A controlled rolling and controlled cooling method for improving surface quality of SAE10B33A steel

Abstract

The application relates to the technical field of metallurgical metal materials, and discloses a controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel, which comprises the following steps: step 1, slow cooling pretreatment of a casting blank; step 2, three-section step heating of the blank; step 3, multi-stage high-pressure water descaling; step 4, gradient temperature control and twist-free rolling; step 5, online uniform temperature regulation after finish rolling; step 6, wire feeding temperature closed-loop control; step 7, Stelmor segmented controlled cooling; step 8, surface protection during coiling and bundling; and step 9, online surface defect detection. The slow cooling pretreatment of the casting blank is combined with the three-section step heating, internal stress is released through slow cooling for greater than or equal to 30 hours, the blank is loaded into a furnace at a temperature of less than or equal to 200 DEG C, three-section temperature control is used, and the blank is kept in the furnace for greater than or equal to 90 minutes, so that the blank is heated uniformly, the overall temperature difference is less than or equal to + / - 25 DEG C, the surface oxidation and the local decarburization degree are reduced, the initial surface state of the blank is improved, and the surface defects caused by the heating link are reduced.

Description

Technical Field

[0001] This invention relates to the field of metallurgical materials technology, specifically to a controlled rolling and cooling method for improving the surface quality of SAE10B33A steel. Background Technology

[0002] The surface quality of medium-carbon boron-containing cold heading steel depends on the process control of rolling and cooling. The parameter settings of the controlled rolling and cooling process directly affect the surface condition of the wire rod. In conventional rolling production, the billet is directly charged into the furnace for heating without sufficient slow cooling, and the residual stress inside the billet cannot be released; the billet heating is controlled by a single temperature range, resulting in insufficient heating uniformity and a high degree of surface oxidation; descaling is only performed once, and the surface oxide scale is not thoroughly removed, which is easily pressed into the billet and forms surface defects after entering the rolling process; the rolling temperature is not controlled in stages according to gradients, and the final rolling temperature fluctuates greatly, making the wire rod surface prone to local decarburization; the cooling after wire drawing uses a uniform air volume and speed, and the cooling rate of different parts of the coil is inconsistent, resulting in poor internal structure uniformity. The original defects carried by the billet will continue to expand during the rolling and cooling process.

[0003] In actual production, under conventional controlled rolling and cooling methods, a large number of surface cracks and scabs are detected after online inspection of wire rods. Some batches need to be scrapped due to surface defects. When downstream enterprises perform cold heading, surface defects of wire rods can cause cracking of formed parts, affecting the use of products. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a controlled rolling and cooling method for improving the surface quality of SAE10B33A steel. This method has advantages such as reducing surface oxidation and local decarburization, and improving the initial surface condition of the billet, thus solving the problem of local decarburization that easily occurs on the surface of wire rods.

[0005] (II) Technical Solution To achieve the above-mentioned goals of reducing surface oxidation and local decarburization and improving the initial surface condition of billets, this invention provides the following technical solution: a controlled rolling and cooling method for improving the surface quality of SAE10B33A steel, comprising the following steps: Step 1: slow cooling pretreatment of billets; Step 2: three-stage step heating of billets; Step 3: multi-stage high-pressure water descaling; Step 4: gradient temperature-controlled twist-free rolling; Step 5: online uniform temperature control after finishing rolling; Step 6: closed-loop control of wire drawing temperature; Step 7: Stellmore segmented controlled cooling; Step 8: surface protection for coiling and bundling; Step 9: online full inspection of surface defects, wherein Step 1: slow cooling pretreatment of billets; Use an overhead crane to smoothly lift qualified continuous casting billets to the slow cooling pit, and stack them neatly according to the furnace number, leaving a 60-90mm ventilation gap between the billets to ensure uniform slow cooling temperature. After all the billets are put into the pit, the pit is completely covered and sealed with high-temperature resistant insulation cotton. The sealing edges are compacted to prevent air leakage, and the temperature inside the slow cooling pit is controlled to be stable at 600~750℃. Strictly control the slow cooling time to ≥30h, and check the temperature inside the pit every 8h during this period to ensure that the temperature fluctuation is ≤±30℃; After slow cooling, the surface temperature of the billet is detected by an infrared thermometer. Once the overall temperature drops to ≤200℃, it is then smoothly transferred to the heating furnace loading platform by an overhead crane. High-temperature billets are prohibited from being directly loaded into the furnace.

