CN102728815A - Vacuum self-gravity pouring high-static pressure strong-pouring die-casting forming equipment and technique thereof - Google Patents

Abstract

The invention relates to a vacuum self-weight pouring high static pressure strong pouring die-casting forming equipment, comprising an aluminum melting furnace, the aluminum melting furnace is connected with a holding furnace and an opening and closing valve is arranged on the connecting pipe, and the holding furnace passes through a feeding pipe It is connected with the lower end side of the barrel, the oil cylinder is set above the barrel and drives the barrel piston to run up and down in the barrel, the feed port of the barrel is located in the running stroke of the barrel piston, and the barrel Located above the mold tooling assembly, the mold tooling assembly is provided with an aluminum liquid pouring channel connected to the discharge port of the barrel, the aluminum liquid pouring channel is connected to the mold cavity, and the mold type The inner chamber of the cavity and the pouring head are connected with a vacuum pipeline through a slit-type vacuuming channel, and the vacuum pipeline is connected to a vacuum buffer tank, and the vacuum buffer tank is connected to a vacuum pump. The present invention also relates to a corresponding casting forming process. The invention ensures that the formed workpiece not only has excellent mechanical properties of vacuum casting, but also has good surface properties of high-pressure die casting.

Description

A vacuum self-weight pouring high static pressure strong pouring die-casting forming equipment and its process

technical field

The invention relates to a vacuum self-weight pouring high static pressure strong pouring die-casting forming equipment and a process thereof.

Background technique

In my country, the existing aluminum and aluminum workpieces are formed by casting and die-casting processes, and there are pores in the workpieces of the two forming processes to varying degrees. During die-casting, because the material enters the mold cavity quickly in the form of spray, the gas and alumina are not discharged in time, forming pores and internal structure changes of the workpiece, resulting in defects in the mechanical properties of the die-casting parts. When pouring, the material does not form a spray shape but also has air holes. The mechanical properties of the poured workpiece are good, but it is not easy to form a good working surface, especially some workpieces with special shapes are not easy to form.

At present, the problem of pores inside the workpiece is being discussed at home and abroad, and there are also studies and discussions at home and abroad on vacuum die casting. Huazhong University of Science and Technology has a student's graduation thesis discussion but has not entered into practical use. It uses vacuum to suck the material into the barrel and then injects it. However, the vacuum suction must consume the self-weight of the balanced material. Once the material is in balance, it will no longer be able to absorb the material, and how to convey and stop the conveying of the material. These technical problems all have difficulties in the implementation process. A single die casting cannot effectively improve the mechanical properties of die castings, but only reduces the formation of internal pores.

In Japan, Germany, and Huazhong University of Science and Technology in Wuhan, my country, there are reports on vacuum die-casting machines. They all use high-temperature materials for injection die-casting, and it is difficult to achieve better mechanical properties of the workpiece. There are three main methods.

One is the German Vacural method. The aluminum melting furnace is directly connected to the injection chamber through the liquid riser, and only the melt is sucked into the injection chamber by vacuuming, and then the cavity is continuously vacuumed to a predetermined value before injection molding. . But this process must close the feed port, otherwise the drop potential energy between the barrel and the furnace liquid level will reduce the vacuum in the cavity.

The second is the German MFT method, which is divided into 4 steps: ① Quantitative pouring of materials into the barrel, ② Slow injection of the material by the piston of the injection chamber so that the air in the injection chamber is naturally discharged to the top of the cavity, and then quickly evacuated, ③When the injection chamber piston advances until the feeding material occupies 1/3~1/2 of the injection chamber space, immediately close the vacuum to achieve rapid injection, ④After the injection is completed, the pressure is maintained and the mold is left for cooling; this method For the material feeding of the barrel, the feeding method of the quantitative mechanism is adopted, or the feeding method of the artificial quantitative device is used; step ② is to use the energy absorption principle of the vacuum energy-absorbing tank, and when the vacuum valve is opened, the vacuum can be quickly operated. At the same time, when the mold is designed A large gate is used to make the melt enter the cavity quickly. At this time, the energy comes from two aspects: one is vacuum suction, and the other is the propulsion force of the barrel piston.

The third is the Swiss Fondaly vacuum die-casting machine. Its working principle is basically the same as that of the German MFT method. It uses the material cylinder to be placed under the mold cavity, and the vacuum is set above the mold. First, the material is quantitatively fed to the injection chamber of the material cylinder. Then slow injection to vacuumize, turn off the vacuum valve and switch to fast injection. In the prior art, whether it is ordinary die casting or the several vacuum die casting methods listed in the above comparative information, the surface quality of the workpiece is achieved by the rapid injection impact force and pressure of the die casting machine in the later stage of feeding the mold cavity. Although this method has a good surface quality of the workpiece, due to the rapid injection, the material is fed in a spray shape, which affects the forming crystallization and mechanical properties of the final workpiece.

Contents of the invention

In view of the deficiencies of the prior art, the purpose of the present invention is to provide a vacuum self-weight casting high static pressure strong casting die-casting forming equipment and its process which have both the excellent mechanical properties of vacuum casting and the good surface properties of high-pressure die-casting.

