Construction process of continuous casting tundish dry material and tundish

Abstract

The invention relates to the field of metallurgy, in particular to a construction technology of a continuous casting tundish dry material and a tundish. According to the continuous casting tundish dry material construction technology, the thickness of a certain dry material is increased, the existing thickness of a tundish wall dry material is adjusted to be larger than or equal to 60 mm from 50-55 mm, and the thickness of a tundish bottom dry material is adjusted to be larger than or equal to 90 mm from 60 mm; meanwhile, the condition of the vibration process is adjusted, the original vibration time of 3 min is adjusted to be larger than or equal to 8 min, and vibration motors are changed into double motors; the baking conditions are adjusted, the baking time is shortened from original 70-90 min to 40-60 min, and the cooling and demolding time is prolonged to be larger than or equal to 4 h; by regulating and controlling the factors, the erosion resistance of the whole dry material is improved, and the service life of the dry material is further prolonged.

Description

Technical Field

[0001] The invention relates to the field of metallurgy, and in particular to a construction process for a continuous casting tundish with dry materials and the tundish. Background Art

[0002] The continuous casting process for steel is as follows: ladle → tundish → mold → secondary cooling → strand straightening → cutting → roller conveying → strand casting. The tundish is a crucial refractory container in the steelmaking process, receiving molten steel from the ladle before distributing it to the individual molds through the tundish nozzle. Its primary function is to store molten steel. The stronger the corrosion resistance of the refractory material, the longer the storage time, allowing for a greater number of continuous casting furnaces and reducing heat exchange, strand casting, steel consumption, and refractory costs.

[0003] The tundish generally consists of a body, cover, downspout, and stopper. The body comprises an outer shell and an inner lining, with the outer layer made of metal and the inner lining made of refractory material. The inner lining primarily consists of an insulation layer, a permanent layer, and a working layer. The insulation layer is adjacent to the outer shell, while the permanent layer lies between them, with the working layer in contact with the molten steel.

[0004] The tundish working layer is essential for protecting the tundish's proper operation. The development of the continuous casting tundish working layer progresses through the following stages: insulation board, coating or spraying material, and dry lining. Compared to coating materials, dry linings offer advantages such as ease of construction, long service life, and improved residual lining disassembly, making them widely used in the continuous casting tundish metallurgical industry.

[0005] The dry material in the tundish is an amorphous refractory material formed by vibration without adding water / liquid binder. Its construction process mainly includes: spreading the dry material on the bottom of the tundish → installing the diaphragm into the tundish → pouring the dry material between the permanent layer and the diaphragm along the tundish wall → vibrating → igniting the burner in the diaphragm for baking → demoulding the diaphragm after it cools down to obtain the working layer.

[0006] In actual industrial production, as the service time increases, the slag line erosion thickness of the dry material working layer of the tundish increases, affecting product quality and causing safety hazards (such as working layer collapse, etc.), which limits the service life of the tundish. Therefore, improving the service life of the tundish has become an urgent problem to be solved in this field. Summary of the Invention

[0007] In view of this, the present invention provides a construction process for dry material in a continuous casting tundish and a tundish. The construction process for dry material in a continuous casting tundish provided by the present invention can effectively increase the service life of the tundish.

[0008] The present invention provides a construction process for continuous casting tundish dry material, comprising the following steps:

[0009] (A) Laying the dry material on the bottom of the tundish to form the bottom dry material;

[0010] Wherein, the thickness of the bottom dry material is ≥90mm;

[0011] (B) placing the fetal membrane into the tundish, and pouring the dry material between the permanent layer and the fetal membrane along the wall of the tundish to form the wall dry material;

[0012] Wherein, the thickness of the wall dry material is ≥60mm;

[0013] (C) vibrating the tundish;

[0014] (D) baking the tundish;

[0015] (E) The fetal membrane is cooled and demoulded;

[0016] in,

[0017] Calculated in percentage by mass, the dry material includes: MgO ≥ 80%, CaO ≤ 2.5%, Al2O3 ≤ 1.5%, SiO2 ≤ 4.5%, Fe2O3 ≤ 2.0, and C total ≤ 3.0%.

[0018] Preferably, in step (A), the thickness of the bottom bag dry material is 90 to 95 mm.

