Magnesium alloy anti-gravity filling atmospheric pressure solidification device and solidification method using the same

Abstract

A magnesium alloy counter-gravity filling atmospheric pressure solidification device comprises a melting furnace (1), a crucible (2), a sealed furnace cover (3), a liquid riser (4), a gradient contact (6), a mold top contact (7), an open flame retardant mold (8) control cabinet (11), a pressure tank (12), etc. A magnesium alloy counter-gravity filling atmospheric pressure solidification method using the above-mentioned magnesium alloy counter-gravity filling atmospheric pressure solidification device comprises the following steps and contents in sequence: preparing an open flame retardant mold (8); pre-treatment of the open flame retardant mold (8) before filling; pre-treatment contents of smelting alloy; smelting alloy; counter-gravity pouring. The present invention can effectively solve the problem of burning and explosion in existing magnesium alloy sand casting, reduce oxidation in the process of magnesium alloy liquid filling and solidification, and has excellent technical effect.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium alloy casting, and in particular to a method and a device for solidifying a magnesium alloy by anti-gravity filling under atmospheric pressure. Background Art

[0002] In the field of casting technology, counter-gravity casting is a casting pouring process. It is a method to make the metal in the crucible flow upward along the riser under pressure to overcome gravity and other resistance to fill the mold and obtain the casting under pressure. The counter-gravity casting technology can extract pure alloy liquid from the middle of the crucible to smoothly fill the casting cavity, while solidifying the entire mold under the action of external force, thereby improving the quality of the casting.

[0003] One of the typical applications of anti-gravity casting is magnesium alloy castings. Magnesium alloys are chemically very active and are flammable and explosive at high temperatures. There have been many major safety accidents in China where magnesium alloy castings have burned and exploded during the casting process.

[0004] At present, sand mold anti-gravity casting technology has been widely used in the development and batch production of high-end aluminum and magnesium alloy castings in the fields of aviation, aerospace, and vehicles. However, the molds used for anti-gravity casting of various castings are all closed cavities, and the exhaust capacity of the molds is limited. During the pouring process, after the high-temperature magnesium alloy liquid contacts the sand mold, the air and resin curing agent inside the sand mold are decomposed by heat to produce a large amount of flammable gas that cannot be removed in time, resulting in a rapid increase in cavity pressure. High-pressure gas can easily penetrate into the magnesium alloy liquid, causing choking defects and preventing the casting from being fully formed. The alloy liquid is also very easy to react with flammable gases and air in the mold to oxidize and explode, posing a safety risk.

[0005] Therefore, there is an urgent need for a method to inhibit oxidation in magnesium alloy casting to solve the problem of oxidation and even combustion of magnesium alloys during anti-gravity casting, ensure production safety, and meet the needs of complete forming and quality control of complex structure castings. Summary of the invention

[0006] The invention provides a magnesium alloy counter-gravity filling and atmospheric pressure solidification device and a magnesium alloy counter-gravity filling and atmospheric pressure solidification method using the device (ie, a magnesium alloy counter-gravity filling casting method).

[0007] The technical solution of the present invention is:

[0008] A method and device for inhibiting the oxidation of the melt during the anti-gravity filling solidification process of a magnesium alloy, the key technology of which is: it comprises a smelting furnace 1, a crucible 2, a sealed furnace cover 3, a riser 4, a molten metal cut-off device 5, a gradient contact 6, a mold top contact 7, an open flame-retardant mold 8, a mold gas replacement device 9, a flame retardant spraying device 10, a control cabinet 11, and a pressure tank 12; wherein:

[0009] A crucible 2 is placed in the smelting furnace 1, an air inlet valve and an exhaust valve are installed on the furnace body of the smelting furnace 1, a sealing furnace cover 3 is installed above the smelting furnace, and a graphite packing sealing structure or an asbestos packing sealing structure is arranged between the sealing cover 3 and the flange sealing groove in the smelting furnace 1;

[0010] The riser pipe 4 is installed at the center of the sealed furnace cover 3. The flange bottom surface of the riser pipe 4 and the center of the sealed furnace cover 3 are connected and sealed by bolts, and an asbestos pad is placed between the two.

