CN114669596A - Method for preparing medium-high carbon strip steel by semi-endless rolling and medium-high carbon strip steel - Google Patents
Method for preparing medium-high carbon strip steel by semi-endless rolling and medium-high carbon strip steel Download PDFInfo
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- CN114669596A CN114669596A CN202210226212.6A CN202210226212A CN114669596A CN 114669596 A CN114669596 A CN 114669596A CN 202210226212 A CN202210226212 A CN 202210226212A CN 114669596 A CN114669596 A CN 114669596A
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- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
- B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
- B21B1/26—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process by hot-rolling, e.g. Steckel hot mill
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Abstract
The application provides a method for preparing medium-high carbon strip steel by semi-endless rolling and the medium-high carbon strip steel, and the method comprises the following steps: providing a medium-high carbon semi-endless steel billet subjected to descaling treatment; carrying out heating treatment for continuous rolling on the medium-high carbon semi-endless steel billet; and continuously rolling the semi-endless steel billet subjected to the heating treatment to obtain the medium-high carbon strip steel, wherein the continuous rolling adopts at least 5 stands for continuous rolling, the convexity of a working roll of at least the last stand is-100-200 mu m, and the reduction rate is more than 10%. The method for preparing the medium-high carbon strip steel by semi-endless rolling can stably produce the ultra-thin wide medium-high carbon strip steel, so that the medium-high carbon strip steel has the advantages of good plate shape, small thickness difference, high yield, low energy consumption and the like.
Description
Technical Field
The application relates to the technical field of steel preparation, in particular to a method for preparing medium-high carbon strip steel by semi-endless rolling and the medium-high carbon strip steel.
Background
With the continuous development of the continuous casting and rolling of the thin slab, the steel type which can be rolled by the continuous casting and rolling process of the thin slab is greatly expanded, in the production of the existing continuous casting and rolling production line of the thin slab, medium-high carbon steel is rolled by adopting a single slab, the ultra-thin strip steel rolled by the single slab has great difficulty, and in the process of hot rolling of the medium-high carbon steel, the medium-high carbon steel has high strength and great brittleness, the head part is easy to be rolled and broken and the tail part is easy to be flapped when the medium-high carbon strip steel with thin specification (1.4 mm-2.0 mm) is produced, and the plate shape and the size are poorly controlled because the medium-high carbon strip steel is in a tension state when the head part is threaded and the tail part is thrown, and the convexity control is inferior to other steels even in the stable rolling stage.
Disclosure of Invention
The embodiment of the application provides a method for preparing medium-high carbon strip steel by semi-endless rolling and the medium-high carbon strip steel, and solves the technical problems of high carbon content, high production difficulty, and poor plate shape and size control of the medium-high carbon strip steel.
In one aspect, an embodiment of the present application provides a method for preparing medium-high carbon strip steel by semi-endless rolling, including:
providing a medium-high carbon semi-endless billet subjected to descaling treatment;
heating treatment for continuous rolling is carried out on medium-high carbon semi-endless billets;
continuously rolling the heated semi-endless steel billet to obtain medium-high carbon strip steel,
wherein, the continuous rolling adopts at least 5 frames for continuous rolling, the convexity of a working roll of at least the last frame is-100-200 μm, and the reduction rate is more than 10 percent.
In some embodiments of the present application, the medium-high carbon semi-endless steel billet has a carbon content of 0.25% to 1.3%.
In some embodiments of the present application, the inlet temperature of the continuous rolling is 1050 ℃ to 1100 ℃, and the finishing temperature is 890 ℃ to 910 ℃.
In some embodiments of the present application, the continuous rolling employs 7-stand continuous rolling.
In some embodiments of the present application, the continuous rolling is performed under the following conditions:
the rolling reduction of the No. 1 frame is 50-60%, and the rolling speed is 0.5-0.6 m/s;
The rolling reduction of the No. 2 frame is 55-65%, and the rolling speed is 1.2-1.4 m/s;
the rolling reduction of the No. 3 frame is 55-60%, and the rolling speed is 2.5-3.8 m/s;
the rolling reduction of the 4 th frame is 35-40%, and the rolling speed is 6-7 m/s;
the rolling reduction of the 5 th frame is 25 to 30 percent, and the rolling speed is 7.5 to 8.5 m/s;
the rolling reduction of the 6 th frame is 15-20%, and the rolling speed is 10.5-12 m/s;
the rolling reduction of the 7 th frame is 10-15%, and the rolling speed is 12.5-14 m/s.
In some embodiments of the present application, there is provided a descaled medium-high carbon semi-endless steel billet comprising: pouring the molten steel on a continuous casting machine at a pulling speed of 4.5-5 m/min to obtain a medium-high carbon semi-endless billet with the length of 50-269 m, and then carrying out descaling treatment.
In some embodiments of the present application, the tapping temperature of the heat-treated semi-endless steel billet is 1150 ℃ to 1180 ℃.
In some embodiments of the present application, the time of the heating treatment is 20min to 50min, the heating treatment adopts a weak reducing atmosphere, and the air-fuel ratio is 2.0 to 3.0.
In some embodiments of the present application, the heating process includes a high temperature section, a medium temperature section, and a low temperature section, wherein the temperature of the high temperature section is 1220 ℃ to 1250 ℃, the high temperature section occurs in a first zone, a second zone, a third zone, and a fourth zone of the heating furnace, the temperature of the medium temperature section is 1200 ℃ to 1230 ℃, the temperature of the medium temperature section occurs in a fifth zone and a sixth zone of the heating furnace, the temperature of the low temperature section is 1190 ℃ to 1210 ℃, and the low temperature section occurs in a seventh zone of the heating furnace.