In order to achieve the above object, the first technical solution of the present invention is: a vacuum self-weight pouring high static pressure strong casting die-casting forming equipment, including an aluminum melting furnace, a holding furnace, a barrel, a barrel piston, an oil cylinder, a mold tooling assembly, a vacuum A buffer tank and a vacuum pump, the aluminum melting furnace is connected to the holding furnace and the opening and closing valve is arranged on the connecting pipe, the holding furnace is connected to the lower end side of the barrel through the feeding pipe, and the oil cylinder is set on the barrel above and drives the barrel piston to run up and down in the barrel, the barrel inlet is located in the stroke of the barrel piston, the barrel is located above the mold tooling assembly, and the mold tooling assembly is provided with The molten aluminum pouring channel connected with the discharge port of the barrel, the molten aluminum pouring channel is connected with the mold cavity, the inner chamber of the mold cavity and the pouring head are connected to the vacuum pipeline through the slit-type vacuuming channel The vacuum pipeline is connected to a vacuum buffer tank, and the vacuum buffer tank is connected to a vacuum pump.

Further, the upper liquid level in the holding furnace is higher than the molten liquid contact surface of the mold cavity.

Further, the holding furnace is connected with an air compressor and the connecting pipeline is provided with an inlet valve, and the holding furnace is provided with a pressure gauge, a vent valve and a safety valve.

Further, a section of the delivery pipe close to the feed inlet of the barrel is provided with a delivery pipe heater.

Further, the cross-sectional area of the oil cylinder is larger than that of the barrel.

Further, a seal is installed at the contact position between the upper end of the barrel and the piston rod of the barrel.

Further, the cylinder piston rod is provided with a cooling water inlet and outlet pipe for passing cooling water into the rod.

Further, the slit-type vacuuming channel is a flat channel, and the height of the flat opening is 0.15-0.25 mm.

Further, a material preheating zone is provided above the aluminum melting furnace.

Further, the mold tooling assembly is provided with a downward working point of the mold and two separate preheating zones for mold workpieces.

In order to achieve the above object, the second technical solution of the present invention is: a vacuum self-weight pouring high static pressure die-casting forming process, including the above-mentioned vacuum self-weight pouring high static pressure strong pouring die-casting forming equipment, carried out according to the following steps: ( 1) Put the preheated aluminum ingot into the aluminum melting furnace for overheating and melting, and set the melting superheating temperature to 680-800°C; (2) The molten aluminum enters the holding furnace through the opening and closing valve for heat preservation. The heat preservation temperature is controlled between 670~780°C; (3) Connect and fix the mold tooling assembly with the barrel. Initially, the barrel piston is located at the lower end of the barrel and blocks the feed port of the barrel. Open the vacuum valve, Start the vacuum pump so that the air in the mold cavity and the air under the barrel are evacuated through the vacuum pipe, so that the mold cavity and the barrel are in a vacuum state; (4) While evacuating, the cylinder push rod moves upward to drive the barrel piston upward OK, when the upward stroke exceeds the top of the barrel feed port, the upward movement is stopped. At this time, the holding furnace is connected to the barrel through the feeding pipe, and the aluminum liquid is quickly poured from the holding furnace into the barrel under the action of vacuum and the self-weight of the aluminum liquid. and the mold cavity; (5) When the aluminum liquid is filled to the lower side of the barrel piston, the cylinder push rod moves downward to drive the barrel piston to move downward so that the excess aluminum liquid automatically returns to the holding furnace through the barrel feeding port, When the barrel piston moves downwards and exceeds the bottom of the barrel feed port, it will automatically close the barrel feed port and naturally form quantitative feeding. At this time, the barrel piston pressurizes the workpiece and then the barrel piston continues to run downward to achieve Apply high static pressure to the workpiece to achieve pressure holding, and cool the workpiece while holding the pressure; (6) After a certain period of time after holding the pressure and cooling, the general holding time is controlled at 1 to 15 seconds, and the mold retention cooling time is controlled at 5 seconds. ~30 seconds, the cylinder push rod moves downward, and the mold tooling assembly moves downward at the same time, and the material head in the barrel leaves the barrel with the mold and enters the downward working point of the mold; (7) Under mechanical action, the mold and the workpiece move to a Mold workpiece separation preheating zone, for workpiece demoulding treatment; (8) When the mold enters the above-mentioned mold workpiece separation preheating zone, the heated mold located in another mold workpiece separation preheating zone enters the downward working point of the mold and rises at the same time Combined with the barrel, the piston of the barrel returns to the next wheel.

Further, in step (4), a feed tube heater is provided on a section of the feeding pipe connecting the aluminum melting furnace and the barrel near the feeding port of the barrel, so that the feeding port of the barrel is in contact with the barrel piston The melt in the plane layer of the surface keeps flowing.

Further, in step (4), for more complex workpieces and workpieces with special requirements, it is necessary to increase the pressure of the material on the cavity surface at the moment when the material is in contact with the mold cavity during the self-weight vacuum pouring process, and first rush into the closed holding furnace The pressure gas is pressurized, and the aluminum liquid is finally poured from the holding furnace into the barrel and the mold cavity quickly under the action of vacuum, the weight of the aluminum liquid and the pressure.

Further, in steps (7) and (8), mold preheating devices are installed in the separate preheating zones of the two mold workpieces.

