Production method for increasing number of continuous casting furnaces of dual-phase steel

Abstract

The invention discloses a production method for increasing the number of continuous casting furnaces of dual-phase steel. The production method is characterized by comprising the following steps: 1, component range; 2, molten steel purity; 3, controlling the temperature of molten steel; fourthly, the baking effect of the refractory material is guaranteed; 5, equipment precision control; 6, optimizing the insertion depth of the submersed nozzle; seventhly, a crystallizer and primary cooling are conducted; eighthly, secondary cooling is conducted, according to the steel type characteristics of the dual-phase steel, a secondary cooling system adopts a weak cooling mode, and dynamic control over secondary cooling water is finally achieved according to the micro-unit heat balance principle; 9, the pulling speed is controlled, casting is started at the normal pulling speed of 0.8 m / min to 1.2 m / min and the weight of a tundish is 25 tons, casting is started manually, and a withdrawal and straightening machine is started according to a normal casting program; the pulling speed is set to be 0.4 m / min before casting, and after a new blank is taken out of a crystallizer, the pulling speed is gradually increased to the typical pulling speed. The invention aims to provide the production method for increasing the number of continuous casting furnaces of the dual-phase steel, so that the number of continuous casting furnaces is increased.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting production technology, and in particular relates to a production method for increasing the number of consecutive castings of duplex steel. Background Technology

[0002] With the continuous advancement of automotive lightweighting, the application fields of duplex steel are constantly expanding, and the market demand for duplex steel is constantly increasing. As the main steel type of the first generation of automotive steel, duplex steel accounts for a very large proportion in automotive bodies and parts.

[0003] In continuous casting production, due to the carbon content of duplex steel (0.08%-0.15%), the presence of peritectic reaction leads to large-scale shrinkage of the billet, which easily causes severe fluctuations in the crystallizer level. These fluctuations can affect crystallizer lubrication and heat transfer balance, and cause slag entrapment and steel leakage. Defects such as billet bulging and depressions caused by crystallizer level fluctuations, as well as internal quality problems like center segregation, center porosity, and cracks, are important factors affecting the number of consecutive casting heats. Therefore, designing a reasonable cooling system, casting speed, improving steel purity, and strengthening equipment management are important methods to increase the number of consecutive casting heats. Summary of the Invention

[0004] The purpose of this invention is to provide a production method for increasing the number of consecutive casting furnaces of duplex steel.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention discloses a production method for increasing the number of consecutive casting heats of duplex steel, comprising:

[0007] I. Ingredient Range

[0008] The chemical composition by mass percentage is shown in the table below:

[0009]

[0010] The remainder consists of Fe and unavoidable impurities;

[0011] II. Purity of Molten Steel

[0012] By adjusting the refining slag composition, ensuring sufficient refining time, and implementing a proper argon blowing regime, inclusions are made to float, thus improving the purity of the molten steel. The argon flow rate at the long nozzle of the ladle in the continuous casting process is 10-15 m³ / s. 3 / h, the argon blowing flow rate at the tundish stopper rod water inlet should be 2-6L / min, the three-way argon back pressure should be positive, the slag detection in the ladle should be adjusted to 10%, and the molten steel sampling in the tundish should be carried out when the ladle has 140 tons and 80 tons of molten steel, with a deviation of ±5t.

[0013] The composition of the refining slag and the argon blowing regime are shown in the table below:

[0014]

[0015] III. Steel Temperature Control

[0016] To ensure the self-opening rate of the first ladle heat, prevent oxygen burning in the ladle, and reduce downtime, it is essential to maintain good bottom blowing conditions in the ladle. When pouring the first heat from the tundish, the tundish lining temperature is much lower than the molten steel temperature, absorbing a large amount of heat from the molten steel. If the molten steel temperature drops too quickly, pouring failure is likely. Therefore, the temperature of the first heat from the tundish should be 10℃-15℃ higher than normal pouring. Furthermore, cold ladles, overhaul ladles, and new ladles are prohibited from being used to avoid such accidents. The tundish temperature should be controlled between 15-30℃.

