Investment casting shell casting method for optimizing casting quality based on three-dimensional modeling

Abstract

An investment casting shell casting method for optimizing casting quality based on three-dimensional modeling belongs to the technical field of mold casting shell manufacturing, aims to solve the problem that an existing investment casting shell causes defects of a casting, and comprises the following steps: manufacturing a shell sample, and pouring a casting sample by adopting the shell sample; detecting the casting sample to obtain the defect of the casting sample and the position of the defect; constructing a three-dimensional model of the casting sample according to the casting sample and the defect, and calculating the size and thickness of the defect according to the three-dimensional model; and a chilling block is selected according to the size and thickness of the defect, the chilling block is attached to the defect part, a wax sealing layer is attached to the outer side of the defect of the chilling block, and shell manufacturing is completed. The method is used for investment casting.

Description

Technical Field

[0001] The invention relates to an investment casting shell casting method for optimizing casting quality based on three-dimensional modeling, and belongs to the technical field of mold casting shell manufacturing. Background Art

[0002] Investment casting is also called lost wax casting. It is a method of coating several layers of refractory materials on the surface of the investment pattern (usually made of wax), drying and hardening it, melting the investment pattern to make an integral shell, and then calcining it at high temperature to ceramicize the integral shell, and then pouring it to obtain the casting. The investment casting process has the advantages of good casting surface quality, high dimensional accuracy, a wide range of applicable alloys, complex castings, and flexible batches. At present, investment castings cover almost all industrial fields such as aviation, aerospace, military industry, energy, petrochemicals, transportation, engineering machinery, and many other industries such as medical care, sports, and art.

[0003] Although investment casting technology continues to improve, with the development of the equipment manufacturing industry, the shapes of metal structural parts are more complex and the precision requirements are higher. In particular, the requirements for castings in industries such as aerospace, military, and energy are becoming more stringent. The investment casting process also faces some difficulties and challenges:

[0004] For castings with inner cavity structures, due to the limitation of the inner cavity size, after the shell is coated with a certain number of layers, both ends of the cavity are completely blocked by refractory materials. When pouring the casting, during the cooling and solidification of the alloy liquid, the inner cavity dissipates heat slowly, and the alloy solidifies for a long time, which is prone to casting defects such as shrinkage and looseness. In order to solve this defect, chills can be made or iron sand can be placed at the defective position of the casting after the shell is made. However, if the amount of chills or iron sand is too little, the defect will still exist. If the amount of chills or iron sand is too much, the shell will be too thick at this point, and the casting will still have defects at this point. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the existing investment casting shell causes defects in castings, and to provide an investment casting shell casting method based on three-dimensional modeling to optimize the casting quality.

[0006] The invention discloses an investment casting shell casting method for optimizing casting quality based on three-dimensional modeling, which comprises:

[0007] S1. Make a shell specimen and use the shell specimen to cast the casting specimen;

[0008] S2. Detect the casting sample to obtain the defects of the casting sample and the locations of the defects;

[0009] S3. construct a three-dimensional model of the casting sample based on the casting sample and the defect, and calculate the size and thickness of the defect based on the three-dimensional model;

[0010] S4. Select chill according to the size and thickness of the defect, attach the chill to the defect, attach a wax seal layer to the outside of the chill defect, and complete the shell manufacturing.

[0011] Preferably, the casting is tested by ultrasonic testing in S2.

[0012] Preferably, the defects of the casting described in S2 include: pores, shrinkage cavities and shrinkage.

[0013] Preferably, the specific method of constructing a three-dimensional model of the casting sample according to the casting sample and the defects in S3 includes:

[0014] S3-1, dividing the casting sample into different parting surface blocks according to the parting surface;

[0015] S3-2, extracting the features of each parting surface block;

[0016] S3-3, obtaining feature constraints of each parting surface block;

[0017] S3-4. Construct a three-dimensional model of the casting specimen according to the characteristics and characteristic constraints of each parting surface block.

[0018] Preferably, the parting surface described in S3-1 includes: a straight parting surface, an inclined parting surface, a stepped parting surface and a curved parting surface.