[0011] The open flame retardant casting mold 8 is arranged above the sealed furnace cover 3, and an asbestos pad is also placed between the bottom of the open flame retardant casting mold 8 and the upper plane of the flange of the riser 4, and the open flame retardant casting mold 8 is sealed by its own weight or by placing a heavy object on the open flame retardant casting mold 8 to press it tightly;

[0012] The open riser top surface of the open flame retardant casting mold 8 is provided with a mold top contact 7, a separate slot runner is provided inside the open flame retardant casting mold 8, the separate slot runner is connected to the mold cavity and the riser of the open flame retardant casting mold 8, and 3 to 20 gradient contacts are provided on the side wall of the separate slot runner, all of which are arranged in a gradient manner at the same height, and the interval height is 10 to 200 mm;

[0013] One end of the pressure tank 12 is an air inlet connected to the mixed gas pressurizing device, and the other end is an air outlet connected to the air inlet valve of the smelting furnace 1. The pressure tank 12 is filled with mixed protective gas; the pressure in the tank is 0.4-2.0MPa;

[0014] The control cabinet 11 is connected to the air inlet valve and the exhaust valve of the smelting furnace 1 so as to receive the signals of the internal gradient contact 6 and the mold top contact 7 of the open flame-retardant casting mold 8 in real time, adjust the opening of the air inlet valve and the exhaust valve, and control the pressure in the furnace.

[0015] The method and device for inhibiting melt oxidation during the anti-gravity filling and solidification process of magnesium alloys described in the present invention preferably also include the following technical contents:

[0016] A molten metal cutoff device 5 is also provided between the open flame-retardant mold 8 and the sealed furnace cover 3 in the magnesium alloy anti-gravity filling and solidification process to inhibit melt oxidation. The molten metal cutoff device 5 is a rectangular steel plate with holes on the steel plate that allow the molten metal to pass through. When the molten metal fills the mold cavity, the steel plate can be pushed horizontally into the mold to cut off the passage of the molten metal in the mold.

[0017] In the magnesium alloy anti-gravity filling and solidification device under atmospheric pressure, a separate slot runner is arranged inside the open flame-retardant casting mold 8, and the separate slot runner is connected to the cavity and riser of the open flame-retardant casting mold 8. 3 to 20 gradient contacts are arranged on the side wall of the separate slot runner, all of which are arranged in a gradient at the same height, and the interval height is 10 to 200 mm.

[0018] The device for suppressing the oxidation of the melt during the anti-gravity filling and solidification process of the magnesium alloy is also provided with a mold gas replacement device 9 and a flame retardant spraying device 10; wherein:

[0019] The spraying outlet of the flame retardant spraying device 10 is arranged correspondingly at the flame retardant inlet on the upper part of the open flame retardant casting mold 8;

[0020] Before the open flame-retardant casting mold 8 is filled with casting, the casting mold is first placed in the gas replacement device 9. The gas replacement device 9 uses a closed tank body to wrap the open flame-retardant casting mold 8 and is provided with a negative pressure exhaust and a positive pressure air inlet; so that the open flame-retardant casting mold 8 can be evacuated of negative pressure as a whole, the air in the open flame-retardant casting mold 8 can be removed, and then flame-retardant gas can be introduced into the casting mold.

[0021] The device for suppressing oxidation of the melt during the anti-gravity filling and solidification process of the magnesium alloy is also provided with a structure capable of introducing compressed gas into the smelting furnace 1 and controlling the pressure and input amount of the introduced gas;

[0022] These structures meet the following requirements: the alloy liquid can be transported along the riser 4 to the inside of the open flame-retardant casting mold 8; when the alloy liquid level inside the casting mold reaches the corresponding height, each gradient contact 6 can be connected in sequence, and an electrical signal can be sent to the control cabinet 11, so that the control cabinet 11 can timely adjust the air pressure in the smelting furnace 1 as required, and continuously reduce the filling speed of the alloy liquid inside the open flame-retardant casting mold 8; when the metal liquid reaches the top of the casting mold, it is required to control the metal liquid filling speed to close to 0, and use the metal liquid cut-off device 5 to cut off the metal liquid at the bottom of the open flame-retardant casting mold 8, so that the alloy liquid can finally stay stably in the area of ​​the mold top contact 7 until the casting solidifies.