[0006] Preferably, step 2 involves three-stage step heating of the billet; Before feeding the heating furnace, clean the residual iron oxide scale and debris inside the furnace, turn on the furnace circulation fan, and adjust the walking beam to a horizontal state; A single-row loading method is adopted, in which billets are placed stably on the walking beam, with the billet spacing controlled at 90~110mm, and stacking or tilting during loading is avoided.

[0007] Preferably, step 2 involves three-stage step heating of the billet; Performs three-stage precise temperature control heating: Preheating section: Set furnace temperature ≤680℃, move the walking beam at a constant speed, and heat for 26~32 minutes. Slowly increase the temperature to avoid rapid surface oxidation. Heating section: Set furnace temperature to 1100~1140℃, heating time to 32~38min, to ensure that the core and surface of the billet are heated simultaneously; The heat soaking section is set at a furnace temperature of 1080~1120℃ and a heat soaking time of 32~42min to eliminate the temperature difference between the inside and outside of the billet. The billet is in the furnace for a total time of ≥90 minutes. Before exiting the furnace, it is tested with a multi-point infrared thermometer to ensure that the overall temperature difference of the billet is ≤±25℃. After the standard is met, the furnace door is opened to discharge the billet.

[0008] Preferably, step 3 involves multi-stage high-pressure water descaling. First descaling before rough rolling: After the billet exits the furnace, it is immediately transported to the descaling box at the rough rolling inlet. The sealing door of the descaling box is closed, the high-pressure water pump is turned on, the descaling pressure is adjusted to 19~25MPa, the billet running speed is controlled to 1.0~1.6m / s, and the descaling is repeated 2~3 times to completely remove the primary iron oxide scale. Secondary descaling before intermediate rolling: After rough rolling, the billet is transported to the descaling box at the entrance of the intermediate rolling mill. The descaling pressure is maintained at 19~25MPa. The descaling covers the entire surface of the billet in one pass, with no areas missed. Descaling rolling auxiliary treatment: After secondary descaling, the roll gap of the intermediate rolling mill is adjusted to be 0.2~0.4mm smaller than that of conventional rolling mill. The residual iron oxide scale is broken by rolling pressure to prevent the iron oxide scale from being pressed into the billet and forming surface defects.

[0009] Preferably, step 4 involves gradient temperature-controlled twist-free rolling. Replace all U-shaped rolls before rolling, use a feeler gauge to adjust the roll gap accuracy to ≤ ±0.05mm, and check that the roll surface is free of scratches and wear to avoid scratching the wire surface during rolling. The process employs a twist-free high-speed rolling technique with four-stage gradient temperature control. Roughing mill: Control the initial rolling temperature to 1060~1090℃, set a large reduction, and ensure uniform deformation of the billet surface; Intermediate rolling mill: Control the rolling temperature to 980~1020℃, stabilize the mill speed, and avoid excessively rapid temperature drop of the billet; Pre-finishing mill: Control the rolling temperature to 930~970℃, gradually reduce the amount of deformation, and optimize the wire forming accuracy; Finishing mill: Real-time monitoring of the final rolling temperature, and by adjusting the mill speed and the water volume in the water cooling section, the final rolling temperature is stabilized at 870~930℃, with temperature fluctuation ≤±15℃; During the rolling process, the condition of the rolls and the roll gap accuracy are checked every 30 minutes, and the iron oxide scale adhering to the roll surface is cleaned in a timely manner.

[0010] Preferably, step 5 involves online temperature control after finishing rolling; A segmented water-cooling device is installed at the outlet of the finishing mill, and the angle of the water-cooling nozzles is adjusted to 45° to ensure that the water-cooling covers the entire circumference of the wire. The water flow rate in the water-cooling section is automatically adjusted to 12~18m based on the real-time temperature at the finishing mill exit. 3 / h, to avoid stress concentration on the wire surface caused by rapid cooling; After water cooling, a uniform temperature section is set up, and the wire is air-cooled for 8~12m to make the surface and core temperatures tend to be consistent, and smoothly transition to the spinning temperature range.

