An unbalanced tundish

Abstract

The present invention belongs to the technical field of tundishes in continuous casting of iron and steel metallurgy, and particularly relates to an unbalanced tundish. The present invention redesigned the outer wall shape of the tundish, making the outer arc wall and the inner arc wall of the impact zone, as well as the side wall of the pouring zone opposite to the pouring nozzle, all parallel to the target flow direction of the molten steel, thereby reducing the erosion of the molten steel on the inner wall of the tundish and improving the distribution of the molten steel flow field; in addition, the present invention also provides an integral flow stabilizer in the impact zone. By integrally forming the protective wall and the slag retaining wall of the integral flow stabilizer, the floating of the flow stabilizer can be avoided, providing better protection for the bottom and side walls of the impact zone, and the tapping direction of the slag retaining wall is parallel to the target flow direction of the molten steel, which is obtained through simulation research, ensuring that the molten steel flows from the impact zone to the side of the pouring zone far away from the impact zone, thus contributing to optimizing the molten steel flow field in the tundish, extending the residence time of the molten steel in the tundish, and improving the uniformity of the temperature and inclusion content among different casting cycles in the tundish.

Description

Technical Field

[0001] The present invention belongs to the technical field of tundishes in continuous casting of iron and steel metallurgy, and particularly relates to an unbalanced tundish. Background Art

[0002] As a buffer device for molten steel from the ladle to the continuous casting machine, the tundish has unique metallurgical effects in removing inclusions in the molten steel, equalizing the temperature and composition of the molten steel, etc. With the increasingly strict quality requirements, the tundish is no longer used as a simple container, but efforts are made to further remove inclusions in the tundish and prevent secondary pollution of the molten steel. By setting reasonable flow control devices such as dams, weirs, and weirs in the tundish, on the one hand, the molten steel has a longer residence time in the tundish to facilitate the floating of inclusions and improve the cleanliness of the molten steel; on the other hand, the molten steel can flow reasonably in the tundish, the dead zone is as small as possible, the flow field distribution and temperature distribution in the tundish are improved, and the composition of the molten steel is made as uniform as possible, thereby improving the quality of the cast billet.

[0003] To increase production capacity, most high-efficiency continuous casting machines at home and abroad adopt a multi-machine multi-strand design. Due to the large number of strands in the continuous casting machine, a double-tundish setting is adopted for the tundish, and the shape of the tundish is L-shaped. When pouring molten steel into such a tundish, a double-nozzle design is used for the ladle, that is, there are two nozzles under one ladle, and the molten steel can be injected into the two tundishes simultaneously. At this time, the flow stabilizer in the tundish can only be designed under the ladle, that is, on one side of the tundish, which is called an unbalanced tundish design. The impact zone of such a tundish is asymmetrically arranged on one side. However, for the existing unbalanced tundish structures, such as the tundish structures in Chinese patent documents CN213857037U (202022250947.1) and CN202701326U (201220176058.8), the flow stabilizer is vertically arranged with the center line of the tundish nozzle injection flow, which is not conducive to the reasonable distribution of the tundish flow field. There are the following defects: (1) Since the impact zone area of the tundish is small and the distance from the ladle pouring point to the refractory on the side wall of the impact zone is close, especially on the opposite side of the two tundishes, the refractory in the impact zone is severely scoured and eroded, resulting in a low service life of the tundish and being prone to tundish breakthrough accidents in the impact zone after long-term use, posing a great safety hazard to normal production. (2) The closer to the impact zone, the more active the molten steel flow, the greater the liquid level fluctuation in the tundish, and the more severe the scouring and erosion of the tundish slag line; the temperature deviation of the molten steel between strands in the tundish is large, more than 5 °C. For the strands close to the impact zone, the temperature of the molten steel in the tundish is high, and high-temperature breakout accidents are prone to occur. For the strands far from the impact zone, the temperature of the molten steel in the tundish is low, and low-temperature freezing accidents are prone to occur; the residence time deviation of the molten steel between strands is large. For the strands close to the impact zone, the inclusion content is high, and for the strands far from the impact zone, the inclusion content is low, resulting in unstable quality of the cast billet. Summary of the Invention

