A method for eliminating back bearing marks on a twenty-high rolling mill

Abstract

The present invention relates to a technology for improving the quality of cold-rolled steel strip produced by a twenty-high mill. Specifically, it relates to a method for eliminating backing bearing marks on the surface of steel strip produced by a twenty-high mill, thereby simultaneously increasing the service life and operating rate of the second intermediate roll. The method for eliminating backing bearing marks on a twenty-high mill comprises the following steps: (1) designing the backing bearing roll profile; (2) implementing a roll system roughness matching technique; and (3) improving the lubrication performance of an emulsion. After implementation of the present invention, the backing bearing mark defect on the steel plate surface is completely eliminated, and the replacement cycle of the second intermediate roll is increased by 40% compared to before implementation.

Description

Technical Field

[0001] The present invention relates to a technology for improving the quality of cold-rolled strip steel of a twenty-high rolling mill, and specifically relates to a method for eliminating backing bearing marks on the surface of the strip steel of a twenty-high rolling mill, while improving the service life and operating rate of two intermediate rollers. Background Art

[0002] The rolls of the twenty-high Sendzimir mill are arranged symmetrically in a "1-2-3-4" tower configuration. The first tier consists of the working rolls, which contact the strip; the second, third, and fourth tiers are the first and second intermediate rolls, respectively; and the fourth tier consists of the support rolls, installed in the plum-shaped bores of the rolling mill arch. The backing bearing, saddle, and mandrel form a single unit, known as the support rolls.

[0003] Currently, high-end silicon steel is rolled domestically using the Sendzimir mill. The main products rolled are high-magnetic induction oriented silicon steel and ultra-high-grade non-oriented silicon steel. Due to the high silicon content of the rolled products, high-temperature normalization, and high reduction ratios per pass, rolling pressures can reach up to 800 tons. Under high loads, the contact area between the backup roll backing bearing and the second intermediate roll forms depressions due to wear from high-speed rolling and high pressure. The contact area between the second intermediate roll and the backup roll backing bearing and the non-contact area differs due to varying degrees of wear, resulting in distinct zones of varying diameters. These zones on the second intermediate roll body, passing through the first intermediate roll and work rolls, ultimately create a band-like color difference on the steel plate surface, alternating between light and dark, with consistent spacing, aligned with the rolling direction. To mitigate backing bearing marking, the only approach is to reduce the service life of the second intermediate roll by 30% and the first intermediate roll by 25%. However, this is not a complete solution, resulting in high production costs, poor quality, and limited market competitiveness.

[0004] The 20-roll Sendzimir mill, due to the high hardness and strength of the rolled product and its high rolling speed, achieves an actual rolling pressure of 600-800 tons. Because the backing bearings of the support rolls are arranged alternately, they intermittently act on the two intermediate rolls, forming a tactile backing bearing mark on the two intermediate rolls. This mark is ultimately transmitted to the steel plate surface via the first intermediate roll and the working roll, resulting in a regular, indelible backing bearing mark defect consistent with the rolling direction. The present invention designs and develops a new backing bearing roller profile with a tapered edge. Simultaneously, a process technology is designed to optimize the roughness of the backing bearing and the first and second intermediate rolls, resolving the issue of backing bearing mark defects on the strip surface. This completely eliminates backing bearing marks on the steel plate surface, significantly reducing the defective product rate. The service life of the two intermediate rolls is increased by over 25%, reducing roll wear and the number of roll changes, thereby improving operating efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for eliminating the backing bearing mark of a twenty-high rolling mill in response to the above problems.

[0006] The object of the present invention is achieved as follows: A method for eliminating the backing bearing mark of a twenty-high rolling mill, comprising the following steps: (1) backing bearing roller shape design: a taper is designed on both sides of the outer cylindrical plane of the bearing, the taper length is a=10~25mm, and the taper height is a transition section of b=0.05~0.3mm, so that a transition zone is formed at the contact point between the edge of the bearing and the two intermediate rollers to avoid stress concentration at the contact edge; (2) roller system roughness matching technology: the backing bearing roughness is controlled between 0.1~0.3μm, the surface roughness of the two intermediate rollers is also controlled between 0.15~0.4μm, and the surface roughness of the first intermediate roller is selected to be 0.25~0.5μm; (3) emulsion lubrication performance improvement: the emulsion concentration is controlled between 4%~7%, the iron powder content in the emulsion is controlled between 80~200ppm, the emulsion saponification value is controlled between 100~180mgKOH / g, and the emulsion particle size is controlled between 3~9μm.

