Pure iron is a very soft metal. It can neither make a knife or a cast iron or a rake. But when pure iron contains a certain amount of carbon, it becomes the steel we use in all aspects. When the carbon content of pure iron is 0.02% or more, it becomes a low carbon steel which can be drawn with a low hardness and rolled a thin white iron plate. The steel in the range of 0.25% to 0.6% carbon in iron is called medium carbon steel, and its hardness is medium, which can be rolled into construction steel, steel plates, nails and other products. When the carbon content of iron is 0.6% to 2.0%, it becomes a high-carbon steel which can be made into a high hardness and can be made into a knife or a mold. The combination of low, medium and high carbon steel is called “carbon steelâ€. If the carbon content in the iron exceeds 2.0%, it becomes a hard and brittle cast iron pot, radiator, plow, etc. Generally, pig iron has a carbon content of 3.5% to 5.5%. Therefore, the difference between pure iron, steel and pig iron is mainly due to the difference in carbon content in iron.
In the production of iron and steel, the iron ore is first reduced to iron by carbon in the ironmaking blast furnace, while the iron also absorbs 4.5%-5.5% of carbon, and then the pig iron is put into the steelmaking furnace. Carbon and other impurities are removed by oxidation with oxygen to reduce to the required level, i.e., carbon steels of various carbon contents. According to the "World Steel Association" report "International Steel Association" statistics in the first half of 2002 (January to June), China's steel output was 84.8 million tons, ranking first in the world; the world's top ten steel producing countries ranked in the same order: 2 Japan 52.3 million tons, 3rd US 44.4 million tons, 4th Russia 28.4 million tons (CIS 48.4 million tons), 5th Germany 22.4 million tons (EU 15 countries total 80.4 million tons), 6th Korea 2230 10,000 tons, the 7th Ukraine 16.5 million tons, the 8th Brazil 14.1 million tons, the 9th India 14 million tons, the 10th Italy 13.4 million tons; the UK 6.07 million tons, ranked 17th.
With the development of science and technology, carbon steel can not meet the needs of modern industry, agriculture and national defense in terms of strength, hardness, toughness, elasticity and corrosion resistance. Metallurgists have found that adding some other elements to the steel can improve the performance of carbon steel, make carbon steel obtain superior and special properties, expand its use and scope of use, and develop various alloy steels. On the basis of ordinary carbon steel, as long as less than 5% of the total content of silicon, manganese, iron, titanium, niobium, boron, rare earth and other alloying elements can be used to produce ordinary carbon steel with higher strength than the equivalent carbon content. 30-40% of low-alloy high-strength steel, one ton of steel can be used for 1.3-1.4% ton of ordinary carbon steel. If 6-15% chromium is added to carbon-containing 1% carbon steel, various advanced ball steels and rolling bearing steels can be produced. Adding 13-19% chromium to the steel becomes magnetic stainless steel. If 9% nickel is added to the steel, it becomes non-magnetic stainless steel. Therefore, it is impossible to identify whether it is stainless steel or not, because it is used in life. Most stainless steel is magnetic and can be sucked up by magnets. A steel containing 8-27% chromium and 4.5-6.5% aluminum in a steel containing less than 0.06% carbon is called an electrothermal alloy, and is drawn into an electric furnace, and the highest temperature can be heated to 1200 °C. A steel spring made of 1% manganese added to medium carbon steel has excellent elasticity. The addition of 2% manganese and a small amount of molybdenum in high carbon steel can be made into a particularly high hardness, which can be used for the long life of the knife, mold and crusher. Adding 9-18% tungsten and a small amount of vanadium to the steel becomes high-speed steel. A small amount of molybdenum and chromium are added to the mild steel to become a heat-resistant and non-skinning steel at a high temperature. Adding 2.5-4% silicon to low carbon steel can be made into a very good magnetic permeability, and can be used to roll silicon steel sheets for motors and transformers. The low carbon steel with 12% aluminum and 25% nickel is a permanent magnet alloy that can be used to make permanent magnets. Adding appropriate amount of silicon to high carbon steel can produce graphite steel, which is both wear-resistant and lubricious. It can be used to manufacture mechanical parts and bearings that are not suitable for use during use. The addition of rare earth metals to steel can increase the toughness of steel. The addition of rare earth metals and magnesium to pig iron can become a ductile iron with the same strength and toughness as steel. Boron is an indispensable non-metallic element in amorphous alloys and high-tech NdFeB alloys. The addition of various metals and non-metallic elements to iron and steel can make its performance versatile and versatile. The addition of various metals and non-metallic elements to steel can create a variety of high-tech new metal materials for industrial and agricultural, national defense, science and technology, and life applications.
