RU2270257C2 - Method of production of the steel used for production of steel cord, superfine springs and cable ropes - Google Patents

Abstract

FIELD: ferrous metallurgy; methods of production of the steel used for production of the steel cord, superfine springs and chain cables.

SUBSTANCE: the invention is pertaining to the field of ferrous metallurgy, in particular, the method of production of the steel used for production of the steel cord, superfine springs and chain cables requiring the heightened purity in respect to the contents of the shares of all sorts of nonmetallic impurities, and also the high-carbon spring steels of the heightened quality of the 70 "extra" type. The method provides for smelting of the metal in the steel-smelting aggregate, its heat tapping into a ladle, an aluminum deoxidation, doping with a ferromanganese and ferrosilicon feeding, treatment of the metal and argon flushing by the aggregate of the metal final melting or by the furnace-ladle aggregate, the following casting of the steel. In the beginning of the tapping a carburizer is injected into the ladle and right after it for deoxidation introduce aluminum in amount of 0.5-1.0 kg/t, and after the aluminum addition during the tapping conduct a doping with ferromanganese addition agents feeding in with the subsequent partial introduction of ferrosilicon in the lower marking limit or in full by the aggregate for the metal final melting or by the furnace-ladle aggregate. The invention allows to produce a high-quality steel with the low degree of pollution with the nonmetallic impurities of all types, that allows to increase technological effectiveness of production of the rope wire and the metal cord at all production stages from smelting to drawing and to improve quality of the final products.

EFFECT: the invention ensures production of the high-quality steel with the low degree of pollution with the all types nonmetallic impurities, the increased technological effectiveness of the rope wire and the metal cord production at all production stages from smelting to drawing and the improved quality of the final products.

3 cl, 1 ex

Description

The invention relates to metallurgy, in particular to a technology for the production of high-carbon steel grades for the manufacture of cord and rope wire, requiring high purity in the content of non-metallic inclusions of all kinds, as well as high-carbon spring steels of high quality type 70 "extra".

A known method of smelting high-carbon steel for high-strength wire, mainly in a converter, including scrap filling, cast iron casting, input of slag-forming materials, purging with a gaseous oxidizing agent, for example, oxygen in two periods, introducing into the converter in 1.5 ... 3.0 min. Before the end of the first period of purging of urtite in the amount of 1-3 kg / t of steel, downloading intermediate slag, deoxidation and alloying of steel in the ladle with ferromanganese and ferrosilicon additives [1].

The disadvantages of this method are that non-metallic inclusions formed in the process of steelmaking in the form of sulfides and silicates are practically not removed from liquid steel and have a negative impact on the manufacturability of further processing and impair the quality of the finished product. This is especially true for brittle and non-deformable silicates.

There is also a method of deoxidation of carbon steel containing 0.45 ... 0.80% carbon, including deoxidation in a furnace with manganese, in a ladle with silicon and aluminum, and in an aluminum mold, in order to reduce the amount of alumina and brittle silicates, to increase processability metal when drawing and increasing the yield, aluminum is introduced into the ladle in an amount of 60-130 g / t of steel, and in the molds - in portions with an increase of every 0.01% of the actual decrease in carbon content by 2 g / t of steel, and the ratio of the total amount aluminum data in the bucket and the mold, to the silicon introduced into the ladle is maintained in the ratio 1: (15-80) [2].

The disadvantages of this method is the presence in the finished steel of silicates and especially aluminum oxides, which cannot be removed from the metal volume during deoxidation of the steel in the mold and have a negative impact on the processability of the drawing process (increased breakage), and also worsen the service characteristics of cord and cable steels, in particular, lead to a reduction in multi-cycle fatigue.

The closest in technical essence to the claimed invention is a method for producing steel for metal cord, including smelting metal in a steelmaking unit, releasing it into a ladle with simultaneous deoxidation in a ladle, feeding silicocalcium and aluminum, alloying with manganese ferroalloys and casting steel, while silicocalcium and aluminum are fed into the bucket with a flow rate selected in the ratio (40-60): 1, and after alloying with manganese ferroalloys, vacuum is carried out under the cover slag with a basicity of 1.8-2.2 with the sum of oxides manganese and iron is not more than 1.5%, after which they are treated at a metal finishing plant with the addition of a refining slag mixture from calcium, silicon and barium oxides taken in the ratio (30-35) :( 50-60): (10-15), and steel casting is carried out on a continuous casting machine, maintaining a constant casting speed [3].

This invention is taken as a prototype.

The disadvantages of this method are the high content in the cast steel of liquid inclusions of the oxide type, which is a complex compound of silicon oxides and calcium nSiO ₂ mCaO. These inclusions are prone to coagulation and are well wetted by steel, which sharply worsens the efficiency of their removal during evacuation and processing at a metal finishing plant. This circumstance is aggravated by the fact that the method for producing steel for steel cord under consideration does not provide for metal exposure in the ladle immediately before continuous casting for at least 30 minutes, which would remove inclusions by surfacing and assimilating them with slag. As a result, the finished steel is contaminated with non-metallic inclusions, which affects the performance characteristics of the cord. Another disadvantage of this method of producing steel is the high cost of silicocalcium and one of the components of the refining slag mixture - barium oxide, which leads to higher prices for products without a significant increase in quality.

