System and method for preventing steel ladle top slag entrapment through automobile plate

Abstract

The invention discloses a system and method for preventing steel ladle top slag entrapment through an automobile plate, the system comprises a slag avoiding device and a porous flow controller, the slag avoiding device is made of a hot-rolled steel plate, the slag avoiding device is in a double-inverted-cone shape, the slag avoiding device comprises orifices which are located at the top and formed by inverted-cone-shaped cone bottoms, the double inverted cones correspond to the two orifices, and before an RH dip pipe is inserted into a steel ladle, the porous flow controller is arranged on the steel ladle. The slag-avoiding device is placed on the slag surface of the steel ladle, and the RH dip pipe is inserted into an orifice of the slag-avoiding device; the multi-hole flow controller is fixed above the upper nozzle of the steel ladle, the multi-hole flow controller is provided with a flow channel communicated with the upper nozzle of the steel ladle, the flow channel forms a top hole in the top of the multi-hole flow controller, and the flow channel respectively forms side holes in a plurality of vertical sides of the multi-hole flow controller. By means of the system, the situation that ladle slag enters molten steel is reduced, the number and density of inclusions in a casting blank are greatly reduced after casting is finished, the surface quality defects are greatly reduced after a plate blank is rolled, and the serious surface defects existing in a ladle changing transition blank are overcome.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, and in particular to a system and method for preventing ladle top slag from rolling up on automobile plates. Background Art

[0002] Automobile plates have extremely high requirements for surface quality. In recent years, with the improvement of molten steel cleanliness, the total oxygen content in the molten steel of automobile plates can be controlled to 0.0015%, and endogenous inclusions are effectively controlled. At the same time, the phenomenon of slag entanglement caused by the adhesion of inclusions at the nozzle is also greatly reduced, and the protective slag defects are also effectively controlled. However, the surface defects caused by calcium aluminates are difficult to control, especially in the ladle transition billet. The main reason for this type of defect is that the ladle top slag is involved in the molten steel and inherited into the ingot, eventually causing surface defects during rolling or processing.

[0003] Traditional processes generally downgrade the transition billets for ladle replacement and do not use them as automobile outer panels. At the same time, in the later stage of ladle casting, the residual steel operation is adopted to prevent the slag vortex on the top of the ladle from being drawn into the molten steel. However, this operation has a great impact on the yield rate and metal recovery rate, and has high manufacturing costs. Summary of the invention

[0004] The present application provides a system and method for preventing ladle top slag from rolling up on automobile plates, which solves the technical problem of ladle top slag rolling up into molten steel in the prior art.

[0005] The present application provides a system for preventing slag rolling from the top of a ladle for automobile plates, comprising a slag avoider and a porous flow controller, wherein the slag avoider is made of a hot-rolled steel plate and has a double inverted cone shape, the slag avoider comprising an orifice formed by the bottom of the inverted cone and located at the top, the double inverted cone corresponding to two orifices, before the RH dip tube is inserted into the ladle, the slag avoider is placed on the slag surface of the ladle and the RH dip tube is inserted into the orifice of the slag avoider; the porous flow controller is fixed above the upper water inlet of the ladle, the porous flow controller is provided with a flow channel connected to the upper water inlet of the ladle, the flow channel forms a top hole at the top of the porous flow controller, and the flow channel forms side holes on multiple vertical sides of the porous flow controller.

[0006] In some embodiments, the porous flow controller and the ladle upper water inlet are processed by integral die casting.

[0007] In some embodiments, the porous flow controller is arranged in a square shape, and the porous flow controller includes a total of four side holes located on four vertical sides, and one side hole is arranged on each vertical side.

[0008] In some embodiments, the top hole is configured as a round hole, and the side hole is configured as a square hole.

[0009] In some embodiments, the diameter of the top hole is 40-60% of the inner diameter of the ladle casting nozzle, and the total area of ​​the four side holes is 1.5 times to 1.8 times the cross-sectional area of ​​the ladle casting nozzle.

[0010] In some embodiments, the slag avoider is made of a hot-rolled steel plate with a thickness of 5.0 mm to 6.5 mm.

