CN113215373B - Method for eliminating fine line defect at edge of boron-containing steel - Google Patents
Method for eliminating fine line defect at edge of boron-containing steel Download PDFInfo
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- CN113215373B CN113215373B CN202110398209.8A CN202110398209A CN113215373B CN 113215373 B CN113215373 B CN 113215373B CN 202110398209 A CN202110398209 A CN 202110398209A CN 113215373 B CN113215373 B CN 113215373B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
Abstract
The invention provides a method for eliminating the fine line defect at the edge of boron-containing steel, belonging to the technical field of steel rolling, and the method comprises the steps of obtaining a plate blank with the boron mass fraction of 0.0005-0.001%; heating and rough rolling the plate blank to obtain an intermediate blank; performing finish rolling on the intermediate billet at an inlet temperature of 1050-1070 ℃ and an outlet temperature of 880-920 ℃ to obtain strip steel; and coiling the strip steel at the temperature of 620-660 ℃ to obtain the boron-containing steel with good surface quality. The boron-containing steel provided by the method has no linear defects and is used for cold rolling without fracture and cracking problems; the method is simple, high in applicability and remarkable in effect.
Description
Technical Field
The invention belongs to the technical field of steel rolling, and particularly relates to a method for eliminating the defect of a fine line on the edge of boron-containing steel.
Background
The boron-containing steel is a product obtained after slab hot rolling and can be used as a raw material for cold rolling and subsequent processing, so that the surface quality of the boron-containing hot rolled coil directly influences the subsequent treatment of the strip steel surface in the next procedure, including oil coating, hot galvanizing, electrogalvanizing, electrotinning, phosphating, passivation, fingerprint resistance, color coating and other process treatments. The cold-rolled sheet with high-grade surface is mainly used for panels of medium-high-grade cars, and along with the improvement of science and technology and the improvement of living demands of people, the requirements of industries such as modern household appliance manufacturing industry, building materials and the like on the surface quality of the cold-rolled sheet are higher and higher. For the surface of a high-grade cold-rolled sheet, optical inspection is required to be free of defects, and the surface of the sheet is required to be polished by oilstone to be free of defects.
At present, the boron-containing steel hot-rolled edge part often has linear defects, generally occurs on the upper surface of a hot coil, and the expression forms of thin lines on the edge part are greatly different due to the difference of alloy elements of steel types. The occurrence of the edge fine line-shaped defects affects the use of users, the defects need to be cut off for subsequent processing, and the risk of cracking or strip breakage in the cold rolling process is increased if the subsequent cold rolling is needed.
Disclosure of Invention
The invention provides a method for eliminating the fine line defect on the edge of boron-containing steel, which aims to solve the technical problem that the use of a user is influenced due to the fine line defect on the edge of the boron-containing steel in the prior art.
The invention provides a method for eliminating fine line defects on the edge of boron-containing steel, which comprises the following steps,
obtaining a plate blank with the boron mass fraction of 0.0005-0.001%;
heating and rough rolling the plate blank to obtain an intermediate blank;
performing finish rolling on the intermediate billet at an inlet temperature of 1050-1070 ℃ and an outlet temperature of 880-920 ℃ to obtain strip steel;
and coiling the strip steel at the temperature of 620-660 ℃ to obtain the boron-containing steel with good surface quality.
Furthermore, in the finish rolling process, the reduction rate of the second pass is 40-45%, and the reduction rate of the third pass is 30-35%.
Further, the rolling force of the finish rolling F2 stand is 22000-28000KN, and the rolling force of the finish rolling F3 stand is 20000-26000KN.
Further, the difference between the temperature of the rough rolling inlet and the temperature of the rough rolling outlet is 150-170 ℃; the difference between the central temperature and the edge temperature of the intermediate blank in the width direction is 5-15 ℃.
Further, the rough rolling is carried out by adopting a first rough rolling machine and a second rough rolling machine; the rolling frequency of the first roughing mill is 1 pass; the rolling frequency of the second roughing mill is 5 passes, and the width reducing amount of the 1 st pass and the 3 rd pass is respectively less than 15mm and less than 10mm when the second roughing mill rolls.