[0019] Preferably, in step (B), the thickness of the wall-wrapped dry material is 60 to 65 mm.

[0020] Preferably, in step (C), the vibration motor used for the vibration is a dual vibration motor.

[0021] Preferably, in step (C), the frequency of the dual vibration motor is 50-60 Hz.

[0022] Preferably, in step (C), the vibration time is ≥8 min.

[0023] Preferably, in step (C), the vibration time is 8 to 10 minutes.

[0024] Preferably, in step (D), the baking time is 40 to 60 minutes.

[0025] Preferably, in step (D), the baking temperature is 250-300°C, and the heating rate is preferably 10-12°C / min;

[0026] In step (E), the cooling time is ≥4h.

[0027] The present invention provides a tundish, which is manufactured by the construction process described in the above technical solution.

[0028] The invention provides a continuous casting tundish dry material construction process, which is a method for prolonging the service life of the tundish. For a certain dry material, the dry material thickness is increased, the existing thickness of the dry material on the tundish wall is adjusted from 50-55 mm to ≥60 mm, and the thickness of the dry material on the tundish bottom is adjusted from 60 mm to ≥90 mm. At the same time, the conditions of the vibration process are adjusted, the original vibration time is adjusted from 3 min to ≥8 min, and the vibration motor is changed to a dual motor. The baking conditions are also adjusted, the baking time is shortened from 70 to 90 min to 40 to 60 min, and the cooling and demoulding time is extended to ≥4 h. Through the regulation of the above various factors, the corrosion resistance of the overall dry material is improved, thereby improving its service life. DETAILED DESCRIPTION

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0030] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0031] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] As used herein, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Furthermore, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0033] In this document, when referring to a range, if the unit is followed only by the right endpoint, it means that the units of the left and right endpoints are the same. For example, 40-60min means that the units of both the left endpoint "40" and the right endpoint "60" are min.

[0034] A construction process for continuous casting tundish dry material comprises the following steps:

[0035] (A) Laying the dry material on the bottom of the tundish to form the bottom dry material;

[0036] Wherein, the thickness of the bottom dry material is ≥90mm;

[0037] (B) placing the fetal membrane into the tundish, and pouring the dry material between the permanent layer and the fetal membrane along the wall of the tundish to form the wall dry material;

[0038] Wherein, the thickness of the wall dry material is ≥60mm;

[0039] (C) vibrating the tundish;

[0040] (D) baking the tundish;

[0041] (E) The fetal membrane is cooled and demoulded;

[0042] in,

[0043] Calculated in percentage by mass, the dry material includes: MgO ≥ 80%, CaO ≤ 2.5%, Al2O3 ≤ 1.5%, SiO2 ≤ 4.5%, Fe2O3 ≤ 2.0, and C total ≤ 3.0%.

[0044] [About dry materials]:

[0045] In the present invention, the dry material components mainly include, by mass percentage, MgO ≥ 80%, CaO ≤ 2.5%, Al2O3 ≤ 1.5%, SiO2 ≤ 4.5%, Fe2O3 ≤ 2.0, and C total ≤ 3.0%.

[0046] In the present invention, the dry material can be prepared by the following preparation method: crushing and screening the raw materials, grinding, batching, stirring and mixing to obtain the dry material.

[0047] in:

[0048] The raw materials include magnesia ore / magnesite and additives, wherein the additives are not particularly limited and conventional additives in the art can be used.

[0049] The crushing and screening process / requirements include: using a jaw crusher and a roller crusher to feed the material, maintaining uniform feeding during the process to avoid blockage. After the vibrating screen begins discharging material, the operator and quality inspector must immediately check whether the particle size is appropriate. After normal production, the operator and quality inspector must conduct random inspections of each particle size. If the inspection fails, the machine will be shut down immediately for processing. The screening standards are as follows (i.e., the distribution of particles in each particle size range in terms of mass percentage):

[0050] Particles 3mm≤<5mm: 10%~20%;

[0051] Particles with a size of 1mm≤<3mm: 10% to 20%;

[0052] Particles with a size of 0.5 mm or less and less than 1 mm: 10% to 20%;

[0053] Particles with a size of less than 0.5 mm: 40% to 70%.