The present invention integrates vacuum self-weight casting and high pressure holding forming, which has the following advantages.

1. The use of a vacuum cavity enables the workpiece to effectively solve the problem of cavity gas entering the workpiece during the forming process.

2. Vacuum self-weight casting makes the flow rate of the pouring melt into the cavity faster, which can improve the mechanical properties of the castings to a certain extent. The experiment proves that the mechanical properties of the castings are better when the pouring melt reaches 20m/s. At the same time, the workpiece is formed by low-pressure casting and high-pressure die-casting, and the comprehensive mechanical strength of the workpiece formed by low-pressure casting is better than that of high-pressure die-casting. Therefore, for many special requirements, the workpiece is not formed by high-pressure die-casting, but by low-pressure casting. For example, the hub of a car is formed by low-pressure casting. Vacuum self-weight casting is adopted, due to the increase of flow rate, not only the mechanical properties of the cast workpiece are improved, but also the internal pores of the formed part are effectively reduced, and the quality of the cast workpiece is greatly improved. According to the experiment, the same structure, the same material and the same shape workpieces are compared with self-weight vacuum casting and ordinary die casting, the tensile strength can be increased by 20.3%, the elongation can be increased by 83.1%, the toughness and bending resistance are significantly improved, and the bending resistance The performance is more than doubled, and there is no difference in surface appearance and performance by naked eyes.

3. The vacuum self-weight casting forming die-casting process is adopted first vacuum self-weight pouring and then high-pressure holding pressure, which ensures that the formed workpiece has both excellent mechanical properties of vacuum casting and good surface properties of high-pressure die-casting, especially suitable for low melting point metal materials and Aluminum alloy, lead alloy, magnesium alloy and other low melting point alloys.

4. Vacuum self-weight pouring forming die-casting process is adopted firstly for vacuum self-weight casting and then for high-pressure holding, which is easy to realize high-pressure pressurization and holding. Because the feeding of the present invention is completely realized by vacuum, self-weight, potential energy and melt pressure, the subsequent pressurization and pressure holding are mainly to improve the surface quality of the workpiece, to fill special parts of the special surface and to supplement the shrinkage of the workpiece during the cooling process. Increase the static pressure on the melt. However, this method is different from the existing die-casting machines. In the prior art, if the workpiece has a special shape and the quality of the material is large, a large-tonnage hydraulic system must be used, because there must be sufficient cylinder area, volume and pressure to ensure the rapid prototyping and Pressurize. However, according to the formula S1×F1=S2×F2, the present invention adopts the method that the oil cylinder pressure is small, the oil cylinder area is large and the barrel area is small to realize the large pressure pressurization of the barrel work, because the pressure transmission of the liquid is different from that in the unit square area The transmission pressure is the same, so as to achieve the purpose of pressurization and pressure maintenance of small drive and large pressure. The key is that there is no need for a large injection volume in the later pressurization and pressure holding process, only the pressure per unit area is required, and the cylinder piston travels very short from the pressurization action to the pressure holding action process, which only needs to meet the cold shrinkage of the workpiece and the surface. The amount of material filling required for aesthetics and the filling material required for the tightness of the internal structure of the workpiece are sufficient.

Description of drawings

Fig. 1 is a schematic diagram of the structure of an embodiment of the present invention.

Figure 2 is a schematic diagram of the structure of the holding furnace.

Figure 3 is a schematic diagram of vacuuming the mold and barrel.

Figure 4 is a schematic diagram of the mold and barrel feeding.

Figure 5 is a schematic diagram of the return flow of excess material liquid in the mold and barrel.

Fig. 6 is a schematic diagram of pressurizing the mold and the material liquid of the barrel by the piston of the barrel.

Fig. 7 is a schematic diagram of maintaining pressure of the cylinder piston on the mold and the cylinder feed liquid.

In the figure: 1-melting aluminum furnace, 2-opening and closing valve, 3-heating furnace, 4-feeding pipe heater, 5-barrel, 6-barrel piston, 7-oil cylinder, 8-mold tooling assembly, 9-vacuum pipe, 10-vacuum valve, 11-vacuum buffer tank, 12-vacuum pump, 13-feeding pipe, 14-aluminum liquid pouring channel, 15-spreading head, 16-slit vacuum channel, 17- Inlet valve, 18-Pressure gauge, 19-Deflation valve, 20-Safety valve, 21-Air compressor, 22-Seal, 23-Cooling water inlet and outlet pipe, A-Mould down working point, B, C-Mould Workpiece separation preheating zone, D-material preheating zone.

Detailed ways

The present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments.

Referring to Figures 1 and 2, a vacuum self-weight pouring high static pressure strong pouring die-casting forming equipment includes an aluminum melting furnace 1, a holding furnace 3, a barrel 5, a barrel piston 6, an oil cylinder 7, a mold tooling assembly 8, and a vacuum buffer Tank 11 and vacuum pump 12, the aluminum melting furnace 1 is connected to the holding furnace 3 and the opening and closing valve 2 is arranged on the connecting pipe, the holding furnace 3 is connected to the lower end side of the barrel 5 through the feeding pipe 13, The oil cylinder 7 is arranged above the barrel 5 and drives the barrel piston 6 to run up and down in the barrel 5. The feed port of the barrel 5 is located in the running stroke of the barrel piston 6, and the barrel 5 is located in the mold tooling. Above the assembly 8, the mold tooling assembly 8 is provided with an aluminum liquid pouring flow channel 14 connected with the discharge port of the barrel 5, and the aluminum liquid pouring flow channel 14 is connected with the mold cavity. The inner chamber of the mold cavity and the pouring head 15 communicate with the vacuum pipe 9 through the slit-type vacuuming channel 16 , the vacuum pipe 9 is connected to the vacuum buffer tank 11 , and the vacuum buffer tank 11 is connected to the vacuum pump 12 .