The addition of various metals and non-metallic elements to iron steel creates a variety of high-tech materials for a variety of properties and applications. However, most of these metals and non-metals are not or should not be directly added to the molten steel in the state of pure metal and non-metal element monomer during steel making. For example, the melting point of metals such as tungsten, molybdenum and niobium is too high, more than double the temperature of steelmaking, the temperature of steelmaking is about 1600 °C, and the melting point of tungsten is as high as 3380 °C, the melting point of molybdenum is 2600 °C, and the melting point of bismuth is 2500 °C, so It is difficult to melt in molten steel. In addition, the specific gravity of these metals is too high. The specific gravity of liquid steel is about 7 g/ml, while the specific gravity of tungsten is as high as 19.3 g/ml. The specific gravity of vanadium and titanium is low. The specific gravity of titanium is 4.5 g/ml, and the vanadium is 6.1 g/ml. The melting point is high, the vanadium is 1860 ° C, the titanium is 1690 ° C, and it is easy to oxidize. It is oxidized and burned a lot on the molten steel surface, the loss is too large, and it is difficult to control the content, and the monomer metal preparation process is complicated, the production cost High, expensive and so on. Therefore, it is not suitable to be directly added to the molten steel during steel making in the state of pure metal and non-metal monomer. To this end, metallurgists have studied the production of these elements and iron alloys, called "iron alloys." The melting point of these elements and iron alloy is close to that of steel, the specific gravity is similar to that of steel, and it is not easy to be oxidized. The production process is simpler than the production of pure metal and non-metal, and the production cost is much lower than that of pure monomer metal and non-metal. Low, especially suitable for steelmaking and production of various high-tech materials. Therefore, ferroalloys have become an important material in the steelmaking and new materials industries.
The varieties of ferroalloys are developed and developed according to the development needs of the steel and new metal materials industry. The current ferroalloy varieties are dozens of binary and multi-element ferroalloys. The most widely used binary iron alloys are: ferrosilicon and ferromanganese. , ferrochrome, tungsten iron, ferromolybdenum, ferroniobium, ferrovanadium, ferrotitanium, boron iron, ferrophosphorus, aluminum iron, etc., more than three yuan: manganese silicon (iron), silicon calcium (iron), silicon chromium ( Iron), silicon aluminum (iron), silicon germanium (iron), rare earth silicon iron, rare earth silicon magnesium iron.
Ferroalloys have two main uses: one is to use as a deoxidizer; in steelmaking and in the production of various new metal materials, oxygen is used to remove impurities in steel and molten metal, and oxygen is also absorbed in steel and molten metal. The performance of steel and metal materials is greatly reduced, so it is necessary to add some strong binding ability to oxygen, and the oxide can be smoothly removed from the steel and metal material liquid, thereby reducing the oxygen content in the steel and metal material liquid. The element, the process is called deoxidation of steel and metal materials, and the iron alloy used for deoxidation is called deoxidizer. Commonly used deoxidizers are ferrosilicon, ferromanganese, aluminum iron, silicon calcium (iron), silicon manganese (iron), silicon germanium (iron), silicon aluminum (iron) and the like. The second use is to make alloying agents. Various kinds of iron alloys are added to carbon steel to adjust its chemical composition, and various alloy steels and new metal materials can be produced.
Ferroalloys are produced by a small amount of special iron alloys such as metal chromium, ferrotitanium, etc., and some of them are produced by electric furnaces. For example, the production of 1 ton of ferrosilicon, electricity consumption of about 8500 kWh (degrees), such electricity for 20 tons of steel can be used to refine the electric furnace steel, which is 20 times the steel for the electric furnace, such as for life can supply 1 The use of a 200-liter refrigerator for 23 years shows that the electricity consumption is large. Therefore, although the use of ferroalloys is very important, it is very important in the national economy, science and technology and national defense. However, since 1995, due to the rapid development of China's ferroalloys, the output has ranked first in the world. In 2001, the world's ferroalloy production was 16.2 million tons, while China's output was 4.5 million tons, accounting for a quarter of the world's production. The top 5 of the world's ferroalloy production is the second: the second CIS (mainly Russia) ) 2.8 million tons, the third place South Africa 2.5 million tons, the fourth place Japan 1.2 million tons, the fifth place India 750,000 tons. In addition to meeting the needs of China's steel and new metal materials industry, China's ferroalloy production has an annual export of 10-12% of total output. Of course, it also earns a lot of money, but because its energy consumption is too high, especially power consumption is large, it is not appropriate to build a large number of factories and increase production in large quantities. According to statistics, the current consumption of ferroalloys has accounted for 1% of the country's total power generation, accounting for 4% of the total electricity consumption of the steel industry, and its energy-saving potential is enormous. Today, China's scientific research workers have carried out scientific research on energy conservation and consumption reduction on the basis of current production, further developed energy-saving production new technology and further created special high-efficiency ferroalloys suitable for high-tech new materials and national defense science and defense industry. New varieties have made great progress and have reached and approached the international advanced level...
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