A metal mold for preparing aluminum alloy tensile test specimen

Abstract

A metal mold for preparing aluminum alloy tensile test specimens, including a pouring cup, a sprue, a cross runner, a filter, an entrail, a riser and a rotary bait; the cross-sectional area of ​​the sprue gradually decreases from top to bottom, the upper end is connected to the pouring cup, and the lower end of the sprue is smoothly connected to the cross runner; the cross runner is placed directly below the cavity, and the two are connected through the entrail, a ceramic filter is provided at the connection, and the riser is provided at the vertical highest point of the cavity; the rotary bait is generally a cylindrical structure, and an exhaust hole is attached to the upper end, which is flush with the upper end surface of the riser, and the bottom end is connected to and tangent to the end of the cross runner. The present invention not only ensures the filling rate, but also effectively reduces the turbulence and splashing of the molten metal during the pouring process, improves the mechanical properties of the casting, the product process qualification rate, and the production efficiency; the rotary bait can effectively reduce the casting defects such as air entrainment, inclusions, and double-layer oxide film in the casting, significantly improves the casting quality and molding rate, reduces the production cost, and avoids unnecessary aluminum liquid loss.

Description

Technical Field

[0001] The invention belongs to the field of aluminum alloy casting, and specifically relates to a bottom-pouring metal mold, on the basis of which a rotating bait device is added to eliminate some casting defects and improve the casting quality, and is suitable for the casting molding of small aluminum alloy castings. Background Art

[0002] In industrial casting production, traditional gravity casting is widely used because of its convenient operation and low cost. Due to the characteristics of aluminum alloy, hydrogen absorption will occur during the casting process, resulting in casting defects such as pores and cracks. This defect is generated during the smelting process, and a good degassing effect can be achieved by adding salt substances. In recent years, some domestic and foreign studies have shown that most of the defects in castings are generated during the filling process, such as the entrapment defects caused by the turbulence of the molten metal surface in the unfilled runner. With the advancement of detection methods, more and more evidence shows that defects such as pores, microcracks, shrinkage cavities and shrinkage in castings are strongly related to the entrapment of oxide films produced by oxidation of the metal surface. The above defects generated during the filling process are all due to the unscientific and unreasonable design of metal molds and pouring methods. At present, the most widely used in China is still the top-casting gravity metal mold, which affects the quality and mechanical properties of castings in many aspects. Based on this situation, a metal mold with a more scientific and reasonable design that effectively avoids casting defects during the metal liquid filling process has far-reaching significance for the entire casting industry. Summary of the invention

[0003] The purpose of the present invention is to solve the defects and irrationalities of traditional gravity metal molds and to improve the potential deficiencies that may exist in traditional bottom metal molds. A scientific and reasonable metal mold for preparing aluminum alloy tensile specimens is provided. Through this metal mold, the metal liquid flows stably and smoothly during the filling process, effectively eliminating casting defects.

[0004] The present invention is achieved through the following technical solutions.

[0005] The metal mold for preparing an aluminum alloy tensile test specimen of the present invention comprises a pouring cup, a sprue, a cross runner, a filter sheet, an inner runner, a tensile rod test specimen, a riser, a rotary bait, and an exhaust hole.

[0006] The sprue is a cone that is larger at the top and smaller at the bottom. The upper end is connected to the pouring cup, and the pouring cup is provided with a plug that can be plugged in and out. The lower end of the sprue is connected to the cross runner, making a smooth transition between the two. The cross runner is located directly below the tensile rod specimen, and the two are connected by an inner runner. A filter is provided at the connection, and the riser is provided at the vertical highest point of the cavity. The rotary bait is generally a cylindrical structure, and an exhaust hole is attached to the upper end. The exhaust hole is flush with the upper end surface of the riser, and its bottom end is connected to and tangent to the end of the cross runner.