[0023] The present invention also claims a method for inhibiting melt oxidation during the anti-gravity filling solidification process of a magnesium alloy, which comprises the following steps and contents in sequence:

[0024] Step 1: Prepare an open flame retardant mold 8

[0025] When preparing the open flame-retardant casting mold 8, 1-12% of flame retardant is mixed into the resin sand; when the open flame-retardant casting mold 8 is filled and solidified, it can decompose flame-retardant gas, thereby diluting the combustible gas decomposed by the resin sand casting mold when heated, and reducing the oxidation combustion of the magnesium alloy;

[0026] Step 2: Pretreatment of open flame retardant mold 8 before filling

[0027] Before filling the open flame-retardant mold 8, first place the open flame-retardant mold 8 in the mold gas replacement device 9, and evacuate the entire open flame-retardant mold 8 to a negative pressure of -1 to -10 KPa; remove the air in the open flame-retardant mold 8, and then introduce a flame-retardant gas into the open flame-retardant mold 8 at a positive pressure of 1 to 10 KPa; so as to replace the air in the mold with the flame-retardant gas; and take the open flame-retardant mold 8 out of the mold gas replacement device 9;

[0028] Step 3: Pre-treatment of smelting alloy

[0029] The open flame-retardant mold 8 pretreated in step 2 is placed above the sealed furnace cover 3 above the smelting furnace 1, and a molten metal cut-off device 5 is pre-arranged between the open flame-retardant mold 8 and the sealed furnace cover 3, and the reserved hole in the molten metal cut-off device 5 that allows the molten metal to pass through is placed on the passage connecting the riser pipe 4 and the liquid filling channel in the open flame-retardant mold 8, so that the riser pipe 4 and the liquid filling channel in the open flame-retardant mold 8 can be connected;

[0030] Step 4: Melting the alloy

[0031] First, take the dried magnesium alloy ingot and put it into the crucible. When the alloy ingot reaches 450℃, the furnace automatically supplies protective gas, which is SF6 and CO. 2 ; When the temperature of the melt rises to above 650℃, sprinkle a protective solvent onto the surface of the magnesium alloy melt according to the type of alloy and the alloy liquid level; after the charge is melted, add the preheated intermediate alloy at 700-740℃; when the alloy melt temperature reaches 730-780℃, refine the alloy. After refining, let it stand for 30min-60min, adjust the melt temperature to the pouring temperature, and wait for casting.

[0032] Step 5: Anti-gravity pouring

[0033] Compressed gas is introduced into the smelting furnace 1 and the pressure and input amount of the gas are controlled; the alloy liquid is transported to the inside of the open flame-retardant casting mold 8 along the liquid riser 4, and when the alloy liquid level inside the open flame-retardant casting mold 8 reaches the corresponding height, each gradient contact 6 can be connected in turn, and an electrical signal is sent to the control cabinet 11, so that the control cabinet 11 can timely adjust the air pressure in the smelting furnace 1 as required, and continuously reduce the filling speed of the alloy liquid inside the open flame-retardant casting mold 8;

[0034] When the molten metal reaches the top of the open flame-retardant casting mold 8, it is required to control the molten metal filling speed to close to 0, and use the molten metal cut-off device 5 to cut off the molten metal at the bottom of the open flame-retardant casting mold 8, so that the alloy liquid can be stably retained in the mold top contact point 7 area until the casting solidifies;

[0035] The magnesium alloy anti-gravity filling and atmospheric pressure solidification method preferably further comprises the following requirements:

[0036] During the counter-gravity pouring process, when the alloy liquid reaches the top of the riser, a solid flame retardant is sprayed onto the surface of the molten metal to prevent and eliminate surface oxidation and combustion of the casting riser in contact with the atmosphere.

[0037] The solid flame retardant composition is 30% to 40% anhydrous magnesium chloride, 30% to 40% potassium chloride, and 40% to 20% barium chloride. The solid flame retardant powder is dehydrated and dried before use. The solid flame retardant uses low-melting-point inorganic compounds to melt into liquid at low temperatures, spread on the surface of magnesium alloy castings to form a continuous and complete covering layer, isolating the air and thus playing a protective role.

