Manufacturing process for bends in coated sand shell cores

Abstract

This invention provides a manufacturing process for curved cores in coated sand shells. The curved core box used in the manufacturing process includes an upper core box and a lower core box that work together. The manufacturing process includes steps such as assembling an venting device, installing a mating mold, sand injection for core making, disassembling the venting device, and mold opening and core removal. The venting device includes multiple venting rods and a wire control ring. The venting rods are curved round rods corresponding to the curved core. Multiple venting rods are inserted into the wire control ring. Multiple limiting holes are radially arranged on the annular wall of the wire control ring. A first wire control block and a second wire control block are respectively fitted onto both ends of the venting rods. Both the first and second wire control blocks are disc-shaped sleeves. A sand injection port is opened on the outer wall of the first wire control block. Using this invention, the core making process is simple, time-saving, and labor-saving. Furthermore, it ensures smooth venting during the production of curved cores, improving the yield rate of the castings obtained after subsequent casting.

Description

Technical Field

[0001] This invention relates to a sand core casting process, specifically a process for producing curved sections of coated sand cores. Background Technology

[0002] Coated sand is a resin-bonded sand made by coating a layer of phenolic resin film onto the surface of raw sand such as silica sand, zircon sand, and chromite sand using cold or hot methods. Its English name is Resin Coating Sand, abbreviated as RCS. In casting production, coated sand is used to manufacture hollow shell molds or cores with diameters of several millimeters or tens of millimeters. This molding and core-making method is called the shell process, also known as shell molding or shell core making. Since its invention, the shell process has become increasingly mature. Furthermore, with the development of the chemical and materials industries and the progress of the machinery and equipment manufacturing industry, my country's coated sand and its molding (core) processes and equipment have also developed rapidly. However, for shell molding or shell core making, if the coated sand core has bends, the difficulty in venting at these bends can lead to defects such as porosity and sand holes, which can severely damage the core and affect the production schedule of the casting.

[0003] Currently, common venting methods used by manufacturers when creating bends in coated sand cores include: applying refractory coating to the bends of the coated sand core and drying it for later use; pouring molten iron at a high temperature of approximately 1450-1550℃ during casting to extend the cooling time and ensure sufficient time for gas in the sand core to escape from the molten iron; and using high-temperature resistant coated sand during production. However, the problems associated with these methods are well-known. For example, thick coatings are prone to peeling, leading to pinholes; thin coatings easily cause sand adhesion, making later cleaning difficult; high-temperature molten iron pouring can easily cause the bends of the coated sand core to deform, resulting in castings with unacceptable dimensions; using high-temperature resistant coated sand increases production costs; and the venting methods generally require high-precision, time-consuming, and labor-intensive processes, easily leading to various casting defects and ultimately, casting scrap. Summary of the Invention

[0004] The main objective of this invention is to provide a manufacturing process for bends in coated sand shell cores, thereby solving the problem of venting difficulties in the existing coated sand shell core manufacturing process.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A manufacturing process for a curved core for a coated sand shell core, the process comprising a curved core box including an upper core box and a lower core box for mating use, and including the following steps:

[0007] S01. Assemble the exhaust device: The exhaust device includes multiple exhaust rods and a wire control ring. The wire control ring is an annular sleeve with multiple limiting holes radially through its annular wall. The exhaust rods are curved round rods corresponding to the bend. Multiple exhaust rods are inserted into the wire control ring, and the length of the exhaust rods is greater than the length of the bend. A first wire control block and a second wire control block are respectively fitted at both ends of the exhaust rods. Both the first and second wire control blocks are disc-shaped sleeves with irregular holes that mate with the exhaust rods. A sand-shooting port is opened on the outer wall of the first wire control block.

[0008] S02, Assembly Mold: The exhaust device assembled in step S01 is placed into the inner cavity formed by the lower core box and the upper core box mold. The first wire control block and the second wire control block are used to seal the two ends of the curved core box respectively. The inner cavity of the curved core box is connected to the outside through the sand injection port.

[0009] S03, Sand shooting core making: The coated sand is injected into the inner cavity of the curved core box through the sand shooting nozzle using a sand shooting machine, and then left to stand until the sand core solidifies and forms.

[0010] S04. Disassemble the exhaust device: After the sand core has solidified and formed, first remove the exhaust rod located in the center, and then remove the multiple exhaust rods from the curved core box.

[0011] S05. Mold opening and core removal: Separate the upper core box and the lower core box, remove the first and second wire control blocks located at both ends of the curved core box, take out the formed shell core, fill the limiting hole and trim the shell core.

[0012] The exhaust rod is made of tough steel wire.

[0013] The system comprises seven exhaust rods, with one placed in the center and the remaining six arranged in a petal-like pattern around the perimeter. The central exhaust rod extends beyond the end of the curved core box by a greater length than the other six rods. Each exhaust rod has a hook at its end for easy gripping and applying force. This facilitates subsequent removal of the exhaust rods, improving work efficiency.

[0014] Furthermore, both the first wire control block and the second wire control block are disc-shaped structures with steps.

