A tundish and separation method for facilitating inclusion separation of low carbon steel liquid

Abstract

The application provides a tundish facilitating low-carbon steel molten steel inclusion separation, which comprises a tundish body connected with a long nozzle and a submerged nozzle, front and rear stop walls are arranged in sequence between the long nozzle and the submerged nozzle along the flow direction of the molten steel, the front and rear stop walls are vertically arranged, and the edges of the front and rear stop walls are fixedly connected with the inner wall of the tundish body; a plurality of front guide holes are arranged on the front stop wall in an array, and a plurality of rear guide holes are arranged on the rear stop wall in an array; a gas curtain mechanism is further arranged between the front and rear stop walls, and the gas curtain mechanism comprises a diffusion type gas permeable brick arranged at the bottom of the tundish body. The application also provides a molten steel inclusion separation method. The application effectively prolongs the residence time of the molten steel in the gas curtain separation zone, and greatly improves the molten steel inclusion separation environment and improves the inclusion removal rate through the cooperation of the front and rear stop walls and the gas curtain mechanism.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steelmaking, in particular to a tundish facilitating the separation of inclusions in low-carbon molten steel and a separation method. BACKGROUND

[0002] The tundish is an important vessel between the ladle and the mould for improving the flow field and temperature field of the molten steel, has multiple metallurgical functions such as optimizing the flow of the molten steel, separating inclusions, controlling overheating and homogenizing heat, and is an important link for improving the steel yield and quality; the role of the tundish cannot be ignored for the smooth operation of continuous casting or for ensuring the purity of the molten steel to meet the requirements. Generally speaking, a large-capacity tundish will make the flow state of the molten steel more complex, making the separation of inclusions more difficult, especially for low-carbon steel. In order to make the large-capacity tundish still have good separation effect of inclusions, flow control devices such as retaining walls, dams, weirs and turbulence inhibitors are often used, and through the cooperation of these flow control devices, the flow direction and heat diffusion of the molten steel and the behavior of non-metallic inclusions in the tundish can be significantly determined, the actual residence time of the molten steel is increased, the piston zone is increased, the dead zone is reduced, and the removal of inclusions is more beneficial to floating.

[0003] In recent years, in order to improve the removal effect of inclusions in the molten steel, many scholars and researchers have designed various types of flow control schemes and inclusion removal methods for different tundish structures and steel grades. Chinese patent 201220030924.2 discloses a tundish retaining wall with a gas permeable brick, which can change the flow state of the molten steel, reduce the "dead zone" existing on both sides of the tundish retaining wall, promote the uniformity of the composition and temperature of the molten steel in the tundish, and also remove inclusions in the steel. However, the gas permeable brick of this invention is a conventional gas permeable brick, the gas holes in the brick are relatively large and not uniform enough, which is not conducive to improving the removal rate of small-particle inclusions, and large-size bubbles are easy to cause the exposure of the molten steel after breaking when floating to the slag layer, causing secondary oxidation of the molten steel.

[0004] Chinese patent 201810291164.2 discloses a flow control type tundish structure capable of filtering inclusions in molten steel, comprising a tundish divided into three section interval type cavities, including an impact area cavity in the middle and pouring area cavities on both sides, a long pouring nozzle is vertically arranged at the center position of the impact area cavity, the molten steel flows out from the long pouring nozzle and pours into the impact area cavity, and a turbulence inhibitor opposite to the long pouring nozzle is arranged at the bottom of the cavity below the long pouring nozzle, the molten steel flowing out from the long pouring nozzle collides with the turbulence inhibitor after buffering and mixing; a filter assembly is arranged between the impact area cavity and the pouring area cavities on both sides, which filters the buffered and mixed molten steel in the impact area cavity and then sends it into the pouring area cavities on both sides, and the pouring area cavities are provided with water outlets at the bottom of the cavity, and the filtered molten steel flows into the pouring area cavities and then flows out from the water outlets. However, the technical solution only realizes the collision and separation of inclusions through the structure of slag blocking filter wall, dam flow guide groove and dam flow guide hole, but due to the disorder of molten steel collision, the collision and separation of small inclusions are uncontrollable, and the separation effect is poor.

