Control method for improving head thickness precision of low-carbon steel strip steel

Abstract

The invention relates to the technical field of hot continuous rolling of low-carbon steel, in particular to a control method for improving the head thickness precision of low-carbon steel strip steel. The method specifically comprises the following steps that (1) the thickness of an adopted raw material plate blank ranges from 200 mm to 230 mm; (2) the tapping temperature of the heating furnace is controlled to be 1160-1200 DEG C; (3) controlling the thickness of an intermediate billet at a finish rolling inlet to be 38-48mm; 4) controlling the inlet temperature of a finishing mill according to the change of the target thickness of the product; 5) controlling the threading speed of the strip steel to be 10-12m / s; (6) the rigidity of an F1-F7 finishing mill is controlled to range from 4600 KN / mm to 5400 KN / mm; (7) determining the roll gap cooling water input quantity according to the target thickness of the product; (8) the rolling force deviation of a single rack is controlled to be reduced to be within + / -50 tons; 9) transmitting the rolling mill roll gap data corrected by the secondary model to an AGC thickness control system so as to control the thickness of the head of the strip steel; and (10) the deviation between the actual value and the set value of the thickness of the head of the strip steel is controlled within + / -0.18 mm. Energy consumption can be reduced, and the index qualification rate of the head of the low-carbon steel can be guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of hot-rolled low-carbon steel, in particular to a control method for improving the thickness accuracy of a low-carbon steel strip head. Background Art

[0002] Low carbon steel (mild steel) is carbon steel with a carbon content of less than 0.25%. It is also called soft steel because of its low strength, low hardness and softness. It includes most ordinary carbon structural steels and some high-quality carbon structural steels. Most of them are used for engineering structural parts without heat treatment, and some are used for mechanical parts that require wear resistance after carburizing and other heat treatments.

[0003] The thickness accuracy of hot-rolled strip is one of the important indicators of product quality, and the thickness accuracy of the strip head is an important component of the thickness accuracy of hot-rolled strip. Energy conservation and consumption reduction are important development trends at present and in the future. With the intensification of global climate change and the increasing shortage of resources, energy conservation and consumption reduction have become key factors in promoting the sustainable development of the economy and society. In order to save energy and reduce consumption, existing steel companies generally adopt the method of gradually reducing the actual furnace discharge temperature to reduce energy consumption. However, during the cooling process, the thickness deviation of the strip head is large, which makes the thickness qualification rate of low-carbon steel products lower, and the product removal rate caused by thickness defects increases significantly, resulting in a decrease in the yield rate index. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a control method for improving the thickness accuracy of a low-carbon steel strip head, which can both reduce energy consumption and ensure the qualified rate of low-carbon steel head indicators.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A control method for improving the thickness accuracy of a low-carbon steel strip head comprises the following steps:

[0007] 1) The thickness of the raw material slab used is 200-230mm;

[0008] 2) The temperature of the heating furnace is controlled at 1160~1200℃;

[0009] 3) Control the thickness of the intermediate billet at the entrance of finishing rolling to 38-48 mm;

[0010] 4) Control the finishing mill inlet temperature according to the change of product target thickness:

[0011] If the target thickness is ≤2.2mm, the finishing mill inlet temperature is controlled at 1035-1060℃;

[0012] If the target thickness is greater than 2.2 mm, the finishing mill inlet temperature is controlled at 1015-1040°C;

[0013] 5) Control the strip threading speed to 10-12 m / s;

[0014] 6) The stiffness of F1-F7 finishing mill is controlled at 4600~5400KN / mm;

[0015] 7) Determine the amount of cooling water to be added to the roll gap based on the target thickness of the product;

[0016] 8) The finishing mill inlet temperature, strip threading speed, intermediate billet thickness at the finishing mill inlet and the amount of cooling water input into the roll gap are input into the finishing mill secondary model. The secondary model calculates based on the above data to continuously reduce the deviation between the set value and the actual value of the mill roll gap, and controls the rolling force deviation of the single stand to within ±50 tons;

[0017] 9) Transmitting the mill roll gap data corrected by the secondary model to the AGC thickness control system to control the strip head thickness;

[0018] 10) The deviation between the actual value of the strip head thickness and the set value is controlled within ±0.18mm.

[0019] Furthermore, in step 1), the thickness of the raw material slab used is 200 mm.

[0020] Furthermore, in step 3), if the target thickness is ≤2.2 mm, then 38 mm ≤ the thickness of the intermediate billet at the finishing entrance ≤42 mm.