[0011] Preferably, step 6 involves closed-loop control of the spinning temperature; Before the wire enters the spinning machine, a dual-point infrared thermometer is installed to monitor the wire temperature in real time, and the data is transmitted synchronously to the central control system. The central control system automatically adjusts the spinning machine speed and water cooling intensity based on temperature measurement data to stabilize the spinning temperature at 880~920℃, with temperature fluctuation ≤±10℃. During the spinning process, observe the coiling state and adjust the spinning tube angle in a timely manner to ensure that the coiled shape is regular, without sticking, and without dragging or scratches.

[0012] Preferably, step 7 involves Stello segmented cooling; After the coils enter the Stellmore cooling line, they undergo a segmented cooling process of weak cooling at the front and slow cooling at the back. Front cooling zone: Set the roller conveyor speed to 0.13~0.17m / s, turn on the fan air volume to 55%~75%, and slowly control the phase change rhythm to avoid uneven cooling and cracks. Rear cooling zone: Keep the roller conveyor speed constant, reduce the fan air volume to 25%~45%, extend the cooling time, refine the internal structure, and reduce the strip structure level; The temperature of the coil is monitored throughout the cooling process. After cooling is complete, the coil is transported to the air-cooling area and allowed to cool naturally to room temperature. Forced air cooling is prohibited.

[0013] Preferably, step 8: surface protection of coiling and bundling; After the coil cools to room temperature, turn on the winding equipment and use a flexible clamping device to grab the coil with moderate clamping force to avoid surface damage caused by bumps and drags. After the coil is assembled, the bundling operation is carried out. The bundling pressure is controlled at 7 to 13 tons and the pressure is evenly distributed around the coil. A flexible protective pad is placed between the bundling tape and the coil to prevent indentations and abrasions. After bundling, the coils are hoisted smoothly to the finished product stacking area. Rubber mats are placed on the coils during stacking to prevent them from coming into direct contact with the hard ground.

[0014] Preferably, step 9 involves online full inspection of surface defects. Before the finished products are bundled, the entire surface of each wire is scanned by an online thermal inspection device to automatically identify defects such as cracks, scars, pits, and iron oxide scale indentation, and the location of the defects is marked in real time. Defect judgment: Wires with surface defect depth > 0.1mm are directly cut and rejected; wires with short and shallow defects are sampled for acid washing verification. Wires that pass the pickling verification are classified and stored in the warehouse according to furnace number and specifications; unqualified wires are isolated separately, properly labeled, and returned for processing. Record the detection data, defect type and treatment results for each furnace to form a complete surface quality control file.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention provides a controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel, which has the following beneficial effects: 1. The controlled rolling and cooling method for improving the surface quality of SAE10B33A steel combines slow cooling pretreatment of the billet with three-stage step heating. Through slow cooling for ≥30h to release internal stress and low-temperature charging at ≤200℃, combined with three-stage temperature control and a furnace time of ≥90min, the billet is heated evenly with an overall temperature difference of ≤±25℃, reducing the degree of surface oxidation and local decarburization, improving the initial surface condition of the billet, and reducing surface defects caused by the heating process.

[0016] 2. The controlled rolling and cooling method for improving the surface quality of SAE10B33A steel involves multi-stage high-pressure water descaling combined with descaling rolling. Descaling is performed twice at a pressure of 19~25MPa, combined with a descaling process that reduces the roll gap by 0.2~0.4mm. This method thoroughly cleans the iron oxide scale on the billet surface, reduces the amount of iron oxide scale pressed into the billet, improves the surface smoothness of the wire rod, and optimizes the basic surface quality of the wire rod.

[0017] 3. The controlled rolling and cooling method for improving the surface quality of SAE10B33A steel combines gradient temperature control with twist-free rolling and online uniform temperature control in finishing rolling. U-shaped rolls are used to control the roll gap accuracy to ≤±0.05mm. Four-level gradient temperature control reduces the final rolling temperature fluctuation to ≤±15℃. Combined with 45° water-cooled nozzles and air-cooled uniform temperature section, the wire rod deformation is uniform and the temperature transition is stable, reducing surface scratches and subcutaneous microcracks, and controlling local decarburization of the surface.

[0018] 4. The controlled rolling and cooling method for improving the surface quality of SAE10B33A steel combines closed-loop control of the wire drawing temperature with Stellmore segmented controlled cooling to stabilize the wire drawing temperature at 880~920℃ with fluctuations ≤±10℃. Combined with the segmented cooling process of weak cooling in the front section and slow cooling in the back section, the coil forming is regular and the cooling is uniform, reducing the difference in internal structure, inhibiting the expansion of original defects in the billet, and reducing the probability of surface cracks.

