CN112371937A - Method for improving center segregation of peritectic steel of ultra-thick plate blank - Google Patents
Method for improving center segregation of peritectic steel of ultra-thick plate blank Download PDFInfo
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- CN112371937A CN112371937A CN202011190247.6A CN202011190247A CN112371937A CN 112371937 A CN112371937 A CN 112371937A CN 202011190247 A CN202011190247 A CN 202011190247A CN 112371937 A CN112371937 A CN 112371937A
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Abstract
The invention provides a method for improving peritectic steel center segregation of an ultra-thick plate blank, which comprises the following steps of: 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 all C1.0, and the internal quality of peritectic 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 peritectic steel of an ultra-thick plate blank aiming at the continuous casting production of the ultra-thick plate blank with the thickness specification exceeding 450 mm.
Background
Typically, slabs having a gauge of greater than 450mm are divided into super-thick slabs and steels having a carbon content in the range of 0.09% ≦ C (wt%) < 0.14% are divided into peritectic 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 literatures; regarding the W-shaped solidification end of slab continuous casting, it is widely considered that the secondary cooling method is closely related. 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 No. 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 region 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 peritectic steel of an ultra-thick plate blank, which implements a more scientific and effective pressing strategy on the ultra-thick plate blank so as to adapt to the characteristics of a W-shaped liquid core. In addition, another object of the present invention is to solve the defect that the segregation of the ultra-thick slab is serious at 1/4 and 3/4 positions in the casting width direction, thereby improving the internal quality of the ultra-thick slab.
The invention is realized by the following technical scheme: a method for improving the center segregation of peritectic steel of an 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;
next, the rolling reduction was determined from the solid phase ratio:
when fs is more than or equal to 0.05 and less than 0.35, the reduction is 1.0-4.5 mm; when fs is more than or equal to 0.35 and less than 0.55, the reduction is 1.5-5.0 mm; when fs is more than or equal to 0.55 and less than 0.90, the reduction is 2.0-6.5 mm; when fs is more than or equal to 0.90 and less than or equal to 1.0, the reduction is 3.0-8.0 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 is2Is to be fixedPhase zone depression temperature, deg.C;
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 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 peritectic 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 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-shaped solidification end of peritectic steel of an ultra-thick slab.
Detailed Description
The invention provides a method for improving the center segregation of peritectic steel of an ultra-thick plate blank, wherein the solidification end schematic diagram of the plate blank is W type 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) the two-phase region, i.e., the position indicated by L1 in fig. 1, is subjected to reduction treatment, and first, the solid fraction at the center point of the reduction position of the cast slab is calculated 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 a certain point in a two-phase region is DEG C;
next, the rolling reduction was determined from the solid phase ratio:
when fs is more than or equal to 0.05 and less than 0.35, the reduction is 1.0-4.5 mm; when fs is more than or equal to 0.35 and less than 0.55, the reduction is 1.5-5.0 mm; when fs is more than or equal to 0.55 and less than 0.90, the reduction is 2.0-6.5 mm; when fs is more than or equal to 0.90 and less than or equal to 1.0, the reduction is 3.0-8.0 mm;
2) the solid phase region, i.e., the position indicated by L2 in fig. 1, is subjected to reduction treatment, and first, the temperature difference at the casting reduction position is calculated 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 80 ℃, no pressure is applied;
when dt is less than or equal to 80 ℃, the reduction is 1.5-5.0 mm.
Preferably, when the rolling reduction is determined based on the solid phase ratio:
when fs is more than or equal to 0.05 and less than 0.35, the reduction is 1.0-4.5 mm; when fs is more than or equal to 0.35 and less than 0.55, the reduction is 1.5-3.0 mm; when fs is more than or equal to 0.55 and less than 0.90, the reduction is 3.0-4.5 mm; when fs is more than or equal to 0.90 and less than or equal to 1.0, the reduction is 4.5-8.0 mm.
Example 1
Selecting ultra-thick plate blank peritectic steel with the thickness specification of 460mm and the carbon content of 0.096wt% for processing, wherein the steel comprises the following components: c0.096, Si 0.197, Mn 1.478, P0.022, S0.002, Als 0.025. In the continuous casting process, the super-thick plate blank is subjected to pressing treatment, and the method comprises the following specific steps:
(1) in the two-phase region, when fs is more than or equal to 0.05 and less than 0.35, the reduction is 4.5 mm; when fs is more than or equal to 0.35 and less than 0.55, the reduction is 5.0 mm; when fs is more than or equal to 0.55 and less than 0.90, the reduction is 6.5 mm; when fs is more than or equal to 0.90 and less than or equal to 1.0, the reduction is 8.0 mm; in the solid phase region, when dt is less than or equal to 80 ℃, the reduction is 5 mm.
