Manufacturing method for inhibiting generation of black spots on surface of alloy decrement plate

Abstract

The invention belongs to the technical field of alloy manufacturing, and particularly relates to a manufacturing method for inhibiting generation of black spots on the surface of an alloy decrement plate. The method comprises the following process steps: (1) heating process; (2) rolling process; (3) a rapid cooling process; and (4) straightening process. The problem of black spots on the surface of the alloy decrement plate is effectively solved, the surface quality of the steel plate is improved, and the market competitiveness is improved.

Description

Technical Field

[0001] This invention belongs to the field of alloy manufacturing technology, and specifically relates to a manufacturing method for suppressing the generation of black spots on the surface of alloy reduction plates. Background Technology

[0002] With the improvement of medium and heavy plate production capacity, medium and heavy plate products are gradually moving towards "low cost and reduced weight." During the post-rolling cooling process of medium and heavy plates, the cooling temperature gradually moves towards the low-temperature zone, and the cooling rate continuously increases. This leads to uneven cooling, resulting in black spots on the steel plate surface, commonly known as "spotted dogs." These black spots are primarily caused by the indentation of iron oxide scale, combined with residual iron oxide scale from rolling and abnormal cooling process control, resulting in an unsightly appearance and affecting usability to some extent. The alloy reduced-weight plate mentioned in this application refers to medium and heavy plates produced using Q325C or Q325T billets with a thickness of 12mm to 40mm, an upper yield strength ≥355MPa, a tensile strength of 475MPa to 630MPa, and an elongation after fracture ≥20%.

[0003] To address this issue, Zhongnan Steel's plate production line increased the number of descaling passes during rolling, reduced the number of water intake groups in the ultra-fast cooling manifold, lowered the flow rate in the ultra-fast cooling manifold, and adjusted the micro-acceleration control and head / tail shielding functions of the ultra-fast cooling roller conveyor. Specifically, the roller conveyor micro-acceleration control is based on changes in the steel plate length, with the roller acceleration ranging from 0.005 to 0.02 m / s². 2 The cooling system is adjusted between different flow rates. The head and tail shielding uses a flow rate shielding method, where the flow rate is low within a certain range at the head and tail, and normal in the middle, to improve the uniformity of steel plate cooling and thus reduce black spots on the plate surface. Zhongnan Steel's ultra-fast cooling system for its plate production line is a double-frame cooling system, using inclined nozzle jet cooling throughout. It has 24 sets of manifolds, all with high density, divided into A and B zones. The upper frame is movable, and every four sets form a group. The first three sets of manifolds in each group spray in the same direction as the steel plate's movement, while the last set sprays in the opposite direction to form a soft water seal.

[0004] The above methods can alleviate the problems of temperature difference, plate shape, and black spots at the beginning, middle, and end of the steel plate to some extent. However, due to the excessively rapid temperature drop of the steel plate after increasing the number of descaling passes, it is difficult to control the plate shape during subsequent rolling. Furthermore, due to the large number of cooling manifolds and their complex arrangement, technicians have not yet found an effective method to control black spots on the plate surface. They simply set the parameters of a few manifolds randomly without any regularity or standardization, resulting in unstable cooling uniformity of the steel plate. Therefore, the problem of black spots on the surface of alloy weight reduction plates has not been significantly improved to date.

[0005] The prior art CN202511640799.5 discloses a method and device for controlling black marks on the surface of thick plates. However, after on-site investigation and testing, the applicant found that the method can only improve the black marks on the surface of thick plates and cannot completely remove the black spots on the surface of alloy reduction plates. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of black spots on the surface of steel plates and to provide a manufacturing method for suppressing the formation of black spots on the surface of alloy reduction plates. Through extensive experimentation, the applicant unexpectedly discovered that under certain specific parameters, the cooling uniformity of the steel plate is significantly improved, effectively solving the problem of black spots and enhancing the surface quality of the steel plate. The method includes the following process steps: (1) Heating process; (2) Rolling process: For alloy reduction plates with a thickness of 12mm ≤ 25mm, when using forward pass forming, the penultimate pass does not remove scale, and the last pass removes scale; when using reverse pass forming, the penultimate pass removes scale, and the last pass does not remove scale. For alloy reduction plates with a thickness of 25mm < 40mm, reverse pass forming is adopted, descaling is performed in the penultimate pass, and descaling is performed in the final pass. (3) Rapid cooling process: For alloy reduction plates with a thickness of 12mm to 25mm, the roller speed is 1.0-1.3m / s; the acceleration is 0.01-0.015m / s². 2 ; relative to a water volume of 100m 3 / h, water ratio is 1.7-2.2; For alloy reduction plates with a thickness of 25mm to 40mm, the roller speed is 0.7-1.0m / s and the acceleration is 0.006-0.008m / s². 2 ; relative to a water volume of 100m 3 / h, water ratio is 2.2-2.6; (4) Straightening process.

