RU2228384C1 - Steel modifier - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: invention provides aluminum-based modifier containing 10-15% magnesium, 12-15% calcium, and 8-10% barium the form of dense granules fraction 1.0-1.5 mm. Modifier allows regulated deoxidation first mainly by aluminum and then by high-active elements. EFFECT: intensified desulfurization and increased modifying activity with respect to sulfides, nitrides, and silicates resulting in higher steel quality. 2 tbl

Description

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

Known modifier for steel (a. S. USSR No. 1216235, class C 22 C 35/00, publ. 03/07/1986) containing silicon, manganese, aluminum, carbon, boron, molybdenum, titanium and iron in the following ratio components, wt.%:

Silicon 1.0-9.0

Manganese 0.5-2.0

Aluminum 2.0-5.0

Carbon 2.5-4.5

Boron 0.2-0.7

Molybdenum 0.1-0.4

Titanium 3.0-18.0

Iron Else

The presence in the known modifier in significant quantities of silicon, carbon, boron and titanium limits the use of this modifier, for example, in the production of low-silicon steel grades, as well as steels that do not contain boron and titanium. The content of boron in an amount of 0.2-0.7 wt.% Leads to a deterioration in the quality of the steel if the degree of assimilation of boron from the modifier exceeds 15%, and brittle hard-to-remove silicates formed as a result of silicon deoxidation reduce the possibility of deep metal desulfurization and lead to deterioration quality steel.

In addition, the modifying effect of boron and titanium is effective only with respect to nitrides, and titanium to a small extent with respect to oxides, therefore, the contamination of steel with non-metallic inclusions when using the known modifier is significant, which leads to a deterioration in the quality of steel.

The closest analogue of the claimed invention is a complex modifier (a.s. USSR No. 1382868, class C 22 C 35/00, publ. March 23, 1988) containing niobium, zirconium, vanadium, boron, calcium, aluminum, silicon, titanium, manganese, rare earth 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 Else

Signs of the closest analogue, coinciding with the essential features of the claimed invention: the presence of calcium and aluminum in the modifier.

The well-known complex modifier is intended for a limited range of steels containing reinforcing additives - niobium, molybdenum, vanadium, boron, titanium, nitrogen, and cannot be used also for high-strength structural, but low-silicon or economically alloyed steel grades, i.e. not containing, for example, niobium, zirconium, molybdenum. The presence in the known complex modifier of silicon in an amount of 7-10 wt.% Worsens the conditions of metal desulfurization due to the formation of silicates in its volume, as well as the presence of residual silicon. The content in the complex modifier of active elements - calcium and rare-earth metals in an amount twice that of aluminum and silicon, i.e. elements having a significantly lower affinity for oxygen, leads to the irrational use of highly active elements for metal deoxidation with the formation of refractory oxides of rare-earth elements, the removal of which is difficult due to the lack of necessary thinning additives, which leads to an increase in metal contamination by nonmetallic inclusions and a decrease in the modifying properties of active elements in relation to the resulting non-metallic inclusions and deterioration in the quality of steel. The decrease in modifying properties when using the well-known complex modifier is also exacerbated if the degree of assimilation of the complex boron modifier exceeding 30% is exceeded, which leads to exceeding the allowable limit of boron content in the metal and deterioration in the quality of steel.

The basis of the invention is the task of improving the modifier for steel by optimizing its qualitative and quantitative composition.

The technical result is the provision of regulated deoxidation primarily by aluminum, and then by highly active elements, which contributes to intense desulfurization and increase modifying properties with respect to sulfides, nitrides and silicates, which improves the quality of steel.

