A method for improving the shape of a very thick plate

Abstract

The application discloses a method for improving the plate shape of a super-thick plate, and relates to the technical field of steel rolling, and comprises the following steps: controlling the tapping temperature of a heat treatment process to be 1080-1160 DEG C, and the temperature uniformity of a blank to be less than or equal to 50 DEG C; controlling the width of a rolling blank to be less than the rolling width, and controlling the blank spread ratio to be 1.05-1.20; adjusting the blank reduction amount system; adjusting the blank flattening system; adjusting the water spraying process of the steel plate; placing the plate with a thickness greater than 130 mm on a slow cooling rack to be slowly cooled, and controlling the lower limit of the piling and cooling temperature to be 500-750 DEG C. The heating, rolling, cooling and piling and cooling processes of the super-thick steel plate are optimized, the occurrence rate of buckling is effectively reduced, the actual quality of the steel plate is improved, and the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel rolling, in particular to a method for improving the plate shape of a heavy plate. BACKGROUND

[0002] For the heavy plate of common structure, die steel and other conventional rolling, due to the thick thickness of the steel plate, slow temperature drop, fewer rolling passes, small reduction, limited plate shape optimization measures, the plate shape of the steel plate is poor, and the initial rolling plate shape qualified rate is only 38%. SUMMARY

[0003] The present application relates to the technical field of steel rolling, in particular to a method for improving the plate shape of a heavy plate.

[0004] In order to solve the above technical problems, the technical scheme of the present application is as follows:

[0005] A method for improving the plate shape of a heavy plate, comprising:

[0006] The tapping temperature of the heating process is controlled to be 1080-1160℃, and the temperature uniformity of the billet is less than or equal to 50℃;

[0007] The width of the rolling billet is controlled to be less than the rolling width, and the billet spread ratio is controlled to be 1.05-1.20;

[0008] When the rolling thickness is greater than or equal to 350mm, the pass reduction is controlled to be less than or equal to 20mm; when the rolling thickness is less than 350mm, the reduction of the first 3-5 passes before rough rolling is greater than or equal to 35mm, and the reduction of the remaining passes is less than or equal to 20mm;

[0009] When the length of the rolling piece is less than or equal to 4850mm, three times of 90° transverse leveling are carried out, and the leveling force is set to be 500-1200 tons; when the length of the rolling piece is greater than 4850mm and less than 6500mm, two times of 30° inclined leveling are carried out, and the leveling force is set to be 500-1000 tons, and then one time of longitudinal leveling is carried out; when the length of the rolling piece is greater than or equal to 6500mm, three times of longitudinal leveling are carried out, and the leveling force is set to be 500-800 tons;

[0010] When the thickness of the plate piece is greater than 350mm, the re-red temperature is controlled to be 710±40℃; when the thickness of the plate piece is greater than 250mm and less than or equal to 350mm, the re-red temperature is controlled to be 730±40℃; when the thickness of the plate piece is greater than 150mm and less than or equal to 250mm, the re-red temperature is controlled to be 750±40℃; when the thickness of the plate piece is greater than 130mm and less than or equal to 150mm, the re-red temperature is controlled to be 770±40℃;

[0011] The plate with thickness greater than 130 mm is placed on the slow cooling rack to be slowly cooled, and the lower limit of the stack cooling temperature is controlled to be 500-750℃.

[0012] As a preferred scheme of the method for improving the plate shape of the heavy plate according to the application, before the tapping temperature of the controlled heating process is 1080-1160℃ and the temperature uniformity of the blank is less than or equal to 50℃, the method further comprises:

[0013] The slabs with the stack cooling time of 0-2h, the stack cooling time of 2-8h and the stack cooling time greater than 8h are respectively concentrated into the furnace, and the charging temperature is 500-650℃.

[0014] As a preferred scheme of the method for improving the plate shape of the heavy plate according to the application, when the tapping temperature of the controlled heating process is 1080-1160℃ and the temperature uniformity of the blank is less than or equal to 50℃, the method further comprises:

[0015] The temperature of the lower surface of the blank is controlled to be higher than the temperature of the upper surface by 20℃.

