RU2245390C1 - Material for steel refining - Google Patents

Abstract

FIELD: iron metallurgy, in particular steel smelting industry.

SUBSTANCE: claimed material contains (mass %): viterite concentrate 40-42; aluminum 38-40; lime 5-12; magnesium 6-8; titanium 1-2. Invention allows increasing the refining ability of material due to modification low valence sulfur and phosphorus compounds in metal melt.

EFFECT: steel of improved quality.

1 tbl, 1 ex

Description

The invention relates to the field of ferrous metallurgy and can be used in steelmaking.

A complex modifier is known (USSR AS No. 1382868, class C 22 C 35/00, published March 23, 1988) containing niobium, zirconium, vanadium, boron, calcium, aluminum, silicon, titanium, manganese, and rare earths metals, molybdenum, nitrogen and iron in the following ratio of components, wt.%:

Niobium 7-20

Zirconium 8-15

Vanadium 5-15

Boron 0.1-0.3

Calcium 0.8-10

Aluminum 1-10

Silicon 7-10

Titanium 1-5

Manganese 15-25

Rare earth metals 6-12

Molybdenum 2-20

Nitrogen 0.5-2

Iron The rest.

The presence of silicon in the known complex modifier prevents the modification of low-valent sulfur and phosphorus compounds, which leads to a deterioration in the quality of steel. The content in the complex modifier of active elements - calcium and rare earth metals in an amount twice as high as the content of less active elements - deoxidizers (aluminum and silicon), leads to the formation of refractory difficult to remove oxides of rare earth elements during metal processing, which affects the quality of the finished steel due to the increased its pollution.

The closest analogue of the claimed invention is a briquette for the deoxidation of steel and cast iron (RF Patent No. 2023044, class C 22 C 35/00, publ. 11/15/1994), containing barium-containing material in the form of witeritstrontianite concentrate, calcined at 1200-1250 K , aluminum powder, 65% ferrosilicon and fluorspar in the following ratio of components, wt.%:

The firing product of Witeritstrontianite concentrate 53-55

Aluminum Powder 7-12

65% Ferrosilicon Powder 29-32

Fluorspar 2-3

Binder 2-4

Signs of the closest analogue, coinciding with the essential features of the claimed invention: the presence in the composition of the material for refining steel barium-containing concentrate and aluminum.

The presence of ferrosilicon in the composition of the known briquette for steel and cast iron hindering the modification of low-valent sulfur and phosphorus compounds in the metal melt, which leads to an increased content of sulfur and phosphorus in the finished steel and impairs the quality of the steel. In addition, as a result of the metallothermic reaction of barium and strontium reduction, strong BaSi ₂ and SrSi ₂ silicides are formed, which leads to a decrease in the activity of barium and strontium elements, which have a high affinity for sulfur and phosphorus. As a result, adverse conditions are created to ensure desulfurization and dephosphorization, and the use of the known briquette is reduced only to the deoxidation of steel with the formation of hard to remove calcium silicates and various aluminous inclusions from corundum to herzenite. This leads to contamination of the steel with non-metallic inclusions and a deterioration in its quality.

The basis of the invention is the task of improving the material for the refinement of steel, providing the conditions of reductive dephosphorization and desulfurization by optimizing the qualitative and quantitative compositions.

The expected technical result is an increase in the refining ability of the material due to the modification of low-valent sulfur and phosphorus compounds in the metal melt, which improves the quality of the steel.

