CN109852891B - Corner crack control method for low-carbon boron-containing steel continuous casting slab - Google Patents

Corner crack control method for low-carbon boron-containing steel continuous casting slab Download PDF

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CN109852891B
CN109852891B CN201711244979.7A CN201711244979A CN109852891B CN 109852891 B CN109852891 B CN 109852891B CN 201711244979 A CN201711244979 A CN 201711244979A CN 109852891 B CN109852891 B CN 109852891B
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江中块
蔡兆镇
宋景欣
牛振宇
朱苗勇
朱坤
王恩龙
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Shanghai Meishan Iron and Steel Co Ltd
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Abstract

The invention relates to a corner crack control method of a low-carbon boron-containing steel continuous casting slab. The method of the invention comprises the following steps: (1) controlling components; (2) controlling the molten iron ratio in the smelting process of the converter to be 85.0-87.0%, adopting a bottom blowing mode in the whole process, blowing nitrogen firstly and then blowing argon to blow to the bottom in the blowing process, wherein the use ratio of the nitrogen to the argon is 1: 9; (3) controlling the content of C at the smelting end point to be 0.035 +/-0.02, and controlling the tapping temperature to be 1660 +/-5 ℃; (4) tapping by adopting a semi-deoxidation process in the smelting tapping process of the converter; (5) deoxidizing agent and alloying are carried out simultaneously in the tapping process; (6) after steel is discharged, directly transferring the steel ladle to an argon station for argon blowing refining; (7) in the continuous casting process, strong cooling control is adopted in wide and narrow surface foot roll areas, two to four areas of vertical bending sections and 1 section of arc section of the continuous casting billet, and then conventional cooling control is adopted in 2-8 sections of the arc. The invention realizes the stable control of the incidence rate of corner cracks of the casting blank by the low-carbon boron-containing steel to be less than 0.1 percent.

Description

Corner crack control method for low-carbon boron-containing steel continuous casting slab
The technical field is as follows:
the invention relates to a corner crack control method for a low-carbon boron-containing steel continuous casting slab, belonging to the technical field of steel continuous casting.
Background art:
boron-containing steels are an important component of microalloyed steels. The addition of boron element into steel can obviously improve the hardenability of steel, the high-temperature strength and creep strength of heat-resistant steel, and the red hardness of high-speed steel and the cutting capability of cutters, and is widely applied to modern steel production. However, in the actual continuous casting production process of boron-containing steel, the corners of the casting blank are frequently subjected to transverse crack defects, so that severe cracks and tilted quality defects appear at the edges of a rolled material. Therefore, the produced continuous casting blank mostly needs to be offline for corner flame cleaning, and the on-site production rhythm is seriously disturbed.
As the frequent corner crack defect in the production process of the boron-containing steel continuous casting billet is an industrial common technical problem, the research and development work aiming at the corner crack control technology of the boron-containing steel continuous casting billet at home and abroad is deeper. However, the steel types related to the corner crack control of the existing boron-containing steel continuous casting billet are mainly peritectic and medium-carbon boron-containing steel, the corner crack control of the low-carbon boron-containing steel continuous casting billet is less, and the control measures are mainly concentrated as follows: (1) molten steel components are controlled, and the solute content of structure grain boundary P, S and the like in the casting blank solidification process is reduced; (2) ti is added in the refining process, and the nitrogen fixation effect of the molten steel is realized by utilizing the characteristic of preferential combination of Ti and N in steel, so that BN precipitation in the solidification process of a continuous casting billet is reduced, and the grain boundary strength of a casting blank corner structure is improved; (3) the water distribution of the secondary cooling arc and the straightening area is controlled by the weak cooling strength, so that the casting blank has higher surface temperature in the bending and straightening processes to avoid a third brittle temperature area of the steel; (4) adjusting the taper, vibration and cooling strength, physical property parameters of the casting powder and the like of the crystallizer, slowly cooling the initial solidification structure of the casting blank, reducing the vibration marks on the surface of the casting blank and preventing the corner cracks of the casting blank from being generated.
However, in the actual continuous casting production process of boron-containing steel, the main reason for generating the corner cracks is that BN is precipitated in the surface layer structure of the casting blank, so that the grain boundaries are embrittled to generate crack defects. Therefore, the key point for fundamentally controlling the generation of the boron-containing steel is to control the precipitation amount of the grain boundary BN in the continuous casting process of the boron-containing steel. At present, no process or method for effectively controlling the corner cracks of a continuous casting billet in the continuous casting production process of low-carbon boron-containing steel by iron and steel enterprises exists.
