Ladle filler sand for steel ladle and filling method thereof

Abstract

The invention discloses stuffing sand for a steel ladle and a filling method of the stuffing sand, and belongs to the technical field of steelmaking. The stuffing sand filling mode is that the first stuffing sand, the second stuffing sand and the third stuffing sand are sequentially arranged from the bottom of the steel ladle to the top. The first stuffing sand comprises the following raw materials in percentage by mass: 50-60% of limestone, 10-20% of magnesium oxide and 20-30% of calcium oxide; the second stuffing sand comprises the following raw materials in percentage by mass: less than or equal to 10% of rare earth oxide, 20-30% of magnesium oxide, 20-30% of limestone, 5-10% of carbon powder and 20-30% of silicon dioxide; and the third stuffing sand comprises the following raw materials in percentage by mass: 10%-20% of ferric oxide, 10%-20% of silicon dioxide, 30%-40% of chromic oxide, 10%-20% of aluminum oxide and 10%-20% of calcium oxide. The self-opening rate of the ladle filler sand reaches 100%, meanwhile, the first ladle filler sand can form tiny bubbles and calcium oxide after entering the molten steel, impurities in the molten steel are captured and float upwards to a tundish slag layer, and the molten steel purification effect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking, and in particular to drainage sand for a ladle and a filling method thereof. Background Art

[0002] Ladle drainage sand is a key material used to achieve automatic ladle pouring during the steelmaking process. Its main function is to form a sintered layer at the bottom of the ladle to prevent molten steel from flowing out before pouring. When the ladle slide is opened, the unsintered drainage sand falls into the tundish under its own weight, and the sintered layer breaks under the static pressure of the molten steel, thereby achieving automatic outflow of molten steel. Drainage sand is usually composed of high-melting-point materials (such as chromium, silicon, etc.), which contain a large amount of oxidizing substances (such as SiO2, Al2O3, etc.). Although drainage sand plays an important role in the steelmaking process, its composition and properties have a significant impact on the purity of molten steel. In particular, the oxidizing substances therein may become the main source of foreign inclusions in the steel, reducing the quality of the steel.

[0003] Currently, research on ladle drainage sand focuses primarily on improving the self-opening rate and reducing its impact on molten steel purity. Chromium-based drainage sand is widely used due to its high self-opening rate and reliability, but it is expensive and can deteriorate molten steel quality. The paper "The Effect of Drainage Sand Charge on the Self-Opening Rate and Molten Steel Cleanliness" proposes optimizing the drain sand charge and filling pattern to reduce total oxygen contamination and aluminum loss in molten steel. The paper "The Use and Management of Drainage Sand in Steel Plants" emphasizes strengthening management and process control to stabilize the ladle self-opening rate at above 99.60%. In addition, patent CN202311644128.7 discloses a method for improving the self-opening rate of the electric furnace tapping port. By optimizing the drainage sand filling process, the self-opening rate is increased to more than 98%; patent CN202210682374.0 adopts different particle sizes and hollow drainage sand filling methods to reduce the impact of drainage sand on the cleanliness of molten steel; patent CN202311711637.7 discloses a drainage sand containing an oxidant, which generates a fragile sintering layer through redox reaction to improve the self-opening rate.

[0004] Although the existing technology has made certain progress in improving the self-opening rate of the ladle, the following defects still exist: First, the oxidizing substances (such as SiO2, Al2O3, etc.) in the drainage sand can easily enter the molten steel at high temperature, forming oxide inclusions and reducing the purity of the steel; second, although the filling method and material optimization of the existing drainage sand can improve the self-opening rate, it is impossible to completely avoid the drainage sand remaining in the molten steel and affecting the quality of the molten steel; finally, when the drainage sand fails to open by itself, forced drainage methods such as oxygen burning must be adopted, which not only increases production costs, but also causes secondary oxidation of the molten steel, and even causes interruption of the continuous casting production line, increasing quality risks and production costs.