[0054] The grinding process and requirements include: When feeding the mill, the material entering the mill must be less than 40mm in particle size. Quality inspectors and operators will jointly adjust the mill parameters; immediately after the mill begins discharging material, the powder particle size must be checked for compliance. After normal production, operators and quality inspectors will conduct random inspections of each particle size. If any particle size fails, the equipment will be adjusted immediately. The screening standards are as follows (i.e., the distribution of particles in each size range, expressed as a percentage by mass):

[0055] Particles with a size of >180 mesh: <10%;

[0056] Particles with a size of 320 mesh and a particle size of 180 mesh: 15% to 25%;

[0057] Particles with a particle size of less than 320 mesh: 75% to 85%.

[0058] The batching process involves the operator selecting the appropriate silo and setting the appropriate quantities based on the production recipe. After verification by a quality inspector, batching begins. Each material is subject to a tolerance of ±2kg, and the entire truckload is subject to a tolerance of ±5kg. Before adding the prepared materials to the mixer, the operator must confirm that there are no anomalies before normal operation can begin.

[0059] The mixing process / requirements include: (1) Before adding additives and other small materials manually, electronic scales and other measuring instruments must be cleaned and calibrated to confirm that there are no abnormalities before adding. The materials to be added must be within the validity period and free of moisture and caking. The allowable deviation of the weight of the ingredients is ±0.5kg. (2) The order of adding materials: first add the materials in the buffer bin, then add additives, resin powder, etc. The total mixing time requirement: dry materials should not be less than 8 minutes. During the production process, the quality inspector takes samples for inspection, and the dry materials are required to be 3-4kg.

[0060] [About Step A]:

[0061] In the present invention, the dry material is first laid on the bottom of the tundish, and the laying process is carried out to lay the material evenly and evenly until it reaches a certain thickness, thereby obtaining the bottom dry material. In the present invention, the thickness of the bottom dry material is ≥90mm, preferably 90-95mm, and specifically 90mm, 91mm, 92mm, 93mm, 94mm, or 95mm. Excessive thickness will affect the capacity of the tundish.

[0062] [About Step B]:

[0063] In the present invention, after the dry material at the bottom of the ladle is laid in step (A), the fetal membrane is placed in the intermediate ladle, and a gap is formed between the fetal membrane and the permanent layer for holding the dry material; wherein, when placing the fetal membrane, care is taken to adjust its position so that the gap around the fetal membrane and the permanent layer is consistent, so that the thickness of the dry material on the wall of the ladle formed is uniform.

[0064] In the present invention, after the lining is placed, dry material is poured along the tundish wall between the permanent layer and the lining to form the lining wall dry material. In the present invention, the thickness of the lining wall dry material is ≥ 60 mm, preferably 60-65 mm, specifically 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, or 65 mm. Excessive thickness will reduce the tundish capacity.

[0065] [About Step C]:

[0066] In the present invention, after the material distribution in steps (A) and (B) is completed, the tundish is vibrated. The vibration motor used for the vibration is a dual-vibration motor. The frequency of the dual-vibration motor is preferably 50-60 Hz, specifically 50 Hz, 55 Hz, or 60 Hz. The vibration duration is preferably ≥ 8 minutes, preferably 8-10 minutes, specifically 8 minutes, 9 minutes, or 10 minutes. This vibration improves the density of the castable (i.e., the dry material being poured), removes bubbles, and thereby increases the density and strength of the castable.

[0067] [About Step D]:

[0068] In the present invention, after the vibration in step (C) is completed, baking is performed, specifically, the burner in the fetal membrane is ignited to bake the castable. In the present invention, the baking temperature is preferably 250-300°C, specifically 250°C, 260°C, 270°C, 280°C, 290°C, and 300°C. The heating rate of the baking is preferably 10-12°C / min, specifically 10°C / min, 11°C / min, and 12°C / min. The baking time is preferably 40-60min, specifically 40min, 45min, 50min, 60min, etc., mainly depending on the hot and cold conditions of the mold. The cold mold mainly preheats the mold for about 10 minutes in the early stage.