In some embodiments of the present application, the pressure of the descaling process is 8 to 12 bar.
In some embodiments of the present application, before the continuous rolling of the semi-endless steel slab, the method further comprises: and (3) carrying out fine descaling on the heated semi-endless billet by using a hot-rolling fine descaling machine, wherein the descaling pressure of a front collecting pipe of the hot-rolling fine descaling machine is 200-240 bar, and the descaling pressure of a rear collecting pipe is 300-340 bar.
In some embodiments of the present application, the method further comprises, after the medium-high carbon strip steel is subjected to continuous rolling: and carrying out laminar cooling on the continuously rolled medium-high carbon strip steel, and coiling the cooled medium-high carbon strip steel to form a finished steel coil, wherein the coiling temperature is 650-730 ℃.
On the other hand, the embodiment of the application provides a medium-high carbon steel strip, which is prepared by the method for preparing the medium-high carbon steel strip through the semi-endless rolling in any one of the embodiments.
Compared with the prior art, the invention has at least the following beneficial effects:
the method for preparing the medium-high carbon steel strip through the semi-endless rolling provides medium-high carbon semi-endless steel billets, and only once strip threading and tail throwing are performed by adopting the semi-endless rolling technology, so that the difficulty of strip threading at the head of the thin strip steel is reduced, the problems of rolling breakage, tail throwing, overlapping rolling and the like are solved, and the defect of plate shape caused by the fact that the medium-high carbon steel strip is subjected to strip threading and tail throwing tension losing is reduced. In the continuous rolling process, the convexity of the working roll of the last stand is-100-200 μm, and the reduction rate is more than 10%, so that the deviation of the thickness and the flatness of the medium-high carbon strip steel is further reduced. The ultra-thin wide medium-high carbon strip steel can be stably produced by adopting semi-endless rolling, so that the medium-high carbon strip steel has the advantages of good plate shape, small thickness difference, high yield, low energy consumption and the like.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for preparing medium-high carbon steel strip by semi-endless rolling according to an embodiment of the present application;
FIG. 2 is a schematic flow diagram of a portion of the method of FIG. 1 providing a descaled medium to high carbon semi-endless steel slab;
FIG. 3 is a flatness effect graph of a medium-high carbon steel strip provided in example 1 of the present application;
FIG. 4 is a flatness effect graph of a medium-high carbon steel strip provided by comparative example 1 of the present application;
FIG. 5 is a flatness effect graph of a medium-high carbon steel strip provided by comparative example 2 of the present application;
FIG. 6 is a thickness effect diagram of a medium-high carbon steel strip provided in embodiment 1 of the present application;
FIG. 7 is a thickness effect diagram of a medium-high carbon steel strip provided by comparative example 1 of the application;
FIG. 8 is a thickness effect diagram of a medium-high carbon steel strip provided by comparative example 2 of the application;
FIG. 9 is a convexity effect diagram of a medium-high carbon steel strip provided in embodiment 1 of the present application;
FIG. 10 is a convexity effect diagram of a medium-high carbon steel strip provided by comparative example 1 of the present application;
FIG. 11 is a convexity effect diagram of a medium-high carbon steel strip provided by comparative example 2 of the present application;
fig. 12 is a graph of a low crown roll profile for a seventh frame provided by the present application.
Detailed Description
Features and exemplary embodiments of various aspects of the present application will be described in detail below, and in order to make objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are intended to be illustrative only and are not intended to be limiting. It will be apparent to one skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present application by illustrating examples thereof.
It is noted that, herein, 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. Also, 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. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
In order to solve the problems of the prior art, the embodiment of the application provides a method for preparing medium-high carbon strip steel by semi-endless rolling and the medium-high carbon strip steel. The method for preparing medium-high carbon steel strip by semi-endless rolling provided by the embodiment of the application is firstly described below.
See fig. 1. Fig. 1 of the present application shows a schematic flow chart of a method for preparing medium-high carbon steel strip by semi-endless rolling according to an embodiment of the present application.
As shown in fig. 1, a first embodiment of the present application provides a method for preparing medium-high carbon steel strip by semi-endless rolling, which includes:
s10, providing medium-high carbon semi-endless billets subjected to descaling treatment;
s20, heating the medium-high carbon semi-endless steel billet for continuous rolling;
s30, continuously rolling the heated semi-endless steel billet to obtain medium-high carbon strip steel,
wherein, the continuous rolling adopts at least 5 stands for continuous rolling, and the convexity of the working roll of at least the last stand is-100 mu m-200 mu m and the reduction rate is more than 10 percent.
According to the embodiment of the invention, the medium-high carbon semi-endless billet has the following chemical composition in percentage by mass: 0.25-1.3 wt% of C, 0.001-0.1 wt% of Al, 0.0010-0.0050 wt% of Ca, and the balance of Fe, alloy elements and inevitable impurities; the alloy element is one or more of 0.05 to 1.5 wt% of Si, 0.1 to 2.0 wt% of Mn, 0.001 to 1.5 wt% of Ni, 0.01 to 1.5 wt% of Cr, 0.001 to 1.5 wt% of Mo, 0.001 to 1.5 wt% of V, 0.001 to 1.5 wt% of W, 0.001 to 1.5 wt% of Cu, and 0.001 to 0.15 wt% of Ti, and the content thereof. C plays a very important role in increasing the strength of steel as interstitial atoms in steel, has the greatest influence on the yield strength and tensile strength of steel, and is an important element determining the strength and hardness of a material. However, the C content is high, which easily causes component segregation and even the phenomena of loosening and shrinkage.
