Preparation method of ultra-low carbon steel continuous casting billet, ultra-low carbon steel continuous casting billet and steel product

Abstract

The present application discloses a method for preparing an ultra-low carbon steel continuous casting billet, an ultra-low carbon steel continuous casting billet and a steel product. The method comprises: passing molten steel in a tundish through a crystallizer at a speed of 1.4 to 1.6 m / min to obtain molten steel in the crystallizer, wherein the carbon content of the molten steel in the tundish is ≤0.006%; cooling the molten steel in the crystallizer to produce a continuous casting billet, wherein the cooling of the crystallizer comprises using first cooling water in a first direction and second cooling water in a second direction; the flow rate of the first cooling water is 5600 L / min to 5900 L / min, and the flow rate of the second cooling water is 570 L / min to 580 L / min; when the width of the ultra-low carbon steel continuous casting billet is 900 mm to 1200 mm, the crystallizer taper coefficient is 1.2%; when the width of the ultra-low carbon steel continuous casting billet is 1201 mm to 1500 mm, the crystallizer taper coefficient is 1.1%; and when the width of the ultra-low carbon steel continuous casting billet is 1501 mm to 1800 mm, the crystallizer taper coefficient is 1.0%. The method of the present application reduces the steel seepage phenomenon of the ultra-low carbon steel continuous casting billet.

Description

Technical Field

[0001] The present application belongs to the technical field of steel plate smelting, and specifically relates to a method for preparing an ultra-low carbon steel continuous casting billet, an ultra-low carbon steel continuous casting billet, and a steel product. Background Art

[0002] Continuous casting is the process of directly casting molten steel into billets. High-efficiency continuous casting has become an economical and efficient production process in the metallurgical industry both domestically and internationally. Key aspects of continuous casting include molten steel temperature control, mold design and operation, slab casting speed control, secondary cooling, and mold slag control in the tundish. These processes effectively improve billet quality and production efficiency.

[0003] Ultra-low carbon steel ingot infiltration occurs when the molten steel flows and solidifies unevenly within the mold during the continuous casting process, causing liquid steel to penetrate the partially solidified shell or the interior of the ingot, resulting in defects. Prior art efforts to address this issue have generally focused on optimizing the structure and process of the tundish. However, improvements to this phenomenon have been limited. Therefore, a new process is urgently needed to further improve the pass rate of infiltration in ultra-low carbon steel ingots. However, improvements to the mold are lacking. Summary of the Invention

[0004] In view of this, the present application provides a preparation method of ultra-low carbon steel continuous casting billets, ultra-low carbon steel continuous casting billets and steel products, aiming to provide a method that can significantly improve the steel infiltration phenomenon of ultra-low carbon steel billets, increase the available amount of ultra-low carbon steel billets, and improve the quality of ultra-low carbon steel.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing an ultra-low carbon steel continuous casting billet, comprising:

[0006] Passing the tundish molten steel through the crystallizer at a speed of 1.4-1.6 m / min to obtain a crystallizer molten steel, wherein the carbon content of the tundish molten steel is ≤0.006%;

[0007] Cooling the molten steel in the crystallizer to produce a continuously cast billet, wherein the cooling includes using first cooling water in a first direction and second cooling water in a second direction; the first direction is the direction in which the cooling water acts on the wide surface of the crystallizer; the second direction is the direction in which the cooling water acts on the narrow surface of the crystallizer;

[0008] The flow rate of the first cooling water is 5600 L / min to 5900 L / min, and the flow rate of the second cooling water is 570 L / min to 580 L / min;

[0009] When the width of the ultra-low carbon steel continuous casting billet is 900 mm to 1200 mm (the narrowest width is 900 mm), the mold taper coefficient is 1.2%;

[0010] When the width of the ultra-low carbon steel continuous casting billet is 1201 mm to 1500 mm, the mold taper coefficient is 1.1%;

[0011] When the width of the ultra-low carbon steel continuous casting billet is 1501 mm to 1800 mm, the crystallizer taper coefficient is 1.0%.

