KR20080104295A - Lost-wax casting method associated with pressure-crystallization and apparatus for carrying out the method - Google Patents

Abstract

The present invention relates to a casting method for extruding a melt from a metal receiver into a cavity of a molding mask mold, which method is carried out at a temperature above the liquid phase and at a pressure at which a maximum flow rate state without a spray of liquid metal is achieved. The pressure rises to a value sufficient to refill the mold by the shrinkage size of the casting during crystallization of the melt. The apparatus for carrying out the method according to the invention comprises a receiving container having a ring-shaped flange and which is covered with a metal container in the form of a detachable cup and a molded mask mold, the neck of the receiving container Was provided with a detachable fire resistant sleeve. The flange was arranged to have an inner diameter adapted to the outer diameter of the sleeve, in which case the inner diameter of the flange was set smaller than the inner diameter of the cup.

Description

LOST-WAX METHOD ASSOCIATED WITH PIEZOCRYSTALLISATION AND A DEVICE FOR CARRYING OUT SAID METHOD}

The present invention relates to a lost-wax casting method associated with piezo-crystallisation and an apparatus for carrying out the method.

Casting methods by extruding metal into a mold in the case of pressure-crystallization are known from patent number 2015829, in which the melt enters the extrusion chamber when the steel is overheated by a value of 30 to 60 ° C. above the liquid phase temperature. Poured and held until a hard metal shell is formed in the wall of the extrusion chamber before extrusion. The disadvantage of this method is that the solid liquid phase of the melt may appear when holding the metal in the extrusion chamber. When the liquid phase is exposed to pressure, the pressure works best as is known. As such, the pressure action declines when previously cooled metal is poured into the mold from the extrusion chamber where further crystallization takes place. This phenomenon can occur due to the loss of thin fluids in the manufacture of thin sections of castings of unsuitable quality and in the formation of corrugated casting surfaces or in relation to shrinkage due to lack of liquid phase in the supply and overall Significant loss of casting quality can be seen.

The next claimed method is a lost-wax casting method associated with pressure-crystallization according to patent number 2048954, in which a previously molded mask mold is fixed to an upper table above the metal receiver and the melt is Extruded by a stamp, in which case the extrusion is carried out until the casting solidifies at a temperature at which crystallization of the alloy begins and at a pressure of 0.3 to 0.5 MPa applied to the melt, and the injection rate and injection time of the casting It is set at 2 to 5 kg / s by mass flow rate.

A disadvantage of the known method is the low strength of the ceramic mask mold, which is typically suitable for free casting injection but not for casting under pressure. The strength of the mask mold and the maximum possible operating pressure, together with the number of layers laminated in the manufacture of the multilayer mold, the fabrication materials and binders used, the strict adherence to the operating data during the manufacture, the molding conditions in the casting injection vessel Field, casting dimensions and casting fabrication material, casting injection conditions and other characteristic values. As a result, it is difficult to theoretically calculate the pressure inside the mask mold. As a result, when manufacturing a new product by the above casting method, it is necessary to check the assumed pressure every time by starting from the actual strength of the mold. There is. In addition, when the mask mold is manufactured, fine cracks may be formed in the mold jacket, for example, during the calcification of the mask mold, and such fine cracks do not adversely affect the quality of the casting product during free casting injection. However, applying pressure may cause the mold to break.

A casting device associated with pressure-crystallization is known from patent number 2116865, which comprises a metal container disposed on a lower table and a receiving container installed on the upper table to receive a mask mold, in which case the The metal receiver is formed by a pedestal and a replaceable cup, and a thermal insulation layer is provided between the pedestal and the bottom of the cup, while the receptacle consists of a housing, a cover and a neck. The replaceable cup in this case has an opening on its bottom face for outgassing.