[0007] A pouring cup is set at the entrance of the metal mold. Its outer side is designed to be cylindrical and the middle is funnel-shaped, so that the molten metal forms a certain pressure in the pouring cup, thereby achieving the effect of low-pressure casting, increasing the initial speed of the molten metal entering the metal mold, and improving the filling rate of the bottom-pouring metal mold to a certain extent.

[0008] The vertical height of the sprue is greater than or equal to the total height of the tensile rod specimen, the riser, and the ingode, and is 90° to the cross runner. Its upper end is connected to the lower outlet of the pouring cup, and its lower end is connected to the inlet of the cross runner. The cross-sectional area of ​​the sprue gradually decreases from top to bottom to reduce the entrapment defects caused by the difficulty of molten metal filling the sprue.

[0009] No gate is set at the connection between the cross runner and the straight runner, and a direct transition is adopted. The transition should be smooth, the length of the cross runner should be greater than the total length of the horizontal discharge of the casting, and the height of the cross runner gradually narrows along the end direction. The initial height of the cross runner is the critical height of the alloy, and the terminal height depends on 1 / 2 of the critical height of the alloy. For example, if the critical height of aluminum alloy is 12mm, the initial height of the cross runner is 12mm, and the terminal height of the cross runner is 6mm, which is 1 / 2 of the critical height. In this way, when multiple castings are filled, the filling time and sequence of the castings are consistent to eliminate the difference in casting performance caused by different filling and solidification times.

[0010] A speed reduction device is set in the metal mold, and a filter is placed at the connection between the cross runner and the ingates to reduce the flow speed of the molten metal to eliminate the entrapment defect caused by turbulence. The filter is a foam ceramic filter with a pore density of 15ppi, an area larger than the total area of ​​the ingates, and completely covers the ingates.

[0011] The riser is set at the highest point of the casting position in the mold cavity, and is placed at the upper end of the hot section along the horizontal length direction of the casting. This invention does not need to set side risers and blind risers at the inner runner position, and can complete shrinkage compensation by gravity and pressure. The size of the riser depends on the size of the casting, and its main size is the root diameter, which is about 1.1~1.8 times the diameter of the hot section of the casting.

[0012] The spinner bait is composed of a cylinder and a vent hole. As an additional cylindrical cross-section body, it is usually arranged at the end of the runner, and the runner is connected to it at its eccentric position, that is, the runner is tangent to the spinner bait. At this time, the spinner bait is a typical vortex system. In addition, a vent hole is arranged on the top of the spinner bait to connect to the outside world, so that gas can be discharged from the metal mold.

[0013] The metal mold for preparing aluminum alloy tensile specimens described in the present invention is mainly used to prepare standard aluminum alloy tensile specimens or small-sized aluminum alloy castings with complex structures and high performance requirements. It can achieve the effect of low-pressure pouring through the gravity of the metal liquid itself, and improve the casting defects caused by traditional gravity pouring and traditional bottom pouring, thereby improving the casting yield, production efficiency and mechanical properties.

[0014] Compared with the traditional gravity metal mold and the traditional bottom metal mold, the beneficial effects of the present invention are:

[0015] 1. The gate of the metal mold is located at the bottom of the stretch rod style, which is different from the traditional gravity casting where it is set at the top or both sides. This design can avoid splashing and turbulence caused by direct contact between the molten metal and the cavity in the initial stage of filling.

[0016] 2. The present invention is designed with a speed reduction device, and a filter is arranged at the connection between the cross runner and the inner runner. Its main function is to reduce the flow velocity of the molten metal when it enters the mold cavity, thereby reducing the entanglement defects caused by turbulence and making the filling smooth and stable. Its other function is to filter out certain impurities, oxides, and bubbles, making the molten metal purer, thereby improving the mechanical properties of the casting.

