RU2285727C2 - Method of production of steel at normalized content of sulfur - Google Patents

Abstract

FIELD: ferrous metallurgy; production of steels at normalized content of sulfur and off-furnace treatment of liquid melt in ladle with powder reagents.

SUBSTANCE: proposed method includes off-furnace treatment of liquid steel de-oxidized by aluminum and de-sulfurized to sulfur content of 0.025% and below first with calcium-containing powder wire and then with sulfur-containing powder wire. Calcium-containing wire is introduced in two stages: at first stage, calcium is introduced in the amount of 20-40% of its total amount required for modification of steel and at second stage, remaining 60-80% of calcium are added. Between these two stages of introduction of calcium-containing wire, liquid metal is subjected to degassing.

EFFECT: reduction of reject; low cost of process.

Description

The invention relates to ferrous metallurgy, in particular to the production of steels with a normalized sulfur content with out-of-furnace treatment of liquid melt in the ladle with powder reagents.

As a prototype, a method has been adopted for the production of automatic steel (with a normalized sulfur content), including after-furnace treatment with deoxidized aluminum and desulfurized to a sulfur content of 0.015%, first calcium-containing and then sulfur-containing flux-cored wires [1].

The disadvantage of the prototype is the introduction of calcium-containing wire in one go, which does not allow a significant amount of transformed non-metallic oxysulfide inclusions to float before treatment with sulfur-containing wire, which leads to a deterioration of the spillability of the metal, deterioration in quality and to increased rejects. In addition, desulfurization of steel before modifying the steel to a sulfur content of 0.015% leads to a significant increase in the cost of steel production.

The problem solved by the invention is to improve the method of production of steel with a normalized sulfur content by changing the input mode of calcium-containing materials, carrying out it in two stages with regulation of the consumption of calcium-containing materials at each stage.

The technical result obtained by using the claimed invention consists in the complete modification and globularization of all non-metallic inclusions, reducing the contamination of steel with non-metallic inclusions, improving the spillability and quality of the metal, reducing scrap, reducing the technological edge and overall costs for steel production.

The solution to this problem is ensured by the fact that the method of producing steel with a normalized sulfur content includes the after-furnace treatment of deoxidized aluminum and desulfurized to a sulfur content of 0.025% and below liquid steel, first calcium-containing and then sulfur-containing flux-cored wires.

According to the invention, the calcium-containing wire is introduced in two stages, with 20 ... 40% of the total amount of calcium needed to modify the steel being introduced in the first stage, the remaining 60 ... 80% calcium is added in the second stage, and between the stages of the input of the calcium-containing wire evacuation of liquid metal.

There is a causal relationship between the essential features and the technical result — the complete modification and globularization of all non-metallic inclusions, the reduction of steel contamination with non-metallic inclusions, the improvement of spillability and metal quality, the reduction of scrap, the reduction of technological scrap and overall steel production costs, which is explained by the following way. It is known that in order to obtain steels with good machinability characteristics, metal must be subjected to doping with sulfur, in which calcium has already been completely modified and globularized by all non-metallic inclusions. On the one hand, this can be achieved by lowering the sulfur content before introducing calcium-containing materials, and, as was established by the latest studies, it is enough to reduce sulfur to a sulfur content of 0.025% and lower. But calcium-containing materials must be introduced in two stages. The introduction of calcium-containing wire at the first stage with a flow rate of 20 ... 40% calcium of the total amount required for steel modification, with a sulfur content of 0.025% and below, provides the primary modification of non-metallic inclusions and the formation of oxysulfide inclusions of both regular globularized and not fully globularized forms . Between the two stages of the input of the calcium-containing wire, the liquid metal is evacuated without fail, since only it contributes to the emergence and removal of the formed small and medium oxysulfide (not fully globularized) non-metallic inclusions. After the initial modification and removal of the bulk of non-metallic inclusions, a second portion of calcium-containing materials is introduced in an amount of 60 ... 80% of the total amount of calcium, which already provides the final and complete modification and globularization of the remaining inclusions. Under such processing conditions, the alloying of metal with sulfur from the wire will occur stably, providing the specified sulfur content, the required characteristics of the steel and the complete castability of the metal.

