A flatness control method for martensitic stainless steel

Abstract

The present invention belongs to the field of metallurgical steel rolling technology under the category of metallurgical science and technology, and specifically relates to a plate shape control method for martensitic stainless steel, comprising: increasing the target crown of the finishing mill in the finishing rolling process according to the thickness of the steel plate; increasing the coiling tension according to the principle that the smaller the thickness of the steel plate, the greater the coiling tension; and reducing the tension between the finishing mill stands. The plate shape control method for martensitic stainless steel of the present invention successfully solves the serious edge wave problem of martensitic stainless steel. During the subsequent rolling process, the plate shape reaches a normal control level, without obvious double-sided or single-sided wave shape. The martensitic stainless steel is directly cold-rolled without flattening, the plate shape quality is greatly improved, and the economic benefits are significant.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical steel rolling technology under the category of metallurgical science and technology, and particularly relates to a plate shape control method for martensitic stainless steel. Background Art

[0002] Equipment layout diagram of TISCO 1549 hot rolling production line Figure 1 As shown, the hot rolling line is divided into a furnace area, a roughing area, a finishing area, and a coiling area. The main production process of this hot rolling line is that the slab is first heated in a heating furnace according to the process temperature. After heating to the target temperature, it first enters the roughing mill for rolling. The roughing rolls control the width, and the flat rolls control the thickness. Reversible rolling is performed in the roughing mill, generally in 5 to 7 passes. After rolling in the roughing mill, the strip reaches the preset target thickness, width, and temperature. After that, it enters the finishing mill for seven-stand flat roll continuous rolling, bringing the strip to the preset target thickness and temperature. The strip then undergoes laminar cooling control to reach the target coiling temperature. Finally, the strip is formed into a coil by a coiler.

[0003] Martensitic stainless steel is a very special type of stainless steel with high strength, high hardness and corrosion resistance. It is widely used in steam turbines, medical equipment, cutting tools and other fields.

[0004] The production process of martensitic stainless steel in TISCO includes four steps: ironmaking, steelmaking, hot rolling and cold rolling. Starting from the hot rolling line, the detailed production process of martensitic stainless steel is as follows: Figure 2 shown.

[0005] In the martensite production process, compared with other steel grades, the most prominent problem is the flatness of martensite. The flatness of martensite is normally controlled during the hot rolling process, and the flatness test and observed flatness are also normal. However, there is an obvious rule: after the strip is cooled, during the cold rolling process, each coil has very serious edge waves (such as Figure 3A and 3B ), mainly double-sided waves, with unilateral waves in the middle. The wave height is generally above 80mm, and reaches more than 200mm in severe cases, resulting in frequent failures such as cold rolling speed reduction and belt breakage.

[0006] To address the severe edge wave problem of martensitic stainless steel after cooling, particularly the widespread double-sided wave, conventional shape improvement methods have been implemented in hot rolling, including targeted intermediate wave rolling and timely adjustment of single-sided wave. However, tracking the shape of the steel during the cold rolling process has yielded little substantial improvement. To ensure normal cold rolling, the following hot rolling improvement measures were implemented: After bell-type annealing, martensitic stainless steel must undergo a flattening process before it can be transferred to the cold rolling process. However, this additional process significantly increased the production cost of martensitic stainless steel and affected the flattening delivery time of other thin-gauge products. Summary of the Invention

[0007] The main purpose of the present invention is to solve the problem that the hot-rolled plate shape of martensitic stainless steel is normal but the cold-rolled plate shape after cooling is serious with wavy edges. In order to eliminate the influence of internal stress after cooling, a plate shape control method for martensitic stainless steel is provided.

[0008] Specifically, the plate shape control method for martensitic stainless steel of the present invention includes:

[0009] Increase the target crown of the finishing mill in the finishing process according to the thickness of the steel plate;

[0010] Increase the coiling tension based on the principle that the smaller the thickness of the steel plate, the greater the coiling tension;

[0011] Reduce the tension between the finishing mill stands.

[0012] In the above-mentioned flatness control method for martensitic stainless steel, the target convexity calculation method is as follows:

[0013] C40_new=C40×coff_p

[0014] Where C40_new is the target convexity, μm;

[0015] C40 is the original target convexity, μm;

[0016] coff_p is the convexity correction coefficient.

