A method and apparatus for dehumidifying and deoxidizing a mold, and a method for using the apparatus

Abstract

The application discloses a method and device for dehumidifying and deoxidizing a casting mold and a use method of the device. The method comprises the following steps: step one, assembling a pouring bottom plate and each casting mold on a supporting bottom plate; step two, buckling a sealed tank body on the supporting bottom plate to form a sealed mold cavity; step three, heating the environment temperature in the sealed tank body to dry the casting mold; step four, making the relative humidity in the sealed tank body less than 10%; step five, replacing the air in the mold cavity with argon until the oxygen content at the end of the dry area of the casting mold is less than 3%; and step six, transferring the pouring bottom plate and the casting mold to a low-pressure pouring platform, and continuously feeding the argon into the mold cavity during the waiting pouring process. The application effectively overcomes the risk of explosion during the pouring and solidification of the casting, effectively prevents the generation of casting defects such as porosity and air hole, improves the delicacy of the casting, and improves the qualified rate of the casting.

Description

Technical Field

[0001] This invention relates to the field of low-pressure casting, specifically to a method, apparatus, and method of using a mold for dehumidification and deoxygenation. Background Technology

[0002] Currently, when casting large and complex magnesium alloy parts using low-pressure casting, 3D printing core technology is often employed to shorten the delivery cycle of the castings.

[0003] While 3D printing core technology overcomes the constraints of complex casting structures and can significantly shorten the casting development cycle, the high resin binder content and hygroscopic nature of 3D printed cores necessitate the use of drying methods to obtain dry molds. However, moisture re-entry occurs during core assembly and before pouring, greatly diminishing the drying effect. During pouring and solidification, the mold is subjected to high-temperature scorching by the molten alloy, forming dry and condensation zones on the mold surface. The dry zone refers to the area where the temperature from the molten alloy to the mold is 100°C. In this area, the temperature exceeds 100°C, causing free water to evaporate and the resin binder to decompose, resulting in the generation of a large amount of gas. The condensation zone, located between 100°C and 50°C, has a moisture content as high as (10-15)%, which is (2-3) times the normal moisture content. Due to the excessive moisture in this area, free water even appears between the sand grains, clogging the pores and significantly reducing the permeability of the sand mold. If the gas generated in the mold drying zone cannot be quickly discharged from the cavity, increasing the gas pressure at the cavity interface, it will infiltrate the liquid metal, causing porosity or defects in the casting. Furthermore, because 3D-printed cores cannot contain boric acid and sulfur flame retardants and have relatively complex structures, most core surfaces cannot be coated with magnesium alloy-specific flame-retardant paint, failing to create a flame-retardant protective atmosphere on the cavity surface. If the oxygen level between the sand grains in the cavity and mold drying zone exceeds a certain standard, there is a risk of deflagration during the pouring and solidification of the alloy. Summary of the Invention

[0004] The purpose of this invention is to provide a method, apparatus, and method of using the mold for dehumidification and deoxygenation. This invention effectively overcomes the risk of deflagration during casting and solidification, while also effectively preventing casting defects such as porosity and gas bubbles, thereby improving the quality and yield of castings.

[0005] The technical solution of this invention is: a method for dehumidifying and deoxygenating a casting mold, which is carried out according to the following steps:

[0006] Step 1: Assemble the casting base plate and each mold on the supporting base plate;

[0007] Step 2: Attach the sealed tank body to the supporting base plate to form a sealed cavity;

[0008] Step 3: Heat the internal environment of the sealed container to dry the mold;

[0009] Step 4: Ensure the relative humidity inside the sealed container is less than 10%;

[0010] Step 5: Replace the air in the mold cavity with argon gas until the oxygen content at the end of the mold drying zone is less than 3%;

[0011] Step 6: Transfer the casting base plate and mold to the low-pressure casting platform. While waiting for casting, continuously introduce argon gas into the cavity.

