Method for improving control of tailing in finishing of hot continuous rolling

Abstract

The application belongs to the technical field of hot continuous rolling finishing rolling, and particularly relates to a control method for improving tailing in hot continuous rolling finishing rolling, which comprises the following steps: after gradient heating treatment of a slab, rough rolling and finishing rolling are performed; in the gradient heating treatment, the head heating temperature of the slab is 1180 DEG C to 1200 DEG C, the intermediate part heating temperature is 10 DEG C to 15 DEG C higher than the head heating temperature, and the tail heating temperature is 10 DEG C to 15 DEG C higher than the intermediate part heating temperature. The control method for improving tailing in hot continuous rolling finishing rolling provided by the application adopts a gradient heating mode, so that when the slab enters the finishing rolling, the temperature difference between the head and the tail of the slab is small, the tail is easy to deform, and thus the tailing risk is reduced.

Description

Technical Field

[0001] This invention belongs to the field of hot continuous rolling finishing technology, and specifically relates to a method for improving the control of tailing during hot continuous rolling finishing. Background Technology

[0002] Tail-end breakage in hot strip mill finishing is a major challenge in the production of thin-gauge (e.g., 1.5mm~3.0mm) and high-strength steel grades. Tail-end breakage manifests as the strip tail deviating from the rolling centerline as it leaves the mill, folding or tearing into the downstream stand, leading to roll surface damage, product defects, and steel pile-up accidents, severely restricting production efficiency and cost control. Traditional control methods rely on manual intervention and local adjustments, but most operators struggle to cope with the coupled effects of multiple factors. Therefore, a new strategy for solving the tail-end breakage problem in finishing mills urgently needs to be established.

[0003] Tail-off is caused by a combination of factors: 1) Due to the contact between the hot-rolled slab and air, the temperature at the tail of the strip continuously decreases, and the actual temperature at the tail of the hot-rolled strip is the lowest. Under the action of AGC (Automatic Thickness Control), the roll gap decreases, and the inconsistency of the roll gaps on both sides of the mill leads to an increase in the tail-off deviation, resulting in tail-off; 2) The tail-off control strategy of the finishing mill AGC is unreasonable. Due to the low temperature of the strip tail at the entrance of the finishing mill, in order to ensure the stability of the thickness of the hot-rolled finished product, the finishing mill AGC control strategy is to add a 100μm~200μm pressure roll gap at the tail of the strip, which increases the risk of tail-off; 3) The finishing mill speed setting is unreasonable. Low-speed rolling will cause the temperature of the strip tail to drop sharply, increasing the risk of tail-off. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for improving the control of tailing during hot continuous rolling finishing. This addresses at least one aspect of solving the above-mentioned technical problems.

[0005] This invention is achieved through the following technical solution: This invention provides a method for improving the control of tailing during hot continuous rolling finishing, comprising the following steps: After the slab undergoes gradient heating treatment, it is subjected to rough rolling and finish rolling. In the gradient heating process, the head of the slab is heated at 1180℃~1200℃, the middle part is heated at 10℃~15℃ higher than the head, and the tail part is heated at 10℃~15℃ higher than the middle part.

[0006] In some possible implementations, the length of the head accounts for 20% to 35% of the total length of the slab.

[0007] In some possible implementations, the length of the middle section accounts for 30% to 60% of the total length of the slab.

[0008] In some possible implementations, the length of the tail portion accounts for 20% to 35% of the total length of the slab.

[0009] In some possible implementations, the thickness of the intermediate billet obtained by rough rolling is 30 mm to 55 mm.

[0010] In some possible implementations, the steel grade has a strength of 600MPa to 700MPa, and the thickness of the intermediate billet is 48mm to 55mm.

[0011] In some possible implementations, the steel grade has a strength of 700MPa to 800MPa, and the thickness of the intermediate billet is 43mm to 48mm.

[0012] In some possible implementations, the steel grade has a strength of 800MPa to 900MPa, and the thickness of the intermediate billet is 35mm to 43mm.

[0013] In some possible implementations, the steel grade has a strength of 900 MPa or higher, and the thickness of the intermediate billet is 30 mm to 35 mm.

[0014] In some possible implementations, during the finishing rolling, the tail reduction of the strip is 0 μm to 150 μm.

[0015] In some possible implementations, the steel grade has a strength of 600MPa to 700MPa, and the tail reduction of the strip is 100μm to 150μm.

[0016] In some possible implementations, the steel grade has a strength of 700MPa to 800MPa, and the tail reduction of the strip is 50μm to 100μm.