[0017] IV. Ensure the baking effect of refractory materials

[0018] The baking condition of the tundish and submerged entry nozzle is a prerequisite for ensuring successful tundish start-up casting. If the tundish temperature is too high, the residual steel and slag on the ladle cover are easily melted and detached, clogging the tundish entry nozzle. If the temperature is too low, phenomena such as flocculation and seizure may occur, leading to continuous casting failure. During normal start-up casting, the tundish baking should ensure that the tundish temperature is above 1100℃ and the submerged entry nozzle is baked to above 950℃. The weight during the casting process is 60-75t, and the casting is stopped for 15-25t.

[0019] V. Equipment Precision Control

[0020] Increase the frequency of inspection, measurement and calibration between casting sessions; adjust the status and accuracy of inspection equipment, check and measure the crystallizer alignment and the status of crystallizer thermocouples, avoid liquid level fluctuations during production, address unplanned casting stoppages caused by adhesion alarms, and check the ladle turret and ladle sliding gate to ensure normal rotation and operation, enabling continuous casting of multiple furnaces.

[0021] VI. Optimization of Immersion Type Inlet Insertion Depth

[0022] With the increase in the number of continuous casting furnaces, the number of slag lines has been increased from 3 to 4, with a distance of 20mm between the slag lines. The heights of the ladle cars are 60mm, 40mm, 20mm, and 0mm respectively to avoid slag line overlap, which could lead to nozzle erosion and breakage. After the slag lines are used up, a quick replacement of the ladle nozzle is performed.

[0023] VII. Crystallizer and Primary Cooling

[0024] Crystallizer throughput: When using a chamfered crystallizer, the narrow-side copper plate throughput is ≤50,000 tons, and the wide-side copper plate throughput is ≤100,000 tons;

[0025] Single cooling regime: water flow rate 4800L / min on the wide side and 515L / min on the narrow side. The temperature difference between the crystallizer water and the set value should be ≤10℃. The water flow rate on the narrow side can be increased appropriately. The deviation between the actual value and the set value should be ≤5%.

[0026] Adjust the bottom opening and taper: the taper coefficient of the crystallizer bottom opening is 1.20%, and the shrinkage coefficient of the bottom opening is 1.007; the deviation between the actual taper value and the set value is ≤0.3%;

[0027] Crystallizer liquid level: After the liquid level in the crystallizer stabilizes after casting, the actual liquid level must be measured. The target liquid level fluctuation should be ≤ ±3mm.

[0028] Crystallizer vibration parameters: two-stage control, peritectic steel vibration parameters;

[0029]

[0030] 8. Secondary Cooling

[0031] Based on the characteristics of duplex steel, the secondary cooling system adopts a "weak cooling" mode. According to the principle of micro-unit thermal balance, dynamic control of the secondary cooling water is ultimately achieved; see Table 1:

[0032] Cooling water partition Zone 1 Zone 2 Zone 3 4th District 5th District District 6 7th District 8th District District 9 District 10 District 11 Target temperature ℃ 1055 1010 970 950 940 920 910 910 900 900 900

[0033] IX. Speed ​​Control:

[0034] Normal casting speed is 0.8m / min-1.2m / min. For a tundish weight of 25 tons, start casting manually and start the leveling machine according to the normal casting procedure. Before casting, set the casting speed to 0.4m / min. After the new billet exits the crystallizer, gradually increase the casting speed to the typical casting speed.

[0035] Furthermore, in the precision control of the equipment, the deviation of the arc of the sector segment measured before pouring is less than ±0.30mm, and the deviation of the opening degree is less than ±0.50mm.

[0036] Further, check and measure the alignment of the crystallizer. The thermocouples in the crystallizer are in normal condition. Seal any abnormal thermocouples in advance to avoid unplanned pouring stoppages due to factors such as adhesion alarms.

