RU2286398C2 - Method for metal casting with the use of lining slag as consumable electrode - Google Patents

Abstract

FIELD: special electric metallurgy and foundry, in particular, casting of any metals, including high-melting point and chemically active metals.

SUBSTANCE: method involves forming blank to be melted-through by fusing together consumable electrode and burden to be charged on cooled pan resulted in formation of bottom lining slag of desired thickness capable of retaining melt bath; removing pan and further regulating melting process by means of contactless feeler sensors for discharge of resultant melt into mold; providing additional melting of electrode by the time shrinkage blister is to be withdrawn from ingot, with amount of remaining hard part of blank to be molten-through must be sufficient for manufacture of subsequent electrode.

EFFECT: increased efficiency and wider range of utilization of equipment owing to reduced consumption of power, decreased production cycle, increased utilization of recycled wastes in melting process, reduced sizes of production zone and equipment.

3 cl, 4 dwg

Description

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

As an analogue of the present invention, application RU 98105924 [1] was adopted, where the melt is produced in a melted billet with subsequent exposure to increased pressure to move it into a stamp located at a certain distance below the workpiece, while the stamp is moved towards the falling melt until it collides with harvesting. This analogue allows you to process any metals, including refractory and chemically active.

The closest technical solution - the prototype - is a method of skull melting of metal (skull - consumable electrode) in an intermediate tank with ingot casting, in which the melt is averaged well, it is cleaned of light and heavy impurities, and a defect-free crystal structure is formed during casting. The method includes the preparation of the melt in a separate intermediate tank with its subsequent transfusion and crystallization in the mold or mold [2] (p. 226-230).

Melting methods in an intermediate tank with casting of ingots provide a high density of ingots, a uniform chemical composition 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 use of the fused billet as an intermediate tank allows to increase the heating volume of the molten bath by reducing the thermal effect from the bottom. The vertical arrangement of the heater, tank and mold sharply reduces the dimensions of the furnace and the time it takes to move the melt into the mold. In this case, a good removal of volatile and gaseous impurities from the melt occurs, intensive mixing and averaging of the composition. The use of the skull as a consumable electrode allows to reduce costs when involving production wastes upon receipt of the finished product.

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 involved recyclable waste during melting, reducing the size of the production site and equipment.

This goal is achieved by the fact that the known method of casting metal using a skull as a consumable electrode, with a set of molten bath in the melted workpiece and its further discharge into a stamp located below the workpiece, is characterized in that the melted workpiece is formed when the consumable electrode and the charge are fused. on a cooled tray, after a bottom skull is formed of a certain thickness, capable of holding the molten bath, the tray is removed and further the melting process is regulated It is made using non-contact tracking sensors so that the formed melt merges into the stamp, and the remaining electrode is melted by the time the shrink shell is removed from the ingot, while the remaining solid part of the billet should be sufficient for the manufacture of the subsequent electrode. During penetration, discharge and crystallization of the melt, in addition to gravity, mechanical and electromagnetic vibrations, as well as gas pressure, can be imposed on it. The consumable electrode for melting is made from the remaining part of the billet, which is cut into sectors, and then these parts are welded together, forming a rod shape, a charge can be added to the sectors during welding.

The proposed method implements the installation shown in figure 1. The installation includes a melting chamber 1, in which a cooled and movable pallet 7 is placed (the pallet can be opened not only moving to the side, but also downwards according to the opening of the hatch (Fig. 2a) or by the type of cylinder outlet (Fig. 2b)), onto which a certain portion of the charge 11 is loaded, upon heating of which due to the electric arc 4 generated on the consumable electrode 2 and controlled by the solenoid 12, the melt 5 melts, filling the space on the cooled tray 7 and the cooled case 1. This forms a skull 6 in the form of cylines pa, wherein the typed defined melt bath 5. After the molten charge 11, a certain length is fused consumable electrode 2 is formed and defined skull 6 capable of holding a melt 5, a cooled pan 7 is retracted to the side. Thus, freeing from heat exposure the lower part of the skull 6, which has reached a certain thickness h and freeing up space for observing the process of smelting a certain volume of the melt pool for the proximity sensor 8, by which the melting mode is adjusted. For more complete control over the process of sensors, several can be installed, for observing the melt from above and for observing various points below the disk and under the disk. Having determined the thickness h on the skull 6 by the sensor 8, the melting process is started to be controlled by changing the power current on the arc 4 of the consumable electrode 2, the distance on the arc gap 4 and due to the magnetic field of the solenoid 12, and the melt bath 5 is controlled so that the moment of penetration of the bottom skull 6, the consumable electrode 2 was practically fused, but when the melt 5 was drained into the stamp 9, the remaining electrode 2 should be enough to remove the resulting central cavity during shrinkage in the product.

In order for high-quality metal refining, the cavity of the installation 1 body is evacuated through the pipe 3, and the melt pool 5 is mixed due to the electromagnetic field of the solenoid 12, thereby freezing heavy inclusions in the peripheral part of the skull 6. Refractory and insoluble inclusions, by themselves, at more intensive heat treatment are not dangerous, since their critical volume decreases and they go into the category of crystallization centers, which positively affect the refinement of the product structure. Therefore, in the proposed method, getting into the peripheral part of the skull, these inclusions then go into the consumable electrode and are further processed by the heat of the arc. Moreover, if their critical size remains high enough, then under the action of centrifugal forces they will again be frozen into the peripheral part of the skull and the process will be repeated until these particles reach an acceptable size. Thus, the process is self-regulating, that is, despite the bottom discharge of the melt, it is possible to free itself from harmful inclusions having a critical mass and volume. After the melting process is over, the mass of the remaining skull 6 in the workpiece should be sufficient to prepare a consumable electrode 2 from it, which is used for subsequent melting.

