Method for reducing side support mark defects on strip surface

Abstract

The present invention relates to the field of production quality control of stainless steel eighteen-roller five-stand emulsion cold rolling mill, and in particular to a method for removing side support print defects on the surface of strip steel of stainless steel emulsion cold rolling mill. The method for removing side support print defects on the surface of strip steel of stainless steel emulsion cold rolling mill comprises the following steps: step 1: the diameter difference of the side support rollers of the same stand is controlled to within 0.01 mm, so that the surface of each side support roller is evenly stressed during rolling; step 2: the roughness of the side support rollers is precisely controlled according to different steel grades; step 3: under different rolling speed conditions, the forward slip value of the stand is controlled by adjusting the emulsion concentration; step 4: the conductivity of the rinsing water in the degreasing section is controlled to 6.9-9.0 ms / cm, the conductivity of the brush washing machine water is controlled to 2.0-3.0 ms / cm, and the brush roller needs to be put into use normally. This method can eliminate defective products caused by side support bearing prints and reduce the production cost of stainless steel products.

Description

Technical Field

[0001] The invention relates to the field of production quality control of a stainless steel eighteen-roller five-stand emulsion cold tandem mill, and in particular to a method for reducing side support mark defects on a strip surface. Background Art

[0002] After the stainless steel strip is rolled to the finished thickness through the 5-stand emulsion continuous rolling mill, it passes through the processes of degreasing, annealing, pickling, leveling, etc. to become the finished stainless steel coil. However, due to the structural characteristics of the 18-roller rolling mill, when producing high-grade surface 304, 316, 430 and other steel grades, a side support bearing mark defect distributed along the longitudinal direction of the strip often appears on the strip surface, which seriously affects the surface quality of stainless steel products. This defect is caused by the back bearing of the lateral support of the 18-roller rolling mill being transmitted to the working roll through the side support roller and finally showing on the strip surface. This defect seriously restricts the improvement of the surface quality of stainless steel.

[0003] The cause of the side support bearing mark defect is the unavoidable design defect in the equipment structure itself. Before this application, there was no effective means to control the occurrence of such defects in the 18-roller cold rolling mill. It can only be solved by frequently replacing the working rolls and intermediate rolls. The disposal cost is high and a large number of defective products caused by the side support bearing marks will be produced.

[0004] Without changing the original design of the 18-roller 5-stand emulsion cold rolling mill, the present invention studies the diameter accuracy and roughness of the side support rolls and adjusts the process conditions of the pre-rolling slip value and the emulsion concentration, thereby completely solving the side support bearing mark defects produced on the surface of stainless steel produced by the cold rolling mill and ensuring high surface quality of the product. Summary of the invention

[0005] The purpose of the present invention is to provide a method for reducing the side support mark defects on the surface of the strip in view of the above problems.

[0006] The object of the present invention is achieved in this way: a method for reducing side support print defects on the surface of strip steel, comprising the following steps: step one: the diameter difference of the side support rollers of the same frame is controlled to within 0.01mm, so that the surface of each side support roller is evenly stressed during rolling; step two: the roughness of the side support rollers is accurately controlled according to different steel grades; step three: under different rolling speed conditions, the forward slip value of the frame is controlled by adjusting the emulsion concentration; step four: the conductivity of the degreasing section rinsing water is controlled at 6.9-9.0ms / cm, the conductivity of the brush washing machine water is controlled at 2.0-3.0ms / cm, and the brush rollers need to be put into use normally.

[0007] In step 2, the roughness of the side support roller is precisely controlled according to different steel grades. Specifically, the roughness of the side support roller of steel grade 304 is controlled to be 0.75-0.84, the roughness of the side support roller of steel grade 316 is controlled to be 0.85-0.94, and the roughness of the side support roller of steel grade 430 is controlled to be 0.95-1.05.

[0008] In step three, under different rolling speed conditions, the forward slip value of the frame is controlled by adjusting the emulsion concentration. Specifically, when the rolling speed V is less than 150 m / min, the emulsion concentration is 2.5-2.9%, when the rolling speed is 150 m / min≤V<300 m / min, the emulsion concentration is 3.0-3.4%, and when the rolling speed V≥300 m / min, the emulsion concentration is 3.5-4.5%.

[0009] In step 4, the conductivity of the rinsing water in the degreasing section is controlled at 6.9-9.0ms / cm, and the conductivity of the scrubbing water is controlled at 2.0-3.0ms / cm. Specifically, when the emulsion concentration is 2.5-2.9%, the conductivity of the rinsing water is 6.9-7.5ms / cm, and the conductivity of the scrubbing water is 2.0-2.3ms / cm; when the emulsion concentration is 3.0-3.5%, the conductivity of the rinsing water is 7.6-8.3ms / cm, and the conductivity of the scrubbing water is 2.4-2.7ms / cm; when the emulsion concentration is 3.5-4.5%, the conductivity of the rinsing water is 8.4-9.0ms / cm, and the conductivity of the scrubbing water is 2.7-3.0ms / cm.

[0010] The beneficial effects of the present invention are: the method can eliminate defective products caused by side support bearing marks, reduce the production cost of stainless steel products, reduce the labor intensity of on-site personnel, and improve product quality. The main economic benefits are calculated as follows:

[0011] The number of defective products caused by the side support bearing print is 5 rolls per month on average, and the average weight of each roll is 20 tons. The loss per ton is about 1,000 yuan. One roll will cause a loss of 20,000 yuan, and the loss can be reduced by 20,000*5*12=1.2 million yuan per year. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described below in conjunction with the accompanying drawings.

