Method for quickly changing steel grade in tundish of slab continuous casting machine and application of method

Abstract

The invention discloses a method for quickly changing steel grades of a tundish of a slab continuous casting machine and application of the method, and relates to the technical field of steel smelting. Comprising the steps that after a tundish of a previous furnace is cast, the tundish of the previous furnace is moved out, and a tundish of a new furnace is replaced for casting. The difference of the mass percentage content of carbon in the molten steel in the tundish of the last furnace and the mass percentage content of carbon in the molten steel in the tundish of the new furnace is smaller than or equal to 0.35%, and the mass percentage content of carbon in the molten steel in the tundish of the last furnace is smaller than 0.50%. By controlling the content of carbon in two adjacent furnaces of molten steel, accidents such as casting blank connecting mark pull-off, pull-leakage and nozzle nodulation and blockage in the quick change process can be effectively avoided, the success rate of quick change of steel grades in the tundish is increased, the productivity of a slab continuous casting machine can be increased, meanwhile, the quality of slabs obtained through continuous casting can be guaranteed, and the production cost is reduced. And wide application of the continuous casting tundish quick-change technology is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and in particular, to a method for quickly changing steel grades in a tundish of a slab continuous caster and its application. Background Art

[0002] In the current metallurgical industry, the way to increase the production capacity of a slab continuous caster mainly relies on implementing continuous casting production. Therefore, the tundish quick change technology is a method to reduce the number of times of stopping casting and production preparation of the caster, improve the slab production capacity, and improve the operation rate of the caster.

[0003] Although the tundish quick change technology has the above advantages, in the actual application process, due to the different steel grades smelted in different heats, accidents such as breakout of the casting seam, breakout, and nozzle clogging often easily occur during the quick change process, resulting in the failure of the quick change, which will cause great losses to steel smelting.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for quickly changing steel grades in a tundish of a slab continuous caster and its application.

[0006] The present invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for quickly changing steel grades in a tundish of a slab continuous caster, including removing the tundish of the previous heat after the casting of the tundish of the previous heat is completed, and replacing it with a new tundish for casting.

[0008] The difference in the mass percentage content of carbon between the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat is less than or equal to 0.35%, and the mass percentage content of carbon in the molten steel in the tundish of the previous heat is less than 0.50%.

[0009] In an optional embodiment, the difference in the mass percentage content of manganese between the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat is 0.15 - 0.25%.

[0010] In an optional embodiment, the mass percentage content ratio of manganese to silicon in the molten steel in the tundish of the new heat is 2.8 - 3.2.

[0011] In an optional embodiment, the mass percentage content of sulfur in the molten steel in the tundish of the previous heat is less than or equal to 0.045%.

[0012] In an optional embodiment, the mass percentage content of aluminum in the molten steel in the tundish of the previous heat is less than or equal to 0.8%.

[0013] In an alternative embodiment, the difference in the mass percentage content of chromium in the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat is less than or equal to 2%.

[0014] In an alternative embodiment, the difference in the mass percentage content of carbon in the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat is less than or equal to 0.30%.

[0015] In a second aspect, the present invention provides an application of the method according to any one of the foregoing embodiments in improving the continuous casting efficiency during steel smelting.

[0016] The present invention has the following beneficial effects:

[0017] The present invention provides a method for quickly changing steel grades in the tundish of a slab continuous caster and its application. By controlling the carbon content in the molten steel of two adjacent heats, accidents such as breakout and leakage of the cast slab and clogging of the nozzle due to nodulation during the quick change can be effectively avoided, and the success rate of quickly changing steel grades in the tundish can be improved. This can not only increase the production capacity of the slab continuous caster, but also ensure the quality of the slab obtained by continuous casting, which is conducive to the wide application of the tundish quick change technology for continuous casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a topographical view of the joint after quick change of the method provided in Embodiment 1 of the present invention;

[0020] Figure 2 It is a topographical view of the joint after quick change of the method provided in Comparative Example 1 of the present invention;

[0021] Figure 3 It is a topographical view of the joint after quick change of the method provided in Comparative Example 2 of the present invention;

[0022] Figure 4 It is a topographical view of the joint after quick change of the method provided in Comparative Example 9 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0024] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0025] In a first aspect, the present invention provides a method for quickly changing the type of steel in a tundish of a slab continuous casting machine, comprising removing the tundish of the previous furnace after casting is completed, and replacing the tundish of a new furnace for casting.