[0012] In the aforementioned method for dehumidifying and deoxygenating the casting mold, the drying process in step three is as follows: turn on the heaters evenly distributed around the casting mold, heat the ambient temperature inside the tank to 80°C and maintain it;

[0013] In the aforementioned method for dehumidifying and deoxygenating the casting mold, the ambient temperature inside the sealed container is maintained at 80°C for 1.5 to 3 hours.

[0014] In the aforementioned method for dehumidifying and deoxidizing the casting mold, step five involves the following steps:

[0015] a. After depressurizing the sealed cavity to 0.4 atm, argon gas is introduced to raise the pressure to 1 atm and then allowed to stand.

[0016] b. Detect the oxygen content at the end of the mold drying zone;

[0017] c. Continue repeating steps a and b until the oxygen content reaches the requirement of less than 3%.

[0018] In step a of the aforementioned method for dehumidifying and deoxygenating the casting mold, the settling time is 20 minutes.

[0019] The aforementioned method for dehumidifying and deoxygenating the casting mold also includes step seven: after the casting has been poured and cooled to room temperature, the casting is removed by sand removal.

[0020] The aforementioned method for dehumidifying and deoxygenating casting molds utilizes the following apparatus: a sealed tank, a supporting base plate, a heater, a dehumidifier, a vacuum pump, a safety valve, an argon cylinder, an oxygen content detection device, a thermocouple, and a pressure gauge. The sealed tank and supporting base plate form a sealed cavity using an end-face sealing block locking structure. The sealed tank is equipped with a safety valve, thermocouple, and pressure gauge. The safety valve ensures the normal operation of the tank. The thermocouple is used to monitor the internal temperature in real time. The pressure gauge is used to monitor the internal pressure in real time. The heater is connected to an external power source via a pre-embedded sealing wire on the supporting base plate; turning on the heater heats the internal environment. The dehumidifier... The inlet and outlet are connected to the sealed tank; the vacuum pump is also connected to the sealed tank; the argon cylinder is connected to an American standard flange ball valve on the support base plate for purging and deoxygenation; the oxygen content detection device is also connected to an American standard flange ball valve on the support base plate for detecting the oxygen content at the end of the mold drying zone; the sealed tank is opened, the pouring base plate and mold are transferred to the low-pressure pouring platform, and argon gas is continuously introduced into the cavity while waiting for pouring, until the argon gas valve is closed just before pouring; after the casting is poured and cooled to room temperature, the casting is removed by sand removal, cut and cleaned to obtain a complete casting.

[0021] The method of using the aforementioned device includes the following steps:

[0022] Step 1: Assemble the casting base plate and each mold on the support base plate, and evenly arrange two heaters around the mold.

[0023] Step 2: Secure the sealed tank body with pressure blocks, and obtain a sealed cavity by setting a sealing strip between the tank body and the supporting base plate;

[0024] Step 3: Turn on the heater to heat the ambient temperature inside the tank to 80℃ and maintain it for 1.5 to 3 hours to dry the mold;

[0025] Step 4: Open the dehumidification inlet and outlet valves, start the dehumidifier to circulate and dry the mold. When the relative humidity inside the sealed tank is less than 10%, close the inlet and outlet valves.

[0026] Step 5: Open the vacuum pump valve and start the vacuum pump to reduce the pressure in the sealed cavity. When the pressure reaches 0.4 atm, open the argon valve and start the argon cylinder to introduce argon into the cavity to replace the air inside. When the pressure reaches 1 atm, close the argon valve and let it stand for 20 minutes. Then, open the oxygen content detection valve and detect the oxygen content at the end of the mold drying area. Repeat step 5 until the oxygen content reaches less than 3%.

[0027] Step 6: Open the sealed tank, transfer the pouring base plate and mold to the low-pressure pouring platform, and continuously introduce argon gas into the cavity while waiting for pouring. The argon gas valve can only be closed before pouring.

[0028] Step 7: After the casting is poured and cooled to room temperature, remove the casting by removing the sand.

