A turbocharger wheel (4) and shaft (1) assembly exhibits a frustoconical geometry of welding zone contact surfaces extending to the outer circumference of the shaft (1). This frustoconical geometry not only allows continuous centering of the parts (1, 4) during joining, it also eliminates the problem of stress propagation along a plane. The location of the electron beam is shifted so that only the radially outer segment of the frustoconical contact surface is joined by welding, leaving a radially inner unmelted and unfused zone for maintaining firm contact of the oblique surfaces.

A piston rod manufacturing method of manufacturing a piston rod by joining a solid rod main body and a solid rod head includes a first step of joining respective end surfaces of the rod main body and the rod head by friction welding; and a second step of performing boring process on an axial center portion from the rod head side so as to penetrate through a joining face between the rod main body and the rod head.

A method for manufacturing a piston with a re-molten reinforced combustion chamber throat is provided. The manufacturing steps includes: a) piston rough machining: machining allowances of the combustion chamber throat and the combustion chamber bottom are 1-3 mm; b) piston washing and degreasing treatment; c) coating or spraying a surfactant on the combustion chamber throat and the combustion chamber bottom that need to be re-molten, wherein the surfactant formula comprises the components TiO.sub.2, SiO.sub.2, CuCl.sub.2 and MnCl.sub.2 that are mixed in percentage: 1-30% of TiO.sub.2, 1-30% of SiO.sub.2, 1-40% of CuCl.sub.2 and 1-50% of MnCl.sub.2; after the four components are uniformly mixed, a suspension is prepared by using acetone as a solvent a mass ratio of 1:(3-8); d) re-melting the piston by using an A-TIG welding method; and f) after re-melting, processing the piston into a finished product.

A method for manufacturing a piston with a re-molten reinforced combustion chamber throat is provided. The manufacturing steps includes: a) piston rough machining: machining allowances of the combustion chamber throat and the combustion chamber bottom are 1-3 mm; b) piston washing and degreasing treatment; c) coating or spraying a surfactant on the combustion chamber throat and the combustion chamber bottom that need to be re-molten, wherein the surfactant formula comprises the components TiO.sub.2, SiO.sub.2, CuCl.sub.2 and MnCl.sub.2 that are mixed in percentage: 1-30% of TiO.sub.2, 1-30% of SiO.sub.2, 1-40% of CuCl.sub.2 and 1-50% of MnCl.sub.2; after the four components are uniformly mixed, a suspension is prepared by using acetone as a solvent a mass ratio of 1: (3-8); d) re-melting the piston by using an A-TIG welding method; and f) after re-melting, processing the piston into a finished product.

A heavy duty piston for an internal combustion engine comprises a thermally conductive composition filling 10 to 90 vol. % of a sealed cooling gallery. The thermally conductive composition includes bismuth and/or tin. For example, the thermally conductive composition can be a single-phase binary mixture of bismuth and tin. The thermally conductive composition has improved thermal properties, for example a melting point around 139 C., a thermal conductivity around 22 W/m.Math.K, and a thermal diffusivity around 1.43 E-5 m.sup.2/s. The thermally conductive composition is not reactive and does not include toxic or cost-prohibitive metals. During high temperature operation, as the piston reciprocates in the cylinder bore, the thermally conductive composition flows throughout the cooling gallery to dissipate heat away from the upper crown and thus improve efficiency of the engine.

Pistons and methods of making the same are disclosed. An exemplary piston assembly may include a piston crown and skirt. The crown may include a crown collar wall extending downward toward a free end of the crown collar wall. The skirt may include a pair of oppositely disposed pin bosses that each define piston pin bores configured to receive a piston pin for securing a connecting rod between the pin bosses. The skirt may further include a radially inner skirt mating surface abutted along a radially inner interface region with the radially inner crown mating surface, and a radially outer skirt mating surface abutted along a radially outer interface region with the radially outer crown mating surface such that a cooling gallery is substantially enclosed. The skirt may further include an inner collar wall extending upwards to the free end of the crown collar wall.

A steel piston achieving increased thermal brake efficiency in an internal combustion engine is provided. The piston includes a crown presenting a combustion surface, an outer side wall depending from the combustion surface, an outer cooling gallery, and an undercrown cooling gallery. The outer cooling gallery extends circumferentially along the outer side wall beneath the combustion surface. According to one embodiment, the outer cooling gallery is sealed and filled with air, argon, helium, xenon, or carbon dioxide as a cooling media. In this embodiment, the undercrown cooling gallery is filled with air as a cooling media and includes an open inlet hole having a diameter being from 2% to 4% of an outer diameter of the piston. Alternatively, the undercrown cooling gallery is filled with air, argon, helium, xenon, or carbon dioxide as a cooling media, and the inlet hole is sealed.

Exemplary piston assemblies and methods of making the same are disclosed. An exemplary piston may include a piston body defining a piston axis, the piston body having a skirt and forming a lower surface of a cooling gallery. The body may include radially inner and outer body mating surfaces. The piston may further include a cooling gallery ring cooperating with the piston body to form the cooling gallery. The piston body and cooling gallery ring may be joined together along radially inner and radially outer interface regions to form a generally one-piece piston assembly. In some exemplary approaches, mating surfaces of the body and ring may be positioned adjacent a support surface configured to inhibit or prevent weld spatter formed in a process joining the ring and body from the cooling gallery.

A piston for an internal combustion engine may include a substantially circular body composed of an aluminum containing base material defining a top portion having at least one cavity. At least one coating layer may be disposed on at least one area defined by at least one of the top portion and the at least one cavity. The at least one coating layer may include at least one chemical compound derived from a chemical reaction between the base material of the body and the at least one coating layer in response to friction generated by a dragging movement of a non-consumable rotary pin with the at least one coating layer.

An exemplary piston may include a piston body having radially inner and outer body mating surfaces. The piston may further include a cooling gallery ring cooperating with the piston body to form a continuous upper combustion bowl surface and a cooling gallery. The cooling gallery ring may have radially inner and outer ring mating surfaces abutted along their corresponding radially inner and outer body mating surfaces, such that the cooling gallery is substantially enclosed. The piston body and cooling gallery ring may be joined together along the radially inner and radially outer interface regions to form a generally one-piece piston assembly. The radially outer interface region may be elongated in a direction parallel to the piston axis, e.g., facilitating a laser welding joining process.