Abstract: A composite magnetic member formed of a single material having a ferromagnetic section with high soft magnetism and a non-magnetic or the like section with sufficiently low magnetic (feebly magnetized or non-magnetic) and sufficient low MS temperature and a process for producing the member are provided. A composite magnetic member made of a single material of martensitic stainless steel including Ni having two sections of a ferromagnetic section having maximum permeability not less than 200 and coercive force not more than 2000 A/m and a feebly magnetized section having permeability not more than 2 and MS temperature not more than -30.degree. C.

Abstract: A method of thermal or thermochemical treatment of precision steel components having different wall thicknesses comprising the steps of a) hardening (8), b) low temperature cooling (9) and c) annealing (10), wherein the precision steel components are subjected to a low temperature cooling of only selected parts of the precision steel component to effect a reduction in the occurrence of primary residual austenite in the selected parts thereof.

Abstract: A hollow article is made by providing and diffusion bonding the opposing parts of an article made of an alpha-beta titanium alloy. Hydrogen is introduced into the surface of an internal cavity before, during, or after diffusion bonding. The article is heat treated with the hydrogen present, typically by solution treating and aging the hydrogen-containing bonded article. The result is the production of a microstructure at the internal surface of the cavity that is resistant to fatigue-crack initiation, while retaining a microstructure throughout the rest of the article that is resistant to fatigue-crack propagation. After heat treating, the hydrogen Is removed from the article, and any further heat treating and other operations are completed.

Abstract: A piston shoe (10) of an axial piston pump or motor is crimped to an annular piston head (42) and has a flat shoe wear surface (12) that contacts a cam plate (22). A back flange (14) of the shoe (10) also wears against an auxilliary cam plate (24). In order for the piston shoe (10) to operate within a fuel environment, the piston shoe (10) must be corrosion resistant, compatible with fuel, and provide the desired wear resistance. The piston shoe (10) is made of a cold workable cobalt based alloy which is compatible with fuel and provides corrosion resistance. The wear surface (12) which bears against the cam plate (22) and the back flange (14) which bears against the auxilliary cam plate (24) are provided with a thermal diffusion boride treatment which provides the desired wear resistance. In order to restore sufficient ductility to flange (16) of the shoe (10) that will be cold worked, a solution treatment is performed at a temperature range of 2050.degree. to 2250.degree. F. in a non-oxidizing environment.

Abstract: High-carbon pearlitic steel rails have high strength, wear resistance, ductility and toughness are manufactured by applying special rolling to produce fine-grained pearlite blocks in steels containing 0.60 to 1.20% carbon, 0.10 to 1.20 % silicon, 0.40 to 1.50% manganese and one or more elements selected, as required, from the group of chromium, molybdenum, vanadium, niobium and cobalt, thus imparting high wear resistance and an elongation of not less than 12% and a V notch Charpy impact value of not lower than 25 J/cm.sup.2. The high-carbon rails having high wear resistance, ductility and toughness assure safe railroad services in cold districts.

Abstract: A gas-turbine moving blade made of a Ni-base superalloy containing less grain boundary strengthening elements, in which a blade portion is formed of a single crystal and the rest is formed of columnar crystals, and a gas turbine including the moving blade. A thermal efficiency of the gas turbine can be improved to 35% or more, and a thermal efficiency of complex power generation with a steam turbine can be improved to 45% or more.

Abstract: A method is provided for obtaining a uniform grain size on the order of about ASTM 5 or coarser in at least a portion of an article formed from a .gamma.' precipitation strengthened nickel-base superalloy. The method comprises forming an article by: providing a billet, preheating the billet above 2000.degree. F. for at least 0.5 hours, working at least a portion to near-net shape at working conditions including a first strain rate of less than about 0.01 per second and at a subsolvus temperature at or near the recrystallization temperature, supersolvus heating to form a grain size in the portion of at least 5 ASTM, and cooling to reprecipitate .gamma.' within the article. The method can be utilized to form a .gamma.' precipitation strengthened nickel-base superalloy article whose grain size varies uniformly between portions thereof, so as to yield a desirable microstructure and property gradient in the article in accordance with the in-service temperature and stress-state gradient experienced by the article.

