Die casting mold

Abstract

A die casting mold, comprising: a fixed half, wherein the fixed half comprises a first mold base, a first mold plate, and a gate; and a movable half, wherein the movable half comprises a second mold base and a second mold plate, and the second mold plate is provided with a second mold cavity and a second mold core located at the center of the second mold cavity. The second mold core is of a shell-like structure having an open bottom, a quenching device is arranged below the movable half, and the quenching device is assembled such that when the movable half is separated from the fixed half, the quenching device is capable of cooling the second mold core to make the second mold core contract. In the die casting mold, after the mold is opened, the quenching device can be used to cool the second mold core to enable controllable contraction of the second mold core, thereby reducing the friction between the second mold core and the inner wall of a target part, facilitating demolding of the target part, improving the production efficiency, and reducing the production costs.

Description

Die casting mold TECHNICAL FIELD

[0001] The present application belongs to the technical field of die casting molding of electronic parts, and particularly relates to a die casting mold. BACKGROUND

[0002] In the die casting process, a mold core needs to be arranged to form the center hole of the part. However, during the cooling and solidification process of the part, a certain shrinkage will occur, which will cause a large holding force between the part and the mold core. This holding force will cause the part to be difficult to demold. To solve the above problem, the existing technology generally designs a certain draft angle on the inner wall of the part. However, the setting of the draft angle will cause the inner wall of the part to be conical, which may not be the shape required by the part. Therefore, mechanical processing of the inner wall is still needed after die casting, which is a complicated process, prolongs the manufacturing cycle, and increases the manufacturing and transportation costs. Another solution is to set the mold core as a multi-petal structure. After die casting, each mold petal is driven to shrink to separate the mold core from the part. However, this method will produce excess parting lines on the inner wall of the part, which also needs to be trimmed by machining. Another technical solution is to use an ejection rod to exert a large pushing force on the part to force demolding. This method will cause wear to the mold by the part, and is not suitable for thin-walled parts, otherwise it will cause deformation and scrap of the thin-walled part. SUMMARY

[0003] In view of the above-mentioned shortcomings of the prior art, the present application aims to provide a die casting mold which can facilitate the demolding of deep cylindrical parts.

[0004] To achieve the above-mentioned and other related purposes, the present application provides a die casting mold for die casting a target part, the target part comprising a cylindrical portion, the cylindrical portion having a flange extending radially outward at one end, the die casting mold comprising:

[0005] a fixed mold, the fixed mold comprising a first mold base, a first mold plate, and a sprue, the first mold plate being provided with a first mold cavity and a first mold core at the center of the first mold cavity, the first mold cavity being in communication with the sprue;

[0006] a movable mold, located below the fixed mold and movably arranged up and down relative to the fixed mold, the movable mold comprising a second mold base and a second mold plate, the second mold plate being provided with a second mold cavity and a second mold core at the center of the second mold cavity; when the movable mold is closed with the fixed mold, the first mold cavity, the second mold cavity, the first mold core, and the second mold core form a mold cavity matching the shape of the target part;

[0007] The second mold core is a shell-shaped structure with an open bottom, and the movable mold is provided with a quenching device below, which is configured to cool the second mold core when the movable mold is separated from the fixed mold, so that the second mold core shrinks.

[0008] In an optional embodiment of the present application, the quenching device comprises a liquid nitrogen spray head mounted above a fixed base, which is configured to protrude into the second mold core when the movable mold is lowered to a first preset height relative to the fixed mold; the liquid nitrogen spray head is in communication with a liquid nitrogen storage tank through a pipeline, and a stop valve is arranged on the pipeline.

[0009] In an optional embodiment of the present application, the movable mold is provided with a stripper rod movably connected to the second mold base and the second mold plate in the vertical direction, and a plurality of stripper rods are provided, and the upper ends of at least some of the stripper rods are arranged corresponding to the flanges of the target parts.

[0010] In an optional embodiment of the present application, a first linkage mechanism is arranged between the movable mold and the fixed base, which is configured to drive the stop valve to open and apply a preset size of jacking force to the stripper rod when the movable mold is lowered to the first preset height, and to drive the stop valve to close when the stripper rod lifts the target part under the action of the jacking force.

