Sleeve, production method thereof and mixture for production of same

Abstract

Procedure for the production of sleeves for mini-deadheads, in which a fluoride-free mixture, consisting of microspheres of aluminium silicate, an oxidizable metal, such as powdered aluminium, an oxidizable agent, magnesium as initiator element of the exothermic reaction, are introduced by blowing in a mould fitted with two cores to produce a sleeve provided with two openings, one of which is closed with a plug before being used.

Description

FIELD OF THE INVENTION [0001] This invention refers to exothermic sleeves for obtaining mini-deadheads applicable in the obtaining of cast pieces, especially in ductile iron, in the procedure for its production by blowing and curing and in the mixture which constitutes said sleeve. BACKGROUND OF THE INVENTION [0002] The production of cast metallic pieces comprises the pouring of the molten metal into a mould, the solidification of the metal by cooling and the de-moulding or extraction of the piece formed by means of the removal or destruction of the mould. [0003] The moulds can be metallic or they can be formed by aggregates of different materials (ceramics, graphite and, mainly, sand). These moulds need to have some sprues or runners for communication between the internal cavity and the exterior, through which the molten metal is poured in the moulding or casting phase. Due to the contraction of the metal during the cooling process, some overflows have to be foreseen in the mould w...

AI Technical Summary

Benefits of technology

[0018] The starting point for this is, in the first place, blowing the mixture which will constitute the fluoride-free sleeve, into a mould which has two cores which, on one hand, will make possible the extraction of the sleeve once cured and, on the other hand, the obtaining of two orifices: one of them in the actual mouth of the sleeve, the orifice of which has a double interior circumferential chamfer, capable of producing an equivalent notch in the deadhead when the sleeve performs its function at the time of the casting. Another orifice in the base opposite the mouth, which will be closed, after the sleeve is cured, with a cheap material, because that area of the sleeve has no operational function in the casting process and only needs to be closed for the purpose of preventing sand or other undesirable materials from falling inside the deadhead.

[0030] The use of these sleeves allows the manufacture of high quality pieces, without degradation of the graphite nodules in the deadhead-piece contact zone, at reduced cost, comparatively less than that of other conventional procedures which deliver pieces of similar quality based on contact between the deadhead and the piece through an intermediate biscuit.

Problems solved by technology

This result is achieved by increasing the exothermic load of the sleeve, but this increased exothermicity gives rise to undesired collateral problems, such as: 1.

The excess of residual aluminium in the deadhead, which is later recast, gives rise to problems with pores in the molten pieces.

Degradation of the nodules in the area of contact of the sleeve with the piece which results in the rejection of pieces through non-compliance with the specifications for nodulation required by the client.

This second problem is originated by the excess of fluorine proceeding from the fluorinated materials which are habitually used as initiating charge in the exothermic reaction.

This biscuit, its production and securing to the sleeve, signify a substantial additional expense.

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