Casting process for improving performance of aluminum alloy based on rapid chilling of 3D printing sand mold

Abstract

The invention belongs to the technical field of metal casting, and particularly relates to a casting process for improving aluminum alloy performance based on 3D printing sand mold rapid chilling, which comprises the steps of process design, 3D printing sand mold design, mold flow analysis, 3D printing sand mold, casting molding and casting treatment. A 3D printing sand mold technology is utilized, a process design scheme can be flexibly applied, a casting channel can be designed for the sand mold, a cooling channel can also be designed for the sand mold, the 3D printing sand mold can achieve a complex structure which is difficult to manufacture through a traditional method, meanwhile, design of a cavity channel is flexible and diverse, the channel is designed in the sand mold along with the mold, and therefore the whole casting can be uniformly solidified; therefore, the overall performance stability is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal casting, and particularly relates to a casting process for improving the performance of aluminum alloy based on rapid chilling of 3D printed sand molds. Background Art

[0002] The aluminum alloy casting process is a manufacturing process in which molten aluminum alloy is poured into a mold and cooled and solidified to form a shape. Traditional aluminum alloy casting processes usually use sand molds or metal molds. Aluminum alloys are commonly used for chassis parts of vehicle bodies due to their excellent properties. In order to further improve the overall performance of the chassis parts, integral casting is often used during casting.

[0003] However, the traditional aluminum alloy casting process has the following problems: (1). The traditional sand mold manufacturing cycle is long, and it is difficult to achieve complex structures; (2). The cooling rate of the castings is relatively slow, the grains are coarse, and the mechanical properties are insufficient; (3). The internal cooling of the castings is uneven, and thermal stress or deformation is likely to occur.

[0004] Moreover, the vehicle body chassis parts require relatively high strength and high elongation rate ≥ 8%, etc. At present, the elongation rate of traditional sand mold casting is relatively low, and the highest elongation rate is only 3 - 4%, which cannot meet its usage requirements.

[0005] In addition, the traditional casting process is complex, which specifically includes process steps such as product design, process design, sand core design, mold design, mold manufacturing, mold core making, core assembly and pouring, and casting treatment. During the implementation process, there are limitations for the casting of complex castings, and at the same time, the need for sand core cooperation for positioning will affect the core assembly accuracy. Summary of the Invention

[0006] Object of the Invention: The object of the present invention is to provide a casting process for improving the performance of aluminum alloy based on rapid chilling of 3D printed sand molds to solve the above technical problems.

[0007] Technical Solution: To achieve the above object, the present invention provides a casting process for improving the performance of aluminum alloy based on rapid chilling of 3D printed sand molds, including the following steps: S1, Process Design: According to the three-dimensional data of the product, complete the three-dimensional modeling of the casting, and conduct casting design for the casting, and design the gating system, chill blocks, etc. for the product; S2, 3D Printed Sand Mold Design: According to the designed gating system and structures such as chill blocks, design the 3D printed sand mold, and consider casting process parameters such as parting surface, draft angle, machining allowance, etc., and convert them into STL format files to prepare for 3D printing the sand mold; S3, Mold Flow Analysis: Conduct mold flow analysis according to the casting process; S4, 3D printing of sand mold: Use a 3D printing device to print the sand mold layer by layer according to the three-dimensional model of the casting. Design a cavity channel inside the sand mold, and the layout of the cavity channel matches the geometric shape of the casting. Arrange cooling pipelines inside the cavity channel; S5, casting molding: Melt the aluminum alloy raw material to a predetermined temperature and remove impurities in the melt; Pour the molten aluminum alloy into the 3D printed sand mold and wait for it to initially solidify; After the casting initially solidifies, pass a cooling medium through the cavity channel in the sand mold; S6, casting processing: Perform post-processing on the casting after the cooling air is finished.

[0008] Further, the specific method of the mold flow analysis in step S3 is: Through filling and solidification simulation of the process design, predict the metal liquid flow state, temperature field distribution and potential defects, and optimize the gating system and riser design. Through mold flow analysis, defects that may occur in the product, such as porosity, burning, insufficient filling, etc., can be predicted and avoided.

[0009] Further, the sand mold material in step S4 is silica sand and binder, and the diameter range of the cavity channel is 5 - 20 mm.

[0010] Further, the binder includes resin sand with a particle size of 70 / 140 mesh and furan resin binder.

[0011] Further, the 3D printed sand mold adopts selective laser sintering (SLS) or binder jetting technology, and layer by layer accumulates silica sand containing resin and binder to make the 3D printed sand mold.

[0012] Further, in step S5, the aluminum alloy raw material is melted to 740°C ± 3°C and injected into the cavity of the 3D printed sand mold by a low-pressure process method. Control the pouring temperature and speed during injection to avoid defects such as porosity and cold shut.

