Not only can it make rice more delicious, but it can also create an "ocean ranch". There are so many surprises about iron that you don't know!

1. Iron and life from idioms

Iron is not only a metal element, but its extended meaning is also closely related to life.

1.1 Used to describe something that is very strong, firm, or resolute

An iron-clad regime: a metaphor for a solid political power or status.

Wall of iron and steel: a metaphor for something that is very strong and indestructible.

Iron-clad city: a metaphor for a city with strong fortifications.

As solid as a rock: a metaphor for being so tightly bound that it cannot be broken down.

Decisive and resolute: a metaphor for being firm and decisive in words and actions, without hesitation or procrastination (Figure 1).

Figure 1: Decisive (Picture from the Internet)

Heart of stone: a heart as hard as iron or stone. It means a person who has a very hard heart and is not moved by emotions.

1.2 Used to describe integrity and firmness

Ironclad evidence is as solid as a mountain: used to describe evidence that is so conclusive that it cannot be shaken like a mountain.

Impartial and impartial: describes being fair and strict without considering personal feelings (Figure 2).

Figure 2: Impartiality (Photo from the Internet)

Golden rules and iron laws: a metaphor for creeds that must be followed and cannot be changed.

A done deal: a metaphor for something that has been decided and cannot be changed.

1.3 Used to describe strong will

A man of integrity: refers to a person who is upright, strong and unyielding.

Copper enclosure and iron cavalry: a metaphor for a solid formation.

Wear through the iron inkstone: Wear through the iron inkstone. It is a metaphor for studying hard and having perseverance.

1.4 Refers to weapons such as swords and guns

Unarmed: without any weapon in hand.

Golden Swords and Iron Horses: describes the majestic posture of soldiers and generals holding guns and riding horses.

Cut iron like mud: describes an extremely sharp weapon.

1.5 Used to describe something worthless

Turning gold into iron: It is used to describe changing a good article into a bad one. It is also used to describe doing a good thing badly.

Scrap copper and iron: refers to all kinds of old and useless objects.

2. Make our life better

Steel has played a great role in our lives. From an embroidery needle to a giant ship, steel is present in every aspect of our lives. The areas where steel is used are constantly expanding. From residential buildings to skyscrapers, to countless bridges and spires, steel is everywhere around us. Steel makes our lives better[1].

2.1 Make rice more delicious

Steel makes rice taste better? Are you surprised to see such a statement? What is the relationship between steel and rice? Plant growth is related to fertilizers, and the most important fertilizers are nitrogen, phosphorus and potassium. We are all familiar with this. But did you know that silicon fertilizer is considered the fourth largest element fertilizer after nitrogen, phosphorus and potassium? The slag, a byproduct of blast furnace ironmaking, is rich in silicate and can be used as fertilizer for the cultivation of silicon-loving crops such as rice, wheat and corn. Among them, rice is the most sensitive to silicon fertilizer.

Rice is one of the crops that absorbs the most silicon. The silicon content in the dry matter of stems and leaves can reach 10%~20%. For every 100 kg of rice produced, the rice plant absorbs 17~18 g of silica. Silicon can promote the silicification of the plant epidermis and enhance resistance to rice blast. Silicon is deposited in the epidermal tissue of the plant, making the rice leaves upright (Figure 4), which improves the photosynthetic efficiency of the crop; enhances drought resistance, cold resistance, and lodging resistance, increases effective tillering; enhances the resistance of crops to diseases and pests, reduces diseases and pests, and improves quality. Applying an appropriate amount of silicon fertilizer can enhance rice's disease resistance, increase fruit set rate, increase yield, and improve rice quality.

Figure 4 Comparison of rice with and without silicon fertilizer (Picture from the Internet)

2.2 Steel slag helps build “ocean ranch”

As shown in Figure 5, "marine ranching" refers to the use of the natural marine ecological environment, large-scale fishery facilities and a systematic management system in a certain sea area to gather artificially released economic marine organisms, and to carry out planned and purposeful release of marine resources such as fish, shrimp, shellfish and algae at sea, just like grazing cattle and sheep on land.

