Lost foam casting production system and process for riser feeding

Abstract

The invention discloses an evanescent mode casting production process for riser feeding, relates to a pouring process, and aims to solve the technical problems of flywheel shell shrinkage cavity and shrinkage porosity caused by the influence of molten metal self-shrinkage, pattern decomposition products and unreasonable design of a pouring system in the conventional flywheel shell pouring process. The technology comprises the steps that firstly, the modulus of a riser and the modulus of a fed part of a casting are set, and the modulus of the riser is larger than the modulus of the fed part of the casting; 2, a casting structure is obtained, and the type of a riser is selected according to the casting structure to ensure the feeding efficiency; and 3, analog simulation is conducted on the selected riser type to generate a simulated pouring system, simulated pouring is conducted on the casting through the simulated pouring system, and the feasibility of the technology is judged according to the pouring result. The invention further discloses an evanescent mode casting production system for riser feeding. The production efficiency is improved, and the shrinkage cavity occurrence rate in the casting pouring process is effectively reduced.

Description

A Lost Foam Casting Production System and Process with Riser Feeding Technical Field

[0001] This invention relates to casting processes, and more specifically, to a lost foam casting production system and process with riser feeding. Background Technology

[0002] In the automotive industry, ductile iron is widely used in key components such as engine blocks, crankshafts, and wheel hubs to meet the requirements of high strength and lightweighting. In the machinery industry, it is often used to manufacture machine tool beds, gears, hydraulic components, etc. Due to its comprehensive mechanical properties and processability, it has become an economical alternative to some steel and alloy materials, which is of great significance for improving equipment performance and reducing manufacturing costs.

[0003] Figure 3 shows the original casting system process for the flywheel housing. The melting and exiting temperature range is controlled between 1560 and 1580℃, the casting temperature is between 1480 and 1500℃, the casting negative pressure is -0.04 to -0.06 MPa, the negative pressure holding time is 900s, and the chemical composition is shown in the table below.

[0004]

[0005] When the mechanical properties of the samples were tested, the results met the requirements of the QT450-10 standard, and the spheroidization rate reached level 3, which is consistent with the technical specifications of the ductile iron flywheel housing. However, during the trial production and processing of the flywheel housing, defects such as shrinkage porosity, shrinkage cavities, and inclusions were observed, especially in the geometric hot spot area, where shrinkage cavities were particularly significant (see Figure 4).

[0006] Causes of shrinkage cavities and porosity in flywheel housings: 1. Metal liquid shrinkage: When liquid metal cools and solidifies, it goes through three stages: liquid shrinkage, solidification shrinkage and solidification shrinkage. If the liquid shrinkage and solidification shrinkage cannot be filled by the subsequent molten metal, shrinkage cavities will be formed.

[0007] 2. Impact of Pattern Decomposition Products: Foam patterns rapidly decompose and vaporize under the impact of molten metal, generating a large amount of gas. If the sand mold has poor permeability or poor venting, the gas is easily trapped inside or at the interface of the molten metal, hindering the flow of the molten metal and resulting in localized failure to compensate for shrinkage, forming shrinkage cavities.

[0008] 3. Inappropriate gating system design: If the riser is poorly designed (e.g., too small or poorly positioned), it cannot effectively provide feeding molten metal, and shrinkage cavities are prone to form in thick parts of the casting. Pouring speeds that are too fast or too slow may result in incomplete pattern decomposition and increased gas, while slow speeds may cause the molten metal to solidify prematurely before feeding. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a lost foam casting production system and process with riser feeding to address the shortcomings of the prior art. This solves the technical problems of shrinkage cavities and porosity in flywheel shells caused by the shrinkage of the molten metal itself, the influence of pattern decomposition products, and unreasonable design of the gating system in the existing flywheel shell casting process.

[0010] This invention discloses a lost foam casting production process using risers for feeding. The process includes: Step 1: Setting the modulus of the riser and the modulus of the feeding portion of the casting, wherein the modulus of the riser is greater than the modulus of the feeding portion; Step 2: Obtaining the casting structure and selecting a riser type based on the casting structure to ensure feeding efficiency; Step 3: Simulating the selected riser type to generate a simulated gating system, and simulating the casting's pouring using the simulated gating system. If no shrinkage cavity area is found on the simulated casting, the process is deemed feasible, and a target gating system is generated based on the riser type; if a shrinkage cavity area is found on the poured casting, the process is deemed infeasible.