In this embodiment, the holding furnace 3 is connected with an air compressor 21 and the connecting pipeline is provided with an air intake valve 17, and the holding furnace 3 is provided with a pressure gauge 18, an air release valve 19 and a safety valve 20, which can be first Pressurized gas is poured into the closed holding furnace 3 to pressurize to increase the pressure of the material on the cavity surface at the moment of contact with the mold cavity when the material is fed in the self-weight vacuum casting process, to meet the casting of more complex workpieces and special requirements.

In this embodiment, a feed pipe heater 4 is provided on a section of the feed pipe 13 close to the feeding port of the barrel 5 to ensure that the feed port of the barrel 5 and the contact surface of the piston 6 of the barrel are provided with a flat layer solution. Fluidity, that is, to ensure the process temperature, it should be noted that the flow of materials must be smooth.

In this embodiment, the cross-sectional area of the oil cylinder 7 is larger than that of the barrel 5 . According to the inverse relationship between the cross-sectional area of the oil cylinder 7 and the cross-sectional area (S) of the barrel 5, and the pressure (F) (cylinder piston S1/barrel piston S2=barrel F2/oil cylinder F1), a large-diameter oil cylinder and a small-diameter material The cylinder can increase the pressure of the cylinder under the same power condition, and it is easy to realize high pressure holding and pressurization.

In this embodiment, the entire vacuum closed circuit of the present invention is easy to control the high vacuum degree, and the sealing member 22 is installed on the upper end of the barrel 5 where it contacts the piston rod of the barrel, so as to ensure the vacuum degree of the system. The piston rod of the barrel is provided with a cooling water inlet and outlet pipe 23 for passing cooling water into the rod, so as to ensure the normal operation of the equipment. Because the present invention adopts the vacuum self-weight method for feeding, it does not need to rely on the barrel piston 6 to advance the feeding, so the barrel piston 6 does not need to be lubricated, and the gas produced by the workpiece due to lubrication can be effectively reduced.

In this embodiment, the slot-type vacuum channel 16 is a flat channel, and the height of the flat opening is 0.15-0.25 mm, so that the slot-type vacuum channel 16 can only circulate gas but not melt and must be easy to clean.

In this embodiment, a material preheating zone D is set above the aluminum melting furnace 1; a mold downlink working point A and two mold workpiece separation preheating zones B and C are set below the mold tooling assembly 8 .

Referring to Figures 1 to 7, a vacuum self-weight pouring high static pressure casting die-casting process is carried out according to the following steps.

(1) Put the preheated aluminum ingot into the aluminum melting furnace 1 for overheating and melting. The melting temperature of aluminum is 660.4°C, and the overheating temperature for melting is set at 680-800°C; If it is too high, it should be determined according to the actual workpiece, process and other conditions. The superheated melt absorbs the water vapor in the air during the melting process and decomposes it into _H2 and _O2 , so that the _H2 in the water vapor enters the molten aluminum, and the hydrogen content in the molten aluminum varies with the rises with increasing temperature. At 700°C, every 100g of molten aluminum contains 10ml of hydrogen, and at 900°C, it rises to 30ml, but this is reversible. For example, when the molten aluminum at 900°C drops to 700°C, the content of hydrogen will increase from 30ml/ 100g drops to 10ml/100g.

(2) The molten aluminum enters the holding furnace 3 through the opening and closing valve 2 for heat preservation. The temperature of heat preservation depends on the technological conditions of the workpiece. The temperature of the workpiece with complex structure and thin surface should be appropriately higher. The structure is simple, The temperature of the workpiece with a large material path should be controlled to be lower. In principle, the temperature of the heat preservation is controlled between 670~780°C.

(3) Connect and fix the mold tooling assembly 8 with the barrel 5. Initially, the barrel piston 6 is located at the lower end of the barrel 5 and blocks the feed port of the barrel 5. Open the vacuum valve 10 and start the vacuum pump 12 to make the mold shape The air in the cavity and the air below the barrel are evacuated through the vacuum pipe 9, so that the mold cavity and the barrel 5 are in a vacuum state; but there is a technical problem in this process that is the treatment of the vacuum suction port of the mold, and the gap vacuum channel of the mold 16 must be able to flow only gas but not melt and must be easy to clean. The solution is to use a flat channel for the slotted vacuum channel 16. Generally, the height of the flat opening of the control channel is between 0.15 mm and 0.25 mm. The width and length are determined according to the actual workpiece and process conditions, which can prevent the melt from entering the slotted vacuum channel 16. The surface tension of the molten metal is large, and the surface tension will change significantly with the change of temperature. The molten metal can be prevented from entering the gap vacuum channel 16 by adjusting the temperature of the molten metal and the height of the flat mouth.