[0007] The backing bearing roller grinding described in (1) is as follows: the entire grinding process includes four processes: rough grinding, semi-finishing grinding, fine grinding, and polishing grinding, and the total grinding amount is controlled between 0.25 and 0.4 mm; rough grinding is to control the grinding amount and the basic roller curve; rough grinding is divided into 8 to 12 passes, and the feed amount per pass is 0.025 to 0.04 mm; semi-finishing grinding is divided into 3 to 7 passes, and the feed amount per pass is 0.001 to 0.005 mm; fine grinding is divided into 2 to 4 passes, and the feed amount per pass is 0.001 to 0.003 mm; polishing is divided into 1 to 2 passes, and the feed amount is 0.

[0008] (2) The surface roughness of the middle backing bearing is ≤ the surface roughness of the second intermediate roller ≤ the surface roughness of the first intermediate roller.

[0009] The beneficial effects of the present invention are as follows: 1. After the implementation of the present invention, the bearing mark defect on the backing of the steel plate surface is completely solved. 2. After the implementation of the present invention, the replacement cycle of the second intermediate roller is increased by 40% compared with before the implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be further described below in conjunction with the accompanying drawings.

[0011] Figure 1 It is a curve diagram of the outer cylindrical roller shape of the support roller backing bearing described in the present invention.

[0012] a: Cone length of the transition cone at the edge of the backing bearing; b: Cone height of the transition cone at the edge of the backing bearing; R4: Chamfer of the backing bearing edge; L: Total width of the backing bearing.

[0013] Note: The above curve is the roller curve of the support roller backing bearing. The present invention adds transition cones on both sides of the backing bearing to reduce the stress concentration and friction concentration problems caused by the contact between the bearing edge and the two middle parts.

[0014] Figure 2This is a diagram explaining the causes of back bearing marks.

[0015] 1. Saddle, 2. Mandrel, 3. Backing bearing, 4. Second intermediate roller, 5. First intermediate roller, 6. Working roller, 7. Strip steel.

[0016] Explanation: The figure above is a schematic diagram of the roll system configuration of a 20-high mill. The dashed boxes show the two intermediate rolls, the first intermediate roll, and the work rolls corresponding to the backup roll backing bearings. Within the dashed box, the contact areas between the two intermediate rolls and the backing bearings wear under the high rolling pressure and high speed, forming "depressions" (within the dashed box). Outside the dashed box, the areas of the two intermediate rolls not in contact with the backing bearings become "protrusions" as rolling progresses, with a distinct demarcation line between the "depressions" and "protrusions." The two intermediate rolls contact the first intermediate roll, and the "depressions" and "protrusions" on the roll bodies of the two intermediate rolls exert uneven forces on the first intermediate roll. The "protrusions" exert greater forces on the first intermediate roll, resulting in greater wear; the "depressions" exert less forces on the first intermediate roll, resulting in less wear. Similarly, the first intermediate roll contacts the work roll, and the work roll contacts the steel plate, ultimately forming regular backing bearing marks on the steel plate surface. DETAILED DESCRIPTION

[0017] With the development of society and the progress of science and technology, the upgrading and innovation of materials are getting faster and faster. The twenty-high mill is responsible for the production of high-difficulty and high-precision products for cold-rolled strip steel. Taking electrical silicon steel as an example, high-precision and advanced products are all rolled on the twenty-high mill. In recent years, with the improvement of the technical quality requirements of non-oriented electrical steel for electric vehicles and oriented electrical steel for transformers, the silicon content of electrical steel is getting higher and higher, the hardness is getting higher and higher, and the rolling force is getting higher and higher, which increases the force between the roller systems. The backing bearing print defect not only affects the product quality, increases the frequency of roller replacement, but also has a great impact on production efficiency. The present invention mainly starts from the mechanism of backing bearing print generation, and solves the backing bearing print defect by implementing backing bearing roller shape technology, roller system roughness matching technology and improving the lubricity of emulsion.

