Methods for casting components

Abstract

A method for casting components from a magnesium alloy, comprising the following steps: Providing a semi-finished product (10) comprising a magnesium alloy and a magnesium fire-retardant additive, namely as the magnesium alloy MgAlZn or MgAlMn or MgZE and as the magnesium fire-retardant additive CaO; Melting the semi-finished product (10) to a melt (13) in a closed melting chamber (12) of a metering furnace (11), wherein the melting takes place under a protective gas atmosphere; Discharging the melt (13) from the melting chamber (12) of the metering furnace (11) via a heated trough (15) and filling the melt (13) via the trough (15) into at least one sand casting mold (14), wherein the discharge of the melt from the metering furnace (11) and the filling of the melt (13) into the sand casting mold(s) (14) take place in a protective gas-free atmosphere; Solidifying the melt in the sand casting mold(s) (14) Sand casting mold (14) and removal of the component from the sand casting mold (14).

Description

The invention relates to a method for casting components made of a magnesium alloy in a sand molding process (sand casting).In practice, it is already known in principle to produce components from magnesium alloys by casting. This has the problem that magnesium alloys are readily flammable and can therefore easily get into fire, such magnesium fire being prevented up to now by casting in sand moulds taking place completely under a protective gas atmosphere. However, this requires a high level of process engineering and apparatus engineering complexity in order to avoid health impairment of persons working in a foundry. A further problem consists in the handling of the melt of the magnesium alloy, namely when supplying the melt to lost casting moulds, since this can hitherto be carried out exclusively manually.DE 102 01983 A1 discloses a casting apparatus for casting metallic components made of aluminum or magnesium. A melt of aluminum or magnesium is introduced into a crucible. The melt subsequently solidifies.CH 51 989 A1 discloses a method for melting and casting magnesium and its alloys, wherein calcium oxide is added to the metal to be melted.HASSE, S. (ed.): FOUNDRYLEXIKON. 19th edition, Berlin: Fachverlag Schile & Schon GmbH, 2008. S.137, 887 - ISBN 978-3-7949-0753-3 discloses a charging device for casting plants in general. A furnace feed, a coupon furnace feed and a molding sand feed are disclosed.FRIEDRICH, H.E.; MORDIKE, B.L.: Magnesium Technology - Metallurgy, Design Data, Applications. Berlin, Heidelberg: Springer-Verlag, 2006, pages 198, 199-ISBN 3-540-20599-3 discloses different magnesium alloys.Proceeding from this, the object of the invention is to create a novel method for casting components made of a magnesium alloy.This object is achieved by a method for casting magnesium alloy components according to claim 1.According to the invention, the method comprises the following steps: providing a semi-finished product which has a magnesium alloy and a magnesium fire protection additive; melting the semi-finished product to form a melt in a metering furnace; removing the melt-in particular by means of a feed pump-from the metering furnace via a heated trough and filling the melt via the trough into at least one sand casting mould; solidifying the melt in the or each sand casting mould and removing the component from the sand casting mould.The method according to the invention takes into account the problems of the prior art. Thus, a semi-finished product is used which, in addition to a magnesium alloy, has a magnesium fire protection additive, with which it is possible to prevent the magnesium alloy from getting into fire under an atmospheric oxygen atmosphere. Therefore, a protective gas atmosphere can be dispensed with as much as possible. Known methods for casting components made of a magnesium alloy use as such a protective gas namely sulphur hexafluoride or SF6, which is, however, environmentally harmful. In the method according to the invention, this inert gas can be dispensed with to the greatest possible extent; instead, the argon which is substantially more unproblematic can be used. With the aid of the metering furnace and the heated trough, automatic handling of the melt, namely automatic feeding of the melt into at least one sand casting mold, is also possible. This enables in particular a reproducible filling of the sand moulds and thus the introduction of quality assurance in sand casting by automated documentation of the casting parameters.The semi-finished product has MgAlZn or MgAlMn or MgZE as magnesium alloy and CaO as magnesium fire protection additive; the expression ZE generally stands for a combination of zinc and rare earths. Such a semi-finished product is particularly preferably suitable for producing magnesium components by casting from a metering furnace into a sand mould. The components formed in this case have a high strength. Furthermore, the