[0029] The advantages of this invention are: This invention provides a method for drying, dehumidifying, and deoxygenating casting molds, comprising: Step 1, assembling the pouring base plate and each casting mold on the supporting base plate, and evenly arranging two heaters around the casting mold; Step 2, fastening and locking the sealing tank, and obtaining a sealed cavity by setting a sealing strip between the tank and the supporting base plate; Step 3, turning on the heaters to heat the ambient temperature inside the tank to 80°C and maintaining it continuously (maintaining time: 3 hours for large castings, 2.5 hours for medium castings, and 1.5 hours for small castings), thereby drying the casting molds; Step 4: Open the dehumidification inlet and outlet valves, and start the dehumidifier to circulate and dry the mold. When the humidity of the gas inside the tank is less than 10%, close the inlet and outlet valves. Step 5: Open the vacuum pump valve and start the vacuum pump to reduce the pressure in the sealed cavity. When the pressure reaches 0.4 atm, open the argon valve and start the argon cylinder to introduce argon into the cavity to replace the air inside the cavity. When the pressure reaches 1 atm, close the argon valve. After standing for 20 minutes, open the oxygen content detection valve to detect the oxygen content at the end of the mold drying area. Before the oxygen content reaches the requirement of less than 3%, repeat step five; Step six: Open the sealed tank, transfer the pouring base plate and mold to the low-pressure pouring platform, and continuously introduce argon gas into the cavity while waiting for pouring, until the argon gas valve is closed just before pouring; Step seven: After the casting is poured and cooled to room temperature, remove the casting by sand removal; This method dries and dehumidifies the mold, expands the drying zone of the mold, reduces the area of ​​moisture condensation, and allows the resin binder to be heated when the molten metal enters the cavity. The gases generated during volatilization diffuse effectively through the drying zone before the casting forms a crust, thus effectively preventing porosity and defects in the casting. Simultaneously, this method deoxygenates the mold, reducing the oxygen content in the mold cavity and the gaps between sand grains in the drying zone to below 3%. Furthermore, by continuously introducing argon gas into the mold cavity after opening the sealed container and before pouring, the increase in oxygen content is minimized, effectively preventing the risk of deflagration caused by a violent chemical reaction between the molten alloy and oxygen. This method is particularly suitable for large, thin-walled magnesium alloy castings with high mass under low pressure. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart of the method for drying, dehumidifying, and deoxygenating a casting mold provided by the present invention.

[0031] Figure 2 This is a schematic diagram of the device for drying, dehumidifying, and deoxygenating the mold provided by the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1—Sealed tank body; 2—Supporting base plate; 3—Heater; 4—Vacuum pump; 5—Safety valve

[0034] 6—Argon cylinder; 7—Oxygen content detection device; 8—Oxygen content detection device; 9—Thermocouple; 10—Pressure gauge. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0036] Example 1. A method for drying, dehumidifying, and deoxidizing a casting mold, see [link to example]. Figure 1 ,include:

[0037] Step 1: Assemble the casting base plate and each mold on the support base plate, and evenly arrange two heaters around the mold.

[0038] Step 2: Secure the sealed tank body with pressure blocks, and obtain a sealed cavity by setting a sealing strip between the tank body and the supporting base plate;

[0039] Step 3: Turn on the heater and heat the ambient temperature inside the tank to 80°C and maintain it for the following durations: 3 hours for large molds, 2.5 hours for medium molds, and 1.5 hours for small molds. Dry the molds.

[0040] Step 4: Open the dehumidification inlet and outlet valves, start the dehumidifier to circulate and dry the mold. When the relative humidity inside the sealed tank is less than 10%, close the inlet and outlet valves.

[0041] Step 5: Open the vacuum pump valve and start the vacuum pump to depressurize the sealed cavity. When the pressure reaches 0.4 atm, open the argon valve and start the argon cylinder to introduce argon gas into the cavity to replace the air inside. When the pressure reaches 1 atm, close the argon valve and let it stand for 20 minutes. Then, open the oxygen content detection valve and detect the oxygen content at the end of the mold drying area. Repeat step 5 until the oxygen content reaches less than 3%.

