Sand mold of low-modulus shaft disc nodular iron casting and mold structure of low-modulus shaft disc nodular iron casting
By setting fins with fast thermal conductivity on the disc and cylinder periphery of low-modulus ductile iron castings, the problem of shrinkage defects in production is solved, the production cost is reduced and the production rate is improved, and casting production without shrinkage defects is achieved.
Patent Information
- Application Number
- CN202411451397.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-01-07
AI Technical Summary
Low-modulus ductile iron parts are prone to shrinkage defects in production, resulting in high production costs and low yield. The existing processes require large and more shrinkage risers to avoid defects, but this reduces the yield rate and increases the Production cost.
Multiple fins are arranged in the disk part and the outer periphery of the cylinder of the shaft disk ductile iron parts. The fins conduct heat faster than sand and cool faster than castings. They are used to replace the shrinkage riser and reduce the expansion effect when the fins solidify. Shrinkage defects of castings.
By setting up fins, the retraction of the riser in traditional processes is avoided, production costs are reduced, production rate is improved, waste products are reduced, and there is no shrinkage defect inside the castings is improved, and product quality and corporate economic benefits are improved.
Smart Images
Figure CN119259916A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a sand mold and a mold structure of a cast iron part, and in particular to a sand mold and a mold structure of a low-modulus shaft disk ductile iron part, which belongs to the field of casting. Background Art
[0002] In the field of metal material sand casting, ductile iron is an excellent metal material. Compared with steel parts, ductile iron parts have the advantages of good processing performance, good wear resistance, high yield strength ratio, good seismic resistance, light specific gravity, and low production cost, so its application field is becoming more and more extensive. However, the solidification characteristics of ductile iron during smelting and casting are paste-like solidification, which is prone to shrinkage defects. At present, the foundry industry has a set of mature theories and process methods for ductile iron parts with a modulus greater than Mc≥2.5cm, and rationally utilizes the expansion effect of graphite precipitation during the solidification of ductile iron metal liquid to eliminate shrinkage defects. This process requires the casting to have a larger modulus and a harder casting mold, otherwise it is impossible to produce qualified products, so low-modulus ductile iron parts cannot be designed and produced using this theory. The foundry industry also has a mature theory and process method, which is similar to the process design of steel castings. Ductile iron castings are solidified sequentially and risers are used to feed shrinkage to produce castings without shrinkage defects. However, this production process requires larger and more shrinkage feed risers for the production of ductile iron castings with a modulus below 2.5 cm. Otherwise, shrinkage defects are prone to occur in hot spots and relatively thick wall areas of the castings. However, such a production process has a low process yield and high production costs, making it unprofitable for manufacturers. If this process with more and larger risers is not used, it will be difficult to produce qualified products.
[0003] The material of the shaft disc is ductile iron, with a modulus Mc=1.68cm, and a modulus less than 2.5, which is a standard low-modulus casting. According to traditional theories and process methods, a feeding riser must be set. Figure 2 This is a schematic diagram of the vertical structure of the existing shaft disc casting. Figure 3 The horizontal structure diagram of the existing shaft disc casting is shown in the figure. The figure is a schematic diagram of the structure of the casting after the sand mold is removed. Figure 2 In order to avoid shrinkage defects, two large risers 001 are set on the disc surface of the shaft disc. Figure 3 In order to avoid shrinkage defects, large risers 001 and 004 are set above the disc and cylinder as cross runners, otherwise it cannot be guaranteed that there will be no shrinkage defects inside the casting. However, this production process has a low yield rate and high casting cost, and will not bring economic benefits to the company, which stumped the company's technical personnel for a while.
[0004] The success of low modulus ductile iron shaft and disc is not only related to the success of the product production, but also to the company's future production of low modulus ductile iron. How to produce qualified products without shrinkage defects at a lower cost while ensuring product quality? Low modulus ductile iron shaft and disc is a topic that companies and even the foundry industry urgently need to solve. Summary of the invention
[0005] In view of the current situation that low modulus ductile iron shaft discs face high casting costs and low yield rates in production, the company has established a research and development team and achieved success. The present invention provides a sand mold and mold structure for low modulus shaft disc ductile iron castings, by setting a certain number of fins on the disc part and the mold surface corresponding to the cylinder of the shaft disc ductile iron casting, and setting a smaller safety riser at the highest point of the pouring position to replace larger and more shrinkage feed risers, the purpose of which is to avoid larger and more shrinkage feed risers, reduce shrinkage defects that are prone to occur in production, ensure product quality, reduce casting costs, and open up a new casting method for the future production of low modulus ductile iron castings.