(4) While evacuating, the push rod of the oil cylinder 7 moves upward to drive the cylinder piston 6 to move upward. When the upward stroke exceeds the upper part of the material cylinder 5, the upward movement stops. At this time, the holding furnace 3 passes through the material delivery pipe 13 and the material The cylinder 5 is connected, and the aluminum liquid is quickly poured from the holding furnace 3 into the material cylinder 5 and the mold cavity under the action of the vacuum and the self-weight of the aluminum liquid.

In practice, a feed pipe heater 4 is provided on a section of the feeding pipe 13 connected to the aluminum melting furnace 1 and the barrel 5 near the feeding port of the barrel 5 to ensure that the feeding port of the barrel 5 and the piston of the barrel are 6 The fluidity of the solution in the plane layer of the contact surface, that is, to ensure the process temperature, attention should be paid to the smooth flow of materials.

(5) When the liquid aluminum is filled to the lower side of the barrel piston 6, the push rod of the oil cylinder 7 moves downward to drive the barrel piston 6 to move downward so that the excess aluminum liquid automatically returns to the holding furnace 3 through the feeding port of the barrel 5, When the barrel piston 6 moves downward beyond the bottom of the barrel 5 feed port, it will automatically close the barrel 5 feed port and then naturally form quantitative feeding. At this time, the barrel piston 6 pressurizes the workpiece and then the barrel piston 6 continues. Run downwards to apply high static pressure to the workpiece to achieve pressure maintenance. While maintaining pressure, the workpiece is cooled. Cooling is divided into two types: natural cooling and medium cooling. Natural cooling is based on the cooling of the mold itself to dissipate heat through heat conduction. , Medium cooling is to introduce cooling medium into the mold for forced cooling.

In practice, for more complex workpieces and workpieces with special requirements, it is necessary to increase the pressure of the material on the cavity surface at the moment when the material is in contact with the mold cavity during the self-weight vacuum pouring process, and the closed holding furnace can be used in step (4). The method of injecting pressure gas, the specific pressurization value per unit area depends on the process, and the range of pressurization > 12kg/ ^cm2 can be set to adjust, and the aluminum liquid is finally poured from the holding furnace quickly under the action of vacuum, aluminum liquid weight and pressure into the barrel and mold cavity.

According to the inverse relationship between the cross-sectional area of the oil cylinder 7 and the cross-sectional area (S) of the barrel 5, and the pressure (F) (cylinder piston S1/barrel piston S2=barrel F2/oil cylinder F1), a large-diameter oil cylinder and a small-diameter material The cylinder can increase the pressure of the cylinder under the same power condition, and it is easy to realize high pressure holding and pressurization. Because after the vacuum pouring, the mold cavity and the barrel 5 have been filled with solution. The final pressurization and pressure holding are to change the surface state of the casting workpiece and prevent the workpiece from shrinking and wrinkling, cold shut, shrinkage cavity, undercasting and other incomplete defects.

(6) After a certain period of time after pressure holding and cooling, the specific time depends on the size and complexity of the workpiece. Generally, the pressure holding time is controlled at 1 to 15 seconds, the cooling time of the mold is controlled at 5 to 30 seconds, and the push rod of cylinder 7 is downward. Running, the mold tooling assembly 8 moves downward at the same time, and the material head in the barrel 5 leaves the barrel 5 along with the mold and enters the downward working point A of the mold.

(7) Under mechanical action, the mold and the workpiece are translated to the mold and workpiece separation preheating zone B for workpiece demoulding treatment. The workpiece demoulding treatment includes the separation of the mold and the workpiece, and the separation of the material head and the workpiece.

(8) After the mold enters the above-mentioned mold workpiece separation preheating zone B, the heated mold located in another mold workpiece separation preheating zone C enters the downward working point A of the mold and simultaneously rises to combine with the barrel 5, and the barrel piston 6 Return to the next round of work; two mold workpiece separation preheating zones B and C are equipped with mold preheating devices.

A technical point in the implementation process of the present invention is to ensure the pressure of the melt on the wall of the cavity when the melt enters the cavity and the contact surface of the cavity when the self-weight casting is adopted.

The instantaneous pressure of the ordinary pouring melt on the wall comes from the height of the gate, the specific gravity of the melt and the pouring force of the melt. Because the height of this pouring gate is limited, the melt enters the cavity to overcome the friction of the runner and due to the mold and The temperature drop of the melt caused by the temperature difference of the melt increases the surface tension rapidly and reduces the fluidity, which also increases the friction force. Therefore, the instantaneous pressure of the ordinary pouring melt entering the contact surface between the cavity and the mold surface is >0.5kg/cm ² ; if it is not considered In the case of internal friction in the cavity, a pressure of 0.5 kg/cm ² is generated when the height of the material opening is 1.3 meters.