[0021] Furthermore, in step 3), if the target thickness is greater than 2.2 mm, then 42 mm < the thickness of the intermediate billet at the entrance of finishing rolling ≤ 48 mm.

[0022] Furthermore, in step 5), if the target value of the final rolling temperature is ≤880°C, the strip threading speed is ≤10.5m / s.

[0023] Furthermore, in step 5), if the target value of the final rolling temperature is greater than 880°C, then the strip threading speed is 10.5 m / s < ≤ 12 m / s.

[0024] Furthermore, in step 7), if the target thickness is ≤2.2 mm, cooling water is added to the roll gap of the F1-F3 finishing mill.

[0025] If the actual finishing temperature is greater than the target finishing temperature by more than 15°C, the roll gap cooling water of the F4 finishing mill is added.

[0026] Furthermore, in step 7), if the target thickness is greater than 2.2 mm, cooling water is added to the roll gap of the F1-F4 finishing mills.

[0027] If the actual finishing temperature is greater than the target finishing temperature by more than 15°C, the roll gap cooling water of the F5 finishing mill is added.

[0028] Compared with the existing method, the beneficial effects of the present invention are:

[0029] Under the premise that the actual temperature of the heating furnace is relatively low, the present invention improves and innovates the rolling process, accurately controls the hot rolling process temperature, controls the thickness of the intermediate billet at the finishing entrance, the amount of cooling water input into the roll gap and the rolling speed, and realizes the stable control of the strip head temperature. Combined with the self-learning function of the AGC control and the secondary model, the purpose of accurately controlling the strip head thickness is achieved, and the thickness qualification rate of low-carbon steel products is greatly improved. It is achieved that both energy consumption is reduced and the qualification rate of low-carbon steel head indicators is guaranteed.

[0030] The present invention has been actually applied in production. By adopting the method of the present invention, the target furnace temperature of low carbon steel can be controlled to about 1180°C, and at the same time, the inlet temperature of the finishing mill can be ensured to meet the requirements of the control range. When the rolling mill stiffness is 480 tons / mm and the strip threading speed reaches 11m / s, the amount of water input into the roll gap of F1-F5 is controlled, and the model automatically calculates the set roll gap according to the current parameters. The deviation between the actual value of the strip head thickness and the set value can meet the requirement of ±0.18mm. DETAILED DESCRIPTION

[0031] The present invention discloses a control method for improving the thickness accuracy of the head of a low-carbon steel strip. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0032] A control method for improving the thickness accuracy of a low-carbon steel strip head comprises the following steps:

[0033] 1. The thickness of the raw material slab used is 200-230mm.

[0034] 2. Control the thickness of the intermediate billet at the entrance of finishing rolling to 38-48mm.

[0035] 3. The temperature control range of low carbon steel heating furnace is 1160~1200℃.

[0036] 4. Control the inlet temperature of the finishing mill according to the change of product target thickness:

[0037] If the target thickness is ≤2.2mm, the finishing mill inlet temperature is controlled at 1035-1060℃;

[0038] If the target thickness is greater than 2.2 mm, the inlet temperature of the finishing mill is controlled at 1015-1040°C.

[0039] 5. According to the different target values ​​of the final rolling temperature, set a reasonable strip threading speed. The general trend is that the target value is relatively low, the threading speed is low, and vice versa; the threading speed range is 10.0m / s to 12m / s.

[0040] If the target final rolling temperature is ≤880°C, the strip threading speed is ≤10.5m / s.

[0041] If the target final rolling temperature is greater than 880°C, the strip threading speed is 10.5m / s<≤12m / s.

[0042] 6. Detect and maintain the consistency of rolling mill stiffness. The rolling mill stiffness control range of finishing mills F1-F7 is 4600~5400KN / mm, ensuring that the fluctuation range of the roll gap setting value during the strip rolling process is small.

[0043] 7. According to the different target thickness of the product, set different amounts of cooling water input into the roll gap to ensure the stability of strip cooling control during the rolling process.

[0044] If the target thickness is ≤2.2mm, the roll gap cooling water of F1-F3 finishing mills is added, and the roll gap cooling water of F4 is added when the water temperature is high. If the actual value of the final rolling temperature is more than 15℃ higher than the target value of the final rolling temperature, the roll gap cooling water of F4 finishing mill is added.

[0045] If the target thickness is greater than 2.2mm, the roll gap cooling water of the F1-F4 finishing mills is added, and the F5 roll gap water temperature is high. If the actual value of the final rolling temperature is greater than the target value of the final rolling temperature by more than 15°C, the roll gap cooling water of the F5 finishing mill is added.