[0017] In the above-mentioned flatness control method for martensitic stainless steel, the range of the convexity correction coefficient is as follows:

[0018] Steel plate thickness (mm) Convexity correction coefficient coff_p [5.0,+∞) 1.1～1.3 [4.0,5.0) 1.3～1.5 [3.0,4.0) 1.5～1.7 (-∞,3.0) 1.7～2.1 .

[0019] In the above-mentioned flatness control method for martensitic stainless steel, the value range of the original target convexity is as follows:

[0020] Steel plate thickness (mm) Original target convexity C40 (μm) [5.0,+∞) 45 [4.0,5.0) 35 [3.0,4.0) 30 (-∞,3.0) 25 .

[0021] For the above-mentioned shape control method for martensitic stainless steel, the coiling tension calculation method is as follows:

[0022] cten_new=cten×coff_c

[0023] Where cten_new is the winding tension, N / mm 2 ;

[0024] cten is the original winding tension, N / mm 2 ;

[0025] coff_c is the winding tension correction coefficient.

[0026] In the above-mentioned shape control method for martensitic stainless steel, the value range of the coiling tension correction coefficient is as follows:

[0027] Steel plate thickness (mm) Winding tension correction coefficient coff_c [5.0,+∞) 1.30～1.32 [3.5,5.0) 1.32～1.38 (-∞,3.5) 1.38～1.40 .

[0028] In the above-mentioned shape control method for martensitic stainless steel, the value range of the original coiling tension is as follows:

[0029]

[0030]

[0031] In the above-mentioned plate shape control method for martensitic stainless steel, the finishing rolling process uses 7 stands to roll the martensitic stainless steel plate.

[0032] In the above-mentioned plate shape control method for martensitic stainless steel, the tension between the stands in the finishing rolling process is as follows:

[0033]

[0034] The technical solution of the present invention has the following beneficial effects:

[0035] The plate shape control method for martensitic stainless steel of the present invention successfully solves the serious edge wave problem of martensitic stainless steel. The plate shape reaches a normal control level during the subsequent rolling process, without obvious double-sided or single-sided wave plate shape. The martensitic stainless steel is directly cold-rolled without flattening, the plate shape quality is greatly improved, and the economic benefits are significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Various other advantages and benefits will become apparent to those skilled in the art by reading the following detailed description of the preferred embodiment.The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention.

[0037] Figure 1This is a schematic diagram of the TISCO 1549 hot rolling production line;

[0038] Figure 2 Schematic diagram of the detailed production process of martensitic stainless steel;

[0039] Figure 3A and Figure 3B This is a photo of the cold-rolled martensitic stainless steel plate before the implementation of the present invention;

[0040] Figure 4A and Figure 4B This is a photo of the cold-rolled martensitic stainless steel plate after the implementation of the present invention;

[0041] Explanation of symbols: 1 is a heating furnace (4 units); 2 is a high-pressure water descaling box; 3 is a roughing vertical roll mill (VE0); 4 is a roughing flat roll mill (R0); 5 is a heat preservation cover; 6 is a rotary drum shear; 7 is a finishing mill stand (7 additional stands); 8 is a convexity meter; 9 is a width gauge; 10 is a thickness gauge; 11 is a flatness meter; 12 is a laminar cooling unit; 13 is a coiler. DETAILED DESCRIPTION

[0042] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0043] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0044] The overall technical solution of this invention is to employ a flatness control method that utilizes high crown in the finishing mill, high tension between coiling and finishing, and low tension in the finishing stand. This method addresses the severe double-sided ripples caused by internal stress in the cold rolling process of martensitic stainless steel. By continuously adjusting parameters in actual production, the optimal flatness is ultimately achieved. This allows martensitic stainless steel to be directly cold-rolled without flattening, significantly improving flatness and achieving significant economic benefits.

[0045] The hot rolling control system adopts two-level computer control, namely the process control computer (L2 computer) control and the basic automation computer (L1) control. The control parameters involved in the technology of the present invention mainly include crown, coiling tension, and finishing tension. The control process is as follows:

[0046] S1: Determine parameters such as the target crown, coiling tension, and inter-stand tension in the finishing mill by the L2-level computer;

[0047] S2: Send the calculation results of the L2-level computer to the SDH module (setting proxy module) of the L1 computer in the form of a message;

[0048] S3: Establish a communication channel from the SDH to the relevant control modules of the L1;

[0049] S4: Read the message data value, transfer it to the drive system control block, and execute and control the specific parameters.

