Method for improving double-strand folding control

Abstract

The invention discloses a method for improving double-strand folding control, which comprises the following steps of: (1) controlling the size of a blank, and increasing the width of a rolled piece by 50mm when the broadening ratio is greater than or equal to 1.5; when the broadening ratio is smaller than 1.5, the width of the rolled piece is increased by 20 mm; rolling a plate with the thickness greater than or equal to 50mm, and adding 50mm to the head and the tail of a rolled Rolling a plate with the thickness of less than 50mm, and adding 60mm to the head and the tail of the rolled piece; (3) inspection: (1) measuring the width before cutting, if the width is insufficient due to double-strand folding, contacting an operator to confirm, and moving a cutter after confirmation; and (2) coloring four corners of the steel plate after double edges of the steel plate are cut off, checking whether cracks exist or not, performing uniform cutting after ruler placement according to sampling technical requirements, and timely contacting an operator to perform field confirmation if the cracks are found, so that the rolling plate shape and the size accuracy are accurately controlled by optimizing the rolling process and controlling the multi-pass PPO plane shape, and the quality of the steel plate is improved. In the cutting process, whether double-strand folding of the cutting face is cut clean is checked, four vertex angles are subjected to dye penetrant inspection, and the steel plate yield is effectively increased.

Description

Technical Field

[0001] The invention relates to a control method, in particular to a method for improving double-strand folding control, and belongs to the technical field of metallurgical processing. Background Art

[0002] With the increase in demand for orders for wide and thick plates, and the expansion of production at the No. 0 continuous casting machine, the billet thickness has expanded from 260-320mm to 370-460mm, expanding the product variety and specifications of the wide and thick plate rolling mill. The billet specifications have gradually expanded, and the large aspect ratio production (aspect ratio ≥1.5) of thick-gauge billets (usually refers to slabs or flat billets with a thickness of ≥50mm) is a key technology for the manufacture of wide and thick plates, special alloys and high-end structural materials. At present, this field has made important progress in technology, equipment and materials, but still faces many challenges.

[0003] At present, when thick-gauge billets are used to produce products with large aspect ratios, the coordination of the aspect ratio and the extension ratio is not within a reasonable range, resulting in excessive deviations in the head, tail and middle convexity of the thick plate rolled plate, with the maximum exceeding 60mm. The amount of trimming increases, seriously affecting the yield rate.

[0004] Therefore, developing a method for improving the double-strand folding control that can overcome the above defects has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to propose a method for improving the control of double-strand folding in view of the shortcomings of the above-mentioned existing technologies. By optimizing the rolling process and performing multi-pass PPO plane shape control, the rolled plate shape and dimensional accuracy are precisely controlled. During the cutting process, the double-strand folding of the cutting surface is checked to see if it is cut cleanly. The four top corners are subjected to color flaw detection inspection, thereby effectively improving the yield rate of the steel plate.

[0006] The technical solution of the present invention to solve the above technical problems is: A method for improving double-strand folding control, comprising the following steps: (1) Control the size of the blank When the width ratio is ≥1.5, the width of the rolled piece shall be increased by 30-60mm; When the design width ratio is less than 1.5, the width of the rolled piece shall be increased by 20-50mm; For plates with a thickness of ≥50mm, add 50-80mm to the head and tail of the rolled piece; For plates with a thickness less than 50mm, add 60-90mm to the head and tail of the rolled piece; (2) Optimization of rolling process During rolling, the heating temperature is 1150±20℃, the soaking time is ≥55.2min, the heating time is 414-736min, the temperature uniformity is <15℃, and the temperature difference between the head and tail of the slab is <15℃; (3)Inspection ① Before the oxy-fuel cutting operator starts cutting, measure the width. If it is found that the width is insufficient due to double-strand folding, immediately contact the operator to confirm on-site. Only after confirmation can the cutting knife be operated; ② After bilateral cutting of the steel plate, color the four corners of the steel plate to check for cracks. After placing the ruler according to the sampling technical requirements, cut evenly. If cracks are found, immediately contact the operator to confirm on-site.

[0007] The further limited technical solution of the present invention is: Further, in the method for improving the control of double-strand folding described above, when controlling the ruler placement of the billet in step (1), when the spreading ratio ≥ 1.5, add 40 mm to the ruler placement of the rolled piece width; when the spreading ratio < 1.5, add 20 mm to the ruler placement of the rolled piece width; for plates with a rolling thickness ≥ 50 mm, add 50 mm to the ruler placement at the head and tail of the rolled piece; for plates with a rolling thickness < 50 mm, add 60 mm to the ruler placement at the head and tail of the rolled piece.