components have good corrosion resistance.The semi-finished product is melted in a closed melting chamber of the metering furnace under protective gas, wherein the melt from the melting chamber is preferably supplied automatically to the trough by means of a pump, and wherein the melt is preferably discharged automatically from the metering furnace via the trough and conveyed in the direction of the or each sand casting mold. The cooperation of the melting chamber, the pump and the heated chute permits automatic handling of the melt, namely automatic discharge thereof from the metering furnace and automatic filling thereof into the or each sand casting mould.The discharge of the melt from the metering furnace and the introduction of the melt into the or each sand casting mold take place in an atmosphere free from inert gas. This reduces the process and apparatus complexity.The use of sand moulds as casting moulds is advantageous in particular in the prototype production of magnesium casting components in small quantities, since such lost sand moulds can be provided economically and quickly compared to conventional, permanent casting moulds.Preferred developments of the invention are evident from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being restricted thereto. The following shows: FIG. 1 shows a sketch to illustrate the method according to the invention for casting components made of a magnesium alloy.The present invention relates to a method for producing magnesium alloy components by casting in sand moulds.In a first step of the method according to the invention, a semi-finished product 10 is provided which has a magnesium alloy and a magnesium fire protection additive. The semi-finished product has MgAlZi or MgAlMn or MgZE as magnesium alloy. As a magnesium fire protection additive, the semi-finished product 10 comprises calcium oxide (CaO).The semi-finished product 10 made of the magnesium alloy and the magnesium fire protection additive is positioned in a metering furnace 11, namely in a melting chamber 12 of the metering furnace 11, in a second step of the method according to the invention.The melting of the semi-finished product 10 in the closed melting chamber 12 of the metering furnace 11 takes place under protective gas, since the protective gas cannot escape from the closed melting chamber 12.In a third step of the method according to the invention, the melt 13 is discharged from the metering furnace 11, namely in the direction of at least one sand casting mold 14 to be filled with the melt 13, wherein the discharge of the melt 13 from the metering furnace 11 in the direction of the sand casting molds 14 takes place with the aid of a heated trough 15. Via the heated trough 15, the melt 13 discharged from the metering furnace 11 is introduced into the respective sand casting mold 14.The transfer of the melt 13 from the melting chamber 12 of the metering furnace 11 into the heated trough 15 takes place with the aid of a pump 16, which draws the melt 13 from the melting chamber 12 with the aid of a removal tube 17 and transfers it into the heated trough 15.The discharge of the melt 13 from the metering furnace 11 and the filling of the melt 13 into the respective sand casting mold 14 take place in an atmosphere which is substantially free from inert gas. This makes it possible to avoid adverse health effects for persons working in the foundry or on the metering furnace installation 11 and on the sand moulds 14.The melt 13 then solidifies to form the component in the sand casting mold 14 and the component is removed from the sand casting mold 14.

Claims

Method for casting components made of a magnesium alloy, comprising the following steps: providing a semi-finished product (10) which has a magnesium alloy and a magnesium fire protection additive, namely MgAlZn or MgAlMn or MgCE as the magnesium alloy and CaO as the magnesium fire protection additive; melting the semi-finished product (10) to form a melt (13) in a closed melting chamber (12) of a metering furnace (11), wherein the melting takes place under protective gas; discharging the melt (13) from the melting chamber (12) of the metering furnace (11) via a heated trough (15) and filling the melt (13) via the trough (15) into at least one sand casting mold (14), wherein the discharging of the melt from the metering furnace (11) and the filling of the melt (13) into the or each sand casting mold (14) are carried out in an atmosphere free of inert gas; solidifying the melt in the or each sand casting mold (14) and removing the component from the sand casting mold (14).Method according to claim 1, characterised in that the melt (13) is automatically supplied from the melting chamber (12) to the channel (15) by means of a pump (16), and that the melt (13) is automatically discharged from the metering furnace (11) via the channel (15) and conveyed in the direction of the or each sand casting mould (14).

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