According to the embodiment of the invention, the semi-endless rolling is continuous casting and drawing the semi-endless billet with the length of 50-269 m which is 2-7 times of the length of a common billet on a thin slab continuous casting and rolling unit, and the rolling mill is used for continuous rolling. Only one-time strip threading and tail throwing are performed in the headless rolling, the difficulty of the strip threading at the head of the thin strip steel is reduced, the problems of rolling breakage, tail throwing, overlapping rolling and the like are solved, and the defect of plate shape caused by the tension loss of the strip threading and the tail throwing is reduced. In the continuous rolling process, constant tension is kept between the racks, so that the deviation of the thickness and the straightness of the medium-high carbon strip steel is further reduced.
According to the embodiment of the invention, the high-carbon semi-endless billet is higher in carbon content, and the scale on the surface of the billet is thicker than that of the ordinary billet. Therefore, before preparing the medium-high carbon semi-endless billet, a descaler is required to be used for descaling to remove the scale on the surface, so that the phenomenon that water and oil adsorbed in the scale or on the surface layer react with carbon in steel to cause decarburization in the subsequent heating treatment process is avoided, and the surface quality of the high-carbon semi-endless billet entering the heating furnace is ensured.
According to the embodiment of the invention, the convexity of the working roll of at least the last frame is a certain fixed value between-100 mu m and 200 mu m, namely the low-convexity roll shape, the reduction rate of more than 10 percent is ensured, the thickness edge drop of the strip steel is effectively reduced, and the small-convexity rolling is realized. The roll shape of a conventional working roll is generally a CVC roll shape, the convexity range of the CVC roll shape is-1.5 mm (when the working roll is moved to-100 mm in a negative mode) to 0.35mm (when the working roll is moved to 100mm in a positive mode), the roll moving position is always limited, the roll bending force is also regulated to be limited, and the actual convexity of the finally prepared strip steel is larger. Meanwhile, the shifting position of the working roll is unchanged for a long time, so that the working roll is unevenly worn, and the strip shape of the strip steel is poor. In order to reduce the edge drop of the finished product strip steel, reduce the convexity and reduce the uneven wear of the roller. And the convexity is 20-40 μm in order to meet the finished product target convexity of the medium-high carbon strip steel. According to the convexity requirement of the medium-high carbon strip steel, the thermal expansion and bending of the rollers are considered, the roller shape of the last working roller of the finished product rack is set to be a low-convexity roller shape, the convexity is-100-200 mu m, and uniform roller shifting is adopted in the rolling process, so that the roller abrasion is reduced, the strip steel edge drop is reduced, and the low convexity and good strip shape of the medium-high carbon strip steel are ensured.
According to an embodiment of the invention, the reduction of the last work roll is more than 10%. Based on the fact that the strength and the hardness of medium-high carbon steel are higher than those of common low carbon steel, when the reduction rate of the last working roll is too low, the deformation of a steel billet on the last working roll is small, the effect of low-convexity roll shape cannot be effectively exerted, and when the reduction rate of the last working roll is too high, the rolled thin steel billet is easy to break, so that production accidents are caused.
The reduction rate is calculated by the formula: the reduction ratio Δ H is the reduction amount, which is the difference between the height H before rolling and the height H after rolling, where H is the height before rolling/H × 100%.
In some embodiments, the crown of the work roll of at least the last stand is between-100 μm and 200 μm. It is understood that the crown of the work roll of the last frame is any of-100 μm, -75 μm, -25 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200 μm.
In some embodiments, the reduction of the work rolls of at least the last stand is greater than 10%. It is understood that the reduction of the work rolls of the last stand is 10%, 12%, 13% and 15%. The reduction ratio may be in any combination of the above values.
In some embodiments, the rolling speed is from 12.5m/s to 14 m/s. It is understood that the rolling speeds are 12.5m/s, 13m/s, 13.5m/s and 14 m/s. The rolling speed may be in any combination of the above values.
Specifically, the continuous rolling adopts 7-stand continuous rolling, wherein the convexity of a working roll of a 7 th stand is-100-200 mu m, and the reduction rate is more than 10%. Or 7 stands are adopted for continuous rolling, wherein the convexity of the working roll of the 6 th stand is-100-200 μm, the reduction rate is 10-15%, and the convexity of the working roll of the 7 th stand is-100-200 μm, and the reduction rate is more than 10%. Specifically, the continuous rolling adopts 6-stand continuous rolling, wherein the convexity of a working roll of a 6 th stand is-100-200 mu m, and the sum reduction rate is more than 10%. Or the continuous rolling adopts 6 stands, wherein the convexity of the working roll of the 5 th stand is 100-200 μm and the reduction ratio is 10-20%, and the convexity of the working roll of the 6 th stand is 100-200 μm and the reduction ratio is more than 10%. Namely, the convexity of the working roll of the last stand of the above-mentioned at least 5 stands continuous rolling is-100 μm-200 μm, and the working rolls of other stands can be correspondingly adjusted according to the actual working requirements or cost.
In some embodiments, the inlet temperature of the continuous rolling is 1050 ℃ to 1100 ℃, and the finishing temperature is 890 ℃ to 910 ℃. The reasonable finish rolling temperature can ensure that the metallographic structure of the medium-high carbon steel structure is converted from austenite to ferrite and pearlite, and is favorable for grain refinement.
In some embodiments, the continuous rolling is 7-stand continuous rolling.