(2) 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, and the internal quality of peritectic steel of the ultra-thick plate blank is obviously improved.
Example 2
Aiming at the extra-thick plate blank peritectic steel with the thickness specification of 480mm and the carbon content of 0.091wt%, the steel comprises the following components: c0.091, Si 0.192, Mn 1.486, P0.014, S0.002 and Als 0.025. In the continuous casting process, the super-thick plate blank is subjected to pressing treatment, and the method comprises the following specific steps:
(1) in the two-phase region, when fs is more than or equal to 0.05 and less than 0.35, the reduction is 1.0 mm; when fs is more than or equal to 0.35 and less than 0.55, the reduction is 1.5 mm; when fs is more than or equal to 0.55 and less than 0.90, the reduction is 2.0 mm; when fs is more than or equal to 0.90 and less than or equal to 1.0, the reduction is 3.0 mm; in the solid phase region, when dt is less than or equal to 80 ℃, the reduction is 1.5 mm.
(2) 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, and the internal quality of peritectic steel of the ultra-thick plate blank is obviously improved.
According to the method, the problem of relatively serious W-shaped solidification segregation in actual production of the first 475mm ultra-thick plate blank casting machine in China can be solved by adopting the 475mm ultra-thick plate blank casting machine and adopting a specific pressing process, the technical pertinence is strong, the process is simple and easy to realize, and the method can be realized by utilizing the existing equipment without modification. 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 peritectic 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 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 peritectic 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;
next, the rolling reduction was determined from the solid phase ratio:
when fs is more than or equal to 0.05 and less than 0.35, the reduction is 1.0-4.5 mm; when fs is more than or equal to 0.35 and less than 0.55, the reduction is 1.5-5.0 mm; when fs is more than or equal to 0.55 and less than 0.90, the reduction is 2.0-6.5 mm; when fs is more than or equal to 0.90 and less than or equal to 1.0, the reduction is 3.0-8.0 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 80 ℃, no pressure is applied;
when dt is less than or equal to 80 ℃, the reduction is 1.5-5.0 mm.
2. The method for improving the center segregation of the peritectic steel of the ultra-thick slab according to claim 1, wherein the method comprises the following steps: when the reduction is determined from the solid phase ratio:
when fs is more than or equal to 0.05 and less than 0.35, the reduction is 1.0-4.5 mm; when fs is more than or equal to 0.35 and less than 0.55, the reduction is 1.5-3.0 mm; when fs is more than or equal to 0.55 and less than 0.90, the reduction is 3.0-4.5 mm; when fs is more than or equal to 0.90 and less than or equal to 1.0, the reduction is 4.5-8.0 mm.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115401178A (en) * | 2021-05-28 | 2022-11-29 | 宝山钢铁股份有限公司 | Screw-down process determination method for improving internal quality of gear steel |
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| JP2001259809A (en) * | 2000-03-23 | 2001-09-25 | Nkk Corp | Continuous casting method |
| CN101362195A (en) * | 2008-09-12 | 2009-02-11 | 攀钢集团研究院有限公司 | Bloom continuous-casting dynamic gentle pressure amount control method- |
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| 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 |
| CN103878331A (en) * | 2014-03-27 | 2014-06-25 | 中国重型机械研究院股份公司 | Sector segment structure capable of compositely pressing continuous casting solidification tail end of extra-thick plate |
| 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 |
-
2020
- 2020-10-30 CN CN202011190247.6A patent/CN112371937A/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001259809A (en) * | 2000-03-23 | 2001-09-25 | Nkk Corp | Continuous casting method |
| CN101362195A (en) * | 2008-09-12 | 2009-02-11 | 攀钢集团研究院有限公司 | Bloom continuous-casting dynamic gentle pressure amount control method- |
| CN102387878A (en) * | 2009-04-14 | 2012-03-21 | 新日本制铁株式会社 | Continuous casting facility |
| 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 |
| CN103878331A (en) * | 2014-03-27 | 2014-06-25 | 中国重型机械研究院股份公司 | Sector segment structure capable of compositely pressing continuous casting solidification tail end of extra-thick plate |
| 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 |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115401178A (en) * | 2021-05-28 | 2022-11-29 | 宝山钢铁股份有限公司 | Screw-down process determination method for improving internal quality of gear steel |
| CN115401178B (en) * | 2021-05-28 | 2023-07-07 | 宝山钢铁股份有限公司 | Reduction process determination method for improving internal quality of gear steel |
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