CN115044833B - High-surface-quality 65Mn cold-rolled sheet and manufacturing method thereof - Google Patents
High-surface-quality 65Mn cold-rolled sheet and manufacturing method thereof Download PDFInfo
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- CN115044833B CN115044833B CN202210666557.3A CN202210666557A CN115044833B CN 115044833 B CN115044833 B CN 115044833B CN 202210666557 A CN202210666557 A CN 202210666557A CN 115044833 B CN115044833 B CN 115044833B
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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
- 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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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
- 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
- C21D8/0236—Cold 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
- C22C38/04—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
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
The application particularly relates to a high-surface-quality 65Mn cold-rolled sheet and a manufacturing method thereof, which belong to the technical field of steel preparation, wherein the cold-rolled sheet comprises the following chemical components in percentage by mass: c:0.60% -0.78%, mn:0.8% -1.5%, si:0.20 to 0.35 percent, 0.02 to 0.05 percent of Al, P:0 to 0.015 percent, S:0 to 0.01 percent, cr:0.20% -0.4%, and the balance of Fe and unavoidable impurities; the purity and proper strength of molten steel are ensured by controlling the components of the coarse steel billets, particularly, the addition of Cr element reduces the adhesion of iron scale to improve the pickling quality, and the defect of white spots on the 65Mn surface of the medium carbon steel can be easily solved under the condition that the production condition and the performance are not influenced, so that the cold rolled steel strip with high surface quality is obtained.
Description
Technical Field
The application belongs to the technical field of steel preparation, and particularly relates to a high-surface-quality 65Mn cold-rolled sheet and a manufacturing method thereof.
Background
The medium carbon steel 65Mn is low-cost high-quality carbon steel, has higher strength and hardness after heat treatment, has better mechanical property, and is widely applied to the production of metallurgical saw blades and the like.
At present, the surface white spot defect appears in the production of the steel grade, as shown in figure 1, the hot rolling and the acid washing are slight, the cold rolling of the strip steel is quite obvious, and the white spot defect causes the degradation of the product.
Disclosure of Invention
The application aims to provide a high-surface-quality 65Mn cold-rolled sheet and a manufacturing method thereof, which are used for solving the problem that white spot defects appear on the surface of the existing 65Mn steel.
The embodiment of the application provides a high-surface-quality 65Mn cold-rolled sheet, which comprises the following chemical components in percentage by mass: c:0.60% -0.78%, mn:0.8% -1.5%, si:0.20 to 0.35 percent, 0.02 to 0.05 percent of Al, P:0 to 0.015 percent, S:0 to 0.01 percent, cr:0.20% -0.4%, and the balance of Fe and unavoidable impurities.
Optionally, the chemical components of the cold-rolled sheet include, in mass fraction: c:0.65% -0.73%, mn:1.0% -1.3%, si:0.25% -0.30%, 0.03% -0.04% of Al, P:0.005% -0.010%, S:0.003 to 0.007 percent, cr:0.25% -0.35%, and the balance of Fe and unavoidable impurities.
Optionally, the metallographic structure of the cold-rolled sheet is as follows in volume fraction: 5% -20% of ferrite and 80% -95% of pearlite.
Alternatively, the ferrite has a grain size of 10 μm to 15 μm and the pearlite has a grain size of 20 μm to 30 μm.
Based on the same inventive concept, the embodiment of the application also provides a preparation method of the high-surface-quality 65Mn cold-rolled sheet, which comprises the following steps:
obtaining a billet;
carrying out hot rolling on the steel billet to obtain a hot rolled plate;
pickling the hot rolled plate; obtaining a pickling plate;
and cold rolling the acid-washed sheet to obtain a cold-rolled sheet.
Optionally, the hot rolling comprises finish rolling, wherein double-row descaling is adopted in the finish rolling process, and the pressure of the double-row descaling is 18-20 MPa.
Optionally, 25% -35% of cooling water is started on the first three frames of the finish rolling.
Optionally, the hot rolling includes coiling, and the coiling temperature is 550 ℃ to 630 ℃.
Optionally, the hot rolling includes cooling, the cooling includes slow cooling and fast cooling, the cooling speed of the slow cooling is 0.005 ℃/s-0.01 ℃/s, the time of the slow cooling is 5h-10h, and the cooling speed of the fast cooling is 0.1 ℃/s-0.5 ℃/s.
Optionally, the cold rolling adopts eighteen-roller single-stand rolling, and the reduction rate of the last two passes in the eighteen-roller single-stand rolling is below 15%.