[0007] The manufacturing method described above for suppressing the generation of black spots on the surface of the alloy reduction plate uses an ultra-fast cooling system (ADCOS-PM system).

[0008] The above-mentioned manufacturing method for suppressing the generation of black spots on the surface of alloy reduction plates refers to the presence of dense dot-like or patchy black marks in the middle of the plate surface. These black spots can easily cause the middle of the steel plate to bulge, forming a "turtle back" bending defect. The "black spot" area is also prone to processing cracks.

[0009] In the above manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate, the water volume in step (3) refers to the flow rate, with the unit being m³ / s. 3 / h, in this method, 100m 3The fluctuation of / h should not exceed 5%, otherwise black spots will appear on the resulting alloy reduction plate; the water ratio is for the flow rate of the upper manifold and the flow rate of the lower manifold, and the flow rate of the lower manifold = water volume × water ratio.

[0010] The above-mentioned manufacturing method for suppressing the formation of black spots on the surface of alloy weight-reduction plates includes the following chemical composition of the slab by mass percentage: C:0.17-0.20%, Si:0.15-0.30%, Mn:1.10-1.30%, P≤0.022%, S≤0.010%, Als≤0.008%, Ti:0.016-0 .028%, CEV≤0.44%; Cu≤0.30%, Cr≤0.29%, Ni≤0.30%, B≤0.0005%, As≤0.15%, and Cr+Ni+Cu+Mo≤0.70%.

[0011] As a preferred embodiment, in the above-mentioned manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate, in step (1), the temperature of the first heating section is 1000-1100℃, the temperature of the second heating section is 1200-1300℃, the temperature of the soaking section is 1220-1280℃, and the heating time is 170-180min. Improving the uniformity of the heating temperature of the slab is beneficial to improving the descaling effect on the plate surface.

[0012] As a preferred embodiment, in the above-mentioned manufacturing method for suppressing the generation of black spots on the surface of alloy reduction plates, in step (2), for alloy reduction plates with a thickness of 12mm ≤ 25mm, the initial rolling temperature is 1040-1100℃, the finishing rolling initial rolling temperature is 900-950℃, the final rolling temperature is 780-810℃ when using forward rolling passes, and the final rolling temperature is 800-830℃ when using reverse rolling passes. This is beneficial to the stability of steel plate performance.

[0013] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (2), for alloy reduction plates with a thickness of 25mm < ≤ 40mm, the initial rolling temperature is 1040-1100℃, the initial finishing rolling temperature is 850-950℃, and the final rolling temperature is 790-820℃. This is beneficial to the stability of the steel plate performance.

[0014] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (3), for alloy reduction plates with a thickness of 12mm≤25mm, the initial cooling temperature is 750-800℃ and the reheating temperature is 580-620℃. This is beneficial to the stability of the steel plate performance.

[0015] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (3), for alloy reduction plates with a thickness of 25mm < 40mm, the initial cooling temperature is 760-810℃ and the reheating temperature is 590-630℃. This is beneficial to the stability of the steel plate performance.

[0016] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (3), for alloy reduction plates with a thickness of 12mm ≤ 25mm, the shielding parameters satisfy: the head shielding length is 100-500mm, and the head shielding coefficient is 0.65-0.75; the tail shielding length is 2000-5000mm, and the tail shielding coefficient is 0.75-0.85. This is beneficial to the uniformity of the cooling temperature of the steel plate and improves the shape of the cooling plate.

[0017] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (3), for alloy reduction plates with a thickness of 25mm < ≤ 40mm, the shielding parameters satisfy: the head shielding length is 1000-2000mm, and the head shielding coefficient is 0.7-0.8; the tail shielding length is 1000-3000mm, and the tail shielding coefficient is 0.8-0.9. This is beneficial to the uniformity of the cooling temperature of the steel plate and improves the shape of the cooling plate.