The technical result is achieved in that the material for refining steel containing barium-containing concentrate and aluminum, according to the invention additionally contains magnesium, titanium and lime, and as barium-containing concentrate contains viterite concentrate in the following ratio, wt.%:

Viterite concentrate 40-42

Aluminum 38-40

Lime 5-12

Magnesium 6-8

Titanium 1-2

In the process of steel refining, the proposed material creates conditions for the modification of low-valent sulfur and phosphorus compounds in the melt. This effect is achieved by the fact that the composition of the material is selected in such a way that the amount of aluminum in the proposed material significantly exceeds the amount of the highly active element - magnesium, so the activity of aluminum is higher than the activity of magnesium and the deoxidation of steel occurs mainly due to aluminum. And part of the magnesium metal not spent on deoxidation is aimed at restoring barium, which is part of the witerite concentrate, according to the total reaction:

Moreover, when a significant part of the oxygen in the metal is bound to aluminum, conditions are created for the reductive dephosphorization of the metal, accompanied by intense desulfurization by reactions:

Reactions (2) - (5) are due to the high affinity of the Ba and Ti elements for phosphorus, which under the conditions of deoxidation of the metal (P _O2 ≤ 1.0 · 10 ^-15 atm) form phosphides well removed from the metal. With high deoxidation, reactions (6) and (7) also occur with the formation of magnesium sulfides.

With the formation of sulfide and phosphide compounds of magnesium, barium and titanium, the contamination of steel with non-metallic inclusions decreases as a result of the assimilation of these sulfides and phosphides by integumentary slag. Absorption of sulphides by integumentary slag is due to the high temperature of the metal during its processing, which ensures high sulfur absorption capacity of the slag. Phosphides, such as barium, due to its negligible solubility in liquid steel, simply cannot exist in the volume of liquid metal and are also absorbed together with titanium phosphides by slag.

The choice of boundary limits for the content of components in the proposed material is due to the following.

The content of viterite concentrate in an amount of 40-42 wt.% Provides, after the reduction of barium from it, a deep reducing dephosphorization process is carried out with the formation of low-valent barium phosphides easily removed from the liquid metal. The content of viterite concentrate in the material for refining steel in an amount of less than 40 wt.% Does not provide barium sufficient for deep dephosphorization to enter the melt, and an increase in the content of viterite concentrate of more than 42 wt.% Is impractical due to its irrational use and deterioration of the conditions of barium magnetothermal reduction, leading to its low recovery, contamination of the metal of the viterite concentrate unreacted with magnesium, which leads to a worsening of the conditions of reductive phosphorus ation, reducing metal refining rates from sulfur and oxygen and deterioration of the steel.

The presence in the composition of the material for refining lime steel in an amount of 5-12 wt.% Due to the need to bind formed in the process of deoxidation of metal alumina inclusions and remove them into the slag. The content of lime in an amount of less than 5 wt.% Does not provide complete binding of aluminous inclusions to easily removable globules, and the content of more than 12 wt.% Of lime worsens the conditions of reductive dephosphorization and desulfurization due to a decrease in the activity of barium, titanium and magnesium. In addition, the presence of lime regulates the thermality of the mixture during the exothermic reaction of barium reduction.

Aluminum in the proposed material in an amount of 38-40 wt.% Is used as the main deoxidizer and passivator of more active elements - magnesium and reduced barium, reducing their activity with respect to oxygen and thereby providing conditions for reductive dephosphorization and desulfurization. A decrease in the aluminum content to less than 38% does not provide a deep deoxidation of the metal, leads to irrational consumption of magnesium for deoxidation of the metal, a decrease in the degree of barium reduction, a decrease in the depth of reductive dephosphorization, and a decrease in the desulfurization indices, which leads to a deterioration in the quality of the metal. Increasing the aluminum content to values above 40 wt.% Is also impractical due to its irrational consumption, the possibility of increasing aluminum oxides in the metal that are not associated with CaO, which leads to a deterioration in the quality of the metal.

Magnesium, which is part of the material for refining steel in an amount of 6-8 wt.%, Is used to restore barium from a viterite concentrate and modify the manganese and iron sulfides formed in the metal. A decrease in the magnesium content in the material for steel refining to values below 6 wt.% Does not ensure the recovery of the amount of barium from the viterite concentrate sufficient for deep reduction dephosphorization, and an increase in the magnesium content of more than 8 wt.% Leads to irrational consumption of magnesium and an increase in the metal content magnesium oxides formed as a result of metal deoxidation and worsening conditions of reductive dephosphorization, which leads to deterioration in the quality of steel.

