WO2010068140A1

WO2010068140A1 - Method and apparatus for electron-beam or plasma-jet melting of metal from a crystallizer into a crystallizer

Info

Publication number: WO2010068140A1
Application number: PCT/RU2009/000678
Authority: WO
Inventors: Анатолий Евгеньевич ВОЛКОВ
Original assignee: Volkov Anatoliy Evgenevich
Priority date: 2008-12-10
Filing date: 2009-12-09
Publication date: 2010-06-17
Also published as: RU2008148779A; RU2489506C2

Abstract

The invention relates to the sphere of foundry work and can be used for casting any metals, including high-melting and chemically active metals. Electron-beam or plasma-jet melting of metal from a crystallizer into a crystallizer is carried out in a vacuum melting chamber (2) that is equipped with electron-beam or plasma-jet guns (1) which have moveable beams (8) and are arranged in the upper part of the melting chamber (2). The apparatus comprises two crystallizers (4) and (5), one of which is intended for a melting stock (6) while the second is intended for an ingot (13) and is cooled. The crystallizer (4) is arranged inside the melting chamber (2) above the crystallizer (5) and is offset from the latter, thereby ensuring that the metal (9) can be transferred. The crystallizer (5) is fastened by the edges thereof behind the tray (3) of the melting chamber (2) in such a way that the upper part of the crystallizer (5) communicates with the melting chamber (2) while the lower part of said crystallizer is located below the melting chamber. The crystallizer (4) has a slot (11) in the lateral part thereof on the side on which the crystallizer (5) is situated. The entire length of the slot (11) is covered by a removable plate (10) which is formed from refined metal corresponding to the metal melting stock. The melting stock (6) is melted in conjunction with zone refining by periodically scanning the surface of the metal (9) with the beam (8) in a direction from the plate (10) to the opposite side of the crystallizer (4) over a set period of time.

Description

METHOD AND DEVICE OF ELECTRON BEAM OR

PLASMA FUSION FROM CRYSTALIZER IN

CRYSTALIZER

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

BACKGROUND OF THE INVENTION Various structures of electron-beam or plasma devices are widely known in the literature and technology that make it possible to realize a method of melting metals.

A known method and device for plasma or electron beam melting in a flat crystallizer developed by the American company "Frapel" [A.A. Andreev "Smelting and casting of titanium alloys", Moscow, "Metallurgy". 1994, pp. L79 ÷ 180]. In the known method, the charge is melted by a plasma torch in a flat crystallizer, which is made moving inside the melting chamber filled with argon, while the plasma torch is made with the possibility of its movement up and down, as well as with the possibility of the beam moving around the central axis, the charge from the loading device is portioned loaded into the mold, each subsequent portion is loaded as the previously loaded portion of the charge is melted until the ingot reaches the desired thickness or m ssy. The resulting ingot is subsequently used as a consumable electrode in a vacuum-arc remelting. Furnaces with electron beam (plasma) heating are available on an industrial scale.

The main advantage of the plasma or electron beam method of melting into a flat crystallizer is the possibility of producing flat ingots of a sufficiently high quality cleaning up. The main disadvantages include the complexity of the equipment, due to the need to place a moving mold inside the melting chamber, and, as a consequence, the need to make a significant size melting chamber. The large size of the melting chamber leads to significant energy consumption for its evacuation and filling with argon. In addition, the known method has a sufficiently long production cycle, does not provide the full penetration depth of the mixture and has limited possibilities of averaging the chemical composition of the mixture. The closest technical solution is an industrial furnace for electron beam remelting with a cold hearth of the American company Johnson [A.A. Andreev “Smelting and casting of titanium alloys”, Moscow, “Metallurgy”, 1994, pp. L82 ÷ 184), containing four electron-beam guns, with a total capacity of 2000 kW, a bunker in communication with a vacuum melting chamber, inside of which there is a cooled the crucible and the mold, while the cooled crucible is installed above the mold, and the mold is made sliding. The source material in the form of a charge, sponge, powder or granules is supplied at a certain speed from the charge hopper to a cooled crucible, in which the charge is melted under the influence of an electron beam. The resulting liquid metal drops or (with sufficient electron beam power) flow continuously from the cooled crucible into a sliding cooled crystallizer, forming an ingot of the required size. Such a remelting method can also be referred to as electron beam remelting with an intermediate capacity or melting from a crystallizer to a crystallizer.