[0017] In some possible implementations, the steel grade has a strength of 800MPa to 900MPa, and the tail reduction of the strip is 25μm to 50μm.

[0018] In some possible implementations, the steel grade has a strength of 900 MPa or higher, and the tail reduction of the strip is 0 μm to 25 μm.

[0019] In some possible implementations, the exit rate of the finishing mill is 5 m / s or higher.

[0020] In some possible implementations, the steel grade has a strength of 600MPa to 700MPa, and the exit speed of the finishing mill is 5m / s to 6m / s.

[0021] In some possible implementations, the steel grade has a strength of 700MPa to 800MPa, and the exit speed of the finishing mill is 6m / s to 8m / s.

[0022] In some possible implementations, the steel grade has a strength of 800MPa to 900MPa, and the exit speed of the finishing mill is 8m / s to 10m / s.

[0023] In some possible implementations, the steel grade has a strength of 900 MPa or higher, and the exit speed of the finishing mill is 10 m / s or higher.

[0024] The method for controlling tailing in hot continuous rolling finishing provided by this invention has at least the following beneficial technical effects compared with the prior art: The present invention provides a method for improving the control of tail-wagging in hot continuous rolling finishing. It adopts a gradient heating mode to make the temperature difference between the head and tail of the slab small when it enters the finishing mill, and the tail is easy to deform, thereby reducing the risk of tail-wagging. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described and illustrated below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0026] Obviously, the following description is merely some examples or embodiments of the present invention. Those skilled in the art can apply the present invention to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, modifications to design, manufacturing, or production based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient disclosure of the present invention.

[0027] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand the invention and is not intended to limit the subject matter of the claims.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0029] The main process flow for hot continuous rolling of metal coils is as follows: (1) heating the raw material slab in a heating furnace; (2) rough rolling to achieve initial thinning; (3) finish rolling to achieve secondary thinning and reach the target specifications; (4) cooling the steel plate to the target temperature and performing microstructure control; (5) coiling the rolled plate. In this process, the heating temperature, intermediate slab thickness and finish rolling process all affect the tail-end breakage phenomenon of the steel strip.

[0030] To mitigate the risk of strip breakage due to tailing, this invention provides a method for controlling tailing during hot continuous rolling finishing. By controlling the heating temperature, intermediate billet thickness, and finishing rolling process, the risk of tailing during finishing is reduced, ultimately improving the yield of the steel strip.

[0031] The following is a detailed description of a method for improving the control of tailing in hot continuous rolling finishing according to an embodiment of the present invention.

[0032] This invention provides a method for improving the control of tailing during hot continuous rolling finishing, comprising the following steps: S10. After the slab undergoes gradient heating treatment, it is subjected to rough rolling and finish rolling; In the gradient heating process, the head of the slab is heated at 1180℃~1200℃, the middle section is heated at 10℃~15℃ higher than the head, and the tail section is heated at 10℃~15℃ higher than the middle section.

[0033] The improved hot continuous rolling finishing mill tail-wagging control method provided in this invention adopts a gradient heating mode, which makes the temperature difference between the head and tail of the slab small when it enters the finishing mill, and the tail is easy to deform, thereby reducing the risk of tail-wagging.

[0034] In some embodiments, in step S10 above, the length of the head accounts for 20% to 35% of the total length of the slab.

[0035] In some embodiments, in step S10 above, the length of the middle portion accounts for 30% to 60% of the total length of the slab.

[0036] In some embodiments, in step S10 above, the length of the tail portion accounts for 20% to 35% of the total length of the slab.

[0037] In some embodiments, in step S10 above, the thickness of the intermediate billet obtained by rough rolling is 30 mm to 55 mm.

[0038] In some embodiments, the steel grade strength is 600MPa~700MPa, and the intermediate billet thickness is 48mm~55mm. In some embodiments, the steel grade strength is 700MPa~800MPa, and the intermediate billet thickness is 43mm~48mm. In some embodiments, the steel grade strength is 800MPa~900MPa, and the intermediate billet thickness is 35mm~43mm. In some embodiments, the steel grade strength is above 900MPa, and the intermediate billet thickness is 30mm~35mm. In this case, by controlling the thickness of the intermediate billet, the overall reduction in finishing rolling is controlled, thereby reducing the risk of tailing.

[0039] In some embodiments, during the finishing rolling process in step S10, the tail end of the strip is reduced by 0 μm to 150 μm.

[0040] In some embodiments, the steel grade strength is 600MPa~700MPa, and the tail reduction of the strip is 100μm~150μm.

