Anti-gravity pouring tool and method for aluminum alloy investment precision casting

Abstract

The invention relates to the technical field of investment casting, in particular to an anti-gravity pouring tool and method for aluminum alloy investment precision casting, and the tool comprises a bottom plate and an annular sliding rail; the annular sliding rail is mounted on the top surface of the bottom plate; a pouring hole is formed in the center of the bottom plate; a plurality of sliding blocks are installed on the annular sliding rail in a sliding mode, and each sliding block is provided with a locking structure. A stand column is vertically installed on the top of each sliding block. A transverse pressing rod is installed on each stand column, and a pressing screw is arranged at the cantilever end of each transverse pressing rod in a screwed mode. And the lower end of the pressing screw rod is used for pressing a shell placed on the bottom plate. According to the tool, rapid fixing and stable pouring of the shell are achieved, and the production efficiency is remarkably improved. Compared with a traditional sand filling pouring process, a sand box does not need to be adopted for carrying out sand filling operation, pouring can be carried out after the preheated shell is clamped and fixed through the anti-gravity pouring tool, and the pouring efficiency is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of investment casting, and particularly relates to an anti-gravity pouring tooling and method for precision investment casting of aluminum alloys. Background Art

[0002] Anti-gravity casting technology means that the driving force for filling the mold with liquid metal is opposite to the direction of gravity, and the molten metal flows along the opposite direction of gravity. In anti-gravity casting, the molten metal actually fills the mold under the combined action of gravity and an externally applied driving force. The externally applied driving force is the dominant force during the filling process of the molten metal, which enables the molten metal to overcome its own gravity, the resistance in the mold cavity, and other external forces to complete the filling of the mold. Due to the existence of the externally applied driving force, anti-gravity casting becomes a controllable process. During the filling process of the molten metal, different filling speeds can be achieved by controlling the magnitude of the externally applied force to meet the requirements of different processes; at the same time, the casting solidifies under the action of a relatively large force, improving the feeding capacity of the molten metal and reducing casting defects such as shrinkage cavities, gas holes, and pinholes.

[0003] The prior art, such as the patent with the publication number CN215966276U, discloses an anti-gravity pouring device using a silica sol mold shell, including a sand box, a melting crucible, a crucible base, heating furnace wires, a riser tube, etc.

[0004] During the traditional anti-gravity investment casting pouring process, the mold shell is placed in the sand box, and then the sand box is filled with sand. The sand serves to fix the mold shell. However, during the production process, most of the mold shells need to be preheated to 300°C - 500°C before pouring. The traditional anti-gravity pouring method has the following problems:

[0005] (1) If the mold shell is preheated separately and then taken out for installation and sand filling, the sand filling takes a long time, resulting in rapid cooling of the mold shell, and the temperature of the mold shell has dropped during pouring, failing to achieve the effect of mold shell preheating.

[0006] (2) If the mold shell is placed in the sand box for sand filling and then preheated together, this method can ensure the preheating temperature of the mold shell. However, after pouring, due to the large heat storage capacity of the sand, the casting cools slowly, resulting in metallurgical defects such as shrinkage cavities, shrinkage porosity, and pinholes in the casting. Summary of the Invention

[0007] The main object of the present invention is to propose an anti-gravity pouring tooling and method for precision investment casting of aluminum alloys, aiming to solve the above technical problems.

[0008] To achieve the above object, on the one hand, the present invention provides an anti-gravity casting tooling for precision investment casting of aluminum alloy, including a bottom plate and an annular slide rail; the annular slide rail is installed on the top surface of the bottom plate; a pouring hole is provided at the center of the bottom plate; a plurality of sliders are slidably installed on the annular slide rail, and a locking structure is provided on each slider; a vertical column is installed on the top of each slider, a horizontal pressure bar is installed on each column, and a pressing screw is screwed on the cantilever end of the horizontal pressure bar; the lower end of the pressing screw is used to press the investment shell placed on the bottom plate.

[0009] Preferably, the locking structure is a top screw, which is screwed on the slider and used to press against the annular slide rail.

[0010] Preferably, an annular groove is provided on the outer cylindrical surface of the annular slide rail, and the top end of the top screw is arranged in the annular groove.

[0011] Preferably, the horizontal pressure bar is of a telescopic rod structure.

[0012] Preferably, the horizontal pressure bar is rotatably installed on the column.