[0006] The technical scheme of the present invention is: a sand mold and a mold structure of a low-modulus shaft disk ductile iron casting, wherein the shaft disk ductile iron casting comprises a disc and a cylinder, and a plurality of fins are arranged on the mold surface corresponding to the hot node portion and the disc surface with a thick wall thickness and the outer circumference of the cylinder when the shaft disk ductile iron casting is cast, wherein the heat conduction speed of the fins is faster than that of the sand mold, and the cooling speed of the fins is faster than that of the casting; Further, the fin is in a straight line or a curved line, and the fin is fixedly or movably arranged on the mold surface; Further, the fins are arranged in the radial direction of the surface of the disc, and the plurality of fins are arranged radially with the center of the disc as the center; Furthermore, the fins are arranged on the outer circumference of the cylinder, the fins are arranged in the axial direction of the outer circumference of the cylinder, and the angles of the multiple fins on the outer circumference of the cylinder are equal; Furthermore, the thickness of the fin is less than or equal to the wall thickness of the casting where the fin is located, and the height of the fin is 10 to 50 mm; Furthermore, the plurality of fins are connected to the disc surface of the shaft disc and the outer peripheral surface of the cylinder as a whole after casting; Furthermore, the low modulus shaft disk ductile iron part is horizontally molded and vertically poured, and its pouring system is vertical pouring. A straight pouring gate is arranged in the vertical pouring, and a pouring cup is connected above the straight pouring gate, and an inner gate is connected below the straight pouring gate, and the inner gate is connected to the lower half of the cylindrical cavity.
[0007] The present invention has the following positive effects: by arranging a plurality of fins on the disc surface and the outer periphery of the cylinder of the shaft disc, it is possible to avoid arranging larger and more shrinkage feeders according to the traditional process, and it is possible to reduce the consumption of manpower, material resources and financial resources; by utilizing the fact that the heat conduction speed of the fins is faster than that of the sand mold, and the cooling speed of the fins is faster than that of the casting, it is possible to accelerate the local cooling speed of the casting, and it is possible to avoid larger and more shrinkage feeders; during solidification, the fins and the casting body have a difference in solidification time due to different cooling speeds; when the fins solidify, the precipitation expansion force of the graphite acts on the casting, which can reduce the shrinkage defects of the casting, and can produce castings without internal shrinkage defects; utilizing these characteristics of the fins, it is possible not to arrange shrinkage feeders, and thus to produce qualified castings without shrinkage defects. The present invention solves the problem that small modulus ductile iron castings cannot be cast without feeders, improves the production process yield, reduces waste, improves the internal quality of the casting, reduces production costs, improves the economic benefits of the enterprise, and meets the needs of high-end equipment. The invention solves a problem that has long troubled technicians in the foundry industry, namely, how to produce small-modulus ductile iron shaft discs with high quality and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 A schematic diagram of the molding structure of the central axle disc casting of the present invention.
[0009] Figure 2 Schematic diagram of the vertical molding structure of the existing shaft disc casting.
[0010] Figure 3 Schematic diagram of the horizontal molding structure of the existing shaft disc casting.
[0011] Explanation of the numbers: 001—riser, 002—cup, 003—sprue, 004—runner, 005—ingate, 006—casting, 007—vent, 008—fin, 009—disc, 010—cylinder. DETAILED DESCRIPTION
[0012] The specific embodiments of the present invention are described below with reference to the accompanying drawings, wherein Figure 1 It is a schematic diagram of the structure of the casting after the sand is removed. In the sand, the mold becomes a cavity after the mold is removed, and the casting is formed after the molten iron is poured into the cavity. The three are consistent without considering the thermal shrinkage of the casting.