Figure 5 Modernized marine ranch (Photo from the Internet)

About 70% of the Earth's surface is ocean. China is the only major fishing country in the world where aquaculture exceeds fishing. The area of ​​sea available for aquaculture is far more than 1.2 million square kilometers. If the corresponding sea areas are fully utilized, the high-quality protein produced can be comparable to the output of 1.8 billion mu of arable land.

The prospect of "ocean ranching" is so wonderful, so what does it have to do with steel? Artificial reefs made of steel slag are rich in natural minerals, providing a home for marine algae, fish and shellfish, protecting the diversity of marine species. At the same time, the algae attached to the artificial reefs can also absorb carbon dioxide in the water.

2.3 Steel brings joy to our lives

Have you ever experienced the thrilling roller coaster at an amusement park (Figure 6)? Imagine that without steel, you would not be able to enjoy the fun of a roller coaster. Roller coasters first appeared in Paris, France in 1817, and soon became popular in the United States. By 1920, they were so popular that most amusement parks would install one or more roller coasters. Later, due to the Great Depression and other reasons, roller coasters lost their appeal in a short period of time. However, with the emergence of steel tube track roller coasters, it regained the favor of consumers. Compared with the original wooden roller coasters, steel roller coaster tracks are higher, faster, and safer. According to statistics, more than 95% of roller coasters in the world are made of steel.

Figure 6 Roller coaster (picture from the Internet)

2.4 Steel brings us richer sound quality

The music played on the piano (Figure 7) can make people intoxicated, and different music can give people different feelings. Passionate music makes us yearn for life; soft music brings us into a friendly world. What is the relationship between beautiful music and steel? It turns out that the piano strings are made of strong and tough high-carbon steel. The high-carbon steel is heated to more than 900 ℃ and then immersed in molten lead at 430~520 ℃ for annealing. The final product has high strength and high elasticity, which is suitable for making piano strings.

Figure 7 Piano (Picture from the Internet)

2.5 Steel brings convenience to our transportation

The means of transportation that transport us from one place to another - cars, trains, and airplanes - are mainly made of steel. The steel used in cars has been mentioned in a previous article [2]. Railways leave a mark on everyone's journey. The green carriages once took us to all directions, and the sound of the whistle sounded joy and hope. Today, more and more streamlined EMU trains travel between cities, and China has built the world's largest high-speed railway network. As of 2020, China has 39,844 km of high-speed rail, while the world's second to tenth largest countries have a total of only 28,084 km. China's high-speed rail mileage accounts for more than 58% of the world's total (Figure 8).

Figure 8 The top 10 countries in the world in terms of high-speed rail mileage (picture from the Internet)

Railways in mainland China transport 85% of wood, 80% of crude oil, 60% of coal, and 40% of steel. The rapid development of railways has put forward higher requirements for steel, an important raw material for train production. Hot-rolled high-strength weathering steel for railway vehicles has the characteristics of high strength, high toughness, easy welding and easy forming.

Aircraft (Figure 9) have greatly improved the efficiency of human travel and extended the distance of travel. They are the preferred means of transportation for business trips and international travel. For the production of each aircraft, steel mills need to provide special high-strength steel and high-temperature alloys, titanium alloys and other advanced materials for landing gear. The "home" of the aircraft - the aircraft R&D center building and production plant are the places where thick iron plates, color-coated plates, steel pipes, etc. can show their skills.

Figure 9 Aircraft (Picture from the Internet)

With the subway, people can get to and from get off work on time more often. The subway is the most commonly used means of public commuting in the city, and it has greatly alleviated the congestion of urban road traffic. In a busy modern city, it is impossible to imagine a day without the subway. The steel used in subway trains also requires high strength, weather resistance, and corrosion resistance. The iron core of the traction motor that allows the subway to run is also high-grade non-oriented electrical steel.

In addition, whether it is daily commuting or sports outing, a handy bicycle will increase your riding pleasure. Compared with ordinary hot-rolled plates, hot-rolled pickled plates have good surface quality, high dimensional accuracy, improved surface finish, and enhanced appearance. They are widely used in bicycle parts, various welded pipes, and various shapes of stampings.

