Submersed nozzle capable of improving uniformity of flow field in thick slab crystallizer

Abstract

The invention relates to a submersed nozzle capable of improving the uniformity of a flow field in a thick slab crystallizer, and belongs to the technical field of continuous casting processes in the metallurgical industry. According to the technical scheme, two steel tapping holes (2) of the submersed nozzle are symmetrically arranged in the radial direction, and the sections of the steel tapping holes (2) are rectangular; the nozzle bottom (3) is a concave bottom, and the inner surface of the concave bottom is wavy; the tapping hole (2) is close to the nozzle bottom (3); the upper surface and the lower surface of the tapping hole (2) are respectively provided with a flow guide island (5) which protrudes towards the interior of the rectangle; the four corners of the tapping hole (2) are arc-shaped corners (6) protruding towards the outer portion of the rectangle, and the arc-shaped corners (6) and the flow guide islands (5) are connected to form a wave shape. The method has the beneficial effects that the form of the molten steel stream can be changed, so that the molten steel stream is more uniform in the thickness direction, the bias flow in the thickness direction is reduced, the flow field uniformity of molten steel in the thick slab crystallizer is improved, and the impact speed of the molten steel stream to a local area when the molten steel stream reaches a narrow side can be reduced.

Description

Technical Field

[0001] The invention relates to an immersed nozzle capable of improving the uniformity of the flow field in a thick slab crystallizer, and belongs to the technical field of continuous casting process in the metallurgical industry. Background Art

[0002] As the core component of the three major parts of the continuous casting machine production process, the submerged nozzle can isolate the air, regulate and control the flow of molten steel in the crystallizer. A good nozzle shape design can promote the floating of inclusions in the molten steel, reduce defects in the casting, and promote the uniform melting of the protective slag. Therefore, the design of the submerged nozzle has a very large impact on the stable production and quality control of the continuous casting machine.

[0003] The tapping hole of a traditional slab submerged nozzle is usually an elliptical or keyway-shaped profile, and the bottom of the nozzle is a flat bottom or a concave bottom. The optimization of the submerged nozzle usually involves adjusting the bottom shape and size, adjusting the angle and area of ​​the tapping hole, etc.

[0004] These optimizations can achieve relatively ideal results on slab continuous casting machines with conventional thickness. However, on thick slabs, especially those with a thickness of more than 300 mm, due to the increase in the thickness of the crystallizer, the design of conventional nozzles is prone to some deficiencies in use, mainly manifested in: as the thickness increases, the molten steel stream is more likely to deviate, and the molten steel is prone to deviate and become unstable in the crystallizer during the process of flowing out of the steel outlet. The molten steel may be locally updated more slowly at the meniscus, resulting in poor melting of the protective slag, thereby causing a series of quality and even production problems. Summary of the invention

[0005] The object of the present invention is to provide an immersed nozzle that can improve the uniformity of the flow field in a thick slab crystallizer, change the shape of the molten steel flow stream, make it more uniform in the thickness direction, reduce the deviation in the thickness direction, improve the uniformity of the flow field of the molten steel in the thick slab crystallizer, and reduce the impact speed of the molten steel flow stream on the local area when it reaches the narrow side, thereby solving the problems existing in the background technology.

[0006] The technical solution of the present invention is: The invention discloses an immersion nozzle which can improve the uniformity of the flow field in a thick slab crystallizer. The immersion nozzle has two steel outlet holes which are arranged radially symmetrically and have a rectangular cross section. The bottom of the nozzle is a concave bottom, and the inner surface of the concave bottom is wavy.

[0007] The steel tapping hole is close to the bottom of the water nozzle.

[0008] A guide island protruding toward the inside of the rectangle is respectively provided on the upper side and the lower side of the steel outlet.

[0009] The guide island is arc-shaped.

[0010] The four corners of the steel outlet are all arc-shaped corners protruding outside the rectangle, and the arc-shaped corners and the guide island are connected to form a wave shape.

[0011] The radius R4 of the arc angle is 5-15 mm, and the radius R5 of the guide island is 8-20 mm.

[0012] The present invention designs the bottom of the nozzle to be a concave bottom, that is, a bowl-shaped bottom, and the inner surface of the bowl bottom is wavy, which can promote the vortex formation and turbulent energy conversion of the molten steel flow in the bottom area of ​​the nozzle and improve the local turbulence intensity. The wavy bowl bottom structure can effectively break the asymmetry of the flow, so that the Reynolds number in the local flow area changes, which is helpful for the mixing of the molten steel in the area and the formation of vortices, thereby helping to improve the deviation phenomenon caused by turbulent uncertainty and promote more uniform flow.