[0011] In some embodiments, the orifice diameter of the slag avoider is 60 mm to 100 mm larger than the outer diameter of the RH immersion tube, and the cone height of the slag avoider is 100 mm to 150 mm.

[0012] In some embodiments, the slag avoider includes a manipulator fixing ring installed at the top position, and the manipulator fixing ring cooperates with the manipulator to place the slag avoider on the slag surface of the ladle.

[0013] A method for preventing ladle top slag from rolling up is disclosed. The system for preventing ladle top slag from rolling up is applied to the above-mentioned automobile plate. The method comprises: before RH refining, the ladle reaches the ladle hanging position, a slag avoider is placed on the slag surface of the ladle, and the placement position of the slag avoider is directly below a dipping tube; after the slag avoider is placed, the ladle car enters the processing position, and during the ladle lifting process, the lifting speed is controlled at 0.3-0.5m / min; after ensuring that the dipping tube is inserted into the double holes of the slag avoider, the ladle is continuously lifted so that the dipping tube pushes the slag avoider into molten steel, and after the slag avoider is melted and the molten steel enters the vacuum chamber, vacuum treatment is started until the refining is finished.

[0014] In some embodiments, conventional casting is performed after refining, and the casting passes through a porous flow controller, and the ladle weighs m to satisfy m=πD 4 / 4·((HL sl +100)·ρ st +L sl ·ρ sl ), the casting is stopped immediately, where D is the inner diameter of the ladle, H is the height of the porous flow controller, and L sl is the slag thickness, ρ st is the density of molten steel, ρ sl is the density of steel slag.

[0015] The beneficial effects of the present application are as follows: a system is provided for preventing slag from rolling up on the top of the ladle for automobile plates. Before the start of RH refining, a "double inverted cone" slag avoider is placed on the slag surface of the ladle, and the slag avoider is located directly below the dip tube. As the ladle is lifted, the dip tube is first inserted into the "double inverted cone" slag avoider, and then the slag avoider is pushed into the molten steel and melted, effectively preventing the ladle slag from entering the dip tube and the vacuum chamber; when building the ladle for smelting automobile plates, an integrated element of an upper water inlet and a porous flow controller is used. When conventional casting is performed after the refining is completed, the molten steel enters the upper water inlet from the top hole and the side hole of the porous flow controller respectively. A part of the molten steel enters from the side hole, reducing the amount of liquid entering from the top hole. The molten steel entering from the surrounding side holes has a lateral component due to its direction, and this part of the lateral component has a lateral force on the ladle. The slag vortex can offset each other to a certain extent, thereby reducing the degree of the slag vortex and improving the degree of harm caused by the vortex generated at the downspout in the later stage of ladle casting. In this way, the entry of ladle slag into the molten steel is reduced. After the casting is completed, it is found that the number and density of inclusions in the ingot are greatly reduced. The surface quality defects of the slab after rolling are greatly reduced, and the serious surface defects of the transition billet after changing ladle are improved. The transition billet after changing ladle can continue to be used as the outer panel of the automobile, maintaining the process yield and metal recovery rate, and maintaining the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0017] Figure 1 A schematic diagram of the system for preventing ladle top slag from rolling over during RH vacuum refining of automotive plates provided in this application;

[0018] Figure 2 for Figure 1 Schematic diagram of the specific structure of the medium-porous flow controller.

[0019] The accompanying drawings are marked with: 100 - vacuum chamber, 110 - immersion tube, 200 - slag avoider, 210 - manipulator fixing ring, 300 - slag layer, 400 - ladle, 500 - porous flow controller, 510 - top hole, 520 - side hole, 600 - ladle water inlet. DETAILED DESCRIPTION

[0020] The embodiment of the present application solves the technical problem of ladle top slag being rolled into molten steel in the prior art by providing a system for preventing ladle top slag from rolling into molten steel on automobile plates.