[0013] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0014] The present invention is specifically as follows:

[0015] 1. The diameter difference of the four side support rollers of the same frame is controlled within 0.01mm, so that the side support rollers are evenly stressed during rolling; to verify the effectiveness, three groups of reference tests were prepared, the diameters of the side supports 1, 2, and 3 in Group A are the same, and the diameter of the 4# roller is 0.02mm larger; the 1-3# rollers in Group B are the same as those in Group A, and the diameter of the 4# roller is 0.04mm larger; the 1-3# rollers in Group C are the same as those in Group A, and the diameter of the 4# roller is 0.06mm larger. Through on-site production test comparison, the side supports in Group A, which have the smallest diameter difference, are more evenly stressed.

[0016] Reducing the difference in side support dimensions can improve the force symmetry of the roller system. As can be seen from Table 1, with the change in size, the force on the side support with a larger roller diameter increases significantly, so the size of the side support roller needs to be standardized.

[0017]

[0018] 2.According to the different steel grades, the roughness of the side support roller is precisely controlled. The generation of the side support mark defect goes through three processes: the generation of the side support roller surface defect, the transmission of the side support roller surface defect, and the transmission of the working roller surface defect. Controlling the roughness of the side support roller is to reduce the generation of the side support roller surface defect from the source. There are two reasons for the generation of the side support roller surface mark defect. One is that the side support backing bearing and the side support roller rotate asynchronously, and the other is the lubrication and cooling conditions of the contact area between the side support backing bearing and the side support roller surface. Through on-site comparative tests, it is concluded that when the roughness of the side support roller is controlled at 0.7-1.2μ, the side support roller surface mark can be reduced. At the same time, different roughness gradient processes are developed for different steel grades, see Table 2. In view of the lubrication and cooling requirements of bearings at different speeds, a matching lubrication process is developed, see Table 3.

[0019]

[0020] 3. Under different rolling speeds (5-stand exit speed), the forward slip values ​​of the five stands were controlled separately by adjusting the emulsion concentration.

[0021]

[0022] 4. The conductivity of the rinsing water in the degreasing section is controlled at 7~9ms / cm, the conductivity of the scrubber water is controlled at 2~3ms / cm, and the brush roller needs to be put into use normally.

[0023]

[0024] By studying the diameter accuracy and roughness of the side support rollers and adjusting the process conditions of the pre-rolling slip value and emulsion concentration, the coordinated control of these aspects can completely solve the surface defects of the side support bearing marks produced during the continuous rolling of stainless steel cold strip. Example

[0025] When producing 430, the roughness of the side support roller is controlled to 0.98, the emulsion concentration is set to 3.3% when the outlet speed of the 5# frame is 265m / min, and the computer interface shows that the forward slip value of the 1-3 frame is 0.78, and the forward slip value of the 4-5 frame is 0.66. At the same time, the conductivity of the rinsing water in the degreasing rinsing section after the continuous rolling mill is set to 7.9 ms / cm, and the conductivity of the brushing water is set to 2.9 ms / cm. At this time, the strip is uniform and bright, without defects visible to the naked eye, and the surface quality is excellent. Example

[0026] When producing 304, the roughness of the side support roller is controlled to 0.77, the emulsion concentration is set to 2.8% when the outlet speed of the 5# frame is 175m / min, and the computer interface shows that the forward slip value of the 1-3 frame is 0.55, and the forward slip value of the 4-5 frame is 0.48. At the same time, the conductivity of the rinsing water in the degreasing rinsing section after the continuous rolling mill is set to 7.1 ms / cm, and the conductivity of the brushing water is set to 2.3 ms / cm. At this time, the strip is uniform and bright, without defects visible to the naked eye, and the surface quality is excellent.

[0027] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A method for reducing side support mark defects on the surface of a strip, characterized in that: The following steps are involved: Step 1: The diameter difference of the side support rollers of the same frame is controlled within 0.01mm, so that the side support roller surfaces are evenly stressed during rolling; Step 2: Accurately control the roughness of the side support roller according to different steel grades; Step 3: Under different rolling speed conditions, the forward slip value of the stand is controlled by adjusting the emulsion concentration; Step 4: The conductivity of the rinsing water in the degreasing section is controlled at 6.9-9.0ms / cm, the conductivity of the scrubber water is controlled at 2.0-3.0ms / cm, and the brush roller needs to be put into use normally; In step 2, the roughness of the side support roller is precisely controlled according to different steel grades. Specifically, the roughness of the side support roller of steel grade 304 is controlled to be 0.75-0.84, the roughness of the side support roller of steel grade 316 is controlled to be 0.85-0.94, and the roughness of the side support roller of steel grade 430 is controlled to be 0.95-1.05; In step 3, under different rolling speed conditions, the forward slip value of the stand is controlled by adjusting the emulsion concentration. Specifically, when the rolling speed V is less than 150 m / min, the emulsion concentration is 2.5-2.9%, when the rolling speed is 150 m / min≤V<300 m / min, the emulsion concentration is 3.0-3.4%, and when the rolling speed V≥300 m / min, the emulsion concentration is 3.5-4.5%; In step 4, the conductivity of the rinsing water in the degreasing section is controlled at 6.9-9.0ms / cm, and the conductivity of the scrubbing water is controlled at 2.0-3.0ms / cm. Specifically, when the emulsion concentration is 2.5-2.9%, the conductivity of the rinsing water is 6.9-7.5ms / cm, and the conductivity of the scrubbing water is 2.0-2.3ms / cm; when the emulsion concentration is 3.0-3.5%, the conductivity of the rinsing water is 7.6-8.3ms / cm, and the conductivity of the scrubbing water is 2.4-2.7ms / cm; when the emulsion concentration is 3.5-4.5%, the conductivity of the rinsing water is 8.4-9.0ms / cm, and the conductivity of the scrubbing water is 2.7-3.0ms / cm.

Images