Mould for lost foam casting

Abstract

The utility model discloses an evanescent mode casting mould which comprises a box body, an inner sand mould and an outer sand mould are arranged in the box body, a cavity is formed between the inner sand mould and the outer sand mould, a sprue is arranged on one side of the cavity, one end of the sprue penetrates through the outer sand mould, the other end of the sprue is communicated with a cross gate arranged at the bottom of the cavity, and the cross gate is connected with flow gates at two ends of the cavity. And the cavity is communicated relative to the inner gate and the bottom of the cavity through a plurality of mold filling auxiliary structures. According to the utility model, the problems of slag entrapment, gas entrapment and cold shut caused by downward flowing of molten iron in the mold in the pouring process can be avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of lost foam casting, in particular to a mold for lost foam castings. Background Art

[0002] Automotive stamping dies are produced using lost foam casting. Depending on the structure and dimensions of the casting, a foam model is created using polystyrene (EPS) or other expandable plastic beads. These models undergo a series of pre-expansion, aging, and molding processes. The foam model is then coated with a special high-temperature-resistant coating and dried. The processed model is connected to a gating system and embedded in resin sand to form a closed mold cavity. Molten metal is poured into the mold cavity. Because the model is fusible, when the molten metal contacts the model, it quickly vaporizes and disappears, leaving behind a cavity in the same shape as the model. The molten metal cools and solidifies in the cavity, forming the desired casting. During this process, the molten metal fills every detail of the model, ensuring the dimensional accuracy and surface quality of the casting. After the casting cools and solidifies, it is removed from the flask and cleaned. This involves removing any remaining sand, coatings, and other impurities, and performing any necessary heat treatment or machining.

[0003] Since automobile molds are usually produced in single pieces, some single-piece structures are very complex. When pouring molten iron after designing the casting mold, some structures have dead corners. The molten iron needs to be filled to a certain height first and then flow back downward to fill the mold. During the downward flow of molten iron, defects such as slag entanglement, air entanglement, and cold shut are easily generated, resulting in quality risks in the final casting. Utility Model Content

[0004] The utility model aims to provide a mold for lost foam castings, which can avoid the problems of slag entanglement, air entanglement and cold shut caused by the downward flow of molten iron inside the mold during the pouring process.

[0005] The technical solution adopted by the utility model is that the mold of the lost foam casting includes a box body, an inner sand mold and an outer sand mold are arranged inside the box body, a cavity is formed between the inner sand mold and the outer sand mold, a straight runner is provided on one side of the cavity, one end of the straight runner passes through the outer sand mold, and the other end is connected to a horizontal runner arranged at the bottom of the cavity, and the horizontal runner is connected to the inner gates at both ends of the cavity;

[0006] The cavity is connected to the inner gate and the bottom of the cavity through a plurality of filling auxiliary structures.

[0007] The utility model is also characterized in that:

[0008] The inner sand mold is located between the runner and the cavity.

[0009] Several filling auxiliary structures are evenly distributed in one direction along the cavity.

[0010] The filling auxiliary structure includes an inner tube, the two ends of the inner tube are an inlet and an outlet respectively, the inlet is connected to the inside of the cavity relative to the inner gate position, and the outlet is connected to the inside of the cavity relative to the bottom of the cavity.

[0011] The inner tube adopts Tesla valve structure.

[0012] The outer sand mold is provided with a plurality of exhaust channels relative to the top of the mold cavity. The bottom ends of the exhaust channels are communicated with the inside of the mold cavity, and the tops of the exhaust channels pass through the outer sand mold for exhaust.

[0013] A plurality of cooling air pipes are arranged around the outer sand mold relative to the mold cavity, and the cooling air pipes are connected to the external cooling source.

[0014] There are several air holes evenly distributed around the wall of the cooling air pipe.

[0015] The beneficial effects of the utility model are:

[0016] The mold of the lost foam casting of the utility model is provided with a filling auxiliary structure, a sprue, a runner, and an inner gate. Before the pouring process, the structural stability of the casting can be increased by cooperating with the casting and the filling auxiliary structure.

[0017] Furthermore, during the solidification and cooling process of the casting, the relatively thin filling auxiliary structure provides better heat dissipation and faster cooling, preempting the overall solidification and shrinkage of the casting. This provides tensile stress and prevents shrinkage and deformation. During pouring, molten iron flows directly through the filling auxiliary structure into blind spots in the casting, ensuring rapid and smooth filling of the casting, reducing top-down splashing, slag entrainment, and air entrainment, ensuring that blind spots are filled intact. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the mold of the lost foam casting of the utility model;

[0019] Figure 2 It is a bottom view of the mold cavity of the lost foam casting of the utility model;

[0020] Figure 3 The utility model is a structural schematic diagram of a filling auxiliary structure in a mold of a lost foam casting.