And what the present invention adopts is self-weight vacuum high-level slot method pouring, and the instantaneous pressure of molten liquid entering cavity contact surface comes from the vacuum degree of cavity, molten liquid self-weight and the height difference between the liquid surface on the holding furnace and the instant contact surface of mold liquid And the pressure in the holding furnace (for complex workpieces, pressurized gas should be applied to the closed holding furnace), the vacuum degree of the cavity, the specific gravity of the melt, and the fluidity of the melt (the temperature of the furnace liquid is a key indicator affecting fluidity), which determines the melting temperature. The flow rate of the liquid flowing through the gate of the mold and the pressure of the instantaneous contact surface between the molten liquid and the mold are actually a kind of kinetic energy impact force converted from potential energy, and this potential energy is determined by the specific gravity, height difference, pressure in the holding furnace and vacuum degree. decided.

The height difference between the upper liquid level of the holding furnace and the contact surface of the mold cavity is set at 2.6 meters. Without considering the friction between the mold flow channel and the mold surface, the melt The pressure on the contact surface with the mold cavity is 1.9kg/cm ² ; if a pressure of 3kg is applied to the holding furnace, it is (1.9+3)=4.9kg/cm ² , and the specific pressure value in the furnace is based on the workpiece and process requirements. cold. This process is actually a form of potential energy to kinetic energy conversion. For the same melt, the ultimate pressure is determined by the height, fluidity vacuum, temperature difference between the mold and the melt, and the pressure in the holding furnace. For some complex structures Parts can be taken to improve the preheating temperature of the mould, and increase the height of the holding furnace relative to the mold to apply pressure in the holding furnace. The height difference of the high position holding furnace of the present invention is adjustable.

In the implementation process, pressurization and pressure maintenance should be implemented immediately after the self-weight pouring is completed, and it should be implemented under the technological conditions of the melt temperature in the cavity > 640 ° C. The adjustment during the specific implementation process corresponds to the adjustment of the technological requirements of the workpiece. The preheating temperature of the mold and the holding temperature of the holding furnace melt.

The height of the high-position holding furnace tank is limited only by the self-weight vacuum casting method. In actual work, if the pressure generated by the instantaneous function of the contact surface between the melt and the cavity cannot meet the requirements for good surface performance, it cannot solve the shrinkage and filling of the workpiece. However, die casting produces a large pressure of 100~300kg/cm ² , so it can form a good surface and prevent problems such as shrinkage and shrinkage. In the present invention, a pressure of 100-300kg/ ^cm2 is applied after pouring, while the pressure is maintained for 1-15 seconds, and the mold is left to cool for 5-30 seconds, so as to ensure that the workpiece has a good outer surface and excellent mechanical properties.

During the implementation of the present invention, for some workpieces with relatively complex structures, in the self-weight vacuum casting process, because the gate resistance in the mold is large, the workpiece material is easily cooled by the mold at the gate, which will cause the kinetic energy pressure of the instantaneous contact surface between the material and the mold to drop and cannot meet the requirements. Process requirements. In this case, the method of adjusting the height of the holding furnace alone cannot meet the process requirements. A closed holding furnace should be used to add pressure gas, which can be pressurized according to the process conditions within the range of >12kg/ ^cm2 , so that It can effectively increase the self-weight vacuum pouring speed and the instantaneous kinetic energy pressure of materials and molds, and the increased pressure value corresponds to the pressure value of the holding furnace pressure air. As shown in Figure 2: firstly open the intake valve 17, pressurize air to the holding furnace 3 at a constant value of 0~12kg/ ^cm2 , when the material reaches the lower position of the holding furnace 3, open the air release valve 19, and then the aluminum melting furnace 1 Feed to the holding furnace 3 Stop feeding at high liquid level.

In the present invention, the quantitative feeding is a self-quantitative process in the self-weight vacuum pouring process, because the mold cavity and the barrel are in the vacuum position. In the state of Figure 3, vacuumize the barrel 5 and the cavity; when entering the state of Figure 4, automatic pouring is realized, due to vacuum suction + material weight + potential energy of height difference between liquid level and mold cavity + pressure applied in the holding furnace, At this time, the material in the holding furnace 3 will be automatically fed through the feed port of the barrel 5, and it will be filled with all vacuum spaces below the lower plane of the barrel piston 6, including the mold cavity space to realize the self-quantitative work process.

The present invention is carried out in a vacuum during the molten liquid conveying process, and the melted liquid does not contact with the air. The aluminum melting furnace 1 or holding furnace forms an oxide layer on the upper surface of the completely melted melt, which can effectively prevent the melt from absorbing hydrogen after melting; it can also be filled with inert gas in the closed aluminum melting furnace 1 and the closed holding furnace The method to reduce the hydrogen content in the melt (the gas in the melt is mainly hydrogen, the content accounts for 80~90%).

In the present invention, the opening and closing control of the molten liquid entering the vacuum cavity and the material cylinder is realized by the up and down movement of the material cylinder piston. The present invention is different from the existing vacuum die-casting machine, the vacuum is not set before the high-speed casting, but is set in the whole process of pouring; the existing die-casting machine must use lubricant because of the rapid operation of the injection piston of the barrel Lubricate. When the barrel piston 6 is in the position shown in Figure 3 when vacuuming, close the feed port of the barrel 5 to carry out the vacuuming work. When the vacuum degree reaches 0.9 high pressure, the cylinder piston 6 moves upward to the position shown in Fig. 4, at this time vacuum self-weight pouring is realized, and the material fills the cavity and the lower space of the cylinder 5. When in the position shown in Figure 5, the barrel piston 6 moves downward, and part of the material overflows back to the holding furnace 3 at the bottom of the barrel 5, and when the barrel piston 6 descends to the position shown in Figure 6, it realizes charging. Pressure, due to the effect of the pressure, the barrel piston 6 will continue to go down to the position shown in Figure 7. At this time, the working oil pump realizes low-speed high-torque work, and the barrel piston 6 is in the pressure-holding stage. This fundamentally solves the closure control of the hydraulic conveying process of the high-temperature furnace and the influence of the temperature difference of the control valve body, which leads to changes in the temperature, fluidity and performance of the melt. At the same time, the gas generated by the high-temperature decomposition of the lubricant due to the use of the lubricant to lubricate the injection piston of the barrel is excluded.