The known method for the purpose and scheme of its implementation is similar to the method of plasma remelting, widely used in industry. However, in contrast to the method of plasma remelting, in the known method, a deeper purification of metal from gas impurities, since the molten metal in a vacuum is retained for a long time, providing the necessary quality of metal refining.

The disadvantages of the known method and device for its implementation include the large overall dimensions of the mold and, accordingly, the large overall dimensions of the melting chamber, which requires significant energy consumption for evacuating the melting chamber and for drawing out evaporating gases and metals from the melting chamber. Large overall dimensions of the melting chamber lead to heat loss during the melting process, require significant production areas for the placement and implementation of the melting process. Since a new portion of the charge constantly enters the cooled crucible, one or two guns are installed to melt it, and the crucible, at the end of which the metal is melted, is heated by its volume and, due to its considerable mass, takes part of the heat, and, therefore, excessively consumes part of the energy of the beam guns. Moreover, the molten metal is in a shallow crucible and, pouring into a cooled sliding mold, consumes heat at the stage of forming the ingot, which additionally leads to unproductive losses of thermal energy of one of the guns. It is known that beam furnaces surpass all known metal melting furnaces, for example, titanium (vacuum-arc, plasma, induction, skull, etc.) with refining capabilities, but they do not allow to obtain a strictly regulated, uniformly distributed chemical composition along the length ingot. Currently, attempts 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 justify expectations of metallurgists. SUMMARY OF THE INVENTION

In the present invention, the task was to reduce the size of the smelting plants and to increase the efficiency of the metal melting process by reducing energy consumption, increasing the volume of smelted metal, while reducing the production cycle and maintaining the refining properties of electron beam furnaces.

The problem is solved by the fact that the claimed device for electron beam or plasma smelting of metal from a crystallizer into a mold, which contains a vacuum melting chamber equipped with electron beam or plasma guns made with the possibility of moving their rays and placed in the upper part of the melting chamber, mold, one of which is designed for the charge, and the second for the ingot and is made cooled, the mold for the charge is located inside the melting chamber above the mold for the ingot and is shifted relative to the latter, providing the possibility of overflow of metal from the mold into the mold, characterized in that the melting chamber is made with a removable tray, the molds are installed in the melting chamber and mounted on a removable tray, while the mold for the ingot is fixed by the edges to the tray of the melting chamber so so that its upper part is connected to the mold with the melting chamber, and its lower part is under the melting chamber, the mold for the charge is installed n inside the melting chamber and is equipped with a groove that is made in the side of the mold for the charge from the side of the mold for the ingot, the length of the groove is less than the height of the side wall of the mold for the mixture, the groove is covered over the entire length by a removable plate made of refined metal corresponding to the metal of the mixture.

In the inventive device, when melting the charge, two crystallizers are used, placed one above the other, so that 9 000678

5, the melt from the crystallizer for the charge (upper crystallizer) flows into the mold for the ingot (lower crystallizer) through a special groove, which is mainly made in the form of a slit. The mold for the charge (upper mold) combines the functions of the charge container and the intermediate tank or the cooled crucible, and the groove, which is made in its side wall, is covered along its entire length with a plate of the same metal as the charge, but already refined. In this case, the mold groove for the charge does not reach a certain distance to its bottom, excluding the possibility of overflow of contaminants accumulating in the lower part of the mold for the charge. To increase productivity and reduce the cost of melting, the mold for the charge (upper mold) can be made almost completely overlapping the transverse plane of the melting chamber, with the exception of the sector that communicates with the mold for the ingot (bottom mold).