[0026] The difference in the mass percentage of carbon in the molten steel in the tundish of the previous furnace and the molten steel in the tundish of the new furnace is less than or equal to 0.35%, and the mass percentage of carbon in the molten steel in the tundish of the previous furnace is less than 0.50%.

[0027] According to the mass percentage of carbon in the steel grade, steel can generally be divided into high carbon steel, medium carbon steel and low carbon steel. Among them, the mass percentage of carbon in high carbon steel is greater than or equal to 0.50%, the mass percentage of carbon in medium carbon steel is between 0.25% and 0.50% (including 0.25% and excluding 0.50%), and the mass percentage of carbon in low carbon steel is less than 0.25%.

[0028] The present invention proposes that when the mass percentage of carbon is greater than or equal to 0.50%, that is, when the molten steel in the tundish is high-carbon steel, it is not suitable for use as the molten steel in the tundish of the previous furnace in the quick-change technology of the continuous casting tundish. The reason is that high-carbon steel has poor fluidity and a wide solidification temperature range, which is not conducive to long-term retention in the molten steel crystallizer, and is prone to uneven growth of the billet shell. When the molten steel in the tundish of the previous furnace is high-carbon steel, and the new furnace quick-change steel is low-carbon steel, due to the large difference in C content, if the quick-change is performed directly, it will lead to loose connection at the joint of the ingot, too large gap, and easy to pull off at the joint after entering the straightening machine.

[0029] Therefore, the mass percentage of carbon in the molten steel in the previous furnace tundish can be, for example, any value among 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.49%, or a range value between any two values.

[0030] In addition, the inventors have also found that during the quick change process, if the mass percentage of carbon in the steel of two adjacent furnaces is greatly different, the molten steel in the joint part of the crystallizer will not be fully solidified during the connection process after the quick change, and it is easy to leak steel at the joint after exiting the lower mouth of the crystallizer. Therefore, the mass percentage difference of carbon in the molten steel in the tundish of the previous furnace and the molten steel in the tundish of the new furnace is controlled to be less than or equal to 0.35%, which can avoid quality defects in the quick change process.

[0031] Preferably, the difference in mass percentage of carbon in the molten steel in the tundish of the previous furnace and the molten steel in the tundish of the new furnace is less than or equal to 0.30%.

[0032] Therefore, the difference in the mass percentage content of carbon in the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat can be, for example, any value among 0%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, or 0.35%, or a range value between any two of these values.

[0033] In an alternative embodiment, the difference in the mass percentage content of manganese in the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat is 0.15 - 0.25%, and can be, for example, any value among 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, or 0.25%, or a range value between any two of these values.

[0034] In an alternative embodiment, the mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat is 2.8 - 3.2, and can be, for example, any value among 2.8, 2.9, 3.0, 3.1, or 3.2, or a range value between any two of these values.

[0035] By controlling the manganese content and silicon content of the molten steel in adjacent tundishes within the above ranges, the generation of deoxidizing agent silicon dioxide can be reduced to ensure the fluidity and pourability of the molten steel during the quick change process, and prevent nozzle coking during the tundish starting process during the quick change, which may lead to nozzle blockage and cause the failure of the quick change.

[0036] In an alternative embodiment, the mass percentage content of sulfur in the molten steel in the tundish of the previous heat is less than or equal to 0.045%. A high sulfur content in the molten steel will lead to an increase in inclusions in the molten steel. In the later stage of drawing the molten steel in the tundish, as the tundish molten steel level drops, the inclusions formed by high-sulfur steel are likely to block the upper nozzle of the tundish, causing the steel flow to interrupt and resulting in the failure of the quick change.

