RU2319752C2 - Method for induction melting of metal and apparatus for performing the same - Google Patents

Abstract

FIELD: foundry.

SUBSTANCE: apparatus has cold crucible with bottom skull shutoff plate, and inductor. Crucible is provided with vertical recesses widening in upward direction. Each part of crucible has triangular section, with base of said triangle being oriented toward melt. Method involves placing blank into crucible so that after melting of blank its meniscus is positioned above upper cut of crucible and below upper part of inductor; providing directed melting of blank from the top to the bottom; after melting-through of shutoff plate, performing bottom discharge of melt into mold; controlling melting process using light sensors. Heating of melt may be additionally provided from the top using electric arc, plasma or electronic-beam heating source. Also, melt may be exposed to low-frequency or supersonic action.

EFFECT: reduced consumption of power and production cycle, increased weight of metal upon melting process, and reduced sizes of melting apparatus.

4 cl, 5 dwg

Description

The present invention relates to the field of foundry and can be used for casting any metals, including refractory and chemical actives.

As an analogue of the present invention, a method of induction melting and casting of metals is adopted, including installing a bottom skull plate in a cold crucible, loading a metal billet into a cold crucible on a skull cap, melting the metal and setting the molten bath in the crucible (RU 2101639C1, F27B 14/08, 10.01 .1998) [1].

As the closest analogue of the claimed device adopted device for induction melting and casting of metals, containing a cold crucible, bottom skull plug, inductor [1].

The closest technical solution as a prototype is a method of induction smelting of metal in suspension, in which there is a good averaging of the melt, its purification from light and heavy impurities, and when cast, a defect-free crystalline structure is formed. The method includes the preparation of the melt in a special inductor with its subsequent pouring and crystallization in the mold or mold [2] (p. 9-21). Suspended smelting methods with ingot casting provide high ingot density, uniform chemical composition, high metal purity, and a fairly uniform crystalline structure. This method has found application for the manufacture of round and flat ingots of small cross section [2].

The aim of the invention is to increase the efficiency of use and expand technical capabilities by reducing energy consumption, shortening the production cycle, increasing the mass of metal during melting, and reducing the dimensions of the equipment.

This goal is achieved in that the known method of induction melting and casting of metals includes the installation of a bottom skull plate in a cold crucible, loading the metal billet into a cold crucible, and differs in that the billet is placed in a cold crucible so that after its melting the meniscus of the melt is located above the upper cut crucible and below the upper part of the inductor, carry out directional melting of the workpiece from top to bottom, and after melting the skull plug, bottom melt is drained into the mold. Using non-contact light sensors, the melting process of the workpiece is regulated, the moment of penetration of the skull cap is fixed, and low-frequency or ultrasonic influence on the melt is carried out by the signal from the sensors. The melt is additionally heated from above by electric arc, plasma, electron-beam heating sources. A device for induction melting and casting of metals containing a cold crucible, bottom skull plug, inductor, characterized in that it is provided with a shape located under the skull plug along the axis of the crucible, the crucible is made with vertical cuts, broadening upward, with each section of the crucible in cross section made in the form of a triangle facing the base of the melt.

The bottom discharge installation shown in Fig. 1 includes a stationary housing 1, to which a movable lower housing 2 is drawn, inside of which there is a bottomless crucible 7, the inner contour of which is made in the form of a cone or hemisphere tapering down or up in order to reliably hold bottom skull. The crucible is surrounded externally by inductor 8, inside the crucible 7 there is a metal melt 16 and its skull 17. The visual observation of the melting process is carried out through the peeper 10, and automatically through non-contact light sensors 3 that respond to the thermal radiation of the metal. The tightness of the installation is ensured by the cover 13 and vacuum seals 15. A vacuum is created and gas is injected using the nozzle 5. The mold or mold 9 is located along the axis of the crucible 7 under its bottom, into which a waveguide 14 can be installed, through which the melt 16 Further low-frequency or ultrasonic vibrations transmitted from the emitter 12 are transmitted. To refine the melt 16 in the crucible 7 and to accelerate its discharge, the emitter 11 is mounted on the crucible. Form 9 is located on the lifting pipe 6, through which additional Create a vacuum in the mold.