The inventive method of electron beam or plasma melting from a crystallizer to a crystallizer consists in loading a charge into a charge crystallizer located inside a vacuum melting chamber with a removable tray, melting the charge by heating it with electron beam guns or plasma torches to form a molten metal, the resulting molten metal is poured into the ingot mold, supported by its edges on a removable tray and located below and with an offset relative to the catalyst for I charge, the discharge of molten metal from the mold for the charge is carried out through a groove located in its side wall, by melting the corresponding sector of the removable plate covering the groove, while the removable plate is made of refined metal corresponding to the metal of the mixture, the melting of the plate is carried out sequentially from top to bottom as the formation of the molten metal in the mold for the charge, the molten metal in the mold for the ingot cooled with the formation of the ingot, and impurities accumulated on the bottom of the mold for the charge are removed.

The proposed method is periodic and its essence is that the charge is loaded into the crystallizer for the charge in full, and after evacuation of the melting chamber, the charge is sequentially melted by heating with electron beam guns or plasma torches. In the process of metal melting, it is refined from impurities, after which the refined melt is poured in portions into the mold for ingot. The refined metal is drained into an ingot mold (lower mold) through a smelting plate made of the same refined metal. The mold for the ingot is cooled and stationary, located outside the melting chamber, i.e. an ingot is formed during cooling of the mold. The plate is laid in the mold for the charge (upper mold) is carried out before loading the charge. To obtain an ingot with zone cleaning using periodic scanning of the surface of the metal. Periodic scanning is carried out by appropriately controlling the beams of the electron beam guns or plasmatrons, so that the first line of the molten metal is formed in the direction from the melted plate to the opposite side of the mold for the charge. After scanning the metal in one or several passes, that is, after performing zone cleaning, the deposited metal bath from the cleaned plane of the upper mold merges into the mold for the ingot (lower mold). The metal is drained due to the fact that only the part of the plate that corresponds to the depth of the melted and cleaned melt pool is melted with a beam or plasmatron. The purified metal melt is poured into the ingot mold (lower mold) due to the fact that as a result of penetration a removable plate at an appropriate height of the side wall of the mold for the charge (upper mold), the groove opens at the level of the molten metal and the molten metal merges. The process is repeated until the metal is completely drained from the crystallizer for the charge (upper crystallizer). After the removable plate is melted along the entire length of the groove, the entire metal melt is poured into the ingot mold (lower mold), except for the metal that remains on the bottom of the mold for the charge (upper mold). The manufacture of a groove with a length shorter than the height of the side wall of the mold for the charge, prevents the ingot from becoming contaminated with impurities deposited on the bottom of the mold for the charge (upper mold). To clean the metal, the hydrodynamic cleaning method is used, in which heavy impurities settle on the bottom of the mold for the charge, since the groove does not reach its bottom vertically, forming a ledge that holds heavy impurities. To ensure that heavy impurities do not enter the formed ingot, the metal is melted in such a way that the metal melt is cleaned of heavy and light inclusions on the approach to the removable plate. When cleaning metal from heavy inclusions, such a melting mode is selected, when the beam first melts the melt bath of a certain depth, and then melts the plate that closes the vertical groove to a shallower depth, thereby allowing the melt to drain, leaving heavy inclusions at the bottom of the bath in the upper mold. At the end of melting, 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, forming a natural obstacle for heavy inclusions. From light inclusions, the metal is completely cleaned 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 9 000678

8 are removed through a vacuum pumping system. Subsequently, by melting the removable plate, only pure melt is poured into the lower mold, since the removable plate is made of the same refined metal, and the obtained melt was cleaned in the allotted time for this by using known methods of zone cleaning.

