Dynamic specification changing method for cold continuous rolling

Abstract

The invention discloses a cold continuous rolling dynamic specification changing method. The technical problems that in the prior art, the specification changing rolling speed between steel types with large rolling characteristic difference is low, and the yield is low are solved. The method comprises the steps that first strip steel and second strip steel are sequentially subjected to cold continuous rolling through a cold rolling unit, wherein the rolling force generated when a connecting welding seam passes through any rack of the cold rolling unit is 110%-130% of the set rolling force generated when the low-strength one of the first strip steel and the second strip steel passes through the corresponding rack; the strip tail of the first strip steel and the strip head of the second strip steel are subjected to low-speed rolling at the speed of 30-80 m / min, and in the low-speed rolling process, the additional tension of the hot-rolled strip steel is 105-125% of the set tension. According to the method provided by the invention, the specification changing efficiency is improved, the plate shape and thickness precision is ensured, and the yield is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of cold tandem rolling, and specifically relates to a method for dynamically changing specifications of cold tandem rolling. Background Art

[0002] Tandem cold rolling mills have high rolling speeds and strong rolling capacity, and are therefore widely used for strip steels with similar rolling characteristics. However, the rolling characteristics of some different strip steels vary greatly. For example, due to differences in material properties such as alloy composition and microstructure, the rolling parameters used in rolling different strip steels also vary greatly. Therefore, when switching between different specifications, the dynamic specification change method cannot be directly used, or strip breakage is prone to occur during use. As a result, the weld must be coiled empty to the coiler before the raw plate is started. This method not only wastes the production efficiency of the rolling mill, but also causes a loss in yield rate. For some varieties, starting the mill is very difficult, and the operation requirements of the rolling mill are very high, and it is very easy for the strip to break when starting the mill.

[0003] Therefore, there is an urgent need to improve the rolling rate and yield rate between two types of steel strips with large differences in rolling characteristics. Summary of the Invention

[0004] In order to solve the current technical problems of low rolling rate and low yield of two strip steels with greatly different rolling characteristics, the present application provides a method for dynamic specification change of cold tandem rolling.

[0005] The present application provides a method for dynamically changing gauges in cold tandem rolling, which is applicable to a first steel strip and a second steel strip sequentially connected by a connecting weld, wherein the first steel strip and the second steel strip are made of different materials, and the method comprises:

[0006] The first steel strip and the second steel strip are sequentially cold rolled through the cold rolling mill, wherein:

[0007] The rolling force of the connecting weld when passing through any stand of the cold rolling mill is 110-130% of the set rolling force of the lower strength of the first and second strips passing through the corresponding stand;

[0008] The tail of the first steel strip and the head of the second steel strip are rolled at a low speed of 30-80 m / min. During the low speed rolling process, the additional tension of the hot-rolled steel strip is 105-125% of the set tension.

[0009] In some embodiments, during the low-speed rolling process, the rolling force F of the stand where the hot-rolled strip is located, the bending force V of the working rolls, and the width W of the hot-rolled strip meet the following relationship: V=a*W+b*F, wherein: the value range of a is -0.0001 to -0.01; the value range of b is 0.003 to 0.027.

[0010] In some embodiments, the difference ΔV1 between the working roll bending force for rolling the first strip and the working roll bending force for rolling the second strip, and the difference ΔF1 between the rolling force when rolling the tail of the first strip and the rolling force when rolling the head of the second strip meet the following relationship: ΔV1 = b*ΔF1.

[0011] In some embodiments, the speed of low-speed rolling the tail of the first steel strip and the head of the second steel strip is 40-60 m / min.

[0012] In some embodiments, during the low-speed rolling process, the additional tension of the hot-rolled strip is 110-120% of the set tension.

[0013] In some embodiments, the tail of the first steel strip is 5 to 15 m before the connecting weld, and the head of the second steel strip is 5 to 15 m after the connecting weld.

[0014] In some embodiments, when the width of the first steel strip is greater than the width of the second steel strip, the tapered section of the working roll is moved toward the rolling centerline after the connecting weld exits the cold rolling mill.

