Method for controlling recarburization in continuous casting process of ultra-low carbon steel

Abstract

The invention relates to the technical field of steel and iron smelting, and particularly discloses an ultra-low carbon steel continuous casting process recarburization control method which comprises the steps that the continuous casting pouring process comprises the steps that a steel ladle containing refined molten steel is conveyed to a rotary table, and after the rotary table rotates to the pouring position, the molten steel is injected into a tundish; the tundish distributes the molten steel into each crystallizer through a water gap; molten steel recarburization is controlled through a carbon-free tundish covering agent; when conventional low-carbon steel types and medium-carbon steel types are produced, a low-carbon tundish covering agent is used in a matched mode; the tundish covering agent adding mode comprises the steps that for a first casting furnace, after the liquid level of molten steel in a tundish exceeds a slag blocking wall, 50-150 kg of the tundish covering agent is added; when the molten steel level in the tundish reaches the lower edge of a long nozzle of a large ladle, 250-350 kg of the tundish covering agent continues to be added, and the total amount of the tundish covering agent of the first furnace is not larger than 700 kg after casting is started; and for a continuous pouring furnace, the quantity of the added tundish covering agent is added in real time according to the weight of molten steel in a tundish.

Description

Technical Field

[0001] The present application relates to the technical field of steel smelting, and in particular to a method for controlling carbon increase in a continuous casting process of ultra-low carbon steel. Background Art

[0002] Ultra-low carbon steel refers to steel with a carbon content of less than 0.05% for cold rolling. One of the technical difficulties in the production of this type of steel is the control of carbon content. Its production process is complex and the manufacturing technology is strict.

[0003] Carbon has a great influence on the performance of ultra-low carbon steel. Therefore, carbon is a harmful element in ultra-low carbon steel, and the carbon content of the finished product in ultra-low carbon steel should be as low as possible. When developing ultra-low carbon steel smelting technology, in order to obtain ultra-low carbon steel with a carbon content of less than 0.05% or even lower, the control link is generally to prevent the carbon increase of molten steel during the process of converter decarburization, refining and continuous casting into billets. The biggest control difficulty of carbon increase of molten steel is in the continuous casting process.

[0004] Carbon addition during the continuous casting process will affect the quality of the slab, and excessive carbon mass fraction will cause product degradation and low yield rate. Summary of the invention

[0005] The purpose of this application is to provide a method for controlling carbon increase in the continuous casting process of ultra-low carbon steel, so as to solve the problem in the prior art that carbon increase in the continuous casting process will affect the quality of the slab, and excessive carbon mass fraction will cause product degradation and low yield rate.

[0006] To achieve the above-mentioned purpose, the embodiment of the present application provides a method for controlling carbon increase in a continuous casting process of ultra-low carbon steel, comprising: the continuous casting process comprises:

[0007] The ladle containing refined molten steel is transported to the turntable. After the turntable rotates to the pouring position, the molten steel is poured into the tundish.

[0008] The tundish then distributes the molten steel to each crystallizer through the nozzle;

[0009] Using carbon-free tundish covering agent to control carbon increase of molten steel;

[0010] When producing conventional low-carbon steel and medium-carbon steel, low-carbon tundish covering agent is used in conjunction with the other materials.

[0011] The methods of adding tundish covering agent include:

[0012] For the first furnace, when the liquid steel level in the tundish exceeds the slag retaining wall, add 50kg-150kg of tundish covering agent;

[0013] When the steel liquid level in the tundish reaches the lower edge of the ladle long nozzle, continue to add 250kg-350kg of tundish covering agent. The total amount of tundish covering agent for the first batch of pouring should not exceed 700kg.

[0014] For continuous pouring furnaces, the amount of tundish covering agent added is added in real time according to the weight of the molten steel in the tundish.

[0015] Optionally, the total carbon content in the low-carbon tundish covering agent is controlled within 30%.