The mold for the charge (upper mold) is displaced relative to the mold for the ingot (lower mold) so that the drain is located in its center or near the edge of the mold for the ingot (lower mold). Both molds are mounted on a pallet of the melting chamber. The removal of the pan with molds can be provided by stationary hydraulic and pneumatic devices or by independent mechanisms, for example, by driving up an electric car. The place for sealing the melting chamber is mainly its connection to the pallet, which allows for good access to loading and unloading and to reduce the risk of leakage into the melting chamber. Unloading of crystallizers is carried out on the opposite side of the vacuum nozzle connected to the vacuum system.

To increase the productivity of the process at each stage of melting, scanning, penetration of the plate and heating, several electron-beam guns or plasma torches can simultaneously work. To reduce the cost of melting, one electron beam gun or one plasmatron can be used. When using one active gun, use the possibility of deviation of the beam from the central axis. In this case, alternately deposit the metal in the upper mold, then melt the removable plate, opening the groove for draining the metal, and also heat the metal in the lower mold. With the simultaneous use of several guns, the remelted volume of the metal and the melting rate can be significantly increased. The charge is loaded into the crystallizer for the charge (upper crystallizer) can be carried out both with prepress and without prepress. Prepressing the charge before loading allows to reduce its melting time, increase the volume of metal smelting, as well as reduce losses on the evaporation of alloying elements.

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

BEST MODES FOR CARRYING OUT THE INVENTION Specific embodiments of the inventive method and device are described below with reference to the accompanying drawings.

The inventive method is carried out using the installation, the cross section A-A and a top view of which is shown in figure 1.

The device contains electron beam guns 1, the housing of each 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 pallet 3, on which a cooled mold for the charge (upper mold) 4 is conical in shape and a mold for the ingot (lower mold) 5. Crystallizers 4 and 5 are made of copper. The melting chamber 2 with the pallet 3 are mounted using bolted connections, through the sealing vacuum rubber. In the upper mold 4, the mixture 6 is pressed or pressed into the briquette 6. After the crystallizers 4 and 5 are mounted on the pallet 3, the required vacuum is created in the melting chamber 2 through the pipe 7. Upon reaching the required vacuum depth, the charge is melted by heating with an electron beam 8 to form a metal bath 9. The charge 6 is melted over the entire area of the mold 4 for the charge, not reaching a certain distance to its perimeter, i.e. with the exception of the area located near the walls of the mold 4 for the charge. Ray 8 678

10 emanating from one or more guns 1, is moved along the metal surface until the contour of the metal bath 9 reaches the walls of the mold 4 for the charge, i.e. the melting of the charge b is carried out in such a way that the beam 8 at the stage of forming the metal bath 9 does not melt the walls of the mold 4 for the charge. The mixture 6, molten over the entire upper plane of the mold 4, forms a metal bath 9, which is refined under the influence of beam 8 for a certain time, i.e. the molten metal bath 9 is cleaned of light, heavy and gas inclusions. Upon reaching the metal bath 9 of a certain depth h, the melt is poured into the mold 5 for ingot due to penetration by the beam 8 of a plate 10 made of the same metal as the charge 6, but only previously refined. The plate 10 is installed in the mold 4 for the charge before loading the charge b, so as to overlap the vertical groove 11 made in the side wall of the mold 4 for the charge. The groove 11 does not reach the bottom of the mold 4 for the charge, i.e. ends at a certain height d from the bottom of the mold 4. The depth of penetration of the plate 10 and the opening of the groove 11 should be less than the depth of the melt bath h, about 20 ÷ 30%. The process is monitored using sensors 12, combined with security cameras installed in the body of the melting chamber 2. The metal bath 9, merging into the crystallizer 5, forms an ingot 13. So that the structure of the ingot 13 is cavity-free and qualitatively melted, the metal to be merged can be heated electronically beam 8. If in the future the ingot 13 is sent for re-remelting (for example, arc), then this heating is not required. The electron guns 1 should be installed in such a way in the melting chamber 2 so that they can most effectively overlap the surface in the mold 4, melt the plate 10 and heat, if necessary, the molten metal in the mold 5. 678

