Lift tube throat heating method for low-pressure casting machine

Abstract

The invention relates to a riser tube throat heating method for a low-pressure casting machine, which is characterized in that an induction heater in a heating host is sleeved at the throat of a riser tube, and a steel flange is arranged in the middle of the induction heater; when the heating main machine introduces high-frequency alternating current into the induction heater, an alternating magnetic field is generated around the induction heater, the steel flange generates an eddy current effect under the action of the magnetic field, and internal electrons violently move and are converted into heat energy, so that the temperature of the steel flange rapidly rises, and heat is conducted to molten aluminum through the pipe wall of the liquid rising pipe; and the temperature of the molten aluminum at the throat of the riser tube is maintained within the range required by the process. Integrated control is carried out through the heating machine, precise temperature control over the throat opening of the liquid rising pipe is achieved through the electromagnetic induction principle, the steel flange is designed in the middle of the induction heater, after the temperature of the steel flange rises, heat can be conducted to the liquid rising pipe and then transferred to molten aluminum, and the problem of molten aluminum solidification is effectively solved.

Description

Technical Field

[0001] The present invention relates to a method for heating the throat of a riser pipe, in particular to a method for heating the throat of a riser pipe used in a low-pressure casting machine, and belongs to the technical field of low-pressure casting. Background Art

[0002] During the casting process, molten aluminum rises from a crucible through a riser tube into the mold cavity. The throat of the riser tube serves as a critical channel for the molten aluminum's flow. Due to its large heat dissipation area and prolonged residence time, the temperature of the molten aluminum is prone to significant drops, making heating necessary. Furthermore, when the molten aluminum temperature falls below the liquidus, a solidified layer forms, blocking the flow path and affecting casting continuity. The shedding of the solidified layer can cause slag inclusions in the casting, and frequent cleaning of solidified material increases equipment maintenance costs and downtime. Conventional external heating methods (such as resistance heating) suffer from low heating efficiency, uneven temperature distribution, and fragility, making them incapable of meeting the requirements of high-precision casting processes.

[0003] Therefore, it is of great significance to develop a method for heating the throat of a riser pipe with high efficiency and safety. Summary of the Invention

[0004] In response to the above-mentioned technical problems of the prior art, the purpose of the present invention is to provide a method for heating the throat of a riser pipe for a low-pressure casting machine, which is integratedly controlled by a heating main unit, and achieves precise temperature control of the throat of the riser pipe through the principle of electromagnetic induction. A steel flange is designed in the middle of the induction heater. After the temperature of the steel flange rises, the heat can be conducted to the riser pipe and then transferred to the aluminum liquid, effectively solving the problem of aluminum liquid solidification.

[0005] To achieve the above object, the present invention is achieved through the following technical solutions: A method for heating the throat of a riser pipe of a low-pressure casting machine comprises: an induction heater in a heating main unit is sleeved on the throat of the riser pipe; a steel flange is provided in the middle of the induction heater; when the heating main unit passes high-frequency alternating current to the induction heater, an alternating magnetic field is generated around the induction heater, and the steel flange generates an eddy current effect under the action of the magnetic field, and the violent movement of electrons inside is converted into heat energy, causing the temperature of the steel flange to rise rapidly. The heat is conducted to the aluminum liquid through the wall of the riser pipe, thereby maintaining the temperature of the aluminum liquid at the throat of the riser pipe within the process requirements.

[0006] The steel flange is annular and fits tightly against the outer wall of the throat of the riser pipe, transferring heat to the aluminum liquid through heat conduction.

[0007] The induction heater is an induction coil, and a non-contact coupling design is adopted between the induction coil and the steel flange.

[0008] The induction coil is wound with a hollow copper tube, and the outside of the induction coil is covered with a high-temperature resistant insulating material.

[0009] The induction coil adopts medium frequency heating.

[0010] The induction coil uses a low-voltage, high-current method to achieve heating.

[0011] The heating host is an integrated heating host, which adopts a PLC control system to monitor and adjust the heating power, temperature and time parameters in real time; the integrated heating host is equipped with a human-computer interaction interface, supports process parameter preset and data storage functions; the integrated heating host has a built-in over-temperature protection module and an over-current protection module.

[0012] The PLC control system collects temperature data in real time through a thermocouple buried at the throat of the riser pipe, and dynamically adjusts the current frequency of the induction coil to control the deviation between the heating temperature and the set value within an allowable range.