[0018] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (3), side spray, center spray and inlet / outlet compressed air purging devices are simultaneously activated to improve the residual water purging effect during the steel plate cooling process and improve the plate surface quality. This is beneficial to the uniformity of the steel plate cooling temperature and improves the cooling plate shape.

[0019] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (4), for alloy reduction plates with a thickness of 12mm≤thickness≤25mm, the straightening process meets the following requirements: straightening reduction is 2-2.5mm, tilting is 1.0-2.0mm, straightening force is 300-500t, and straightening is performed twice. This is beneficial for improving the flatness of the steel plate.

[0020] As a preferred embodiment, in the manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate described above, in step (4), for alloy reduction plates with a thickness of 25mm < ≤ 40mm, the straightening process meets the following requirements: straightening reduction of 2.5-3.5mm, tilting of 0.5-1.0mm, straightening force of 600-1000t, and straightening 2-3 times. This is beneficial for improving the flatness of the steel plate.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Significantly improves the surface quality of steel plates: By optimizing the descaling strategy during the rolling process (dynamically adjusting the final descaling scheme for different thicknesses and rolling directions), and combining it with precise control of the roller speed, acceleration, and water ratio in the rapid cooling process, the generation of black spots is fundamentally eliminated. 2. Highly applicable and with clearly defined operating procedures: Differentiated rolling, rapid cooling, and straightening process parameters are provided for steel plates of different thicknesses from 12 to 40 mm, forming a standardized operating procedure. This solves the problems of high randomness in parameter settings and unstable results in existing technologies, and significantly improves production efficiency and product consistency.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0023] Figure 1 The alloy reduction plate obtained in Comparative Example 1; Figure 2 The alloy reduction plate obtained in Comparative Example 2; Figure 3 The alloy reduction plate with no black spots on the surface obtained in Example 3; Figure 4 The alloy reduction plate with no black spots on the surface obtained in Example 1. Detailed Implementation

[0024] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0025] In this embodiment of the invention, the main equipment used is an ultra-fast cooling system (ADCOS-PM system).

[0026] In this embodiment of the invention, steps not described in detail are conventional techniques in the art.

[0027] In this embodiment of the invention, the chemical composition of the slab satisfies the following: including, by mass percentage: C: 0.17-0.20%, Si: 0.15-0.30%, Mn: 1.10-1.30%, P≤0.022%, S≤0.010%, Als≤0.008%, Ti: 0.016-0.028%, CEV≤0.44%; Residual elements: Cu≤0.30%, Cr≤0.29%, Ni≤0.30%, B≤0.0005%, As≤0.15%, and Cr+Ni+Cu+Mo≤0.70%.

[0028] Example 1 This embodiment provides a manufacturing method for suppressing the formation of black spots on the surface of an alloy reduction plate.

[0029] For 16mm thick alloy reduced-weight steel plates (low alloy plates): 1. Heating process: The temperature of the first heating section is 1000-1100℃, the temperature of the second heating section is 1200-1300℃, the temperature of the soaking section is 1220-1280℃, and the heating time is 176min.

[0030] 2. Rolling process: initial rolling temperature 1050℃, finishing rolling initial rolling temperature 950℃, final rolling temperature 790℃ (using forward passes to form the product); descaling: no descaling in the penultimate pass, descaling in the last pass (using forward passes to form the product), 11 rolling passes.

[0031] 3. Rapid cooling process: initial cooling temperature 760℃, re-heating temperature 610℃; roller speed 1.3m / s, acceleration 0.015m / s². 2 Water volume 100m 3 / h, water ratio 1.7 / 1.9 / 1.8 (the water ratio can be adjusted in three stages for ultra-fast cooling. The ultra-fast cooling system has a total of 24 groups of water, with groups 1-4, 5-12, and 13-24 controlled at 1.7 / 1.9 / 1.8 respectively); shielding parameters: head shielding length 100mm, head shielding coefficient 0.7; tail shielding length 5000mm, tail shielding coefficient 0.8.

[0032] 4. Straightening process: Straightening reduction 2.0mm, tilting amount 1.2mm, straightening force 300t, straightening 2 passes.

[0033] The performance data of the alloy reduction plate obtained in Example 1 are as follows: Table 1

[0034] The alloy reduction plate with no black spots on the surface obtained in Example 1 is as follows: Figure 4 As shown.