[0016] Optionally, the total carbon content in the mold slag is controlled within 5.2%, and the melting characteristics of the mold slag are optimized by the Li2O component.

[0017] Optionally, the material quality and composition of the dry material in the tundish refractory material are reselected to eliminate the effect of tundish collapse caused by too low carbon mass fraction.

[0018] Optionally, for continuous pouring heats, ensure that the covering agent can completely cover the molten steel, and the amount per heat shall not exceed 100kg.

[0019] Optionally, measures to improve the operation of adding protective slag into the crystallizer include: adding material with an automatic slag feeder, adding it evenly in a circular distribution manner, not adding too much slag each time, and adding it continuously in small amounts and multiple batches.

[0020] Optionally, measures to improve the operation of adding protective slag into the crystallizer also include: when the casting speed of the casting machine exceeds 3.5m / min, the EM-BR crystallizer electromagnetic braking technology should be used.

[0021] Optionally, the tundish coating contains no carbon.

[0022] The embodiments of the present application have the following advantages:

[0023] Compared with the prior art, the above technical solution provides a method for controlling carbon increase in the continuous casting process of ultra-low carbon steel. During the continuous casting pouring process, the tundish covering agent and protective slag play a major role in carbon increase. During the production process, the carbon mass fraction of the tundish covering agent and protective slag and the liquid level fluctuation during the pouring process are controlled. The raw and auxiliary materials used for continuous casting have a great influence on the carbon increase of the molten steel. The method of the present application effectively controls the mass fraction of the carbon element contained in the tundish covering agent, and adopts a reasonable method of adding the tundish covering agent and protective slag. The present application adopts the crystallizer electromagnetic braking technology to effectively reduce the liquid level fluctuation of the molten steel, thereby effectively controlling the carbon increase of the molten steel in the crystallizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0025] Figure 1 A flow chart of a method for controlling carbon increase in an ultra-low carbon steel continuous casting process provided in at least one embodiment of the present application. DETAILED DESCRIPTION

[0026] The following is a description of the implementation of the present application by specific specific embodiments. People familiar with the technology can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0027] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0028] The present application embodiment provides a method for controlling carbon increase in an ultra-low carbon steel continuous casting process, referring to Figure 1 ,include:

[0029] The continuous casting process includes:

[0030] The ladle containing refined molten steel is transported to the turntable. After the turntable rotates to the pouring position, the molten steel is poured into the tundish.

[0031] The tundish then distributes the molten steel to each crystallizer through the nozzle;

[0032] Using carbon-free tundish covering agent to control carbon increase of molten steel;

[0033] When producing conventional low-carbon steel and medium-carbon steel, low-carbon tundish covering agent is used in conjunction with the other materials.

[0034] The methods of adding tundish covering agent include:

[0035] For the first furnace, when the liquid steel level in the tundish exceeds the slag retaining wall, add 50kg-150kg of tundish covering agent;

[0036] When the steel liquid level in the tundish reaches the lower edge of the ladle long nozzle, continue to add 250kg-350kg of tundish covering agent. The total amount of tundish covering agent for the first batch of pouring should not exceed 700kg.

[0037] For continuous pouring furnaces, the amount of tundish covering agent added is added in real time according to the weight of the molten steel in the tundish.

[0038] In some embodiments, the total carbon content in the low-carbon tundish covering agent is controlled within 30%.

[0039] In some embodiments, the total carbon content in the mold slag is controlled within 5.2%, and the melting characteristics of the mold slag are optimized by the Li2O component.

[0040] In some embodiments, the material quality and composition of the dry material in the tundish refractory material are reselected to eliminate the effect of tundish collapse caused by too low carbon mass fraction.

[0041] In some embodiments, for continuous pouring heats, the covering agent is ensured to completely cover the molten steel, and does not exceed 100 kg per heat.