[0013] Taking into account the increase in the thickness dimension of the crystallizer, a simple-shaped tapping hole cannot guarantee the stability of the molten steel stream after it flows out. Therefore, the tapping hole is designed as a rectangular structure with a guide island. This can make the flow pattern of the molten steel after it flows out of the submerged nozzle outlet more stable, especially in the thickness direction of the crystallizer, which can reduce the impact of the deviation of the molten steel stream.

[0014] The beneficial effects of the present invention are: it can change the shape of the molten steel stream to make it more uniform in the thickness direction, reduce the deviation in the thickness direction, improve the flow field uniformity of the molten steel in the thick slab crystallizer, and also reduce the impact speed of the molten steel stream on the local area when it reaches the narrow side. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a stereogram of the present invention; Figure 2 for Figure 1 A cross-sectional view of Figure 3 It is a side view of the present invention; Figure 4 It is a front view of the present invention; Figure 5 for Figure 3 AA section view; Figure 6 for Figure 4 BB cross-section diagram; Figure 7 This is a cross-sectional view of the bottom of the submerged nozzle of the present invention; Figure 8 This is a diagram showing the shape of the steel tapping hole at the bottom of the submerged nozzle of the present invention; Fig. 9 Comparison of the flow field velocity cloud diagram at the center section of the conventional nozzle and the nozzle of the present invention; Fig.10 Comparison of the velocity cloud diagram of the cross-sectional flow field at the outlet of the conventional nozzle and the nozzle of the present invention; Fig.11 Comparison of the flow field velocity cloud diagrams at 1 / 4 of the width direction of the conventional nozzle and the nozzle of the present invention; Fig.12 Comparison of linear flow rates at 1 / 2 and 1 / 4 thickness positions at the cross section of 1 / 4 width of the conventional nozzle and the nozzle of the present invention; In the figure: immersed nozzle 1, steel outlet hole 2, nozzle bottom 3, wave 4, guide island 5, arc corner 6. DETAILED DESCRIPTION

[0016] The present invention will be further described below by way of examples with reference to the accompanying drawings.

[0017] Refer to the attached Figure 1-8 The invention discloses an immersion nozzle which can improve the uniformity of the flow field in a thick slab crystallizer. The immersion nozzle has two outlet holes 2 which are arranged radially symmetrically and have a rectangular cross section. The bottom 3 of the nozzle is a concave bottom, and the inner surface of the concave bottom is wavy.

[0018] In this embodiment, refer to the attached Figure 1-8 The inner diameter of the immersion nozzle inlet is 80mm. The nozzle bottom 3 is designed to be bowl-shaped, and the bowl bottom surface has waves 4. The crest of the wave 4 is as follows: the radius of the central concave part is R1 = 8~15mm, the radius of the convex parts on both sides is R3 = 10~15mm, and the concave and convex parts are transitioned to the whole nozzle part through fillets, and the transition fillet radius is R2 = 5~10mm. Figure 7 shown.

[0019] The bottom 3 of the nozzle is designed as a wave-shaped bowl bottom, which can enhance the turbulence intensity of the molten steel flow from the tundish to the crystallizer and reduce the deviation state of the molten steel in the submerged nozzle.

[0020] The steel tapping hole 2 is close to the bottom 3 of the nozzle, and the cross section of the steel tapping hole 2 is rectangular. Figure 8 As shown, its width is 60mm and its height is 85mm. A guide island 5 protruding toward the inside of the rectangle is provided on each wide surface. The guide island 5 is arc-shaped, and its radius R5 is 8-20mm. The four corners of the steel tapping hole 2 are all arc-shaped corners 6 protruding toward the outside of the rectangle, and their radius R4 is 5-15mm. The arc-shaped corners 6 and the guide island 5 are connected to form a wave shape. The steel tapping hole 2 of this shape can improve the uniformity of the flow field in the thickness direction of the thick slab crystallizer. At the same time, through the wavy bowl bottom 3 and the steel tapping hole 2 with the guide island 5, the unevenness of the molten steel stream in the thickness direction of the crystallizer after flowing out of the immersion nozzle steel tapping hole can be reduced, the stability of the flow field morphology in the thickness direction can be improved, and the scouring speed of the molten steel stream on the narrow side shell can be reduced.

