A method of casting thin-walled bronze parts
By combining purple clay sculpture patterns and a two-cavity casting system with low-tin bronze and high-temperature boiling refining, the high cost and wall thickness control problems of bronze sculpture casting patterns have been solved, enabling convenient modification of complex shapes and environmentally friendly and efficient casting.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANJING CHENGUANG ART ENG CO LTD
- Filing Date
- 2022-12-13
- Publication Date
- 2026-05-12
AI Technical Summary
Existing bronze sculpture casting patterns are costly, difficult to modify, and have difficulty controlling wall thickness. Complex-shaped castings are difficult to produce and contain heavy metals such as lead.
The design is based on Zisha clay sculpture, with calcium plastic skin forming the wall thickness. It adopts a top-pouring open casting system with two cavities in one mold, combined with low-tin bronze material and high-temperature boiling refining to reduce the amount of resin sand. It also uses an alcohol-based brown corundum coating that is easy to form.
It enables convenient modification of complex artistic forms, controls wall thickness uniformity, reduces costs and environmental risks, and improves casting efficiency and copper liquid quality.
Smart Images
Figure CN116422833B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of casting, and more particularly to a method for casting thin-walled bronze parts. Background Technology
[0002] Bronze sculpture is a form of sculptural art. It refers to sculptures made of bronze (an alloy of copper, tin, and lead), a hard material. Most bronze sculptures are made using the casting method, which involves heating the sculpting material to several hundred degrees Celsius, melting it into a liquid state, pouring this liquid into a mold, and allowing it to cool and solidify. Finally, the sculptor performs surface finishing on the solid within the mold.
[0003] Common bronze alloys possess an unusual and desirable property: they expand slightly before solidifying, filling the mold. Then, as the bronze cools, it contracts slightly, making it easier to separate from the mold. They also have good strength and ductility (no brittleness), giving them a significant advantage over other ceramic materials or marble sculptures, as it is relatively easy to depict human figures in poses and movements in bronze.
[0004] However, bronze sculpture casting patterns are generally made of hard materials such as fiberglass or metal, which presents problems such as high cost, difficulty in mold making, and difficulty in modification. At the same time, for castings with complex shapes, it is difficult to control the wall thickness or to manufacture them in a complicated manner. Moreover, bronze sculptures often use tin bronze as raw material, which has a high tin content and is therefore expensive. Alternatively, heavy metals such as lead may be added to improve casting performance. Summary of the Invention
[0005] Objective of the Invention: To address the shortcomings and defects of existing technologies, this invention provides a casting method for thin-walled bronze parts. It utilizes purple clay to sculpt the model, allowing for the creation of complex artistic forms and facilitating shape modifications. The use of easily moldable calcium-plastic skin to form the wall thickness ensures uniform wall thickness and ease of operation. The top-pouring open gating system, employing a two-cavity mold structure, improves molding efficiency, reduces resin sand usage, lowers molding costs, and is free of lead and other heavy metals, making it more environmentally friendly and healthier.
[0006] Technical solution: The present invention provides a method for casting thin-walled bronze parts, characterized by comprising the following steps:
[0007] 1) Pattern making: Sculpt the pattern with purple clay according to the design drawing, and turn the pattern into a plaster mold for subsequent casting. The pattern is in a dry state. First, apply epoxy polyurethane paint to the surface, and then apply a release agent. The release agent includes 5% to 8% aluminum powder and 92% to 95% rosin by weight.
[0008] 2) Resin sand molding;
[0009] 3) Smelting and casting: The smelting material is low-tin bronze, which includes the following components by mass percentage: 3.5% to 4.5% tin, 7% to 9% zinc, and the remainder copper; the smelting equipment is a medium-frequency induction furnace; the deoxidizer is a P-Cu master alloy containing 10% to 15% phosphorus by mass.
[0010] The charging sequence for low-tin bronze is as follows: flux → electrolytic copper and recycled material → 2 / 3P-Cu → Zn → Sn → 1 / 3P-Cu; high-temperature boiling refining is adopted, with the temperature raised to 1320℃~1350℃; the casting temperature is 1100℃~1200℃.
[0011] 4) Sand removal: After the casting cools in the sand mold, the casting is removed by removing the sand. The pouring cup, sprue, vent riser, ingate, branch sprue, main sprue, sub-sprue, burrs, and flash are all removed by carbon arc gouging. The cut areas are then shoveled or ground flat to obtain thin-walled bronze parts.
[0012] Step 2) of resin sand molding includes the following steps:
[0013] 1) Preparation of furan resin sand: Furan resin sand molding is adopted. The raw materials of resin sand are quartz sand, resin and curing agent. The raw materials are added into a mobile sand mixer and stirred to prepare furan resin sand.
