RU2489506C2 - Method and device of electron-beam or plasma smelting of metal from crystalliser to crystalliser - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: loading of metal charge and its subsequent smelting with an electron beam or plasma is performed to an upper crystalliser provided with a vertical slot, into which prior to loading of metal charge there installed is a plate from molten metal cleaned from impurities, which covers the above slot; surfacing is performed in an upper crystalliser of a molten metal bath with the depth of not more than 50 mm, without penetration of the above plate; a slot is penetrated with an electron beam or plasma in the above plate to the depth of that is less than depth of the surfaced molten metal bath by 20-30% and refined portion of molten metal is drained to the lower crystalliser for formation of an ingot. In the upper crystalliser there made is a vertical slot covered with a plate from molten metal cleaned from impurities with formation of a projection to retain heavy impurities during the melting process, and the above crystallisers are installed on a tray.

EFFECT: invention allows improving use efficiency and enlarging technical capabilities owing to reducing power consumption, shortening of a production cycle, increasing metal weight at surfacing and reducing the equipment dimensions.

5 cl, 1 tbl, 2 dwg

Description

The 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 invention, a method of electron beam remelting with a cold hearth [1] is adopted. In this method, the source material in the form of a charge, sponge, powder or granules moves with a certain speed from the charge hopper into the cooled crystallizer. In the crystallizer, the metal melts and the formed liquid metal drops or (with sufficient electron beam power) flows continuously into a sliding cooled crystallizer, forming an ingot of the required size. This method of remelting can also be called electron beam remelting with an intermediate capacity. By purpose and implementation scheme, it is completely identical to plasma remelting widely used in industry. However, in contrast to plasma remelting, a deeper purification of metal from gas impurities is possible here, when the melt in vacuum is held for a sufficiently long time required for metal refining.

The closest technical solution, as a prototype, is a method of zone melting of metals, which involves loading a metal charge and sequentially melting it with an electron beam or plasma by scanning the surface to form a metal melt refined from light and heavy impurities, the refined portions of which are periodically poured into the lower mold for the formation of the ingot [2].

The task 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. The problem is achieved in that the method of zone melting of metals, including loading a metal charge and its sequential melting by an electron beam or plasma by scanning the surface with the formation of a molten metal refined from light and heavy impurities, the refined portions of which are periodically poured into the lower mold to form an ingot, this loading of the metal charge and its sequential melting by an electron beam or plasma is carried out in the upper mold, made m with a vertical groove, in which, before loading the metal charge, a plate of remelted metal cleaned of impurities is installed, overlapping the groove, melting in the upper mold of the molten metal bath with a depth of not more than 50 mm, without melting the plate, and the groove is melted with an electron beam or plasma in the said plate to a depth less than the depth of the weld pool of the melt by 20 ÷ 30% and the refined portion of the molten metal is poured into the lower mold to form an ingot, with the pressure at the bottom of the upper mold of a metal melt containing heavy impurities. In the upper crystallizer, the mixture is melted by an electron beam or plasma by periodically scanning its surface to form a metal melt refined from light and heavy impurities; at the same time, separate electron-beam guns or plasmatrons are used at each stage of melting, penetration of the plate, and heating of the metal melt in the lower crystallizer or at all the stages mentioned, a single electron beam gun or plasmatron is used.

A device for zone melting of metals containing an electron beam or plasma gun, an ingot mold, which is located in a melting chamber with a vacuum nozzle connected to a vacuum system, characterized in that it is equipped with an upper mold for sequentially melting the metal charge to form refined from light and heavy impurities of the metal melt placed above the mold to form an ingot, a pallet with a mechanism for its removal, hermetically connected with a melting chamber, while in the upper mold there is a vertical groove overlapped by a plate of refined metal that is free from impurities to form a step to hold heavy impurities during the melting process, and the molds are mounted on a pallet, the upper mold is made V-shaped, almost completely overlapping the transverse plane melting chamber of the furnace, with the exception of the sector allocated for the drainage of refined molten metal.

The proposed method is carried out using the installation shown in figure 1. The installation contains an electron beam gun 1, the housing of which can be located at different angles with respect to the axis of the housing of the melting chamber 2, which is closed from below by a pan 3, on which a copper cooled upper mold 4 and a lower crystallizer 5 are mounted. Camera 2 with a pallet 3 are mounted with using bolted connections, through sealing vacuum rubber. The mixture 6, which is not pressed or pressed into the briquette, is loaded into the crystallizer 4, after the crystallizer is installed on the pallet, a vacuum is created in the melting chamber through the nozzle 7. Upon reaching the required vacuum depth, the mixture is melted by the electron beam 8. The charge 6 will begin to melt over the entire area, formed by the upper mold 4, not reaching a certain distance to its perimeter. The beam from one or several guns will move along the metal surface until the contour of the liquid metal bath 9 reaches, at a certain distance, the copper surface of the upper mold 4. That is, it will be necessary to seek to melt as much metal as possible, without melting the mold 4. The mixture begins to melt along the entire upper plane of the mold, forming a metal bath of a certain depth, so that for a certain time it was possible to produce refined metal from light kih, heavy and gas inclusions.

