Constant-liquid-level low-pressure casting device without liquid rising pipe and casting method

Abstract

The constant-liquid-level low-pressure casting device without the liquid rising pipe comprises a double-chamber heat preservation furnace, the double-chamber heat preservation furnace comprises a liquid rising chamber and a pressurizing chamber, a communicating channel is arranged between the liquid rising chamber and the pressurizing chamber, and a control assembly used for controlling opening and closing of the communicating channel is arranged on the communicating channel. A first heater and a second heater are arranged at the bottom of the liquid lifting chamber and the bottom of the pressurizing chamber respectively, a feeding port, a pressurizing pipeline and a pressure relief pipeline are arranged on the pressurizing chamber, and a bypass assembly used for adjusting the pressure of the liquid lifting chamber is arranged on the upper side of the liquid lifting chamber. And the nitrogen supply and control system comprises a nitrogen making machine, a control valve group and a control system for controlling the control valves. The invention further provides a casting method based on the device. The problems that in the filling process of molten metal, molten metal fluctuates greatly along with pressurization and pressure relief, oxide skin is generated between the molten metal and a furnace body, the quality of the molten metal is affected, the filling speed is unstable, and the gas entrapment phenomenon of products is caused are solved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy low-pressure casting, and in particular to a constant liquid level low-pressure casting device without a riser and a casting method. Background Art

[0002] The existing low-pressure casting technology uses air pressure to move the molten metal in the insulation furnace into the mold cavity through a riser for casting. It has two prominent problems. The first problem is that the existing low-pressure casting must use a riser to input the aluminum alloy liquid into the mold cavity. The riser is immersed in high-temperature aluminum alloy liquid for a long time. The iron riser is easily corroded, causing the aluminum liquid to increase iron and even leak, resulting in waste. The second problem is that the riser height changes continuously with the increase in the number of casting molds, and then the riser height of the aluminum alloy liquid also changes continuously. The speed at which the aluminum liquid enters the mold cavity fluctuates greatly, and the product quality consistency is poor.

[0003] In order to solve the problem of poor corrosion resistance of iron riser tubes, people invented ceramic riser tubes. Ceramic riser tubes are expensive, with each tube costing up to several thousand yuan, and have poor resistance to sudden cooling and heating. During furnace changing operations or replenishing molten aluminum, they often break and become scrapped. In addition, slag nodules are easily generated on the inner wall of ceramic riser tubes, affecting the purity of the molten aluminum and the stability of the rising liquid.

[0004] In order to solve the problem of unstable casting quality caused by the drop in the liquid level in the furnace, people have adopted a pressure compensation method, that is, according to the drop in the liquid level caused by casting a mold, the corresponding air pressure is increased to compensate for the increase in pressure required for the increase in the liquid rise height. Since the cross-section of the furnace is variable, the change of the liquid level with the number of castings is not a linear law. The compensation accuracy is not high and it is difficult to stabilize the product quality.

[0005] The present invention is proposed to solve the problem of increased costs caused by the pollution or easy damage of the riser tube to the aluminum liquid in the existing low-pressure casting, and to solve the problem of unstable product quality caused by the continuous decrease of the liquid level in the existing low-pressure casting furnace with the increase of the number of castings. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects in the prior art that the circuit board needs auxiliary fixtures and has more process flows, and to provide a constant liquid level low-pressure casting device without a riser tube to solve the problem that during the filling process of molten metal, the metal liquid fluctuates greatly with the pressurization and pressure relief, and oxide scale is generated between the metal liquid and the furnace body, which affects the quality of the metal liquid; the metal liquid level is controlled to be stable so that the filling stroke of each mold is consistent, avoiding the formation of a condensation layer, and the filling efficiency is improved because the stroke is guaranteed; the problem of unstable filling speed leading to air entrainment in the product is solved.

