RU2334796C1 - Method of steel production - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to iron and steel industry, particularly to production of boron containing steel. The invention includes melting of steel in a converter, its oxidation, out-of-furnace treatment of steel, adding of ferroboron and blasting with argon through bottom tuyers during out-of-furnace treatment of steel. Out-of-furnace treatment of steel is performed on the assembly "furnace-ladle". Then a balancing blasting of steel with argon is performed and contents of boron and manganese in steel are evaluated. Desulphurisation of steel is carried out in the ladle. Further the thickness of slag is measured. Ferroboron is added simultaneously with blasting of steel with argon. Consumption of ferroboron is determined depending on contents of manganese and boron in metal, on requirements to contents of boron in metal, on thickness of slag in the ladle, and on contents of boron in ferroboron. The method allows to achieve required contents of boron in steel.

EFFECT: achieving required contents of boron in steel.

1 ex

Description

The invention relates to the field of ferrous metallurgy, and specifically to the production of boron-containing steel.

Known methods for the production of boron-containing steel, with the introduction of boron-containing additives in the steelmaking unit or steel ladle in the form of complex alloys or ferroboron (Boron, calcium, niobium and zirconium in cast iron and steel, M., "Engineering", 1961, S. 15- 19).

A disadvantage of the known methods is the introduction of expensive deoxidizers in the form of a boron-containing alloy and ferroboron into the furnace and at the outlet will lead to unstable assimilation of boron-containing additives, anisotropy of properties, sorting of finished products by mechanical properties (hardenability).

The closest analogue of the claimed invention is a method for the production of steel, including the smelting of the intermediate in the converter, deoxidation, alloying, introduction of nitride-forming elements, refining with synthetic slag in the ladle during the smelting process and the metal is blown with an inert gas, boron-containing additives are added to the ladle during the purge process after reduction the content of iron oxide in the slag up to 0.2-2.0 wt.% (USSR No. 918314, IPC С21С 7/00, publ. 07.04.1982).

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

Steel, obtained in a known manner, has insufficient yield suitable for mechanical properties (hardenability), the implementation of the method leads to an increase in the cost of steel.

Found in the known method, the technological method of introducing expensive deoxidizers at the outlet will lead to unstable assimilation of them, uneven distribution over the volume of the bucket, anisotropy of properties, decrease in yield by mechanical properties, and the use of silicocalcium and silico-zirconium cannot be applied in the production of low-silicon steels.

At the same time, the addition of boron-containing additives when the content of iron oxides is in the range of 0.5-2.0% will lead to unstable burning of boron-containing additives, and the sorting of finished products by mechanical properties.

In addition, refining with synthetic slag at the outlet, conducting chemical analysis of ladle slag to determine the iron oxide content and the use of strong nitride-forming elements that contribute to the formation of non-metallic inclusions in the metal, which are very difficult to remove during out-of-furnace treatment when blowing through an argon lance even when it is in a different position , involves the use of additional equipment for the manufacture of synthetic slag, time for chemical analysis of slag ka, as well as the additional costs of crane time for tilting the ladle slag.

The basis of the invention is the task of improving the method of steel production, by changing the technology of out-of-furnace treatment, in particular the introduction of boron.

The expected technical result is the receipt of the required boron content in the metal, the formation of non-metallic inclusions in the metal, which are easily removed during the out-of-furnace treatment, the improvement of the quality of steel and the increase of the yield by mechanical properties.

The technical result is achieved by the fact that in the method of steel production, including steelmaking in the converter, its deoxidation, out-of-furnace treatment of steel, addition of ferroboron and argon purging through bottom tuyeres during out-of-furnace treatment of steel, according to the invention, out-of-furnace processing of steel is carried out on a ladle furnace then an averaging of steel by argon is carried out and the content of boron and manganese in the steel is determined, steel is desulphurized in the ladle, after which slag thickness is measured, and the ferroboron additive is carried out together with the steel purge with argon with a flow rate determined from the ratio:

P _fb = (4.2 + 38.7 × Mn _ost -30500 × V _ost + 9600 × V _goth + 0.04 × h _sp ) × 100 / V _fb ,

where R _fb - the consumption of ferroboron, kg,

Mn _ost - the manganese content in the metal before entering the ferroboron,%,

In the _rest - the boron content in the metal before entering the ferroboron,%,

In _goth - the required boron content in steel,%,

h _sl - the thickness of the slag in the bucket, mm,

In _fb - boron content in ferroboron,%.

