SU865925A1 - Method of smelting bearing steel - Google Patents

Description

(54) METHOD OF MOLTING BEARING STEEL

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The invention relates to ferrous metalworkers 1, namely to smelting steel in electric arc furnaces for subsequent refining melts.

A method of producing bearing steel is known, in which metal is smelted in a steelmaking unit with a base lining with preliminary deoxidation and refining in a ladle with synthetic slag.

In order to obtain non-metallic inclusions of sulphide and silicate types in steel, the steel is deoxidized before being released to the content before being released; oxygen is not more than O, O06% and refined in a ladle with synthetic slag based on silica J.

The disadvantage of this method of steelmaking is the need to provide in the electric steelmaking shop a special electric arc furnace for producing synthetic silica-based slag.

There is also known a method for producing steel, which includes steelmaking and finishing by temperature and chemical composition under slag with a basicity of 2.5-3.5 and subsequent treatment with acidic slags. The difference of this method lies in conducting fine-tuning of the melting under the slag, which is 0.7-1.2% of the weight of the charge, and 5–10 minutes before the melting is released, the slag basicity is reduced to 0.3–0.7 by adding silica-containing materials;

10 power is increased by 2O-ZO% from the optimal f2j.

The disadvantage of this method of smelting is that, at the end of the period prior to IS, vodka is guided in an acidic slag lining furnace with a basic magnesite lining. slag with a basicity less than 0.7. This leads to a strong corrosive magnesite lining on the slag on su to