[0007] To achieve the above object, the present invention provides a low-pressure casting device with a constant liquid level and without a riser tube, comprising:

[0008] A double-chamber insulation furnace, the double-chamber insulation furnace comprises a liquid rise chamber and a pressurizing chamber, a communication channel is arranged between the liquid rise chamber and the pressurizing chamber, a control component for controlling the opening and closing of the communication channel is arranged on the communication channel, a first heater and a second heater are arranged at the bottom of the liquid rise chamber and the pressurizing chamber respectively, a feeding port, a pressurizing pipe and a pressure relief pipe are arranged on the pressurizing chamber, a bypass component for adjusting the pressure of the liquid rise chamber is arranged on the upper side of the liquid rise chamber, and a gate is arranged on the top of the liquid rise chamber;

[0009] A nitrogen supply and control system, comprising a nitrogen generator, a control valve group and a control system for controlling the control valve, wherein the nitrogen generator is connected to the pressurized pipeline and the bypass component through the control valve.

[0010] Furthermore, the control assembly includes a stopper rod cylinder disposed on one side of the pressurized chamber and a pressurized chamber stopper rod connected to the stopper rod cylinder, and a movable cavity for the pressurized chamber stopper rod to move is provided on the side wall of the pressurized chamber, and the pressurized chamber stopper rod is placed in the movable cavity. The movable cavity can completely accommodate the pressurized chamber stopper rod, so that when the communication channel is opened, the pressurized chamber stopper rod will not be blocked, and when the communication channel needs to be closed, the pressurized chamber stopper rod can be freely extended to close the communication channel.

[0011] Furthermore, a sealed cavity is provided on the other side of the communication channel relative to the active cavity, the sealed cavity is adapted to the position of the active cavity, the size of the sealed cavity matches the pressure chamber stopper rod, the end of the pressure chamber stopper rod forms a plug-in portion, an inclined step portion is formed between the plug-in portion and the pressure chamber stopper rod, and the shape of the sealed cavity matches the plug-in portion and the step portion. The sealed cavity can be provided to allow the pressure chamber stopper rod to be inserted, thereby improving the sealing performance when closing the communication channel, especially by providing the coordination of the step portion and the plug-in portion, further improving the sealing performance of the pressure chamber stopper rod to the communication channel, thereby preventing the circulation of molten metal.

[0012] Furthermore, the pressurizing chamber is also provided with a first pressure sensor, and the upper end of the liquid lifting chamber is provided with a liquid level sensor. The first pressure sensor and the liquid level sensor can monitor the pressure in the pressurizing chamber and the height of the liquid level in the liquid lifting chamber, and cooperate with the control system and other components.

[0013] Furthermore, the bypass assembly includes a bypass pipe connected to the upper side of the liquid lifting chamber, a bypass cylinder arranged on one side of the bypass pipe, and a gas-permeable brick connected to the bypass cylinder, the gas-permeable brick is placed between the bypass pipe and the liquid lifting chamber to separate the two, a bypass valve for opening and closing the bypass pipe is arranged in the bypass pipe, and the bypass pipe is connected to the nitrogen generator. Nitrogen enters the liquid lifting chamber through the gas-permeable brick, but the molten metal cannot flow out of the gas-permeable brick, which plays a one-way flow role.

[0014] Furthermore, the control valve group includes a proportional valve group and an angle seat valve, the pressurized pipeline is provided with a first pipeline and a second pipeline in parallel, and the angle seat valve and the proportional valve group are respectively provided on the first pipeline and the second pipeline. A multi-threaded nitrogen delivery mode is formed by the angle seat valve and the proportional valve, which can more accurately control the nitrogen flow rate and thus control the filling speed of the molten metal.

[0015] Furthermore, the proportional valve group includes a control proportional valve and a detection proportional valve, a third pipeline connected in parallel with the first pipeline and the second pipeline is also arranged on the pressurized pipeline, the control proportional valve is arranged on the second pipeline, the detection proportional valve is arranged on the third pipeline, a first safety valve and a second safety valve are arranged on the second pipeline and the third pipeline respectively, and a pressure transmitter is arranged behind the detection proportional valve (73). By controlling the nitrogen flow rate through the dual proportional valves in conjunction with the first pressure sensor, the metal liquid filling speed can be more accurately controlled, so that the filling speed changes linearly, thereby solving the problem of metal liquid generating air entrainment due to unstable aluminum liquid filling speed.

