Optimized cooling process for large flat-bulb steel

Abstract

The invention relates to the technical field of metal material processing, in particular to a large-scale flat-bulb steel optimized cooling process which comprises the following steps: S1, temperature homogenization treatment; s2, primary cooling is carried out, and shock cooling is avoided; s3, a spraying device is used for cooling the flat-bulb steel, and conditions are created for subsequent partition cooling operation; s4, the flat body part of the flat-bulb steel is covered with a heat insulation material; s5, carrying out subarea differential cooling; s6, carrying out temperature equalization processing; s7, carrying out secondary spray cooling to reduce the temperature to a target range; s8, slowly cooling until the temperature is reduced to room temperature; s9, stress relief treatment is conducted, and the structural stability of a finished product is guaranteed; according to the method, through partitioned differential cooling, slow cooling control and mechanical vibration aging treatment, the temperature uniformity and internal stress release in the cooling process of the flat-bulb steel are remarkably improved, and the mechanical property and structural stability of a product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal material processing, and in particular to an optimized cooling process for large-scale bulb flat steel. Background Art

[0002] With the continuous development of large-scale projects such as heavy industry and shipbuilding, bulb flat steel is widely used in fields such as ships, bridges and heavy machinery due to its high strength and structural stability. The production process of bulb flat steel includes multiple steps such as hot rolling forming and cooling treatment, and the cooling process is crucial to the final performance of the bulb flat steel. During the production process, the thickness and shape of the bulb flat steel are uneven, resulting in significant temperature gradients in different parts. Internal stress and structural unevenness are easily generated during the cooling process, especially the difference in cooling rate between the ball head and the flat body, which leads to stress concentration and deformation. In addition, in order to improve the mechanical properties of the bulb flat steel, stress release and structural stability treatment are required after cooling treatment to ensure its reliability and durability in subsequent use.

[0003] The existing cooling process mainly relies on natural cooling or simple water spray cooling, which makes it difficult to achieve precise temperature control of various parts of the bulb flat steel, especially the inability to effectively control the zone cooling of the ball head and flat body, resulting in uneven cooling rate and inaccurate temperature control, which ultimately leads to residual internal stress, deformation and unstable performance of the product. In addition, the existing process lacks an effective stress elimination method, which poses a potential safety hazard to the bulb flat steel in subsequent use. Summary of the invention

[0004] Based on the above objectives, the present invention provides an optimized cooling process for large-scale bulb flat steel.

[0005] An optimized cooling process for large bulb flat steel comprises the following steps: S1: Temperature homogenization treatment, placing the newly rolled bulb flat steel in a holding furnace and keeping it in a high temperature environment for a specified time to make the internal and external temperatures of the bulb flat steel uniform; S2: Preliminary cooling: the bulb flat steel after temperature homogenization treatment is moved out of the holding furnace and placed on the cooling platform. The overall temperature of the bulb flat steel is gradually reduced by natural convection to avoid sudden cooling. S3: Spray cooling: after the initial cooling, the bulb flat steel is cooled by a spray device, and the water mist parameters are controlled to reduce the bulb flat steel temperature to a predetermined range, thus creating conditions for subsequent zone cooling operations; S4: Covering with insulation material. After spray cooling, the flat part of the bulb flat steel is covered with insulation material to prepare for zoned differentiated cooling. S5: Differentiated cooling in different areas: the ball head area not covered with insulation material is cooled intensively, and the spray device is continued to be used. The flat body area is cooled slowly because it is covered with insulation material, so as to achieve cooling rate control in different areas. S6: Temperature balancing treatment: after the partition cooling is completed, all cooling operations are suspended for a period of time to redistribute the internal heat of the bulb flat steel and achieve internal temperature balance; S7: Secondary spray cooling, remove the heat insulation material at the flat part, and spray cool the entire bulb flat steel again to reduce the temperature to the target range; S8: Slow cooling, transfer the bulb flat steel after secondary spray cooling to a slow cooling environment, and use a slow cooling method until it cools to room temperature; S9: Stress relief treatment. After cooling to room temperature, the bulb flat steel is subjected to mechanical vibration aging treatment to release residual stress and ensure the structural stability of the finished product.

[0006] Optionally, the S1 specifically includes: S11: The bulb flat steel just rolled is taken out from the rolling mill at intervals not exceeding 10 seconds to reduce heat loss, and is quickly transferred to a holding furnace; S12: placing the spherical flat steel in a holding furnace, and setting the holding furnace temperature to 800-900°C; S13: Keep the flat steel ball at a constant temperature in the holding furnace for 5-10 minutes to allow the internal and external temperatures of the flat steel ball to be fully balanced.

