Method for adjusting sizes of inner ring, outer ring and connecting section of large annular piece

Abstract

The invention provides a method for adjusting the sizes of an inner ring, an outer ring and a connecting section of a large annular piece, which comprises the following steps of: drawing a three-dimensional diagram of a casting, splitting the inner ring, the outer ring and a connecting plate part of the three-dimensional diagram, giving different shrinkage rates to the inner ring and the outer ring, and determining the shrinkage rates and angles of the connecting plate part of the inner ring and the outer ring by adopting methods such as multi-section adjustment. Then the models are combined, model manufacturing and pouring are conducted through a 3D printing method, and after the size of a casting meets the design drawing requirement, an overall wax pattern mold is manufactured; the shrinkage of the casting and the shrinkage rate change of the wax piece are both combined into a mold of the wax mold, after the wax mold is pressed, additional size control is not needed, after the size of the pressed wax mold is checked, the wax piece is directly combined, and then a shell is coated to pour the casting. The method has the advantages that the final casting size is guaranteed, and the casting size adjusting difficulty is reduced. The profile tolerance precision of the casting is improved, the size adjustment production time during split wax mold splicing is shortened, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of investment casting, and in particular to a method for adjusting the sizes of inner and outer rings and connecting sections of a large annular part. Background Art

[0002] The calculation formula for the linear shrinkage rate of castings is as follows: ε = (L mold - L part) / L part, ε is the linear shrinkage rate of castings, "L mold" is the mold size, unit millimeter, and "L part" is the casting size, unit millimeter.

[0003] The castings are produced by investment casting. The linear shrinkage from the mold to the final casting ranges from 1% to 3%. The linear shrinkage of the casting includes the shrinkage of the wax pattern, the shrinkage of the shell refractory material, and the shrinkage of the metal from pouring to cooling. The linear shrinkage of the metal itself is 1-2%, the linear shrinkage of the wax part itself is 0.2-1%, and the linear shrinkage of the shell material is 0.05-1.5%.

[0004] For large annular castings with an outer diameter of 1500mm, the mold size should be designed to be 1530mm based on a shrinkage rate of 2%. The shrinkage of the casting from the model to the final casting is 30mm. Such a large shrinkage amount will result in unqualified final dimensions of the casting if the given deviation of the shrinkage rate is large.

[0005] A large annular casting produced by investment casting consists of inner and outer rings and a support plate in the middle. During the casting process, due to the different structures and heat dissipation speeds of different parts, the shrinkage rates of the larger diameter outer ring and the smaller diameter inner ring are inconsistent, and the shrinkage rate in the height direction does not change much due to the relatively small size. Due to the inconsistent shrinkage of the inner and outer rings during forming, the angle of the support plate of the casting with an inclined support plate will change, making it difficult to control the size of the casting.

[0006] The usual practice is to give a shrinkage rate for large annular castings, a shrinkage rate in the circumferential direction and a shrinkage rate in the height direction. Since the shrinkage rates of the inner and outer rings are inconsistent, this will cause dimensional deviations in the inner and outer rings of the casting. It is necessary to put the soft wax mold after pressing into the fixture, and use the toughness of the wax part to stretch or compress the dimensions of the inner and outer rings of the wax part. After the wax part is cooled to room temperature in the fixture, it is taken out for assembly and shell making. This method of using a fixture to adjust the size of the casting needs to use the characteristic that the wax part with a certain temperature will produce a small amount of plastic deformation during the force process to ultimately ensure the size of the casting.

[0007] The disadvantage of this method is that the size control of the wax part is guaranteed by external force deformation. The deformation of the wax part in the fixture can cause large local deformation, which ultimately makes the local surface contour of the casting poor. This size adjustment method is to adjust the size of the local area of ​​the wax part, which may cause the angle of the casting support plate to be distorted; when the wax part is adjusted in the fixture, if the wax part is pressed for too long, the temperature of the wax part will drop too much, and the hardness of the wax part will increase. When adjusting the size, the wax part may be damaged and needs to be pressed again, which will extend the production time.

[0008] This method of adjusting the size of the wax model after pressing is used to make a split wax model, and then the size is adjusted using a splicing tool; for integral wax model castings, only the roundness and relative height dimensions caused by the deformation of the wax part itself can be corrected, and it is very difficult to adjust the angle or diameter. Summary of the invention

[0009] The purpose of the present invention is to solve the problem of dimensional accuracy control of large annular castings. The different real shrinkage rates of the inner and outer rings of the castings are all incorporated into the wax model, and the mold is manufactured using the model with the real shrinkage rate. This method of adjusting the size of the inner and outer rings of the wax mold can better solve the problem of the size tolerance of the inner and outer rings of the casting and the angle tolerance of the connecting section caused by inconsistent shrinkage rates. This method controls the dimensional accuracy of the casting from the source, avoids the use of mechanical deformation to adjust the size of the wax part, makes the dimensional accuracy of the casting higher, and the actual size of the casting can better meet the requirements of the design drawings.