Disclosure of Invention
The invention aims to provide a method for controlling corner cracks of a low-carbon boron-containing steel continuous casting slab, aiming at the existing problems, and the method strictly ensures that nitrogen is not added in the continuous casting production process by strictly controlling the nitrogen content in the converter smelting, tapping process, external refining and the like, and carrying out offline tightness inspection and adjustment, argon seal protection in the continuous casting process and the like on continuous casting protection casting. On the basis, a secondary cooling integral, particularly a high-temperature area forced cooling controlled cooling process is adopted, so that the crystal boundary BN of the casting blank corner structure is greatly reduced and separated out in the continuous casting process of the low-carbon boron-containing steel, and the incidence rate of the corner cracks of the casting blank is stably controlled to be less than 0.1 percent.
The above purpose is realized by the following technical scheme:
a method for controlling corner cracks of a low-carbon boron-containing steel continuous casting slab comprises the following steps:
(1) controlling components: the low-carbon boron-containing steel comprises the following components in percentage by weight: 0.025 to 0.050, Si: less than or equal to 0.035, Mn: 0.13-0.22, P: less than or equal to 0.02, S: 0.015 or less, Alt: 0.025 to 0.050, B: 0.001-0.002 wt%, and iron in balance;
(2) the molten iron ratio in the smelting process of the converter is controlled to be 85.0-87.0%, a bottom blowing mode is adopted in the whole process, nitrogen is blown firstly in the blowing process, then argon is blown, and the converter is blown to the bottom by one gun, so that the blowing is prevented from being supplemented, and the use ratio of the nitrogen to the argon is 1: 9;
(3) controlling the content of C at the smelting end point to be 0.035 +/-0.02, and controlling the tapping temperature to be 1660 +/-5 ℃;
(4) tapping by adopting a semi-deoxidation process in the smelting tapping process of the converter;
(5) deoxidizing agent and alloying are carried out simultaneously in the tapping process;
(6) after steel is discharged, directly transferring the steel ladle to an argon station for argon blowing refining;
(7) in the continuous casting process, strong cooling control is adopted in wide and narrow surface foot roll areas, two to four areas of vertical bending sections and 1 section of arc section of the continuous casting billet, conventional cooling control is adopted in the sections 2-8 of the arc, and the specific water amount per ton steel is 1.2-1.35L.
The method for controlling the corner cracks of the low-carbon boron-steel continuous casting slab comprises the following specific steps of (4): when the steel ladle is transferred to an argon station for oxygen determination, the oxygen content in the steel is about 200 +/-100 ppm, when the bottom of the steel ladle is fully paved with molten steel, a modifier is added into the steel ladle, the addition amount is 2.3-2.5 kg per ton of steel, and on the basis, an accelerator of 2.0kg per ton of steel is added.
The method for controlling the corner cracks of the low-carbon boron-containing steel continuous casting slab comprises the following specific steps of (5) simultaneously deoxidizing agent and alloying in the tapping process: the deoxidizer is Al-Mn-Ca deoxidizer, the alloying raw material is medium carbon ferromanganese, the addition amount of the deoxidizer is 2.0-2.5 kg/ton steel, and the medium carbon ferromanganese is 1.0-1.5 kg/ton steel.
The method for controlling the corner cracks of the low-carbon boron-containing steel continuous casting slab comprises the following specific steps of (6): blowing argon at the early stage of argon station refining, selecting 400NL/min for blowing argon, stirring for 3-4 min, then performing aluminum supplement wire deoxidation, wherein the adding amount of an aluminum wire is 1 kg/ton of steel, selecting a boron wire for boron microalloying at the last stage of argon station refining, adding 0.14kg of boron steel per ton of boron wire, adding the boron wire, and then performing 400NL/min argon stirring treatment for 2-3 min to ensure that boron in the steel is uniformly distributed; and finally, transferring the argon flow to 150NL/min for stirring, wherein the stirring time is more than or equal to 5min, and the total refining time is controlled to be 14min to 22min, so that molten steel components with the N content of 22 ppm to 27ppm and other components meeting the requirements of (1) are obtained.