[0005] Therefore, there is an urgent need to develop a drainage sand that can not only ensure a high self-opening rate but also significantly reduce the impact on the purity of molten steel, so as to meet the requirements of modern steelmaking for high quality and high efficiency. Summary of the Invention

[0006] The purpose of the present invention is to provide drainage sand for a ladle and a filling method thereof. The application of the drainage sand can improve the self-opening rate of the ladle. At the same time, the drainage sand flowing into the molten steel can self-purify the molten steel, avoiding the secondary oxidation of the molten steel by the drainage sand, and has a significant effect on the production of pure steel.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] On one hand, the present invention provides drainage sand for a ladle, wherein the drainage sand is filled in the following order from the bottom of the ladle upwards: first drainage sand, second drainage sand, and third drainage sand;

[0009] The raw material mass content of the first drainage sand is: 50% to 60% limestone, 10% to 20% magnesium oxide, and 20% to 30% calcium oxide;

[0010] The raw material mass content of the second drainage sand is: rare earth oxide ≤ 10%, magnesium oxide 20% to 30%, limestone 20% to 30%, carbon powder 5% to 10%, and silicon dioxide 20% to 30%;

[0011] The raw material mass content of the third drainage sand is: 10% to 20% of ferric oxide, 10% to 20% of silicon dioxide, 30% to 40% of chromium oxide, 10% to 20% of aluminum oxide, and 10% to 20% of calcium oxide.

[0012] In the above technical solution, further, the raw materials of the first drainage sand are all powders, and the particle size of the first drainage sand is 0.2-1.0 mm.

[0013] In the above technical solution, further, the raw materials of the second drainage sand are all powders, and the particle size of the second drainage sand is 1.0 to 2.0 mm.

[0014] In the above technical solution, further, the raw materials of the third drainage sand are all powders, and the particle size of the third drainage sand is 0.2 to 2.0 mm.

[0015] Another aspect of the present invention provides a method for filling the above-mentioned drainage sand, the method comprising the following steps:

[0016] (1) Filling the molten steel channel of the ladle upper nozzle with the first drainage sand;

[0017] (2) The lower part of the inner hole of the nozzle seat brick is filled with the second drainage sand, and the upper part is filled with the third drainage sand. The part of the third drainage sand exposed outside the inner hole is naturally accumulated into an arch structure;

[0018] (3) Bake the bottom of the ladle at a temperature of 1000-1200°C for 3-5 minutes.

[0019] In the above technical solution, further, the filling height of the second drainage sand is 0.3 to 0.5 times the height of the inner hole.

[0020] The first drainage sand of the present invention is filled in the upper water inlet. On the one hand, it plays a role of downward drainage when the steel plate slide is opened. On the other hand, after the first drainage sand flows into the molten steel in the middle package, it plays a role of purifying the molten steel; the second drainage sand is filled in the lower part of the inner hole of the seat brick and is used to support the third drainage sand. The top of the third drainage sand is in direct contact with the molten steel, and an arched sintering layer is formed under the action of sintering.

[0021] The beneficial effects of the present invention are:

[0022] 1. The drainage sand of the present invention can improve the self-opening rate of the ladle, and the self-opening rate reaches 100%. At the same time, the first drainage sand can form tiny bubbles and calcium oxide after entering the molten steel, capture inclusions in the molten steel and float them to the slag layer of the tundish, thereby purifying the molten steel.

[0023] 2. The second drainage sand of this invention incorporates rare earth oxides. These oxides have a strong affinity for oxygen and sulfur in molten steel, forming stable rare earth oxides and rare earth sulfides. This effectively reduces the oxygen and sulfur content in the steel, reduces the number and size of inclusions, and improves the purity of the steel. Furthermore, the rare earth oxides alter the morphology and distribution of inclusions in the steel, transforming them from long strips or flakes to spherical or short columns, improving the anisotropy of the steel and enhancing its toughness, fatigue properties, and resistance to hydrogen-induced cracking.

[0024] 3. After the drainage sand is filled, the bottom of the ladle is baked, which makes it easier for the third drainage sand to form a stable sintered layer in advance, avoiding the formation of an irregular arch structure that causes a decrease in the self-opening rate.

[0025] 4. The drainage sand of the present invention reduces the amount of alumina and silicon dioxide, thereby avoiding secondary oxidation of the molten steel by the drainage sand.