[0021] The submerged nozzle mentioned above will be modeled and the flow field simulated and calculated, and compared with the ordinary nozzle.

[0022] Casting conditions: mold width: 2000 mm, mold thickness: 300 mm, casting speed 0.75 m / min.

[0023] The 1 / 2 model is used for modeling and calculation. Figure 9-12 This is a comparison diagram of the flow field effects of a common nozzle and the present invention, where: Attached Fig. 9 Comparison of the velocity cloud diagrams of the flow fields at the center cross-sections of a conventional nozzle and the nozzle of the present invention. It can be seen that after the conventional nozzle flows out from the steel outlet hole of the immersion nozzle, the speed is relatively fast and the flow streams are relatively concentrated; while the flow streams of the nozzle designed in the present invention are slightly dispersed, and the overall speed is reduced. It can be seen from the comparison in the velocity cloud diagram that the nozzle of the present invention is more uniform in overall velocity distribution.

[0024] Fig.10 The velocity cloud diagram of the cross-sectional flow field at the outlet of a conventional nozzle is compared with that of the nozzle of the present invention. It can be seen from the comparison that the maximum velocity of the conventional nozzle is 2.0447 m / s, and the maximum velocity of the nozzle designed by the present invention is 1.8609 m / s. The velocity at the steel outlet position is significantly reduced, and the overall velocity distribution cloud diagram is more uniform.

[0025] Fig.11 The flow field velocity cloud diagrams at 1 / 4 of the width direction of the crystallizer of the conventional nozzle and the nozzle of the present invention are compared. It can be seen from the comparison that at this position, the molten steel flow of the nozzle of the ordinary design is relatively concentrated, and the area with faster speed is concentrated in a smaller area. The high-speed area of ​​the molten steel flow of the nozzle designed by the present invention is relatively dispersed and the distribution is more uniform.

[0026] Fig.12 Comparing the linear flow velocities at 1 / 2 thickness and 1 / 4 thickness positions at 1 / 4 width sections of the conventional nozzle and the nozzle of the present invention, it can be clearly seen that at 1 / 2 thickness center of the 1 / 4 width section, the flow velocity of the conventional nozzle is relatively concentrated and relatively large, while the flow velocity drops sharply at 1 / 4 thickness position, that is, the molten steel flow velocity of this nozzle design is very concentrated; by comparing the velocity curves of the nozzle of the present invention at the same position, it can be seen that the flow velocity at 1 / 2 thickness center is significantly reduced, and the flow velocity drops less at 1 / 4 thickness position, that is, the flow velocity distribution is relatively uniform in the entire thickness direction.

[0027] In summary, under the same working conditions, the nozzle of the present invention reduces the speed of molten steel flowing out of the steel outlet hole of the submerged nozzle, and the speed distribution is more uniform, thereby improving the stability and uniformity of the overall flow field of the molten steel in the crystallizer.

Claims

1. An immersion nozzle capable of improving the uniformity of the flow field in a thick slab crystallizer, characterized in that: The steel outlet holes (2) of the submerged nozzle are two radially symmetrically arranged, and their cross-sections are rectangular; the bottom (3) of the nozzle is a concave bottom, and the inner surface of the concave bottom is wavy.

2. The submerged nozzle capable of improving the uniformity of the flow field in the thick slab crystallizer according to claim 1, characterized in that: The steel outlet hole (2) is close to the bottom (3) of the water nozzle.

3. The submerged nozzle capable of improving the uniformity of the flow field in the thick slab crystallizer according to claim 2, characterized in that: A guide island (5) protruding toward the inside of the rectangle is respectively provided on the upper and lower sides of the steel outlet hole (2).

4. The submerged nozzle capable of improving the uniformity of the flow field in the thick slab crystallizer according to claim 3, characterized in that: The guide island (5) is arc-shaped.

5. The submerged nozzle capable of improving the uniformity of the flow field in the thick slab crystallizer according to claim 4, characterized in that: The four corners of the steel outlet hole (2) are all arc-shaped corners (6) protruding outside the rectangle, and the arc-shaped corners (6) and the guide island (5) are connected to form a wave shape.

6. The submerged nozzle capable of improving the uniformity of the flow field in the thick slab crystallizer according to claim 5, characterized in that: The radius R4 of the arc corner (6) is 5-15 mm, and the radius R5 of the guide island (5) is 8-20 mm.

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