[0005] Therefore, how to solve the difficulty of separating inclusions in the existing low carbon steel molten steel in the tundish and realize the simultaneous and effective separation of large particle inclusions and small inclusions has become a difficult problem to be solved at present. SUMMARY

[0006] To solve the above problems existing in the prior art, the purpose of the present application is to provide a tundish and separation method for facilitating the separation of inclusions in low carbon steel molten steel.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is:

[0008] A tundish for facilitating the separation of inclusions in low carbon steel molten steel, comprising a tundish body connected with a long nozzle of a ladle, an immersion type water outlet is arranged at the bottom of the tundish body, a front dam and a rear dam are arranged in sequence along the flow direction of the molten steel between the long nozzle and the immersion type water outlet, the front dam and the rear dam are both vertically arranged, and the edges of the front dam and the rear dam are both fixedly connected with the inner wall of the tundish body; a plurality of front flow guide holes are arranged on the front dam, and a plurality of rear flow guide holes are arranged on the rear dam; a gas curtain mechanism is further arranged between the front dam and the rear dam, the gas curtain mechanism comprises a dispersion type gas brick arranged at the bottom of the tundish body, and the dispersion type gas brick is connected with a tundish sealing argon pipe.

[0009] The further improvement of the present application is that the inlet end of the front flow guide hole is higher than the outlet end and is downwardly inclined, and the inlet end of the rear flow guide hole is lower than the outlet end and is upwardly inclined.

[0010] The further improvement of the present application is that the angle alpha between each row of front guide holes and the horizontal direction is reduced by equal angle from top to bottom, and the equal angle reduction value delta alpha is 3-5 degrees; the angle beta between each row of rear guide holes and the horizontal direction is increased by equal angle from top to bottom, and the equal angle increase value delta beta is 3-5 degrees.

[0011] The further improvement of the present application is that the vertical distance H0 between the geometric center of the uppermost row of front guide holes and the working liquid level of the tundish is 100-150 mm, the vertical distance between the geometric center of the lowermost row of front guide holes and the bottom of the tundish body is 100 mm, and the rest of the rows of front guide holes are arranged at equal intervals in the vertical direction; the front baffle and the rear baffle are symmetrically arranged.

[0012] The further improvement of the present application is that the front guide holes and the rear guide holes can be circular holes or rectangular holes, and the equivalent diameter of the front guide holes and the rear guide holes is 20-40 mm.

[0013] The further improvement of the present application is that the dispersion type porous plug is composed of a gas permeable layer, a dense layer and an argon passage, the dense layer is a brick body shell, the dense layer is filled with the gas permeable layer, and the argon passage is embedded at the bottom of the gas permeable layer and communicates with the gas permeable layer; the length of the dispersion type porous plug is consistent with the inner cavity width of the tundish, and the width of the dispersion type porous plug is 120-150 mm.

[0014] The further improvement of the present application is that the distance between the front baffle and the rear baffle is 5-10 times the width of the dispersion type porous plug; the distance between the long nozzle and the geometric center of the lower end surface of the front baffle is 10-15 times the distance between the front baffle and the rear baffle; and the distance between the submerged outlet and the geometric center of the lower end surface of the rear baffle is 8-10 times the distance between the front baffle and the rear baffle.

[0015] A separation method based on a tundish device for facilitating the separation of low-carbon steel inclusions, specifically after the molten steel flows into the tundish through the long nozzle, under the continuous guidance of the front guide holes and the rear guide holes, the molten steel flows in a V shape in the gas curtain separation zone, and under the blowing of the argon gas curtain, the inclusions in the molten steel continuously float to the top of the molten steel, and the molten steel enters the continuous casting machine through the submerged outlet for continuous casting.

[0016] The further improvement of the present application is that the argon blowing amount of the gas curtain mechanism is 0.3-0.8 m³ / h.

[0017] The further improvement of the present application is that the argon blowing amount of the gas curtain mechanism during the steady-state pouring process is M m 3 / h, and when non-steady-state pouring is performed, the argon blowing amount of the gas curtain mechanism is reduced by 10-15% M for every 10% reduction in the liquid level height of the molten steel.

[0018] Due to the adoption of the above technical scheme, the present application has achieved the following technical progress:

[0019] The present application provides a separation method for facilitating the separation of inclusions in low-carbon steel molten steel, which effectively promotes the floating removal rate of inclusions in the molten steel by setting a front baffle, a rear baffle and a gas curtain mechanism between the two baffles in the tundish, and significantly improves the cleanliness of the molten steel.