[0021] In the figure, 1. box, 2. outer sand mold, 3. inner sand mold, 4. sprue, 5. runner, 6. inner gate, 7. cavity, 8. filling auxiliary structure, 9. cooling air pipe, 10. exhaust channel, 11. inlet, 12. outlet, 13. inner pipe. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Example 1

[0024] The mold of the utility model lost foam casting is as follows Figure 1 As shown, the mold comprises a box body 1, inside which an inner sand mold 3 and an outer sand mold 2 are arranged, a cavity 7 is formed between the inner sand mold 3 and the outer sand mold 2, and a sprue 4 is provided on one side of the cavity 7. One end of the sprue 4 passes through the outer sand mold 2 for pouring molten iron, and the other end is connected to a runner 5 provided at the bottom of the cavity 7. The runner 5 is connected to the ingates 6 at both ends of the cavity 7. The inner sand mold 3 is located between the runner 5 and the cavity 7.

[0025] That is, the molten iron is drained into the runner 5 through the sprue 4. As the molten iron is continuously poured into the sprue 4, the molten iron in the runner 5 moves upward through the ingates 6 and enters the cavity 7.

[0026] The cavity 7 is connected to the ingate 6 and the bottom of the cavity 7 through a number of filling auxiliary structures 8. The filling auxiliary structures 8 not only enhance the structural stability of the formed casting, but also provide better heat dissipation and faster cooling during solidification and cooling because they are separate from the cavity 7. This allows the casting to solidify and shrink before it shrinks, providing tensile stress to the casting and preventing shrinkage and deformation.

[0027] The main purpose is to set a filling auxiliary structure 8 at the position of the inner gate 6 to directly introduce the molten iron entering the cavity 7 into the dead corner position of the cavity 7 through the filling auxiliary structure 8, so that the height of the molten iron in the middle part of the cavity 7 is consistent with the height of the molten iron on both sides of the cavity 7. There is no need for the molten iron to be filled to a certain height first and then return to flow downward to fill the mold, thereby avoiding the generation of defects such as slag entanglement, air entanglement, and cold shut.

[0028] Furthermore, the filling auxiliary structure 8 is merely a through pipe containing a cavity.

[0029] Example 2

[0030] The mold of the lost foam casting of the present invention includes a box body 1, an inner sand mold 3 and an outer sand mold 2 are arranged inside the box body 1, a cavity 7 is formed between the inner sand mold 3 and the outer sand mold 2, a sprue 4 is provided on one side of the cavity 7, one end of the sprue 4 passes through the outer sand mold 2 for pouring molten iron, and the other end is connected to a runner 5 arranged at the bottom of the cavity 7, the runner 5 is connected to the inner gate 6 at both ends of the cavity 7, and the cavity 7 is connected to the inner gate 6 and the bottom of the cavity 7 through a number of filling auxiliary structures 8.

[0031] like Figure 2 As shown, in order to ensure that the height of the molten iron entering the area between the mold cavity 7 and the molten iron poured into the two sides of the mold cavity 7 is roughly the same, several filling auxiliary structures 8 are evenly distributed in one direction along the mold cavity 7. At the same time, the size of the filling auxiliary structure 8 can be matched with the appropriate size according to the size of the casting structure and the distance.

[0032] Furthermore, if Figure 3 As shown, the filling auxiliary structure 8 includes an inner tube 13, which adopts a Tesla valve structure. The two ends of the inner tube 13 are respectively an inlet 11 and an outlet 12. The inlet 11 is located relative to the ingates 6 and communicates with the interior of the cavity 7. The outlet 12 is located relative to the bottom of the cavity 7 and communicates with the interior of the cavity 7.

[0033] The Tesla valve is a passive, one-way valve that conducts in one direction but blocks in the reverse direction. It accelerates the fluid when flowing in the forward direction, but restricts its movement when flowing in the reverse direction. Therefore, in this embodiment, molten iron in the filling auxiliary structure 8 enters the inner tube 13 from the inlet 11 and, under the Tesla valve structure, flows rapidly toward the outlet 12, increasing the speed at which the molten iron enters the center of the mold cavity 7. The molten iron can flow directly through the filling auxiliary structure 8 into the blind spots of the mold cavity 7, enabling rapid and smooth filling of the casting, reducing top-down splashing, slag entrainment, and air entrapment, ensuring that blind spots are filled properly.

