rolling contact surface is more than or equal to 3%. An average grain size of the precipitated compound in the raceway surface or the rolling contact surface is less than or equal to 0.3 m.

A method of imparting compressive residual stress to a first plurality of balls includes a) placing the balls between a first body having a first surface and a second body having a second surface, the first surface including a smooth contact portion, the smooth contact portion being substantially flat or convex and having a surface hardness greater than or equal to an initial surface hardness of the balls, b) imparting a compressive stress along a first diameter of the balls by pressing the first body toward the second body or the second body toward the first body or the first and second bodies toward one another with a force, and c) causing relative movement between the first surface and the second surface while maintaining the force at or above a minimum level to impart the compressive stress along other diameters of the balls different than the first diameter.

A method of imparting compressive residual stress to a first plurality of balls includes a) placing the balls between a first body having a first surface and a second body having a second surface, the first surface including a smooth contact portion, the smooth contact portion being substantially flat or convex and having a surface hardness greater than or equal to an initial surface hardness of the balls, b) imparting a compressive stress along a first diameter of the balls by pressing the first body toward the second body or the second body toward the first body or the first and second bodies toward one another with a force, and c) causing relative movement between the first surface and the second surface while maintaining the force at or above a minimum level to impart the compressive stress along other diameters of the balls different than the first diameter.

The present invention relates to a steel composition carburizable and/or nitritable, comprising, in percentages by weight of the total composition: Carbon: 0.05-0.40, preferably 0.10-0.30; Chromium: 2.50-5.00, preferably 3.00-4.50; Molybdenum: 4.00-6.00; Tungsten: 0.01-1.80, preferably 0.02-1.50; Vanadium: 1.00-3.00, preferably 1.50-2.50; Nickel: 2.00-4.00; Cobalt: 2.00-8.00, preferably 3.00-7.00; Iron: balance as well as the inevitable impurities, optionally further comprising one or more of the following elements: Niobium: 2.00; Nitrogen: 0.50, preferably 0.20; Silicon: 0.70, preferably 0.05-0.50; Manganese: 0.70, preferably 0.05-0.50; Aluminum: 0.15, preferably 0.10; the combined niobium+vanadium content being in the range 1.00-3.50; and the carbon+nitrogen content being in the range 0.05-0.50.

It further relates to the method of production thereof, the steel blank obtained and a mechanical device comprising the latter.

A carburisable steel alloy suitable for bearing components comprising, in percent by weight: C 0.05-0.5 wt. % Cr 2.5-5.0 wt. %, Mo 4-6 wt. %, W 2-4.5 wt. %, V 1-3 wt. %, Ni 2-4 wt. %, Co 2-8 wt. %, optionally one or more of the following elements: Nb 0-2 wt. % N 0-0.5 wt. % Si 0-0.7 wt. %, Mn 0-0.7 wt. %, Al 0-0.1 5 wt. %, wherein the combined amount of Nb+V is within the range 1-3.5 wt. %, the combined amount of C+N is within the range 0.05-0.5 wt. %, the balance being Fe and unavoidable impurities.

A carburisable steel alloy suitable for bearing components comprising, in percent by weight: C 0.05-0.5 wt. % Cr 2.5-5.0 wt. %, Mo 4-6 wt. %, W 2-4.5 wt. %, V 1-3 wt. %, Ni 2-4 wt. %, Co 2-8 wt. %, optionally one or more of the following elements: Nb 0-2 wt. % N 0-0.5 wt. % Si 0-0.7 wt. %, Mn 0-0.7 wt. %, Al 0-0.1 5 wt. %, wherein the combined amount of Nb+V is within the range 1-3.5 wt. %, the combined amount of C+N is within the range 0.05-0.5 wt. %, the balance being Fe and unavoidable impurities.