[0018] 1. Design and application of new roller-shaped technology for backing bearings

[0019] When the original backing bearing was ground, the roller profile was a straight line. Under high-pressure, high-speed rolling and wear, the contact surface between the second intermediate roller and the bearing formed a depression, resulting in a "Great Wall" mark on the roller surface. This mark was eventually reflected on the steel plate surface, forming a backing bearing mark defect.

[0020] According to the bearing stress characteristics, tapers are designed on both sides of the outer cylindrical plane of the bearing, with a taper length of a=10~25mm and a taper height of b=0.05~0.3mm as a transition section. This forms a transition zone at the contact point between the bearing edge and the two intermediate rollers to avoid stress concentration at the contact edge.

[0021] The innovation of the above-mentioned backing bearing roller grinding is that the difficulty of the specific grinding process is to overcome the difficulty of using a 30mm~40mm wide grinding wheel to grind the taper at a position of 10~25mm on the edge of the bearing. According to the normal program design, it is impossible to grind. The specific innovative grinding process is described as follows: (1) During grinding, the designed workpiece width is 30~70mm larger than the actual workpiece width. (2) The entire grinding process includes four processes: rough grinding, semi-finishing grinding, fine grinding, and polishing. (3) The total grinding amount is controlled between 0.25~0.4mm. Among them: rough grinding is mainly to control the grinding amount and the basic roller curve. Rough grinding is divided into 8~12 passes, and the feed amount per pass is about 0.025~0.04mm. Semi-finishing grinding is divided into 3~7 passes, and the feed amount per pass is 0.001~0.005mm. Fine grinding is divided into 2~4 passes, and the feed amount per pass is 0.001~0.003mm. Polishing is divided into 1~2 passes with a feed rate of 0.

[0022] 2. Roller roughness matching technology

[0023] The surface roughness of the support roller backing bearing and the second intermediate roller is large. Under the conditions of high rolling pressure and high-speed rolling, the contact part between the second intermediate roller and the backing bearing is severely worn, which is another major reason for the depression of the contact part.

[0024] To address these issues, the roller system roughness was optimized. The backing bearing surface roughness was controlled between 0.1 and 0.3 μm, the second intermediate roller surface roughness was also controlled between 0.15 and 0.4 μm, and the first intermediate roller surface roughness was selected to be between 0.25 and 0.5 μm. Specifically, the backing bearing surface roughness was ≤ the second intermediate roller surface roughness ≤ the first intermediate roller surface roughness.

[0025] 3. Improved lubrication performance of emulsion

[0026] To further reduce wear between rollers, the lubrication properties of the emulsion were enhanced. The following improvements were made to the emulsion's various parameters: emulsion concentration was controlled between 4% and 7%, iron powder content was controlled between 80 and 200 ppm, saponification value was controlled between 100 and 180 mgKOH / g, and particle size was controlled between 3 and 9 μm.

[0027] Example 1

[0028] This invention uses the Mitsubishi Hitachi 21-type 20-high rolling mill as an example. Its backup roll backing bearing has a diameter of 406.4 mm and a width of 171 mm. The two intermediate rolls have a nominal diameter of 235 mm, the first intermediate roll has a nominal diameter of 138 mm, and the work rolls have a nominal diameter of 80 mm. The products produced primarily include thin-gauge, ultra-high-grade non-oriented silicon steel and high-magnetic-induction oriented silicon steel. The two intermediate rolls serve as drive rolls, achieving a maximum rolling speed of 1000 m / min and a maximum rolling pressure of 1080 tons.

[0029] 1. Backing bearing taper design

[0030] The taper design standards for both sides of the bearing are: cone length a is 20mm, and cone height b is 0.2mm.

[0031] The grinding method is:

[0032] ① The grinding wheel used for grinding the backing bearing is 40mm wide and made of green silicon carbide with a grit size of 100. When setting the grinding wheel, the workpiece width is 50mm larger than the actual width, that is, the workpiece width is set to 221mm.

[0033] ②The grinding program is designed as shown in the table below.

[0034] 2. Specific design of roller roughness

[0035] ① The surface roughness of the backing bearing is selected to be 0.25μm.

[0036] ② The surface roughness of the second intermediate roller is selected to be 0.3μm.

[0037] ② The surface roughness of the intermediate roller is selected to be 0.35μm.