[0012] According to an embodiment of one aspect of the present application, the tundish molten steel is passed through the crystallizer at a speed of 1.5 m / min to obtain the crystallizer molten steel, wherein the carbon content of the tundish molten steel is ≤0.006%;

[0013] Cooling the molten steel in the crystallizer to produce a continuous casting billet, wherein the crystallizer cooling includes using first cooling water in a first direction and second cooling water in a second direction;

[0014] The flow rate of the first cooling water is 5900 L / min, and the flow rate of the second cooling water is 580 L / min;

[0015] When the width of the ultra-low carbon steel continuous casting billet is 1200 mm, the mold taper coefficient is 1.2%;

[0016] When the width of the ultra-low carbon steel continuous casting billet is 1500 mm, the mold taper coefficient is 1.1%;

[0017] When the width of the ultra-low carbon steel continuous casting billet is 1800 mm, the mold taper coefficient is 1.0%.

[0018] According to an embodiment of one aspect of the present application, multiple pairs of foot rollers are included between the crystallizer and the ultra-low carbon steel continuous casting billet, and the crystallizer includes crystallizer support rollers; the multiple pairs of foot rollers include a first pair of foot rollers, a second pair of foot rollers, a third pair of foot rollers and a fourth pair of foot rollers in the vertical direction, and the deviation values ​​of the arcs of the first pair of foot rollers, the second pair of foot rollers, the third pair of foot rollers and the fourth pair of foot rollers from the crystallizer support rollers are +0.5mm, +1.0mm, +1.5mm and +2.0mm respectively.

[0019] According to an embodiment of one aspect of the present application, the method further includes: making the basicity of the protective slag located on the surface of the molten steel inside the crystallizer 0.9 to 0.98.

[0020] According to an embodiment of one aspect of the present application, the method further includes: setting the melting point of the protective slag located on the surface of the molten steel inside the crystallizer to 1020°C to 1080°C.

[0021] According to an embodiment of one aspect of the present application, the protective slag includes, in percentage by mass: SiO2: 30% to 40%, Al2O3: 2% to 5%, Fe2O3: 0.5% to 1.2%, CaO: 30% to 35%, MgO: 0.5% to 1.85%, R2O: 5% to 12%, F: 5% to 8%, FC: 1% to 3.85% and unavoidable impurities, wherein R2O represents the sum of the masses of K2O and Na2O.

[0022] According to an embodiment of one aspect of the present application, the tundish molten steel includes, by mass percentage, 0.0015% to 0.0025% C, 0.015% to 0.020% P, 0.02% to 0.05% Al, 0.25% to 0.35% Mn, 0.10% to 0.20% Si, 0.010% to 0.015% S, and the remainder is Fe and unavoidable impurities.

[0023] According to an embodiment of one aspect of the present application, the tundish molten steel comprises, by mass percentage, 0.0025% to 0.0060% C, 0.015% to 0.020% P, 0.03% to 0.05% Al, 0.20% to 0.30% Mn, 0.15% to 0.25% Si, 0.012% to 0.018% S, and the remainder is Fe and unavoidable impurities.

[0024] In a second aspect, an embodiment of the present application provides an ultra-low carbon steel continuous casting billet, which is produced by the preparation method of the first aspect.

[0025] In a third aspect, an embodiment of the present application provides a steel product, which is produced by hot rolling and cooling the ultra-low carbon steel continuous casting billet produced by the preparation method of the first aspect or the ultra-low carbon steel continuous casting billet of the second aspect.

[0026] This application has at least the following beneficial effects:

[0027] The method provided in this application adopts a specific crystallizer cooling intensity, namely the first cooling water flow rate and the second cooling water flow rate, in the ultra-low carbon steel production process, based on the molten steel flow rate in the tundish and the casting speed of the ultra-low carbon steel continuous casting billet. Different crystallizer taper coefficients are used to prepare ultra-low carbon steel casting billets of different widths. This can reduce the steel penetration defect at the corners of the ultra-low carbon steel continuous casting billet, thereby reducing the problem of scarring on the edges of hot-rolled products. This method provides a new process solution for solving the problem of steel penetration at the corners of ultra-low carbon steel continuous casting billets, which can improve the apparent quality of ultra-low carbon steel continuous casting billets, reduce the amount of grinding required for continuous casting billets off the production line, increase the hot charging and hot delivery ratio, reduce overall costs, and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the implementation regulations of this application, the following is a brief introduction to the drawings required for use in the embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 The figure shows the appearance of the steel-infiltrated corner of the ultra-low carbon steel ingot of the comparative example of the present application.

