Table of Contents
Introduction to Chemical Element-Copper
Copper, with the chemical symbol Cu, is a soft metal that appears reddish-orange with a metallic luster when freshly cut. It has excellent ductility, along with high electrical and thermal conductivity, which makes it widely used in cables, electronics, and electrical components. Copper can form various alloys with other metals, such as sterling silver for jewelry, cupronickel for marine hardware and coins, and constantan for strain gauges and thermocouples. Bronze and brass are the most representative copper alloys, known for their superior mechanical properties and low electrical resistivity. Additionally, copper is a durable metal that can be recycled multiple times without losing its properties.
Common Questions about Polishing Copper
1. Common Types of Copper
Brass: An alloy composed of copper and zinc, known for its excellent mechanical properties and wear resistance. It is commonly used to make precision instruments, marine parts, bullet casings, and coins (such as the 5-yen coin).
Bronze: An alloy made by mixing pure copper (red or purple copper) with tin or other metals (such as lead or aluminum). Freshly made bronze items have a golden-brown appearance. Aluminum bronze has high strength, excellent wear resistance, and corrosion resistance, making it often used to manufacture high-load bushings, gears, and ship propellers.
Cupronickel: Also known as copper-nickel alloy, it has strong hardness, good plasticity, and excellent corrosion resistance, with high electrical resistivity and resistance to rust. These properties make it widely used in jewelry, water supply equipment, instruments, and coin manufacturing.
2. What Kind of Surface Does Copper Produce After Polishing?
Polishing copper can create a smooth, reflective, mirror-like finish on the metal surface.
3. Does Copper Oxidize Easily?
Brass is resistant to corrosion, but when exposed to air, it can oxidize, causing black spots and an odor on its surface. While this patina is often considered part of brass’s appeal, the black spots become more noticeable as oxidation progresses. Additionally, exposure to water or sweat may cause a greenish “verdigris” similar to rust on iron.
4. Common imperfections
Orange Peel Effect: When coarse-grained aluminum alloy or copper alloy sheets undergo drawing, bending, or stretching, the product surface may exhibit a rough texture similar to orange peel. This phenomenon reflects uneven deformation between the grains.
Oxidation: When copper reacts slowly with oxygen in the air, or when molds are not cleaned promptly or the humidity is too high, surface oxidation spots can form, affecting the appearance and performance of the mold.
Scratches: After grinding, copper materials tend to adhere to the abrasive surface, causing scratches as the tool rotates, making it difficult to achieve a higher gloss.
5. Difficulties in polishing copper compared with other metals
Low Hardness: Compared to other metals, copper has lower hardness, making it prone to scratches and dents if polishing speeds are too high. It is more challenging to polish compared to harder metals.
Clogging of Abrasives: Copper’s high ductility makes it prone to sticking to abrasive grains, reducing their cutting force and affecting the heat dissipation capability.
Issues Affecting Subsequent Surface Polishing of Copper
Material Selection for Molds: The surface material of molds in contact with copper can affect the oxidation rate of copper, as different material surface characteristics influence the adhesion of moisture and oxygen, accelerating the oxidation process.
Heat Treatment Process: The process of heating and cooling metals or alloys to alter their physical and chemical properties. These treatments are aimed at improving the strength, hardness, toughness, and wear resistance of materials.
Surface Roughness of the Mold: Roughness plays a key role in the mold’s functionality, as smoother surfaces reduce friction, improve the surface finish of the formed product, and make demolding easier.
Shape of the Mold Surface: It affects the difficulty and uniformity of polishing. Complex curves, edges, and corners may lead to uneven polishing and lower overall surface quality.
Polishing Process: It significantly impacts the polishing results, including gloss, efficiency, and surface quality. Different polishing techniques (such as buff polishing, sandpaper polishing, or abrasive polishing) have distinct characteristics in terms of speed, suitable materials, and final surface condition.
Choice of Polishing Tools: Various polishing tools (like buffing wheels, abrasive pads, or sandpaper) differ in material, hardness, and shape. Improper selection may result in surface scratches, uneven wear, or failure to achieve the desired gloss.
The initial surface quality of the workpiece directly impacts the time and difficulty of subsequent polishing. Understanding the various factors in the processing stages and choosing the appropriate processing methods can significantly enhance production efficiency, achieving greater results with less effort.