[0015] In some embodiments, when the width of the first steel strip is less than the width of the second steel strip, the tapered section of the working roll is moved away from the rolling centerline before the connecting weld enters the cold rolling mill.

[0016] In some embodiments, the hot-rolled steel strip has a thickness of 1.5 to 3.0 mm, and the mass fraction of Si in one of the first steel strip and the second steel strip is ≥2.0%, and the mass fraction of Si in the other steel strip is <2.0%.

[0017] In some embodiments, the width difference between the first steel strip and the second steel strip is ≤ 240 mm.

[0018] According to an embodiment of the present application, a method for dynamically changing gauges in cold tandem rolling is provided, which is applicable to a first steel strip and a second steel strip sequentially connected by a connecting weld, wherein the first steel strip and the second steel strip are made of different materials. The method comprises: sequentially passing the first steel strip and the second steel strip through a cold rolling mill for tandem cold rolling, wherein the rolling force applied when the connecting weld passes through any stand of the cold rolling mill is 110-130% of the set rolling force of the lower strength of the first steel strip and the second steel strip passing through the corresponding stand;

[0019] The tail of the first steel strip and the head of the second steel strip are rolled at a low speed of 30-80 m / min. During the low speed rolling process, the additional tension of the hot-rolled steel strip is 105-125% of the set tension.

[0020] The present application ensures thickness accuracy and improves rolling stability by controlling the rolling force of the connecting weld when it passes through the frame; by controlling the additional tension of the connecting weld and its vicinity, it offsets part of the rolling force during low-speed operation, reduces the difference in rolling force between the low-speed rolling and high-speed stable rolling stages, improves the stability of the cold rolling process, avoids the problem of edge crack defects in steels with high rolling strength and poor plasticity, and thus improves the quality of cold-rolled products.

[0021] The method for dynamic specification change of cold rolling provided in the present application is applicable to two strip steels of different materials. It can dynamically change specification rolling online without stopping the machine and has high production efficiency. By controlling the low-speed rolling in the transition area and coordinating the control of the rolling force and additional tension, the stability of the rolling process is ensured and the product quality is improved. The length of the strip steel in the dynamic specification change stage is short, which improves the yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A process step diagram of a method for dynamic gauge changing of cold tandem rolling in one or more embodiments of the present application is shown. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to understand the present application more clearly, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of this application.

[0024] The rolling efficiency can be improved by connecting multiple strips in sequence and then cold rolling them in a continuous rolling mill. Generally, two adjacent strips are connected by welding.

[0025] The first embodiment of the present application provides a method for dynamic specification change of cold tandem rolling, which is suitable for cold tandem rolling of a first strip steel and a second strip steel connected by a connecting weld with different materials. The rolling process is stable and the length of the strip steel in the dynamic specification change stage is short.

[0026] See also Figure 1 The method for dynamically changing specifications of cold tandem rolling provided in the embodiment of the present application includes:

[0027] The first steel strip and the second steel strip are sequentially cold rolled through the cold rolling mill, wherein:

[0028] S1. The rolling force of the connecting weld when passing through any stand of the cold rolling mill is 110-130% of the set rolling force of the lower strength of the first and second strips passing through the corresponding stand;

[0029] The connecting weld will slow down when passing through the cold rolling mill, and the connecting transition part of the first strip and the second strip will be rolled at a low speed to improve the stability of the connecting weld when passing through the cold rolling mill. However, under low-speed cold rolling conditions, a larger rolling force needs to be controlled to ensure the thickness accuracy of the rolling. However, excessive rolling force may also cause ultra-thin slippage or strip breakage. Therefore, the rolling force of the connecting weld when passing through any frame is 110-130% of the set rolling force of the lower strength of the first strip and the second strip passing through the corresponding frame. This can not only improve the rolling stability, but also ensure the rolling thickness accuracy.