[0010] The present invention provides a method for adjusting the size of inner and outer rings and connecting sections of a large annular part. The method comprises the following steps: firstly drawing a three-dimensional drawing of a casting, then splitting the inner and outer rings and the connecting plate parts of the three-dimensional drawing, giving different shrinkage rates to the inner and outer rings, and determining the shrinkage rate and angle of the connecting plate parts of the inner and outer rings by adopting methods such as multi-section adjustment, then merging the models, and making and pouring the models by using a 3D printing method. After the size of the casting meets the requirements of the design drawing, an integral wax mold is made. The method is used to directly ensure the size of the wax part during the mold pressing process, and the shrinkage of the casting and the shrinkage rate change of the wax part are all merged into the wax mold. After the wax mold is pressed, no additional size control is required. After the size of the wax mold after pressing is checked, the wax parts are directly combined, and then the shell is coated and the casting is poured.

[0011] The wax parts after pressing only need to be placed on the mold to avoid axial deformation of the wax parts in the height direction under gravity. The wax mold does not need to be adjusted by external force. Therefore, this method is more concise and the dimensional accuracy of the casting is high.

[0012] This method is used to make the whole wax part, and the size of the wax part is directly used to ensure the size of the casting, eliminating the method of using a clamp to squeeze or stretch the wax part to adjust the size of the wax part, so that the size and contour of the casting can better meet the requirements of the design drawings.

[0013] The support plate is positioned after the inner and outer rings are set to different shrinkage rates. The following three methods are used:

[0014] The first treatment method is suitable for castings with the same cross-sections in the length direction of the support plate. Set the outer ring and the support plate to the same shrinkage rate, and set the inner ring to a smaller shrinkage rate. In this way, there will be a certain distance between the support plate and the inner ring after drawing. In addition, there is a deviation in the angle of the connection line between the support plate and the inner and outer rings. The support plate needs to be rotated a certain angle and appropriately extended to achieve the connection between the support plate and the inner ring. This situation is suitable for the case where the shrinkage rate of the outer ring is large and the shrinkage rate of the inner ring is small. When the shrinkage rate of the inner ring is large, the support plate will penetrate into the inner ring. After rotating the support plate a certain angle, the support plate needs to be appropriately shortened;

[0015] The second method is to set the support plate to the average of the shrinkage rates of the inner and outer rings. The shrinkage rate of the outer ring should be greater than (or less than) that of the inner ring. After the shrinkage rate of the support plate is taken as the median, there is an intersection and a certain angle between the support plate connection line and the center lines of the inner and outer ring support plates. The enlarged support plate is rotated with the intersection as the rotation point to align the two center lines. Then the support plate is enlarged for a second time to connect the inner and outer rings. After merging, the drawing of the entire model is completed.

[0016] The third processing method is to set the inner and outer rings to different shrinkage rates, extract the inner and outer cross-sectional curves of the support plate stretched and formed, adjust the position of the cross-sectional centerline of the support plate formed according to the shrinkage rates of the inner and outer rings, scale the different inner and outer ring cross-sections of the support plate according to the shrinkage rates of the inner and outer rings, give different shrinkage rates according to distances, and then stretch the different cross-sections into a support plate body, and then merge the inner and outer rings and the support plate parts into one.

[0017] The specific steps for processing the support plate model are as follows:

[0018] (1) Split the 3D model of the ring into three parts: the outer ring, the support plate, and the inner ring. Remove the adapter R at the connection part.