[0030] Figure 2 The micrograph of the steel infiltration at the corner of the ultra-low carbon steel ingot of the comparative example of the present application is shown.

[0031] Figure 3 A schematic structural diagram of the middle ladle and crystallizer in an embodiment of the present application is shown.

[0032] Figure 4 A schematic diagram of the relative positions of the arcs of the crystallizer and the crystallizer support rollers in an embodiment of the present application is shown.

[0033] Among them, 1. Tundish, 2. Crystallizer, 3. Crystallizer intermediate roller. DETAILED DESCRIPTION

[0034] In order to make the application purpose, technical solutions and beneficial technical effects of this application clearer, the application is further described in detail below with reference to the embodiments. It should be understood that the implementation regulations described in this specification are only for the purpose of explaining this application and are not intended to limit this application.

[0035] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range. In addition, although not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value can serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0036] In the description of this application, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number, and “a variety” in “one or more” means two or more.

[0037] The above disclosure of the present application is not intended to describe every disclosed embodiment or every implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided through a series of examples, and these implementation regulations can be used in various combinations. In each example, the enumeration is only intended to be representative and should not be construed as exhaustive.

[0038] Preparation method of ultra-low carbon steel continuous casting billet

[0039] In a first aspect, an embodiment of the present application provides a method for preparing an ultra-low carbon steel continuous casting billet, comprising:

[0040] Passing the tundish molten steel through the crystallizer at a speed of 1.4-1.6 m / min to obtain a crystallizer molten steel, wherein the carbon content of the tundish molten steel is ≤0.006%;

[0041] Cooling the molten steel in the crystallizer to produce a continuously cast billet, wherein the cooling includes using first cooling water in a first direction and second cooling water in a second direction; the first direction is the direction in which the cooling water acts on the wide surface of the crystallizer; the second direction is the direction in which the cooling water acts on the narrow surface of the crystallizer;

[0042] The flow rate of the first cooling water is 5600 L / min to 5900 L / min, and the flow rate of the second cooling water is 570 L / min to 580 L / min;

[0043] When the width of the ultra-low carbon steel continuous casting billet is 900 mm to 1200 mm (the narrowest width is 900 mm), the mold taper coefficient is 1.2%;

[0044] When the width of the ultra-low carbon steel continuous casting billet is 1201 mm to 1500 mm, the mold taper coefficient is 1.1%;

[0045] When the width of the ultra-low carbon steel continuous casting billet is 1501 mm to 1800 mm, the crystallizer taper coefficient is 1.0%.

[0046] According to the embodiments of the present application, the carbon content of the molten steel in the middle package is ≤0.006%, indicating that this type of molten steel used to prepare ultra-low carbon steel has the characteristics of fast billet drawing speed and thin solidified billet shell. Therefore, when the molten steel in the middle package passes through the crystallizer at a speed of 1.4~1.6 m / min and the drawing speed of the ultra-low carbon steel continuous casting billet is 1.4 m / min to 1.6 m / min, the flow rate of the first cooling water and the flow rate of the second cooling water are within the above-mentioned range, which can reduce the uneven flow and solidification of the molten steel in the crystallizer, resulting in the liquid molten steel penetrating into the partially solidified shell or the interior of the billet, forming defects.

[0047] The first direction can be understood as the direction in which the cooling water acts on the wide surface of the crystallizer or the longitudinal direction in a top view of the crystallizer. The second direction can be understood as the direction in which the cooling water acts on the narrow surface of the crystallizer or the width direction in a top view of the crystallizer. The flow rates of the first cooling water and the second cooling water within the above ranges can further increase the shrinkage of the solidified shell of the molten steel, especially the shrinkage of the initial solidified shell in the meniscus region.