[0013] A sand mold and mold structure of a low-modulus shaft-disk ductile iron casting, the shaft-disk ductile iron casting comprises a disk 009 and a cylinder 010, a plurality of fins 008 are arranged on the mold surface corresponding to the heat node portion of the shaft-disk ductile iron casting 006 and the surface of the disk 009 with a thick wall and the outer circumference of the cylinder 010, the heat conduction speed of the fins 008 is faster than that of the sand mold, and the cooling speed of the fins 008 is faster than that of the casting 006. During solidification, the fins 008 and the casting 006 body have a difference in solidification time due to different cooling speeds, and the precipitation expansion force of graphite acts on the casting when the fins 008 solidifies, which can reduce the shrinkage defects of the casting, and can produce the casting 006 without internal shrinkage defects. By utilizing these characteristics of the fins 008, it is not necessary to set a shrinkage feed riser, thereby producing a qualified casting without shrinkage defects.
[0014] The fins 008 are linear or curved, and the fins 008 are fixedly or movably arranged on the mold surface.
[0015] The fins 008 are arranged in the radial direction of the surface of the disk 009, and a plurality of fins 008 are arranged radially with the center of the disk as the center.
[0016] The fins 008 are arranged on the outer circumference of the cylinder 010 , and the fins 008 are arranged in the axial direction of the outer circumference of the cylinder 010 , and the angles of the multiple fins 008 on the outer circumference of the cylinder 010 are equal.
[0017] The thickness of the fin 008 is less than or equal to the wall thickness of the casting 006 where the fin 008 is located, and the height of the fin is between 10 and 50 mm.
[0018] The plurality of fins 008 are connected to the surface of the disk 009 of the shaft disk and the outer peripheral surface of the cylinder 010 as a whole after casting.
[0019] The low modulus shaft disk ductile iron casting is horizontally molded and vertically cast. The casting system is vertically cast. A straight pouring gate 003 is provided in the vertical casting. The straight pouring gate 003 is connected to a pouring cup 002 above and an inner pouring gate 005 below. The inner pouring gate 005 is connected to the lower half of the cylindrical cavity. In addition, an exhaust hole 007 is provided on the surface of the disk. In this embodiment, no cross runner 004 is provided.
[0020] ① First, according to the structural characteristics of the ductile iron shaft disc produced, process analysis and evaluation are carried out to determine the preliminary process plan; ② Design and draw casting production process diagrams, including designing sand boxes and drawing sand box diagrams; designing chillers and drawing chiller diagrams; designing pouring and riser gates; designing fins, including fin distribution location, quantity, and size; ③ Design and draw mold drawings for modeling; ④ Purchase the sand boxes, chillers, molds and various materials needed for production; ⑤ Make molding molds and pouring and riser molds, make sand boxes, make chillers, and inspect whether the molds, sand boxes, and chillers are qualified; ⑥ Modeling, core making, coating, drying, core loading and box packing; ⑦ Melt the molten iron while carrying out step ⑥; ⑧ Molten iron is discharged from the furnace and spheroidized; ⑨ Pouring. Pour the molten iron that has passed the spheroidization treatment into the casting mold; ⑩ Keep warm, cool naturally to below 300℃, then unpack and remove sand; ⑪ Grinding, removing fins on the casting surface and inspecting.
[0021] ⑫ Heat treatment and inspection. Finally, qualified shaft disc castings are obtained.
[0022] In the above implementation steps, the steps may vary slightly for different castings, different casting materials and different production methods, and the shape and size of the fins may vary, but the process of setting the fins on the surface of the casting pattern is consistent.
[0023] Figure 1 The shaft disc shown is a ductile iron casting actually produced by our company, with a weight of 69kg, a modulus of Mc=1.68cm, and a material grade of QT450-10. The first trial production process was a vertical pouring process with two large shrinkage feed risers on the top. Inspection revealed that both the lower cylindrical part and the upper disc part had internal shrinkage defects. The second trial production process was a horizontal pouring process, with large feed risers used for shrinkage feed for both the disc part and the cylindrical part. Inspection results showed that shrinkage defects existed inside the disc part. The third trial production process was carried out using the process technology of the present invention, with fins set on the disc part and the cylindrical part molds. The thickness of the fins was 4 to 7mm, the height of the fins was 30mm, the molding was horizontal, the pouring was vertical, and the rest was carried out according to conventional production methods. The results showed that there were no shrinkage defects inside the castings, and the process yield rate was increased from 68% to 78%. The mass production process has remained unchanged since then, and the quality is good.