[0007] Optionally, the S2 specifically includes: S21: Remove the bulb flat steel after temperature homogenization treatment from the holding furnace, keep the transfer time no more than 15 seconds to reduce temperature fluctuations, and place it on a cooling platform; S22: Maintain the ambient temperature around the cooling platform at 20-25°C, cool by natural convection, and control the height of the cooling platform to 20-30 cm from the ground; S23: Keep the bulb flat steel on the cooling platform for 2-4 minutes, and let the surface temperature gradually decrease by natural convection. The temperature reduction rate is controlled at 2-5℃ / s.

[0008] Optionally, the S3 specifically includes: S31: After the initial cooling of the bulb flat steel is completed, the spray device is started and the water mist particle size is set to 20-50μm to evenly cover the surface of the bulb flat steel; S32: Adjust the spray pressure to 0.5-0.8MPa so that the water mist acts evenly on the surface of the bulb flat steel; S33: Maintain the spray cooling time for 1-3 minutes, gradually reduce the surface temperature of the ball flat steel to 650-700℃, and create temperature conditions for subsequent zone cooling.

[0009] Optionally, the S4 specifically includes: S41: After spray cooling is completed, fix the ball flat steel on the cooling platform to ensure that the flat body is exposed; S42: Choose ceramic fiber felt or aluminum silicate fiber felt as the insulation material, with a thickness of 5-10 mm, and evenly cover the flat body of the bulb flat steel with the insulation material to isolate it from the ball head; S43: Use a clamp to fix the insulation material to ensure that it does not move or fall off during the cooling process; S44: After the insulation material is covered, the ball flat steel is transferred to the zoned cooling area to prepare for the zoned differentiated cooling operation.

[0010] Optionally, the S5 specifically includes: S51: After the insulation material is covered, the spray device is started to perform enhanced cooling on the ball head part that is not covered with the insulation material, and the water mist particle size is set to 15-30 μm; S52: Adjust the spray pressure to 0.8-1.0MPa so that the water mist is concentrated on the ball head; S53: Maintain the spray cooling time for 3-5 minutes, and control the temperature of the ball head to gradually drop to 600-650°C; S54: During the spray cooling period, the insulation material of the flat body is not removed to ensure that the flat body is cooled slowly and the temperature is controlled at 650-700℃.

[0011] Optionally, the S6 specifically includes: S61: After the zone cooling is completed, immediately suspend all spray cooling operations to ensure that the bulb flat is in a static state without any external cooling intervention; S62: Leave the bulb flat steel in an air environment for 2-4 minutes to allow the heat inside and outside the bulb flat steel to be naturally transferred without cooling interference to achieve heat redistribution.

[0012] Optionally, the S7 specifically includes: S71: After the temperature equalization process is completed, remove the insulation material covering the flat body part; S72: Restart the spray cooling device and adjust the water mist particle size to 10-30 μm; S73: Set the spray pressure to 0.3-0.5MPa and maintain the spray cooling time for 2-4 minutes to gradually reduce the surface temperature of the bulb flat steel to 450-500℃.

[0013] Optionally, the S8 specifically includes: S81: After the secondary spray cooling is completed, the flat steel ball is transferred from the cooling platform to the slow cooling environment and placed in the slow cooling pit to ensure that the flat steel ball is evenly covered with insulation material; S82: Adjust the thickness of the insulation material of the slow cooling pit to 20-30 cm to slow down the heat exchange rate between the bulb flat steel and the outside world; S83: Keep the bulb flat steel in a slow cooling environment for 4-6 hours, control the cooling rate to 5-10°C per hour, and gradually reduce its temperature to room temperature.

[0014] Optionally, the S9 specifically includes: S91: After the bulb flat steel has cooled to room temperature, place it on a mechanical vibration device and ensure that the bulb flat steel is stably fixed to avoid displacement or offset during vibration; S92: Set the frequency of the mechanical vibration device to 20-50 Hz, start the vibration device, and apply uniform vibration to the bulb flat steel to act on the overall structure; S93: Control the vibration treatment time to 2-4 hours and maintain a constant vibration frequency; S94: After the vibration aging treatment is completed, the ball flat steel is removed from the vibration device to obtain a finished ball flat steel product after optimized cooling.