[0004] The object of the present invention is to provide an unbalanced tundish. The present invention redesigned the outer wall shape of the tundish, making the outer arc wall and the inner arc wall of the impact zone and the side wall of the casting zone opposite to the casting nozzle parallel to the target flow direction of the molten steel, thereby reducing the erosion of the inner wall of the tundish by the molten steel and playing a role in guiding the flow of the molten steel, improving the distribution of the molten steel flow field; in addition, the present invention also provides an integral flow stabilizer in the impact zone. By integrally forming the protective wall and the slag retaining wall of the integral flow stabilizer, the floating of the flow stabilizer can be avoided, better protecting the bottom and side walls of the impact zone, and the steel outlet direction of the slag retaining wall is parallel to the target flow direction of the molten steel, which is obtained through simulation research, ensuring that the molten steel flows from the impact zone to the side of the casting zone far from the impact zone, thus helping to optimize the molten steel flow field in the tundish, prolonging the residence time of the molten steel in the tundish, and improving the uniformity of the temperature and inclusion content between different casting batches in the tundish.

[0005] To achieve the above object, the present invention provides the following technical solution: an unbalanced tundish, comprising a tundish body and an integral flow stabilizer, wherein the tundish body includes an impact zone and a casting zone;

[0006] The casting zone is a right trapezoid structure, the impact zone is located outside the side wall of the lower base of the trapezoid of the casting zone, and the integral flow stabilizer is arranged in the impact zone;

[0007] The casting zone is provided with casting nozzles at intervals parallel to the short waist side wall of the trapezoid on one side of the short waist side wall of the trapezoid, and the long waist side wall of the casting zone, that is, the side wall of the casting zone opposite to the casting nozzle, is arranged parallel to the target flow direction of the molten steel;

[0008] The extension of the long waist side wall of the casting zone trapezoid serves as the outer arc wall of the impact zone, and the inner arc wall of the impact zone intersecting with the lower base side wall of the casting zone trapezoid is parallel to the outer arc wall;

[0009] The upper end surface of the integral flow stabilizer is flush with the upper end surface of the tundish body. The integral flow stabilizer includes a protective wall for protecting the side wall of the impact zone and a slag retaining wall for steel outlet. The bottom of the protective wall, the slag retaining wall and the integral flow stabilizer are integrally formed to form an impact cavity. The slag retaining wall is arranged between the impact zone and the casting zone, and the steel outlet direction of the slag retaining wall is parallel to the target flow direction of the molten steel; due to the integral formation of the protective wall and the slag retaining wall, the connection parts between adjacent protective walls and the connection parts between the slag retaining wall and the protective wall have better strength and are not easily cracked, and can simultaneously play the role of protecting the side wall of the impact zone and prolonging the residence time of the molten steel in the tundish;

[0010] The target flow direction of the molten steel ensures that the molten steel flows from the impact zone to one side of the side wall of the upper base of the trapezoid in the pouring zone, that is, it ensures that the molten steel flows from the impact zone to the side away from the impact zone in the pouring zone. According to the analysis results of the tundish water simulation experiment, after the ladle molten steel is injected into the tundish impact zone, the molten steel flows along the target flow direction of the molten steel, the average residence time of the tundish molten steel is extended by more than 15 seconds, and the dead zone of the molten steel is reduced by about 5%, which is more conducive to the floating of inclusions and the uniformity of the tundish molten steel temperature.

[0011] Another technical solution of the present invention is that the slag retaining wall is perpendicular to the target flow direction of the molten steel;

[0012] The slag retaining wall is provided with a slag discharge port and a diversion port from top to bottom. The diversion port is arranged parallel to the target flow direction of the molten steel, and the diameter of the diversion port is 120 - 150 mm. The size of the diversion port cannot be too large or too small. If the size of the diversion port is too large, the driving force of the molten steel flow is insufficient, affecting the target flow direction of the molten steel; if the size of the diversion port is too small, the flow rate of the molten steel flowing out of the impact chamber is too slow, and it is easy to overflow from the slag discharge port at the upper part of the flow stabilizer. Therefore, in the present invention, the diameter of the diversion port is controlled within 120 - 150 mm.