[0016] As a preferred scheme of the method for improving the plate shape of the heavy plate according to the application, when the length of the rolled piece is less than 4850mm, the roll gap is set to be the thickness of the steel plate +3.0-6.0mm; when the length of the rolled piece is greater than 4850mm and less than 6500mm, the roll gap is set to be the thickness of the steel plate +2.0-4.5mm; and when the length of the rolled piece is greater than or equal to 6500mm, the roll gap is set to be the thickness of the steel plate +2.0-4.0mm.

[0017] As a preferred scheme of the method for improving the plate shape of the heavy plate according to the application, when the thickness of the plate is greater than 350mm, the re-red temperature is controlled to be 710±40℃; when the thickness of the plate is greater than 250mm and less than or equal to 350mm, the re-red temperature is controlled to be 730±40℃; when the thickness of the plate is greater than 150mm and less than or equal to 250mm, the re-red temperature is controlled to be 750±40℃; and when the thickness of the plate is greater than 130mm and less than or equal to 150mm, the re-red temperature is controlled to be 770±40℃, and the method further comprises:

[0018] The water ratio of the water spraying process is controlled to be 1.40-1.55.

[0019] As a preferred scheme of the method for improving the plate shape of the heavy plate according to the application, the stack cooling time of the plate is greater than or equal to 96h.

[0020] The beneficial effects of the application are:

[0021] The present application optimizes the heating, rolling, cooling and stack cooling process of the heavy steel plate, effectively reduces the occurrence rate of buckling, improves the physical quality of the steel plate and reduces the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 The flowchart of the method for improving the plate shape of the heavy plate provided by the present application. DETAILED DESCRIPTION

[0024] In order to make the content of the present application more easily understood, the present application will be further described in detail according to the specific embodiments and in combination with the drawings.

[0025] Figure 1 The flowchart of the method for improving the plate shape of the heavy plate provided by the present application. The method is mainly improved from the heating process, rolling process, water pouring process and stack cooling process. Specifically, the following steps are included:

[0026] Step S101: The slabs with stack cooling time of 0-2h, stack cooling time of 2-8h and stack cooling time greater than 8h are respectively concentrated into the furnace, and the charging temperature is 500-650℃.

[0027] Specifically, the heavy plate slabs with stack cooling time of 0-2h are concentrated into the furnace, the heavy plate slabs with stack cooling time of 2-8h are concentrated into the furnace, and the heavy plate slabs with stack cooling time greater than 8h are concentrated into the furnace.

[0028] Step S102: The temperature of the slab is controlled to be 1080-1160℃, and the temperature uniformity of the slab is less than or equal to 50℃.

[0029] Specifically, after the slab is charged into the furnace, the furnace temperature of the heating furnace soaking section is set to 1200℃, the three-addition furnace temperature is set to 1220℃, the two-addition furnace temperature is set to 1180℃, and the one-addition furnace temperature is set to 900℃. The temperature of the slab is controlled to be 1080-1160℃, and the temperature uniformity of the slab is less than or equal to 50℃.

[0030] At the same time, in order to improve the original lying head plate shape of the slab, the lower surface temperature is controlled to be slightly higher than the upper surface temperature during the heating process.

[0031] In the embodiment, the temperature of the lower surface of the blank is controlled to be 20℃ higher than the temperature of the upper surface.

[0032] Step S103: The width of the rolling blank is controlled to be less than the rolling width, and the spreading ratio of the blank is controlled to be 1.05-1.20.

[0033] Specifically, when the rolling process is performed, the blank needs to be designed. Specifically, when the thickness of the rolled product is greater than or equal to 250mm, a blank with a cross-sectional thickness of 460mm is used. The rest of the rolling specifications prefer to ensure a double compression ratio to obtain sufficient rolling pass amount, thereby improving the plate shape.

[0034] At the same time, the width of the blank is controlled to be slightly less than the rolling width, and the spreading ratio of the blank is controlled to be 1.05-1.20 to increase the transverse spreading pass and improve the transverse plate shape.