[0016] A constant liquid level low-pressure casting method without a riser tube is also provided, comprising the following steps:

[0017] S1, molten metal insulation: open the pressurizing chamber stopper between the liquid lifting chamber and the pressurizing chamber to make the liquid levels in the liquid lifting chamber and the pressurizing chamber equal; start the first heater and the second heater in the liquid lifting chamber and the pressurizing chamber to control the temperature of the molten metal in the double-chamber insulation furnace to the set temperature and keep it warm;

[0018] S2, pressurized filling: open the angle seat valve and proportional valve group of the nitrogen inlet pipe to increase the pressure in the pressurized chamber. When the pressure sensor in the pressurized chamber detects that the pressure in the furnace reaches the first pressure value, the nitrogen fills the entire pressurized chamber, the angle seat valve is closed, and the proportional valve group is still in the open state, increasing the pressure in the pressurized chamber. The molten metal in the liquid rise chamber begins to rise slowly. The control system continuously monitors the pressure in the pressurized chamber and continuously adjusts the opening and closing state of the proportional valve group to make the molten metal rise steadily at the first speed; when the liquid level reaches the gate position, the opening of the proportional valve group is increased, and the rising speed of the molten metal is increased to the second speed. The molten metal quickly fills the mold cavity, and the second speed is greater than the first speed;

[0019] S3, pressure-maintaining solidification: Continue to increase the pressure in the pressurizing chamber, the molten metal in the liquid-raising chamber begins to rise slowly to supplement the liquid contraction of the molten metal, the control system continuously monitors the pressure in the pressurizing chamber, and continuously adjusts the opening and closing state of the proportional valve group, the pressure in the liquid-raising chamber is maintained at the set second pressure value, and the pressure is maintained, waiting for the molten metal to solidify;

[0020] S4, pressure relief and reflux: When the pressure holding time reaches the set value, the bypass valve cylinder opens the bypass valve and introduces nitrogen into the bypass valve to reduce the pressure in the liquid lifting chamber. At the same time, the pressure relief valve starts to release pressure. When it is detected that the liquid level in the liquid lifting chamber drops to the set position below the gate, the pressure relief is suspended, and the pressure chamber stopper closes the communication channel between the pressure chamber and the liquid lifting chamber, so that the liquid level in the liquid lifting chamber no longer drops and remains at a constant position, completing the casting;

[0021] S5, molten metal replenishment: open the feeding port of the pressurizing chamber and the pressurizing chamber stopper rod, add the qualified molten metal into the double-chamber insulation furnace, when the liquid level of the rising chamber reaches the set position, close the pressurizing chamber stopper rod between the rising chamber and the pressurizing chamber, and repeat the steps from S1 to S3.

[0022] Furthermore, in step S2, the first set value is 0-18 Kpa, the first speed is 20-50 mm / s, and the second speed is 50-100 mm / s.

[0023] Furthermore, the setting position in step S4 is 30-50 mm below the gate.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention eliminates the need for a riser pipe, thereby reducing production costs, increasing mold filling speed, and preventing accidents such as riser pipe rupture and blockage, thereby improving casting stability.

[0026] (2) During casting, the liquid level and lifting height of the double chambers can be kept constant, eliminating the difference in the quality of castings of different molds. The molten metal between the lifting chamber and the pressurizing chamber will not flow back, ensuring that the lifting and filling stroke is consistent each time, and the molten metal is always suspended in a fixed position below the gate of the lifting chamber, shortening the molten metal filling stroke, while reducing the reflux of the molten metal, avoiding the formation of a condensation layer on the furnace wall, and improving product quality.

[0027] (3) The pressure in the pressurizing chamber is controlled in a closed loop. The pressure controlled by the proportional valve group is compared with the pressure in the pressurizing chamber. The pressure is corrected in real time, which maintains a stable output of pressure and makes the products produced uniform.

[0028] (4) By controlling the nitrogen flow rate through the dual proportional valve, the metal liquid filling speed can be controlled more accurately, making the filling speed change linearly, thus solving the problem of air entrainment in the metal liquid caused by the unstable filling speed of the aluminum liquid.