[0013] Another technical solution of the present invention is that the slag discharge port is a trapezoidal groove located at the center of the upper end face of the slag retaining wall, and the two diversion ports are symmetrically arranged with respect to the center line of the slag retaining wall. Setting the slag discharge port as a trapezoidal groove can reduce the impact wear of the slag on the side wall of the slag discharge port.

[0014] Another technical solution of the present invention is that there are 5 pouring nozzles, and the target flow direction of the molten steel is parallel to the connection line between the center of the impact zone and the center of the second pouring nozzle arranged in the direction of the side wall of the upper base of the pouring zone.

[0015] Another technical solution of the present invention is that the integral flow stabilizer further includes a flow stabilizer inner liner and an impact plate, and the flow stabilizer inner liner and the impact plate are arranged at the bottom of the impact chamber from top to bottom;

[0016] The flow stabilizer inner liner and the impact plate of the flow stabilizer are integrally formed by pressing and then casting with the protective wall and the slag retaining wall. In the present invention, the flow stabilizer inner liner and the impact plate of the flow stabilizer are formed by pressing, with better impact resistance. Moreover, the flow stabilizer inner liner and the impact plate of the flow stabilizer are integrally cast with the protective shell of the flow stabilizer, with better bonding strength between them and not easily cracking and floating. After the molten steel is stabilized by the flow stabilizer inner liner and then poured into the impact chamber, it can reduce the erosion of the connection parts of the adjacent protective walls and the connection parts of the slag retaining wall and the protective wall by the molten steel, and make the steel slag float quickly.

[0017] The technical solution of the present invention also includes: the protective wall and the slag retaining wall are made of corundum, and the flow stabilizer flow stabilizing inner liner and the impact plate are both made of magnesia-carbon. The protective wall and the slag retaining wall made of corundum have the characteristics of high melting point, strong resistance to molten slag erosion, high refractoriness and good chemical stability; while the flow stabilizer flow stabilizing inner liner and the impact plate are both made of magnesia-carbon, which still have temperature strength at high temperature and have good oxidation resistance, erosion resistance and corrosion resistance.

[0018] The technical solution of the present invention also includes: the main phase of the corundum is corundum, and the mass fraction content of Al2O3 is greater than 90%; to ensure that the corundum is more heat-resistant, the Al2O3 content (mass fraction) is greater than 90%, so that the melting point of the corundum reaches 2050 °C;

[0019] The magnesia-carbon includes fused magnesia with a purity of 97.3%, sintered magnesia with a purity of 97% and graphite with a purity of 95%.

[0020] The technical solution of the present invention also includes: the cross-section of the flow stabilizer flow stabilizing inner liner is circular. Setting the cross-section of the flow stabilizer flow stabilizing inner liner as circular plays a buffering role, can improve the flow field of the molten steel in the impact cavity, reduce the erosion of the molten steel on the root of the slag retaining wall and the protective wall and the connection of the side wall of the flow stabilizer, and avoid cracking of the integral flow stabilizer.

[0021] The technical solution of the present invention also includes: the thickness of the slag retaining wall is 200 - 250 mm, and the thickness of the slag retaining wall is twice the thickness of the protective wall. Since the slag retaining wall is on the side of tapping the molten steel and is subjected to greater impact of the molten steel, to improve the erosion resistance, the thickness of the slag retaining wall is set to 200 - 250 mm to avoid damage to the slag retaining wall on the tapping side of the flow stabilizer in the tundish in the later stage and destroy the flow field, and to ensure uniform erosion of the flow stabilizer, the thickness of the slag retaining wall is set to twice the thickness of the protective wall.