The method for controlling the corner cracks of the low-carbon boron-steel continuous casting slab comprises the following steps of (7), performing strong cooling control on a wide and narrow surface foot roll area, a second to fourth area of a vertical bending section and 1 section of an arc section of the continuous casting slab, performing conventional cooling control on 2-8 sections of the arc, and specifically controlling the specific water amount per ton steel to be 1.2-1.35L: the water content of the inner arc and the outer arc of the wide-surface foot roller of the casting blank is 9.5-10.2% of the total water content, the water content of the narrow-surface foot roller is 4.2-4.5% of the total water content, the water content of the inner arc and the outer arc of the second area of the vertical bending section is 11.6-12.4% of the total water content, the water content of the inner arc and the outer arc of the third area is 11.8-12.6% of the total water content, the water content of the inner arc and the outer arc of the fourth area is 13.0-13.8% of the total water content, the water content of the inner arc and the outer arc of the fifth area of the arc 1 section is 7.7-8.4% of the total water content, the water content of the inner arc and the outer arc of the six areas corresponding to the arc 2 and the 3 sections is 6.7-7.4% of the total water content, the water content of the inner arc and the outer.
Has the advantages that:
1. the method comprises the following steps of (1) rapidly cooling the structure in a casting blank corner precipitation temperature area, and dispersing and precipitating BN in the surface structure crystal of the casting blank as much as possible; (2) the content of N in molten steel is strictly controlled, or elements such as Ti which are precipitated prior to the combination of B and N in the solidification process of steel are added to the steel, thereby reducing the precipitation amount of BN grain boundary. However, for low-carbon boron-containing steel, because most of the low-carbon boron-containing steel is used as a subsequent cold rolling raw material, a certain content of Ti element is added into the steel, and great fluctuation of the performance of a cold-rolled coil is easily caused. Therefore, the total precipitation amount of surface texture grain boundary BN in the solidification process of the continuous casting billet is radically reduced, the corner cracks of the boron-containing steel continuous casting billet are effectively controlled, and the crack control effect is very stable;
2. the method adopts the smelting, refining and continuous casting protection casting to control the content of N in the boron-containing steel, abandons the traditional method of adopting additional Ti measures to fix nitrogen in molten steel in the production process of boron-containing steel such as peritectic and medium carbon and the like, and can not cause fluctuation to the performance of subsequent cold-rolled products;
3. in the aspect of controlling the surface temperature of the casting blank, the whole casting blank is controlled by strong cooling, so that the control difficulty is low, the implementation process is stable, and the protection of continuous casting equipment is facilitated.
The specific implementation mode is as follows:
a method for controlling corner cracks of a low-carbon boron-containing steel continuous casting slab comprises the following steps:
(1) controlling components: the low-carbon boron-containing steel comprises the following components in percentage by weight: 0.025 to 0.050, Si: less than or equal to 0.035, Mn: 0.13-0.22, P: less than or equal to 0.02, S: 0.015 or less, Alt: 0.025 to 0.050, B: 0.001-0.002 wt%, and iron in balance;
(2) the molten iron ratio in the smelting process of the converter is controlled to be 85.0-87.0%, a bottom blowing mode is adopted in the whole process, nitrogen is blown firstly in the blowing process, then argon is blown, and the converter is blown to the bottom by one gun, so that the blowing is prevented from being supplemented, and the use ratio of the nitrogen to the argon is 1: 9;
(3) controlling the content of C at the smelting end point to be 0.035 +/-0.02, and controlling the tapping temperature to be 1660 +/-5 ℃;
(4) tapping by adopting a semi-deoxidation process in the smelting tapping process of the converter;
(5) deoxidizing agent and alloying are carried out simultaneously in the tapping process;
(6) after steel is discharged, directly transferring the steel ladle to an argon station for argon blowing refining;
(7) in the continuous casting process, strong cooling control is adopted in wide and narrow surface foot roll areas, two to four areas of vertical bending sections and 1 section of arc section of the continuous casting billet, conventional cooling control is adopted in the sections 2-8 of the arc, and the specific water amount per ton steel is 1.2-1.35L.
The method for controlling the corner cracks of the low-carbon boron-steel continuous casting slab comprises the following specific steps of (4): when the steel ladle is transferred to an argon station for oxygen determination, the oxygen content in the steel is about 200 +/-100 ppm, when the bottom of the steel ladle is fully paved with molten steel, a modifier is added into the steel ladle, the addition amount is 2.3-2.5 kg per ton of steel, and on the basis, an accelerator of 2.0kg per ton of steel is added.
The method for controlling the corner cracks of the low-carbon boron-containing steel continuous casting slab comprises the following specific steps of (5) simultaneously deoxidizing agent and alloying in the tapping process: the deoxidizer is Al-Mn-Ca deoxidizer, the alloying raw material is medium carbon ferromanganese, the addition amount of the deoxidizer is 2.0-2.5 kg/ton steel, and the medium carbon ferromanganese is 1.0-1.5 kg/ton steel.