[0030] Generally speaking, a cold rolling mill is equipped with 5 to 7 stands. For example, a cold rolling mill with 6 stands is composed of the first, second, third, fourth, fifth, and sixth stands along the cold rolling direction. Assuming that the connecting weld passes through the third stand, the rolling force applied by the third stand to the connecting weld is 110 to 130% of the set rolling force of the lower-strength strip between the first and second strips passing through the third stand. The set rolling force of the lower-strength strip passing through the third stand refers to the set rolling force when the lower-strength strip is rolled at a normal rate (high-speed stable rolling, for example, a rolling rate of 800 to 1500 m / min).

[0031] When the strength of the first steel strip is higher than that of the second steel strip, the rolling of the first steel strip is more difficult, and the set rolling force when the first steel strip passes through the frame is greater than the set rolling force when the second steel strip passes through the frame. At this time, the connecting weld takes the set rolling force when the second steel strip passes through the frame as a benchmark, and increases by 10% to 30%, which can ensure the rolling stability of the connecting weld and its nearby positions; if the connecting weld takes the set rolling force when the first steel strip passes through the frame as a benchmark, the rolling force at the weld is too large, which may cause the connecting weld and the strip near the second steel strip to be too thin, resulting in strip breakage.

[0032] If the strength of the first strip is lower than that of the second strip, rolling the first strip is easier. The set rolling force when the first strip passes through the mill is lower than the set rolling force when the second strip passes through the mill. In this case, the joint weld is based on the set rolling force when the first strip passes through the mill, with a 10% to 30% increase. This ensures rolling stability at the joint weld and its surrounding areas. If the joint weld is based on the set rolling force when the second strip passes through the mill, there is a risk of the joint weld breaking due to excessive rolling force and excessively thin first strip.

[0033] During low-speed rolling, the rolling force at the tail of the first strip is 110-130% of the set rolling force of the first strip, improving the thickness accuracy and rolling stability of the tail of the first strip. The rolling force at the head of the second strip is 110-130% of the set rolling force of the second strip, improving the thickness accuracy and rolling stability of the tail of the second strip.

[0034] S2, the tail of the first strip and the head of the second strip are rolled at a low speed of 30-80 m / min. During the low-speed rolling process, the additional tension of the hot-rolled strip is 105-125% of the set tension.

[0035] As previously mentioned, rolling the tail of the first strip and the head of the second strip at a low speed ensures that the connecting weld and its vicinity pass stably through the cold rolling mill, improving the stability of the tandem cold rolling process. If the rolling speeds of the tail of the first strip and the head of the second strip are too low, production efficiency may be reduced to a certain extent, extending the length of the strip during the dynamic gauge change stage. If the rolling speeds of the tail of the first strip and the head of the second strip are too high, the risk of strip breakage may be increased to a certain extent, and thickness accuracy may also be affected to a certain extent.

[0036] During the low-speed rolling of the tail of the first strip and the head of the second strip, the additional tension of the hot-rolled strip is increased, thereby reducing the rolling force of the corresponding stands. When the other parts of the first and second strips (excluding the middle portion between the head and tail) are steadily rolled at high speed, no additional tension is applied. This reduces the difference between the stand rolling force during low-speed rolling and the stand rolling force during stable high-speed rolling. In other words, the difference between the stand rolling force during rolling the tail of the first strip and the head of the second strip and the stand rolling force during stable high-speed rolling is reduced, thereby improving the rolling stability of the first and second strips. When the tail of the first strip passes through the tandem rolling mill, the additional tension applied to the tail of the first strip is 105-125% of the set tension of the first strip. When the head of the second strip passes through the tandem rolling mill, the additional tension applied to the head of the second strip is 105-125% of the set tension of the second strip.

[0037] The rolling force during low-speed rolling of the strip is higher than the rolling force during high-speed stable rolling. If the additional tension of the hot-rolled strip is too small, the rolling force will be too large to a certain extent, which may easily overload the rolling mill and cause equipment damage. For strip steel with relatively high strength, such as electrical steel with Si mass fraction ≥2.0%, the material itself is hard and strong but has poor plasticity. Edge crack defects are very likely to occur under such high rolling force.