In the present invention, the material is preheated above the aluminum melting furnace, and the heat conduction and heat radiation of the aluminum melting furnace are used to heat the material. When heated to 500°C, the moisture and crystal water on the surface of the material can be removed first, and the surface moisture can be removed below 500°C. , which can effectively reduce the hydrogen dissolved in the melt due to the decomposition of water on the surface of the material, and can also use heat energy.

Because the present invention adopts the method of combining vacuum self-weight pouring and high-pressure pressurization, as long as a small barrel is installed and a low-power die-casting machine is used, the workpiece die-casting that can only be realized with a high-power and a large barrel can be completed. Because the melt is transported by the vacuum self-weight melting hydraulic pressure, it does not need to be transported by the injection force of the large barrel, which can reduce the power of the drive motor in the hydraulic system and effectively save energy. For example, the effect is better when the permanent magnet motor is used in the hydraulic system to drive and increase the speed. The invention is especially implemented to the die-casting process of the motor rotor, which can obviously improve the efficiency of the motor. At present, the die-casting method is used for the aluminum injection of the motor rotor. Due to the air in the cavity, the air in the barrel and the decomposed gas used in the lubricant during the process, the squirrel cage bar and the rings at both ends of the rotor after die-casting have uneven pores and holes. A large amount of aluminum oxide, which affects the efficiency of the motor. Especially in the current development of high-efficiency motors, the cast aluminum quality of the rotor is the key. The implementation of the present invention can improve the die-casting quality of the motor rotor and thus improve the efficiency of the motor, which can produce significant economic and social benefits and has a huge market application prospect.

In the present invention, the moment when the molten liquid enters the mold cavity in the stage of self-weight potential energy vacuum pouring and the pressure of the contact surface of the mold cavity depend on the process conditions. +The size of the air pressure applied to the holding furnace is formed by the potential energy conversion formed by these factors. The molten fluid is in a state of circulation, which is caused by kinetic energy, and at the same time, a large pressure is generated to form an impact force on the surface of the cavity. The formation of this impact force is beneficial to the surface quality of the special surface, and at the same time, the temperature difference of the melt is naturally adjusted. , The temperature of the liquid on the contact surface of the melt and the cavity drops, which causes the fluidity of the melt to drop rapidly and affects the quality of the working surface. The effect of this kind of circulation makes the liquid self heat balance to ensure the fluidity and the surface quality of the workpiece, and at the same time, it is conducive to the precipitation of hydrogen contained in the melt as the liquid temperature drops.

However, ordinary pouring kinetic energy is very small and cannot overcome the rapid drop in fluidity caused by the contact surface resistance between the mold and the melt and the temperature difference, and cannot form a circulation phenomenon. For simple workpieces, it can only be a weak circulation phenomenon, and there is no certain circulation velocity and pressure. It is impossible to form a good workpiece surface, so the use of self-weight potential energy vacuum casting can obtain good surface quality of the workpiece at this stage and effectively reduce the internal hydrogen content of the melt during the pouring process, and then pressurize and maintain pressure, and it is easy to obtain a good surface quality. Formed workpieces.

The surface quality of the workpiece formed by the present invention depends on the self-weight, potential energy and vacuum self-quantitative pouring. The pressure at each point of the cavity contact surface is the same. This large static pressure is realized according to the inverse ratio of the force generated by the inverse ratio between the large working oil cylinder and the small pressure injection cylinder. The effect of this large static pressure forms a good surface quality of the workpiece. The use of this method makes the mold have a long service life, does not form jet damage to the surface of the mold, is not easy to form cold shrinkage on the surface of the workpiece, and ensures the internal mechanical properties of the workpiece.

However, the quality of the final formed surface of the current ordinary die-casting or vacuum die-casting is realized by the impact force and pressure generated by the rapid injection of the cylinder piston after casting. Although this pressure injection method can obtain good surface quality, the service life of the mold is affected to a certain extent because the fast injection material has a great jet impact force on the mold. Forming crystallization and mechanical properties of the workpiece.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (10)