[0019] Preferably, in S3-1, the casting sample is divided into different parting surface blocks according to the parting surface, and the division criteria include:

[0020] The projection area of ​​the casting on the parting surface is minimal;

[0021] The parting surface causes the casting to remain on the movable mold side during demolding.

[0022] Preferably, the specific method for extracting the features of each parting surface block in S3-2 includes:

[0023] S3-2-1. Select the maximum contour line of the casting in the demoulding direction as the parting line;

[0024] S3-2-2, determine whether the parting lines are located in the same plane, if yes, execute S3-2-3, otherwise execute S3-2-6;

[0025] S3-2-3, determine whether the parting line is in a single direction, if yes, obtain the parting surface feature, otherwise execute S3-2-4;

[0026] S3-2-4, determine whether the angle of the parting line is less than 180°, if so, obtain the parting surface feature, otherwise execute S3-2-5;

[0027] S3-2-5, obtain the extension line of the parting line and obtain the parting surface features;

[0028] S3-2-6. Determine whether the parting lines are on the same surface. If so, scan to obtain the parting surface features. Otherwise, project to obtain the parting surface features.

[0029] Preferably, the specific method of obtaining the feature constraints of each parting surface block in S3-3 includes:

[0030] The characteristic constraints of each parting surface block are:

[0031]

[0032] Among them, g i (R,T) represents the characteristic constraint condition of parting surface i, f i (R, T) represents the coordinate function of the parting surface i, R and T represent the conversion relationship between the measurement coordinate system and the three-dimensional model coordinate system, d i (R, T) represents the directed distance from the measured data point of the parting surface i to the three-dimensional model, ε i Indicates the minimum machining allowance of parting surface i.

[0033] Preferably, the specific method of calculating the size and thickness of the defect according to the three-dimensional model in S3 includes:

[0034] Defect radial size:

[0035]

[0036] Among them, L S Indicates the radial dimension of the defect in the core, l S Indicates the radial dimension of the defect in the die, L M Indicates the radial working size of the core, l M Indicates the radial working size of the die, δ z Indicates casting mold tolerance, represents the average shrinkage of the casting, x represents the positive coefficient, and ΔM represents the dimensional tolerance of the casting;

[0037] Defect height size:

[0038]

[0039] Among them, H S Indicates the height dimension of the defect in the core, h S Indicates the height dimension of the defect in the die, H MIndicates the height working dimension of the core, h M Indicates the height working dimension of the die;

[0040] Distance between defect and casting center:

[0041]

[0042] Among them, C M Indicates the center distance of the casting, C S Indicates the distance between the defect and the center of the casting.

[0043] Preferably, the method of selecting a chill according to the size and thickness of the defect in S4, attaching the chill to the defect, attaching a wax seal layer to the outside of the chill defect, and completing the shell manufacturing includes:

[0044] S4-1. Select the chill according to the size and thickness of the defect. The diameter of the chill is 5-8mm.

[0045] S4-2, process the two ends of the cold iron into round heads;

[0046] S4-3, wrapping a layer of melted wax around the cold iron, and after the wax cools and solidifies, repeating the wrapping of the wax;

[0047] S4-4, when the wax liquid layer reaches any of the following conditions, execute S4-5: the wax liquid layer is 3-6 layers, and the wax liquid layer thickness reaches 0.5mm;

[0048] S4-5. Determine whether the thickness of both ends of the cold iron reaches 2 mm. If not, execute S4-3. If yes, complete the shell manufacturing.

[0049] The invention proposes an investment casting shell casting method for optimizing casting quality based on three-dimensional modeling, which has the following advantages:

[0050] 1. Install the chiller on the corresponding part of the wax mold. The chiller can absorb the heat of the alloy liquid and play the role of temperature regulation, heat dissipation and cooling during the solidification process of the alloy, so that the part where the chiller is placed will no longer have loose defects.