[0013] The integrated heating host is communicated with the main control system of the low-pressure casting machine, receives process signals of the filling stage / pressure holding stage, starts the heating program only in the pressure holding stage, and automatically reduces the heating power to the temperature maintenance mode in the filling stage.

[0014] The over-temperature protection module is equipped with a dual judgment mechanism. When the throat temperature exceeds the set threshold or the temperature rise rate of the steel flange is greater than 10°C / s, the power supply is immediately cut off and an audible and visual alarm is triggered.

[0015] The beneficial effects of the present invention are as follows: The present invention is a method for heating the riser throat of a low-pressure casting machine. This method utilizes integrated control via a heating main unit, achieving precise temperature control of the riser throat using the principle of electromagnetic induction. An induction heater acts on a steel flange at the riser throat, generating electromagnetic eddy currents that raise the temperature of the steel flange. Heat is then transferred from the steel flange through the riser pipe to the molten aluminum, solving the problem of aluminum solidification at the riser throat. This addresses the need for high aluminum temperature or long holding times during casting production. Furthermore, the present invention innovatively introduces casting stage identification technology. By analyzing the real-time pressure curve of the low-pressure casting machine, it intelligently determines the filling and holding stages, activating full-power heating only during the holding stage, when the risk of aluminum molten retention is highest, to achieve an optimal balance between energy consumption and heating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a schematic cross-sectional view of the present invention; Among them, 1 is the heating host, 2 is the rising tube, 3 is the induction heater, 4 is the steel flange, 5 is the crucible, and 6 is the aluminum liquid. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0018] like Figure 1 and 2 As shown, the present invention is mainly used in a low-pressure casting machine. A riser tube 2 is provided in the crucible 5, and the riser tube 2 is inserted into the aluminum liquid 6 in the crucible 5. The heating method at the throat of the riser tube 2 is: The induction heater 3 in the heating unit 1 is mounted over the throat of the riser tube 2. The induction heater 3 is an induction coil wound around a hollow copper tube and coated with high-temperature-resistant insulation material. A steel flange 4 is located at its center, serving as the induction heating element. The steel flange 4 is annular and fits snugly against the outer wall of the riser tube 3 at the throat, transferring heat to the molten aluminum through heat conduction. During heating, the heating unit 1 supplies high-frequency alternating current (above 100 kHz) to the induction heater 3. This generates an alternating magnetic field around the induction heater 3. This magnetic field creates eddy currents in the steel flange 4, converting the intense motion of electrons within the flange into heat energy. This rapidly increases the temperature of the flange 4, which is then transferred to the molten aluminum through the wall of the riser tube 2, maintaining the molten aluminum temperature at the throat of the riser tube 3 within the required process range.

[0019] Furthermore, the induction coil and the steel flange 4 of the present invention adopt a non-contact coupling design to avoid mechanical wear.

[0020] Furthermore, the heating host 1 in the present invention is an integrated heating host, which adopts a PLC control system. The PLC control system collects temperature data in real time through a thermocouple buried at the throat of the riser pipe, dynamically adjusts the current frequency of the induction coil, and controls the deviation between the heating temperature and the set value within the allowable range. It can monitor and adjust the heating power, temperature and time parameters in real time. It is equipped with a human-computer interaction interface and supports process parameter preset and data storage functions. It has a built-in over-temperature protection module and an over-current protection module. The over-temperature protection module is equipped with a dual judgment mechanism. When the throat temperature exceeds the set threshold or the temperature rise rate of the steel flange is greater than 10°C / s, the power supply is immediately cut off and an audible and visual alarm is triggered to ensure the safe operation of the equipment. In addition, the integrated heating host is connected to the main control system of the low-pressure casting machine, receives process signals of the filling stage / pressure holding stage, and starts the heating program only during the pressure holding stage. During the filling stage, the heating power is automatically reduced to the temperature maintenance mode.

[0021] The heating host 1 in the present invention establishes communication with the main control system of the low-pressure casting machine and obtains the pressurization curve and stage signal of the casting machine in real time. During the filling stage, the heating power is automatically reduced to maintain only the basic temperature; after entering the pressure holding stage, the power is increased to compensate for heating. The specific control relationship of the PLC control system, the process parameter preset and storage method, the over-temperature and over-current protection module, etc. can all adopt the modules or methods commonly used in the field. They are not the protection content of the present invention and are not described here.