[0038] From the above analysis, it can be seen that this application controls the rolling force and additional tension of the connecting weld as it passes through the stands, allowing specifications to be changed online without stopping the mill, thereby shortening the length of the variable-specification strip. By controlling the rolling force of the connecting weld as it passes through any stand of the cold rolling mill, rolling stability is improved; by controlling the additional tension of the connecting weld and its vicinity, the rolling force during low-speed rolling is reduced, reducing the difference in rolling force between low-speed rolling and high-speed stable rolling, improving the stability of the cold rolling process, and avoiding the edge crack defect problem caused by rolling steel with high rolling strength and poor ductility, thereby improving the quality of cold-rolled products.

[0039] In addition to the above-mentioned rolling force control and additional tension control, in order to further improve the plate shape effect of dynamic variable gauge cold rolling and improve the stability of the rolling process, it is also necessary to control the rolling force F of the stand, the work roll bending force V, and the width W of the hot-rolled strip. Specifically, in some embodiments, during the low-speed rolling process, the rolling force F of the stand where the hot-rolled strip is located, the work roll bending force V, and the width W of the hot-rolled strip meet the following relationship:

[0040] V=a*W+b*F

[0041] Where: V is the bending force of the working roll, in tons or KN; W is the width of the hot-rolled strip, in mm. When rolling the tail of the first strip, the width at this time is the width of the first strip. When rolling the head of the second strip, the width here is the width of the second strip. F is the actual rolling force of any stand of the continuous rolling mill, without considering the weld length and angle, in tons or KN. a is the coefficient of variation of the working roll bending force with the width of the hot-rolled strip, and the value range of a is -0.0001 to -0.01. b is the coefficient of variation of the working roll bending force with the rolling force, and the value range of b is 0.003 to 0.027.

[0042] Controlling the bending roll force can control the crown of hot-rolled strip after cold tandem rolling. As can be seen from the above formula, the bending roll force, rolling force, and width of the hot-rolled strip are in a matching relationship. When the rolling force of the stand is high, the bending roll force of the work roll of the stand is also high, ensuring that the strip does not have edge waves after cold rolling, that is, improving the flatness accuracy. When the width of the hot-rolled strip is wide, the bending roll force of the work roll is low, and when the width of the hot-rolled strip is narrow, the bending roll force of the work roll is high to ensure the flatness of the strip.

[0043] In some embodiments, the difference ΔV1 between the work roll bending forces for rolling the first steel strip and the second steel strip, and the difference ΔF1 between the rolling forces for rolling the tail of the first steel strip and the leading edge of the second steel strip, conform to the following relationship: ΔV1 = b * ΔF1. The work roll bending forces remain constant throughout the entire coil rolling process, resulting in the same bending forces during high-speed and low-speed rolling. Controlling ΔV1 = b * ΔF1 ensures the shape accuracy of the first steel strip after rolling, thereby improving the stability of the rolling process.

[0044] In this application, the units of rolling force and bending roll force are both KN, which can also be converted into tons, 10KN≈1 ton.

[0045] The rolling forces when the first steel strip and the second steel strip are rolled stably at high speed are the aforementioned respective set rolling forces.

[0046] In some embodiments, the speed of low-speed rolling of the tail of the first steel strip and the head of the second steel strip is 40-60 m / min.

[0047] In some embodiments, during the low-speed rolling process, the additional tension of the hot-rolled strip is 110-120% of the set tension.

[0048] In some embodiments, the tail of the first steel strip is 5 to 15 m before the connecting weld, and the head of the second steel strip is 5 to 15 m after the connecting weld.