[0022] The technical solution of the present invention also includes: the impact zone is pentagonal. To ensure uniform erosion of the flow stabilizer, the impact zone is designed as pentagonal, that is, the integral flow stabilizer is also pentagonal.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] By redesigning the outer wall shape of the tundish, the present invention makes the outer arc wall, the inner arc wall of the impact zone and the side wall of the casting zone opposite to the casting nozzle parallel to the target flow direction of the molten steel, thereby reducing the erosion of the molten steel on the inner wall of the tundish and playing a role in guiding the flow of the molten steel, making the flow trend of the molten steel in the impact zone after pouring consistent with the target flow direction of the molten steel, improving the distribution of the molten steel flow field and reducing the erosion of the side wall of the impact zone.

[0025] In addition, the present invention also provides an integral flow stabilizer in the impact zone. The upper end surface of the integral flow stabilizer is flush with the upper end surface of the tundish body, so that the molten steel can be buffered in the impact cavity, thereby reducing the fluctuation of the molten steel liquid level and enabling the rapid floating of the steel slag. By integrally forming the protective wall and the slag retaining wall of the integral flow stabilizer, the floating of the flow stabilizer can be avoided, providing better protection for the bottom and side walls of the impact zone. Moreover, the steel discharge direction of the slag retaining wall is parallel to the target flow direction of the molten steel, which is obtained through simulation research, ensuring that the molten steel flows from the impact zone to the side of the casting zone far away from the impact zone, thus helping to optimize the molten steel flow field in the tundish, extending the residence time of the molten steel in the tundish, and improving the temperature and inclusion content uniformity among different casting streams. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural view of the unbalanced tundish of the present invention;

[0027] Figure 2 is a perspective view of the unbalanced tundish of the present invention;

[0028] Figure 3 is a schematic structural view of the integral flow stabilizer of the present invention;

[0029] Figure 4 is a perspective view of the integral flow stabilizer of the present invention;

[0030] In the figure, 1 is the tundish body, 11 is the impact zone, and 12 is the casting zone;

[0031] 111 is the outer arc wall, and 112 is the inner arc wall;

[0032] 2 is the integral flow stabilizer, 21 is the protective wall, 22 is the slag retaining wall, 23 is the impact cavity, 24 is the flow stabilizer inner liner, and 25 is the impact plate;

[0033] 221 is the slag discharge port, and 222 is the diversion port;

[0034] 3 is the casting nozzle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention will be described in detail below with reference to the accompanying drawings:

[0036] As Figures 1 - 4 shown, an unbalanced tundish includes a tundish body 1 and an integral flow stabilizer 2. The tundish body 1 includes an impact zone 11 and a casting zone 12.

[0037] The casting zone 12 is a right trapezoidal structure. The impact zone 11 is located outside the side wall of the lower base of the trapezoid of the casting zone 12. The integral flow stabilizer 2 is arranged in the impact zone 11. The impact zone 11 is a pentagon.

[0038] A pouring nozzle 3 is arranged at one side of the short waist side wall of the trapezoid in parallel and at intervals with respect to the short waist side wall of the trapezoid in the pouring area 12, and the long waist side wall of the pouring area 12 is arranged parallel to the target flow direction of the molten steel.

[0039] The extension of the long waist side wall of the trapezoid in the pouring area 12 serves as the outer arc wall 111 of the impact area 11, and the inner arc wall 112 where the impact area 11 intersects with the lower bottom side wall of the trapezoid in the pouring area 12 is parallel to the outer arc wall 111.

[0040] The upper end surface of the integral flow stabilizer 2 is flush with the upper end surface of the tundish body 1. The integral flow stabilizer 2 includes a protective wall 21 for protecting the side wall of the impact area 11 and a slag retaining wall 22 for tapping steel. The protective wall 21, the slag retaining wall 22 and the bottom of the integral flow stabilizer 2 are integrally formed to form an impact chamber 23. To improve its erosion resistance, the thickness of the slag retaining wall 22 is 200 mm, and the thickness of the slag retaining wall 22 is twice the thickness of the protective wall 21. The slag retaining wall 22 is arranged between the impact area 11 and the pouring area 12, and the tapping direction of the slag retaining wall 22 is parallel to the target flow direction of the molten steel.