[0013] Preferably, a high-temperature resistant rubber gasket is provided at the lower end of the pressing screw.

[0014] Preferably, a plurality of lifting rings are evenly distributed at the edge position of the top surface of the bottom plate.

[0015] On the other hand, the present invention also provides an anti-gravity casting method for precision investment casting of aluminum alloy. Using the above anti-gravity casting tooling, it includes the following steps:

[0016] S1. Pouring preparation: Lift and place the anti-gravity casting tooling on the anti-gravity casting machine.

[0017] S2. Investment shell preheating: Put the investment shell into a preheating furnace for preheating.

[0018] S3. Investment shell fixing: Place the preheated investment shell on the bottom plate, so that the pouring cup on the investment shell is buckled on the bottom plate and aligned with the pouring hole; adjust the position of the slider, and use the locking structure to lock the slider on the annular slide rail; rotate the pressing screw so that the pressing screw moves downward and presses tightly against the investment shell.

[0019] S4. Implement pouring.

[0020] S5. Cooling treatment: After pouring is completed, loosen the pressure bar bolt and take out the investment shell for cooling.

[0021] Preferably, in step S2, the investment shell is preheated in a segmented heating manner:

[0022] The first stage: from room temperature to 200 °C, with a heating rate of 50 °C / h;

[0023] The second stage: 200 - 350 °C, with a heating rate of 30 °C / h;

[0024] The third stage: 350 - 500 °C, with a heating rate of 20 °C / h.

[0025] Preferably, in the step S4, casting is carried out by means of counter-gravity casting, and the process parameters are as follows:

[0026] Casting pressure: 0.8 - 1.2 MPa;

[0027] Pressure holding time: 30 - 60 s;

[0028] Casting temperature: 700 - 750 °C.

[0029] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0030] (1) Improve production efficiency and casting quality. By using the counter-gravity casting tooling provided by the present invention, rapid fixing and stable casting of the mold shell are realized, significantly improving production efficiency. Compared with the traditional sand filling casting process, the counter-gravity casting method provided by the present invention does not require sand filling operation in a sand box. After the preheated mold shell is clamped and fixed by the counter-gravity casting tooling, casting can be carried out, greatly improving the casting efficiency. In addition, since no sand box is used, it can be quickly cooled after casting, effectively solving metallurgical defects such as shrinkage porosity, shrinkage cavity, and pinholes caused by slow cooling after counter-gravity casting of aluminum alloy investment casting.

[0031] (2) Reduce labor intensity. Casting without sand filling reduces the complexity and labor intensity of manual operations. At the same time, the structural design of the tooling makes the installation and removal of the mold shell more convenient, further reducing the labor intensity of workers.

[0032] (3) Strong adaptability. This tooling can quickly fix mold shells of different sizes and has strong adaptability. No matter how complex the shape of the mold shell is, as long as it is within the adjustment range of the tooling, rapid fixing and stable casting can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0034] Figure 1Schematic diagram after the shell mold is fixed by the counter-gravity casting tooling provided by the present invention;

[0035] Figure 2 Bottom view of the counter-gravity casting tooling provided by the present invention.

[0036] Explanation of the reference numerals in the attached drawings: 1, bottom plate; 1a, pouring hole; 2, annular slide rail; 3, slider; 4, column; 5, cross pressure bar; 6, pressing screw; 7, shell mold; 7a, shell mold body; 7b, sprue; 7c, pouring cup; 7d, riser; 8, tightening screw; 9, lifting ring. Specific embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the attached drawings). If the specific posture changes, the directional indications will also change accordingly.

[0039] Combined with Figure 1 , Figure 2 As shown, on the one hand, this embodiment provides a counter-gravity casting tooling for precision investment casting of aluminum alloy, including a bottom plate 1 and an annular slide rail 2; the annular slide rail 2 is installed on the top surface of the bottom plate 1; a pouring hole 1a is provided at the center of the bottom plate 1; a plurality of sliders 3 are slidably installed on the annular slide rail 2, and a locking structure is provided on each slider 3; a column 4 is vertically installed on the top of each slider 3; a cross pressure bar 5 is installed on each column 4, and a pressing screw 6 is screwed on the cantilever end of the cross pressure bar 5; the lower end of the pressing screw 6 is used to press the shell mold 7 placed on the bottom plate 1.