[0050] This invention mainly adjusts three parameters: the target crown of the finishing mill (i.e., the target crown of the finished product), the tension between coiling and finishing (referred to as coiling tension for short), and the inter-stand tension in the finishing mill (referred to as finishing tension for short), so as to improve or offset the internal stress after cooling and improve the strip shape after cooling.

[0051] Before the implementation of this invention, the original target crown, original coiling tension, and original inter-stand tension of martensitic stainless steel were determined by the following methods:

[0052] Original target crown

[0053] The original target crown of martensitic stainless steel is determined according to the thickness, as shown in Table 1.

[0054] Table 1 Original target crown of martensitic stainless steel

[0055] Steel plate thickness (mm) Original target convexity C40 (μm) [5.0,+∞) 45 [4.0,5.0) 35 [3.0,4.0) 30 (-∞,3.0) 25

[0056] It should be noted that the expression "[a, b)" appearing in Table 1 and subsequent tables means a ≤ thickness < b; "[c, +∞)" means c ≤ thickness; "(-∞, d)" means thickness < d.

[0057] The above crown refers to the C40 crown, and its specific meaning is:

[0058] C40 crown = thickness of the center line of the strip - average thickness at 40 mm from the edges on both sides.

[0059] All the rolls of the seventh finishing stand of the 1549 production line of Taiyuan Iron and Steel are plain rolls with original cambers. To achieve the target crown, during the rolling process, it mainly depends on the bending force of the seventh stand.

[0060] Original coiling tension

[0061] The coiling tension refers to the coiling unit tension (all coiling tensions in the full text refer to the coiling unit tension), that is, the coiling tension per unit area of the strip cross-section, denoted as cten. cten is determined according to the steel grade and thickness, as shown in Table 2.

[0062] Table 2 Original coiling tension of martensitic stainless steel

[0063]

[0064] Original finishing mill stand tension

[0065] The inter-stand tension of the finishing mill refers to the inter-stand unit tension (all inter-stand tensions in the whole text refer to inter-stand unit tension), that is, the tension of the strip per unit area of ​​the cross-section between stands, and is expressed as ten(i) (i represents the stand number, such as F0~F1 stands, i is 0, and then 1, 2, 3, 4, and 5 respectively). The inter-stand unit tension is determined according to the steel type and thickness, as shown in Table 3.

[0066] Table 3 Original tension between stands of finishing mill

[0067]

[0068]

[0069] The present invention is mainly aimed at a hot-rolled plate shape control method invented to solve the serious edge wave problem of martensitic stainless steel during the cold rolling process. The overall technical solution of the present invention is to adopt a plate shape control method with large crown of the finishing rolling unit, large tension in coiling, and small tension in finishing rolling. The specific technical solution includes three aspects.

[0070] Target convexity

[0071] The target convexity is increased to different degrees according to different thicknesses. It is determined specifically by the following method: based on the original target convexity, a martensitic stainless steel convexity correction coefficient is added, as shown in the following formula.

[0072] C40_new=C40×coff_p (1)

[0073] Where C40_new is the target convexity, μm;

[0074] C40 is the original target convexity, μm;

[0075] coff_p is the convexity correction coefficient.

[0076] Among them, the convexity correction coefficient is related to the thickness of the steel plate and is implemented according to Table 4.

[0077] Table 4 Martensitic stainless steel convexity correction coefficient coff_p

[0078] Steel plate thickness (mm) Convexity correction coefficient coff_p [5.0,+∞) 1.1～1.3 [4.0,5.0) 1.3～1.5 [3.0,4.0) 1.5～1.7 (-∞,3.0) 1.7～2.1

[0079] It should be noted that the expression "a~b" appearing in all tables of this patent means "a<index≤b", such as "1.1~1.3" in Table 4 means "1.1<convexity correction coefficient≤1.3".

[0080] Winding tension

[0081] The technical approach to determining coiling tension is to maximize coiling tension without causing excessive coiling current (i.e., excessive coiling current) to prevent scrap. Furthermore, considering the double-sided wave phenomenon that occurs during cold rolling, the thinner the strip, the more severe the double-sided wave. Therefore, the principle of increasing coiling tension is applied to thinner strips.

[0082] The specific method for determining the coiling tension is: based on the original coiling tension, add a martensitic stainless steel coiling tension correction coefficient, as shown in the following formula.

[0083] cten_new=cten×coff_c (2)

[0084] Where cten_new is the winding tension, N / mm 2 ;

[0085] cten is the original winding tension, N / mm 2 ;

[0086] coff_c is the winding tension correction coefficient.