2.6 Iron can kill bacteria and disinfect

We already know that silver and copper can kill bacteria and disinfect. But did you know that iron can also do so? Sodium ferrite (Na2FeO4) can be used to disinfect drinking water. The iron element in sodium ferrite is +6 valence, which is an oxygen-containing salt of high-valent iron and has strong oxidizing properties. Its oxidizing properties are stronger than potassium permanganate, so it can kill bacteria and disinfect. Moreover, the reduction product of Na2FeO4 is Fe3+, which can be hydrolyzed into colloidal Fe(OH)3, which has adsorption properties and can cause suspended matter in water to condense and settle. Therefore, using Na2FeO4 to treat drinking water can not only kill bacteria but also purify water.

3. Steel supports our lives

3.1 Iron is one of the essential elements of the human body

Our bodies need iron to function [3]. Although the amount is not large, we cannot survive without it (Figure 10). An adult has about 4 to 5 g of iron in their body, of which 72% is in the form of hemoglobin, 3% is in the form of myoglobin, 0.2% is in the form of other compounds, and the rest is reserve iron. Reserve iron is mainly stored in the liver, spleen, and bone marrow in the form of ferritin. The recommended daily iron intake for adults is 10 to 15 mg, and pregnant women need 30 mg per day.

Figure 10 Iron is one of the elements that make up the human body (picture from the Internet)

Iron has many functions for the human body. Iron is involved in the transport and storage of oxygen. Iron is a component of hemoglobin, which is a carrier for transporting oxygen. It transports oxygen to every part of the body for people to breathe and oxidize, to provide energy, digest food, and obtain nutrition. Myoglobin in the human body exists in the muscles, contains ferrous heme, and also binds oxygen, which is the "oxygen bank" in the muscles. When exercising, the oxygen in myoglobin is released to supply the oxygen needed for muscle activity at any time. The heart, liver, and kidneys, which have high physiological activity and biochemical functions, store a lot of iron in the mitochondria.

Iron can also promote development, increase resistance to disease, regulate tissue respiration, prevent fatigue, constitute hemoglobin, prevent and treat anemia caused by iron deficiency, and restore good blood color to the skin.

3.2 Common symptoms and signs of iron deficiency

When the body does not have enough iron, it can cause iron deficiency symptoms and eventually lead to iron deficiency anemia. The following are 10 common signs and symptoms of iron deficiency [4] (Figure 11).

Figure 11 Symptoms of iron deficiency anemia (picture from the Internet)

(1) Unusual fatigue. Feeling very tired is one of the most common symptoms of iron deficiency. This symptom occurs because the body lacks the iron needed to make a protein called hemoglobin, which helps carry oxygen throughout the body.

(2) Pallor. Pale skin or paleness of the inner lower eyelids is also a common symptom of iron deficiency. Hemoglobin in red blood cells gives blood its red color, so low levels during iron deficiency make the blood less red. This is why people with iron deficiency lose their healthy skin color. This pallor in people with iron deficiency can appear all over the body or be limited to one area.

(3) Shortness of breath. Hemoglobin helps red blood cells carry oxygen throughout the body. When hemoglobin levels are low during iron deficiency, oxygen levels are also low. This means that muscles will not get enough oxygen to carry out normal activities, so as the body tries to get more oxygen, the breathing rate increases, causing shortness of breath.

(4) Headache and dizziness. Because the hemoglobin content in red blood cells is low, not enough oxygen reaches the brain and blood vessels in the brain may swell, causing pressure and headache.

(5) Palpitations. Obvious heartbeats, also known as palpitations, are another symptom of iron deficiency anemia. They may be related to oxygen supply.

(6) Dry skin and hair. Iron deficiency lowers hemoglobin levels in the blood, reducing the amount of oxygen available to cells that cause hair growth.

(7) Swelling and pain in the tongue and mouth. Symptoms include a swollen, inflamed, pale, or unusually smooth tongue.

(8) Restless Legs Syndrome. This is a strong urge to move the legs involuntarily while at rest. It causes unpleasant and strange crawling or itching sensations in the feet and legs.

(9) Brittle or spoon-shaped nails. In the early stages of iron deficiency, nails become brittle and easily broken. In the later stages, the nails may become concave in the middle and convex at the edges, presenting a spoon-shaped round appearance.