1. A vacuum self-weight casting high static pressure strong casting die-casting forming equipment, comprising an aluminum melting furnace, a holding furnace, a barrel, a barrel piston, an oil cylinder, a mold tooling assembly, a vacuum buffer tank and a vacuum pump, characterized in that: The aluminum melting furnace is connected with the holding furnace and the opening and closing valve is arranged on the connecting pipe. The holding furnace is connected with the lower end side of the barrel through the feeding pipe. The oil cylinder is set above the barrel and drives the barrel piston to The barrel runs up and down, the barrel inlet is located in the barrel piston stroke, the barrel is located above the mold tooling assembly, and the mold tooling assembly is provided with a device connected to the barrel outlet. The molten aluminum pouring channel communicates with the mold cavity, the inner chamber of the mold cavity and the pouring head communicate with the vacuum pipeline through the slit-type vacuuming channel, and the vacuum pipeline Connected to a vacuum surge tank, which is connected to a vacuum pump. 2. A kind of vacuum self-weight pouring high static pressure strong casting die-casting forming equipment according to claim 1, characterized in that: the holding furnace is connected with an air compressor and the connecting pipe is provided with an inlet valve, and the holding furnace It is equipped with pressure gauge, air release valve and safety valve. 3. The vacuum self-weight pouring high static pressure casting die-casting forming equipment according to claim 1, characterized in that: a section of the feed pipe close to the feed opening of the barrel is provided with a feed pipe heater. 4. The vacuum self-weight pouring high static pressure casting die-casting forming equipment according to claim 1, characterized in that: the cross-sectional area of the oil cylinder is larger than that of the barrel. 5. A vacuum self-weight pouring high static pressure strong casting die-casting forming equipment according to claim 1, characterized in that: the upper end of the barrel is in contact with the piston rod of the barrel with a seal; The piston rod is provided with a cooling water inlet and outlet pipe for passing cooling water into the rod. 6. A vacuum self-weight casting high static pressure strong casting die-casting forming equipment according to claim 1, characterized in that: a material preheating zone is set above the aluminum melting furnace; a material preheating zone is set below the mold tooling assembly There are mold downlink working points and two separate preheating zones for mold workpieces. 7. A vacuum self-weight pouring high static pressure strong casting die-casting forming process, characterized in that it comprises a vacuum self-weight pouring high static pressure strong pouring die-casting forming equipment as claimed in claim 1, and is carried out according to the following steps: (1 ) Put the preheated aluminum ingot into the aluminum melting furnace for superheating and melting, and set the melting superheating temperature to 680-800°C; (2) The melted aluminum liquid enters the holding furnace through the opening and closing valve for heat preservation. The temperature is controlled between 670~780°C; (3) Connect and fix the mold tooling assembly with the barrel. Initially, the barrel piston is located at the lower end of the barrel and blocks the feed port of the barrel. Open the vacuum valve and start The vacuum pump makes the air in the mold cavity and the air under the barrel evacuated through the vacuum pipe, so that the mold cavity and the barrel are in a vacuum state; (4) While evacuating, the cylinder push rod moves upward to drive the barrel piston to move upward , when the upward stroke exceeds the upper part of the feeding port of the barrel, the upward movement is stopped. At this time, the holding furnace is connected with the barrel through the feeding pipe, and the aluminum liquid is quickly poured from the holding furnace into the barrel and the barrel under the action of the vacuum and the self-weight of the aluminum liquid. Mold cavity; (5) When the aluminum liquid is filled to the lower side of the barrel piston, the cylinder push rod moves downward to drive the barrel piston to move downward so that the excess aluminum liquid automatically returns to the holding furnace through the barrel feeding port. When the barrel piston moves downward and exceeds the bottom of the barrel feed port, it will automatically close the barrel feed port and naturally form quantitative feeding. At this time, the barrel piston can pressurize the workpiece and then the barrel piston continues to run downward to apply High static pressure to achieve pressure holding, cooling the workpiece while holding the pressure; (6) After a certain period of time after holding the pressure and cooling, the general holding time is controlled at 1-15 seconds, and the cooling time of the mold is controlled at 5-30 seconds Seconds, the cylinder push rod moves downward, the mold tooling assembly moves downward at the same time, and the material head in the barrel leaves the barrel along with the mold and enters the downward working point of the mold; (7) Under mechanical action, the mold and workpiece translate to a mold workpiece Separate the preheating zone for workpiece demoulding treatment; (8) After the mold enters the above-mentioned mold workpiece separation preheating zone, the heated mold located in another mold workpiece separation preheating zone enters the downward working point of the mold and rises and feeds simultaneously. The barrel is combined, and the piston of the barrel returns to the next wheel. 8. A vacuum self-weight pouring high static pressure strong pouring die-casting forming process according to claim 7, characterized in that: in step (4), the feeding pipe connecting the aluminum melting furnace and the barrel is fed close to the barrel One section of the feed port is provided with a feed pipe heater, so that the plane layer melt on the contact surface between the feed port of the barrel and the piston of the barrel keeps flowing. 9. A vacuum self-weight casting high static pressure casting die-casting forming process according to claim 7 or 8, characterized in that: in step (4), the self-weight vacuum casting process needs to be increased for more complex workpieces and workpieces with special requirements The pressure of the material on the surface of the cavity at the moment of contact with the mold cavity when the material is fed, first rushes the pressure gas into the closed holding furnace to pressurize, and the aluminum liquid is finally realized from the holding furnace under the action of vacuum, the weight of the aluminum liquid and the pressure. Rapid pouring into barrels and mold cavities. 10. A vacuum self-weight pouring high static pressure casting die-casting forming process according to claim 7, characterized in that: in steps (7) and (8), the separation preheating zones of the two mold workpieces are both equipped with mold preheating heat device.

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