SU1033551A1 - Method for smelting steel - Google Patents

Abstract

1. A STEEL SCRAPPING METHOD, including loading of the charge, its melting, and finishing of the melting successively under the basic and acidic slags, characterized in that. in order to improve the quality of steel and reduce the consumption of silica-containing ferroalloys, after the acidic slag is induced, the metal is blown in a stream of carrier gas with a mixture of silica, amorphous graphite and manganese in a ratio of 1:

Description

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The invention relates to ferrous metallurgy, more specifically to methods for smelting steel by a duplex process. There is a known method of smelting high quality steel by a duplex process: the main is an acidic open-hearth furnace with silicon being reduced in the process of refining the liquid semi-product in an acidic furnace to its content in the metal not less than 0.22% G. The disadvantages of this method are low productivity of steel-smelting units due to , difficulties in synchronizing the operation of the basic and acidic furnaces and of the metal for the duration of metal finishing in an acidic furnace. The closest to the invention to the technical essence and achieves the result is a method of steel smelting, including loading of the charge, its melting, finishing of the webs consistently under the main and acidic donkeys 2. The disadvantages of the known method include high consumption of silicon-containing ferroalloys, due to the fact that the process of silicon reduction along the metal finishing process under acidic slag does not receive significant development, since the furnace slopes are neutral (based on CrjOj or) and low the isotropy of the properties of steel products obtained by this method. The decrease in the isotropy of the steel properties is explained by the presence of non-metallic inclusions such as chrome, mystic spindles or aluminosilicates that are deformed during the processing of the ingots by pressure. The aim of the invention is to improve the quality of steel and reduce the consumption of silicon-containing ferroalloys. The goal is achieved in that according to the method of steelmaking, which includes loading the charge, melting it, fine-tuning the smelting successively under the main and acidic rocks, after pointing the sour slag, the metal is blown into the carrier gas a mixture of silica, amorphous graphite and manganese in the ratio of 1: (0.4-0, b) :( 0.7-0.9) with a total consumption of a mixture of 4.5-20.5 kg / t. Moreover, oxygen or air is used as a carrier gas. The joint introduction to the metal of the ppHiiKOB of creamy and amorphous graphite ensures the reduction of the cream by the reaction –f 2 {POPs-Q. (s (SiO) The tsarganz powder introduced into the mixture, oxidized in the carrier gas metal, compensates for the heat spent on the silicon reduction reaction by carbon. A decrease in the carbon ratio of less than 0.4 leads to a violation of the stoichiometric codTH of silica and carbon by the reaction { I) which affects the contamination of the metal with inclusions of silica glass. An increase in the carbon content ratio above 0.6 leads to the carburization of the liquid metal, which increases the duration of the boiling period. A decrease in the manganese ratio of less than 0.7 leads to a significant cooling of the smelting bath as a result of the lack of heat to compensate for the endothermic effect of the silicon reduction reaction. An increase in the ratio of manganese in excess of 0.9 leads to a strong liquefaction of sour slag. manganese oxides No. 1 with oxides and metal saturation with gases from the furnace atmosphere. When reducing the consumption of the mixture is less than 4.5 kg / t of steel, the process is restored. Neither silicon nor changes in the composition of nonmetallic inclusions receive significant development. With an increase in consumption of more than 20.5 kg / t of steel, the synchronicity of refining and heating of the metal is disturbed. . The steelmaking method is as follows. Melting is carried out in one furnace with a neutral lining. The charge materials used are alloyed own-produced waste, solid charge billet and high-quality cast iron. The proportion of pig iron in the metal portion of the mixture is 45-55%. The carbon content of the melt is. 1.7-2.5%. Under the lime slags, the liquid semi-solid products are made to reach a carbon content in the metal of 0.60-0.75%, which exceeds the lower limit, and the sulfur and phosphorus contents to the limits specified by the chemical composition of the steel grade. After this, ferromanganese is applied to the furnace, at the rate of obtaining manganese in the metal within the limits of 0.300, 40, and compulsory downloading (up to 90%) of the basic slag is made. Sour slag is induced by recycled slag and fireclay in the amount of 3.5-4.0% and 0.5% by weight of the liquid metal, respectively. To intensify the process of carbon oxidation, after maneuvering the acidic speck into the furnace, manganese ore is planted. After 30-45 minutes after the acidic slag has been set, the metal is blown through the compressed air or oxygen with a mixture of silica, amorphous graphite and manganese in a ratio of 1: {0.4-0.6) f (0.70, 9). The total consumption of the mixture for the period of finishing the metal under the acidic slag is 4.5-2 O, 5 kg / ton of steel. .After obtaining the required amount of carbon and reduced silicon, the endings were made with Mp S 0.33fO, 25} OD, 40f.0.50j 0.3 Steel was smelted in an inductive furnace with a capacity of 151) kg with a crucible made of a mixture of iron and chromium (85-90%) and bauxite (10-15 fC to increase the slag activity on it after complete metal melting, a graphite ring was crushed. To heal the reptiles above the surface, slag and maintain high temperatures, it was heated by burners located under a certain angle; to its surface. after the acidic slag was injected into the liquid metal with a mixture of silica amorphous graphite and manganese, it was supplied through a lined steel tube 20 mm in diameter, immersed in metal to a depth of 200250 mm. The course of smelting was given in steel 1. - 4TH ingots with a mass of 30 kg. For comparison / Opinion, the smelting is carried out according to the well-known method I. I in Table 2 and 3 show the results) Tats of research on the effect of technology. GIs of steelmaking on the isotropy coefficient of the mechanical properties of products from it and composition .., metal inclusions. Example 2. The proposed method smelted steel grade 38ХНЗИ with a chemical composition according to GOST 4543 more deoxidation of the metal with ferromanganese and further alloying. The metal is released from the furnace with an overheating of 100-150 ° C above the temperature of the melt — NIN of the steel grade. Example 1. The proposed method is used to produce steel grade A 38KHNMMFA with chemical composition. GOST -71.8% .. Cr N1 Mo V 20; 3.00f O, 35 5: -iO, iO j; 50; 3.50j-0.45f 0.18} 0.025. in 150 kg of induction furnace with crucible of distensillimanite. The process of smelting and the order of blowing metal with a mixture of crème nezama, amorphous graphite and manganese is similar to that shown in Example 1. A somewhat more intensive reduction of silicon was observed in the course of refining the liquid metal under the acidic slag. Restoration of chromium Vmetal was not observed. The effect of steelmaking technology in an induction furnace with a crucible of 1 distensillimannt on the properties of its products and the composition of non-metallic inclusions is given in Table. 4 and 5. Reducing the consumption of silica-content. ferroalloys, in terms of ferrosilicon FS25, when smelted in furnaces lined with chromium iron and distensillimanite is 12.0 kg / ton of steel. When using the proposed method of smelting high-grade steel, the most appropriate approach is to manufacture a furnace from dstensil: Limanite, since this eliminates the reduction of chromium and lining, which is undesirable when smelting, for example, carbon steel grades. The production of steel using the pre & i method ensures a reduction in the consumption of silica-containing ferroalloys and an increase in the quality of the steel produced. Table 1

