CN114619006A - Method for controlling inclusions in pipeline steel during ladle replacement - Google Patents
Method for controlling inclusions in pipeline steel during ladle replacement Download PDFInfo
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- CN114619006A CN114619006A CN202210134617.7A CN202210134617A CN114619006A CN 114619006 A CN114619006 A CN 114619006A CN 202210134617 A CN202210134617 A CN 202210134617A CN 114619006 A CN114619006 A CN 114619006A
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- ladle
- argon
- tundish
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/50—Pouring-nozzles
- B22D41/502—Connection arrangements; Sealing means therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/50—Pouring-nozzles
- B22D41/58—Pouring-nozzles with gas injecting means
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- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention discloses a method for controlling inclusions in pipeline steel during ladle change, which comprises the following steps: (1) the whole anti-oxidation operation is well carried out: installing a ladle down nozzle argon blowing device, wherein the argon blowing device enables the periphery of the ladle down nozzle to keep an argon atmosphere, oxygen and nitrogen in air are prevented from being sucked into molten steel, and the argon pressure reaches 0.22-0.27 Mpa; argon is blown between the tundish upper nozzle and the submerged nozzle, and the pressure of the argon reaches 0.18-0.22 Mpa; a graphite sealing ring is arranged at the long water gap; the thickness of the molten steel covering agent in the tundish reaches more than 50mm but not more than 80 mm; (2) the operation method during the improved furnace transfer comprises the following steps: the operation of the high liquid level of the tundish is ensured, and the liquid level of the tundish is not lower than 30 tons when the next ladle is pulled open. According to the invention, the whole-course protection casting is adopted when the casting machine casts the pipeline steel, and the operation during ladle changing between furnaces is improved, so that the excessive inclusion of the pipeline steel caused by unstable process during the ladle changing period in the continuous casting of multiple furnaces is avoided.
Description
Technical Field
The invention relates to a method for controlling inclusions in pipeline steel during ladle change.
Background
Pipeline steels require high strength, high impact toughness, low ductile to brittle transition temperature, excellent Hydrogen Induced Cracking (HIC) and sulfide stress corrosion cracking resistance, and good weldability. Therefore, the pipeline steel is required to have high purity and ultralow phosphorus, oxygen and sulfur, and simultaneously, the non-metallic inclusions in the steel are required to be better controlled. The large-scale non-metallic inclusion destroys the continuity of a steel matrix, not only seriously affects the quality of the steel plate, but also adversely affects the use and processing performance of the steel plate, and due to the complexity of pipeline conveying media and service conditions, in order to ensure the pipeline safety, severe requirements, especially major pipeline engineering, are provided for oil and gas pipeline steel, and even the requirements for each inclusion in the pipeline steel X42 steel are less than or equal to 2.0.
When steel is smelted by a converter, particularly high-performance steel, the important prerequisites of improving the performance of the steel are to prevent molten steel pollution and reduce the content of non-metallic inclusions in the steel. By optimizing the smelting process, namely optimizing the deoxidation and slagging system, the alloy adding mode, the argon blowing system, the calcium treatment process, the protective casting and other process systems, large inclusions in steel are fully floated, secondary oxidation of molten steel is avoided, and the inclusions in the steel are effectively controlled.
Although the measures are adopted in the smelting process to effectively control the inclusions in the steel, the inclusions enter molten steel to cause excessive inclusion of pipeline steel during multi-furnace continuous casting and during furnace ladle changing due to the process particularity, and according to statistics, about 50% of billets generated in the furnace ladle changing period are degraded due to excessive inclusion. The ladle changing time is an unstable casting state, and inclusions are easy to enter molten steel, so that the following problems mainly exist:
1. when the steel ladle casting is finished, a small amount of steel slag inevitably enters the tundish and carries partial inclusions.
2. When the new ladle is pulled away, the drainage sand enters the molten steel and also carries partial inclusions.
3. When the tundish is replaced, particularly when different steel types are mixed for casting, the liquid level of the tundish is reduced, and partial impurities in the tundish enter the crystallizer under the action of low-liquid-level vortex.
The Chinese patent with the application number of 201610312965.3 discloses a method for controlling inclusions in X80 pipeline steel, which optimizes the process from the whole processes of molten iron pretreatment, converter, refining, RH and continuous casting to further improve the purity of molten steel, so that the thickness grades of A, B, C, D four types of inclusions in X80 pipeline steel are all less than or equal to 1.0, and the product quality of X80 pipeline steel is obviously improved. However, the method disclosed in this document cannot prevent inclusions from entering molten steel during the ladle change operation between furnaces in the continuous casting of molten steel.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a method for controlling inclusions in pipeline steel during ladle change.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention discloses a method for controlling inclusions in pipeline steel during ladle change, which comprises the following steps:
(1) the whole anti-oxidation operation is well carried out:
(1.1) installing a ladle down nozzle argon blowing device, wherein the argon blowing device keeps an argon atmosphere around the ladle down nozzle to prevent oxygen and nitrogen in air from absorbing molten steel, and the argon pressure reaches 0.22-0.27 Mpa;
(1.2) blowing argon between a tundish upper nozzle and a submerged nozzle, wherein the pressure of the argon reaches 0.18-0.22 Mpa;
(1.3) installing a graphite sealing ring at the long nozzle;
(1.4) the thickness of the molten steel covering agent in the tundish reaches more than 50mm but not more than 80mm
(2) The operation method during the improved furnace transfer comprises the following steps:
and (2.1) the water gap is cleaned by burning, and the residual steel washed away from the water gap is prevented from entering the clean molten steel.
