CN112453342A - Method for improving center segregation of low-carbon steel of ultra-thick plate blank - Google Patents
Method for improving center segregation of low-carbon steel of ultra-thick plate blank Download PDFInfo
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- CN112453342A CN112453342A CN202011190259.9A CN202011190259A CN112453342A CN 112453342 A CN112453342 A CN 112453342A CN 202011190259 A CN202011190259 A CN 202011190259A CN 112453342 A CN112453342 A CN 112453342A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
Abstract
The invention provides a method for improving low-carbon steel center segregation of an ultra-thick plate blank, which is used for carrying out pressing treatment on the ultra-thick plate blank and comprises the following steps: 1) the two-phase region is subjected to a pressure reduction treatment, firstly, according to the formula fs = (Tl-T)1) (T1-TS) calculating the casting blank solid phase ratio: secondly, determining the reduction according to the solid phase rate; 2) subjecting the solid phase region to a pressure reduction treatment, first, according to the formula dt = TS-T2Calculating the temperature difference of the casting blank reduction position: secondly, the rolling reduction is determined according to the temperature difference: when dt is more than 80 ℃, no pressure is applied; when dt is less than or equal to 80 ℃, the reduction is 1.5-5.0 mm. The invention has the advantages that: the method of the invention has simple process and easy realization, and can be realized by utilizing the existing equipment. When the scheme is adopted, the center segregation grades of the 1/4, 1/2 and 3/4 positions of the width of the casting blank are not lower than C1.0, and the internal quality of the low-carbon steel of the ultra-thick plate blank is obviously improved.
Description
Technical Field
The invention belongs to the technical field of steelmaking continuous casting, and particularly provides a method for improving the center segregation of low-carbon steel of an ultra-thick plate blank aiming at the continuous casting production process of the ultra-thick plate blank with the thickness specification exceeding 450 mm.
Background
Generally, slabs with a thickness gauge of more than 450mm are classified as super-thick slabs, and steels having a carbon content in the range of C (wt%) < 0.09% are classified as low carbon steels. In the process of slab continuous casting solidification, two defects which cannot be eliminated exist, namely center segregation which cannot be avoided due to selective crystallization, and W-shaped solidification tail end in the process of casting blank solidification. The cause and the harm of the slab continuous casting center segregation are elaborated in detail in various domestic and foreign documents: the columnar crystal solidification bridging and the slab bulging are considered to be main reasons for forming the center segregation, and the center segregation of the casting blank can be effectively controlled by using a dynamic soft reduction technology; the W-shaped solidification end of the slab continuous casting is considered to be closely related to the secondary cooling method. Regarding the technology for controlling the center segregation of the W-shaped solidification tail end of the ultra-thick slab, the domestic theoretical basic research is few, and the production practice of the ultra-thick slab is not available before, and no major breakthrough is made in the technical field of comprehensive control of the center segregation of the ultra-thick slab in China.
The invention patent with the patent number of CN201811567253.1 discloses a slab dynamic secondary cooling and soft reduction control system, which determines the total reduction amount and the reduction interval according to the position of a casting blank solidification two-phase area predicted by a dynamic heat tracking model and the characteristics of different steel types, dynamically optimizes the roll gap value of each reduction sector section, and achieves the purpose of reducing the center segregation and the center porosity defect of the casting blank.
In the domestic practice of 480mm straight arc type ultra-thick plate blank continuous casting production for the first time, the center segregation and W-shaped solidification tail end of the ultra-thick plate blank are found to be more serious compared with medium plate blanks, the internal quality of the ultra-thick plate blank cannot be effectively improved by adopting the conventional soft reduction technology, but at present, no experience for reference exists in the domestic high-quality ultra-thick plate blank with 480mm thickness specification, and only continuous exploration, optimization and innovation can be realized in the production practice. Aiming at the more serious W-shaped solidification tail end of the ultra-thick plate blank, a specific soft reduction comprehensive control technology is adopted, so that the internal quality of the ultra-thick plate blank is improved, and the method is a great technical innovation of the invention.
