SU602560A1 - Single-slag process of smelting stainless steel - Google Patents

Description

(54) SLEEP STAINLESS The invention relates to the electrometallurgy of steel and can be used in the smelting of alloyed steels in main arc furnaces. Methods for smelting stainless steels in main arc furnaces by remelting waste using gaseous oxygen with a single-slag process involve the restoration of oxidizing slag in a furnace and conducting the finishing of metal under reduced lime-silicate slag with subsequent deoxidation of steel in a furnace or in a ladle. There is a known method of smelting stainless steels in main arc furnaces by remelting waste using oxygen by a single-slag process, which consists in the following. in order to increase chromium recovery and shorten the duration of smelting, after blowing the melt with oxygen into the furnace, lime (25–35 kg per 1 ton of melt), lumpy 45% ferrosilicon in the amount of 28–50 kg / t, is introduced into the furnace before ferrochrome is introduced; during the time of melting the ferrochrome and further the slag is deoxidized with 65% ferrosilicon powder (8 kg / t); after the ferrochrome melts, the metal is liquefied in the furnace with lump aluminum (1 kg / ton); The final metal deoxidation is produced by aluminum (1 kg / t), which is placed on the jet at the ROCESS MELTING TALEY release melt or in a ladle together with ferrotitanium before melting release. Increasing lime consumption up to 35 kg / t and deoxidizing agents up to 50 kg / t allows to obtain sufficiently deoxidized slag before melting, in which the total content of iron oxides, manganese and chromium is 7-12 ° / o, and through the removal of chromium during smelting stainless steels without oxidizing slag. The increase in slag by b-12 rel / s. However, with this method of smelting stainless steels, an increase in lime consumption of up to 35 kg / t to increase the basic slag contributes to a considerable saturation of the metal with hydrogen (especially in summer time) and an increase in the metal rejection of surface defects, resulting in substantial losses of expensive metal shavings when re-rolling; The furnace capacity is reduced by 10-20 minutes due to the prolonged period of slag formation. The high consumption of silicon-containing deoxidizers (28-50 kg / t) increases the silicon content in the metal to 0.70-0.80%, which significantly reduces the plastic properties of stainless steels and increases the rejection of the metal at the first redistribution of “flaws.

and in the production of thin-walled pipes, by internal “captives.

The high consumption of deficient BS / o-ferrosilicon (8 kg / t), the need for the use of scarce and expensive powdered aluminum.

A large slag ratio (more than 7% by weight of the metal) with a content of 7-12% heavy oxides reduces the uptake of titanium from 50-60% to 30-45% and does not ensure the stable preparation of the chemical composition of stainless steels with a narrow limit of chromium and titanium Especially when metal titanium production waste is used to alloy steel.

The aim of the invention is to improve the quality of steel and reduce the consumption of expensive ferroalloys and deoxidizers.

This goal is achieved by the fact that the oxidative period slag is deoxidized with electrothermal silumin slag in an amount of 8.00-10.20 kg per 1 t-melt with a ratio of lime, ferrosilicochrome and slag from silumin 1.00: 0.67-0.71: 0.66-0.76, the slag is additionally deoxidized with 65% ferrosilicon powder in the amount of 2.0 kg / t, and the smelting is drained while doping with titanium in the ladle and metal deoxidation with lump aluminum (1 kg / t) in contrast to from a known method of smelting stainless steels by a single-slag process, according to which after Melt (25-35 kg / ton), 45% ferrosilicon (28-50 kg / ton) are added to the furnace using molten oxygen in a furnace, while smelting ferrochrome and then further slag is liquefied by 65% ferrosilicon powder (8 kg / t), after the ferrochromium is melted, the metal is deoxidized in the furnace with lump aluminum (1 kg / t), the final deoxidation of the metal not doped with titanium is produced with lump aluminum (1 kg / t), which sits on the jet at the melting output, and the steel doped titanium, an additive of powdered aluminum (1 kg / t) in a ladle together with ferrotitanium before the release of smelting.

