SU863662A1 - Steel deoxidizer - Google Patents

Description

(54) STEEL REFLECTOR

one

This invention relates to ferrous metallurgy, in particular to mixtures of steel deoxidation.

There is a known method of steel deoxidation with solid carbon by blowing metal with powdered carbonizers in a carrier gas stream. This method reduces the oxygen content in the metal before the final sedimentation by deoxidation of Cll

However, as a rule, deoxidation is accompanied by uncontrolled carburization of steel. The disadvantages of the process are also severe restrictions on the fractional composition of nopovuKa, the load of the gas-powder jet, the depth of the tuyere. the particles, not having time to dissolve in the metal, slag the foam, and the small particles are removed from the bath by reverse gas flows. Powder delivery systems are complex and unstable. All this limits the use of powdered carbonitizers in steelmaking.

It is known to use for the treatment of steel flux-ferroalloy briquettes, content, wt.%:

65% ferrosilicon25 Fluorspar o50 Known to K25

using sulfide-alcohol stillage as bbc. Flux-ferroalloy briquettes are effective in processing high-quality calm steels, in particular, when

10 to treat them to reduce the sulfur content of C2.

However, this does not achieve mixing and uniform degassing of the metal, since the briquette with

15 interaction with the metal does not form a gas phase of reducing nature. The use of this briquette for the treatment of calm, boiling and semi-quiet steel steels

20 is not economically feasible.

There is also known a method for treating steel with a monolithic carbonaceous material, which is forcibly introduced into a metal bath and the necessary time is kept there, causing boiling, deoxidation and degassing of the metal. Monolithic carbon block is prepared from 80% coke and 20% binder - coal

30 pes FDD.

The disadvantage of this carbonaceous deoxidizer is that with low initial oxygen content in the metal, for example, in high-carbonaceous or silicon-deoxidized steel, deoxidation is accompanied by carburization from the very beginning of the treatment, which is undesirable, since it is possible that the carbon analysis is not relevant. The reason for such a course of the process is that with a low initial boiling intensity, the stability of the gas interlayer around the monolithic carbon deoxidizer decreases, the contact of the metal with solid carbon improves, and carbonization of the steel occurs. At the same time, the mixing intensity is low and the mass transfer of oxygen from the bath volume to the reaction zone is not sufficiently effective. In addition, the high thermal conductivity of graphite and carbon electrodes, when used as a steel deoxidizer, delays the onset of the reaction because of the freezing of the metal-slag crust on its surface, which increases the processing time.

The purpose of the invention is to increase the efficiency of deoxidation and reduce the degree of metal carburization.

The goal is achieved by the fact that coke and coal tar pitch are additionally added to the deoxidizer, with the following ratio of components, wt%:

Coke .40-75

Known to 10-30

Coal

peck15-30

The process of interaction of a liquid metal with a deoxidizing agent can be represented as follows:

{SO}.

(V)

SO GO

Ссз {sow

+ +

Sooa

(2) L-TB + {c 03} (3)

uijT-g

CaCOi

2 {СО} () + 2С

The carbon dioxide produced as a result of reactions (2) and (3) is regenerated by solid carbon heated to the temperature of the liquid steel, with the gas volume doubling. Therefore, even with a low intensity of carbon oxidation reactions (1) and (2), monolithic Carbon is shielded from the metal, effective mixing of the bath and oxygen transfer to the reaction zone. The driving force of the deoxidizing agent, as in the well-known method, where the scheme of interaction of deoxidizing agents with metal is represented only by reactions (1), (2) and (4), depends on the difference in partial pressures CO, equilibrium with metal and solid carbon.

To maintain a high motive force of the deoxidation process, it is necessary to ensure the fullest possible regeneration of CO, and this at liquid steel temperatures depends only on the arrival of CO / by reaction (41, i.e., the content of lime in the deoxidation material and the kinetics of the regeneration process.

