DE202014100884U1 - Slag conditioner for desulfurization in secondary metallurgy of steel - Google Patents

Abstract

Slag conditioner, in particular for the desulphurization in secondary metallurgy of steel, this being a compact obtainable by compacting particles without addition of binder, and containing: a) 10 to 40% by weight of aluminum oxide, b) 0 to C) 8 to 65 wt .-% calcium carbide, d) 2 to 20 wt .-% calcium oxide, e) 0 to 10 wt .-% of at least one alkali metal oxide and / or at least one alkaline earth metal oxide except calcium oxide and f) 0 to 10 wt .-% of at least one additive.

Description

The present invention relates to a slag conditioner for desulfurization in the secondary metallurgy of steel and a slag containing it.

For the production of pig iron, a mixture of iron ore and coke, which functions both as an energy carrier and as a reducing agent for the iron ore, is usually reduced to pig iron in a blast furnace. Due to the comparatively high sulfur content of coke, comparatively high amounts of sulfur are introduced into the pig iron melt in this process. Since a high sulfur content adversely affects the mechanical properties of both cast iron and pig iron, the sulfur introduced during the extraction of pig iron must be removed from the pig iron and / or the steel made from it to obtain the desired sulfur content adjust.

For the removal of sulfur from pig iron and / or steel, a variety of desulfurization have been proposed, which, for example, pneumatically or mechanically introduced into the molten steel or molten steel and there reduce the sulfur to a sulfide compound, such as calcium sulfide, which in the pig iron melt rises and gets into the slag, with which it is later removed from the pig iron. As the reducing agent for desulfurization, for example, magnesium, magnesium alloys, soda, quick lime and calcium carbide are known. In addition, it is known to add a further compound to such reducing agents in order to increase their effectiveness in the desulfurization of pig iron and / or steel. So will in the DE 22 52 796 C3 discloses a desulfurizing agent containing, in addition to calcium carbide or calcium cyanamide as the reducing agent, a solid, hydrogen-containing compound such as polyethylene or polyamide. Furthermore, from the EP 0 226 994 B1 a desulfurizing agent containing calcium carbide and dried coal.

In steelmaking, desulphurisation proceeds exclusively or at least almost exclusively via the boundary phase reaction slag / steel. There are three main stages of secondary metallurgy to distinguish, namely first the tapping, secondly the ladle furnace treatment and thirdly the casting of the steel.

During the tapping, a new slag is formed outside the smelting unit by deliberate addition of slag conditioner or slag forming agent while at the same time preventing the oxygen-rich slag from running out of the smelting unit. This pre-desulfurization is carried out by intensive contact of steel and added slag components during tapping. Depending on the steel quality, the slag conditioners in the tapping process are to be dimensioned such that the ladle slag to be formed approaches the technical lime saturation. The addition of calcium carbide during the tapping has a strong deoxidizing effect and can be used as an oxygen reducing element in the steel.

In the ladle furnace treatment, a complete melting of the added slag conditioners or slag formers, a reduction of the remaining metal oxides to a low-oxide slag (especially iron oxide and manganese oxide) and thus the formation of a desulfurization slag. In this case, the actual basic composition of the ladle slag takes place at the tapping. At the ladle furnace, only minor but sometimes decisive changes to the slag composition can be initiated. Again, calcium carbide additions are often used to specifically reduce entrained iron oxide as well as other metal oxides in the slag.

In the casting of steel, the slag formed has the function of thermal insulation, the inclusion of non-metallic inclusions and, above all, the avoidance of reoxidation of the steel.

Conventionally, powdery slag conditioners are used in secondary metallurgy because powders are easy to feed, are easy to dose and, since the individual powder grains have a large surface, easily and quickly dissolve in the molten steel. However, due to the high temperature of the molten steel, a considerable proportion of the powder grains of the slag conditioner is thermally discharged from the molten steel, so that this proportion does not enter the molten steel, which adversely affects the efficiency achieved with the slag conditioner.