[0019] 5. The controlled rolling and cooling method for improving the surface quality of SAE10B33A steel adopts surface protection measures throughout the entire coiling and bundling process. Through flexible clamping, uniform bundling pressure of 7 to 13 tons, and the use of protective pads and rubber pads, the coils are protected from bumps, indentations and scratches during transportation, forming and bundling, thus maintaining the integrity of the finished product surface and improving the stability of the finished product's appearance quality.

[0020] 6. The controlled rolling and cooling method for improving the surface quality of SAE10B33A steel forms a closed loop of quality control through online full inspection of surface defects. It scans and identifies surface defects one by one and rejects defective parts with a depth > 0.1mm. It is supplemented by pickling to verify shallow defects, timely screening of unqualified products, improving the consistency of finished product surface quality, and making the wire better adaptable to the downstream large deformation cold heading processing needs. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] This solution provides a technical solution, specifically a controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel, including the following steps: Step 1: Slow cooling pretreatment of the billet; Use an overhead crane to smoothly lift qualified continuous casting billets to the slow cooling pit, and stack them neatly according to the furnace number, leaving a 60-90mm ventilation gap between the billets to ensure uniform slow cooling temperature. After all the billets are put into the pit, the pit is completely covered and sealed with high-temperature resistant insulation cotton. The sealing edges are compacted to prevent air leakage, and the temperature inside the slow cooling pit is controlled to be stable at 600~750℃. Strictly control the slow cooling time to ≥30h, and check the temperature inside the pit every 8h during this period to ensure that the temperature fluctuation is ≤±30℃; After slow cooling, the surface temperature of the billet is detected by an infrared thermometer. Once the overall temperature drops to ≤200℃, it is then smoothly transferred to the heating furnace loading platform by an overhead crane. High-temperature billets are prohibited from being directly loaded into the furnace. Step 2: Three-stage step heating of the billet; Before feeding the heating furnace, clean the residual iron oxide scale and debris inside the furnace, turn on the furnace circulation fan, and adjust the walking beam to a horizontal state; A single-row loading method is adopted to place the billets stably on the walking beam, with the billet spacing controlled at 90~110mm, and stacking or tilting during loading is prohibited. Performs three-stage precise temperature control heating: Preheating section: Set furnace temperature ≤680℃, move the walking beam at a constant speed, and heat for 26~32 minutes. Slowly increase the temperature to avoid rapid surface oxidation. Heating section: Set furnace temperature to 1100~1140℃, heating time to 32~38min, to ensure that the core and surface of the billet are heated simultaneously; The heat soaking section is set at a furnace temperature of 1080~1120℃ and a heat soaking time of 32~42min to eliminate the temperature difference between the inside and outside of the billet. The billet is in the furnace for a total time of ≥90 minutes. Before being taken out of the furnace, it is tested with a multi-point infrared thermometer to ensure that the overall temperature difference of the billet is ≤±25℃. After the standard is met, the furnace door is opened to discharge the billet. Step 3: Multi-stage high-pressure water descaling; First descaling before rough rolling: After the billet exits the furnace, it is immediately transported to the descaling box at the rough rolling inlet. The sealing door of the descaling box is closed, the high-pressure water pump is turned on, the descaling pressure is adjusted to 19~25MPa, the billet running speed is controlled to 1.0~1.6m / s, and the descaling is repeated 2~3 times to completely remove the primary iron oxide scale. Secondary descaling before intermediate rolling: After rough rolling, the billet is transported to the descaling box at the entrance of the intermediate rolling mill. The descaling pressure is maintained at 19~25MPa. The descaling covers the entire surface of the billet in one pass, with no areas missed. Descaling rolling auxiliary treatment: After secondary descaling, the roll gap of the intermediate rolling mill is adjusted to be 0.2~0.4mm smaller than that of conventional rolling mill. The residual iron oxide scale is broken by rolling pressure to prevent the iron oxide scale from being pressed into the billet and forming surface defects. Step 4: Gradient temperature controlled twist-free rolling; Replace all U-shaped rolls before rolling, use a feeler gauge to adjust the roll gap accuracy to ≤ ±0.05mm, and check that the roll surface is free of scratches and wear to avoid scratching the wire surface during rolling. The process employs a twist-free high-speed rolling technique with four-stage gradient temperature control. Roughing mill: Control the initial rolling temperature