[0038] The beneficial effects of the present invention are:

[0039] The method and device for inhibiting the oxidation of the melt during the anti-gravity filling and solidification process of the magnesium alloy of the present invention can effectively solve the problem that the existing magnesium alloy sand casting is prone to combustion and explosion. By introducing a flame-retardant gas into the mold before casting, the air in the mold is discharged, and the oxidation of the magnesium alloy liquid during the filling and solidification process is reduced. Based on the anti-gravity casting method, the magnesium alloy liquid is filled into the open mold from bottom to top. When the alloy liquid level inside the mold reaches the corresponding height, each gradient contact is connected in sequence, and the control cabinet adjusts the air pressure in the smelting furnace to continuously reduce the filling speed of the alloy liquid inside the mold. When the alloy liquid reaches the top of the mold, the metal liquid at the bottom of the mold is cut off by a cut-off device, and finally the alloy liquid is stably retained in the contact area at the top of the mold. After the casting is completed, the alloy is cooled and solidified under atmospheric pressure, and a flame retardant is sprayed on the surface of the metal liquid to prevent and eliminate the surface oxidation and combustion of the casting in contact with the atmosphere. The casting equipment comprises the smelting furnace, crucible, sealed furnace cover, riser, molten metal cut-off device, gradient contact, mold top contact, open flame retardant mold, mold gas replacement device, flame retardant spraying device, control cabinet, and pressure tank. The present invention is particularly suitable for magnesium alloy sand casting, and has excellent technical effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram showing the composition principle of Example 1;

[0041] Figure 2 A schematic diagram of the use principle of the mold gas replacement device 9;

[0042] Figure 3 It is a molten metal cutting device 5. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the embodiments and the accompanying drawings, but is not limited thereto.

[0044] Example 1

[0045] A magnesium alloy anti-gravity filling and atmospheric pressure solidification device, such as Figure 1-Figure 3 As shown; the key technology is: it includes a smelting furnace 1, a crucible 2, a sealed furnace cover 3, a riser 4, a molten metal cut-off device 5, a gradient contact 6, a mold top contact 7, an open flame retardant mold 8, a mold gas replacement device 9, a flame retardant spraying device 10, a control cabinet 11, and a pressure tank 12; wherein:

[0046] A crucible 2 is placed in the smelting furnace 1. An air inlet valve and an exhaust valve are installed on the furnace body of the smelting furnace 1. A sealing furnace cover 3 is installed above the smelting furnace. A packing sealing structure of a magnesium alloy anti-gravity filling solidification process suppressing melt oxidation device is arranged between the sealing cover and the flange sealing groove in the smelting furnace 1.

[0047] The riser pipe 4 is installed at the center of the sealed furnace cover 3. The flange bottom surface of the riser pipe 4 and the center of the sealed furnace cover 3 are connected and sealed by bolts, and an asbestos pad is placed between the two.

[0048] The open flame retardant casting mold 8 is arranged above the sealed furnace cover 3, and an asbestos pad is also placed between the bottom of the open flame retardant casting mold 8 and the upper plane of the flange of the riser 4, and the open flame retardant casting mold 8 is sealed by its own weight or by placing a heavy object on the open flame retardant casting mold 8 to press it tightly;

[0049] The open riser top surface of the open flame retardant casting mold 8 is provided with a mold top contact 7, a separate slot runner is provided inside the open flame retardant casting mold 8, the separate slot runner is connected to the mold cavity and the riser of the open flame retardant casting mold 8, and 3 to 20 gradient contacts are provided on the side wall of the separate slot runner, all of which are arranged in a gradient manner at the same height, and the interval height is 10 to 200 mm;

[0050] One end of the pressure tank 12 is an air inlet connected to the mixed gas pressurizing device, and the other end is an air outlet connected to the air inlet valve of the smelting furnace 1. The pressure tank 12 is filled with mixed protective gas; the pressure in the tank is 0.4-2.0MPa;

[0051] The control cabinet 11 is connected to the air inlet valve and the exhaust valve of the smelting furnace 1 so as to receive the signals of the internal gradient contact 6 and the mold top contact 7 of the open flame-retardant casting mold 8 in real time, adjust the opening of the air inlet valve and the exhaust valve, and control the pressure in the furnace.

[0052] A molten metal cutoff device 5 is also provided between the open flame-retardant mold 8 and the sealed furnace cover 3 in the magnesium alloy anti-gravity filling and solidification device under atmospheric pressure. The molten metal cutoff device 5 is a rectangular steel plate with holes on the steel plate that allow the molten metal to pass through. When the molten metal fills the mold cavity, the steel plate can be pushed horizontally into the mold to cut off the passage of the molten metal in the mold.

[0053] In the magnesium alloy anti-gravity filling and solidification device under atmospheric pressure, a separate slot runner is arranged inside the open flame-retardant casting mold 8, and the separate slot runner is connected to the cavity and riser of the open flame-retardant casting mold 8. 3 to 20 gradient contacts are arranged on the side wall of the separate slot runner, all of which are arranged in a gradient at the same height, and the interval height is 10 to 200 mm.

