A method for improving the warping of the rolled head of a thick plate

Abstract

This invention discloses a method for improving the warping / buckling issue during the rolling of heavy plates, relating to the field of rolling process technology. The method includes: adjusting the temperature difference between the upper and lower surfaces of the slab based on its thickness and width, wherein the temperature difference decreases with increasing slab thickness and width; adjusting the number of water-passing cycles and the reheating time after water-passing based on the thickness of the intermediate slab, wherein the number of water-passing cycles and the reheating time after water-passing both increase with increasing intermediate slab thickness; and periodically measuring and adjusting the height of the rolling line. This invention improves the control level of warping / buckling during rolling by adjusting the temperature difference between the upper and lower surfaces of the slab, the number of water-passing cycles for the intermediate slab, the reheating time after water-passing, and the height of the rolling line. This effectively reduces damage to the conveying and output rollers and the rolling mill itself during rolling, and also effectively reduces the first-time warping rate in heavy plate mills, reducing the cost of subsequent secondary processing.

Description

Technical Field

[0001] This invention relates to the field of rolling technology, and in particular to a method for improving the warping of the rolled edge of thick plates. Background Technology

[0002] Currently, the occurrence of head warping during the rolling process of heavy plates is relatively high, posing a significant control challenge. Many factors influence head warping, including: the temperature difference between the upper and lower surfaces of the furnace tapping temperature, the water penetration of the intermediate billet, large temperature differences between the head and tail, the reduction distribution in the rolling schedule, the ratio of upper and lower roll speeds, the height of the rolling line, variations in steel grade, and the temperature difference between the upper and lower surfaces. Head warping also affects the rate of plate warping. For thick plates, head warping at both ends results in head and tail warping, while head warping results in head and tail wavy bends. For thin plates, head warping at both ends easily produces head and tail W-bends, while head warping results in small head and tail wavy bends. Furthermore, head warping can cause irreversible damage to the rolling mill itself and the input and output roller tables, making its impact relatively significant. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for improving the rolling of thick plates with raised buckles.

[0004] To solve the above technical problems, the technical solution of the present invention is as follows:

[0005] A method for improving the warping of rolled thick plates includes:

[0006] The temperature difference between the upper and lower surfaces of the slab is adjusted based on the thickness and width of the slab. The temperature difference between the upper and lower surfaces of the slab decreases as the thickness of the slab increases and as the width of the slab increases.

[0007] The number of water-piercing cycles and the reheating time after water-piercing are adjusted based on the thickness of the intermediate billet. The number of water-piercing cycles increases with the increase of the thickness of the intermediate billet, and the reheating time after water-piercing also increases with the increase of the thickness of the intermediate billet.

[0008] Measure and adjust the height of the rolling line regularly.

[0009] As a preferred embodiment of the method for improving the warping of the rolled thick plate according to the present invention, wherein: adjusting the temperature difference between the upper and lower surfaces of the slab based on the thickness and width of the slab includes:

[0010] When the thickness of the slab is greater than or equal to 150 mm and less than 220 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 40℃; if the width of the slab is greater than or equal to 2070 mm and less than or equal to 2570 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 35℃; if the width of the slab is greater than 2570 mm and less than or equal to 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 30℃.

[0011] When the slab thickness is greater than or equal to 220mm and less than 260mm, if the slab width is greater than or equal to 2070mm and less than 2070mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 35℃; if the slab width is greater than or equal to 2070mm and less than 2270mm, the temperature difference between the upper and lower surfaces should be adjusted to 30℃; if the slab width is greater than or equal to 2270mm and less than 2570mm, the temperature difference between the upper and lower surfaces should be adjusted to 28℃; if the slab width is greater than or equal to 2570mm and less than 2770mm, the temperature difference between the upper and lower surfaces should be adjusted to 25℃.

[0012] When the thickness of the slab is greater than or equal to 260 mm and less than 320 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 25℃; if the width of the slab is greater than or equal to 2070 mm and less than 2570 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 20℃; if the width of the slab is greater than or equal to 2570 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 15℃.

[0013] When the thickness of the slab is greater than or equal to 320 mm and less than 370 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 15℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 10℃.

[0014] When the thickness of the slab is greater than or equal to 370 mm and less than 400 mm, if the width of the slab is greater than or equal to 2070 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 10℃; if the width of the slab is greater than or equal to 2070 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 7℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 5℃.

[0015] When the thickness of the slab is greater than or equal to 400 mm and less than 460 mm, if the width of the slab is greater than or equal to 2070 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 10℃; if the width of the slab is greater than or equal to 2070 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 5℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 3℃.