(10) Other potential signs. Iron deficiency may cause strange food cravings. Cravings for strange foods or non-food items are called "pica," which often include cravings for ice, clay, dirt, chalk, or paper. Iron deficiency anemia may be associated with depression in adults, causing a person to feel depressed. Iron deficiency means less oxygen is delivered to the hands and feet, resulting in cold hands and feet.

3.3 Sources of Iron in Food

Iron is widely available in food: high-quality sources include beef, brown sugar, clam meat, dried fruit, egg yolk, pig and sheep kidney, lean meat, brown sugar, egg yolk, pig kidney, sheep kidney, dried fruit (dried apricots, raisins), brewer's yeast, seaweed, blackstrap molasses and oatmeal, etc.; general sources include fish, grains, spinach, lentils, peas, mustard leaves, broad beans, melon seeds (pumpkin, zucchini and other seeds), etc.; trace sources include dairy products, vegetables and fruits. In addition, cooking tomatoes or other acidic foods in a cast iron pot can also add iron, as the pot will infiltrate the healthy iron into the food.

3.4 Elements that promote iron absorption

Iron in food is mainly divided into hemoglobin iron (animal source) and non-hemoglobin iron (plant source). Hemoglobin iron has a higher absorption rate in the human body, while non-hemoglobin iron has a lower absorption rate. In order to improve the absorption rate of iron, in addition to eating fish, meat, and poultry foods rich in hemoglobin, you can also use some substances that promote iron absorption.

(1) Vitamin C is a reducing agent. In addition to its antioxidant function, it can also reduce trivalent iron to divalent iron, which is more easily absorbed and utilized by the human body. At the same time, vitamin C will also complex with iron to form unstable ferrous ascorbate, and can release iron from other binding compounds, thereby promoting the absorption of non-iron hemoglobin iron and increasing the body's resistance to disease.

(2) In addition to increasing the body's resistance, vitamin A also has the function of improving the body's absorption and transport of iron.

(3) B vitamins. Vitamin B2 can promote the absorption of iron from the intestines, while vitamin B6 can increase the utilization of iron by the bone marrow. In addition, B vitamins can also increase our appetite.

(4) Copper can promote the absorption of iron. When copper is deficient, the amount of iron absorbed by the small intestine decreases, and the synthesis of hemoglobin also decreases, which will directly lead to iron deficiency anemia in the human body.

4. Other knowledge and interesting facts about steel

4.1 Environmentally friendly consumer products with a service life of more than 100 years

People often think that the steel industry is a polluting industry because it uses coal. However, if we consider the entire life cycle from raw material mining to processing, steel is actually the product with the lowest unit emissions among building materials. Steel is the only building material that can be used for more than 100 years. In addition, 90% of steel can be recycled, which is difficult for other materials. 1 ton of steel can be recycled 40 times, so the actual cumulative usage is more than 10 tons [5].

Steel is also an environmentally friendly consumer product. For example, environmentally friendly high-strength steel used in automobile plates and galvanized plates for automobile fuel tanks are thinner than ordinary steel plates, which can reduce the weight of the car, improve fuel economy, and thus reduce harmful emissions.

4.2 Why are bricks and tiles divided into blue and red

Bricks and tiles (Figure 12) are made of fired clay. The iron contained in the clay is converted into red iron oxide (Fe2O3) after firing. If it is allowed to cool naturally, red bricks and tiles are obtained. If water is sprinkled from the top of the kiln to lower the temperature near the end of firing, a large amount of CO and H2 will be produced in the kiln, making the kiln a reducing atmosphere. The red iron oxide is converted into black ferrous oxide (FeO) and ferroferric oxide (Fe3O4), and the resulting bricks and tiles are blue.

Figure 12 Red bricks and green tiles (picture from the Internet)

4.3 Why do words written with blue-black ink gradually turn black?

Blue-black ink is a mixture, in which the blue is a soluble blue dye that fades easily over time. Its other main component is the light green ferrous tannate generated by the reaction of tannic acid and ferrous sulfate, and the color is not very obvious. When writing on paper with blue-black ink, the handwriting is blue. Then the ferrous tannate in the blue-black ink reacts with the oxygen in the air to form ferric tannate. Ferric tannate is a black precipitate that is insoluble in water, so the words written with blue-black ink will gradually change from blue to black. If blue-black ink accidentally contaminates clothes, you should use a reducing substance to remove the stain, such as a 2% mass fraction of oxalic acid solution, which can reduce the insoluble black ferric tannate to soluble ferrous tannate and be dissolved by water to wash away the stain.