[0015] Furthermore, multiple control coils are provided, each fitted onto different positions of multiple exhaust rods.

[0016] In step S02, before using the upper and lower core boxes, the upper and lower core boxes are cleaned and inspected, and a release agent is evenly applied to the inner cavity of the upper and lower core boxes.

[0017] Furthermore, in step S02, limiting posts that match the limiting holes are installed in the cavities of the lower core box and the upper core box respectively, and the exhaust device is installed in the inner cavity formed after the lower core box and the upper core box are closed through the limiting hole on the control ring.

[0018] In step S03, the curved core box is preheated to 220-240℃ before sand shooting. During sand shooting, the temperature of the curved core box is maintained at 220-240℃, the sand shooting time is 4-5s, the sand shooting pressure is 0.4-0.5MPa, and after sand shooting, it is left to stand for 120s to allow the sand core to solidify.

[0019] The beneficial effects of this invention are:

[0020] The manufacturing process for the curved section of the coated sand shell core described in this invention can be used in the production of sand cores with curved sections, or in the production of partial curved sections of sand cores. The core-making process of this invention is simple, time-saving, and labor-saving, and it facilitates venting when making the curved shell core, thereby improving the pass rate of the casting products obtained in the later casting process. Attached Figure Description

[0021] Figure 1 This is a flowchart of the manufacturing process of the present invention;

[0022] Figure 2 This is a schematic diagram of the structure in which the exhaust device is placed inside the lower core box in this invention;

[0023] Figure 3 This is a schematic diagram of the structure after the core is assembled;

[0024] Figure 4 A schematic diagram showing the state of the core box inside the curved track after sand shooting has completed the core forming process.

[0025] Figure 5 This is a schematic diagram of the lower core box structure;

[0026] Figure 6 This is a schematic diagram of the structure of the shell core removed from the core box;

[0027] Figure 7 This is a schematic diagram of the structure of the first wire control block;

[0028] Figure 8 This is a schematic diagram of the second wire control block.

[0029] Explanation of reference numerals in the attached figures

[0030] 1. Lower core box; 2. Upper core box; 3. Exhaust rod; 4. First wire control block; 5. Wire control ring; 6. Limiting post; 7. Sand core; 8. Second wire control block; 9. Sand injection port. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] This invention primarily addresses the difficulty of venting during the fabrication of curved coated sand cores. Therefore, it mainly introduces the processing steps that can solve this problem. Other essential core-making steps, such as the selection and mixing of coated sand, the use of a demolding machine, the tools and equipment used for core making, and the sand-shooting process parameters, will not be specifically described in this invention. Those skilled in the art can select them as needed.

[0033] The curved core box used in the manufacturing process described in this invention includes an upper core box and a lower core box used in conjunction. Figure 1 The main process steps of this invention specifically include:

[0034] S01. Assemble the exhaust system:

[0035] The venting device includes multiple venting rods and wire control rings. The wire control rings are annular sleeves with multiple limiting holes radially penetrating their annular walls. The venting rods are curved round rods corresponding to the bends, facilitating extraction after the sand core has solidified. Multiple venting rods are threaded through the wire control rings, with the length of each venting rod exceeding the length of the bend, allowing it to extend into the bend core box. The ends of the venting rods are equipped with hooks for easy gripping and force application to smoothly extract them from the bend core box. Multiple wire control rings can be selected based on the length of the bend, positioned at different locations to effectively secure the multiple venting rods. In this embodiment, two wire control rings are provided, symmetrically positioned corresponding to the mid-section of the bend. Figure 2 Only one of them is shown in the figure; the other one is set to correspond to the limit post 6.

[0036] A first wire control block and a second wire control block are respectively fitted at both ends of the venting rod. The structures of the first wire control block and the second wire control block are as follows: Figure 7 and Figure 8 As shown, all are disc-shaped sleeves with irregularly shaped holes, which mate with the venting rod. The disc-shaped sleeves of the first and second wire control blocks have a stepped structure, with the smaller end positioned at the outermost end of the curved core box during use to ensure effective sealing of both ends of the curved core box.

[0037] In this embodiment, the exhaust rod is made of tough steel wire, and seven exhaust rods are provided, arranged as follows: Figures 2-4As shown, one rod is placed in the center, and the remaining six rods are arranged in a petal shape around the perimeter. The venting rod in the middle protrudes beyond the end of the curved core box by a longer length than the other six rods. The irregular holes of the first and second wire control blocks are correspondingly petal-shaped holes, and an opening is provided on the outer wall of the first wire control block as a sand injection port. See [reference needed]. Figure 7 .

[0038] S02. Assembly Mold: Place the exhaust device assembled in step S01 into the inner cavity formed by the lower core box and the upper core box. Of course, when using the curved core box, it is necessary to first check whether the fit between the upper core box and the lower core box meets the requirements, clean the inner cavity of the curved core box, and evenly apply or spray the release agent in the inner cavity. The release agent should be a conventional commercially available product.

