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Classification of scrap iron and steel
The wastes produced in the production process of steel mills, as well as the materials in scrapped equipment and parts, are composed of steel or pig iron, collectively referred to as scrap steel.
According to the different sources of output, scrap iron products can be roughly divided into self-produced scrap iron, processed scrap iron, depreciated scrap iron and social scrap iron.
1) Self-produced scrap steel: also known as "returned scrap steel" or "recovered scrap steel", which mainly comes from the waste produced during steelmaking and cast steel production when ferrous metal smelting is delayed. The output of self-produced scrap depends on steel output, that is, the higher the crude steel output and output, the more self-produced scrap. According to the data in 2020, the yield of crude steel in China is about 96%. Self-produced scrap steel is usually only recycled in steel mills, and less flows to the market. In recent years, with the increase of crude steel output in China, the supply of self-produced scrap steel has increased year by year. In 20021year, China's self-produced scrap steel output is about 60 million tons, accounting for about 24% of China's total scrap steel supply.
2) Processing scrap steel: also known as "short-term scrap steel", mainly comes from the cold and hot of ferrous metal smelting and machining, and most of them are stamping waste, chips and material heads. Because of the high quality and average quality, the treated scrap steel can usually be recycled in a short time. The output of processed scrap depends on steel consumption and processing output, that is, the greater the steel consumption, the lower the processing output and the more scrap processed. In 202 1 year, the output of processed scrap steel in China is about 50 million tons, accounting for about 17% of the total supply of scrap steel in China.
3) Deprecated scrap steel: also known as "long-term scrap steel", mainly comes from scrap steel formed after various metal products, equipment and building structures have been used for a certain number of years. Typical sources include scrapped cars, machinery and equipment, airplanes, ships, containers and steel structures. The output of depreciated scrap steel depends on the accumulation of steel and the recovery period of steel. For example, the traditional car scrapping cycle is about 15 years, while the normal service life of steel structure engineering buildings is about 50 years. Since 20 17, the supply of depreciated scrap steel in China has increased rapidly, nearly doubling in the past five years. In 20021year, the output of depreciated scrap steel in China was about1.700 million tons, accounting for about 60% of the total supply of scrap steel in China.
4) Social waste: also known as "garbage waste", mainly comes from scrap steel produced in daily necessities, such as cans, furniture, household appliances, etc., and also includes accumulated scrap blocks and salvaged sunken ships. The source is quite complicated. Due to the difficulty of recycling and quality control (the chemical composition of scrap steel is too complicated), the proportion of social scrap steel production to the total supply of scrap steel is very small.
To sum up, the characteristics of self-produced scrap steel and processed scrap steel are: under the condition of relatively stable steelmaking and steel processing technology, the supply locks the output and demand of steel, so the supply is relatively stable; And due to strong quality controllability, internal circulation can be realized or the furnace can be quickly recycled as raw materials. The annual output of depreciated scrap steel is large, and quality control is more difficult than self-produced scrap steel and processed scrap steel. However, due to better recycling sources and higher quality than social scrap steel, it is expected to become the main growth point of scrap steel supply in China. There are relatively few scrap steel in society, and there are great defects in the difficulty of recycling and quality control.
According to the national standard GB/T4223-20 17, scrap steel is subdivided into scrap iron and scrap steel. Among them, it can not be used according to the original purpose, but can be recycled for smelting steel waste and steel, which is smelting waste steel; Iron and steel products that cannot be used according to the original purpose and are used for other purposes instead of smelting, recycling and rolling are non-smelting scrap. Among them, the national standard only classifies the scrap steel for smelting in detail.
1) Scrap iron for smelting: The carbon content of scrap iron is generally more than 2%. The sulfur content of the first-grade scrap iron shall not exceed 0.07% and the phosphorus content shall not exceed 0.4%; The sulfur content and phosphorus content of Class II iron filings and alloy iron filings are not more than 0. 12% and 1% respectively. The iron content of blast furnace additives is not less than 65%. Classification by weight and shape, as specified in table 1.
2) Scrap steel for smelting: the carbon content of scrap steel is generally less than 2%, and the sulfur content and phosphorus content are generally not more than 0.05%. Residual elements in unalloyed scrap steel shall meet the following requirements: nickel shall not exceed 0.3%, chromium shall not exceed 0.3%, and copper shall not exceed 0.3%. Except for manganese and silicon, the total content of other residual elements does not exceed 0.6%. According to the overall dimensions and the weight of a single piece, scrap steel can be divided into 10 types, such as heavy scrap steel, medium scrap steel and light scrap steel specified in Table 2.
In addition to general classification, national standards also stipulate other technical requirements for scrap steel. Including but not limited to the corrosion of scrap steel, the content of alloying elements, the composition of scrap steel, the control of toxic substances, etc. Therefore, the inspection items of scrap steel quality include the overall size, weight and thickness of a single piece; Inclusion and cleanliness; Harmful substances and radioactive substances; Sampling inspection of chemical elements; Calculation of specific gravity of scrap pile, etc.
As a supplement and perfection of scrap steel, the country issued GB/T39733-2020 in 2020, which divided 18 different brands of recycled steel raw materials in detail and defined the treatment methods of each brand. Unlike scrap steel, which needs secondary processing to meet the furnace charging requirements, according to national regulations, the recovered steel raw materials must be furnace charging products that can be directly used for furnace charging. At present, the recycling of scrap steel in China is still dominated by scrap steel, but the import standard of scrap steel has turned to recycled steel raw materials.