[0037] Therefore, the mass percentage content of sulfur in the molten steel in the tundish of the previous heat can be, for example, any value among 0.005%, 0.010%, 0.015%, 0.020%, 0.025%, 0.030%, 0.035%, 0.040%, or 0.045%, or a range value between any two of these values.

[0038] In an alternative embodiment, the mass percentage content of aluminum in the molten steel in the tundish of the previous heat is less than or equal to 0.8%. A relatively high aluminum content in the molten steel will form more alumina inclusions. In the later stage of drawing the molten steel in the tundish, as the tundish molten steel level drops, the alumina inclusions will cause nozzle coking and result in the interruption of the steel flow, leading to the failure of the quick change.

[0039] Therefore, the mass percentage content of aluminum in the molten steel in the tundish of the previous heat can be, for example, any value among 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8% or a range value between any two of these values.

[0040] In an alternative embodiment, the difference in the mass percentage content of chromium between the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat is less than or equal to 2%. A relatively high chromium content in the molten steel can affect the solidification temperature range and thermophysical properties of the steel, making it impossible to effectively connect at the joint, and prone to breakout or leakage accidents after the molten steel exits the mold.

[0041] Therefore, the difference in the mass percentage content of chromium between the molten steel in the tundish of the previous heat and the molten steel in the tundish of the new heat can be, for example, any value among 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, or 2.0% or a range value between any two of these values.

[0042] In a second aspect, the present invention provides an application of the method according to any one of the foregoing embodiments in improving the continuous casting efficiency during the steel smelting process.

[0043] In an alternative embodiment, it is applied to the tundish quick change technology for continuous casting. The tundish quick change technology for continuous casting includes any one of the hydraulic quick change method, manual quick change method, high liquid level immersion quick change technology, low liquid level quick change technology, or fixed diameter nozzle quick change technology.

[0044] Example 1

[0045] This example provides a method for quickly changing the steel grade in the tundish of a slab continuous caster, including the following steps:

[0046] The molten steel in the tundish of the previous heat is low-carbon steel (Q235B), and its composition by mass percentage is: C 0.18%, Mn 0.45%, Si 0.25%, S 0.025%, Al 0.05%, Cr 0.10%.

[0047] The molten steel in the tundish of the new heat is low-carbon steel (Q345B), and its composition by mass percentage is: C 0.20%, Mn 0.60%, Si 0.20%, S 0.030%, Al 0.06%, Cr 0.15%.

[0048] The difference in carbon content between the two heats of molten steel is 0.02%, the difference in manganese content is 0.15%, and the difference in chromium content is 0.05%. And the mass percentage content of carbon in the molten steel in the tundish of the previous heat is 0.18%, the mass percentage content of sulfur is 0.025%, and the mass percentage content of aluminum is 0.05%. The mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat of the two heats of molten steel is 3.0.

[0049] The above two ladles of molten steel are quickly replaced using the continuous casting tundish quick change technology. The specific method is as follows:

[0050] When the casting of the previous tundish is completed, the tundish car is hydraulically driven out of the casting position. After the new tundish is preheated to 1100 °C, it is accurately aligned above the mold. The new tundish is started for casting, and the casting speed is gradually increased from 0.8 m / min to 1.2 m / min. The solidification state at the joint is monitored in real time, and the water volume in the secondary cooling zone is adjusted to 200 L / min.

[0051] After quickly replacing using the method provided in this embodiment, the quick change success rate is 100%, the productivity of the continuous casting machine is increased by 15%, and there are no quality defects at the connection of the cast slabs, as Figure 1 shown.

[0052] Example 2

[0053] This embodiment provides a method for quickly changing the steel grade of the tundish of a slab continuous casting machine, including the following steps:

[0054] The molten steel in the previous tundish is medium carbon steel (45 steel), and its composition by mass percentage is: C 0.42%, Mn 0.65%, Si 0.30%, S 0.035%, Al 0.30%, Cr 0.50%.

[0055] The molten steel in the new tundish is medium carbon steel (40Cr), and its composition by mass percentage is: C 0.40%, Mn 0.80%, Si 0.25%, S 0.040%, Al 0.35%, Cr 1.60%.