One or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:
the high-surface-quality 65Mn cold-rolled sheet provided by the embodiment of the application ensures the cleanliness and proper strength of molten steel through the control of the components of the coarse steel billets, particularly the addition of Cr element, reduces the adhesion of iron oxide scale, improves the pickling quality, and can easily solve the white spot defect on the surface of the medium carbon steel 65Mn under the condition of not affecting the production condition and performance, thereby obtaining the cold-rolled steel strip with high surface quality.
The foregoing description is only an overview of the present application, and is intended to be implemented in accordance with the teachings of the present application in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present application more readily apparent.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a surface topography of a prior art prepared strip;
FIG. 2 is a surface topography of a cold rolled sheet provided in comparative example 1 of the present application;
FIG. 3 is a surface topography of a cold rolled sheet provided in comparative example 2 of the present application;
FIG. 4 is a surface topography of a cold rolled sheet provided in comparative example 3 of the present application;
FIG. 5 is a surface topography of a cold rolled sheet according to example 1 of the present application;
fig. 6 is a flow chart of a method provided by an embodiment of the present application.
Detailed Description
The advantages and various effects of the present application will be more clearly apparent from the following detailed description and examples. It will be understood by those skilled in the art that these specific embodiments and examples are intended to illustrate the application, not to limit the application.
Throughout the specification, unless specifically indicated otherwise, the terms used herein should be understood as meaning 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 application belongs. In case of conflict, the present specification will control.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present application are commercially available or may be prepared by existing methods.
The technical scheme of the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:
applicants found during the course of the application that: in the prior art, as described in Chinese patent application No. CN201911414449.1, 65Mn is pickled to form iron scale residues, which are considered to be SiO caused by high Si content in steel 2 The iron scale is adhered to the surface of a substrate after pickling, the pickling quality is poor due to compactness, the Si element is reduced by adding the V element into the components, but the cost is increased due to the addition of the V element, and the iron scale is still thicker due to the fact that the coiling temperature is set higher in the innovation point of the patent, and the surface quality cannot be obviously improved through component control; the Chinese patent application CN202110736559.0 provides a manufacturing method of an ultrathin 65Mn cold-rolled wide steel strip, wherein the pickling speed is controlled to be 120-135 m/min, the acid liquor concentration is controlled to be 120-180 g/l, the acid liquor temperature is controlled to be 70-78 ℃, so that the clean pickling of iron scales on the surface of a coiled plate is ensured, but in actual production, the problem cannot be effectively solved by only relying on the pickling process.
These methods are only single-point in view and are not governed from a full-flow point of view. The application combines the characteristics of 65Mn steel types, performs coupling control from the component design of the steel types and the optimization of hot rolling and cold rolling processes, and finally solves the quality defect of the product.
According to an exemplary embodiment of the present application, there is provided a high surface quality 65Mn cold-rolled sheet having chemical components including, in mass fraction: c:0.60% -0.78%, mn:0.8% -1.5%, si:0.20 to 0.35 percent, 0.02 to 0.05 percent of Al, P:0 to 0.015 percent, S:0 to 0.01 percent, cr:0.20% -0.4%, and the balance of Fe and unavoidable impurities.
The mechanism for controlling the components of the cold-rolled sheet is as follows:
the function of C is to form pearlite structure, ensure its better hardness, C:0.6 to 0.78 percent, the content of C element is lower than 0.6 percent, the hardness is difficult to ensure, and the content exceeds 0.78 percent, so that the deformation toughness of the material is poor.
The steel is added with a certain amount of Si and Mn elements, mainly solid solution strengthening is performed to ensure the strength, the strength cannot be too high, the Si element is generally smaller than 0.35%, the Mn element is smaller than 1.5%, the Mn element is a good deoxidizer, the purity of the steel is ensured, the Mn is also an S removing agent, and the Mn content needs to be larger than 0.8%.
The residual P and S elements affect the purity and plasticity of the steel, especially for medium carbon steel, with a stringent requirement of less than 0.015%.
The steel is also added with a certain amount of Cr elements, and the addition of 0.2-0.4% of Cr elements can properly reduce the addition of C and Si elements, so that the surface quality is improved by reducing the adhesion of iron sheets, and the hardness is not reduced.
