Special steel production technology

Special steel is generally refers to steel with special performance or special purposes. Compared with the ordinary steel has higher strength and toughness, physical properties, chemical properties, biocompatibility and process performance. Because of its special performance, determines its in the national economy and military industry occupies an extremely important position. Therefore, in the production of special steel, requires the use of special process equipment technology to realize the special chemical composition, special organization and performance. The definition of special steel in the world there is no clear regulation, the statistical classification of special steel is not exactly the same. Our country special steel definition similar to Japan, Europe, including three categories of high quality carbon steel, alloy steel, alloy steel, usually for high quality carbon structural steel, alloy structural steel, carbon tool steel, alloy tool steel, high-speed tool steel, bearing steel, spring steel, Carbon spring steel and alloy spring steel) , heat resistant steel, and stainless steel. Because of high temperature alloy and precision alloy in the production of special steel plant, also incorporate these two kinds of alloy steel among statistics [ 1] 。 In the field of special steel, in addition to high quality carbon structural steel, carbon tool steel and carbon spring steel, the rest are alloy steel, alloy steel accounts for about 70% of the special steel. At present, special steel has nearly 2000 brands in the world, about 50000 varieties specifications, hundreds of inspection standard. With the development of science and technology, expanding the need for special steel production and varieties, the quality requirements also more and more strict and harsh. In recent years, around the improve the efficiency of special steel, quality, variety, performance, reduce the cost of special steel, energy saving, environment friendly and adopted a series of new technologies, new processes, new equipment, made of special steel refinement degree of cleanliness, evenness, and dimensional accuracy is greatly improved. Special steel production process mainly has three kinds of [ 2] : 1) The electric furnace process ( The short process) : electric - Secondary refining - Continuous casting - Rolling. 2) The converter process ( Long process) : the blast furnace - Hot metal pretreatment - Converter - Secondary refining - Continuous casting - Rolling. 3) Special metallurgy: special smelting ( Such as vacuum induction melting, cold crucible melting, electroslag remelting, vacuum arc remelting, electron beam melting, plasma melting, etc. ) — Forging or rolling. To point out here is that some of the steel production is still have to go to molding - Breakdown - Rolling or forging process. Because of the early special steel mainly adopts arc furnace smelting process, habits formed special steel must use electric furnace smelting, special steel plant is the electric furnace steel mills. And objective fact is there is electric furnace is only can have a good economic benefit, production of special steel special steel only by electric furnace smelting. This is mainly due to the early electric furnace steelmaking as determined by the nature of the characteristics and special steel itself: 1) Electric furnace with scrap steel alloying elements is available; 2) Electric furnace steelmaking is heated by electric arc, its temperature is much higher than 2000 ℃, and the molten steel temperature can accurate control over a long period of time, such mini-mill in hard metal smelting, alloying composition and technological aspects such as flexible a converter has incomparable superiority; 3) Steelmaking was the cycle is long, low production efficiency, high cost, Scrap, expensive electricity) And the furnace capacity is small, easy to increase carbon, nitrogen, etc. Just special steel