[0015] Beneficial effects of the present invention: The present invention achieves precise control of the cooling rates of the ball head and flat body of the bulb flat steel by introducing specific steps such as zoned differentiated cooling and slow cooling control during the cooling process, and adopts multi-stage processes such as spray cooling, heat insulation covering, temperature balance and slow cooling treatment to ensure that the temperature gradient of the bulb flat steel is stable during the cooling process, and the internal and external temperatures are uniform, which significantly reduces the internal stress concentration and structural unevenness caused by temperature differences during the cooling process, ensures the shape and dimensional accuracy of the bulb flat steel, and in addition, by controlling the cooling rate and temperature range, avoids sudden cooling during the cooling process, and effectively improves the overall mechanical properties of the product.

[0016] The present invention, by introducing mechanical vibration aging treatment, further releases the residual stress in the bulb flat steel through reasonable vibration frequency and time, thereby improving the structural stability and durability of the product. The process method is applicable to the production of bulb flat steels of various specifications, which can not only improve the service life of the bulb flat steels, but also meet the demand for high-performance steels of large structures, and provide more reliable material guarantees for heavy projects such as shipbuilding and bridge construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of a cooling process optimized for large bulb flat steel according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the zoned differentiated cooling process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0020] It should be noted that the references to "one embodiment", "embodiment", "exemplary embodiments", "some embodiments" and the like in the specification indicate that the embodiments described may include specific features, structures or characteristics, but not every embodiment may include the specific features, structures or characteristics. In addition, when a specific feature, structure or characteristic is described in conjunction with an embodiment, it should be within the knowledge of a person skilled in the art to implement such feature, structure or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0021] In general, a term can be understood, at least in part, from its use in context. For example, depending, at least in part, on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular sense, or can be used to describe a combination of features, structures, or characteristics in the plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but can instead, depending, at least in part, on the context, allow for the presence of other factors that are not necessarily explicitly described.

[0022] Example 1 like Figure 1-Figure 2 As shown, an optimized cooling process for large bulb flat steel includes the following steps: S1: Temperature homogenization treatment, placing the newly rolled bulb flat steel in a holding furnace and keeping it in a high temperature environment for a specified time to make the internal and external temperatures of the bulb flat steel uniform; S2: Preliminary cooling: the bulb flat steel after temperature homogenization treatment is moved out of the holding furnace and placed on the cooling platform. The overall temperature of the bulb flat steel is gradually reduced by natural convection to avoid sudden cooling. S3: Spray cooling: after the initial cooling, the bulb flat steel is cooled by a spray device, and the water mist parameters are controlled to reduce the bulb flat steel temperature to a predetermined range, thus creating conditions for subsequent zone cooling operations; S4: Covering with insulation material. After spray cooling, the flat part of the bulb flat steel is covered with insulation material to prepare for zoned differentiated cooling. S5: Differentiated cooling in different areas: the ball head area not covered with insulation material is cooled intensively, and the spray device is continued to be used. The flat body area is cooled slowly because it is covered with insulation material, so as to achieve cooling rate control in different areas. S6: Temperature balancing treatment: after the partition cooling is completed, all cooling operations are suspended for a period of time to redistribute the internal heat of the bulb flat steel and achieve internal temperature balance; S7: Secondary spray cooling, remove the heat insulation material at the flat part, and spray cool the entire bulb flat steel again to reduce the temperature to the target range; S8: Slow cooling, transfer the bulb flat steel after secondary spray cooling to a slow cooling environment, and use a slow cooling method until it cools to room temperature; S9: Stress relief treatment. After cooling to room temperature, the bulb flat steel is subjected to mechanical vibration aging treatment to release residual stress and ensure the structural stability of the finished product.

[0023] The temperature homogenization process in S1 specifically includes: S11: The bulb flat steel just rolled is taken out from the rolling mill at intervals not exceeding 10 seconds to reduce heat loss, and is quickly transferred to a holding furnace; S12: Place the spherical flat steel in a holding furnace, set the holding furnace temperature to 850°C, and keep the temperature in the furnace stable; S13: Maintain the constant temperature of the ball flat steel in the insulation furnace for 7 minutes to ensure that the internal and external temperatures of the ball flat steel are fully balanced.

[0024] The initial cooling in S2 specifically includes: S21: Remove the bulb flat steel after temperature homogenization treatment from the holding furnace, keep the transfer time no more than 15 seconds to reduce temperature fluctuations, and place it on a cooling platform; S22: Maintain an ambient temperature of 23°C around the cooling platform and cool by natural convection. The height of the cooling platform is controlled at 25 cm from the ground to facilitate air circulation; S23: Keep the bulb flat steel on the cooling platform for 3 minutes, and let the surface temperature gradually decrease by natural convection. The temperature reduction rate is controlled at 4°C / s.