Titanium, which is part of the material for steel refining in an amount of 1-2%, has a high affinity for phosphorus and, under conditions of a deoxidized metal (P _О2 ≤ 1.0 · 10 ^-15 atm), forms easily removable titanium phosphides. Its content in the material for refining steel in an amount of less than 1 wt.% Does not ensure the completeness of reductive dephosphorization, and the content of more than 2 wt.% Limits the use of the material for refining steel with titanium-containing steels.

Example.

The proposed material for steel refining was made as follows.

An alloy was made from aluminum, magnesium and titanium by alloying the corresponding components in a steelmaking unit, followed by spraying the melt into granules with a fraction of 0.1-1.5 mm. The obtained alloy granules were mixed with the remaining components of the material — viterite concentrate and lime. Viterite concentrate contains 82% of BaCO ₃ , the rest is other impurities.

The processing of liquid metal (steel grade 3sp) was carried out with a material for refining steel of the proposed composition and a well-known briquette - the closest analogue for the deoxidation of steel and cast iron.

Material for steel refining was introduced into the volume of liquid metal, and after processing, samples were taken and analyzed for sulfur and phosphorus. By the content of sulfur and phosphorus before and after processing the metal with the proposed material, the degree of dephosphorization and desulfurization was determined.

Processing of steel with a known briquette for deoxidizing steel and cast iron was carried out by feeding briquettes to a metal mirror, after which metal samples were also taken, analyzed for sulfur and phosphorus, and the degree of dephosphorization and desulfurization was determined.

The compositions of the materials used and indicators of the degree of dephosphorization and desulfurization are presented in the table (No. 1-5 - the proposed material, No. 6 - the known briquette - the closest analogue).

The above results show that when using the proposed material for steel refining, two processes were simultaneously carried out - dephosphorization and desulfurization, and the numerical indicators of these processes indicate a high degree of each of them. This is explained by the creation of conditions favorable for reductive dephosphorization, which is also accompanied by desulfurization, i.e. The process of modifying low-valent sulfur and phosphorus compounds is underway.

When using the known briquette for the deoxidation of steel and cast iron, the degree of dephosphorization is noticeably lower, and there is no desulfurization. This is due to the fact that the presence of barite and strontium viterite concentrate in the form of strong BaSi ₂ and SrSi ₂ silicides recovered from the calcination product in the metal does not provide conditions for reductive dephosphorization, and a part of the phosphorus removed from the metal is in the form of barium phosphates. The barium and strontium silicides formed as a result of the aluminum and silicothermic reaction, being strong compounds, reduce the activity of barium and strontium with respect to phosphorus; therefore, dephosphorization occurs under oxidizing conditions, its degree is low, and there is no desulfurization under oxidative conditions.

Table No. The content of components, wt.%: The degree of dephosphorization,% Power
desulfurization,% Viterite concentrate Lime Aluminum Magnesium Titanium 1 42.0 5,0 38,0 6.0 1,0 85.0 65.0 2 40,0 8.0 39.0 7.0 1,5 83.0 63.0 3 41.0 12.0 40,0 8.0 2.0 87.0 60.0 4 42.0 8.0 39.0 7.0 1.4 84.0 61.0 5 40,0 12.0 40,0 8.0 2.0 85.0 64.0 6 *) - - 10.0 - - 12.0 - *) The briquette for deoxidation and modification of steel and cast iron additionally contains, wt.%: The product of firing of witeritstrontianite concentrate - 54; powder of 65% ferrosilicon - 30; fluorspar - 3; binder - 3.

Claims (1)

Material for steel refining, containing barium-containing concentrate and aluminum, characterized in that it additionally contains magnesium, titanium and lime, and as barium-containing concentrate contains viterite concentrate in the following ratio, wt.%: Viterite concentrate 40-42 Aluminum 38-40 Lime 5-12 Magnesium 6-8 Titanium 1-2