A method for improving the shape control of a crack arrest steel plate

Abstract

The application provides a control method for improving the shape of a crack arrest steel plate, comprising: (1) heating system control: determining the furnace time and soaking temperature according to the thickness of the billet, so that the upper surface of the billet is 25-40 DEG C higher than the soaking temperature of the lower surface; (2) final pass reduction control: in the rough rolling stage, the spread pass sledge ratio is +1.0 to +3.0, and the longitudinal rolling pass sledge ratio is +3.0 to +5.0; in the finish rolling stage, the rolling force of the last two finish rolling machines is 4800-5600 t, the last pass reduction is greater than or equal to 4.5 mm, and the sledge ratio is +3.0 to +6.0; the finish rolling speed is less than or equal to 3 m / s; and (3) straightening parameter control: according to different thicknesses of the steel plate, adopting a pre-straightening machine 1-pass straightening process and a hot straightening machine 4-pass straightening process matched with the steel plate.

Description

TECHNICAL FIELD

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

[0002] The crack arrest steel thick steel plate has high toughness and welding performance under the condition of ensuring high strength, that is, when the component has potential defects or cracks, the crack arrest steel can prevent the crack from expanding in a small range and prevent major accidents from occurring under the action of dynamic load and impact load. Since 2016, in order to fill the domestic gap and take advantage of the low-temperature large reduction and controlled cooling technology of the 5500 production line, the production of thick ship plates, bridge steels and offshore steels has been increasing. Since the crack arrest steel has been imported domestically, the 5500 production line has continuously improved the process and rolling strategy, and has successfully developed and mass-produced crack arrest steel, which has been successfully used in the world's first liquefied natural gas-powered 23000 container ship. However, in the production process, it is found that the original control means cannot meet the production needs of the crack arrest steel, and the rolled steel plate has the phenomenon of broken waves and goose head bending, which leads to the fact that the hot straightening cannot be completed. Due to the high standard requirement of the plate surface, the surface damage is large after turning to the flattening treatment, and finally the plate shape and unevenness cannot meet the requirements. The plate shape qualified rate is only 82.75%, and the steel plate scrap rate is 5.25%.

[0003] The main reasons for the low plate shape qualified rate are as follows: first, the heating system is not reasonable. Since the crack arrest steel requires low-temperature heating, the starting rolling temperature is low, and there is no specific setting for the three heating sections and the soaking section, so the uniformity of the billet temperature cannot be guaranteed. Second, the current automatic rolling is adopted, and the final pass reduction is given by the secondary computer. When rolling the steel plate, due to the unreasonable final pass reduction, the adjustment of the snowshoe ratio value loses its effect, which leads to the fact that the thick steel plate tail head hits the roller way, and the "broken wave goose head bending" defect is easily produced, which directly affects the plate shape qualified rate.

[0004] A kind of steel plate shape control method (CN201510206455.3) provides a kind of steel plate shape control method, three-level computer system according to rectangularization coefficient μ=elongation ratio / (spread width ratio-1)= (steel plate target length / billet length) / 〔(steel plate target width / billet width)-1〕Calculation formula, calculate the μ value of the slab to be rolled: secondary computer system according to μ Value selects rolling strategy, if μ≤20, 3T rolling mode of longitudinal rolling-horizontal rolling-longitudinal rolling is adopted;If μ>20, 2T rolling mode of longitudinal rolling-horizontal rolling is adopted.It can effectively improve the specification shape of steel plate, ensure the rectangular size of steel plate, reduce the head and tail narrow defects in the process of steel plate flame cutting, reduce the size of steel plate spot rate, make the spot rate caused by the head and tail narrow of steel plate reduce from 0.16% to 0.03%, thereby greatly improve the quality qualified rate of steel plate, reduce spot loss, increase enterprise economic benefit.But this patent mainly solves the problem of steel plate rectangularization, cannot solve the problem of thick specification TMCP steel plate shape.

[0005] A kind of thin specification TMCP plate shape control method of mixed edge wave and middle wave (CN201910006890.X) discloses a kind of thin specification TMCP plate shape control method of mixed edge wave and middle wave, the plate shape control method is by light, heavy two different along width direction differentiating reduction + two different plastic deformation rate reduction matching settings to control the thin specification TMCP plate shape of light middle wave big edge wave or light edge wave big middle wave, produce the thin specification TMCP plate of mixed edge wave and middle wave with good plate shape.But this patent mainly solves the problem of thin specification steel plate shape, cannot solve the problem of thick specification TMCP steel plate shape.