[0019] (2) Find the drawing center line of the support plate in the inner and outer directions. The center point of the entire casting enlargement is selected on the height section of the drawing center line of the support plate to ensure that the height relative to the center of the support plate remains unchanged after different parts are given different enlargement ratios;

[0020] (3) Different magnification ratios are given to the inner and outer ring models of the casting, and the shrinkage rate of the outer ring should be 0.05%-0.3% larger (or smaller) than that of the inner ring;

[0021] (4) Different drawing methods are used to construct models for different types of casting support plates;

[0022] 1) For castings with the same cross-sections in the inner and outer directions of the center line of the support plate, for example, the outer ring and the support plate are set to the same shrinkage rate (the enlargement ratio range is 1.5%-3%), and the inner ring is set to a smaller shrinkage rate (1.2%-2.7%). In this way, after drawing, there will be a certain distance and angle between the support plate and the inner ring. It is necessary to measure the deviation angle α between the center connection line of the inner and outer ring support plate of the model and the center line of the support plate entity. With the intersection of the outer ring diameter and the center line of the support plate as the rotation point, the support plate is rotated α degrees to make the center line of the support plate entity coincide with the center lines of the inner and outer rings, and the support plate is extended to connect with the inner ring;

[0023] 2) For the support plate with variable cross-section, the shrinkage rate of the support plate is set to the average of the shrinkage rates of the inner and outer rings. The support plate model enlarged by the average is located between the inner and outer rings. At this time, there is an intersection and a certain angle between the center line of the support plate entity and the connecting line of the center of the support plate on the inner and outer rings. The intersection is used as the rotation point to rotate the support plate model so that the two center lines are aligned. Then, the support plate is enlarged for a second time according to a point on the center line of the support plate, and the two ends of the support plate are connected to the inner and outer rings. After merging the three entities, the model is drawn;

[0024] 3) For more complex support plate components, different drawing section curves of the support plate are extracted, and the center line of the drawing section of the support plate is adjusted to align the center line of the drawing section with the line connecting the center points of the inner and outer ring support plates after enlargement. The drawing section is given a gradually decreasing (or increasing) enlargement ratio from the outside to the inside. The drawing section of the support plate covers the outer side of the outer ring and the inner side of the inner ring. The different sections are stretched into the support plate body, and the inner and outer rings and the support plate parts are merged after shearing;

[0025] (5) All three methods above can complete the drawing of the support plate part graphics. For different types of support plates, select the corresponding drawing method;

[0026] (6) After the inner and outer rings and the support plate are combined into an integral model, a transition R is added to connect the support plate and the inner and outer rings, and the transition R is given a corresponding magnification ratio: the outer ring transition R is given according to the outer ring magnification ratio, and the inner ring transition R is given according to the inner ring magnification ratio;

[0027] (7) If the connection between the support plate and the inner and outer rings is a through-hole structure, the through-hole structure in the wall thickness direction of the inner and outer rings should be consistent with the angle of the inner cavity of the support plate to avoid the appearance of joint marks at the connection between the inner and outer rings and the support plate in the wall thickness direction;

[0028] (8) For the height direction of the casting, a single shrinkage rate is given;

[0029] (9) Printing a 3D wax mold of the model drawn according to this method, completing the combined shell casting of the wax part, measuring the casting size, correcting the model in the area where the size has deviation, and finally forming a verified model;

[0030] (10) To determine the final model size of a casting, several rounds of different shrinkage rate adjustments are required, and finally the casting after pouring is used for verification. This adjustment method can simplify the verification cycle and reduce the trial production cost;

[0031] (11) Using the verified model to open the wax mold, complete the production of the large annular integral wax mold;

[0032] (12) For the thick and large parts of the wax parts, in order to reduce the roundness deviation during the pressing process, a cooling device is appropriately added during the wax mold pressing process, or cooling measures are taken to increase the cooling rate of the thick and large parts of the wax parts and reduce the problem of increased dimensional shrinkage of the wax parts after demolding;

[0033] (13) After the wax parts are pressed, only the height direction needs to be made into a mold to ensure the height dimension. That is, the circumferential direction of the wax parts does not need to be processed to meet the dimension requirements.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The method for adjusting the size of the inner and outer rings and the connecting section of a large annular part described in the present invention is suitable for adjusting the annular casting model with a large difference in the diameter of the inner and outer rings. The method controls the size of the wax mold to avoid using a clamp to adjust the size of the wax part after pressing, thereby ensuring the final size of the casting and reducing the difficulty of adjusting the size of the casting. This method is extended to all annular castings with a large difference in the diameter of the inner and outer rings, improves the contour accuracy of the casting, reduces the size adjustment production time when the split wax mold is spliced, and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0037] Figure 1 Schematic diagram of inner and outer rings of casting;

[0038] Figure 2 Different shrinkage ratio diagrams are given for the inner and outer rings;

[0039] Figure 3 The support plate is enlarged according to the median magnification ratio of the inner and outer rings, and there is an angle diagram between the support plate and the center line of the inner and outer rings;

[0040] Figure 4 Schematic diagram of the distance between the support plate and the inner and outer rings after the center lines are aligned;