The method using the proposed device is as follows: in the bottomless crucible 7, which may be a copper cooled split crucible [3], (p. 243), a skull cap 17 of a certain thickness and geometry along the side and bottom contours is installed so that further prevent premature discharge of the melt at the point of contact with the crucible. The level of the bottom of the stub can be located at a certain distance h from the lower cut of the inductor (Fig. 1), i.e. below the cut. The level of the bottom of the plug may be located above the lower cut of the inductor due to the design features of the cold split crucible, which weakens the magnetic effect on the lower part.

The design features of the cold crucible to reduce heat loss in its body used for this method can be as follows:

- the workpiece, made in the form of a single truncated cone or cylinder, is installed in a cold crucible so that after its melting the upper level of the formed melt becomes higher than the upper cut of the cold crucible by a value of H (Fig. 5 (a)), and the upper part of the inductor should located above the level formed by the melt by the value of D [4] (p. 65). That is, due to the fact that a meniscus forms on top of the crucible furnaces, the latter will absorb the main heating power coming from the inductor, thereby providing directional melting from top to bottom;

- slotted vertical sections in a cold inductor, using the forces of surface tension and pressure reduction in the melt from the bottom up, have the form of a truncated cone with a broadening up (Fig. 5 (b)), i.e. e> s;

- the bottom of the workpiece to reduce heat loss in the metal, as well as to facilitate monitoring of the process, may be located above the continuous mounting ring of the petals of the inductor at a distance μ (Fig. 5 (a));

- electric losses in the coldest crucible are proportional to the length of the current path in the crucible body; therefore, to reduce them, each section of the crucible can be made in the form of a triangle, a truncated pyramid or hemisphere, where the base faces the molten metal (Fig. 5 (c)).

Preparation for operation of the installation begins as follows, from above or below, into the crucible 7, with the lid 13 open or the housing 2 allotted downward, a workpiece 16 is loaded with a certain geometry, after which the lid is closed, and the housing 2 is set down from the bottom to the lifting pipe 6 when the housing 2 is withdrawn to its lowermost position form 9, into which the waveguide 14 connected to the emitter 12 automatically falls. Oscillations through the waveguide are transmitted not only to the melt, but, if necessary, can be directly transmitted from the emitter to form 9. The upper cut rmy 9 is located below the bottom of the plug determines the distance l, which allows to further lower proximity sensors 3 detect the heating of ledge 17 to the center thereof, and parallel to the bottom edge of the ledge. The bottomless crucible 7 can be loaded with a single billet preliminarily melted in this crucible, only with the bottom of FIG. 3 closed, due to the water-cooled tray 18. In this case, after cooling the metal, the tray 18 is removed and the installation is ready for operation. In addition, the necessary volume of metal can be smelted in a crucible with a bottom that is separate and similar in its internal geometry, but in an induction, plasma, electron-beam, or vacuum-arc type specially designed for this purpose, and then the metal can be cold loaded into crucible 7. After loading the crucible 7, the lower housing 2 is pressed against the housing 1, and if necessary, vacuum is pumped out through the pipe 5 to the required residual pressure. If a non-reactive metal melts in the crucible, the installation does not require protective housings 1 and 2 to create an inert sphere, thereby simplifying its design. Then there is an alternating current supply to the inductor, 8, which can be single-turn, multi-turn, and also consist of inductors with separate coil power. In this case, the metal melts vertically directed from top to bottom, until the bottom skull is melted. The upper and lower non-contact tracking sensors 3 provide the necessary control of the current power at the inductor 8, so that this process is directional, and in addition they regulate the time spent in the main metal bath 16 in the liquid state and determine the time of its discharge into the mold 9, directional melting can provided also by mechanical movement of the crucible or inductor vertically. The moment of discharge of the metal 16 into the mold 9 is fixed by one of the proximity sensors 3, from which a signal is supplied to preform the mold 9 to the crucible 7 and, if necessary, the emitter 11 is switched on, which accelerates the discharge of the melt from the crucible, as well as the emitter 12, grinding the structure through the waveguide 14 coming in the form of metal. At the time of discharge, for better filling, an additional vacuum is pumped out of the mold through the nozzle 6, and inert gas can be pumped through the nozzle 5, which exerts pressure on the mirror of the molten bath. After the crystallization of the metal in the mold and its cooling has taken place, the lower case is brought down, after which the mold is removed from the installation. Further, the entire manufacturing process of the product is repeated. In order for the remainder of the skull to be removed through the bottom of the crucible, the latter may have a shape that extends along the inner contour downward, Fig. 4. A similar crucible is loaded from below and the installed bottom skull is held until it begins to heat due to the shape, which is temporarily lifted up. After heating the bottom skull or the entire loading installation, it expands, and the metal itself can already be held in the crucible, then the form is set to its original position.

