Method for controlling C-shaped warping defect of eighteen-roller single-stand high-strength steel

Abstract

The invention discloses a method for controlling the C-shaped warping defect of eighteen-roller single-stand high-strength steel, and belongs to the technical field of solving the C-shaped warping defect of a steel plate. The method comprises the following steps: carrying out hot rolling, acid pickling and eighteen-roller reversible rolling on a descaled plate blank of a casting blank, the roller diameter difference between the upper roller diameter and the lower roller diameter of the middle roller of the eighteen-roller reversible rolling mill ranges from 2 mm to 5.5 mm, and the lower roller diameter is larger than the upper roller diameter. According to the method for controlling the C-shaped warping defect of the eighteen-roller single-stand high-strength steel, the roughness of the working rollers, the roller diameter difference of the middle rollers, the rolling force of the rolling mill and the strip steel tension are strictly controlled, the plate shape and stress problems in the rolling process are effectively controlled, and finally the warping height is controlled to be within the range of + / -(0.35-0.5) mm / m.

Description

Technical Field

[0001] The invention belongs to the technical field of solving the C-shaped warping defect of steel plates, and specifically is a method for controlling the C-shaped warping defect of high-strength steel with an eighteen-roller single frame. Background Art

[0002] The C-shaped warping defect is a plate shape defect in the width direction caused by the difference in deformation between the upper and lower surfaces of the high-strength strip during the production process of the 18-roll single-stand. When the upper surface of the strip extends more and the lower surface extends less, the strip will show a downward C-shaped warp; on the contrary, if the lower surface extends more, the strip will show an upward C-shaped warp. This defect is particularly common in the production of high-strength steel in the 18-roll single-stand, especially in products with a thickness of 0.2mm to 8mm. C-shaped warping not only affects the plate shape quality of the strip, but may also cause equipment damage and strip scratches during subsequent processing.

[0003] While ensuring that the product can be processed smoothly in subsequent steps, it is crucial to maintain a good plate shape of the strip. However, after reversible rolling under high pressure, C-shaped warping defects often occur in the strip. In response to this problem, CN201910505222.1 proposes a method for leveling semi-process electrical steel, which produces semi-process electrical steel plates by performing secondary cold rolling on annealed cold-hardened electrical steel plates on a leveling machine, and then performs straightening through a straightening machine to reduce the incidence of C-shaped warping defects. This method reduces defects by adjusting the leveling roller shape, and uses a straightening machine to make up for the shortcomings of the leveling machine. CN201110113728.1 provides a method for producing semi-process cold-rolled non-oriented electrical steel, which ensures the quality indicators of finished steel with small deformation through secondary leveling and light pressing processes, and then performs trimming and oiling treatment, while the present invention focuses on solving the process problems of products with large deformation. In addition, CN200610031808.1 provides a method for producing semi-process cold-rolled silicon steel by thin slab continuous casting and rolling process, which mainly adjusts the process of smelting and hot rolling, but does not involve the cold rolling process.

[0004] The present invention optimizes the roller diameter ratio, surface roughness and segmented control of inlet and outlet tension by conducting extensive process tests on products of different specifications. Through these optimization measures, C-shaped warping defects can be effectively controlled. Summary of the invention

[0005] The present invention overcomes the above technical problems and provides a method for controlling the C-shaped warping defect of high-strength steel of an 18-roll single stand. The method can effectively control the C-shaped warping by exploring the rolling process of the 18-roll single stand.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The present invention provides a method for controlling C-shaped warping defects of high-strength steel, comprising the following steps: hot rolling, pickling and eighteen-roll reversible rolling of the descaled slab;

[0008] The roller diameter difference between the upper roller diameter and the lower roller diameter of the intermediate roller of the 18-roller reversible rolling mill is 2-5.5 mm, preferably 2-5 mm; wherein the lower roller diameter is greater than the upper roller diameter.

[0009] In some preferred embodiments, the ingot comprises the following chemical components in mass percentage: [C] = 0.62-0.7%, [Mn] = 0.90-1.2%, [P] ≤ 0.035%, [Si] = 0.17-0.37%, [S] ≤ 0.035%.

[0010] In some preferred embodiments, the thickness of the ingot is 220-250 mm.

[0011] In some preferred embodiments, the width of the casting billet is 900-2100 mm.

[0012] In some preferred embodiments, the hot rolling is performed by 5 to 7 hot rolling mills, and the reduction of F1 of each hot rolling mill is 40 to 65%, the reduction of F2 is 40 to 65%, and the reduction of F7 is 10 to 30%.

[0013] In some preferred embodiments, the temperature of the slab entering the furnace during hot rolling is ≥ 900°C, preferably 900-1250°C.