[0035] Example 2 The difference from Example 1 is as follows: 2. Rolling process: Final rolling temperature 810℃ (using reverse pass rolling); Descaling: descaling in the second to last pass, no descaling in the last pass (using reverse pass rolling).

[0036] The performance data of the alloy reduction plate obtained in Example 2 are as follows: Table 2

[0037] Example 3 This embodiment provides a manufacturing method for suppressing the formation of black spots on the surface of an alloy reduction plate.

[0038] For 30mm thick alloy reduced-weight steel plates (low alloy plates): 1. Heating process: The temperature of the first heating section is 1000-1100℃, the temperature of the second heating section is 1200-1300℃, the temperature of the soaking section is 1220-1280℃, and the heating time is 176min.

[0039] 2. Rolling process: initial rolling temperature 1050℃, finishing rolling initial rolling temperature 950℃, final rolling temperature 800℃ (using reverse passes to form the product); the last two passes are descaled, and the rolling process is 13 passes.

[0040] 3. Rapid cooling process: initial cooling temperature 780℃, reheating temperature 625℃; roller speed 0.8m / s, acceleration 0.01m / s². 2 Water volume 100m 3 / h, water ratio 2.3 / 2.5 / 2.4; shading parameters: head shading length 1000mm, head shading coefficient 0.75; tail shading length 2000mm, tail shading coefficient 0.85.

[0041] 4. Straightening process: Straightening reduction 3.0mm, tilting amount 0.8mm, straightening force 700t, straightening 2 times.

[0042] The performance data of the alloy reduction plate obtained in Example 3 are as follows: Table 3

[0043] The alloy reduction plate with no black spots on the surface obtained in Example 3 is as follows: Figure 3 As shown.

[0044] Comparative Example 1 The difference from Example 1 is as follows: Cooling temperature: 815℃; Red return temperature: 611℃; Water volume: 120m³ 3 / h, roller speed 1.5m / s, acceleration 0.018m / s² 2 With a water ratio of 1.6, the resulting alloy reduction plate is as follows: Figure 1 As shown.

[0045] Comparative Example 2 The difference from Example 2 is that: Cooling temperature: 812℃; Red return temperature: 619℃; Water volume: 120m³ 3 / h, roller speed 1.65m / s, acceleration 0.018m / s² 2 With a water ratio of 1.6, the resulting alloy reduction plate is as follows: Figure 2 As shown.

[0046] Comparative Example 3 The difference from Example 3 is that: Based on an initial cooling temperature of 822℃, a red glow temperature of 620℃, and a water volume of 150m³. 3 / h, roller speed 0.65m / s, acceleration 0.016m / s² 2 Water ratio 1.6, prepared by method The resulting alloy reduction plate has black spots on its surface.

[0047] Comparative Example 4 The only difference from Example 1 is that the second-to-last descaling process resulted in black spots on the surface of the alloy reduction plate. The only difference from Example 1 is that the final pass does not remove scale, resulting in black spots on the surface of the alloy reduction plate. The only difference from Example 1 is that the water volume is 110m³. 3 / h, the surface of the resulting alloy reduction plate has black spots; The only difference from Example 1 is that the water volume is 90m³. 3 / h, the surface of the resulting alloy reduction plate has black spots; The only difference from Example 1 is that the water ratio is 1.5 / 1.7 / 1.6, and the resulting alloy reduction plate has a bending degree >8mm / 2m; The only difference from Example 1 is that the water ratio is 2.2 / 2.4 / 2.3, and the resulting alloy reduction plate has a bending degree of >8mm / 2m.

[0048] Comparative Example 5 The only difference from Example 2 is that the penultimate step does not remove scale, resulting in black spots on the surface of the alloy reduction plate. The only difference from Example 2 is that the final descaling pass resulted in black spots on the surface of the alloy reduction plate.