[0020] The method of the present application makes the molten steel flow into the gas curtain separation zone through the front guide hole on the front baffle, and then flow into the pouring zone through the rear guide hole on the rear baffle, and the flow direction of the molten steel in the gas curtain separation zone is in the shape of V, which can make the molten steel flow into the gas curtain separation zone from the impact area of the tundish faster, facilitate the faster action of the bottom gas curtain, and the efficiency of purifying the molten steel will be faster; in addition, the rear guide hole inclined upward has a certain lifting effect on the molten steel, effectively prolongs the residence time of the molten steel in the gas curtain separation zone, and improves the removal rate of inclusions.

[0021] The present application sets a gas curtain mechanism for blowing argon upward between the front baffle and the rear baffle, forms a diffuse type gas curtain baffle, and the diffuse type gas curtain baffle can blow the molten steel upward, and the larger inclusions in the molten steel are continuously floated and separated by the blowing; as for the tiny inclusions in the molten steel, the small bubbles formed by diffusion have surface tension, and gradually adsorb the tiny inclusions in the molten steel during the floating process until the slag layer on the surface of the molten steel, and the inclusions are released after the bubbles burst, and the inclusions are absorbed by the surface slag layer, so that the large inclusions and tiny inclusions in the molten steel are effectively separated at the same time, and the removal effect of the inclusions in the molten steel is improved. At the same time, the extension of the residence time of the molten steel gives the inclusions enough floating time, so that the inclusions in the molten steel can be fully separated and floated, and the cleanliness of the molten steel entering the pouring zone is further improved.

[0022] The inclination angle of the front guide hole and the rear guide hole of the present application changes according to the height and other angles of the position, which can ensure that each stream of molten steel can flow in the shape of V, and has enough floating time of inclusions; and also avoids the dead volume of the tundish by changing the flow rate, eliminates the inclusions remaining in the dead angle of the tundish, and the flow of the molten steel is more stable and smooth; and can make the molten steel in the tundish evenly distributed to each crystallizer for solidification, significantly improving the consistency of each stream of the multi-stream tundish.

[0023] The tundish of the present application has the advantages of simple structure, reasonable design, convenient installation and operation, low maintenance cost in later period, wide application range, i.e. it can replace the original tundish, or can be improved and optimized based on the structure of the original tundish, and is suitable for single-stream slab tundish and multi-stream T-shaped tundish, and has strong practicability. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1This is a schematic diagram of the overall structure of the present invention;

[0025] Figure 2 This is a side view of the front retaining wall structure.

[0026] Figure 3 for Figure 1 A magnified structural diagram of part A in the middle;

[0027] Figure 4 This is a top view of the structure of a dispersion-type permeable brick.

[0028] Figure 5 This is a partial sectional view of the front retaining wall.

[0029] Figure 6 This is a partial sectional view of the rear retaining wall.

[0030] In the diagram, 1 is the tundish body, 2 is the immersion outlet, 3 is the front baffle, 4 is the rear baffle, 5 is the front guide hole, 6 is the rear guide hole, 7 is the diffused permeable brick, 7-1 is the permeable layer, 7-2 is the dense layer, and 7-3 is the argon channel. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings.

[0032] A type of tundish that facilitates the separation of inclusions in molten low-carbon steel, such as... Figure 1 As shown, the system includes a tundish body 1, which is connected to the ladle via a long nozzle. A submerged inlet outlet 2, connected to the continuous casting machine's crystallizer, is located at the bottom of the tundish body 1. A front baffle wall 3 and a rear baffle wall 4 are sequentially arranged between the long nozzle and the submerged inlet outlet 2 along the flow direction of the molten steel. Both the front and rear baffle walls 3 and 4 are vertically arranged, and their edges are fixedly connected to the inner wall of the tundish body 1. An upward-blowing argon gas curtain mechanism is also provided between the front and rear baffle walls 3 and 4. The tundish is divided into three areas by the front and rear baffle walls 3 and 4: the front end of the front baffle wall 3 is the tundish impact zone, the rear end of the rear baffle wall 4 is the casting zone, and the area between the front and rear baffle walls 3 and 4 is the gas curtain separation zone.

