Method for producing small-size cast pieces of high-active metals and alloys and plant for performing the same

FIELD: manufacture of dentures, jewelry, small-size articles.

SUBSTANCE: apparatus includes melting and pouring chamber where non-consumable electrode and crucible of graphite are arranged. Inner surface of crucible is covered with refractory tungsten non-interacting with melt. Apparatus for tilting crucible includes carcass having two mutually parallel vertical grooves. In mutually opposite grooves rollers are arranged with possibility of limited motion. Said rollers are secured to ends of levers through hinges joined with crucible. Carcass includes movable support for crucible secured to wall of carcass. Said support may be moved in horizontal plane. In order to set designed gap, crucible and apparatus for tilting it are moved upwards till contact of billet with end of electrode; then movable support of crucible is introduced and crucible is moved downwards till support. After melting billet said support is withdrawn. Crucible falls down and tilts along path providing motion of point of crucible inner surface at side of draining mostly spaced from axis of crucible in tilting plane along vertical line.

EFFECT: less consumption of power, improved quality of cast products, shortened time period for manufacturing cast products.

2 cl, 1 dwg

The invention relates to foundry and is designed to produce small castings from high-level (high reactivity with oxygen) metals and alloys such as titanium, titanium alloys, niobium, tantalum, Nickel, chromium, cobalt and can be used for the production of dental prostheses, as well as jewelry and small items in the engineering industry.

In the production of shaped castings of titanium and titanium alloys are the most used way of obtaining skull in vacuum arc furnaces. In such furnaces titanium melt accumulates in the skull from the same titanium alloy as the melt. Skull layer in the crucible is formed during the melting process or applied to the inner surface of the crucible pre-and serves as an electrode and a protective layer of the base material of the crucible. One of the main requirements to such boards is the lack of contact of the liquid metal from the furnace design elements that are not protected by the skull. The crucibles in such furnaces are made of different materials, cooled without cooling. Known melting and pouring units (ROM) using a cold metal crucibles, allowing namorazhivat the crust on their inner surfaces. They use water, gas (helium) or LM is cometlike (silicon-sodium eutectic cooling the walls. The presence of cooling complicates the design of the ROM, in addition, water cooling leads to the danger of explosion. Known ROM with copper crucible without cooling, where the crucible itself is cooler. Famous skull melting furnace with crucible made of graphite, cooled and not cooled. However, due to prolonged contact of the liquid metal with graphite crucible is the contamination of the metal with carbon. The practice of melting titanium graphite skull crucible shows that it is not possible to completely eliminate the increase of carbon content in cast material.

Known melting and pouring vacuum melting and obtain castings of titanium alloy (patent RF №2092758, CL F27 14/04). The system includes a vacuum system with a vacuum chamber, skull graphite crucible installed in a vacuum chamber, the node arc melting of a consumable titanium electrode site fill container mould centrifugal table, installed in the vacuum chamber, remote control unit, and skull graphite crucible equipped with an electromagnetic device eliminate burnout skull layer and the saturation of the alloy impurities, and the container mold device of the heated mold. When this skull crucible made uncooled. In PLA is safe and casting chamber melting crucible is installed in the rotary mechanism. The crucible is mounted an electromagnetic device, comprising simultaneously with the formation of an arc between the end of the consumable electrode and the metal at the bottom of the crucible. Setting the estimated gap between the end face of the electrode and molten harvesting is carried out manually before each fusible movement of the electrode holder, pouring the melt into the mold is performed by tilting the crucible using the rotary mechanism.

The unit has the following disadvantages:

- use consumable titanium electrode is not possible to reliably obtain the specified degree of superheat of the metal, as the process is unstable, which reduces the efficiency and uniformity of the melt;

the crucible is made of graphite, and the practice of melting titanium in a graphite crucible shows that it is not possible to completely eliminate the increased content of carbon in cast metal;

- despite the fact that graphite crucible has a low thermal conductivity compared to metal crucibles, skull melting technology determines the heat dissipation through the walls of the crucible, therefore, the use of heat from the arc, inefficient, this leads to increasing energy consumption and decreasing the efficiency of the plant;

- installation design is complicated by the presence of electromagnetic devices eliminate burnout skull layer and the device is CMV heated mold.