[0049] Comparative Example 6 The only difference from Example 3 is that the penultimate step does not remove scale, resulting in black spots on the surface of the alloy reduction plate. The only difference from Example 3 is that the final pass does not remove scale, resulting in black spots on the surface of the alloy reduction plate. The only difference from Example 3 is that the water volume is 110m³. 3 / h, the surface of the resulting alloy reduction plate has black spots; The only difference from Example 3 is that the water volume is 90m³. 3 / h, the surface of the resulting alloy reduction plate has black spots; The only difference from Example 3 is that the water ratio is 2.0 / 2.2 / 2.1, and the resulting alloy reduction plate has a bending degree >8mm / 2m; The only difference from Example 3 is that the water ratio is 2.6 / 2.8 / 2.7, and the resulting alloy reduction plate has a bending degree of >8mm / 2m.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A manufacturing method for suppressing the formation of black spots on the surface of an alloy reduction plate, characterized in that, The method includes the following process steps: (1) Heating process; (2) Rolling process: For alloy reduction plates with a thickness of 12mm ≤ 25mm, when using forward pass forming, the penultimate pass does not remove scale, and the last pass removes scale; when using reverse pass forming, the penultimate pass removes scale, and the last pass does not remove scale. For alloy reduction plates with a thickness of 25mm < 40mm, reverse pass forming is adopted, descaling is performed in the penultimate pass, and descaling is performed in the final pass. (3) Rapid cooling process: For alloy reduction plates with a thickness of 12mm ≤ 25mm, the roller conveyor speed is 1.0-1.3m / s; The acceleration is 0.01-0.015 m / s². 2 ; relative to a water volume of 100m 3 / h, water ratio is 1.7-2.2; For alloy reduction plates with a thickness of 25mm to 40mm, the roller speed is 0.7-1.0m / s and the acceleration is 0.006-0.008m / s². 2 ; relative to a water volume of 100m 3 / h, water ratio is 2.2-2.6; (4) Straightening process.

2. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, The chemical composition of the slab includes, by mass percentage: C:0.17-0.20%, Si:0.15-0.30%, Mn:1.10-1.30%, P≤0.022%, S≤0.010%, Als≤0.008%, Ti:0.016-0 .028%, CEV≤0.44%; Cu≤0.30%, Cr≤0.29%, Ni≤0.30%, B≤0.0005%, As≤0.15%, and Cr+Ni+Cu+Mo≤0.70%.

3. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (1), the temperature of the first heating section is 1000-1100℃, the temperature of the second heating section is 1200-1300℃, the temperature of the soaking section is 1220-1280℃, and the heating time is 170-180min.

4. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (2), for alloy reduction plates with a thickness of 12mm≤thickness≤25mm, the initial rolling temperature is 1040-1100℃, the finishing rolling initial rolling temperature is 900-950℃, the final rolling temperature is 780-810℃ when using forward passes, and the final rolling temperature is 800-830℃ when using reverse passes.

5. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (2), for alloy reduction plates with thickness ≤ 40 mm and a thickness of 25 mm, the initial rolling temperature is 1040-1100℃, the initial rolling temperature for finishing is 850-950℃, and the final rolling temperature is 790-820℃.

6. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (3), for alloy reduction plates with a thickness of 12mm≤thickness≤25mm, the cooling temperature is 750-800℃ and the reddening temperature is 580-620℃.

7. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (3), for alloy reduction plates with a thickness of 25mm < 40mm, the cooling temperature is 760-810℃ and the red temperature is 590-630℃.

8. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (3), For alloy reduction plates with a thickness of 12mm ≤ 25mm, the shielding parameters meet the following requirements: head shielding length is 100-500mm, head shielding coefficient is 0.65-0.75; tail shielding length is 2000-5000mm, tail shielding coefficient is 0.75-0.

85. For alloy reduction plates with a thickness of 25mm < 40mm, the shielding parameters are as follows: head shielding length is 1000-2000mm, head shielding coefficient is 0.7-0.8; tail shielding length is 1000-3000mm, tail shielding coefficient is 0.8-0.

9.

9. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (3), the side spray, center spray and inlet / outlet compressed air purging devices are put into operation simultaneously to improve the residual water purging effect during the steel plate cooling process and improve the plate surface quality.

10. The manufacturing method for suppressing the generation of black spots on the surface of the alloy reduction plate according to claim 1, characterized in that, In step (4), For alloy reduction plates with a thickness of 12mm ≤ 25mm, the straightening process meets the following requirements: straightening reduction of 2-2.5mm, tilting of 1.0-2.0mm, straightening force of 300-500t, and straightening in 2 passes. For alloy reduction plates with a thickness of 25mm < 40mm, the straightening process should meet the following requirements: straightening reduction of 2.5-3.5mm, tilting of 0.5-1.0mm, straightening force of 600-1000t, and straightening in 2-3 passes.

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