[0017] 3. The sprue and runner of the present invention are different from the horizontal regular shape of the traditional bottom metal mold. The sprue adopts a tapered design with a large top and a small bottom to solve the problem that the molten metal is not fully filled in the sprue, and the runner also adopts a design that gradually narrows from left to right, so that the filling can be completed simultaneously when casting multiple castings. The connection between the two adopts a smooth arc transition to ensure that the molten metal is always full in the metal mold, so that the turbulence loses the spatial condition.

[0018] 4. The present invention sets the riser at the top of the stretching rod pattern, and after filling, gravity is used to achieve the shrinkage compensation effect, thereby eliminating shrinkage cavities and shrinkage to make the filling more complete. The traditional gravity metal mold will set a blind riser at the inner runner to achieve the shrinkage compensation effect. The present invention can effectively reduce the process of blind riser removal, protect the casting from damage by the operation, and greatly improve production efficiency and casting quality.

[0019] 5. The spinning bait is an additional device added on the basis of the traditional bottom metal mold. It consists of a cylinder and a vent. As an additional cylindrical cross-section body, it is usually set at the end of the runner, and the runner is connected to it at its eccentric position, that is, the runner is tangent to the spinning bait. At this time, the spinning bait acts as a typical vortex system. Usually, the liquid at the front of the molten metal usually cools faster, and there will be air entrainment and non-metallic impurities. These cold and poor quality molten metals will be attracted into the spinning bait due to the centripetal force. The purpose of this design should be: the flow rate of the molten metal decreases, the liquid alloy is degassed, and non-metallic impurities are captured in the spinning bait. In addition, there is a vent on the top that is connected to the outside world, so that gas can be discharged from the metal mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a three-dimensional diagram of a traditional bottom injection metal mold.

[0021] Figure 2 It is a three-dimensional diagram of the bottom injection metal mold of the present invention.

[0022] Figure 3 Fracture morphology of tensile rod specimen formed by traditional bottom injection metal mold.

[0023] Figure 4 Fracture morphology and energy spectrum point scanning of tensile rod specimen formed by traditional bottom injection metal mold.

[0024] Figure 5 The fracture morphology of a tensile rod sample formed by the bottom injection metal mold of the present invention.

[0025] Figure numerals: 1- pouring cup; 2- straight runner; 3- horizontal runner; 4-filter; 5-inner runner; 6-tensile rod specimen; 7-riser; 8-spinning bait; 9-vent; 10-traditional pouring cup; 11-traditional straight runner; 12-traditional horizontal runner. Implementation

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Example

[0027] A metal mold for preparing an aluminum alloy tensile test specimen comprises a pouring cup 1, a sprue 2, a runner 3, a filter 4, an inner runner 5, a tensile rod test specimen 6, a riser 7, a rotary bait 8, and a vent 9.

[0028] The sprue 2 is a cone that is larger at the top and smaller at the bottom. The upper end is connected to the pouring cup 1, and the pouring cup 1 is provided with a plug that can be plugged in and out. The lower end of the sprue 2 is connected to the cross runner 3, so that the two have a smooth transition; the cross runner 3 is located directly below the tensile rod specimen 6, and the two are connected by an inner runner 5. A filter plate 4 is provided at the connection, and the riser 7 is provided at the vertical highest point of the cavity; the rotary bait 8 is generally a cylindrical structure, and an exhaust hole 9 is attached to the upper end. The exhaust hole 9 is flush with the upper end surface of the riser 7, and its bottom end is connected to and tangent to the end of the cross runner 3.

[0029] A pouring cup 1 is arranged at the entrance of the metal mold, and its outer side is designed to be cylindrical and the middle is funnel-shaped, so that the molten metal forms a certain pressure in the pouring cup 1, thereby achieving the effect of low-pressure casting, increasing the initial speed of the molten metal entering the metal mold, and improving the filling rate of the bottom-pouring metal mold to a certain extent.