[0042] Step 6: Open the sealed tank, transfer the pouring base plate and mold to the low-pressure pouring platform, and continuously introduce argon gas into the cavity while waiting for pouring. The argon gas valve can only be closed before pouring.

[0043] Step 7: After the casting is poured and cooled to room temperature, remove the casting by removing the sand.

[0044] Another aspect of the present invention provides an apparatus for drying, dehumidifying, and deoxygenating a casting mold, see [link to relevant documentation]. Figure 2 It can be used to achieve the above-mentioned methods for drying, dehumidifying, and deoxygenating the mold.

[0045] The device mainly includes: a sealed tank 1, a supporting base plate 2, a heater 3, a dehumidifier 4, a vacuum pump 5, a safety valve 6, an argon cylinder 7, an oxygen content detection device 8, a thermocouple 9, and a pressure gauge 10.

[0046] Example 2. Figure 1 This is a schematic diagram of the method for drying, dehumidifying, and deoxygenating the mold provided by the present invention. Figure 2 This is a schematic diagram of the device for drying, dehumidifying, and deoxygenating the mold provided by the present invention, with reference to... Figure 1 and Figure 2 The method for drying, dehumidifying, and deoxygenating a casting mold provided by the present invention includes:

[0047] Step 1: Assemble the casting base plate and each mold on the support base plate, and evenly arrange two heaters around the mold.

[0048] Step 2: Secure the sealed tank body with pressure blocks, and obtain a sealed cavity by setting a sealing strip between the tank body and the supporting base plate;

[0049] Step 3: Turn on the heater to heat the ambient temperature inside the tank to 80℃ and maintain it (maintaining time: 3 hours for large molds, 2.5 hours for medium molds, and 1.5 hours for small molds) to dry the molds;

[0050] Step 4: Open the dehumidification inlet and outlet valves, start the dehumidifier to circulate and dry the mold. When the humidity of the gas inside the tank is less than 10%, close the inlet and outlet valves.

[0051] Step 5: Open the vacuum pump valve and start the vacuum pump to reduce the pressure in the sealed cavity. When the pressure reaches 0.4 atm, open the argon valve and start the argon cylinder to introduce argon gas into the cavity to replace the air inside. When the pressure reaches 1 atm, close the argon valve and let it stand for 20 minutes. Then, open the oxygen content detection valve to detect the oxygen content at the end of the mold drying area. Repeat step 5 until the oxygen content reaches less than 3%.

[0052] Step 6: Open the sealed tank, transfer the pouring base plate and mold to the low-pressure pouring platform, and continuously introduce argon gas into the cavity while waiting for pouring. The argon gas valve can only be closed before pouring.

[0053] Step 7: After the casting is poured and cooled to room temperature, remove the casting by removing the sand.

[0054] Exemplary, the present invention provides a method for drying, dehumidifying, and deoxygenating a mold. First, the mold cavity is sealed after assembly. The ambient temperature inside the container is heated to 80°C and maintained continuously using a heater to dry the mold. Then, a dehumidifier is used to heat and dry the mold in the sealed environment until the humidity of the gas inside the container is less than 10%, at which point dehumidification is complete. Next, a vacuum pump is used to remove oxygen through gas replacement until the oxygen content at the end of the mold drying zone is less than 3%, at which point gas replacement is complete. The sealed container is opened, and the pouring base plate and mold are transferred to a low-pressure pouring platform. During the waiting period before pouring, argon gas is continuously introduced into the mold cavity until just before pouring, at which point the argon gas valve is closed. After the casting is poured and cooled to room temperature, the casting is removed by sand removal, cut, and cleaned to obtain a complete casting.

[0055] Example 3. To achieve the above-described method for drying, dehumidifying, and deoxygenating the mold, this invention provides an apparatus for drying, dehumidifying, and deoxygenating the mold. For example... Figure 2 As shown, the device includes: a sealed tank 1, a supporting base plate 2, a heater 3, a dehumidifier 4, a vacuum pump 5, a safety valve 6, an argon cylinder 7, an oxygen content detection device 8, a thermocouple 9, and a pressure gauge 10.