[0037] Furthermore, before casting begins, the ladle turret and ladle sliding gate are inspected to ensure normal rotation and operation, enabling continuous casting of multiple furnaces.

[0038] Furthermore, during normal pouring, the tundish is baked for 150-155 minutes. When the baking device is lifted, the temperature of the tundish is measured to be 1130℃. The immersion gate is then baked to 967℃.

[0039] Furthermore, the typical pulling speed is 1.0-1.2 m / min.

[0040] Furthermore, this method increases the number of consecutive casting furnaces from 5 to 24.

[0041] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0042] The proposed method for increasing the number of consecutive casting heats of duplex steel has been continuously tested and experimented with under the aforementioned conditions, achieving good application results. Initially, the smelting speed of duplex steel was only 1 m / min, with a consecutive casting heat count of 5 heats. Through the aforementioned invention, the smelting speed of duplex steel was increased from 1 m / min to 1.2 m / min, and the consecutive casting heat count increased from 5 heats to 24 heats.

[0043] Since adopting this invention, duplex steel production capacity has been significantly increased, the monthly production frequency and casting intervals for duplex steel have been reduced, and the smelting capacity of duplex steel has been fully released. Furthermore, through the implementation of these measures, the surface and internal quality of duplex steel has been guaranteed, effectively increasing the annual output of duplex steel. Attached Figure Description

[0044] The present invention will be further described below with reference to the accompanying drawings.

[0045] Figure 1 This is a production trend chart. Detailed Implementation

[0046] A production method for increasing the number of consecutive casting heats of duplex steel includes the following steps:

[0047] I. Ingredient Range

[0048] Taking the 150276th casting of the 2150mm twin-strand slab continuous casting machine at Baotou Steel Rare Earth Steel Plate Plant as an example, this casting cycle consists of 24 heats. The chemical composition of the tundish by mass percentage meets the requirements in the table below:

[0049]

[0050] The remainder consists of Fe and unavoidable impurities;

[0051] II. Steel Purity Control

[0052] For casting 150276, the argon blowing flow rate at the long nozzle of the casting package should be controlled at 10-15 m³ / h. 3 / h, using solid stopper rods. The argon blowing flow rate at the top nozzle of the tundish stopper rod should be 2-6L / min, with positive back pressure for all three argon streams. The slag detection rate in the ladle should be adjusted to 10%. Steel samples should be taken from the tundish when the ladle contains 140 tons and 80 tons of steel, with a deviation of ±5t.

[0053] II. Steel Temperature Control

[0054] 150276 Casting Plan: HC340 / 590DP+Z 1650×24 heats, liquidus temperature of steel grade: 1516℃, 04# ladle (normal turnover ladle, good bottom blowing) first heat 1#RH steel loading temperature 1601℃, 10℃ higher than the normal steel loading temperature.

[0055] IV. Ensure the baking effect of refractory materials

[0056] For pour 150276, a No. 15 intermediate ladle (Shandong Guomao, hollow coating material) was used. The baking time for the intermediate ladle was 3:45-6:55, and the ladle was baked for 190 minutes. For normal pours, the intermediate ladle was baked for 150-155 minutes. The temperature of the intermediate ladle was measured at 1130℃ when the baking machine was lifted. The immersion gate was baked to 967℃.

[0057] V. Equipment Precision Control

[0058] Before casting batch 150276, the deviation of the arc of the sector section was measured to be less than ±0.30mm, and the deviation of the opening was less than ±0.50mm. The crystallizer alignment was checked and measured, and the thermocouples of the crystallizer were in normal condition. Abnormal thermocouples were sealed in advance to avoid unplanned casting stoppages due to factors such as adhesion alarms. Before casting started, the ladle turret and the ladle sliding gate were checked and found to be rotating and operating normally, enabling continuous casting of multiple furnaces.