[0033] like Figure 2 As shown, the front baffle 3 has n rows of front guide holes 5 evenly spaced from top to bottom. The n rows of front guide holes 5 are numbered from top to bottom as row 1, row 2, ..., row i, ..., row n, where n is a positive integer. Each row contains several horizontally evenly distributed front guide holes 5. The geometric center distance between two adjacent front guide holes 5 in the same row is 100mm to 150mm. The two adjacent rows of front guide holes 5 are staggered.

[0034] The geometric center of the first row of front guide holes 5 is perpendicularly positioned at a distance H0 from the working liquid surface of the tundish to prevent free-level protective slag from entering the front guide holes 5 and entraining molten steel. The geometric center of the nth row of front guide holes 5 is at least 100mm from the bottom surface of the front baffle 3 to ensure that the molten steel can fully contact the argon gas after entering the gas curtain separation zone. The vertical spacing between the geometric centers of adjacent rows of front guide holes 5 is 15mm to 35mm, which can be reasonably selected based on the specific type and specifications of the tundish, as well as the flow rate of the molten steel.

[0035] like Figure 5 As shown, the inlet end of the front guide hole 5 is higher than the outlet end and is inclined downwards, and the angle α between each row of front guide holes 5 from top to bottom and the horizontal direction is... i The angle gradually decreases. Specifically, the angle α1 between the first row of front guide holes 5 and the horizontal direction is 30°~45°, and the angle α1 between the nth row of front guide holes 5 and the horizontal direction is... n The angle is 5°~10°, and the angle difference Δα between the two adjacent rows of front guide holes 5 and the horizontal direction is 3°~5°. The appropriate angle should be selected according to the specifications of the tundish and the specific conditions such as the flow rate of the molten steel.

[0036] The front baffle 3 and the rear baffle 4 are symmetrical structures. Specifically, the rear baffle 4 has m rows of rear guide holes 6 evenly spaced from top to bottom. The m rows of rear guide holes 6 are numbered 1, 2, ..., j, ..., m from top to bottom, where m is a positive integer. Each row contains several equally spaced rear guide holes 6, and the geometric center distance between two adjacent rear guide holes 6 in the same row is 100mm to 150mm; adjacent rows of rear guide holes 6 are staggered.

[0037] The geometric center of the first row of rear guide holes 6 is perpendicularly distance h0 from the working liquid surface of the tundish to 100mm~150mm to prevent free-level protective slag from entering the rear guide holes 6 and being drawn into the molten steel. The geometric center of the nth row of rear guide holes 6 is at least 100mm from the bottom surface of the rear baffle 4. The vertical spacing between the geometric centers of adjacent rows of rear guide holes 6 is 15mm~35mm, which can be reasonably selected based on the specific type and specifications of the tundish, as well as the flow rate of the molten steel.

[0038] like Figure 6 As shown, the inlet end of the rear guide hole 6 is lower than the outlet end and is inclined upwards, and the angle β between the rear guide hole 6 and the horizontal direction from top to bottom is... i The angle gradually increases. Specifically, the angle β1 between the first row of rear guide holes 6 and the horizontal direction is 135°~150°, and the angle β1 between the m-th row of rear guide holes 6 and the horizontal direction is... mThe angle difference Δβ between the two adjacent rows of rear flow guide holes 6 and the horizontal direction is 3°-5°, and is reasonably selected according to the specifications of the tundish and the flow rate of the molten steel.

[0039] The front flow guide hole 5 and the rear flow guide hole 6 can be a circular hole or a rectangular hole, and can be adjusted according to the production conditions on site. The equivalent diameter of the front flow guide hole 5 and the rear flow guide hole 6 is preferably 20mm-40mm, which can ensure the normal flow of the molten steel and avoid the blockage of the flow guide hole by the steel slag, thereby avoiding frequent shutdown for cleaning and maintenance, and realizing long-term normal operation and use.

[0040] The height of the front baffle wall 3 and the rear baffle wall 4 is the same as the depth of the tundish pool, and the thickness of the front baffle wall 3 and the rear baffle wall 4 is 90mm-120mm, which ensures that it remains stable under the impact of the molten steel.