[0011] In an optional embodiment of the present application, the stop valve is a press-type stop valve, the first linkage mechanism comprises a floating plate movably connected to the fixed base in the vertical direction and a first compression spring arranged between the floating plate and the fixed base, and the first compression spring is configured to drive the floating plate to move upward by its elastic force; the upper end of the floating plate is provided with a jack, and a plurality of jacks are arranged corresponding to each stripper rod, and the stop valve is arranged below the floating plate; when the movable mold is lowered to the first preset height, the target part in the clamping state with the second mold core passes through the stripper rod and the jack to drive the floating plate to move downward in turn, so as to extrude the stop valve, open the stop valve, and compress the first compression spring; when the second mold core shrinks after cooling, the friction between the target part and the second mold core decreases, the target part, the stripper rod, the jack and the floating plate move upward under the action of the elastic force of the first compression spring, so as to realize the demolding of the target part, and at the same time, the floating plate is separated from the stop valve, so as to close the stop valve.

[0012] In an optional embodiment of the present application, the fixed base is provided with a boss, the liquid nitrogen spray head is mounted on the boss, the upper end of the boss is provided with a heat preservation cover, the heat preservation cover comprises a cylindrical body and an end cover, the cylindrical body is movably connected with the boss in the vertical direction, the end cover is fixedly connected with the top end of the liquid nitrogen spray head, the cylindrical body surrounds the outer periphery of the liquid nitrogen spray head, and the cylindrical body can be combined with the end cover to shield the liquid nitrogen spray head when the cylindrical body goes up, and the side surface of the liquid nitrogen spray head can be exposed when the cylindrical body goes down.

[0013] In an optional embodiment of the present application, a second compression spring is arranged between the cylindrical body and the boss, the second compression spring is assembled in such a way that the elastic force thereof can drive the cylindrical body to go up, the upper end of the cylindrical body is provided with a radial flange, the radial flange and the projection of the bottom surface of the second mold core in the vertical direction coincide with each other, and when the movable mold is lowered to the first preset height, the second mold core can drive the cylindrical body to go down, so that the liquid nitrogen spray head is exposed in the second mold core cavity.

[0014] In an optional embodiment of the present application, the boss is provided with an exhaust hole, one end of the exhaust hole is located at the top end of the boss, and the other end of the exhaust hole is located at the side surface of the boss.

[0015] In an optional embodiment of the present application, the second mold plate is provided with a sprue and a runner communicating with the second mold cavity, and at least part of the ejection rod is arranged correspondingly to the sprue and the runner.

[0016] In an optional embodiment of the present application, the first mold plate is detachably connected with the first mold base, and the second mold plate is detachably connected with the second mold base.

[0017] The technical effect of the present application is that the die casting mold provided by the present application can cool the second mold core after the mold is opened by using the rapid cooling device, so that the second mold core produces controllable shrinkage, thereby reducing the friction between the second mold core and the inner wall of the target part, facilitating the demolding of the target part, realizing rapid demolding, ensuring the integrity and cylindricity of the part profile, saving the subsequent machining process, improving the production efficiency, and reducing the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a perspective view of a target part provided by an embodiment of the present application;

[0019] Fig. 2 is a perspective view of a die casting mold provided by an embodiment of the present application;

[0020] Fig. 3 is a top view of the die casting mold provided by an embodiment of the present application after the fixed mold is removed;

[0021] Fig. 4 is a cross-sectional view of Fig. 3 along A-A;

[0022] Fig. 5 is a perspective view of the movable mold at a first preset height according to an embodiment of the present application;

[0023] Fig. 6 is a cross-sectional view of the movable mold at a first preset height according to an embodiment of the present application;

[0024] Fig. 7 is a perspective view of a target part and the movable mold in a demolding state according to an embodiment of the present application;

[0025] Fig. 8 is a cross-sectional view of a target part and the movable mold in a demolding state according to an embodiment of the present application;

[0026] Fig. 9 is a perspective view of a fixed mold according to an embodiment of the present application, which is flipped 180° relative to an actual use state for the purpose of observing the bottom structure of the fixed mold;

[0027] BRIEF DESCRIPTION OF THE DRAWINGS 10: target part; 11: cylindrical portion; 12: flange; 20: first mold base; 21: first mold plate; 211: first mold cavity; 212: first mold core; 22: gate; 30: second mold base; 31: second mold plate; 311: second mold cavity; 312: second mold core; 313: runner; 314: sprue; 315: ejector rod; 40: fixed base; 41: boss; 42: cylindrical body; 421: radial flange; 43: end cover; 44: vent hole; 50: floating plate; 51: ejector pin; 60: liquid nitrogen nozzle; 61: stop valve; 70: first compression spring; 80: second compression spring. DETAILED DESCRIPTION

[0028] The present application is described in more detail by the following specific examples. Other advantages and effects of the present application can be easily understood by those skilled in the art from this disclosure. The present application can be implemented or applied in other different specific embodiments, and various modifications or changes can be made to the details in this specification without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0029] It should be noted that the drawings in the following embodiments only schematically illustrate the basic concept of the present application, and only show the components related to the present application in the drawings, not drawn according to the number, shape and size of the components in actual implementation. The shape, number and proportion of each component in actual implementation can be arbitrarily changed, and the layout pattern of the components can be more complex.