[0039] Limiting posts that mate with the limiting holes are installed in the cavities of the lower and upper core boxes, respectively. See [reference needed]. Figure 5 The venting device is installed in the cavity formed after the lower and upper core boxes are closed, through the limiting hole on the wire control ring. After the venting device is in place, ensure that the first and second wire control blocks are used to seal both ends of the curved core box respectively. At this time, the cavity of the curved core box is connected to the outside through the sand injection port, such as... Figure 3 As shown.

[0040] S03. Sand Shot Core Making: Preheat the curved core box to 220-240℃, then use a sand shot machine to inject coated sand into the inner cavity of the curved core box through the sand shot nozzle, and let it stand for the sand core to solidify and form; during the sand shot process, maintain the temperature of the curved core box at 220-240℃, the sand shot time at 4-5s, and the sand shot pressure at 0.4-0.5MPa. After the sand shot is completed, let it stand for 120s to allow the sand core to solidify.

[0041] S04. Disassemble the venting device: After the sand core has solidified, pull out the multiple venting rods from the curved core box. Note that you need to pull out the venting rod located in the center first, and then pull out the venting rods around the perimeter. This can reduce the difficulty and improve efficiency.

[0042] S05. Mold Opening and Core Removal: Separate the upper and lower core boxes, remove the first and second wire control blocks located at both ends of the curved core box, and remove the formed shell core. See below. Figure 6 Then, a small amount of coated sand was used to fill the limiting holes on the shell core and the shell core was trimmed.

[0043] In this invention, multiple venting rods, a first wire control block, and a second wire control block are pre-embedded in the sand core. After solidification, they are extracted from the sand core to form a curved shell core with both ends connected to the outside. This solves the problem of venting difficulties in manufacturing the curved section of the coated sand shell core, thereby solving the problem of defects such as sand holes and porosity in castings caused by venting of the shell core during the casting production process, ensuring the quality of casting products and improving economic efficiency.

[0044] The above description is merely a preferred embodiment of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A manufacturing process for a curved channel for a coated sand shell core, the curved channel core box used in the manufacturing process comprising an upper core box and a lower core box used in conjunction, characterised in that It comprises the following steps: S01, assembling the exhaust device: the exhaust device comprises a plurality of exhaust rods and a wire control ring, the wire control ring is an annular sleeve, a plurality of limiting holes are radially and throughly arranged on the annular wall of the wire control ring, the exhaust rod is a curved circular rod corresponding to the curved channel, a plurality of exhaust rods are all arranged in the wire control ring, the length of the exhaust rod is greater than the length of the curved channel; the two ends of the exhaust rod are respectively sleeved with a first wire control block and a second wire control block, the first wire control block and the second wire control block are both disc-shaped sleeves with special-shaped holes, the special-shaped holes are matched with the exhaust rod, and a sand shooting port is arranged on the outer side wall of the first wire control block; S02, assembling the mold: placing the exhaust device assembled in step S01 into the inner cavity formed by the closed mold of the upper core box and the lower core box, the first wire control block and the second wire control block are used to block the two ends of the curved channel core box respectively, and the inner cavity of the curved channel core box is communicated with the outside through the sand shooting port; S03, sand shooting core making: the coated sand is shot into the inner cavity of the curved channel core box through the sand shooting port by a sand shooting machine, and the sand core is left to solidify and form; S04, disassembling the exhaust device: after the sand core is solidified and formed, the exhaust rod located at the center is first extracted, and then a plurality of exhaust rods are extracted from the curved channel core box; S05, mold opening and core taking: separating the upper core box from the lower core box, taking away the first wire control block and the second wire control block located at the two ends of the curved channel core box, taking out the formed shell core, filling the limiting holes and trimming the shell core; The exhaust rod is a steel wire with toughness; The exhaust rod comprises seven rods, one of which is placed at the center, and the remaining six rods are arranged in a petal shape, the length of the exhaust rod located at the center and protruding out of the end of the curved channel core box is longer than that of the remaining six rods, and a hook is arranged at the end of the exhaust rod to facilitate force exertion; In step S02, a limiting column matched with the limiting hole is installed in the cavity of the lower core box and the upper core box, and the exhaust device is arranged in the inner cavity formed after the lower core box and the upper core box are closed through the limiting hole on the wire control ring; In step S03, the curved channel core box is preheated to 220-240℃ before sand shooting; In step S03, during the sand shooting process, the temperature of the curved channel core box is maintained at 220-240℃, the sand shooting time is 4-5s, the sand shooting pressure is 0.4-0.5MPa, and the sand core is left to solidify for 120s after the sand shooting is completed.

2. A manufacturing process for a curved channel of a coated sand shell core according to claim 1, wherein: The first wire control block and the second wire control block are both disc-shaped structures with steps.

3. The manufacturing process for a curved channel for a coated sand shell core of claim 1, wherein: The wire control ring is provided with a plurality of wire control rings, which are respectively sleeved at different positions of the plurality of exhaust rods.

4. The manufacturing process for a curved channel for a coated sand shell core of claim 1 wherein: Before step S02, the upper core box and the lower core box are cleaned and inspected, and the inner cavities of the upper core box and the lower core box are evenly coated with a release agent.

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