[0025] Spray cooling in S3 specifically includes: S31: After the initial cooling of the bulb flat steel is completed, the spray device is started and the water mist particle size is set to 35 μm to evenly cover the surface of the bulb flat steel; S32: Adjust the spray pressure to 0.6MPa, so that the water mist acts evenly on the surface of the bulb flat steel and controls the cooling intensity; S33: Maintain the spray cooling time for 2 minutes, gradually reduce the surface temperature of the ball flat steel to 680°C, and create temperature conditions for subsequent zone cooling.

[0026] The covering insulation materials in S4 specifically include: S41: After spray cooling is completed, fix the ball flat steel on the cooling platform to ensure that the flat body is exposed so that it can be covered with insulation material; S42: Ceramic fiber felt is selected as the thermal insulation material with a thickness of 8 mm. The thermal insulation material is evenly covered on the flat body of the bulb flat steel to isolate it from the ball head. S43: Use a clamp to fix the insulation material to ensure that it does not move or fall off during the cooling process; S44: After the insulation material is covered, the ball flat steel is transferred to the zoned cooling area to prepare for the zoned differentiated cooling operation.

[0027] Partitioned differentiated cooling in S5 specifically includes: S51: After the insulation material is covered, the spray device is started to perform enhanced cooling on the ball head part that is not covered with the insulation material, and the water mist particle size is set to 20 μm to increase the cooling density; S52: Adjust the spray pressure to 0.9 MPa so that the water mist is concentrated on the ball head to speed up the cooling speed of this area; S53: Maintain the spray cooling time for 4 minutes, and control the temperature of the ball head to gradually drop to 630°C; S54: During the spray cooling, the heat insulation material of the flat body is not removed to ensure that the flat body cools down slowly and the temperature is controlled at 680℃ to achieve differential control of the cooling rate of the ball head and the flat body.

[0028] The temperature balancing process in S6 specifically includes: S61: After the zone cooling is completed, immediately suspend all spray cooling operations to ensure that the bulb flat is in a static state without any external cooling intervention; S62: The bulb flat steel is left to stand in an air environment for 3 minutes to allow the heat inside and outside the bulb flat steel to be naturally transferred without cooling interference to achieve heat redistribution.

[0029] Secondary spray cooling in S7 specifically includes: S71: After the temperature equalization treatment is completed, remove the insulation material covering the flat body to ensure that all parts of the bulb flat steel are exposed to the cooling environment; S72: Restart the spray cooling device, adjust the water mist particle size to 20μm, and evenly cover the surface of the bulb flat steel to ensure consistent overall cooling effect; S73: Set the spray pressure to 0.4 MPa and maintain the spray cooling time for 3 minutes to gradually reduce the surface temperature of the bulb flat steel to 450-500°C; ensure that the bulb flat steel reaches the target temperature range as a whole, in preparation for the subsequent slow cooling step.

[0030] Slow cooling in S8 specifically includes: S81: After the secondary spray cooling is completed, the flat steel ball is transferred from the cooling platform to the slow cooling environment and placed in the slow cooling pit to ensure that the flat steel ball is evenly covered with insulation material; S82: Adjust the thickness of the insulation material of the slow cooling pit to 25 cm to slow down the heat exchange rate between the bulb flat steel and the outside world and control the stability of the slow cooling process; S83: Keep the bulb flat steel in a slow cooling environment for 5 hours, control the cooling rate to 8°C per hour, and gradually reduce its temperature to room temperature.

[0031] The stress relief treatment in S9 specifically includes: S91: After the bulb flat steel has cooled to room temperature, place it on a mechanical vibration device and ensure that the bulb flat steel is stably fixed to avoid displacement or offset during vibration; S92: Set the frequency of the mechanical vibration device to 35 Hz, start the vibration device, and apply uniform vibration to the bulb flat steel to act on the overall structure; S93: Control the vibration treatment time to 3 hours, maintain a constant vibration frequency, and ensure that the vibration effect is evenly distributed on the entire surface and inside of the bulb flat steel; S94: After the vibration aging treatment is completed, the ball flat steel is removed from the vibration device to obtain a finished ball flat steel product after optimized cooling.