During the period of chromium-containing purge and its melt with oxygen, chromium oxide (SCO3) forms insoluble refractory chromium spinellide (CaC), MgO, FeO crystals in the slag; chromium composition type ASgO, ySiOj. Increasing the basicity of the slag by increasing the consumption of lime to 25-35 kg / t leads to the formation in real conditions of electric smelting of calcium chromite of the type lCaO,. reducing the reactivity of the slag. Due to the physicochemical properties, alumina (AlgOs) can simultaneously replace chromium oxide in spinel groups, in calcium chromites and chromium oxide in chromium silicates. Taking this into account, in order to limit the occurrence of chromium-containing complexes and facilitate their decomposition, it is necessary to increase the alumina content in chromium slags with a corresponding decrease in the calcium oxide content, and to produce more complete and accelerated recovery of chromium, manganese and iron from slag, aluminum, the product of which (AlaOO significantly reduces 5 The active concentration of silica (SiOj) and increases the silicon deoxidizing ability. Introduction to the composition of magnesia-silicate chromium-containing slag, aluminum, alumina and cryolite in the form of electrothermal silumin slag, the required amount of silicon and calcium oxide, significantly speeds up slag formation and creates favorable thermodynamic and kinematic conditions for the rapid and complete reduction of chromium, manganese and iron when slag is deoxidized by aluminum and silicon. Increase in alumina ( HLU;) up to 28-33 wt.% In the slag, containing. Wt.%: CaO 28-33, SiO. 28-33, MgO 10-15, contributes to the effective liquefaction of chromium-containing slag. Slag of such composition at

0 weight ratio SiOo: CaO 1.00:: 0.85-1.00: 1.00-0.85 has a melting point of 1450-1480 ° C. Fusible calcic aluminosilicate slags have a high reactivity to initiate the transition of sulfur from the metal to the slag phase, have

lower gas permeability than calcareous silicate, contribute to the increase and stabilization of the absorption of titanium.

Reduction of lime consumption during the refining period from 25-35 kg / t to 10.5-15.5 kg / t for

Q account of the corresponding increase in the content of alumina (A12Oz) in the slag reduces the saturation of the metal with hydrogen.

Electrothermal silumin slag contains ingredients in ratios, wt%: aluminum, aluminum 25; silicon 8; alumina 55, cryolite 5;

the rest of iron, manganese and titanium up to 100. The introduction of slag silumin and slag-added ferrosilicochrome with lime added to the slag oxidative period accelerates slag formation, reduces the silica activity and increases the deoxidizing ability of silicon, resulting in a content of chromium oxides in the slag 10-12 minutes after entering deoxidizers are reduced from 28-35 wt.% to 3-4 wt.%.

The additional treatment of the slag with 65% ferrosilicon powder makes it possible to remove the chromium, manganese, and iron from the slag and maintain its sufficient liquid mobility until the melting is released. At the same time, the silicon content in the metal is stably maintained in the range of 0.25-0.35%.

The costs of silumin silage, ferrosilicochrome and 65% ferrosilicon slag costs depend on the actual content in the mixture of acid-oxidizing elements, the composition of the furnace lining and the oxidation of the melt after purging it with oxygen.

Claims (1)