[0041] In some embodiments, the steel grade strength is 700MPa~800MPa, and the tail reduction of the strip is 50μm~100μm.

[0042] In some embodiments, the steel grade strength is 800MPa~900MPa, and the tail reduction of the strip is 25μm~50μm.

[0043] In some embodiments, the steel grade has a strength of 900 MPa or higher, and the tail reduction of the strip is 0 μm to 25 μm.

[0044] In some embodiments, in step S10 above, the finishing mill exit speed is 5 m / s or higher.

[0045] In some embodiments, the steel grade strength is 600MPa~700MPa, and the exit speed of the finishing mill is 5m / s~6m / s.

[0046] In some embodiments, the steel grade strength is 700MPa~800MPa, and the exit speed of the finishing mill is 6m / s~8m / s.

[0047] In some embodiments, the steel grade strength is 800MPa~900MPa, and the exit speed of the finishing mill is 8m / s~10m / s.

[0048] In some embodiments, the steel grade has a strength of 900 MPa or higher, and the exit speed of the finishing mill is 10 m / s or higher.

[0049] The following description, in conjunction with specific embodiments, provides further details. For ease of explanation, the hot rolling process in the following embodiments and comparative examples is as follows: (1) Heating furnace heats the raw material slab; (2) Rough rolling achieves initial thinning; (3) Finish rolling achieves secondary thinning; (4) Cool the steel plate to the target temperature (820℃~860℃); (5) Coil the rolled plate.

[0050] Example 1 Example 1, taking the rolling of LG600T (steel strength of 600MPa) as an example, provides a method for improving the control of tailing in hot continuous rolling finishing, the steps of which are as follows: E10. After the slab undergoes gradient heating treatment, it is subjected to rough rolling and finish rolling.

[0051] In the gradient heating process, the head of the slab accounts for 20% of the total length of the slab and is heated at 1180℃; the middle part accounts for 50% of the total length of the slab and is heated at 1190℃; and the tail part accounts for 30% of the total length of the slab and is heated at 1205℃.

[0052] The thickness of the intermediate slab in the rough rolling process is 50 mm; The tail reduction of the finishing mill is 150 μm, and the exit speed of the finishing mill is 6 m / s.

[0053] Example 2 Example 2, taking the rolling of LG700T (steel strength of 700MPa) as an example, provides a method for improving the control of tailing in hot continuous rolling finishing, the steps of which are as follows: E11. After the slab undergoes gradient heating treatment, it is subjected to rough rolling and finish rolling.

[0054] In the gradient heating process, the head of the slab accounts for 25% of the total length of the slab and is heated at 1190℃; the middle part accounts for 50% of the total length of the slab and is heated at 1205℃; and the tail part accounts for 25% of the total length of the slab and is heated at 1215℃.

[0055] The thickness of the intermediate slab in the rough rolling process is 45 mm; The tail reduction of the finishing mill is 80 μm, and the exit speed of the finishing mill is 7 m / s.

[0056] Example 3 Example 3, taking the rolling of LG800T (steel strength of 800MPa) as an example, provides a method for improving the control of tailing in hot continuous rolling finishing, the steps of which are as follows: E12. After the slab undergoes gradient heating treatment, it is subjected to rough rolling and finish rolling.

[0057] In the gradient heating process, the head of the slab accounts for 20% of the total length of the slab and is heated at 1200℃; the middle part accounts for 60% of the total length of the slab and is heated at 1210℃; and the tail part accounts for 20% of the total length of the slab and is heated at 1225℃.

[0058] The thickness of the intermediate slab in the rough rolling process is 40 mm; The tail reduction of the finishing mill is 30 μm, and the exit speed of the finishing mill is 9 m / s.

[0059] Example 4 Example 4, taking LG960QT (steel strength of 900MPa and above) as an example, provides a method for improving the control of tailing during hot continuous rolling finishing, the steps of which are as follows: E13. After the slab undergoes gradient heating treatment, it is subjected to rough rolling and finish rolling.

[0060] In the gradient heating process, the head of the slab accounts for 25% of the total length of the slab and is heated at 1200℃; the middle part accounts for 50% of the total length of the slab and is heated at 1215℃; and the tail part accounts for 25% of the total length of the slab and is heated at 1230℃.

[0061] The thickness of the intermediate slab in the rough rolling process is 35 mm; The tail reduction of the finishing mill is 20 μm, and the exit speed of the finishing mill is 10 m / s.

[0062] Comparative Example 1 Comparative Example 1, taking the rolling of LG600T (steel strength of 600MPa) as an example, provides a hot continuous rolling finishing method, the steps of which are as follows: D10. After the slab is heated, it is subjected to rough rolling and finish rolling.