[0034] Furthermore, a plurality of exhaust channels 10 are provided on the top of the outer sand mold 2 relative to the mold cavity 7 . The bottom ends of the exhaust channels 10 are connected to the interior of the mold cavity 7 , and the tops of the exhaust channels 10 pass through the outer sand mold 2 for exhaust.

[0035] When the molten iron enters the runner 5 or the cavity 7, the generated gas can be discharged through the exhaust channel 10, so as to avoid the gas remaining in the cavity 7 and causing quality problems in the formed casting.

[0036] Example 3

[0037] On the basis of Example 2, in order to better accelerate the cooling speed of the casting, a plurality of cooling air pipes 9 are provided around the outer sand mold 2 relative to the mold cavity 7, and the cooling air pipes 9 are connected to the external cooling source.

[0038] Furthermore, a plurality of air holes are evenly opened around the wall of the cooling air pipe 9 .

[0039] When the molten iron enters the mold cavity 7 and the casting is completed, cold air is input into the cooling pipe 9. The cooling gas in the cooling pipe will be output from the pores around the wall of the cooling pipe 9 into the outer sand mold. The cooling gas is evenly distributed around the mold cavity 7. After 30 minutes, the input cold air source is turned off to cool the casting immediately. The required casting is obtained after natural cooling.

[0040] When the mold of the lost foam casting of the present invention is in use, a cavity 7 for the casting to be cast is formed by the outer sand mold 2 and the inner sand mold 3, molten iron is poured into the sprue 4, and the molten iron flows into the runner 5 and then enters the cavity 7 along the ingates 6. The molten iron rises steadily in the cavity 7 until the entire cavity 7 is filled. At this time, cold air is input into the cooling pipe 9, and the cold air cools the molten iron in the cavity 7 through the air holes on the cooling pipe 9. After half an hour, the cooling air source is turned off, and the casting is taken out after it is naturally cooled to room temperature, and the remaining sand, coating and other impurities are removed to obtain the desired casting.

Claims

1. The mold of lost foam casting is characterized by: The invention comprises a box body (1), wherein an inner sand mold (3) and an outer sand mold (2) are arranged inside the box body (1), a mold cavity (7) is formed between the inner sand mold (3) and the outer sand mold (2), a sprue (4) is provided on one side of the mold cavity (7), one end of the sprue (4) passes through the outer sand mold (2), and the other end is connected to a runner (5) arranged at the bottom of the mold cavity (7), and the runner (5) is connected to the inner gate (6) at both ends of the mold cavity (7); The mold cavity (7) is connected to the inner gate (6) and the bottom of the mold cavity (7) through a plurality of filling auxiliary structures (8).

2. The mold for lost foam casting according to claim 1, characterized in that: The inner sand mold (3) is located between the runner (5) and the mold cavity (7).

3. The mold for lost foam casting according to claim 1, characterized in that: A plurality of the filling auxiliary structures (8) are uniformly distributed in one direction along the mold cavity (7).

4. The mold for lost foam casting according to claim 3, characterized in that: The filling auxiliary structure (8) includes an inner tube (13), and the two ends of the inner tube (13) are an inlet (11) and an outlet (12), respectively. The inlet (11) is connected to the interior of the mold cavity (7) relative to the position of the ingode (6), and the outlet (12) is connected to the interior of the mold cavity (7) relative to the bottom of the mold cavity (7).

5. The mold for lost foam casting according to claim 4, characterized in that: The inner tube (13) adopts a Tesla valve structure.

6. The mold for lost foam casting according to any one of claims 1 to 5, characterized in that: The outer sand mold (2) is provided with a plurality of exhaust channels (10) at the top relative to the mold cavity (7), the bottom ends of the exhaust channels (10) are communicated with the interior of the mold cavity (7), and the tops of the exhaust channels (10) pass through the outer sand mold (2) for exhaust.

7. The mold for lost foam casting according to any one of claims 1 to 5, characterized in that: A plurality of cooling air pipes (9) are arranged around the outer sand mold (2) relative to the mold cavity (7), and the cooling air pipes (9) are connected to an external cooling source.

8. The mold for lost foam casting according to claim 7, characterized in that: A plurality of air holes are evenly distributed around the wall of the cold air pipe (9).

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