Abstract: A planar sheet of structurally hardened aluminum alloy, having, after quenching and aging, mechanical strength which varies continuously in a particularly defined direction of the planar sheet. The planar sheet is produced in a process comprising quenching and final aging, where the final aging comprises heating for a defined period of time a first portion of the plate or sheet including a first edge to a first temperature T and a second portion of the plate or sheet including an opposite edge to a second temperature t<T.

Abstract: A process for differentially heat treating a turbine disk of a gas turbine engine so as to produce a dual property disk. The process is applicable to superalloy disks, and achieves substantially uniform yet different temperatures in the rim and hub of the disk during heat treatment, so as to attain specific and different properties for the rim and hub. The process includes the steps of heat treating the entire disk to achieve a uniform structure having a fine grain size and fine precipitates. A device for heating the rim of the disk is then disposed at the disk's periphery, such that the rim is maintained at a substantially uniform temperature above the gamma prime solvus temperature of the superalloy so as to dissolve gamma prime precipitates present in the rim and cause grain growth in the rim.

Abstract: A railway-track element is disclosed not only for normal track but also for rail points. The track element is formed of vacuum-treated steel containing at least 0.53 to 0.62% C, 0.65 to 1.1% Mn, 0.8 to 1.3% Cr, 0.05 to 0.11% Mo, 0.05 to 0.11% V and .ltoreq.0.02% P, the balance being iron plus the usual production-related impurities. The track element is in the form of a rail made of rolled pearlitic steel. If the track element is to be used for points, the starting material is a length of rolled rail with a martensitic structure produced by heat treatment at least in the rail head area.

Abstract: The present invention resides in a method for making an internal combustion engine intake valve. An iron aluminum alloy, in the form of a coil or bar stock, is provided. The alloy comprises 76.05 to 90.15 weight percent iron, 9 to 13.3 weight percent aluminum, 0.05 to 0.35 weight percent carbon, and 0.5 to 3 weight percent of a refractory metal, and/or 0.3 to 1.5 weight percent of titanium in combination with, or in place of, the refractory metal. The coil or bar stock is extruded to a poppet valve preform configuration at a heading temperature in the range of 800.degree. to 2,000.degree. F. and a true strain of about 0.5 to 2.2. The preform configuration is then headed to a pre-machined configuration while maintaining the head of such preform at an effective heading temperature up to 2,200.degree. F. said heading being carried out at a true strain of about 1.4 to 2.3.

Abstract: A sucker rod coupling 10 having a high ultimate tensile strength, resistance to corrosion, and resistance to surface cracking arising out of a method of making the sucker rod coupling 10, which employs a five-step process of forming a coupling 10. First, a hollow cylindrical core 12 from a heat treatable steel is formed. Second, a thin coating 18 of metallic alloy is applied to the outer surface of the core 12. Third, the core 12 is heat treated. Fourth, threads 20 are partially cut in the inner surface of the core 12. Fifth, the threads 20 are cold worked to transform the partially cut threads 20 into finished threads 20 and to place the thread roots 22 in compression.

Abstract: A sucker rod coupling 10 having a high ultimate tensile strength, resistance to corrosion, and resistance to surface cracking arising out of a method of making the sucker rod coupling 10, which employs a five-step process of forming a coupling 10. First, a hollow cylindrical core 12 from a heat treatable steel is formed. Second, a thin coating 18 of metallic alloy is applied to the outer surface of the core 12. Third, the core 12 is heat treated. Fourth, threads 20 are partially cut in the inner surface of the core 12. Fifth, the threads 20 are cold worked to transform the partially cut threads 20 into finished threads 20 and to place the thread roots 22 in compression.

Abstract: A hard wear-resistant film is formed on a substrate in an atmosphere of an inert gas by using a target of a composition of Al.sub.a Ti.sub.b (wherein "a" and "b" stand for atomic percentages respectively in the ranges of 62 at %.ltoreq.a.ltoreq.85 at % and 15 at %.ltoreq.b.ltoreq.38 at %, providing a+b=100 at %) or Al.sub.c Ta.sub.d (wherein "c" and "d" stand for atomic percentages respectively in the ranges of 60 at %.ltoreq.c.ltoreq.80 at % and 20 at %.ltoreq.d.ltoreq.40 at %, providing c+d=100 at %) and by a sputtering process or ion plating process while varying continuously or stepwise the feed rate of a nitrogen-containing reaction gas into a chamber. The film consequently formed has a composition and structure thereof continuously or stepwise varied from a substantially amorphous metal of a part being in contact with the substrate to an (Al, Ti)N or (Al, Ta)N crystalline ceramic phase with the nitrogen content continuously or stepwise increased in the direction of the surface of the film.