[0049] In some embodiments, when the width of the first steel strip is greater than the width of the second steel strip, the tapered section of the working roll is moved toward the rolling centerline after the connecting weld exits the cold rolling mill. The working roll includes a tapered section and a straight section sequentially connected in the axial direction, and the cross-sectional diameter of the tapered section increases sequentially from the tapered section to the straight section. The thickness of the steel strip can be adjusted by shifting the working rolls with the tapered sections. Each frame includes two working rolls, which are arranged vertically opposite to each other. The two tapered sections are respectively located on the operating side and the transmission side of the continuous rolling mill, that is, the tapered sections of the two working rolls are arranged in opposite directions. After the connecting weld exits the cold rolling mill, the tapered section of the working roll is moved toward the rolling centerline, that is, the tapered section of the working roll is moved toward the central cross-section of the working roll along the axial direction. During the movement, the two oppositely arranged working rolls move in opposite directions. The wider strip is rolled first, followed by the narrower strip, meaning the rolling width decreases from wide to narrow. After the connecting weld passes, the tapered section is moved toward the rolling centerline. This ensures the shape accuracy of the wider first strip and the stability of the gauge change. The movement of the two work rolls in each stand is (W2-W1) / 2, where W1 is the width of the first strip and W2 is the width of the second strip.

[0050] In some embodiments, when the width of the first steel strip is less than the width of the second steel strip, the tapered section of the working roll is moved away from the rolling center line before the connecting weld enters the cold rolling mill, and the movement amount is (W2-W1) / 2, where W1 is the width of the first steel strip and W2 is the width of the second steel strip.

[0051] The narrower strip is rolled first, followed by the wider strip, meaning the strip width is gradually increased. The tapered sections of both work rolls in the mill are moved outward before the weld is made, ensuring the shape accuracy of the second strip at the head. If the work roll positions are adjusted after the weld is made and the cold rolling mill exits, the second strip's head is prone to large or medium waves or even rolling defects, affecting the strip shape and potentially causing the strip to break and damage the rolls.

[0052] In some embodiments, the thickness of the hot-rolled steel strip is 1.5-3.0 mm, the width difference between the first steel strip and the second steel strip is ≤240 mm, and the thickness difference of the raw materials meets the welding requirements of the welding machine.

[0053] In some embodiments, one of the first and second steel strips has a Si mass fraction of 2.0% or greater, while the other has a Si mass fraction of less than 2.0%. Steel strips with a Si mass fraction of 2.0% or greater exhibit high strength, high brittleness, and are difficult to roll. Steel strips with a Si mass fraction of less than 2.0% exhibit low strength, good ductility, and are easy to roll.

[0054] For two strips with completely different rolling characteristics, the strip with Si mass fraction ≥2.0% may be in front and the strip with Si mass fraction <2.0% may be in the back; or the strip with Si mass fraction <2.0% may be in front and the strip with Si mass fraction ≥2.0% may be in the back. The method of dynamic specification change of cold rolling provided in this application is applicable to any of the above situations.

[0055] The following specific examples are given to further illustrate the method for dynamic specification change of cold rolling provided by the present application:

[0056] For example, consider two adjacent steel strips, silicon steel and carbon steel. The silicon steel is 1150 mm wide, has a silicon content of 2.2%, and a finished thickness of 0.35 mm. The carbon steel is 1200 mm wide, has a silicon content of 0.2%, and a finished thickness of 0.3 mm. Silicon steel has greater strength than carbon steel. Tables 1 and 2 list the rolling process parameters for silicon steel and carbon steel, respectively. The set rolling force can also be the actual rolling force, and S1 to S6 are the stand numbers of the tandem mill, arranged sequentially along the rolling direction of the strip.

