CN109848383B - Flexible reduction method for improving internal quality of casting blank - Google Patents
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Abstract
A flexible reduction method for improving the internal quality of a casting blank is characterized in that a large-roll-diameter supporting roll is arranged at an inlet of a sector section, and a large-diameter oil cylinder is adopted to apply large sector section clamping force. The rest rollers of the sector section adopt medium-diameter supporting rollers with larger roller diameter than the conventional sector section. In the continuous casting process, the position of the solidification tail end of the casting blank is calculated according to the casting process conditions, and the fan-shaped section at the corresponding position is selected for reduction according to the solid phase rate of the solidification tail end of the casting blank. The method not only can solve the problem of the center segregation of the casting blank by utilizing the soft reduction, but also can solve the problems of the shrinkage and the looseness of the casting blank by utilizing the high-strength roller to carry out the high-deformation-rate heavy reduction and the low-deformation-rate heavy reduction on the solidified tail end of the liquid core of the casting blank.
Description
Technical Field
The invention relates to a flexible reduction method for improving the internal quality of a casting blank, in particular to a continuous casting sector section reduction method for improving the internal quality of the casting blank.
Background
In the production process of metallurgical continuous casting, the internal and external quality of the cast strand is a matter of great concern to the metallurgist. The internal quality of the casting blank is mainly expressed in that the components are uniform, no looseness, no shrinkage cavity, no cracks and the like, and a product with compact internal structure and no defects is expected to be produced. The internal defects are caused by natural shrinkage of molten steel at the final stage of solidification, and by setting parameters of the continuous casting process, such as a large cross section, a casting temperature, a cooling system, a roll gap, and the like. These drawbacks are determined by the design and production method of the existing continuous casting machine and are difficult to avoid. The current methods for solving the internal quality defects of the casting blank comprise low-temperature casting, electromagnetic stirring and soft reduction. However, in the later stage of casting blank solidification, because the internal liquid core is close to a solid state, electromagnetic stirring is difficult to play a role, the problem of central porosity cannot be well solved due to the relationship between reduction and position under light reduction, segregation can be reduced by low-temperature casting, and internal porosity caused by inherent characteristics of casting blank solidification cannot be completely avoided. Therefore, the method does not play a key role in shrinkage and shrinkage cavity and looseness caused by the late solidification stage of the casting blank, and the technology for heavily pressing the solidified tail end of the casting blank can well solve the problem of shrinkage and shrinkage cavity of the late solidification stage of the casting blank.
Chinese patent CN106735026A discloses a single-point heavy reduction method, which utilizes a pair of supporting rollers of a sector section to reduce the casting blank, and implements heavy reduction in a short time at one point.
Chinese patents CN106001476A and CN 102921914B disclose a two-stage continuous casting and heavy reduction method, which solves the problems of casting blank segregation and loosening by adopting light reduction and heavy reduction for large square blanks and wide and thick plate blanks, and the method adopts a plurality of fan-shaped sections to carry out reduction in a longer distance range, has lower deformation rate and is a low deformation rate deformation method, has certain limitation on product specification and steel grade, has better effect on solving the problem of casting blank segregation, and has better effect on solving the problem of thicker casting blank loosening.
Chinese patents CN104057049B and CN104858383A propose a continuous casting machine sector section and a heavy pressing method thereof for heavy pressing at the solidification tail end of a continuous casting slab, which are characterized in that a large-roll-diameter driving roller is arranged in the middle of the sector section, which is equivalent to the deformation of a rolling pass of a large-roll-diameter rolling mill, so that the improvement of the loosening of the central area of the continuous casting slab is facilitated.
