Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/02—Sand moulds or like moulds for shaped castings
  • B22C9/04—Use of lost patterns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D18/00—Pressure casting; Vacuum casting
  • B22D18/02—Pressure casting making use of mechanical pressure devices, e.g. cast-forging
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D18/00—Pressure casting; Vacuum casting
  • B22D18/04—Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould

Definitions

• the invention relates to a method for investment casting with crystallization under pressure and a device for its implementation.
• patent N ° 2015829 A known method of casting by squeezing metal into a mold with crystallization under pressure, patent N ° 2015829, which consists in the fact that the molten metal is poured into the squeezing chamber with overheating for steel mainly at 30-60 ° C above the liquidus temperature, and before squeezing, they are held until freezing to the walls of the squeeze metal crust chamber.
• the disadvantage of this method is that the exposure of the metal in the squeezing chamber can bring the melt to a solid-liquid phase.
• pressure is most effective when transmitted to the liquid phase. Therefore, in the process of pouring from the squeezing chamber into the mold, during which further crystallization takes place, of the already cooled metal, the pressure efficiency decreases. This may result in insufficient shedding of thin spots of the casting, wavy surface of the casting due to loss of fluidity or lead to shrinkage defects due to the lack of a liquid phase for feeding, and in general, lead to a significant loss in the quality of the casting.
• the disadvantage of this method is the low strength of ceramic shell molds, intended, with their generally accepted manufacturing technology, for free pouring, and not under pressure.
• the strength of the shell molds and, accordingly, the maximum possible working pressure depends on the number of layers applied in the manufacture of multilayer molds, on the basic materials and binders used, the accuracy of observing the technological modes of their manufacture, the conditions for their molding in the container for pouring, the dimensions and material of the casting, and the pouring regimes and other parameters. Therefore, it is difficult to theoretically calculate the pressure in the shell mold, and for the manufacture of new products by this casting method, each time an experimental verification of the accepted pressure is required based on the actual mold strength.
• microcracks can occur on the mold shell, which do not affect the casting quality during free pouring, but when pressure is applied, they can lead to rupture of the mold.
• a device for casting with crystallization under pressure containing a metal detector, installations on the lower table, a container with a shell shape, mounted on the upper table, the metal receiver is made in the form of a base and a removable glass, between the bottoms of which a heat-insulating layer is placed, and the container is made of a body, a lid and a neck.
• gas outlet openings are made at the base of the replaceable cup.
• a disadvantage of the known device is that after the metal is poured into the metal receptacle, a crystallized alloy layer (metal crust) begins to form at the entire height of its side walls, preventing the punch from moving in the metal receiver and the melt to flow through the neck of the container into the mold, which in turn can lead to a defect incomplete form.
• the influence of this crust after filling the mold with the melt during its crystallization is especially negative, when the thickness of the crust in the metal detector on the path of movement of the punch intensively increases and prevents the extrusion of metal from the press residue into the mold for feeding the casting during its shrinkage when crystallization is completed. This reduces the quality of casting and minimizes the advantages of injection molding, since pressure is no longer applied to the melt, but to the metal crust in the metal receiver.
• the single technical task of the group of inventions is to improve the quality of casting due to the possibility of applying more pressure to the melt in the hardened shell form obtained by forming a crystallization layer of the melt adjacent to its inner walls (metal shell) while reducing the negative effect of the crystallization process of the crust formed in the metal receiver , preventing the extrusion of the melt into the shell form.
• a single technical result when implementing the group of inventions according to the object-method is achieved due to the fact that extrusion of the melt into the cavity of the molded shell mold is carried out at a temperature above the liquidus and pressure, which ensures, when filling the shell mold, the maximum flow rate of liquid metal without spraying, after filling the shell mold with the melt in its cavity, they are maintained at the level obtained during extrusion during the crystallization time of the melt layer adjacent to the wall shell mold, and after that the whole of the crystallization of the melt in the shell mold smoothly increased to a pressure sufficient to form refilling by the volume shrinkage of the casting.
• a single technical result in the implementation of the group of inventions for the object device is achieved due to the fact that the outer surface of the neck of the container is equipped with a removable refractory sleeve, and a lined, ring-shaped flange is installed on the open edge of the metal receptacle with the possibility of mating in its inner diameter with the outer diameter of the refractory sleeve , and the inner diameter the lined flange is smaller than the inner diameter of the lined cup.