Disclosure of Invention
The invention aims to provide a method for improving the center segregation of low-carbon steel of an ultra-thick plate blank,
the invention is realized by the following technical scheme: the method for improving the center segregation of the low-carbon steel of the ultra-thick plate blank is characterized in that the ultra-thick plate blank is subjected to pressing treatment in the continuous casting process, and the method comprises the following specific steps:
1) and (3) carrying out reduction treatment on the two-phase region, and firstly, calculating the solid phase ratio of the central point of the reduction position of the casting blank according to the following formula:
fs =(Tl-T1)/(T1-TS)；
wherein, Tl is the liquidus temperature, DEG C; TS is solidus temperature, DEG C; t is1The temperature of the central point of the casting blank reduction position in the two-phase region is measured in DEG C;
secondly, determining the reduction of the two-phase region:
when fs is more than or equal to 0.02 and less than 0.44, the reduction is 1.5-6.5 mm; when fs is more than or equal to 0.44 and less than 0.92, the reduction is 3-8.5 mm; when fs is more than or equal to 0.92 and less than or equal to 1.0, the reduction is 3-9 mm;
2) and (3) carrying out reduction treatment on the solid phase region, and firstly, calculating the temperature difference of the casting blank reduction position according to the following formula:
dt=TS- T2；
wherein TS is the solidus temperature, DEG C; t is2The temperature of the lower point of the solid phase zone, DEG C;
secondly, the rolling reduction is determined according to the temperature difference:
when dt is more than 30 ℃, no pressure is applied;
when dt is less than or equal to 30 ℃, the reduction is 1.5-5.0 mm.
The invention has the advantages that: the method can solve the problem of relatively serious W-type solidification segregation in actual production of the first domestic 475mm ultra-thick plate blank casting machine, has strong technical pertinence and simple process, is easy to realize, and can be realized by utilizing the existing equipment. When the scheme is adopted, the center segregation grades of the 1/4, 1/2 and 3/4 positions of the width of the casting blank are all C1.0, the internal quality of the low-carbon steel of the ultra-thick plate blank is obviously improved, the problem of the center segregation of the casting blank with the thickness of more than 450mm is effectively solved, and the technical support and guarantee are provided for the smooth and stable production of the first 475mm ultra-thick plate blank continuous casting machine in China.
Drawings
FIG. 1 is a schematic view of the W-type solidification end of a low-carbon steel of an ultra-thick slab.
Detailed Description
The invention provides a method for improving center segregation of low-carbon steel of an ultra-thick plate blank, wherein the solidification end schematic diagram of the plate blank is W-shaped as shown in figure 1, wherein L1 is a two-phase region, and L2 is a solid-phase region. In the continuous casting process, the method carries out pressing treatment on the ultra-thick plate blank, and comprises the following specific steps:
1) and (3) carrying out reduction treatment on the two-phase region, and firstly, calculating the solid phase ratio of the central point of the reduction position of the casting blank according to the following formula:
fs =(Tl-T1)/(T1-TS)；
wherein, Tl is the liquidus temperature, DEG C; TS is solidus temperature, DEG C; t is1The temperature of the central point of the casting blank reduction position in the two-phase region is measured in DEG C;
secondly, determining the reduction of the two-phase region:
when fs is more than or equal to 0.02 and less than 0.44, the reduction is 1.5-6.5 mm; when fs is more than or equal to 0.44 and less than 0.92, the reduction is 3-8.5 mm; when fs is more than or equal to 0.92 and less than or equal to 1.0, the reduction is 3-9 mm;
2) and (3) carrying out reduction treatment on the solid phase region, and firstly, calculating the temperature difference of the casting blank reduction position according to the following formula:
dt=TS- T2；
wherein TS is the solidus temperature, DEG C; t is2The temperature of the lower point of the solid phase zone, DEG C;
secondly, the rolling reduction is determined according to the temperature difference:
when dt is more than 30 ℃, no pressure is applied;
when dt is less than or equal to 30 ℃, the reduction is 1.5-5.0 mm.
Preferably: when the reduction is determined from the solid phase ratio:
when fs is more than or equal to 0.02 and less than 0.44, the reduction is 1.5-4 mm; when fs is more than or equal to 0.44 and less than 0.92, the reduction is 4-7 mm; when fs is more than or equal to 0.92 and less than or equal to 1.0, the reduction is 7-9 mm.