[0069] During the baking process of the dry material working layer of the tundish of the present invention, as the temperature of the tundish increases, the phenolic resin therein gradually solidifies, and the solidified resin decomposes at 200-800°C, releasing gases such as CO2, CO, CH4, H2 and H2O, while leaving fixed carbon to form a carbon network structure. Although the amount of this gas is not as large as the amount of water vapor generated by the coating, if the heating rate is fast and the binder decomposes too quickly, a large amount of gas will accumulate and expand. In addition, the volume density of the dry material working layer is greater than that of the coating working layer. In severe cases, the working layer will collapse during baking. Therefore, after the dry material in the tundish is thickened, the baking time of the present invention is adjusted from the original 70-90 minutes to 40-60 minutes. Combined with the control of the heating rate, the temperature uniformity can be better maintained, which is beneficial to improving the performance of the castable.

[0070] [Regarding Step E]:

[0071] In the present invention, after the baking in step (D) is completed, cooling and demoulding are carried out. In the present invention, the cooling is preferably natural drying cooling. The cooling time is preferably ≥4h, more preferably 4-5h, specifically 4h or 5h, mainly determined by the thickness of the dry material. The thicker the material, the longer the cooling time. The baking time in step (C) of the present invention is shortened, and the cooling time in step (E) is extended from 3h in the original process to more than 4h, to ensure sufficient natural drying and thus ensure the performance of the castable. After the above-mentioned cooling, demoulding is carried out to form a working layer on the surface of the permanent layer of the tundish.

[0072] Under the influence of external factors such as variety plan fulfillment and production plan anomalies, the casting cycle of the continuous casting tundish will exceed the specified time range. Statistical analysis shows that the main problem of the tundish that has been used beyond the cycle before is that the erosion depth of the slag line increases with the extension of the casting cycle. For example, the original thickness of the dry material at the bottom of the tundish for 720 minutes is 60mm, and the thickness of the dry material at the wall is 50-55mm. The average slag line erosion of 104 overdue tundishes was about 30mm after statistical offline inspection. Among them, the slag line erosion ≥50mm occurred once, which was a quality problem of the material itself. The quality of the other parts was stable and under control. In order to prevent the recurrence of slag line erosion ≥50mm and avoid major safety hazards, the present invention appropriately increases the thickness of the working layer dry material to increase the casting cycle. The dry material in the tundish consists of two parts: the dry material at the bottom and the dry material at the wall. The thickness parameters are determined according to the design and use requirements of the tundish (for example, for the above-mentioned dry material, the original thickness of the dry material at the wall is 50-55mm, and the thickness of the dry material at the bottom is 60mm). The present invention adjusts the existing thickness of the dry material on the wall of the ladle from 50-55mm to ≥60mm, effectively solving the problem of slag line erosion of the dry material on the wall of the ladle. At the same time, the durability and impact resistance of the dry material at the bottom of the ladle need to be enhanced simultaneously, and the thickness of the dry material at the bottom of the ladle is adjusted from 60mm to ≥90mm. Although increasing the thickness can extend the casting cycle, its thickness cannot be increased blindly. It must also be determined based on the actual use of the ladle upper water inlet, stopper rod, retaining wall, dam, baffle, etc. on site. The present invention comprehensively examines and analyzes various factors and adapts and matches various aspects, and finally determines that the thickness of the wall and bottom of the ladle are respectively within the preferred ranges shown above. After the dry material in the ladle is thickened, the present invention also adjusts the conditions of the vibration process, adjusting the original vibration time from 3min to ≥8min, and changing the vibration motor to a dual motor. In addition, after the dry material in the ladle is thickened, the present invention also adjusts the baking conditions, shortening the baking time from the original 70~90min to 40~60min to ensure the uniformity of the baking temperature; at the same time, the natural drying and cooling time is extended to allow it to dry naturally enough before demolding. The present invention adjusts the cloth thickness, vibration conditions, baking conditions, and cooling and demoulding time, thereby improving the performance of the castable working layer, increasing the service life of the working layer, and further increasing the service life of the tundish.

[0073] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0074] Dry material composition: MgO 88%, CaO 2.0%, Al2O3 1.0%, SiO2 4.0%, Fe2O3

[0075] 2.0%, C 3.0%. The preparation method is as mentioned above.

[0076] Comparative Example 1

[0077] (A) Spread the dry material evenly and flatly on the bottom of the tundish to form a 60mm thick dry material on the bottom of the tundish.

[0078] (B) Place the fetal membrane into the tundish, and pour the dry material between the permanent layer and the fetal membrane along the wall of the tundish to form a 55mm thick wall of dry material.