[0029] (5) The temperature of the molten metal is controlled by zones to compensate in real time for the temperature drop of the molten metal caused by feeding, pouring, pressurization, etc., so that the pouring temperature of the molten metal is consistent. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a structural schematic diagram of a constant liquid level low-pressure casting device without a riser provided by the present invention;

[0032] Figure 2 It is a schematic diagram of the connected pressurized state of a constant liquid level low-pressure casting device without a riser tube provided by the present invention;

[0033] Figure 3 It is a schematic diagram of a state in which the liquid level of a constant liquid level low-pressure casting device without a riser provided by the present invention falls back;

[0034] Figure 4 It is the gas path principle diagram of the present invention.

[0035] Included in the figure are:

[0036] 1. Double-chamber insulation furnace; 11. Pressurized chamber; 111. Active chamber; 112. Sealed chamber; 113. Second heater; 114. First pressure sensor; 115. Feeding port; 116. Pressurized pipe; 1161. First pipe; 1162. Second pipe; 1163. Third pipe; 1164. First safety valve; 1165. Second safety valve; 117. Pressure relief pipe; 1171. Pressure relief valve; 1172. Third safety valve; 12. Lifting chamber; 121. First heater; 122. Liquid level sensor; 123. Gate; 124, docking flange; 13, connecting channel; 14, control component; 141, stopper cylinder; 142, pressurized chamber stopper; 1421, plug-in part; 1422, step part; 2, molten metal; 3, bypass component; 31, bypass pipe; 32, bypass cylinder; 33, air brick; 34, bypass valve; 4, mold; 5, nitrogen generator; 6, gas storage tank; 7, control valve group; 71, angle seat valve; 72, control proportional valve; 73, detection proportional valve; 731, pressure transmitter; 8, oil-water separator; 9, dryer. DETAILED DESCRIPTION

[0037] The technical scheme in this embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in this embodiment of the present invention. Obviously, the described embodiment is one embodiment of the present invention, not all embodiments of the present invention. Based on this embodiment of the present invention, all other embodiments of the present invention obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Please refer to Figures 1 to 4 The first embodiment of the present invention provides a low-pressure casting device with a constant liquid level without a riser, comprising:

[0039] The double-chamber insulation furnace 1 comprises a liquid riser 12 and a pressurizing chamber 11, wherein the volume of the pressurizing chamber 11 is larger than that of the liquid riser 12, so as to ensure that the liquid riser 12 can be filled during operation to avoid insufficient molten metal 2. A connecting passage 13 is provided between the liquid riser 12 and the pressurizing chamber 11, and a control component 14 for controlling the opening and closing of the connecting passage 13 is provided on the connecting passage 13. In this embodiment, the control component 14 comprises a stopper rod cylinder 141 provided on one side of the pressurizing chamber 11 and a pressurizing chamber stopper rod 142 connected to the stopper rod cylinder 141. A stopper rod 142 for the pressurizing chamber is provided on the side wall of the pressurizing chamber 11. The rod 142 is movable in the active cavity 111, and the pressurized chamber stopper rod 142 is placed in the active cavity 111. In order to increase the blocking effect of the pressurized chamber stopper rod 142 on the connecting channel 13, a closed cavity 112 is provided on the other side of the connecting channel 13 relative to the active cavity 111. The closed cavity 112 is adapted to the position of the active cavity 111, and the size of the closed cavity 112 matches the pressurized chamber stopper rod 142. A plug-in portion 1421 is formed at the end of the pressurized chamber stopper rod 142, and an inclined step portion 1422 is formed between the plug-in portion 1421 and the pressurized chamber stopper rod 142, and the shape of the closed cavity 112 matches the plug-in portion 1421 and the step portion 1422.

[0040] like Figure 1 As shown, a first heater 121 and a second heater 113 are respectively provided at the bottom of the lifting chamber 12 and the pressurizing chamber 11, a first pressure sensor 114 is also provided at the pressurizing chamber 11, and a liquid level sensor 122 is provided at the upper end of the lifting chamber 12. The first heater 121 and the second heater 113 are used to heat the molten metal 2 in the lifting chamber 12 and the pressurizing chamber 11 to maintain the temperature consistency of the molten metal 2 in the two chambers. The first pressure sensor 114 is used to cooperate with the control system to monitor the pressure in the pressurizing chamber 11 in real time, so as to facilitate the control system to control the flow rate of nitrogen release and then control the internal pressure of the pressurizing chamber 11. Similarly, the liquid level sensor 122 monitors the liquid level position of the lifting chamber 12.

