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 and apparatus for heat treatment of an object, such as for hardening of objects with complex shapes such as crankshafts, includes the steps of projecting an energy beam such as a laser beam onto a surface of the object, operating a scanner so as to repetitively scan the beam to displace a primary spot in accordance with a first scanning pattern so as to establish an effective spot on the object, and displacing the effective spot in relation to the surface of the object. The beam follows an optical path between the scanner and the surface of the object. A beam deflector device is placed in the optical path to redirect the beam. The beam deflector device can be placed close to the surface of the object.

A method and apparatus for heat treatment of an object, such as for hardening of objects with complex shapes such as crankshafts, includes the steps of projecting an energy beam such as a laser beam onto a surface of the object, operating a scanner so as to repetitively scan the beam to displace a primary spot in accordance with a first scanning pattern so as to establish an effective spot on the object, and displacing the effective spot in relation to the surface of the object. The beam follows an optical path between the scanner and the surface of the object. A beam deflector device is placed in the optical path to redirect the beam. The beam deflector device can be placed close to the surface of the object.

The invention relates to a method for the impact treatment of transition radii (8) of a crankshaft (4), in particular transition radii (8) between connecting rod bearing journals (5) and crank webs (7) and/or transition radii (8) between main bearing journals (6) and the crank webs (7) of the crankshaft (4). In order to apply an impact force (FS) to at least one of the transition radii (8) along the respective transition radius (8) circulating about the crankshaft (4) in an annular manner, a heavily loaded region (BMAX), a lightly loaded region (BMIN), and intermediate regions (BZW) lying therebetween are defined, and an impact treatment is then carried out such that the impact force (FS) introduced into the intermediate regions (BZW) is increased in the direction of the heavily loaded region (BMAX).

The invention relates to a device for the impact treatment of transition radii (8) of a crank-shaft (4), in particular transition radii (8) between connecting rod bearing journals (5) and crank webs (7) and/or transition radii (8) between main bearing journals (6) and the crank webs (7) of the crankshaft (4). The device comprises an impact device (1) in order to introduce an impact force (FS) into at least one transition radius (8), wherein the impact device (1) has multiple impact heads (21) which are paired with the same transition radius (8).

An induction-hardened crankshaft is provided that offers an excellent balance of fatigue strength, machinability and quench-cracking resistance. An induction-hardened crankshaft has a chemical composition of, in mass %: 0.30 to 0.60% C; 0.01 to 1.50% Si; 0.4 to 2.0% Mn; 0.01 to 0.50% Cr; 0.001 to 0.06% Al; 0.001 to 0.02% N; up to 0.03% P; 0.005 to 0.20% S; 0.005 to 0.060% Nb; and balance Fe and impurities, the non-induction-hardened portion having a microstructure mainly composed of ferrite-pearlite and having a fraction of ferrite Fα satisfying the expression (1) provided below, the induction-hardened portion having a microstructure mainly composed of martensite or tempered martensite, and having a prior austenite grain diameter not larger than 30 μm,

Fα≥150×[C %]+84   (1), where the C content in mass % in the induction-hardened crankshaft is substituted for [C %].

An induction-hardened crankshaft is provided that offers an excellent balance of fatigue strength, machinability and quench-cracking resistance. An induction-hardened crankshaft has a chemical composition of, in mass %: 0.30 to 0.60% C; 0.01 to 1.50% Si; 0.4 to 2.0% Mn; 0.01 to 0.50% Cr; 0.001 to 0.06% Al; 0.001 to 0.02% N; up to 0.03% P; 0.005 to 0.20% S; 0.005 to 0.060% Nb; and balance Fe and impurities, the non-induction-hardened portion having a microstructure mainly composed of ferrite-pearlite and having a fraction of ferrite Fα satisfying the expression (1) provided below, the induction-hardened portion having a microstructure mainly composed of martensite or tempered martensite, and having a prior austenite grain diameter not larger than 30 μm,

Fα≥150×[C %]+84   (1), where the C content in mass % in the induction-hardened crankshaft is substituted for [C %].

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 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 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.