Technological progress has constantly changed the methods of obtaining steel. In the XIX century. And the first half of the XX century. Successively replaced each other Bessemer, Thomas and Martin processes. The introduction of the first two was determined by the composition of the ores and the iron obtained from them for conversion into steel. Emerged in the second half of the XIX century. The open-hearth method was universal, independent of the quality of pig iron and allowed to melt steel of various qualities (in the USSR it was the main one in the years of industrialization and still remains so in a number of Russian enterprises).
With the development of science, two processes proved to be the most effective in the steel-smelting division. In the oxygen-converter process, steel is produced from molten iron and scrap for 30-35 minutes instead of 6-8 hours for melting in an open-hearth furnace. In arc electric furnaces from scrap and cast iron, the melting process requires 50-70 min. Therefore in the middle of XX century. The rapid and wide introduction of the oxygen-converter method began. By 1997, its share in world steel production reached 60%. Marten furnaces now produce only 7% of the world’s steel, and they are quickly decommissioned.
The construction of oxygen-converter shops with the simultaneous dismantling of open-hearth furnaces requires large capital outlays. Therefore, even industrially developed countries with powerful metallurgy conducted reconstruction for a quarter of a century: Japan completed the transition to the converter method of steel production in the early 1970s, Germany, Great Britain and France – by the early 80’s, and the US only by the 90’s. In Russia and the PRC, it is still ongoing. The converter way radically changed the whole structure of the steel industry in the world as a whole and individual countries. In the USA, it accounts for 61% of the steel produced, in France – 64, Japan – 68. Britain – 74, Germany – 76, and in Luxembourg – 100%.
Electric steelmaking is the second most important process in steel production. Its development was promoted by relatively small costs even for large electric arc furnaces, their quick commissioning, and widespread use of scrap. The growth of obtaining electric steel was favored by the construction of many midi- and mini-plants. This led to economic benefits from the introduction of this process (the share of electric steel in the world is 33%). Significant influence is exerted by the magnitude of the cost of electricity, especially at HPPs. In the countries of the young ferrous metallurgy (Taiwan, the Republic of Korea, Brazil, etc.), electric steel accounts for 50 to 100% of the metal smelting, and in the main producing countries of steel (Japan, the USA, Western European countries) from 24 to 40% (Italy – 58%).
In the steelmaking industry, an eco-efficient method of continuous casting of steel was particularly important. His installations were first developed and implemented in the USSR and widely used in the world. They reduce production waste (“rubber”) by 20-30%, reducing the cost of their remelting. In 1995 this method spread 76% of all steel in the world. In Japan, France, Germany, Italy, in the continuous casting plant (UNRS), all the smelted steel was cast.
A new technology of revolutionary importance for the iron and steel industry is the production of steel directly from metallized pellets, bypassing the smelting of cast iron. The economic and environmental benefits of this process (direct reduction of iron – PVZH) are obvious. The rate of growth of production by the method of UWW is much higher than the blast furnace one: in 1995, 31 million tons of metal were produced in the world. Installations of the PVZ require a significant amount of energy (mainly natural gas). This encouraged them to be placed in fuel-surplus countries and regions. Asia accounts for 40% of the metal produced by this technology, South America -35%. In large producers of steel in North America, Western Europe, and also in Russia there were only a few pilot plants.
As in the production of cast iron, great changes have taken place in the world geography of obtaining steel. New technologies for the smelting of steel, especially in small enterprises, allowed them to be placed outside the old traditional centers and areas of the metallurgical industry of the developed countries of the world. They had a very strong influence on the creation of steelmaking enterprises in the newly industrialized countries, where they were built in areas that were not developed in industrial terms, often lacking primary raw materials for metallurgical production. So, a significant amount of steel (up to 2.5 million tons in 1995) gives Saudi Arabia.
During the period from 1950 to 1995, The main result of the shifts in the geography of the world steelmaking industry was its powerful growth in Eastern Europe and Asia. Their total share in the smelting of steel increased from 22 to 55%. However, the growth rate was less than in the receipt of pig iron in these regions, which is explained by the narrower market demand for steel in underdeveloped machine building. At the same time, the share of western regions fell more than half from 77% to 37%. In South America, Africa and Australia, smelting began to grow faster than cast iron: there were also large producers of metal. Significant shifts occurred in the acquisition of steel among the countries of the world. The long leadership of the United States ended in the mid-1970s, when the championship passed to the USSR and was retained by it until 1991. With the collapse of the USSR, Japan emerged ahead, and since 1997 – the PRC.
Rolling – the final (output) product of the final stage of the whole cycle of ferrous metallurgy. Its cost is 2-5 or more times higher than the cost of steel, it goes directly to consumers in all sectors of the national economy. Rolling is the main commodity of foreign trade in ferrous metallurgy products. World statistics does not give the cost parameters of the rolled products, limited only to its weight. Rolled products are very diverse, their composition – the range – in the countries of developed machine building reaches 20-30 thousand items and continues to grow and update depending on market requirements.
The main types of rolling production are as follows:
1) sheet metal (thin sheet is especially valuable up to 3 mm – up to 30-45% of all rolled products in different countries);
2) high-quality metal – round, shaped, etc. (10-30% of rolled products);
3) blanks for welded pipes and the pipes themselves – all-rolled, etc. (5-10%);
4) wire rod – hot-rolled wire (3-8%);
5) railway rolling – rails, etc. (4-5%).
At present, exceptional importance for a number of branches of machine building, primarily electronic, instrument-making and others, has acquired precision rolling, which is characterized by very high dimensional accuracy.
Pipe-rolling production in connection with the development of pipeline transport is very large: in the 90’s. Produced annually 66-70 million tons, of which 1/2 was welded (15% of a large diameter), and 1/3 – all-drawn. The main producers of pipes in 1990 – the USSR (more than one-fourth in the world), Japan (1/6), China, Germany and the United States. The creation of a powerful pipe production in the USSR was caused by the great need for them to pump oil and gas in the 1960s and 1970s. And the refusal of Western countries in the cold war to supply them to our country.
Scientific and technological progress has improved the quality of rolled metal (coating of other metals, plastics, varnishes), allowed the production of bent rolled sections, etc. This significantly improves the quality of products from rolled products.