A disadvantage of the known device is that after injecting the metal into the metal receiver, a crystallized alloy layer (hard metal shell) begins to form over the entire height of the sidewall of the metal receiver, which alloy layer in the metal receiver. This impedes the movement of the stamp and the action of the melt being guided into the mold through the neck of the receiving vessel, which can lead to errors such as insufficient filling of the mold. In such a device, such a hard metal shell grows heavily on the stamp proceeding path inside the metal container, and during the casting shrinkage process after the end of crystallization, the operation of extruding the metal from the press residue into the mold for casting is hindered. The hard metal shells are particularly disadvantageous in the crystallization process after filling the mold with the melt. This deteriorates the quality of the casting product and minimizes the advantages of casting under pressure because the pressure no longer acts on the melt, but rather on the hard metal shell in the metal receiver. to be.

A common technical challenge of the inventive groups to which the present invention pertains is the formation of a melt layer in contact with the inner wall (metal jacket) of the mask mold during crystallization, thereby forming a rigid layer which is formed inside the metal receiver and impedes the extrusion of the melt into the mask mold. To reduce the disadvantages of the crystallization process of the metal shell and to improve the quality of the casting product against high pressure loads that may be applied to the melt inside the hardened mask mold. One common technical result when implementing the invention group related to the method is that the process of extruding the melt into the cavity of the molded mask mold is at a temperature and pressure above the liquid phase—at this pressure the Maximum flow is ensured without a nebulizer-in which case the pressure inside the cavity of the mask mold after filling the mask mold with melt reaches an extrusion process during the crystallization time of the melt layer in contact with the wall of the mask mold And then the pressure is gradually raised to a pressure sufficient to refill the mold by the shrinkage value of the casting during the crystallization time of the entire melt inside the mask mold.

One common technical result when implementing a group of inventions related to the device is that a ring-shaped flange is provided on the open edge of the cup of the metal container, with a detachable fire resistant sleeve provided on the outer surface of the neck of the container Is provided by adapting the inner diameter of the flange to the outer diameter of the fire resistant sleeve, in which case the inner diameter of the coated flange is set smaller than the inner diameter of the coated cup. In this case the difference between the inner diameter of the coated cup and the inner diameter of the fire resistant ring in the radial dimension exceeds the total thickness of the melt layer on one side, the melt layer being fire resistant and when injecting a casting from the wall of the coated cup. When fixed at the wall of the sleeve, it crystallizes until crystallization ends.

This feature group associated with the "method" of the present invention is considered new and features progressiveness for a variety of reasons, as follows. The melt extrusion process into the cavity of the molded mask mold is carried out at a temperature above the liquid phase, resulting in excellent thin liquid and mold to create favorable conditions for thermal conduction when forming a metal coating on the inner surface of the mask mold. Contact between the wall and the melt is ensured. Detection of pressure begins with the process of filling the mold with liquid metal without a nebulizer at a defined rate. The maximum flow rate of liquid metal and with it the maximum injection speed can be calculated theoretically (Borissow, GP "Dawlenie w uprawlenii litejnyzmi prozessami" (Druck bei der Steuerung von Giessverlaeufen), Kiew, Verl. Nauk. Dumka, 1988, S 121, Formel IV-18). The theoretical pressure can be actually set in device technology (for example when the liquid drive device is a problem) and can be monitored with reference to the instructions of the pressure meter of the liquid drive device for storing the metal receiver. It is necessary to fill the mold quickly in order to be able to obtain a uniform thickness of the metal coating formed later inside the ceramic mask mold. After filling the mold with melt, the pressure inside the cavity of the mold is maintained at the height reached during extrusion. This prerequisite relates to the minimum requirements necessary to safely protect the ceramic mold against breakage during crystallization of the melt layer in contact with the wall of the mask mold, as long as the metal coating is formed on the inner surface of the ceramic mask mold. . The thickness of the metal coating reacts in proportion to the crystallization time of the casting, and for adjacent layers it can be accepted at a height of 5% to 10% based on the crystallization time of the thinnest section of the casting. The pressure then gradually increases to a value sufficient to refill the mold by the shrinkage size of the casting during the remaining crystallization time of the entire melt in the mask mold. The gradual rise in pressure reduces the risk of breaking the ceramic mold. The pressure is sufficient if the amount of castings fed from the press residue into the metal receiver is assured by the shrinkage size upon crystallization. Shrinkage is a value known in most of the casting alloys discussed. As such, sufficient pressure after storing the metal receiver can be detected relative to the mold during the crystallization process which reacts proportionally to the shrinkage size or by eliminating the deficiency caused by shrinkage in the quality control of the casting. Overall, the metal coating on the inner surface of the mask mold raises the operating pressure while also improving the quality of the casting.