In some embodiments, the chemical composition of the cold rolled sheet comprises, in mass fractions: c:0.65% -0.73%, mn:1.0% -1.3%, si:0.25% -0.30%, 0.03% -0.04% of Al, P:0.005% -0.010%, S:0.003 to 0.007 percent, cr:0.25% -0.35%, and the balance of Fe and unavoidable impurities.
In some embodiments, the metallographic structure of the cold rolled sheet is as follows in volume fraction: 5-20% ferrite and 80-95% pearlite.
The ferrite with the volume fraction of 5-20% has the effect of ensuring certain plasticity of the steel plate, and the adverse effect of the volume fraction with the excessive value is that cold rolling plasticity is good, but the adverse effect of the deformation with the excessive value is that the plasticity is low and the surface is cracked;
the pearlite with the volume fraction of 80-95% has the function of ensuring that the steel plate has certain wear resistance, and the adverse effect of overlarge volume fraction value is that the steel plate has overlarge hardness, poorer deformation and overlarge small adverse effect is that the hardness is overlarge and the wear resistance is low.
In some embodiments, the ferrite has a grain size of 10-15 μm and the pearlite has a grain size of 20-30 μm.
The effect of ferrite with the grain size of 10-15 mu m is to ensure that the steel plate has certain uniform deformability, and the adverse effect of overlarge grain size is uneven cold rolling deformation and inconsistent pearlite deformation; the excessively small adverse effect is that the cold rolling deformation is small and the cracking is easy.
The effect of the pearlite with the grain size of 20-30 μm is to ensure the uniform hardness and wear resistance of the steel plate, the adverse effect of the excessive grain size is uneven hardness, the wear resistance is reduced, the adverse effect of the excessively small grain size is over high hardness and easy cracking.
According to another exemplary embodiment of the present application, there is provided a method for preparing a high surface quality 65Mn cold-rolled sheet as described above, the method comprising:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
in some embodiments, the hot rolling includes finish rolling, the finish rolling employing double row descaling at a pressure of 18MPa to 20MPa; and the first three frames of the finish rolling are started with 25 to 35 percent of cooling water.
The double-row descaling is started in the finish rolling, the descaling pressure is 18-20MPa, and 30% cooling water is started in the three frames before the finish rolling, so that the effective removal of the oxidized iron sheet in the finish rolling process is ensured, and defects caused by the pressing in of the oxidized iron sheet in the finish rolling process are avoided.
In some embodiments, hot rolling includes coiling, the temperature of which is 530 ℃ to 630 ℃.
The coiling temperature is controlled to be 550-630 ℃, and the thickness of the iron sheet is increased due to the excessively high coiling temperature, so that the acid pickling removal is not facilitated, the strength is easily increased due to the excessively low coiling temperature, and the cold rolling stability is not facilitated.
In some embodiments, hot rolling includes cooling, including slow cooling at a cooling rate of 0.005 ℃/s to 0.01 ℃/s, and rapid cooling at a cooling rate of 0.1 ℃/s to 0.5 ℃/s for a period of 5 hours to 10 hours.
Immediately entering a slow cooling pit for 5-10 hours after coiling is changed into rapid cooling, the slow cooling time is strictly limited after coiling, ferrite net shape in a hot rolling structure is possibly caused by slow cooling for less than 5 hours, cold rolling plasticity is poor, internal oxidation of a matrix is possibly caused by slow cooling for more than 10 hours, deformation of a cold rolling surface layer is serious due to the occurrence of internal oxidation, rolling cracks appear, and white spot defects appear macroscopically.
S3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
In some embodiments, the cold rolling employs eighteen-roll stand-alone rolling with a reduction of 15% or less for the last two passes in the eighteen-roll stand-alone rolling.
After pickling, eighteen-roller single-frame rolling is adopted, and particularly the pass reduction rate of the last two frames is below 15%. By controlling the pass reduction, the uneven deformation of the surface layer of the strip steel caused by overlarge friction is reduced, so that the rolling cracking of the surface layer is reduced, and the severity of white spot defects is reduced.
The method ensures the cleanliness and proper strength of molten steel by controlling the components of the rough steel billets, particularly ensures the addition of Cr element, reduces the adhesion of iron oxide scales and improves the pickling quality, and simultaneously reduces the oxidation of a substrate by controlling the hot rolling dephosphorization system, the coiling temperature and the cooling system process and solves the problem of white spot defect on the surface of a product caused by unreasonable control of components and process parameters by matching with the cold rolling reduction process adjustment.
The high surface quality 65Mn cold-rolled sheet and the method of manufacturing the same according to the present application will be described in detail with reference to examples, comparative examples and experimental data.