[0006] A kind of steel plate shape and thickness optimization control system (CN102989786A) provides a kind of steel plate shape and thickness optimization control system, it includes rolling mill primary control and is provided with rolling table for rolling mill primary control rolling mill secondary control, the rolling mill primary control includes automatic roll gap control and the data processing module connected with the automatic roll gap control, and the rolling mill primary control further includes the last pass leveling module for optimizing plate shape control and the semi-automatic roll gap module for optimizing plate thickness control connected with the automatic roll gap control and the automatic roll gap control compensation amount adjustment and amplitude limiting control intervention module for automatic roll gap control weight and amplitude limiting value.This application technical scheme, under the premise of guaranteeing thickness precision, the shape of thick specification steel plate is improved, especially the problem of small broken wave is greatly improved;At the same time, subsequent leveling and cold straightening process is reduced, process cost is saved, and economic benefit is considerable;And reduce the quality objection caused by flatness, improve the cognition of customer.The low-temperature rolling thick steel plate shape problem cannot be completely solved in this patent, steel plate climbing phenomenon often occurs, leveling force is too small to effectively solve the problem of large water TMCP crack arrest steel plate shape, and too large leveling force will lead to steel plate rolling thin problem.

[0007] Therefore, there is a need for a method capable of effectively solving the plate shape problem of low-temperature steel plates such as TMCP super-wide crack arrest steel and the like. SUMMARY

[0008] According to the above technical problem, a control method for improving the shape of a crack arrest steel plate is provided.

[0009] The technical means adopted by the present application are as follows:

[0010] A control method for improving the shape of a crack arrest steel plate, comprising:

[0011] (1) Heating system control:

[0012] The heating temperature and soaking temperature are determined according to the thickness of the billet, and the correlation between the temperature difference between the upper and lower surfaces of the heating furnace and the rolling buckling and warping of the super-thick steel plate is studied in depth, so that the soaking temperature of the upper surface of the billet is 25-40°C higher than that of the lower surface;

[0013] (2) Control of the final pass reduction:

[0014] In the rough rolling stage, the lower surface cooling device before the rough rolling mill is used to control the buckling and warping, and the spread pass sled ratio is +1.0 to +3.0, and the longitudinal rolling pass sled ratio is +3.0 to +5.0, to avoid buckling of the rough rolling mill;

[0015] In the finishing rolling stage, double-stand rolling is adopted, the rolling force of the last two finishing rolling mills is 4800-5600t, the thickness of the previous passes is adjusted by the thickness compensation function of the finishing rolling mill and the pass air function, to ensure that the last pass reduction is ≥4.5mm, the sled ratio is +3.0 to +6.0, the rolling force advantage of the rolling mill is used to improve the initial plate shape, and the finishing rolling speed is ≤3m / s;

[0016] (3) Control of straightening parameters:

[0017] According to different thicknesses of the steel plate, a one-pass straightening process of a pre-straightening machine suitable for the steel plate is adopted:

[0018] When the thickness of the steel plate is 70mm≤thickness≤80mm, the pre-straightening inlet correction value is +0.3mm to +0.5mm, the pre-straightening outlet correction value is -0.6mm to -0.4mm, and the straightening speed is 1.0m / s to 1.5m / s;

[0019] When the thickness of the steel plate is 80mm<thickness≤95mm, the pre-straightening inlet correction value is +0.55mm to +0.7mm, the pre-straightening outlet correction value is -0.76mm to -0.62mm, and the straightening speed is 1.0m / s to 1.3m / s;

[0020] When the thickness of the steel plate is 95mm, the pre-straightening inlet correction value is +0.75mm~+0.95mm, the pre-straightening outlet correction value is -0.92mm~-0.78mm, and the straightening speed is 0.5m / s-0.7m / s;

[0021] According to the steel plates with different thicknesses, the four-pass straightening process of the hot straightener 4 is adopted:

[0022] When the thickness of the steel plate is 70mm≤80mm, the hot straightening inlet correction value is +0.5mm~+0.65mm, the hot straightening outlet correction value is -0.80mm~-0.55mm, and the straightening speed is 1.0m / s~1.5m / s;

[0023] When the thickness of the steel plate is 80mm<95mm, the hot straightening inlet correction value is +0.65mm~+0.85mm, the hot straightening outlet correction value is -0.95mm~-0.80mm, and the straightening speed is 1.0m / s~1.3m / s;

[0024] When the thickness of the steel plate is 95mm, the hot straightening inlet correction value is +0.85mm~+1.10mm, the hot straightening outlet correction value is -1.2mm~-0.95mm, and the straightening speed is 0.5m / s~0.7m / s.

