Method for manufacturing a cerabeads core for heat-resistant cast parts

Abstract

The present invention relates to a manufacturing method for increasing the strength of a Cerabeads core to improve cost and time waste factors in post-processing and quality during the production of finished cast products by increasing the heat resistance of the core during high-temperature casting of heat-resistant cast parts, thereby improving burrs and veneing phenomena inside the casting without breakage or deformation of the core. The invention is characterized by comprising the steps of mixing Cerabeads sand containing Cerabeads yarn, solid resin, hexamine, and resin, feeding it into an automatic molding machine and shooting it into a mold at a pressure of 20 kg / cm² to 30 kg / cm², and then firing it for at least 60 minutes to form a core, cutting the formed Cerabeads core to inspect the uniformity of the thickness of the internal firing layer of 8 to 10 mm, and applying a molding agent to the surface of the Cerabeads core and then drying it.

Description

Technology Field

[0001] The present invention is a manufacturing method for increasing the strength of a Cera Beads core to improve cost and time waste factors in post-processing and quality during the production of finished cast products by increasing the heat resistance of the core during high-temperature casting of heat-resistant cast parts, thereby preventing breakage and deformation of the core even during casting operations at a molten metal temperature of 1300°C to 1450°C and improving burrs and veneing phenomena inside the casting. Background Technology

[0002] Generally, metal casting is a processing method in which a material (mainly metals such as iron, aluminum alloys, copper, and brass) is heated to a temperature higher than its melting point to become liquid, poured into a mold, and solidified. The form used for casting is called a mold, and the product made by casting is called a casting.

[0003] A casting consists of a mold that forms the external shape and a core installed inside the mold to create an internal space; while the external shape of the casting can be improved through post-casting machining, it is natural that the space created inside the casting is difficult to improve through post-casting machining.

[0004] Ceramic cores are an important technical element for ensuring the precision and purposefulness of machine parts, and are a precision core method used when complex parts requiring heat resistance and strength, or when internal parts susceptible to burrs, baling, and bending phenomena are required in precision castings and cast products.

[0005] These ceramic cores are commonly used in the casting of military equipment, engines, transmissions, agricultural machinery transmissions, clutch housings, etc., and are molded products that maintain internal cleanliness and surface finish, thereby preventing interference and cracking between parts when various internal gears and other parts are operated as a finished vehicle. In the manufacturing process of parts, Cerabees sand cores using molds are widely used.

[0006] A typical ceramic core consists of a mixture of organic compounds, such as polymeric materials or surfactants, to hold ceramic particles, such as zirconia or silica, in place of the molded body or to improve miscibility with the ceramic particles.

[0007] According to conventional ceramic core manufacturing methods, there are difficulties in core dissolution after casting, and due to low strength and heat resistance, the ceramic core shrinks during sintering, causing shape distortion or breakage. Additionally, burrs or vaining or bending frequently occur inside the casting, requiring many post-processing steps after the casting is completed. Consequently, there are disadvantages such as quality degradation and significant waste of time and cost for improvement. Prior art literature

[0008] Republic of Korea Patent Registration No. 10-2206188 (Registration Date: January 18, 2021) The problem to be solved

[0009] The present invention, devised in consideration of the problems of the aforementioned conventional ceramic core, aims to improve strength and heat resistance by optimizing the additive composition and mixing process of Cerabees Sand when manufacturing a ceramic core, thereby preventing deformation of the core during sintering, and to improve casting quality and prevent waste of time and cost associated with manufacturing by minimizing secondary processing steps caused by problems such as burrs occurring inside the casting during casting.

[0010] In addition, it is an important objective to manufacture a core having a uniform internal sintered layer (8–10 mm) by improving the compression sintering conditions, and to improve the core surface quality and the surface roughness and cleanliness of the casting through the coating of a molding agent. means of solving the problem

[0011] The present invention for achieving the above objective is characterized by comprising the steps of mixing Cerabees sand comprising Cerabees yarn, solid resin, hexamine, and resin, feeding the Cerabees sand into an automatic molding machine and shooting it into a mold at a pressure of 20 kg / cm² to 30 kg / cm², and then firing it for at least 60 minutes to form a core, cutting the formed Cerabees core to inspect the uniformity of the thickness of the internal firing layer of 8 to 10 mm, and then dipping or brushing a molding agent onto the surface of the Cerabees core and drying it at 100 to 150°C. Effects of the invention

[0012] According to the present invention, excellent heat resistance and mechanical strength are secured by including solid phenolic resin and hexamethylenetetramine (HMTA) in an optimal ratio, and the phenomenon of core breakage is suppressed.