[0046] 8. Improve and correct the thickness control parameters of the secondary model, input the finishing mill inlet temperature, strip threading speed, intermediate billet thickness at the finishing mill inlet and the amount of cooling water input into the roll gap secondary model. The secondary model calculates based on the above data to continuously reduce the deviation between the set value and the actual value of the mill roll gap, and control the rolling force deviation of the single stand to within ±50 tons.

[0047] 9. Optimize the AGC thickness automatic control function, improve the response speed of the closed-loop control of the head thickness, and reduce the thickness fluctuation in production. Input the mill roll gap data corrected by the secondary model into the AGC thickness control system to control the strip head thickness.

[0048] 10. Control the deviation between the actual value of the strip head thickness and the set value within ±0.18mm.

[0049] Embodiment 1:

[0050] A control method for improving the thickness accuracy of a low-carbon steel strip head comprises the following steps:

[0051] 1. The thickness of low carbon steel slab is 200mm, and the temperature control range of heating furnace is 1180±10℃.

[0052] 2. Taking 2.65mm thick low carbon steel SPHC as an example, FT0 (finishing mill inlet temperature): 1030±5℃, and the slab thickness at the finishing mill inlet is 42mm.

[0053] 3. The target final rolling temperature of 2.65mm low carbon steel is 890±10℃, and the threading speed is controlled at 11m / s.

[0054] 4. According to the test, the rolling mill stiffness control range of the finishing mill F1-F7 is 470-490 tons / mm.

[0055] 5. The finishing mill has fixed input of cooling water for the roll gaps of F1-F4, and no other cooling water is input.

[0056] 6. The first level of the finishing mill is equipped with rolling force AGC, impact compensation and monitoring AGC.

[0057] 7. The secondary model is calculated based on the existing data. The deviation between the roll gap setting value and the feedback value of F1-F7 is small, and the deviation between the rolling force set by the rolling mill and the actual rolling force fluctuates within ±30 tons.

[0058] 8. The accuracy of low carbon steel head thickness can reach ±0.05mm, meeting the control requirements.

[0059] Embodiment 2:

[0060] A control method for improving the thickness accuracy of a low-carbon steel strip head comprises the following steps:

[0061] 1. The thickness of low carbon steel slab is 200mm, and the temperature control range of heating furnace is 1190±10℃.

[0062] 2. Taking 2.2mm thick low carbon steel SPHC as an example, FT0: 1040±5℃, the slab thickness at the entrance of the finishing mill is 40mm.

[0063] 3. The target final rolling temperature of 2.2mm low carbon steel is 900±10℃, and the threading speed is controlled at 11.2m / s.

[0064] 4. According to the test, the rolling mill stiffness control range of the finishing mill F1-F7 is 480-490 tons / mm.

[0065] 5. The finishing mill has fixed input of cooling water for the roll gaps of F1-F3, and no other cooling water is input.

[0066] 6. The first level of the finishing mill is equipped with rolling force AGC, impact compensation and monitoring AGC.

[0067] 7. The secondary model is calculated based on the existing data. The deviation between the roll gap setting value and the feedback value of F1-F7 is small, and the deviation between the rolling force set by the rolling mill and the actual rolling force fluctuates within ±30 tons.

[0068] 8. The accuracy of low carbon steel head thickness can reach ±0.06mm, meeting the control requirements.

[0069] Embodiment 3:

[0070] A control method for improving the thickness accuracy of a low-carbon steel strip head comprises the following steps:

[0071] 1. The thickness of low carbon steel slab is 200mm, and the temperature control range of heating furnace is 1170±10℃.

[0072] 2. Taking 3.5mm thick low carbon steel SPHC as an example, FT0: 1020±5℃, the slab thickness at the entrance of the finishing mill is 44mm.

[0073] 3. The target final rolling temperature of 3.5mm low carbon steel is 880±10℃, and the threading speed is controlled at 10.2m / s.

[0074] 4. According to the test, the rolling mill stiffness control range of the finishing mill F1-F7 is 470-480 tons / mm.

[0075] 5. The finishing mill has fixed input of cooling water for the roll gaps of F1-F4, and no other cooling water is input.

[0076] 6. The first level of the finishing mill is equipped with rolling force AGC, impact compensation and monitoring AGC.

[0077] 7. The secondary model is calculated based on the existing data. The deviation between the roll gap setting value and the feedback value of F1-F7 is small, and the deviation between the rolling force set by the rolling mill and the actual rolling force fluctuates within ±40 tons.