All of the above features related to the "apparatus" of the present invention are new and are provided with a detachable fire resistant sleeve on the outer surface of the neck of the receiving container, wherein the sleeve is in the metal container so that the metal receiver is filled with melt and coated It is characterized by the progressiveness starting from the content of not contacting the wall of the finished cup. In this case, the crystallized melt layer which is formed not only when performing the injection on the cold wall of the coated cup but also when performing the injection on the cold wall of the fire resistant sleeve has a relative relationship between the cup and the sleeve if there is a gap between the cup and the sleeve. Does not interfere with exercise The gap is formed by a coated flange disposed on the upper edge of the detachable coated cup, the inner diameter of the flange being set smaller than the inner diameter of the coated cup. As the outer diameter of the fire resistant sleeve is fitted to the outer diameter of the coated flange after gap adjustment, a closed space appears when the melt is extruded into the mask mold. The size of the gap is selected once in a test manner starting from the implantation process that takes the longest at fixation and until the end of crystallization. In the radial dimension, the gaps exceeding the total thickness of the melt layer which crystallizes until crystallization is terminated at the side of the melt layer on one side, i.e. at the time of injection and at the time of crystallization at the wall of the coated cup and at the wall of the fire resistant sleeve do. The melt layer crystallized below the bottom plane of the coated flange does not exert any noticeable resistance to movement, since the melt layer has no carriers. The fire resistant sleeve was formed detachably, since after the injection was finished the sleeve was gripped on the side by the solidified press residue and from the neck of the receiving container together with the metal receiver when the lower table was lowered. This is because it is released and held inside the metal receiver. Thus, the aforementioned feature group associated with the device does not interfere with the operation of the metal receiver in the neck of the receiving vessel in the case of rapid operation in various manners and in a stationary state, as a result of the inner wall of the ceramic metal mold Technical challenges for strengthening the mask mold are overcome by forming an additional metal coating on the inner surface of the ceramic metal mold upon crystallization of the melt layer as long as it contacts.

1 is a schematic diagram of a lost-wax casting apparatus associated with pressure-crystallization for carrying out the method proposed by the present invention.

The lost-wax casting device associated with the pressure-crystallization comprises a stator 1 having a fixed upper table 2 and a movable lower table 3 which can be driven by the liquid drive device 4. By the upper table 2 the receiving container 5 is fixedly connected to the mask mold 6 molded with the filling. A detachable fire resistant sleeve 8 is arranged on the neck 7 of the receiving container 5, which sleeve is fixed to the lower end of the neck 7 by a closure 9. The closure 9 is also responsible for the filling in the receiving container 5 and the injection channel with the opening 10 in the mask mold 6. On the lower table 3 there is a metal receiver 11 having a pedestal 12, and inside the groove 13 of the pedestal there is an airtight inner sheath in a detachable cup 14 while maintaining a guaranteed clearance. 15) is provided. The closure 9 and the sheath 15 consist of a core molding compound, for example a mixture of water and glass. At the top of the jacket of the detachable cup 14 is provided a gas vent opening 16. On the upper edge of the detachable cup 14 is arranged a flange 18 covering the cavity side. The intermediate bore of the fire resistant sleeve 8 and the sheathed flange 18 forms a gap-adjusted fitting unit on its outer and inner surfaces, respectively. The flange and sleeve are provided with an inlet chamfer for mutual centering of the coated flange 18 and the fire resistant sleeve 8. The size E shown in the figures is a melt layer on one side that crystallizes at the time of injection and at the time of fixation at the wall of the coated cup 14 and at the wall of the fire resistant sleeve 8 until crystallization is finished. Exceeds the total thickness. The lower table 3 is based on a rod of the liquid drive device 4 fixedly coupled with the stator 1.