eleven

Figure 2 shows the inventive installation section B-B and a top view similar to the installation according to Fig. 1, characterized in that plasmatrons 1 are used for heating, and the crystallizer 4 is made V-shaped, which allows three to five times more metal to be accommodated in comparison with a round or cone-shaped crystallizer and allows filling almost the entire perimeter of the melting chamber 2 with the exception of a small sector through which the metal bath 9 is drained into the lower mold 5. Figure 2 shows a sector with an angle of 90 ° through which the metal is drained, but this sector can also occupy a smaller angle. This design of the mold allows the metal to be cleaned not only of heavy and light inclusions, but also to clean metal and non-metallic inclusions present in the alloy due to zone melting. So, for example, in one half of the mold 4, beam 8, fusing a narrow strip 14, drives it from one wall of the mold 4 to the other from side A to C and from side B to D. The melt strip always passes in one direction, like a light strip in the scanner, reaching sides C and D, beam 8 again begins to melt the metal from sides B and A. By melting the metal this way one or more times, depending on the requirements for cleaning the metal, the metal bath 9 is melted to a depth h, then the plate 10 is melted and the molten metal bath 9 merges into crist alligator 5 for the ingot. Next, the cleaning process is repeated until the charge b is completely re-melted, with the exception of only its mass, in which there are inclusions and which forms a skull on the bottom of the mold 4. The installation depicted in Fig. 2 is very compact, but at the same time it is capable of smelting very large amount of metal.

The technical result achieved by the claimed device (Fig. 1) is illustrated by the following comparative analysis with an electron beam furnace (known ELP) operated by Composite OJSC (Korolev, Moscow Region) - four electron beam guns of 250 each 678

12 kW, 0200 ingot, 1.5 m long, 200 kg total weight (when loading titanium charge 220 kg). The volume of the furnace is 10 m ³ , the volume of the pipelines of the vacuum system is 12 m ³ , the pumping time is 1.5 hours, the melting time is 1 hour, the cooling time is 1.5 hours, i.e. full cycle of the furnace - 4 hours. Unloading-loading, which is 1.5 hours, takes extra time. The cost of the furnace is about 1 million € (36 million rubles), which consists of the cost of the main components listed in Table 1.

A comparative analysis was carried out in relation to the claimed device — New ELP (table 1), which includes four electron beam guns, each with a power of 250 kW, a mold 4 for a charge with a diameter of 800 mm and a depth of 600 mm, a charge of a titanium charge with a tight package of 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 due to lower heat losses.

As can be seen from table 1, when comparing the known ELP and the new ELP, it can be noted that the new ELP with the same number of guns 1 at the same time allows melt 1000 kg of titanium versus 210 kg (known ELP), i.e. the volume of smelted metal increases significantly. At the same time, the dimensions of the new EBL are Z ^χ Zx 4m, while the dimensions of the known EBL are 15x 20 ^χ 12m.

In addition, due to the fact that in a new EBP all electron beam guns can be directed to smelting a metal bath 9 in a mold 4, the following advantages are achieved: - mold 4, having a depth of 600 mm and when smelting a liquid metal bath 9 with a depth of not more 50mm, does not lose its heat on heating the bottom of the mold 4;

charge 6, having a packaged (but not fused structure), has a low thermal conductivity, therefore, almost all the energy is used for useful molten metal bath 9; 2009/000678

13

-after draining the next portion of the molten metal bath 9, the rays 8 begin to melt the next layer of metal already heated to the melting point, located in the mold 4;

- part of the energy of the beam 8 is only sometimes used to melt the plate 10 and, if necessary, to heat the metal in the mold 5.