In some embodiments, the continuous rolling is performed under the following conditions:
the rolling reduction of the No. 1 frame is 50-60%, and the rolling speed is 0.5-0.6 m/s;
the rolling reduction of the No. 2 frame is 55-65%, and the rolling speed is 1.2-1.4 m/s;
the rolling reduction of the No. 3 frame is 55-60%, and the rolling speed is 2.5-3.8 m/s;
the rolling reduction of the 4 th frame is 35-40%, and the rolling speed is 6-7 m/s;
the rolling reduction of the 5 th frame is 25 to 30 percent, and the rolling speed is 7.5 to 8.5 m/s;
the rolling reduction of the 6 th frame is 15-20%, and the rolling speed is 10.5-12 m/s;
the rolling reduction of the 7 th frame is 10-15%, and the rolling speed is 12.5-14 m/s.
According to the embodiment of the invention, the thickness of the medium-high carbon strip steel after the continuous rolling is 1.4-2.0 mm after the continuous rolling by the 7-frame continuous rolling. The method for preparing the medium-high carbon strip steel by the semi-endless rolling realizes the production of the thin medium-high carbon strip steel, improves the quality stability and the yield of the medium-high carbon strip steel, can ensure that the whole steel billet keeps certain tension to realize stable rolling by the semi-endless rolling, avoids prediction errors caused by thermal expansion and abrasion of a roller, and ensures that the medium-high carbon strip steel has good straightness, small thickness difference, high yield and low energy consumption.
According to the embodiment of the invention, the continuous rolling process is divided into stages F1-F3 (1 st frame to 3 rd frame) and stages F4-F7 (4 th frame to 7 th frame). And in the stage F1-F3, austenite is completely recrystallized and rolled, so that the coarse austenite of the casting blank is fully refined. The stage F4-F7 is austenite rolling in a non-recrystallization zone, so that austenite grains are crushed, the ferrite nucleation position is increased, the ferrite structure refinement is promoted, the ferrite is uniformly nucleated, and the formation of a ferrite-pearlite banded structure caused by the segregation of alloy elements is avoided. Moreover, the reduction from the stage F1-F3 to the stage F4-F7 tends to ensure that the strip steel has good plate shape.
In some embodiments, the medium-high carbon semi-endless steel billet subjected to the descaling treatment with the thickness of 55mm to 70mm enters a 1 st machine frame in a 7-frame continuous rolling unit, the medium-high carbon semi-endless steel billet subjected to the descaling treatment with the thickness of 55mm to 70mm has the rolling reduction of 50 percent to 60 percent of the 1 st machine frame, the rolling speed is 0.5m/s to 0.6m/s, the convexity of a working roll of the 1 st machine frame is-1.5 mm to 0.35mm, the thickness of the medium-high carbon steel strip rolled from the 1 st machine frame is 22mm to 35mm, the medium-high carbon steel strip rolled from the 1 st machine frame enters a 2 nd machine frame, the rolling reduction of the 2 nd machine frame is 55 percent to 65 percent, the rolling speed is 1.2m/s to 1.4m/s, the convexity of the working roll of the 2 nd machine frame is-1.5 mm to 0.35mm, the thickness of the medium-high carbon steel strip rolled from the 2 nd machine frame is 7.7mm to 15.75mm, and the medium-high carbon steel strip rolled from the 2 nd machine frame enters a 3 rd machine frame, the rolling reduction of the 3 rd stand is 55 to 60 percent, the rolling speed is 2.5 to 3.8m/s, the convexity of the working roll of the 3 rd stand is-1.0 to 0.35mm, the thickness of the medium-high carbon strip steel rolled from the 3 rd stand is 4.0 to 7.1mm, the medium-high carbon strip steel rolled from the 3 rd stand enters the 4 th stand, the rolling speed of the 4 th stand is 35 to 40 percent, the rolling speed is 6 to 7m/s, the convexity of the working roll of the 4 th stand is-1.0 to 0.35mm, the thickness of the medium-high carbon strip steel rolled from the 4 th stand is 2.5 to 4.0mm, the medium-high carbon strip steel rolled from the 4 th stand enters the 5 th stand, the rolling speed of the 5 th stand is 25 to 30 percent, the rolling speed is 7.5 to 8.5m/s, the convexity of the working roll of the 5 th stand is-0.7 to 0.35mm, the convexity of the working roll of the 5 th stand is 3 to 0.5 mm, the medium-high carbon strip steel rolled from the 5 th frame enters the 6 th frame, the reduction ratio of the 6 th frame is 15-20%, the rolling speed is 10.5-12 m/s, the convexity of the working roll of the 6 th frame is-0.7-0.35 mm, the thickness of the medium-high carbon strip steel rolled from the 6 th frame is 1.5-2.22 mm, the medium-high carbon strip steel rolled from the 6 th frame enters the 7 th frame, the reduction ratio of the 7 th frame is 10-15%, the rolling speed is 12.5-14 m/s, the convexity of the working roll of the 7 th frame is-100-200 μm, and the thickness of the medium-high carbon strip steel rolled from the 7 th frame is 1.4-2.0 mm.
Fig. 2 shows a schematic partial flow chart of a descaling processed middle-high carbon semi-endless steel billet in the method according to an embodiment of the present application.
As shown in fig. 2, in some embodiments, S10 specifically includes:
s11, providing molten steel;
s12, pouring the molten steel on a continuous casting machine at a drawing speed of 4.5-5 m/min to obtain medium-high carbon semi-endless billets with the length of 50-269 m;
and S13, carrying out descaling treatment on the medium-high carbon semi-endless steel billet to obtain the medium-high carbon semi-endless steel billet subjected to descaling treatment.