• the difference between the inner diameters of the lined glass and the refractory ring in the radial dimension is greater than the total thickness of the one-sided melt layer, which crystallized during pouring on the holding wall to the end of crystallization of the lined glass and the wall of the refractory sleeve.
• the specified set of features for the object-method is new and has an inventive step based on the following.
• Extrusion of the melt into the cavity of the molded shell mold is carried out at a temperature above liquidus, which ensures good fluidity and contact of the melt with the walls of the mold to create favorable heat transfer conditions when forming a metal shell on the inner surface of the shell mold.
• Pressure is determined from the condition that there is no spray of liquid metal in the form when it is filled at a certain speed. In this case, the maximum flow rate, and through it the pouring rate, of liquid metal can be calculated theoretically [G. Borisov Pressure in the management of foundry processes. - Kiev: Nauk. Dumka, 1988., p. 121, formula IV-18].
• this design pressure can be set by hardware and controlled by the pressure gauge on the hydraulic actuator for moving the metal receiver. Rapid filling of the mold is necessary to obtain a uniform thickness of the subsequent formation of a metal shell on the inner surface of the ceramic shell mold. After filling the mold with the melt, the pressure in its cavity is maintained at the level reached during the extrusion process. This condition provides the minimum requirements for ensuring the safety of the ceramic mold from destruction during the crystallization of the melt layer adjacent to the walls of the shell mold when a metal shell forms on the inner surface of the ceramic shell mold.
• the thickness of this metal shell is proportional to the crystallization time of the casting and for the adjacent layer 5-10% of the crystallization time of the thinnest casting sites can be taken.
• the pressure is gradually increased to sufficient to refill the mold by the amount of shrinkage of the casting.
• a smooth increase in pressure reduces the risk of destroying the ceramic mold.
• Sufficient is the pressure at which the casting from the press residue in the metal receiver is supplied with the amount of shrinkage during crystallization.
• the shrinkage value for most cast alloys used is a known characteristic. Therefore, the sufficiency of pressure can be determined by the movement of the metal relative to the mold during the crystallization process, which is proportional to the amount of shrinkage, or by the absence of shrinkage defects during the quality control of the casting.
• the metal shell on the inner surface of the shell mold allows to increase the working pressure, while ensuring higher quality castings.
• the specified set of features for the object device is new and has an inventive level based on the fact that the outer surface of the neck of the container is equipped with a removable refractory sleeve that allows it to be in the metal receiver without touching the walls of the molten lined glass.
• the crystallized melt layer formed during the pouring on cold walls of both the lined glass and the refractory sleeve will not impede their relative movement if there is a gap between them.
• This gap is formed by a lined flange mounted on the upper edge of the removable lined glass and having an inner diameter smaller than the inner diameter of the lined glass.
• the outer diameter of the refractory sleeve mates along a movable fit with the inner diameter of the lined flange, which provides a closed space when extruding the melt into a shell mold.
• the value of this gap is selected experimentally once according to the longest process of pouring exposure to the end of crystallization. In the radial dimension, he more than the total thickness of the one-sided melt layer, which crystallized during the pouring of the exposure to the end of crystallization on the wall of the lined glass and the wall of the refractory sleeve, is taken. The crystallized melt layer under the lower plane of the lined flange does not provide significant resistance to movement, since it has no support underneath.
• the refractory sleeve is removable, since at the end of the casting process it seizes on the side surface with a hardened press residue and when lowering the lower table with a metal receiver, it is removed from the neck of the container and remains in the metal receiver.
• the given set of features of the device allows for unhindered movement of the metal receiver in the neck of the container at various speed modes and with possible stops, ensuring the technical task of hardening the shell mold by obtaining an additional metal shell on the inner surface of the ceramic shell mold during crystallization of the melt layer adjacent to its inner walls.
• Figure 1 shows a device for investment casting with crystallization under pressure by which the proposed casting method is carried out.
• a casting investment casting device with crystallization under pressure consists of a bed 1 with a fixed upper table 2 and a lower table 3, movable from the hydraulic actuator 4.
• a container 5 with a shell mold 6 molded into the filler is rigidly attached to the upper table.
• On the neck 7 of the container 5 is installed removable refractory sleeve 8, which is held on the lower plane of the neck 7 by the shutter 9.
• the shutter 9 also holds the filler in the container 5 and the filling channel with the hole 10 of the shell form 6.
• Metal is installed on the lower table 3 a receiver 11 containing a base 12, in the grooves 13 of which with a guaranteed clearance there is a removable cup 14 with an internal gas-permeable lining 15.