[0059] VI. Optimization of Immersion Type Inlet Insertion Depth

[0060] Casting number 150276 is planned as 17 heats, with casting time from 6:55 AM on August 6, 2025 to 12:39 AM on August 7, 2025, totaling 17 hours and 43 minutes. The slag line usage is as follows:

[0061]

[0062]

[0063] VII. Crystallizer and Primary Cooling

[0064] 1. Steel throughput of the crystallizer: When using a chamfered crystallizer, the copper throughput of the narrow side should be ≤50,000 tons and the copper throughput of the wide side should be ≤100,000 tons.

[0065] 2. Single cooling regime: water flow rate 4800L / min on the wide side and 515L / min on the narrow side, crystallizer water temperature difference ≤10℃.

[0066] 3. 150276 casting section: 1650mm, adjust the bottom opening and taper: crystallizer bottom opening: 1662mm, taper coefficient 1.2%, set taper: 10.0 taper, actual taper: 10.0mm, deviation between actual value and set value ≤0.3%.

[0067] 4. Crystallizer liquid level: After the liquid level of the crystallizer stabilized after the start of casting for the 150276th batch, the actual liquid level was measured to be 100mm from the top of the crystallizer. The actual liquid level was normal, and the liquid level fluctuation was ≤±3mm.

[0068] 5. Crystallizer vibration parameters: Two-stage control, peritectic steel vibration parameters

[0069] 8. Secondary Cooling

[0070]

[0071]

[0072] IX. Implementation of the Anti-Bloating System

[0073] The anti-bulging function calculates the wavelength generated by liquid surface fluctuations and uses the roller spacing of the curved or arc-shaped section at the position of periodic fluctuations to deduce the bulging frequency of liquid surface fluctuations and the harmonic number generated at this position. The anti-bulging model selects the corresponding wavelength model to control the stopper rod action by detecting the actual frequency of the casting machine fluctuations in order to control the periodic liquid level fluctuations generated by automotive dual-phase steel.

[0074] 10. Speed ​​Control:

[0075] For casting cycle 150276, the normal casting speed is 1.2 m / min. The tundish weight is 25 tons. Casting is started manually, and the straightening machine is started according to the normal casting procedure. Before casting, the casting speed is set to 0.4 m / min. After the new billet exits the crystallizer, the casting speed is gradually increased to the typical casting speed of 1.0 m / min. Casting is normal.

[0076] Production trend chart as follows Figure 1 As shown.

[0077] Since adopting this invention, duplex steel production capacity has been significantly increased, the monthly production frequency and casting intervals for duplex steel have been reduced, and the smelting capacity of duplex steel has been fully released. Furthermore, through the implementation of these measures, the surface and internal quality of duplex steel has been guaranteed, effectively increasing the annual output of duplex steel.