[0030] The vertical height of the sprue 2 is greater than or equal to the total height of the tensile rod sample 6, the riser 7, and the ingates 5, and is 90° with the runner 3. Its upper end is connected to the lower outlet of the pouring cup 1, and its lower end is connected to the inlet of the runner 3. The cross-sectional area of ​​the sprue 2 gradually decreases from top to bottom to reduce the entrapment defect caused by the difficulty of the molten metal to fill the sprue.

[0031] No gate is set at the connection between the runner 3 and the sprue 2, and a direct transition is adopted. The transition should be smooth, the length of the runner 3 should be greater than the total length of the horizontal discharge of the casting, and the height of the runner 3 is slowly narrowed along the end direction. The initial height of the runner 3 is the critical height of the alloy, and the terminal height depends on 1 / 2 of the critical height of the alloy. For example, if the critical height of aluminum alloy is 12mm, the initial height of the runner 3 is 12mm, and the terminal height of the runner 3 is 6mm, which is 1 / 2 of the critical height. In this way, when multiple castings are filled, the filling time and sequence of the castings are consistent to eliminate the difference in casting performance caused by different filling and solidification times.

[0032] A speed reduction device is provided in the metal mold, and a filter sheet 4 is placed at the connection between the runner 3 and the ingrate 5, so as to reduce the flow speed of the molten metal and eliminate the entrapment defect caused by turbulence. The filter sheet 4 is a foam ceramic filter sheet with a pore density of 15ppi, an area larger than the total area of ​​the ingrate 5, and completely covers the ingrate 5.

[0033] The riser 7 is set at the highest point of the casting position of the mold cavity, and is placed at the upper end of the hot section along the horizontal length direction of the casting. This invention does not need to set side risers and blind risers at the inner runner position, and can complete shrinkage compensation by gravity and pressure. The size of the riser depends on the size of the casting, and its main dimension is the root diameter, which is about 1.1~1.8 times the diameter of the hot section of the casting.

[0034] The spin lure 8 is composed of a cylinder and a vent hole. As an additional cylindrical cross-section body, it is usually arranged at the end of the runner, and the runner 3 is connected to it at its eccentric position, that is, the runner 3 is tangent to the spin lure 8. At this time, the spin lure 8 is a typical vortex system. In addition, a vent hole 9 is arranged on the top thereof to connect to the outside world, so that gas can be discharged from the metal mold.

[0035] Comparative Example 1. Conventional bottom injection metal mold casting experiment.

[0036] Taking the casting as an aluminum alloy tensile rod specimen as an example, this specimen is a small casting, which is convenient for filling and mechanical property analysis. The material is A356 aluminum alloy, with a horizontal length of 170mm, a working end length of 50mm, and a wall thickness of 12mm.

[0037] Through the traditional bottom injection metal mold, the structure of the metal mold is as follows Figure 1 As shown, it includes a traditional pouring cup 10, a traditional sprue 11, and a traditional runner 12. The traditional sprue is provided with a pouring cup at the upper end, which is a cylinder with an outline size of 90×90mm. The traditional sprue is a vertical rectangle with an outline size of 232×20×16mm. In order to prevent the splashing and air entrainment of the molten metal due to the unreasonable transition at the connection between the sprue and the runner, a pouring nest is provided at the connection. The cross-runner section is still set to a regular rectangle, and its length is adjusted according to the size of the casting, i.e., the length. Figure 1 The structure diagram of the traditional bottom-injection metal mold, the number of castings is 2, and the outline size of the traditional cross runner is 172×13×8mm. The casting is connected to the traditional cross runner 12 by an endogate. The cross section of the endogate is set to a rectangle with a certain curvature on both sides. Its outline size is 9×16×25mm; the riser is set at the upper end of the hot node and the top of the casting, and its outline size is 18×40×45mm. Production verification of the casting shows that the molten metal inside the sprue cannot be well filled in the initial stage of filling. At the same time, the cross runner also has a similar phenomenon. Due to the gravity of the molten metal, a certain pressure is caused. The flow rate of the molten metal in the traditional metal mold is much greater than the critical speed, resulting in splashing, turbulence and other phenomena, resulting in the existence of entanglement defects in the casting and damaging the performance of the casting. In addition, when multiple castings are formed, each casting is not filled at the same time, resulting in a large difference in the performance of each casting.