[0057] Table 1 Silicon steel stable (high speed) rolling process parameters Rack number S1 entrance S1 S2 S3 S4 S5 S6 Set rolling force-high speed (tons) / 903 894 766 663 661 582 Set tension (tons) 14.7 28.9 19.8 13.3 10.2 8 2.5 Reduction rate (%) / 38 36.5 31.3 28 22.9 11 Working roll shift value (mm) / -70 -50 -30 0 0 -20 Intermediate roller shifting value (mm) / 0 0 0 0 0 0 Working roll bending force (tons) / 5 6 7 4 3 2 Intermediate roll bending force (tons) / 14 15 16 16 16 8

[0058] Table 2 Carbon steel stable rolling process parameters Rack number S1 entrance S1 S2 S3 S4 S5 S6 Set rolling force-high speed (tons) / 765 774 666 637 561 491 Set tension (tons) 13.1 23.3 15.8 12 8.2 6.3 2.5 Reduction rate (%) / 35 37 31.2 26 24 12 Working roll shift value (mm) / -70 -50 -30 0 0 -20 Intermediate roller shifting value (mm) / 0 0 0 0 0 0 Working roll bending force (tons) / 2.5 3.5 3.6 3.5 2.5 1.5 Intermediate roll bending force (tons) / 14 15 16 16 16 8

[0059] Example 1

[0060] The first roll of strip steel is silicon steel, and the second roll of strip steel is carbon steel. The first roll of strip steel is first rolled into the cold rolling mill, and the second roll of strip steel is then rolled into the cold rolling mill. The strength of the second strip steel is lower.

[0061] Rolling of the tail of the first coil and the head of the second coil:

[0062] When rolling the tail of the first silicon steel coil, 10 meters before the connecting weld enters the first stand (S1), the cold rolling mill slows down to 50m / min, executes the steel grade change program, shuts down all automatic thickness control functions of the cold rolling mill, and enters the manual roll gap adjustment mode. When the connecting weld of the first silicon steel coil and the second carbon steel coil passes the last stand (S6), the cold rolling mill starts to increase speed and carry out normal rolling of the second carbon steel coil.

[0063] The rolling force of the silicon steel strip tail passing through the S1 to S6 stands is 110-130% of the set rolling force of the silicon steel. The rolling force of each stand can be seen in Table 3.

[0064] The rolling force of the connecting weld passing through the S1 to S6 stands is 110-130% of the set rolling force of carbon steel. The specific rolling force of each stand is shown in Table 3.

[0065] The rolling force of the carbon steel strip passing through the S1 to S6 stands is 110-130% of the set rolling force of carbon steel. Please refer to Table 3 for the rolling force of each stand.

[0066] The difference ΔF1 between the rolling force when rolling the tail of the first steel strip and the rolling force when rolling the head of the second steel strip can be seen in Table 3.

[0067] During the low-speed rolling process, the additional tension of the hot-rolled strip is 115% of the set tension.

[0068] Table 3 Rack number S1 S2 S3 S4 S5 S6 Silicon steel tail rolling force (tons) 1042 1090 961 843 812 698 Carbon Steel Strip Rolling Force - Low Speed ​​(tons) 865 875 763 732 656 588 Rolling force of weld (tons) 865 875 763 732 656 588 Rolling force difference △F1 (tons) 177 215 198 111 156 110 The difference in bending roll force between silicon steel and carbon steel △V1 (tons) 2.5 2.5 3.4 0.5 0.5 0.5

[0069] When the strip deformation zone of the first stand enters the final stand and the deviation between the actual strip thickness and the set thickness at each stand is less than 50 microns, the automatic thickness control function of the tandem mill is activated, allowing the tandem mill to accurately adjust the thickness of each stand and gradually increase the speed to a stable rolling speed. During low-speed rolling, the additional tension for silicon steel and carbon steel is 110% of the respective set tensions.

[0070] Before dynamic specification change (before the connecting weld reaches the S1 stand), the tapered sections of the working rolls and intermediate rolls of the S1 stand to the S6 stand are moved 25 mm away from the rolling center line in advance according to the width of the carbon steel.

[0071] When the connecting weld of the first roll of silicon steel and the second roll of carbon steel reaches the coiler, the weld shearing program is not executed. After the dynamic specification change is successful, the shearing program is executed to shear the strip steel with unqualified thickness.