[0078] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A production method for increasing the number of continuous casting furnaces for duplex steel, characterized by: Comprise: I. Ingredient range The chemical composition in mass percent is shown in the following table: The rest is Fe and unavoidable impurities; II. Molten steel purity By adjusting reasonable refining slag components, sufficient refining time, reasonable argon blowing system to make inclusions float and improve the purity of molten steel, argon flow rate of long nozzle of ladle is 10-15 m 3 / h, argon flow rate of stopper nozzle of tundish is required to be 2-6 L / min, three-way argon back pressure is positive, detection of slag under ladle is adjusted to 10%, sampling of molten steel in tundish is carried out when the molten steel in ladle is 140 tons and 80 tons, deviation is ±5 t; refining slag components and argon blowing system are as follows: III. Molten steel temperature control In order to ensure the self-opening rate of the first furnace ladle, prevent the ladle from burning oxygen, and reduce downtime, the bottom blowing condition of the ladle should be good; the first furnace in the tundish has a much lower lining temperature than the molten steel temperature, absorbing a large amount of heat from the molten steel; if the molten steel temperature drops too fast, it is easy to fail to open the casting, so the first furnace molten steel temperature in the tundish should be 10-15℃ higher than the normal casting, and cold ladles, overhaul ladles, and new ladles are prohibited from going online to avoid such accidents, and the tundish temperature is controlled at 15-30℃; IV. Ensure the roasting effect of refractory The roasting condition of the tundish and the submerged entry nozzle is the prerequisite for ensuring the success of the tundish opening; if the tundish temperature is too high, the residual steel and slag on the ladle cover will melt and fall off, blocking the upper nozzle of the tundish; if the temperature is too low, it is easy to appear flocculation and other phenomena, leading to continuous casting failure; the normal tundish roasting ensures that the tundish temperature is above 1100℃, the submerged entry nozzle is roasted to above 950℃, and the weight during casting is 60-75t, and the stop casting is 15-25t; V. Equipment precision control Increase the inspection, measurement and calibration frequency between casting; adjust the inspection equipment state and precision, check the measurement of the crystallizer, the state of the crystallizer thermocouple, avoid liquid level fluctuation during production, and check the ladle rotating table, ladle sliding nozzle to ensure normal rotation, normal action, and realize multi-furnace continuous casting; VI. Optimization of submerged entry nozzle insertion depth With the increase of continuous casting furnace number, the original 3 slag lines are increased to 4 slag lines, the distance between slag lines is 20mm, and the tundish car height is 60mm, 40mm, 20m, 0mm respectively to avoid slag line overlap, leading to nozzle erosion and fracture, and fast changing tundish nozzle operation after the end of the slag line; VII. Crystallizer and primary cooling Crystallizer steel volume: chamfered crystallizer is used, narrow side copper plate ≤50000 tons, wide side copper plate ≤100000 tons; Primary cooling system: water flow wide side 4800L / min, narrow side 515L / min, crystallizer water temperature difference ≤10℃, narrow side water flow can be appropriately increased, actual value and set value deviation ≤5%; Adjust the lower mouth and taper: crystallizer lower mouth taper coefficient 1.20%, lower mouth shrinkage coefficient 1.007; taper actual value and set value deviation ≤0.3%; Crystallizer liquid level: after the crystallizer liquid level stabilizes, the actual liquid level must be measured, and the target liquid level fluctuation is ≤±3mm; Crystallizer vibration parameters: secondary control, peritectic steel vibration parameters; VIII. Secondary cooling According to the characteristics of dual-phase steel, the secondary cooling system adopts "weak cooling" cooling mode, and finally realizes the dynamic control of secondary cooling water according to the principle of micro-unit heat balance; see table 1: IX. Drawing speed control: Normal drawing speed 0.8m / min-1.2m / min, tundish weight 25 tons opening, manual opening, starting the drawing and straightening machine with the normal opening program; set the drawing speed to 0.4m / min before opening, and gradually increase the drawing speed to the typical drawing speed after the new billet exits the crystallizer.

2. The production method of increasing the number of continuous casting furnace of dual phase steel according to claim 1, characterized in that: The arc deviation of the measured sector before pouring is less than ±0.30mm, and the opening deviation is less than ±0.50mm.

3. The production method of increasing the number of continuous casting furnace of dual phase steel according to claim 1, characterized in that: The measurement of the crystallizer is checked, the thermal couple of the crystallizer is normal, the abnormal thermal couple is sealed in advance to avoid unplanned pouring caused by sticking alarm and other factors.

4. The production method of increasing the number of continuous casting furnace of dual phase steel according to claim 1, characterized in that: The tundish rotation table and the sliding nozzle of the ladle are checked before pouring, the rotation is normal, the action is normal, and multi-furnace continuous casting is realized.

5. The production method of increasing the number of continuous casting furnace of dual phase steel according to claim 1, characterized in that: The tundish is roasted for 150-155min during normal pouring, the temperature of the tundish measured by lifting the roaster is 1130℃, and the immersion nozzle is roasted to 967℃.

6. The production method of increasing the number of continuous casting furnace of dual phase steel according to claim 1, characterized in that: The typical pulling speed is 1.0-1.2m / min.

7. The production method of increasing the number of continuous casting furnace of dual phase steel according to claim 1, characterized in that: The number of continuous casting furnaces is increased from 5 to 24.

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