Example 1
A manufacturing method of a high surface quality 65Mn cold-rolled sheet, C:0.64%, mn:1.08%, si:0.23%, al 0.02%, P:0.01%, S:0.006%, cr:0.39%, the balance being Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started, double-row descaling is carried out, the descaling pressure is 20MPa, the first three frames are started with 30% cooling water, the coiling temperature is set to 537 ℃, and the initial cooling water enters a slow cooling pit after coiling for 5 hours and is immediately changed into rapid cooling. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the last two times is 13.6%.
Example 2
A manufacturing method of a high surface quality 65Mn cold-rolled sheet, C:0.60%, mn:0.8%, si:0.20 percent, 0.02 percent of Al and P:0.01%, S:0.006%, cr:0.20%, the balance being Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started, double-row descaling is carried out, the descaling pressure is 20MPa, the first three frames are started with 30% cooling water, the coiling temperature is set to 537 ℃, and the initial cooling water enters a slow cooling pit after coiling for 5 hours and is immediately changed into rapid cooling. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the last two times is 13.6%.
Example 3
A manufacturing method of a high surface quality 65Mn cold-rolled sheet, C:0.78%, mn:1.5%, si:0.35%, al 0.05%, P:0.01%, S:0.006%, cr:0.40%, the balance being Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started, double-row descaling is carried out, the descaling pressure is 20MPa, the first three frames are started with 30% cooling water, the coiling temperature is set to 537 ℃, and the initial cooling water enters a slow cooling pit after coiling for 5 hours and is immediately changed into rapid cooling. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the last two times is 13.6%.
Example 4
A manufacturing method of a high surface quality 65Mn cold-rolled sheet, C:0.70%, mn:1.2%, si:0.28%, al 0.03%, P:0.01%, S:0.006%, cr:0.30%, the balance being Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started to remove scales in double rows, the scale removal pressure is 18MPa, the first three frames are started to cool water with the concentration of 30%, the coiling temperature is set to 600 ℃, and the materials enter a slow cooling pit after coiling for 10 hours and are immediately changed into rapid cooling. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the last two times is 13.6%.
Example 5
A manufacturing method of a high surface quality 65Mn cold-rolled sheet, C:0.70%, mn:1.2%, si:0.28%, al 0.03%, P:0.01%, S:0.006%, cr:0.30%, the balance being Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started to remove scales in double rows, the scale removal pressure is 19MPa, the first three racks are started to cool water with the concentration of 30%, the coiling temperature is set to 630 ℃, and the process of entering a slow cooling pit after coiling for 7 hours is changed into rapid cooling. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the last two times is 13.6%.
Comparative example 1
A manufacturing method of a 65Mn cold-rolled sheet comprises the following steps of: 0.75%, mn:0.93%, si:0.33%, al 0.024%, P:0.014%, S:0.008%, cr:0.17%, the balance being Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started to remove scales in double rows, the scale removal pressure is 19.5MPa, the first three frames are started to cool water with the concentration of 30%, the coiling temperature is set to 650 ℃, and the coiled water enters a slow cooling pit for 24 hours. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the last two times is 14%.
Comparative example 2
A manufacturing method of a 65Mn cold-rolled sheet comprises the following steps of: 0.62%, mn:1.31%, si:0.29%, al 0.032%, P:0.011%, S:0.009%, cr:0.28%, and the balance of Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started to remove scales in double rows, the scale removal pressure is 18MPa, the first three frames are not started to cool water, the coiling temperature is set to 630 ℃, and the coiled materials enter a slow cooling pit for 8 hours. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the last two times is 21%.
Comparative example 3
A manufacturing method of a 65Mn cold-rolled sheet comprises the following steps of: 0.68%, mn:1.19%, si:0.27%, al 0.043%, P:0.012%, S:0.01%, cr:0.31%, the balance being Fe and unavoidable impurities.
The whole process comprises the following steps:
s1, obtaining a steel billet;
s2, hot rolling the steel billet to obtain a hot rolled plate;
s3, pickling the hot rolled plate; obtaining a pickling plate;
s4, cold rolling the acid-washed plate to obtain a cold-rolled plate.
The values of the process parameters in the steps are as follows: the finish rolling is started to remove scales in double rows, the scale removal pressure is 20MPa, the first three frames are started to cool water with the concentration of 30%, the coiling temperature is set to 590 ℃, and the materials enter a slow cooling pit for 12 hours after coiling and are immediately changed into rapid cooling. After pickling, adopting an eighteen-roller single-frame rolling, and the reduction rate of the second rolling is 14.8%.