[0041] The gas curtain mechanism includes a dispersion type gas permeable brick 7 arranged at the bottom of the tundish body 1. Figure 3 、 Figure 4 As shown in the drawings, the dispersion type gas permeable brick 7 is composed of a gas permeable layer 7-1, a dense layer 7-2 and an argon passage 7-3. The dense layer 7-2 is a brick shell, the dense layer 7-2 is filled with the gas permeable layer 7-1, the argon passage 7-3 is embedded at the bottom of the gas permeable layer 7-1 and is in communication with the gas permeable layer 7-1, and the other end of the argon passage 7-3 is in communication with the tundish sealing argon main pipe. Argon enters through the argon passage 7-3 and is sprayed upward in a planar manner by the gas holes of the gas permeable layer 7-1, forming a gas curtain baffle wall with a certain width.

[0042] The dense layer 7-2 is sintered from sintered corundum and zirconium corundum refractory materials as main materials, the gas permeable layer 7-1 is composed of zirconium aluminum silicon gas permeable material, the dense layer 7-2 and the gas permeable layer 7-1 are bonded by a binder, i.e. pure calcium aluminate cement, to form an integral body, which has better slag resistance, wear resistance and erosion resistance. The porosity of the gas holes of the gas permeable layer 7-1 is 25%-30%, and the pore size of the gas holes is ≤0.2mm, so as to ensure that the formed bubbles are more fine and the formed gas is more uniform, and the smaller the bubbles, the more conducive to the floating removal of small particle inclusions.

[0043] The length of the dispersion type gas permeable brick 7 is consistent with the inner cavity width of the tundish, the width of the dispersion type gas permeable brick 7 is 120mm-150mm, and the width is too small to reduce the gas curtain effect, the contact area of argon and molten steel is small, and the separation effect of inclusions in the molten steel is affected; if the width is too large, the gas curtain effect is too strong, which may cause the molten steel to splash or be exposed. The dispersion type gas permeable brick 7 is located at 1 / 4 to 3 / 4 between the front baffle 3 and the rear baffle 4, combined with the inclined guide of the front guide hole 5 and the rear guide hole 6, to ensure that the molten steel is blown by the gas curtain baffle when approaching and falling to the bottom of the tundish, and the rising time of the inclusions in the molten steel is prolonged. Generally, the position of the front baffle 3 of the application is close to the impact area of the tundish, and the speed of the molten steel passing through the front baffle 3 guide hole is larger than that of the rear baffle 4, so the gas curtain position is close to the front baffle 3. Through the action of the gas curtain, the impact speed of the molten steel is slowed down, thereby prolonging the motion trajectory of the molten steel, which is beneficial to the floating removal of inclusions; at the same time, under the driving action of the gas curtain, the molten steel has a certain kinetic energy when flowing to the outer pouring area of the rear baffle 4, so that the molten steel is more easily flowed to the far end area of the tundish, and the proportion of the dead zone volume is reduced.

[0044] The distance between the front baffle 3 and the rear baffle 4 is 5-10 times the width of the dispersion type gas permeable brick 7; and the distance between the long nozzle and the geometric center of the lower end surface of the front baffle 3 is 10-15 times the distance between the front baffle 3 and the rear baffle 4, so as to prevent the flow state of the molten steel in the impact area of the tundish from being disturbed. The distance between the tundish submerged outlet 2 and the geometric center of the lower end surface of the rear baffle 4 is 8-10 times the distance between the front baffle 3 and the rear baffle 4, so as to prevent the molten steel from flowing out too early, shorten the residence time of the molten steel, and insufficient removal of inclusions.

[0045] The separation method of the inclusions in the molten steel is to use the above-mentioned tundish equipment, after the molten steel flows into the tundish through the long nozzle, under the continuous guidance of the front guide hole 5 and the rear guide hole 6, the molten steel flows in a V shape in the gas curtain separation area, and under the blowing of the argon gas curtain, the inclusions in the molten steel are continuously floated up.

[0046] In the separation process of the inclusions in the molten steel, the argon blowing amount of the gas curtain mechanism has a significant influence on the separation effect. If the argon blowing amount is too large, it is easy to cause the molten steel surface to be exposed or the molten steel to splash, and if the argon blowing amount is too small, the gas curtain baffle cannot be formed, and the floating effect of the inclusions in the molten steel cannot be ensured. The argon blowing amount of the gas curtain mechanism is 0.3m³ / h-0.8m³ / h, and the actual argon blowing amount can be determined comprehensively according to the tundish capacity, liquid level height and casting speed and other casting conditions, to avoid causing the tundish working liquid level to fluctuate greatly.

