A casting method for preventing cracks in arc parts of castings

Abstract

The present invention belongs to the field of casting technology and mainly relates to a casting method for preventing cracks in the arc part of a casting. Drawing software is used to draw a profile curved surface with the same curvature as the intersection area of ​​the casting body and the blades, and then the profile curved surface is split and cut from top to bottom according to a set distance. The cutting line is used as the reference axis of the channel to set the channel. The channel is a hollow structure and is not connected to the casting cavity. Several channels are added through the layout to increase the yield of the molding sand in the solidification stage of the casting, reduce the generation of local stress of the casting in the solidification stage, and significantly reduce the incidence of casting crack defects in the arc area of ​​the casting.

Description

Technical Field

[0001] The invention belongs to the technical field of casting, and mainly relates to a casting method for preventing cracks in arc parts of castings. Background Art

[0002] Due to the large variations in tonnage and weight, hydropower turbine castings currently feature irregularly curved surfaces. Compared to conventional castings, the amount of casting repairs required is difficult to control. Furthermore, the outer surfaces of the castings are often machined, and customers generally require high dimensional accuracy. Therefore, from the as-cast state to the final product shipped, the castings undergo multiple processes for appearance and dimensional refinement. Ultrasonic testing and other specialized inspection methods detect defects in the turbine and blade roots. Due to the structural characteristics of the turbine casting, the blade spacing is small, and the surfaces are mostly irregular. This increases the difficulty of repairing defects and the workload of the process, increasing labor and time consumption, and extending the production cycle. Summary of the Invention

[0003] The present invention aims to provide a casting method that prevents cracks in the arc portion of a casting. This method primarily addresses the problem of concentrated cracks and defects in the arc region where the casting body (including the upper crown and lower ring) intersects with the blades of a hydropower runner casting. Furthermore, during the runner casting rework process, structural limitations of the runner casting lead to multiple, repeated rework and finishing, which wastes costs and resources. This is primarily achieved through the following technical solutions:

[0004] A casting method for preventing cracks in an arc portion of a casting, wherein the casting comprises a casting body and blades, wherein the casting body and the blades are integrally cast. The casting method for the arc portion of the casting mainly comprises the following steps:

[0005] Step 01: Use drawing software to draw a profile curved surface with a set distance in the area where the casting body and the blade intersect, wherein the curvature of the profile curved surface is consistent with the profile curved surface of the blade;

[0006] Step 02, setting a reference axis of the channel on the profile surface;

[0007] Step 03, determining the size and position of the channel according to the casting process information;

[0008] Step 4: Make the casting sand mold and set the channel.

[0009] Furthermore, step 01 also includes replicating the completed profile curve surface in two to three groups along the normal direction of the blade profile surface. This arrangement is intended to improve the yield of the molding sand in the area where the casting body and the blade intersect. Excessive replication or a large range of replications can affect the strength of the molding sand in other areas of the casting, causing casting defects.

[0010] Furthermore, the step 02 specifically includes splitting and cutting the profile curve surface from top to bottom according to a set distance, and the splitting and cutting is divided into several groups, wherein the cutting line serves as the reference axis of the channel; after such splitting and cutting, the range of the channel can be controlled within the intersection area of ​​the casting body and the blade.

[0011] Furthermore, in step 03, the diameter of the channel is set to 8 mm to 10 mm; if the diameter of the channel is set too large, it will affect the strength of the molding sand in the arc area. When the molten steel is poured into the mold cavity of the casting, the surface of the molding sand is baked by the high-temperature molten steel, which will cause its strength to decrease, thereby causing sand sticking defects on the surface of the casting; if the diameter is set too small, the channel cannot play a role in enhancing the yieldability of the molding sand.

[0012] Furthermore, in step 03, the distance between the channel and the surface of the intersection area of ​​the blade and the casting body is 20 mm to 70 mm. This size area value can not only improve the yield of the molding sand in the arc area, but also will not affect the layout setting of other process information of the casting.

[0013] Furthermore, in step 03, the distance between adjacent channels is 10 mm to 15 mm. This arrangement not only increases the collapsing effect of the molding sand between adjacent channels, but also avoids the situation where the molding sand far away from the intersection area of ​​the casting body and the blade cannot be collapsed due to the large channel spacing.

[0014] Furthermore, in step 03, the channel layout area covers the range of 100mm*100mm of the arc area where the casting body and the blade intersect, and the range value of this area is mainly determined by the height between the end face of the runner casting blade and the casting body and the distance between two adjacent blades.

[0015] Furthermore, the channel is not connected to the mold cavity of the casting; the channel does not serve to exhaust gas, but is only used to increase the yield of the molding sand in the arc area where the casting body and the blade intersect, so when setting it, it is ensured that the channel is on the outer surface of the casting.