[0013] In addition, by controlling the loss on ignition within an appropriate range, the amount of gas generated during the molding process is reduced, thereby mitigating gas-related defects, shortening the molding cycle, and improving the solidification speed.

[0014] In addition, the mechanical bonding structure between the resin curing layer and the inorganic particles is enhanced, improving the core's crush resistance, wear resistance, and dimensional stability during casting. Consequently, this has the effect of being highly useful for applications such as forming cores with complex shapes, castings subjected to high thermal loads, and products where gas defect suppression is critical. Brief explanation of the drawing

[0015] Figure 1 is a flowchart of the manufacturing process according to the present invention. Specific details for implementing the invention

[0016] Hereinafter, the configuration of the present invention is to be described in detail. This description is based on embodiments for implementing the present invention and is not intended to limit the technical concept pursued by the present invention to the form described in the embodiments described in this document, and should be understood to include various modifications, equivalents, and / or alternatives of the embodiments of the present invention.

[0018] [Cerabees Sand Additive Preparation Steps]

[0019] Cerabees Sand is manufactured including the following composition.

[0020] Cerabiz yarn

[0021] Solid resin

[0022] Hexamine

[0023] resin

[0024] (Mixing and blending in 600kg units)

[0026] Cerabees yarn contains the following chemical composition (weight ratio below):

[0027] SiO₂: 49.9%

[0028] Al₂O₃: 2.41%

[0029] MgO: 35.2%

[0030] CaO: 0.54%

[0031] Na₂O: 0.01%

[0032] K₂O: 0.04%

[0033] Fe₂O₃: 10.0%

[0034] NiO: 0.12%

[0035] The composition is controlled to have a Loss on Ignition (LOI) of 0.02%, which refers to the proportion of components that volatilize or burn away when Cera Beads Sand (or minerals, ceramic raw materials, etc.) is heated at high temperatures. (This value indicates the amount of components contained in the sand, such as moisture, organic matter, and carbonates, that burn or evaporate upon heating.)

[0036] The content of the above components, converted to 100% SiO₂, is Al₂O₃: 4.83%, MgO: 70.54%, CaO: 1.08%, Na₂O: 0.02%, K₂O: 0.08%, Fe₂O₃: 20.04%, NiO: 0.24%.

[0038] Solid resin refers to a solid thermosetting resin used to bind and harden core sand; generally, it is a binder that melts when heat is applied and then hardens to make the core rigid.

[0039] Representative examples include phenolic resin (PF Resin), urea resin or melamine-urea resin, and epoxy solid resin.

[0041] Hexamethylenetetramine (HMTA) refers to a white solid powder used as a curing agent for Novolac solid phenolic resins, and is an essential curing agent that helps solid phenolic resins cure with heat in shell molding and hot-box processes.

[0043] [Compression Plastic Forming Step]

[0044] Feed the mixed Cerabees sand into the automatic molding machine.

[0045] Shooting into the mold with a pressure in the range of 20 kg / cm² to 30 kg / cm².

[0046] Ensure core strength by applying a firing time of at least 60 minutes. (Firing time is adjusted according to product size and thickness.)

[0048] [Core extraction stage]

[0049] The fired Cera Beads core is automatically ejected from the mold using a conveyor.

[0051] [Core Inspection Phase]

[0052] Cut the core and perform a sampling inspection to check if the internal plastic thickness (8~10 mm) is uniform, and

[0053] Check for bending and cracking, and check for abnormal heat resistance.

[0055] [Shape Processing Step]

[0056] A molding agent is coated to improve the surface roughness of the casting.

[0057] Use a water-soluble or alcohol-based diluting agent and dilute uniformly in a stirrer.