(2.2) the following operations are taken when the package is changed: the high liquid level operation of the tundish is ensured as much as possible, the liquid level of the tundish is not lower than 30 tons when the next ladle is pulled open, if the liquid level of the tundish meets different steel types and is poured in a mixed mode or cannot be ensured to be more than 30 tons due to tight rhythm of molten steel and the like, the total flow is controlled to be 30 tons after the next ladle is pulled open, the flow is slowly controlled to be at the working liquid level after 30 tons, and inclusion is reduced from entering the molten steel to the minimum extent.
Further, in the (2.2), the total flow is controlled to 30 tons after the next packet is pulled, wherein the total flow is 13 tons per minute before 30 tons and 7 tons per minute after 30 tons.
Further, the pressure of argon gas in (1.1) reached 0.25 MPa.
Further, the pressure of argon gas in (1.2) reached 0.2 MPa.
Compared with the prior art, the invention has the following beneficial technical effects:
the casting machine adopts the whole-process anti-oxidation operation when casting the pipeline steel, so as to avoid the oxidation of the molten steel to form oxide inclusions; the operation method during the ladle transfer between heats is improved, and foreign impurities are reduced from entering molten steel. By adopting the method, the degradation of the casting blank is reduced from 50% to below 10% due to the excessive inclusion in the period of ladle to ladle between heats, degraded products are obviously reduced, and considerable economic benefit is created.
Drawings
The invention is further illustrated in the following description with reference to the drawings.
FIG. 1 is a tundish level control curve during a change of ladle according to the present invention.
Detailed Description
The following embodiments are described in order to provide those skilled in the art with a more complete, precise and thorough understanding of the inventive concepts and technical solutions.
Example 1
This example is to control inclusions in steel in the steel during the ladle change period between furnaces of pipeline steel X52 by the control method of the present invention:
installing a ladle down nozzle argon blowing device, wherein the argon blowing device enables the periphery of the ladle down nozzle to keep an argon atmosphere, oxygen and nitrogen in air are prevented from being sucked into molten steel, and the argon pressure reaches 0.25 Mpa; argon is blown between the tundish upper nozzle and the submerged nozzle, and the pressure of the argon reaches 0.2 Mpa; a graphite sealing ring is arranged at the long water gap; the thickness of the molten steel covering agent in the tundish is 50 mm. When the water gap is burnt and washed in the secondary furnace, the residual steel washed away from the water gap is prevented from entering clean molten steel; when the molten steel in the ladle is about to be cast, the liquid level of the tundish is lifted to 42 tons from the working liquid level to the overflow liquid level, so that more operation time is spent, the liquid level of the tundish is not lower than 30 tons when the next furnace is pulled open, and then the liquid level of the tundish is slowly controlled to flow to 38 tons (7 tons per minute). The inclusion condition after the casting blank is rolled into the steel plate in the period of changing the ladle between the furnaces is shown in Table 2.
Example 2
This example is to control inclusions in steel in the steel during the ladle change period between furnaces of pipeline steel X60 by the control method of the present invention:
installing a ladle down nozzle argon blowing device, wherein the argon blowing device enables the periphery of the ladle down nozzle to keep an argon atmosphere, oxygen and nitrogen in air are prevented from being sucked into molten steel, and the argon pressure reaches 0.25 Mpa; argon is blown between a tundish upper nozzle and a submerged nozzle, and the pressure of the argon reaches 0.2 Mpa; a graphite sealing ring is arranged at the long water gap; the thickness of the molten steel covering agent in the tundish is 80 mm. When the water gap is burnt and washed in the furnace secondary chamber, the residual steel washed out from the water gap is prevented from entering clean molten steel; when the molten steel in the ladle is about to be cast, the liquid level of the tundish is lifted to 42 tons from the working liquid level to the overflow liquid level, so that more operation time is spent, the liquid level of the tundish is not lower than 30 tons when the next furnace is pulled open, and then the liquid level of the tundish is slowly controlled to flow to 38 tons (7 tons per minute). The inclusion condition after the casting blank is rolled into the steel plate in the ladle changing period between the furnaces is shown in the table 2.