[0008] In the method for improving the control of double-strand folding described above, when inspecting in step (3), color the four corners of the steel plate with a penetrant and a solvent-suspended wet developer. The specific coloring steps are as follows: ① Penetration: Spray the penetrant using a nozzle on the detection range at the four corners of the steel plate. The distance between the nozzle and the inspected surface is 20 - 30 mm, and the spraying direction should form an angle of 30° - 40° with the detection part. The penetration time of the penetrant ≥ 10 min; ② Cleaning: First, wipe successively with a dry, clean, non-shedding cloth until most of the excess penetrant is removed, and then wipe with a clean non-shedding cloth or paper dipped in the cleaning agent until all is wiped clean; however, it should be noted that there should be no reciprocating wiping, and the cleaning agent should not be directly rinsed on the inspected surface; ③ Imaging: Spray with a solvent-suspended developer. After the inspected surface is naturally dried at room temperature, shake the beads in the spray can before spraying to make the developer uniform. The distance between the nozzle and the detection part is 300 - 400 mm, and the spraying direction should form an angle of 30° - 40° with the detection surface. Note that the application of the developer should be thin and uniform, and the imaging time ≥ 7 min, then dry; ④ Observation and recording: The evaluation of defect display is carried out under white light. The white light illumination at the inspected surface of the workpiece ≥ 1000 lx, and then detect.

[0009] When using existing portable equipment for on-site detection and the visible light illumination decreases, add an auxiliary light source. A magnifying glass with a magnification of 5 - 10 times can be used to observe when identifying small displays.

[0010] In the method for improving the control of double-strand folding described above, the detection range is the detection area and 25 mm on each side.

[0011] In the method for improving the control of double-strand folding described above, in step ③, drying is carried out by natural drying or blowing dry with warm air at 30℃ - 50℃.

[0012] The beneficial effects of the present invention are: At present, when thick-gauge billets with large width ratio are produced, there is a concave shape in the middle of the length and width directions of the plate. The middle concave shape is not cut cleanly and cracks appear at the corners. The present invention optimizes the rolling process, such as the billet setting of the zero-number machine, the rolling control pass, and the rolling model. By developing multi-pass PPO plane shape control technology, the rolled plate shape and dimensional accuracy are accurately controlled. The cutting process checks whether the double-strand folding of the cutting surface is cut cleanly, and the four top corners are inspected by color flaw detection to improve the yield rate of the steel plate.

[0013] The present invention optimizes the rolling process, controls the heating temperature and the steel-outlet temperature according to the middle and upper limits, prolongs the soaking time, improves the temperature uniformity, and makes the force in the thickness direction of the billet uniform during rolling on the upper and lower surfaces of the billet and the thickness center of the slab, thereby reducing the occurrence of double strands due to the different elongation caused by the force deviation in the width direction caused by the temperature difference between the middle position of the billet and the upper and lower surfaces.

[0014] The present invention strictly limits the nozzle to 20-30 mm from the inspected surface, and the angle between the spray direction and the inspection site should be 30°-40°, ensuring that the inspection site is completely covered by the penetrant and remains moist during the entire penetration time.

[0015] This invention increases the width of the blank of the zero-type machine by 30-60mm to ensure the size control. After the implementation of this project, all the increased width is recovered; (2) the yield rate is increased by 0.5%, the monthly output is 61,000 tons, the cost per ton of steel is reduced by 7 yuan, and the annual benefit is 5.124 million yuan; (3) the incidence of insufficient width of the steel plate at the head and tail is reduced by 60%, the annual occurrence volume is 1,224 tons, the unplanned loss per ton of steel is 1,200 yuan, and the annual benefit is 881,000 yuan. DETAILED DESCRIPTION Example 1