4.4 Freshly squeezed apple juice turns brown in the air

Apple juice is a favorite drink, but because apple juice contains Fe2+, Fe2+ will be oxidized to Fe3+ in the air, so the color will turn brown. If vitamin C is added when juicing, this phenomenon can be effectively prevented.

5. Conclusion

Finally, a seven-character poem is used as a summary of "Iron".

With a long and continuous history,

Billions of tons of production.

Reduction and deoxidation to prepare iron,

Steel is made by oxidation and carbon control.

It contains a lot of carbon, manganese, chromium and nickel.

The quenching return is being processed.

It is indispensable to production and life.

Beautiful, healthy and high morale.

References:
[1] Zhang Ying. Steel makes our lives better. China Metallurgical News, 2019–07–05 (2)

[2] Jia Chengchang. The most used metal: Interesting facts about iron (1). Metal World, 2023(4):22

[3] Steel Headlines. Surprising discovery: Steel actually supports our lives! (2017–06–13) [2023–10–20].

[4] CNC Nutrition Coach. Ten signs and symptoms of iron deficiency in the human body. (2020–10–29) [2023–10–20].

[5] Thermal spraying and remanufacturing. Discover the beauty of steel in life. (2017–06–11) [2023–10–20].

About the author: Jia Chengchang, professor and doctoral supervisor at University of Science and Technology Beijing. Graduated from the Department of Metal Materials of Beijing Iron and Steel Institute in 1982 with a bachelor's degree. Obtained a master's degree from Tohoku University, Japan in 1987. Obtained a doctorate from Tohoku University, Japan in 1990. Postdoctoral fellow and chief engineer at Kanagawa Science City, Japan from 1990 to 1994. Won more than 30 national invention patents. Published more than 300 papers in domestic and foreign academic journals, including more than 100 papers retrieved by SCI and nearly 200 papers retrieved by EI. Edited nearly 20 academic monographs: "Composites Tutorial", "Introduction to Ceramic Matrix Composites", "Sintered Metal Oil-bearing Bearings", "Introduction to Metal Matrix Composites", "Superhard Materials and Tools", "Metal Powder Gel Injection Molding", "Sintering Practice and Scientific Foundation", "Professor Han Fenglin's Papers", etc. He has won the second prize of Science and Technology Progress of the Ministry of Education, the first prize of Excellent Textbooks of China Metallurgical Education Association, the first prize of National Teaching Achievement in Higher Education (participated), the first prize of Education and Teaching Achievement of Beijing, the second prize of Excellent Journal of China Nonferrous Metals Society, the Outstanding Worker of China Metal Society, the Outstanding Instructor of the "Challenge Cup" National College Student Science and Technology Competition, the Outstanding Editorial Board Member of "Journal of Composite Materials" of the Composite Materials Society, "I Love My Teacher - the Best Teacher in My Mind" of Beijing University of Science and Technology, Advanced Individual in Teacher Ethics, Outstanding Party Member, Advanced Worker, First Prize for Teaching Achievement, SCI Inclusion Award for Scientific Papers and other honors. Main social part-time jobs: Honorary Director of China Composite Materials Society, Honorary Director of Powder Metallurgy Branch of China Metal Society, Executive Director of Powder Metallurgy Branch of China Mechanical Engineering Society, Director of Powder Metallurgy and Ceramics Branch of China Nonferrous Metals Society, Honorary Director of Powder Metallurgy Branch of China Steel Structure Association, Distinguished Expert of China Nonferrous Processing Association, Director of Powder Branch of China Building Materials Industry Association, Distinguished Expert of Powder Metallurgy Branch of China Machinery Association, Editorial Board Member of Journal of Composite Materials, Consultant of Powder Metallurgy Technology, Editorial Board Member of Powder Metallurgy Industry, Editorial Board Member of China Molybdenum Industry, Editorial Board Member of Powder Metallurgy Materials Science and Engineering, Editorial Board Member of China Materials Science and Equipment, Editorial Board Member of Metal World, and Guest Contributor