[0016] As a preferred embodiment of the method for improving the warping of thick plate rolling according to the present invention, wherein: adjusting the number of water-passing cycles and the reheating time after water-passing based on the thickness of the intermediate billet includes:

[0017] When the thickness of the intermediate billet is less than or equal to 60mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 3, and the reheating time after quenching is controlled to be greater than or equal to 25s.

[0018] When the thickness of the intermediate billet is greater than 60mm and less than or equal to 80mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 5, and the reheating time after quenching is controlled to be greater than or equal to 30s.

[0019] When the thickness of the intermediate billet is greater than 80mm and less than or equal to 100mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 6, and the reheating time after quenching is controlled to be greater than or equal to 40s.

[0020] When the thickness of the intermediate billet is greater than 100mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 7, and the reheating time after quenching is controlled to be greater than or equal to 50s.

[0021] In a preferred embodiment of the method for improving the warping of thick plate rolling as described in this invention, the method for measuring the height of the rolling line includes:

[0022] Measure the thickness H1 of the support roller pad, the radius R of the support roller, and the diameter d of the lower working roller;

[0023] The height of the rolling line is calculated using the formula H=C+H1+R+d, where H is the height of the rolling line and C is the stand constant.

[0024] As a preferred embodiment of the method for improving the warping of thick plate rolling according to the present invention, wherein: adjusting the height of the rolling line includes:

[0025] During the roughing pass, the height of the rolling line is adjusted to 803~808mm, and during the finishing pass, the height of the rolling line is adjusted to 809~815mm.

[0026] The beneficial effects of this invention are:

[0027] This invention improves the control level of head warping and head buckling during rolling by adjusting the temperature difference between the upper and lower surfaces of the slab, the number of times the intermediate slab is quenched, the reheating time after quenching, and the height of the rolling line. This effectively reduces the damage of the slab to the conveying and output rollers and the rolling mill itself during the rolling process. At the same time, it can also effectively improve the first occurrence rate of warping in heavy plate mills and reduce the cost of subsequent secondary processing. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating the method for improving the rolling of thick plates with raised buckles provided by the present invention. Detailed Implementation

[0030] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0031] Figure 1 The flowchart illustrates the method for improving the rolling of thick plates with raised ends provided in this application embodiment. The method includes steps S101 to S103, and the specific steps are described below:

[0032] Step S101: Adjust the temperature difference between the upper and lower surfaces of the slab based on the thickness and width of the slab, wherein the temperature difference between the upper and lower surfaces of the slab decreases as the thickness of the slab increases and decreases as the width of the slab increases.

[0033] Specifically, establish a data statistics table for controlling buckle lifting, and record in detail the occurrence of buckle lifting when steel plates have different end faces and different rolling sizes.

[0034] Taking the continuous casting cross-section of common thick plates as an example: the thickness of the slabs are 150mm, 220mm, 260mm, 320mm, 370mm, and 460mm respectively. The width of the slabs are 2070mm, 2270mm, 2570mm, and 2770mm respectively.

[0035] First, the thickness of the slab cross-section affects the control of curling head. Statistical analysis of curling head phenomena in steel plates shows that the thinner the slab, the more frequently curling heads occur. The reason is that, comparing 150mm slab thicknesses with 260mm and 320mm slab thicknesses, under the same reduction, the compression ratio of the 150mm slab is greater than that of the 260mm and 320mm slabs. The deformation resistance of the 150mm slab is also worse than that of the 260mm and 320mm slabs.

[0036] Secondly, the wider the slab cross-section, the more prone the slab is to warping. The reason is as follows: when comparing the same width during rolling, the narrower the width of the continuously cast cross-section, the greater the widening, which in turn requires a larger reduction. The larger the reduction, the greater the probability of the steel plate warping during the rolling process.

[0037] Therefore, based on the above data, the temperature difference between the upper and lower surfaces of the slab is adjusted. Specifically, the temperature difference between the upper and lower surfaces of the slab decreases as the slab thickness increases and as the slab width increases.

[0038] In this embodiment, when the thickness of the slab is greater than or equal to 150 mm and less than 220 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab is adjusted to 40°C; if the width of the slab is greater than or equal to 2070 mm and less than or equal to 2570 mm, the temperature difference between the upper and lower surfaces of the slab is adjusted to 35°C; if the width of the slab is greater than 2570 mm and less than or equal to 2770 mm, the temperature difference between the upper and lower surfaces of the slab is adjusted to 30°C.

