Casting Procedure, Particularly for an Engine Cylinder Head

Abstract

Cast parts having internal cavities or passages are produced by using a main core and one or more secondary cores. The secondary cores are associated with the main core by coating the secondary cores with a material which dissolves on contact with mold metal. The cores to be coated can also be formed by hollow inserts made of a heat resistant material, filled with sand polymerized resin.

Description

[0001] This application is a continuation of application Ser. No. 10 / 530,196 filed Apr. 4, 2005, now abandoned, which was the U.S. national stage of international application PCT / IT02 / 00771 filed Dec. 9, 2002, which claims priority from Italian Patent Application BS2002A000088, filed Oct. 4, 2002, all of which applications are incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention relates in general to the technology of metal casting. In particular, it relates to gravity chills and low-pressure processes that use cores to produce cavities in the casting. A typical example of such casting process is that used for making engine cylinder heads, where internal cores are necessary to produce the water jacket for the engine cooling water, the intake and exhaust ducts, and any other secondary cavity. BACKGROUND OF THE INVENTION [0003] Generally, for medium and large productions, engine cylinder heads are cast using a fixed outside mold, called a chill. Interna...

AI Technical Summary

Benefits of technology

[0016] An object of the present invention is to obviate the disadvantages of the prior art mentioned above, by providing a new casting procedure which allows one to obtain higher quality castings, thereby reducing the amount of scrap due to dimensional defects, and further introducing new design prospects.

[0017] Another object of the invention is to provide a casting procedure which allows a perfect relative positioning between each core and an easy insertion of the cores into the mold or into another core, whichever their shape.

[0018] Another object is to provide a casting procedure which allows considerable simplification of the core boxes, that is, without complex shapes, undercuts and connected moving parts, and which is therefore cheaper, more reliable and easier to achieve.

[0019] Another object of the invention is to provide a chill casting process for engine cylinder heads which allows one to make cores for intake and exhaust ducts without any deformation on the outside thickness and with the most varied and complex shapes. This may result in better engine performance and more advanced engines as regards exhaust gases.

[0020] Yet another object of the invention is to provide a casting procedure for engine cylinder heads which allows embedding inserts for the ducts into the casting, the inserts being made of a refractory material capable of standing the heat generated by the molten metal in order to obtain perfectly smooth ducts which should contribute to improving the engine efficiency.

Problems solved by technology

When casting in a chill with sand and polymerized resin cores, the main difficulty is perfectly positioning the inside of the part to be cast, that is the cores, with the outside, so as to obtain the required dimensional accuracy.

This reduces the size of the water jacket core, making it more brittle and at the same time lower efficiency of the cooling circuit.

However, this results in higher production costs and lower quality of the finished product, particularly because of the casting flashes that may project into the water circulation compartment, and due to casting blowholes that may develop from the possible contact of molten metal with the half-core fixing adhesive.

But is has the disadvantage—in the case of an engine cylinder head casting—that the duct shapes, even though coated, are not optimal since their surfaces are molded and therefore directly finished by the polystyrene surfaces.

The necessary use of glue, actually, is the primary cause of blowholes.

Thus, this process is seldom used.

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