Further, the heating comprises soaking, wherein the soaking temperature is 1200-1230 ℃, and the soaking time is 30-40min; the total heating time is 160-200min.
Further, the obtained slab with the boron mass fraction of 0.0005-0.001% comprises,
obtaining molten steel with boron mass fraction of 0.0005-0.001%;
continuously casting the molten steel to obtain a plate blank; in the continuous casting, the temperature of the straightening section is more than 950 ℃.
Furthermore, in the continuous casting, the drawing speed is 1.5-1.7m/min.
Furthermore, in the molten steel, the mass fraction of C is 0.015-0.04%, the mass fraction of Al is 0.02-0.05%, the mass fraction of Mn is 0.2-0.3%, and the mass fraction of Si is 0.03-0.05%.
Further, the thickness of the slab is 230-250mm, and the width of the slab is 1000-1800mm.
One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
the invention provides a method for eliminating fine line defects at the edge of boron-containing steel, wherein more fine BN in the steel is precipitated along a grain boundary and pins the grain boundary due to the characteristic that boron is partially aggregated at the grain boundary within the temperature range of 750-850 ℃, so that the migration of the grain boundary is inhibited, the probability of grain boundary fracture is improved, the high-temperature plasticity of steel is reduced, the grain boundary fracture is more likely to occur, and the linear defects are caused; therefore, the temperature range of 750-850 ℃ is avoided by controlling the finish rolling and coiling temperature in the production process, so that the problem of linear defects caused by crystal fracture is avoided. The boron-containing steel provided by the method has no defect, and is used for cold rolling without fracture and cracking problems; the method is simple, high in applicability and remarkable in effect.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a macroscopic view of fine line defects at the edge of boron-containing steel;
FIG. 2 shows the microscopic appearance of fine line defects at the edge of boron-containing steel;
FIG. 3 is an enlarged view of a portion of FIG. 2;
FIG. 4 is a high temperature plasticity curve of boron-containing steel provided by an embodiment of the present invention;
FIG. 5 is a surface topography of boron-containing steel after pickling according to an embodiment of the present invention;
fig. 6 is a surface topography of the boron-containing steel after cold rolling according to the embodiment of the present invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are illustrative of the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically indicated, various raw materials, reagents, instruments, equipment and the like used in the present invention may be commercially available or may be prepared by existing methods.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
In order to solve the technical problems, the embodiment of the invention provides the following general ideas:
the embodiment of the invention provides a method for eliminating fine line defects on the edge of boron-containing steel, which comprises the following steps,
s1, obtaining a plate blank with the boron mass fraction of 0.0005-0.001%;
wherein the obtained slab with the boron mass fraction of 0.0005-0.001% can be obtained by the following method:
s101, obtaining boron-containing steel liquid with the boron mass fraction of 0.0005-0.001%;
b element is added into the steel, so that coarse BN high-temperature austenite can be preferentially precipitated, and thus the precipitation of fine AlN is inhibited, and the coarsening of crystal grains is weakened; in addition, austenite grain boundaries of B atoms are segregated, and ferrite nucleation can be inhibited to control grain coarsening; moreover, the preferential combination of B and N can effectively reduce the content of free N in the steel and reduce the occurrence of the aging problem.
As an implementation mode of the embodiment of the invention, in the boron-containing molten steel, the mass fraction of C is 0.015-0.04%, the mass fraction of Al is 0.02-0.05%, the mass fraction of Mn is 0.2-0.3%, and the mass fraction of Si is 0.03-0.05%.
The boron-containing steel is low-carbon aluminum killed steel, the C content of the boron-containing steel is 0.015-0.04%, the temperature of a phase transformation point is higher due to the lower C content, and the problem that the thin line defect of the edge part is easy to occur due to the fact that the temperature difference exists between the edge part and the middle part in the width direction of the strip steel in the rolling process, the edge part in the width direction of the strip steel is easy to enter a two-phase region of eutectoid ferrite and austenite or a single-phase region of ferrite to roll, and the large difference exists between the edge part and the middle part is caused.
S102, continuously casting the boron-containing molten steel to obtain a plate blank; in the continuous casting, the temperature of the straightening section is more than 950 ℃.