[0025] Preferably, when the thickness of the billet is 240mm≤280mm, the total furnace time is 4.0~4.5h, the soaking time is 50~70 minutes, and the soaking temperature is 1160℃~1170℃.

[0026] Preferably, when the thickness of the billet is 280mm≤300mm, the total furnace time is 4.5~5.0h, the soaking time is 70~90 minutes, and the soaking temperature is 1180℃~1190℃.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] Due to the above three-step comprehensive measures, the uniform consistency of the heating temperature of the crack arrest steel billet can be ensured, the rolling pressure is reasonably controlled, the last pass reduction of the finishing mill is adjusted, the plate shape is controlled by using the large rolling force of the rolling mill and the snowshoe rolling speed, the defects of "broken waves" and "goose head bends" at the tail of the steel plate are avoided, the pre-straightening and straightening parameters are optimized, the conditions of the stress release and phase change of the steel plate in the straightening process are improved, the post-straightening effect is greatly improved, the plate shape qualified rate of the crack arrest steel finished plate is increased from 82.75% to 98.59%, the transfer pressure rate is greatly reduced, and the production cost is significantly reduced.

[0029] The product produced by the method can be widely applied to low-temperature rolling thick steel plates with a finishing rolling surface temperature of 720 DEG C in the fields of shipbuilding, bridge, pressure vessel, building and engineering machinery, etc., to ensure the flatness of the steel plates.

[0030] Based on the above reasons, the present application can be widely promoted in the field of crack arrest steel and the like. DETAILED DESCRIPTION

[0031] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] The present application discloses a control method for improving the shape of crack arrest steel plate, comprising:

[0033] (1) Heating system control:

[0034] The heating time in the furnace and the soaking temperature are determined according to the thickness of the billet, and the correlation between the temperature difference between the upper and lower surfaces of the heating furnace and the buckling and warping of the thick steel plate is deeply studied, so that the soaking temperature of the upper surface of the billet is higher than that of the lower surface by 25-40 DEG C;

[0035] When the billet thickness is 240mm≤steel billet thickness<280mm, the total heating time in the furnace is 4.0-4.5h, the soaking time is 50-70 minutes, and the soaking temperature is 1160 DEG C-1170 DEG C.

[0036] When the billet thickness is 280mm≤steel billet thickness≤300mm, the total heating time in the furnace is 4.5-5.0h, the soaking time is 70-90 minutes, and the soaking temperature is 1180 DEG C-1190 DEG C.

[0037] (2) Control of the final pass reduction:

[0038] In the rough rolling stage, the buckling and warping control is performed by using the lower surface cooling device before the rough rolling mill in combination with the rolling pass, and the snowshoe ratio of the spreading pass is +1.0 to +3.0, and the snowshoe ratio of the longitudinal rolling pass is +3.0 to +5.0, to avoid buckling of the rough rolling mill;

[0039] In the finishing rolling stage, double-stand rolling is adopted, the rolling force of the last two finishing rolling mill passes is 4800-5600t, the thickness of the previous passes is adjusted by the thickness compensation function of the finishing rolling mill and the pass emptying function, to ensure that the reduction of the last pass is greater than or equal to 4.5mm, the snowshoe ratio is +3.0 to +6.0, the initial plate shape is improved by using the rolling force advantage of the rolling mill, and the finishing rolling speed is less than or equal to 3m / s;

[0040] (3) Straightening parameter control:

[0041] According to different thickness of steel plate with its adaptation of pre-straightening machine 1 pass straightening process:

[0042]

[0043] According to different thickness of steel plate with its adaptation of hot straightening machine 4 pass straightening process:

[0044]

[0045] By the above method, the plate shape qualified rate of the crack arrest steel finished plate is increased from 82.75% to 98.59%, the transfer pressure flattening rate is greatly reduced, and the production cost is significantly reduced.