In some embodiments, the chemical composition of the molten steel and the chemical composition of the medium-high carbon semi-endless steel billet have the following chemical compositions: 0.25 to 1.3 wt% of C, 0.001 to 0.1 wt% of Al, 0.0010 to 0.0050 wt% of Ca, and the balance of Fe, alloy elements and unavoidable impurities; the alloy element is one or more of 0.05 to 1.5 wt% of Si, 0.1 to 2.0 wt% of Mn, 0.001 to 1.5 wt% of Ni, 0.01 to 1.5 wt% of Cr, 0.001 to 1.5 wt% of Mo, 0.001 to 1.5 wt% of V, 0.001 to 1.5 wt% of W, 0.001 to 1.5 wt% of Cu, and 0.001 to 0.15 wt% of Ti, and the content thereof.
In some embodiments, the continuous casting machine includes a first continuous casting machine and a second continuous casting machine, and the molten steel is fed into the first continuous casting machine and the second continuous casting machine for casting, i.e., completing the continuous casting work. The method comprises the steps that medium-high carbon semi-endless billets cast by a first casting machine are conveyed into a descaling box to be descaled and then enter a first heating furnace to be heated, single-billet casting is carried out by a second casting machine while medium-high carbon semi-endless billets are cast by the first casting machine, billets produced by a second casting machine are conveyed into the descaling box to be descaled and then enter a second heating furnace to be heated and stored, a gap of semi-endless rolling is carried out in the first casting machine and the first heating furnace, and the billets are rolled on a rolling line through a swinging section of the second heating furnace.
According to the embodiment of the invention, the drawing speed of continuous casting is 4.5-5 m/min, and the higher drawing speed can ensure that the medium-high carbon semi-endless steel billet enters the descaling box and the heating furnace at higher temperature, and can also improve the production efficiency.
In some embodiments, the tapping temperature of the heated semi-endless steel billet is 1150 ℃ to 1180 ℃.
In some embodiments, the heating treatment time is 20min to 50min, the heating treatment adopts a weak reducing atmosphere, and the air-fuel ratio is 2.0 to 3.0.
According to the embodiment of the invention, the heating temperature and the tapping temperature need to be kept higher continuously, the furnace time is more than 20min and long, so that the heating effect of the long semi-endless steel billet is ensured, the head-tail temperature difference of the semi-endless steel billet is reduced, the semi-endless steel billet is uniformly heated, and the strength is greatly improved. The air-fuel ratio is the ratio of the mass between air and fuel in the mixture. In addition, the air-fuel ratio is 2.0-3.0, the reducing atmosphere in the furnace is also used for ensuring the full combustion of coal gas, because the carbon content of the semi-endless billet is high, the surface of the semi-endless billet is easy to generate iron scales and is not easy to remove, the thickness of the oxide on the surface of the semi-endless billet is controlled by ensuring the reducing atmosphere, on one hand, the burning loss is reduced, and on the other hand, the descaling is facilitated.
In some embodiments, the heating treatment comprises a high temperature section, a medium temperature section and a low temperature section, wherein the temperature of the high temperature section is 1220-1250 ℃, the high temperature section occurs in a first zone, a second zone, a third zone and a fourth zone of the heating furnace, the temperature of the medium temperature section is 1200-1230 ℃, the temperature of the medium temperature section occurs in a fifth zone and a sixth zone of the heating furnace, the temperature of the low temperature section is 1190-1210 ℃, and the low temperature section occurs in a seventh zone of the heating furnace.
According to the embodiment of the invention, under the condition of meeting the rolling stability, the high-temperature heating at the front section and the low-temperature heating at the middle and rear sections are adopted, so that the temperature of the semi-endless billet is homogenized, and the heating decarburization and the texture coarsening of medium-high carbon steel are reduced. The metallographic structure of the thin slab continuous casting and rolling heating furnace is austenite, the central segregation elements can obtain enough diffusion power by front-stage high-temperature heating, and the central segregation elements can obtain enough homogenization time by middle-stage low-temperature heating, so that the component segregation can be reduced under the conditions of ensuring the heating mass and reducing decarburization.
Optionally, the time for the integral heating treatment of the semi-endless steel billet in the furnace is 20 min-50 min, so as to ensure the tapping temperature of the semi-endless steel billet to be 1150 ℃ to 1180 ℃. Each district temperature setting, half endless steel billet intensive heating is guaranteed in first district to fourth district, and the fifth district is to the seventh district so that the temperature of half endless steel billet is abundant homogenization, guarantees half endless steel billet heating effect, reduces half endless steel billet head-to-tail difference in temperature, guarantees that half endless steel billet is heated evenly, and in addition, adopts three district to carry out the soaking, and the extension of soaking time is favorable to the abundant austenitization of steel billet internal organization, and then makes the carbon obtain more abundant diffusion and homogenization in the steel. In addition, the temperature of the seventh area is 1190-1210 ℃, so that the temperature of the heating furnace for the semi-endless billet is improved on the premise that the tapping temperature of the semi-endless billet meets 1150-1180 ℃, thereby being beneficial to sufficient austenitizing of the internal structure of the semi-endless billet, further leading carbon in the semi-endless billet to be more sufficiently diffused and homogenized, further reducing the defects of carbon segregation and component segregation, uneven structure, central cracks and the like caused by the carbon segregation, and leading the furnace-generated scale of the semi-endless billet to be as small as possible.