[0054] The magnesium alloy anti-gravity filling and solidification device under atmospheric pressure is also provided with a mold gas replacement device 9 and a flame retardant spraying device 10; wherein:

[0055] The spraying outlet of the flame retardant spraying device 10 is arranged correspondingly at the flame retardant inlet on the upper part of the open flame retardant casting mold 8;

[0056] Before the open flame-retardant casting mold 8 is filled with casting, the casting mold is first placed in the gas replacement device 9. The gas replacement device 9 uses a closed tank body to wrap the open flame-retardant casting mold 8 and is provided with a negative pressure exhaust and a positive pressure air inlet; so that the open flame-retardant casting mold 8 can be evacuated of negative pressure as a whole, the air in the open flame-retardant casting mold 8 can be removed, and then flame-retardant gas can be introduced into the casting mold.

[0057] The magnesium alloy anti-gravity filling atmospheric pressure solidification device is also provided with a structure capable of introducing compressed gas into the smelting furnace 1 and controlling the pressure and input amount of the introduced gas;

[0058] These structures meet the following requirements: the alloy liquid can be transported along the riser 4 to the inside of the open flame-retardant casting mold 8; when the alloy liquid level inside the casting mold reaches the corresponding height, each gradient contact 6 can be connected in sequence, and an electrical signal can be sent to the control cabinet 11, so that the control cabinet 11 can timely adjust the air pressure in the smelting furnace 1 as required, and continuously reduce the filling speed of the alloy liquid inside the open flame-retardant casting mold 8; when the metal liquid reaches the top of the casting mold, it is required to control the metal liquid filling speed to close to 0, and use the metal liquid cut-off device 5 to cut off the metal liquid at the bottom of the open flame-retardant casting mold 8, so that the alloy liquid can finally stay stably in the area of ​​the mold top contact 7 until the casting solidifies.

[0059] Example 2

[0060] The method for solidifying a magnesium alloy under atmospheric pressure by using the magnesium alloy counter-gravity filling and atmospheric pressure solidification device described in Example 1 comprises the following steps and contents in sequence:

[0061] Step 1: Prepare an open flame retardant mold 8

[0062] When preparing the open flame-retardant mold 8, 1 to 12% of flame retardant is mixed into the resin sand; when the open flame-retardant mold 8 is filled and solidified, it can decompose flame-retardant gas, thereby diluting the combustible gas decomposed by the resin sand mold under heat, and reducing the oxidation combustion of the magnesium alloy;

[0063] Step 2: Pretreatment of open flame retardant mold 8 before filling

[0064] Before filling the open flame-retardant mold 8, first place the open flame-retardant mold 8 in the mold gas replacement device 9, and evacuate the entire open flame-retardant mold 8 to a negative pressure of -1 to -10 KPa; remove the air in the open flame-retardant mold 8, and then introduce a flame-retardant gas into the open flame-retardant mold 8 at a positive pressure of 1 to 10 KPa; so as to replace the air in the mold with the flame-retardant gas; and take the open flame-retardant mold 8 out of the mold gas replacement device 9;

[0065] Step 3: Pre-treatment of smelting alloy

[0066] The open flame-retardant mold 8 pretreated in step 2 is placed above the sealed furnace cover 3 above the smelting furnace 1, and a molten metal cut-off device 5 is pre-arranged between the open flame-retardant mold 8 and the sealed furnace cover 3, and the reserved hole in the molten metal cut-off device 5 that allows the molten metal to pass through is placed on the passage connecting the riser pipe 4 and the liquid filling channel in the open flame-retardant mold 8, so that the riser pipe 4 and the liquid filling channel in the open flame-retardant mold 8 can be connected;

[0067] Step 4: Melting the alloy

[0068] First, take the dried magnesium alloy ingot and put it into the crucible. When the alloy ingot reaches 450℃, the furnace automatically supplies protective gas, which is SF6 and CO. 2 . When the temperature of the melt reaches 650℃, sprinkle the protective solvent on the surface of the magnesium alloy melt. After the charge is melted, add the preheated Al-Mn master alloy, zinc ingot, and pure aluminum ingot at 700-730℃. When the alloy melt temperature reaches 730-760℃, the alloy is refined with magnesite. After the refining is completed, let it stand for 30-60 minutes, and adjust the melt temperature to the pouring temperature before waiting for casting.

