Method for deep modification of RH refining slag

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a deep modification method for RH refining slag, the slag is modified by adopting an aluminum-barium-based alloy, the density of the aluminum-barium-based alloy is greater than that of the slag, and the aluminum-barium-based alloy is easy to enter steel slag and react with oxides of iron and manganese in the slag when being added from the slag surface to efficiently modify the slag; the problems of long retention time, serious burning loss and large smoke generation amount of modifier aluminum and the like with relatively low density on the slag surface are avoided; when being added from molten steel in an RH vacuum chamber, the steel slag modifier can quickly float to a steel slag interface because the density of the steel slag modifier is far smaller than that of the molten steel, the slag is modified below the slag, and oxygen transfer of the slag to the molten steel is better controlled. Due to the fact that the solubility of barium in molten steel is very low and the reducing capacity of barium is high, the aluminum-barium-based alloy is adopted for slag modification, loss caused by dissolution of barium in the molten steel can be avoided, oxide of iron and oxide of manganese in the slag can be well reduced, and the content of the oxide of iron and the content of the oxide of manganese in the slag can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for deep modification of RH refining slag. Background Art

[0002] In the production of high-cleanliness steel, when the slag is highly oxidizing, the slag will transfer oxygen to the molten steel, generate inclusions in the molten steel, and reduce the cleanliness of the molten steel, thereby causing problems such as excessive inclusions in the steel and nozzle blockage during continuous casting. In the production of high-cleanliness steel, lime is often added to the slag to dilute the concentration and activity of iron oxide and manganese oxide in the slag, increase the viscosity of the slag, and control the transfer of oxygen from the slag to the molten steel. However, this method requires a large amount of lime to be added, and the modification effect is limited.

[0003] In the production of high-clean steel, the slag is often modified by adding aluminum particles and aluminum-calcium modifiers from the top of the ladle slag to the slag. However, due to the low density of aluminum particles and aluminum-calcium modifiers, it is not easy to enter the slag when added, and they stay on the slag surface for a long time, causing serious burn damage. Aluminum is the main deoxidizer and slag modifier in current steel production. Although aluminum has a strong affinity for oxygen, its specific gravity is small. When the slag is added to the slag surface during slag modification, the speed of entering the slag is slow, and it often reacts with air on the slag surface to produce serious smoke and dust, causing serious burn damage and low utilization rate. It is difficult to efficiently reduce the iron oxide and manganese oxide in the slag, and the slag modification effect is often poor. The sum of the iron oxide and manganese oxide content is difficult to control below 5.0wt%. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a method for deep modification of RH refining slag.

[0005] According to one aspect of the present invention, the present invention provides the following technical solution:

[0006] A method for deep modification of RH refining slag. After RH refining and deoxidation, aluminum-barium based alloy is added to molten steel in an RH vacuum chamber and then circulated for 3-10 minutes to achieve deep modification of RH refining slag.

[0007] A method for deep modification of RH refining slag is disclosed. After RH refining is completed, an aluminum-barium based alloy is added to the slag surface in the RH ladle to achieve deep modification of the RH refining slag.

[0008] As a preferred embodiment of the method for deep modification of RH refining slag described in the present invention, the barium content in the aluminum-barium based alloy added to the molten steel in the RH vacuum chamber is ≥20wt%, the particle size of the aluminum-barium based alloy is 15-120mm, and the amount of the aluminum-barium based alloy added is 0.4-2.0kg / ton of steel.

[0009] As a preferred embodiment of the method for deep modification of RH refining slag described in the present invention, the barium content in the aluminum-barium based alloy added to the slag surface in the RH refining ladle is ≥10wt%, the particle size of the aluminum-barium based alloy is 10-100mm, and the amount of the aluminum-barium based alloy added is 0.4-2.5kg / ton of steel.

[0010] As a preferred embodiment of the method for deep modification of RH refining slag described in the present invention, when adding aluminum-barium based alloy to the slag surface of the RH refining ladle, the alloy is added evenly from all parts of the slag surface.

[0011] As a preferred embodiment of the method for deep modification of RH refining slag described in the present invention, the content of aluminum and barium in the aluminum-barium based alloy is greater than 50wt%, and the density is 3.0-6.0g / cm 3 .

[0012] As a preferred embodiment of the method for deep modification of RH refining slag described in the present invention, the FeO content in the RH refining slag after deep modification is less than 7.0wt%, and the FeO content in the slag at the steel-slag interface is less than 5.0wt%.

[0013] As a preferred embodiment of the method for deep modification of RH refining slag described in the present invention, before adding the aluminum-barium based alloy, the slag is preliminarily modified with a modifier before the RH start-up cycle refining to reduce the FeO content in the slag to below 12.0wt%.

[0014] As a preferred embodiment of the method for deep modification of RH refining slag described in the present invention, the modifying agent used before the RH start-up cycle refining includes aluminum, aluminum calcium and lime.