[0013] Further, the cooling medium in step S5 is dry ice gas or dry ice particles. The cooling time is 5 - 15 min.

[0014] Even further, step S6 includes: A1, Remove the 3D printed sand mold wrapping the casting by vibration demolding and take out the casting; A2, Remove the gating and riser, and perform surface treatments such as shot blasting and grinding; A3, Use a four-axis or five-axis machining center to complete the machining of precision parts; A4, Verify the internal quality of the casting through dimensional measurement, penetrant inspection, and X-ray inspection.

[0015] From the above technical solutions, it can be seen that the present invention has the following beneficial effects: 1. The present invention provides a casting process for improving the properties of aluminum alloys based on rapid quenching of 3D printed sand molds. Using 3D printed sand mold technology, the process design scheme can be flexibly applied. Not only can the sand mold be designed with casting channels, but also cooling channels can be designed. 3D printed sand molds can achieve complex structures that are difficult to manufacture by traditional methods. At the same time, the design of the cavity channels is flexible and diverse, and the channel conformal design is in the sand mold, which can enable the overall uniform solidification of the casting, thereby ensuring stable overall performance.

[0016] 2. The present invention has high efficiency in cooling and uniformity. By introducing dry ice into the cavity channels, rapid and uniform cooling of the casting can be achieved, the grain structure can be refined, and the mechanical properties can be improved.

[0017] 3. Using the casting process described in the present invention can reduce thermal stress and deformation. Uniform cooling reduces the thermal stress inside the casting and reduces the risk of deformation.

[0018] 4. Compared with traditional processes, the casting process described in the present invention uses 3D printing technology, which improves the degree of freedom of the sand mold structure and makes the design more flexible; at the same time, the process steps are simplified, and molds do not need to be made to achieve high-efficiency flexible manufacturing; there is no need for sand core cooperation and positioning, which improves the casting quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the process flow chart of a casting process for improving the properties of aluminum alloys based on rapid quenching of 3D printed sand molds described in the present invention; Figure 2 is the 3D scanning measurement size table; Figure 3 is the low-pressure parameter table for low-pressure casting. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] As Figure 1 shown, a casting process for improving the properties of aluminum alloys based on rapid quenching of 3D printed sand molds includes the following steps: S1, Process design: According to the three-dimensional data of the product, complete the three-dimensional modeling of the casting, and conduct casting design for the casting, including the design of the casting system, chill blocks, etc. for the product; S2, 3D printed sand mold design: According to the designed casting system, chill blocks and other structures, design the 3D printed sand mold. Casting process parameters such as parting surfaces, draft angles, and machining allowances need to be considered and converted into STL format files to prepare for 3D printing the sand mold; S3, Mold flow analysis: Conduct mold flow analysis according to the casting process; S4, 3D printing of sand mold: Using a 3D printing device, layer by layer print a sand mold according to the three-dimensional model of the casting. Design a cavity channel inside the sand mold, and the layout of the cavity channel matches the geometric shape of the casting. Arrange cooling pipelines inside the said cavity channel; S5, pouring and molding: Melting the aluminum alloy raw material to a predetermined temperature and removing impurities in the melt; Pouring the molten aluminum alloy into the 3D printed sand mold and waiting for it to initially solidify; After the casting initially solidifies, introduce a cooling medium through the cavity channel in the sand mold; S6, casting treatment: Conduct post-treatment on the casting after the cold air blowing is completed.

[0022] For the casting process based on 3D printed sand mold with rapid quenching to improve the performance of aluminum alloy described in the present invention, by utilizing the 3D printed sand mold technology, the process design scheme can be flexibly applied. Not only can the sand mold be designed with casting channels, but also cooling channels can be designed. The 3D printed sand mold can achieve complex structures that are difficult to manufacture by traditional methods. At the same time, the design of the cavity channel is flexible and diverse, and the channel is designed according to the shape in the sand mold, which can enable the overall casting to solidify uniformly, thereby ensuring the stability of the overall performance. By introducing dry ice through the cavity channel, rapid and uniform cooling of the casting can be achieved, refining the grain structure and improving the mechanical properties. As Figure 2 shown, the scanned data sizes are all within the tolerance range, and uniform cooling reduces the thermal stress inside the casting and reduces the risk of deformation.

[0023] Among them, the specific method of the mold flow analysis in the step S3 is: Through filling and solidification simulation of the process design, predict the metal liquid flow state, temperature field distribution and potential defects, and optimize the gating system and riser design.

[0024] Specifically, in the step S4, the sand mold material is silica sand and binder, and the diameter range of the cavity channel is 5 - 20 mm.