[0014] In some preferred embodiments, the edge temperature of the slab during hot rolling is ≥ 900°C, preferably 900-1000°C, wherein the edge of the slab refers to the portion of the slab within 10-20 cm from the width edges of both sides.

[0015] In some preferred embodiments, the hot rolling start temperature is 1020-1250°C; the hot rolling finish temperature is 780-930°C.

[0016] In some preferred embodiments, the coiling temperature of the hot rolling is 580-720°C.

[0017] In some preferred embodiments, the pickling method is turbulent hydrochloric acid pickling; wherein the concentration of hydrochloric acid used for pickling is 80-120 g / L; and the pickling line speed is 120-160 m / min.

[0018] In some preferred embodiments, the eighteen-roll reversible rolling is performed for 4 to 7 passes, wherein the last pass uses a textured working roll and the remaining passes use smooth rolls;

[0019] For example, the eighteen-roll reversible rolling is performed in four passes, wherein the last pass uses a roughened working roll and the first three passes use smooth rolls.

[0020] In some preferred embodiments, the rolling force of the eighteen-roll reversible rolling mill is 600 to 1200 tons.

[0021] In some preferred embodiments, the tension of the strip steel during the 18-roll reversible rolling is 5 to 20 N / mm. 2 .

[0022] In some preferred embodiments, the roughness of the optical roller is 0.6-1.0 μm.

[0023] In some preferred embodiments, the roughness of the textured working roller is 2.0-3.0 μm.

[0024] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention can more effectively control the plate shape and stress distribution during the rolling process by precisely controlling the upper and lower roller diameters of the intermediate rollers in the 18-roller reversible rolling. By controlling the number of passes of the 18-roller reversible rolling and using a combination of a roughened work roller and a smooth roller, as well as regulating the roughness of the smooth roller and the roughened work roller, the surface quality of the strip can be improved and surface defects can be reduced. Precisely controlling the tension of the strip and the rolling force of the rolling mill helps to reduce stress concentration and poor plate shape during the rolling process. Thus, the adjustment of the above parameters effectively reduces C-shaped warping defects.

[0027] 2. By adjusting the reduction of the hot rolling unit and controlling the slab's furnace entry temperature, edge temperature, start rolling temperature, final rolling temperature and coiling temperature, the rolling quality can be improved and defects generated during the hot rolling process can be reduced.

[0028] 3. The method for controlling the C-shaped warping defect of the eighteen-roll single-frame high-strength steel of the present invention can effectively control the warping height of the C-shaped warping defect within ±0.5 mm / m. In some preferred embodiments, the warping height is within ±(0.35~0.5) mm / m. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an apparent image of the C-shaped warping of the high-strength steel plate prepared in Example 1.

[0030] Figure 2 This is the C-shaped warping appearance picture of the high-strength steel plate prepared in Comparative Example 1. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0033] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] If not otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0035] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0036] If not otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0038] If not specifically stated, in the present invention, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0039] Example 1

[0040] Calculated by mass percentage, the composition of the ingot is [Si]=0.22%, [Mn]=0.98%, [P]≤0.03%, [S]≤0.03%, [C]=0.65%, and the remainder is iron and unavoidable impurities.

[0041] The thickness of the ingot is 232 mm and the width of the ingot is 1220 mm.

[0042] The slab obtained after descaling the ingot is hot rolled, pickled and rolled by 18-roll reversible rolling to obtain the finished steel;

[0043] (1) Hot rolling: the slab furnace temperature is 920°C, the start rolling temperature is 1060°C, the final rolling temperature is 880°C, and the coiling temperature is 610°C;

[0044] The edge temperature of the slab is 910°C; the edge of the slab refers to the portion of the slab within a range of 10 to 20 cm from the width edges of both sides.

[0045] The hot rolling is carried out by 7 hot rolling units; among them, the reduction of F1 of each unit is 45%, the reduction of F2 is 42%, and the reduction of F7 is 23%.

[0046] (2) Pickling: The pickling method is turbulent hydrochloric acid pickling; the concentration of hydrochloric acid used for pickling is 90g / L, and the pickling line speed is 135m / min.

[0047] (3) Eighteen-roller reversible rolling: Eighteen-roller reversible rolling is performed in four passes, wherein the first three passes use smooth rolls and the last pass uses a roughened working roll;

[0048] The tension of the strip is 12N / mm 2 ;

[0049] The rolling force of the rolling mill is 1100 tons;

[0050] The roller diameter difference between the upper roller diameter and the lower roller diameter of the middle roller is 4mm, wherein the lower roller diameter is greater than the upper roller diameter;

[0051] The roughness of the smooth roller is 0.95 μm;

[0052] The roughness of the last pass of texturing work roll is 2.5μm;

[0053] The thickness of the steel coil after eighteen-roll reversible rolling is 2.3mm and the weight of the steel coil is 28 tons.