[0056] The sealed tank 1 and the supporting base plate 2 utilize end-face sealing blocks for locking to create a sealed cavity, facilitating drying, dehumidification, and deoxygenation of the sealed environment within the tank. The sealed tank 1 is equipped with a safety valve 6, a thermocouple 9, and a pressure gauge 10. The safety valve 6 ensures the tank operates normally. The thermocouple 9 monitors the tank temperature in real time. The pressure gauge 10 monitors the tank pressure in real time. The heater 3 is connected to an external power source via a pre-embedded wire on the supporting base plate. Turning on the heater 3 heats the tank environment to 80°C and maintains this temperature (3 hours for large molds, 2.5 hours for medium molds, and 1.5 hours for small molds), drying the molds. The dehumidifier 4 is connected to the sealed tank via ASME flange ball valves at the dehumidification inlet and outlet. Opening the dehumidifier allows for circulating drying and dehumidification of the molds within the sealed environment. Dehumidification ends when the relative humidity of the gas inside the tank is less than 10%. Vacuum pump 5 is connected to the sealed tank via an ASME flange ball valve. Starting the vacuum pump depressurizes the sealed cavity. Argon cylinder 7 is connected to the support base plate via an ASME flange ball valve for deoxygenation via gas replacement. Oxygen content detection device 8 is connected to the support base plate via an ASME flange ball valve to detect the oxygen content at the end of the mold drying zone. Gas replacement ends when the oxygen content at the end of the mold drying zone is less than 3%. The sealed tank is opened, and the pouring base plate and mold are transferred to the low-pressure pouring platform. During the waiting period before pouring, argon gas is continuously introduced into the cavity until just before pouring, at which point the argon gas valve is closed. After the casting is poured and cooled to room temperature, the casting is removed by sand removal, cut, and cleaned to obtain a complete casting.

[0057] Example 4. A method and apparatus for drying, dehumidifying, and deoxygenating a casting mold can significantly reduce the relative humidity of the casting environment, expand the drying area of ​​the mold, and improve the venting capacity of the mold, thereby effectively avoiding the occurrence of porosity and defects in the casting. Simultaneously, applying this method and apparatus can reduce the oxygen content of the combustion-supporting gas inside the mold cavity to a safe range of less than 3%. Furthermore, during the period from opening the sealed container to pouring (less than 1 hour), argon gas is continuously introduced into the mold cavity to minimize the increase in oxygen content, thus effectively avoiding the risk of deflagration caused by a violent chemical reaction between the alloy liquid and oxygen. Taking a magnesium alloy (WE43A) main casing casting as an example, under traditional casting methods, there are as many as 15 porosity areas exceeding level 3 on the casting, and the probability of the casting exploding reaches 16%. By adopting the technical solution of this invention, the combustion and explosion rate of the casting is reduced to 0, and the number of loose parts exceeding level 3 on the casting is reduced to 2. This shows that the method can effectively solve the problem of low-pressure casting explosion of large magnesium alloy castings, while improving the venting capacity of the mold and effectively avoiding the generation of loose and porosity defects.