[0072] Example 2

[0073] In Example 2, the first steel strip is carbon steel, and the second steel strip is silicon steel. During the low-speed rolling (70 m / min) of the first and second steel strips:

[0074] The rolling force for the tail of the carbon steel strip passing through stands S1 to S6 is shown in Table 4. The rolling force for the connecting weld passing through stands S1 to S6 is 110-130% of the set rolling force for carbon steel. The specific rolling force for each stand is shown in Table 4. The rolling force for the head of the silicon steel strip passing through stands S1 to S6 is 110-130% of the set rolling force for carbon steel. The rolling force for each stand is shown in Table 4. The difference ΔF1 between the rolling force for rolling the tail of the carbon steel strip and the rolling force for rolling the head of the silicon steel strip is shown in Table 4.

[0075] During the low-speed rolling process, the additional tension of the hot-rolled strip is 110% of the set tension.

[0076] After the connection weld exits the corresponding frame, the cone section of the working roll is moved 25 mm toward the rolling center line.

[0077] Table 4 Rack number S1 S2 S3 S4 S5 S6 Carbon steel rolling force-low speed (tons) 880 890 766 733 645 565 Silicon steel strip rolling force-low speed (tons) 1038 1028 881 762 760 669 Rolling force of weld (tons) 880 890 766 733 645 565 Rolling force difference △F1 (tons) 158 138 115 29 115 104 The difference in bending roll force between silicon steel and carbon steel △V1 (tons) 2.5 2.5 3.4 0.5 0.5 0.5

[0078] Example 3

[0079] In Example 3, the first coil of steel strip was silicon steel, and the second coil of steel strip was carbon steel. During the low-speed rolling (40 m / min) of the first and second coils, the rolling force applied to the tail of the silicon steel strip through stands S1 to S6 was 110-130% of the set rolling force for silicon steel. The rolling forces for each stand are shown in Table 5. The rolling force applied to the connecting weld through stands S1 to S6 was 110-130% of the set rolling force for carbon steel. The specific rolling forces for each stand are shown in Table 5. The rolling force applied to the head of the carbon steel strip through stands S1 to S6 was 110-130% of the set rolling force for carbon steel. The rolling forces for each stand are shown in Table 5. The difference ΔF1 between the rolling force applied to the tail of the first strip and the rolling force applied to the head of the second strip can be found in Table 5.

[0080] During the low-speed rolling process, the additional tension of the hot-rolled strip is 110% of the set tension.

[0081] After the weld seam is connected to the corresponding stand, move the cone section of the working roll 25mm away from the rolling center line, and increase the roll shifting value of the working roll and the intermediate roll of the stand.

[0082] Table 5

[0083] Table 6 Quality of the tail of the first strip and the head of the second strip

[0084] The method of dynamic specification change of cold rolling provided in Examples 1 to 3 did not cause strip breakage, improved rolling stability, no wave shape, good plate shape, no edge cracks, good appearance quality, the length of the strip steel with dynamic specification change is short, and the loss of hot-rolled coil length does not exceed 30m. Compared with the 100m loss of stopping the specification change, this application saves about 70 meters, further improving the yield rate.

[0085] The method for dynamic specification change of cold tandem rolling provided by the present application has at least the following advantages:

[0086] (1) Control the rolling force of the connecting weld when it passes through any stand of the cold rolling mill to be 110-130% of the set rolling force of the strip steel on the lower strength side passing through the corresponding stand, which can not only ensure the rolling stability but also shorten the rolling length of the strip steel in the variable specification range.

[0087] (2) Controlling the additional tension of the connecting weld and its vicinity further reduces the rolling force at low speed, reduces the difference in rolling force between low-speed rolling and high-speed stable rolling, improves the stability of the cold rolling process, avoids the edge crack defect problem caused by rolling steel with high strength and poor plasticity, and thus improves the quality of cold-rolled products.

[0088] (3) The bending roll force is compensated according to the strip width, and the bending roll force, rolling force and strip width are controlled to improve the strip shape accuracy.

[0089] (4) The roll shifting value in the transition area is set according to the roll shifting value of the wider strip, ensuring the stability of the variable specifications during cold rolling. The roll shifting value of the working roll and the intermediate roll when the connecting weld passes through the stand is controlled to ensure the strip shape.