[0048] The mold taper coefficient refers to the mold's shrinkage rate in the height direction. Furthermore, employing a specific taper coefficient can effectively compensate for the volumetric shrinkage of ultra-low carbon steel continuous casting billets of a specific width during solidification, ensuring good contact between the billet of that width and the mold wall, reducing gaps and preventing molten steel penetration. A taper coefficient that is too large or too small can affect shell formation. Excessive taper can lead to an overly thick shell and increased internal stress, while too small a taper can result in an overly thin shell and insufficient strength, both of which increase the risk of penetration.

[0049] The mold taper coefficient takes into account the situation that different molds are used to cast different billet widths. The above design is more in line with the shrinkage characteristics of the continuous casting billet at the bottom of the crystallizer, which is beneficial to reducing the steel infiltration phenomenon of ultra-low carbon steel continuous casting billets and improving the hot charging ratio.

[0050] Ultra-low carbon steel continuous castings with quality defects require grinding. The temperature of the ingots on the production line is approximately 500-900 degrees Celsius. Grinding requires cooling the ingots to room temperature, burning off the infiltrated steel with a high-temperature torch, and then reheating them before they enter the continuous production line. The normal temperature of the next process is 400-600 degrees Celsius. Only after grinding can the ingots be rolled. Defect-free slabs do not require grinding and are sent directly to the next process. The hot charging rate measures the proportion of ingots that do not require grinding.

[0051] In some optional embodiments, the tundish molten steel is passed through the crystallizer at a speed of 1.5 m / min to obtain a crystallizer molten steel, wherein the carbon content of the tundish molten steel is ≤0.006%;

[0052] Cooling the molten steel in the crystallizer to produce a continuous casting billet, wherein the crystallizer cooling includes using first cooling water in a first direction and second cooling water in a second direction;

[0053] The flow rate of the first cooling water is 5900 L / min, and the flow rate of the second cooling water is 580 L / min;

[0054] When the width of the ultra-low carbon steel continuous casting billet is 1200 mm, the mold taper coefficient is 1.2%;

[0055] When the width of the ultra-low carbon steel continuous casting billet is 1500 mm, the mold taper coefficient is 1.1%;

[0056] When the width of the ultra-low carbon steel continuous casting billet is 1800 mm, the mold taper coefficient is 1.0%.

[0057] In some optional embodiments, multiple pairs of foot rollers are included between the crystallizer and the low carbon steel continuous casting billet, and the crystallizer includes crystallizer support rollers; the multiple pairs of foot rollers include a first pair of foot rollers, a second pair of foot rollers, a third pair of foot rollers and a fourth pair of foot rollers in the vertical direction, and the deviation values ​​of the arcs of the first pair of foot rollers, the second pair of foot rollers, the third pair of foot rollers and the fourth pair of foot rollers from the crystallizer support rollers are +0.5mm, +1.0mm, +1.5mm and +2.0mm respectively.

[0058] like Figure 3 As shown, a schematic diagram of the positions of the tundish ladle 1, the crystallizer 2 and the crystallizer support rollers 3 is shown.

[0059] Figure 4 In the middle, the left figure shows the first pair of foot rollers, the second pair of foot rollers, the third pair of foot rollers and the fourth pair of foot rollers, and the original relative distances between the arcs of the first pair of foot rollers, the second pair of foot rollers, the third pair of foot rollers and the fourth pair of foot rollers and the crystallizer support rollers respectively; the right figure shows the first pair of foot rollers, the second pair of foot rollers, the third pair of foot rollers and the fourth pair of foot rollers, and the deviation values ​​of the arcs of the first pair of foot rollers, the second pair of foot rollers, the third pair of foot rollers and the fourth pair of foot rollers and the crystallizer support rollers respectively are d1: +0.5mm, d2: +1.0mm, d3: +1.5mm, d4: +2.0mm.