[0014] 2) Core fabrication: Use a sand-enclosing plate to enclose the pattern and make a core frame. Pour furan resin sand into the core frame and allow it to self-harden at room temperature to form a resin sand core.
[0015] 3) Skinning: Remove the pattern and apply skinning to the inner core block according to the wall thickness of 5mm-8mm. The skinning material is polyethylene foam board-calcium plastic skin. The skinning is arranged from the top and bottom ends of the pattern towards the middle and is attached to the pattern.
[0016] 4) Outer core fabrication: The inner core is surrounded by a sand-enclosing plate to form an outer frame. Furan resin sand is poured into the outer frame and self-hardened at room temperature to obtain the resin sand outer core.
[0017] 5) Gating runner layout: After the inner and outer cores are made and cured, apply parting paint to the top surface and then arrange the gating runners.
[0018] 6) Coating application: Open the inner and outer cores, remove the thick calcium plastic skin, and apply coating to the surface of the mold. The coating is an alcohol-based brown corundum coating. Stir the coating evenly before use and dilute it with 1% to 5% alcohol by volume. The refractoriness of the coating is >1700℃. After igniting the alcohol, the coating is burned and dried to complete the resin sand molding.
[0019] In step 5), the gating system is arranged using a two-cavity open gating system. This system includes a sprue, a runner, and an ingate, with a cross-sectional ratio of F between the sprue, runner, and ingate. 直 :F 横 :F 内 The ratio is 1:1.2 to 1.5:1.2 to 2; the gating system is made of calcium plastic board or PS foam board.
[0020] The ingates are evenly distributed along the upper end of the mold, the spacing between the ingates is greater than or equal to their width, and the thickness of the ingates is less than or equal to the wall thickness of the casting.
[0021] The horizontal runner includes branch horizontal runners, a main horizontal runner, and sub-horizontal horizontal runners; the length of the branch horizontal runners can cover the entire ingate, and the cross-sectional area of the branch horizontal runners is larger than that of the sub-horizontal horizontal runners; the sub-horizontal horizontal runners guide liquid metal to flow evenly into each branch horizontal runner, and the cross-sectional area of the sub-horizontal horizontal runners is smaller than that of the main horizontal runner; the main horizontal runner is used for the arrangement of the sub-horizontal runners.
[0022] A filter screen is installed below the horizontal pouring channel.
[0023] The number of sprues is 1 to 2; the structure of the vent riser is a flat structure, and the thickness of the lower opening of the vent riser is less than or equal to the wall thickness of the casting.
[0024] The number of gas vents is 2, and the gas vents are arranged at both ends of the top surface of the casting.
[0025] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention uses purple clay to sculpt patterns, allowing for the creation of complex artistic forms and facilitating shape modifications. Artistic castings often have complex shapes and numerous curved surfaces; this invention utilizes easily moldable calcium-plastic skin to form thick walls, ensuring uniform wall thickness and ease of operation. Based on the solidification characteristics of tin bronze, this invention employs a top-pouring open gating system with a two-cavity mold structure, improving molding efficiency, reducing resin sand usage, lowering molding costs, and being free of lead and other heavy metals, making it more environmentally friendly and healthier. This invention uses high-temperature boiling refining to obtain high-quality copper liquid. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the vertical structure of the present invention;
[0027] Figure 2 This is a schematic diagram of the transverse structure of the present invention;
[0028] In the diagram, 1 is the pouring cup, 2 is the sprue, 3 is the vent riser, 4 is the filter screen, 5 is the ingate, 6 is the casting, 7 is the auxiliary runner, 8 is the main runner, and 9 is the sub-runner. Detailed Implementation
[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0030] The present invention provides a method for casting thin-walled bronze parts, characterized by comprising the following steps:
[0031] 1. Pattern making: Sculpt the pattern using purple clay according to the design drawing, and turn the pattern into a plaster mold for subsequent casting. The pattern is in a dry state. First, apply epoxy polyurethane paint to the surface, and then apply a release agent. The release agent includes 5% to 8% aluminum powder and 92% to 95% rosin by weight.
[0032] II. Resin Sand Molding:
[0033] 1. Preparation of furan resin sand: Furan resin sand is used for molding. The raw materials for the resin sand are quartz sand, resin and curing agent. The raw materials are added to a mobile sand mixer and stirred to prepare furan resin sand.
[0034] 2. Core fabrication: Use a sand-enclosing plate to enclose the pattern and make a core frame. Pour furan resin sand into the core frame and allow it to self-harden at room temperature to form the resin sand core.
[0035] 3. Applying the veneer: Remove the mold and apply the veneer to the inner core block according to the wall thickness of 5mm-8mm. The veneer material is polyethylene foam board-calcium plastic skin. The veneer is applied from the top and bottom ends of the mold surface towards the middle, and it should fit the mold surface tightly without any "soft" feeling.
