Refining operation method for reducing mass rephosphorization of molten steel after converter slagging

Abstract

The invention discloses a refining operation method for reducing a large amount of rephosphorization of molten steel after converter slagging, and belongs to the technical field of steelmaking. S2, after converter roughing slag, top slag lime is increased firstly, and then the refining furnace is informed of converter roughing slag; s3, after tapping is finished, the bottom blowing flow is controlled according to the diameter of the rolling position of the slag surface; and S4, the steel ladle reaches a refining waiting position, and the bottom blowing flow continues to be controlled according to the diameter of the slag surface rolling position. S5, the steel ladle reaches a refining work station, the temperature is raised at a low gear, slag is added, and lime is added into fluorite in two batches; s6, after the slag charge is molten, temperature measurement and sampling are conducted, aluminum particles are added in batches, and the bottom blowing flow is controlled; s7, in the refining process, the temperature of molten steel is controlled; s8, after the white slag is generated, the bottom blowing flow is increased; s9, after component adjustment is completed, adding a covering agent, and transferring to a refining waiting position for soft blowing; and S10, controlling time at a refining working position, starting to a waiting position, carrying out soft blowing for more than 8 minutes, and hoisting for continuous casting.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steelmaking, and particularly relates to a refining operation method for reducing the rephosphorization of molten steel after converter slag. BACKGROUND

[0002] Phosphorus is a ubiquitous element in steel, and its presence in steel can significantly affect the performance of steel, especially causing the so-called "cold brittleness" phenomenon. Specifically, when the ambient temperature gradually decreases, the toughness and ductility of steel with high phosphorus content will decrease significantly, becoming more fragile, and thus more likely to suddenly break when subjected to external forces. For this reason, in order to ensure that the steel maintains good mechanical properties and safety during use, most types of steel have very strict requirements and control standards for phosphorus content during production.

[0003] In the process of steelmaking, the dephosphorization operation is a crucial step, and this process is mainly carried out in the converter. The basic principle of dephosphorization is to convert the phosphorus elements dissolved in the molten steel into phosphates that are insoluble in the molten steel through an oxidation reaction, and then effectively transfer these phosphates to the slag, thereby reducing the phosphorus content in the molten steel. The main chemical equation involved in this dephosphorization reaction process is as follows:

[0004] 2[P] + 5(FeO) + 4(CaO) = (3CaO·P2O5) + 5[Fe];

[0005] Therefore, the converter slag often contains a large amount of phosphate components. In order to effectively control the slagging problem during the converter production process, various methods such as slag stopper, slag stop mark, etc. are usually used to prevent excessive discharge of slag. However, during large-scale production, due to various non-steady-state factors such as operation fluctuations, equipment state changes, etc., it is still inevitable to have slagging phenomenon. Once these slags enter the refining furnace treatment link, under the action of high temperature and chemical reaction, they will cause the rephosphorization of molten steel, i.e. the phosphorus elements that have been removed re-enter the molten steel. This process ultimately leads to the phosphorus content in the molten steel exceeding the standard limit, affecting the quality and performance of the steel. SUMMARY

[0006] In order to solve the problems raised in the above-mentioned background technology, the present invention provides a refining operation method for reducing the large amount of rephosphorization of molten steel after the converter slag is removed, and utilizes the LF refining furnace equipment widely used in the steelmaking process of steel enterprises. This equipment is particularly suitable for the refining process flow of steel enterprises. Through this equipment, the rephosphorization phenomenon that occurs in the molten steel after the converter slag is removed during the refining process can be effectively reduced at a relatively low cost. Specifically, by performing refining treatment according to this operation method, the rephosphorization amount of the molten steel can be strictly controlled within 0.005%, thereby ensuring that the composition of the molten steel meets the expected standard requirements and guarantees the quality and performance of the steel. This process not only improves the refining efficiency, but also significantly reduces production costs, providing strong support for the efficient production and quality control of steel enterprises.

[0007] The present invention provides a refining operation method for reducing the large amount of phosphorus regeneration in molten steel after slag removal in a converter, which adopts the following technical solutions:

[0008] A refining operation method for reducing a large amount of rephosphorization of molten steel after slagging in a converter, comprising:

[0009] S1. Perform double slag blocking operation in the converter;

[0010] S2. After the converter is unslaged, first increase the top slag and white ash by 290kg to 310kg, and then notify the refining furnace to unslag the converter;

[0011] S3. After tapping, control the bottom blowing flow rate according to the diameter of the slag surface rolling area of ​​200mm to 300mm;

[0012] S4. Move the ladle to the refining waiting position and continue to control the bottom blowing flow rate according to the diameter of the slag surface rolling area of ​​200mm to 300mm.