[0032] Example 2 S1: Take the newly rolled flat steel from the rolling mill at intervals of no more than 10 seconds and quickly transfer it to a holding furnace to reduce heat loss. The temperature of the holding furnace is set at 800°C. The flat steel is placed in the furnace to maintain a constant temperature for 5 minutes to make the internal and external temperatures uniform, thereby providing a stable temperature basis for subsequent cooling. S2: Remove the temperature-homogenized bulb flat steel from the holding furnace, keeping the transfer time no longer than 15 seconds to avoid large temperature fluctuations; place it on a cooling platform, maintain the ambient temperature at 20°C, and gradually cool it by natural convection. The height of the cooling platform from the ground is controlled at 20 cm. Keep the bulb flat steel on the cooling platform for 2 minutes, and control the natural cooling rate to 2°C / s to prevent internal stress accumulation caused by sudden cooling; S3: After the initial cooling, the spray device is started to cool the bulb flat steel evenly. The water mist particle size is set to 20μm and the spray pressure is adjusted to 0.5MPa to ensure that the surface of the bulb flat steel is evenly covered. The spray cooling lasts for 1 minute, and the surface temperature of the bulb flat steel is gradually reduced to 650℃, creating a temperature condition suitable for subsequent zone cooling; S4: After the spray cooling is completed, the flat steel ball is fixed on the cooling platform to expose the flat body. Aluminum silicate fiber felt with a thickness of 5 mm is selected as the heat insulation material and evenly covers the flat body of the flat steel ball to isolate it from the ball head. The heat insulation material is fixed with a clamp to ensure that it will not move or fall off during the cooling process, so as to prepare for the subsequent zoned differentiated cooling. S5: After the insulation material is covered, the spray device is started to enhance the cooling of the ball head part that is not covered with the insulation material. The water mist particle size is set to 15μm, the spray pressure is controlled at 0.8MPa, and the cooling time is 3 minutes, so that the temperature of the ball head part is gradually reduced to 600℃; at the same time, the flat body part is slowly cooled due to the effect of the insulation material, and the temperature is controlled at 650℃, so as to achieve cooling rate control in different areas; S6: After the partition cooling is completed, immediately suspend all cooling operations to ensure that the bulb flat steel is in a static state without any external cooling intervention. Keep the bulb flat steel in the air environment for 2 minutes to redistribute the internal and external heat through natural conduction without cooling interference, achieve heat balance, and provide stable temperature conditions for subsequent operations; S7: After the temperature equalization treatment is completed, remove the insulation material covering the flat body, restart the spray cooling device, adjust the water mist particle size to 10μm, set the spray pressure to 0.3MPa, and maintain the spray cooling time for 2 minutes, so that the surface temperature of the bulb flat steel gradually drops to 450℃, laying the foundation for subsequent slow cooling; S8: After the secondary spray cooling is completed, the flat steel ball is transferred from the cooling platform to the slow cooling environment and placed in the slow cooling pit. The surrounding area is evenly covered with a 20 cm thick insulation material to slow down the heat exchange between the flat steel ball and the outside world. The flat steel ball is kept in the slow cooling environment for 4 hours, and the cooling rate is controlled at 5°C per hour to gradually reduce its temperature to room temperature, thereby obtaining a uniform cooling effect; S9: After the bulb flat steel is cooled to room temperature, it is placed on a mechanical vibration device to ensure that the bulb flat steel is stably fixed to prevent displacement or offset during the vibration process. The frequency of the mechanical vibration device is set to 20 Hz, and the vibration device is started to make uniform vibration act on the overall structure of the bulb flat steel. The vibration treatment time is controlled within 2 hours. After the vibration aging treatment is completed, the bulb flat steel is removed from the vibration device to obtain a finished product with good structural stability.