They should cause an emergency burning of the furnace, in particular in the case of a delay in smelting from the furnace, which is often sufficient under production conditions. A second disadvantage of the known method is the need to melt a considerable amount of silica-containing material by melting to reduce the basicity of the furnace slag from 2.5-3.5 to O, 3-O.7. This requires additional power consumption and an increase in the power input to the furnace by 20-30% of the optimum. The closest in technical essence and the achieved effect to the described invention is a method of smelting ball bearing icTanH, including melting the charge, targeting a reducing lime slag, introducing a quartzite-containing material into the furnace and producing steel h. The disadvantages of this method are: 1. The deposition of acidic slag with a basicity of 0.7-O, 9 in the main electric arc furnace. This leads to additional wear of the magnesite lining, an increase in the content of magnesium oxide in the furnace slag, and an increase in the specific consumption of magnesite powder for filling the lining. Bath electric arc furnace. 2. The low liquid mobility of slags with a basicity of 1.0-1.3 in the CaOSi 02-ML) -AE2O system, which is the basis of electric furnace slags. In particular, the capacity of such slags increases dramatically when the temperature drops to 15 ° C and lower, which makes it difficult to drain the slag from the furnace into the ladle, move the stopper to the casting, drain the slag from the ladle after the end of the casting and cause calcium aluminates to become contaminated and magnesian spinel forming metal in the metal on the basis of droplets of viscous furnace slag entangled in steel. The desulfurization capacity of the slag wastes of svnosgyo 6,7-0,9 is very low. The purpose of the invention is to obtain non-metallic oxide deposits in steel, mainly in corundum, an increase in desulfuraac steel, and an increase in the yield of rolled products. The goal is achieved by the fact that, in particular, the tydshtaikov gal involves melting the charge, suggested reductive lime work, the introduction of quartzite-containing material into the furnace into a steel alloy, the material contained in the furnace in amounts of 0.3-O, 5% of the weight of the raw material, 5% of the weight of the raw material injected into the furnace. In the first portion, doubled for 46 mV before the addition to the rt-containing additive. MsrepiKai, and the remaining amount is -8 minutes after the addition of the quartzite-containing material and discharged the first quarter of the heat from the furnace at a rate equal to / 2–1 / 3 the release rate of the rest of the float, and after the release, the steel in the ovs is deactivated in the amount of 0, 03, O6% by weight of steel. Crushed varcite, quartz sand, etc. can be used as a quartzite-containing material; crushed fluorspar, pellets of fluorine concentrate, etc. are used as phyahorite-containing material. When the furnace slag has a basicity of 1, О1, 3 and its amount is about 4% by weight of steel, introduction An amount of your material in an amount of less than 0.3% by weight of the steel will provide an increase in the calcium fluoride content in the slag by less than 7.5%, which is not enough to obtain the optimum liquid mobility of such slag. The introduction of a fluorite-containing material in an amount of more than 0.5% by weight of steel causes an increase in the calcium fluoride content in the slag by more than 12.5%. Such a slag has already excessive fluid mobility and will not be economical. The introduction of fluorite-containing material into the furnace 4-6 minutes before adding the quartzite-containing material and 5-8 minutes after adding the quartzite-containing material, i.e. 2-10 minutes before the melt is released, due to the short duration of the diluting effect on the slag fluorine ions formed during the dissociation of calcium fluoride in the slag. Such a method of introducing phpurite-containing material provides, firstly, sufficient liquid mobility of the slag before adding the quarate-containing material to it, which significantly dissolves the latter in the slag and, secondly, the necessary fluidity of the furnace slag immediately before and during the smelting production. The introduction of a quartzite-containing material before the addition of less than half of the total amount of phoo-containing material provides sufficient slag dilution to quickly dissolve the quartzite-containing material in it. On the other hand, the introduction of more than half of the total amount of fluorite-containing material in front of the additive to the Evarcite-containing material reduces the degree of liquid mobility of the 1X1A1a before the smelting, which causes the steel to become contaminated during the discharge into the ladle with slag inclusions. The introduction of fluorite containing material less than 4 minutes before adding a quartzite-containing material is not enough to produce a homogeneous liquid-moving slag. The introduction of the remaining amount of fpuorite-containing material less than 5 minutes after the addition of the quartzite-containing material is impractical., Because with the addition of quartzite-containing material and 15 minutes before tapping flyuoritsoderzhaschy material will Preece wives more than 1O minutes before tapping. During this time, the liquefying effect of fluoride ions on I slag will decrease. On the other hand, the introduction of the remaining amount of phosphorite-containing material more than 8 minutes after the addition of the quartzite-containing material will not provide the optimum liquid mobility of the slag before the melt is released, as with the addition of quartzite-containing material in Yu. until the release of the phosphorite-containing material for the assimilation of slag, less than 2 minutes remain, which is not enough to obtain a homogeneous liquid-mobile slag. To desulfurize steel with slag, it is necessary to ensure active metal treatment in the ladle with furnace slag. For this, the slag must be asleep in the ladle at the beginning of the smelting production. Drainage of slag from the furnace occurs most fully when the first quarter of the heat is released at a rate of 1 / 2-2 / 3 of the discharge rate of the rest of the heat, since this does not obstruct the entire outlet cross section and metal does not prevent slag discharge. TlpH discharging the first quarter of the heat with a rate of less than 1/2 the speed of discharge of the remaining heat will cause an excessive increase in the melting release time, which will cause additional oxidation of the metal jet and reduce the intensity of the slag mixing with the metal in the ladle. When the first quarter of the heat is drained at a rate of more than 2/3 of the rest melting rate, the rest of the heat will overlap the entire cross section of the metal outlet and the slag will be drained together with the steel. Deoxidation of steel after the release; in the ladle with aluminum in the amount of O, 03-O, 06% of the weight of the steel ensures the presence of oxide nonmetallic moisture in the metal, mainly in the form of corundum, as was established on experienced smeltings. The consumption of aluminum is less than 0, OZ% of the weight of the steel is not enough for complete deoxidation of the metal. With an aluminum