[0011] As a further improvement, the method for selecting the riser type according to the casting structure is as follows: the riser type includes top riser, side riser, and internal riser; when the casting structure is a thick casting, the riser type is selected as top riser; when the casting structure is a medium-thickness casting or a casting with a complex structure, the riser type is selected as side riser; when the casting structure is a casting with high machining precision requirements, the riser type is selected as internal riser.

[0012] Furthermore, the top riser is located at the highest and thickest part of the casting, the side riser is located at the thick wall of the side of the casting, and the inner riser is completely placed inside the sand mold.

[0013] Furthermore, in step one, the modulus of the riser is 1.2 to 1.5 times the modulus of the portion of the casting that is being fed.

[0014] Furthermore, in step three, the selected riser type is simulated using ProCAST to generate a simulated gating system.

[0015] A lost foam casting production system with riser feeding includes a pouring cup, a sprue, a runner, and an ingate. The system also includes a top riser and a side riser generated according to the above-mentioned lost foam casting production process with riser feeding. The top riser is connected to the runner and is disposed on the casting. The side riser is disposed on the thick wall of the side of the casting.

[0016] Beneficial Effects: The advantages of this invention are as follows: This invention sets the modulus of the riser and the modulus of the feeding portion of the casting, with the riser modulus being greater than the feeding portion modulus; obtains the casting structure, selects the riser type based on the casting structure to ensure feeding efficiency; simulates the selected riser type to generate a simulated gating system, and simulates casting through the gating system. If no shrinkage cavity area is found on the cast casting, the process is deemed feasible; if a shrinkage cavity area is found on the cast casting, the process is deemed infeasible. This provides practical basis for riser selection for similar thick castings, improves production efficiency, effectively reduces the occurrence rate of shrinkage cavities during casting, is applicable to castings of various sizes, has a simple process, and lowers the operating threshold. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the lost foam casting production system with riser feeding according to the present invention; Figure 2 is a simulation diagram of the lost foam casting production process with riser feeding according to the present invention; Figure 3 is a schematic diagram of the existing process gating system; Figure 4 is a schematic diagram of the existing flywheel housing shrinkage cavity.

[0018] Wherein: 1-pouring cup, 2-sprue, 3-sprue, 4-ingate, 5-top riser, 6-side riser, 7-casting. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention. Referring to Figures 1-2, a lost foam casting production process for riser feeding according to the present invention includes the following steps: First, the solidification sequence of the risers must be ensured: This is a prerequisite for successful feeding, and the requirement that "the casting solidifies first, and the riser solidifies later" must be met. This is usually achieved through the "modulus principle," setting the modulus (volume / heat dissipation area) of the riser and the modulus of the feeding part of the casting, with the modulus of the riser being greater than the modulus of the feeding part of the casting. In step one, the modulus of the riser is 1.2 to 1.5 times the modulus of the feeding part of the casting. The larger the modulus, the slower the solidification.

[0020] Step 2: Obtain the casting structure and gating method, and select the riser type based on the casting structure and gating method to ensure feeding efficiency. The method for selecting the riser type based on the casting structure is as follows: riser types include top risers, side risers, and internal risers.

[0021] When the casting structure is a thick casting, the riser type is selected as a top riser. The top riser is set at the highest and thickest part of the casting, and the feeding range is large.

[0022] When the casting structure is of medium thickness or complex structure, the riser type is selected as a side riser. The side riser is set at the thick wall of the side of the casting, which facilitates molding.

[0023] When the casting structure requires high precision in machining, the riser type should be an internal riser. The internal riser is completely placed inside the sand mold, which results in slow heat dissipation and high utilization of molten metal, but attention should be paid to venting.

[0024] By selecting the riser type according to the casting structure and pouring method, it becomes applicable to a variety of casting types, improves operational flexibility, and is not limited to existing technologies suitable for small and medium-sized castings with complex structures, thus effectively improving pouring efficiency.

[0025] Step 3: Simulate the selected riser type to generate a simulated gating system. Simulate the pouring of the casting using this system. If no shrinkage cavities are found on the simulated casting, the process is deemed feasible, and a target gating system is generated based on the selected riser type. If shrinkage cavities are found on the simulated casting, the process is deemed infeasible. In Step 3, ProCAST is used to simulate the selected riser type to generate the simulated gating system. Figure 2 shows the defect distribution of the flywheel housing as displayed in the simulation.