Due to melting, the molten metal bath formed 9, having reached a certain depth h, is poured into the lower mold 5 by beam melting of the plate 10, which consists of pure metal, installed in the mold 4 before loading the charge 6, so as to overlap the vertical a groove 11 cut through without reaching the bottom by a certain height d. The penetration depth of the plate should be less than the depth of the melt pool, approximately 20 ÷ 30%. The depth of penetration of the groove and the entire melting process is monitored by sensors 12, combined with security cameras installed in the housing 2. Metal merging into the mold 5 forms an ingot 13. In order for its structure to be cavity-free and qualitatively melted, the metal can be heated by an electron beam 8. If the metal is subsequently re-melted, this heating is not required. The electron guns 1 must be mounted in such a way on the housing 2 so that they can most effectively overlap the surface in the upper mold 4, melt the groove in the plate 10 and heat, if necessary, the metal to be drained in the lower mold 5.

Figure 2 shows the installation, where the upper mold 4 is a square V-shaped mold, which allows you to hold three to five times more metal, compared with a round mold.

This mold can fill almost the entire perimeter of chamber 2, with the exception of a small sector through which metal will merge into the lower mold. Figure 2 shows a sector with an angle of 90 °, through which there is a drain, but this sector can occupy a smaller angle. This design of the mold allows the metal to be cleaned not only from heavy and light inclusions, but also to clean due to zone melting from metallic and non-metallic inclusions present in the alloy. So, for example, in one half of the mold, the beam, fusing a narrow strip 14, drives it from one wall of the mold to the other. That is, in FIG. 2, from side A to C and from side B to D. The melt strip always passes in one direction, as a light strip in the scanner, reaching sides C and D, the beam again begins to melt the metal from sides B and A. Having melted the metal in this way one or several times, depending on the requirements for cleaning the metal, the metal is melted to a depth h, then the plate 10 is melted and the melt is poured into the lower crystallizer 5. Next, the cleaning process is repeated until the charge is completely re-melted, except for only its mass in which inclusions remain skull which forms on the bottom of the upper mold 4. The furnace depicted in Figure 2, is very compact, but at the same time is able to melt a very large amount of metal.

Features of the proposed method are as follows.

- This method can produce an ingot of round, square or rectangular shape, with one or more guns (or plasmatrons), without the use of filling feed and exhaust devices for metal, due to the remelting of metal from the upper to the lower stationary molds.

- The upper crystallizer simultaneously serves as a storage tank for the charge and an intermediate tank in which the heavy and light impurities are cleaned, i.e. It combines the functions of a bunker with an intermediate tank, where the charge is loaded and metal is cleaned, in addition, due to zone smelting, cleaning of associated metals and non-metals is ensured.

- The charge is loaded into the upper mold both with prepress and without prepress.

- From the upper mold, the metal merges in a certain place through a groove extending vertically, almost over the entire height of the mold.

- The place of discharge of metal is located above the lower mold in its center or near the edge of the mold.

- To clean the metal in the upper mold, the method of hydrodynamic cleaning is used, heavy impurities settle on its bottom, since the groove does not reach the bottom vertically, thereby creating a ledge that holds heavy impurities.

- To ensure that heavy impurities do not get into the melt being drained, before loading the charge, the groove is closed with a cleaned metal plate so that the resulting melt from the mixture is cleaned of heavy and light impurities on the way to this plate. In the future, by melting this plate to a certain depth, only the clean melt will fall into the lower crystallizer to drain the obtained melt bath, since the metal of the plate was previously cleaned and the melt obtained from the charge was cleaned earlier in the time allotted for this.

- The upper and lower molds are mounted on a pallet, which is also a lid for the furnace.

- Energy saving occurs due to the screening of the liquid phase from the crystallizer, the solid phase of the metal separating them.

- The furnace can contain one working gun, alternately depositing metal in the upper mold, then cutting a slot for its drain in the plate and then heating the metal in the lower mold, using the possibility of deviation of the beam from the central axis. With the simultaneous use of several guns, the remelted volume of the metal and the melting rate will increase significantly.

- So, by using the possibility of deviation of the beam from the central axis, the furnace design is greatly simplified without requiring the use of mechanisms for feeding the charge, moving the mold and drawing the ingot, which significantly increases its reliability and significantly reduces its cost.