[0013] S5. Move the ladle to the refining work station, raise the temperature at low gear, add 50kg to 100kg of slag, add fluorite and white ash in two batches, and control the total ash content at 6kg / t of molten steel;

[0014] S6. After the slag is melted, measure the temperature and take samples. Add 20kg to 40kg of aluminum particles in batches according to the color and shape of the slag, spread them on the slag surface, and slowly perform the white slag operation. The bottom blowing flow rate is 200Nl / min to 300Nl / min;

[0015] S7. During the refining process, the temperature of the molten steel is controlled within the upper and lower limits of the steel grade's top temperature;

[0016] S8, after the white slag, increase the bottom blowing flow rate to increase the contact area between the molten steel and the slag;

[0017] S9, after the ingredients are adjusted, add the covering agent and transfer to the refining waiting position for soft blowing;

[0018] S10. The time at the refining work station is controlled within 25 minutes, and the work station is moved to the waiting position for soft blowing for more than 8 minutes before being hoisted to continuous casting.

[0019] Preferably, S1 includes performing conventional slag blocking and slag blocking operations in the converter.

[0020] Preferably, in S2, the top slag lime is increased by 290 kg, 310 kg or 300 kg.

[0021] Preferably, in S3 and S4, the bottom blowing flow rate is controlled according to the diameter of the slag surface rolling point of 200 mm, 250 mm or 300 mm.

[0022] Preferably, in S5: 50 kg, 60 kg, 70 kg, 80 kg, 90 kg or 100 kg of slag is added.

[0023] Preferably, in S6: 20 kg, 30 kg or 40 kg of aluminum particles are added in batches.

[0024] Preferably, in S7: when the steel grade is Q235BP, the upper and lower limits of the upper stage temperature are 1575°C and 1585°C respectively.

[0025] Preferably, in S8: the bottom blowing flow rate is 300Nl / min to 350Nl / min.

[0026] Preferably, in S8: the bottom blowing flow rate is 300 Nl / min or 350 Nl / min.

[0027] Preferably, the refining equipment is a LF refining furnace.

[0028] In summary, the present invention has the following beneficial technical effects:

[0029] This invention utilizes the LF refining furnace equipment widely used in steelmaking processes by steel companies. This equipment plays a crucial role in the refining process flow. This innovative application not only achieves efficient refining at a relatively low cost, but also significantly reduces the problem of large amounts of rephosphorization in the molten steel after slagging from the converter during the refining process. Specifically, refining according to the operating method of the present invention can strictly control the rephosphorization amount of the molten steel to within 0.005%. This control level greatly improves the stability of the molten steel composition and ensures that the molten steel composition fully meets all process requirements and product quality standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purpose, design control system and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] Please refer to Figure 1 A refining operation method for reducing the large amount of rephosphorization of molten steel after slag removal from a converter comprises the following steps:

[0033] S1. Perform double slag blocking operation in the converter;

[0034] During the converter smelting process, operators strictly adhere to process requirements and implement a double slag-stopping system to improve molten steel purity and reduce impurities. Specifically, this involves using a slag stopper twice during tapping after the converter blowing process. The first stopper prevents the slag from flowing out with the molten steel, and the second stopper further prevents any remaining slag from entering the ladle. This refined double slag-stopping system effectively improves molten steel quality, meeting the high standards required for subsequent refining and continuous casting processes.

[0035] S2. After the converter is unslaged, first increase the top slag and white ash by 290kg to 310kg, and then notify the refining furnace to unslag the converter;

[0036] S3. After tapping, control the bottom blowing flow rate according to the diameter of the slag surface rolling area of ​​200mm to 300mm;

[0037] S4. Move the ladle to the refining waiting position and continue to control the bottom blowing flow rate according to the diameter of the slag surface rolling area of ​​200mm to 300mm.

[0038] S5. Move the ladle to the refining work station, raise the temperature at low gear, add 50kg to 100kg of slag, add fluorite and white ash in two batches, and control the total ash content at 6kg / t of molten steel;

[0039] S6. After the slag is melted, measure the temperature and take samples. Add 20kg to 40kg of aluminum particles in batches according to the color and shape of the slag, spread them on the slag surface, and slowly perform the white slag operation. The bottom blowing flow rate is 200Nl / min to 300Nl / min;

[0040] S7. During the refining process, control the temperature of the molten steel within the upper and lower limits of the steel grade's top temperature to avoid rephosphorization caused by high temperature;

[0041] S8. After the white slag is removed, the bottom blowing flow rate is appropriately increased to increase the contact surface between the molten steel and the slag, thereby increasing the probability of adsorbing inclusions;

[0042] S9, after the ingredients are adjusted, add the covering agent and transfer to the refining waiting position for soft blowing;

[0043] S10. The time at the refining work station is controlled within 25 minutes, and the work station is moved to the waiting position for soft blowing for more than 8 minutes before being hoisted to continuous casting.