The hot-rolled edge part fine line defects of boron-containing steel generally occur on the upper surface of a hot coil, and the expression forms of edge part fine lines are greatly different due to the difference of alloy elements of steel types. The thin lines at the edge of the boron-containing low-carbon hot coil are mainly distributed in a linear shape along the rolling direction and are shown in figure 1. In the invention, the linear defect is within 10mm from the side part in the width direction, the innermost part is the longitudinal crack appearance of the crenellated side part, the microscopic appearance (see figure 2 and figure 3) is observed, more small cracks are seen on the surface, the depth of the crack is about 30-50um, most of the cracks have a certain angle with the vertical direction, most of the cracks incline to the right side, but the linear defect also has the characteristics of left side inclination and bidirectionality; the linear defects in the invention also comprise more surface cracks existing at the hot edge rolling of the boron-containing steel, and the depth of the cracks is 48-52 mu m. The thin lines on the edge part affect the use of users, the defects need to be cut off for subsequent processing, and the risk of cracking or strip breakage in the cold rolling process can be increased if the subsequent cold rolling is needed. Analyzing the high-temperature plasticity of the boron-containing steel by using a high-temperature tensile experiment method, and finding that the plasticity is obviously reduced within the range of 750-850 ℃ and is reduced to below 70 percent (see figure 4); the characteristic that boron element in the boron-containing steel is segregated at the grain boundary enables more fine BN in the steel to be precipitated along the grain boundary and pin the grain boundary, so that the migration of the grain boundary is inhibited, the probability of grain boundary fracture is improved, and the high-temperature plasticity of the steel is reduced, therefore, the boron-containing steel is more prone to the grain boundary fracture within the temperature range of 750-850 ℃, and linear defects are caused. The boron-containing steel casting blank is easy to crack mainly because the thermoplasticity of the steel is reduced due to the influence of BN along grain boundary precipitation, and the crack is generated when the stress strain is excessively applied in the continuous casting process. The continuous casting process adopts a weak cooling mode, the straightening and breaking temperature is controlled to be more than 950 ℃, and a large amount of BN precipitation embrittlement crystal boundaries can be avoided.
As an implementation mode of the embodiment of the invention, in the continuous casting, the drawing speed is 1.5-1.7m/min.
The drawing speed is controlled to be 1.5-1.7m/min, so that the elongation percentage reduction temperature range of the straightening section avoiding high-temperature drawing in the continuous casting process is 850 ℃, the plasticity is reduced near the temperature, and linear defects are easy to occur.
As an implementation mode of the embodiment of the invention, the thickness of the slab is 230-250mm, and the width of the slab is 1000-1800mm.
S2, heating and rough rolling the plate blank to obtain an intermediate blank;
as an implementation manner of the embodiment of the invention, the heating comprises soaking, the soaking temperature is 1200-1230 ℃, and the soaking time is 30-40min; the total heating time is 160-200min.
The temperature difference of the plate blank can be ensured within 20 ℃ through the control of the heating process, so that the temperature uniformity of each part of the strip steel in the rolling process is improved. If the temperature difference of the plate blank is too large, the temperature of the edge part of the strip steel in the width direction is reduced more in the rolling process, so that the edge part of the strip steel is rolled in a two-phase region of prior eutectoid ferrite and austenite, the tissues of the edge part and the middle part of the strip steel are different, mixed crystal tissues appear in the transition regions of the edge part and the middle part, linear cracks appear at the position about 30-50cm away from the edge part of the strip steel, and the linear cracks develop into peeling defects (see figure 2); in addition, the problems of metal flowing and flanging in the edge rolling process can be reduced by ensuring the temperature difference of the plate blank within 20 ℃. Therefore, temperature uniformity is ensured in the middle and sides of the slab during heating to minimize the side widening and metal flow during hot rolling.
By adopting the heating process, the soaking temperature and time of the plate blank can be ensured, and the steel grade can be ensured to be completely burnt. The soaking temperature is too high, which easily causes thick austenite to influence the quality of finished products, and the soaking temperature is too low to easily cause the temperature of the rolling process to fall into a two-phase region. The serious burning loss is easily caused by the overlong soaking time, and the condition of burning-proof is easily caused by the overlong soaking time. The burning loss is easy to be serious due to overlong heating total time, and the situation of burning-tight is easy to occur due to overlong heating total time.