[0021] Automobile plates have extremely high requirements for surface quality. In recent years, with the improvement of molten steel cleanliness, the total oxygen content in automobile plate molten steel can be controlled to 0.0015%, and endogenous inclusions are effectively controlled. At the same time, the phenomenon of slag entrainment caused by the adhesion of inclusions at the nozzle is also greatly reduced, and the protective slag defects are also effectively controlled. However, the surface defects caused by calcium aluminates are difficult to control.

[0022] Especially in the ladle transition billet, the main reason for this type of defect is that the ladle top slag is drawn into the molten steel and inherited into the ingot, eventually causing surface defects during rolling or processing.

[0023] Traditional processes generally downgrade the transition billets for ladle replacement and do not use them as automobile outer panels. At the same time, in the later stage of ladle casting, the residual steel operation is adopted to prevent the slag vortex on the top of the ladle from being drawn into the molten steel. However, this operation has a great impact on the yield rate and metal recovery rate, and has high manufacturing costs.

[0024] The inventors found that the ladle slag enters the molten steel mainly from the following two processes: first, when the RH immersion tube is inserted into the ladle before refining begins, a large amount of ladle slag is sucked into the vacuum chamber. As the refining cycle proceeds, a large amount of liquid slag droplets exist in the molten steel, which are difficult to completely remove; second, in the later stage of ladle casting, a vortex is generated at the downspout, causing vortex slag to roll up.

[0025] Therefore, the inventor invented a system for preventing slag from rolling up on the top of the ladle for automobile plates, which specifically solves the above two problems.

[0026] Example 1

[0027] The present embodiment provides a system for preventing slag from rolling up on the top of a ladle for automobile plates, comprising a slag avoider and a porous flow controller.

[0028] Figure 1 The start process of RH vacuum refining is shown, involving a vacuum chamber 100, an RH immersion tube 110, and a ladle 400. A slag layer 300 is formed on the upper layer of the ladle 400. A ladle upper water inlet 600 is provided below the ladle 400. After the refining is completed, conventional casting is performed through the upper water inlet 600, and the upper water inlet of the ladle corresponds to the lower water inlet.

[0029] Please refer to Figure 1 The slag avoider 200 is in the shape of a double inverted cone. The slag avoider 200 is made of hot-rolled steel plates, preferably ultra-low carbon hot-rolled steel plates, which will not cause degradation of molten steel. The cone has a cone bottom. When the slag avoider is arranged in an inverted cone, the cone bottom of the cone is located on the upper side, and the cone tip of the cone is located on the lower side. The cone bottom of the inverted cone forms an orifice. The slag avoider includes an orifice located at the top, and the double inverted cone corresponds to two orifices.

[0030] Before the RH dipping tube is inserted into the ladle, the slag avoider is placed on the slag surface of the ladle. After the slag avoider is placed, the ladle car enters the processing position. During the ladle lifting process, ensure that the RH dipping tube is inserted into the double holes of the slag avoider. Continue to lift the ladle so that the dipping tube pushes the slag avoider into the molten steel. After the slag avoider is melted and the molten steel enters the vacuum chamber, vacuum treatment is started until the refining is completed, effectively preventing the ladle slag from entering the dipping tube and the vacuum chamber.

[0031] like Figure 1 As shown, a manipulator fixing ring 210 is installed at the top of the slag avoider, and the manipulator fixing ring 210 cooperates with the manipulator to place the slag avoider on the slag surface of the ladle.

[0032] In some embodiments, the slag avoider is made of a hot-rolled steel plate with a thickness of 5.0 mm to 6.5 mm.

[0033] In some embodiments, the diameter of the orifice defining the slag avoider is 60 mm to 100 mm larger than the outer diameter of the RH immersion tube, and the conical height of the slag avoider is 100 mm to 150 mm.

[0034] In this system, please refer to Figure 1 and Figure 2 The porous flow controller 500 is fixed above the ladle upper water inlet 600. The porous flow controller 500 is provided with a flow channel connected to the ladle upper water inlet 600. The flow channel forms a top hole 510 at the top of the porous flow controller, and the flow channel forms side holes 520 on multiple vertical sides of the porous flow controller.