[0030] Die casting is a common metal casting process that works by heating metal material to a liquid state and then injecting it into a pre-designed mold cavity under pressure and speed to rapidly solidify and obtain the desired shape and size of the casting. A metal mold is used to create the shape of the casting during die casting, which requires appropriate cooling system, sprue, air inlet, and other structural designs to ensure that the metal liquid fills the entire mold cavity and rapidly solidifies. After the metal raw material is heated to a liquid state, it is filled into the preheated mold cavity by spraying or injection, and a certain pressure can be applied during the filling process to avoid the generation of pores and defects. Die casting process can achieve rapid production of large quantities of metal parts, with hundreds to thousands of parts per hour, suitable for large-scale production needs. Through precise design of the mold and control of the pressure and speed during the filling process, high-precision and complex-shaped castings can be obtained, reducing the need for subsequent processing. During the die casting process, the metal liquid fills the mold cavity, usually resulting in a smooth and almost defect-free surface, reducing or avoiding subsequent surface treatment processes. Due to rapid solidification and smaller grain structure, die castings usually have good compactness and mechanical properties, meeting the requirements of high strength and high wear resistance. Compared with other processing methods, die casting process can usually make more efficient use of metal materials and reduce waste. Die casting can produce complex shapes and details, such as thin-walled structures and fine concave-convex surfaces, meeting the creative requirements of designers and engineers.

[0031] However, when die casting a deep cylindrical part as shown in FIG. 1, a mold core needs to be set to form the center hole of the part. However, during the cooling and solidification process of the part, a certain shrinkage will occur, which will cause a large holding force between the part and the mold core. This holding force will cause the part to be difficult to demold. To solve the above problem, the prior art generally designs a certain draft angle on the inner wall of the part. However, the setting of the draft angle will cause the inner wall of the part to be conical, which may not be the shape required by the part. Therefore, mechanical processing of the inner wall is still needed after die casting, which is a complicated process, prolongs the manufacturing cycle, and increases the manufacturing and transportation costs. Another solution is to set the mold core as a multi-petal structure, and after die casting, the mold core is separated from the part by driving the petals to shrink. However, this method will produce excess parting lines on the inner wall of the part, which also needs to be trimmed by machining. Another technical solution is to use an ejection rod to apply a large pushing force to the part to force it to demold. This method will cause wear to the mold by the part, and is not suitable for thin-walled parts, otherwise it will cause deformation and scrap of the thin-walled part. Therefore, the present application provides a die casting mold that can achieve controllable shrinkage of the mold core by rapid cooling of the mold core, thereby facilitating the demolding of deep cylindrical parts, while ensuring the quality of the molded parts and improving the die casting efficiency.

[0032] Please refer to figure 1, the present application is applicable to the processing of target part 10, target part 10, for example, can be a lamp shell, target part 10 includes cylindrical part 11, one end of cylindrical part 11 is provided with flange 12 extending radially outward.

[0033] Please refer to figures 2-9, the embodiment of the present application provides a die casting die, including fixed mold and movable mold;The fixed mold includes first mold base 20, first mold plate 21 and gate 22, the first mold plate 21 is provided with first mold cavity 211 and first mold core 212 located in the center of first mold cavity 211, the first mold cavity 211 is communicated with the gate 22;Movable mold is located below the fixed mold and is arranged movably up and down relative to the fixed mold, the movable mold includes second mold base 30 and second mold plate 31, the second mold plate 31 is provided with second mold cavity 311 and second mold core 312 located in the center of second mold cavity 311;When the movable mold and the fixed mold are closed, the first mold cavity 211, the second mold cavity 311, the first mold core 212 and the second mold core 312 form a cavity matched with the shape of the target part 10;Wherein the second mold core 312 is a shell structure with open bottom, the movable mold is provided with a rapid cooling device below, the rapid cooling device is assembled to cool the second mold core 312 when the movable mold and the fixed mold are separated, so that the second mold core 312 shrinks.