[0038] 3. Design of emulsion indicators

[0039] ①The emulsion concentration is controlled at 5±0.5%.

[0040] ②The iron powder content in the emulsion is controlled at 150±10ppm.

[0041] ③The saponification value of the emulsion is controlled between 120~150mgKOH / g.

[0042] ④The particle size of the emulsion is controlled to be 5.5±0.5μm.

[0043] This specific implementation is only the best example and is not a limitative implementation of the technical solution of the present invention.

[0044] Example 2

[0045] Taking the ZR22B52 20-high rolling mill as an example, the backup roll backing bearing has a diameter of 300.2 mm and a width of 172 mm. The two intermediate rolls have a nominal diameter of 172 mm, the first intermediate roll has a nominal diameter of 102 mm, and the work rolls have a nominal diameter of 63.5 mm. The products produced are primarily thin-gauge, ultra-high-grade non-oriented silicon steel and high-magnetic-induction oriented silicon steel. The two intermediate rolls serve as drive rolls, with a maximum rolling speed of 800 m / min and a maximum rolling pressure of 820 tons.

[0046] 1. Backing bearing taper design

[0047] The taper design standards for both sides of the bearing are: cone length a is 18mm, and cone height b is 0.15mm.

[0048] The grinding method is:

[0049] ① The grinding wheel used for grinding the backing bearing is 30mm wide and made of green silicon carbide with a grit size of 80. When setting the grinding wheel, the workpiece width is 40mm larger than the actual width, that is, the workpiece width is set to 212mm.

[0050] ②The grinding program is designed as shown in the table below.

[0051]

[0052] 2. Specific design of roller roughness

[0053] ① The surface roughness of the backing bearing is selected to be 0.3μm.

[0054] ② The surface roughness of the second intermediate roller is selected to be 0.35μm.

[0055] ② The surface roughness of the intermediate roller is selected to be 0.35μm.

[0056] 3. Design of emulsion indicators

[0057] ①The emulsion concentration is controlled at 4.5±0.5%.

[0058] ②The iron powder content in the emulsion is controlled at 110±10ppm.

[0059] ③The saponification value of the emulsion is controlled between 100~150mgKOH / g.

[0060] ④The particle size of the emulsion is controlled to 4±0.5μm.

[0061] This specific implementation is only the best example and is not a limitative implementation of the technical solution of the present invention.

[0062] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by any technician in this field within the scope of the present invention are included in the patent scope of the present invention.

Claims

1. A method for eliminating backing bearing marks of a twenty-high rolling mill, characterized in that: The following steps are involved: (1) Backing bearing roller shape design: tapers are designed on both sides of the outer cylindrical plane of the bearing, with a taper length of a = 10 ~ 25 mm and a taper height of b = 0.05 ~ 0.3 mm, so that a transition zone is formed at the contact between the bearing edge and the two intermediate rollers to avoid stress concentration at the contact edge; (2) Roller roughness matching technology: the backing bearing roughness is controlled between 0.1~0.3μm, the surface roughness of the second intermediate roller is also controlled between 0.15~0.4μm, and the surface roughness of the first intermediate roller is selected to be 0.25~0.5μm; (3) Improvement of emulsion lubrication performance: emulsion concentration is controlled between 4% and 7%, iron powder content in emulsion is controlled between 80 and 200 ppm, saponification value of emulsion is controlled between 100 and 180 mgKOH / g, and particle size of emulsion is controlled between 3 and 9 μm; The backing bearing roller grinding described in (1) is as follows: the entire grinding process includes four processes: rough grinding, semi-finishing grinding, fine grinding, and polishing grinding, and the total grinding amount is controlled between 0.25 and 0.4 mm; rough grinding is to control the grinding amount and the basic roller profile curve; rough grinding is divided into 8 to 12 passes, and the feed amount per pass is 0.025 to 0.04 mm; semi-finishing grinding is divided into 3 to 7 passes, and the feed amount per pass is 0.001 to 0.005 mm; fine grinding is divided into 2 to 4 passes, and the feed amount per pass is 0.001 to 0.003 mm; polishing is divided into 1 to 2 passes, and the feed amount is 0; (2) The surface roughness of the middle backing bearing is ≤ the surface roughness of the second intermediate roller ≤ the surface roughness of the first intermediate roller.

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