In some embodiments, the pressure for descaling is 8bar to 12 bar. And descaling by using a descaling box. For example, the pressure for descaling is 8bar, 9bar, 10bar, 11bar and 12 bar. The descaling pressure can also be any combination of the above values. Thereby removing all or most of the iron oxide scale on the surface of the high-carbon semi-endless billet.
In some embodiments, before the continuous rolling of the semi-endless billet, the method further comprises: and (3) carrying out fine descaling on the heated semi-endless billet by using a hot-rolling fine descaling machine, wherein the descaling pressure of a front collecting pipe of the hot-rolling fine descaling machine is 200-240 bar, and the descaling pressure of a rear collecting pipe is 300-340 bar.
According to the embodiment of the invention, the semi-endless billet is subjected to descaling treatment before being subjected to heating treatment, but the surface of the semi-endless billet is regenerated with scale after being subjected to heating treatment, so that finish descaling is performed by using a hot-rolling finish descaling machine, the hot-rolling finish descaling machine is arranged at the output end of the semi-endless billet in a heating furnace to directly descale the semi-endless billet after being discharged from the furnace, the descaling pressure of a front header of the hot-rolling finish descaling machine is 200-240 bar, and the descaling pressure of a rear header is 300-340 bar, so as to ensure that the scale is removed completely and improve the surface quality of a finished product.
In some embodiments, the method further comprises the following steps after the medium-high carbon strip steel is subjected to continuous rolling: and carrying out laminar cooling on the continuously rolled medium-high carbon strip steel, and coiling the cooled medium-high carbon strip steel to form a finished steel coil, wherein the coiling temperature is 650-730 ℃.
According to the embodiment of the invention, the medium-high carbon steel strip with the thickness of 1.4-2.0 mm rolled by the continuous rolling unit is subjected to laminar cooling by a laminar cooler, the medium-high carbon steel strip is cut by a flying shear after being cooled, and the cut steel strip is coiled by a first coiling machine or a second coiling machine to form a finished steel coil.
Embodiments of the second aspect of the present application provide a medium-high carbon steel strip, which is prepared by the method for preparing the medium-high carbon steel strip through the semi-endless rolling in any one of the above embodiments.
According to the embodiment of the invention, a semi-endless rolling process is adopted, on the premise of meeting the steel type process system, the convexity of the working roll of the last frame in continuous rolling is-100-200 μm and the reduction rate is more than 10%, and the working roll is in a low-convexity roll shape, so that the convexity of the high-carbon strip steel can be effectively improved, and the edge drop is reduced. By adopting a semi-endless rolling process, constant tension is kept between the racks in the continuous rolling process, so that the thickness and flatness deviation of the medium-high carbon strip steel are further reduced, the ultrathin medium-high carbon strip steel with good plate shape and small thickness difference is produced, the yield is improved, and the energy consumption is reduced.
Examples
Example 1
In this example, a medium-high carbon steel strip was produced using a semi-endless rolling method.
Firstly, providing a medium-high carbon semi-endless billet subjected to descaling treatment by the following specific operations:
providing molten steel, wherein the chemical components of the molten steel and the chemical components of the medium-high carbon semi-endless billet have the following chemical compositions: 0.65 wt% of C, 0.03 t% of Al, 0.0015% of Ca, 0.2 t% of Si, 0.8 t% of Mn, and the balance of Fe and inevitable impurities.
Pouring the molten steel in a first casting machine on a continuous casting machine, wherein the drawing speed is 5m/min, and the length of the obtained medium-high carbon semi-endless steel billet is 188 m.
And (3) conveying the medium-high carbon semi-endless steel billet into a descaling box for descaling treatment, wherein the descaling pressure is 10bar, and obtaining the medium-high carbon semi-endless steel billet subjected to descaling treatment.
Then, the provided medium-high carbon semi-endless billet is sent to a first heating furnace for continuous rolling and heating treatment. The heating treatment comprises a high-temperature section, a middle-temperature section and a low-temperature section, wherein the temperature of the high-temperature section is 1250 ℃, the high-temperature section is generated in a first zone, a second zone, a third zone and a fourth zone of a heating furnace, the temperature of the middle-temperature section is 1230 ℃, the middle-temperature section is generated in a fifth zone and a sixth zone of the heating furnace, the temperature of the low-temperature section is 1190 ℃, the temperature of the low-temperature section is generated in a seventh zone of the heating furnace, the heating treatment time is 50min, the heating treatment adopts weak reducing atmosphere, the air-fuel ratio is 2.0, and the tapping temperature of the semi-endless billet subjected to the heating treatment is 1150 ℃.
And (3) feeding the heated semi-endless steel billet into a 7-stand continuous rolling unit for continuous rolling, wherein the continuous rolling is carried out under the following conditions: the rolling reduction of the No. 1 frame is 55 percent, the rolling speed is 0.6m/s, and the convexity of the working roll of the No. 1 frame is-1.5 mm-0.35 mm; the reduction rate of the No. 2 frame is 60%, the rolling speed is 1.3m/s, and the convexity of the working roll of the No. 2 frame is-1.5 mm-0.35 mm; the rolling reduction of the No. 3 frame is 55%, the rolling speed is 3m/s, and the convexity of the working roll of the No. 3 frame is-1.0 mm-0.35 mm; the rolling reduction of the 4 th frame is 40%, the rolling speed is 6m/s, and the convexity of the working roll of the 4 th frame is-1.0 mm-0.35 mm; the rolling reduction of the 5 th frame is 30%, the rolling speed is 8m/s, and the convexity of the working roll of the 5 th frame is-0.7 mm-0.35 mm; the rolling reduction of the 6 th frame is 15%, the rolling speed is 11m/s, and the convexity of the working roll of the 6 th frame is-0.7 mm-0.35 mm; the rolling reduction of the 7 th stand is 12%, the rolling speed is 13m/s, the working roll is in a low-convexity roll shape, the convexity of the working roll is 50 mu m, and the medium-high carbon strip steel is obtained, and the thickness of the medium-high carbon strip steel is 1.7 mm.