[0090] (4) The method for dynamic gauge change in cold rolling provided by this application can ensure that the cold rolling mill does not experience drastic roll gap changes during dynamic gauge change, thereby achieving dynamic adjustment between two strips of different materials. Compared with the traditional method of starting rolling with raw plate due to the large difference in rolling characteristics between the first and second strips, this application does not require the cold rolling mill to be shut down, thereby improving production efficiency and yield rate.

[0091] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0092] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise" and "counterclockwise" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0093] In this application, unless otherwise specified or limited, the terms "connect," "fix," etc. should be understood broadly. For example, "fix" can mean fixed connection, detachable connection, or integration; it can mean mechanical connection or electrical connection; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0094] In addition, the terms "first," "second," and so on, used in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0095] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for dynamically changing gauges in cold tandem rolling, applicable to a first steel strip and a second steel strip sequentially connected by a connecting weld, wherein the first steel strip and the second steel strip are made of different materials, characterized in that: The method comprises: The first steel strip and the second steel strip are sequentially cold rolled through the cold rolling mill, wherein: The rolling force of the connecting weld when passing through any stand of the cold rolling mill is 110-130% of the set rolling force of the lower strength of the first and second strips passing through the corresponding stand; The tail of the first steel strip and the head of the second steel strip are rolled at a low speed of 30-80 m / min. During the low speed rolling process, the additional tension of the hot-rolled steel strip is 105-125% of the set tension.

2. The method for dynamic specification change of cold rolling according to claim 1, characterized in that: During the low-speed rolling process, the rolling force F of the stand where the hot-rolled strip is located, the bending force V of the working rolls, and the width W of the hot-rolled strip conform to the following relationship: V=a*W+b*F, where: the value range of a is -0.0001 to -0.01; the value range of b is 0.003 to 0.

027.

3. The method for dynamic specification change of cold rolling according to claim 2, characterized in that: The difference ΔV1 between the working roll bending force for rolling the first strip and the working roll bending force for rolling the second strip, and the difference ΔF1 between the rolling force when rolling the tail of the first strip and the rolling force when rolling the head of the second strip meet the following relationship: ΔV1=b*ΔF1.

4. The method for dynamic gauge changing of cold tandem rolling according to any one of claims 1 to 3, characterized in that: The speed of low-speed rolling of the tail of the first steel strip and the head of the second steel strip is 40 to 60 m / min.

5. The method for dynamic gauge changing of cold tandem rolling according to any one of claims 1 to 3, characterized in that: During the low-speed rolling process, the additional tension of the hot-rolled strip is 110-120% of the set tension.

6. The method for dynamic gauge changing of cold tandem rolling according to any one of claims 1 to 3, characterized in that: The tail of the first steel strip is 5 to 15 meters before the connecting weld, and the head of the second steel strip is 5 to 15 meters after the connecting weld.

7. The method for dynamic gauge changing of cold tandem rolling according to any one of claims 1 to 3, characterized in that: When the width of the first steel strip is greater than the width of the second steel strip, the tapered section of the working roll is moved toward the rolling center line after the connecting weld exits the cold rolling mill.

8. The method for dynamic gauge changing of cold tandem rolling according to any one of claims 1 to 3, characterized in that: When the width of the first steel strip is less than the width of the second steel strip, the tapered section of the working roll is moved away from the rolling center line before the connecting weld enters the cold rolling mill.

9. The method for dynamic gauge changing of cold tandem rolling according to any one of claims 1 to 3, characterized in that: The thickness of the hot-rolled steel strip is 1.5-3.0 mm. In the first steel strip and the second steel strip, the mass fraction of Si in one of the first steel strip and the second steel strip is ≥2.0%, and the mass fraction of Si in the other steel strip is <2.0%.

10. The method for dynamic gauge changing of cold tandem rolling according to any one of claims 1 to 3, characterized in that: The width difference between the first steel strip and the second steel strip is ≤240 mm.

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