RH slagging method

Abstract

The invention belongs to the technical field of steelmaking, and discloses an RH slagging method, which specifically comprises the following steps of: adding lime not exceeding 2kg / t to thicken top slag without deoxidizing and modifying steel ladle top slag at the back of a converter; after RH aluminum adding final deoxidation, slag materials are added into a vacuum chamber for first-stage slagging, and the appropriate thickness of formed slag in a steel ladle is 20-40 mm; then adding slag charge or synthetic slag into the vacuum chamber to carry out second-stage slagging, wherein the thickness of the formed slag in the steel ladle is preferably 10-20 mm; top slag is not subjected to deoxidation modification in RH; lime accounts for 92% or above in slag charge used in the first-stage slagging, and fluxed slag charge accounts for 8% or below in the slag charge used in the first-stage slagging; slag materials used in the second-stage slagging comprise lime, fluorite, bauxite and synthetic slag. According to the method disclosed by the invention, the slag with isolation, dilution and inclusion adsorption effects is produced for RH, so that not only is the oxidability harm of the top slag greatly reduced, but also deoxidation modification is not needed, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking and relates to a RH slag making method. Background Art

[0002] If the RH top slag is highly oxidizing, there will be more inclusions in the steel, greater aluminum loss during continuous casting, poor castability of molten steel, and a high defect rate of steel. Therefore, the oxidizing hazards of the RH top slag must be strictly controlled.

[0003] At present, the mainstream method for steel mills to control the oxidizability of RH top slag is to deoxidize and reform it after steel is tapped from the converter and to deoxidize and reform it again before RH leaves the station. However, the reforming effect is limited, and it is impossible to stably control the TFe of the RH top slag to below 3%.

[0004] Some companies add deoxidation modifiers before RH leaves the station and blow argon into the ladle for stirring, which can improve the modification effect, but it will cause secondary pollution of the molten steel and is not advisable.

[0005] The Chinese patent application with publication number CN 115505685 A provides a method for controlling the oxidative hazards of RH top slag of ultra-low carbon steel. The method makes slag in a RH vacuum chamber and isolates the original oxidative top slag of RH from the molten steel after entering the ladle, thereby achieving good results in controlling the oxidative hazards. However, the method does not completely eliminate the deoxidation and reforming of the converter, and the price of the slag used to ensure the adsorption capacity of inclusions is high, resulting in a relatively high overall cost. Summary of the invention

[0006] The object of the present invention is to provide a RH slag making method, which effectively reduces the slag material cost on the basis of controlling the oxidative damage effect of the top slag and the adsorption effect of inclusions.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: A RH slag making method comprises the following steps: After the converter is tapped, the top slag is not deoxidized and modified, and no more than 2kg / t of lime is added for thickening; After the final deoxidation by adding aluminum in RH, slag is added into the vacuum chamber for the first stage of slagging, and the slag is relatively viscous and has good isolation properties. The slag thickness in the ladle is preferably 20-40 mm. Then, slag or synthetic slag is added to the vacuum chamber for the second stage of slag making, and slag with strong absorption of inclusions is made, and the thickness of the slag in the ladle is preferably 10-20 mm; No deoxidation and modification of the top slag is performed in RH.

[0008] Furthermore, in the present invention, the top slag is not deoxidized and modified after steel is tapped from the converter, that is, no modifier or slag material for adjusting the slag composition is added after steel is tapped from the converter.

[0009] Furthermore, in the first stage of slag making of the present invention, 1-2 minutes after RH aluminum final deoxidation, lime accounts for more than 92% of the slag used, and flux slag accounts for less than 8%; when adding in batches, the batch interval is more than 1 minute.

[0010] Furthermore, the flux slag of the present invention includes fluorite.

[0011] Furthermore, the second stage slag making of the present invention starts 1-2 minutes after the slag material is added in the first stage, and the slag material ratio is controlled so that CaO / Al2O3 in the slag after slag formation is 1.4±0.2.

[0012] Furthermore, the slag used in the second stage of slag making of the present invention includes lime, fluorite, bauxite, synthetic slag, etc., and the particle size range is 5 to 30 mm, preferably 5 to 15 mm.

[0013] Furthermore, the method of the present invention is applicable to the RH single refining process between converter and continuous casting.

[0014] The inventive principle and beneficial technical effects of the technical solution of the present invention are: After the converter is tapped, the ladle top slag is thickened when it is too thin. Thick slag is not easy to react or fuse.

[0015] In the first stage of RH, low-cost lime is used as the main slag material. The slag is viscous and has good isolation properties, which can reduce the thickness of the slag layer and reduce the cost.

[0016] The second stage RH slag has both isolation and dilution effects, and works together with the first stage slag to make the bottom slag in contact with molten steel TFe ≤ 3%.