2.00. 0.35 Traces 0.035 0.040 00-00 1.84 0.30 - 0.031 0.025 00-30 Slag Download + Lime 1500 g 00-30 1.70 0.30 - 0.026 0.021 01-00 1.35 0.28 - 0.020 0.015 01-30 01-30 Downloading slag + lime 1500 g 1.17 0.28 - 0.017 0.013 02-00 FMN75 - 340 g 02-05 02-08 Downloading the recovery slab Recycled acid slag 6QQ t: + chamo. 02-12 Time of sampling inn samples, h-mim 1.05 0.15 - 0.017 0.0 02-30 Iron ore 900 g 02-40 0.89 0.12 0.01 - 03-00 FMN - 560 g + H - 1 - 3300 g 03-05 0.67 0.12 0.03 - 03-30 Purging with a mixture of SiO + C (amorph 03-30 0.54 0.14 0.10 - 04-00 0.49 0, 15 0.12 - 04-30 Purging with a mixture of Si02 C (amorph 04-30 0.41 0.16 0.22 05-00 0.38 0.18 0.22 05-15 FMN75 - 570 g 05-15 05- 18 ФХО25 - 2680 g 05-18 ФВд35 - 990 g 06-00 Issue

Smelting method isotropic coefficient

steel --- g-- -.---

Kg j K «I K4, c

Known 0.63 0.65 0.58 Offered 0.88 0.82 0.76

 The ratio of the properties in the transverse and longitudinal directions is taken as the coefficient of isotropy. The value of ukova for both options was 2,

Smelting method Chemical composition of nonmetallic inclusions,%

"Si02 I jPeO-i-MnO j

Known 52.6 10.2 18.9 Ost. The proposed 64.9 8.8 20.0 Oot.

Table of Contents one

Moe

 a b and c a.

. T a b l and c a 3 The chemical composition of the metal ilEEIlIIZII SI I S I PI Cr LNI 0.27 0.29 0.35 p 750 g 0.40 0.48 n 1200 g

Isotropy coefficient.

g ---- t

8 Cf I K a „

0,670,700,65

0,860,840,82

Hilshchesky composition of non-metallic inclusions,%

Si02 I AljO 1

44.8 38.8 11.0 Ost. 68.3 9.2 19.0 Ost.

Table 4

Table 5

Claims (1)

2. Copyright certificate of the USSR: "75255, _cl. С 21 С 5/04, 1946., (57.1. METHOD OF STEEL Smelting / including charge loading, melting, finishing melting successively under the main and acidic slags, characterized in that. In order to improve the quality of steel and reduce the consumption of silicon-containing ferroalloys, after inducing acidic slag, the metal is blown in a jet of carrier gas with a mixture of silica, amorphous graphite and manganese in a ratio of 1: (0.4-0.6) :( 0.74), 9) with a total flow rate of 4.5- 20.5 kg / t of steel. 2. The method according to claim 1, characterized in that, as a gas carrier, oxygen is used. , 3. The method of pop. 1, characterized in that, as a gas carrier use compressed air.