The object of the present invention is therefore to provide a slag conditioner which effectively forms a slag of suitable composition in molten steel, which is easily conveyed and readily metered, which is excellently soluble in molten steel, and which can nevertheless be introduced easily and without losses into a molten steel ,

• a) 10 bis 40 Gew.-% Aluminiumoxid,
• b) 0 bis 30 Gew.-% Siliciumdioxid,
• c) 8 bis 65 Gew.-% Calciumcarbid,
• d) 2 bis 20 Gew.-% Calciumoxid,
• e) 0 bis 10 Gew.-% wenigstens eines Alkalimetalloxids und/oder wenigstens eines Erdalkalimetalloxids außer Calciumoxid und
• f) 0 bis 10 Gew.-% wenigstens eines Additivs.

According to the invention, this object is achieved by the provision of a slag conditioner, in particular for the desulfurization in the secondary metallurgy of steel, which is a compact which is obtainable by compacting particles without addition of binder, which contains:

• a) 10 to 40% by weight of aluminum oxide,
• b) 0 to 30% by weight of silica,
• c) 8 to 65 wt.% calcium carbide,
• d) 2 to 20% by weight of calcium oxide,
• e) 0 to 10 wt .-% of at least one alkali metal oxide and / or at least one Erdalkalimetalloxids except calcium oxide and
• f) 0 to 10 wt .-% of at least one additive.

Preferably, all particles used in the compaction have a composition as specified above.

This solution is based on the surprising finding that a slag conditioner with the above composition not only effectively forms a slag of suitable composition in molten steel, but in particular also easily conveyed and well dosed is moreover easily and without losses in a molten steel can be introduced. By having the slag conditioner according to the invention in the form of a compact, it has a greater weight than individual powder grains, and therefore it can be easily and without losses introduced into molten steel. Nevertheless, due to its shape, the slag conditioner according to the invention is easy to convey and can be metered well and can be excellently dissolved in molten steel. The latter is due to the fact that the compact contains no binder and thus the individual grains of the compact are mechanically interconnected only by compaction, but not glued together, which would make it difficult to dissolve the compact in the molten steel and also to the undesirable entry of Binder as an impurity would lead to the molten steel. After all, the slag conditioner according to the invention is characterized by high efficiency, good pumpability, excellent meterability and excellent solubility in molten steel.

For the purposes of the present invention, a compact is understood to mean any body which is obtained by compacting smaller particles, in particular powder particles. Thus, this term includes in particular pellets, briquettes, agglomerates, granules, conglomerates and the like.

Furthermore, the term binder in the context of the present invention refers to substances by which solids having a fine degree of division, in particular powder, are glued together. A slag conditioner which is obtainable by compacting particles without addition of binder is thus to be understood as slag conditioners which are obtainable from particles which do not contain binders by compaction, wherein neither a binder is added before compaction nor during compaction.

Binders are for example dolomite, bitumen, water glass, Rohligninsulfonat and calcium carbonate. For this reason, it is provided according to the invention, in particular, that the slag conditioner contains no compound which is selected from the group consisting of dolomite, bitumen, water glass, Rohligninsulfonat and calcium carbonate.

Basically, the present invention is not limited in terms of the pressure used in the compaction. Rather, the compaction is carried out so that a compact arises in which the individual particles are sufficiently connected to each other so firmly that the compact is not thermally discharged from the molten steel, but easily introduced in molten steel, but the connection of the individual particles not so It is clear that the pellet is not easily dissolved in this after penetration into molten steel. Good results are obtained, in particular, when the slag conditioner is obtainable by compacting particles having a compacting pressure of from 1 MPa to 100 MPa, preferably from 5 to 50 MPa, more preferably from 10 to 30 MPa and most preferably from 15 to 20 MPa.

A good compaction of the starting particles to a good molten steel insert on the one hand and good solubility of the compact in molten steel on the other hand can be achieved in particular when the slag conditioner is obtainable by compacting particles having a mean particle diameter (d ₅₀ ) of 0.01 to 10 mm, preferably from 0.05 to 5 mm and particularly preferably from 0.1 to 2 mm. For the purposes of the present patent application, the mean d ₅₀ particle diameter is understood to mean the average particle diameter which is less than 50% of the particles present, ie 50% of all particles present have a smaller particle diameter than the d ₅₀ value. Preferably, all particles used have a composition as specified above.

Good slagging properties are obtained, in particular, when slag conditioners, and preferably all of the particles composing them, contain from 20 to 40% by weight of alumina. Preferably, this contains 25 to 35 wt .-% of alumina and particularly preferably 27.5 to 32.5 wt .-% alumina, such as about 32 wt .-% alumina.

