Electric Arc Furnaces for Lower-carbon Steel Production

Electric Arc Furnaces for Lower-carbon Steel Production  - Overview of the Development of Electric Furnace Smelting of Low Carbon Steel

The current mainstream steelmaking process is converter steelmaking process and electric furnace steelmaking process. The electric furnace steelmaking process has low pollutant emissions, flexible organization, and a wide variety of varieties. Its output accounts for about 27% of the global steel production, while China's current electric furnace steelmaking output is only 10% of the total steel production. UHP graphite electrodes, as conductors, meet the requirements of electric arc furnace overall steelmaking. In 2019, China's steel production reached 996 million tons, accounting for 53% of the global steel production. The development of electric furnaces can reduce carbon emissions, greenhouse gas emissions, and protect the earth's environment.

The electric furnace short process is a steelmaking process that uses social scrap steel to achieve a circular economy and all-scrap steel smelting. Pollutant emissions are only 20% of the long process of the blast furnace converter.

The advantages of the blast furnace converter process are: large output and low cost per ton of steel. At present, the cost of converter steel is 400~500 yuan lower than that of electric furnace steel; its disadvantage is serious environmental pollution.

From 2016 to early 2018, when the production cost of converters was higher than that of electric furnaces, electric furnaces had advantages in smelting ordinary carbon steel. When the production cost of electric furnace steelmaking is low and the country has strict requirements on environmental protection, steel companies will give priority to electric furnace steelmaking technology.

1. Introduction to the development of electric furnace steelmaking

The mature period of traditional electric furnace steelmaking is from 1945 to the advent of LF furnace in 1982. Traditional electric furnace steelmaking technology is a process based on melting period, oxidation period and reduction period, and mainly produces special steel. After 1980, continuous casting gradually replaced mold casting, ultra-high power electric furnaces and electric furnace oxygen technology appeared, and the modern electric furnace steelmaking stage began.

The electric furnace steelmaking process can not only produce special steel, but also ordinary carbon steel (ordinary carbon steel is the representative steel type of ordinary steel, including long products and flat products, and ordinary steel has a carbon content of 0.06~0.38%, and a phosphorus and sulfur content of 0.035~0.050%). For example, in the Middle East and North America, ordinary carbon steel is mainly produced by electric furnace short process. Modern electric furnace steelmaking technology uses the electric furnace as a primary refining furnace, and the task of the electric furnace reduction period is completed by LF and other external refining equipment. The oxygen blowing process is added to realize the input of chemical energy.

The short process based on electric furnace equipment is the process in which iron-containing raw materials mainly made of scrap steel are transformed into terminal steel products after refining in electric furnaces, LF furnaces, continuous casting machines, long rolling mills or flat rolling mills. Converter steelmaking is provided with molten iron by blast furnaces. The raw materials of blast furnaces come from iron-containing raw materials such as sintering and pelletizing, and coke is provided by coke ovens, so the converter blast furnace process is also called the long process.

The characteristics of the short-process production process of the electric furnace are: the smelting cycle of continuous casting and electric furnace is 40~50min, with a fast pace; hot charging or cast-rolling headless rolling, from scrap steel to finished product only takes 2~3h. Electric furnace steelmaking, especially the short-process bar and wire long product production line for producing plain carbon steel, is spread all over the world to meet the needs of local economy and society.

The carbon dioxide emissions from converter and electric furnace steelmaking processes are very different. The long-process process of blast furnace converter reduces iron-containing ore to iron, and smelting 1t of steel will emit 2200kgCO2; the short-process process of electric furnace melts scrap steel, then deoxidizes and alloys, without the process of large-scale reduction of iron oxide, and the carbon dioxide emissions are greatly reduced. Smelting 1t of steel will emit 120kgCO2, as shown in Figure 1. Therefore, the electric furnace steelmaking process is more environmentally friendly than the blast furnace converter process.

According to data from the World Steel Association, as shown in Table 1, the proportion of electric furnace steel in the United States, India and other countries increased from 2006 to 2019, the proportion of electric furnace steel in South Korea decreased, and the proportion of electric furnace steel in Germany and Japan did not change much. However, the proportion of electric furnace steel in developed countries such as Japan, the United States, South Korea, and Germany is higher than that in China.

When developed countries develop to a certain stage, the accumulated scrap steel in society increases, and the scrap steel is recycled through the electric furnace steelmaking process. The development path of the steel industry in developed countries provides ideas and experience for China's steel industry to optimize the process structure, optimize China's steel process structure through the electric furnace steelmaking process, reduce pollution emissions, protect the environment, and achieve green steelmaking and intelligent manufacturing.

It is estimated that by 2030, China's annual social scrap steel accumulation will reach 320 million to 350 million tons, and by 2035, China's annual social scrap steel accumulation will reach 446 million tons. The scrap steel resources required for electric furnaces are sufficient, which will lay the foundation for China to develop electric furnace steelmaking. For more information on the electric furnace steelmaking market, please contact us.