[0087] Among them, the coiling tension correction coefficient is related to the thickness of the steel plate and is specifically implemented according to Table 5.

[0088] Table 5 Martensitic stainless steel coiling tension correction coefficient coff_c

[0089] Steel plate thickness (mm) Winding tension correction coefficient coff_c [5.0,+∞) 1.30～1.32 [3.5,5.0) 1.32～1.38 (-∞,3.5) 1.38～1.40

[0090] Tension between finishing mill stands

[0091] Prior to the implementation of this invention, the inter-stand tension in the finishing mill was controlled based on a high tension strategy. However, excessive tension can mask the actual double-sided or single-sided corrugation between the stands, making it difficult to detect when strip corrugation occurs between the stands. In particular, single-sided corrugation cannot be adjusted promptly during operation, resulting in a hidden corrugation. However, if the inter-stand tension is too low, it can also cause false sleeves between the stands, leading to scrap. After continuous testing and verification, the final inter-stand tension for the finishing mill is shown in Table 6.

[0092] Table 6 Tension between the finishing mill stands of the present invention

[0093]

[0094]

[0095] Compared with the existing technology, the newly invented martensitic stainless steel plate shape control method successfully solves the serious edge wave problem of martensitic stainless steel after cooling, especially the double-side wave problem. The edge wave height of the cold rolling process is reduced from more than 80mm to less than 15mm. There is no obvious double-side wave or single-side wave plate shape. Martensitic stainless steel can be directly cold-rolled without flattening, with significant economic benefits. The improved martensitic stainless steel cold rolling process plate shape is as follows Figure 4A and Figure 4B shown.

[0096] Example

[0097] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. In the following examples, the experimental methods without specific conditions are based on conventional methods and conditions.

[0098] Example 1:

[0099] This embodiment rolls 1CR13 stainless steel, steel coil number: 92A760001, steel grade: 12CR13; billet thickness 200mm, billet width 1240mm, rough rolling target thickness 35mm; finished strip target thickness 6.00mm, target width 1255mm.

[0100] The plate shape control parameters for this steel are as follows:

[0101] 1. Determine the target convexity

[0102] According to Table 1, the original target convexity is 45 μm.

[0103] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.2.

[0104] According to formula (1), the final target convexity is determined as:

[0105] C40_new=C40×coff_p=45×1.2=54(μm)

[0106] To achieve the target crown, the calculated bending roll forces (kN) for the finishing rolling mills F0 to F6 were 1305, 953, 890, 457, 315, 211, and 125, respectively. After rolling, the actual crown of this steel was 56.5 μm.

[0107] 2. Determine the winding tension.

[0108] According to Table 2, the original winding unit tension is 14.0N / mm 2 .

[0109] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.31.

[0110] According to formula (2), the final winding tension is determined as:

[0111] cten_new=cten×coff_c=14.0×1.31=18.34(N / mm 2 )

[0112] 3. Determine the tension between the finishing rolling stands

[0113] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 3.5; F1~F2: 5.5; F2~F3: 7.5; F3~F4: 10.5; F4~F5: 13.5; F5~F6: 15.5.

[0114] According to the above parameters, the plate shape of the coil during the cold rolling process is tracked, and basically no edge waves occur along the entire length, meeting the cold rolling production requirements.

[0115] Example 2:

[0116] This embodiment rolls 1CR13 stainless steel, steel coil number: 92A760101, steel grade: 12CR13; billet thickness 200mm, billet width 1220mm, rough rolling target thickness 35mm; finished strip target thickness 4.60mm, target width 1225mm.

[0117] The plate shape control parameters for this steel are as follows:

[0118] 1. Determine the target convexity

[0119] According to Table 1, the original target convexity is 35 μm.

[0120] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.38.

[0121] According to formula (1), the final target convexity is determined as:

[0122] C40_new=C40×coff_p=35×1.38=48.3(μm)

[0123] To achieve the target crown, the calculated bending roll forces (kN) for the finishing rolling mills F0 to F6 were 1536, 1011, 960, 516, 497, 302, and 157, respectively. After rolling, the actual crown of this steel was 48.9 μm.

[0124] 2. Determine the winding tension.

[0125] According to Table 2, the original winding unit tension is 16.0N / mm 2 .

[0126] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.34.