Example 3
In this example, the control method of the present invention was used to control the inclusion content in steel during the ladle change period between furnaces in the mixed casting of pipeline steel X65 and other steel grades:
installing a ladle down nozzle argon blowing device, wherein the argon blowing device enables the periphery of the ladle down nozzle to keep an argon atmosphere, oxygen and nitrogen in air are prevented from being sucked into molten steel, and the argon pressure reaches 0.25 Mpa; argon is blown between the tundish upper nozzle and the submerged nozzle, and the pressure of the argon reaches 0.2 Mpa; a graphite sealing ring is arranged at the long water gap; the thickness of the molten steel covering agent in the tundish is 70 mm. When the water gap is burnt and washed in the secondary furnace, the residual steel washed away from the water gap is prevented from entering clean molten steel; continuous casting of pipeline steel and other steel grades is carried out, mixed casting operation needs to be carried out in a heat, the liquid level of a tundish is controlled to 12 tons, the liquid level of the tundish is controlled to 30 tons rapidly (13 tons per minute) after the ladle is pulled open, and then the liquid level of the tundish is controlled to 38 tons slowly (7 tons per minute). The inclusion condition after the casting blank is rolled into the steel plate in the period of changing the ladle between the furnaces is shown in Table 2.
Comparative example
The comparative example is the inclusion content in the steel during the ladle change period between the times of casting X60:
installing a ladle down nozzle argon blowing device, wherein the argon blowing device enables the periphery of the ladle down nozzle to keep an argon atmosphere, oxygen and nitrogen in air are prevented from being sucked into molten steel, and the argon pressure reaches 0.25 Mpa; argon is blown between the tundish upper nozzle and the submerged nozzle, and the pressure of the argon reaches 0.2 Mpa; a graphite sealing ring is arranged at the long water gap; when the water gap is burnt and washed in the secondary furnace, the residual steel washed away from the water gap is prevented from entering clean molten steel; different from the embodiment 2, the thickness of the molten steel covering agent in the tundish reaches 110 mm. The liquid level of the tundish is reduced to be below 30 tons in the ladle changing process, and the full flow (13 tons per minute) is directly controlled to be 38 tons after the ladle is pulled out. The inclusion condition after the casting blank is rolled into the steel plate in the period of changing the ladle between the furnaces is shown in Table 2.
Table 1 shows the casting control conditions of examples 1-3 and comparative examples:
TABLE 1 operation at change of package for each example and comparative example
TABLE 2 Steel plate inclusions in examples and comparative examples
As can be seen from the above table: according to the embodiment 1-3 controlled by the method, after the steel plate is rolled by the casting blank at the furnace time ladle changing time period, the thickness grades of A, B, C, D types of inclusions are all less than or equal to 2.0.
Therefore, when the pipeline steel is produced, on the premise of preventing molten steel pollution and reducing the content of non-metallic inclusions in the steel by taking measures in smelting, the whole-process anti-oxidation operation is adopted by the casting machine, the operation method in the process of ladle change between furnaces is improved, and the phenomenon that the inclusions of casting blanks exceed the standard in the period of ladle change between furnaces is obviously reduced.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (4)
1. A method for controlling inclusions in pipeline steel during ladle change is characterized by comprising the following steps:
(1) the whole anti-oxidation operation is well carried out:
(1.1) installing a ladle down nozzle argon blowing device, wherein the argon blowing device keeps an argon atmosphere around the ladle down nozzle to prevent oxygen and nitrogen in air from absorbing molten steel, and the argon pressure reaches 0.22-0.27 Mpa;
(1.2) blowing argon between a tundish upper nozzle and a submerged nozzle, wherein the pressure of the argon reaches 0.18-0.22 Mpa;
(1.3) installing a graphite sealing ring at the long nozzle;
(1.4) the thickness of the molten steel covering agent in the tundish reaches more than 50mm but not more than 80mm
(2) The operation method during the improved furnace transfer comprises the following steps:
(2.1) burning and washing the water gap, and preventing the residual steel washed away from the water gap from entering clean molten steel;
(2.2) the following operations are taken when the package is changed: the high liquid level operation of the tundish is ensured as much as possible, the liquid level of the tundish is not lower than 30 tons when the next ladle is pulled open, if the liquid level of the tundish meets different steel types and is poured in a mixed mode or cannot be ensured to be more than 30 tons due to tight rhythm of molten steel and the like, the total flow is controlled to be 30 tons after the next ladle is pulled open, the flow is slowly controlled to be at the working liquid level after 30 tons, and inclusion is reduced from entering the molten steel to the minimum extent.
2. The method for controlling inclusions in pipeline steel during ladle change according to claim 1, wherein in the step (2.2), the total flow is controlled to 30 tons after the next ladle is pulled, wherein the total flow is 13 tons per minute before 30 tons and 7 tons per minute after 30 tons.
3. The method for controlling inclusions in pipeline steel during ladle change according to claim 1, wherein the argon pressure in the (1.1) is 0.25 Mpa.
4. The method for controlling inclusions in pipeline steel during ladle change according to claim 1, wherein the argon pressure in the (1.2) is 0.2 Mpa.
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|---|---|---|---|---|
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2022
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