[0036] 4. Outer core fabrication: Use a sand-enclosing plate to enclose the inner core to create an outer frame. Pour furan resin sand into the outer frame, and allow it to self-harden and solidify at room temperature to obtain the resin sand outer core.
[0037] 5. Gating System Layout: After the inner and outer cores are manufactured and cured, parting paint is applied to the top surface, and the gating system is then laid out. A two-cavity open gating system is used, comprising a sprue 2, a runner, and an ingate 5. The cross-sectional ratio of the sprue 2, runner, and ingate 5 is F. 直 :F 横 :F 内The ratio is 1:1.2~1.5:1.2~2; the gating system is made of calcium-plastic board or PS foam board. The ingate 5 is evenly distributed along the upper end of the mold, with the spacing between ingates 5 being greater than or equal to their width, and the thickness of the ingate 5 being less than or equal to the wall thickness of the casting 6. The runner includes branch runners 7, a main runner 8, and sub-runners 9; the length of the branch runners 7 can cover all the ingates 5, and the cross-sectional area of the branch runners 7 is greater than the cross-sectional area of the sub-runners 9; the sub-runners 9 guide the liquid metal to flow evenly into each branch runner 7, and the cross-sectional area of the sub-runners 9 is smaller than the cross-sectional area of the main runner 8; the main runner 8 is used for the arrangement of the sub-runners 9, and should be as short as possible while still meeting the requirements for the arrangement of the sub-runners 9. A filter screen 4 is installed below the runner. The number of sprues 2 is 1~2; one is sufficient for small and medium-sized castings; two can be arranged for large castings. The vent riser 3 has a flat structure, and the thickness of the lower opening of the vent riser 3 is less than or equal to the wall thickness of the casting 6. There are two vent risers 3, which are arranged at the two farthest ends of the top surface of the casting 6.
[0038] 6. Coating application: Open the inner and outer cores, remove the thick calcium plastic skin, and apply coating to the surface of the mold. The casting coating acts as a barrier and isolation between the casting and the mold to prevent sand from sticking. The coating is an alcohol-based brown corundum coating. Stir the coating evenly before use and dilute it with 1% to 5% alcohol by volume. The coating has a refractoriness of >1700℃. After the coating is burned and dried by igniting the alcohol, the resin sand molding is completed.
[0039] III. Smelting and Casting: The smelting material is low-tin bronze, which consists of the following components by mass percentage: 3.5%–4.5% tin, 7%–9% zinc, and the remainder copper; the smelting equipment is a medium-frequency induction furnace; the deoxidizer is a P-Cu master alloy containing 10%–15% phosphorus by mass; the charging sequence of the low-tin bronze is: flux → electrolytic copper and recycled material → 2 / 3 P-Cu → Zn → Sn → 1 / 3 P-Cu; high-temperature boiling refining is used, with the temperature raised to 1320℃–1350℃; the casting temperature is 1100℃–1200℃.
[0040] IV. Sand removal and cleaning: After the casting 6 is cooled in the sand mold, the sand is removed by removing the sand from the mold. The pouring cup 1, sprue 2, vent riser 3, ingate 5, branch runner 7, main runner 8, sub-runner 9, burrs, and flash of casting 6 are all removed by carbon arc gouging. The cut areas are then shoveled or ground flat to obtain a thin-walled bronze part.
[0041] Compared with the prior art, the present invention has the following beneficial effects:
[0042] 1. Using purple clay for sculpting allows for the creation of complex artistic forms, facilitating modifications and easily creating hard plaster molds for casting. Plaster molds are softer than conventional fiberglass, wooden, or metal molds, allowing for easy demolition when mold opening is difficult, thus ensuring the integrity of the sand mold and the quality of the casting. 2. Artistic castings often feature complex shapes and numerous curved surfaces. The use of easily moldable calcium-plastic coatings to form thick walls ensures uniform wall thickness, simplifies operation, and increases work efficiency. 3. Based on the solidification characteristics of tin bronze, a top-pouring open gating system with a two-cavity mold structure is employed, improving molding efficiency, reducing resin sand usage, and lowering molding costs. 4. Low-tin bronze is used, with a low tin content, reducing costs. It is also free of lead and other heavy metals, making it more environmentally friendly and healthier. 5. High-temperature boiling refining yields high-quality copper liquid, is simple to operate, requires no additives, and produces copper liquid with few impurities. 6. Using alcohol-based brown fused alumina coating eliminates the need for specialized baking equipment, reducing the time and equipment required for sand mold baking, resulting in high operational efficiency and low cost. Alcohol-based brown fused alumina coating also exhibits excellent high-temperature resistance, preventing sand adhesion to castings and ensuring high quality.