[0026] When this process is deemed infeasible, the following measures can be taken: the material of the selected riser type can be set as an insulating riser or a heat-generating insulating riser to extend the feeding time.

[0027] The real-time pouring temperature and the location distribution of shrinkage cavity areas are obtained. When the location distribution of shrinkage cavity areas is concentrated in the thick part of the casting or far from the riser area, the volume of the casting is obtained. When the volume of the casting is greater than or equal to the casting volume threshold, the casting type is determined to be a large casting, and the real-time pouring temperature is set to a preset first pouring temperature. In this embodiment, the first pouring temperature is 1440℃. When the volume of the casting is less than the casting volume threshold, the casting type is determined to be a small casting, and the real-time pouring temperature is set to a preset second pouring temperature. In this embodiment, the second pouring temperature is 1260℃.

[0028] Shrinkage cavities occur in ductile iron castings produced by lost foam casting due to thermal stress. Considering the structural characteristics of thick-walled cast steel parts, the feeding efficiency of top risers, side risers, and internal risers was compared. It was found that the feeding range of top risers is more uniform in medium-thickness parts, providing a practical basis for riser selection for similar castings. The feasibility of the optimized riser scheme was verified by ProCAST simulation, and the production qualification rate and economic benefits were significantly improved.

[0029] A lost foam casting production system with riser feeding includes a pouring cup 1, a sprue 2, a runner 3, and an ingate 4. The system also includes a top riser 5 and a side riser 6 generated according to the above-mentioned lost foam casting production process with riser feeding. The top riser 5 is connected to the runner 3. The top riser 5 is disposed on the casting 7, and the side riser 6 is disposed on the thick wall of the side of the casting 7.

[0030] In this embodiment, the flywheel housing is a thick casting, therefore a top riser + side riser gating process is adopted. The improved gating system is shown in Figure 1. The improved gating system includes a pouring cup 1, a sprue 2, a runner 3, an ingate 4, a top riser 5, and a side riser 6. This embodiment uses this new process for small-batch production, and no shrinkage cavities reappear at the bolt holes after machining, proving the feasibility of this process.

[0031] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A lost foam casting production process with riser feeding, characterized in that, This process This includes step one: setting the modulus of the riser and the modulus of the feeding portion of the casting, wherein the modulus of the riser is greater than the modulus of the feeding portion of the casting; Step 2: Obtain the casting structure and select the riser type based on the casting structure to ensure feeding efficiency; Step 3: Simulate the selected riser type to generate a simulated gating system, and simulate casting through the simulated gating system. If no shrinkage cavity area is found on the simulated casting, the process is deemed feasible and a target gating system is generated based on the riser type; if a shrinkage cavity area is found on the simulated casting, the process is deemed infeasible.

2. The lost foam casting production process with riser feeding according to claim 1, characterized in that, The method for selecting the riser type based on the casting structure is as follows: the riser type includes top riser, side riser, and internal riser; when the casting structure is a thick casting, the riser type is selected as top riser; when the casting structure is a medium-thickness casting or a casting with a complex structure, the riser type is selected as side riser; when the casting structure is a casting with high machining precision requirements, the riser type is selected as internal riser.

3. The lost foam casting production process with riser feeding according to claim 2, characterized in that, The top riser is located at the highest and thickest part of the casting, the side riser is located at the thick wall of the side of the casting, and the internal riser is completely placed inside the sand mold.

4. The lost foam casting production process with riser feeding according to claim 1, characterized in that, In step one, the modulus of the riser is 1.2 to 1.5 times that of the modulus of the feeding portion of the casting.

5. The lost foam casting production process with riser feeding according to claim 1, characterized in that, In step three, the selected riser type is simulated using ProCAST to generate a simulated gating system.

6. A lost foam casting production system with riser feeding, comprising a pouring cup (1), a sprue (2), a runner (3), and an ingate (4), characterized in that, The system also includes a top riser (5) and a side riser (6) generated according to a lost foam casting production process for riser feeding according to any one of claims 1-5, wherein the top riser (5) is connected to the sprue (3), the top riser (5) is disposed on the casting (7), and the side riser (6) is disposed on the thick wall of the side of the casting (7).

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