RU2243268C1 - Method of melting niobium-containing steel - Google Patents

Abstract

FIELD: ferrous metallurgy; making low-carbon steels by means of vacuum oxidizing refining units.

SUBSTANCE: proposed method includes loading the charge containing carbon and manganese, melting, heating the metal in steel-making unit and oxidation refining at top blowing with oxygen and evacuation. Niobium-containing ferroalloy is introduced into metal after evacuation in form on niobium-containing powder wire at the following relationship: Q_p.w.Nb=100xQ_st x(0.288-0.018x(Mn)-10.178x(C)+8.989x[Nb]_req./[Nb]_p.w., where Q_p.w.Nb is consumption of powder wire ferroniobium filler (by filler), kg; Q_st is mass of molten steel, t: (Mn), (C) content of manganese and carbon in sample of metal before introduction of powder wire with ferroniobium, %; [Nb]_req. is required content of niobium in steel, %; [Nb]_p.w. is content of niobium in powder wire, %.

EFFECT: increased yield of good material; enhanced stability of steel teeming ladles.

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Description

The invention relates to ferrous metallurgy, specifically to methods for producing low carbon steels using vacuum oxidative refining plants, and can be used in steelmaking shops of metallurgical plants.

A known method of smelting stainless steel, including filling a charge containing carbon and silicon, melting, heating the metal in a furnace and its subsequent oxidative refining under vacuum with oxygen purging from above and argon from below (Cremisio RS Hornaker RW Vakuum duplexing-frech lauk at existing melting techniques. J. Vac. Sci and Technol, 1972, 9, No. 6, p. 1306-1314).

The disadvantages of this method include the use of waste niobium in the mixture. Niobium has a high affinity for oxygen, and therefore, during purging with oxygen, niobium will oxidize, which will lead to the non-receipt of the required niobium content, its overuse, increase the cost of steel, reduce yield.

The closest analogue of the claimed invention is a method of smelting niobium-containing stainless steel, including filling a charge containing carbon and manganese, melting, heating the metal in a furnace and its subsequent oxidative refining under vacuum with oxygen purging from above and argon from below, niobium-doped wastes are introduced into the metal charge , with the ratio of the contents of carbon, niobium and silicon in the metal charge (1-3) :( 17-19) :( 7-11), and the metal is heated in the furnace to 1750-1820 ° C, and the vacuum oxidizing refining is carried out at a ratio of oxygen and argon consumption 13-40 (see the description of the AS of the USSR No. 945184, С 21 С 5/52, publ. 23.07.82 Bulletin No. 27).

Signs of the closest analogue that coincide with the essential features of the claimed invention: filling a charge containing carbon and manganese, melting, heating the metal in a steelmaking unit and its subsequent oxidative refining with an oxygen purge from above, evacuation.

The known method does not provide the desired technical result for the following reasons.

Found in the known method, the technological method of reducing niobium fumes due to the introduction of 45% ferrosilicon into the filling will lead to a rise in the cost of the steelmaking process.

In addition, the oxidation of silicon will cause an increase in the amount of slag with a low basicity, a decrease in the resistance of the steelmaking unit, and the need for lime additives to neutralize silicon oxides in the slag.

At the same time, evacuation at a residual pressure in the chamber of 10 mm Hg It does not allow to fully degass the metal, which leads to an increase in the burning of niobium.

The basis of the invention is the task of improving the method of steelmaking, in which by choosing the optimal oxidation of the metal, achieved by deep vacuum processing, to obtain the required niobium content, at the lowest cost, to increase the yield.