[0047] In the tundish pouring process, the argon blowing amount in the steady pouring and the unsteady pouring is adjusted in time, generally, the argon blowing amount in the unsteady pouring is less than that in the steady pouring. The argon blowing amount in the steady pouring process is set as Mm 3 / h, when the unsteady pouring is carried out, the argon blowing amount is reduced by 10%~15% M corresponding to the reduction of 10% of the liquid level height of the molten steel, so as to ensure the effect of the gas curtain barrier wall and avoid causing the slag entrapment to cause the secondary pollution of the molten steel.

[0048] The application will be described in detail below in combination with the embodiments.

[0049] Embodiment 1

[0050] A double-flow slab tundish with a pouring section of 1020*200 mm 2 is adopted, the front barrier wall 3 and the rear barrier wall 4 are arranged in the tundish, the height of the front barrier wall 3 and the rear barrier wall 4 is 990 mm, which is the same as the depth of the tundish molten pool, the thickness of the front barrier wall 3 and the rear barrier wall 4 is 100 mm, and the front barrier wall 3 and the rear barrier wall 4 are symmetrically arranged.

[0051] Specifically, on the front barrier wall 3, the geometric center distance of two adjacent front guide holes 5 in the same row is 100 mm, the vertical distance between the geometric center of the first row of front guide holes 5 and the working liquid surface of the tundish is 100 mm, the distance between the geometric center of the lowermost row of front guide holes 5 and the bottom surface of the front barrier wall 3 is 100 mm, and the vertical row spacing is 35 mm. The included angle α1 between the first row of front guide holes 5 and the horizontal direction is 30°, the included angle α n between the lowermost row of front guide holes 5 and the horizontal direction is 10°, and the included angle α i between the front guide holes 5 from top to bottom and the horizontal direction decreases by 5°.

[0052] On the rear barrier wall 4, the geometric center distance of two adjacent rear guide holes 6 in the same row is 100 mm, the vertical distance between the geometric center of the first row of rear guide holes 6 and the working liquid surface of the tundish is 100 mm, the distance between the geometric center of the lowermost row of rear guide holes 6 and the bottom surface of the rear barrier wall 4 is 100 mm, and the vertical row spacing is 35 mm. The included angle β1 between the first row of rear guide holes 6 and the horizontal direction is 150°, the included angle β n between the lowermost row of rear guide holes 6 and the horizontal direction is 170°, and the included angle β i between the rear guide holes 6 from top to bottom and the horizontal direction increases by 5°.

[0053] The front guide holes 5 and the rear guide holes 6 are circular holes, and the equivalent diameters are both 20 mm.

[0054] The size of the diffused type gas permeable brick 7 is 200mm*120mm*120mm, the distance between the front dam wall 3 and the rear dam wall 4 is 8 times the width of the diffused type gas permeable brick 7; the distance between the geometric center of the lower end surface of the front dam wall 3 and the long nozzle is 10 times the distance between the front dam wall 3 and the rear dam wall 4, and the distance between the geometric center of the lower end surface of the rear dam wall 4 and the submerged water outlet is 8 times the distance between the front dam wall 3 and the rear dam wall 4.

[0055] During pouring, the tundish pulling speed is 1.35 m / min.

[0056] (I) steady pouring state

[0057] During steady pouring, the steel flow rate in the long nozzle is about 1.8 m / s, and the argon blowing amount of the gas curtain mechanism is 0.4 m 3 / h.

[0058] The speed of the molten steel reaching the front dam wall 3 via the tundish impact zone is about 0.1 m / s, and after passing through the front guide hole 5, it accelerates downward to more than 0.2 m / s. After the action of the gas curtain dam wall, the downward flowing molten steel is gradually lifted, promoting the floating of inclusions, and the tiny bubbles of the gas curtain dam wall further wrap the inclusions to float to the slag layer; after the molten steel passes through the gas curtain dam wall, it enters the pouring zone under the action of the rear guide hole 6 on the rear dam wall 4, and after forming a circulation at the upper part, it flows towards the submerged nozzle.

