RU2673117C2 - Method of casting of melt of metal obtained by melting solid metal stem by means of induction heating - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to the field of metallurgy. Solid metal rod is melted by induction heating in the melting chamber. Move and squeeze the molten metal from the melting chamber under pressure using a piston. As the piston, the solid part of the melted metal rod is used.EFFECT: simplified casting process, as well as the possibility of manufacturing products 3D printing.1 cl, 2 dwg

Description

The method is used for batch or continuous production of melts of various metals. In batch production, the method can be used in various kinds of casting processes using molds. The method, also, after coordinating the feed rates of the solid rod and the power of the induction heater, can be used for continuous casting of the obtained molten metal with simultaneous continuous supply of the metal rod to the heating zone. In this case, it can be applied in the process of printing three-dimensional objects (3D printing).

Currently, there are several known methods of casting metals in which molten metal is fed into the mold under pressure.

1. Centrifugal casting (source: MANUFACTURING JEWELERY IN HOME, Moscow, ONIX 21st Century, Center for Human Values, 2005, UDC 73/76, BBC 37.27, L55 Link on the Internet: http://jtech.com.ua/ article / view / id / 482)

In this casting method, molten metal is obtained separately in a melting furnace, and then placed in molten form, poured into a bowl, in a casting device. To implement the casting process in the bowl create excess pressure, which is created by centrifugal force when the casting mechanism is untwisted. Under the action of centrifugal force, the metal rises to the level of the opening of the bowl and enters the cavity of the mold.

The disadvantages of this method are the inconvenience of moving the molten metal between the melting furnace and the casting mechanism, as well as the principle of creating pressure due to centrifugal force. As you know, centrifugal force is directly proportional to the angular velocity of rotation and the radius of rotation, therefore, to create significant pressures, you have to either increase the dimensions of the device or increase the speed of rotation (and, therefore, increase the power of the engine that creates the rotation and improve the balance of the rotation mechanism). It is often impossible to increase the dimensions, and it is difficult to increase the speed.

2. Vacuum casting (source: MANUFACTURING JEWELERY IN HOME, Moscow, ONIX 21st Century, Center for Human Values, 2005, UDC 73/76, BBC 37.27, L55 Link on the Internet: http://jtech.com.ua/ article / view / id / 482)

The vacuum casting method is based on removing air from the mold through the bottom and side openings of the flask during pouring. The air pressure in the flask decreases to 100-300 mm Hg. and due to the difference in atmospheric pressure, which presses on the mirror of the cast metal, and rarefaction in the mold cavity, high-quality castings reproduce the relief of the mold.

The disadvantage of this method is the limit of the maximum pressure exerted on the molten metal, which is limited by atmospheric pressure.

3. Injection molding

(source: SPECIAL CASTING METHODS A.M. Zborbirsk Donetsk National Technical University

UDC 621.74 (075.8)

Lecture notes on the discipline "Special casting methods" / Auth. Picker A.M. - Donetsk: SEI “DonNTU”, 2007. - 158 p.

Link on the Internet:

http://uas.su/books/spesialmethodsforcasting/41/razdel41.php)

This method involves obtaining a molten metal in a furnace or a melting chamber and the subsequent supply of already molten metal to a device (pressing chamber) that creates excess pressure for casting. In this case, the overpressure is created by the piston, which is a separate unit of the casting machine. When moving the piston, it presses on the molten metal and the metal is extruded into the mold.

The disadvantage of this method is either the inconvenience of transporting molten metal from the melting furnace to the foundry - if these devices are separated - or excessive energy consumption for maintaining the metal in the molten state in the melting chamber, from where it is sucked into the pressing chamber - if the melting chamber (furnace) and the pressing chamber is located within one mechanism. Also, the separation of the melting chamber and the pressing chamber and the execution of the piston of the pressing chamber as a separate element of the casting machine complicates the design of the casting mechanism. This method is taken as the closest analogue.

The proposed method is as follows.

A solid metal rod 1 is fed into the channel 2 (Fig. 1), which is empty until the rod is fed into it. As the rod feeds into the heating zone II, which is the melting chamber, with the feed direction I → II, the rod falls under the action of induction currents excited in the rod by an induction coil 4. Under the influence of induction currents, the rod melts, turning into a melt 5. In this case, in zone I, the rod 1 remains solid, as it is not exposed to induction currents. The resulting melt 5 enters the extrusion zone 6, from where it can be extruded in any direction; at the same time, the excess pressure necessary for extrusion will be created by the solid part of the rod 1, if a force is applied to it in the direction I → II. In this case, the solid part of the rod 1 at the boundary of zones I and II will act as a piston. Thus, zone II, being a melting chamber, is also a pressing chamber. The magnitude of the generated pressure will depend on the gap III between the channel wall 2 and the wall of the rod 1. The smaller the gap, the more pressure the metal rod (piston) can create 1. This pressure is limited by the surface tension of the molten metal in the gap III, which prevents the metal from flowing between the wall of the channel 2 and the rod 1, which, according to the Laplace formula, is inversely proportional to the size of this gap. It should be noted that the proposed method can provide continuous production of a molten metal, if you coordinate the feed rate of the rod 1 into the heating zone II and the rate of molten metal induction heater. If the metal of the feed rod melts at a feed rate, the melt formation process will become continuous. The described feature can be used when applying the method in 3D printing devices.

It should be noted that metals that are not ferromagnets are heated by induction currents rather weakly. In this case, to obtain the melt, a modification of the method described above can be applied when the metal melts in zone II not directly under the influence of induction currents, but from the action of a heated non-metallic (or metal made of ferromagnet) conductor 7 (Fig. 2), which is placed inside the dielectric 3 and heats up from the action of induction currents more intensively than metal, which is not a ferromagnet. As such a non-metallic conductor, for example, graphite can be used, and, in the case of an insert from a ferromagnet, steel. In this case, the material from which the conductor 7 is made must have a melting point higher than the metal of the rod 1 heated by it.

By applying the described method, the effect of reducing the complexity of the casting machine, and, therefore, reducing its price and increasing the safety of use in production and domestic processes, is achieved. Also, the application of the method allows continuous methods to achieve continuous casting of the molten metal, which can be applied in the processes of additive production (3D printing).

Claims (1)

 A method of casting a molten metal, comprising melting a solid metal rod by induction heating in the melting chamber, moving and extruding the molten metal from the melting chamber under pressure using a piston, characterized in that the solid part of the molten metal rod is used as the piston.

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