[0054] Figure 1 This is an apparent diagram of the C-shaped warping of the high-strength steel plate after eighteen-roll reversible rolling in this embodiment.

[0055] Example 2

[0056] The difference between this embodiment and embodiment 1 is that:

[0057] The roller diameter difference between the upper roller diameter and the lower roller diameter of the middle roller is 3.5mm;

[0058] The rolling force of the working roll is 1020 tons;

[0059] The unit tension of the strip steel rolled by 18 rolls reversible rolling is 18N / mm 2 .

[0060] The steel coil after 18-roll reversible rolling weighs 26.5 tons;

[0061] Other steps and parameters are the same as in Example 1.

[0062] Example 3

[0063] The difference between this embodiment and embodiment 1 is that:

[0064] The roller diameter difference between the upper roller diameter and the lower roller diameter of the middle roller is 4.2mm;

[0065] The rolling force of the working roll is 1020 tons;

[0066] The unit tension of the strip steel rolled by 18 rolls reversible rolling is 18N / mm 2 ;

[0067] The thickness of the steel coil after eighteen-roll reversible rolling is 1.5mm and the weight of the steel coil is 27 tons.

[0068] Other steps and parameters are the same as in Example 1.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is:

[0071] The roughness of the last pass of texturing work roll is 2.0 μm;

[0072] The difference between the upper and lower roller diameters of the middle roller is 6mm;

[0073] The rolling force of the working roll is 1020 tons;

[0074] The unit tension of the strip steel rolled by 18 rolls reversible rolling is 18N / mm 2 ;

[0075] The thickness of the steel coil after eighteen-roll reversible rolling is 1.5mm and the weight of the steel coil is 25 tons.

[0076] Other steps and parameters are the same as in Example 1.

[0077] Figure 2 This is the appearance diagram of the C-shaped warping of the high-strength steel plate after 18-roll reversible rolling in this comparative example.

[0078] Test Case

[0079] The warpage height test method of the C warpage in the above embodiments and comparative examples is tested with reference to the platform detection method of YB / T6021-2022, and the test results are shown in Table 1. The unit of the warpage height mm / m represents the change in the bending height of the material per meter of length, and when the value is positive, the C warpage is upward, and when the value is negative, the C warpage is downward.

[0080] Table 1

[0081]

[0082]

[0083] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods. The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel, characterized in that: The following steps are involved: The descaled slab is hot rolled, pickled and rolled using eighteen rolls in a reversible manner; The roller diameter difference between the upper roller diameter and the lower roller diameter of the intermediate roller of the eighteen-roller reversible rolling is 2 to 5.5 mm; wherein the lower roller diameter is greater than the upper roller diameter.

2. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 1, characterized in that: The ingot includes the following chemical components in mass percentage: [C]=0.62-0.7%, [Mn]=0.90-1.2%, [P]≤0.035%, [Si]=0.17-0.37%, [S]≤0.035%.

3. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 1, characterized in that: The thickness of the ingot is 220-250 mm; And / or, the width of the ingot is 900-2100 mm.

4. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 1, characterized in that: The hot rolling is performed by 5 to 7 hot rolling mills, and the reduction of F1 of each hot rolling mill is 40 to 65%, the reduction of F2 is 40 to 65%, and the reduction of F7 is 10 to 30%.

5. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 4, characterized in that: The furnace temperature of the slab during hot rolling is ≥900°C; And / or, the edge temperature of the slab during hot rolling is ≥900°C, wherein the edge of the slab refers to the portion of the slab within 10 to 20 cm from the width edges of both sides; And / or, the hot rolling start temperature is 1020-1250°C, and the hot rolling finish temperature is 780-930°C; And / or, the coiling temperature of the hot rolling is 580-720°C.

6. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 1, characterized in that: The pickling method is turbulent hydrochloric acid pickling.

7. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 6, characterized in that: The concentration of hydrochloric acid used for pickling is 80-120 g / L; And / or, the pickling line speed is 120 to 160 m / min.

8. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 1, characterized in that: The eighteen-roller reversible rolling is performed in 4 to 7 passes, wherein the last pass uses a roughened working roll and the remaining passes use smooth rolls.

9. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 8, characterized in that: The tension of the strip steel in the 18-roller reversible rolling is 5 to 20 N / mm 2 ; And / or, the rolling force of the eighteen-roll reversible rolling mill is 600 to 1200 tons.

10. The method for controlling the C-shaped warping defect of 18-roller single-stand high-strength steel according to claim 8, characterized in that: The roughness of the smooth roller is 0.6-1.0 μm; And / or, the roughness of the textured working roll is 2.0-3.0 μm.

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