Process for producing machine components from cast mineral

Details Process for producing machine components from cast mineral Process for producing machine components from cast mineral

1996-10-18

1998-08-18

Theisen, Mary Lynn

Plastic and nonmetallic article shaping or treating: processes

Treatment of material by vibrating, jarring, or agitating...

By reciprocating or vibrating mold

264102, 264109, 264112, B29C 3942

Patent

active

057955140

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a process for producing machine components from highly corrosion- and wear-resistant cast mineral especially for the manufacture of monolithically cast pump housing or pump parts, in which process the vehicle is first mixed with the filler in a positive mixer and the finished mixture is poured into a mold and cured.
Such a process is known, for example from DE-A-42 06 603. Cast mineral for pump parts is understood to be, for example a mixture of chemically stable and temperature-resistant reaction resin with suitable fillers such as, for example silicon carbide, quartz sand, glass, ceramics etc. For enhancing the resistance to chemicals and the resistance to wear of such pump parts, the mixture contains as much filler as possible and as little reaction resin as possible. By adjusting a favorable grain distribution, such a highly filled cast mineral contains, for example 10 to 40% by weight reaction resin and 60 to 90% by weight filler. A special problem in the manufacture of, for example pump housings or pump pistons for rotary pumps from such cast mineral is the relatively low tensile strength of said material. Such excessively low tensile strength is substantially caused by the fact that the reaction resin used as the vehicle fails to combine with the filler particles with adequate strength. The poor embedding and fixing of the filler particles also has the consequence that filler particles become detached from the composite on highly stressed surfaces, which leads to undesirable erosions on the surfaces in spite of the high resistance of the filler particles to wear.
In the manufacture of pump housings from cast mineral, it has already been attempted to compensate the lack of tensile strength of the material by a multi-shell structure, and by intermediate layers of, if need be, prestressed reinforcements. However, such a multi-shell structure, as compared to the single-piece, monolithic cast piece, leads to unacceptably high manufacturing costs due to the successive casting of the individual shells.
Another problem in the manufacture of thick-walled machine components from highly filled cast mineral is the poor machinability of the finished blank. It is consequently extremely difficult to carry out, if need be, remachining work on the finished blank.
The problem of the invention is to further develop the process of the type specified above in a way such that the manufactured monolithic cast piece is provided with a superior tensile strength and a superior inner coherence, and that it can be reworked in a simple way, if necessary.
For solving said problem, the invention proposes on the basis of the process specified above that mixer at a temperature of higher than 20.degree. C. and at a pressure of under 80 mbar, particularly under 20 mbar; temperature of higher than 60.degree. C., and the slightly cured casting is removed from the mold; if need be; and 120.degree. C.
The process according to the invention has the special advantage that the mixture is completely degasefied before it is poured into the casting mold. In this way, especially the air unavoidably introduced together with the filler is completely removed from the mixture. Like the air, all gases forming during the mixing the synthetic resin-hardener system, and the residual moisture are safely removed from the mixture. As no air inclusions at all can get into the mixture even with rising casting, the casting overall is provided with a structure that is free of bubbles and pore the highest possible degree. Due to the fact that in the process according to the invention, all intermediate spaces between the filler particles are completely filled with vehicle, the resulting casting has distinctly superior strength properties as compared to the state of the art, and, moreover, it is significantly more resistant to erosion.
By using a hot-curing synthetic resin-hardener system, it is possible in the process according to the invention to influence the curing process in a controlled way, i.e., the keep the mixture liquid during

REFERENCES:
patent: 3644608 (1972-02-01), Valentine
patent: 5492661 (1996-02-01), Weddigen et al.

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