[0127] According to formula (2), the final winding tension is determined as:

[0128] cten_new=cten×coff_c=16.0×1.34=21.44(N / mm 2 )

[0129] 3. Determine the tension between the finishing rolling stands

[0130] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 4.3; F1~F2: 6.2; F2~F3: 8.4; F3~F4: 11.9; F4~F5: 14.4; F5~F6: 16.4.

[0131] According to the above parameters, the plate shape of the coil during the cold rolling process is tracked, and basically no edge waves occur along the entire length, meeting the cold rolling production requirements.

[0132] Example 3:

[0133] This embodiment rolls 1CR13 stainless steel, steel coil number: 92A760302, steel grade: 12CR13; billet thickness 200mm, billet width 1220mm, rough rolling target thickness 35mm; finished strip target thickness 3.50mm, target width 1225mm.

[0134] The plate shape control parameters for this steel are as follows:

[0135] 1. Determine the target convexity

[0136] According to Table 1, the original target convexity is 30 μm.

[0137] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.6.

[0138] According to formula (1), the final target convexity is determined as:

[0139] C40_new=C40×coff_p=30×1.6=48(μm)

[0140] To achieve the target crown, the calculated bending roll forces (kN) for the finishing rolling mills F0 to F6 were 1536, 1011, 960, 516, 497, 302, and 157, respectively. After rolling, the actual crown of this steel was 48.9 μm.

[0141] 2. Determine the winding tension.

[0142] According to Table 2, the original winding unit tension is 16.0N / mm 2 .

[0143] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.38.

[0144] According to formula (2), the final winding tension is determined as:

[0145] cten_new=cten×coff_c=16.0×1.38=22.08(N / mm 2 )

[0146] 3. Determine the tension between the finishing rolling stands

[0147] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 6.0; F1~F2: 7.0; F2~F3: 10.0; F3~F4: 14.0; F4~F5: 16.0; F5~F6: 19.0.

[0148] According to the above parameters, the plate shape of the coil in the cold rolling process is tracked. The full-length plate shape is normal, and the maximum double-sided wave height is 9mm, which meets the requirements of cold rolling production.

[0149] Example 4:

[0150] This embodiment rolls 1CR13 stainless steel, steel coil number: 92A760405, steel grade: 12CR13; billet thickness 200mm, billet width 1150mm, rough rolling target thickness 35mm; finished strip target thickness 2.95mm, target width 1175mm.

[0151] The plate shape control parameters for this steel are as follows:

[0152] 1. Determine the target convexity

[0153] According to Table 1, the original target convexity is 25 μm.

[0154] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is taken as 1.9.

[0155] According to formula (1), the final target convexity is determined as:

[0156] C40_new=C40×coff_p=25×1.8=45(μm)

[0157] To achieve the target crown, the calculated bending roll forces (kN) for the finishing mills F0 through F6 were 550, 723, 300, 211, 105, 97, and -56, respectively. After rolling, the actual crown of this steel was 46.1 μm.

[0158] 2. Determine the winding tension.

[0159] According to Table 2, the original winding unit tension is 18.0N / mm 2 .

[0160] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.39.

[0161] According to formula (2), the final winding tension is determined as:

[0162] cten_new=cten×coff_c=18.0×1.39=25.02(N / mm 2 )

[0163] 3. Determine the tension between the finishing rolling stands

[0164] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 7.0; F1~F2: 7.5; F2~F3: 10.5; F3~F4: 14.5; F4~F5: 16.5; F5~F6: 19.7.

[0165] According to the above parameters, the plate shape of the coil in the cold rolling process is tracked. The full-length plate shape is normal, and the maximum double-sided wave height is 8mm, which meets the requirements of cold rolling production.

[0166] Example 5:

[0167] This embodiment rolls 2CR13 stainless steel, steel coil number: 92A769801, steel grade: 20CR13; billet thickness 200mm, billet width 1240mm, rough rolling target thickness 35mm; finished strip target thickness 5.00mm, target width 1255mm.

[0168] The plate shape control parameters for this steel are as follows:

[0169] 1. Determine the target convexity

[0170] According to Table 1, the original target convexity is 45 μm.

[0171] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.3.

[0172] According to formula (1), the final target convexity is determined as:

[0173] C40_new=C40×coff_p=45×1.3=58.5(μm)

[0174] To achieve the target crown, the calculated values ​​of the bending roll force (KN) of each stand of the finishing rolling F0~F6 are: -134, -53, -93, -48, -122, -214, -101 respectively. After rolling, the actual crown of this steel piece is 57.3μm

[0175] 2. Determine the winding tension.