[0056] The difference in carbon content between the two ladles of molten steel is 0.02%, the difference in manganese content is 0.15%, and the difference in chromium content is 1.10%. And the mass percentage of carbon in the molten steel in the previous tundish is 0.42%, the mass percentage of sulfur is 0.035%, and the mass percentage of aluminum is 0.30%. The mass percentage ratio of manganese to silicon in the molten steel in the new tundish of the two ladles of molten steel is 3.2.

[0057] The above two ladles of molten steel are quickly replaced using the continuous casting tundish quick change technology of Example 1. There are no defects detected by ultrasonic inspection at the joint, and the production efficiency is increased by 12%.

[0058] Example 3

[0059] This embodiment provides a method for quickly changing the steel grade of the tundish of a slab continuous casting machine, including the following steps:

[0060] The molten steel in the tundish of the previous heat was low-carbon steel (SPHC), and its composition by mass percentage was: C 0.08%, Mn 0.30%, Si 0.05%, S 0.015%, Al 0.02%, Cr 0.03%.

[0061] The molten steel in the tundish of the new heat was low-carbon steel (DC01), and its composition by mass percentage was: C 0.10%, Mn 0.45%, Si 0.15%, S 0.020%, Al 0.04%, Cr 0.05%.

[0062] The difference in carbon content between the two heats of molten steel was 0.02%, the difference in manganese content was 0.15%, and the difference in chromium content was 0.02%. And the mass percentage of carbon in the molten steel in the tundish of the previous heat was 0.08%, the mass percentage of sulfur was 0.015%, and the mass percentage of aluminum was 0.02%. The mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat of the two heats of molten steel was 3.0.

[0063] The above two heats of molten steel were quickly changed using the continuous casting tundish quick change technology of Example 1, and the surface quality rating of the slab after quick change reached Grade A.

[0064] Comparative Example 1

[0065] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0066] The molten steel in the tundish of the previous heat was high-carbon steel, and its composition by mass percentage was: C 0.58%, Mn 0.75%, Si 0.3%, S 0.05%, Al 1.0%, Cr 0.20%.

[0067] The molten steel in the tundish of the new heat was medium-carbon steel, and its composition by mass percentage was: C 0.40%, Mn 0.80%, Si 0.25%, S 0.040%, Al 0.35%, Cr 1.60%.

[0068] The difference in carbon content between the two heats of molten steel was 0.18%, the difference in manganese content was 0.05%, and the difference in chromium content was 1.4%. And the mass percentage of carbon in the molten steel in the tundish of the previous heat was 0.58%, the mass percentage of sulfur was 0.05%, and the mass percentage of aluminum was 1.0%. The mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat of the two heats of molten steel was 3.2.

[0069] The above two heats of molten steel were quickly changed using the continuous casting tundish quick change technology of Example 1, and there was a breakout at the joint, as Figure 2 shown.

[0070] Comparative Example 2

[0071] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0072] The molten steel in the tundish of the previous heat was low-carbon steel, and its composition by mass percentage was: C 0.18%, Mn 0.15%, Si 0.25%, S 0.025%, Al 0.05%, Cr 0.10%.

[0073] The molten steel in the tundish of the new heat was low-carbon steel, and its composition by mass percentage was: C 0.20%, Mn 0.45%, Si 0.20%, S 0.030%, Al 0.06%, Cr 0.15%.

[0074] The difference in carbon content between the two heats of molten steel was 0.02%, the difference in manganese content was 0.30%, and the difference in chromium content was 0.05%. And the mass percentage of carbon in the molten steel in the tundish of the previous heat was 0.18%, the mass percentage of sulfur was 0.025%, and the mass percentage of aluminum was 0.05%. The mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat of the two heats of molten steel was 3.0.

[0075] The above two heats of molten steel were quickly changed using the continuous casting tundish quick change technology of Example 1, and the situation of nozzle nodulation and blockage occurred, as Figure 3 shown.

[0076] Comparative Example 3

[0077] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0078] The molten steel in the tundish of the previous heat was low-carbon steel, and its composition by mass percentage was: C 0.08%, Mn 0.30%, Si 0.05%, S 0.015%, Al 0.02%, Cr 0.03%.