[0060] Generally, the first pair of foot rollers is located below the mold, providing effective support and reducing bulging. The distance between the first pair of foot rollers and the lower edge of the mold support rollers is 240 mm. In this application, the deviation between the first pair of foot rollers and the mold support rollers is +0.5 mm. This deviation provides effective support and avoids bulging.

[0061] The second pair of foot rollers is located below the mold and below the first pair of foot rollers, providing effective support and reducing bulging. The distance between the second pair of foot rollers and the lower edge of the mold support rollers is 480 mm. In this application, the deviation between the second pair of foot rollers and the mold support rollers is +1.0 mm. This deviation provides effective support and avoids bulging.

[0062] The third pair of foot rollers is located below the mold and below the second pair of foot rollers, providing support. The distance between the third pair of foot rollers and the lower edge of the mold support rollers is 720 mm. In this application, the deviation between the third pair of foot rollers and the mold support rollers is +1.5 mm. This deviation provides effective support and avoids bulging.

[0063] The fourth pair of foot rollers is located below the mold and below the third pair of foot rollers, providing effective support and reducing bulging. The distance between the fourth pair of foot rollers and the lower edge of the mold support rollers is 960 mm. In this application, the deviation between the fourth pair of foot rollers and the mold support rollers is +2.0 mm. This deviation provides effective support and avoids bulging.

[0064] The first, second, third, and fourth pairs of foot rollers are located in the second, or width, direction of the mold, referred to as the narrow side. Zero or negative deviations can lead to insufficient support for the solidifying shell on the narrow side of the mold, increasing the probability of steel infiltration. This can lead to the spread of steel infiltration in the slab and prevent effective control of steel infiltration.

[0065] In some optional embodiments, the method further comprises:

[0066] The basicity of the protective slag located on the surface of the molten steel inside the crystallizer is 0.9 to 0.98.

[0067] According to the embodiment of the present application, SiO2 material can be added to reduce the CaO content, so that the basicity of the protective slag is 0.9 to 0.98.

[0068] According to the embodiments of the present application, the basicity of the protective slag is within the above-mentioned range, which is beneficial to reducing the oxygen content in the molten steel and forming a good deoxidation environment, thereby helping to reduce the carbon content in the molten steel. High oxygen content easily causes carbon in the molten steel to react with oxygen to generate CO gas, increasing the activity of carbon. The basicity of the protective slag is within the above-mentioned range, indicating that the chemical properties of the protective slag are relatively stable, and it can effectively isolate oxygen and moisture in the air, reduce the penetration of oxygen and moisture into the molten steel, and thus reduce the carbon content in the molten steel. The basicity of the protective slag is within the above-mentioned range, indicating that the protective slag has good lubrication properties, can effectively reduce the friction between the molten steel and the wall of the crystallizer, avoid local high temperatures caused by frictional heat, reduce the diffusion of carbon in the molten steel, and thus reduce the occurrence of steel infiltration in the ingot.

[0069] In some optional embodiments, the method further comprises:

[0070] The melting point of the protective slag located on the surface of the molten steel inside the crystallizer is 1020 ℃ to 1080 ℃.

[0071] According to the embodiment of the present application, the temperature of the molten steel inside the crystallizer is 1545°C to 1560°C. The temperature of the molten steel differs from the temperature of the protective slag by 450°C. This indicates that the melting point of the protective slag is relatively low. When the melting point of the protective slag is within the above range, it can be melted faster in the crystallizer to form a liquid covering layer. The protective slag has good lubricity and reactivity, and is convenient for absorbing oxygen and impurities in the molten steel. Its good fluidity and coverage can effectively isolate oxygen and moisture in the air, reduce the entry of external carbon sources into the molten steel, and thus reduce steel seepage. If the melting point is higher than the above range, the protective slag is not easy to melt in the crystallizer, has poor fluidity and poor coverage, and is prone to forming uneven coverage or partially exposed areas, making it easier for oxygen and moisture in the air to penetrate into the molten steel, increasing the risk of steel seepage.

[0072] In summary, the basicity and melting point of the mold slag are beneficial to the solidification of the solidified shell in the second direction and reduce the risk of steel infiltration. Higher basicity and melting point are not conducive to the solidification of the solidified shell on the narrow side.