[0035] Step S104: When the rolling thickness is greater than or equal to 350mm, the pass reduction amount is controlled to be less than or equal to 20mm; when the rolling thickness is less than 350mm, the reduction amount of the first 3-5 passes before rough rolling is greater than or equal to 35mm, and the reduction amount of the remaining passes is less than or equal to 20mm.

[0036] Specifically, the above reduction amount system is used as the reduction amount system of the rolling process, that is, for the blank with a rolling thickness greater than or equal to 350mm, small reduction amount rolling is adopted, and the pass reduction amount is controlled to be less than or equal to 20mm. For the blank with a rolling thickness less than 350mm, a large reduction amount is used first, and then a small reduction amount is used. The pass reduction amount of the first 3-5 passes before rough rolling is greater than or equal to 35mm, and the reduction amount of the remaining passes is less than or equal to 20mm.

[0037] Step S105: When the rolling piece length is less than or equal to 4850mm, three times of 90° transverse leveling is performed, and the leveling force is set to 500-1200 tons; when the rolling piece length is greater than 4850mm and less than 6500mm, two times of 30° oblique leveling is performed, and the leveling force is set to 500-1000 tons, and then one time of longitudinal leveling is performed; when the rolling piece length is greater than or equal to 6500mm, three times of longitudinal leveling is performed, and the leveling force is set to 500-800 tons.

[0038] Specifically, the above-mentioned leveling system is adopted as the leveling system for the rolling process. When the length of the rolled piece is less than or equal to 4850 mm, three 90° transverse leveling operations are performed, with the roll gap set to the steel plate thickness + 3.0-6.0 mm and the leveling force set to 500-1200 tons. When the length of the rolled piece is greater than 4850 mm but less than 6500 mm, two 30° oblique leveling operations are performed, with the roll gap set to the steel plate thickness + 2.0-4.5 mm and the leveling force set to 500-1000 tons. Then, a longitudinal leveling operation is performed, following the original roll gap setting, i.e., the roll gap is set to the steel plate thickness + 2.0-4.5 mm. When the length of the rolled piece is greater than or equal to 6500 mm, three longitudinal leveling operations are performed, with the roll gap set to the steel plate thickness + 2.0-4.0 mm and the leveling force set to 500-800 tons.

[0039] Understandably, the number of leveling operations may be increased depending on the shape of the slab on site.

[0040] Step S106: When the plate thickness is greater than 350mm, control the red glow temperature to 710±40℃; when the plate thickness is greater than 250mm and less than or equal to 350mm, control the red glow temperature to 730±40℃; when the plate thickness is greater than 150mm and less than or equal to 250mm, control the red glow temperature to 750±40℃; when the plate thickness is greater than 130mm and less than or equal to 150mm, control the red glow temperature to 770±40℃.

[0041] Specifically, to reduce thermal warping, the steel plates are cooled by water. Different water-cooling processes are set for different thicknesses to prevent uneven heating. When the steel plate thickness is greater than 350mm, the heating temperature is controlled at 710±40℃; when the steel plate thickness is greater than 250mm and less than or equal to 350mm, the heating temperature is controlled at 730±40℃; when the steel plate thickness is greater than 150mm and less than or equal to 250mm, the heating temperature is controlled at 750±40℃; and when the steel plate thickness is greater than 130mm and less than or equal to 150mm, the heating temperature is controlled at 770±40℃.

[0042] Meanwhile, to reduce the phenomenon of the head and tail being flat, the water ratio is controlled at 1.40-1.55, and a small water volume mode is used, with 1-14 water groups activated for watering.

[0043] Step S107: Place plates with a thickness greater than 130mm on a slow cooling platform for slow cooling, and control the lower limit of the stacking temperature to 500-750℃.

[0044] Specifically, the following stacking cooling process is adopted: For steel plates with a thickness of 130mm or more, they are placed on a slow cooling platform for slow cooling, the cooling fan is turned on, and the lower limit stacking cooling temperature is controlled at 500-750℃.

[0045] Meanwhile, the cold-stacked steel plates are wider at the bottom and narrower at the top, longer at the bottom and shorter at the top, with the width difference between two adjacent plates not exceeding 600mm and the length difference not exceeding 1200mm.