From the above patent analysis, it can be seen that the current technical route under heavy pressure is mainly composed of two: one is that a sector section or a plurality of sector sections are adopted to implement a certain heavy pressing amount in a longer distance, so that the pressing is at a low deformation rate, and the weight is more than that for solving the segregation problem; the other is that a single roller is adopted to implement a certain weight reduction at one point, and the weight is higher than the weight of the single roller in order to solve the loosening problem. Two defects of a common casting blank exist at the same time, and the two defects can be simultaneously solved by a reduction technology. The continuous casting process is not a steady-state process, and the solidified tail end of the liquid core of the casting blank can move due to the change of the casting process conditions, so that the problem of the change of the reduction position of a single fan-shaped section or a single press roller due to the fixed position and length of the single fan-shaped section or the single press roller is difficult to meet under the change of the casting conditions. Moreover, the conventional fan-shaped section of the casting machine has a small roll diameter, and the rigidity and the strength of the conventional fan-shaped section of the casting machine are not enough to meet the heavy-pressing process requirement of high deformation rate, so that a high-strength fan-shaped section supporting roll needs to be designed.
Disclosure of Invention
The invention aims to provide a flexible reduction method for improving the internal quality of a casting blank, which can solve the problem of central segregation of the casting blank by utilizing soft reduction and can solve the problems of shrinkage cavity and porosity of the casting blank by utilizing a high-strength roller to carry out high-deformation-rate heavy reduction and low-deformation-rate heavy reduction technology at the solidification tail end of a liquid core of the casting blank.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a flexible reduction method for improving the internal quality of a cast blank comprises the following steps:
1) adopting 3-5 same type sector sections, wherein the sector section consists of at least four pairs of supporting rolls and at least one pair of driving rolls, a large-roll-diameter supporting roll is arranged at an inlet of the sector section, large sector-section pressure is adopted, and medium-roll-diameter supporting rolls with larger roll diameters than those of the conventional sector section are adopted as the rest of the rollers of the sector section; the roller diameter of the large supporting roller is 1000mm, and the roller diameter of the medium-diameter supporting roller and the roller diameter of the driving roller are 500mm and 200 mm; the pressure of an inlet oil cylinder at the inlet of the fan-shaped section is 200-1500t, the pressure of an outlet oil cylinder at the outlet of the fan-shaped section is 200-1200t, and the pressure of a driving oil cylinder of the driving roller is 100-500 t;
2) in the continuous casting process, the position of the solidification tail end of a casting blank is calculated according to the casting process conditions, and the sector section of the corresponding position is selected for reduction according to the solid phase rate of the solidification tail end of the casting blank:
if the final product of the steel grade is in a thin specification, the thickness is less than 10mm, the requirement on the casting blank segregation is strict only, the segregation requirement is less than the Mannesmann standard of 2.5, a soft reduction mode is directly used, a soft reduction process with the deformation rate of 0.1-10mm/m is carried out on 1-3 fan-shaped sections in a region with the casting blank solid phase rate of 0.3-0.9, and the reduction amount is 1-10 mm;
if the final product of the steel grade is in a thin specification, the thickness is less than 10mm, but the requirements on the segregation and the porosity of a casting blank are strict, the segregation is less than Mannesian standard 2.0, and the center of the casting blank is not obviously loosened and shrunk, a low-deformation-rate heavy reduction process with the deformation rate of 0.16-25mm/m is carried out on 1-3 fan-shaped sections in the range of the solid phase rate of 0.9-1, the reduction is 8-45mm, a soft reduction process with the deformation rate of 0.1-10mm/m is carried out on the fan-shaped sections before the heavy reduction fan-shaped sections in the region of the solid phase rate of 0.3-0.9 of the casting blank, and the reduction is 1-10 mm;
if the final product of the steel grade is in a thick specification and the thickness is more than 4mm, the requirements on the casting blank reduction ratio and the porosity are high, the requirement on the reduction ratio is more than 2, and obvious porosity and shrinkage are avoided, 1 sector section inlet large-roll-diameter support roll is utilized to implement a high-deformation-rate heavy reduction process with the deformation rate of 10-3000mm/m in a casting blank solid phase ratio area of 0.9-1, the reduction is 3-30mm, the sector section before the heavy reduction of the sector section is subjected to soft reduction with the deformation rate of 0.1-10mm/m in a casting blank solid phase ratio area of 0.3-0.9, and the reduction is 1-10 mm;
under the condition of adopting the heavy reduction process, no matter the deformation rate is low or high, the sector section needs to be reduced by 1-5mm with the deformation rate of 0.1-10mm/m after the sector section is pressed down by heavy, so that the deformation rebound of the casting blank is prevented.