consumption of more than 0.06% w of steel weight, the residual aluminum content in the metal exceeds the optimum value, which adversely affects the quality of the steel. The advantage of this method is determined by the importance of increasing the yield of ingots of steel bearings after refining remelts. Nowadays, for example, ingots weighing up to 5.5 tons are produced using electroslag remelting using cast consumable electrodes. This circumstance imposes high requirements on the nature of oxide nonmetallic inclusions in the source metal for refining melting and sulfur content in it. t, corundum. The smelting of bearing steel according to the proposed invention ensures the presence of oxide nonmetallic inclusions in it mainly in the form of corundum and the sulfur content is not more than O, O15%. This is due to the fact that refining slag of high liquid mobility is produced for the production of smelting. The latter ensures that exogenous calcium and magnesium oxide-based slag inclusions are released into the metal. Secondly, the treatment of staples with slag with a basicity not higher than 1.3 presumes the development of the process of reduction of calcium and magnesium from the slag due to the low activity of calcium oxide and magnesium, in this type of slag. This protects the metal from subsequent contamination with calcium and magnesium based oxide inclusions. Thus, in the final deoxidation of steel in an aluminum ladle, corundum is the main type of oxide inclusions in it. The invention due to the normalization of the smelting draining rate provides for acid treatment of the metal in the ladle with kiln slag. This is especially important for obtaining a sulfur content of no more than 0.015% in steel, meaning that the basicity of kiln slag is no more than 1.3. The normalization of the rate of discharge of the heat creates the possibility of melting bearing steel on the fresh charge, after melting of which the metal can contain up to 0, O40% sulfur. The smelting of bearing steel according to the invention makes it possible to increase the by-product usable use of electroslag ingots by 12-18%. Smelting bearing steel with a reduction in the basicity of the refining slag before the start of smelting to a minimum of 1.0 will not reduce the durability of the magnesite lining of modern heavy-duty electric arc furnaces with a specific moshnostys furnace transformers of 500-600 vVA / ton For such furnaces, the resistance of the lining is an important issue due to their high working voltages, i.e. on long electric arcs. 1 Example. In an electric arc furnace, IUX15 bearing steel is melted on a fresh charge with full oxidation. After the charge has been melted, the oxidation period has been carried out and the oxidizing slag has been downloaded, a reduction lime lime slag in the amount of 14 kg / ton, quartzite 4 kg / ton and fluorspar 4 kg / ton is induced. Slag during the recovery period is deoxidized with coke powder. 15 minutes before the melting is released, incinerated calcined quartz sand is deposited in the amount of 11 kg / g, i.e. 275 kg for smelting. 4 minutes prior to the addition of silica sand, fluorspar was introduced into the furnace in an amount of 0.15% of the weight of the steel, i.e. 38 kg for smelting. Eight minutes after the addition of quartz, fluorspar was introduced into the furnace in an amount of 0.15% of the weight of the steel, i.e. 38kg for smelting. Before discharge into the ladle, the slag contains, wt.%: CaO 37.8 | iO 37.8; 13.8; CaFi 7.5; FeO 3.0. The basicity of the slag is 1 O. The first quarter of smelting is produced at a rate equal to 1/2 of the rest rate of smelting, namely, the first quarter of smelting is produced at a speed of 4 t / min, the rest of smelting at a rate of 8 t / min. After the release, the steel is deoxidized in the ladle with aluminum in the amount of O, O6% by weight of the steel, i.e. 15 kg for smelting. The sulfur content in the finished steel is O, O15%, the aluminum content is O, OZ%. The metal is poured on a semi-continuous steel casting plant into two billets 8 5 of which 4 consumable electrodes were prepared for ESR. After the ESR ingots were rolled to the tube billet Ø 180mm, when testing for contamination by nonmetallic inclusions in Q 120mm, the yield of finished steel from the first test increased by 18%. Example 2. In a 25 t electric arc furnace, bearing steel ShK15 was melted on a fresh charge with full oxidation. After the charge has been melted, the oxidation period has been carried out and the oxidizing slag has been loaded, 45% ferrosilicon is introduced into the metal by 0.250, 27% silicon, carbon ferrochrome at the lower limit of the chromium content and lime is reduced in an amount of 15 kg / ton, quartzite 4 kg / t and fluorspar 4 kg / t. Slag during the recovery period is deoxidized with coke powder in 2-3 portions of the total amount of 3-4 kg / ton. 12 minutes before the melting into the furnace, calcined and quartz sand is applied in the amount of 10 kg / t, i.e. 250 kg for smelting. 5 minutes prior to the addition of silica sand, pellets of fluorite concentrate were introduced into the furnace in the amount of 0.2% of the steel weight, i.e. 5O kg for smelting. After 6 min after the addition of silica sand, pellets of fluorite concentrate are introduced into the furnace in an amount of 0.2% of the weight of the steel, i.e. 50 kg for smelting. The adjustment of the silicon content in the steel was made by adding 65% ferrosilide to the ladle. Before pouring into the ladle, the furnace slag contains, wt%: CaO 41.0; SlO 35.6; / v 11.2; CaPl 10.0; FeO 2.8. The basicity of the CaO slag 1.17. 5-1 О 2 The release of the first quarter of melting is carried out at a speed equal to 3/5 of the speed of the rest of the melting, namely, the first quarter of melting is released at a speed of 5 t / min, the rest of the melting at a speed of 8 t / min. After the release, the steel is deoxidized in the ladle with aluminum in the amount of 0, O4% of the steel aes, i.e. 10 kg on melt. The sulfur content in the finished steel is 0, O12%, the aluminum content is O, O2%. The metal is poured on the installation of semi-continuous casting of steel into billets with a section of 370 mm square. Cast billets are cut in half into consumable electrodes, which are remelted in furnaces of electroslag remelting into ingots weighing 5.5 tons. After rolling the ingots, finished cpifHHp 1О5-13О mm was obtained. You

Claims (1)

Claim A method of smelting bearing steel, including melting the charge, introducing reducing lime slag, introducing a quartzite-containing material into the furnace and releasing steel, characterized in that, in order to obtain oxide non-metallic inclusions in steel, it is excellent in the form of corundum, to increase steel desulfurization and increase yield rolled, fluorite-containing material is introduced into the furnace in an amount of 0.3-0.5% by weight of steel in equal portions, the first portion being introduced in 4-6 minutes. before the addition of quartzite-containing material, and the rest 5-8 minutes after the addition of quartzite-containing material and the first quarter of the smelting is released from the furnace at a rate equal to 1 / 2-1 / 3 of the rate of release of the rest of the smelting, after which the steel in the ladle is deoxidized in an amount of 0, 03-0.06% by weight of steel.