[0041] The pressurizing chamber 11 is provided with a feeding port 115, a pressurizing pipe 116 and a pressure relief pipe 117. A bypass assembly 3 for adjusting the pressure of the lifting chamber 12 is provided on the upper side of the lifting chamber 12. The bypass assembly 3 includes a bypass pipe 31 connected to the upper side of the lifting chamber 12, a bypass cylinder 32 provided on one side of the bypass pipe 31, and an air-permeable brick 33 connected to the bypass cylinder 32. The air-permeable brick 33 is placed between the bypass pipe 31 and the lifting chamber 12 to separate the two. A bypass valve 34 for opening and closing the bypass pipe 31 is provided in the bypass pipe 31. A gate 123 is provided on the top of the lifting chamber 12. A docking flange 124 for mounting the mold 4 is provided on the side of the gate 123. The mold 4 is mounted through the docking flange 124.

[0042] The other end of the pressure relief pipe 117 is led out of the double-chamber insulation furnace 1, and can be connected to an external recovery device to recover the waste gas. A pressure relief valve 1171 is provided at the output end of the pressure relief pipe 117 to control the opening and closing of the pressure relief pipe 117. At the same time, in order to increase safety, a third safety valve 1172 is also provided on the pressure relief pipe 117, and the third safety valve 1172 is a one-way valve.

[0043] The nitrogen supply and control system includes a nitrogen generator 5, a control valve group 7, and a control system for controlling the control valve. The control system adopts a PLC controller. The nitrogen generator 5 is connected to the pressurized pipeline 116 and the bypass component 3 through the control valve. To facilitate the storage of nitrogen, in this embodiment, there is still a gas storage tank 6 between the nitrogen generator 5 and the control valve group 7. The gas storage tank 6 is connected to the bypass pipeline 31 and the pressurized pipeline 116 respectively; Figure 4 As shown, the control valve group 7 of the present embodiment includes a proportional valve group and an angle seat valve 71. A first pipeline 1161, a second pipeline 1162 and a third pipeline 1163 are arranged in parallel on the pressurized pipeline 116, wherein the proportional valve group includes a control proportional valve 72 and a detection proportional valve 73, and a pressure transmitter 731 is arranged behind the detection proportional valve 73. The angle seat valve 71, the control proportional valve 72 and the detection proportional valve 73 are respectively arranged on the first pipeline 1161, the second pipeline 1162 and the third pipeline 1163. To further ensure safety, a first safety valve 1164 and a second safety valve 1165 are respectively arranged on the second pipeline 1162 and the third pipeline 1163, and the first safety valve 1164 and the second safety valve 1165 are both one-way valves.

[0044] As a preferred method, when the nitrogen generator 5 generates nitrogen, a certain amount of pollutants such as water vapor will be generated. If such pollutants are directly input into the pressurized chamber 11, the purity of the molten metal 2 will be affected to a certain extent, resulting in the appearance of defective products. In order to avoid interference with the composition of the molten metal 2, an oil-water separator 8 and a dryer 9 are successively arranged between the gas storage tank 6 and the control valve to purify the nitrogen entering the control valve. In order to ensure the pressurization demand of the pressurized chamber 11, the pressure of the nitrogen in the gas storage tank 6 is set to 0.6-0.8Mpa, corresponding to the control of the pressure in the tank. The gas storage tank 6 of the present invention can adopt a pressure gas storage tank 6, which can be used by directly adjusting the pressure of the nitrogen in the tank by the pressure gas storage tank 6.