[0046] The present application is described in detail in the following three embodiments:

[0047] Example 1

[0048] The chemical composition and mass percentage of the crack arrest steel are as follows: C≤0.11%, Mn≤2.0%, Si≤0.60%, S≤0.007%, P≤0.020%, Cr≤0.26%, Mo≤0.25%, Ni≤1.1%, Nb: 0.02%-0.05%, V: 0.05%-0.08%, and the balance is Fe and impurities. The billet thickness is 250mm, and the production steel plate thickness is 70*2580mm, and the specific control method is:

[0049] (1) Heating system control:

[0050] The furnace time is 4.2h, the soaking temperature is 1162℃, the soaking time is 65min, and the soaking temperature of the upper table is 31℃ higher than that of the lower table;

[0051] (2) Rolling parameter control:

[0052] The down table cooling device before the rough rolling mill is used to control the buckling head regulation together with the rolling pass; the snowshoe ratio of the spreading pass is +1, the snowshoe ratio of the longitudinal rolling pass is +3, and the buckling head of the rough rolling mill is avoided; the rolling force of the last two finishing rolling mills is controlled at 5000-5300t, the thickness of the previous passes and the pass emptying function are adjusted by the thickness compensation function of the finishing rolling mill, the reduction amount of the last pass of the finishing rolling mill is ensured to be 5.2mm, the snowshoe ratio is +3.0, the initial plate shape is improved by using the rolling force advantage of the rolling mill, and the speed of the finishing rolling mill is 3.0m / s;

[0053] (3) Straightening parameter control:

[0054] The pre-straightening machine 1 pass and the straightening machine 4 pass straightening process are adopted;

[0055] The specific pre-straightening parameters according to the thickness of the steel plate are as follows:

[0056]

[0057] The specific hot straightening parameters according to the thickness of the steel plate are as follows:

[0058]

[0059] Example 2

[0060] The chemical composition of the crack arrest steel and the mass percentage are as follows: C≤0.11%, Mn≤2.0%, Si≤0.60%, S≤0.007%, P≤0.020%, Cr≤0.26%, Mo≤0.25%, Ni≤1.1%, Nb: 0.02%-0.05%, V: 0.05%-0.08%, and the balance is Fe and impurities. The billet thickness is 300 mm, and the production steel plate thickness is 84*3580 mm, and the specific control method is as follows:

[0061] (1) Heating system control:

[0062] The furnace time is 4.8 h, the soaking temperature is 1182°C, the soaking time is 80 min, and the soaking temperature of the upper table is 36°C higher than that of the lower table;

[0063] (2) Rolling parameter control:

[0064] The buckling head control is performed by using the lower table cooling device before the rough rolling mill in combination with the rolling pass; the snowshoe ratio of the spreading pass is +3, the snowshoe ratio of the longitudinal rolling pass is +4, the buckling head of the rough rolling mill is avoided; the rolling force of the last finishing rolling mill pass is controlled to be 5100-5300 t, the thickness of the previous passes and the pass emptying function are adjusted by using the ZPC thickness compensation system of the finishing rolling mill, the reduction amount of the last pass of the finishing rolling mill is ensured to be 4.9 mm, the snowshoe ratio is +3, the initial plate shape is improved by using the rolling force advantage of the rolling mill, and the speed of the finishing rolling mill is 2.7 m / s;

[0065] (3) Straightening parameter control:

[0066] The straightening process of one pass of the pre-straightening machine and four passes of the straightening machine is adopted;

[0067] The specific pre-straightening parameters according to the thickness of the steel plate are as follows:

[0068]

[0069] The specific hot straightening parameters according to the thickness of the steel plate are as follows:

[0070]

[0071] Example 3

[0072] The chemical composition of the crack arrest steel and the percentage by mass are as follows: C≤0.11%, Mn≤2.0%, Si≤0.60%, S≤0.007%, P≤0.020%, Cr≤0.26%, Mo≤0.25%, Ni≤1.1%, Nb: 0.02%-0.05%, V: 0.05%-0.08%, and the balance of Fe and impurities. The billet thickness is 300 mm, and the production steel plate thickness is 98*4580 mm, and the specific control method is:

[0073] (1) Heating system control:

[0074] The furnace time is 5.0 h, the soaking temperature is 1188℃, the soaking time is 80 min, and the soaking temperature of the upper table is 39℃ higher than that of the lower table;

[0075] (2) Rolling parameter control:

[0076] The buckling head control is performed by using the lower table cooling device before the rough rolling mill in cooperation with the rolling pass; the snowmobile ratio of the spreading pass is +3, the snowmobile ratio of the longitudinal rolling pass is +4, and the buckling head of the rough rolling mill is avoided; the rolling force of the last finishing rolling mill pass is controlled to be 5300-5600t, the thickness of the previous passes is finely adjusted through the thickness compensation function of the finishing rolling mill, the reduction amount of the last pass of the finishing rolling mill is 4.5 mm, the snowmobile ratio is +3, the initial plate shape is improved by using the rolling force advantage of the rolling mill, and the speed of the finishing rolling mill is 2.0 m / s;

[0077] (3) Straightening parameter control:

[0078] The pre-straightening machine 1 pass and the straightening machine 4 pass straightening process is adopted;

[0079] The specific pre-straightening parameters according to the thickness of the steel plate are as follows:

[0080]

[0081] The specific hot straightening parameters according to the thickness of the steel plate are as follows:

[0082]

[0083] The improvement effect comparison table of the above three embodiments is shown in the following table, and it can be obviously seen that the plate shape qualified rate is obviously improved.

[0084]

[0085] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of improving the shape of a crack arrest steel plate, characterized by, Comprise: (1) heating system control: According to the billet thickness to determine the furnace time and soaking temperature, the upper surface of the billet than the lower surface of the soaking temperature is high 25~40℃; (2) the last pass reduction control: In the roughing stage, the use of roughing machine before the lower surface cooling device with rolling pass to control buckling head, and the spread width pass sled ratio is +1.0~+3.0, the longitudinal rolling pass sled ratio is +3.0~+5.0, to avoid buckling head roughing mill; In the finishing stage, the last two finishing mill pass rolling force is 4800-5600t, the last pass reduction ≥4.5mm, sled ratio is +3.0~+6.0; finishing speed ≤3m / s; (3) straightening parameter control: According to the different thickness of the steel plate with its adaptive pre straightening machine 1 pass straightening process: 70mm≤steel plate thickness≤80mm, pre straightening inlet correction value is +0.3mm~+0.5mm, pre straightening outlet correction value is-0.6mm~-0.4mm, straightening speed is 1.0m / s~1.5m / s; 80mm<steel plate thickness≤95mm, pre straightening inlet correction value is +0.55mm~+0.7mm, pre straightening outlet correction value is-0.76mm~-0.62mm, straightening speed is 1.0m / s~1.3m / s; 95mm<steel plate thickness, pre straightening inlet correction value is +0.75mm~+0.95mm, pre straightening outlet correction value is-0.92mm~-0.78mm, straightening speed is 0.5m / s-0.7m / s; According to the different thickness of the steel plate with its adaptive hot straightening machine 4 pass straightening process: 70mm≤steel plate thickness≤80mm, hot straightening inlet correction value is +0.5mm~+0.65mm, hot straightening outlet correction value is-0.80mm~-0.55mm, straightening speed is 1.0m / s~1.5m / s; 80mm<steel plate thickness≤95mm, hot straightening inlet correction value is +0.65mm~+0.85mm, hot straightening outlet correction value is-0.95mm~-0.80mm, straightening speed is 1.0m / s~1.3m / s; 95mm<steel plate thickness, hot straightening inlet correction value is +0.85mm~+1.10mm, hot straightening outlet correction value is-1.2mm~-0.95mm, straightening speed is 0.5m / s~0.7m / s.

2. The control method for improving the shape of a crack arrest steel plate according to claim 1, characterized by, 240mm≤billet thickness<280mm, total furnace time is 4.0~4.5h, soaking time 50~70 minutes, soaking temperature is 1160℃~1170℃.

3. The method of claim 1, wherein the shape of the crack arrest steel plate is improved by controlling the composition of the steel plate. 280mm≤billet thickness≤300mm, total furnace time is 4.5~5.0h, soaking time 70~90 minutes, soaking temperature is 1180℃~1190℃.

Images