Further, the fan-shaped section is provided with a pair of driving rollers, and the driving rollers are located in the middle of the fan-shaped section.
Preferably, the segment is provided with two drive rollers, wherein one pair of drive rollers is located at the segment entrance position and the other pair of drive rollers is located at the middle position.
The method of the invention arranges a large-roll-diameter supporting roll at the entrance of the sector section and adopts a large-diameter oil cylinder to implement large sector section clamping force. The rest rollers of the sector section adopt medium-diameter supporting rollers with larger roller diameter than the conventional sector section. In order to meet the change of the solidification tail end position of the liquid core of the casting blank caused by the change of the casting process conditions, a plurality of same type of fan-shaped sections are required to be configured to implement the reduction process.
The method can solve the problem of loosening and shrinkage cavity by using the sector section under heavy pressing and solve the problem of segregation by using the previous sector section under light pressing according to different product requirements. Multiple heavy pressing down sectors can increase the process flexibility and enlarge the process window. The sector section adopts a structure that a large roll diameter is matched with a medium roll diameter, and can be used for carrying out high deformation rate heavy pressing and low deformation rate heavy pressing from a process angle. From the equipment angle, the large roll diameter can improve the strength of the roll, avoid the deformation of the roll, ensure the precision of the roll gap of the sector section and prolong the service life of the sector section.
The invention has the beneficial effects that:
in the continuous casting process of the casting blank, in order to solve the problems of casting blank segregation and looseness and shrinkage cavity formed at the solidification end, a reduction process is required to be carried out at the solidification end of the casting blank, and the reduction process comprises a light reduction process in a two-phase region of the casting blank and a heavy reduction technology at the solidification end of a liquid core. Wherein the heavy pressing technology comprises heavy pressing at a high deformation rate and heavy pressing at a low deformation rate. In order to adapt to the position change of the liquid core caused by the change of the casting conditions, a plurality of heavy reduction fan-shaped sections of the same type need to be configured. In order to implement heavy reduction, the sector supporting roller is larger than the conventional sector supporting roller, and in order to implement single-roller heavy reduction with high deformation rate, the sector inlet is provided with a large-roller-diameter supporting roller. The technology can combine the previous sector section to implement a soft reduction process, and simultaneously solve the problems of casting blank segregation and loose shrinkage cavity.
Drawings
FIG. 1 is a schematic drawing of a billet reduction segment according to an embodiment of the present invention.
Detailed Description
Referring to fig. 1, the present invention has a plurality of same type of segment, which can meet the requirement of the position change of the liquid core end caused by different process conditions. 3-5 same-specification heavy-pressing fan-shaped sections are arranged in the figure 1, and different fan-shaped sections can be used interchangeably. The fan-shaped section comprises an upper frame 1, a lower frame 2, a large-roll-diameter supporting roller 3, an inlet oil cylinder 4, a driving roller 5, a driving oil cylinder 6, a middle-roll-diameter supporting roller 7 and an outlet oil cylinder 8 which are arranged on the upper frame and the lower frame.
The diameter of the large-diameter support roller 3 is 1000mm for 300-. The single-cylinder pressure of the inlet cylinder 4 is 200-1500t, the single-cylinder pressure of the outlet cylinder 8 is 200-1200t, and the pressure of the driving cylinder 6 is 100-500 t. The drive roller 5 can be arranged at roller number 1-4, or a two-pair drive roller pattern can be used.
The casting blank reduction process not only can implement the soft reduction process for the casting blank, but also can implement single-point high deformation rate heavy reduction and single-section or multi-section low deformation rate heavy reduction.
Taking a casting blank with the thickness of 300mm as an example, the section width is from 900-. At least three heavy hold down segments are required to meet the process requirements. When the drawing speed is 0.6m/min, the position of the solid phase ratio of the liquid core is 0.3-0.9 is N-1 and N-1 sector, and the position of the solid phase ratio of the solidified end of the liquid core is N +1 sector.