[0051] 2. For defective parts of castings, calculate the size and thickness of the defects based on the three-dimensional model, select chilled iron or iron sand according to the size and thickness, fit the chilled iron to the defective parts, and then fit the wax seal layer on the outside of the chilled iron so that the chilled iron can perfectly complement the defective parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a flowchart of the investment casting shell casting method for optimizing casting quality based on three-dimensional modeling according to the present invention;

[0053] Figure 2It is a flowchart of extracting the features of each parting surface block according to the present invention;

[0054] Figure 3 It is a schematic diagram of the cross-sectional structure of the cold iron and wax seal layer attached at the defect. DETAILED DESCRIPTION

[0055] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0056] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0057] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0058] Embodiment 1:

[0059] Combine the following Figure 1 and Figure 2 The present embodiment is described as follows: an investment casting shell casting method for optimizing casting quality based on three-dimensional modeling, which comprises:

[0060] S1. Make a shell specimen and use the shell specimen to cast the casting specimen;

[0061] S2. Detect the casting sample to obtain the defects of the casting sample and the locations of the defects;

[0062] S3. construct a three-dimensional model of the casting sample based on the casting sample and the defect, and calculate the size and thickness of the defect based on the three-dimensional model;

[0063] S4. Select chill according to the size and thickness of the defect, attach the chill to the defect, attach a wax seal layer to the outside of the chill defect, and complete the shell manufacturing.

[0064] Furthermore, the casting is tested by ultrasonic testing as described in S2.

[0065] Furthermore, the defects of the casting described in S2 include: pores, shrinkage cavities and shrinkage.

[0066] Furthermore, the specific method of constructing the three-dimensional model of the casting sample according to the casting sample and the defects in S3 includes:

[0067] S3-1, dividing the casting sample into different parting surface blocks according to the parting surface;

[0068] S3-2, extracting the features of each parting surface block;

[0069] S3-3, obtaining feature constraints of each parting surface block;

[0070] S3-4. Construct a three-dimensional model of the casting specimen according to the characteristics and characteristic constraints of each parting surface block.

[0071] Furthermore, the parting surface described in S3-1 includes: a straight parting surface, an inclined parting surface, a stepped parting surface and a curved parting surface.

[0072] Furthermore, in S3-1, the casting sample is divided into different parting surface blocks according to the parting surface, and the division criteria include:

[0073] The projection area of ​​the casting on the parting surface is minimal;

[0074] The parting surface causes the casting to remain on the movable mold side during demolding.

[0075] Furthermore, the specific method for extracting the features of each parting surface block in S3-2 includes:

[0076] S3-2-1. Select the maximum contour line of the casting in the demoulding direction as the parting line;

[0077] S3-2-2, determine whether the parting lines are located in the same plane, if yes, execute S3-2-3, otherwise execute S3-2-6;

[0078] S3-2-3, determine whether the parting line is in a single direction, if yes, obtain the parting surface feature, otherwise execute S3-2-4;

[0079] S3-2-4, determine whether the angle of the parting line is less than 180°, if so, obtain the parting surface feature, otherwise execute S3-2-5;

[0080] S3-2-5, obtain the extension line of the parting line and obtain the parting surface features;

[0081] S3-2-6. Determine whether the parting lines are on the same surface. If so, scan to obtain the parting surface features. Otherwise, project to obtain the parting surface features.

[0082] Furthermore, the specific method of obtaining the feature constraints of each parting surface block in S3-3 includes:

[0083] The characteristic constraints of each parting surface block are:

[0084]

[0085] Among them, g i(R,T) represents the characteristic constraint condition of parting surface i, f i (R, T) represents the coordinate function of the parting surface i, R and T represent the conversion relationship between the measurement coordinate system and the three-dimensional model coordinate system, d i (R, T) represents the directed distance from the measured data point of the parting surface i to the three-dimensional model, ε i Indicates the minimum machining allowance of parting surface i.

[0086] Furthermore, the specific method of calculating the size and thickness of the defect according to the three-dimensional model in S3 includes:

[0087] Defect radial size:

[0088]

[0089] Among them, L S Indicates the radial dimension of the defect in the core, l S Indicates the radial dimension of the defect in the die, L M Indicates the radial working size of the core, l M Indicates the radial working size of the die, δ z Indicates casting mold tolerance, represents the average shrinkage of the casting, x represents the positive coefficient, and ΔM represents the dimensional tolerance of the casting;

[0090] Defect height size:

[0091]

[0092] Among them, H S Indicates the height dimension of the defect in the core, h S Indicates the height dimension of the defect in the die, H M Indicates the height working dimension of the core, h M Indicates the height working dimension of the die;

[0093] Distance between defect and casting center:

[0094]

[0095] Among them, C M Indicates the center distance of the casting, C S Indicates the distance between the defect and the center of the casting.