[0176] According to Table 2, the original winding unit tension is 15.0N / mm 2 .

[0177] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.32.

[0178] According to formula (2), the final winding tension is determined as:

[0179] cten_new=cten×coff_c=15.0×1.32=19.8(N / mm 2 )

[0180] 3. Determine the tension between the finishing rolling stands

[0181] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 4.0; F1~F2: 6.0; F2~F3: 8.0; F3~F4: 11.0; F4~F5: 14.0; F5~F6: 16.0.

[0182] According to the above parameters, the plate shape of the coil during the cold rolling process is tracked, and basically no edge waves occur along the entire length, meeting the cold rolling production requirements.

[0183] Example 6:

[0184] This embodiment rolls 2CR13 stainless steel, steel coil number: 92A769802, steel grade: 20CR13; billet thickness 200mm, billet width 1090mm, rough rolling target thickness 35mm; finished strip target thickness 4.50mm, target width 1115mm.

[0185] The plate shape control parameters for this steel are as follows:

[0186] 1. Determine the target convexity

[0187] According to Table 1, the original target convexity is 35 μm.

[0188] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.4.

[0189] According to formula (1), the final target convexity is determined as:

[0190] C40_new=C40×coff_p=35×1.4=49(μm)

[0191] To achieve the target crown, the calculated bending roll forces (kN) for the finishing rolling mills F0 to F6 were 1055, 1134, 869, 511, 302, 95, and 50, respectively. After rolling, the actual crown of this steel was 48.2 μm.

[0192] 2. Determine the winding tension.

[0193] According to Table 2, the original winding unit tension is 17.5N / mm 2 .

[0194] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.34.

[0195] According to formula (2), the final winding tension is determined as:

[0196] cten_new=cten×coff_c=17.5×1.34=23.45(N / mm 2 )

[0197] 3. Determine the tension between the finishing rolling stands

[0198] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 4.5; F1~F2: 6.2; F2~F3: 8.5; F3~F4: 12.0; F4~F5: 14.5; F5~F6: 16.5.

[0199] According to the above parameters, the plate shape of the coil during the cold rolling process is tracked, and basically no edge waves occur along the entire length, meeting the cold rolling production requirements.

[0200] Example 7:

[0201] This embodiment rolls 2CR13 stainless steel, steel coil number: 92A769901, steel grade: 20CR13; billet thickness 200mm, billet width 1090mm, rough rolling target thickness 35mm; finished strip target thickness 3.50mm, target width 1105mm.

[0202] The plate shape control parameters for this steel are as follows:

[0203] 1. Determine the target convexity

[0204] According to Table 1, the original target convexity is 30 μm.

[0205] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.6.

[0206] According to formula (1), the final target convexity is determined as:

[0207] C40_new=C40×coff_p=30×1.6=48(μm)

[0208] To achieve the target crown, the calculated bending roll forces (kN) for the finishing mills F0 to F6 were 521, 101, 65, -51, -203, -300, and -307, respectively. After rolling, the actual crown of this steel was 49.3 μm.

[0209] 2. Determine the winding tension.

[0210] According to Table 2, the original winding unit tension is 17.5N / mm 2 .

[0211] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.38.

[0212] According to formula (2), the final winding tension is determined as:

[0213] cten_new=cten×coff_c=17.5×1.38=24.15(N / mm 2 )

[0214] 3. Determine the tension between the finishing rolling stands

[0215] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 6.0; F1~F2: 7.0; F2~F3: 10.0; F3~F4: 14.0; F4~F5: 16.0; F5~F6: 19.0.

[0216] According to the above parameters, the plate shape of the coil in the cold rolling process is tracked. The full-length plate shape is normal, and the maximum double-sided wave height is 7mm, which meets the cold rolling production requirements.

[0217] Example 8:

[0218] This embodiment rolls 2CR13 stainless steel, steel coil number: 92A767103, steel grade: 20CR13; billet thickness 200mm, billet width 1070mm, rough rolling target thickness 35mm; finished strip target thickness 2.93mm, target width 1095mm.

[0219] The plate shape control parameters for this steel are as follows:

[0220] 1. Determine the target convexity

[0221] According to Table 1, the original target convexity is 25 μm.

[0222] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.9.

[0223] According to formula (1), the final target convexity is determined as:

[0224] C40_new=C40×coff_p=25×1.9=47.5(μm)

[0225] To achieve the target crown, the calculated bending force values ​​(kN) for each finishing stand were: -103, -205, 326, 207, 237, 102, and -258. After rolling, the actual crown of this steel was 48.5μm.