[0046] In addition, each storage location is secured with a pressure plate at the top, and the length of the pressure plate must not be less than the length of the nearest steel plate. The steel plates must be cooled for at least 96 hours.

[0047] The heavy plate plant rolled 18,647 tons of conventionally rolled heavy plates using the above method, with a warping rate of 8.47%, which is 54.05% lower than the previous warping rate of 62.52%. The monthly cost reduction benefit is: 80 yuan / ton * 18,647 tons * 54.05% = 806,300 yuan.

[0048] Therefore, this invention optimizes the heating, rolling, cooling, and stacking processes of extra-thick steel plates, effectively reducing the occurrence rate of warping, improving the actual quality of the steel plates, and reducing production costs.

[0049] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method of improving the shape of a rolled plate from an extra-heavy plate, characterized in that: The method comprises the following steps: controlling the tapping temperature of the heating process to be 1080-1160℃, and the temperature uniformity of the blank to be less than or equal to 50℃; controlling the width of the rolling blank to be less than the rolling width, and the blank spread ratio to be 1.05-1.20; when the rolling thickness is greater than or equal to 350mm, the pass reduction is controlled to be less than or equal to 20mm; when the rolling thickness is less than 350mm, the pass reduction of the first 3-5 passes before rough rolling is greater than or equal to 35mm, and the pass reduction of the remaining passes is less than or equal to 20mm; when the length of the rolled piece is less than or equal to 4850mm, three 90° transverse leveling is performed, and the leveling force is set to be 500-1200 tons; when the length of the rolled piece is greater than 4850mm and less than 6500mm, two 30° oblique leveling is performed, and the leveling force is set to be 500-1000 tons, and then one longitudinal leveling is performed; when the length of the rolled piece is greater than or equal to 6500mm, three longitudinal leveling is performed, and the leveling force is set to be 500-800 tons; when the thickness of the plate piece is greater than 350mm, the red temperature is controlled to be 710±40℃; when the thickness of the plate piece is greater than 250mm and less than or equal to 350mm, the red temperature is controlled to be 730±40℃; when the thickness of the plate piece is greater than 150mm and less than or equal to 250mm, the red temperature is controlled to be 750±40℃; when the thickness of the plate piece is greater than 130mm and less than or equal to 150mm, the red temperature is controlled to be 770±40℃; the plate piece with a thickness greater than 130mm is placed on a slow cooling rack for slow cooling, and the lower limit of the stack cooling temperature is controlled to be 500-750℃.

2. The method of improving plate shape of a super-thick plate according to claim 1, characterized by: In the process of controlling the tapping temperature of the heating process to be 1080-1160℃, and the temperature uniformity of the blank to be less than or equal to 50℃, the method further comprises the following steps: controlling the temperature of the lower surface of the blank to be 20℃ higher than the temperature of the upper surface.

3. The method of improving the shape of a plate rolled from a super-thick slab according to claim 1, characterized in that: When leveling the rolled piece with a length less than 4850mm, the roll gap is set to be the thickness of the steel plate+3.0-6.0mm; when leveling the rolled piece with a length greater than 4850mm and less than 6500mm, the roll gap is set to be the thickness of the steel plate+2.0-4.5mm; when leveling the rolled piece with a length greater than or equal to 6500mm, the roll gap is set to be the thickness of the steel plate+2.0-4.0mm.

4. The method of improving the shape of a plate rolled from a super-thick slab according to claim 1, characterized in that: In the process of controlling the red temperature of the plate piece to be 710±40℃ when the thickness of the plate piece is greater than 350mm, 730±40℃ when the thickness of the plate piece is greater than 250mm and less than or equal to 350mm, 750±40℃ when the thickness of the plate piece is greater than 150mm and less than or equal to 250mm, and 770±40℃ when the thickness of the plate piece is greater than 130mm and less than or equal to 150mm, the method further comprises the following steps: controlling the water ratio of the water spraying process to be 1.40-1.

55.

5. The method of improving the shape of a plate rolled from a super-thick slab according to claim 1, characterized in that: The stack cooling time of the plate piece is greater than or equal to 96h.

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