[0044] In order to further understand the concept of the present invention, the following is a detailed description:

[0045] S1 specifically includes: conventional slag blocking operation of converter, standard slag blocking operation and double slag blocking operation.

[0046] S2 specifically includes: after the converter slag is unloaded, the top slag ash increases by 290kg, 310kg or 300kg, and the refining furnace converter slag is notified;

[0047] After the converter completes slagging, the amount of white ash in the top slag will be increased accordingly, potentially by 290 kg, 310 kg, or 300 kg, depending on actual needs. This adjustment is intended to ensure a smooth smelting process and consistent product quality. At the same time, relevant departments must immediately notify the refining furnace operators of the converter slagging situation so they can make timely process adjustments and preparations to ensure the continuity and efficiency of the entire smelting process.

[0048] S3 specifically includes: controlling the bottom blowing flow rate after tapping, preferably with a diameter of 200mm to 300mm at the slag surface rolling point, to prevent slag crusting;

[0049] After the tapping process is successfully completed, the bottom blowing flow rate must be carefully controlled and adjusted to ensure that the slag surface tumbles within an appropriate range, with the diameter of the tumble maintained between 200 and 300 mm. This control scale is intended to effectively prevent the slag from forming crusts due to insufficient fluidity in high-temperature environments, thereby ensuring a smooth smelting process and uniform slag distribution, avoiding operational risks and reduced production efficiency caused by crusting.

[0050] S4 specifically includes: moving the ladle to the refining waiting position, and continuing to control the bottom blowing flow rate according to the diameter of the slag surface rolling area of ​​200mm to 300mm.

[0051] As the ladle moves from the furnace to the refining holding station, operators must continuously monitor the dynamic changes in the slag surface. To ensure optimal refining results, the bottom blowing flow rate must be strictly controlled within a 200-300 mm diameter range at the slag surface tumbling point, in accordance with process requirements. This precise control optimizes slag stirring and promotes uniformity of molten steel composition, thereby improving refining efficiency and quality. Throughout the entire operation, relevant parameters must be closely monitored to ensure the stability and accuracy of the bottom blowing flow rate, ensuring a smooth refining process.

[0052] In S3 and S4, the bottom blowing flow rate is controlled according to the diameter of the slag surface rolling point of 200mm, 250mm or 300mm.

[0053] S5 specifically includes: after the ladle reaches the refining work station, the temperature is raised at a low level, 50kg to 100kg of slag is added (for example, 50kg or 60kg or 70kg or 80kg or 90kg or 100kg), fluorite is added in two batches of white ash, and the total ash amount is controlled at 6kg / t of molten steel.

[0054] After the ladle is transported to the refining station, the low gear is first activated to heat up the molten steel to ensure that the temperature of the molten steel is gradually raised to the appropriate refining temperature. During this process, a certain amount of slag remover is added to the molten steel according to actual needs. The specific amount added varies between 50 kg and 100 kg, and can be 50 kg, 60 kg, 70 kg, 80 kg, 90 kg, or 100 kg. The specific value is flexibly adjusted according to the actual situation of the molten steel and the refining requirements. At the same time, fluorite, as a flux, is divided into two batches and evenly added to the white ash to ensure that it is fully mixed and reacted. Throughout the entire process, the total ash content is strictly controlled and accurately measured according to the standard of 6 kg per ton of molten steel to ensure that the refining effect and molten steel quality meet the expected standards.

[0055] S6 specifically includes: measuring the temperature and taking samples after the slag is melted, adding 20kg to 40kg (e.g., 20kg, 30kg, or 40kg) of aluminum pellets in batches according to the color and shape of the slag, evenly spreading them on the slag surface, and slowly performing the white slag operation. The bottom blowing flow rate is 200Nl / min to 300Nl / min;

[0056] Once the slag is completely melted, temperature measurements and sampling are performed to ensure data accuracy and smooth operation. Next, based on the observed changes in the slag's color and morphology, aluminum pellets ranging from 20 kg to 40 kg are added in targeted batches. The specific amount added can be flexibly adjusted based on actual conditions; for example, 20 kg, 30 kg, or 40 kg of aluminum pellets may be added. These pellets are evenly spread over the slag surface, ensuring uniform coverage for subsequent white slag processing. Throughout the entire process, white slag processing requires slow and meticulous operation to avoid problems caused by improper operation. Simultaneously, the bottom blowing flow rate must be strictly controlled, maintaining it within a range of 200 to 300 standard liters per minute to ensure optimal bottom blowing results.