Thus, in order to completely modify and globularize all non-metallic inclusions, reduce the contamination of steel with non-metallic inclusions, improve the spillability and quality of the metal, reduce rejects, reduce technological cuts and overall steel production costs, in the production of steels with normalized sulfur content calcium-containing materials during out-of-furnace processing must be entered in two stages with regulation of calcium consumption at each stage and metal evacuation between the two stages of calcium input containing wire.

The claimed method for the production of steel with a normalized sulfur content is used as follows.

In an electric arc furnace, steel of a given grade is smelted, released into a 100-ton ladle, deoxidizing, including aluminum, and other technological operations. During the smelting and production of metal, special technological operations are carried out (slag cut-off, additive of a refining slag mixture with a flow rate of 2.0 kg / t, etc.), which provide a metal content of 0.025% and lower. Then the ladle with liquid metal is transferred to the out-of-furnace steel processing unit, where averaging blowing is performed, a sample is taken and the chemical analysis of steel is determined. In the case of obtaining the necessary sulfur and aluminum content, the first portion of calcium-containing wire is introduced into the ladle with a flow rate of 0.034 kg / t of calcium (23% of the total amount required for steel modification, 50 m of flux-cored wire filled with SK30 silicocalcium 225 g / m). After entering the first portion of the calcium-containing wire, the metal is evacuated for 10 minutes. After this, a second portion of calcium-silicon wire is introduced in an amount of 170 m (flow rate - 0.114 kg / t for calcium, 67% of the total amount of calcium). After entering the second portion of the calcium-containing flux-cored wire for 2 ... 3 minutes, a gentle inert gas is blown, and then a sulfur-containing flux-cored wire is introduced into the bucket to ensure the necessary sulfur content. After entering the sulfur-containing wire for 2 ... 3 minutes, a soft inert gas is blown, after which the ladle with liquid metal is transferred to the casting, during which samples are taken to determine the chemical composition of the metal and non-metallic inclusions. According to this technology, 20 treatments were performed. At all heats, the specified sulfur content in the metal was achieved, the amount of nonmetallic inclusions amounted to an average of 0.012%, the metal was cast without comment, the technological cutoff was 1.2 kg / t, the scrap was 0.005 t / t.

On the same electric arc furnace 10 melts of steel were smelted according to the prototype method. Liquid steel was poured into a ladle and deoxidized with aluminum. During the smelting and production of metal, special technological operations are carried out (slag cut-off, additive of a refining slag mixture with a flow rate of 5.0 kg / t, etc.), which provide a sulfur content in the metal of 0.015% and lower. Then, the ladle with liquid metal is transferred to the out-of-furnace steel processing unit, where an averaging purge is performed, a sample is taken and the chemical analysis of the steel is determined. In the case of obtaining the required sulfur and aluminum content, a calcium-containing wire with a flow rate of 220 m is introduced into the bucket. After entering the second portion of the calcium-containing flux-cored wire, an inert gas is blown for 2 ... 3 minutes, and then a sulfur-containing flux-cored wire is introduced into the bucket to ensure the required content sulfur. After entering the calcium-containing flux-cored wire for 2 ... 3 minutes, a soft inert gas is blown, and then a sulfur-containing flux-cored wire is introduced into the bucket to ensure the required sulfur content. After entering the sulfur-containing wire for 2 ... 3 minutes, a soft inert gas is blown, after which the ladle with liquid metal is transferred to the casting, during which samples are taken to determine the chemical composition of the metal and non-metallic inclusions. On comparative melts, the specified sulfur content in the metal was achieved, however, the amount of non-metallic inclusions averaged 0.042%, 10% of the metal could not be poured due to sticking of the holes of steel pouring glasses with non-metallic inclusions, the technological cut-off was 12.5 kg / t, scrap - 0.025 t / t, the cost of processing the prototype method was 5.2 US dollars higher than the claimed method.

Information sources

1. FR 2542761 A, 1984.

2. BY 6064 C1, C 21 C 7/04, 12/30/2004.

Claims (1)

A method for the production of steel with a normalized sulfur content, including out-of-furnace treatment with aluminum deoxidized and desulfurized to a sulfur content of 0.025% and below, liquid steel, first calcium-containing and then sulfur-containing flux-cored wires, characterized in that the calcium-containing wire is introduced in two stages, with 20 being introduced in the first stage ... 40% of the total amount of calcium needed for steel modification, in the second stage, the remaining 60 ... 80% of calcium is planted, and between the stages of the input of the calcium-containing wire, ny degassing the liquid metal.