[0034] The die casting die provided by the present application can cool the second mold core 312 by using the rapid cooling device after opening the mold, so that the second mold core 312 shrinks controllably, thereby reducing the friction between the second mold core 312 and the inner wall of the target part 10, facilitating the demolding of the target part 10, realizing rapid demolding, ensuring the integrity and cylindricity of the part profile, saving the subsequent machining process, improving the production efficiency and reducing the production cost.

[0035] Please refer to figures 4, 6 and 8, in an optional embodiment of the present application, the rapid cooling device includes liquid nitrogen nozzle 60, the liquid nitrogen nozzle 60 is installed above a fixed base 40, the liquid nitrogen nozzle 60 is assembled to protrude into the second mold core 312 when the movable mold is lowered to a first predetermined height relative to the fixed mold;The liquid nitrogen nozzle 60 is communicated with liquid nitrogen storage tank through pipeline, and the pipeline is provided with stop valve 61. The present application cools the second mold core 312 by using liquid nitrogen, it should be understood that the boiling point of liquid nitrogen is very low, when liquid nitrogen contacts with the second mold core 312, it will evaporate quickly to take away the heat of the second mold core 312, realizing rapid cooling and shrinking of the second mold core 312.

[0036] Please refer to figures 4, 6, 8, in an optional embodiment of the present application, the movable mold is provided with a stripper rod 315, the stripper rod 315 is movably connected with the second mold base 30 and the second mold plate 31 along the vertical direction, the stripper rod 315 is provided with multiple, at least part of the upper end of the stripper rod 315 is correspondingly arranged with the flange 12 of the target part 10. The stripper rod 315 is used to lift the target part 10 from the second mold cavity 311, so that the operator or the manipulator can take out the target part 10 from the mold, it should be noted that when the second mold core 312 is not cooled, there is a large holding force between the target part 10 and the second mold core 312, at this time the stripper rod 315 will be kept in the depressed state.

[0037] Please refer to figures 4, 6, 8, in an optional embodiment of the present application, the movable mold and the fixed base 40 are provided with a first linkage mechanism, the first linkage mechanism is assembled so that when the movable mold is lowered to the first preset height, the first linkage mechanism can drive the stop valve 61 to open, and exert a preset size of the lifting force on the stripper rod 315, and when the stripper rod 315 lifts the target part 10 under the action of the lifting force, the first linkage mechanism can drive the stop valve 61 to close. Specifically, the stop valve 61 is a press type stop valve, the first linkage mechanism includes a floating plate 50 and a first compression spring 70, the floating plate 50 is movably connected with the fixed base 40 along the vertical direction, the first compression spring 70 is located between the floating plate 50 and the fixed base 40, and the first compression spring 70 is assembled so that the elastic force of the first compression spring 70 can drive the floating plate 50 to move upward; the upper end of the floating plate 50 is provided with a jack 51, multiple jacks 51 are respectively and correspondingly arranged with each stripper rod 315, the stop valve 61 is located below the floating plate 50; when the movable mold is lowered to the first preset height, the target part 10 in the holding state with the second mold core 312 passes through the stripper rod 315 and the jack 51 to drive the floating plate 50 to move downward in turn, so as to extrude the stop valve 61, open the stop valve 61, and compress the first compression spring 70; when the second mold core 312 is cooled and shrunk, the friction force between the target part 10 and the second mold core 312 is reduced, the target part 10, the stripper rod 315, the jack 51 and the floating plate 50 move upward under the action of the elastic force of the first compression spring 70, so as to realize the demolding of the target part 10, at the same time, the floating plate 50 is separated from the stop valve 61, so as to close the stop valve 61.

[0038] Please refer to figures 4, 6, 8, the specific demolding process of the die casting mold provided by the present application is as follows:

[0039] The state of the movable mold and the fixed mold after separation and before reaching the first preset height is shown in Figure 4, at this time the floating plate 50 is in the high position under the action of the first compression spring 70, with the downward movement of the movable mold, the ejector rod 315 on the floating plate 50 is in contact with the top rod 51, because there is a large holding force between the target part 10 and the second mold core 312, the ejector rod 315 cannot move upward, and then with the downward movement of the movable mold, the floating plate 50 is pressed to the low position, as shown in Figure 6, at this time the stop valve 61 is triggered to open, and at the same time the liquid nitrogen nozzle 60 is just located in the shell cavity of the second mold core 312, the liquid nitrogen cools the second mold core 312, with the cooling and shrinking of the second mold core 312, the friction between the target part 10 and the second mold core 312 gradually decreases, until it cannot resist the elastic force of the first compression spring 70, at this time the floating plate 50, the top rod 51, the ejector rod 315 and the target part 10 gradually move upward under the elastic force of the first compression spring 70, until the floating plate 50 reaches the designed stroke, at this time the target part 10 is lifted from the second mold cavity 311, and the floating plate 50 is separated from the stop valve 61, the stop valve 61 is closed, and then the injection of liquid nitrogen is stopped. The first linkage mechanism realizes the automatic demolding of the target part 10 and the automatic start and stop of the liquid nitrogen nozzle 60, saves the complex electric control system, simplifies the equipment structure, and reduces the equipment cost.

[0040] Please refer to Figures 4, 6 and 8, in an optional embodiment of the present application, the fixed base 40 is provided with a boss 41, the liquid nitrogen nozzle 60 is installed on the boss 41, the upper end of the boss 41 is provided with a heat preservation cover, the heat preservation cover includes a cylindrical body 42 and an end cover 43, the cylindrical body 42 is movably connected with the boss 41 in the vertical direction, the end cover 43 is fixedly connected with the top end of the liquid nitrogen nozzle 60, the cylindrical body 42 surrounds the outer periphery of the liquid nitrogen nozzle 60, and when the cylindrical body 42 moves upward, it can combine with the end cover 43 to shield the liquid nitrogen nozzle 60, and when the cylindrical body 42 moves downward, the side surface of the liquid nitrogen nozzle 60 can be exposed. Further, the second compression spring 80 is arranged between the cylindrical body 42 and the boss 41, the elastic force of the second compression spring 80 can drive the cylindrical body 42 to move upward, the upper end of the cylindrical body 42 is provided with a radial flange 421, the radial flange 421 and the projection of the bottom surface of the second mold core 312 in the vertical direction coincide with each other, when the movable mold descends to the first preset height, the second mold core 312 can drive the cylindrical body 42 to move downward, so that the liquid nitrogen nozzle 60 is exposed in the shell cavity of the second mold core 312. When the movable mold moves downward, the cylindrical body 42 can be automatically pressed down, and when the movable mold moves upward, the cylindrical body 42 can be automatically reset, reducing the loss of cold energy of the liquid nitrogen nozzle 60 in the die casting process, so that the second mold core 312 can be cooled to the target temperature faster in the demolding process.

[0041] Referring to FIG. 4, 6, 8, in an optional embodiment of the present application, the boss 41 is provided with an exhaust hole 44, one end of the exhaust hole 44 is located at the top end of the boss 41, and the other end of the exhaust hole 44 is located at the side of the boss 41. The exhaust hole 44 can avoid high pressure in the cavity of the second mold core 312, and ensure that the liquid nitrogen can be smoothly injected.

[0042] Referring to FIG. 2, 3, 5, 7, in an optional embodiment of the present application, the second mold plate 31 is provided with a runner 313 and a slag groove 314 which communicate with the second mold cavity 311, and at least part of the stripper rod 315 is arranged corresponding to the runner 313 and the slag groove 314. The first mold plate 21 is detachably connected with the first mold base 20, and the second mold plate 31 is detachably connected with the second mold base 30.

[0043] In summary, the die casting mold provided by the present application can cool the second mold core 312 by using the rapid cooling device after the mold is opened, so that the second mold core 312 produces controllable shrinkage, thereby reducing the friction between the second mold core 312 and the inner wall of the target part 10, facilitating the demolding of the target part 10. The present application realizes rapid demolding while ensuring the integrity and cylindricity of the part profile, saves the subsequent machining process, improves the production efficiency, and reduces the production cost. The first linkage mechanism realizes automatic demolding of the target part 10 and automatic starting and stopping of the liquid nitrogen spray head 60, saves the complex electric control system, simplifies the equipment structure, and reduces the equipment cost. When the movable mold is lowered, the cylindrical body 42 can be automatically pressed down, and when the movable mold is raised, the cylindrical body 42 can be automatically reset, reducing the loss of cooling capacity of the spray head assembly during the die casting process, so that the second mold core 312 can be cooled to the target temperature faster during the demolding process.