[0035] When building a ladle for smelting automobile plates, a component with an upper water inlet and a porous flow controller integrated is used, and the porous flow controller and the upper water inlet can be made by an integrated die-casting process. When conventional casting is performed after refining, the molten steel enters the upper water inlet from the top hole and the side hole of the porous flow controller, and a part of the molten steel enters from the side hole.

[0036] In the original scheme without a porous flow controller, the molten steel directly enters the upper water inlet from the top.

[0037] After applying the porous flow controller of the present application, a part of the molten steel enters from the side holes, reducing the amount of liquid entering from the top hole. The molten steel entering from the surrounding side holes can be divided into vertical and lateral components due to its special direction. The lateral components offset the slag vortex, thereby reducing the degree of the slag vortex.

[0038] By reducing the degree of slag vortex, the degree of harm caused by vortex generated at the downspout in the late stage of ladle casting is improved, thereby reducing the entry of ladle slag into molten steel.

[0039] The system for preventing ladle top slag from rolling on automobile plates of the present application is used to carry out targeted treatment from two aspects: slag avoidance and slag vortex rolling. After the casting is completed, it is found that the number and density of inclusions in the ingot are greatly reduced, and the surface quality defects of the slab after rolling are greatly reduced, which improves the serious surface defects of the ladle-changing transition billet. The ladle-changing transition billet can continue to be used as automobile outer panels, maintain the process yield and metal recovery rate, and maintain the manufacturing cost.

[0040] In some embodiments, see Figure 2 The multi-hole flow controller is arranged in a square shape. The multi-hole flow controller includes a total of 4 side holes located on 4 vertical sides, and each vertical side is provided with a side hole. The multi-hole flow controller can be called a 5-hole flow controller. For further information, please refer to Figure 2 The top hole is set as a round hole and the side holes are set as square holes.

[0041] Furthermore, the opening sizes of the top hole and the side holes are limited, the aperture of the top hole is 40-60% of the inner diameter of the ladle casting nozzle, and the total area of ​​the four side holes is 1.5 times to 1.8 times the cross-sectional area of ​​the ladle casting nozzle.

[0042] Example 2

[0043] The system for preventing ladle slag from rolling up in the automobile plate of the application embodiment 1 is used. This embodiment provides a method for preventing ladle slag from rolling up in the automobile plate, including placing a slag avoider on the slag surface of the ladle when the ladle reaches the ladle hanging position before RH refining, and the placement position of the slag avoider is directly below the dipping tube. After the slag avoider is placed, the ladle car enters the processing position, and during the ladle lifting process, the rising speed is controlled at 0.3-0.5m / min. After ensuring that the dipping tube is inserted into the double holes of the slag avoider, continue to lift the ladle so that the dipping tube pushes the slag avoider into the molten steel, and after the slag avoider is melted and the molten steel enters the vacuum chamber, vacuum treatment begins until the refining is completed.

[0044] After refining, conventional casting is carried out. The casting passes through a porous flow controller and the ladle weighs m to satisfy m=πD 4 / 4·((HL sl +100)·ρ st +L sl ·ρ sl ) conditions, stop casting immediately.

[0045] Among them, m is the weight of the ladle, which also represents the liquid level in the ladle. The unit of m is kg.

[0046] D is the inner diameter of the ladle, in mm.

[0047] H is the height of the porous flow controller, in mm, please refer to Figure 1 and Figure 2 , H also represents the distance from the highest point of the flow controller to the bottom wall of the ladle.

[0048] L sl is the slag thickness in mm.

[0049] ρ st is the density of molten steel, for example 7.3×10 -6 kg / mm.

[0050] ρ sl is the density of steel slag, for example 3.5×10 -6 kg / mm.

[0051] During the steel liquid refining process, before the ladle reaches the ladle hanging position, the ladle slag thickness L is measured first. sl , and then use a manipulator to place a double inverted cone slag avoider on the slag surface of the ladle.

[0052] In the later stage of ladle casting, the ladle casting residue is strictly controlled according to the above formula, which can effectively avoid vortex slag without the need for large-scale steel retention operations.

[0053] This method is suitable for large ladles with a capacity of more than 150 tons.