[0038] Comparative Example 2. Experiment of casting of bottom-injection metal mold of the present invention.

[0039] Based on the aluminum alloy tensile rod sample mentioned in Comparative Example 1, the aluminum alloy tensile sample of the present invention is used to prepare a metal mold for casting:

[0040] like Figure 2As shown, a metal mold for preparing an aluminum alloy tensile specimen comprises a pouring cup 1, a sprue 2, a runner 3, a filter 4, an ingode 5, a tensile rod pattern 6, a riser 7, a rotary bait 8, and an exhaust hole 9, wherein: according to the outline size of the casting, it is an aluminum alloy tensile rod specimen with a horizontal length of 170 mm, the sprue 2 is arranged on the left side of the cavity, placed vertically, its top is connected to the bottom of the pouring cup 1, and the bottom is connected to the runner 3, no gate nest is arranged at the connection but a smooth transition is adopted, and its curvature radius is 8 mm and 17 mm, the sprue 2 is a cone with a larger upper part and a smaller lower part, and its height should be equal to the total height of the tensile rod specimen 6, the ingode 5, and the riser 7, the upper cross-sectional area is 20 mm×16 mm, the bottom cross-sectional area is 13 mm×9 mm, and the height is 232 mm. This design allows the molten metal to completely fill the sprue at the initial stage of filling, eliminating the spatial conditions for turbulence and splashing of the molten metal, making filling more stable. In addition, the pluggable plug set in the gate cup also serves this purpose.

[0041] The runner 3 is placed horizontally under the casting. Similar to the design concept of the sprue 2, its cross-sectional area gradually decreases and is tapered as a whole, so that when multiple castings are filled, the time to complete the filling is similar, thereby eliminating the large performance differences between castings caused by uneven filling time. The runner size is 172mm, and the cross-sectional area is 13×8mm and 13×5mm.

[0042] The filter plate 4 of the deceleration device is arranged at the connection between the runner 3 and the ingrate 5 to greatly reduce the flow rate of the molten metal when entering the mold cavity, thereby reducing turbulence and splashing, and making the molten metal filling more stable. The filter plate is a foam ceramic filter plate 4 with a pore density of 15ppi. Its effective area depends on the size and number of the castings and is larger than the total area of ​​the ingrate 5. In the present invention, the area of ​​the filter plate 4 is 88×32mm;

[0043] Based on the casting of the present invention, the aluminum alloy tensile rod specimen is a simple small-sized casting, and a single casting only needs to be provided with one ingrate 5, which is provided above the filter plate 4 directly below the casting, and its cross section is set to be a rectangle with a certain curvature on both sides, and its outline size is 9×16×25mm.

[0044] The riser 7 is arranged at the upper end of the hot spot of the casting and the top of the tensile rod sample 6, and its main dimensions are that the root diameter is 18mm, which is 1.1 to 1.8 times the diameter of the hot spot of the casting, and the height is 45mm.

[0045] The rotating bait 8 is an additional device added on the basis of the traditional bottom metal mold, which consists of a cylinder and an exhaust hole 9. As an additional cylindrical cross-section body, it is usually set at the end of the runner, and the runner 3 is connected to it at its eccentric position, that is, the runner 3 is tangent to the rotating bait 8. At this time, the rotating bait 8 acts as a typical vortex system. Usually, the liquid at the front of the molten metal usually cools faster, and there will be air entrainment and non-metallic impurities. These cold and poor quality molten metals will be attracted into the rotating bait 8 due to the centripetal force. The purpose of this design is to reduce the flow rate of the molten metal, degas the liquid alloy, and capture non-metallic impurities in the rotating bait 8. In summary, the rotating bait 8 can be placed at the end of the metal mold or between the sprue 2 and the casting, but it is found through practice that it is set at the end of the metal mold to improve the performance of the casting the most. Its size should be greater than or equal to the volume of the casting, otherwise it will be filled prematurely and cause the molten metal to reflux if it is too small. In the present invention, the size of the spinner bait 8 is 90 mm x 30 mm in diameter. In addition, a vent hole 9 is provided on the top thereof to connect to the outside world, so that gas can be discharged from the metal mold.