Example 1
If the final product of the steel grade is in a thin specification and the thickness is less than 10mm, only the requirement on the casting blank segregation is strict, and the requirement on the segregation is less than the Mannesmann standard 2.0, a soft reduction mode is directly used, and the N-1 and N-1 fan-shaped sections are used for carrying out soft reduction of 1-10mm with the deformation rate of 0.1-10mm/m, so that the process can effectively improve the center segregation of the casting blank.
Example 2
If the final product of the steel grade is in a thin specification and the thickness is less than 10mm, but the requirements on the segregation and the porosity of the casting blank are strict, the segregation is less than the Mannesmann standard 2.0 and the center of the casting blank is not obviously porous and shrinkage cavity, the N-1 segment and the N-1 segment are adopted to carry out 1-10mm soft reduction with the deformation rate of 0.1-10mm/m, the N +1 segment is adopted to carry out 8-45mm low-deformation-rate hard reduction with the deformation rate of 0.16-25mm/m, and the N +2 segment is adopted to carry out 1-5mm reduction with the deformation rate of 0.1-10mm/m to play a role in keeping.
Example 3
If the final product is in a thick specification, the thickness is more than 4mm, the requirements on the looseness and the reduction ratio of the casting blank are high, the requirements on the reduction ratio is more than 2, and no obvious looseness or shrinkage cavity exists, 1-10mm soft reduction with the deformation rate of 0.1-10mm/m can be carried out on N-1 and N-1 sector sections, then 3-30mm heavy reduction with the deformation rate of 10-3000mm/m is carried out by adopting a single roller with the large roller diameter at the inlet of the N +1 sector section, 1-5mm reduction with the deformation rate of 0.1-10mm/m is carried out on the residual roller of the N +1 sector section, and then the 1-5mm reduction with the deformation rate of 0.1-10mm/m is carried out on the N +2 sector section to play a role in keeping.
The method can flexibly implement the reduction process on the casting blank. According to the requirements of steel grades and products, the soft reduction technology can be independently implemented, the soft reduction technology can be used in combination with single-roller high-deformation-rate heavy reduction, the soft reduction technology can be used in combination with single-section or multi-section low-deformation-rate heavy reduction, and the requirements of different casting blanks and product quality can be met. The supporting roller with the single large roller diameter and the middle roller diameter can meet the pressing technological requirement, avoid the equipment precision defect caused by insufficient roller strength, reduce the equipment weight and save the investment.
Claims (3)
1. A flexible reduction method for improving the internal quality of a cast blank comprises the following steps:
1) adopting 3-5 same type sector sections, wherein the sector section consists of at least four pairs of supporting rollers and at least one pair of driving rollers, a large-roller-diameter supporting roller is arranged at an inlet of the sector section, large oil cylinder pressure is adopted, and medium-roller-diameter supporting rollers with larger roller diameters than those of the conventional sector section are adopted as the rest rollers of the sector section; the roller diameter of the large supporting roller is 1000mm, and the roller diameter of the medium-diameter supporting roller and the roller diameter of the driving roller are 500mm and 200 mm; the pressure of an inlet oil cylinder at the inlet of the fan-shaped section is 200-1500t, the pressure of an outlet oil cylinder at the outlet of the fan-shaped section is 200-1200t, and the pressure of a driving oil cylinder of the driving roller is 100-500 t;
2) in the continuous casting process, the position of the solidification tail end of a casting blank is calculated according to the casting process conditions, and the sector section of the corresponding position is selected for reduction according to the solid phase rate of the solidification tail end of the casting blank:
if the final product of the steel grade is in a thin specification, the thickness is less than 10mm, and the casting blank segregation requirement is less than the Mannesian standard of 2.5, adopting a soft reduction mode, and adopting 1-3 fan-shaped sections to carry out a soft reduction process with the deformation rate of 0.1-10mm/m in a region with the casting blank solid phase ratio of 0.3-0.9, wherein the reduction amount is 1-10 mm;
if the final steel product is in a thin specification and the thickness is less than 10mm, the casting blank segregation is less than 2.0 of Mannesian standard, and the center of the casting blank has no obvious looseness and shrinkage cavity, wherein 1-3 fan-shaped sections are subjected to a low-deformation-rate heavy reduction process with the deformation rate of 0.16-25mm/m in the range of 0.9-1 solid phase rate, the reduction is 8-45mm, and the fan-shaped sections before the heavy reduction of the fan-shaped sections are subjected to a light reduction process with the deformation rate of 0.1-10mm/m in the region of 0.3-0.9 solid phase rate of the casting blank, and the reduction is 1-10 mm;
if the final product of the steel grade is in a thick specification, the thickness is more than 4mm, the casting blank reduction ratio is more than 2, and obvious looseness and shrinkage are avoided, 1 sector section inlet large-roll-diameter supporting roll is utilized to implement a high-deformation-rate heavy reduction process with the deformation rate of 10-3000mm/m in a casting blank solid phase ratio 0.9-1 area, the reduction amount is 3-30mm, the sector section before the sector section is pressed down again is subjected to light reduction with the deformation rate of 0.1-10mm/m in a casting blank solid phase ratio 0.3-0.9 area, and the reduction amount is 1-10 mm;
under the condition of adopting the heavy pressing process, the sector section after the sector section is pressed down again needs to be pressed down at the deformation rate of 0.1-10mm/m and the pressing amount of 1-5 mm.
2. A flexible reduction method to improve the internal quality of a cast slab according to claim 1 wherein said segments are provided with a pair of drive rolls positioned at the center of the segments.
3. A flexible reduction method to improve the internal quality of a cast slab according to claim 1 wherein said segment is provided with two pairs of drive rolls, one pair of which is located at the entry point of the segment and the other pair of which is located at the middle point.
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| CN110802207B (en) * | 2019-11-12 | 2021-09-24 | 苏州大学 | Combined pressing method for continuous casting billet |
| CN113523216B (en) * | 2021-06-23 | 2024-04-05 | 中冶南方连铸技术工程有限责任公司 | Continuous casting single-roller weight pressing control method and system |
| CN113714280A (en) * | 2021-08-23 | 2021-11-30 | 南京钢铁股份有限公司 | Production process for improving microscopic pores of high-carbon chromium bearing steel 100Cr6 bar |
| CN115780757B (en) * | 2023-01-31 | 2023-05-09 | 东北大学 | Solidifying tail end depressing method and depressing device for controlling central quality of casting blank |
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| DE10236367A1 (en) * | 2002-08-08 | 2004-02-19 | Sms Demag Ag | Dynamic control of a casting strand made from steel on both sides of roll segments used in a continuous casting installation comprises using the roll segments in a cold strand, hot strand and/or soft reduction region |
| AT506976B1 (en) * | 2008-05-21 | 2012-10-15 | Siemens Vai Metals Tech Gmbh | METHOD FOR CONTINUOUSLY GASING A METAL STRUCTURE |
| JP5741402B2 (en) * | 2011-11-25 | 2015-07-01 | 新日鐵住金株式会社 | Continuous casting method for circular section slabs |
| CN104001891B (en) * | 2014-06-17 | 2016-08-31 | 中冶连铸技术工程有限责任公司 | On-Line Control Method under a kind of continuous small-billet casting dynamic soft-reduction and weight |
| CN105689664B (en) * | 2014-11-27 | 2017-11-28 | 宝钢工程技术集团有限公司 | Fan-shaped section and its application method under weight for improving the loose shrinkage cavity defect of slab |
| CN104722731A (en) * | 2015-04-17 | 2015-06-24 | 中冶赛迪工程技术股份有限公司 | Method for eliminating central looseness of casting blank and improving density of casting blank |
| CN104874758B (en) * | 2015-05-11 | 2017-11-17 | 中冶连铸技术工程有限责任公司 | Continuous casting weight pressing control method |
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