[0044] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

[0045] In the description herein, many specific details are provided, such as examples of components and / or methods, to provide a thorough understanding of embodiments of the application. Persons skilled in the art will recognize, however, that an embodiment of the application can be practiced without one or more of the specific details. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of an embodiment of the application.

Claims

1. A die casting mold for die casting a target part, the target part including a cylindrical portion, one end of the cylindrical portion being provided with a flange extending radially outward, characterized by, The die-casting die comprises: a fixed die comprising a first die seat, a first die plate provided with a first die cavity and a first die core in the center of the first die cavity, and a sprue; a movable die located below the fixed die and vertically movable relative to the fixed die, the movable die comprising a second die seat and a second die plate provided with a second die cavity and a second die core in the center of the second die cavity; when the movable die is closed with the fixed die, the first die cavity, the second die cavity, the first die core and the second die core form a cavity matching the shape of the target part; wherein the second die core is a shell-shaped structure with an open bottom, and a quenching device is arranged below the movable die, the quenching device being configured to cool the second die core when the movable die is separated from the fixed die, so that the second die core shrinks; the quenching device comprises a liquid nitrogen spray head mounted above a fixed base, the liquid nitrogen spray head being configured to protrude into the second die core when the movable die is lowered to a first predetermined height relative to the fixed die; the liquid nitrogen spray head is in communication with a liquid nitrogen storage tank through a pipeline, and a stop valve is arranged on the pipeline; a plurality of unloading rods are arranged on the movable die and are vertically connected to the second die seat and the second die plate, at least part of the unloading rods being arranged corresponding to the flanges of the target part; a first linkage mechanism is arranged between the movable die and the fixed base, the first linkage mechanism being configured to drive the stop valve to open and apply a predetermined amount of jacking force to the unloading rods when the movable die is lowered to the first predetermined height, and the first linkage mechanism being configured to drive the stop valve to close when the unloading rods lift the target part under the action of the jacking force; the stop valve is a press-type stop valve, the first linkage mechanism comprising a floating plate and a first compression spring, the floating plate being vertically connected to the fixed base, the first compression spring being arranged between the floating plate and the fixed base, and the first compression spring being configured to drive the floating plate to move upward by its elastic force; a plurality of jacks are arranged on the upper end of the floating plate, one jack corresponding to one unloading rod, and the stop valve being arranged below the floating plate; when the movable die is lowered to the first predetermined height, the target part in the clamping state with the second die core passes through the unloading rods and the jacks in turn to drive the floating plate to move downward, so as to squeeze the stop valve, open the stop valve and compress the first compression spring; when the second die core shrinks after being cooled, the friction between the target part and the second die core decreases, the target part, the unloading rods, the jacks and the floating plate move upward under the elastic force of the first compression spring, so as to realize the demolding of the target part, and the floating plate is separated from the stop valve, so as to close the stop valve.

2. The die casting mold according to claim 1, characterized in that, The fixed base is provided with a boss, the liquid nitrogen spray head is installed on the boss, the boss is provided with a heat preservation cover at the upper end, the heat preservation cover comprises a cylindrical body and an end cover, the cylindrical body is movably connected with the boss in the vertical direction, the end cover is fixedly connected with the top end of the liquid nitrogen spray head, the cylindrical body surrounds the outer periphery of the liquid nitrogen spray head, the cylindrical body can be combined with the end cover to shield the liquid nitrogen spray head when the cylindrical body goes up, and the side of the liquid nitrogen spray head can be exposed when the cylindrical body goes down; The second compression spring is arranged between the cylindrical body and the boss, the second compression spring is assembled in a manner that the elastic force thereof can drive the cylindrical body to go up, the upper end of the cylindrical body is provided with a radial flange, the radial flange and the projection of the bottom surface of the second mold core in the vertical direction coincide with each other, when the movable mold is lowered to the first preset height, the second mold core can drive the cylindrical body to go down, so that the liquid nitrogen spray head is exposed in the second mold core cavity.

3. The die casting mold according to claim 2, characterized in that, The boss is provided with an exhaust hole, one end of the exhaust hole is located at the top end of the boss, and the other end of the exhaust hole is located at the side of the boss.

4. The die casting mold according to claim 1, characterized by The second mold plate is provided with a sprue and a slag groove in communication with the second mold cavity, and at least part of the discharge rod is arranged correspondingly to the sprue and the slag groove.

5. The die casting mold according to claim 1, characterized by The first mold plate is detachably connected with the first mold base, and the second mold plate is detachably connected with the second mold base.

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