[0024] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. The present invention can be applied to the casting production of other ductile iron castings.
[0025] Although the shaft disc is used in this embodiment, the present invention is also applicable to other ductile iron castings with low modulus. Castings with larger external dimensions can be divided into multiple regions and implemented according to the above process. In this case, the modulus should be the regional modulus of the casting, and the fins should be set according to the regional structure of the casting. The fin height can also be flexibly set according to the size of the casting.
[0026] The present invention can avoid setting larger and more shrinkage feed risers according to the traditional process by arranging a plurality of fins 008 on the disk surface 008 of the shaft disk and the outer periphery of the cylinder 010, thereby reducing the consumption of manpower, material resources and financial resources; by utilizing the fact that the heat conduction speed of the fins 008 is faster than that of the sand mold and the cooling speed of the fins 008 is faster than that of the casting 006, the local cooling speed of the casting 006 can be accelerated, and larger and more shrinkage feed risers are eliminated; during solidification, the fins and the casting body have a difference in solidification time due to different cooling speeds; when the fins solidify, the precipitation expansion force of the graphite acts on the casting, which can reduce the shrinkage defects of the casting and produce castings without internal shrinkage defects; utilizing these characteristics of the fins, it is not necessary to set shrinkage feed risers, thereby producing qualified castings without shrinkage defects; the present invention solves the problem that small modulus ductile iron castings cannot be cast without risers, improves the production process yield, reduces waste, improves the internal quality of the casting, reduces production costs, improves the economic benefits of the enterprise, and meets the needs of high-end equipment. The invention solves a problem that has long troubled technicians in the foundry industry, namely, how to produce small-modulus ductile iron shaft discs with high quality and high efficiency.
Claims
1. A sand mold and mold structure of a low-modulus shaft-disk ductile iron casting, the shaft-disk ductile iron casting comprising a disc and a cylinder, characterized in that: During casting of the shaft disk ductile iron casting, a plurality of fins are arranged on the mold surface corresponding to the hot spots easily generated, the thick-walled disk surface and the cylindrical outer circumference. The heat conduction speed of the fins is faster than that of the sand mold, and the cooling speed of the fins is faster than that of the casting.
2. A sand mold and mold structure of a low modulus shaft and disk ductile iron casting, characterized in that: The fins are linear or curved, and are fixedly or movably arranged on the mold surface.
3. The sand mold and mold structure of a low modulus shaft disk ductile iron casting according to claim 1, characterized in that: The fins are arranged in the radial direction of the surface of the disc, and a plurality of fins are arranged radially with the center of the disc as the center.
4. The sand mold and mold structure of a low modulus shaft disk ductile iron casting according to claim 1, characterized in that: The fins are arranged on the outer circumference of the cylinder, the fins are arranged in the axial direction of the outer circumference of the cylinder, and the angles of the multiple fins on the outer circumference of the cylinder are equal.
5. The sand mold and mold structure of a low modulus shaft disk ductile iron casting according to claim 1, characterized in that: The thickness of the fin is less than or equal to the wall thickness of the casting where the fin is located, and the height of the fin is between 10 and 50 mm.
6. The sand mold and mold structure of a low modulus shaft disk ductile iron casting according to claim 1, characterized in that: The plurality of fins are connected to the disc surface of the shaft disc and the outer peripheral surface of the cylinder as a whole after casting.
7. The sand mold and mold structure of a low modulus shaft disk ductile iron casting according to claim 1, characterized in that: The low modulus shaft disk ductile iron casting is horizontally molded and vertically cast, and its casting system is vertical casting. A straight pouring gate is arranged in the vertical casting, and a pouring cup is connected to the top of the straight pouring gate, and an inner gate is connected to the bottom, and the inner gate is connected to the lower half of the cylindrical cavity.