As an implementation manner of the embodiment of the invention, the difference between the temperature of the rough rolling inlet and the temperature of the rough rolling outlet is 150-170 ℃; the difference between the central temperature and the edge temperature of the intermediate blank in the width direction is 5-15 ℃.
Through measuring the transverse temperature distribution of the strip after the strip passes through an R2 rolling mill (a second rolling mill), the temperature of the edge of the strip is lower than that of the central part by about 50-100 ℃, and the temperature of the operating side is lower than that of the driving side, so that the transverse temperature distribution corresponds to the situation that thin lines at the edge are more likely to appear at the edge of the strip, particularly at the operating side;
therefore, the temperature difference between the center and the edge in the width direction is ensured, and the edge part in the width direction of the strip steel is prevented from falling into a two-phase region for rolling, so that rolling cracking caused by tissue difference is avoided; meanwhile, the temperature difference between the rough rolling inlet and the rough rolling outlet is controlled, so that the temperature distribution uniformity of the intermediate billet, particularly the temperature uniformity of the head and the tail of the intermediate billet can be improved, and the cracking problem caused by the structure difference due to the fact that the temperature of the edge in the width direction of the strip steel is increased due to the fact that the temperature of the tail of the strip steel is too low is avoided.
As an implementation manner of the embodiment of the present invention, the rough rolling is performed by using a first rough rolling mill and a second rough rolling mill; the rolling frequency of the first roughing mill is 1 pass; the rolling frequency of the second roughing mill is 5 passes, and the width reducing amount of the 1 st pass and the 3 rd pass is respectively less than 15mm and less than 10mm when the second roughing mill rolls.
The width reduction amount of the 1 st pass and the 3 rd pass is controlled, so that the problems of metal flowing and flanging at the edge part can be reduced, and the phenomenon of obviously larger edge part compression deformation is ensured not to occur, thereby avoiding the defect of linear cracks at the edge part of the hot rolled plate.
S3, performing finish rolling on the intermediate blank at an inlet temperature of 1050-1070 ℃ and an outlet temperature of 880-920 ℃ to obtain strip steel;
in the temperature range of 750-850 ℃, the edges of the strip steel along the width direction are coarse strip ferrite, the central part is a mixture of proeutectoid ferrite and austenite, the transition region is a mixed crystal structure, and the mixed crystal structure is easy to cause linear defects. And controlling the outlet temperature of the finish rolling temperature to avoid the temperature range of 750-850 ℃, thereby avoiding the problem of linear defects caused by crystal fracture.
The temperature of a finish rolling inlet is too high, an iron sheet is too thick, and the surface quality is reduced; the finish rolling inlet temperature is too low, the edge temperature is reduced and falls into a two-phase region or a single-phase region for rolling, so that the structural abnormality occurs, and the fine line defect of cracking is caused.
The outlet temperature of the finish rolling is too high, so that the material structure is abnormally thick.
In one embodiment of the present invention, in the finish rolling process, the reduction ratio of the second pass is 40 to 45%, and the reduction ratio of the third pass is 30 to 35%.
In the finish rolling process, the reduction rate of each pass should be reasonably distributed, and the cracking of a phase interface caused by overlarge single pass is avoided.
As an embodiment of the invention, the rolling force of the finish rolling F2 stand is 22000-28000KN, and the rolling force of the finish rolling F3 stand is 20000-26000KN. And in the finish rolling, the surface quality of the hot coil is ensured by starting double-pass descaling, the rolling loads of F2 and F3 in the finish rolling process are reduced, and the linear defects are eliminated.
The main function of the finish rolling F1 rack is to prevent slipping and biting problems, so the finish rolling F1 rack generally does not carry out large reduction, and the rolling forces of the finish rolling F2 and the finish rolling F3 racks are controlled mainly to reasonably distribute each rolling pass to avoid overlarge rolling force of a single pass to cause phase interface cracking.