[0059] (II) non-steady pouring state

[0060] The non-steady state includes the states of starting pouring, changing ladle and stopping pouring, etc. At this time, the tundish steel level is unstable, especially when the liquid level is lowered and the long nozzle flow is doubled, which is easy to cause steel slag mixing, and the conditions for the removal of inclusions are poor. Under the non-steady pouring, the molten steel liquid level is lowered, and the argon blowing amount of the gas curtain mechanism is reduced to 0.2 m 3 / h~0.3 m 3 / h. The remaining operation process is the same as that during steady pouring.

[0061] Comparative Example 1

[0062] The tundish specifications, tundish pulling speed, long nozzle steel flow rate and other parameters used in Comparative Example 1 are the same as those in Example 1, the difference lies in that the tundish adopts a conventional double-flow slab tundish with a pouring section of 1020*200 mm 2 , and the tundish does not set the front dam wall 3 and the rear dam wall 4.

[0063] The residence time of the molten steel in the tundish was monitored, and the ultrasonic flaw detection was performed on the cast slab. The inclusion rating in the prepared steel slab was performed (the rating method can be found in GB / T 10561-2005 Standard Rating Diagram Microscopic Test Method for Determining Non-metallic Inclusion Content in Steel), and the proportion of the number of steel slab samples with inclusion rating of 2.0 or more to the total number of steel slab samples was calculated. The test results are shown in Table 1.

[0064] Table 1 Data comparison table of Example 1 and Comparative Example 1

[0065]

[0066] Example 2

[0067] The tundish structure used in Example 2 is the same as that in Example 1, except that the tundish withdrawal speed is increased to 1.5 m / min.

[0068] (I) Steady pouring state

[0069] The steady pouring time is about 2.0 m / s, and the argon blowing amount of the gas curtain mechanism is 0.5 m 3 / h.

[0070] The speed of the molten steel reaching the front baffle 3 via the tundish impact area is about 0.18 m / s, and after passing through the front guide hole 5, it accelerates downward to more than 0.25 m / s.

[0071] (II) Non-steady pouring state

[0072] Under the non-steady pouring state, the molten steel level drops, and the argon blowing amount of the gas curtain mechanism is reduced to 0.2 m 3 / h~0.3 m 3 / h according to the molten steel level. The remaining operation process is the same as that in the steady pouring state.

[0073] Comparative Example 2

[0074] The tundish specifications, tundish withdrawal speed, and long nozzle molten steel flow rate used in Comparative Example 2 are the same as those in Example 2, except that the tundish adopts a conventional double-flow slab tundish with a pouring section of 1020x200 mm 2 , and the front baffle 3 and the rear baffle 4 are not set.

[0075] The residence time of the molten steel in the tundish was monitored, and the ultrasonic flaw detection was performed on the cast slab. The inclusion rating in the prepared steel slab was performed (the rating method can be found in GB / T 10561-2005 Standard Rating Diagram Microscopic Test Method for Determining Non-metallic Inclusion Content in Steel), and the proportion of the number of steel slab samples with inclusion rating of 2.0 or more to the total number of steel slab samples was calculated. The test results are shown in Table 2.

[0076] Table 2 Data comparison table of example 2 and comparative example 2

[0077]

[0078] As can be seen from the above examples, the present application can effectively control the flow of molten steel, so that the residence time in the tundish, especially in the gas curtain separation zone, is significantly prolonged, which can generally prolong the residence time by 20% to 25%; the molten steel flows in a V-shaped manner after entering the gas curtain separation zone, and cooperates with the argon gas curtain sprayed from the bottom to promote and entrain the inclusions in the molten steel, so that the inclusions float to the slag layer on the top of the molten steel and are not easy to flow out from the submerged outlet, thereby improving the quality of the casting blank and the strip steel, the qualified rate of the casting blank ultrasonic detection is more than 97.5%, the proportion of the number of steel blank samples with inclusion rating of 2.0 or more to the total number of steel blank samples is reduced to 6.5% or less, which indicates that the inclusions in the molten steel are effectively separated. Especially after the drawing speed is increased, the flow rate of the molten steel is significantly accelerated and the removal rate of the inclusions is obviously reduced, the use of the device of the present application can effectively prolong the residence time of the molten steel, and the action of the bubbles ensures that the cleanliness of the molten steel in the tundish maintains a high level under the condition of high drawing speed, which promotes the development of high-efficiency continuous casting.

