Under the background of China's economy shifting from high-speed growth stage to high-quality development stage, the future development direction of China's steel industry is a common concern of Chinese steel workers. Based on the actual situation and development of China's steel industry, this paper analyzes the relationship between the long process of blast furnace-converter and the short process of direct reduction-electric furnace, and puts forward the idea of ​​perfecting long process development and short process to promote steel transformation and upgrading. The research and positioning of the steel process has greatly affected the future development direction of China's steel industry. Global steel processes can be broadly summarized into two types: 1) Long process (blast furnace ironmaking, converter steelmaking long process); 2) Short process (direct reduction of ironmaking, short process of electric steelmaking). Due to historical reasons, China's steel industry long process technology dominates. China's annual output of 800-100 million tons of steel is long-process manufacturing, and the production capacity of direct reduced iron is only 300,000-400,000 tons. This situation should be changed. China, Japan, and Europe are dominated by long-flow processes, while gas-based direct reduction-electric furnace steelmaking processes are mostly used in North America, the Middle East, Southeast Asia, and India. There is only one reason for this development trend: the former has a shortage of gas resources, and the latter has relatively abundant natural gas resources, or gas resources and coking coal resources determine the positioning of the steel process. Steel selection process, has always been a vague topic, especially in China, only a long process, not a short process reference, and therefore can not be precise choice but to utilize and choose according to the specific circumstances of the country or region. China's ecological environment is characterized by shortage of natural gas and relatively abundant coal resources. The long process of selecting blast furnace ironmaking is not unreasonable, or the blast furnace-converter process formed by long-term history supports China as a global steel country. In some countries and regions such as India, due to the shortage of coking coal resources, the steel process uses a short process. In 2017, India's steel output was 101.4 million tons, and direct reduced iron production was 25.9 million tons. It is a country that uses large-scale direct reduction-electric steelmaking short-run steel processes. North American steel technology has undergone sudden changes in recent years. In particular, after the breakthrough in shale gas mining technology, it has provided high-quality gas resources for direct reduction of ironmaking. Large-scale direct reduction devices have been put into operation successively, which has promoted the transformation and upgrading of large steel plants. Table 1 shows recent years in North America. Gas-based direct reduced iron project. First of all, in recent decades, the global long-flow blast furnace ironmaking process has become increasingly mature, rapid and steady development, meeting the needs of the global market. In 2017, global blast furnace pig iron production reached 1.174 billion tons, and China accounted for 60.5%, reaching 710.8 million tons. Over the years, the large-scale equipment of iron-making technology is the development trend of iron-making technology. The significantly improved blast furnace operating coefficient and production efficiency have greatly improved the economic and technical indicators of the blast furnace process. Secondly, the development of China's steel industry is particularly prominent in energy-saving and environmental-friendly technologies (such as the promotion of CDQ technology), improving the ecological environment of the steel industry and becoming the ballast stone for steel production. In particular, it should be mentioned that the long process brings high-quality and high-energy gas resources to the development of the steel industry - coke oven gas, which can make up for the short-term development of direct reduction of iron-making in the development of natural gas shortage areas, and constitute a further ballast in the future development of steel. Stone, to ensure that the steel ship and the waves break forward. Direct reduction of ironmaking based on the principle of hydrogen metallurgy, from carbon metallurgy to hydrogen metallurgy is a revolution in the steel industry, it will certainly promote the transformation and upgrading of the steel industry. Direct reduction uses hydrogen to reduce ironmaking, so the first thing to solve is hydrogen resources. Global direct reduction ironmaking generally uses natural gas to be converted, reformed, and cracked to form H2+CO as a reducing agent to complete the iron making process. However, in a steel plant with a shortage of natural gas and a long process, the use of coke oven gas as a reducing agent to achieve a short process is the best choice. There are two reasons for this: 1) Coke oven gas with high chemical energy produced in long process does not need to purchase natural gas, and the quality and quantity meet the needs of direct reduction process; 2) Coke oven gas contains more than 60% hydrogen, It is much better than natural gas and is an energy-saving and efficient reducing agent. Direct reduction ironmaking technology is mature and widely recognized by the steel industry. The capacity of single-module of gas-based shaft furnace has been continuously expanded, from 200,000 tons per year to 30, 50, 180, 250, and 3 million tons; the quality of DRI has been continuously improved, and the metallization rate has increased from 90%-92% to 94%- 96%; breakthrough in DRI technology for coke oven gas production is a major innovation in the steel industry, driving new developments in steel transformation and upgrading. After years of research and practice has proved that the realization of direct reduction steel plant - EAF shortened process, with the next eight features and benefits to. 1) According to statistics, the CO2 emission of blast furnace iron tonnage iron is 1600kg, and the direct reduction iron ton iron CO2 emission is 800kg. According to this calculation, the annual output of 1 million tons of steel mills will reduce CO2 emissions by 800,000 tons per year. According to the transaction cost of CO2 per ton of 40 US dollars per ton, the annual CO2 transaction cost is 32 million US dollars, which will greatly reduce the cost burden of enterprises. . 