The essence of the proposed technical solution is to determine the flow rate of ferroboron to obtain the required boron content in steel in the form of a solid solution, which provides the required level of mechanical properties of steel.

Calculation of the consumption of ferroboron depending on the manganese content in the steel and slag thickness in the steel pouring ladle makes it possible to obtain the required boron content in the steel, to form non-metallic inclusions in the metal that are easily removed during out-of-furnace treatment, and increase the yield by mechanical properties.

The hardenability of carbon steels increases significantly with alloying with manganese, to a lesser extent with alloying of chromium and silicon. The hardenability of steel is greatly influenced by the simultaneous addition of several alloying elements with a small amount of each than the addition of one alloying element, but in large quantities.

The addition of a regulated amount of boron can reduce the surface energy of austenite grains and increase the stability of supercooled austenite in the supermartensitic temperature region, which makes it possible to obtain the required level of hardenability of steel.

This method is illustrated by the following example.

Steel grade 08YUR was smelted in a 370-ton oxygen converter. During the production of smelting, 3 tons of lime, 0.6 tons of fluorspar, 0.6 tons of secondary aluminum AB 87, 1.4 tons of ferromanganese FMN78 were added to a ladle equipped with tuyeres for bottom purging.

Out-of-furnace melting processing was carried out at the ladle furnace.

After averaging with argon, a metal sample was taken, which was analyzed by the spectral method. The metal contained: carbon 0.06%, manganese 0.29%, sulfur 0.028%, phosphorus 0.014%, chromium 0.03%, nickel 0.04%, copper 0.06%, boron 0.0004%.

Then, aluminum wire rod, lime, fluorspar were added to the metal, the metal was desulfurized and the slag thickness in the ladle was measured, which was 200 mm.

After that, the required amount of ferroboron FB20 containing 20% boron was calculated to obtain a boron content of 0.003% in steel according to the formula

P _fb = (4.2 + 38.7 × 0.29-30500 × 0.0004 + 9600 × 0.003 + 0.04 × 200) × 100/20, which amounted to 200 kg.

After adding the required amount of ferroboron and carrying out an averaging purge, the melt was transferred to a continuous casting machine.

Continuous casting of steel was carried out on four streams into slabs with a cross section of 1340 × 250 × 8000 mm and 1310 × 250 × 9100 mm. 360.8 tons of slabs containing 0.06% carbon, 0.02% silicon, 0.33% manganese, 0.016% phosphorus, 0.012% sulfur, 0.018% chromium, 0.03% nickel, 0.04% copper were cast 0.07% aluminum, 0.003% boron, 0.004% nitrogen.

With this method of steel production, the required boron content in the finished steel is obtained, the content of non-metallic inclusions is reduced, the yield by mechanical properties is increased, production and profit are increased.

Claims (1)

A method of steel production, including steel smelting in a converter, its deoxidation, out-of-furnace steel processing, ferro-boron addition and argon purging through bottom tuyeres during out-of-furnace steel processing, characterized in that out-of-furnace steel processing is performed on a ladle furnace, then an averaging is carried out the steel is purged with argon and the content of boron and manganese in the steel is determined, steel is desulphurized in the ladle, after which the slag thickness is measured, and the ferroboron is added together with the steel is purged with argon with the flow rate determined from the ratio P _fb = (4.2 + 38.7-Mn _ost -30500 · V _ost + 9600 · V _goth + 0.04 · _hl ) · 100 / V _fb , where R _fb - consumption of ferroboron, kg; Mn _ost - the manganese content in the metal before entering the ferroboron,%; In the _rest - the boron content in the metal before entering the ferroboron,%; In _goth - the required boron content in steel,%; h _sl - the thickness of the slag in the bucket, mm; In _fb - boron content in ferroboron,%.