The amount of vorzusehendem in the slag conditioner according to the invention Silica depends primarily on the type of steel melt to be treated. Since the sum of alumina and silica in the slag to be formed is preferably about 40% by weight, the slag conditioner of the invention, when intended for a low-silica molten steel, contains comparatively much silica, whereas the slag conditioner according to the invention, when used for a silicon-rich molten steel is provided comparatively little or no silica contains.

In particular, according to a first preferred embodiment of the present invention, the slag conditioner contains less than 5% by weight of silica, preferably less than 4% by weight of silicon dioxide, particularly preferably less than 3% by weight, if it is intended for a silicon-rich molten steel melt. Silica, most preferably less than 2% by weight of silica, and most preferably less than 1% by weight of silica.

In contrast, the slag conditioner, in particular, when intended for a low-silica molten steel, according to an alternative, second preferred embodiment of the present invention, contains more than 5 to 30% by weight of silica, more preferably more than 5 to 15% by weight of silica, and most preferably 7.5 to 12.5 weight percent silica, such as about 10 weight percent silica.

In a further development of the inventive concept, it is proposed that the slag conditioner 20 to 60 wt .-% calcium carbide, preferably 30 to 50 wt .-% calcium carbide and particularly preferably 35 to 45 wt .-% calcium carbide, such as about 40 wt .-% calcium carbide , contains.

Preferably, the slag conditioner contains 5 to 15% by weight of calcium oxide, preferably 7.5 to 15.5% by weight of calcium oxide and more preferably 9 to 11% by weight of calcium oxide, such as about 10% by weight of calcium oxide.

Good results are obtained with regard to slag conditioning, in particular, when the slag conditioner more than 0 to 9 wt .-%, preferably 2.5 to 7.5 wt .-% and particularly preferably 4 to 6 wt .-% of at least one alkali metal oxide and / or at least one alkaline earth metal oxide except calcium oxide.

In principle, the slag conditioner may comprise as alkali metal oxide or alkaline earth metal oxide, apart from calcium oxide, all known alkali metal oxides or alkaline earth metal oxides other than calcium oxide. Preferred in terms of price and effectiveness are those selected from the group consisting of magnesium oxide, barium oxide, sodium oxide, potassium oxide, and any combination of two or more of the aforementioned compounds.

Preferably, the slag conditioner contains more than 0 to 9 wt .-%, preferably 2.5 to 7.5 wt .-% and particularly preferably 4 to 6 wt .-% of at least one additive.

Basically, the present invention is not limited with respect to the additive. In particular, good results are obtained when the additive is selected from the group consisting of cryolite, sodium borate, calcium fluoride and any combination of two or more of the aforementioned compounds.

Preferably, the sum of the amounts of alumina and silica in the slag conditioner, in particular when it is intended for a low-silica molten steel, is from 30 to 40% by weight, and preferably from 35 to 40% by weight.

According to an alternative embodiment, the sum of the amounts of alumina and silica in the slag conditioner, in particular when it is intended for a silicon-rich molten steel melt, is 20 to 40% by weight and preferably 25 to 35% by weight.

• a) 20 bis 40 Gew.-% Aluminiumoxid,
• b) 1 bis 15 Gew.-% Siliciumdioxid,
• c) 30 bis 50 Gew.-% Calciumcarbid,
• d) 2 bis 15 Gew.-% Calciumoxid,
• e) 2,5 bis 7,5 Gew.-% Alkalimetalloxide und Erdalkalimetalloxide außer Calciumoxid und
• f) Rest auf 100 Gew.-% wenigstens eines Additivs enthält.

In a further development of the inventive concept, it is proposed that the slag conditioner:

• a) 20 to 40% by weight of aluminum oxide,
• b) 1 to 15% by weight of silica,
• c) from 30 to 50% by weight of calcium carbide,
• d) 2 to 15% by weight of calcium oxide,
• e) 2.5 to 7.5 wt .-% alkali metal oxides and alkaline earth metal oxides except calcium oxide and
• f) remainder to 100 wt .-% of at least one additive.