[0041] Specifically, the slag retaining wall 22 is perpendicular to the target flow direction of the molten steel. The slag retaining wall 22 is provided with a slag discharging port 221 and a diversion port 222 from top to bottom. The diversion port 222 is arranged parallel to the target flow direction of the molten steel, and the diameter of the diversion port 222 is 120 mm. The slag discharging port 221 is a trapezoidal groove located at the center of the upper end surface of the slag retaining wall 22, and the two diversion ports 222 are symmetrically arranged with respect to the center line of the slag retaining wall 22.

[0042] The target flow direction of the molten steel ensures that the molten steel flows from the impact area 11 to one side of the upper bottom side wall of the trapezoid in the pouring area 12.

[0043] Specifically, in this embodiment, there are 5 pouring nozzles 3, and the target flow direction of the molten steel is parallel to the connection line between the center of the impact area 11 and the center of the second pouring nozzle 3 arranged in the direction of the upper bottom side wall of the trapezoid in the pouring area 12.

[0044] The integral flow stabilizer 2 further includes a flow stabilizer inner liner 24 and an impact plate 25, and the flow stabilizer inner liner 24 and the impact plate 25 are arranged at the bottom of the impact chamber 23 from top to bottom. That is, the flow stabilizer inner liner 24 and the impact plate 25 are embedded in the bottom of the integral flow stabilizer 2.

[0045] The flow stabilizer inner liner 24 and the impact plate 25 are integrally formed by casting with the protective wall 21 and the slag retaining wall 22 after being press-molded. Among them, the cross-section of the flow stabilizer inner liner 24 is circular.

[0046] The protective wall 21 and the slag retaining wall 22 are made of corundum, and the flow stabilizer inner liner 24 and the impact plate 25 are both made of magnesia-carbon.

[0047] The corundum-based material has corundum as its main phase, and the mass fraction of Al2O3 is greater than 90%. The magnesia-carbon material includes fused magnesia with a purity of 97.3%, sintered magnesia with a purity of 97%, and graphite with a purity of 95%.

[0048] Application effect of the double tundish with the unbalanced tundish structure of the present invention:

[0049] (1) It effectively solves the problem of unreasonable flow field distribution caused by the asymmetric arrangement on one side of the impact zone of the L-shaped double tundish, prolongs the residence time of molten steel, and improves the temperature and inclusion content uniformity among different tundish streams.

[0050] To verify the tundish temperature control effect, a temperature measuring probe was used to detect the tundish nozzle temperature of the tundish adopting the above scheme, 60 groups of data were obtained and analyzed by comparison. The average maximum temperature difference among different streams was 3.6°C, and the temperature difference control between tundish streams was good. There were 3 tundish breakouts in 2022, all of which were breakout at the start of casting, not high-temperature breakout near the impact zone side, and no low-temperature frozen nozzle accidents occurred.

[0051] To verify the inclusion content in the cast slab, 30 heats of threaded steel rolled products were sampled for inclusion grade detection. The total inclusion grade was between 2.0 and 6.0, and the average total inclusion grade was 3.85. The qualified rate of the total inclusion grade ≤ 5.0 was 96.67%. No large inclusions larger than 200μm were found, and the overall inclusion control was good.

[0052] (2) The service life of the double tundish was increased to an average of 62 hours, the number of tundishes used throughout the year was reduced by 127 pairs. This greatly reduced the refractory consumption of tundishes, large tundish long nozzles, and tundish submerged nozzles, etc., reduced the losses of steel materials such as frequent replacement of tundish cut heads, cut tails, and tundish pouring residues, improved the operation rate of the continuous casting machine, and increased the output.

[0053] Comparative example

[0054] Service condition of the existing double tundish with the unbalanced tundish structure:

[0055] (1) The average service life of the double tundish was 36 hours.