Abstract: A magnetically graduated steel bar is provided with a magnetic scale that has a steel composition consisting, on a weight basis, of 0.02-0.10% C, 0.50-1.0% Mn, 0.50-1.0% Si, 17-20% Cr, 5-8% Ni, 0.05-0.20% C plus N, and a balance of Fe and incidental impurities. The steel contains 30-60 vol % of a cold working induced martensite and is given a nonmagnetic austenitic structure by local melting. The steel bar has a tensile strength of at least 130 kgf/mm.sup.2 and a fatigue strength of at least 60 kgf/mm.sup.2.

Abstract: The spheroidal graphite cast iron member having a surface layer portion mostly composed of a ferrite phase and having a thickness of at least 1 mm, and an inner portion composed of a pearlite phase and a ferrite phase, the surface layer portion having a ferritization ratio of 70% or more which is larger than that of the inner portion by at least about 15% is produced by (a) pouring a spheroidal graphite cast melt into a casting mold; (b) removing the casting mold by shake-out after the completion of solidification of the melt, while substantially the entire portion of the resulting cast iron product is still at a temperature of its A.sub.1 transformation point or higher; (c) when the temperature difference between the surface layer portion and the inner portion has become 40.degree.-60.degree. C., introducing the cast iron product into a uniform-temperature furnace kept at 750.degree.-900.degree. C.

Abstract: A superalloy article has a nickel-based superalloy substrate containing TCP-phase forming elements such as rhenium, chromium, tantalum and tungsten. A carbide precipitate-containing region is formed within the substrate extending to a carbide depth below a surface of the substrate, preferably by depositing carbon on the surface of the substrate and diffusing the carbon into the substrate. An aluminum-rich diffusion layer extends from the surface of the substrate to an aluminide depth below the surface of the substrate. Preferably, the carbide depth is about the same as the aluminide depth. The presence of the carbide precipitates inhibits the formation of the deleterious TCP-phase.

Abstract: A sucker rod coupling 10 having a high ultimate tensile strength, resistance to corrosion, and resistance to surface cracking arising out of a method of making the sucker rod coupling 10, which employs a five-step process of forming a coupling 10. First, a hollow cylindrical core 12 from a heat treatable steel is formed. Second, a thin coating 18 of metallic alloy is applied to the outer surface of the core 12. Third, the core 12 is heat treated. Fourth, threads 20 are partially cut in the inner surface of the core 12. Fifth, the threads 20 are cold worked to transform the partially cut threads 20 into finished threads 20 and to place the thread roots 22 in compression.

Abstract: A high tensile steel sheet excelling in workability and stretch flanging formability, which is of a composite texture composed of a ferrite phase and a 2nd phase selected from the group consisting of martensite, bainite, pearlite, retained austenite and cold-transformed ferrite, wherein the volume fraction of the 2nd phase is not less than about 1.3 times higher at an outer region of the steel sheet than the volume fraction of the 2nd phase in a central region of the sheet thickness.

Abstract: The present invention resides in a method for making an internal combustion engine intake valve. An iron aluminum alloy, in the form of a coil or bar stock, is provided. The alloy comprises 76.05 to 90.15 weight percent iron, 9 to 13.3 weight percent aluminum, 0.05 to 0.35 weight percent carbon, and 0.5 to 3 weight percent of a refractory metal, and/or 0.3 to 1.5 weight percent of titanium in combination with, or in place of, the refractory metal. The coil or bar stock is extruded to a poppet valve preform configuration at a heading temperature in the range of 800.degree. to 2,000.degree. F. and a true strain of about 0.5 to 2.2. The preform configuration is then headed to a pre-machined configuration while maintaining the head of such preform at an effective heading temperature up to 2,200.degree. F., said heading being carried out at a true strain of about 1.4 to 2.3.

Abstract: A method and apparatus for heat-treating nickel base superalloy articles to provide different properties in different regions of the article. An initially fine grain microstructure is heated such that a portion of the article is held above the .gamma.' solvus temperature long enough to provide a coarse grain microstructure while the remainder of the article remains below the .gamma.' solvus temperature and retains the fine grain microstructure. The coarse grain microstructure provides a reduced rate of fatigue crack growth rate while the fine grain microstructure retains good tensile properties. The invention is particularly applicable to the fabrication of turbine disks for gas turbine engines.