[0078] 8. The accuracy of low carbon steel head thickness can reach ±0.06mm, meeting the control requirements.

[0079] The present invention can control the target furnace temperature of low carbon steel to about 1180°C, and at the same time ensure that the inlet temperature of the finishing mill meets the requirements of the control range. When the rolling mill stiffness is 480 tons / mm and the strip threading speed reaches 11m / s, the amount of water input into the roll gap of F1-F5 is controlled, and the model automatically calculates the set roll gap according to the current parameters. The deviation between the actual value of the strip head thickness and the set value can meet the requirement of ±0.18mm.

[0080] The present invention can reduce energy consumption, and at the same time, can effectively control the thickness accuracy of the hot-rolled low-carbon steel head, improve the uniformity of the strip head thickness, reduce problems such as rolling waste and cutting waste caused by thickness fluctuations, and thus ensure the qualified rate of the low-carbon steel head index.

[0081] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A control method for improving the thickness accuracy of a low-carbon steel strip head, characterized in that: The specific steps include: 1) The thickness of the raw material slab used is 200-230mm; 2) The temperature of the heating furnace is controlled at 1160~1200℃; 3) Control the thickness of the intermediate billet at the entrance of finishing rolling to 38-48 mm; 4) Control the finishing mill inlet temperature according to the change of product target thickness: If the target thickness is ≤2.2mm, the finishing mill inlet temperature is controlled at 1035-1060℃; If the target thickness is greater than 2.2 mm, the finishing mill inlet temperature is controlled at 1015-1040°C; 5) Control the strip threading speed to 10-12 m / s; 6) The stiffness of F1-F7 finishing mill is controlled at 4600~5400KN / mm; 7) Determine the amount of cooling water to be added to the roll gap based on the target thickness of the product; 8) The finishing mill inlet temperature, strip threading speed, intermediate billet thickness at the finishing mill inlet and the amount of cooling water input into the roll gap are input into the finishing mill secondary model. The secondary model calculates based on the above data to continuously reduce the deviation between the set value and the actual value of the mill roll gap, and controls the rolling force deviation of the single stand to within ±50 tons; 9) Transmitting the mill roll gap data corrected by the secondary model to the AGC thickness control system to control the strip head thickness; 10) The deviation between the actual value of the strip head thickness and the set value is controlled within ±0.18mm.

2. A control method for improving the thickness accuracy of a low-carbon steel strip head according to claim 1, characterized in that: In step 1), the raw material slab used has a thickness of 200 mm.

3. The control method for improving the thickness accuracy of the head of a low-carbon steel strip according to claim 1 is characterized in that: In step 3), if the target thickness is ≤2.2 mm, then 38 mm ≤ the thickness of the intermediate billet at the finishing rolling entrance ≤42 mm.

4. A control method for improving the thickness accuracy of a low-carbon steel strip head according to claim 1, characterized in that: In step 3), if the target thickness is greater than 2.2 mm, then 42 mm < the thickness of the intermediate billet at the entrance of finishing rolling ≤ 48 mm.

5. The control method for improving the thickness accuracy of the head of a low-carbon steel strip according to claim 1 is characterized in that: In step 5), if the target value of the final rolling temperature is ≤880°C, the strip threading speed is ≤10.5m / s.

6. A control method for improving the thickness accuracy of the head of a low-carbon steel strip according to claim 1, characterized in that: In step 5), if the target value of the final rolling temperature is greater than 880°C, the strip threading speed is 10.5 m / s and less than 12 m / s.

7. A control method for improving the thickness accuracy of a low-carbon steel strip head according to claim 1, characterized in that: In step 7), if the target thickness is ≤2.2 mm, cooling water is added to the roll gap of the F1-F3 finishing mill.

8. The method for improving the thickness accuracy of the head of a low-carbon steel strip according to claim 1 is characterized in that: In step 7), if the actual value of the final rolling temperature is greater than the target value of the final rolling temperature by more than 15°C, cooling water is added to the roll gap of the F4 finishing mill.

9. The control method for improving the thickness accuracy of the head of a low-carbon steel strip according to claim 1 is characterized in that: In step 7), if the target thickness is greater than 2.2 mm, cooling water is added to the roll gap of the F1-F4 finishing mill.

10. The control method for improving the thickness accuracy of the head of a low-carbon steel strip according to claim 1, characterized in that: In step 7), if the actual value of the final rolling temperature is greater than the target value of the final rolling temperature by more than 15°C, cooling water is added to the roll gap of the F5 finishing mill.