Comparative example 1
And (3) preparing the medium-high carbon strip steel by single billet rolling.
Firstly, providing a medium-high carbon steel billet subjected to descaling treatment by the following specific operations:
Providing molten steel, wherein the chemical components of the molten steel and the chemical components of the medium-high carbon semi-endless steel billet have the following chemical compositions: 0.65 wt% of C, 0.03 t% of Al, 0.0015% of Ca, 0.2 t% of Si, 0.8 t% of Mn, and the balance of Fe and unavoidable impurities.
Performing single-billet casting on the molten steel in a second continuous casting machine on the continuous casting machine to obtain a medium-high carbon steel billet with the length of 35 m;
sending the medium-high carbon steel billet into a descaling box for descaling treatment, wherein the descaling pressure is 12bar, and obtaining the medium-high carbon steel billet subjected to descaling treatment;
then, the medium-high carbon steel billet is sent into a second heating furnace for heating treatment, wherein the heating treatment comprises a high-temperature section, a medium-temperature section and a low-temperature section, the temperature of the high-temperature section is 1250 ℃, the high-temperature section is generated in a first zone, a second zone, a third zone and a fourth zone of the heating furnace, the temperature of the medium-temperature section is 1230 ℃, the medium-temperature section is generated in a fifth zone and a sixth zone of the heating furnace, the temperature of the low-temperature section is 1190 ℃, the low-temperature section is generated in a seventh zone of the heating furnace, the heating treatment time is 50min, the heating treatment adopts weak reducing atmosphere, the air-fuel ratio is 2.0, and the tapping temperature of the heated steel billet is 1150 ℃;
and then, feeding the semi-endless steel billet after the heating treatment into a rolling line for single-billet rolling, selecting a working roll with a CVC roll shape, and performing F1-F7 rolling, wherein the convexity of the working roll of F1-F7 is respectively-1.5-0.35 mm, -1.0-0.35 mm, -0.7-0.35 mm, the rolling speed of F1-F7 is respectively 0.5m/s, 1.4m/s, 3.4m/s, 5.7m/s, 8m/s, 10m/s and 11.6m/s, the reduction ratio of F1-F7 is respectively 56%, 61%, 58%, 36%, 27%, 18% and 11.5%, and the medium-high carbon steel strip with the thickness of 1.7mm is obtained.
Comparative example 2
The difference between comparative example 2 and example 1 is: the working roll of the No. 7 frame (F7) is in a CVC roll shape, and the convexity of the working roll is-0.7 mm-0.35 mm.
The flatness, thickness and convexity of the medium-high carbon strip steel obtained in the embodiment 1, the comparative example 1 and the comparative example 2 are detected by using a multifunctional X-ray detector of shapeline. And comparing the flatness deviation result, the thickness deviation result and the convexity deviation result of the medium-high carbon strip steel.
Referring to fig. 3 to 11, fig. 3 is a flatness effect graph of a medium-high carbon steel strip provided in embodiment 1 of the present application; FIG. 4 is a flatness effect graph of a medium-high carbon steel strip provided by comparative example 1 of the present application; FIG. 5 is a flatness effect graph of a medium-high carbon steel strip provided by comparative example 2 of the present application; FIG. 6 is a thickness effect diagram of a medium-high carbon steel strip provided in embodiment 1 of the present application; FIG. 7 is a thickness effect diagram of a medium-high carbon steel strip provided by comparative example 1 of the application; FIG. 8 is a thickness effect diagram of a medium-high carbon steel strip provided by comparative example 2 of the application; FIG. 9 is a convexity effect diagram of a medium-high carbon steel strip provided in embodiment 1 of the present application; FIG. 10 is a convexity effect diagram of a medium-high carbon steel strip provided by comparative example 1 of the present application; fig. 11 is a convexity effect diagram of the medium-high carbon steel strip provided by comparative example 2 of the present application.
As shown in fig. 3 to 5, it can be seen that the flatness of the middle and high carbon steel strip obtained by the method of preparing the middle and high carbon steel strip by the semi-endless rolling according to some embodiments of the present application is better than the flatness control effect of the middle and high carbon steel strip obtained by the single blank rolling and the CVC roll shape of F7.
As shown in fig. 6 to 8, it can be seen that the thickness deviation amplitude of the medium-high carbon steel strip obtained by the method for preparing the medium-high carbon steel strip by the semi-endless rolling in some embodiments of the present application is significantly smaller than that of the medium-high carbon steel strip obtained by the single-slab rolling, CVC roll forming of F7.
As shown in fig. 9 to 11, it can be seen that the crown deviation amplitude of the medium-high carbon steel strip obtained by the method for preparing the medium-high carbon steel strip by the semi-endless rolling in some embodiments of the present application is significantly smaller than that of the medium-high carbon steel strip obtained by the single-slab rolling, CVC roll forming of F7.
Referring to fig. 12, fig. 12 is a graph showing a low crown roll profile of a seventh frame provided for embodiment 1 of the present application.