[0041] Figure 5 Increase the shrinkage rate at the middle point of the support plate to connect the inner and outer rings;

[0042] Figure 6 Use different shrinkage rates for different sections of inner and outer rings and support plates to create a schematic diagram of the casting model;

[0043] Figure 7 Schematic diagram of the adjustment ratio of the inner and outer ring sizes and the support plate sizes;

[0044] In the figure, 1-outer ring, 2-support plate, 3-inner ring. DETAILED DESCRIPTION

[0045] The present invention will be further explained below in conjunction with specific implementation plans, but the present invention is not limited thereto. The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0046] like Figure 7 Shown:

[0047] (1) Due to different scaling ratios, the center point of the entire casting scaling is selected at the height of the center line of the support plate drawing.

[0048] (2) The shrinkage rate of the outer ring is set to 2%, that is, outer ring size = casting size × (1 + 2%).

[0049] (3) The shrinkage rate of the inner ring is 1%, that is, the inner ring size = casting size × (1 + 1%).

[0050] (4) The shrinkage rate of the support plate is given by the average shrinkage rate of the inner and outer rings, which is 1.5%, that is, support plate size = casting size × (1 + 1.5%).

[0051] (5) Connect the center points of the support plate after the outer ring and the inner ring are scaled to form a straight line. This straight line intersects with the center line of the support plate given at a shrinkage rate of 1.5% to obtain an intersection point. Measure the angle between the two straight lines. Use the intersection of the two center lines as the rotation point to rotate the support plate to the angle.

[0052] (6) Select the middle point of the support plate and enlarge the support plate a second time so that the support plate connects the inner and outer rings to realize the generation of the entire casting entity.

[0053] (7) The height of the casting is given a shrinkage rate of 1.5%, that is, the height dimension = casting dimension × (1 + 1.5%).

[0054] (8) 3D print the wax part according to the enlarged casting model, then complete the combined shell casting of the wax part and complete the size inspection.

[0055] (9) After slightly modifying the dimensional deviation, the wax part is re-made and the casting is measured after pouring, and the final selection of the shrinkage rate of the casting model is completed.

[0056] (10) Create an integral wax mold based on the model after two rounds of adjustments.

[0057] Matters not covered by the present invention are known technologies.

[0058] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for adjusting the size of inner and outer rings and connecting sections of a large annular component, characterized in that: First, draw a three-dimensional drawing of the casting, then split the inner and outer rings and the connecting plate parts of the three-dimensional drawing, give different shrinkage rates to the inner and outer rings, and use multi-section adjustment and other methods to determine the shrinkage rate and angle of the inner and outer ring connecting plate parts. Then merge the models, use the 3D printing method to make the model and pour it. After the size of the casting meets the requirements of the design drawing, make an integral wax mold. This method is used to directly ensure the size of the wax part during the mold pressing process, and the shrinkage of the casting and the shrinkage rate change of the wax part are all incorporated into the wax mold. After the wax mold is pressed, there is no need for additional size control. After the size of the wax mold after pressing is checked, the wax parts are directly combined, and then the shell is coated and the casting is poured. The pressed wax parts only need to be placed on the mold to prevent axial deformation of the wax parts in the height direction under gravity conditions. The wax mold does not need to be subjected to external force to adjust the size. Therefore, this method is simpler and the dimensional accuracy of the casting is high.

2. The method for adjusting the size of the inner and outer rings and the connecting section of a large annular component according to claim 1, characterized in that: The support plate is positioned after the inner and outer rings are set to different shrinkage rates. The following three methods are used: The first treatment method is suitable for castings with the same cross-sections in the length direction of the support plate. The outer ring and the support plate are set to the same shrinkage rate, and the inner ring is set to a smaller shrinkage rate. In this way, there will be a certain distance between the support plate and the inner ring after drawing. In addition, there is a deviation in the angle of the connection line between the support plate and the inner and outer rings. The support plate needs to be rotated a certain angle and appropriately extended to achieve the connection between the support plate and the inner ring. The second method is to set the support plate to the average of the shrinkage rates of the inner and outer rings. The shrinkage rate of the outer ring is greater than that of the inner ring. After the shrinkage rate of the support plate is taken as the median, there is an intersection and a certain angle between the support plate connection line and the center lines of the inner and outer ring support plates. The enlarged support plate is rotated with the intersection as the rotation point to align the two center lines. Then the support plate is enlarged for a second time to connect the inner and outer rings. After merging, the drawing of the entire model is completed. The third processing method is to set the inner and outer rings to different shrinkage rates, extract the inner and outer cross-sectional curves of the support plate stretched and formed, adjust the position of the cross-sectional centerline of the support plate formed according to the shrinkage rates of the inner and outer rings, scale the different inner and outer ring cross-sections of the support plate according to the shrinkage rates of the inner and outer rings, give different shrinkage rates according to distances, and then stretch the different cross-sections into a support plate body, and then merge the inner and outer rings and the support plate parts into one.