The method for controlling the corner cracks of the low-carbon boron-containing steel continuous casting slab comprises the following specific steps of (6): blowing argon at the early stage of argon station refining, selecting 400NL/min for blowing argon, stirring for 3-4 min, then performing aluminum supplement wire deoxidation, wherein the adding amount of an aluminum wire is 1 kg/ton of steel, selecting a boron wire for boron microalloying at the last stage of argon station refining, adding 0.14kg of boron steel per ton of boron wire, adding the boron wire, and then performing 400NL/min argon stirring treatment for 2-3 min to ensure that boron in the steel is uniformly distributed; and finally, transferring the argon flow to 150NL/min for stirring, wherein the stirring time is more than or equal to 5min, and the total refining time is controlled to be 14min to 22min, so that molten steel components with the N content of 22 ppm to 27ppm and other components meeting the requirements of (1) are obtained.
The method for controlling the corner cracks of the low-carbon boron-steel continuous casting slab comprises the following steps of (7), performing strong cooling control on a wide and narrow surface foot roll area, a second to fourth area of a vertical bending section and 1 section of an arc section of the continuous casting slab, performing conventional cooling control on 2-8 sections of the arc, and specifically controlling the specific water amount per ton steel to be 1.2-1.35L: the water content of the inner arc and the outer arc of the wide-surface foot roller of the casting blank is 9.5-10.2% of the total water content, the water content of the narrow-surface foot roller is 4.2-4.5% of the total water content, the water content of the inner arc and the outer arc of the second area of the vertical bending section is 11.6-12.4% of the total water content, the water content of the inner arc and the outer arc of the third area is 11.8-12.6% of the total water content, the water content of the inner arc and the outer arc of the fourth area is 13.0-13.8% of the total water content, the water content of the inner arc and the outer arc of the fifth area of the arc 1 section is 7.7-8.4% of the total water content, the water content of the inner arc and the outer arc of the six areas corresponding to the arc 2 and the 3 sections is 6.7-7.4% of the total water content, the water content of the inner arc and the outer.
Taking the casting blank corner crack control in the process of producing DC51D + Z low-carbon boron-containing steel with the cross section of 230mm multiplied by 1530mm at the stable drawing speed of 1.4m/min as an example, the method specifically comprises the following steps:
(1) the produced DC51D + Z low-carbon boron-containing steel comprises the following target components: c: 0.04, Si: 0.020, Mn: 0.19, P: 0.014, S: 0.013, Alt: 0.038, B: 0.0012;
(2) the smelting process adopts 250t converter to smelt, smelts the raw materials and is molten iron and scrap steel, and the molten iron ratio control is at 85.0%, and whole adoption bottom blowing mode is adopted, and the blowing adopts nitrogen gas converting earlier stage, and middle and later stages adopt argon gas converting, and the converting process adopts a rifle form converting to the end, firmly stops the reblowing technology, and nitrogen gas and argon gas proportion of use are 1: 9;
(3) the DC51D + Z low-carbon boron-containing steel has the advantages that the target C content at the smelting end point of the converter is controlled to be 0.04, and the tapping temperature is 1660 +/-5 ℃;
(4) tapping by adopting a semi-deoxidation process in the tapping process after smelting in the converter, wherein the tapping oxygen content control target is as follows: the oxygen content in the steel is about 200ppm when the steel ladle is transferred to the argon station for oxygen determination. The principle of adding slag charge in the tapping process is as follows: when the molten steel is spread to the bottom of the ladle, Al is added into the ladle as the main component2O3And a modifier for CaO, both of which containThe amounts are respectively: (SiO2 content: 2.7%, CaO content: 65.3%, Al content: 2.7%)2O311.1 percent of the aluminum alloy, 8.6 percent of CaF2 and 4.8 percent of Al, the addition amount is about 2.3-2.4 kg of steel per ton, and about 2.0kg of accelerator is added into the steel per ton, and the specific components are as follows: (4.5% of SiO2, 27.1% of CaO, 5.2% of MgO, 26.9% of Al2O3, 3.9% of CaF2 and 24.7% of Al);
(5) and a deoxidizer and alloying are simultaneously carried out in the tapping process, wherein the deoxidizer is a compound of Al, Mn and Ca with the content ratio of 16: 3: 1 (the main components of the Al-Mn-Ca slag include 0.28% of C, 0.28% of Si, 12.25% of Mn, 0.017% of P, 0.016% of S, 57.29% of Al, 0.016% of Ti and 3.29% of Ca), and the alloying materials are medium carbon ferromanganese, the main components of which include 1.33% of C, 0.56% of Si, 79.69% of Mn, 0.193% of P, 0.008% of S and the balance of Fe, and the addition amount of the deoxidizer is about 2 kg/ton steel and about 1.2 kg/ton steel;