S4, coiling the strip steel at the temperature of 620-660 ℃ to obtain the boron-containing steel with good surface quality.
The coiling temperature is below 660 ℃, so that the temperature range of 750-850 ℃ can be avoided, and the problem of linear defects caused by crystal fracture is avoided.
The coiling temperature is too high, which easily causes the problem of coarse crystal defects. The coiling temperature is too low, so that the downstream rolling force is too large, and a cold rolling production line is influenced.
In addition, the linear defects in the present invention mean cracks in the rolling direction of the strip in the range of 30 to 50cm from the edge in the width direction, and when the cracks are severe, the macro-morphology appears as peeling (as shown in fig. 2).
The method for eliminating the boron-containing edge fine line defect according to the present invention will be described in detail with reference to examples, comparative examples and experimental data.
Examples 1 to 5 and comparative example 1
Examples 1-5 and comparative example 1 provide a method for eliminating linear defects in boron-containing low carbon aluminum killed steel, which comprises:
1. smelting to obtain molten steel, and continuously casting the molten steel to obtain a plate blank, wherein the chemical components and the size of the plate blank are shown in table 1. In the continuous casting process, the temperature of the straightening section was controlled, and the continuous casting pulling rate was controlled, as shown in table 2.
2. The slab is placed in a heating furnace for heating, the heating comprises a first heating section, a second heating section and a soaking section, and the process control of each section is shown in table 2.
3. And (4) roughly rolling the plate blank heated in the step 2 in a mode of 1+5 to obtain an intermediate blank. Wherein the RT2 roughing mill is a reversible mill, and the width reduction amounts of the 1 st pass and the 3 rd pass, as well as the roughing inlet temperature and the roughing outlet temperature when rolling with the RT2 roughing mill are specifically shown in table 2.
4. The intermediate slab obtained in the step 3 was subjected to finish rolling including F1, F2, F3, F4, F5 and F6 stands, and the rolling force and reduction ratio of the F2 and F3 stands were controlled as shown in table 3.
5. And 4, cooling the strip steel laminar flow obtained after the finish rolling in the step 4, and then coiling to obtain the boron-containing steel with good surface quality. The coiling temperature is shown in Table 3.
TABLE 1
TABLE 2
TABLE 3
TABLE 4
| Numbering | Thickness/mm of boron-containing steel | Surface quality | Cracking or breaking ratio% |
| Example 1 | 2.5 | Good surface quality and no |
0 |
| Example 2 | 2.5 | Good surface quality and no defectTrap for storing |
0 |
| Example 3 | 2.5 | Good surface quality and no |
0 |
| Example 4 | 2.5 | Good surface quality and no |
0 |
| Example 5 | 2.5 | Good surface quality and no |
0 |
| Comparative example 1 | 2.5 | Has cracks with a crack depth of 35 μm | 5 |
The results of surface observation of the boron-containing steels rolled in examples 1 to 5 of the present invention and comparative example 1 are shown in table 4.
As can be seen from Table 4, the boron-containing steel provided by the embodiments 1-5 of the present invention has good surface quality and no defects; the boron-containing steel is cold-rolled, the production process is smooth, and the problems of cracking and strip breakage are avoided. The boron-containing steel provided in comparative example 1 had crack-line defects, and as shown in FIG. 3, when it was used for cold rolling, the rate of occurrence of strip breakage or cracking was 5%.
As can be seen from FIG. 5, the boron-containing steel provided by the embodiment of the present invention has no fine line defect after pickling, and has good surface quality; as can be seen from FIG. 6, the boron-containing steel provided by the invention has no cracking defect at the edge part after cold rolling and good edge quality.
