When you open a can of Coke or charge your phone, you may not expect that your fingertips are touching the masterpiece of human material engineering - aluminum discs. This metal disc, as thin as a cicada's wing, is quietly changing our world.
- What is an aluminum disc?
Imagine pressing an aluminum block into a piece of "metal paper" and then cutting it into a circle - this is an aluminum disc. Its thickness ranges from 0.005 mm (10 times thinner than a hair) to 3 mm, and its diameter can be as small as a button or as large as a car tire. Interesting features Lightweight champion: Aluminum weighs only 1/3 of iron at the same volume Invisible shield: The surface oxide film makes it corrosion-resistant (even difficult to be corroded by coke acid) Transformation master: Can be stamped into cans and stretched into battery shells Lab experiment: Try to fold aluminum foil, you will find that it is not easy to break - this is due to the ductility of aluminum (1 gram of aluminum can be stretched into a 3-meter-long filament!)
Cans: A mechanical miracle of 0.28 mm You may not know that each can is stamped from a 22cm diameter aluminum disc, the can body is only 0.1mm thick, and the bottom is thickened to 0.28mm to withstand pressure Why is it a disc? The round shape can evenly disperse the liquid pressure and avoid cracking at the corners (square cans require thicker materials) Environmental protection knowledge: Recycling 1 ton of aluminum discs = saving 14,000 kWh of electricity (enough for a family for 3 years)
"Energy film" in the battery The smartphone battery contains a thinner aluminum disc - the positive electrode current collector (thickness of about 0.015mm). Its secret mission: Acting as a "highway" for electric current, carrying positive electrode materials (such as lithium cobalt oxide), and resisting electrolyte corrosion Technological breakthrough: Scientists use etching technology to create micron-level pits on the surface of aluminum sheets, increasing battery capacity by 15% (principle: increasing the material attachment area)
How to make a perfect aluminum disc? Four key steps: Melting: Aluminum ingot + silicon/magnesium alloy melted into "metal soup" Hot rolling: Pressed into 3mm thick plate (like rolled dough) Cold rolling: Repeated rolling to target thickness (accuracy of ±0.001mm) Fine cutting: Rotating die cut into a circle (smooth edge without burrs) Why do we need precise dimensions? The thickness of aluminum sheet in cans is 0.01mm → 20,000 tons of aluminum is wasted every year Battery aluminum foil thickness fluctuates → Mobile phone battery life is reduced by 10%
Extended reading: If you are interested in industrial aluminum size standards, you can refer to the material science chapter in "https://aluminumstock.com/what-is-an-aluminum-circle/?".