[0042] In some embodiments, measures to improve the operation of adding protective slag into the crystallizer include: adding material with an automatic slag feeder, adding it evenly in a circular distribution manner, not adding too much slag each time, and adding it continuously in small amounts and multiple batches.

[0043] In some embodiments, measures to improve the operation of adding protective slag into the crystallizer also include: when the casting speed of the casting machine exceeds 3.5m / min, the EM-BR crystallizer electromagnetic braking technology should be used.

[0044] In some embodiments, the tundish coating contains no carbon.

[0045] Specifically, 1. Improvement of raw materials and auxiliary materials

[0046] Without affecting the raw material properties, the carbon content in the tundish covering agent and protective slag should be reduced as much as possible.

[0047] (1) In order to meet the needs of producing ultra-low carbon steel grades, a carbon-free tundish covering agent was developed, which can effectively control the carbon increase of molten steel during the matching process;

[0048] (2) When producing conventional low-carbon steel and medium-carbon steel, a low-carbon tundish covering agent is used, and the total carbon content is controlled within 30%;

[0049] (3) In order to control the effect of carbon enrichment in mold slag on carbon increase of low-carbon steel grades, the total carbon content in the mold slag is controlled within 5.2%, and the melting characteristics of the mold slag are optimized by the Li2O component.

[0050] (4) Since carbon plays a role in the skeleton and bonding of the tundish refractory material, a carbon mass fraction that is too low will cause the tundish working layer to collapse. Therefore, for the refractory material used in the tundish, it is not possible to simply reduce the carbon content. The material quality and composition of the dry material need to be reselected to eliminate the impact of the tundish collapse caused by the low carbon mass fraction.

[0051] 2. Improvement on the method of adding covering agent to the tundish:

[0052] (1) For the first pouring furnace, when the molten steel level in the tundish exceeds the slag retaining wall, add about 100 kg of tundish covering agent. When the molten steel level in the tundish reaches the lower edge of the ladle long nozzle, continue to add about 300 kg of tundish covering agent. The total amount of tundish covering agent for the first pouring furnace shall not exceed 700 kg.

[0053] (2) For continuous pouring furnaces, the amount of covering agent added to the tundish is added in real time according to the weight of the molten steel in the tundish. In principle, it is sufficient to ensure that the covering agent can completely cover the molten steel. The amount per furnace shall not exceed 100 kg.

[0054] (3) The tundish covering agent should be added smoothly, evenly and orderly to minimize the fluctuation of the molten steel level caused by the feeding.

[0055] 3. Measures to improve the operation of adding protective slag in the crystallizer include:

[0056] (1) It is preferred to use an automatic slag feeder to add materials, thereby reducing the unevenness of manual addition and the impact on liquid level fluctuations; when manual addition of protective slag is necessary, it should be added evenly in a circular manner. The amount of slag added each time should not be too large, and it should be added continuously in small amounts and batches.

[0057] (2) When the casting speed exceeds 3.5m / min, the EM-BR crystallizer electromagnetic braking technology should be used. Practice has proved that electromagnetic braking can effectively reduce the fluctuation of the molten steel level in the crystallizer, thereby effectively controlling the carbon increase effect caused by the slag roll of the molten steel.

[0058] 4. The coating of the tundish does not contain carbon.

[0059] 5. Pay attention during operation to ensure the stability of the thickness of the protective slag and liquid slag, and at the same time control the large fluctuations of the liquid level in the ladle and crystallizer.

[0060] In summary, compared with the prior art, in the continuous casting process, the tundish covering agent and protective slag play a major role in carbon increase. During the production process, the carbon mass fraction of the tundish covering agent and protective slag and the liquid level fluctuation during the casting process are controlled. The raw and auxiliary materials used for continuous casting have a great influence on the carbon increase of the molten steel. The method of the present application effectively controls the mass fraction of the carbon element contained in the tundish covering agent, and adopts a reasonable method of adding the tundish covering agent and protective slag. The present application adopts the crystallizer electromagnetic braking technology to effectively reduce the liquid level fluctuation of the molten steel, thereby effectively controlling the carbon increase of the molten steel in the crystallizer.