[0079] The molten steel in the tundish of the new heat was low-carbon steel, and its composition by mass percentage was: C 0.10%, Mn 0.6%, Si 0.24%, S 0.020%, Al 0.04%, Cr 0.05%.

[0080] The difference in carbon content between the two heats of molten steel was 0.02%, the difference in manganese content was 0.15%, and the difference in chromium content was 0.02%. And the mass percentage of carbon in the molten steel in the tundish of the previous heat was 0.08%, the mass percentage of sulfur was 0.015%, and the mass percentage of aluminum was 0.02%. The mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat of the two heats of molten steel was 2.5.

[0081] The molten steel in the above two furnaces was quickly changed using the continuous casting tundish quick change technology of Example 1. The new furnace of molten steel had insufficient deoxidation and poor fluidity, which affected the smooth progress of continuous casting.

[0082] Comparative Example 4

[0083] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0084] The molten steel in the previous furnace tundish was low-carbon steel, and its composition by mass percentage was: C 0.18%, Mn 0.45%, Si 0.25%, S 0.050%, Al 0.05%, Cr 0.10%.

[0085] The molten steel in the new furnace tundish was low-carbon steel, and its composition by mass percentage was: C 0.20%, Mn 0.60%, Si 0.20%, S 0.030%, Al 0.06%, Cr 0.15%.

[0086] The difference in carbon content between the two furnaces of molten steel was 0.02%, the difference in manganese content was 0.15%, and the difference in chromium content was 0.05%. And the mass percentage of carbon in the molten steel in the previous furnace tundish was 0.18%, the mass percentage of sulfur was 0.050%, and the mass percentage of aluminum was 0.05%. The mass percentage ratio of manganese to silicon in the molten steel in the new furnace tundish of the two furnaces of molten steel was 3.0.

[0087] The molten steel in the above two furnaces was quickly changed using the continuous casting tundish quick change technology of Example 1, and the phenomenon of clogging the nozzle with inclusions occurred.

[0088] Comparative Example 5

[0089] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0090] The molten steel in the previous furnace tundish was medium-carbon steel, and its composition by mass percentage was: C 0.42%, Mn 0.65%, Si 0.30%, S 0.035%, Al 1.2%, Cr 0.50%.

[0091] The molten steel in the new furnace tundish was medium-carbon steel, and its composition by mass percentage was: C 0.40%, Mn 0.80%, Si 0.25%, S 0.040%, Al 0.35%, Cr 1.60%.

[0092] The carbon content difference between the two heats of molten steel is 0.02%, the manganese content difference is 0.15%, and the chromium content difference is 1.10%. Moreover, in the molten steel in the tundish of the previous heat, the mass percentage of carbon is 0.42%, the mass percentage of sulfur is 0.035%, and the mass percentage of aluminum is 1.2%. The mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat of the two heats of molten steel is 3.2.

[0093] The quick change of the above two heats of molten steel was carried out using the tundish quick change technology of Example 1, and the phenomenon of alumina clogging the nozzle occurred.

[0094] Comparative Example 6

[0095] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0096] The molten steel in the tundish of the previous heat is medium carbon steel, and its composition by mass percentage is: C 0.42%, Mn 0.65%, Si 0.30%, S 0.035%, Al 0.30%, Cr 3.0%.

[0097] The molten steel in the tundish of the new heat is medium carbon steel, and its composition by mass percentage is: C 0.40%, Mn 0.80%, Si 0.25%, S 0.040%, Al 0.35%, Cr 0.50%.

[0098] The carbon content difference between the two heats of molten steel is 0.02%, the manganese content difference is 0.15%, and the chromium content difference is 2.50%. Moreover, in the molten steel in the tundish of the previous heat, the mass percentage of carbon is 0.42%, the mass percentage of sulfur is 0.035%, and the mass percentage of aluminum is 0.30%. The mass percentage ratio of manganese to silicon in the molten steel in the tundish of the new heat of the two heats of molten steel is 3.2.