[0226] 2. Determine the winding tension.

[0227] According to Table 2, the original winding unit tension is 19.0N / mm 2 .

[0228] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.39.

[0229] According to formula (2), the final winding tension is determined as:

[0230] cten_new=cten×coff_c=19.0×1.39=26.41(N / mm 2 )

[0231] 3. Determine the tension between the finishing rolling stands

[0232] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 7.0; F1~F2: 7.5; F2~F3: 10.5; F3~F4: 14.5; F4~F5: 16.5; F5~F6: 19.7.

[0233] According to the above parameters, the plate shape of the coil in the cold rolling process is tracked. The full-length plate shape is normal, and the maximum double-sided wave height is 9mm, which meets the requirements of cold rolling production.

[0234] Example 9:

[0235] This embodiment rolls 3CR13 stainless steel, steel coil number: 92A692801, steel grade: 30CR13; billet thickness: 200 mm, billet width: 1240 mm, rough rolling target thickness: 35 mm; finished strip target thickness: 5.00 mm, target width: 1255 mm.

[0236] The plate shape control parameters for this steel are as follows:

[0237] 1. Determine the target convexity

[0238] According to Table 1, the original target convexity is 45 μm.

[0239] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.3.

[0240] According to formula (1), the final target convexity is determined as:

[0241] C40_new=C40×coff_p=45×1.3=58(μm)

[0242] To achieve the target crown, the calculated values ​​of bending roll force (KN) for each stand of finishing rolling F0~F6 are: 1026, 556, 238, 305, 135, 221, -106. After rolling, the actual crown of this steel is 59.7μm.

[0243] 2. Determine the winding tension.

[0244] According to Table 2, the original winding unit tension is 16.0N / mm 2 .

[0245] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.32.

[0246] According to formula (2), the final winding tension is determined as:

[0247] cten_new=cten×coff_c=16.0×1.32=21.12(N / mm 2 )

[0248] 3. Determine the tension between the finishing rolling stands

[0249] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 4.0; F1~F2: 6.0; F2~F3: 8.0; F3~F4: 12.0; F4~F5: 14.0; F5~F6: 16.5.

[0250] According to the above parameters, the plate shape of the coil during the cold rolling process is tracked, and basically no edge waves occur along the entire length, meeting the cold rolling production requirements.

[0251] Example 10:

[0252] This embodiment rolls 3CR13 stainless steel, steel coil number: 92A692902, steel grade: 30CR13; billet thickness 200mm, billet width 1090mm, rough rolling target thickness 35mm; finished strip target thickness 4.50mm, target width 1115mm.

[0253] The plate shape control parameters for this steel are as follows:

[0254] 1. Determine the target convexity

[0255] According to Table 1, the original target convexity is 35 μm.

[0256] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.4.

[0257] According to formula (1), the final target convexity is determined as:

[0258] C40_new=C40×coff_p=35×1.4=49(μm)

[0259] To achieve the target crown, the calculated bending roll forces (kN) for the finishing mills F0 to F6 were 375, 226, 697, 505, 233, 129, and -32, respectively. After rolling, the actual crown of this steel was 47.3 μm.

[0260] 2. Determine the winding tension.

[0261] According to Table 2, the original winding unit tension is 18.0N / mm 2 .

[0262] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.34.

[0263] According to formula (2), the final winding tension is determined as:

[0264] cten_new=cten×coff_c=18.0×1.34=24.12(N / mm 2 )

[0265] 3. Determine the tension between the finishing rolling stands

[0266] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 4.5; F1~F2: 6.5; F2~F3: 8.5; F3~F4: 11.5; F4~F5: 13.5; F5~F6: 17.0.

[0267] According to the above parameters, the plate shape of the coil during the cold rolling process is tracked, and basically no edge waves occur along the entire length, meeting the cold rolling production requirements.

[0268] Example 11:

[0269] This embodiment rolls 3CR13 stainless steel, steel coil number: 92A693001, steel grade: 30CR13; billet thickness: 200 mm, billet width: 1090 mm, rough rolling target thickness: 35 mm; finished strip target thickness: 3.50 mm, target width: 1105 mm.

[0270] The plate shape control parameters for this steel are as follows:

[0271] 1. Determine the target convexity

[0272] According to Table 1, the original target convexity is 30 μm.