The problem to which the invention is directed is to produce high-quality steel with a low degree of contamination with non-metallic inclusions of all types, which will improve the manufacturability of the production of wire rope and metal cord at all stages from smelting to drawing and improve the quality of finished products.

The problem is achieved by the fact that the proposed method of producing steel for metal cord, high-quality springs and ropes, which includes the smelting of metal in a steelmaking unit, its release into the ladle, deoxidation with aluminum, alloying with ferromanganese and ferrosilicon additives, metal processing and argon purging at a metal finishing plant or in the ladle furnace unit, the subsequent casting of steel, at the same time at the beginning of production a carburizer is introduced into the ladle and immediately after it aluminum is introduced in the amount of 0.5-1.0 kg / t for deoxidation, and after aluminum is introduced, alloying is carried out along the way with the addition of ferromanganese with subsequent partial introduction to the lower marking limit or completely on the metal finishing unit or on the ladle furnace unit. Moreover, a converter is used as a steel-smelting unit and metal is released into the ladle at a carbon content of 0.05-0.15%. Steel is casted into ingots weighing 4 ... 10 tons or at a continuous casting plant.

Stopping the melting in the case of steel smelting in the converter at a carbon content of 0.05-0.15% will make it possible to obtain an intermediate product with an optimal content of elements such as silicon, sulfur, phosphorus and a fairly low oxygen content. The deep deoxidation of the intermediate by the addition of the optimal amount of aluminum at the beginning of the release from the steelmaking unit, immediately after the introduction of the carburizer and before the addition of other deoxidizers, provides the formation of deoxidation products mainly in the form of alumina particles, which are almost completely removed as a result of sparging of the metal during discharge into the ladle and during purges at a metal finishing plant or at a ladle-furnace assembly. Ferromanganese is added in the course of metal production after aluminum is introduced, and ferrosilicon is partially introduced last of all during production or completely on the metal finishing unit or on the ladle furnace unit, which ultimately allows to obtain steel with a low content of non-metallic inclusions.

Stopping melting in the case of steelmaking in a converter on carbon less than 0.05% leads to a significant increase in the oxygen content in steel, which leads to the formation of a large number of non-metallic inclusions of the oxide type. On the other hand, if melting on carbon stops at more than 0.15%, the finished steel will have a sulfur and phosphorus content higher than the maximum permissible technical documentation values.

An additive of aluminum in an amount of less than 0.5 kg / t does not allow for deep deoxidation, which leads to a high residual oxygen content in the steel, and, as a result, to the formation of silicate-type inclusions during further deoxidation. The addition of aluminum in an amount of more than 1.0 kg / t will lead to the fact that not all aluminum will bind to oxides, and its residual content in steel will exceed the maximum permissible values according to regulatory documentation (not more than 0.005%).

An example of a specific implementation.

A carbon intermediate was smelted in a 140-ton converter and, at a content of 0.1% carbon, metal was discharged into the ladle. At the beginning of production, a carburizer in the amount of 900 kg was introduced, immediately after the carburizer was introduced, aluminum was calculated at a rate of 0.7 kg / t, then ferromanganese in an amount of 300 kg. Then, on a ladle-furnace assembly, 550 kg of ferrosilicon was added to steel simultaneously with argon purging. Then the metal was poured into molds weighing 4.5 and 6.5 tons (combined composition). Next, the steel was rolled in square meters. 200 mm with further rolling into a wire rod with a diameter of 6.0 mm, followed by sampling for analysis of contamination by non-metallic inclusions. The pollution assessment was carried out in accordance with GOST 1778 "Metallographic methods for the determination of non-metallic inclusions", scale Ш4. The test results showed the following content of non-metallic inclusions: oxides - 1.0 max., Sulfides - 0.5 max., No silicates were found.

Thus, the steel smelted by the proposed method has a lower contamination by non-metallic inclusions compared to the steel adopted as a prototype. Obtaining high-quality steel by the proposed method will improve the manufacturability of the production of wire rope, high-quality springs and steel cord at all stages from smelting to drawing and improve the quality of the finished product. In addition, the steel produced by the proposed method has lower production costs.

Information sources

1. Copyright certificate No. 1712424, cl. C 21 C 5/28, 1992

2. Copyright certificate No. 607846, cl. C 21 C 7/06, 1978

3. RF patent No. 2212451, cl. C 21 C 7/00 - adopted as a prototype.

Claims (3)

1. A method of producing steel for metal cord, high-quality springs and ropes, including smelting metal in a steel-smelting unit, releasing it into a ladle, deoxidizing with aluminum, alloying with ferromanganese and ferrosilicon additives, metal processing and argon purging at a metal finishing unit or ladle furnace unit, subsequent steel casting, characterized in that at the beginning of production a carburizer is introduced into the bucket and immediately after it aluminum is introduced in the amount of 0.5-1.0 kg / t for deoxidation, and after aluminum is introduced, alloying is performed downstream release additives ferromanganese followed by partial input ferrosilicon marking the lower limit or completely on the machine by the metal finishing unit or ladle furnace. 2. The method according to claim 1, characterized in that a converter is used as the steelmaking unit, while the metal is discharged into the ladle at a carbon content of 0.05-0.15%. 3. The method according to claim 1, characterized in that the casting of steel is carried out in ingots weighing 4 ... 10 tons or in a continuous casting installation.