Abstract: A coating film of a carbon allotrope is formed on a substrate by continuously supplying a fine carbon powder onto the substrate and simultaneously irradiating the fine carbon powder with a laser beam of a high output level thereby inducing sublimation of the fine carbon powder, and quenching the sublimated fine carbon powder to cause deposition thereof on the substrate.

Abstract: A cylindrical, iron-based sintered slug comprising an iron-based sintered alloy having a surface hardness represented by an HRB of 40-90 is formed such that its interior porosity is 5% or less but greater than 0%, the porosities of both its surface layer regions lying at most 1 mm below its outer and inner surfaces are fixed at at least 3% or less but greater than 0% and the distribution of pores in each of the surface layers is decreased gradually toward the surface.

Abstract: A sliding member having a layer of FeS.sub.2 on its surface is formed by sulphonitriding the member by heatint it at 480.degree. C.-600.degree. C. in the presence of both 10-500 ppm of a hydrogen sulfide gas and 20-70 vol % ammonia gas. An alternate heating method involves performing a primary heat treatment on the sliding member at 450.degree.-540.degree. C. in the presence of 50-200 ppm of a hydrogen sulfite gas and a 10-70 vol % ammonia gas, then ceasing the supply of the ammonia gas, slowly reducing the temperature to between 200.degree.-350.degree. C., and performing a secondary heat treatment at that temperature level.

Abstract: A catheter guide wire is provided for guiding a catheter into a body cavity such as a blood vessel. The base material constituting the wire is made of an elastic alloy wire and subjected to a heat treatment such that its flexibility is sequentially increased from its proximal to distal end portions. A thermoplastic resin or/and a coil spring can be applied to at least the distal end portion of the wire base material. A method of manufacturing the catheter guide wire is also provided. The method is characterized in that the leading end side of the base material is divided into a plurality of areas and subjected to a heat treatment by changing the heat treatment temperature and the time conditions in units of the areas so that the flexibility of the base material is sequentially increased from the proximal to distal end portions of the leading end side.

Abstract: A method of hardening the surface of titanium and its alloys, and other structural metals which form hard carbides, by treating the surface thereof with a moving, discontinuous carbon arc.The metal surface to be hardened, and a carbon electrode are made opposite poles of an electric current source, and moved and/or rotated with respect to each other so that a multiplicity of discontinuous electric arcs are produced between the carbon electrode and the metal surface.Carbon particles transfer through the arc and alloy within craters of the instantly liquified and chilled substrate, producing a surface layer which, in the case of titanium, is hard and tough and adherent enough to form the working surface of abrasive cutting tools.The process improves the appearance and durability of consumer items and reduces friction and wear on machine parts.

Abstract: A boronized sliding material, which comprises a boronized layer formed on a steel substrate, characterized in that the steel substrate has a sorbitic structure or mixed, sorbitic and pearlite structure.

Abstract: A structural member made of titanium or titanium alloy has a metal structure at its surface layer portion formed of a plurality of kinds of .beta.-phases of different characteristics which are present in combination.

Abstract: A multimetallic article of manufacture comprising a body (40) of a first metallic material with discrete regions (65) therein of a second metallic material is manufactured by the in situ alloying of a third material with the first material. The alloying is performed by depositing the third material at locations on the body where the first material is melted by an energy beam (45) such as a carbon dioxide laser or electron beam.

Abstract: A cylindrical, iron-based sintered slug comprising an iron-based sintered alloy having a surface hardness represented by an HRB of 40-90 is formed such that its interior porosity is 5% or less but greater than 0%, the porosities of both its surface layer regions lying at most 1 mm below its outer and inner surfaces are fixed at at least 3% or less but greater than 0% and the distribution of pores in each of the surface layers is decreased gradually toward the surface.

Abstract: An austempered ductile iron alloy with a mixed austenitic-bainitic structure is made by a method which enables the iron to withstand high cyclical stresses while having a high resistance to abrasion. Articles such as automobile roller-follower camshafts that are made from the iron alloy may have portions thereof selectively austempered to reduce the overall cost and time required to manufacture the article.