[0073] In some optional embodiments, the protective slag includes, in mass percentage, the following: SiO2: 30% to 40%, Al2O3: 2% to 5%, Fe2O3: 0.5% to 1.2%, CaO: 30% to 35%, MgO: 0.5% to 1.85%, R2O: 5% to 12%, F: 5% to 8%, FC: 1% to 3.85% and unavoidable impurities, wherein R2O represents the sum of the masses of K2O and Na2O.

[0074] In some optional embodiments, the protective slag includes, in mass percentage, the following: SiO2: 33.1%, Al2O3: 3.95%, Fe2O3: 0.98%, CaO: 32.47%, MgO: 1.78%, R2O: 5%-12%, F: 5%-8%, FC: 1%-3.85% and unavoidable impurities.

[0075] In some optional embodiments, the tundish molten steel comprises, by mass percentage, 0.0015% to 0.0025% C, 0.015% to 0.020% P, 0.02% to 0.05% Al, 0.25% to 0.35% Mn, 0.10% to 0.20% Si, 0.010% to 0.015% S, and the remainder is Fe and unavoidable impurities.

[0076] In some optional embodiments, the tundish molten steel comprises, by mass percentage, 0.0025% to 0.0060% C, 0.015% to 0.020% P, 0.03% to 0.05% Al, 0.20% to 0.30% Mn, 0.15% to 0.25% Si, 0.012% to 0.018% S, and the remainder is Fe and unavoidable impurities.

[0077] In a second aspect, an embodiment of the present application provides an ultra-low carbon steel continuous casting billet, which is produced by the preparation method of the first aspect.

[0078] Ultra-low carbon steel ingots naturally possess high toughness and ductility due to their ultra-low carbon content. Reducing carburization at the edges and corners of ultra-low carbon steel ingots results in more uniform mechanical properties throughout the ingot, thereby improving the toughness and ductility of the ingot. Reducing carburization at the edges and corners of ultra-low carbon steel ingots improves ingot utilization, reduces edge trimming, and contributes to improved product processing performance and economic benefits.

[0079] In some optional embodiments, the grinding amount of the ultra-low carbon steel continuous casting slab is ≤0.5%.

[0080] Grinding amount = ultra-low carbon steel continuous casting billet edge cutting and grinding quality / ultra-low carbon steel continuous casting billet sample quality in the length direction

[0081] In a third aspect, an embodiment of the present application provides a steel product, which is produced by hot rolling and cooling the ultra-low carbon steel continuous casting billet produced by the preparation method of the first aspect or the ultra-low carbon steel continuous casting billet of the second aspect.

[0082] By removing the infiltrated part at the edge of the ultra-low carbon steel ingot, the edge of the steel product produced will be free of scarring. Scarring of steel products is a type of surface defect, usually manifested as raised or sunken carbide accumulation on the surface. These defects will significantly affect the mechanical properties, processing performance and service life of ultra-low carbon steel.

[0083] Example

[0084] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and all instruments used in the examples are commercially available.

[0085] Example 1

[0086] This embodiment provides a method for preparing an ultra-low carbon steel ingot, comprising the following steps:

[0087] The tundish steel liquid includes, by mass percentage: The tundish steel liquid includes, by mass percentage: 0.0015% to 0.0025% C, 0.015% to 0.020% P, 0.02% to 0.05% Al, 0.25% to 0.35% Mn, 0.10% to 0.20% Si, 0.010% to 0.015% S, the remainder being Fe and unavoidable impurities.

[0088] The tundish molten steel passes through the crystallizer at a speed of 1.5m / min to obtain the crystallizer molten steel, wherein the carbon content of the tundish molten steel is ≤0.0060%; the drawing speed of the ultra-low carbon steel continuous casting billet is 1.5m / min,

[0089] Cooling the molten steel in the crystallizer to produce a continuous casting billet, wherein the cooling includes using first cooling water in a first direction and second cooling water in a second direction;

[0090] The water volume on the wide side of the crystallizer is 5900L / min, and the water volume on the narrow side is 580L / min.