As shown in FIG. 12, the fitting curve is a low-convexity roll-shape curve designed for the working rolls of the F7 stand and is formed by fitting on the basis of a quadratic curve, the roll shape of the last working roll of the finished stand is set to be a low-convexity roll shape, and uniform roll shifting is adopted in the rolling process so as to reduce the abrasion of the rolls, reduce the edge drop of the strip steel and ensure the low convexity and good plate shape of the medium-high carbon strip steel.
According to the method, the ultra-thin wide medium-high carbon strip steel can be stably produced by adopting the semi-endless rolling, so that the medium-high carbon strip steel has good plate shape, small thickness difference and high yield, the poor plate shape caused by strip threading and tail throwing tension losing is reduced, the deviation range of the straightness, the thickness and the convexity of the head and the tail of the medium-high carbon strip steel is reduced, and the quality of the medium-high carbon strip steel is effectively ensured.
As described above, only the specific embodiments of the present application are provided, and it can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the system, the module and the unit described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again. It should be understood that the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the present application, and these modifications or substitutions should be covered within the scope of the present application.
Claims (13)
1. A method for preparing medium-high carbon strip steel by semi-endless rolling is characterized by comprising the following steps:
providing a medium-high carbon semi-endless steel billet subjected to descaling treatment;
carrying out heating treatment for continuous rolling on the medium-high carbon semi-endless steel billet;
Continuously rolling the semi-endless steel billet after the heating treatment to obtain medium-high carbon strip steel,
wherein, the continuous rolling adopts at least 5 stands for continuous rolling, the convexity of the working roll of at least the last stand is-100-200 μm, and the reduction rate is more than 10%.
2. The method for preparing medium-high carbon steel strip by semi-endless rolling according to claim 1, wherein the medium-high carbon semi-endless billet has a carbon content of 0.25-1.3%.
3. The method for preparing medium-high carbon steel strip by semi-endless rolling according to claim 1, wherein the inlet temperature of the continuous rolling is 1050-1100 ℃, and the finishing temperature is 890-910 ℃.
4. The method for preparing medium-high carbon steel strip by semi-endless rolling according to claim 1, wherein the continuous rolling adopts 7-stand continuous rolling.
5. The method for producing medium-high carbon steel strip by semi-endless rolling according to claim 4, characterized in that the continuous rolling is carried out under the following conditions:
the rolling reduction of the No. 1 frame is 50-60%, and the rolling speed is 0.5-0.6 m/s;
the rolling reduction of the No. 2 frame is 55-65%, and the rolling speed is 1.2-1.4 m/s;
the rolling reduction of the No. 3 frame is 55-60%, and the rolling speed is 2.5-3.8 m/s;
The rolling reduction of the 4 th frame is 35 to 40 percent, and the rolling speed is 6 to 7 m/s;
the rolling reduction of the 5 th frame is 25 to 30 percent, and the rolling speed is 7.5 to 8.5 m/s;
the rolling reduction of the 6 th frame is 15-20%, and the rolling speed is 10.5-12 m/s;
the rolling reduction of the 7 th frame is 10-15%, and the rolling speed is 12.5-14 m/s.
6. The method for preparing the medium-high carbon steel strip by the semi-endless rolling according to claim 1, wherein the step of providing the medium-high carbon semi-endless steel blank subjected to the descaling treatment comprises the following steps:
pouring the molten steel on a continuous casting machine at the drawing speed of 4.5-5 m/min to obtain medium-high carbon semi-endless billets with the length of 50-269 m, and then carrying out descaling treatment.
7. The method for preparing medium-high carbon steel strip by semi-endless rolling according to claim 1, wherein the tapping temperature of the semi-endless billet after the heat treatment is 1150 ℃ to 1180 ℃.
8. The method for preparing the medium-high carbon steel strip through the semi-endless rolling according to claim 7, wherein the heating treatment time is 20-50 min, the heating treatment adopts a weak reducing atmosphere, and the air-fuel ratio is 2.0-3.0.
9. The method for preparing medium-high carbon steel strip by semi-endless rolling according to claim 7, wherein the heating treatment comprises a high temperature section, a medium temperature section and a low temperature section,
The temperature of the high-temperature section is 1220-1250 ℃, the high-temperature section is generated in a first zone, a second zone, a third zone and a fourth zone of a heating furnace, the temperature of the medium-temperature section is 1200-1230 ℃, the medium-temperature section is generated in a fifth zone and a sixth zone of the heating furnace, the temperature of the low-temperature section is 1190-1210 ℃, and the low-temperature section is generated in a seventh zone of the heating furnace.
10. The method for preparing medium-high carbon steel strip by semi-endless rolling according to claim 1, wherein the pressure of the descaling process is 8bar to 12 bar.
11. The method of producing medium-high carbon steel strip by semi-endless rolling according to claim 1, wherein before the semi-endless billet is subjected to continuous rolling, the method further comprises:
and carrying out fine descaling on the semi-endless billet subjected to the heating treatment by using a hot-rolling fine descaling machine, wherein the descaling pressure of a front collecting pipe of the hot-rolling fine descaling machine is 200-240 bar, and the descaling pressure of a rear collecting pipe is 300-340 bar.
12. The method for preparing the medium-high carbon steel strip through the semi-endless rolling according to claim 1, wherein the method further comprises the following steps after the medium-high carbon steel strip is subjected to the continuous rolling:
and carrying out laminar cooling on the continuously rolled medium-high carbon strip steel, and coiling the cooled medium-high carbon strip steel to form a finished steel coil, wherein the coiling temperature is 650-730 ℃.
13. A medium-high carbon steel strip, characterized by being produced by the method for producing a medium-high carbon steel strip by semi-endless rolling according to any one of claims 1 to 12.
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