A forged crankshaft (1) includes a carbon steel containing S, wherein in a portion corresponding to a machined outer circumferential surface of a shaft part such as journals (J), crank pins (P), a front part (Fr), and a flange (Fl), a ratio x/y of an area rate x of sulfide in a position (X) corresponding to a parting surface of a die for finish forging to an area rate y of sulfide in a position (Y) corresponding to a bottom of a die impression of the die for finish forging is equal to or lower than 1.5. The forged crankshaft (1) can avoid an occurrence of machined surface cracks on the journals (J) and the crank pins (P) after the outer circumferential surface is machined.

A method of heat treating a workpiece, the method including projecting a laser beam from a laser source onto said workpiece, so as to produce a laser spot on said workpiece; projecting the laser spot onto different portions of said workpiece; and while projecting the laser spot, repetitively scanning the laser beam in two dimensions so as to produce a two-dimensional equivalent effective laser spot on said workpiece and thereby temper, reduce hardness of, enhance ductility of, and/or reduce brittleness of at least one of the different portions of the workpiece.

A method of laser hardening of a surface area of a workpiece, such as a surface of a journal of a crankshaft, including the steps of generating a relative movement between the surface of the workpiece and a laser source to allow a laser spot to subsequently be projected onto different portions of the surface area, and during the relative movement, repetitively scanning the laser beam so as to produce a two-dimensional equivalent effective laser spot on the surface area. The energy distribution of the effective laser spot is adapted so that it is different in a more heat sensitive subarea, such as in an area adjacent to an oil lubrication opening, than in a less heat sensitive subarea, so as to prevent overheating of the more heat sensitive subarea.

A method of heat treating a workpiece, the method including projecting a laser beam from a laser source onto said workpiece, so as to produce a laser spot on said workpiece; projecting the laser spot onto different portions of said workpiece; and while projecting the laser spot, repetitively scanning the laser beam in two dimensions so as to produce a two-dimensional equivalent effective laser spot on said workpiece and thereby temper, reduce hardness of, enhance ductility of, and/or reduce brittleness of at least one of the different portions of the workpiece.

A method of laser hardening of a surface area of a workpiece, such as a surface of a journal of a crankshaft, including the steps of generating a relative movement between the surface of the workpiece and a laser source to allow a laser spot to subsequently be projected onto different portions of the surface area, and during the relative movement, repetitively scanning the laser beam so as to produce a two-dimensional equivalent effective laser spot on the surface area. The energy distribution of the effective laser spot is adapted so that it is different in a more heat sensitive subarea, such as in an area adjacent to an oil lubrication opening, than in a less heat sensitive subarea, so as to prevent overheating of the more heat sensitive subarea.

Method of laser hardening of a surface area of a workpiece, such as a surface of a journal of a crankshaft, comprising: generating a relative movement between the surface of the workpiece and a laser source to allow a laser spot to subsequently be projected onto different portions of said surface area, and during said relative movement, repetitively scanning the laser beam (2) so as to produce a two-dimensional equivalent effective laser spot (5) on said surface area. The energy distribution of the effective laser spot is adapted so that it is different in a more heat sensitive subarea, such as in an area adjacent to an oil lubrication opening, than in a less heat sensitive subarea, so as to prevent overheating of said more heat sensitive subarea.

A wrist pin and method of reducing wear between members thereof, a piston, a connecting rod, and methods of construction thereof are provided. The wrist pin has a first portion extending between opposite ends configured for receipt in piston pin bores and a second portion extending between opposite ends configured for receipt in the pin bores. The second portion is configured for relative movement with the first portion. The piston includes a piston body having axially aligned pin bores, wherein at least one of the pin bores has a feature to prevent relative rotation of a wrist pin member. The connecting rod includes a connecting rod body having small end bore. The small end bore has a contour to allow relative rotation of a first wrist pin member therein and a feature to prevent relative rotation of a second wrist pin member therein.

In a crankshaft 200, one hole 213L formed in a crankpin 213 has a bottom surface having a larger area and a depth from a surface of the crankpin less than those of another hole 213M. In forming the hole 213L and the hole 213M, a preformed product 200 of the crankshaft having a shape smaller than that of a cavity is disposed in a die set and punches are simultaneously inserted into the crankpin 213. By this operation, the hole 213L and the hole 213M are simultaneously formed in each crankpin 213 of the preformed product 200.