(6) after the steel is discharged, the steel is not subjected to LF refining production, and the steel ladle is directly transferred to an argon station for argon blowing refining. And (3) blowing argon at the early stage of argon station refining, selecting 400NL/min for strong argon blowing and stirring for about 3-4 min, and then performing aluminum wire supplementing deoxidation, wherein the adding amount of an aluminum wire is about 1 kg/ton steel. Selecting a boron wire to carry out boron microalloying at the last stage of refining in an argon station, adding 0.14kg of boron wire into each ton of steel, and carrying out strong argon stirring treatment for 2-3 min after adding the boron wire to ensure that boron in the steel is uniformly distributed; finally, stirring weakly, wherein the argon amount is 150NL/min, the guarantee time is more than or equal to 5min, and the total refining time is controlled to be about 17min, so that molten steel components with the N content of 22-25 ppm and other components meeting the requirements of (1) are obtained;
(7) in the protective casting link, in order to prevent nitrogen increase of molten steel caused by improper protective casting of the ladle long nozzle system in the casting process of the molten steel, the ladle nozzle system is subjected to tightness inspection and protection. The ladle long nozzle is a nozzle with a conical bowl-shaped inlet end and is provided with a conical asbestos pad. After casting is started, firstly, gas flame is utilized to carry out airtightness test on a ladle down nozzle and a long nozzle bowl, if flame is absorbed, the airtightness of the position is not good, and the long nozzle is sleeved again. If the tightness meets the requirement, in the casting process, 30-40 NL/min argon is introduced into the joint of the long nozzle bowl part to form an argon sealing state, and the condition that the nitrogen is increased in molten steel due to air suction caused by untight connection between the long nozzle bowl part and the ladle drain nozzle is further prevented.
(8) The off-line tightness of the tundish nozzle adopts argon pressure as a test standard, before the low-carbon boron-containing steel is produced, 10NL/min argon is introduced into the tundish nozzle and the stopper under an off-line condition, and the pressure of 1.0-1.5bar is ensured to be qualified as the tightness. In the steel casting process, the argon blowing flow of the stopper rod is stably controlled to be 5.0L/min, and the argon sealing gas quantity of the submerged nozzle is stably controlled to be 6.0L/min, so that the argon sealing is formed in the link from the tundish to the water gap of the crystallizer;
(9) in the continuous casting process, in order to effectively prevent the BN from being intensively precipitated in the surface austenite structure grain boundary in the solidification process of the continuous casting billet, strong cooling control is adopted in wide and narrow surface foot roll areas, two to four areas of vertical bending sections and 1 section of an arc section of the continuous casting billet, conventional cooling control is adopted in 2-8 sections of the arc, and the ton steel specific water amount is 1.25L. The water flow of the inner arc and the outer arc of the wide-surface foot roll of the casting blank is 416L, the water flow of the narrow-surface foot roll is 188L, the water flow of the inner arc and the outer arc of the two regions of the vertical bending section is 516L, the water flow of the inner arc and the outer arc of the three regions is 586L, the water flow of the inner arc and the outer arc of the five regions of the arc 1 section is 349L, the water flow of the inner arc and the outer arc of the six regions corresponding to the arc 2 and 3 sections is 292L, the water flow of the inner arc and the outer arc of the seven regions of the 4-6 sections is 458L, the water flow of the inner arc and the outer arc of the eight regions of the straightening 7 section and the 8 section is 285L, the water flow of the inner arc and the outer arc of the eight regions of the horizontal.
Based on the smelting, refining, continuous casting protection casting and secondary cooling water distribution processes, if the roll gap precision of the continuous casting machine is met, the incidence rate of corner cracks of the low-carbon boron-containing steel continuous casting billet can be ensured to be less than 0.1%.
It should be noted that the above-mentioned embodiments illustrate only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and that equivalents and substitutions made on the above-mentioned embodiments are included in the scope of the present invention, which is defined by the claims.