Example 1
Aiming at ultra-thick plate blank low-carbon steel with the thickness specification of 460mm and the carbon content of 0.065wt%, the steel comprises the following components: c-0.065, Si-0.018, Mn-0.49, P-0.014, S-0.004 and Als-0.017. In the continuous casting process, the super-thick plate blank is subjected to pressing treatment, and the method comprises the following specific steps:
1) and (3) carrying out reduction treatment on the two-phase region, and firstly, calculating the solid phase ratio of the central point of the reduction position of the casting blank according to the following formula:
fs =(Tl-T1)/(T1-TS)；
wherein, Tl is the liquidus temperature, DEG C; TS is solidus temperature, DEG C; t is1The temperature of the central point of the casting blank reduction position in the two-phase region is measured in DEG C;
secondly, determining the reduction of the two-phase region:
when fs is more than or equal to 0.02 and less than 0.44, the reduction is 6.5 mm; when fs is more than or equal to 0.44 and less than 0.92, the reduction is 8.5 mm; when fs is more than or equal to 0.92 and less than or equal to 1.0, the reduction is 9 mm;
2) and (3) carrying out reduction treatment on the solid phase region, and firstly, calculating the temperature difference of the casting blank reduction position according to the following formula:
dt=TS- T2；
wherein TS is the solidus temperature, DEG C; t is2The temperature of the lower point of the solid phase zone, DEG C;
secondly, the rolling reduction is determined according to the temperature difference:
when dt is more than 30 ℃, no pressure is applied;
when dt is less than or equal to 30 ℃, the reduction is 5.0 mm.
When the scheme is adopted, the center segregation grades of the 1/4, 1/2 and 3/4 positions of the width of the casting blank are all C0.5, and the internal quality of the ultra-thick plate blank low-carbon steel is obviously improved.
Example 2
Aiming at the ultra-thick plate blank low-carbon steel with the thickness specification of 480mm and the carbon content of 0.064wt%, the steel comprises the following components: c-0.064, Si-0.019, Mn-0.48, P-0.013, S-0.004 and Als-0.018. In the continuous casting process, the super-thick plate blank is subjected to pressing treatment, and the method comprises the following specific steps:
1) and (3) carrying out reduction treatment on the two-phase region, and firstly, calculating the solid phase ratio of the central point of the reduction position of the casting blank according to the following formula:
fs =(Tl-T1)/(T1-TS)；
wherein, Tl is the liquidus temperature, DEG C; TS is solidus temperature, DEG C; t is1The temperature of the central point of the casting blank reduction position in the two-phase region is measured in DEG C;
secondly, determining the reduction of the two-phase region:
when fs is more than or equal to 0.02 and less than 0.44, the reduction is 1.5 mm; when fs is more than or equal to 0.44 and less than 0.92, the reduction is 3 mm; when fs is more than or equal to 0.92 and less than or equal to 1.0, the reduction is 3 mm;
2) and (3) carrying out reduction treatment on the solid phase region, and firstly, calculating the temperature difference of the casting blank reduction position according to the following formula:
dt=TS- T2；
wherein TS is the solidus temperature, DEG C; t is2The temperature of the lower point of the solid phase zone, DEG C;
secondly, the rolling reduction is determined according to the temperature difference:
when dt is more than 30 ℃, no pressure is applied;
when dt is less than or equal to 30 ℃, the reduction is 1.5 mm.
When the scheme is adopted, the center segregation grades of the 1/4, 1/2 and 3/4 positions of the width of the casting blank are all C1.5, and the internal quality of the ultra-thick plate blank low-carbon steel is obviously improved.
Aiming at the continuous casting characteristic of the W-shaped solidification tail end of the ultra-thick slab, the method takes the position of the casting blank width 1/2 as a calculation basis, and improves the center segregation of the position of the casting blank width 1/2 by implementing light pressing in a two-phase region L1; in the L2 area of the solid phase area, the soft reduction is continuously applied, the center segregation of the final solidification area of the casting blank is specially solved, namely, the center segregation of B class and above class does not occur in the low carbon steel produced by the ultra-thick plate blank through the comprehensive control technology of the soft reduction of the two-phase area and the soft reduction of the solid phase area, and therefore the internal quality of the ultra-thick plate blank is improved. Meanwhile, the method can solve the problem of relatively serious W-type solidification segregation in actual production of the first domestic 475mm ultra-thick plate blank casting machine, has strong technical pertinence and simple process, is easy to realize, and can be realized by utilizing the existing equipment. When the scheme is adopted, the center segregation grades of the 1/4, 1/2 and 3/4 positions of the width of the casting blank are all C1.0, the internal quality of the low-carbon steel of the ultra-thick plate blank is obviously improved, the problem of the center segregation of the casting blank with the thickness of more than 450mm is effectively solved, and the technical support and guarantee are provided for the smooth and stable production of the first 475mm ultra-thick plate blank continuous casting machine in China.