[0069] Step 5: Anti-gravity pouring

[0070] Compressed gas is introduced into the smelting furnace 1 and the pressure and input amount of the gas are controlled; the alloy liquid is transported to the inside of the open flame-retardant casting mold 8 along the liquid riser 4, and when the alloy liquid level inside the open flame-retardant casting mold 8 reaches the corresponding height, each gradient contact 6 can be connected in turn, and an electrical signal is sent to the control cabinet 11, so that the control cabinet 11 can timely adjust the air pressure in the smelting furnace 1 as required, and continuously reduce the filling speed of the alloy liquid inside the open flame-retardant casting mold 8;

[0071] When the molten metal reaches the top of the open flame-retardant casting mold 8, it is required to control the molten metal filling speed to close to 0, and use the molten metal cut-off device 5 to cut off the molten metal at the bottom of the open flame-retardant casting mold 8, so that the alloy liquid can be stably retained in the mold top contact point 7 area until the casting solidifies;

[0072] The magnesium alloy anti-gravity filling and atmospheric pressure solidification method preferably further comprises the following requirements:

[0073] During the counter-gravity pouring process, when the alloy liquid reaches the top of the riser, a solid flame retardant is sprayed onto the surface of the molten metal to prevent and eliminate surface oxidation and combustion of the casting riser in contact with the atmosphere.

[0074] The preferred solid flame retardant composition is 35% anhydrous magnesium chloride, 35% potassium chloride, and 30% barium chloride. The solid flame retardant powder is dehydrated and dried before use. The solid flame retardant uses low-melting-point inorganic compounds to melt into liquid at low temperatures, spread on the surface of the magnesium alloy casting to form a continuous and complete covering layer, isolating the air, thereby playing a protective role.

[0075] The method and device for solidifying magnesium alloy under atmospheric pressure by anti-gravity filling can effectively solve the problem of burning and explosion in existing magnesium alloy sand casting. By introducing flame-retardant gas into the mold before casting, the air in the mold is discharged to reduce the oxidation of magnesium alloy liquid during filling and solidification. Based on the anti-gravity casting method, the magnesium alloy liquid is filled into the open mold from bottom to top. When the alloy liquid level inside the mold reaches the corresponding height, each gradient contact is connected in sequence, and the control cabinet adjusts the air pressure in the smelting furnace to continuously reduce the filling speed of the alloy liquid inside the mold. When the alloy liquid reaches the top of the mold, the metal liquid at the bottom of the mold is cut off by a cut-off device, and finally the alloy liquid is stably retained in the contact area at the top of the mold. After the casting is completed, the alloy is cooled and solidified under atmospheric pressure, and a flame retardant is sprayed on the surface of the metal liquid to prevent and eliminate the surface oxidation and combustion of the casting in contact with the atmosphere. The casting equipment comprises the smelting furnace, crucible, sealed furnace cover, riser, molten metal cut-off device, gradient contact, mold top contact, open flame retardant mold, mold gas replacement device, flame retardant spraying device, control cabinet, and pressure tank. The present invention is particularly suitable for magnesium alloy sand casting.

Claims

1. Magnesium alloy anti-gravity filling and solidification device under atmospheric pressure, characterized by: It comprises a smelting furnace (1), a crucible (2), a sealed furnace cover (3), a liquid riser (4), a molten metal cut-off device (5), a gradient contact (6), a mold top contact (7), an open flame-retardant mold (8), a mold gas replacement device (9), a flame retardant spraying device (10), a control cabinet (11), and a pressure tank (12); wherein: A crucible (2) is placed in a smelting furnace (1), an air inlet valve and an exhaust valve are installed on the furnace body of the smelting furnace (1), a sealing furnace cover (3) is installed above the smelting furnace, and a graphite packing sealing structure or an asbestos packing sealing structure is arranged between the sealing cover and the flange sealing groove in the smelting furnace (1); The liquid riser (4) is installed at the center of the sealed furnace cover (3), the flange bottom surface of the liquid riser (4) and the center of the sealed furnace cover (3) are connected and sealed by bolts, and an asbestos pad is placed between the two; The open flame-retardant casting mold (8) is arranged above the sealed furnace cover (3), and an asbestos pad is also placed between the bottom of the open flame-retardant casting mold (8) and the upper plane of the flange of the riser (4), and the open flame-retardant casting mold (8) is sealed by its own weight or by placing a heavy object on the open flame-retardant casting mold (8) to press tightly; The open riser top surface of the open flame retardant casting mold (8) is provided with a mold top contact (7); a separate slot type runner is provided inside the open flame retardant casting mold (8); the separate slot type runner is connected to the mold cavity and the riser of the open flame retardant casting mold (8); 3 to 20 gradient contacts are provided on the side wall of the separate slot type runner, all of which are arranged in a gradient manner at the same height, and the spacing height is 10 to 200 mm; One end of the pressure tank (12) is an air inlet connected to the mixed gas pressurizing device, and the other end is an air outlet connected to the air inlet valve of the smelting furnace (1). The pressure tank (12) is filled with mixed protective gas; the pressure in the tank is 0.4-2.0 MPa; The control cabinet (11) is connected to the air inlet valve and the exhaust valve of the smelting furnace (1) so as to receive the signals of the internal gradient contact (6) and the mold top contact (7) of the open flame-retardant casting mold (8) in real time, adjust the opening of the air inlet valve and the exhaust valve, and control the pressure in the furnace.

