CS267554B1 - Metallic mould for iron castings casting - Google Patents

Abstract

it is a metal Torny pro production of cast iron castings. The essence of the solution it is that the metal form is equipped with thermal insulation dilatation through space through the β cavity mold, or cavity mold and dilatation the space is separated by temperature unstable partition. The solution can be used everywhere where they are produced in foundries Castings of graphite cast iron by casting into metal forms.

Description

The invention relates to the construction of a metal mold for the production of cast iron castings.

Hitherto, in the production of graphite cast iron castings produced by casting in metal molds, molds are used which do not allow the excess metal formed during solidification to be discharged outside the cavity of the mold forming the casting. The production of graphite cast iron castings by casting into metal molds has some advantages. In particular, the tightness of castings is appreciated, which is a basic prerequisite for their use, for example for the production of components of hydraulic control and management systems. This foundry production technology presents some problems arising from the increase in the volume of the melt in the mold. The phenomenon is caused and conditioned by the precipitation of graphite in solidifying cast iron. The consequence of increasing the volume of the melt in the inflexible mold results in the formation of crystallization pressures, which are manifested by the fact that they act against the force of the gripping part of the metal mold and expand it. This reduces the dimensional accuracy of the castings in directions perpendicular to the parting plane of the mold. The effect of pressure on the metal mold causes premature cracking and thus reduces the life of the fort. In castings with pre-cast cavities, where sand or ceramic cores are used to shape these cavities, and in castings cast in metal molds with false sand cores forming more complex parts of the outer surface of the casting, molten cast iron enters the core and degrades the casting. that they degrade the quality of internal and external surfaces and are the cause of unsatisfactory geometry of cavities and possibly their impermeability. Defects are usually irreparable and the reason for scrapping the casting.

These disadvantages are eliminated by the metal mold for the production of cast iron castings according to the invention. Its essence lies in the fact that the metal mold is provided with a thermally insulated expansion space, formed by the inner cavity of the thermal insulation insert, made of the molding mixture and connected by at least one channel to the mold cavity. According to another feature, the mold cavity and the expansion space are separated by a partition which is thermally unstable and is formed by a weakened wall or bottom of the thermal insulation insert of the foundry molding compound.

In the metal form, an expansion space is formed outside the melt-forming cavity, which is connected to the casting-forming cavity so that the excess cast iron formed during solidification is forced into this space. It is therefore advantageous that the expansion space is provided with a thermally insulating lining so that the cast iron solidifies in it later than in the casting. This prolongs the effective time with minimal metal consumption.

The advantage of the metal foray for the production of cast iron castings according to the invention is that the mold allows the dilatation of the molten cast iron during solidification, whereby the pressure effect on the mold and the sand or ceramic cores is reduced to metalloetic pressure.

Exemplary embodiments of a metal mold for casting cast iron castings according to the invention are shown in the drawings, where in Fig. 1 an expansion space 7 is arranged in the expansion hole of the metal mold 3, transfer of excess cast iron to the expansion space £ from the cavity 2 of the mold Fig. 2 shows a solution of a metal mold £ in which the expansion space 1 and the thermal insulation insert 4 are part of a sand or ceramic core 5. Even in this case the expansion space £ with the cavity 2 of the mold 6 is connected by channels 6. In Fig. 3 the construction of the metal mold 3 and the expansion space 1, where the bottom of the thermal insulation insert 4 is weakened at the through hole and forms a thin-walled partition 7 , arising as a result of volume changes accompanying the crystallization of graphitic cast irons, disrupts and clears the way for the transfer of excess cast iron to the expansion space The advantage of the embodiment is that the cast iron fills only the cavity 2 of the mold. The cold strength of a thermally unstable partition 7 must be such as to withstand the dynamic pressure

- 2 CS 267 554 B1 of molten cast iron formed during the filling of a metal mold with liquid metal *. Therefore, foundry or sand mixtures with organic binders are preferably used for the production of thermal insulation inserts, which burn me under the effect of heat and lose their ability to bind ceramic or sand slag.

Possible uses of the invention are in all foundries producing castings from graphite cast iron castings.

Claims (2)

A metal mold for casting cast iron castings, characterized in that it is provided with a thermally insulated expansion space (1) formed by the inner cavity of a thermal insulation insert (4) inserted into the expansion hole of a metal mold (3) made of a foundry molding compound, wherein the expansion space (1) is connected to the cavity (2) of the metal mold (3) by at least one channel (6); 2. A metal mold according to claim 1, characterized in that the cavity (2) of the metal mold (3) and the expansion space (1) are separated from each other by a thermally unstable partition (7) formed by a weakened wall or bottom of the thermal insulation insert (4). made of foundry molding compound.