At the time of melt 5 discharge into the die 9, gas pressure can be supplied to the melt through the nozzle 3, and low-frequency vibration and ultrasound can act on the die 9 and the workpiece 6, thereby making it possible to obtain articles of high density, complex shape without shrinkage shells and metal looseness. To increase the thermal effect from the arc 4 on the metal melt 5, the stamp 9, due to the lifting table 10, can be pressed to the workpiece 6 after the bulk of the glass melt 5 from the workpiece 6, the arc 4 can still work for some time, while the melt 5 will be additionally assembled due to the opened skull 6 and moved to the stamp 9. This increases the efficiency of metal use in the product.

So, for example, in the classical method of HRE [2], when fusing the consumable electrode from the skull to the melt, on average only 25% of the total metal is transferred. In the present invention, the efficiency of use can be brought up to 50%, since due to the removable tray on the melt bath, the thermal load is reduced, which contributes to the freezing of the skull. In addition, unlike the prototype, this method allows you to additionally fuse the skull due to the fact that the latter opens when the melt is drained into the stamp, and due to the higher fluidity generated from the melt when mechanical and electromagnetic vibrations are applied to it. The melt flow rate in this method can be increased by applying gas pressure to the moving melt, which simultaneously contributes to the compaction of the metal in the mold and the elimination of porosity. After the melting and pouring process is completed, the resulting product and the remaining disk-shaped skull are removed from the installation. In order to obtain a new consumable electrode from it, the latter, for example, can be cut into four sector parts (Fig. 3), which are then welded together, overlapping each other, and welded to the holder. Thus, it becomes possible to obtain a consumable electrode that closely resembles a conventional cylinder in shape, which allows it to be compactly located in the melting chamber and, in the future, more reliably regulate the melting process. For the manufacture of the electrode, the same setup can be used, and at the moment of fusion of the sectors, their volume can be increased by adding a charge to special crystallizers (Fig. 4). In this case, an electrode of a more regular cylindrical shape is formed and the efficiency of the involvement of circulating waste increases. In contrast to the GRE method [2], where the consumable electrode has a far from perfect shape and where a crucible with a subsequent slope is used to fill the mold, the proposed invention can dramatically simplify the process of melting control, while reducing the dimensions of the internal volume of the installation by at least an order of magnitude.

Unlike the analogue, the proposed method is energetically more economical, since in it, a meltable billet is formed in one transition and without loss of energy for cooling and then new heating, it is also fused with the rest of the consumable electrode. This moment is especially important when receiving ingots and semi-finished products of especially large sizes. So, for example, we take the yield that is suitable when using the GRE method - 25% of the volume of the consumable electrode and the charge being loaded into the crucible, therefore, in order to completely melt 100% according to this scheme, it is necessary to conduct four melts. If we assume that the consumable electrode and the charge being charged are 1000 kg, then at the electric power consumption for titanium of 2 kW / kg, the latter will need E _p for remelting 1 ton the following amount:

1. The consumable electrode will be 750 kg.

E _p = (750 kg · 2 kW / kg) · 4 = 6000 kW.

2. The cost of 1 kW is $ 0.04 (USA), therefore, the cost of electricity will be:

S _e = 6000 kW · 0.04 $ / kW = $ 240.0.

When using the invention, the yield on average reaches - 50% of the volume of the consumable electrode and the charge being loaded into the crucible, therefore, in order to completely melt 100% according to this scheme, it is necessary to make two re-melts. Therefore, 1 ton of volume will require electricity:

E _p = (500 kg · 2 kW / kg) · 2 = 2000 kW.

S _e = 2000 kW · $ 0.04 / kW = $ 80.0.

Electricity costs are reduced exactly three times.

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 the analogue, the present invention provides:

- obtaining products of particularly complex shape of high quality;

- compact device and high energy savings;

- automatic organization of the discharge of the melt from the smelted tank 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.

Therefore, the present invention is expediently considered useful for industrial applications in the production of complex high-quality products from titanium, niobium, zirconium, etc. metals.

LITERATURE

1. RU 98105924 - Patent application (published on December 20, 1999).

2. Andreev A.L. and others. Melting and casting of titanium alloys. - M.: Metallurgy, 1994.

Claims (3)

1. A method of casting metal using a skull as a consumable electrode, including a set of molten baths in the melted billet, further pouring it into a stamp located below the billet, and crystallizing the melt into ingots, characterized in that the melted billet is formed by fusing the consumable electrode and the charge charge on a cooled pan with the formation of a bottom skull of a certain thickness, capable of holding a molten bath, after which the pan is removed and then the melting process is regulated by schyu contactless sensors for tracking drain formed melt into the die, and the remaining electrode doplavlyayut the time of removal of the ingot shrinkage cavity, the solid portion of the workpiece is melted enough to leave the next manufacturing consumable electrode. 2. The method according to claim 1, characterized in that during the melting, discharge and crystallization of the melt, mechanical, electromagnetic oscillations and gas pressure are applied to it. 3. The method according to claim 2, characterized in that the consumable electrode for melting is made from the left solid part of the melted billet, cut into sectors that are welded together to form a rod shape, while adding a batch when welding the sectors.

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