In addition, the device is equipped with prescribed means for automatically adjusting and controlling the operating data of the liquid drive device 4 such as the path, time, traveling speed, pressure of the rod (not shown in the figure).

Specific embodiments of the proposed method and manner of operation of the apparatus are described in detail below with reference to the accompanying drawings.

The ceramic mask mold 6 is calcified according to a conventional technique and then inserted into the receiving container 5 in which the filling is accommodated, in which case the edge of the injection opening 10 is the neck of the receiving container 5. It is arrange | positioned at the height of (7). The neck portion 7 has a fire resistant sleeve 8 raised, while the front of the neck portion 7 opens the closure 9 by a mixture of water and glass while allowing entry into the injection opening 10. Molded while forming. The receiving container 5 is fixed to the upper table 12 of the stator 1, whereby the neck portion 7 runs on the same axis with respect to the metal receiver 11.

The inner cavity of the detachable cup 14 is covered with a mixture of water and glass before the cup is placed on the pedestal 12 of the metal receiver 11. On the upper face of the cup 14 a flange 18 covered with a mixture of water and glass is fixed. The cup 14 placed on the pedestal 12 is centered relative to the neck 7.

By means of the liquid drive, an injection rate of 0.15 to 0.2 m / s and a pressure of 0.2 to 0.3 MPa are set, starting from a theoretical melt flow rate of 7 to 8 kg / s in advance.

Austenitic steel, resistant to corrosion, was poured. The liquid drive device 4 switches without delay so that the liquid metal is poured from the metal receiver 11 into the mold 6 so that the melt is near the sheath of the flange 18 at 25 ° C. ± 1 ° C. above the liquidus temperature. Pour into the metal receiver up to the plane. After the mold 6 is filled, the rod of the liquid drive device 4 stops at the upper position. From this moment, the melt is obtained in 6 to 8 seconds at a set pressure of 0.2 to 0.3 MPa. The pressure is then raised uniformly to a value of 5-6 MPa by the liquid drive within the remaining time of full crystallization, 1.3 to 1.5 minutes (obtained in computer-assisted simulation of the injection process). Within this time, the rod moves by a small value proportional to the shrinkage size of the metal from 2 to 2.5%, in which case the movement encounters an error due to shrinkage when the casting is supplied at a relatively high pressure. The quality of the castings is eventually assured by providing the mechanical properties.

The device has the following mode of operation.

By the upper table 2 of the stator 1 before injection the receiving container 5 is fixedly connected to the mask mold 6 molded therein and to the fire resistant sleeve 8 mounted on the neck 7. In this case, the filling of the accommodating container 5 and the fire resistant sleeve 8 are fixed by the closure 9. In the groove 13 of the pedestal 12 of the metal receiver 11 on the lower table 3 a previously coated cup 14 is inserted. A coated flange 18 is provided on the upper front face of the cup 14. After switching of the liquid drive device 4, the metal receiver 11 moves up to the neck 7 with the fire resistant sleeve 8, which sleeve 14 is made in the horizontal plane with respect to the coated flange 18. By means of the displacement action of, it is centered in the groove 13 of the pedestal 12 thanks to the guaranteed clearance. The metal receiver 11 then descends to return to the starting position. The device is then ready for insertion.