2. The magnesium alloy anti-gravity filling and atmospheric pressure solidification device according to claim 1, characterized in that: A molten metal cut-off device (5) is also provided between the open flame-retardant casting mold (8) and the sealed furnace cover (3) in the magnesium alloy anti-gravity filling and solidification device under atmospheric pressure. The molten metal cut-off device (5) is a rectangular steel plate, and holes are provided on the steel plate to allow the molten metal to pass through. When the molten metal fills the mold cavity, the steel plate can be pushed horizontally into the casting mold to cut off the passage of the molten metal in the casting mold.

3. The magnesium alloy anti-gravity filling and atmospheric pressure solidification device according to claim 2, characterized in that: In the magnesium alloy anti-gravity filling and solidification device under atmospheric pressure, a separate slit runner is arranged inside the open flame-retardant casting mold (8), and the separate slit runner is connected to the mold cavity and the riser of the open flame-retardant casting mold (8). 3 to 20 gradient contacts are arranged on the side wall of the separate slit runner, all of which are arranged in a gradient manner at the same height, and the interval height is 10 to 200 mm.

4. The magnesium alloy anti-gravity filling and atmospheric pressure solidification device according to claim 3, characterized in that: The magnesium alloy anti-gravity filling and atmospheric pressure solidification device is also provided with a mold gas replacement device (9) and a flame retardant spraying device (10); wherein: The spraying outlet of the flame retardant spraying device (10) is arranged correspondingly at the flame retardant inlet at the upper part of the open flame retardant casting mold (8); Before the open flame-retardant casting mold (8) is filled with a casting mold, the casting mold is first placed in a gas replacement device (9). The gas replacement device (9) uses a closed tank body to wrap the open flame-retardant casting mold (8) and is provided with a negative pressure exhaust and a positive pressure air inlet, so that the open flame-retardant casting mold (8) can be evacuated with negative pressure as a whole, the air in the open flame-retardant casting mold (8) can be removed, and then flame-retardant gas can be introduced into the casting mold.

5. The magnesium alloy anti-gravity filling atmospheric pressure solidification device according to any one of claims 1 to 4, characterized in that: The magnesium alloy anti-gravity filling and atmospheric pressure solidification device is also provided with a structure capable of introducing compressed gas into the smelting furnace (1) and controlling the pressure and input amount of the introduced gas; These structures meet the following requirements: the alloy liquid can be transported along the liquid riser (4) to the inside of the open flame-retardant casting mold (8); when the alloy liquid level inside the casting mold reaches a corresponding height, each gradient contact (6) can be connected in sequence, and an electrical signal can be sent to the control cabinet (11), so that the control cabinet (11) can timely adjust the air pressure in the smelting furnace (1) as required, and continuously reduce the filling speed of the alloy liquid inside the open flame-retardant casting mold (8); When the molten metal reaches the top of the mold, it is required to control the filling speed of the molten metal to be close to 0, and use a molten metal cut-off device (5) to cut off the molten metal at the bottom of the open flame-retardant mold (8), so that the alloy liquid can finally stay stably in the mold top contact point (7) area until the casting solidifies.