[0016] This embodiment takes Q390GJCZ25 as an example, with a billet size of 460*2570*4210 mm and a rolled product size of 60*2520*14900 mm, to provide a method for improving double-strand folding control, specifically comprising the following steps: (1) Control the size of the blank If the width ratio is greater than 1.5, the width of the rolled piece is increased by 50mm. The original target width of the rolled piece is 2610mm, and the current width is 2660mm. For plates with a thickness of ≥50mm, add 50mm to the length of the rolled piece at the head and tail; For plates with a thickness less than 50mm, add 60mm to the length of the rolled piece at the head and tail; (2) Optimization of rolling process During rolling, the heating temperature is 1150-1170℃, the soaking time is ≥55.2min, the heating time does not exceed 736min before steel is tapped, the heating time is 414-736min, the temperature uniformity is <15℃, and the temperature difference between the head and tail of the slab is <15℃; (3) Inspection ① The flame cutter should measure the width before cutting. If it is found that the width is insufficient due to double folding, the operator should be contacted for on-site confirmation in time. The cutter can only be used after confirmation. ② After the steel plate is cut on both sides, color the four corners of the steel plate to check for cracks. Cut evenly after setting the ruler according to the sampling technical requirements. If cracks are found, contact the operator for on-site confirmation in time; During coloring, penetrants and solvent-suspended wet developers are used. The penetrants, solvent-suspended developers, and cleaning agents used during coloring are all currently available on the market. The specific coloring steps are as follows: ① Penetration: Use a nozzle to spray the penetrant on the test area of the four corners of the steel plate, i.e. the test area and 25mm on both sides. The nozzle should be 20-30mm away from the tested surface. The spray direction should be at an angle of 30°-40° to the test area. The penetrant duration should be ≥10min. ② Cleaning: First wipe with a dry, clean, lint-free cloth until most of the excess penetrant is removed, then wipe with a clean, lint-free cloth or paper dipped in detergent until it is completely wiped clean; but be careful not to wipe back and forth, and do not use detergent to rinse directly on the surface to be inspected ③ Development: Use solvent-suspended developer for spraying. After the inspected surface is naturally dried at room temperature, shake the beads in the spray can before spraying to make the developer evenly distributed. The distance between the nozzle and the inspection part should be 300-400mm. The angle between the spraying direction and the inspection surface should be 30°-40°. Note that the developer should be applied thinly and evenly. The development time should be ≥7 minutes. Use natural drying or blow-dry with warm air at 30℃-50℃. ④ Observation and Recording: Defect indications are assessed under white light, with the workpiece surface to be inspected maintaining an illumination level of ≥10001x. When using portable equipment for on-site inspection, auxiliary lighting should be added if visible light illumination decreases. A 5-10x magnifying glass can be used for observation to identify subtle details. This invention is primarily applied to the problem of central depressions in the rough edge of thick plate during the rolling process in steel production. This method addresses the issue of central depressions hindering dimensional cutting of steel plates, improves plate shape precision, and increases yield by over 10.25%. Thick plate mills using this method have effectively controlled double-strand folding defects in flame-cut four-sided plate with a thickness of ≥80mm. To date, no double-strand folding defects have occurred, demonstrating significant results.

[0017] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for improving double-strand folding control, characterized in that: The specific steps include: (1) Control the size of the blank When the width ratio is ≥1.5, the width of the rolled piece shall be increased by 30-60mm; When the design width ratio is less than 1.5, the width of the rolled piece shall be increased by 20-50mm; For plates with a thickness of ≥50mm, add 50-80mm to the head and tail of the rolled piece; For plates with a thickness less than 50mm, add 60-90mm to the head and tail of the rolled piece; (2) Optimization of rolling process During rolling, the heating temperature is 1150±20℃, the soaking time is ≥55.2min, the heating time is 414-736min, the temperature uniformity is <15℃, and the temperature difference between the head and tail of the slab is <15℃; (3) Inspection ① The fire cutter should measure the width before cutting. If it is found that the width is insufficient due to double folding, the operator should be contacted for on-site confirmation in time. Only after confirmation can the cutter be used; ② After the steel plate is cut on both sides, color the four corners of the steel plate and check for cracks. Cut evenly after placing a ruler according to the sampling technical requirements. If cracks are found, contact the operator for on-site confirmation in time.

2. The method for improving the double-strand folding control according to claim 1, wherein: In the step (1), when the width ratio of the blank is controlled, the width of the rolled piece is increased by 40 mm when the width ratio is ≥1.5; the width of the rolled piece is increased by 20 mm when the width ratio is <1.5; for plates with a rolling thickness of ≥50 mm, the width of the rolled piece is increased by 50 mm at the head and tail; for plates with a rolling thickness of <50 mm, the width of the rolled piece is increased by 60 mm at the head and tail.

3. The method for improving the double-strand folding control according to claim 1, wherein: During the inspection in step (3), the four corners of the steel plate are stained with a penetrant and a solvent-suspended wet developer. The specific staining steps are as follows: ① Penetration: Use a nozzle to spray the penetrant on the inspection range of the four corners of the steel plate. The nozzle should be 20-30mm away from the inspected surface. The spray direction should be at an angle of 30°-40° to the inspection area. The duration of the penetrant should be ≥10min. ② Cleaning: First wipe with a dry, clean, lint-free cloth, then wipe with a clean, lint-free cloth or paper dipped in detergent until it is completely clean; ③ Development: Use solvent-suspended developer for spraying. After the inspected surface is naturally dried at room temperature, shake the beads in the spray can before spraying to make the developer evenly distributed. The distance between the nozzle and the inspection part should be 300-400mm. The angle between the spraying direction and the inspection surface should be 30°-40°. The development time should be ≥7min and then dried. ④Observation record: The evaluation of defect display is carried out under white light, and the white light illumination at the inspected surface of the workpiece is ≥10001x, and then the inspection is carried out.

4. The method for improving double-strand folding control according to claim 3, wherein: The detection range is the detection area and 25mm on both sides.

5. The method for improving double-strand folding control according to claim 3, wherein: The drying in step ③ is carried out by natural drying or drying with warm air at 30°C-50°C.