[0033] Example 3 S1: Take the newly rolled flat steel from the rolling mill at intervals of no more than 10 seconds and quickly transfer it to a holding furnace to reduce heat loss. The temperature of the holding furnace is set at 900°C. The flat steel is placed in the furnace to maintain a constant temperature for 10 minutes to make the internal and external temperatures uniform, thereby providing a stable temperature basis for subsequent cooling. S2: Remove the temperature-homogenized bulb flat steel from the holding furnace, keeping the transfer time no longer than 15 seconds to avoid large temperature fluctuations; place it on a cooling platform, maintain the ambient temperature at 25°C, and gradually cool it by natural convection. The height of the cooling platform from the ground is controlled at 30 cm. Keep the bulb flat steel on the cooling platform for 4 minutes, and control the natural cooling rate to 5°C / s to prevent internal stress accumulation caused by sudden cooling; S3: After the initial cooling, the spray device is started to cool the bulb flat steel evenly. The water mist particle size is set to 50μm and the spray pressure is adjusted to 0.8MPa to ensure that the surface of the bulb flat steel is evenly covered. The spray cooling lasts for 1 minute, and the surface temperature of the bulb flat steel is gradually reduced to 700℃, creating a temperature condition suitable for subsequent zone cooling; S4: After the spray cooling is completed, the flat steel ball is fixed on the cooling platform to expose the flat body. A ceramic fiber felt with a thickness of 10 mm is selected as the heat insulation material and evenly covers the flat body of the flat steel ball to isolate it from the ball head. The heat insulation material is fixed with a clamp to ensure that it will not move or fall off during the cooling process, so as to prepare for the subsequent zoned differentiated cooling. S5: After the insulation material is covered, the spray device is started to perform enhanced cooling on the ball head part that is not covered with the insulation material. The water mist particle size is set to 30μm, the spray pressure is controlled at 1.0MPa, and the cooling time is 5 minutes, so that the temperature of the ball head part is gradually reduced to 650℃; at the same time, the flat body part is slowly cooled due to the effect of the insulation material, and the temperature is controlled at 700℃, thereby realizing the cooling rate control of different areas; S6: After the partition cooling is completed, immediately suspend all cooling operations to ensure that the bulb flat steel is in a static state without any external cooling intervention. Keep the bulb flat steel in the air environment for 4 minutes to redistribute the internal and external heat through natural conduction without cooling interference, achieve heat balance, and provide stable temperature conditions for subsequent operations; S7: After the temperature equalization treatment is completed, remove the insulation material covering the flat body, restart the spray cooling device, adjust the water mist particle size to 30μm, set the spray pressure to 0.5MPa, and maintain the spray cooling time for 4 minutes, so that the surface temperature of the bulb flat steel gradually drops to 500℃, laying the foundation for subsequent slow cooling; S8: After the secondary spray cooling is completed, the bulb flat steel is transferred from the cooling platform to the slow cooling environment and placed in the slow cooling pit. The surrounding area is evenly covered with a 30 cm thick insulation material to slow down the heat exchange between the bulb flat steel and the outside world. The bulb flat steel is kept in the slow cooling environment for 6 hours, and the cooling rate is controlled at 10°C per hour to gradually reduce its temperature to room temperature, thereby obtaining a uniform cooling effect; S9: After the bulb flat steel is cooled to room temperature, it is placed on a mechanical vibration device to ensure that the bulb flat steel is stably fixed to prevent displacement or offset during vibration. The frequency of the mechanical vibration device is set to 50 Hz, and the vibration device is started to make uniform vibration act on the overall structure of the bulb flat steel. The vibration treatment time is controlled within 4 hours. After the vibration aging treatment is completed, the bulb flat steel is removed from the vibration device to obtain a finished product with good structural stability.

[0034] Comparative Example 1 Step 1: Take the newly rolled bulb flat steel out of the rolling mill and place it in the air to cool naturally for 3 minutes. The internal temperature of the bulb flat steel is about 950°C, and the surface temperature drops rapidly to 800°C due to contact with air, with a large temperature difference between the inside and outside. Step 2: Place the spherical flat steel on a cooling platform, the platform is 30 cm above the ground, the ambient temperature is about 25°C, and the surface temperature drops at an uneven rate due to natural cooling of the ambient temperature, resulting in inconsistent surface and internal temperatures; Step 3: After natural cooling, the bulb flat steel is surface cooled using a spray device. The water mist particle size is about 60 μm, the spray pressure is maintained at 0.4 MPa, and the cooling duration is about 5 minutes until the surface temperature drops to 550 ° C. Step 4: After spray cooling, place the flat steel ball in a room temperature environment to continue natural cooling, so that the entire flat steel ball is cooled to room temperature in a natural environment; Step 5: The cooling process is completed after the bulb flat steel is naturally cooled to room temperature.

[0035] Table 1 Comparison of performance parameters of bulb flat steel after cooling process

[0036] It can be seen from Table 1 above that Example 1 is superior to other examples and comparative examples in multiple key performance indicators. By optimizing the cooling process, including temperature homogenization treatment, zoned differential cooling, appropriate slow cooling, and mechanical vibration aging treatment, the temperature difference between the inside and outside of the finished product is reduced to below 5°C, effectively reducing the residual stress (≤50 MPa), and significantly improving the surface hardness (250 HB) and fatigue life (2 million times) of the finished product. In contrast, in the comparative example, due to the simpler cooling process, the temperature difference between the inside and outside of the finished product is as high as 150°C, resulting in higher residual stress and significant deformation, and the fatigue life of the finished product is only 1 million times, and the impact toughness and tensile strength are also relatively low. Therefore, the cooling process of Example 1 is more suitable for the production of high-quality large-scale bulb flat steel products.