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Supply and cost of scrap steel
In the initial recovery, most of the scrap steel could not be directly recovered by steel mills due to various types and shapes, mixed light and heavy, irregular size and other factors. Therefore, the scrap supply department needs to process different types and specifications of scrap into corresponding specifications according to the requirements of steelmaking production (GB/T4223-20 17 is the recommended standard, and enterprise-level standards are generally adopted in China's iron and steel enterprises at present). Steel mills and scrap dealers are the main bodies of scrap processing, and the processing methods include manual sorting, oxygen cutting, shearing, crushing, packaging and briquetting.
The upstream of scrap recycling industry chain can be divided into solid waste generating units, recycling enterprises and processing bases according to the previous and subsequent processes. Solid waste generating units are the main suppliers of waste wool, mainly involving dismantling enterprises, automobile recycling enterprises and ship dismantling enterprises. Due to the diversity of scrap sources, the upstream main body presents the characteristics of dispersion. Solid waste generating units generally do not involve scrap steel processing. Recycling enterprises are mainly responsible for recycling classified waste wool and selling it to processing bases. Waste wool will be transported to the barge site first (since the main transportation mode of waste wool is automobile transportation, the transportation range is generally within 500 kilometers). After simple classification and stacking, it will be measured by weighbridge. After radiation detection, wool enters the processing link and becomes qualified scrap. The processing base is responsible for processing waste wool. Processing technology can be mainly divided into crushing (including cutting, crushing, drop hammer, etc. ) and packaging (pressed cake or block).
The geographical distribution of scrap resources in China is uneven. More than 80% of China's scrap steel resources are distributed in Beijing, Tianjin, Hebei, Liaoning, Heilongjiang, Shanxi, Jiangsu, Shandong, Shanghai, Hubei, Sichuan, Guangdong and other provinces and cities with concentrated industrial or mining development. In other areas, due to factors such as low transportation convenience and sparse population distribution, less waste steel resources are produced.
Import is one of the sources of scrap steel in China. Before 20 19, China was a net importer of scrap steel, and the average annual import volume from 20 13 to 20 18 was about 2 million tons. From July, 2065438 to Kloc-0, scrap steel was transferred from the Catalogue of Unrestricted Imported Solid Wastes as Raw Materials to the Catalogue of Restricted Imported Solid Wastes as Raw Materials, and the import volume of scrap steel dropped significantly. From 202 1, 1 According to the Announcement on Matters Related to the Total Prohibition of the Import of Solid Wastes, the import of solid wastes including scrap steel is completely banned. On the same day, China's national standard "Recycled Steel Raw Materials" was officially implemented, and the screened recycled steel raw materials can be imported into China. From June to June, 2022, China imported about10.2 million tons of recycled steel raw materials, which was significantly lower than that before 2065.438+09. However, as far as the national scrap consumption base is concerned, it has little effect on the total supply of scrap steel in China.
To sum up, the main costs of scrap steel from production to charging are: recycling, transportation, sorting, processing and packaging costs.
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Consumption and downstream
Scrap steel is a direct substitute for iron ore, and ferrous metal smelting and rolling processing industries are downstream. About 85%-90% of scrap steel is used for steelmaking, and the rest 10%- 15% is used for casting, ironmaking and recycled steel. Compared with iron ore steelmaking (long-process steelmaking), the input-output ratio of scrap steel is close to 1: 1, and it can be directly put into the steelmaking furnace as raw material, which saves the processes of mining, washing, coking and ironmaking, and greatly reduces the emission of harmful substances and the demand for energy. The consumption terminal of scrap steel for smelting is ferrous metal smelting and calendering industry, and the actual flow direction can be divided into converter and electric furnace. Converter is the last step of long-flow blast furnace ironmaking and converter steelmaking. In history, the amount of scrap steel added in China (crude steel output/pig iron output-1) was generally around 10-20%, but the historical high value reached nearly 30%. The raw material of short-flow electric furnace is mainly scrap steel, and the addition ratio is close to 100%. In 20021year, China's molten iron output was about 870 million tons, and crude steel output was about10.03 billion tons, of which the gap of10.60 billion tons came from scrap steel addition and electric furnace steel. Converted scrap steel addition ratio is about 18.4%. Generally speaking, ferrous metal smelting and rolling is the only consumption terminal of scrap steel.
According to 202 1 data of metallurgical industry planning and research institute, the total production capacity of 257 electric arc furnaces in China is about 654.38+800 million tons. The production capacity in East China, South China, Central China and Southwest China is relatively concentrated, accounting for 86% of the total, accounting for 37%, 20%, 16% and 13% respectively. From the perspective of provinces, Jiangsu, Guangdong, Shandong, Sichuan, Hubei and other places have more EAF production capacity. Among them, the production capacity of Jiangsu is 24.05 million tons, that of Guangdong is 20.885 million tons, and that of Hubei14.62 million tons. Generally speaking, electric arc furnaces are mainly distributed in areas rich in scrap steel and power resources (compared with other provinces and cities, they have comparative advantages in cost).
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abstract
Scrap steel is an important link to complete the internal circulation of iron in China. At present, it is estimated that by 2025, the steel saving in China will be close to 654.38+0.4 billion tons. According to the international cumulative amount of 2%-3% steel (referring to the cumulative amount of steel used every year before scrapping) and the proportion of steel scrap (referring to the amount of steel recovered after scrapping), China can produce 280-420 million tons of steel scrap every year, which can greatly alleviate the embarrassing situation that ferrous metal smelting raw materials in China are extremely dependent on imports at present. In addition, because electric furnaces have great advantages over blast furnaces in terms of emissions and environmental protection, scrap steel and electric furnace metallurgy will be the direction to support the green development strategy of China Black Series in the future.