The problem is solved in that in the method of smelting niobium-containing steel, including filling a charge containing carbon and manganese, melting, heating the metal in a steel-smelting unit and its subsequent oxidative refining with oxygen blowing from above, evacuation, a niobium-containing ferroalloy is introduced into the metal after evacuation in the form of cored wire ratio Qpp _Nb = 100 · Q _v · (0,288-0,018 · [Mn] -10,178 · [ C] + 8,989 · [Nb] _treb) / [Nb] _nn

where - Qpp _Nb is the consumption of flux-cored wire with a filler of ferroniobium (for filler), kg;

Q _article - the mass of liquid steel, t;

[Mn], [C] -containment of manganese and carbon in a metal sample before introducing a flux-cored wire with ferroniobium,%;

[Nb] _req - required niobium content in steel,%;

[Nb] _pp - the content of niobium in the cored wire,%;

100; 0.288; 0.018; 10.178; 8,989 - empirical coefficients obtained experimentally.

The essence of the proposed technical solution is to introduce niobium-containing ferroalloys into the metal in the form of niobium-containing flux-cored wire after deoxidation of the metal in the ladle with manganese and vacuum.

The choice of residual pressure and processing time allows the necessary degassing, to obtain the required oxidation of the metal and the niobium content in the finished steel.

This method is illustrated by the following example.

Smelted steel grade 08ps in accordance with GOST 9045-93. 317.5 tons of molten iron containing 4.2% carbon, 0.47% silicon, 0.20% manganese, 0.013% sulfur, 0.046% phosphorus were poured into an oxygen converter; 20 tons of solid pig iron and 62 tons of scrap metal were heaped up from trimmed sheet metal.

The melting was purged in a 370-t oxygen converter. During the production of smelting, 513 kg of ferromanganese FMN70 was added to the ladle. The metal after release from the converter contained 0.04% carbon, 0.10% manganese, 0.009% sulfur, 0.005% phosphorus, 0.01% chromium, 0.02% nickel and 0.02% copper.

Next, the metal was subjected to vacuum in a circulating mode. The metal was subjected to vacuum decarburization for 35 minutes. The residual vacuum at the end of the evacuation was 0.12 mm Hg.

After averaging, 470 kg of aluminum wire was introduced into the metal.

After that, the metal contained 0.006% carbon, 0.11% manganese, 0.008% sulfur, 0.006% phosphorus, 0.01% chromium, 0.02% nickel, 0.02% copper and 0.009% aluminum. Then 280 kg of aluminum and a flux-cored wire filled with ferroniobium containing 65.4% niobium were introduced into the metal to obtain 0.07% niobium in steel. The flux-cored wire consumption was determined from the expression Qpp _Nb = 100 · 359.6 · (0.288-0.018 · 0.11-10.178 · 0.006 + 8.989 · 0.07) / 65.4 = 470 kg.

The finished steel contained 0.006% carbon, 0.12% manganese, 0.007% sulfur, 0.009% phosphorus, 0.01% chromium, 0.02% nickel, 0.02% copper, 0.04% aluminum, and 0.07% niobium.

With this method of production of niobium-containing steels, the required niobium content is obtained at the lowest cost, the yield is increased, the durability of steel casting ladles, the volume of production and profit from sales of products increase.

Claims (1)

A method of smelting niobium-containing steel, including filling a charge containing carbon and manganese, melting, heating the metal in a steelmaking unit and its subsequent oxidative refining with oxygen purging from above, evacuation, introducing a niobium-containing ferroalloy, characterized in that the niobium-containing ferroalloy is introduced into the metal into a metal after vacuum alloying niobium-containing cored wire from the ratio Qpp _Nb = 100 · Q _st · (0.288-0.018 · [Mn] -10.178 · [C] + 8.989 · [Nb] _req / [Nb] _pp, where Qpp _Nb is the consumption of flux-cored wire with a filler of ferroniobium (for filler), kg; Q _article - the mass of liquid steel, t; [Mn], [C] - the content of manganese and carbon in the metal sample before entering the flux-cored wire with ferroniobium,%; [Nb] _req - required niobium content in steel,%; [Nb] _pp - the content of niobium in the cored wire,%; 100; 0.288; 0.018; 10.178; 8,989 - empirical coefficients obtained experimentally.