[0079] (C) The tundish is vibrated using a single vibration motor at a frequency of 50 Hz for 3 minutes.

[0080] (D) Ignite the burner inside the membrane to bake the castable, with a heating rate of 10°C / min, a baking temperature of 250°C, and a baking time of 90 minutes.

[0081] (E) Cool naturally for 3 hours, demould, and form a working layer.

[0082] Example 1

[0083] (A) Spread the dry material evenly and flatly on the bottom of the tundish to form a 90mm thick dry material at the bottom of the tundish.

[0084] (B) Place the fetal membrane into the tundish, and pour the dry material between the permanent layer and the fetal membrane along the wall of the tundish to form a 60mm thick wall of dry material.

[0085] (C) The tundish is vibrated using a dual vibration motor at a frequency of 50 Hz for 8 minutes.

[0086] (D) Ignite the burner inside the membrane to bake the castable, with a heating rate of 10°C / min, a baking temperature of 250°C, and a baking time of 60 minutes.

[0087] (E) Cool naturally for 4 hours, demould, and form a working layer.

[0088] Example 2

[0089] (A) Spread the dry material evenly and flatly on the bottom of the tundish to form a 95mm thick dry material at the bottom of the tundish.

[0090] (B) Place the fetal membrane into the tundish, and pour the dry material between the permanent layer and the fetal membrane along the wall of the tundish to form a 65mm thick wall of dry material.

[0091] (C) The tundish is vibrated using a dual vibration motor at a frequency of 50 Hz for 8 minutes.

[0092] (D) Ignite the burner inside the membrane to bake the castable, with a heating rate of 10°C / min, a baking temperature of 250°C, and a baking time of 40 minutes.

[0093] (E) Cool naturally for 5 hours, demould, and form a working layer.

[0094] Continuous casting was performed on the tundishes of each embodiment and comparative example. The results showed that the slag line erosion thickness of the tundish of Comparative Example 1 reached 50 mm after a 12-hour casting cycle. However, the slag line erosion thickness of the tundish of Example 1 was only 40 mm after a 13-hour casting cycle, and the slag line erosion thickness of the tundish of Example 2 was only 45 mm after a 15-hour casting cycle. This indicates that the method of the present invention significantly improves the service life of the tundish compared to Comparative Example 1.

[0095] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that are not substantially different from the literal description of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A construction process for continuous casting tundish dry material, characterized in that: The following steps are involved: (A) Laying the dry material on the bottom of the tundish to form the bottom dry material; Wherein, the thickness of the bottom dry material is ≥90mm; (B) placing the fetal membrane into the tundish, and pouring the dry material between the permanent layer and the fetal membrane along the wall of the tundish to form the wall dry material; Wherein, the thickness of the wall dry material is ≥60mm; (C) vibrating the tundish; (D) baking the tundish; (E) The fetal membrane is cooled and demoulded; in, Calculated in percentage by mass, the dry material includes: MgO ≥ 80%, CaO ≤ 2.5%, Al2O3 ≤ 1.5%, SiO2 ≤ 4.5%, Fe2O3 ≤ 2.0, and C total ≤ 3.0%.

2. The construction process according to claim 1, characterized in that: In step (A), the thickness of the bottom dry material is 90 to 95 mm.

3. The construction process according to claim 1, characterized in that: In step (B), the thickness of the wall-wrapped dry material is 60 to 65 mm.

4. The construction process according to claim 1, characterized in that: In step (C), the vibration motor used for the vibration is a dual vibration motor.

5. The construction process according to claim 4, characterized in that: In step (C), the frequency of the dual vibration motors is 50-60 Hz.

6. The construction process according to claim 4, characterized in that: In step (C), the vibration time is ≥8 min.

7. The construction process according to claim 6, characterized in that: In step (C), the vibration time is 8 to 10 minutes.

8. The construction process according to claim 1, characterized in that: In step (D), the baking time is 40 to 60 minutes.

9. The construction process according to claim 1 or 8, characterized in that: In step (D), the baking temperature is 250-300°C, and the heating rate is preferably 10-12°C / min; In step (E), the cooling time is ≥4h.

10. A tundish made by the construction process according to any one of claims 1 to 9.