If there is a lack of effective copper polishing solutions, the following experimental results can serve as a reference, offering ideal solutions to address the various challenges encountered during the polishing process.
Copper Polishing Experiment
Copper is a metal with excellent electrical conductivity and ductility, widely used in everyday life and electronic components. However, during the polishing process, challenges such as surface oxidation spots, scratches, and the relatively low hardness of the material often arise, affecting the final surface finish and overall performance. To effectively address these issues, HongWei Laboratory conducted mechanical polishing experiments on copper, exploring how different polishing techniques and conditions affect the polishing outcome. In the experiments, we evaluated the selection of polishing tools and agents to optimize the polishing process, improve the surface finish and durability of copper, and enhance its performance in practical applications.
Tools Preparation
1. Metallographic Grinding and Polishing Machine
2. Polishing pad: Such as electroplating pad, resin pad, cerium oxide leather pad with different abrasive types.
3. Polishing solution: Such as nano diamond polishing solution, alumina/cerium oxide polishing solution, silicon dioxide can be used together.
Polishing Processes of Copper
Electroplating disc-Resin disc-Cerium oxide leather polishing pad-Diamond solution-Cerium oxide-Alumina-Silicon dioxide
※ Starting with coarse polishing, gradually transition from coarse to fine polishing to avoid deep scratches caused by a single polishing session.
Polishing Issues in Experiment
When copper comes into contact with liquids and is not cleaned promptly, white spots can easily form on the surface.
When using cerium oxide pads for polishing copper, if the polishing pad is too soft, it can easily scratch the surface.
Polishing pads that are too soft make it difficult to apply sufficient pressure during the polishing process, making it ineffective at removing surface defects and fine scratches.
Recommended Polishing Tools
Nano diamond polishing solution / Grinding solution / Suspension >>>Polishiing solution
- Best suited for: Mechanical operations.
- Form: Liquid (oil-based/water-based/alcohol-based).
- Polishing can be paired with: Double-sided grinders, chemical mechanical polishing (CMP), and metallographic grinding.
- ※ Since the abrasive is in a free-flowing state, it can polish a large surface area.
- ※ If the workpiece surface is still rough, you can opt for a polishing liquid with larger particle sizes.
Alumina / Cerium oxide polishing solution / Grinding solution / Suspension >>> Polishing solution
- Best suited for: Mechanical operations.
- Status: Liquid
- Scope of application: Generally used after diamond compound
- ※ Possesses the ability of repairing polishing marks on the workpiece.
- ※ Cerium oxide is recommended to be used with tools at low speed.
Polishing pads / Grinding pads >>>> Coming soon, contact sales staff for more details~
- Materials:
- Contains abrasive: Cerium oxide leather, electroplating, resin
- Does not contain abrasive: Silk, cowhide, polyurethane (black velvet), weave, fluff, porous, hard cloth, soft cloth, etc.
Practical Applications of Copper
Copper Pipes and Fittings: Copper pipes and fittings are widely used in construction, refrigeration, and HVAC systems due to their excellent thermal conductivity and corrosion resistance.
Electronics: Copper is extensively used in electronic products, such as printed circuit boards, cables, transformers, and generators.
Marine and Automotive: It is used to manufacture ship and automotive components, including propellers, coolers, and engine parts.
Industrial Machinery: Copper is also widely applied in industrial machinery, such as brakes, drive shafts, and gears.
Conclusion
Copper products are widely used in everyday life, spanning various fields from electronics and plumbing to decorative items. Therefore, understanding how to maintain the luster of metal surfaces is essential knowledge. For restoration professionals, a deep understanding of copper’s properties, copper alloys, and their practical applications can help in selecting the most suitable polishing tools and processing methods. This not only enhances the quality of the restoration but also reduces production costs and shortens processing time, making the entire restoration process more efficient and reliable, ultimately improving the overall quality and lifespan of the products.
Action
- Does the current measurement of surface roughness meet your expected target? >>> Comparison Table of Grinding and Polishing with Surface Roughness
- Common problems and solutions about metals>>> Metal Polishing Defect Repair Guide: Common Problem Solutions and Recommended Quality Materials and Tools
- How to solve >>> Six mold polishing techniques: How many do you know?
- Implement >>> polishing abrasives, polishing equipment, polishing tools
- Review
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