[0039] When the slab thickness is greater than or equal to 220mm and less than 260mm, if the slab width is greater than or equal to 2070mm and less than 2070mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 35℃; if the slab width is greater than or equal to 2070mm and less than 2270mm, the temperature difference between the upper and lower surfaces should be adjusted to 30℃; if the slab width is greater than or equal to 2270mm and less than 2570mm, the temperature difference between the upper and lower surfaces should be adjusted to 28℃; if the slab width is greater than or equal to 2570mm and less than 2770mm, the temperature difference between the upper and lower surfaces should be adjusted to 25℃.

[0040] When the thickness of the slab is greater than or equal to 260 mm and less than 320 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 25℃; if the width of the slab is greater than or equal to 2070 mm and less than 2570 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 20℃; if the width of the slab is greater than or equal to 2570 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 15℃.

[0041] When the thickness of the slab is greater than or equal to 320 mm and less than 370 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 15℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 10℃.

[0042] When the thickness of the slab is greater than or equal to 370 mm and less than 400 mm, if the width of the slab is greater than or equal to 2070 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 10℃; if the width of the slab is greater than or equal to 2070 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 7℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 5℃.

[0043] When the slab thickness is greater than or equal to 400 mm and less than 460 mm, if the slab width is greater than or equal to 2070 mm and less than 2070 mm, adjust the temperature difference between the upper and lower surfaces of the slab to 10℃; if the slab width is greater than or equal to 2070 mm and less than 2270 mm, adjust the temperature difference between the upper and lower surfaces of the slab to 5℃; if the slab width is greater than or equal to 2270 mm and less than 2770 mm, adjust the temperature difference between the upper and lower surfaces of the slab to 3℃.

[0044] Step S102: Adjust the number of water piercing cycles and the reheating time after water piercing based on the thickness of the intermediate billet. The number of water piercing cycles increases with the increase of the thickness of the intermediate billet, and the reheating time after water piercing also increases with the increase of the thickness of the intermediate billet.

[0045] Specifically, in order to improve rolling efficiency and shorten rolling time, intermediate billet water-passing devices are usually added before and after the rolling mill body. The purpose is to reduce temperature control time and improve the cooling capacity of intermediate billets.

[0046] After installing the water-quenching device, the rolling speed is indeed significantly improved. However, the surface temperature of the steel plate will differ greatly from the core temperature of the slab. In fact, the probability of the steel plate curling up increases with the number of water quenching cycles, which also increases the difficulty of controlling the curling of the steel plate.

[0047] Therefore, the control measures adopted are to adjust the number of times the slab is pierced and the reheating time after piercing, as follows:

[0048] When the thickness of the intermediate billet is less than or equal to 60mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 3, and the reheating time after quenching is controlled to be greater than or equal to 25s.

[0049] When the thickness of the intermediate billet is greater than 60mm and less than or equal to 80mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 5, and the reheating time after quenching is controlled to be greater than or equal to 30s.

[0050] When the thickness of the intermediate billet is greater than 80mm and less than or equal to 100mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 6, and the reheating time after quenching is controlled to be greater than or equal to 40s.

[0051] When the thickness of the intermediate billet is greater than 100mm, the number of times the intermediate billet is quenched is controlled to be less than or equal to 7, and the reheating time after quenching is controlled to be greater than or equal to 50s.

[0052] Step S103: Periodically measure and adjust the height of the rolling line.

[0053] Specifically, the rolling line height refers to the height difference between the upper surface of the lower roll of the rolling mill and the upper surface of the stand roll. When the vertical distance between the roll and the stand roll is not adjusted properly, the slab cannot enter the rolling mill roll gap horizontally. In this case, the roll lifts the head of the slab or tilts it downward to bite it in. This asymmetrical biting process causes asymmetrical counterweight.

[0054] From the perspective of rolling process theory, under the condition that other factors are uniform and symmetrical, the ideal rolling line height is Δh / 2, which can ensure that the rolled workpiece is horizontally engaged and straight after rolling. Due to the existence of the "head-up" phenomenon during rolling, appropriately increasing the rolling line height when rolling controlled-roll slabs can suppress the occurrence of head-up during rolling.

[0055] In this embodiment, the range of rolling line height control is appropriately increased, specifically to 803-815 mm. The rolling shape of the roughing and finishing passes is adjusted by controlling the rolling line height, primarily by adjusting the roughing pass to 803-808 mm and the finishing pass to 809-815 mm. This method effectively improves the difficulty of shape control during the rolling process, reducing the incidence of warping caused by rolling warping and the damage to equipment caused by it. It also reduces the cost of post-rolling salvage.