2) According to the statistics of big data, the production cost of direct reduction iron-electric furnace steel per ton steel is lower than the cost of blast furnace-converter steelmaking ton steel by 42 US dollars, and the annual production is 1 million tons, the annual reduction cost is 42 million US dollars, which is traditional steel. The transformation and upgrading of the plant provides a great driving force. 3) According to the actual operating conditions of the factory, the direct reduction of iron from coke oven gas production is 2.6 times the economic benefit of coke oven gas power generation. The direct reduction ironmaking process utilizes the reduction potential of coke oven gas, and the combustion power generation uses the heat energy of the coke oven gas. The calorific value of H2 is 2586 kCal/Nm3, and the calorific value of CH4 is 9000-9500 kCal/Nm3. It is the right choice to use natural gas to generate electricity, and coke oven gas is used as raw material (reducing agent). 4) Since the coke oven gas contains 60% hydrogen and the natural gas contains 0 hydrogen, the use of coke oven gas to produce direct reduced iron can greatly reduce energy consumption and reduce pure oxygen consumption. From this perspective, in areas where natural gas is scarce, the use of coke oven gas to produce direct reduced iron is economically and technically sound. 5) In today's steel joint ventures, the “five-joint†approach (coke oven gas, blast furnace gas, converter gas, coal gas, natural gas) can achieve a balance of coke oven gas supply, replaced by The production of direct reduced iron from a large number of coke oven gas is an energy revolution. 6) Direct reduced iron is pure iron, which is most suitable for producing pure steel in electric furnaces, which can significantly increase the added value of steel and promote supply side reform. 7) 100% pellets are used as raw materials for direct reduction, and 100% direct reduced iron is used as raw material for electric steelmaking. This is a new trend in the development of world steel. The production capacity of the single-module direct reduction unit has reached 2.5 million tons/year. It is not difficult to see that the direct reduction-electric furnace steelmaking short process has great development potential. 8) Direct reduction and docking of direct cast steel or direct reduction - copying of short process of electric steelmaking steelmaking, project landing, becoming an industrial experimental plant for direct reduction of electric furnace steelmaking short process, will be achieved for the transformation and upgrading of large steel joint ventures Technical and production experience. The integration of long and short processes will constitute a steel development model with Chinese characteristics and become the most advanced process in the global steel industry. China's steel industry should be subversive development, promote the development of direct reduced iron, and achieve steel transformation and upgrading. What is carbon steel made of? 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So-called carbon steel actually means the mechanics performance depends on is the carbon content in steel, general not add master alloy elements of the steel is also known as general carbon steel or carbon steel, and also called carbon steel, carbon steel means the carbon content WC is less than two percent of the iron carbon alloy, carbon and carbon steel in addition to outside, also contains a small amount of materials such as silicon, manganese, sulfur and phosphorus.
Generally carbon steel with higher carbon content will be harder and stronger, but the plasticity will be lower.
What are the advantages and disadvantages of carbon steel?
advantages
1. Higher hardness and better wear resistance of carbon steel can be obtained after heat treatment.
2. The hardness of carbon steel in annealed state is very moderate, and it has good machinability.
3, carbon steel raw materials are very common, simple and easy to obtain, and the cost of production is relatively low.
disadvantages
1, the thermal hardness of carbon steel will be poor, because when the working temperature of the tool is more than two hundred degrees, its hardness and wear resistance will drop sharply.
2, the hardenability of carbon steel is very low, water quenching completely quenched the diameter of the general in 15-18 mm, and for the diameter or thickness is only about 6 mm, so it will be relatively easy to deformation and cracking.
What are the classifications of carbon steel
1, according to the use of carbon steel can be divided into carbon structural steel, carbon tool steel and easy to cut structural steel these three categories.
2. According to the smelting method, carbon steel can be divided into open hearth steel, converter steel and electric furnace steel.
3. According to the method of deoxidation, carbon steel can be classified into efferrescent steel, killed steel, semi-killed steel and special killed steel, which are denoted by code F, Z, B and TZ respectively.
According to the carbon content, carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel.
5. According to the content of sulfur and phosphorus, carbon steel can be divided into ordinary carbon steel with higher content, high-quality carbon steel with lower content of phosphorus and sulfur, and high-grade high-quality steel with lower content of phosphorus and sulfur, and finally there is a super grade of high-quality steel these four categories.