[0099] The quick change of the above two heats of molten steel was carried out using the tundish quick change technology of Example 1, and the joint was pulled off and cracked.

[0100] Comparative Example 7

[0101] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0102] The molten steel in the tundish of the previous heat is low carbon steel, and its composition by mass percentage is: C 0.18%, Mn 0.45%, Si 0.25%, S 0.025%, Al 0.05%, Cr 0.10%.

[0103] The molten steel in the new tundish is high-carbon steel, and its composition by mass percentage is: C 0.58%, Mn 0.60%, Si 0.20%, S 0.030%, Al 0.06%, Cr 0.15%.

[0104] The difference in carbon content between the two heats of molten steel is 0.40%, the difference in manganese content is 0.15%, and the difference in chromium content is 0.05%. And the mass percentage of carbon in the molten steel in the previous tundish is 0.18%, the mass percentage of sulfur is 0.025%, and the mass percentage of aluminum is 0.05%. The mass percentage ratio of manganese to silicon in the molten steel in the new tundish of the two heats of molten steel is 3.0.

[0105] The above two heats of molten steel were quickly changed using the continuous casting tundish quick change technology of Example 1, and a steel leakage accident occurred.

[0106] Comparative Example 8

[0107] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster, including the following steps:

[0108] The molten steel in the previous tundish is low-carbon steel, and its composition by mass percentage is: C 0.08%, Mn 0.30%, Si 0.05%, S 0.015%, Al 0.02%, Cr 0.03%.

[0109] The molten steel in the new tundish is low-carbon steel, and its composition by mass percentage is: C 0.10%, Mn 0.7%, Si 0.2%, S 0.020%, Al 0.04%, Cr 0.05%.

[0110] The difference in carbon content between the two heats of molten steel is 0.02%, the difference in manganese content is 0.15%, and the difference in chromium content is 0.02%. And the mass percentage of carbon in the molten steel in the previous tundish is 0.08%, the mass percentage of sulfur is 0.015%, and the mass percentage of aluminum is 0.02%. The mass percentage ratio of manganese to silicon in the molten steel in the new tundish of the two heats of molten steel is 3.5.

[0111] The above two heats of molten steel were quickly changed using the continuous casting tundish quick change technology of Example 1, and phenomena such as excessive deoxidation and nozzle coking occurred.

[0112] Comparative Example 9

[0113] This comparative example provides a method for quickly changing steel grades in the tundish of a slab continuous caster. The steel grade change is the same as that in Example 1, except that the new tundish was not preheated during the quick change process, and cold replacement was directly carried out, resulting in phenomena such as joint cold shut, as Figure 4 shown.

[0114] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for quickly changing steel grades in a tundish of a slab continuous casting machine, characterized in that: The method includes removing the tundish of the previous furnace after the casting is completed, and replacing the tundish of a new furnace for casting; The difference in carbon mass percentage between the molten steel in the previous tundish and the molten steel in the new tundish is less than or equal to 0.35%, and the carbon mass percentage in the molten steel in the previous tundish is less than 0.50%.

2. The method according to claim 1, characterized in that The difference in mass percentage of manganese between the molten steel in the tundish of the previous furnace and the molten steel in the tundish of the new furnace is 0.15-0.25%.

3. The method according to claim 1, characterized in that The mass percentage ratio of manganese to silicon in the molten steel in the tundish of a new furnace is 2.8 to 3.

2.

4. The method according to claim 1, characterized in that: The mass percentage of sulfur in the molten steel in the tundish of the previous furnace is less than or equal to 0.045%.

5. The method according to claim 1, characterized in that The mass percentage of aluminum in the molten steel in the tundish of the previous furnace is less than or equal to 0.8%.

6. The method according to claim 1, characterized in that The difference in mass percentage of chromium between the molten steel in the previous furnace tundish and the molten steel in the new furnace tundish is less than or equal to 2%.

7. The method according to claim 1, characterized in that The difference in mass percentage of carbon between the molten steel in the previous tundish and the molten steel in the new tundish is less than or equal to 0.30%.

8. Use of the method according to any one of claims 1 to 7 in improving continuous casting efficiency during steelmaking.

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