Claims
1. A method for casting thin-walled bronze parts, characterized in that: Includes the following steps: 1) Pattern making: Sculpt the pattern with purple clay according to the design drawing, and turn the pattern into a plaster mold for subsequent casting. The pattern is in a dry state. First, apply epoxy polyurethane paint to the surface, and then apply a release agent. The release agent includes 5%~8% aluminum powder and 92%~95% rosin by weight. 2) Resin sand molding; 3) Smelting and casting: The smelting material is low-tin bronze, which includes the following components by mass percentage: 3.5%~4.5% tin, 7%~9% zinc, and the remainder is copper; the smelting equipment is a medium-frequency induction furnace; the deoxidizer is a P-Cu master alloy with a phosphorus content of 10%~15% by mass. The charging sequence for low-tin bronze is as follows: flux → electrolytic copper and recycled material → 2 / 3 P-Cu → Zn → Sn → 1 / 3 P-Cu; high-temperature boiling refining is adopted, with the temperature raised to 1320℃~1350℃; the casting temperature is 1100℃~1200℃. 4) Sand removal: After the casting (6) is cooled in the sand mold, the sand is removed by punching the mold. The pouring cup (1), sprue (2), vent riser (3), ingate (5), branch sprue (7), main sprue (8), sub-sprue (9), burrs and flash of the casting (6) are all removed by carbon arc gouging. The cut areas are also shoveled or ground flat to obtain thin-walled bronze parts. Step 2) Resin sand molding includes the following steps: 1) Preparation of furan resin sand: Furan resin sand is used for molding. The raw materials for the resin sand are quartz sand, resin and curing agent. The raw materials are added to a mobile sand mixer and stirred to prepare furan resin sand. 2) Core fabrication: Use a sand-enclosing plate to enclose the pattern and make a core frame. Pour furan resin sand into the core frame and allow it to self-harden at room temperature to form a resin sand core. 3) Skinning: Remove the pattern and apply skinning to the inner core block according to the wall thickness of 5mm-8mm. The skinning material is polyethylene foam board-calcium plastic skin. The skinning is arranged from the top and bottom ends of the pattern towards the middle and is attached to the pattern. 4) Outer core fabrication: The inner core is surrounded by a sand-enclosing plate to form an outer frame. Furan resin sand is poured into the outer frame and self-hardens at room temperature to form the resin sand outer core. 5) Gating runner layout: After the inner and outer cores are made and cured, apply parting paint to the top surface and then arrange the gating runners. 6) Coating: Open the inner and outer cores, remove the thick calcium plastic skin, and apply coating to the surface of the mold. The coating is an alcohol-based brown corundum coating. When using the coating, stir it evenly and dilute it with 1% to 5% alcohol by volume. The coating has a refractoriness of >1700℃. After the coating is ignited by alcohol, it is burned and dried to complete the resin sand molding.
2. The casting method for thin-walled bronze parts according to claim 1, characterized in that: In step 5), the gating system is arranged using a two-cavity open gating system. The gating system includes a sprue (2), a runner, and an ingate (5). The cross-sectional ratio of the sprue (2), the runner, and the ingate (5) is F. 直 :F 横 :F 内 The ratio is 1:1.2~1.5:1.2~2; the gating system is made of calcium plastic board or PS foam board.
3. The casting method for thin-walled bronze parts according to claim 2, characterized in that: The ingate (5) is evenly distributed along the upper end of the mold. The spacing of the ingate (5) is greater than or equal to its width, and the thickness of the ingate (5) is less than or equal to the wall thickness of the casting (6).
4. The casting method for thin-walled bronze parts according to claim 2, characterized in that: The horizontal runner includes a branch horizontal runner (7), a main horizontal runner (8), and sub-horizontal runners (9); the length of the branch horizontal runner (7) can cover the entire inner runner (5), and the cross-sectional area of the branch horizontal runner (7) is larger than the cross-sectional area of the sub-horizontal runner (9); the sub-horizontal runner (9) guides the liquid metal to flow evenly into each branch horizontal runner (7), and the cross-sectional area of the sub-horizontal runner (9) is smaller than the cross-sectional area of the main horizontal runner (8); the main horizontal runner (8) is used for the arrangement of the sub-horizontal runners (9).
5. The casting method for thin-walled bronze parts according to claim 4, characterized in that: A filter screen (4) is installed below the horizontal runner.
6. The casting method for thin-walled bronze parts according to claim 2, characterized in that: The number of the direct gating system (2) is 1 to 2; the structure of the vent riser (3) is a flat structure, and the thickness of the lower opening of the vent riser (3) is less than or equal to the wall thickness of the casting (6).
7. The casting method for thin-walled bronze parts according to claim 6, characterized in that: The number of the gas vent risers (3) is 2, and the gas vent risers (3) are arranged at both ends of the top surface of the casting (6).