In a heat treatment method for obtaining a bearing ring for an annular roller bearing whose thickness changes in an axial direction, the heat treatment method includes (A) applying a quenching process to a work which is annular, made of high carbon chromium bearing steel, and having a thickness changing in an axial direction, (B) applying a tempering process to the work which is quenched to entirely soak the work in cooling liquid and inductively heat the work in a state that the work is soaked in the cooling liquid, and (C) applying a finishing process to the work which is tempered.

A shaft part excellent in static torsional strength and torsional fatigue strength containing, by mass %, essential elements of C: 0.35 to 0.70%, Si: 0.01 to 0.40%, Mn: 0.5 to 2.6%, P: 0.050% or less, S: 0.005 to 0.020%, Al: 0.010 to 0.050%, N: 0.005 to 0.025%, and O: 0.003% or less, further containing optional elements, having a balance of Fe and impurities, having a chemical composition satisfying formula (1), having at least one hole at an outer circumferential surface, having a volume ratio (R1) of 4 to 20% of retained austenite at a position of a 2 mm depth from the outer circumferential surface, having a volume ratio of retained austenite at a position of a 2 mm depth from the outer circumferential surface in an axial direction of the hole and at a position of a 20 μm depth from the surface of the hole as R2, and having a reduction rate Δγ of 40% or more of retained austenite found by the formula (A): Δγ=[(R1−R2)/R1]×100: Formula (1): 15.0≤25.9C+6.35Mn+2.88Cr+3.09Mo+2.73Ni≤27.2 (Notations of elements in formula are contents of the elements)

A shaft part excellent in static torsional strength and torsional fatigue strength containing, by mass %, essential elements of C: 0.35 to 0.70%, Si: 0.01 to 0.40%, Mn: 0.5 to 2.6%, P: 0.050% or less, S: 0.005 to 0.020%, Al: 0.010 to 0.050%, N: 0.005 to 0.025%, and O: 0.003% or less, further containing optional elements, having a balance of Fe and impurities, having a chemical composition satisfying formula (1), having at least one hole at an outer circumferential surface, having a volume ratio (R1) of 4 to 20% of retained austenite at a position of a 2 mm depth from the outer circumferential surface, having a volume ratio of retained austenite at a position of a 2 mm depth from the outer circumferential surface in an axial direction of the hole and at a position of a 20 μm depth from the surface of the hole as R2, and having a reduction rate Δγ of 40% or more of retained austenite found by the formula (A): Δγ=[(R1−R2)/R1]×100: Formula (1): 15.0≤25.9C+6.35Mn+2.88Cr+3.09Mo+2.73Ni≤27.2 (Notations of elements in formula are contents of the elements)

Iron-based alloys and articles in strips, sheets, workpieces and the like are converted into high strength steel with a minimum of cost, time and effort, including producing dual phase materials. This is achievable by extremely rapid micro-treating of low, medium, and high carbon iron-based alloys and articles by rapid heating and rapid cooling at least a portion of the alloy/article. This heating step involves nearly immediately heating the iron-based alloy to a selected temperature above its austenite conversion temperature. Then, the alloy is immediately quenched, also at an extremely fast rate, on at least a portion of the iron-based alloy in a quenching unit adjacent the heating unit. This procedure forms high strength alloy in a desired area, depending upon where the treatment was performed.

Iron-based alloys and articles in strips, sheets, workpieces and the like are converted into high strength steel with a minimum of cost, time and effort, including producing dual phase materials. This is achievable by extremely rapid micro-treating of low, medium, and high carbon iron-based alloys and articles by rapid heating and rapid cooling at least a portion of the alloy/article. This heating step involves nearly immediately heating the iron-based alloy to a selected temperature above its austenite conversion temperature. Then, the alloy is immediately quenched, also at an extremely fast rate, on at least a portion of the iron-based alloy in a quenching unit adjacent the heating unit. This procedure forms high strength alloy in a desired area, depending upon where the treatment was performed.

The invention relates to a method for machining a rack and to a rack (1) machined according to said method, for example a steering rack. In said method, the stress pattern that is present after hardening and/or straightening the rack and that has a chaotic internal stress distribution of tensile and compressive stresses is converted into a stress pattern that optimizes the strength and the use of the material and also the diameter of the rack, such that, without altering the structure, at least the region of the gear teeth (2) is pre-stressed, in a functionally combined series of steps of a machining pass, with a deliberately introduced internal compressive stress without tensile stress and with a predominantly uniform stress distribution or stress plane.

A process of manufacturing of segment for carbon thrust bearing uses stainless-steel (SS) round bars/sheets/logs of suitable grade as raw material. The SS round bars/sheets/logs undergo cutting operation to cut into SS billets. The billets successively undergo heating and hot forging processes to form segments of desired shapes. Thereafter, the segment is subjected to heat treatment process i.e. stress relieving, hardening and tempering process successively for obtaining consistent and uniform grain structure, mechanical properties and physical properties of segments which are cost-effective in terms of lower maintenance and lower handling efforts. After heat-treatment process, segment undergoes surface-finishing processes i.e. grinding, lapping and polishing successively for obtaining mirror like surface finishing that gives greater anti-friction property and lower co-efficient of friction. The manufacturing process according to present invention yields consistent grain structure, refine, dense and uniform microstructure of segments which imparts optimum strength, ductility, toughness and resistance to impact and fatigue.

A process of manufacturing of segment for carbon thrust bearing uses stainless-steel (SS) round bars/sheets/logs of suitable grade as raw material. The SS round bars/sheets/logs undergo cutting operation to cut into SS billets. The billets successively undergo heating and hot forging processes to form segments of desired shapes. Thereafter, the segment is subjected to heat treatment process i.e. stress relieving, hardening and tempering process successively for obtaining consistent and uniform grain structure, mechanical properties and physical properties of segments which are cost-effective in terms of lower maintenance and lower handling efforts. After heat-treatment process, segment undergoes surface-finishing processes i.e. grinding, lapping and polishing successively for obtaining mirror like surface finishing that gives greater anti-friction property and lower co-efficient of friction. The manufacturing process according to present invention yields consistent grain structure, refine, dense and uniform microstructure of segments which imparts optimum strength, ductility, toughness and resistance to impact and fatigue.

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.

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.