[0017] RH slag making adopts an isolation method, which does not require deoxidation and modification of the original top slag and is low in cost.

[0018] The present invention does not require additional equipment, is simple to operate, and has strong versatility. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described in detail below through embodiments.

[0020] A RH slag making method is applicable to a single RH refining process; in the production process of "hot iron desulfurization pretreatment-converter-RH-slab continuous casting", the following method is adopted, wherein the unspecified parts are operated according to the conventional method: (1) Prepare slag materials in advance, including lime, fluorite, bauxite, synthetic slag, etc., with a particle size range of 5 to 30 mm, preferably 5 to 15 mm; load the slag materials into the RH silo for standby use.

[0021] (2) After the steel is tapped from the converter, no modifier or slag is added, and only lime not exceeding 1 kg / t is added for thickening.

[0022] (3) After RH aluminum is added for final deoxidation for 1-2 minutes, slag is added to the vacuum chamber to form slag. The amount of slag is calculated based on the slag thickness of 20-40 mm in the ladle. The slag is mainly lime, and no more than 8% of fluorite and other flux slag can be added at the same time. The slag should be viscous but not lumpy. The slag can be added in batches, with an interval of more than 1 minute between batches.

[0023] (4) 1-2 minutes after the addition of lime-based slag, add lime, bauxite, fluorite and other slag or synthetic slag into the vacuum chamber to make slag. The slag amount is calculated based on the slag thickness of 10-20 mm in the ladle; the slag ratio is controlled according to CaO / Al2O3=1.4±0.2 in the slag after slagging.

[0024] (5) 1-2 minutes after all the slag has been added, proceed with the subsequent operations as normal.

[0025] (6) No modifier is added before RH leaves the station. Example 1

[0026] A RH slag making method is applied in the production of SPHD steel by smelting in a molten iron pretreatment-converter-RH-slab continuous casting production line, and the specific steps are as follows: (1) Prepare slag materials in advance, including lime, fluorite, bauxite, etc., with a particle size range of 5 to 15 mm; load the slag materials into the RH silo for standby use.

[0027] (2) After the steel is tapped from the converter, no modifier or slag is added, and only lime is added at 0.8 kg / t to thicken the top slag.

[0028] (3) After RH aluminum final deoxidation for 1 minute, 670 kg of slag was added into the vacuum chamber for the first stage of slag making. The slag included 630 kg of lime and 40 kg of fluorite. The slag thickness in the ladle increased by 20 mm.

[0029] (4) One minute after the first stage slag was added, 335 kg of slag was added into the vacuum chamber for the second stage slag making. The second stage slag included 160 kg of lime, 125 kg of bauxite, and 50 kg of fluorite. The thickness of the slag layer in the ladle increased by 10 mm.

[0030] (5) One minute after the slag is added, the subsequent alloying operation is carried out normally.

[0031] (6) No modifier was added before RH left the station.

[0032] Before RH leaves the station, bottom slag samples are taken, and the TFe weight content is 2.8% and the CaO / Al2O3 is 1.5. The castability of molten steel is good, and the water inlet is not changed for 8 consecutive casts in this casting. Example 2

[0033] A RH slag making method is applied in the production of SPHD steel by smelting in a molten iron pretreatment-converter-RH-slab continuous casting production line, and the specific steps are as follows: (1) Prepare slag materials in advance, including lime, fluorite, bauxite, etc., with a particle size range of 5 to 15 mm; load the slag materials into the RH silo for standby use.

[0034] (2) No modifier was added after the converter tapped the steel, and only lime was added at 1.5 kg / t to thicken the top slag.

[0035] (3) After RH aluminum final deoxidation for 2 minutes, 670 kg of lime was added to the vacuum chamber; 1 minute after the addition, 335 kg of lime was added to the vacuum chamber for the first stage of slagging. After the second addition, the slag thickness in the ladle increased by 30 mm.

[0036] (4) 2 minutes after the addition of 1005 kg of lime, 670 kg of slag was added to the vacuum chamber for the second stage of slag making. The slag used in the second stage of slag making included 320 kg of lime, 250 kg of bauxite, and 100 kg of fluorite. The thickness of the slag layer in the ladle increased by 20 mm.

[0037] (5) 2 minutes after the slag is added, the subsequent alloying operation is carried out normally.

[0038] (6) No modifier was added to RH before leaving the station.