[0045] A constant liquid level low-pressure casting method without a riser tube is also provided, comprising the following steps:

[0046] S1. Keeping the molten metal 2 warm: open the pressurizing chamber stopper rod 142 between the lifting chamber 12 and the pressurizing chamber 11. Specifically, the stopper rod cylinder 141 drives the pressurizing chamber stopper rod 142 to move, so that the pressurizing chamber stopper rod 142 retracts into the movable cavity 111. At this time, the pressurizing chamber 11 is connected with the lifting chamber 12. The molten metal 2 in the pressurizing chamber 11 will enter the lifting chamber 12 through the connecting channel 13, so that the liquid levels of the lifting chamber 12 and the pressurizing chamber 11 are at the same height; start the first heater 121 and the second heater 113 of the lifting chamber 12 and the pressurizing chamber 11, so that the temperature of the molten metal 2 in the double-chamber insulation furnace 1 is controlled at the set temperature of 690℃-780℃ and kept warm.

[0047] S2, pressurized filling: open the angle seat valve 71 and the proportional valve group of the nitrogen inlet pipe, and the nitrogen quickly fills the entire pressurized chamber 11 to increase the pressure in the pressurized chamber 11. When the pressure sensor in the pressurized chamber 11 detects that the pressure in the furnace reaches a first pressure value of 0-18Kpa, after the nitrogen fills the entire pressurized chamber 11 (that is, when the liquid level sensor 122 detects that the liquid level in the liquid lifting chamber 12 begins to rise), the angle seat valve 71 is closed, and the proportional valve group is still in the open state, and the pressure in the pressurized chamber 11 continues to be increased. The metal liquid 2 in the liquid lifting chamber 12 begins to rise slowly. The control system continuously monitors the pressure in the pressurized chamber 11 and continuously adjusts the opening and closing state of the proportional valve group to make the metal liquid 2 rise steadily at a first speed of 20-50mm / s. Specifically, when the pressure value of the pressurized chamber 11 reaches the first pressure value, the angle seat valve 71 is closed, and the control proportional valve 72 and the detection proportional valve are closed. The opening of the valve 73 is reduced, and a small flow of nitrogen is introduced to increase the pressure in the pressurizing chamber 11. According to the Pascal principle, the liquid level in the liquid-raising chamber 12 rises at a set first speed under the action of pressure. At the same time, the first pressure sensor 114 detects the pressure change of the pressurizing chamber 11 in real time. The pressure transmitter 731 also detects the proportional valve 73 to detect the real-time pressure of the proportional valve 73, and converts the air pressure signal into an electrical signal, which is fed back to the PLC controller. The PLC controller compares the pressure of the pressure transmitter 731 with the pressure in the pressurizing chamber 11, thereby adjusting the opening of the proportional valve 73 to keep the pressure in the pressurizing chamber 11 at the set pressure level. When the pressure detected by the first pressure sensor 114 is lower than the set pressure, the control system adjusts the opening of the proportional valve 73 to increase the flow of nitrogen introduced to maintain the pressure in the pressurizing chamber 11 stable.

[0048] When the liquid level reaches the gate 123, the opening of the proportional valve group is increased, and the rising speed of the molten metal 2 is increased to a second speed of 50-100 mm / s, and the molten metal 2 quickly fills the mold cavity, wherein the second speed is greater than the first speed;

[0049] S3, pressure-maintaining solidification: the pressure in the pressurizing chamber 11 continues to increase, and the molten metal 2 in the liquid-raising chamber 12 begins to slowly rise to supplement the liquid contraction of the molten metal 2. The control system continuously monitors the pressure in the pressurizing chamber 11, and continuously adjusts the opening and closing state of the proportional valve group. The pressure in the liquid-raising chamber 12 is maintained at the set second pressure value, and the molten metal 2 is waited to solidify. The second pressure value is 30-120Kpa;

[0050] S4, pressure relief and reflux: when the pressure holding time reaches the set value, the bypass valve 34 cylinder opens the bypass valve 34 and introduces nitrogen into the bypass valve 34 to reduce the pressure in the liquid lifting chamber 12. At the same time, the pressure relief valve 1171 starts to relieve pressure. When it is detected that the liquid level in the liquid lifting chamber 12 drops to the set position, specifically 30-50 mm below the gate 123, the pressure relief is suspended, and the pressurizing chamber stopper rod 142 closes the connecting channel 13 between the pressurizing chamber 11 and the liquid lifting chamber 12, so that the liquid level in the liquid lifting chamber 12 no longer drops and remains at a constant position, completing the casting;