• the shutter 9 and the lining 15 can be made of a rod, for example, liquid glass mixture.
• openings 16 are made for the exit of gas.
• a flange 18 is lined on the side of its cavity.
• the value of "E” shown in the figure is greater than the total thickness of the one-sided melt layer, crystallized during pouring and holding to the end of crystallization on the wall of the lined cup 14 and the wall of the refractory sleeve 8.
• the lower table 3 is mounted on the stem of the hydraulic actuator 4, which is rigidly fixed to the bed one.
• the device is also equipped with standard means of automatic control and management of hydraulic actuator 4 operation parameters: path, time, rod speed, pressure (not shown).
• the ceramic shell mold 6 is made, calcined according to serial technology, then placed in a container 5 with a filler so that the edge of the filling hole 10 is at the level of the end of the neck 7 of the container 5.
• a refractory sleeve 8 is put on the neck 7, and the end of the neck 7 is molded, leaving the entrance the filling hole 10, forming a shutter with a liquid-glass mixture 9.
• the container 5 is fixed on the upper table 2 of the bed 1, so that the neck 7 is aligned with the metal receiver 1 1.
• the internal cavity of the removable glass 14 before setting on the base 12 of the metal detector 11 is lined with a liquid-glass mixture.
• a flange 18 is lined with a liquid-glass mixture.
• the glass 14 mounted on the base 12 is centered relative to the neck 7.
• the hydraulic drive equipment for the estimated melt flow rate of 7-8 kg / s set the pouring speed of 0.15 -0.2 m / s and a pressure in the range of 0.2-0, ZMPa.
• Casting was carried out for corrosion-resistant austenitic steel.
• the melt is poured into the metal receiver 11 at 25 ⁇ 1C ° above the liquidus temperature to a level close to the lining of the flange 18 and immediately turn on the hydraulic actuator 4 and pour liquid metal from the metal receiver 1 1 into the mold 6.
• the hydraulic actuator rod 4 stops in the upper position . From this moment, the melt is maintained at a set pressure of 0.2-0, ZMPa for 6-8c. Then, for the remaining time of complete crystallization of 1.3-1.5 minutes (obtained by computer simulation of the pouring process) the pressure is uniformly raised to 5-6MPa, developed by a hydraulic actuator.
• the device operates as follows. Before starting pouring, the container 5 with the shell mold 6 molded into it and the removable refractory sleeve 8 mounted on its neck 7 is rigidly fastened to the upper table 2 of the bed 1. The filler of the container 5 and the refractory sleeve 8 are held by a shutter 9. On the lower table 3, in the grooves 13 of the base 12 of the metal receiver 11, a pre-lined removable cup 14 is installed.
• a lined flange 18 is installed on the upper end of the glass 14.
• the metal receiver 11 rises to the neck 7, with a refractory sleeve 8, that is centered relative to the lined flange 18 by moving the glass 14 in the horizontal plane due to the guaranteed clearance in the grooves 13 of the base 12. Then the metal detector 11 is lowered to its original position. The device is ready to go.
• Liquid metal is poured into the metal receiver 1 1 to approximately the level the lower plane of the lining of the flange 18.
• the hydraulic actuator 4 is turned on.
• the metal receiver 11 with the glass 14 rises and enters the refractory sleeve 8 of the neck 7 with its lined flange 18, which squeezes the liquid metal into the shell mold 6 through the filling hole 10. and gas (air) is displaced from the glass 14 through its gas permeable lining 15.
• the hydraulic actuator rod 4 stops in the upper position and is held for several seconds.
• the hydraulic actuator 4 is turned on for a return stroke.
• the metal detector 11 is lowered to its original position, capturing with it the refractory sleeve 8 due to the formation of crystallized metal on it. From the lower end of the neck 7, a slight separation of the press residue is facilitated by the weakness of the lining of the shutter 9.
• the container 5 with the finished casting is removed from the upper table 2 of the bed 1 for excavation of the casting.
• the glass 14 metal detector 11 is removed to replace the lining.
• the next set of containers 5 is attached to the device, on the neck of which a refractory sleeve 8 is installed, and the metal receiver 11 of the glass 14. The cycle is repeated.
• the invention will find application in foundry, namely in investment casting with crystallization under pressure, mainly of metal products.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
• Casting Devices For Molds (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
• Continuous Casting (AREA)
• Measuring Fluid Pressure (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (2)

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Citations (4)

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• 2006
  • 2006-02-09 RU RU2006103902/02A patent/RU2312738C1/ru not_active IP Right Cessation
  • 2006-08-29 WO PCT/RU2006/000452 patent/WO2007091915A1/ru active Application Filing
  • 2006-08-29 KR KR1020087022045A patent/KR101302637B1/ko not_active IP Right Cessation
  • 2006-08-29 DE DE112006003535T patent/DE112006003535B4/de not_active Expired - Fee Related
  • 2006-08-29 JP JP2008554174A patent/JP2009525878A/ja active Pending
  • 2006-08-29 UA UAA200810186A patent/UA87085C2/ru unknown
  • 2006-08-29 CN CN2006800525520A patent/CN101365552B/zh not_active Expired - Fee Related
  • 2006-08-29 US US12/278,780 patent/US20090218067A1/en not_active Abandoned
• 2008
  • 2008-08-28 GB GB0815680A patent/GB2448847A/en not_active Withdrawn

Patent Citations (4)

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