Steel is an alloy of iron with carbon, silicon, manganese, phosphorus, sulfur and a small amount of other elements. Except Fe, the content of C plays a major role in the mechanical properties of steel, so it is collectively called iron-carbon alloy. It is the most important and commonly used metal material in engineering technology.
According to the different carbon content, iron-carbon alloys can be divided into steel and pig iron. Steel is an iron-carbon alloy with a carbon content of 0.03% ~ 2%. Carbon steel is the most commonly used common steel, which is easy to smelt, easy to process and low in price, and can meet the use requirements in most cases, so it is widely used. According to the different carbon content, carbon steel is divided into low carbon steel, medium carbon steel and high carbon steel. With the increase of carbon content, the hardness of carbon steel increases and the toughness decreases. Alloy steel is also called special steel. Adding one or more alloying elements on the basis of carbon steel changes the structure and properties of steel, thus having some special properties, such as high hardness, high wear resistance, high toughness and corrosion resistance. The alloying elements often added in steel are silicon, tungsten, manganese, chromium, nickel, molybdenum, vanadium, titanium and so on. China is rich in alloy steel resources. Except for the lack of chromium and the low grade of cobalt and manganese, the reserves of tungsten, molybdenum, vanadium, titanium and rare earth metals are all very high. At the beginning of 2 1 century, the proportion of alloy steel in the total steel output will increase greatly.
Iron-carbon alloy with carbon content of 2% ~ 4.3% is called pig iron. Pig iron is hard and brittle, but it is resistant to compression and wear. According to the different forms of carbon in pig iron, it can be divided into white iron, gray iron and ductile iron. The carbon in white iron is distributed in the form of Fe3C, and the fracture is silvery white. It is hard and brittle, so it can't be machined. It is the raw material for steelmaking, so it is also called steelmaking pig iron. The fracture of gray cast iron with carbon distributed in flake graphite is silver gray, which is easy to cut, cast and wear-resistant. If carbon is distributed in spherical graphite, it is called ductile iron, and its mechanical properties and machinability are close to those of steel. Special cast iron can be obtained by adding special alloying elements to cast iron. If chromium is added, the wear resistance can be greatly improved, which has a very important application under special conditions.
iron and steel industry
Iron and steel industry is also called ferrous metallurgy industry. Iron and steel industry is an important basic industrial sector and the material basis for developing national economy and national defense construction. The level of metallurgical industry is also a sign to measure a country's industrialization.
1. iron and steel industry resources
Iron and steel industry is a huge heavy industry sector. Its raw material, fuel and auxiliary material resources affect the scale, product quality, economic benefit and layout direction of iron and steel industry.
(1) Iron ore is the main raw material of iron and steel industry. Iron mines in ethnic areas are mainly concentrated in Baotou and Bayan Obo areas in Inner Mongolia. Baiyun Obo, formerly known as Baiyun Baogede, means fertile holy mountain in Mongolian. Baiyunebo is a huge polymetallic deposit. Iron ore, rare earth and rare metals are extremely rich in reserves. Iron ore contains 33% iron, associated rare earth 13%, vanadium 0.2% and fluorite 16.5%. Its total reserves of rare earth minerals are more than the sum of other countries in the world.
West Sichuan-Panzhihua area. At present, 47 kinds of industrial reserve minerals have been found in Panxi metallogenic belt, with 207 producing areas, of which 9.886 billion tons are vanadium-titanium magnetite, accounting for 20% of the national iron ore reserves, and the vanadium-titanium reserves are also very rich. The Yalong River and Jinsha River flow through Panzhihua, so Panxi has become a treasure house of hydropower resources and mineral resources.
Xinjiang iron ore is rich in reserves, widely distributed, complete in types and rich in ores. A number of large and medium-sized mineral deposits have been proved. For example, the newly discovered large iron-rich group in Hami-Cihai Iron Mine has an iron grade of 40-65%. There are six medium-sized mines nearby. Another example is the Taibu Taifu iron deposit and the Motosala iron-rich manganese deposit, most of which contain 56% iron.
Yunnan Province is rich in iron ore resources, with the province's reserves reaching 65.438+0.28 billion tons, with rich ore accounting for 654.38+0/4. Origin 7654.38+0, mine 654.38+03. For example, Dahongshan Iron Mine is a large-scale rich mine with gold, iridium, cobalt and other metals.
Other mining areas, such as Guanyin Mountain and Hezhang Iron Mine in Shuicheng, Guizhou, Huangshan and Zunyi in Dushan, Shizuishan in Ningxia, Lingchuan, Huanjiang and Yamai in Guangxi, also have considerable iron ore resources.
