Axle for rail vehicles, made of heat-treated material, wherein in all cylindrical parts (2a) and the transitional parts (2b) along the entire length (L) of the axle (1) surface the axle (1) surface is formed by a reinforced, inductively hardened layer (2) having of uniform depth from the axle (1) surface and this inductively hardened layer (2) continues with a transition layer (3) with a gradually decreasing gradient of reinforcing. Transition layer (3) depth is equal to at least 1.5 times of the depth of the inductively hardened layer (2).

Axle for rail vehicles, made of heat-treated material, wherein in all cylindrical parts (2a) and the transitional parts (2b) along the entire length (L) of the axle (1) surface the axle (1) surface is formed by a reinforced, inductively hardened layer (2) having of uniform depth from the axle (1) surface and this inductively hardened layer (2) continues with a transition layer (3) with a gradually decreasing gradient of reinforcing. Transition layer (3) depth is equal to at least 1.5 times of the depth of the inductively hardened layer (2).

The present invention provides a carburized part having a total amount of TiC, AlN and ZrC, which are precipitate particles, of 4.510.sup.10 mole or less per 1 mm.sup.2 of grain boundary area of prior austenite grains after carburization. According to the present invention, it is possible to provide a carburized part which allows effective inhibition of abnormal grain growth in spite of a carburizing treatment and makes it possible to solve the problem of reduction in properties caused by abnormal grain growth.

The present invention provides a carburized part having a total amount of TiC, AlN and ZrC, which are precipitate particles, of 4.510.sup.10 mole or less per 1 mm.sup.2 of grain boundary area of prior austenite grains after carburization. According to the present invention, it is possible to provide a carburized part which allows effective inhibition of abnormal grain growth in spite of a carburizing treatment and makes it possible to solve the problem of reduction in properties caused by abnormal grain growth.

An apparatus for backward flow forming a material may comprise a mandrel having a headstock at a proximate end of the mandrel, the mandrel configured to rotate about an axis, a plurality of rollers disposed radially outward of the mandrel configured to exert force on the material to form a work piece at a plastic deformation zone, wherein the work piece flows from the plastic deformation zone between the plurality of rollers and the mandrel toward a distal end of the mandrel, and a catcher, coaxial to the mandrel, and removably coupled to the work piece at a traveling end of the work piece.

A tool system for stress relieving a turbocharger turbine wheel longitudinally welded to a hardened rotor shaft. The shaft has a journal bearing region and a turbine-end body forming an A datum surface for receiving an axial bearing. The tool system includes an induction coil and an electronic oscillator, and a tool. The tool forms an opening configured to receive the rotor shaft such that the journal bearing region of the shaft extends into the tool housing while the A datum surface adjoins an end of the tool housing. The induction coil is positioned around the turbine-end body. The housing forms an annular cooling chamber surrounding the journal bearing region of the shaft. The housing forms an inlet passage to provide cooling fluid to the annular chamber, and an outlet passage to remove cooling fluid from the annular chamber.

A tool system for stress relieving a turbocharger turbine wheel longitudinally welded to a hardened rotor shaft. The shaft has a journal bearing region and a turbine-end body forming an A datum surface for receiving an axial bearing. The tool system includes an induction coil and an electronic oscillator, and a tool. The tool forms an opening configured to receive the rotor shaft such that the journal bearing region of the shaft extends into the tool housing while the A datum surface adjoins an end of the tool housing. The induction coil is positioned around the turbine-end body. The housing forms an annular cooling chamber surrounding the journal bearing region of the shaft. The housing forms an inlet passage to provide cooling fluid to the annular chamber, and an outlet passage to remove cooling fluid from the annular chamber.

A steel for cold forging has a predetermined chemical composition, satisfies d+310.0 and SA/SB<0.30, includes 1200/mm.sup.2 or more of sulfides having an equivalent circle diameter of 1.0 to 10.0 m in a microstructure, and has an average distance between the sulfides of less than 30.0 m. Here, d is an average value of equivalent circle diameters of sulfides having an equivalent circle diameter of 1.0 m or more, is a standard deviation of the equivalent circle diameters of the sulfides having an equivalent circle diameter of 1.0 m or more, SA is the number of sulfides having an equivalent circle diameter of 1.0 m or more and less than 3.0 m, and SB is the number of the sulfides having an equivalent circle diameter of 1.0 m or more.

Provided is a rail vehicle axle having an excellent fatigue limit and notch factor. A rail vehicle axle according to the present embodiment has a chemical composition consisting of, in mass %, C: 0.20 to 0.35%, Si: 0.20 to 0.65%, Mn: 0.40 to 1.20%, P: 0.020% or less, S: 0.020% or less, Cu: 0 to 0.30%, Ni: 0 to 0.30%, Cr: 0 to 0.30%, Mo: 0 to 0.08%, Al: 0 to 0.100%, N: 0.0200% or less, V: 0 to 0.060%, and Ti: 0 to 0.020%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2):
0.58C+Si/8+Mn/5+Cu/10+Cr/4+V0.67(1)
Si+0.9Cr0.50(2) where, each element symbol in Formulae (1) and (2) is substituted by the content (mass %) of a corresponding element.

Provided is a rail vehicle axle having an excellent fatigue limit and notch factor. A rail vehicle axle according to the present embodiment has a chemical composition consisting of, in mass %, C: 0.20 to 0.35%, Si: 0.20 to 0.65%, Mn: 0.40 to 1.20%, P: 0.020% or less, S: 0.020% or less, Cu: 0 to 0.30%, Ni: 0 to 0.30%, Cr: 0 to 0.30%, Mo: 0 to 0.08%, Al: 0 to 0.100%, N: 0.0200% or less, V: 0 to 0.060%, and Ti: 0 to 0.020%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2):
0.58C+Si/8+Mn/5+Cu/10+Cr/4+V0.67(1)
Si+0.9Cr0.50(2) where, each element symbol in Formulae (1) and (2) is substituted by the content (mass %) of a corresponding element.