The technical result is achieved in that the modifier for steel, containing calcium and aluminum, according to the invention additionally contains magnesium and barium in the following ratio of components, wt.%:

Magnesium 10-15

Calcium 12-15

Barium 8-10

Aluminum Else

moreover, the modifier is made in the form of dense granules with a fraction of 1.0-1.5 mm

In the process of steel processing, the proposed modifier implements regulated deoxidation of the metal at first primarily by aluminum. This effect is achieved by the fact that the amount of aluminum in the proposed modifier is 1.2-2.2 times higher than the content of elements highly active with respect to oxygen - magnesium, calcium and barium. As a result, a significant part of the oxygen dissolved in the metal is bound by aluminum, which contributes to the enhancement of the modifying properties of highly active elements, as well as to a significant desulfurization of the metal, due to its deep deoxidation involving not only aluminum, but also all the components that make up the modifier. Intensive regulated deoxidation of steel at first primarily by aluminum is accompanied by the formation of a significant amount of aluminate oxide inclusions of various compositions - from corundum to herzenite, which are effectively globularized by calcium, which is part of the modifier with the formation of large non-metallic inclusions, easily assimilated by slag. The presence in the composition of the proposed modifier of such highly active elements with respect to sulfur and phosphorus as magnesium and barium contributes to the modification of non-metallic inclusions - sulfides and phosphides, which also leads to an increase in the quality of steel.

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

The magnesium content in the amount of 10-15 wt.% Provides deep desulfurization and modification of sulfide, oxide, nitride, phosphide and silicate non-metallic inclusions, and also increases the deoxidizing ability of the modifier. The magnesium content in the modifier of less than 10 wt.% Does not provide intensive deoxidation of the metal, its deep desulfurization, reduces modifying properties and degrades the quality of steel. An increase in the magnesium content in the modifier of more than 15 wt.% Is impractical because, taking into account the high elasticity of magnesium vapor at temperatures beyond the furnace and in the presence of other highly active elements of calcium and barium, excess magnesium can be removed into the gas phase.

The presence of calcium modifier in the amount of 12-15 wt.% Provides, along with high deoxidation of the metal, deep desulfurization, modification of non-metallic inclusions, as well as globularization of aluminum oxides. A content of calcium modifier of less than 12 wt.% Reduces its refining effect, and an increase in its content above 15 wt.% Leads to irrational consumption of this component.

Barium, which is part of the modifier in an amount of 8-10 wt.%, Contributes to the effective modification of phosphide inclusions, its presence in the metal significantly reduces the harmful effect of phosphorus in the finished steel. A decrease in barium content of less than 8 wt.% Leads to a decrease in its modifying ability, and an increase in barium content of more than 10 wt.% Due to an increase in the total number of highly active elements with respect to aluminum leads to a decrease in the total modifying effect due to unregulated metal deoxidation, reduction of desulfurization and deterioration in the quality of steel.

Aluminum is a part of the modifier as the main metal deoxidizer; its presence increases the modifying effect of highly active elements, provides deep desulfurization and helps to improve the quality of steel.

Example.

In the foundry smelted four of the proposed and well-known modifiers. The production of the modifier was carried out by fusing the corresponding components in steelmaking units and then spraying the melt into granules with a fraction of 1.0-1.5 mm.

The processing of liquid metal (steel grade 14G2AF) was carried out by modifiers of the proposed composition and the well-known complex modifier of medium composition. The modifier was introduced into the volume of liquid metal, and after processing the metal was poured, rolled, samples were taken and the level of contamination and mechanical properties were examined in them according to standard methods.

The compositions of the modifiers used and the degree of desulfurization are presented in Table 1 (No. 1-3 are proposed, No. 4 are known), and the results of pollution assessment of non-metallic inclusions and mechanical properties are presented in Table 2.

From the above results it is seen that when using the proposed modifier, the desulfurization indices are higher than that of the known one. The level of modifying properties was evaluated by indicators of steel contamination. The results shown in Table 2 indicate that, when processing the steel with the proposed modifier, the contamination with non-metallic inclusions is lower, and the mechanical properties are higher than when processing with the well-known complex modifier.

Claims (1)

Modifier for steel, containing calcium and aluminum, characterized in that it additionally contains magnesium and barium in the following ratio of components, wt.%: Magnesium 10-15 Calcium 12-15 Barium 8-10 Aluminum Else moreover, the modifier is made in the form of dense granules with a fraction of 1.0-1.5 mm