[0091] The width of the ultra-low carbon steel ingot is 1200 mm, and the taper coefficient is set to 1.2% to ensure that the narrow-faced roller supports the solidified ingot shell.

[0092] The deviation values ​​between the narrow side foot rollers of the crystallizer and the copper plate of the crystallizer are: +0.5mm for the first pair of foot rollers, +1.0mm for the second pair of foot rollers, +1.5mm for the third pair of foot rollers and +2.0mm for the fourth pair of foot rollers (+ indicates positive deviation).

[0093] The basicity of the low carbon steel protection slag on the surface of the molten steel in the crystallizer is 0.9 and the melting point is 1020℃.

[0094] Example 2

[0095] The difference between this embodiment and embodiment 1 is that the width of the low-carbon steel ingot is 1500 mm and the taper coefficient is set to 1.1%.

[0096] Example 3

[0097] The difference between this embodiment and embodiment 1 is that the width of the low-carbon steel ingot is 1800 mm, and the taper coefficient is set to 1.0%.

[0098] Example 4

[0099] The difference between this embodiment and embodiment 1 is that the deviation values ​​between the narrow side foot rollers of the crystallizer and the copper plates of the crystallizer are changed from 0mm for the first pair of foot rollers, 0mm for the second pair of foot rollers, 0mm for the third pair of foot rollers and 0mm for the fourth pair of foot rollers.

[0100] Example 5

[0101] This embodiment differs from Example 1 in that the tundish molten steel comprises, by mass percentage, the following: 0.0025% to 0.0060% C, 0.015% to 0.020% P, 0.03% to 0.05% Al, 0.20% to 0.30% Mn, 0.15% to 0.25% Si, 0.012% to 0.018% S, with the remainder being Fe and unavoidable impurities. The ultra-low carbon steel mold slag on the surface of the molten steel in the crystallizer has a basicity of 0.98 and a melting point of 1080°C.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that the water flow rate of the wide side of the crystallizer is 5344L / min, and the water flow rate of the narrow side is 550L / min. Figure 1 The micrograph of the steel infiltration at the edge of the slab of Comparative Example 1 is shown in FIG. Figure 2 shown.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 1 is that the tundish molten steel passes through the crystallizer at a speed of 1.8 m / min.

[0106] Comparative Example 3

[0107] The difference between this comparative example and Example 1 is that the width of the ultra-low carbon steel ingot is 1200 mm, and the taper coefficient is set to 0.8%.

[0108] Comparative Example 4

[0109] The difference between this comparative example and Example 2 is that the difference between this comparative example and Example 1 is that the water volume on the wide side of the crystallizer is 5344 L / min, and the water volume on the narrow side is 550 L / min.

[0110] Comparative Example 5

[0111] The difference between this comparative example and Example 3 is that the difference between this comparative example and Example 1 is that the water volume on the wide side of the crystallizer is 5344 L / min, and the water volume on the narrow side is 550 L / min.

[0112] Test section

[0113] The edge infiltration width of the ultra-low carbon steel ingots prepared in the examples and comparative examples was tested, as well as the grinding amount and the hot charging and hot delivery ratio.

[0114] Grinding amount = (mass of the ingot before grinding - mass after decarburization by flame) / mass of the ingot before grinding

[0115] The hot charging and hot delivery ratio refers to the proportion of the number of ingots that do not require downward trimming to the total number of ingots.

[0116] Table 1 Test results of ultra-low carbon steel ingots of Examples and Comparative Examples.

[0117]

[0118] The above measured performance parameters are averaged.