- The design of the furnace device for implementing the method has a minimum volume of the melting chamber, since the internal configuration of the cavity of this chamber occupies a space only for accommodating molds and moving the beam. This feature allows you to reduce the cost of installation design, reduce the cost of the vacuum system and reduce the time for pumping air from the melting chamber.

- The place of sealing the melting chamber is mainly the connection of this chamber and the pan, which allows to reduce leakage into it and provide good access to loading and unloading.

- The removal of the pan with molds can be provided by stationary hydraulic and pneumatic devices or by independent mechanisms, for example, by approaching electric cars.

- Monitoring of the process is ensured by sensors and movie cameras installed in the body of the melting chamber.

- Unloading of the molds is carried out on the opposite side of the vacuum pipe connected to the vacuum system.

- Prepressing the charge before loading it into the upper mold allows to reduce its melting time, increase the volume of metal smelting, as well as reduce losses on the evaporation of alloying elements.

Heavy inclusions in the melt fall on the bottom of the upper crystallizer; when cleaning metal from heavy inclusions, such a melting mode is selected when the beam first creates a melt bath of a certain depth in the upper mold, not melting the plate covering the vertical groove, then melts it to a shallower depth. Thus, allowing the melt to drain, leaving heavy inclusions on the bottom of the bath in the upper mold. At the end of melting, a part of the metal remains at the bottom of the upper mold, where all heavy inclusions accumulate. To ensure their retention, the groove in the upper mold is not made up to its bottom, thereby forming a natural obstacle for heavy inclusions. The metal will be completely cleaned of light inclusions due to the thermal power of the beam concentrated on the surface of the metal bath, where light inclusions float. When exposed to a beam, they evaporate and are removed through a vacuum pumping system.

Economic feasibility of the project.

Comparison is made with the furnace (Kompozit OJSC, Korolev city), which uses four 250 kW guns and produces an ⌀200 ingot, 1.5 m long, with a total weight of 200 kg (when loading titanium 220 kg). The volume of the furnace is 10 ³ , the volume of the pipelines of the vacuum system is 12 m ³ . Pumping time 1.5 hours, melting 1 hour, cooling 1.5 hours, i.e. The full cycle of the furnace takes 4 hours. Unloading-loading, which is 1.5 hours, takes extra time. The cost of such a furnace is 1 million € or 36 million rubles. The cost of this furnace is distributed between the main nodes. (Table 1).

If the proposed furnace, shown in figure 1, will also contain in its arsenal of 4 el. beam guns, with a power of 250 kW each, the volume of the smelted metal, due to the technological features of the process, will increase significantly. Take the upper mold, with a diameter of 800 mm and a depth of 600 mm, while the mass of titanium loaded with a tight package will be within 1000 kg. Due to the fact that all four guns can be aimed at smelting a metal bath, this will significantly increase the melting rate and will reduce the amount of energy by reducing heat loss.

Compared to analogs, where a new charge is constantly entering the intermediate tank, one or two guns have to be installed to melt it. So, for example, in the case of assembling the furnace according to the classical scheme with an intermediate tank, the container from which titanium is fused at the end, is heated by its volume and due to its significant mass, it takes up part of the heat and, therefore, part of the energy spent by the beam guns on its melting. Therefore, it can be noted that this is one of the main parts of the heat loss of a classical furnace. Further, in this furnace, the metal melt enters a shallow copper cooled vessel, where, when a small mass of metal and a relatively large mass of the cooled crystallizer interact, a significant heat loss occurs, which is removed by the intermediate vessel.

Further, the metal, falling into a copper cooled, sliding mold, is formed into an ingot under the action of the heat of the beam of one of the guns, where the loss of thermal energy also occurs. As you know, today, beam furnaces surpass all known titanium melting furnaces (vacuum-arc, plasma, induction, skull, etc.) with refining capabilities, but at the same time they suffer from the fact that they can’t get a strictly regulated, uniformly distributed chemical composition along the length of the ingot. In this regard, the desire of designers e. Combine beam furnaces to combine the possibility of remelting a mixture of any composition in a single design, refining it from impurities with the yield of a finished ingot, leads to the fact that the costs invested in the construction of the furnace, its operation and maintenance, as well as the quality of the produced ingots do not meet the expectations of metallurgists. In the proposed method, the task was set to use the high refining property of electron beam furnaces to produce sufficiently large volumes of metal at low cost.

Due to the fact that in the proposed furnace all four electric beam guns can be directed to smelting a metal bath in the upper mold, in comparison with a classical furnace, the following advantages are achieved.

1. The upper mold, having a depth of 600 mm, when smelting a liquid bath, with a depth of not more than 50 mm, does not lose its heat to heat the bottom of the mold.

2. The mixture, having a packaged, but not fused structure, has a low thermal conductivity, so more energy is spent on a useful metal melt.

3. After draining the next portion of the molten metal, the rays begin to melt the next layer of metal already warmed up to the melting point.