[0056] It should be noted that after the support roll assembly and work roll assembly are fully installed in the stand, the actual rolling line elevation H of the stand is the sum of the stand constant C, the support roll pad thickness H1, the support roll radius R, and the lower work roll diameter d. That is, H = C + H1 + R + d. Within one support roll changing cycle, H depends on the upper work roll diameter. When the upper work roll diameter is too large or too small, the actual rolling line elevation will deviate significantly from the theoretical rolling line elevation, making it difficult for the rolls to bite the steel. In extreme cases, the steel plate head hitting the inlet stand can easily result in scrap. Therefore, it is necessary to measure and adjust the rolling line height regularly.

[0057] After adopting the above method, the ability to control the shape of thick plates is significantly improved, with the main data referring to S355 grade steel plates. The comparison of data before and after adjustment in Tables 1 and 2 shows that the actual control capability has been improved. Table 1

[0058] Table 2

[0059] Therefore, the technical solution of this application improves the control level of head warping and head buckling during the rolling process by adjusting the temperature difference between the upper and lower surfaces of the slab, the number of times the intermediate slab is quenched, the reheating time after quenching, and the height of the rolling line. This effectively reduces the damage of the slab to the conveying and output rollers and the rolling mill itself during the rolling process. At the same time, it can also effectively improve the first occurrence rate of warping in the wide and thick plate mill and reduce the cost of subsequent secondary processing.

[0060] 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 for improving the warping of rolled thick plates, characterized in that: include: The temperature difference between the upper and lower surfaces of the slab is adjusted based on the thickness and width of the slab. The temperature difference between the upper and lower surfaces of the slab decreases as the thickness of the slab increases and as the width of the slab increases. The number of water-piercing cycles and the reheating time after water-piercing are adjusted based on the thickness of the intermediate billet. The number of water-piercing cycles increases with the increase of the thickness of the intermediate billet, and the reheating time after water-piercing also increases with the increase of the thickness of the intermediate billet. The height of the rolling line is measured and adjusted periodically, and the method for measuring the height of the rolling line includes: Measure the thickness H1 of the support roller pad, the radius R of the support roller, and the diameter d of the lower working roller; The height of the rolling line is calculated using the formula H=C+H1+R+d, where H is the height of the rolling line and C is the stand constant. The adjustment of the temperature difference between the upper and lower surfaces of the slab based on its thickness and width includes: When the thickness of the slab is greater than or equal to 150 mm and less than 220 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 40℃; if the width of the slab is greater than or equal to 2070 mm and less than or equal to 2570 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 35℃; if the width of the slab is greater than 2570 mm and less than or equal to 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 30℃. When the thickness of the slab is greater than or equal to 220mm and less than 260mm, if the width of the slab is greater than or equal to 2070mm and less than 2270mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 30℃; if the width of the slab is greater than or equal to 2270mm and less than 2570mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 28℃; if the width of the slab is greater than or equal to 2570mm and less than 2770mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 25℃. When the thickness of the slab is greater than or equal to 260 mm and less than 320 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2070 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 25℃; if the width of the slab is greater than or equal to 2070 mm and less than 2570 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 20℃; if the width of the slab is greater than or equal to 2570 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 15℃. When the thickness of the slab is greater than or equal to 320 mm and less than 370 mm, if the width of the slab is greater than or equal to 2000 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 15℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 10℃. When the thickness of the slab is greater than or equal to 370 mm and less than 400 mm, if the width of the slab is greater than or equal to 2070 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 7℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 5℃. When the thickness of the slab is greater than or equal to 400 mm and less than 460 mm, if the width of the slab is greater than or equal to 2070 mm and less than 2270 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 5℃; if the width of the slab is greater than or equal to 2270 mm and less than 2770 mm, the temperature difference between the upper and lower surfaces of the slab should be adjusted to 3℃.

2. The method for improving the warping of rolled thick plates according to claim 1, characterized in that: The number of water-piercing cycles and the reheating time after water-piercing of the slab based on the thickness adjustment of the intermediate billet include: When the thickness of the intermediate billet is less than or equal to 60mm, the number of times the billet is pierced by water should be less than or equal to 3, and the reheating time after piercing should be greater than or equal to 25s. When the thickness of the intermediate billet is greater than 100mm, the number of times the billet is quenched is controlled to be less than or equal to 7, and the reheating time after quenching is controlled to be greater than or equal to 50s.

3. The method for improving the warping of rolled thick plates according to claim 1, characterized in that: The adjustment of the rolling line height includes: During the roughing pass, the height of the rolling line is adjusted to 803~808mm, and during the finishing pass, the height of the rolling line is adjusted to 809~815mm.

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