Anti-veining additive for the production of casting molds and cores

Abstract

The present invention belongs to the field of the additives for molding sands used in the manufacture of casting molds and cores. More specifically, the present invention relates to an additive to prevent veining in the manufacture of metal parts, to a molding sand comprising said additive, to a core or mold prepared from said molding sand and to a metal part prepared by means of using one of said cores or molds.

Description

FIELD OF THE INVENTION[0001]The present invention belongs to the field of additives for molding sands used in the manufacture of casting molds and cores. More specifically, the present invention relates to an additive to prevent veining in the manufacture of metal parts, to a molding sand comprising said additive, to a core or mold prepared from said molding sand and to a metal part prepared by means of using one of said cores or molds.BACKGROUND OF THE INVENTION[0002]The castings obtained using cores and molds manufactured with molding sands generally have a series of shape defects that must be later machined to obtaining a dimensionally suitable part. These defects occur because the core or mold experiences heating due to the effect of the molten metal which is poured therein, which causes its expansion and, as a consequence, the occurrence of cracks on its surface. The molten metal penetrates into these cracks, thus forming a type of partitions or lamellas on the surface of the p...

AI Technical Summary

Benefits of technology

The invention provides cores and molds that have the same mechanical performance as traditional sand-based cores and molds, but without the issue of veining. Additionally, the gas produced by the invention is significantly reduced and stabilizes after 20 minutes, similar to other commercial anti-veining additives.

Problems solved by technology

The castings obtained using cores and molds manufactured with molding sands generally have a series of shape defects that must be later machined to obtaining a dimensionally suitable part.

These defects occur because the core or mold experiences heating due to the effect of the molten metal which is poured therein, which causes its expansion and, as a consequence, the occurrence of cracks on its surface.

Nevertheless, in addition to not eliminating the veining in many cases, this technique has the drawbacks of the iron oxide reducing the mechanical strength of the core and, furthermore, the formation of fayalite increases the tendency of penetration causing the outer surface of the part obtained to have irregularities which must be later treated.

The problem again is the reduction of the mechanical strength of the core.

The main drawback of this technique is that since the flour burns, a large amount of gas is produced which, when diffuse, can lead to dimensional problems in the obtained parts.

The drawback of this technique is that the cores obtained have a certain tendency to penetration, the application of paints or other treatments on the surface of the cores obtained being necessary before casting the part.

The problem of these hollow microspheres is that when they are used in amounts less than 10% by weight in the sand mixture they do not give optimal results, i.e., they do not always prevent veining to the extent that is required.

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