[0054] The above method optimizes the design of the two ways of ladle slag entering the molten steel. The "double inverted cone" slag avoider is used to prevent the ladle slag from entering the immersion tube and the vacuum chamber. The porous flow controller and the control method of the ladle casting residue in the later stage of casting are used to avoid vortex slag.

[0055] Example 3

[0056] Based on Example 1 and Example 2, this example provides a specific implementation scheme. In this example, the main component requirements of the ultra-low carbon automobile plate steel are shown in the following table (steel grade component requirement range / %):

[0057] C≤ Si≤ Mn P S≤ Alt Ti 0.0020 0.03 0.06-0.15 ≤0.010 0.012 0.020-0.045 0.050-0.070

[0058] The smelting adopts the "KR+converter+RH+continuous casting" production process. The ladle capacity is 210 tons. The ladle adopts the integral die-cast components of the water inlet and the porous flow controller. The inner diameter of the water inlet is 76mm, the height of the porous flow controller is 68mm, the inner diameter of the top circular hole is 38mm, and the total area of ​​the four side holes is 1.8 times the cross-sectional area of ​​the water inlet. The side holes are 46×46mm square holes, which are located on the four sides of the flow controller respectively.

[0059] During the steel liquid refining process, before the ladle reaches the ladle hanging position, the ladle slag thickness L is measured first. sl The diameter of the steel ladle is 83mm, and then a double inverted cone slag avoider is placed on the surface of the ladle by a manipulator. The slag avoider is placed just below the immersion tube. The slag avoider is made of ultra-low carbon hot-rolled steel plate with a thickness of 5.0mm, an upper inner diameter of 1360mm, and a cone height of 120mm.

[0060] After placement, the ladle car enters the processing position. During the ladle lifting process, the rising speed is controlled at 0.4m / min.

[0061] After ensuring that the dipping tube is inserted into the double holes of the slag avoider, continue to lift the ladle so that the dipping tube pushes the slag avoider into the molten steel. After the slag avoider is melted and the molten steel enters the vacuum chamber, start vacuum treatment until the refining is completed.

[0062] After refining, conventional casting is carried out. Before the end of casting, the liquid level of the ladle must reach the following conditions, and casting should be stopped immediately: m = πD 4 / 4·((HL sl +100)·ρ st +L sl ·ρ sl ).

[0063] Substituting the above data, we can see that casting is stopped when the ladle weighing shows 10.3 tons.

[0064] After casting, the ingot was sampled and analyzed for large inclusions with a size of ≥50μm. The number density was reduced by 28% compared with the traditional process, and the surface quality defects of the slab after rolling were reduced by 43%.

[0065] Example 4

[0066] Based on Example 1 and Example 2, this example provides a specific implementation scheme. In this example, the main component requirements of the ultra-low carbon automobile plate steel are shown in the following table (steel grade component requirement range / %):

[0067] C≤ Si≤ Mn P S≤ Alt Ti 0.0030 0.03 0.06-0.15 ≤0.010 0.012 0.020-0.045 0.050-0.070

[0068] The smelting adopts the "KR+converter+RH+continuous casting" production process. The ladle capacity is 210 tons. The ladle adopts the integral die-cast components of the water inlet and the porous flow controller. The inner diameter of the water inlet is 76mm, the height of the porous flow controller is 68mm, the inner diameter of the top circular hole is 38mm, and the total area of ​​the four side holes is 1.8 times the cross-sectional area of ​​the water inlet. The side holes are 46×46mm square holes, which are located on the four sides of the flow controller respectively.

[0069] During the steel liquid refining process, before RH refining, the ladle reaches the ladle hanging position. The ladle slag thickness is first measured to be 70mm, and then a "double inverted cone" slag avoider is placed on the ladle surface by a manipulator. The slag avoider is placed directly below the immersion tube. The slag avoider is made of ultra-low carbon hot-rolled steel plate with a thickness of 5.0mm, an upper inner diameter of 1360mm, and a cone height of 120mm.

[0070] After placement, the ladle car enters the processing position. During the ladle lifting process, the rising speed is controlled at 0.4m / min.