Abstract: A metallic object is treated to produce tensile residual stress in a known localized area of the metallic object. A metallic object having at least one portion substantially free of tensile residual stress is provided, and a localized area adjacent to or a part of the tensile stress-free area is selected. The localized area is subjected to heating on one surface and cooling on the opposite surface. Upon cooling to ambient temperature, the known localized area has tensile residual stress. The localized area can have cracks formed therein by crack-promotion techniques, such as submersion in boiling magnesium chloride. The area can be tested by attaching electrodes and subjecting the area to a reversing direct current crack growth measurement procedure.

Abstract: Composite materials having improved fracture toughness are formed by dispersing ductile inclusions in a less ductile matrix. The matrices may be formed from metals, such as high-strength aluminum alloys or ceramics. Bonding should be present between the inclusions and the matrix so that cracks in the composite material must pass through the inclusions.

Abstract: The outer surface of an elongated metal component such as a bar is rapidly heated by an induction coil and is thereafter cooled by a quenching spray while being subjected to tensile forces so high that the center portion of the bar approaches yield causing the bar to elongate slightly. The tension on the bar is released thereby obtaining high residual compressive surface stresses in the cooled outer layers of the bar which define an annulus and which shortens the bar slightly until compressive stresses in the surface layers equal the tensile stresses acting on the central sections of the bar thereby greatly improving the fatigue life of the bar.

Abstract: A rear axlecase is manufactured by casting the differential gear housing and the axle housings into an integral body from nodular graphite cast iron, and ensuring good ductility therefor by reducing the hardness as a whole on one hand, and ensuring toughness to bear up under the stress acting on the axles by performing hardening treatment on the root parts of the endtubes of the axle housing.

Abstract: An elongated steel element of enhanced strength suitable for use as reinforcement for concrete or drawing feed stock has a cross section which is heterogenous in structure and strength, the cross section comprising a core, a peripheral layer and a transition region between the core and the peripheral layer, the transition region consisting essentially of higher strength, harder martensite, the peripheral layer being of lower strength than the transition region and the core being of lower strength than the peripheral layer.

Abstract: An amorphous magnetic wire comprises a magnetically hard wire portion for propagating a magnetoelastic wave, and a magnetically soft wire portion for generating or detecting the magnetoelastic wave. This amorphous magnetic wire is obtained by producing a magnetic wire in an amorphous state, wire-drawing the amorphous magnetic wire so as to make the amorphous magnetic wire thinner, and annealing a portion of the magnetic wire to make the portion magnetically soft.

Abstract: An apparatus and process for improving the microstructure of electrically conducting materials is disclosed by the present invention. A revolving heat source applies heat to the surface of the material evenly and quickly. One or more heat sinks quickly cool the material. In the preferred embodiment, the cooling may be done in such a way as to promote as high a degree of directional grain growth as desired or completely nondirectional grain growth.

Abstract: Homogeneous and refined microstructure powders and the method of making them from, for example, liquid metal immiscible systems or very limited solid solubility systems. At least two metals are melted and then rapidly solidified to yield a solid with a segregated, non-uniform microstructure. The resulting rapidly-solidified solid is then reduced to a powder and subjected to high-energy milling for a time sufficient to reduce the segregation to the desired level of uniformity.

Abstract: A process for improving the cold workability of a metallic article is disclosed. The process includes compressive working followed by heat treatment of a metallic article to provide a duplex microstructure including relatively fine grains near the surface and relatively coarse grains near the center of the article. The duplex microstructure improves the surface cracking resistance of the article during subsequent compressive cold forming, such as by cold heading.

Abstract: The invention relates to a material (504), having adjacent regions of differing strength and ductility, that has been formed by rapidly deforming a suitable base metal (501) having a banded structure, such as illustartively a previously cold worked low carbon steel alloy, in order to generate a high rate of change in the internal energy of the base metal. This energy change depressed the transformation temperatures of the base metal and induced an allotropic phase transformation to occur therein. Specifically, prior to being deformed, the base metal is maintained at a fairly low temperature, e.g. at or near room temperature. The tooling, preferably rolls, that is used to provide the deformation is maintained at a modestly elevated temperature.