4. Part of the energy of the beam is only sometimes used to melt the plate to drain the melt, as well as to heat the metal in the lower mold, if necessary.

As mentioned above, due to the fact that beam furnaces suffer from a low melt mixing ability, a significant amount of energy should not be spent on heating and fusion of the ingot for the production of an ingot, which is intended for subsequent remelting. More economically advantageous, the resulting ingot is subsequently remelted by vacuum-arc or induction remelting, in which the mixing capacity of the melt is much higher. At the same time, their refining ability cannot be compared to electron beam smelting.

When comparing the classic and the new ELP furnace, it can be noted that a new furnace with the same guns in the new lineup at the same time will be able to melt 1000 kg of titanium, instead of 210 kg according to the classical scheme. At the same time, its dimensions will be within 3 × 3 × 4 m. A classical furnace occupies dimensions of 15 × 20 × 12 m.

When making the calculations (Table 1), prices were used, which were dictated by the manufacturers of modern furnaces. Therefore, the cost of a new furnace was formed when comparing with a classical furnace.

LITERATURE

[one]. A.A. Andreev. Melting and casting of titanium alloys, - M.: From "Metallurgy". 1994, pp. 182-184.

[2]. RU 2087563 C1, C22D 9/22, 08.20.1997.

Table 1. No. p / p Name of nodes Classical EBL % Namenova
knots New EBL % Note Cost, million rubles Note Cost, million rubles one. Email beam guns 4 things. 2,52 7 Email beam guns 4 things. 2,52 7 2. Power supply 1.2 MW 1.8 5 Power supply 1.2 MW 1.8 5 3. Vacuum systems Productivity on 42 m ³ 4.32 12 Vacuum systems Productivity on 8 m ³ 1,08 3 four. Melting chamber body On 20 m ³ 3.6 10 Melting chamber body On 5 m ³ 0.9 2,5 5. Vacuum piping On 12 m ³ 1.8 5 Vacuum piping On 3 m ³ 0.36 one 6. Charge chamber housing On 5 m ³ 1.8 5 7. Ingot chamber housing 5 m ³ 1.8 5 8. Intermediate capacity 0.72 2 Upper mold 1.8 5 9. Sliding Mold 1,08 3 Bottom mold 1,08 3 10
Mechanical ingot extraction system 2.88 8 eleven Fur. charge feeding system 2.88 8 12 Ingot mine shaft 2.88 8 13 Fixing truss and system
furnace support Dimensions
15 × 20 × 12 m 3.6 10 Fixing truss and system
furnace support Dimensions
3 × 3 × 4 m 0.9 2,5 fourteen Installation and commissioning 4.32 12 Installation and commissioning 1,08 3 Total: 36 one hundred Total: 11.52 32

Claims (5)

1. The method of zone melting of metals, including loading a metal charge and its sequential melting by an electron beam or plasma by scanning the surface with the formation of a metal melt refined from light and heavy impurities, the refined portions of which are periodically poured into the lower mold to form an ingot, characterized in that the charge metal charge and its sequential melting by an electron beam or plasma is carried out in the upper mold, made with a vertical groove, in prior to loading the metal charge, a plate of remelted metal cleaned of impurities is installed, overlapping said groove, fusion of the molten metal in the upper mold of the bathtub with a depth of not more than 50 mm, without fusion of said plate, while the groove in the said plate is melted with an electron beam or plasma to a depth less than the depth of the weld pool of the melt by 20-30% and the refined portion of the molten metal is poured into the lower mold to form an ingot, leaving the upper crystallizer of a molten metal containing heavy impurities. 2. The method according to claim 1, characterized in that the charge is melted in the upper crystallizer by an electron beam or plasma by periodically scanning its surface to form a metal melt refined from light and heavy impurities. 3. The method according to claim 1, characterized in that they use simultaneously separate electron beam guns or plasmatrons at each stage of melting, melting the plate and heating the metal melt in the lower mold or at all the stages mentioned, use one electron beam gun or plasmatron. 4. A device for zone melting of metals containing an electron beam or plasma gun, a mold for forming an ingot, which is located in the melting chamber with a vacuum nozzle connected to a vacuum system, characterized in that it is equipped with an upper mold for sequential melting of the metal charge with the formation refined from light and heavy impurities of the metal melt, placed above the mold to form an ingot, a pallet with a mechanism for its removal, hermetically connected th a melting chamber, while in the upper mold plate is formed from overlapped purified from impurities vertical slot to form a ledge for holding the metal remelted heavy impurities during the melting process, and said molds are mounted on a pallet. 5. The device according to claim 4, characterized in that the upper mold is made V-shaped, almost completely overlapping the transverse plane of the furnace melting chamber, with the exception of the sector allocated for the discharge of refined metal melt.

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