[0071] After ensuring that the dipping tube is inserted into the double holes of the slag avoider, continue to lift the ladle so that the dipping tube pushes the slag avoider into the molten steel. After the slag avoider is melted and the molten steel enters the vacuum chamber, start vacuum treatment until the refining is completed.

[0072] After refining, conventional casting is carried out. Before the end of casting, the liquid level of the ladle must reach the following conditions, and casting should be stopped immediately: m = πD 4 / 4·((HL sl +100)·ρ st +L sl ·ρ sl ).

[0073] Substituting the above data, we can see that casting is stopped when the ladle weight shows 10.4 tons.

[0074] After casting, the ingot was sampled and analyzed for large inclusions with a size of ≥50μm. The number density was reduced by 25% compared with the traditional process, and the surface quality defects of the slab after rolling were reduced by 36%.

[0075] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0076] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A system for preventing slag from rolling up on the top of a ladle for automobile plates, characterized in that: The system comprises: A slag avoider is made of a hot-rolled steel plate, and is in the shape of a double inverted cone. The slag avoider includes an orifice formed by the bottom of the inverted cone at the top, and the double inverted cone corresponds to two of the orifices. Before the RH immersion tube is inserted into the ladle, the slag avoider is placed on the slag surface of the ladle and the RH immersion tube is inserted into the orifice of the slag avoider. A porous flow controller is fixed above the upper water inlet of the ladle. The porous flow controller is provided with a flow channel connected to the upper water inlet of the ladle. The flow channel forms a top hole on the top of the porous flow controller, and the flow channel forms side holes on multiple vertical sides of the porous flow controller.

2. The device according to claim 1, characterized in that The multi-hole flow controller and the ladle water inlet are processed by integral die-casting.

3. The device according to claim 1, characterized in that The multi-porous flow controller is arranged in a square shape, and comprises a total of four side holes located on four vertical sides, with one side hole being arranged on each vertical side.

4. The device according to claim 3, characterized in that The top hole is arranged as a round hole, and the side hole is arranged as a square hole.

5. The device according to claim 4, characterized in that The diameter of the top hole is 40-60% of the inner diameter of the ladle casting nozzle, and the total area of ​​the four side holes is 1.5 times to 1.8 times the cross-sectional area of ​​the ladle casting nozzle.

6. The device according to claim 1, characterized in that The slag avoider is made of hot-rolled steel plate with a thickness of 5.0 mm to 6.5 mm.

7. The device according to claim 1, characterized in that The orifice diameter of the slag avoider is 60mm-100mm larger than the outer diameter of the RH immersion pipe, and the conical height of the slag avoider is 100mm-150mm.

8. The device according to claim 1, characterized in that The slag avoider comprises a manipulator fixing ring installed at the top position, and the manipulator fixing ring cooperates with the manipulator to place the slag avoider on the slag surface of the ladle.

9. A method for preventing slag from rolling up on the top slag of a ladle for automobile plates, characterized in that: The system for preventing ladle top slag from rolling up is applied to automobile plates according to any one of claims 1 to 8, wherein the method comprises: Before RH refining, the ladle reaches the ladle hanging position, and the slag avoider is placed on the slag surface of the ladle, and the placement position of the slag avoider is just below the immersion pipe; After the slag avoider is placed, the ladle car enters the processing position, and during the ladle lifting process, the rising speed is controlled at 0.3-0.5m / min; After ensuring that the dipping tube is inserted into the double holes of the slag avoider, continue to lift the ladle so that the dipping tube pushes the slag avoider into the molten steel. After the slag avoider is melted and the molten steel enters the vacuum chamber, start vacuum treatment until the refining is completed.

10. The method according to claim 9, characterized in that After refining, conventional casting is carried out, and the casting passes through the porous flow controller, and the ladle weighing m meets m=πD 4 / 4·((HL sl +100)·r st +L sl ·r sl ) When the casting is stopped immediately, D is the inner diameter of the ladle, H is the height of the porous flow controller, and L sl is the slag thickness, ρ st is the density of molten steel, ρ sl is the density of steel slag.

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