[0096] Furthermore, the method of selecting a chill according to the size and thickness of the defect in S4, attaching the chill to the defect, attaching a wax seal layer to the outside of the chill defect, and completing the shell manufacturing includes:

[0097] S4-1. Select the chill according to the size and thickness of the defect. The diameter of the chill is 5-8mm.

[0098] S4-2, process the two ends of the cold iron into round heads;

[0099] S4-3, wrapping a layer of melted wax around the cold iron, and after the wax cools and solidifies, repeating the wrapping of the wax;

[0100] S4-4, when the wax liquid layer reaches any of the following conditions, execute S4-5: the wax liquid layer is 3-6 layers, and the wax liquid layer thickness reaches 0.5mm;

[0101] S4-5. Determine whether the thickness of both ends of the cold iron reaches 2 mm. If not, execute S4-3. If yes, complete the shell manufacturing.

[0102] In this embodiment, the cold iron is made of steel or steel bars. If the defective part is relatively small, iron sand can also be used.

[0103] In this embodiment, the division of the parting surface is a relatively complex issue, and there are many factors that affect the parting surface. Whether the division of the parting surface is reasonable and whether the type is selected appropriately will not only affect the complexity of three-dimensional modeling, but also the molding quality of the casting and the actual production process.

[0104] In this embodiment, the projection area of ​​the casting on the parting surface is minimized in order to prevent mold locking and overflow when the projection area is too large.

[0105] In this embodiment, the parting surface allows the casting to stay on the movable mold side during demolding, in order to make the mold frame structure as simple as possible, avoid wasting a lot of time, and facilitate smooth demolding of the casting.

[0106] In the present invention, Figure 3 The figure shows a schematic diagram of the cross-sectional structure of the cold iron and the wax seal layer at the defect, where 1 represents the cold iron, 2 represents the wax seal layer, and 3, 4, 5 and 6 represent the thickened wax seal layer. Cold iron is added to the part where loose defects are prone to occur. The material is steel or steel bar with a smooth surface. The size of the cold iron depends on the part of the loose defect. The diameter is about Φ5-Φ8mm. After confirming the length, the two ends are processed into round heads to avoid sharp corners. A layer of molten wax liquid is wrapped around it. Wait for it to cool and solidify until 3-6 layers or the thickness reaches about 0.5mm. The thickness of the two ends needs to reach about 2mm, and the cold iron is completed. The casting wax mold is made by normal process. When the shell is made to 7-9 layers, the prepared cold iron is placed on the part of the shell where loose defects occur, close and firmly, and the cold iron is fixed with a mixture of sand and silica sol. Then the shell is made normally. During dewaxing, the wax material wrapped around the chill is removed to form a certain gap between the chill and the shell, preventing the shell from expanding and cracking during dewaxing and high-temperature baking due to the inconsistent shrinkage ratio of the chill and the shell. By directly installing the chill on the corresponding part of the wax mold, the chill absorbs the heat of the alloy liquid, so that the part where the chill is placed will not have loose defects.

[0107] The invention provides an investment casting shell casting method for optimizing casting quality based on three-dimensional modeling, which plays the role of temperature regulation, heat dissipation, cooling, etc. during the alloy solidification process by placing a chill inside the shell. At the same time, the shape of the chill can be adjusted according to the structure of the casting, and the secondary use of the chill can be achieved.

[0108] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. An investment casting shell casting method for optimizing casting quality based on three-dimensional modeling, characterized in that: It includes: S1. Make a shell specimen and use the shell specimen to cast the casting specimen; S2. Detect the casting sample to obtain the defects of the casting sample and the locations of the defects; S3. construct a three-dimensional model of the casting sample based on the casting sample and the defect, and calculate the size and thickness of the defect based on the three-dimensional model; S4. Select chill according to the size and thickness of the defect, attach the chill to the defect, attach a wax seal layer to the outside of the chill defect, and complete the shell manufacturing.

2. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 1, characterized in that: S2 describes that ultrasonic testing is used to test the casting.

3. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 1, characterized in that: The defects of the casting described in S2 include: pores, shrinkage cavities and shrinkage.

4. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 1, characterized in that: The specific method of constructing a three-dimensional model of a casting sample according to the casting sample and the defects described in S3 includes: S3-1, dividing the casting sample into different parting surface blocks according to the parting surface; S3-2, extracting the features of each parting surface block; S3-3, obtaining feature constraints of each parting surface block; S3-4. Construct a three-dimensional model of the casting specimen according to the characteristics and characteristic constraints of each parting surface block.

5. The method for casting a shell mold for investment casting based on three-dimensional modeling to optimize casting quality according to claim 4, characterized in that: The parting surface described in S3-1 includes: a straight parting surface, an inclined parting surface, a stepped parting surface and a curved parting surface.

6. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 4, characterized in that: S3-1 divides the casting sample into different parting surface blocks according to the parting surface. The division criteria include: The projection area of ​​the casting on the parting surface is minimal; The parting surface causes the casting to remain on the movable mold side during demolding.

7. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 4, characterized in that: The specific method for extracting the features of each parting surface block in S3-2 includes: S3-2-1. Select the maximum contour line of the casting in the demoulding direction as the parting line; S3-2-2, determine whether the parting lines are located in the same plane, if yes, execute S3-2-3, otherwise execute S3-2-6; S3-2-3, determine whether the parting line is in a single direction, if yes, obtain the parting surface feature, otherwise execute S3-2-4; S3-2-4, determine whether the angle of the parting line is less than 180°, if so, obtain the parting surface feature, otherwise execute S3-2-5; S3-2-5, obtain the extension line of the parting line and obtain the parting surface features; S3-2-6. Determine whether the parting lines are on the same surface. If so, scan to obtain the parting surface features. Otherwise, project to obtain the parting surface features.

8. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 4, characterized in that: The specific method of obtaining the feature constraints of each parting surface block in S3-3 includes: The characteristic constraints of each parting surface block are: Among them, g i (R,T) represents the characteristic constraint condition of parting surface i, f i (R, T) represents the coordinate function of the parting surface i, R and T represent the conversion relationship between the measurement coordinate system and the three-dimensional model coordinate system, d i (R, T) represents the directed distance from the measured data point of the parting surface i to the three-dimensional model, ε i Indicates the minimum machining allowance of parting surface i.

9. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 1, characterized in that: The specific method of calculating the size and thickness of the defect according to the three-dimensional model described in S3 includes: Defect radial size: Among them, L S Indicates the radial dimension of the defect in the core, l S Indicates the radial dimension of the defect in the die, L M Indicates the radial working size of the core, l M Indicates the radial working size of the die, δ z Indicates casting mold tolerance, represents the average shrinkage of the casting, x represents the positive coefficient, and ΔM represents the dimensional tolerance of the casting; Defect height size: Among them, H S Indicates the height dimension of the defect in the core, h S Indicates the height dimension of the defect in the die, H M Indicates the height working dimension of the core, h M Indicates the height working dimension of the die; Distance between defect and casting center: Among them, C M Indicates the center distance of the casting, C S Indicates the distance between the defect and the center of the casting.

10. The method for investment casting shell casting based on three-dimensional modeling to optimize casting quality according to claim 1, characterized in that: The specific method of selecting a chill according to the size and thickness of the defect, attaching the chill to the defect, attaching a wax seal layer to the outside of the chill defect, and completing the shell manufacturing includes: S4-1. Select the chill according to the size and thickness of the defect. The diameter of the chill is 5-8mm. S4-2, process the two ends of the cold iron into round heads; S4-3, wrapping a layer of melted wax around the cold iron, and after the wax cools and solidifies, repeating the wrapping of the wax; S4-4, when the wax liquid layer reaches any of the following conditions, execute S4-5: the wax liquid layer is 3-6 layers, and the wax liquid layer thickness reaches 0.5mm; S4-5. Determine whether the thickness of both ends of the cold iron reaches 2 mm. If not, execute S4-3. If yes, complete the shell manufacturing.

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