Everyone should have drunk soda and used cans. However, if you are asked what is wrapped in the bulging circle on the edge of the soda can, you probably can't answer.
Let me help you eliminate one option first - this layer of circle is not hollow.
I guess you can't figure it out even if you rack your brains. In fact, this layer of circle contains liquid. What kind of liquid is it?
What is wrapped in this layer of circle has a lot to do with the manufacturing process of the aluminum can itself. In fact, the body of the can is punched out of aluminum sheet.
This aluminum sheet is about 0.3 mm thick. When punching, it is placed on a tool called a drawing die.
The aluminum sheet (yellow) is punched into an ashtray shape by a punch and a drawing die
Next, a cylindrical object (punch) will be inserted from top to bottom into the aluminum sheet to form a short cylindrical object, just like an ashtray. This process is called drawing.
However, after only one drawing, the round plate is still very wide and thick, and has not yet reached the final shape of the standard aluminum can. Therefore, it is necessary to continue drawing.
Each time the aluminum sheet is drawn, the short cylinder becomes thinner, the radius becomes smaller, and the height becomes higher.
After several drawing, the round aluminum sheet at the beginning has the shape of a aluminum can.
Now there are only two steps left to complete the production of a can. The remaining two steps are to make the concave bottom of the aluminum can and to seal it with a lid.
A dome-shaped tool is needed to make the concave bottom of the aluminum can. The manufacturing process is similar to that of stamping, which is to press the can on the semi-dome to punch out a concave shape.
Because the concave bottom is like an arch bridge and can withstand greater pressure. All of the above processes take only one seventh of a second. After trimming the top of the can, the aluminum can can be sprayed with outer packaging.
The inside of the aluminum can also be sprayed with a coating, otherwise the acidic beverage will react with the aluminum, and you will drink a lot of aluminum, and your nervous system will become demented.
Next, you need to pull a thin neck out of the can to prevent the thin aluminum can from wrinkling.
Now, it's time to seal the aluminum can.
First, the edge of the neck needs to be bent to form a flange.
Then, it's time for the wonderful double seaming.
The edge of the aluminum can is actually not seamless, but made of 2 aluminum sheets rolled together.
In 1810, tinplate cans were invented. At first, the top and bottom of the aluminum can were directly welded to the round can, so the food inside was often contaminated by welding materials (such as lead).
The double seaming common in aluminum cans today does not have this problem. Double seaming is a relatively new invention. In 1894, the Ams machine company began to produce double-seamed cans.
What is double sealing? Take a look at the picture below. The bevel of the bead and the lid (top) form a spring roll shape.
The process of double sealing, the blue represents the aluminum sheet of the lid of the aluminum can, and the red represents the aluminum sheet of the can body
Double sealing may not look special, but it requires high precision. A difference of 1 mm will cause the sealing process to fail.
However, the double sealing itself cannot completely isolate the inside and outside of the aluminum can. Do you see the gaps in this double sealing?These gaps are filled with liquid sealing compound to prevent the gas in the aluminum can from escaping through the gaps in the bead and to prevent external contaminants from entering the aluminum can.
The blue part is the sealant
The sealant generally contains a mixture of latex, rubber or resin. These substances are dissolved in an oily solvent.
So, the round bead of the aluminum can we usually drink contains an oily liquid. You never expected it.