[0273] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.6.

[0274] According to formula (1), the final target convexity is determined as:

[0275] C40_new=C40×coff_p=30×1.6=48(μm)

[0276] To achieve the target crown, the calculated bending roll forces (kN) for the finishing mills F0 through F6 were -103, 119, 356, 211, 315, -256, and -411, respectively. After rolling, the actual crown of this steel was 50.1 μm.

[0277] 2. Determine the winding tension.

[0278] According to Table 2, the original winding unit tension is 18.0N / mm 2 .

[0279] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.38.

[0280] According to formula (2), the final winding tension is determined as:

[0281] cten_new=cten×coff_c=18.0×1.38=24.84(N / mm 2 )

[0282] 3. Determine the tension between the finishing rolling stands

[0283] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 6.0; F1~F2: 8.0; F2~F3: 10.0; F3~F4: 14.0; F4~F5: 16.0; F5~F6: 19.0.

[0284] According to the above parameters, the plate shape of the coil in the cold rolling process is tracked. The full-length plate shape is normal, and the maximum double-sided wave height is 7mm, which meets the cold rolling production requirements.

[0285] Example 12:

[0286] This embodiment rolls 3CR13 stainless steel, steel coil number: 92A693103, steel grade: 30CR13; billet thickness: 200 mm, billet width: 1070 mm, rough rolling target thickness: 35 mm; finished strip target thickness: 2.95 mm, target width: 1095 mm.

[0287] The plate shape control parameters for this steel are as follows:

[0288] 1. Determine the target convexity

[0289] According to Table 1, the original target convexity is 25 μm.

[0290] According to Table 4, the convexity correction coefficient coff_p of martensitic stainless steel is 1.9.

[0291] According to formula (1), the final target convexity is determined as:

[0292] C40_new=C40×coff_p=25×1.9=47.5(μm)

[0293] To achieve the target crown, the calculated bending force values ​​(kN) for each finishing stand were: -399, -298, -156, 257, 239, -169, and -487. After rolling, the actual crown of this steel was 48.2μm.

[0294] 2. Determine the winding tension.

[0295] According to Table 2, the original winding unit tension is 20.0N / mm 2 .

[0296] According to Table 5, the coiling tension correction coefficient coff_c is taken as 1.39.

[0297] According to formula (2), the final winding tension is determined as:

[0298] cten_new=cten×coff_c=20.0×1.39=27.8(N / mm 2 )

[0299] 3. Determine the tension between the finishing rolling stands

[0300] According to Table 6, the unit tension between each stand of finishing rolling mill (N / mm 2 ) are: F0~F1: 7.0; F1~F2: 8.5; F2~F3: 10.7; F3~F4: 14.5; F4~F5: 16.7; F5~F6: 19.7.

[0301] According to the above parameters, the plate shape of the coil in the cold rolling process is tracked. The full-length plate shape is normal, and the maximum double-sided wave height is 9mm, which meets the requirements of cold rolling production.

[0302] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art will appreciate that these embodiments are intended only to illustrate the present invention and are not to be construed as limiting the scope of the present invention. It should be noted that any equivalent variations and substitutions to these embodiments are to be considered encompassed within the scope of the claims of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A method for controlling the flatness of martensitic stainless steel, characterized in that: Increase the target crown of the finishing mill in the finishing process according to the thickness of the steel plate; Increase the coiling tension based on the principle that the smaller the thickness of the steel plate, the greater the coiling tension; Reduce the tension between the finishing mill stands; The target convexity calculation method is as follows: Where, is the target convexity, μm; C40 is the original target convexity, μm; is the convexity correction coefficient; The value range of the convexity correction coefficient is as follows: ； The value range of the original target convexity is as follows: ； The winding tension calculation method is as follows: Where, is the winding tension, N / mm 2 ; cten is the original winding tension, N / mm 2 ; is the winding tension correction factor.

2. The method for controlling the shape of martensitic stainless steel according to claim 1, wherein: The value range of the winding tension correction coefficient is as follows: 。 3. The method for controlling the shape of martensitic stainless steel according to claim 1 or 2, characterized in that: The value range of the original winding tension is as follows: 。 4. The method for controlling the shape of martensitic stainless steel according to claim 1, wherein: The finishing rolling process uses 7 stands to roll the martensitic stainless steel plate.

5. The method for controlling the shape of martensitic stainless steel according to claim 4, characterized in that: The tension between the stands in the finishing rolling process is as follows: 。

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