[0039] Before RH leaves the station, a slag sample is taken from the lower part. After testing, the TFe weight content is 2.4% and the CaO / Al2O3 is 1.2. The castability of the molten steel is good, and the water inlet is not changed for 8 consecutive casts. Example 3

[0040] A RH slag making method is applied in the production of SPHD steel by smelting in a molten iron pretreatment-converter-RH-slab continuous casting production line, and the specific steps are as follows: (1) Prepare slag materials in advance, including lime, fluorite, bauxite, etc., with a particle size range of 5 to 30 mm; load the slag materials into the RH silo for standby use.

[0041] (2) No modifier was added after the converter steel was tapped, and only lime was added at 1 kg / t to thicken the top slag.

[0042] (3) After RH aluminum final deoxidation for 1.5 minutes, 670 kg of slag was added to the vacuum chamber, including 617 kg of lime and 53 kg of fluorite; 1 minute after the addition, another 670 kg of the above slag was added to the vacuum chamber for the first stage of slag making. After two additions, the slag thickness in the ladle increased by 40 mm.

[0043] (4) One minute after the above slag was added, 335 kg of slag was added into the vacuum chamber for the second stage of slag making. The slag used in the second stage of slag making included 160 kg of lime, 125 kg of bauxite, and 50 kg of fluorite. The thickness of the slag layer in the ladle increased by 10 mm.

[0044] (5) One minute after the slag is added, the subsequent alloying operation is carried out normally.

[0045] (6) No modifier was added before RH left the station.

[0046] Before RH leaves the station, a slag sample is taken from the lower part. After testing, the TFe weight content is 1.5%, and the CaO / Al2O3 is 1.6; the castability of the molten steel is good, and the water inlet is not changed for 8 consecutive casts in this casting. Example 4

[0047] A RH slag making method is applied in the production of SPHD steel by smelting in a molten iron pretreatment-converter-RH-slab continuous casting production line, and the specific steps are as follows: (1) Prepare slag materials in advance, including lime, fluorite, bauxite, etc., with a particle size range of 5 to 30 mm; load the slag materials into the RH silo for standby use.

[0048] (2) No modifier was added after the converter tapped the steel, and only lime was added at 2 kg / t to thicken the top slag.

[0049] (3) After RH aluminum final deoxidation for 2 minutes, 670 kg of lime was added to the vacuum chamber. After 2 minutes, 670 kg of slag was added to the vacuum chamber. The slag included 617 kg of lime and 53 kg of fluorite. After the second addition, the slag thickness in the ladle increased by 40 mm.

[0050] (4) 2 minutes after the above slag was added, 502.5 kg of slag was added into the vacuum chamber for the second stage of slag making. The slag used in the second stage of slag making included 240 kg of lime, 187.5 kg of bauxite, and 75 kg of fluorite. The thickness of the slag layer in the ladle increased by 15 mm.

[0051] (5) 2 minutes after the slag is added, the subsequent alloying operation is carried out normally.

[0052] (6) No modifier was added before RH left the station.

[0053] Before RH leaves the station, a slag sample is taken from the lower part. After testing, the TFe weight content is 1.3% and the CaO / Al2O3 is 1.4. The castability of the molten steel is good, and the water inlet is not changed for 8 consecutive casts.

Claims

1. A RH slag making method, characterized in that: The following steps are included After the converter, the ladle top slag is not deoxidized and reformed, and no more than 2kg / t of lime is added to thicken the top slag; After the final deoxidation by adding aluminum in RH, slag is added into the vacuum chamber for the first stage of slag making, and the slag thickness in the ladle is preferably 20-40mm; Then, slag or synthetic slag is added to the vacuum chamber for the second stage of slag making, and the slag thickness in the ladle is preferably 10-20 mm; No deoxidation and modification of the top slag is performed in RH.

2. The RH slag making method according to claim 1, characterized in that: The first stage of slag making begins with final deoxidation of 1-2 minutes by adding aluminum at RH.

3. The RH slag making method according to claim 1, characterized in that: The slag used in the first stage of slag making contains more than 92% lime and less than 8% flux slag.

4. The RH slag making method according to claim 3, characterized in that: The flux slag includes fluorite.

5. The RH slag making method according to claim 1, characterized in that: When the slag used for slag making in the first stage is added in batches, the interval between batches is more than 1 minute.

6. The RH slag making method according to claim 1, characterized in that: The second stage of slag making begins 1-2 minutes after the slag is added in the first stage, and the slag ratio is controlled according to CaO / Al2O3=1.4±0.2 in the slag after slag formation.

7. The RH slag making method according to claim 1, characterized in that: The slag materials used in the second stage of slag making include lime, fluorite, bauxite and synthetic slag.

8. The RH slag making method according to claim 7, characterized in that: The particle size range of the slag used in the second stage slag making is 5 to 30 mm.

9. The RH slag making method according to claim 7, characterized in that: The particle size range of the slag used in the second stage slag making is 5 to 15 mm.