[0119] The above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any familiarity with the present technology or replacement should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing ultra-low carbon steel continuous casting billets, characterized in that: include: Passing the tundish molten steel through the crystallizer at a speed of 1.4-1.6 m / min to obtain a crystallizer molten steel, wherein the carbon content of the tundish molten steel is ≤0.006%; Cooling the molten steel in the crystallizer to produce a continuously cast billet, wherein the cooling of the crystallizer includes using first cooling water in a first direction and second cooling water in a second direction, wherein the first direction is a direction in which the cooling water acts on a wide surface of the crystallizer; and the second direction is a direction in which the cooling water acts on a narrow surface of the crystallizer; The flow rate of the first cooling water is 5600 L / min to 5900 L / min, and the flow rate of the second cooling water is 570 L / min to 580 L / min; When the width of the ultra-low carbon steel continuous casting billet is 900 mm to 1200 mm, the mold taper coefficient is 1.2%; When the width of the ultra-low carbon steel continuous casting billet is 1201 mm to 1500 mm, the mold taper coefficient is 1.1%; When the width of the ultra-low carbon steel continuous casting billet is 1501 mm to 1800 mm, the crystallizer taper coefficient is 1.0%.

2. The preparation method according to claim 1, characterized in that Passing the tundish molten steel through the crystallizer at a speed of 1.5 m / min to obtain crystallizer molten steel, wherein the carbon content of the tundish molten steel is ≤0.006%; Cooling the molten steel in the crystallizer to produce a continuous casting billet, wherein the crystallizer cooling includes using first cooling water in a first direction and second cooling water in a second direction; The flow rate of the first cooling water is 5900 L / min, and the flow rate of the second cooling water is 580 L / min; When the width of the ultra-low carbon steel continuous casting billet is 1200 mm, the mold taper coefficient is 1.2%; When the width of the ultra-low carbon steel continuous casting billet is 1500 mm, the mold taper coefficient is 1.1%; When the width of the ultra-low carbon steel continuous casting billet is 1800 mm, the mold taper coefficient is 1.0%.

3. The preparation method according to claim 1, characterized in that There are multiple pairs of foot rollers between the crystallizer and the ultra-low carbon steel continuous casting billet, and the crystallizer includes crystallizer support rollers; the multiple pairs of foot rollers include a first pair of foot rollers, a second pair of foot rollers, a third pair of foot rollers and a fourth pair of foot rollers in the vertical direction, and the deviation values ​​of the arcs of the first pair of foot rollers, the second pair of foot rollers, the third pair of foot rollers and the fourth pair of foot rollers from the crystallizer support rollers are +0.5mm, +1.0mm, +1.5mm and +2.0mm respectively.

4. The preparation method according to claim 1, characterized in that The method further comprises: ensuring that the basicity of the protective slag located on the surface of the molten steel inside the crystallizer is 0.9 to 0.

98.

5. The preparation method according to claim 1, characterized in that The method further comprises: setting the melting point of the protective slag on the surface of the molten steel inside the crystallizer to 1020°C to 1080°C.

6. The preparation method according to claim 1, characterized in that The protective slag includes, in percentage by mass: SiO2: 30% to 40%, Al2O3: 2% to 5%, Fe2O3: 0.5% to 1.2%, CaO: 30% to 35%, MgO: 0.5% to 1.85%, R2O: 5% to 12%, F: 5% to 8%, FC: 1% to 3.85% and unavoidable impurities, among which R2O represents the sum of the masses of K2O and Na2O.

7. The preparation method according to claim 1, characterized in that The tundish molten steel comprises, by mass percentage, 0.0015% to 0.0025% C, 0.015% to 0.020% P, 0.02% to 0.05% Al, 0.25% to 0.35% Mn, 0.10% to 0.20% Si, 0.010% to 0.015% S, and the remainder is Fe and unavoidable impurities.

8. The preparation method according to claim 1, characterized in that The tundish molten steel comprises, by mass percentage, 0.0025% to 0.0060% C, 0.015% to 0.020% P, 0.03% to 0.05% Al, 0.20% to 0.30% Mn, 0.15% to 0.25% Si, 0.012% to 0.018% S, and the remainder is Fe and unavoidable impurities.

9. An ultra-low carbon steel continuous casting billet, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. A steel product, characterized in that The ultra-low carbon steel continuous casting billet is prepared by hot rolling and cooling the ultra-low carbon steel continuous casting billet prepared by the preparation method according to any one of claims 1 to 8 or the ultra-low carbon steel continuous casting billet according to claim 9.

Images