Claims (2)
1. A method for improving the center segregation of low-carbon steel of an ultra-thick plate blank is characterized by comprising the following steps: in the continuous casting process, the super-thick plate blank is subjected to pressing treatment, and the method comprises the following specific steps:
1) and (3) carrying out reduction treatment on the two-phase region, and firstly, calculating the solid phase ratio of the central point of the reduction position of the casting blank according to the following formula:
fs =(Tl-T1)/(T1-TS)；
wherein, Tl is the liquidus temperature, DEG C; TS is solidus temperature, DEG C; t is1The temperature of the central point of the casting blank reduction position in the two-phase region is measured in DEG C;
secondly, determining the reduction of the two-phase region:
when fs is more than or equal to 0.02 and less than 0.44, the reduction is 1.5-6.5 mm; when fs is more than or equal to 0.44 and less than 0.92, the reduction is 3-8.5 mm; when fs is more than or equal to 0.92 and less than or equal to 1.0, the reduction is 3-9 mm;
2) and (3) carrying out reduction treatment on the solid phase region, and firstly, calculating the temperature difference of the casting blank reduction position according to the following formula:
dt=TS- T2；
wherein TS is solidus temperature, DEG C；T2The temperature of the lower point of the solid phase zone, DEG C;
secondly, the rolling reduction is determined according to the temperature difference:
when dt is more than 30 ℃, no pressure is applied;
when dt is less than or equal to 30 ℃, the reduction is 1.5-5.0 mm.
2. The method for improving center segregation of low carbon steel of ultra-thick slab according to claim 1, wherein: when the reduction is determined from the solid phase ratio:
when fs is more than or equal to 0.02 and less than 0.44, the reduction is 1.5-4 mm; when fs is more than or equal to 0.44 and less than 0.92, the reduction is 4-7 mm; when fs is more than or equal to 0.92 and less than or equal to 1.0, the reduction is 7-9 mm.
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Citations (5)
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|---|---|---|---|---|
| CN101648212A (en) * | 2009-09-15 | 2010-02-17 | 邢台钢铁有限责任公司 | Bloom continuous casting dynamic soft reduction process for prestressed steel SWRH82B |
| CN101695747A (en) * | 2009-11-03 | 2010-04-21 | 攀钢集团研究院有限公司 | Method for controlling bloom continuous casting dynamic soft-reduction pressure interval |
| EP2441539A1 (en) * | 2010-10-12 | 2012-04-18 | Siemens VAI Metals Technologies GmbH | Energy and output-optimised method and assembly for producing hot rolled steel strips |
| CN102601331A (en) * | 2011-12-09 | 2012-07-25 | 秦皇岛首秦金属材料有限公司 | Method for improving center segregation of extra thick slab with thickness of 400mm |
| CN111360221A (en) * | 2020-04-03 | 2020-07-03 | 中天钢铁集团有限公司 | Method for eliminating central shrinkage cavity and controlling central segregation of 280mm × 320mm section high-carbon steel |
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- 2020-10-30 CN CN202011190259.9A patent/CN112453342A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101648212A (en) * | 2009-09-15 | 2010-02-17 | 邢台钢铁有限责任公司 | Bloom continuous casting dynamic soft reduction process for prestressed steel SWRH82B |
| CN101695747A (en) * | 2009-11-03 | 2010-04-21 | 攀钢集团研究院有限公司 | Method for controlling bloom continuous casting dynamic soft-reduction pressure interval |
| EP2441539A1 (en) * | 2010-10-12 | 2012-04-18 | Siemens VAI Metals Technologies GmbH | Energy and output-optimised method and assembly for producing hot rolled steel strips |
| CN102601331A (en) * | 2011-12-09 | 2012-07-25 | 秦皇岛首秦金属材料有限公司 | Method for improving center segregation of extra thick slab with thickness of 400mm |
| CN111360221A (en) * | 2020-04-03 | 2020-07-03 | 中天钢铁集团有限公司 | Method for eliminating central shrinkage cavity and controlling central segregation of 280mm × 320mm section high-carbon steel |
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Application publication date: 20210309 |