[0015] The beneficial effects of the present invention are as follows:

[0016] The present invention proposes a method for deep modification of RH refining slag, wherein after RH refining and deoxidation, aluminum-barium-based alloy is added to molten steel in the RH vacuum chamber and then the cycle is continued or after RH refining, aluminum-barium-based alloy is added to the slag surface of slag in the RH ladle to achieve deep modification of RH refining slag. The aluminum-barium-based alloy is used for slag modification, and its density is greater than that of slag. When added from the slag surface, it is easy to enter the steel slag, react with the iron and manganese oxides in the slag, and efficiently modify the slag, thereby avoiding the problems of aluminum and other modifiers with low density staying on the slag surface for a long time, serious burning, and large amount of smoke and dust generation; when added from the molten steel in the RH vacuum chamber, since its density is much smaller than that of the molten steel, it can quickly float to the steel slag interface, modify the slag below the slag, and better control the transfer of oxygen from the slag to the molten steel. Since the solubility of barium in molten steel is very low and the reducing ability of barium is strong, the aluminum-barium-based alloy is used for slag modification, which can not only avoid the loss caused by the dissolution of barium in molten steel, but also can better reduce the iron and manganese oxides in the slag and reduce the content of both. DETAILED DESCRIPTION

[0017] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The present invention provides a method for deep modification of RH refining slag. After RH refining and deoxidation, aluminum-barium-based alloy is added from a silo to molten steel in an RH vacuum chamber and then circulated for 3-10 minutes to achieve deep modification of RH refining slag. Part of the aluminum in the aluminum-barium-based alloy added from the silo to the molten steel in the RH vacuum chamber is dissolved in the molten steel, and the rest floats from the molten steel to the steel-slag interface; aluminum and barium in the alloy at the steel-slag interface react with FeO and MnO in the slag lower layer to modify the slag, reduce the oxidizability of the slag near the steel-slag interface, and control the transfer of oxygen from the slag to the molten steel.

[0019] A method for deep modification of RH refining slag, after RH refining is completed, an aluminum-barium-based alloy is added from the top of the ladle to the slag surface of the RH ladle to achieve deep modification of the RH refining slag. The aluminum-barium-based alloy is added from the slag surface to the slag to modify the slag. The aluminum-barium-based alloy has a larger specific gravity than the slag density and can quickly enter the slag layer to modify the slag. Part of the alloy reaches the steel-slag interface. Since the density of the aluminum-barium-based alloy is much smaller than that of molten steel, especially the solubility of barium in molten steel is very low, the alloy stays at the steel-slag interface and the slag is modified at the steel-slag interface.

[0020] Preferably, the barium content in the aluminum-barium-based alloy added to the molten steel in the RH vacuum chamber is ≥20wt%, the particle size of the aluminum-barium-based alloy is 15-120mm, and the amount of the aluminum-barium-based alloy added is 0.4-2.0kg / ton of steel.

[0021] Preferably, the barium content in the aluminum-barium based alloy added to the slag surface in the RH ladle is ≥10wt%, the particle size of the aluminum-barium based alloy is 10-100mm, and the amount of the aluminum-barium based alloy added is 0.4-2.5kg / ton of steel.

[0022] Preferably, when adding the aluminum-barium based alloy to the slag surface of the RH ladle, the alloy is added evenly from all parts of the slag surface.

[0023] Preferably, the aluminum and barium contents in the aluminum-barium based alloy are greater than 50 wt% and the density is 3.0-6.0 g / cm 3 .

[0024] Preferably, the FeO content in the RH refined slag after deep modification is less than 7.0wt%, and the FeO content in the slag at the steel-slag interface is less than 5.0wt%.

[0025] Preferably, before adding the aluminum-barium based alloy, the slag is preliminarily modified with a modifier before the RH start-up cycle refining to reduce the FeO content in the slag to below 12.0 wt%.

[0026] Preferably, the modifying agent used before the RH start-up cycle refining includes aluminum, aluminum calcium, and lime.

[0027] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0028] Example 1

[0029] A factory produces ultra-low carbon IF steel, with a converter output of 210 tons. After the converter is tapped, 200 kg of aluminum particles and 1 ton of lime are added to the ladle slag for preliminary modification before the RH cycle refining is started. After the preliminary modification, the iron oxide content in the ladle slag is 11.2wt%, and the manganese oxide content is 3.8wt%; after the RH refining and deoxidation is completed, 2.0 tons of 50wt% Al+50wt% Ba aluminum-barium alloy is added from the upper silo to the molten steel in the vacuum chamber. The alloy particle size is 50-100mm and the alloy density is 3.15g / cm 3 After the alloy was added, the argon blowing cycle was continued for 5 minutes, and finally the iron oxide content in the ladle slag decreased to 4.2wt%, and the manganese oxide content decreased to 1.1wt%. The iron oxide and manganese oxide contents in the slag near the slag-steel interface were lower than the average iron oxide and manganese oxide contents in the ladle slag.