[0058] This invention provides a method and apparatus for drying, dehumidifying, and deoxygenating casting molds, comprising: Step 1, assembling the casting base plate and each casting mold on a supporting base plate, and evenly arranging two heaters around the casting molds; Step 2, fastening the sealing tank and locking it with pressure blocks to obtain a sealed cavity; Step 3, turning on the heaters to heat the ambient temperature inside the tank to 80°C and maintaining it continuously (maintaining time: 3 hours for large castings, 2.5 hours for medium castings, and 1.5 hours for small castings) to dry the casting molds; Step 4, opening the dehumidifier... Step 5: Open the vacuum pump valve and start the vacuum pump to dehumidify the sealed cavity. When the pressure reaches 0.4 atm, open the argon valve and start the argon cylinder to introduce argon into the cavity to replace the air inside. When the pressure reaches 1 atm, close the argon valve and let it stand for 20 minutes. Then, open the oxygen content detection valve to detect the oxygen content at the end of the mold drying area. Repeat step 5 until the oxygen content reaches less than 3%. Step 6: Open the sealed tank and transfer the pouring base plate and mold to the low-pressure pouring platform. While waiting for pouring, continuously introduce argon into the cavity until just before pouring, then close the argon inlet valve. Step 7: After the casting is poured and cooled to room temperature, remove the casting by removing the sand. By drying and dehumidifying the mold, the drying zone is expanded, and the area of ​​moisture condensation is reduced. This allows the gases generated by the volatilization of the resin binder when the molten metal enters the mold cavity to diffuse effectively through the drying zone before the casting forms a crust, thus effectively preventing porosity and defects in the casting. Simultaneously, deoxygenation treatment of the mold reduces the oxygen content in the mold cavity and the gaps between sand grains in the drying zone to below 3%. Furthermore, by continuously introducing argon gas into the mold cavity after opening the sealed container and before pouring, the increase in oxygen content is minimized, effectively avoiding the risk of deflagration caused by a violent chemical reaction between the molten alloy and oxygen. This method is particularly suitable for large, thin-walled magnesium alloy castings with high mass under low pressure.

Claims

1. An apparatus for drying, dehumidifying and deoxygenating a mold, characterized by comprising: include: The system includes a sealed tank, a supporting base plate, a heater, a dehumidifier, a vacuum pump, a safety valve, an argon cylinder, an oxygen content detection device, thermocouples, and a pressure gauge. The sealed tank and supporting base plate utilize an end-face sealing block locking structure to form a sealed cavity. The sealed tank is equipped with a safety valve, thermocouples, and a pressure gauge. The safety valve ensures the normal operation of the tank; the thermocouples monitor the internal temperature in real time; and the pressure gauge monitors the internal pressure in real time. The heater is connected to an external power source via a pre-embedded sealed wire on the supporting base plate, allowing heating of the internal environment. The dehumidifier's inlet and outlet are connected to... The vacuum pump is also connected to the sealed tank. An argon cylinder is connected to an American standard flange ball valve on the support base plate for oxygen replacement. An oxygen content detection device is also connected to an American standard flange ball valve on the support base plate for detecting the oxygen content at the end of the mold drying zone. The sealed tank is opened, and the pouring base plate and mold are transferred to the low-pressure pouring platform. During the waiting period for pouring, argon gas is continuously introduced into the cavity until the argon gas valve is closed just before pouring. After the casting is poured and cooled to room temperature, the casting is removed by sand removal, cut and cleaned to obtain a complete casting.

2. A method of using the device according to claim 1, characterized in that, Includes the following steps: Step 1: Assemble the casting base plate and each mold on the supporting base plate, and evenly arrange two heaters around the mold; Step 2: Attach the sealing tank and lock it with pressure blocks, and obtain a sealed cavity by setting a sealing strip between the tank and the supporting base plate; Step 3: Turn on the heater to heat the ambient temperature inside the tank to 80℃ and maintain it for 1.5 to 3 hours to dry the mold; Step 4: Open the dehumidification inlet and outlet valves, start the dehumidifier to circulate and dry the mold. When the relative humidity inside the sealed tank is less than 10%, close the inlet and outlet valves. Step 5: Open the vacuum pump valve and start the vacuum pump to reduce the pressure in the sealed cavity. When the pressure reaches 0.4 atm, open the argon valve and start the argon cylinder to introduce argon into the cavity to replace the air inside. When the pressure reaches 1 atm, close the argon valve and let it stand for 20 minutes. Then, open the oxygen content detection valve and detect the oxygen content at the end of the mold drying area. Repeat step 5 until the oxygen content reaches less than 3%. Step 6: Open the sealed tank, transfer the pouring base plate and mold to the low-pressure pouring platform, and continuously introduce argon gas into the cavity while waiting for pouring, until the argon gas valve is closed just before pouring. Step 7: After the casting is poured and cooled to room temperature, remove the casting by removing the sand.

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