For more stable drainage of the melt in the center of the bottom of the skull, the latter may have a concavity at its bottom with a height S towards the melt pool, Figs. 2, 3, provide faster and more economical melting of the melt, as well as more stable deposition of the volume of the melt bath from top to bottom, to provide the introduction to the device of additional heating sources 19 installed above the mirror of the melt bath 16. Additional sources of heating can be: consumable or non-consumable electrode, which provides heating of the bath due to ele arc arc in a vacuum or inert medium, as well as a plasma torch, electron beam, resistance heater.

When melting low-melting metals, using the present invention, electric arc heating is not required, when melting refractory metals by the proposed method, the optimal frequency at the inductor is selected, and the missing power required for melting is supplied from an additional heating source. This combination of heat sources is the most optimal for this method and compares favorably with single heat sources.

In contrast to the analogue [1], where an electric arc is used as the energy source for producing the melt, the present invention most effectively uses induction heating, thereby sharply reducing thermal overheating in the melt. At the same time, at the time of melt discharge, its temperature is more equalized over the volume of the bath, and the magnetic field contributes to the squeezing of the melt from the walls of the crucible, thereby ensuring high efficiency in the use of the merged metal.

Unlike the prototype [2], where the melt is completely held in suspension by the inductor, in the present invention, the melt is held in a crucible. This difference allows you to keep in this state a very large mass of metal that exceeds the prototype, with equal powers of the inductor tens of times. This significantly reduces the cost of equipment and product manufacturing, and in addition increases the mass and speed of melt smelting.

Unlike standard crucible furnaces, where the melt is drained by turning the crucible, this installation can dramatically simplify the dimensions and complexity of the design of the device. But the most important difference is that when the crucible is rotated from its surface, fusible inclusions merge into the mold and the first portion of the melt falling into the lower part of the mold is more heated, and the final portion of the melt has a lower temperature, thereby inclusions and shrinkage axial porosity. This method and device can eliminate such defects in products.

In this regard, the present invention can be considered useful and effective for use in production, reducing the cost of equipment and manufactured products, while allowing to obtain not only semi-finished products, but also products of high complexity with high quality metal structure.

Unlike analogue and prototype, the present invention provides:

- obtaining products of particularly complex shape of high quality;

- compact device and high energy savings;

- automatic organization of the drain of the melt from the smelted billet into molds, molds, etc .;

- intensive cooling of the melt during its crystallization and the simultaneous action of vibration and gas pressure on it;

- reliable automation and process control;

- directional crystallization of the product from the bottom up;

- eliminates the inclusion of fusible inclusions in the form.

Therefore, the present invention is advisable to be considered useful for industrial applications in the production of complex high-quality products not only from ordinary metals, but also from titanium, niobium, zirconium and the like metals.

LITERATURE

1. Patent application (published on January 20, 1999).

2. A.A. Vogel - Induction method for holding liquid metals in suspension. L., Engineering, 1989

3. A.A. Andreev. Melting and casting of titanium alloys. M., Metallurgy, 1994

4. N.I. Fomin. Electric furnaces and induction heating plants. M., Metallurgy, 1979

Claims (4)

1. A method of induction melting and casting of metals, comprising installing a bottom skull plate in a cold crucible, loading a metal blank into a cold crucible onto a skull plug, melting the metal and a melt bath set in a crucible, characterized in that the blank is placed in a cold crucible so that after of its melting, the meniscus of the melt was located above the upper cut of the crucible and below the upper part of the inductor, directional melting of the workpiece is carried out from top to bottom, and after melting of the skull plug, the bottom draining the melt into a mold. 2. The method according to claim 1, characterized in that using contactless light sensors regulate the melting process of the workpiece, fix the moment of penetration of the skull plug and the low-frequency or ultrasonic effect on the melt is carried out by the signal of the sensors. 3. The method according to claim 1, characterized in that the melt is additionally heated from above by electric arc, plasma, electron-beam heating sources. 4. Device for induction melting and casting of metals, containing a cold crucible, bottom skull plug, inductor, characterized in that it is provided with a shape located under the skull plug along the axis of the crucible, the crucible is made with vertical cuts, broadening upward, with each section of the crucible in cross section made in the form of a triangle facing the base of the melt.

Images