[0030] Example 2

[0031] A factory produces ultra-low carbon IF steel, with a converter output of 210 tons. After the converter is tapped, 200 kg of aluminum particles and 1 ton of lime are added to the ladle slag for preliminary modification before the RH cycle refining is started. After the preliminary modification, the iron oxide content in the ladle slag is 10.8wt%, and the manganese oxide content is 2.9wt%. After the RH refining is completed, 2.0 tons of aluminum-barium alloy of 50wt% Al+50wt% Ba is evenly added from the top of the ladle to the ladle slag surface. The alloy particle size is 15-50mm and the alloy density is 3.15g / cm 3 The final iron oxide content in the ladle slag dropped to 4.8wt%, and the manganese oxide content dropped to 1.3wt%. The iron oxide and manganese oxide contents in the slag near the slag-steel interface were lower than the average iron oxide and manganese oxide contents in the ladle slag.

[0032] Example 3

[0033] A factory produces ultra-low carbon IF steel, with a converter output of 210 tons. After the converter is tapped, 200 kg of aluminum particles and 1 ton of lime are added to the ladle slag for preliminary modification before the RH cycle refining is started. After the preliminary modification, the iron oxide content in the ladle slag is 10.2wt%, and the manganese oxide content is 2.8wt%. After the RH refining is completed, 2.0 tons of aluminum-barium-based alloy with a total Al+Ba content of 90wt% is evenly added from the top of the ladle to the ladle slag surface, wherein the Ba content is 50wt%, the Al content is 40wt%, the alloy particle size is 15-50mm, and the alloy density is 3.5g / cm 3 Finally, the iron oxide content in the ladle slag dropped to 4.5wt%, and the manganese oxide content dropped to 1.0wt%. The iron oxide and manganese oxide contents in the slag near the slag-steel interface were lower than the average iron oxide and manganese oxide contents in the ladle slag.

[0034] Example 4

[0035] A factory produces ultra-low carbon IF steel, with a converter output of 210 tons. After the converter is tapped, 200 kg of aluminum particles and 1 ton of lime are added to the ladle slag for preliminary modification before the RH cycle refining is started. After the preliminary modification, the iron oxide content in the ladle slag is 9.2wt%, and the manganese oxide content is 2.8wt%. After the RH refining and deoxidation is completed, 2.0 tons of aluminum-barium-based alloy with a total Al+Ba content of 90wt% is added from the upper silo to the steel liquid in the vacuum chamber, wherein the Ba content is 50wt%, the Al content is 40wt%, the alloy size is 50-100mm, and the alloy density is 3.5g / cm 3 After the alloy was added, the argon blowing cycle was continued for 5 minutes. Finally, the iron oxide content in the ladle slag dropped to 3.2wt%, and the manganese oxide content dropped to 0.9wt%. Moreover, the iron oxide and manganese oxide contents in the slag near the slag interface were lower than the average iron oxide and manganese oxide contents in the ladle slag.

[0036] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for deep modification of RH refining slag, characterized in that: After RH refining and deoxidation, aluminum-barium based alloy is added to the molten steel in the RH vacuum chamber and the circulation is continued for 3-10 minutes to achieve deep modification of the RH refining slag.

2. A method for deep modification of RH refining slag, characterized in that: After RH refining is completed, aluminum-barium based alloy is added to the slag surface in the RH refining ladle to achieve deep modification of the RH refining slag.

3. The method for deep modification of RH refining slag according to claim 1, characterized in that: The barium content in the aluminum-barium-based alloy added to the molten steel in the RH vacuum chamber is ≥20wt%, the particle size of the aluminum-barium-based alloy is 15-120mm, and the addition amount of the aluminum-barium-based alloy is 0.4-2.0kg / ton of steel.

4. The method for deep modification of RH refining slag according to claim 2, characterized in that: The barium content of the aluminum-barium based alloy added to the slag surface in the RH refining ladle is ≥10wt%, the particle size of the aluminum-barium based alloy is 10-100mm, and the addition amount of the aluminum-barium based alloy is 0.4-2.5kg / ton of steel.

5. The method for deep modification of RH refining slag according to claim 2, characterized in that: When adding aluminum-barium based alloy to the slag surface of the RH refining ladle, add it evenly from all parts of the slag surface.

6. The method for deep modification of RH refining slag according to claim 1 or 2, characterized in that: The aluminum and barium content of the aluminum-barium based alloy is greater than 50wt% and the density is 3.0-6.0g / cm 3 .

7. The method for deep modification of RH refining slag according to claim 1 or 2, characterized in that: The FeO content in the RH refining slag after deep modification is less than 7.0wt%, and the FeO content in the slag at the steel-slag interface is less than 5.0wt%.

8. The method for deep modification of RH refining slag according to claim 1 or 2, characterized in that: Before adding the aluminum-barium based alloy, the slag is initially modified with a modifier before the RH start-up cycle refining to reduce the FeO content in the slag to below 12.0 wt%.

9. The method for deep modification of RH refining slag according to claim 8, characterized in that: The modifiers used before the RH start-up cycle refining include aluminum, aluminum calcium, and lime.