As mentioned above, since beam furnaces have a low melt mixing capacity, a significant amount of energy should not be spent on heating and fusion of the ingot, since it is economically feasible to direct the ingot sent for remelting by vacuum-arc or induction remelting, where the mixing ability of the melt is much higher, while the refining ability is low.

INDUSTRIAL APPLICABILITY

The inventive method allows to obtain ingots of round, square or rectangular shapes, to conduct the process with one or more guns (or plasmatrons), to carry out the melting process without the use of filling feed and exhaust devices for evaporating metal. A mold for the charge (upper mold) combines the functions of a hopper and an intermediate tank. Due to the use of the possibility of deviation of the beam from the central axis, the design of the device is greatly simplified, without requiring the use of mechanisms for feeding the charge, moving the mold and drawing the ingot, which significantly increases reliability and significantly reduces the cost. The inventive design 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. Table 1

Claims

CLAIM

1. The method of electron beam or plasma melting from a crystallizer to a crystallizer in a vacuum melting chamber by melting the charge in the crystallizer by electron beam guns or 5 plasmatrons, followed by the formation of a metal ingot in the cooled mold and removing the separated impurities, characterized in that the charge is loaded into a mold for the charge, located inside the vacuum melting chamber with a removable pan, after evacuation of the melting chamber, the charge is melted,

Sequentially heating the upper layer of the charge in the mold for the charge, the formed portion of the metal melt is poured into the mold for the ingot, which is made leaning on its edges on a removable tray and is located below and with an offset relative to the catalyst for the charge, while the metal melt is drained

15 through a groove made on the side wall of the batch mold by melting a removable plate, a shielding groove and made of refined metal corresponding to the metal of the batch, the melting of the removable plate is carried out sequentially from top to bottom as the formation of the metal melt in the mold for the mixture, and 0 impurities accumulated on the bottom of the mold for the charge are removed.

2. The method according to p. L., Characterized in that the mixture is melted simultaneously with zone cleaning, which is carried out by periodically scanning the metal surface in the direction from the melted removable plate to the opposite side of the mold for 5 predetermined times.

3. Device for electron-beam or plasma melting of metal from a crystallizer to a crystallizer, containing a vacuum melting chamber equipped with electron-beam or plasma guns configured to move their rays and 0 located in the upper part of the melting chamber, two molds, one of which designed for the charge, and the second for the formation of the ingot and is made cooled, the mold for the charge is located

SUBSTITUTE SHEET (RULE 26) inside the melting chamber above the mold for the ingot and offset relative to the latter, providing the possibility of overflow of metal from the mold into the mold, characterized in that the melting chamber is made with a removable tray, the molds are installed in the melting chamber and mounted on a removable tray, while the mold for the ingot is fixed by the edges behind the tray of the melting chamber in such a way that with its upper part the mold for the ingot is in communication with the melting chamber, and its lower part is under the melting By the second chamber, the mold for the charge is installed inside the melting chamber and provided with a groove that is made in the side of the mold for the charge on the side of the mold for the ingot, the length of the groove is less than the height of the side wall of the mold for the mixture, the groove is covered over the entire length by a removable plate made of refined metal corresponding to the metal of the mixture.

4. The device according to p.Z., characterized in that the mold for the charge is made almost completely overlapping the transverse plane of the melting chamber, with the exception of the sector allocated for the discharge of molten metal.

5. The device according to p.Z., characterized in that the mold for the charge is made conical in shape.

6. The device according to p.Z., characterized in that the mold for the charge is made in a V-shape.

7. The device according to p.Z., characterized in that the molds are made of copper.

8. The device according to p.Z., characterized in that the mold for the charge is offset relative to the mold for the ingot so that the drain is located in the center of the mold for the ingot.

9. The device according to p.Z., characterized in that the mold for the charge is offset relative to the mold for the ingot so that the drain is located near the edge of the mold for the ingot.

SUBSTITUTE SHEET (RULE 26)