How are metals classified? Is black metal really black?


As society entered the era of informatization, globalization and knowledge from the era of industrialization at the end of the 20th century, the development of social productivity has constantly increased the demands on materials. At the same time, due to the rapid development of science and the maturity of materials production technology, other various metal materials have also developed rapidly, but the status of metal materials as the most important structural and functional materials has always been difficult to shake.

Among all materials, metal can be called a support. Look around, there must be something made of metal or part of it. One of the most striking examples is a mobile phone, without which everyone cannot live, without metal it will become a useless brick.

Copper coils on a PCB

Single, black, bright black

When you mention metal, what image comes to mind? Is it sparkling necklace jewelry or shiny metal pots and pans? I don't know if you've noticed, but when it comes to metal, we never associate it with black, but "black metal" is a really big category of metal!

The word "black" can easily lead people to think that ferrous metals should be black and nonferrous metals should be nonferrous. Based on this, many believe that silver-white iron, chromium and silver-gray manganese should not be "black" metals. Then why should these three and their fusions be included in the black metal category?

The reason is this: ferrous metal is a general term for iron, chromium and manganese in industry, as well as alloys of these three metals. In fact, pure iron and chromium are silvery white, while manganese is silvery gray. Since the surface of steel is usually covered with a layer of black iron oxide, manganese and chromium are mainly used for smelting black alloy steel, so they are mistaken for "ferrous" metals.

Steel and gold respectively represent ferrous and non-ferrous metals. 

Second, a dispute between two metal sects

For metals, the official definition is "substances that are lustrous, have good electrical, thermal, and mechanical properties, and have a positive temperature coefficient of resistance."

Metal is a big family of 86 people. Usually people divide them into two "schools" according to characteristics such as color and nature: ferrous metals and non-ferrous metals. Ferrous metals mainly refer to iron, chromium, manganese and their alloys such as steel, cast iron, iron alloys, cast iron, etc., and non-ferrous metals generally refer to metals other than ferrous metals, also known as non-ferrous metals. metals, which are metals other than iron, chromium, and manganese. A general term for all metals.

Periodical table

Not only are the two titles different, but their returns are also very different! Due to the wide variety of non-ferrous metals, the number of mineral deposits is much larger than that of ferrous metals. Although there are few ferrous mines, the production of each of them is large, bringing the total ferrous metal production to 95% of the world's metal production! Moreover, iron, chromium and manganese are the main raw materials for smelting iron and steel, and iron and steel occupy an extremely important place in the national economy and can also be used as an important symbol to measure national strength.

Third, the source of the interesting name

The English translation of the word "non-ferrous metals" sounds like "Non-ferrous metals", which corresponds to the English translation of the word "ferrous metals" "Ferrous metals". According to an elderly gentleman who has been working in non-ferrous metallurgy for a long time, the process of converting "ferrous metals" and "non-ferrous metals" into "ferrous metals" and "non-ferrous metals" is also an interesting story.

The earliest scholars who translated "ferrous metals" and "non-ferrous metals" believed that if they were directly translated as "iron metals" and "non-ferrous metals" or "ferrous metals" and "non-ferrous metals", although the accuracy of the translation is thought out, it is not concise enough, and it is also very inconvenient to use. So this scientist jumped out of inertial thinking, starting from the optical properties of metals, and carried out a reconstruction in translation.

Pure iron is silvery white in color, but iron, which is often found in people's daily work and life, is black. This is due to the fact that the surface of iron is coated with a black oxide film: iron tetroxide. It is because of this layer of oxide film that iron leaves a black imprint on people, so from this point of view, "ferrous metals" are creatively translated as "ferrous metal".

Rusty steel and pure steel Image Source: Iron and Steel Materials Advanced Research Department, Institute of Metal Research, Chinese Academy of Sciences

With the existence of "ferrous metal" and taking into account the fact that silver is white, gold is golden, copper is yellow, and lead is gray, "non-ferrous metals" have colorful optical properties, therefore "Non-ferrous metals" are translated as "Non-ferrous Since then, "ferrous metals" and "non-ferrous metals" have become "ferrous metals" and "non-ferrous metals" in Chinese, and have gained currency in the industry.

Fourthly, metal, the "pillar" of social development

It can be said that metal materials contributed to the development of human society, since they played a key role in various periods of the transformation of human society. In the history of the social development of mankind, the Bronze and Iron Ages, which arose after the Stone Age, are marked by the use of metal materials.

Bronze tripod with animal face 

After the Second World War, the development of science and technology contributed to the development of new materials. Ductile iron, alloy cast iron, alloy steel, heat resistant steel, stainless steel, nickel alloy, titanium alloy and carbide have been developed one by one and can be applied to real production.

In the modern era, the research and development of metallic materials is not limited to the traditional direction of pure metals and pure alloys. With the improvement of basic theory and technology, new metallic materials were rapidly developed. These include nanometals, high/medium entropy alloys, high temperature structural materials such as directionally solidified columnar crystals and single crystal alloys, metal matrix composites, shape memory alloys, etc. [1-4].

Various metal materials have become an important material basis for the development of human society. Agricultural modernization, industrial upgrading, national defense and scientific and technological upgrading are inseparable from the support of metal materials, ranging from agricultural implements, mechanical parts, and daily utensils such as advanced weapons , such as aircraft, rockets, missiles, satellites, and nuclear submarines, and components or components required for advanced technologies such as nuclear power, television, communications, radar, and electronic computers. , most of them are made of metal.

At present, many countries of the world, especially industrialized countries, are competing for the development of metallurgical and non-ferrous metallurgy and the increase in their strategic reserves of metals. It can be said that metal materials are important basic materials and important strategic materials for the national economy, people's daily life, national defense industry, and scientific and technological development.


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[3] Q. Pan, L. Zhang, R. Feng, Q. Lu, K. An, A. C. Chuang, J. D. Poplawsky, P. K. Liaw, L. Lu, Gradient Cell Structure High Entropy Alloy with Exceptional Strength and Ductility , Science 374(6570) (2021) 984-989.

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