[0057] In S7: When the steel grade is Q235BP, the upper and lower limits of the upper stage temperature are 1575℃ and 1585℃ respectively.

[0058] In S8: the bottom blowing flow rate is 300Nl / min to 350Nl / min. For example, the bottom blowing flow rate is 300Nl / min or 350Nl / min.

[0059] Table 1 is a comparison table of this embodiment and the traditional technology

[0060]

[0061] In the drawings of the embodiments disclosed in the present invention, only the structures involved in the embodiments disclosed in the present invention are involved. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0062] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A refining operation method for reducing the large amount of rephosphorization of molten steel after slag discharge from a converter, characterized in that: include: S1. Perform double slag blocking operation in the converter; S2. After the converter is unslaged, first increase the top slag and white ash by 290kg to 310kg, and then notify the refining furnace to unslag the converter; S3. After tapping, control the bottom blowing flow rate according to the diameter of the slag surface rolling area of ​​200mm to 300mm; S4. Move the ladle to the refining waiting position and continue to control the bottom blowing flow rate according to the diameter of the slag surface rolling area of ​​200mm to 300mm. S5. Move the ladle to the refining work station, raise the temperature at low gear, add 50kg to 100kg of slag, add fluorite and white ash in two batches, and control the total ash content at 6kg / t of molten steel; S6. After the slag is melted, measure the temperature and take samples. Add 20kg to 40kg of aluminum particles in batches according to the color and shape of the slag, spread them on the slag surface, and slowly perform the white slag operation. The bottom blowing flow rate is 200Nl / min to 300Nl / min; S7. During the refining process, the temperature of the molten steel is controlled within the upper and lower limits of the steel grade's top temperature; S8, after the white slag, increase the bottom blowing flow rate to increase the contact area between the molten steel and the slag; S9, after the ingredients are adjusted, add the covering agent and transfer to the refining waiting position for soft blowing; S10. The time at the refining work station is controlled within 25 minutes, and the work station is moved to the waiting position for soft blowing for more than 8 minutes before being hoisted to continuous casting.

2. The refining operation method for reducing a large amount of rephosphorization of molten steel after converter slag removal according to claim 1, characterized in that: S1 includes performing conventional slag blocking and slag blocking operations in the converter.

3. The refining operation method for reducing the large amount of rephosphorization of molten steel after the converter slag is removed according to claim 1, characterized in that: In S2, the top slag lime increases by 290kg, 310kg or 300kg.

4. The refining operation method for reducing the large-scale rephosphorization of molten steel after the converter slag is removed according to claim 1, characterized in that: In S3 and S4, the bottom blowing flow rate is controlled according to the diameter of the slag surface rolling point of 200mm, 250mm or 300mm.

5. The refining operation method for reducing the large amount of rephosphorization of molten steel after the converter slag is removed according to claim 1, characterized in that: In S5: add 50kg, 60kg, 70kg, 80kg, 90kg or 100kg of slag.

6. The refining operation method for reducing a large amount of rephosphorization of molten steel after slag removal from a converter according to claim 1, characterized in that: In S6: add 20kg, 30kg or 40kg of aluminum pellets in batches.

7. The refining operation method for reducing a large amount of rephosphorization of molten steel after slag removal from a converter according to claim 1, characterized in that: In S7: When the steel grade is Q235BP, the upper and lower limits of the upper stage temperature are 1575℃ and 1585℃ respectively.

8. The refining operation method for reducing a large amount of rephosphorization of molten steel after slag removal from a converter according to claim 1, characterized in that: In S8: the bottom blowing flow rate is 300Nl / min to 350Nl / min.

9. The refining operation method for reducing a large amount of rephosphorization of molten steel after slag removal from a converter according to claim 1, characterized in that: In S8: the bottom blowing flow rate is 300 Nl / min or 350 Nl / min.

10. The refining operation method for reducing large amounts of rephosphorization of molten steel after slag removal from a converter according to any one of claims 1 to 9, characterized in that: The refining equipment is LF refining furnace.

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