Since the appearance of the steels prepared in each example was similar, only example 1 and each comparative example will be described below, and the appearance of the cold rolled sheets prepared in example 1 and comparative examples 1 to 3 is shown in fig. 2 to 5.
As can be seen from the macroscopic surface topography figures 2-4 of the cold rolling of the strip steel, the 65Mn prepared in the comparative examples 1-3 of the application has different surface quality, and the comparative example 1 is poor in surface quality mainly due to low Cr content, excessively high coiling temperature and excessively long slow cooling time; comparative example 2 has strip iron sheet and white spot defect on the surface due to unopened finish rolling cooling water and excessive cold rolling pass reduction; comparative example 3 has higher surface quality, but the slow cooling time after coiling is still longer, and the surface of the plate has black and slight white spot defects.
As shown in FIG. 5, which is a graph of the morphology of the steel prepared by the embodiment of the application, the steel prepared by the method has higher surface quality.
One or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:
(1) The method provided by the embodiment of the application ensures the cleanliness and proper strength of molten steel by controlling the components of the rough steel billet, particularly ensures the addition of Cr element, reduces the adhesion of iron oxide scale and improves the pickling quality, and simultaneously reduces the oxidation of a substrate by controlling the hot rolling dephosphorization system, the coiling temperature and the cooling system process and matching with the cold rolling reduction process adjustment, thereby solving the problem of white spot defect on the surface of the product caused by unreasonable control of the components and the process parameters;
(2) The method provided by the embodiment of the application is simple, economical and efficient, and the defect of white spots on the surface of the medium carbon steel 65Mn can be easily solved by using the method under the condition that the production condition and the performance are not influenced, so that the cold-rolled steel strip with high surface quality is obtained.
Finally, it is also 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 application 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. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (4)
1. A high surface quality 65Mn cold rolled sheet, characterized in that the chemical composition of the cold rolled sheet comprises in mass fraction: c:0.60% -0.78%, mn:0.8% -1.5%, si:0.20 to 0.35 percent, 0.02 to 0.05 percent of Al, P:0 to 0.015 percent, S:0 to 0.01 percent, cr:0.20% -0.4%, and the balance being Fe and unavoidable impurities, wherein the metallographic structure of the cold-rolled sheet comprises the following components in percentage by volume: 5% -20% of ferrite and 80% -95% of pearlite, wherein the grain size of the ferrite is 10-15 mu m, the grain size of the pearlite is 20-30 mu m, and the preparation method of the high surface quality 65Mn cold-rolled sheet comprises the following steps: obtaining a billet; carrying out hot rolling on the steel billet to obtain a hot rolled plate; pickling the hot rolled plate; obtaining a pickling plate;
cold rolling the acid-washed plate to obtain a cold-rolled plate;
the hot rolling comprises finish rolling, coiling and cooling, wherein double-row descaling is adopted in the finish rolling process, the pressure of the double-row descaling is 18MPa-20MPa, 25% -35% of cooling water is started in the first three frames of the finish rolling, the cooling comprises slow cooling and quick cooling, the cooling speed of the slow cooling is 0.005 ℃/s-0.01 ℃/s, the time of the slow cooling is 5h-10h, the cooling speed of the quick cooling is 0.1 ℃/s-0.5 ℃/s, the cold rolling adopts an eighteen-roller single-frame rolling, and the reduction ratio of the last two passes in the eighteen-roller single-frame rolling is below 15%.
2. The high surface quality 65Mn cold rolled sheet according to claim 1, wherein the chemical composition of the cold rolled sheet comprises in mass fraction: c:0.65% -0.73%, mn:1.0% -1.3%, si:0.25% -0.30%, 0.03% -0.04% of Al, P:0.005% -0.010%, S:0.003 to 0.007 percent, cr:0.25% -0.35%, and the balance of Fe and unavoidable impurities.
3. A method for producing a high surface quality 65Mn cold-rolled sheet according to any one of claims 1 to 2, wherein the method comprises:
obtaining a billet;
carrying out hot rolling on the steel billet to obtain a hot rolled plate;
pickling the hot rolled plate; obtaining a pickling plate;
and cold rolling the acid-washed sheet to obtain a cold-rolled sheet.
4. A method of producing a high surface quality 65Mn cold rolled sheet according to claim 3, wherein the coiling temperature is 530 ℃ to 630 ℃.
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