[0022] The present invention utilizes a medium-frequency heating induction coil with a frequency range of 500Hz-10kHz to inductively heat the steel flange 4 at the throat of the riser tube 2. This heat generation prevents a drop in temperature at the throat of the riser tube 2. The induction coil does not require water cooling, thus preventing the risk of explosions caused by pipe ruptures during low-pressure aluminum alloy casting processes. Furthermore, the induction coil utilizes a low-voltage, high-current method for heating, resulting in a safe voltage. In a low-pressure casting environment, all metal conductive equipment is used, preventing electric shock accidents caused by rupture of the induction coil due to high temperatures.

[0023] Furthermore, the temperature at the throat drops quickly, resulting in unqualified castings such as loose air holes, and the riser 2 being clogged and unable to be produced. By adding a medium-frequency induction coil, the throat area can be quickly heated. Combined with the characteristics of low-pressure casting, the time it takes for the riser 2 to fill the mold with molten aluminum is very short in each product production cycle. Therefore, the heating device at the throat does not need to be used all the time, and only needs to be heated during the pressure holding stage. Traditional resistance coils or gas heating cannot achieve the effect of rapid heating at any time, and have a short lifespan and require high investment costs. The medium-frequency heating of the present invention avoids the above problems, has fast heating, good stability, long service life, and guaranteed safety.

[0024] The above embodiments are only used to illustrate the inventive concept of the present invention, and are not intended to limit the protection of the rights of the present invention. Any non-substantial changes to the present invention using this concept should fall within the scope of protection of the present invention.

Claims

1. A method for heating the throat of a riser pipe of a low-pressure casting machine, characterized in that: The induction heater in the heating host is installed at the throat of the riser pipe. A steel flange is provided in the middle of the induction heater. When the heating host supplies high-frequency alternating current to the induction heater, an alternating magnetic field is generated around the induction heater. The steel flange generates an eddy current effect under the action of the magnetic field, and the violent movement of internal electrons is converted into heat energy, causing the temperature of the steel flange to rise rapidly. The heat is conducted to the aluminum liquid through the wall of the riser pipe, maintaining the temperature of the aluminum liquid at the throat of the riser pipe within the process requirements.

2. The method for heating the riser throat of a low-pressure casting machine according to claim 1, wherein: The steel flange is annular and fits tightly against the outer wall of the throat of the riser pipe, transferring heat to the aluminum liquid through heat conduction.

3. The method for heating the riser throat of a low-pressure casting machine according to claim 1, wherein: The induction heater is an induction coil, and a non-contact coupling design is adopted between the induction coil and the steel flange.

4. The method for heating the riser throat of a low-pressure casting machine according to claim 3, wherein: The induction coil is wound with a hollow copper tube, and the outside of the induction coil is covered with a high-temperature resistant insulating material.

5. The method for heating the riser pipe throat of a low-pressure casting machine according to claim 3, wherein: The induction coil adopts medium frequency heating.

6. The method for heating the riser pipe throat of a low-pressure casting machine according to claim 3, wherein: The induction coil uses a low-voltage, high-current method to achieve heating.

7. The method for heating the riser throat of a low-pressure casting machine according to claim 1, wherein: The heating host is an integrated heating host, which adopts a PLC control system to monitor and adjust the heating power, temperature and time parameters in real time; it is equipped with a human-computer interaction interface, supports process parameter preset and data storage functions; and has a built-in over-temperature protection module and over-current protection module.

8. The method for heating the riser pipe throat of a low-pressure casting machine according to claim 7, wherein: The PLC control system collects temperature data in real time through a thermocouple buried at the throat of the riser pipe, and dynamically adjusts the current frequency of the induction coil to control the deviation between the heating temperature and the set value within an allowable range.

9. The method for heating the riser throat of a low-pressure casting machine according to claim 7, wherein: The integrated heating host is connected to the main control system of the low-pressure casting machine for communication, receives process signals of the filling stage / pressure holding stage, starts the heating program only in the pressure holding stage, and automatically reduces the heating power to the temperature maintenance mode in the filling stage.

10. The method for heating the riser pipe throat of a low-pressure casting machine according to claim 7, wherein: The over-temperature protection module is equipped with a dual judgment mechanism. When the throat temperature exceeds the set threshold or the temperature rise rate of the steel flange is greater than 10°C / s, the power supply is immediately cut off and an audible and visual alarm is triggered.

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