(2) Coke is the fuel of iron and steel industry. Coking coal resources in ethnic areas are mainly distributed in Wuda, Haibowan in the west of Inner Mongolia and Zhungeer coalfield in the middle, and the coking coal produced is mainly supplied to Baotou Iron and Steel Plant. Liupanshui Coal Mine is one of the important coke bases in China. The coke produced is mainly supplied to Panzhihua Iron and Steel Plant, and also to iron and steel enterprises in Southwest China and Guangdong. The coke produced by Ningxia Shitanjing is mainly supplied to Baotou Steel and Shougang. In addition, Xinjiang and Yunnan also have considerable coking coal production. At present, there are abundant coking coal resources in ethnic areas. It can fully meet the demand of local steel industry in quantity. In terms of distribution, it is also relatively concentrated. Coke from Inner Mongolia, Ningxia and Xinjiang in the north ensures Baotou Steel; The coke in Liupanshui in the south is supplied by Pangang and Liugang.
(3) Auxiliary raw material resources of iron and steel industry. The iron and steel industry needs a lot of iron ore and coke as the main raw materials, as well as auxiliary materials such as manganese ore, limestone, dolomite, fluorite, silica and refractories. According to statistics, an average of 1.6 tons of auxiliary materials is needed to produce one ton of iron.
Manganese ore is called ferrous metal resource and is the raw material of ferroalloy. It can increase the hardness, ductility, toughness and wear resistance of steel, and is also a deoxidizer and desulfurizer for blast furnace. Manganese ore resources in ethnic areas are quite rich. The reserves of manganese ore in China reach about 400 million tons, ranking fourth in the world. The total reserves of manganese ore in Guangxi account for 1/3 of the whole country, covering 34 counties and cities in the whole region, among which Guiping and Qinxian are the most concentrated, accounting for about 50% of the national annual output. Guizhou manganese ore also has considerable reserves, concentrated in the suburbs of Zunyi.
Limestone, dolomite, fluorite, silica and other fluxes have large reserves and are widely distributed. Relatively concentrated in the central and southern regions, of which the northwest region has the most silica.
2. Development and layout of iron and steel industry
The iron and steel industry in ethnic areas only rose after liberation and developed rapidly from scratch. From 65438 to 0990, the steel output in ethnic areas was 3,682,600 tons, and the steel industry has become and is becoming an important aspect of the economy in ethnic areas. The main iron and steel industrial bases in ethnic areas are:
Baotou Iron and Steel Company: It is a newly-built iron and steel industrial base based on 1957 raw material producing area. Using the coal from nearby Baiyun Obo Iron Mine and Shiguaizigou, the resource conditions are very superior. At present, the comprehensive production capacity of Baotou Steel is 6.5438+500,000 tons of steel/year.
Panzhihua Iron and Steel Company: Panzhihua Iron and Steel Company, located in Dukou City, southwest Sichuan Province, was the largest steel base in China's strategic rear area during the Third Five-Year Plan period. Attack at 1970 and attack at 197 1. Panzhihua is one of the five major iron mines in China. Geologists have proved that an ancient rift zone in this area is a rare "cornucopia" with 79 kinds of minerals, 54 of which are industrial reserve. Among them, iron is about10 billion tons, belonging to barium-titanium magnetite, which can be used in Sichuan and Guizhou except for self-sufficiency. The required coal is supplied by Liupanshui, Guizhou. At present, the steel output has reached more than 1 10,000 tons. However, due to the limitation of traffic and other conditions, resources are far from being fully and reasonably utilized. In addition, there are a number of small and medium-sized steel mills distributed in various provinces. For example, Liuzhou Iron and Steel Plant in Guangxi has an annual output of nearly 300,000 tons of steel, and there are also iron and steel industrial sites such as Hechi, Lingchuan, Guixian, Hengxian, Huanjiang and Yamai in the area. Guizhou has Guiyang Steel Works, Shuicheng Steel Works and Zunyi Ferroalloy Works. Yunnan has Kunming Iron and Steel United Company. 1979, an iron and steel joint company was established in Xinjiang, including Bayi Steel Plant and Zhijian Company.
Yamansu iron mine, static iron works and other units. Ningxia has Shizuishan Iron and Steel Plant. Inner Mongolia Hohhot Iron and Steel Plant has a full set of production capacity from coking to steel rolling. Its 650 mill can roll 200,000 tons of steel.
After more than 40 years of efforts, the iron and steel industry in ethnic areas has developed rapidly, showing the characteristics of wide scope, high speed, small factory scale (except Baotou Steel and Panzhihua Iron and Steel), outdated equipment, high cost and rich resources. However, there are still some problems in quantity and quality, which can not meet the growing needs of economic development in ethnic areas, and the utilization rate of resources and economic benefits need to be further improved.