• a) 25 bis 35 Gew.-% Aluminiumoxid,
• b) 2,5 bis 12,5 Gew.-% Siliciumdioxid,
• c) 35 bis 45 Gew.-% Calciumcarbid,
• d) 5 bis 15 Gew.-% Calciumoxid,
• e) 2,5 bis 7,5 Gew.-% Alkalimetalloxide und Erdalkalimetalloxide außer Calciumoxid und
• f) Rest auf 100 Gew.-% wenigstens eines Additivs ausgewählt aus der Gruppe bestehend aus Kryolith, Natriumborat, Calciumfluorid und beliebigen Kombinationen von zwei oder mehr der vorgenannten Verbindungen.

According to a particularly preferred embodiment of the present invention, the slag conditioner consists of:

• a) 25 to 35% by weight of aluminum oxide,
• b) 2.5 to 12.5% by weight of silica,
• c) 35 to 45% by weight of calcium carbide,
• d) 5 to 15% by weight of calcium oxide,
• e) 2.5 to 7.5 wt .-% alkali metal oxides and alkaline earth metal oxides except calcium oxide and
• f) balance to 100 wt .-% of at least one additive selected from the group consisting of cryolite, sodium borate, calcium fluoride and any combination of two or more of the aforementioned compounds.

Good results in terms of registrability in molten steel, deliverability, Dosability, storability and dissolubility in molten steel are obtained in particular when the slag conditioner is present as one or more briquettes, the briquette (s) seen in cross section having a size (length × width) of 10 × 5 to 200 × 100 mm, preferably 25 X 15 mm to 75 x 50 mm, and more preferably from 40 x 20 to 50 x 30 mm, such as about 40 x 25 mm.

Another object of the present invention is a slag containing a slag conditioner described above. Preferably, in the slag, the sum of the amounts of alumina and silica is 30 to 50% by weight, the calcium oxide content is 50 to 70% by weight, and the amount of other ingredients is less than 5% by weight. More preferably, the sum of the amounts of alumina and silica in the slag is 35 to 45% by weight, the calcium oxide content is 55 to 65% by weight, and the amount of other ingredients is less than 2% by weight. Most preferably, the sum of the amounts of alumina and silica in the slag from 37.5 to 42.5 wt .-%, the calcium oxide content 58.5 to 62.5 wt .-% and the amount of other ingredients less than 1 wt .-%. Most preferably, the sum of the amounts of alumina and silica in the slag is 39 to 41 wt .-%, in particular about 40 wt .-%, the calcium oxide content 59 to 61 wt .-%, in particular about 60 wt .-%, and the Amount of other ingredients maximum 0.5 wt .-%.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 2252796 C3 [0003]
• EP 0226994 B1 [0003]

Claims (18)