[0051] S5. Supplementing the molten metal 2: Open the feeding port 115 of the pressurizing chamber 11 and the pressurizing chamber stopper rod 142, add the smelted qualified molten metal 2 into the double-chamber insulation furnace 1, and when the liquid level of the rising chamber 12 reaches the set position, close the pressurizing chamber stopper rod 142 between the rising chamber 12 and the pressurizing chamber 11, and repeat the steps from S1 to S3.

[0052] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A constant liquid level low-pressure casting device without a riser, characterized in that: include: A double-chamber insulation furnace (1), the double-chamber insulation furnace (1) comprising a liquid lifting chamber (12) and a pressurizing chamber (11), a connecting passage (13) being arranged between the liquid lifting chamber (12) and the pressurizing chamber (11), a control component (14) for controlling the opening and closing of the connecting passage (13) being arranged on the connecting passage (13), a first heater (121) and a second heater (113) being arranged at the bottom of the liquid lifting chamber (12) and the pressurizing chamber (11), respectively, a feeding port (115), a pressurizing pipe (116) and a pressure relief pipe (117) being arranged on the pressurizing chamber (11), a bypass component (3) for adjusting the pressure of the liquid lifting chamber (12) being arranged on the upper side of the liquid lifting chamber (12), and a pouring gate (123) being arranged at the top of the liquid lifting chamber (12); A nitrogen supply and control system, comprising a nitrogen generator (5), a control valve group (7) and a control system for controlling the control valve, wherein the nitrogen generator (5) is connected to the pressurized pipeline (116) and the bypass component (3) via the control valve.

2. A constant liquid level low pressure casting device without a riser tube according to claim 1, characterized in that: The control assembly (14) comprises a stopper rod cylinder (141) arranged at one side of the pressurized chamber (11) and a pressurized chamber stopper rod (142) connected to the stopper rod cylinder (141); an active cavity (111) for the pressurized chamber stopper rod (142) to move is provided on the side wall of the pressurized chamber (11); and the pressurized chamber stopper rod (142) is placed in the active cavity (111).

3. A constant liquid level low pressure casting device without a riser tube according to claim 2, characterized in that: The connecting passage (13) is provided with a sealed chamber (112) on the other side relative to the active chamber (111); the position of the sealed chamber (112) is adapted to that of the active chamber (111); the size of the sealed chamber (112) matches that of the pressurized chamber stopper rod (142); a plug-in portion (1421) is formed at the end of the pressurized chamber stopper rod (142); an inclined stepped portion (1422) is formed between the plug-in portion (1421) and the pressurized chamber stopper rod (142); and the shape of the sealed chamber (112) matches that of the plug-in portion (1421) and the stepped portion (1422).

4. The constant liquid level low pressure casting device without a riser tube according to claim 1, characterized in that: The pressurizing chamber (11) is also provided with a first pressure sensor (114), and the upper end of the liquid lifting chamber (12) is provided with a liquid level sensor (122).

5. The constant liquid level low pressure casting device without a riser tube according to claim 1, characterized in that: The bypass assembly (3) comprises a bypass pipe (31) communicating with the upper side of the liquid lifting chamber (12), a bypass cylinder (32) arranged at one side of the bypass pipe (31), and a gas-permeable brick (33) connected to the bypass cylinder (32); the gas-permeable brick (33) is arranged between the bypass pipe (31) and the liquid lifting chamber (12) to separate the two; a bypass valve (34) for opening and closing the bypass pipe (31) is arranged in the bypass pipe (31); and the bypass pipe (31) is connected to the nitrogen generator (5).

6. The constant liquid level low pressure casting device without a riser tube according to claim 1, characterized in that: The control valve group (7) comprises a proportional valve group and an angle seat valve (71); a first pipeline (1161) and a second pipeline (1162) connected in parallel are arranged on the pressurized pipeline (116); the angle seat valve (71) and the proportional valve group are arranged on the first pipeline (1161) and the second pipeline (1162), respectively.