[0037] Table 2 Comparison of other performance parameters

[0038] It can be seen from Table 2 above that Example 1 has the best dimensional stability, reaching within 5 μm / m, ensuring the geometric stability of the bulb flat steel product under high load, which is better than other embodiments and comparative examples; after optimized cooling and mechanical vibration treatment, Example 1 has a surface finish of 0.6 μm Ra value, which is much lower than 3.0 μm of the comparative example, reducing the surface roughness and being suitable for high-demand applications; in terms of antioxidant performance, the antioxidant life of Example 1 reaches 2000 hours, effectively extending the service life of the product and reducing the performance loss caused by surface oxidation; the yield strength of Example 1 reaches 350 MPa, and the thermal expansion coefficient is controlled at 11 × 10⁻ 6 / °C, ensuring the dimensional stability and strength of the finished product in a high temperature environment; the service life of Example 1 is expected to be 20 years, and the wear amount is only 5 mg, which is significantly better than other examples and comparative examples, and is suitable for long-term use in a high wear environment; the toughness of Example 1 is as high as 150 J, and it still maintains a high impact resistance under multiple impacts, and the hardness loss rate is only 2%, ensuring the hardness stability under long-term use. Therefore, the cooling process of Example 1 performs well in dimensional stability, surface finish, oxidation resistance, service life and wear resistance, ensuring the reliability and durability of the product in various use environments.

[0039] The present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention. In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details. In addition, in order to avoid unnecessary confusion about the essence of the present invention, well-known methods, processes, procedures, components and circuits are not described in detail.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An optimized cooling process for large bulb flat steel, characterized in that: The following steps are involved: S1: Temperature homogenization treatment, placing the newly rolled bulb flat steel in a holding furnace and keeping it in a high temperature environment for a specified time to make the internal and external temperatures of the bulb flat steel uniform; S2: Preliminary cooling: the bulb flat steel after temperature homogenization treatment is moved out of the holding furnace and placed on the cooling platform. The overall temperature of the bulb flat steel is gradually reduced by natural convection to avoid sudden cooling. S3: spray cooling: after the initial cooling, the bulb flat steel is cooled by using a spray device, and the water mist parameters are controlled to reduce the bulb flat steel temperature to a predetermined range; S4: Covering with insulation material. After spray cooling, the flat part of the bulb flat steel is covered with insulation material to prepare for zoned differentiated cooling. S5: Differentiated cooling in different areas: the ball head area not covered with insulation material is cooled intensively, and the spray device is continued to be used. The flat body area is cooled slowly because it is covered with insulation material, so as to achieve cooling rate control in different areas. S6: Temperature balancing treatment: after the partition cooling is completed, all cooling operations are suspended for a period of time to redistribute the internal heat of the bulb flat steel and achieve internal temperature balance; S7: Secondary spray cooling, remove the heat insulation material at the flat part, and spray cool the entire bulb flat steel again to reduce the temperature to the target range; S8: Slow cooling, transfer the bulb flat steel after secondary spray cooling to a slow cooling environment, and use a slow cooling method until it cools to room temperature; S9: Stress relief treatment. After cooling to room temperature, the bulb flat steel is subjected to mechanical vibration aging treatment to release residual stress and ensure the structural stability of the finished product.

2. The optimized cooling process for large bulb flat steel according to claim 1 is characterized in that: The S1 specifically includes: S11: The bulb flat steel just rolled is taken out from the rolling mill at intervals not exceeding 10 seconds to reduce heat loss, and is quickly transferred to a holding furnace; S12: placing the spherical flat steel in a holding furnace, and setting the holding furnace temperature to 800-900°C; S13: Keep the flat steel ball at a constant temperature in the holding furnace for 5-10 minutes to allow the internal and external temperatures of the flat steel ball to be fully balanced.