[0026] 5. The present invention does not change the existing process route and can maintain the integrity of the original process system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the filling structure of the drainage sand of the present invention;

[0028] In the figure: 1. Ladle upper nozzle, 2. Nozzle seat brick, 3. Inner hole, 4. First drainage sand, 5. Second drainage sand, 6. Third drainage sand, 7. Sintered drainage sand layer, 8. Part of the third drainage sand exposed outside the inner hole, 9. Lower slide plate, 10. Upper slide plate, 11. Molten steel channel of ladle upper nozzle, 12. Ladle wall, 13. Ladle bottom brick. DETAILED DESCRIPTION

[0029] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0030] Unless otherwise specified, the materials used in the examples of the present invention can be obtained from commercial sources or prepared according to conventional methods well known to those skilled in the art.

[0031] Figure 1 This is a schematic diagram of the filling structure of drainage sand in the present invention. The ladle includes a ladle upper water inlet 1 and a slide mechanism. A water inlet seat brick 2 is provided on the outer periphery of the ladle upper water inlet 1. The water inlet seat brick 2 is provided with an inner hole 3 connected to the ladle upper water inlet 1. The slide mechanism includes an upper slide 10 and a lower slide 9 that cooperate with each other. The upper slide 10 is fixed to the bottom of the ladle upper water inlet 1, and the lower slide 9 is located below the upper slide 10 and is slidably connected to the upper slide 10.

[0032] Example 1

[0033] This embodiment provides a drainage sand for a ladle. The drainage sand is filled in the following order from the bottom of the ladle upwards: first drainage sand, second drainage sand, and third drainage sand; wherein:

[0034] The raw material mass content of the first drainage sand is: limestone 60%, magnesium oxide 20%, calcium oxide 20%, and the powder particle size is 0.2-1.0 mm;

[0035] The raw material content of the second drainage sand is: cerium oxide 10%, magnesium oxide 25%, limestone 25%, carbon powder 10%, silicon dioxide 30%, and the powder particle size is 1.0-2.0 mm;

[0036] The raw material content of the third drainage sand is as follows: 15% of ferric oxide, 15% of silicon dioxide, 40% of chromium oxide, 20% of aluminum oxide, and 10% of calcium oxide. The powder particle size is 0.2-2.0 mm.

[0037] The above-mentioned method for filling drainage sand comprises the following steps:

[0038] (1) Figure 1 As shown, the first drainage sand 4 is filled in the molten steel channel 11 of the ladle upper nozzle;

[0039] (2) Fill the lower part of the inner hole 3 of the nozzle seat brick 2 with the second drainage sand 5, the filling height of the second drainage sand 5 is 0.3 times the height of the inner hole 3 of the nozzle seat brick 2, and fill the upper part of the inner hole 3 of the nozzle seat brick 2 with the third drainage sand 6. The part of the third drainage sand 6 exposed outside the inner hole 3 is naturally piled up into an arch structure;

[0040] (3) Bake the bottom of the ladle at a temperature of 1100°C for 4 minutes.

[0041] The drainage sand is used to produce SPCC steel grades using the BOF-RH-CC process. The composition of the SPCC steel grades is shown in Table 1, with the remainder being iron and unavoidable impurities.

[0042] Table 1 SPCC steel grade composition (mass percentage)

[0043] C Si Mn p S Als 0.071 0.01 0.28 0.0188 0.013 0.02

[0044] After the drainage sand is filled, the ladle receives the molten steel from the converter. After refining is completed, the lower slide 9 is moved, the drainage sand flows out, and pouring is carried out.

[0045] A total of 100 steel castings were carried out, with a self-opening rate of 100%, an average inclusion defect rate of 0.76% in the rolled plate, and an average full oxygen content of 0.0024% in the tundish.

[0046] Example 2

[0047] This embodiment provides a drainage sand for a ladle. The drainage sand is filled in the following order from the bottom of the ladle upwards: first drainage sand, second drainage sand, and third drainage sand; wherein:

[0048] The raw material mass content of the first drainage sand is: 50% limestone, 20% magnesium oxide, 30% calcium oxide, and the powder particle size is 0.2-1.0mm;

[0049] The raw material content of the second drainage sand is: 10% lanthanum oxide, 30% magnesium oxide, 30% limestone, 10% carbon powder, 20% silicon dioxide, and the powder particle size is 1.0-2.0 mm;

[0050] The raw material content of the third drainage sand is as follows: 20% ferric oxide, 20% silicon dioxide, 40% chromium oxide, 10% aluminum oxide, and 10% calcium oxide. The powder particle size is 0.2-2.0 mm.