[0058] Apply to the core by dipping or painting, check that the penetration depth of the coating agent is 0.5 mm, and remove moisture and alcohol components in a drying oven at 100~150℃.

[0059] The molding agent complements the rough surface created by the small particles of the Cera Beads core, significantly improving the internal cleanliness and surface quality of the casting.

[0061] [Examples of the Invention]

[0062] ○ Mixing of raw materials

[0063] Cerabeads sand is manufactured by mixing Cerabeads yarn, solid resin, hexamine, and resin in units of 600 kg. The appropriate mixing ratio is 564 kg of Cerabeads yarn, 27 kg of solid resin, 3 kg of hexamine, 6 kg of resin, etc.

[0064] ○ Automatic molding machine feeding and compression firing

[0065] ○ Shooting pressure inside the mold: 20~30 kg / cm²

[0066] ○ Firing time: Maintain for at least 60 minutes depending on product thickness

[0067] ○ Core internal sintered layer thickness: Ensure 8~10 mm

[0068] ○ Discharge and cooling

[0069] ○ Automatic core ejection from mold via conveyor and cooling

[0070] ○ Cutting inspection

[0071] ○ Check for uniformity of internal sintered layer thickness and presence of cracks

[0072] ○ Coating and drying of molding agent

[0073] ○ Penetration of excipient: 0.5 mm

[0074] ○ Drying oven temperature: 100~150℃

[0075] ○ Packaging and Shipment

[0077] According to the core composition and the core molding method using the same of the present invention, by including solid phenolic resin and hexamethylenetetramine (HMTA) in an optimal ratio, the curing reaction of the resin proceeds stably under high temperature conditions, and a uniform tertiary network structure is formed throughout the core. As a result, the core secures excellent heat resistance and mechanical strength, and the phenomenon of breakage caused by thermal shock, pressure of molten metal, flow shock, etc., occurring during casting is effectively suppressed.

[0078] Furthermore, the composition presented in this invention can maintain a constant amount of organic matter remaining inside the core by controlling the loss on ignition (LOI) within an appropriate range. Consequently, the amount of gas generated during the molding process is reduced, and gas-related defects such as bubble defects or blowholes during metal casting are significantly minimized. In particular, by controlling the loss on ignition, the volatile and residual components of the resin burn uniformly, thereby enabling the stable reproduction of the core fracture point.

[0079] In addition, the composition of the present invention rapidly forms cross-links with the phenolic structure of the novolak resin as formaldehyde generated by the decomposition of hexamethylenetetramine during the heat curing step, thereby shortening the molding cycle and improving the solidification speed. Accordingly, productivity is increased, and there is an advantage that the curing quality is stably maintained even with variations in molding conditions (temperature, time, pressure).

[0080] Furthermore, when inorganic fillers or heat-resistant reinforcing agents are incorporated into the composition, the mechanical bonding structure between the resin curing layer and the inorganic particles is enhanced, resulting in additional effects such as improved crush resistance, wear resistance, and dimensional stability during casting of the core. Due to this series of actions, the present invention exhibits excellent performance when applied to the molding of cores with complex shapes, castings subjected to high thermal loads, and products where gas defect suppression is critical.

[0082] Even if the operation and effects according to the configuration of the present invention were not explicitly described while explaining the embodiments of the present invention as described above, it is natural that the effects predictable by said configuration should also be acknowledged.

Claims

Claim 1 A method for manufacturing a Cerabees core for a heat-resistant cast part, characterized by controlling the loss on ignition of the Cerabees yarn to 0.02%, mixing the Cerabees yarn, a solid resin, hexamine, and resin to produce Cerabees sand, feeding it into an automatic molding machine and shooting it into a mold at a pressure of 20 to 30 kg / cm², firing it for at least 60 minutes to form a core with strength, cutting the formed core to check whether the internal firing layer has a uniform thickness of 8 to 10 mm and to check for bending, cracking, and heat resistance, uniformly diluting a water-soluble or alcohol-diluted molding agent and applying it by dipping or brushing, checking whether the molding agent has penetrated to a depth of 0.5 mm, and drying at 100 to 150°C. Claim 2 delete Claim 3 delete

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