In determining the optimal amount of limestone for processing in a deoxidizing material, the effectiveness criterion is the following condition: the partial pressure of CO in the gas phase of bubbles leaving the metal must be lower or lower.

5, at least, not higher than the CO pressure, determined by the equilibrium reaction (1) and (2).

When the content of lime in the carbonaceous deoxidizer is less than 10%

0, when processing high-carbon steel or only silicon-deoxidized steel, carbonization of the metal occurs, since the gas evolved by the reaction (4) is insufficient for

5 sustainable shielding of the carbon block throughout the entire processing time.

With lime content in a deoxidizing composition, it is more than 30%;

0 the formation of CO, j, by the reaction (G) is greater than the rate of its regeneration by solid carbon by the reaction (.4), and in the rise of cix in the metal of the bubbles, the amount of CO,

5 which significantly impairs deoxidation 4 I.

In addition, when the content of a yeast as part of a deoxidizing agent is more than 30%, the mechanical strength of sintered blocks is significantly reduced.

Coal pitch is used as a binder, as well as an active component of a deoxidizing agent. AT . Depending on the flow rate of the pitch, the physical and mechanical properties of the material, the porosity, the mechanical strength, etc., and the carbon residue resulting from the thermal decomposition of the pitch,

g participates in metal deoxidation reactions and regeneration of carbon dioxide emitted from limestone.

The content in the deoxidizing coal tar pitch 15-30%

It is associated with the preparation of burned deoxidizing units with certain physical and mechanical properties. When the content of coal tar pitch in the mixture is less than 15%, the annealed blocks have low mechanical strength, low heat resistance and are unsuitable for steel processing. When blocks are fired, a large amount of gas is released from the charge containing more than 30% of the coal-black coal;

the physicomechanical properties of the finished products deteriorate, the firing process is unreasonably delayed.

It is advisable to use a deoxidizing agent when treating high-carbon, non-oxidized or low-carbon, deoxidized only with silicon, steel.

Example. The carbonaceous deoxidizing units are prepared from a mixture of coke powders and limestone on a coal tar pitch bond. The material composition of the proposed deoxidizers is given in the table. The blocks are fired in detachable metal forms.

Heat treatment of the blocks is completed at temperatures of 600,650 ° C with an exposure of 1 hour.

The experiments were carried out in the processing of steel in an induction furnace ISP-006 with the main lining. The melting weight is in the range of 40-50 kg and the depth of the metal bath is from 250 to 300 mm.

Steel is treated with carbon blocks fixed in a quartz tube. The diameter of the working part of the blocks is in the range from 20 to 35 mm, height from 25 to 40 mm. The blocks are introduced into the metal throughout the depth of the bath. Excreted

from the bath, gases are captured using a refractory bell immersed for 10–15 mm in metal and the CO / j content is determined on an ORS gas analyzer. Processing of steel blocks of each type duplicate 5-6 times.

For comparison, a monolithic carbon block consisting of 80% coke and 20% Carboniferous pitch was tested as a deoxidizing agent.

As can be seen from the results given in the table, when processing steel with blocks of pure carbonaceous boiling charge, and, consequently, deoxidation of the metal ends on average after 21 s (from 15 to 25 s) and

5 is accompanied by a carbonization average of. When processing the deoxidizing units proposed, the compositions of them are removed from the bath after 30 s with continued boiling

0 metal. The carbon content in the steel per treatment is practically unchanged, and the efficiency of deoxidation increases.

Thus, the proposed solvent makes it possible to increase the efficiency of the deoxidizing agent and to reduce the degree of carbonization of the steel.

Claims (1)

Claim The deoxidizer for steel, including coke and coal tar pitch, 5, characterized in that, in order to increase the efficiency of p'oxidation and reduce the degree of carburization of steel, it additionally contains limestone in the following ratio of components, wt.%: 6C Coke 40-75 VNIIIPI Order 7705/40 Branch of PPP Patent, Limestone 10-30 Coal tar pitch 15-30