7. A constant liquid level low pressure casting device without a riser tube according to claim 6, characterized in that: The proportional valve group comprises a control proportional valve (72) and a detection proportional valve (73); a third pipeline (1163) connected in parallel with the first pipeline (1161) and the second pipeline (1162) is further provided on the pressurized pipeline (116); the control proportional valve (72) is provided on the second pipeline (1162); the detection proportional valve (73) is provided on the third pipeline (1163); a first safety valve (1164) and a second safety valve (1165) are provided on the second pipeline (1162) and the third pipeline (1163), respectively; and a pressure transmitter (731) is provided behind the detection proportional valve (73).

8. A casting method for a constant liquid level low-pressure casting device without a riser according to any one of claims 1 to 7, characterized in that: The steps include: S1, keeping the molten metal (2) warm: opening the pressurizing chamber stopper rod (142) between the lifting chamber (12) and the pressurizing chamber (11) to make the liquid levels of the lifting chamber (12) and the pressurizing chamber (11) equal; starting the first heater (121) and the second heater (113) of the lifting chamber (12) and the pressurizing chamber (11) to control the temperature of the molten metal (2) in the double-chamber heat-keeping furnace (1) to a set temperature and keep the temperature warm; S2, pressurized filling: open the angle seat valve (71) and the proportional valve group of the nitrogen inlet pipe to increase the pressure in the pressurized chamber (11). When the pressure sensor in the pressurized chamber (11) detects that the pressure in the furnace has reached a first pressure value and the nitrogen fills the entire pressurized chamber (11), the angle seat valve (71) is closed and the proportional valve group is still in an open state, increasing the pressure in the pressurized chamber (11). The molten metal (2) in the liquid raising chamber (12) begins to rise slowly. The control system continuously monitors the pressure in the pressurized chamber (11) and continuously adjusts the opening and closing state of the proportional valve group to allow the molten metal (2) to rise steadily at a first speed. When the liquid level reaches the gate (123) position, the opening of the proportional valve group is increased to increase the rising speed of the molten metal (2) to a second speed. The molten metal (2) quickly fills the mold cavity, wherein the second speed is greater than the first speed. S3, pressure-maintaining solidification: the pressure in the pressurizing chamber (11) is continuously increased, and the molten metal (2) in the lifting chamber (12) begins to slowly rise to supplement the liquid contraction of the molten metal (2). The control system continuously monitors the pressure in the pressurizing chamber (11), and continuously adjusts the opening and closing state of the proportional valve group. The pressure in the lifting chamber (12) is maintained at a set second pressure value, and the molten metal (2) is waited for solidification. S4, pressure relief and reflux: when the pressure holding time reaches the set value, the bypass valve (34) cylinder opens the bypass valve (34) and introduces nitrogen into the bypass valve (34) to reduce the pressure in the liquid lifting chamber (12). At the same time, the pressure relief valve (1171) starts to relieve pressure. When it is detected that the liquid level in the liquid lifting chamber (12) drops to the set position below the gate (123), the pressure relief is suspended. The pressurizing chamber stopper rod (142) closes the connecting channel (13) between the pressurizing chamber (11) and the liquid lifting chamber (12), so that the liquid level in the liquid lifting chamber (12) no longer drops and remains at a constant position, thereby completing the casting. S5. Supplementation of molten metal (2): Open the feeding port (115) of the pressurizing chamber (11) and the pressurizing chamber stopper rod (142), and add the qualified molten metal (2) into the double-chamber insulation furnace (1). When the liquid level of the lifting chamber (12) reaches the set position, close the pressurizing chamber stopper rod (142) between the lifting chamber (12) and the pressurizing chamber (11), and repeat the steps S1 to S3 in a cycle.

9. A riser-free constant liquid level low-pressure casting method according to claim 8, characterized in that: In the step S2, the first set value is 0-18 Kpa, the first speed is 20-50 mm / s, and the second speed is 50-100 mm / s.

10. A riser-free constant liquid level low-pressure casting method according to claim 8, characterized in that: The setting position in step S4 is 30-50 mm below the gate (123).

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