The closest the result achieved by the claimed invention is melting and casting device for producing small castings (RF patent No. 2211419, CL F27B 17/00; B22D 13/04 was investigated). The installation provides a method of obtaining small-sized castings from high-level metals and alloys, comprising the following operations:

- adjust the estimated gap between the end electrode and the workpiece by manual installation of the electrode holder in a specific position in a vertical plane;

- evacuation;

- melting of the workpiece by an electric arc non-consumable electrode (the melting is carried out in a cooled copper crucible with the formation of the skull layer);

the output electrode of the crucible by moving the electrode holder with the help of a special mechanism for lifting and lowering;

- tilting the crucible to fill the mold, and the crucible is moved in an arc in a vertical plane.

Installation for implementing this method includes melting and pouring a vacuum chamber, which has a melting node with copper melting crucible having a skull layer of material with the chemical composition of molten metal, rotary table for mounting the mold electrode holder with non-consumable electrodes, on the rod which is fixed cover-REDD and the molybdenum, the site filling of molds. Nonconsumable electrodes are used for a long time, and cover-REDD has the properties of light and heat reflection, which reduces energy loss.

The disadvantages include:

- heat dissipation through the walls of the crucible for forming a skull layer that defines a large energy consumption. Cover the arch of the rod elektrogerate in this installation provides a slight reduction of heat losses;

- copper crucible is cooler and accumulates a significant part of the heat generated by an electric arc (thermal conductivity of copper is very high, it is higher than thermal conductivity of titanium is about 18 times), and when the temperature at the copper significantly reduced mechanical properties, therefore, on the border of the copper-titanium must be set to a temperature lower than the temperature of the reducing strength of copper, and this leads to an increase in the mass of the crucible, its size and dimensions of the installation.

Common deficiencies are considered the ROM include:

- high energy ROM, because the skull melting technology involves the removal of a significant part of heat generated by an electric arc through the walls of the crucible, and therefore, the inability to reduce the technological cycle due to the rational use of energy of the arc;

- low efficiency of plants, SLE is due to large energy losses;

- need to replace the skull layer when changing grades of material;

incomplete utilization of the volume of molten metal, as when pouring into the mold a piece of metal that remains in the crucible, forming a skull layer for the next melt;

- molten metal has a low reheating temperature above its melting temperature, because the temperature increase leads to the decrease of the thickness of the skull layer that you want to maintain the optimum, and this limits the fluidity of the material by pouring it into a mold;

- decrease the tightness of the plants, due to the presence of a movable connection between the electrode holder and the wall of the vacuum chamber;

- the complexity of the design ROM, due to the presence of the mechanism for lifting / lowering of the electrode holder;

the splashing of the melt by pouring into the mold, as the crucible for overturning moves in an arc in a vertical plane, therefore, there is a horizontal component of the inertial force acting on the melt;

- increased complexity and duration of the technological cycle, due to the fact that before each fuse must be installed electrode holder in a specific position in a vertical plane, towards the settlement is Azora between the electrode and the workpiece for ignition of the electric arc, the output from the crucible electrode using the mechanism of the lifting / lowering, the cooling of the crucible walls, replacement of the skull layer when changing grades of material.

From the analysis considered the melting and casting units, it follows that the method of melting furnaces with a skull crucible is high-energy, because the condition of education skull layer is to maintain the temperature of the inner surface of the crucible is not higher than the crystallization temperature of molten metal, and therefore, the heat dissipation through the walls of the crucible. According to the journal "TITAN" No. 3 2003 heat loss through the walls of the crucible in the skull furnaces range from 75 to 92% during the technological cycle. As a result, the efficiency of the skull furnaces is extremely low. The optimal thickness of the skull layer requires strict coordination of melting modes with a choice of crucible material, its thermal conductivity, cooling system, and also determine the shape of the crucible by means of mathematical simulation of thermal process of forming metal castings. Crucibles skull furnaces produce massive, and this leads to an increase in the weight and size of the melting and casting plants. To prevent burning skull layer on the side walls of the crucibles have to install additional devices and this complicates the design. Not excluded the possibility of delamination skull layer at the bottom of the crucible, which leads to the interaction of the molten metal from the crucible material, contamination and reduction in the quality of castings. The necessity of cooling the walls of the crucible lengthens the process cycle of melting and reduces the performance of the installation. Adverse conditions crucible (high temperature gradients in the walls) reduce its service life. Technology of smelting in the skull crucible is not possible to achieve a high reheating temperature of molten metal above its melting temperature, which reduces the fluidity of the metal and its ability to make thin walls when filling in forms.