Claims (4)

1. A method for controlling corner cracks of a low-carbon boron-containing steel continuous casting slab is characterized by comprising the following steps: the method comprises the following steps:
(1) controlling components: the low-carbon boron-containing steel comprises the following components in percentage by weight: 0.025 to 0.050, Si: less than or equal to 0.035, Mn: 0.13-0.22, P: less than or equal to 0.02, S: 0.015 or less, Alt: 0.025 to 0.050, B: 0.001-0.002 wt%, and iron in balance;
(2) the molten iron ratio in the converter smelting process is controlled to be 85.0% -87.0%, a bottom blowing mode is adopted in the whole process, nitrogen is blown firstly in the blowing process, then argon is blown, a gun is blown to the bottom, the blowing is prevented from being blown again, and the use ratio of nitrogen to argon is 1: 9;
(3) controlling the content of C at the smelting end point to be 0.035 +/-0.02, and controlling the tapping temperature to be 1660 +/-5 ℃;
(4) tapping by adopting a semi-deoxidation process in the smelting tapping process of the converter;
(5) deoxidizing agent and alloying are carried out simultaneously in the tapping process;
(6) after steel is discharged, directly transferring the steel ladle to an argon station for argon blowing refining;
(7) in the continuous casting process, strong cooling control is adopted in wide and narrow surface foot roll areas, two to four areas of vertical bending sections and 1 section of an arc section of a continuous casting billet, conventional cooling control is adopted in the sections 2 to 8 of the arc, and the specific water amount per ton steel is 1.2 to 1.35L;
the specific method for argon blowing refining in the step (6) comprises the following steps: blowing argon at the early stage of argon station refining, selecting 400NL/min for blowing argon, stirring for 3-4 min, then performing aluminum supplement wire deoxidation, wherein the adding amount of an aluminum wire is 1 kg/ton of steel, selecting a boron wire for boron microalloying at the last stage of argon station refining, adding 0.14kg of boron steel per ton of boron wire, adding the boron wire, and then performing 400NL/min argon stirring treatment for 2-3 min to ensure that boron in the steel is uniformly distributed; and finally, transferring the argon flow to 150NL/min for stirring, wherein the time is more than or equal to 5min, and the total refining time is controlled to be 14min to 22min, so that molten steel components with the N content of 22 ppm to 27ppm and other components meeting the requirements of (1) are obtained.
2. The method for controlling corner cracks of a low-carbon boron-containing steel continuous casting slab according to claim 1, wherein: the specific method for tapping in the semi-deoxidation process in the step (4) comprises the following steps: when the steel ladle is transferred to an argon station for oxygen determination, the oxygen content in the steel is 200 +/-100 ppm, when the bottom of the steel ladle is fully paved with molten steel, a modifier is added into the steel ladle, the addition amount is 2.3-2.5 kg per ton of steel, and on the basis, an accelerator of 2.0kg per ton of steel is added.
3. The method for controlling corner cracks of a low-carbon boron-containing steel continuous casting slab according to claim 1, wherein: the specific method for simultaneously carrying out the deoxidant and the alloying in the tapping process in the step (5) is as follows: the deoxidizer is Al-Mn-Ca deoxidizer, the alloying raw material is medium carbon ferromanganese, the addition amount of the deoxidizer is 2.0-2.5 kg/ton steel, and the medium carbon ferromanganese is 1.0-1.5 kg/ton steel.
4. The method for controlling corner cracks of a low-carbon boron-containing steel continuous casting slab according to claim 1, wherein: in the step (7), strong cooling control is adopted in the wide and narrow surface foot roll areas, the two-to-four areas of the vertical bending section and the 1 section of the arc section of the continuous casting billet, conventional cooling control is adopted in the 2-8 sections of the arc, and the specific control method for controlling the specific water amount per ton steel to be 1.2-1.35L is as follows: the water content of the inner arc and the outer arc of the wide-surface foot roller of the casting blank accounts for 9.5-10.2% of the total water content, the water content of the narrow-surface foot roller accounts for 4.2-4.5% of the total water content, the water content of the inner arc and the outer arc of the second area of the vertical bending section accounts for 11.6-12.4% of the total water content, the water content of the inner arc and the outer arc of the third area accounts for 11.8-12.6% of the total water content, the water content of the inner arc and the outer arc of the fifth area of the arc 1 section accounts for 7.7-8.4% of the total water content, the water content of the inner arc and the outer arc of the sixth area corresponding to the arc 2 and the arc 3 sections accounts for 6.7-7.4%, the water content of the inner arc and the outer arc of the seventh area of the 4-6 sections accounts for 10.2-10.6% of the total water content, and the water content of the inner arc and the.
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