[0025] A more optimal solution is that the binder includes resin sand with a particle size of 70 / 140 mesh and furan resin binder.

[0026] In a further optimized solution, the 3D printed sand mold adopts selective laser sintering (SLS) or binder jetting technology, and layer by layer stacks silica sand containing resin and binder to make the 3D printed sand mold.

[0027] Among them, in the step S5, the aluminum alloy raw material is melted to 740°C ± 3°C, and is injected into the cavity of the 3D printed sand mold by a low-pressure process method. Control the pouring temperature and speed during injection to avoid defects such as porosity and cold shut. The pouring temperature is 740°C ± 3°C, and the pouring rate can be obtained from pressure / time. As Figure 3As shown in the figure, it is the low-pressure parameter table for low-pressure casting. When using low-pressure casting, the molten metal fills the mold smoothly without splashing, which can avoid entraining gas and scouring the mold wall and core, improving the qualified rate of the casting. At the same time, the casting crystallizes under pressure, resulting in a dense structure, clear contour, smooth surface, and high mechanical properties.

[0028] Among them, the cooling medium in step S5 is dry ice gas or dry ice particles. The cooling time is 5 - 15 minutes. The endothermic sublimation of dry ice realizes the rapid cooling of the casting. At the same time, the rate and time of dry ice injection are controlled. The rate of dry ice injection is 2.5 L / min to ensure uniform cooling of the casting and avoid stress concentration.

[0029] Specifically, step S6 includes: A1, removing the 3D printed sand mold wrapping the casting by vibration demolding and taking out the casting; A2, removing the riser and runner and performing surface treatments such as shot blasting and grinding; A3, completing the machining of precision parts using a four-axis or five-axis machining center; A4, verifying the internal quality of the casting through dimensional measurement, penetrant inspection, and X-ray detection.

[0030] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds, characterized in that, It includes the following steps: S1, Process design: Based on the three-dimensional data of the product, complete the three-dimensional modeling of the casting, and conduct casting design for the casting, including the design of the gating system, chill, etc. for the product; S2, 3D printing sand mold design: According to the designed gating system, chill and other structures, design the 3D printing sand mold, considering casting process parameters such as parting surface, draft angle, machining allowance, etc., and convert it into an STL format file to prepare for 3D printing the sand mold; S3, Mold flow analysis: Conduct mold flow analysis according to the casting process; S4, 3D printing sand mold: Use 3D printing equipment to layer-print the sand mold according to the three-dimensional model of the casting. Design cavity channels inside the sand mold, and the layout of the cavity channels matches the geometric shape of the casting. Arrange cooling pipelines in the cavity channels; S5, Pouring and forming: Melt the aluminum alloy raw material to a predetermined temperature and remove impurities in the melt; Pour the molten aluminum alloy into the 3D printed sand mold and wait for it to initially solidify; After the casting initially solidifies, introduce a cooling medium through the cavity channels in the sand mold; S6, Casting treatment: Conduct post-treatment on the casting after cooling with cold air.

2. A casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds according to claim 1, characterized in that, The specific method of the mold flow analysis in step S3 is: Through filling and solidification simulation of the process design, predict the metal liquid flow state, temperature field distribution and potential defects, and optimize the gating system and riser design.

3. A casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds according to claim 1, characterized in that, In step S4, the sand mold material is silica sand and binder, and the diameter range of the cavity channels is 5 - 20 mm.

4. The casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds according to claim 3, characterized in that, The binder includes resin sand with a particle size of 70 / 140 mesh and furan resin binder.

5. A casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds according to claim 4, characterized in that, The 3D printed sand mold is made by selective laser sintering (SLS) or binder jetting technology, layer by layer stacking silica sand containing resin and binder to make the 3D printed sand mold.

6. A casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds according to claim 1, characterized in that, In step S5, the aluminum alloy raw material is melted to 740°C ± 3°C and injected into the cavity of the 3D printed sand mold by a low-pressure process method. Control the pouring temperature and speed during injection to avoid defects such as porosity and cold shut.

7. A casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds according to claim 1, characterized in that, The cooling medium in step S5 is dry ice gas or dry ice particles. The cooling time is 5 - 15 min.

8. A casting process for improving the properties of aluminum alloy based on rapid quenching of 3D printed sand molds according to claim 1, characterized in that, Step S6 includes: A1, Remove the 3D printed sand mold wrapping the casting by vibration demolding and take out the casting; A2, Remove the gating and riser, and conduct surface treatments such as shot blasting and grinding; A3, Use a four-axis or five-axis machining center to complete the machining of precision parts; A4, Verify the internal quality of the casting through dimensional measurement, penetrant inspection, and X-ray detection.

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