3. The optimized cooling process for large bulb flat steel according to claim 1 is characterized in that: The S2 specifically includes: S21: Remove the bulb flat steel after temperature homogenization treatment from the holding furnace, keep the transfer time no more than 15 seconds to reduce temperature fluctuations, and place it on a cooling platform; S22: Maintain the ambient temperature around the cooling platform at 20-25°C, cool by natural convection, and control the height of the cooling platform to 20-30 cm from the ground; S23: Keep the bulb flat steel on the cooling platform for 2-4 minutes, and let the surface temperature gradually decrease by natural convection. The temperature reduction rate is controlled at 2-5℃ / s.

4. The optimized cooling process for large bulb flat steel according to claim 1 is characterized in that: The S3 specifically includes: S31: After the initial cooling of the bulb flat steel is completed, the spray device is started and the water mist particle size is set to 20-50μm to evenly cover the surface of the bulb flat steel; S32: Adjust the spray pressure to 0.5-0.8MPa so that the water mist acts evenly on the surface of the bulb flat steel; S33: Maintain the spray cooling time for 1-3 minutes, gradually reduce the surface temperature of the ball flat steel to 650-700℃, and create temperature conditions for subsequent zone cooling.

5. The optimized cooling process for large bulb flat steel according to claim 1 is characterized in that: The S4 specifically includes: S41: After spray cooling is completed, fix the ball flat steel on the cooling platform to ensure that the flat body is exposed; S42: Choose ceramic fiber felt or aluminum silicate fiber felt as the insulation material, with a thickness of 5-10 mm, and evenly cover the flat body of the bulb flat steel with the insulation material to isolate it from the ball head; S43: Use a clamp to fix the insulation material to ensure that it does not move or fall off during the cooling process; S44: After the insulation material is covered, the ball flat steel is transferred to the zoned cooling area to prepare for the zoned differentiated cooling operation.

6. The optimized cooling process for large bulb flat steel according to claim 1 is characterized in that: The S5 specifically includes: S51: After the insulation material is covered, the spray device is started to perform enhanced cooling on the ball head part that is not covered with the insulation material, and the water mist particle size is set to 15-30 μm; S52: Adjust the spray pressure to 0.8-1.0MPa so that the water mist is concentrated on the ball head; S53: Maintain the spray cooling time for 3-5 minutes, and control the temperature of the ball head to gradually drop to 600-650°C; S54: During the spray cooling period, the insulation material of the flat body is not removed to ensure that the flat body is cooled slowly and the temperature is controlled at 650-700℃.

7. The optimized cooling process for large bulb flat steel according to claim 1 is characterized in that: The S6 specifically includes: S61: After the zone cooling is completed, immediately suspend all spray cooling operations to ensure that the bulb flat is in a static state without any external cooling intervention; S62: Leave the bulb flat steel in an air environment for 2-4 minutes to allow the heat inside and outside the bulb flat steel to be naturally transferred without cooling interference to achieve heat redistribution.

8. The optimized cooling process for large bulb flat steel according to claim 1 is characterized in that: The S7 specifically includes: S71: After the temperature equalization process is completed, remove the insulation material covering the flat body part; S72: Restart the spray cooling device and adjust the water mist particle size to 10-30 μm; S73: Set the spray pressure to 0.3-0.5MPa and maintain the spray cooling time for 2-4 minutes to gradually reduce the surface temperature of the bulb flat steel to 450-500℃.

9. The optimized cooling process for large bulb flat steel according to claim 1, characterized in that: The S8 specifically includes: S81: After the secondary spray cooling is completed, the flat steel ball is transferred from the cooling platform to the slow cooling environment and placed in the slow cooling pit to ensure that the flat steel ball is evenly covered with insulation material; S82: Adjust the thickness of the insulation material of the slow cooling pit to 20-30 cm to slow down the heat exchange rate between the bulb flat steel and the outside world; S83: Keep the bulb flat steel in a slow cooling environment for 4-6 hours, control the cooling rate to 5-10°C per hour, and gradually reduce its temperature to room temperature.

10. The optimized cooling process for large bulb flat steel according to claim 1, characterized in that: The S9 specifically includes: S91: After the bulb flat steel has cooled to room temperature, place it on a mechanical vibration device and ensure that the bulb flat steel is stably fixed to avoid displacement or offset during vibration; S92: Set the frequency of the mechanical vibration device to 20-50 Hz, start the vibration device, and apply uniform vibration to the bulb flat steel to act on the overall structure; S93: Control the vibration treatment time to 2-4 hours and maintain a constant vibration frequency; S94: After the vibration aging treatment is completed, the ball flat steel is removed from the vibration device to obtain a finished ball flat steel product after optimized cooling.

Images