[0040] Since the slider 3 can slide on the annular slide rail 2, when clamping and removing the shell mold 7, the column 4 can be moved away to avoid obstruction by the column 4.

[0041] Combined with Figure 1As shown, the locking structure is a top screw 8, which is screwed onto the slider 3 and used to press against the annular slide rail 2. Further, an annular groove 2a is provided on the outer cylindrical surface of the annular slide rail 2, and the pressing end of the top screw 8 is arranged in the annular groove 2a. When the column 4 moves into place, it is only necessary to tighten the top screw 8 to fix the slider 3. In addition, since the pressing end of the top screw 8 is stuck in the annular groove 2a, the column 4 can be effectively prevented from tilting.

[0042] Combined with Figure 1 As shown, the cross pressure bar 5 is a telescopic rod structure, and its length can be adjusted according to the size of the shell 7 to ensure that the pressing screw 6 can press against the shell mold 7. Specifically, the cross pressure bar 5 includes an inner tube body and an outer tube body, and the inner tube body is slidably inserted into the rectangular hole of the outer tube body to form a telescopic rod structure.

[0043] In this embodiment, the cross pressure bar 5 is rotatably installed on the column 4. Specifically, the cross pressure bar 5 can rotate around the axis of the column 4 but cannot slide up and down. By using the rotational installation structure of the cross pressure bar 5 combined with the telescopic rod structure, it can better ensure that the pressing screw 6 can press against the shell mold 7.

[0044] In this embodiment, a high-temperature resistant rubber gasket (not shown in the figure) is provided at the lower end of the pressing screw 6 to prevent damage to the surface of the shell mold 7. The high-temperature resistant rubber gasket can be made of fluorosilicone rubber, etc.

[0045] A plurality of lifting rings 9 are evenly distributed at the edge position of the top surface of the bottom plate 1 to facilitate the lifting of the entire tooling.

[0046] On the other hand, this embodiment also provides an anti-gravity casting method for precision investment casting of aluminum alloy, using the above anti-gravity casting tooling, including the following steps:

[0047] S1. Pouring preparation: Lift and place the anti-gravity casting tooling on the anti-gravity casting machine;

[0048] S2. Shell mold preheating: Place the shell mold 7 in a preheating furnace for preheating,

[0049] S3. Shell mold fixing: Place the preheated shell mold 7 on the bottom plate 1 so that the pouring cup 7c on the shell mold 7 is inverted on the bottom plate 1 and aligned with the pouring hole 1a; Adjust the position of the slider 3, and use the locking structure to lock the slider 3 on the annular slide rail 2; Rotate the pressing screw 6 so that the pressing screw 6 moves downward and presses against the shell mold 7;

[0050] S4. Implement pouring;

[0051] S5. Cooling treatment: After pouring is completed, loosen the pressure bar bolt 6 and take out the shell mold for cooling.

[0052] In step S2, the mold shell 7 is preheated by a staged heating method: the first stage: room temperature to 200°C, heating rate 50°C / h; the second stage: 200-350°C, heating rate 30°C / h; the third stage: 350-500°C, heating rate 20°C / h. By setting the three-stage staged heating, the stress cracking problem of the mold shell 7 caused by rapid heating is effectively avoided. The step-type heating curve matches the expansion characteristics of the mold shell material, and actual measurements show that the deformation of the mold shell can be reduced by about 15%. Slow heating ensures the uniformity of the temperature inside the mold shell 7, the solidification of the molten metal is more uniform during pouring, and the porosity inside the casting is reduced to less than 1.5%. The specially designed low-speed heating in the third stage allows the binder to be fully decomposed and reduces the surface inclusion defects of the casting. Compared with the traditional constant-speed heating, the staged heating can save 12-15% of energy consumption and shorten the preheating time by 10%.

[0053] The mold shell 7 includes a mold shell body 7a, a sprue 7b, a pouring cup 7c and a riser 7d. In this embodiment, four sliders 3 are arranged on the annular slide rail 2, so the entire tooling has four columns 4 and four clamping screws 6. In the step S3, when the mold shell 7 is clamped and fixed, one of the clamping screws 6 is pressed against the riser 7d at the top of the mold shell body 7a, and the remaining three clamping screws 6 are pressed against the mold shell body 7a.