The objective of the proposed technical solution as the invention is the reduction of energy consumption by a significant reduction in the absorption of heat by the walls of the crucible, i.e. more efficient use of the energy of the electric arc, increasing the efficiency of the installation, the use of the crucible without replacement when changing the molten material of the workpiece, changing the output electrode of the crucible before tilting the latter to exclude mechanism for lifting / lowering of the electrode holder and enhance the integrity of the ROM, change the installation method of the estimated gap between the electrode and the workpiece required for ignition electrical the OI arc, creating the optimal trajectory of the crucible when tilting it to eliminate splashing of the molten metal by pouring it into a mold.

When the task is achieved by the following technical result: the production of high quality castings with preservation of the chemical composition and homogeneity of the source material, the possibility to raise the temperature of the overheating of the molten metal above its melting temperature, i.e. increasing its fluidity during casting, eliminating splashing of molten metal by pouring it into a mold, full use for casting volume of molten metal by eliminating the need to numerazione on the inner walls of the crucible skull layer, creating favorable conditions crucible (with the exception of high temperature gradients in the walls), the reduction in the duration of the technological cycle, increasing the tightness of the installation, simplifying the design and improving performance.

The technical result is achieved by the fact that in the known method of obtaining small-sized castings from chemically highly active metals and alloys, including the installation of a calculation of the gap between the end electrode and the workpiece, the vacuum melting and casting chamber, the melting of the workpiece the crucible electric arc using a nonconsumable electrode, the output electrode of the crucible, the tilting of the crucible to fill the mold, electric arc melting is carried out in a crucible made of a material with low heat conductivity, such as graphite, and with the inner surface covered with refractory low-reactive material, such as tungsten, does not interact with the melt, the installation of the estimated gap between the workpiece and the tip of the electrode is carried out by joint vertical movement of the crucible and the device tipping up to the contact of the workpiece with the electrode, subsequent fixation device tilting crucible, installed under the bottom of the crucible movable support at a distance equal to the estimated gap between the electrode and the workpiece, and moving down relative to the crucible tipping device crucible to the movable support, the output electrode of the crucible is carried out by moving the crucible down, and when filling the mold crucible tilt sweep, ensuring the displacement of a point on the inner surface of the crucible side drain, the most remote from the axis of the crucible in the plane tipping over on a vertical line.

The technical result is achieved by the fact that in the known device for producing small castings made of chemically highly active metals and alloys, containing the node arc melting, melting and pouring coumou camera the site filling of molds with the centrifugal table, the melting pot, the device tilting of the crucible, the crucible is made of a material with low heat conductivity, such as graphite, with the inner surface covered with refractory low-reactive material, such as tungsten, does not interact with the melt and the crucible and the device tipping made with the possibility of joint and relative reciprocating movement in a vertical plane, the device tipping is a frame consisting of two parallel connected to a wall having two vertical groove, and a pair of oppositely located grooves placed with a limited movement of the rollers on the levers, pivotally connected with the side surface of the crucible in the area of its transition to the bottom, and the other pair of grooves placed with a limited movement of the rollers mounted on the side surface in the upper part of the crucible, the axes of which pass through the point of discharge of the inner surface of the crucible, the most remote from its axis in the plane of tilting, and the stroke length of the rollers is determined from the condition of ensuring the movement of the crucible along the trajectory, providing the movement of the point of discharge on the vertical line of the frame in the upper part is hard, but we have the options to stop crucible and collaboration with the crucible move up, movable in the horizontal plane of the support crucible, fixed in the wall of the frame to install the estimated gap between the end electrode and the workpiece, and the element fixing the position of the frame in a vertical plane.

To verify compliance of the claimed invention to condition inventive step, the applicant conducted an additional search of the known solutions to identify signs that match the distinctive features of the prototype of the features of the proposed method and installation for its implementation.