[0016] Furthermore, the channels are not connected to each other, and the channels serve to increase the yield of the molding sand in the arc area where the casting body and the blades intersect. Therefore, the channels are independently arranged according to the above-mentioned size spacing and are not connected.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention mainly relates to a casting method for preventing cracks from occurring in the arc portion of an integrally cast hydropower runner casting. Drawing software is used to draw a profile curved surface having the same curvature as the intersection area of ​​the casting body and blades. The profile curved surface is then split and cut from top to bottom according to a set distance. The cutting line is used as the reference axis of the channel to set a channel. The channel is a hollow structure and is not connected to the casting cavity. Several channels are added through the layout to increase the yield of the molding sand during the solidification stage of the casting, reduce the generation of local stress in the casting during the solidification stage, and significantly reduce the incidence of casting crack defects in the arc region of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the casting paving channel structure in the embodiment;

[0020] Figure 2 A partial schematic diagram of the casting paving channel structure in the embodiment;

[0021] 10-casting body; 20-blade; 30-channel. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0023] This embodiment mainly relates to an integral casting of a hydropower turbine, including a rotor body 10 and blades 20, wherein the casting body 10 includes an upper crown and a lower ring, that is, the upper crown, the lower ring and the blades are cast as a whole, and its appearance is mainly an irregular curved surface. Therefore, during the casting process, crack defects are easily concentrated in the arc area where the blades 20 intersect with the casting body 10, resulting in multiple and repeated repairs, increasing the production cycle and cost. In order to solve the above problem, the following casting method for preventing cracks in the arc area of ​​the casting is provided, which mainly targets the arc area. The hollow channel structure is set up, and multiple channels are set up according to the casting structure, including the location selection of the hollow channel, size and other key factors. Since the 3D printed sand core of the hydropower wheel is in the casting to solidification stage, the mechanical stress generated by the casting during the solidification stage due to the thermal expansion of the molding sand is constrained within the acute angle range of the casting arc area. Therefore, this embodiment adopts the design of hollow channels in the casting arc area to increase the yield of the molding sand, avoid the increase of cracks due to stress concentration, and reduce the probability of local cracks in the intersection area of ​​the casting body and the blade. See the attached for details. Figures 1 to 2 As shown, its specific technical solution is as follows:

[0024] Step 01: Use drawing software to draw a profile surface of a set distance in the area where the casting body 10 and the blade 20 intersect (including the arc area where both sides of all blades intersect with the casting body). The curvature of the profile surface is consistent with the blade profile surface; the drawn profile surface is copied and drawn in 2 to 3 groups according to the normal direction of the blade profile surface.

[0025] Step 02: Set the reference axis of the channel 30 on the profile surface.

[0026] Specifically, the profile curve surface is split and cut from top to bottom according to the set distance, and the splitting and cutting is carried out into several groups. The cutting line of the profile curve surface is extracted using the drawing software, and the cutting line is used as the reference axis of the channel 30; the drawing software is used again to fill the extracted curves for drawing the channels, and at the same time, the measurement command of the industrial drawing software is used to measure whether the outer circle spacing of each adjacent channel 30 meets the design requirements. If so, subsequent printing can be carried out. If the size of some areas does not meet the design requirements, the relative position of the channel 30 needs to be adjusted in time through the industrial drawing software to meet the use requirements.

[0027] Step 03: Determine the size and position of the channel 30 according to the casting process information of the casting.

[0028] Specifically, the distance between the channel 30 and the blade surface is 20mm to 70mm; the distance between adjacent channels 30 is 10mm to 15mm; the diameter of the channel 30 is set to 8mm to 10mm; the layout area of ​​the channel 30 covers the range of 100mm*100mm of the arc area where the casting body 10 and the blade 20 intersect.

[0029] Step 04: Make a casting sand mold and set the channel 30.

[0030] It should be noted that the channels 30 do not serve to exhaust gas but are merely used to increase the yield of the molding sand in the arc region where the casting body 10 intersects the blades 20. Therefore, the channels 30 are positioned outside the casting body 10. Consequently, the channels 30 are not connected to the casting cavity, nor are the channels 30 connected to each other.

[0031] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A casting method for preventing cracks in arc parts of castings, characterized in that: The casting comprises a casting body and blades, wherein the casting body and the blades are integrally cast. The casting method of the arc portion of the casting mainly comprises the following steps: Step 01: Use drawing software to draw a profile curve surface at a set distance in the area where the casting body and the blade intersect. The curvature of the profile curve surface is consistent with the blade profile surface. Duplicate the drawn profile curve surface into 2 to 3 groups according to the normal direction of the blade profile surface. Step 02: Setting a reference axis of the channel on the profile surface; splitting and cutting the profile surface from top to bottom according to a set distance, and splitting and cutting into several groups, wherein the cutting line serves as the reference axis of the channel; Step 03: Determine the size and position of the channel based on the casting process information; the distance between adjacent channels is 10mm to 15mm; the distance between the channel and the surface of the intersection area of ​​the blade and the casting body is 20mm to 70mm; the channel layout area covers the range of 100mm*100mm within the arc area where the casting body and the blade intersect; the diameter of the channel is set to 8mm to 10mm; Step 04: Make a sand mold for the casting and set up channels, wherein the channels are not connected to the mold cavity of the casting, and the channels are not connected to each other.

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