Slag conditioner, in particular for the desulphurisation of secondary metallurgy of steel, which is a compact obtainable by compacting particles without addition of binder, and which contains: a) 10 to 40% by weight of aluminum oxide, b) 0 to 30% by weight of silica, c) 8 to 65 wt.% calcium carbide, d) 2 to 20% by weight of calcium oxide, e) 0 to 10 wt .-% of at least one alkali metal oxide and / or at least one Erdalkalimetalloxids except calcium oxide and f) 0 to 10 wt .-% of at least one additive. Slag conditioner according to claim 1, characterized in that it contains no compound selected from the group consisting of dolomite, bitumen, water glass, Rohligninsulfonat and calcium carbonate. Slag conditioner according to claim 1 or 2, characterized in that it is obtainable by compacting particles with a compacting pressure of 1 MPa to 100 MPa, preferably from 5 to 50 MPa, more preferably from 10 to 30 MPa and most preferably from 15 to 20 MPa , Slag conditioner according to at least one of the preceding claims, characterized in that it is obtainable by compacting particles having an average particle diameter (d ₅₀ ) of 0.01 to 10 mm, preferably of 0.05 to 5 mm and particularly preferably of 0, 1 to 2 mm. Slag conditioner according to at least one of the preceding claims, characterized in that it contains 20 to 40 wt .-% alumina, preferably 25 to 35 wt .-% alumina and particularly preferably 27.5 to 32.5 wt .-% alumina. Slag conditioner according to at least one of the preceding claims, characterized in that it contains less than 5 wt .-% silica, preferably less than 4 wt .-% silica, more preferably less than 3 wt .-% silica, most preferably less than 2 wt % Silica and most preferably less than 1% by weight silica. Slag conditioner according to at least one of Claims 1 to 5, characterized in that it contains more than 5 to 30% by weight of silica, preferably more than 5 to 15% by weight of silica and particularly preferably 7.5 to 12.5% by weight. Contains% silica. Slag conditioner according to at least one of the preceding claims, characterized in that it contains 20 to 60 wt .-% calcium carbide, preferably 30 to 50 wt .-% calcium carbide and particularly preferably 35 to 45 wt .-% calcium carbide. Slag conditioner according to at least one of the preceding claims, characterized in that it contains more than 0 to 9 wt .-%, preferably 2.5 to 7.5 wt .-% and particularly preferably 4 to 6 wt .-% of at least one alkali metal oxide and / or at least one alkaline earth metal oxide other than calcium oxide. Slag conditioner according to at least one of the preceding claims, characterized in that the at least one alkali metal oxide and / or alkaline earth metal oxide other than calcium oxide is selected from the group consisting of magnesium oxide, barium oxide, sodium oxide, potassium oxide and any combination of two or more of the aforementioned compounds , Slag conditioner according to at least one of the preceding claims, characterized in that it contains more than 0 to 9 wt .-%, preferably 2.5 to 7.5 wt .-% and particularly preferably 4 to 6 wt .-% of at least one additive. Slag conditioner according to at least one of the preceding claims, characterized in that the at least one additive is selected from the group consisting of cryolite, sodium borate, calcium fluoride and any combination of two or more of the aforementioned compounds. Slag conditioner according to at least one of Claims 1 to 5 and 7 to 12, characterized in that the sum of the amounts of aluminum oxide and silicon dioxide is 30 to 40% by weight and preferably 35 to 40% by weight. Slag conditioner according to at least one of claims 1 to 6 and 8 to 13, characterized in that the sum of the amounts of aluminum oxide and silicon dioxide is 20 to 40 wt .-% and preferably 25 to 35 wt .-%. Slag conditioner according to at least one of the preceding claims, characterized in that it contains: a) 20 to 40% by weight of aluminum oxide, b) 1 to 15% by weight of silica, c) 30 to 50% by weight of calcium carbide, d) 5 to 15% by weight of calcium oxide, e) 2.5 to 7.5 wt .-% alkali metal oxides and alkaline earth metal oxides except calcium oxide and f) balance to 100 wt .-% of at least one additive. Slag conditioner according to claim 15, characterized in that it consists of: a) 25 to 35% by weight of aluminum oxide, b) 2.5 to 12.5% by weight of silica, c) 35 to 45% by weight of calcium carbide, d) from 2 to 15% by weight of calcium oxide, e) from 2.5 to 7.5% by weight of alkali metal oxides and alkaline earth metal oxides other than calcium oxide and f) remainder to 100% by weight of at least one additive selected from the group consisting of cryolite, Sodium borate, calcium fluoride and any combination of two or more of the foregoing compounds. Slag conditioner according to at least one of the preceding claims, characterized in that it is present as one or more briquettes, wherein the briquettes seen in cross-section, a size (length × width) of 10 × 5 to 200 × 100 mm, preferably 25 × 15 mm to 75 × 50 mm, and more preferably from 40 × 20 to 50 × 30 mm. A slag containing a slag conditioner according to at least one of the preceding claims, wherein the sum of the amounts of alumina and silica in the slag is 30 to 50% by weight, the calcium oxide content is 50 to 70% by weight and the amount of further ingredients is less than 5% by weight %, preferably the sum of the amounts of aluminum oxide and silicon dioxide in the slag 35 to 45 wt .-%, the calcium oxide content 55 to 65 wt .-% and the amount of other ingredients less than 2 wt .-%, particularly preferably Sum of the amounts of alumina and silica in the slag 37.5 to 42.5 wt .-%, the calcium oxide content 58.5 to 62.5 wt .-% and the amount of other ingredients less than 1 wt .-% and all particularly preferably the sum of the amounts of aluminum oxide and silicon dioxide in the slag is 39 to 41% by weight, the calcium oxide content is 59 to 61% by weight and the amount of further ingredients is at most 0.5% by weight.