The temperature of metal after melting is usually above several thousand degrees, and it also has strong plasticity, which can be used to make alloys and various utensils. But what can hold these metals without being "burned"?

That is the crucible.

What kind of ability do you need to be "competent" for this job?

Everyone has a crucible in their home.

A crucible is an instrument widely used to heat or melt solid materials. In the chemical laboratory, it is a container for heating and reacting experimental materials; in the factory, it is a tool for melting and refining metal liquids, which can be used for melting metals, firing ceramics, chemical reactions, etc.

Don't listen to such a grand each of us has a "crucible" at home.

If you search for crucible-related experiments online, there's a good chance you'll come across an incredible crucible—the potato crucible. That's right, it's the kind of edible potatoes that you can buy in the vegetable market. Seeing this scene is even more incredible. I just said that the crucible is used to smelt metal. Does this mean that potatoes used for everyday cooking can also be used to heat and keep metal thousands of degrees warm?

Don't doubt that potatoes do.

A Douyin blogger once used a potato crucible to melt metal, and the operation is effortless. First, take a potato and poke a hole in it; then put a copper wire and heat it directly with a torch.

As you can see, the copper wire that was put into the potato melted as the side of the potato exposed to the flames was charred and blackened, and the molten copper didn't burn through the potato, but wrapped nicely around the bottom.

The blogger then melted a block of aluminum in a potato crucible. The union of aluminum was also melted, and this time the molten aluminum filled the entire potato crucible compared to the copper before.

The blogger made a hole in the potato crucible, poured aluminum water into the mold, and made a small ingot after cooling, which also proves that the potato crucible is a crucible that can be used in certain situations.

At this time, it can be seen from the edge that the surface of the potato crucible has been cracked and grayed like charred charcoal. This is the "secret" of the crucible containing aluminum water. After the potatoes are burned at high temperatures, the water on the surface evaporates, leaving only a dense layer of carbon. The carbon layer will no longer undergo a large reaction due to high temperature. To put it bluntly, it just can't burn, so it can withstand the high temperature of the spray gun and aluminum water, and firmly grasp the aluminum water.

Why is the crucible not afraid of burning? These materials have been used throughout the ages

The history that human beings have spent together with the world is too long.

The earliest crucible found so far is one found in central Turkey, which was used around the seventh millennium BC. The earliest known sites for smelting in crucibles are parts of Eastern Europe and Iran, dating from the late 6th to early 5th century BC.

The history of using crucibles in China can be traced back thousands of years. For example, crucibles of three shapes were unearthed from the Shang and Zhou bronze casting sites in Henan. One is remade with a gray clay pot or a large mouth statue, and the inside and outside are coated with thick grass mud.

The other has a thick wall, a large mouth, and a long tail underneath, which is convenient for insertion and inversion. It looks like a helmet, commonly known as a "general helmet", with copper slag stuck on it.

There is also a wall tire made entirely of grass mud strips, which is relatively large in shape, with burnt marks on the inner wall and copper slag stuck on it. The pottery body is gray-black, and the outer wall is reddish-brown.

It can be seen that our crucibles were mainly made of clay at that time. It is nothing more than that clay is more resistant to fire, and it is mainly used for copper smelting. At that time, there were no flame spray guns, and the crucible was made very thick for high fire resistance. If the crucible is heated with fire outside the crucible, the thermal efficiency will be very low.

Therefore, to improve thermal efficiency, when smelting copper, the sages put copper and charcoal together into the crucible, and after igniting, blow air into it, which is equivalent to letting copper directly contact the fire, to obtain a better smelting effect. This is also the reason why there are burn marks on the inner walls of these unearthed crucibles.

The following crucibles also follow this "internal heat" principle, only changing in shape and material. The shape was changed to improve sandblasting techniques to achieve and maintain higher furnace temperatures; besides pottery, materials such as sand, quartz, and clay were also mixed. The main purpose is to improve the high-temperature resistance of the crucible. characteristic.

This smelting method has been passed down from generation to generation and has made many parts of the country a large smelting province. For example, Shanxi has had a history of "crucible iron smelting" for more than 2,000 years.

Since modern times, the materials of crucibles have become more diverse and their uses have become more extensive. Classified by material, it can be mainly divided into three categories: graphite crucible, clay crucible, and metal crucible.

Graphite crucible refers to a type of crucible made of graphite, clay, silica, and wax stone, which can withstand high temperatures of 1800 °C. This type of crucible has stable chemical properties, good corrosion resistance, high-temperature resistance, and a small thermal expansion coefficient. The inner wall is smooth, and it is not easy to leak or adhere to the molten material, so it is often used in the smelting of non-ferrous metals and their alloys.

A clay crucible, made of clay, graphite, clinker, or silicon dioxide, has a melting point of 3850°C, a boiling point of 4250°C, and a small coefficient of thermal expansion. It is mainly used for the evaporation, concentration, or crystallization of solutions, and the combustion of solid substances.

There are many types of metal crucibles, including cast iron crucibles for melting alloys, nickel crucibles for strong alkali resistance and corrosion resistance, and platinum crucibles for heating non-metallic materials.

There is also a special quartz crucible, which has been in short supply in recent years because of its advantages such as high purity, strong temperature resistance, large volume, high precision, good heat preservation, energy saving, and stable quality. Use at temperature. It can be used to draw large-diameter monocrystalline silicon for semiconductors and solar energy, and it is also an indispensable basic material for the development of large-scale integrated circuits such as photovoltaics in my country.

The common feature of the above crucibles is high-temperature resistance, but the maximum temperature they can withstand is also different, which explains why they are "not afraid of burning". The so-called is not afraid of burning is actually that the temperature they endured when they work has reached the melting point of the item they smelt but has not reached their melting point, and the thermal conductivity of the crucible is also very strong, which can avoid local heating. The substance inside the crucible melts without damaging or melting the crucible.

For example, silver with a melting point of 961.78 ° C is smelted in a graphite crucible. This temperature can only be reached by raising the temperature to the melting point of silver. Such a temperature will hardly affect the temperature resistance of the graphite crucible at 1800 ° C.

The reason why so many types of crucibles have been invented is that the melting points of the melted substances are different, and the heating temperatures required for different purposes are also different, so the required crucibles must have different tolerance temperatures and characteristics.

How is a non-combustible crucible made?

Metal utensils are made by melting metal in a crucible, so how is the crucible made? Because no tool can hold the "smelting crucible", the crucible is not smelted. Most of the crucibles on the market are made by processing the material into a plastic state, such as breaking the solid material into powder and then forming it by physical pressure such as compression molding, manual molding, rotational molding, and compression molding.

Of course, the metal in some metal crucibles can still be mixed with other materials by melting and then shaped; quartz crucibles are also made by grouting or solidification.

Seeing this, you will find that this crucible is not something against the sky. It is just an ordinary smelting helper, bringing together the wisdom of blacksmiths and researchers throughout the ages. Like thousands of years past, the Crucible is in the future.  , will continue to shine in the fields of alchemy, ceramics, chemicals, etc., and continue to expand the "business scope" to help the development of more industries.

Finally, a warm reminder: Although it is interesting, friends without professional experience should not try it lightly. It is also a very happy way to enjoy watching videos.