[0056] (2) The temperature difference among different streams of the double tundish was large, with an average of 6°C, and the inclusions in the cast slab after pouring were high, and the qualified rate of the total grade ≤ 5.0 was ≤ 60%.

Claims

1. A non-equilibrium tundish, characterized in that: It includes a tundish body (1) and an integral flow stabilizer (2). The tundish body (1) includes an impact zone (11) and a pouring zone (12). The pouring zone (12) is in a right trapezoidal structure. The impact zone (11) is located outside the side wall of the lower base of the trapezoid of the pouring zone (12). The integral flow stabilizer (2) is arranged in the impact zone (11). On one side of the short waist side wall of the trapezoid of the pouring zone (12), pouring nozzles (3) are arranged at intervals parallel to the short waist side wall of the trapezoid. The long waist side wall of the pouring zone (12) is arranged parallel to the target flow direction of the molten steel. The extension of the long waist side wall of the trapezoid of the pouring zone (12) serves as the outer arc wall (111) of the impact zone (11). The inner arc wall (112) where the impact zone (11) intersects with the side wall of the lower base of the trapezoid of the pouring zone (12) is parallel to the outer arc wall (111). The upper end surface of the integral flow stabilizer (2) is flush with the upper end surface of the tundish body (1). The integral flow stabilizer (2) includes a protective wall (21) for protecting the side wall of the impact zone (11) and a slag retaining wall (22) for tapping steel. The bottom of the protective wall (21), the slag retaining wall (22) and the integral flow stabilizer (2) are integrally formed to form an impact cavity (23). The slag retaining wall (22) is arranged between the impact zone (11) and the pouring zone (12). The steel tapping direction of the slag retaining wall (22) is parallel to the target flow direction of the molten steel. The target flow direction of the molten steel ensures that the molten steel flows from the impact zone (11) to one side of the upper base side wall of the pouring zone (12). The slag retaining wall (22) is perpendicular to the target flow direction of the molten steel. The slag retaining wall (22) is provided with a slag discharge port (221) and a diversion port (222) from top to bottom. The diversion port (222) is arranged parallel to the target flow direction of the molten steel. The diameter of the diversion port (222) is 120 - 150 mm. The two diversion ports (222) are symmetrically arranged with respect to the center line of the slag retaining wall (22). There are 5 pouring nozzles (3). The target flow direction of the molten steel is parallel to the connection line between the center of the impact zone (11) and the center of the second pouring nozzle (3) arranged in the direction of the upper base side wall of the pouring zone (12).

2. The unbalanced tundish according to claim 1, wherein: The slag discharge port (221) is a trapezoidal groove located at the center position of the upper end surface of the slag retaining wall (22).

3. The unbalanced tundish according to claim 1, characterized in that: The integral flow stabilizer (2) further includes a flow stabilizer inner liner (24) and an impact plate (25). The flow stabilizer inner liner (24) and the impact plate (25) are arranged at the bottom of the impact cavity (23) from top to bottom. The flow stabilizer inner liner (24) and the impact plate (25) are integrally formed with the protective wall (21) and the slag retaining wall (22) by pressing and then casting.

4. The unbalanced tundish according to claim 3, characterized in that: The protective wall (21) and the slag retaining wall (22) are made of corundum. The flow stabilizer inner liner (24) and the impact plate (25) are both made of magnesia - carbon.

5. The unbalanced tundish according to claim 4, characterized in that: For the corundum, its main phase is corundum, and the mass fraction content of Al2O3 is greater than 90%. The magnesia - carbon includes fused magnesia with a purity of 97.3%, sintered magnesia with a purity of 97% and graphite with a purity of 95%.

6. The unbalanced tundish according to claim 3, characterized in that: The cross - section of the flow stabilizer inner liner (24) is circular.

7. The unbalanced tundish according to claim 1, wherein: The thickness of the slag retaining wall (22) is 200 - 250 mm, and the thickness of the slag retaining wall (22) is twice that of the protective wall (21).

8. The unbalanced tundish according to claim 1, wherein: The impact area (11) is pentagonal.

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