[0061] Note that, unless otherwise directly stated, all features disclosed in this specification (including any attached claims, abstracts and drawings) may be replaced by alternative features for achieving the same, equivalent or similar purposes. Therefore, unless otherwise explicitly stated, each feature disclosed is only an example of a group of equivalent or similar features. Where used, further, preferably, further and more preferably are simple beginnings for elaborating another embodiment based on the aforementioned embodiment, and the content of the further, preferably, further or more preferably followed by the combination with the aforementioned embodiment constitutes a complete construction of another embodiment. Several further, preferably, further or more preferably settings following the same embodiment can be arbitrarily combined to form another embodiment.

[0062] In the implementation of functions and steps, the corresponding functions and steps in various embodiments may also occur in a different order than shown. For example, two consecutive functions and steps may actually be performed or implemented substantially in parallel, and they may sometimes be performed or implemented in the opposite order, depending on the functions involved.

[0063] Although the present application has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope of protection claimed in the present application.

Claims

1. A method for controlling carbon increase in an ultra-low carbon steel continuous casting process, characterized in that: include: The continuous casting process includes: The ladle containing refined molten steel is transported to the turntable. After the turntable rotates to the pouring position, the molten steel is poured into the tundish. The tundish then distributes the molten steel to each crystallizer through the nozzle; Using carbon-free tundish covering agent to control carbon increase of molten steel; When producing conventional low-carbon steel and medium-carbon steel, low-carbon tundish covering agent is used in conjunction with the other materials. The methods of adding tundish covering agent include: For the first furnace, when the liquid steel level in the tundish exceeds the slag retaining wall, add 50kg-150kg of tundish covering agent; When the steel liquid level in the tundish reaches the lower edge of the ladle long nozzle, continue to add 250kg-350kg of tundish covering agent. The total amount of tundish covering agent for the first batch of pouring should not exceed 700kg. For continuous pouring furnaces, the amount of tundish covering agent added is added in real time according to the weight of the molten steel in the tundish.

2. The method for controlling carbon increase in the ultra-low carbon steel continuous casting process according to claim 1, characterized in that: The total carbon content in the low-carbon tundish covering agent is controlled within 30%.

3. The method for controlling carbon increase in the ultra-low carbon steel continuous casting process according to claim 1, characterized in that: The total carbon content in the mold slag is controlled within 5.2%, and the melting characteristics of the mold slag are optimized through the Li2O component.

4. The method for controlling carbon increase in the ultra-low carbon steel continuous casting process according to claim 1, characterized in that: The material quality and composition of the dry material in the tundish refractory are reselected to eliminate the impact of tundish collapse caused by too low carbon mass fraction.

5. The method for controlling carbon increase in the ultra-low carbon steel continuous casting process according to claim 1, characterized in that: For continuous pouring furnaces, ensure that the covering agent can completely cover the molten steel, and the amount per furnace shall not exceed 100kg.

6. The method for controlling carbon increase in the ultra-low carbon steel continuous casting process according to claim 1, characterized in that: Measures to improve the operation of adding protective slag into the crystallizer include: adding material with an automatic slag feeder, adding it evenly in a circular distribution method, not adding too much slag each time, and adding it continuously in small amounts and multiple batches.

7. The method for controlling carbon increase in the ultra-low carbon steel continuous casting process according to claim 6, characterized in that: Measures to improve the operation of adding protective slag in the crystallizer also include: when the casting speed of the casting machine exceeds 3.5m / min, the EM-BR crystallizer electromagnetic braking technology should be used.

8. The method for controlling carbon increase in the ultra-low carbon steel continuous casting process according to claim 1, characterized in that: The tundish coating does not contain carbon.

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