The invention provides a method for eliminating fine line defects on the edge of boron-containing steel, which belongs to the technical field of steel rolling, and more fine BN in the steel is precipitated along a crystal boundary and pins the crystal boundary due to the characteristic that boron elements are segregated at the crystal boundary within the temperature range of 750-850 ℃, so that the migration of the crystal boundary is inhibited, the probability of crystal-boundary fracture is improved, the high-temperature plasticity of steel is reduced, the crystal-boundary fracture is more likely to occur, and linear defects are caused; therefore, the temperature range of 750-850 ℃ is avoided by controlling the finish rolling and coiling temperature in the production process, so that the problem of linear defects caused by crystal fracture is avoided. The boron-containing steel provided by the method has no defect, and is used for cold rolling without fracture and cracking problems; the method is simple, high in applicability and remarkable in effect.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (9)
1. A method for eliminating the fine line defect at the edge of boron-containing steel is characterized by comprising the following steps,
obtaining a plate blank with the boron mass fraction of 0.0005-0.0009%;
heating and rough rolling the plate blank to obtain an intermediate blank; the difference between the temperature of the rough rolling inlet and the temperature of the rough rolling outlet is 150-170 ℃; the difference between the central temperature of the intermediate blank in the width direction and the edge temperature is 5-15 ℃;
performing finish rolling on the intermediate billet at an inlet temperature of 1050-1070 ℃ and an outlet temperature of 910-920 ℃ to obtain strip steel;
and coiling the strip steel at the temperature of 620-660 ℃ to obtain the boron-containing steel with good surface quality.
2. The method for eliminating the fine line defect on the edge of the boron-containing steel as claimed in claim 1, wherein the reduction ratio of the second pass is 40-45% and the reduction ratio of the third pass is 30-35% during the finish rolling.
3. The method for eliminating the fine line defect on the edge of the boron-containing steel according to claim 2, wherein the rolling force of the finish rolling F2 stand is 22000 KN to 28000KN, and the rolling force of the finish rolling F3 stand is 20000 KN to 26000KN.
4. The method for eliminating fine line defects on the edge of boron-containing steel according to claim 1, wherein the roughing is performed by using a first roughing mill and a second roughing mill; the rolling frequency of the first roughing mill is 1 pass; the rolling frequency of the second roughing mill is 5 passes, and the width reducing amount of the 1 st pass and the 3 rd pass is respectively less than 15mm and less than 10mm when the second roughing mill rolls.
5. The method for eliminating the fine line defect at the edge of the boron-containing steel according to claim 1, wherein the heating comprises soaking, the soaking temperature is 1200-1230 ℃, and the soaking time is 30-40min; the total heating time is 160-200min.
6. The method for eliminating fine line defects on the edge of boron-containing steel according to claim 1, wherein the slab with the boron mass fraction of 0.0005-0.0009% is obtained by the method comprising,
obtaining molten steel with the boron mass fraction of 0.0005-0.0009%;
continuously casting the molten steel to obtain a plate blank; in the continuous casting, the temperature of the straightening section is more than 950 ℃.
7. The method for eliminating fine line defects on the edge of a boron-containing steel according to claim 6, wherein the drawing speed in the continuous casting is 1.5-1.7m/min.
8. The method for eliminating fine line defects at the edge of a boron-containing steel as claimed in claim 6, wherein the molten steel contains C0.015 to 0.04 wt%, al 0.02 to 0.05 wt%, mn 0.2 to 0.3 wt%, and Si 0.03 to 0.05 wt%.
9. The method for eliminating fine line defects on the edge of a boron-containing steel according to claim 1, wherein the thickness of the slab is 230-250mm, and the width of the slab is 1000-1800mm.
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| WO2014081779A1 (en) * | 2012-11-20 | 2014-05-30 | Thyssenkrupp Steel Usa, Llc | Process for manufacturing ferritic hot rolled steel strip |
| CN103602783B (en) * | 2013-11-14 | 2016-01-06 | 武汉钢铁(集团)公司 | A kind of method controlling boron-containing low alloy steel limit and split |
| CN105441795B (en) * | 2014-08-22 | 2017-10-27 | 上海梅山钢铁股份有限公司 | A kind of LED lead frame low-carbon cold rolling steel plate and its production method |
| CN107552566B (en) * | 2017-07-11 | 2019-12-03 | 首钢京唐钢铁联合有限责任公司 | A kind of production method controlling ultra-low-carbon steel edge upwarping defect |
| CN111534760B (en) * | 2020-06-08 | 2021-12-21 | 首钢集团有限公司 | Hot-rolled hot-formed steel and preparation method thereof |
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