SU149226A1 - Method of making machine parts - Google Patents

Description

Known are: cases of production of machine parts, for example, exhaust valves of internal combustion engines for heat-resistant sintered powder coatings. However, these methods are not economical, and do not ensure the density of sintered billets.

The proposed method is devoid of these disadvantages. This is achieved in that the blanks are subjected to cold compression.

The dryness of the method is as follows. The ring b, pressed from a powder alloy or a mixture of metal powders, with an outer diameter slightly larger than the diameter of the steel billet, is tightly put on the level of the steel billet neck a (see drawing). Billets with powder rings mounted on the powder rings enter the electric furnace for sintering in a reducing or neutral atmosphere or in vacuum at a temperature of 1000–1300 ° for 1-2 hours (depending on the alloy composition). The preforms are cooled to ambient temperature in the same atmosphere. As a result of sintering, compaction (shrinkage) of the powder alloy occurs and it is “sintering to the steel base. The density of the alloy and its adhesion to the base, however, are still insufficient (usually the residual porosity ranges from 10-15%). To improve adhesion and increase the density, sintered billets are further subjected to cold deformation or heated deformation using known methods (cross rolling, forging, smooth, etc.) with the powder layer being compressed to the diameter of the base metal.

After deformation, the bimetallic billet is again sintered under the same conditions. As a result of this treatment (deformation - sintering), the density of the powder alloy reaches the theoretical value (zero porosity) and a smooth diffusion transition layer is created at the interface of the powder alloy - steel. In order to reduce the temperature of processing (sintering) n in order to avoid

If it is harmful to steel, it is possible to process the cycle "pressure - sintering twice and more times.

Since the heating (sintering) operation is performed in a reducing or neutral medium (in hydrogen, dissociated ammonia, converted natural gas, etc.), etching, measuring, and. and turning the workpiece completely absent. The bimetallic billet then goes on to manufacture from it the well-known deformation spas (pressing, stamping, etc.), for example, ready-made valves of a given shape-size with a protective coating. After pressing, the bimetallic valve (like a conventional steel valve) is subjected to conventional thermal and mechanical processing.

Subject invention

A method of manufacturing machine parts, for example, exhaust valves of internal combustion engines with a heat-resistant coating of sintered powder, characterized in that, in order to increase the density of the sintered blanks, the latter are subjected to compression in the cold state.