[0063] The heating temperature is 1205℃.

[0064] The thickness of the intermediate slab in the rough rolling process is 50 mm; The tail reduction of the finishing mill is 150 μm, and the exit speed of the finishing mill is 6 m / s.

[0065] Comparative Example 2 Comparative Example 2, taking the rolling of LG600T (steel strength of 600MPa) as an example, provides a hot continuous rolling finishing method. The steps are basically the same as in Example 1, except that: The thickness of the intermediate slab in the rough rolling process is 60 mm; The tail reduction of the finishing mill is 200 μm, and the exit speed of the finishing mill is 7 m / s.

[0066] To verify the advancement of the improved hot continuous rolling finishing tail control method provided by the embodiments of the present invention, the yield and mechanical properties of the steel strips obtained by the embodiments of the present invention and the comparative examples were compared and tested. The results are shown in Table 1 below.

[0067] Table 1

[0068] From Table 1 above, at least the following conclusions can be drawn: The improved hot strip finishing mill tail-wagging control method provided in this embodiment of the invention adopts a gradient heating mode, which makes the temperature difference between the head and tail of the slab small when it enters the finishing mill, and the tail is easy to deform, thereby reducing the risk of tail-wagging. Ultimately, while ensuring the steel strength, the strip yield is improved.

[0069] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for controlling tailing during hot continuous rolling finishing, characterized in that, Includes the following steps: After the slab undergoes gradient heating treatment, it is subjected to rough rolling and finish rolling. In the gradient heating process, the head of the slab is heated at 1180℃~1200℃, the middle part is heated at 10℃~15℃ higher than the head, and the tail part is heated at 10℃~15℃ higher than the middle part.

2. The method for controlling tailing in hot continuous rolling finishing as described in claim 1, characterized in that, The length of the head accounts for 20% to 35% of the total length of the slab.

3. The method for controlling tailing in hot continuous rolling mill according to claim 2, characterized in that, The length of the middle section accounts for 30% to 60% of the total length of the slab.

4. The method for improving the control of tailing in hot continuous rolling finishing as described in claim 3, characterized in that, The length of the tail portion accounts for 20% to 35% of the total length of the slab.

5. The method for controlling tailing in hot continuous rolling mill according to claim 4, characterized in that, The thickness of the intermediate billet obtained by rough rolling is 30mm~55mm.

6. The method for controlling tailing in hot continuous rolling mill according to claim 1, characterized in that, It satisfies at least one of the following characteristics (1) to (4): (1) The strength of the steel is 600MPa~700MPa, and the thickness of the intermediate billet is 48mm~55mm; (2) The strength of the steel is 700MPa~800MPa, and the thickness of the intermediate billet is 43mm~48mm; (3) The strength of the steel is 800MPa~900MPa, and the thickness of the intermediate billet is 35mm~43mm; (4) The steel grade has a strength of 900MPa or above, and the thickness of the intermediate billet is 30mm~35mm.

7. The method for controlling tailing in hot continuous rolling mill according to claim 6, characterized in that, During the finishing rolling process, the additional reduction at the tail of the strip is 0μm to 150μm.

8. The method for controlling tailing in hot continuous rolling mill according to claim 7, characterized in that, It satisfies at least one of the following characteristics (1) to (4): (1) The steel grade strength is 600MPa~700MPa, and the tail reduction of the strip is 100μm~150μm; (2) The steel grade strength is 700MPa~800MPa, and the tail reduction of the strip is 50μm~100μm; (3) The steel grade strength is 800MPa~900MPa, and the tail reduction of the strip is 25μm~50μm; (4) The steel grade strength is above 900MPa, and the tail end of the strip is reduced by 0μm~25μm.

9. The method for improving the control of tailing in hot continuous rolling finishing as described in claim 8, characterized in that, The exit speed of the finishing mill is above 5 m / s.

10. The method for controlling tailing in hot continuous rolling mill according to claim 9, characterized in that, It satisfies at least one of the following characteristics (1) to (4): (1) The steel grade strength is 600MPa~700MPa, and the exit speed of the finishing mill is 5m / s~6m / s; (2) The strength of the steel is 700MPa~800MPa, and the exit speed of the finishing mill is 6m / s~8m / s; (3) The strength of the steel is 800MPa~900MPa, and the exit speed of the finishing mill is 8m / s~10m / s; (4) The steel grade strength is above 900MPa, and the exit speed of the finishing mill is above 10m / s.

Images