When smelting ner:; casting steels by remelting waste using oxygen in main electric furnaces with chrome-magnesite lining of the vault and walls, a magic-chromite hearth, after melt blowing, co0-keeping weight. / O: chrome 8.0-14.0; manganese 0.3-2.0; silicon 0.3-0.5; iron 70.5-91.0, the formation of slag contains, kg / t melt: СSОО, 6.5-9.4; CgO 5.3-6.8; MpO 3.1-3.7; FeO 3.6-2.8; SiOo 2.5-3.2; MgO 3.6-5.2; AloO, 0.2-0.5; CaO 0.4-0.5; other oxides 0.4-0.9. With a coefficient of use of silicon for the deoxidation of slag and metal equal to 0.85 for the complete reduction of iron, manganese and chromium from chromium oxide and for the introduction of 0.25-0.35 wt.% Silicon in steel, its total consumption is stoichiometric is, kg / t melt: (2: & -3.6) (3.1 - 3.7). (6..5-Я4) / L5-35; G 5.0 + Tb 6.7-8.7 For the reduction of chromium from chromium oxide, the slag consumption of silumin with an aluminum utilization factor of 0.7 is kg / t: Mr || l 10QiiOO 8 00-10.20; The consumption of ferrbsilicochrome containing 50 wt.% Silicon, taking into account silicon, added silumin, 65% ferrosilicon powder and low carbon ferrochrome, is, kg / t melt: (6.7-8.7) -C3.1-3 , 3) -100 7, o The recommended costs of lime, ferromilicochrome, and silumin slag confirmed by the practice, satisfying the conditions of complete reduction of chromium and obtaining low-melting, reactive slag with its minimum frequency ratio are substantiated by calculation. With a chromium content in the rod within 8.0- 14.0 w / v, the slag consumption of electrothermal silumin and ferrosilicochrome (FSH) 50/40 slag should be 8.00-10.20 and 7, 80 kg / ton of melt, respectively . For a more complete and faster reduction of chromium and obtaining a fusible calc-aluminosilicate slag, in which the ratio, wt.% SiOj: A1 0 .: CaO 1.00:: 0.86-0.98: 0.85-0.99, The ratios of costs from the message, ferrosilicochrome and electrothermal silumin slag must be within 1.00: 0.67-0.71: 0.66-0.76. In order to obtain the recommended silicon content in the finished metal in the range of 0.40 - 0.50 wt.%, The calculated consumption of 65% ferrosilicate powder for slag processing should be 2 kg / ton of melt. The smelting of stainless steels of type O 3-12X18N1 OT, 08-1 OX 17N1ZM2MZT, 08-40X13, and others by a single-slag process is carried out as follows. The slag formed during the smelting of the batch is removed by 70-80% before blowing the melt with oxygen. After the melt is blown, two samples of the metal are taken for carbon, chromium, nickel and other elements, ferrosilicochrome (7.20-10.80 kg / t of melt) is first introduced into the furnace, then 5.0-7.0 is placed on the slag. kg / t slag silumin and lime in the amount of 7.0-10.0 kg / t. Immediately after the introduction of the deoxidizing mixture, the waste of the corresponding steel grades for the melt and the calculated amount of ferrochrome are introduced into the metal. The furnace is turned on at a reduced capacity, during the melting of ferrochrome per slag, 65% ferrosilicon powder (1.0-1.5 kg / ton) is produced, the slag and metal are mixed for 10-15 minutes. After mixing, a metal sample is taken for carbon, manganese, silicon, and in necessary cases for chromium, nickel and other elements, the temperature of the metal is measured, which must be within the limit of 1600 SZO C, and a correction additive is introduced into the melt. The value of which is determined by the results of the analysis of two samples taken at the end of the melt production with oxygen. The adjustment of the chemical composition of the metal in chromium is made 0.20-0.40% below the lower limit. The metal is heated, if necessary, 65/0-foot ferrosilicon powder (0.5-1.0 kg / t) is added to the slag, the metal and the slag are mixed. 5-7 minutes before the melt is released, the reserved part of electrothermal silumin (3.00-3.20 kg / t) and lime (3.50-5.50 kg / t) slag is introduced into the furnace, the slag is mixed with the included current for 2-3 minutes To liquefy the slag, fluorspar or fluorite concentrate (1.5-2.0 kg / t) are introduced into the furnace for 1-2 minutes before the melt is released. To alloy the steel with titanium, 70% ferrotitanium or metal titanium waste is used, which is seated in a ladle before the release of smelting together with lump al.minium (1.0 kg / t). By using the proposed method of smelting stainless steels in main arc furnaces by remelting waste using a single-slag process, metal gas saturation with hydrogen is reduced due to a decrease in lime consumption and a refining period under lime-alumina slag, resulting in reduction of metal rejection; the consumption of aluminum alumina powder is reduced by 1-2 kg / t, powder of 65% ferrosilicon 2-4 times, 45% ferrosilicon (silicochrome) by 20-30 kg / t; duration of melting is reduced by 20-25 minutes; The uptake of titanium increases and stabilizes from 30-45% to 50-60%. Claims One-slag stainless steel smelting process, including melt purging with oxygen, deoxidation of oxidative period slag, deoxidation of metal and alloying titanium steel in a ladle, characterized in that, in order to improve the quality of the metal and reduce the consumption of expensive ferroalloys and deoxidizers, slak oxidant of the period of acidification with slag of electrothermal silumin in the amount of 8.00-10.20 kg per 1 ton of melt with a ratio of lime, (silicon chromium and slag of silumin 1.00: 0.67-0.71: 0.66-0.76 and Slag complement no deoxidized powder 65% solution of ferrosilicon (2 kg / t metal, then melting discarded.