A method for manufacturing a crankshaft for an internal combustion engine with a plurality of journals having a hardened case with a first microstructure. The crankshaft is comprised of a steel comprising between about 0.3 wt % and 0.77 wt % Carbon. The first microstructure of the hardened case of the journals comprises between about 15% and 30% ferrite and a balance of martensite and the resultant subsurface residual stress between 310 MPa and 620 MPa.

A device is disclosed for measuring Barkhausen noise of a crankshaft to identify defects in the crankshaft while the crankshaft is installed on an engine, comprising: a housing configured to attach to a connecting rod; at least one sensor assembly mounted to the housing including at least one Barkhausen noise sensor; and a spring disposed between the housing and the at least one Barkhausen noise sensor to urge the at least one Barkhausen noise sensor into contact with a pin journal of the crankshaft as the crankshaft rotates.

A method for manufacturing a crankshaft for an internal combustion engine with a plurality of journals having a hardened case with a first microstructure. The crankshaft is comprised of a steel comprising between about 0.3 wt % and 0.77 wt % Carbon. The first microstructure of the hardened case of the journals comprises between about 15% and 30% ferrite and a balance of martensite and the resultant subsurface residual stress between 310 MPa and 620 MPa.

A method for manufacturing a crankshaft for an internal combustion engine with a plurality of journals having a hardened case with a first microstructure. The crankshaft is comprised of a steel comprising between about 0.3 wt % and 0.77 wt % Carbon. The first microstructure of the hardened case of the journals comprises between about 15% and 30% ferrite and a balance of martensite and the resultant subsurface residual stress between 310 MPa and 620 MPa.

A device is disclosed for measuring Barkhausen noise of a crankshaft to identify defects in the crankshaft while the crankshaft is installed on an engine, comprising: a housing configured to attach to a connecting rod; at least one sensor assembly mounted to the housing including at least one Barkhausen noise sensor; and a spring disposed between the housing and the at least one Barkhausen noise sensor to urge the at least one Barkhausen noise sensor into contact with a pin journal of the crankshaft as the crankshaft rotates.

A nitrided steel part excellent in bending straightening ability and bending fatigue characteristic enabling reduction of size and decrease of weight of parts or enabling demand for high load capacities to be met, using as a material a steel material containing, by mass %, C: 0.2 to 0.6%, Si: 0.05 to 1.5%, Mn: 0.2 to 2.5%, P: 0.025% or less, S: 0.003 to 0.05%, Cr: 0.05 to 0.5%, Al: 0.01 to 0.05%, and N: 0.003 to 0.025%, and having a balance of Fe and impurities, having formed on the steel surface a compound layer of a thickness 3 m or less comprising iron, nitrogen, and carbon and a hardened layer formed below the compound layer, and having an effective hardened layer depth of 160 to 410 m.

A rack bar includes: a rack tooth row including a plurality of rack teeth meshing with pinion teeth; a hardened layer provided continuously over an entire circumference of the rack tooth row; and a center portion provided inside the hardened layer and having lower hardness than the hardened layer. When the rack bar is viewed in an axial direction of the rack bar, a depth of the hardened layer from the following positions i), ii), and iii) increases in this order: i) a bottom land of the rack teeth; ii) a side of the rack bar relative to the bottom land; and iii) a back of the rack bar relative to the bottom land.

A steel for induction hardening according to an aspect includes, as a chemical composition, predetermined amounts of alloy elements and a remainder including Fe and impurities, in which AlN is 0.000330 to 0.000825, Mn/S is 4.6 to 14.0, a machinability index M is 15.5 to 25.65, an area fraction of AlN having an equivalent circle diameter of more than 200 nm at a position of a diameter of the steel is 20% or less of an area fraction of all AlN having an equivalent circle diameter of 40 nm or more, and a number density of Mn sulfide-based inclusions having a maximum diameter of 0.3 m or more and 10 m or less at the position of the diameter is 100 pieces/mm.sup.2 or more and 2500 pieces/mm.sup.2 or less.

Disclosed is a steel whose composition includes specified wt % of: Ni, Mo, Co, Mo+Co+Si+Mn+Cu+W+V+Nb+Zr+Y+Ta+Cr+C+Al+B+Ti+N, Ni+Co+Mo, Al, Ti, N, Si, Mn, C, S, P, B, H, O, Cr, Cu, W, Zr, Ca, Mg, Nb, V, Ta, Y, the remainder being iron and impurities resulting from production. The inclusion population, observed by image analysis on a polished surface of 650 mm.sup.2 if the steel is in the form of a hot-formed part or a hot-rolled sheet and 800 mm.sup.2 if the steel is in the form of a cold-rolled sheet, does not include non-metal inclusions of an equivalent diameter greater than 10 m. Also disclosed are a product created from the steel, and a manufacturing method.

Disclosed is a steel whose composition includes specified wt % of: Ni, Mo, Co, Mo+Co+Si+Mn+Cu+W+V+Nb+Zr+Y+Ta+Cr+C+Al+B+Ti+N, Ni+Co+Mo, Al, Ti, N, Si, Mn, C, S, P, B, H, O, Cr, Cu, W, Zr, Ca, Mg, Nb, V, Ta, Y, the remainder being iron and impurities resulting from production. The inclusion population, observed by image analysis on a polished surface of 650 mm.sup.2 if the steel is in the form of a hot-formed part or a hot-rolled sheet and 800 mm.sup.2 if the steel is in the form of a cold-rolled sheet, does not include non-metal inclusions of an equivalent diameter greater than 10 m. Also disclosed are a product created from the steel, and a manufacturing method.