Abstract: An amorphous metal-metal composite article comprising a metal and an amorphous metal thin sheet firmly bonded thereto and having high durability and reliability can be obtained by a method, wherein the surface roughness of a metal to be bonded with an amorphous metal thin sheet is adjusted to a certain surface roughness and an explosion shock is applied to an assembly of the metal and the amorphous metal thin sheet superposed thereon, under a condition that the moving velocity of the collision point of the amorphous metal thin sheet to the metal is higher than the sound velocity in the amorphous metal.

Abstract: Case-hardened plate armor disclosed includes a steel plate (14,18) that is heat treated to provide carbonitride surfaces and a tough, ductile core, with the carbonitride surfaces having a toughness of at least 66, and preferably at least 67, on the Rockwell C scale to prevent surface penetration, and with the tough, ductile core being softer than the carbonitride surfaces to prevent brittle fracture. The steel plate (14,18) may be made from either rolled homogenous armor which has a final core hardness in the range of 45 to 50 on the Rockwell C scale, or from high-hard armor which has a final core hardness in the range of 52 to 54 on the Rockwell C scale. The steel plate may be made with holes or may be imperforate depending upon weight requirements.

Abstract: The work-performing member for a farm machine has a cutting edge made of a high-carbon steel containing graphite in structurally free state in an amount of 0.5 to 1.32 percent of the total mass of the material.

Abstract: A carbon or alloy steel heat treated grinding rod having improved wear resistance and breaking resistance for use in a rotating grinding mill. The surface of the rod has a martensitic microstructure having a hardness of at least HRC 55. The core of the rod has a bainitic microstructure having a hardness of at least HRC 40. A preferred rod composition includes at least 0.7% carbon, at least 0.25% of molybdenum, at least 0.25% chromium, less than 0.7% manganese, the balance iron and unavoidable impurities, all percentages by weight.

Abstract: A method of heat treating cold rolled steel strapping comprising rapidly heating the strapping to the dual phase temperature range at a rate of the order of 100.degree. C. per second, with little or more soaking, and rapidly cooling the strapping at a rate of the order of 1000.degree. C. per second to form a microstructure comprising a matrix of recovery annealed cold work ferrite containing martensite and carbides dispersed through the matrix. A heat treatment line for performing this method is described. A heat treated cold rolled steel strapping produced by the method is also described. The steel from which the strapping is made preferably has less than 0.2.degree. C. and includes Ti in the range 0.06 to 0.15% preferably about 0.08% and Nb in the range 0.02 to 0.05% preferably about 0.04%.

Abstract: In the production of composite welded components the workpieces are joined together only partially machined and are then jointly subjected to a heat treatment for hardening their surface, the welding gap formed by their contact surfaces being previously covered with an agent which prevents carbonization of the contact surfaces as a machining-free preparation for welding with electron or laser beams following the heat treatment after individual finishing of the workpieces.

Abstract: An iron-base article such as a camshaft has a remelted layer of high wear resistance on a cam surface, for example. To make such an iron-base article, molten metal is poured into a mold with a chill set therein to cast an iron-base article having a chilled region formed in contact with said chill. Then, metal powder which provides wear resistance upon being mixed is added to at least a portion of said chilled region. A high level of energy is applied to the portion of the chilled region to heat and remelt the same, and the remelted portion is thereafter cooled to form a remelted layer therein.

Abstract: A wear resistance rail which comprises 0.50 to 0.85 wt. % of C, 0.10 to 1.0 wt. % of Si, 0.50 to 1.50 wt. % of Mn, less than 0.035 wt. % of P, less than 0.035 wt. % of S, less than 0.050 wt. % of Al, and the balance of iron and impurities. The web has a high toughness tempered bainite structure, tempered martensite structure or a tempered mixed structure of bainite and martensite and the head rail has high wear resistance which prevents unstable destructive cracks from propagating. The rail can further contain one or more of 0.05 to 1.50 wt. % of Cr, 0.05 to 0.20 wt. % of Mo, 0.03 to 0.10 wt. % of V, 0.10 to 1.00 wt. % of Ni, and 0.005 to 0.050 wt. % of Nb.

Abstract: A method of and an apparatus for remelting and hardening an elongate workpiece such as a shaft having a plurality of axially spaced shaft portions to be processed. The shaft is held in a second position, heated, and thereafter transferred to a first position close and parallel to the second position. The shaft is then held in the first position, and the outer surface of one of the shaft portions is remelted and hardened with a torch. Thereafter, the torch is moved parallel to the shaft to remelt and harden the adjacent shaft portions successively.