[0054] In the step S4, pouring is carried out by counter-gravity pouring, and the process parameters are: pouring pressure: 0.8-1.2MPa; holding time: 30-60s; pouring temperature: 700-750℃. The use of a pouring pressure range of 0.8-1.2MPa can not only ensure the complete filling of thin-walled parts, with a minimum 1mm wall thickness qualification rate of 98%, but also avoid the risk of shell rupture caused by excessive pressure. The 30-60s holding time allows the thick and large parts of the casting to be fully compensated for shrinkage, and the shrinkage defect rate is reduced from 8% in the traditional process to below 2%. The pouring temperature control of 700-750℃ is 50℃ lower than the conventional pouring temperature of aluminum alloys, and the counter-gravity pouring can refine the grain size by 30%. In terms of improved mechanical properties, the tensile strength is increased by 15% and the elongation is increased by 20%.

[0055] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An anti-gravity casting tooling for precision investment casting of aluminum alloy, characterized in that, It includes a bottom plate (1) and an annular slide rail (2); the annular slide rail (2) is installed on the top surface of the bottom plate (1); A pouring hole (1a) is provided at the center of the bottom plate (1); A plurality of sliders (3) are slidably installed on the annular slide rail (2), and a locking structure is provided on each slider (3); A vertical column (4) is vertically installed on the top of each slider (3); A horizontal pressing rod (5) is installed on each column (4), and a pressing screw (6) is screwed on the cantilever end of the horizontal pressing rod (5); the lower end of the pressing screw (6) is used to press the mold shell (7) placed on the bottom plate (1).

2. The anti-gravity casting tooling for precision investment casting of aluminum alloy as described in claim 1, characterized in that, The locking structure is a top screw (8), and the top screw (8) is screwed on the slider (3) and is used to press against the annular slide rail (2).

3. The anti-gravity casting tooling for precision investment casting of aluminum alloy as described in claim 2, characterized in that, An annular groove (2a) is provided on the outer cylindrical surface of the annular slide rail (2), and the pressing end of the top screw (8) is arranged in the annular groove (2a).

4. The counter-gravity casting tooling for precision investment casting of aluminum alloy according to claim 1, characterized in that, The horizontal pressing rod (5) is of a telescopic rod structure.

5. The anti-gravity casting tooling for precision investment casting of aluminum alloy as described in claim 1, characterized in that, The horizontal pressing rod (5) is rotatably installed on the column (4).

6. The anti-gravity casting tooling for precision investment casting of aluminum alloy as claimed in claim 1, wherein, A high-temperature resistant rubber gasket is provided at the lower end of the pressing screw (6).

7. The anti-gravity casting tooling for precision investment casting of aluminum alloy as described in claim 1, characterized in that, A plurality of lifting rings (9) are evenly distributed at the edge position of the top surface of the bottom plate (1).

8. An anti-gravity casting method for precision investment casting of aluminum alloy, characterized in that, Using the counter-gravity pouring tooling according to any one of claims 1 to 7, it includes the following steps: S1. Pouring preparation: Lift and place the counter-gravity pouring tooling on the counter-gravity pouring machine; S2. Mold shell preheating: Place the mold shell (7) in a preheating furnace for preheating, S3. Mold shell fixing: Place the preheated mold shell (7) on the bottom plate (1) so that the pouring cup (7c) on the mold shell (7) is buckled on the bottom plate (1) and aligned with the pouring hole (1a); Adjust the position of the slider (3), and use the locking structure to lock the slider (3) on the annular slide rail (2); Rotate the pressing screw (6) so that the pressing screw (6) moves downward and presses the mold shell (7); S4. Implement pouring; S5. Cooling treatment: After pouring is completed, loosen the pressing rod bolt (6), take out the mold shell and cool it.

9. The anti-gravity casting method for precision investment casting of aluminum alloy as claimed in claim 8, characterized in that, In the step S2, the mold shell (7) is preheated in a segmented heating manner: The first stage: from room temperature to 200 °C, the heating rate is 50 °C / h; The second stage: 200 - 350 °C, the heating rate is 30 °C / h; The third stage: 350 - 500 °C, the heating rate is 20 °C / h.

10. A counter-gravity casting method for precision investment casting of aluminum alloy as claimed in claim 8, wherein, In the step S4, pouring is implemented in a counter-gravity pouring manner, and the process parameters are: Pouring pressure: 0.8 - 1.2 MPa; Pressure holding time: 30 - 60 s; Pouring temperature: 700 - 750 °C.

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