SU1497230A1 - Method of producing ball-bearing steel - Google Patents

Abstract

The invention relates to the field of metallurgy, in particular, to methods for smelting and after-furnace treatment of bearing steel. The purpose of the invention is to improve the quality of the metal and reduce the consumption of chromium, manganese, powdered aluminum and silicon-containing materials. The method includes finishing the metal by chemical composition with lumpy materials in the furnace, treatment in the ladle with the main reducing slag with a mass fraction of iron oxides less than 1.0%, deoxidation with aluminum and after 30-60 with treatment with the main oxidizing slag with a mass fraction of iron oxides 1-3% within 180-600 s. 1 tab.

Description

The invention relates to metallurgy, in particular to methods for smelting bearing steel in electric furnaces,

The purpose of the invention is to increase the quality of the metal, reducing the consumption of chromium, manganese, aluminum and silicon containing materials.

The quality criterion for bearing steel is the durability of manufactured bearings. The durability of bearings in many respects is determined by the quantity and quality of non-metallic inclusions present in the metal. The most harmful inclusions have been found to be globular and nitride. The number and size of non-metallic inclusions, in turn, are determined by the mass fractions of the elements included in their composition: sulfur, oxygen, calcium, titanium, etc. The less these elements are contained in the refined metal, the more pure the steel is sulfide, oxide ( okstedy and globules) and nitride inclusions, the higher its operational properties.

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Vacuuming the bearing steel, its treatment with acidic or oxidative pshakami allows to reduce the contamination of the metal with globular, nitrite inclusions. During the vacuuming of steel, this occurs due to a decrease in the mass fraction of oxygen, and during the treatment with acidic or oxidative slags, due to the limited influx of calcium into the metal. At the same time, the desulphurization issues in these processes are practically not solved, which leads to an increased contamination of the metal with sulfide inclusions.

First of all, according to the proposed method, the treatment of the metal, deoxidized with silicon, is carried out by the main reducing slag (liquid or from solid slag-forming), which increases the efficiency of removal of sulfur and oxygen from the metal to slag. However, in this case, the recovery of calcium from slag by silicon dissolved in the metal is enhanced. Since the subsequent operation is to treat the metal with an oxidizing slag, the excess calcium is bound to oxygen, which is supplied from the slag to the metal, and is subsequently assimilated by the slag in the form of non-metallic inclusions. The addition of silicon occurs in the furnace on the unoxidized metal, i.e. in this case, favorable conditions are created to remove the calcium dissolved in the ferrosilicon.

Due to the fact that chromium and manganese are seated in a metal deoxidized with silicon, their consumption decreases. In this case, slag foaming occurs as a result of the contact of the main reducing slag with the oxidizing one, since the oxidizing shpak in the proposed method contains no more than 3.0. % of iron oxides. Consequently, there is no need to use powdered silicon and aluminum-containing materials.

Optimal and boundary values of the claimed parameters and their. The effect on the purpose of the invention has been determined experimentally in the smelting of bearing steel in 100-ton arc furnaces of the Chelba Metallurgical Plant.

The inexpediency of metal refinement by chemical

analyzing powdered material-. In this case, the cost of steel rises without a noticeable improvement in quality.

Processing the bearing steel in the ladle with a basic reducing slag with a FeO mass fraction of 1.0% results in a decrease in the removal of sulfur and oxygen from the metal to the slag. As a result, contamination became oxides and sulphides. In this case, the consumption of alloying materials also increases markedly.

Processing bearing steel basic oxidizing slag with a mass fraction of FeO 1.0% and FeO 3.0% impractical. In the first case, due to the lack of the oxidizing potential of the slag to remove excess calcium, in the second, due to the excess of oxygen transferring from the slag to the metal. In the first case, the contamination has become globular inclusions, in the second case, the consumption of alloying elements increases, the contamination with oxides increases.

Processing the metal with an oxidizing slag after a period of time less than 30 and more than 60 s (after deoxidation of the metal with aluminum) leads to a deterioration in the performance of the process. In the first case, due to the lack of time to form a homogeneous oxidizing slag, in the second - an unjustified increase in heat loss.

The processing time of the metal with the main oxidizing slag for a time of less than 180 and more than 600 s is not beneficial. In the first case, due to lack of time for the formation and assimilation by slag of non-metallic inclusions, in the second, due to a noticeable increase in heat losses and the influence of the lining of the ladle on the contamination of steel.

PRI me R. In ESPTS-2 of the Chelinsky Metallurgical Combine, a new ShKh15SG bearing steel was smelted in a 100-ton electric arc furnace at the fresh charge. After the end of the oxidation period, the slag was pumped in such a way that, after lumping silicon-containing materials were added to the furnace, there was about 4.0 tons of slag with a FeO mass fraction of 3.0–4.0%,}} And the deviation of these parameters was corrected by adding

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slag mixture consisting of lime, fluorspar and chamotte.

Simultaneously with silicon, chromium (12.5 kg / t) was introduced into the furnace and manganese (11.2 kg / t) was introduced before it was released from the furnace.

After finishing the metal in terms of chemical composition and temperature, the metal was treated in the ladle with liquid lime-alumina slag in the amount of 4.0 tons or solid slag-forming materials. The mass fraction of FeO in such a slag was about 0.5%. Moreover, the furnace was tilted in such a way that the metal without slag entered the ladle and was processed by the main reducing slag. Then furnace furnace slag was poured into the ladle, which, mixed with reducing, formed the main oxidizing slag (mass fraction of FeO 2 2.0%), which, 45 s after the introduction of aluminum, treated the metal for 390 s. The metal was treated with an oxidizing slag by purging the slag metal emulsion with a neutral gas.

The effect of changing the values of the proposed method on the purpose of the invention is presented in the table.

Thus, the technology of smelting and secondary treatment of bearing steel allows, in comparison with

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prototype to reduce the size of non-metallic inclusions (number of points 2.0 decreased in globules from 10 to 6, in oxides from 21 to 8 and sulphides from 18 to 6), reduce the consumption of lumpy chromium from 15.0 to 12.5 kg / t, manganese from 12.5 to 1 1, 2 kg / t, powdered - silicon from 0.40 to 0.0 kg / t, aluminum from 0.35 to 0.0 kg / t.

Claims (1)

Invention Formula The method of obtaining ball bearing steel includes melting of metal, oxidative blowing, alloying of metal with chromium and manganese, treatment in a ladle with reducing slag, alloying and deoxidation of metal with aluminum and silicon, purging with an inert gas, characterized in that, in order to improve metal quality, reduce consumption chromium, manganese, powdered aluminum and silicon-containing materials, silicon is introduced into the furnace simultaneously with chromium, and 30-60 s after treatment in the ladle with reducing slag and deoxidation with aluminum the metal is treated with a basic oxidizing slag with a mass fraction of iron oxides of 1-3% for 180-600 s.