6. A method for solidifying a magnesium alloy under counter-gravity filling and atmospheric pressure using the magnesium alloy counter-gravity filling and atmospheric pressure solidification device according to claim 1, characterized in that: The magnesium alloy anti-gravity filling and atmospheric pressure solidification method comprises the following steps and contents in sequence: Step 1: Preparation of open flame retardant casting mold (8) When preparing the open flame-retardant casting mold (8), 1-12% of a flame retardant is mixed into the resin sand; when the open flame-retardant casting mold (8) is filled and solidified, it can decompose a flame-retardant gas, thereby diluting the combustible gas decomposed by the resin sand casting mold when heated, thereby reducing the oxidation combustion of the magnesium alloy; Step 2: Pretreatment of the open flame retardant mold (8) before filling Before filling the open flame-retardant casting mold (8), the open flame-retardant casting mold (8) is first placed in a casting mold gas replacement device (9), and the open flame-retardant casting mold (8) is evacuated to a negative pressure of -1 to -10 KPa as a whole; air in the open flame-retardant casting mold (8) is removed, and then flame-retardant gas is introduced into the open flame-retardant casting mold (8) at a positive pressure of 1 to 10 KPa; the air in the casting mold is replaced by flame-retardant gas; and the open flame-retardant casting mold (8) is taken out of the casting mold gas replacement device (9); Step 3: Pre-treatment of smelting alloy The open flame-retardant casting mold (8) pretreated in step 2 is placed above the sealed furnace cover (3) above the smelting furnace (1), and a molten metal cut-off device (5) is pre-arranged between the open flame-retardant casting mold (8) and the sealed furnace cover (3), and a hole reserved in the molten metal cut-off device (5) that allows the molten metal to pass through is placed on the passage between the riser pipe (4) and the liquid filling channel in the open flame-retardant casting mold (8), so that the riser pipe (4) and the liquid filling channel in the open flame-retardant casting mold (8) can be connected; Step 4: Melting the alloy First, take the dried magnesium alloy ingot and put it into the crucible. When the alloy ingot reaches 450℃, the furnace automatically supplies protective gas, which is SF6 and CO. 2； When the temperature of the melt rises to above 650℃, a protective solvent is sprinkled onto the surface of the magnesium alloy melt according to the type of alloy and the alloy liquid level. After the charge is melted, the preheated intermediate alloy is added at 700-740℃. When the temperature of the alloy melt reaches 730-760℃, the alloy is refined. After the refining is completed, the alloy is left to stand for 30-60 minutes, and the melt temperature is adjusted to the pouring temperature before waiting for casting. Step 5: Anti-gravity pouring Compressed gas is introduced into the smelting furnace (1) and the pressure and input amount of the introduced gas are controlled; the alloy liquid is transported along the liquid riser (4) to the inside of the open flame-retardant casting mold (8); when the alloy liquid level inside the open flame-retardant casting mold (8) reaches a corresponding height, each gradient contact (6) can be connected in sequence, and an electrical signal is sent to the control cabinet (11), so that the control cabinet (11) can timely adjust the gas pressure in the smelting furnace (1) as required, and continuously reduce the filling speed of the alloy liquid inside the open flame-retardant casting mold (8); When the molten metal reaches the top of the open flame-retardant casting mold (8), it is required to control the molten metal filling speed to close to 0, and use a molten metal cut-off device (5) to cut off the molten metal at the bottom of the open flame-retardant casting mold (8), so that the alloy liquid can finally stay stably in the mold top contact point (7) area until the casting solidifies.

7. The method for solidifying magnesium alloy by counter-gravity filling under atmospheric pressure according to claim 6, characterized in that: During the counter-gravity pouring process, when the alloy liquid reaches the top of the riser, a solid flame retardant is sprayed onto the surface of the molten metal to prevent and eliminate surface oxidation and combustion of the casting riser in contact with the atmosphere.

8. The method for solidifying magnesium alloy under atmospheric pressure by using the device for solidifying magnesium alloy under atmospheric pressure by using the device for solidifying magnesium alloy under atmospheric pressure by using the device for solidifying magnesium alloy under atmospheric pressure by using the counter-gravity filling method according to claim 6 or 7, characterized in that: The solid flame retardant composition is 30% to 40% anhydrous magnesium chloride, 30% to 40% potassium chloride, and 40% to 20% barium chloride; Dehydrate and dry the solid flame retardant powder before use; Solid flame retardants use low-melting-point inorganic compounds to melt into liquid at low temperatures, spread on the surface of magnesium alloy castings to form a continuous and complete covering layer, isolating the air and thus playing a protective role.

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