The search results showed that the claimed invention is not apparent to the expert in the obvious way from the prior art. The search is not identified technical solutions in ways that would involve obtaining a small-sized castings vacuum arc melting in crucibles, the design of which would not require, as in the claimed solution, heat dissipation through the walls for education skull layer, as well as technical solutions for the installation of the calculated gap, the output electrode of the crucible by moving the crucible. Not identified technical solutions for melting and pouring equipment for production of small castings using a crucible made of a material with low conductivity, with the inner surface covered with refractory low reactivity material, do not enter the it into a chemical reaction with the melt, as well as technical solutions to the design of the unit fill with tilting the crucible with the use of lever-roller mechanism. The inventive method for the production of small castings of high-level radioactive metals and alloys and installation for its implementation in their new aggregate and relationships essential features allow to obtain new technical properties not inherent in the known similar technical solutions on attitudes and ways, and also claimed distinctive features of the prototype characteristics, known separately, which allows to make a conclusion on compliance of technical solutions to the criterion of inventive step.

The drawing shows a General view of the equipment for production of small castings of high-level radioactive metals and alloys.

In the melting and casting chamber 1 is placed nonconsumable electrode 2 and the crucible 3, which form a melting node setup. The crucible 3 made of graphite with the inner surface coated tungsten, does not interact with the melt. The crucible 3 is associated with the device tipping over, which is a frame consisting of two parallel connected walls 4 having two parallel vertically arranged groove 5 and 6. In the slots 5 of each wall 4 is placed with the limited movement of the rollers 7, zakreplena the ends of the levers 8, the other end of which is connected by hinges 9 to the side surface of the crucible 3 in the area of its transition to the bottom, and in the grooves 6 of the walls 4 are placed with limited movement of the rollers 10 mounted on the side surface in the upper part of the crucible 3, and the axis of the rollers 10 pass through the point of discharge of the inner surface of the crucible 3, the most remote from its axis in the plane tipping over. In addition, the frame has a vertical reciprocating movement along the guide rails 11 and fixing the stop 12, provided with a thrust plate 13 to the stop of the crucible 3 and ensure move together with the crucible 3 upward, the movable support 14 of the crucible 3, mounted in the wall of the frame of the installation conditions of the estimated gap between the end of electrode 2 and the workpiece 15 with the movement of the crucible 3 down relative to the frame to a support 14. Bearing 14 has the ability to move in a horizontal plane with automatic return stroke for entry and exit from under the bottom of the crucible 3 before tilting the latter. The length of the slots 5 are determined by calculation from the condition allow movement of the crucible 3 according to the desired trajectory moves the crucible 3 up until it stops in the bearing plate 13 and down on the magnitude of the calculated gap and distance required to move the electrode 2 in the crucible 3. To complete the installation conditions of the RA is an even gap accounted body height of the crucible 3 and the magnitude of the calculated gap - the distance between the thrust plate 13 and the bearing 14 is equal to the sum of these quantities. The length of the slots 6 is determined by calculation of the conditions for lowering and rotation of the crucible 3, sufficient to discharge the molten material in the mold. On bottom of the crucible 3 with the workpiece 15. Mold 16 is fixed on the centrifugal table 17.

The method using the claimed device is as follows.

Before melting the workpiece 15 is mounted onto the bottom of the crucible 3. The crucible 3 is manually lifted up and he abutting edges of the walls in the bearing plate 13 of the frame of the device tipping over, drags him away. The frame along the guide rails 11 rises after the crucible 3 and the fixed stop 12 after the surface of the workpiece 15 will affect the end of the electrode 2. The support 14 is slid under the bottom of the crucible 3, between the bottom of the crucible 3 and the support 14 remains a gap equal to the distance between the end of electrode 2 and the surface of molten billet 15 required for ignition of the electric arc. After that, the crucible 3 is released and it falls under its own weight until it touches the bottom support 14, thereby creating the estimated gap between the end of electrode 2 and the surface of the workpiece 15. In this position of the crucible 3, the rollers 7 of the levers 8 are cruising along the slots 5, equal to the amount of movement of the crucible 3 with respect to the electrode , required for the output electrode 2 in the crucible 3. The camera 1 is closed and vacuum. Light electric arc. After melting of the workpiece 15 bearing 14 is automatically drained from the bottom of the crucible 3, which together with the levers 8 drops vertically down, the rollers 7 and 10 also move down the slots 5 and 6. The end of the electrode 2 is outside of the crucible 3. When the rollers 7 of the lower ends of the levers 8 are restricted current path along the grooves 5 and stop, the upper ends of the levers 8, pivotally connected with the crucible 3, begin to move in an arc with radius equal to the length of the lever 8, and the rollers 10 of the crucible 3 continue to move along the slots 6 vertically downwards. The sum of these movements is the tilting of the crucible 3. At this point drain melt the inner surface of the crucible 3, the most remote from its axis in the plane of tilting, moving vertically, which eliminates splashing of the melt by pouring into the mold 16.