[0051] The above-mentioned method for filling drainage sand comprises the following steps:

[0052] (1) Figure 1 As shown, the first drainage sand 4 is filled in the molten steel channel 11 of the ladle upper nozzle;

[0053] (2) Fill the lower part of the inner hole 3 of the nozzle seat brick 2 with the second drainage sand 5, the filling height of the second drainage sand 5 is 0.5 times the height of the inner hole 3 of the nozzle seat brick 2, and fill the upper part of the inner hole 3 of the nozzle seat brick 2 with the third drainage sand 6. The part of the third drainage sand 6 exposed outside the inner hole 3 is naturally piled up into an arch structure;

[0054] (3) Bake the bottom of the ladle at a temperature of 1150°C for 3 minutes.

[0055] The drainage sand was used to produce SPCC steel, and the process route was BOF-RH-CC. The composition of the SPCC steel was the same as that in Example 1.

[0056] After the drainage sand is filled, the ladle receives the molten steel from the converter. After refining is completed, the lower slide 9 is moved, the drainage sand flows out, and pouring is carried out.

[0057] A total of 100 steel castings were carried out, with a self-opening rate of 100%, an average inclusion defect rate of 0.81% in the rolled plate, and an average full oxygen content of 0.0025% in the tundish.

[0058] Comparative Example 1

[0059] The drainage sand used in Comparative Example 1 had a raw material weight content of 45% chromium oxide, 15% aluminum oxide, 10% magnesium oxide, and 30% iron oxide. The drainage sand was filled within the molten steel passage 11 of the ladle nozzle, below the inner hole 3 of the nozzle support brick 2, and above the inner hole 3 of the nozzle support brick 2. The portion of the drainage sand exposed outside the inner hole 3 naturally accumulated into an arched structure.

[0060] The drainage sand was used to produce SPCC steel, and the process route was BOF-RH-CC. The composition of the SPCC steel was the same as that in Example 1.

[0061] After the drainage sand is filled, the ladle receives the molten steel from the converter. After refining is completed, the lower slide is moved to allow the drainage sand to flow out for pouring.

[0062] A total of 100 steel castings were carried out, with a self-opening rate of 90%, an inclusion defect rate of 1.06% in the rolled plate, and an average total oxygen content of 0.0030% in the tundish.

[0063] It can be seen that the ladle self-opening rate of the new drainage sand of the present invention reaches 100%, and the total oxygen value of the tundish and the inclusion defect rate of the rolled plate are lower than those of the conventional drainage sand.

[0064] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A ladle drainage sand, characterized in that: The drainage sand is filled in the following order from the bottom of the ladle upwards: the first drainage sand, the second drainage sand, and the third drainage sand; The raw material mass content of the first drainage sand is: 50% to 60% limestone, 10% to 20% magnesium oxide, and 20% to 30% calcium oxide; The raw material mass content of the second drainage sand is: rare earth oxide ≤ 10%, magnesium oxide 20% to 30%, limestone 20% to 30%, carbon powder 5% to 10%, and silicon dioxide 20% to 30%; The raw material mass content of the third drainage sand is: 10% to 20% of ferric oxide, 10% to 20% of silicon dioxide, 30% to 40% of chromium oxide, 10% to 20% of aluminum oxide, and 10% to 20% of calcium oxide.

2. The ladle drainage sand according to claim 1, characterized in that: The raw materials of the first drainage sand are all powders, and the particle size of the first drainage sand is 0.2-1.0 mm.

3. The ladle drainage sand according to claim 1, characterized in that: The raw materials of the second drainage sand are all powders, and the particle size of the second drainage sand is 1.0-2.0 mm.

4. The ladle drainage sand according to claim 1, characterized in that: The raw materials of the third drainage sand are all powders, and the particle size of the third drainage sand is 0.2-2.0 mm.

5. A method for filling drainage sand for a ladle according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) Filling the molten steel channel of the ladle upper nozzle with the first drainage sand; (2) The lower part of the inner hole of the nozzle seat brick is filled with the second drainage sand, and the upper part is filled with the third drainage sand. The part of the third drainage sand exposed outside the inner hole is naturally accumulated into an arch structure; (3) Bake the bottom of the ladle at a temperature of 1000-1200°C for 3-5 minutes.

6. The filling method according to claim 5, characterized in that The filling height of the second drainage sand is 0.3 to 0.5 times the height of the inner hole.

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