[0079] The above only describes the preferred embodiments of the present application, and any changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A tundish that facilitates the separation of inclusions in molten low-carbon steel, comprising a tundish body (1) connected to a long nozzle of a ladle, and an immersion outlet (2) provided at the bottom of the tundish body (1), characterized in that: A front baffle (3) and a rear baffle (4) are arranged sequentially between the long water inlet and the submerged outlet (2) along the flow direction of the molten steel. Both the front baffle (3) and the rear baffle (4) are vertically arranged, and the edges of the front baffle (3) and the rear baffle (4) are fixedly connected to the inner wall of the tundish body (1). Several front guide holes (5) are arranged in an array on the front baffle (3), and several rear guide holes (6) are arranged in an array on the rear baffle (4). An air curtain mechanism is also provided between the front baffle (3) and the rear baffle (4). The air curtain mechanism includes a diffuse permeable brick (7) set at the bottom of the tundish body (1), and the diffuse permeable brick (7) is connected to the tundish sealing argon main pipe. The inlet end of the front guide hole (5) is higher than the outlet end and is inclined downwards; the inlet end of the rear guide hole (6) is lower than the outlet end and is inclined upwards; the angle α between each row of front guide holes (5) and the horizontal direction decreases equally from top to bottom, and the angle reduction value △α is 3°~5°; the angle β between each row of rear guide holes (6) and the horizontal direction increases equally from top to bottom, and the angle increase value △β is 3°~5°.

2. The tundish according to claim 1, which facilitates the separation of inclusions in molten low-carbon steel, is characterized in that: On the front baffle (3), the geometric center of the uppermost row of front guide holes (5) is 100~150mm away from the working liquid surface of the tundish, and the geometric center of the lowermost row of front guide holes (5) is 100mm away from the bottom of the tundish body (1). The remaining rows of front guide holes (5) are arranged at equal intervals in the vertical direction. The front baffle (3) and the rear baffle (4) are arranged symmetrically.

3. The tundish according to claim 1, which facilitates the separation of inclusions in molten low-carbon steel, is characterized in that: The front guide hole (5) and the rear guide hole (6) are circular or rectangular holes, and the equivalent diameter of the front guide hole (5) and the rear guide hole (6) is 20mm~40mm.

4. The tundish according to claim 1, which facilitates the separation of inclusions in molten low-carbon steel, is characterized in that: The diffuse permeable brick (7) consists of a permeable layer (7-1), a dense layer (7-2), and an argon channel (7-3). The dense layer (7-2) is the outer shell of the brick body. The dense layer (7-2) is filled with the permeable layer (7-1). The argon channel (7-3) is embedded at the bottom of the permeable layer (7-1) and is connected to the permeable layer (7-1). The length of the diffuse permeable brick (7) is consistent with the inner cavity width of the intermediate package. The width of the diffuse permeable brick (7) is 120mm~150mm.

5. The tundish according to claim 1, which facilitates the separation of inclusions in molten low-carbon steel, is characterized in that: The distance between the front baffle (3) and the rear baffle (4) is 5 to 10 times the width of the diffused permeable brick (7); the distance between the long water outlet and the geometric center of the lower end face of the front baffle (3) is 10 to 15 times the distance between the front baffle (3) and the rear baffle (4); the distance between the immersion outlet (2) and the geometric center of the lower end face of the rear baffle (4) is 8 to 10 times the distance between the front baffle (3) and the rear baffle (4).

6. A separation method for an intermediate ladle, based on any one of claims 1 to 5, which is beneficial for separating inclusions in molten low-carbon steel, characterized in that: After the molten steel flows into the tundish through the long nozzle, it flows in a V-shape in the gas curtain separation zone under the continuous guidance of the front guide hole (5) and the rear guide hole (6). Under the blowing of the argon gas curtain, the inclusions in the molten steel are continuously pushed to the top slag layer of the molten steel. The molten steel enters the continuous casting machine through the submerged outlet (2) for continuous casting.

7. The separation method according to claim 6, characterized in that: The argon blowing rate of the gas curtain mechanism is 0.3 m³ / h to 0.8 m³ / h.

8. The separation method according to claim 7, characterized in that: The argon blowing rate of the gas curtain mechanism during the steady-state casting process is M m 3 / h, when unsteady casting is performed, for every 10% decrease in the molten steel level, the argon blowing volume of the gas curtain mechanism is reduced by 10%M~15%M.

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