The claimed combination and interrelation of essential features provide:

- reducing energy consumption due to the low thermal conductivity of the crucible;

- maintenance of the chemical composition and homogeneity of the source material due to the exclusion of its chemical interaction with the surface of the crucible, which leads to higher quality casting;

- oprosti the calculations of melting modes due to the elimination of the necessity to maintain the temperature of the inner surface of the crucible in the narrow limits to maintain skull layer;

- the possibility of increasing the temperature of the overheating of the molten metal above its melting temperature, i.e. increasing its fluidity when filling in a form that improves the quality of castings;

more complete utilization of the volume of molten metal during casting in the mold due to its high programot at the walls of the crucible due to the low thermal conductivity of the latter, and hence, increased capacity;

- the use of thin-walled crucible, because a reduction in wall thickness is limited only by the mechanical characteristics of the material of the crucible, and this leads to a reduction in its weight, dimensions and reduce the size and weight of the unit itself;

- reducing the time of the technological cycle and increase the efficiency of the plant due to more rational use of energy of the electric arc;

- simplification of the design of the facility and increasing tightness of the vacuum chamber by creating a new method and mechanism output electrode of the crucible;

- ensuring optimal trajectory of the crucible when the rollover, which eliminates splashing of molten metal by pouring in a mold;

- simplified installation method the calculation of the gap between the electrode and the workpiece, which reduces process cycle of melting and casting.

Diasabling method and installation for its implementation, as they described in the independent clauses set forth in the claims, confirmed the possibility of their implementation using the steps described in the application means of achieving the above technical result is not inherent in the prototype.

1. The method of obtaining small-sized castings from chemically highly active metals and alloys, including the installation of a calculation of the gap between the end electrode and the workpiece, the vacuum melting and casting chamber, the melting of the workpiece in the crucible electric arc using a non-consumable electrode, the output electrode of the crucible, the tilting of the crucible to fill the mold, characterized in that the electric arc melting is carried out in a crucible made of a material with low heat conductivity and with the inner surface covered with refractory low reactivity material does not interact with the melt, the installation of the estimated gap between the workpiece and the tip of the electrode is carried out by joint vertical movement of the crucible and the device tipping up to contact of the workpiece with the electrode, subsequent fixation device tilting crucible, installed under the bottom of the crucible movable support at a distance equal to the estimated gap between the electrode and the workpiece, and moving down relative to the crucible device tilting of the crucible to vignau support, the output electrode of the crucible is carried out by moving the crucible down, and when filling the mold crucible tilt sweep, ensuring the displacement of a point on the inner surface of the crucible side drain, the most remote from the axis of the crucible in the plane tipping over on a vertical line.

2. Device for producing small castings made of chemically highly active metals and alloys, containing the node arc melting, melting and pouring vacuum chamber, site filling of molds with the centrifugal table, the melting pot, the device tilting of the crucible, wherein the crucible is made of a material with low heat conductivity to the inner surface covered with refractory low reactivity material does not interact with the melt and the crucible and the device tipping made with the possibility of joint and relative reciprocating movement in a vertical plane, the device tipping is a frame consisting of two parallel, bonded walls, having two vertical groove, and a pair of oppositely located grooves placed with a limited movement of the rollers on the levers, pivotally connected with the side surface of the crucible in the area of its transition to the bottom, and in each the second pair of grooves placed with a limited movement of the rollers, fixed on the side surface in the upper part of the crucible, the axes of which pass through the point of discharge of the inner surface of the crucible, the most remote from its axis in the plane of tilting, and the stroke length of the rollers is determined from the condition of ensuring the movement of the crucible along the trajectory, providing the movement of the point of discharge on the vertical line of the frame in the upper part is resistant elements for emphasis crucible and collaboration with the crucible moving up, moving in the horizontal plane of the support crucible, fixed in the wall of the frame for the installation of the estimated gap between the end electrode and the workpiece, and the element fixing the position of the frame in a vertical plane.