3. The method for adjusting the size of the inner and outer rings and the connecting section of a large annular component according to claim 2, characterized in that: The specific steps of model processing are as follows: (1) Split the 3D model of the ring into three parts: the outer ring, the support plate, and the inner ring. Remove the adapter R at the connection part. (2) Find the drawing center line of the support plate in the inner and outer directions. The center point of the entire casting enlargement is selected on the height section of the drawing center line of the support plate to ensure that the height relative to the center of the support plate remains unchanged after different parts are given different enlargement ratios; (3) Different magnification ratios are given to the inner and outer ring models of the casting, and the shrinkage rate of the outer ring is 0.05%-0.3% larger than that of the inner ring; (4) Different drawing methods are used to construct models for different types of casting support plates; 1) For castings with the same cross-sections in the inner and outer centerline directions of the support plate, set the outer ring and the support plate to the same shrinkage rate (magnification range is 1.5%-3%), and set the inner ring to a smaller shrinkage rate (1.2%-2.7%). In this way, there will be a certain distance and angle between the support plate and the inner ring after drawing. It is necessary to measure the deviation angle α between the center connection line of the inner and outer ring support plate of the model and the center line of the support plate entity. With the intersection of the outer ring diameter and the center line of the support plate as the rotation point, rotate the support plate α degrees so that the center line of the support plate entity coincides with the center lines of the inner and outer rings, and extend the support plate to connect with the inner ring; 2) For the support plate with variable cross-section, the shrinkage rate of the support plate is set to the average of the shrinkage rates of the inner and outer rings. The support plate model enlarged by the average is located between the inner and outer rings. At this time, there is an intersection and a certain angle between the center line of the support plate entity and the connecting line of the center of the support plate on the inner and outer rings. The intersection is used as the rotation point to rotate the support plate model so that the two center lines are aligned. Then, the support plate is enlarged for a second time according to a point on the center line of the support plate, and the two ends of the support plate are connected to the inner and outer rings. After merging the three entities, the model is drawn; 3) For more complex support plate components, different drawing section curves of the support plate are extracted, and the center line of the drawing section of the support plate is adjusted to align the center line of the drawing section with the line connecting the center points of the inner and outer ring support plates after enlargement. The drawing section is given a gradually decreasing enlargement ratio from the outside to the inside, and the drawing section of the support plate covers the outer side of the outer ring and the inner side of the inner ring. The different sections are stretched into the support plate body, and the inner and outer rings and the support plate parts are merged after shearing; (5) All three methods above can complete the drawing of the support plate part graphics. For different types of support plates, select the corresponding drawing method; (6) After the inner and outer rings and the support plate are combined into an integral model, a transition R is added to connect the support plate and the inner and outer rings, and the transition R is given a corresponding magnification ratio: the outer ring transition R is given according to the outer ring magnification ratio, and the inner ring transition R is given according to the inner ring magnification ratio; (7) If the connection between the support plate and the inner and outer rings is a through-hole structure, the through-hole structure in the wall thickness direction of the inner and outer rings should be consistent with the angle of the inner cavity of the support plate to avoid the appearance of joint marks at the connection between the inner and outer rings and the support plate in the wall thickness direction; (8) For the height direction of the casting, a single shrinkage rate is given; (9) Printing a 3D wax mold of the model drawn according to this method, completing the combined shell casting of the wax part, measuring the casting size, correcting the model in the area where the size has deviation, and finally forming a verified model; (10) To determine the final model size of a casting, several rounds of different shrinkage rate adjustments are required, and finally the casting after pouring is used for verification. This adjustment method simplifies the verification cycle; (11) Using the verified model to open the wax mold, complete the production of the large annular integral wax mold; (12) For the thick and large parts of the wax parts, in order to reduce the roundness deviation during the pressing process, a cooling device is appropriately added during the wax mold pressing process, or cooling measures are taken to increase the cooling rate of the thick and large parts of the wax parts and reduce the problem of increased dimensional shrinkage of the wax parts after demolding; (13) After the wax parts are pressed, they only need to be molded in the height direction to ensure that the height dimension remains unchanged. The circumferential direction of the wax parts does not need to be processed to meet the size requirements.

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