[0046] The surface quality and mechanical properties of the aluminum alloy tensile rod specimens cast using the above metal mold are significantly improved, the tensile strength is greater than that of the traditional bottom-cast metal mold, and the elongation is also increased by 76.6%. Figure 3 , 4 As shown in Figure 5, compared with the fracture morphology of the tensile rod specimen formed by the traditional bottom injection mold, the SEM morphology of the tensile fracture of the tensile rod specimen cast by the present invention shows that the entrapment defects such as pores, impurities, and oxide films are significantly reduced.

[0047] In summary, the present invention improves the size of the sprue 2 and the runner 3 on the basis of the traditional bottom-injection metal mold, so that the molten metal is always in a full state in the metal mold, eliminating the spatial factor of turbulence, and adding a filter plate of the speed reduction device to effectively reduce the flow speed of the molten metal and eliminate the speed factor of turbulence. An additional device, a rotary bait 8, is added at the end of the metal mold. The liquid at the front of the molten metal usually cools faster and will have air entrainment and non-metallic impurities. These cold and poor-quality molten metals will be attracted into the rotary bait 8 due to the centripetal force, thereby improving the purity of the molten metal and greatly improving the performance of the casting.

[0048] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0049] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A metal mold for preparing aluminum alloy tensile specimens, Its characteristics are Including pouring cup, sprue, runner, filter, ingates, tensile bar specimens, risers, spinner baits, vents; The sprue is a cone with a larger top and a smaller bottom. The upper end is connected to the pouring cup, and the pouring cup is provided with a plug that can be plugged in and out. The lower end of the sprue is connected to the cross runner, and a smooth transition is made between the two. The cross runner is located directly below the tensile rod specimen, and the two are connected by an inner runner. A filter is provided at the connection, and the riser is provided at the vertical highest point of the cavity. The rotary bait is generally a cylindrical structure, and an exhaust hole is attached to the upper end. The exhaust hole is flush with the upper end surface of the riser, and its bottom end is connected to and tangent to the end of the cross runner. A pouring cup is provided at the entrance of the metal mold, the outer side of which is designed to be cylindrical and the middle is funnel-shaped; The vertical height of the sprue is greater than or equal to the total height of the tensile rod sample, the riser and the ingates, and is 90° with the runner. Its upper end is connected to the lower outlet of the pouring cup, and its lower end is connected to the inlet of the runner. The cross-sectional area of ​​the sprue gradually decreases from top to bottom. The connection between the runner and the sprue is directly transitioned, the transition should be smooth, the length of the runner should be greater than the total length of the horizontal discharge of the casting, the height of the runner gradually narrows along the end direction, the initial height of the runner is the critical height of the alloy, and the end height depends on 1 / 2 of the critical height of the alloy; A filter is placed at the connection between the runner and the ingates. The filter is a foam ceramic filter with a pore density of 15ppi. Its area is larger than the total area of ​​the ingates and completely covers the ingates. The riser is set at the highest point of the cavity pouring position and placed at the upper end of the hot section along the horizontal length direction of the casting. The size of the riser depends on the size of the casting, and its root diameter is 1.1~1.8 times the diameter of the hot section of the casting; The rotary bait is composed of a cylinder and an exhaust hole, which is arranged at the end of the flow channel. The runner is connected to the rotary bait at its eccentric position, that is, the runner is tangent to the rotary bait, and an exhaust hole is also arranged on the top.

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