The liquid metal is poured into the metal receiver 1 almost to the bottom plane of the flange coating. The liquid drive device 4 is switched on. The cup 14 of the metal receiver 11 is lifted up, and the coated flange is inserted into the fire resistant sleeve 8 of the neck portion 7, which sleeves the liquid metal through the injection opening 10. 6) Extrude into. In this case, the gas (air) is pushed out of the mask mold 6 through the coating of the mold and from the cup 14 through the hermetic coating of the cup. After injecting the liquid metal into the mask mold 6, the rod of the liquid drive device 4 stays in the upper position for a few seconds. One layer is then formed on the wall of the cover 15 of the cup 14, on the cover of the flange 18 and on the neck portion 7 with the fire resistant sleeve 8 while the liquid metal is contained in the metal receiver 11. Crystallized in After fixing, the pressure inside the liquid drive device 4 rises to an operating value until the crystallization of the liquid metal is finished within the total volume of the casting. Thanks to the difference E between the inner diameter of the coated cup 14 and the inner diameter of the flange 18, the rod of the liquid drive device 4 is not gripped by the solidified metal layer at the time of fixing, consequently the above The rod can move, and thus the casting is fed together with the liquid metal from the metal receiver 11 until the crystallization is finished.

After the crystallization is finished, the liquid drive device 4 is switched to the return operation. Thanks to the binding of the crystallized metal, the metal receiver 11 moves with the fire resistant sleeve 8 so that the metal receiver 11 is lowered and returned to its starting position. At the lower front of the neck 7 the weak coating of the closure 9 facilitates the process of slightly separating the press residue. The receiving container 5 in which the finished casting is received is removed from the upper table 2 of the stator 1 so that the casting can be taken out. The cup 14 of the metal receiver 11 is dismantled for replacement of the sheath. The device is secured with a further set consisting of a receiving vessel, a fire resistant sleeve 8 mounted on the neck of the receiving vessel, and a cup 14 of metal receiver 15. The cycle is repeated.

The invention can be applied in castings, in particular in the lost-wax casting process associated with pressure-crystallization, for producing metal products.

Claims (3)

In a lost-wax casting method associated with pressure-crystallization, wherein the melt is extruded from a metal receiver coated with a refractory fabrication material into a cavity of a molding mask mold disposed above the metal receiver and then fixed under pressure until the crystallization is completed. In The extrusion of the melt into the cavity of the molded mask mold is carried out at a temperature above the liquid phase and at a pressure at which the mask mold is filled at the maximum flow rate without the atomizer of the liquid metal, and after the process of filling the mask mold with the melt The internal pressure is maintained within the crystallization time of the melt layer in contact with the wall of the mask mold at the same value as the pressure during extrusion, and then the mold is then reduced by the shrinkage size of the casting for the remaining crystallization time of the entire melt in the mask mold. Increasing to a value sufficient to refill Lost-wax casting method associated with pressure-crystallization. A metal receiver formed as a pedestal having a detachable cup coated therein with an insulating layer disposed therebetween, the insulating layer being fixed on an upper table above the metal receiver, and arranged on an axis of the metal receiver; In an apparatus for carrying out the lost-wax casting method associated with pressure-crystallization according to claim 1, comprising a receiving container formed as a housing having a neck portion and a cover which are coaxial with respect to The outer surface of the neck of the receiving container is provided with a detachable fire resistant sleeve, while at the open edge of the cup of the metal container a coated ring-shaped flange is arranged, the inner diameter of the flange being outside of the fire resistant sleeve. Adapted to a diameter, wherein an inner diameter of the coated flange is set smaller than an inner diameter of the coated cup Devices for carrying out the lost-wax casting method The method of claim 2, The difference between the inner diameter of the coated cup radially and the inner diameter of the fire resistant ring exceeds the total thickness of the melt layer on one side, the melt layer at the wall of the coated cup and at the time of injection and fixation. Characterized in that it crystallizes until the crystallization ends in the wall of the fire resistant sleeve Apparatus for implementing the lost-wax casting method.

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