to 1060~1090℃, set a large reduction, and ensure uniform deformation of the billet surface; Intermediate rolling mill: Control the rolling temperature to 980~1020℃, stabilize the mill speed, and avoid excessively rapid temperature drop of the billet; Pre-finishing mill: Control the rolling temperature to 930~970℃, gradually reduce the amount of deformation, and optimize the wire forming accuracy; Finishing mill: Real-time monitoring of the final rolling temperature, and by adjusting the mill speed and the water volume in the water cooling section, the final rolling temperature is stabilized at 870~930℃, with temperature fluctuation ≤±15℃; During the rolling process, the condition of the rolls and the roll gap accuracy are checked every 30 minutes, and the iron oxide scale adhering to the roll surface is cleaned in a timely manner. Step 5: Online temperature control after finishing rolling; A segmented water-cooling device is installed at the outlet of the finishing mill, and the angle of the water-cooling nozzles is adjusted to 45° to ensure that the water-cooling covers the entire circumference of the wire. The water flow rate in the water-cooling section is automatically adjusted to 12~18m based on the real-time temperature at the finishing mill exit. 3 / h, to avoid stress concentration on the wire surface caused by rapid cooling; After water cooling, a uniform temperature section is set up, and the wire is air-cooled for 8~12m to make the surface and core temperatures tend to be consistent and smoothly transition to the spinning temperature range. Step 6: Closed-loop control of spinning temperature; Before the wire enters the spinning machine, a dual-point infrared thermometer is installed to monitor the wire temperature in real time, and the data is transmitted synchronously to the central control system. The central control system automatically adjusts the spinning machine speed and water cooling intensity based on temperature measurement data to stabilize the spinning temperature at 880~920℃, with temperature fluctuation ≤±10℃. During the spinning process, observe the coiling state and adjust the angle of the spinning tube in a timely manner to ensure that the coiled shape is regular, without sticking, and without dragging or scratches. Step 7: Stello segmented cooling; After the coils enter the Stellmore cooling line, they undergo a segmented cooling process of weak cooling at the front and slow cooling at the back. Front cooling zone: Set the roller conveyor speed to 0.13~0.17m / s, turn on the fan air volume to 55%~75%, and slowly control the phase change rhythm to avoid uneven cooling and cracks. Rear cooling zone: Keep the roller conveyor speed constant, reduce the fan air volume to 25%~45%, extend the cooling time, refine the internal structure, and reduce the strip structure level; The temperature of the coil is monitored throughout the cooling process. After cooling is completed, the coil is transported to the air-cooling area and allowed to cool naturally to room temperature. Forced air cooling is prohibited. Step 8: Surface protection for coiling and bundling; After the coil cools to room temperature, turn on the winding equipment and use a flexible clamping device to grab the coil with moderate clamping force to avoid surface damage caused by bumps and drags. After the coil is assembled, the bundling operation is carried out. The bundling pressure is controlled at 7 to 13 tons and the pressure is evenly distributed around the coil. A flexible protective pad is placed between the bundling tape and the coil to prevent indentations and abrasions. After bundling, the coils are hoisted smoothly to the finished product stacking area. Rubber mats are placed on the coils during stacking to prevent them from coming into direct contact with the hard ground. Step 9: Online full inspection of surface defects; Before the finished products are bundled, the entire surface of each wire is scanned by an online thermal inspection device to automatically identify defects such as cracks, scars, pits, and iron oxide scale indentation, and the location of the defects is marked in real time. Defect judgment: Wires with surface defect depth > 0.1mm are directly cut and rejected; wires with short and shallow defects are sampled for acid washing verification. Wires that pass the pickling verification are classified and stored in the warehouse according to furnace number and specifications; unqualified wires are isolated separately, properly labeled, and returned for processing. Record the detection data, defect types and processing results for each furnace to form a complete surface quality control archive. Furthermore, this method combines slow cooling pretreatment of the billet with three-stage step heating. Through slow cooling for ≥30h to release internal stress and low-temperature charging at ≤200℃, combined with three-stage temperature control and a furnace time of ≥90min, the billet is heated evenly with an overall temperature difference of ≤±25℃, reducing surface oxidation and local decarburization, improving the initial surface condition of the billet, and reducing surface defects caused by the heating process. Furthermore, this method combines multi-stage high-pressure water descaling with descaling rolling, using 19~25MPa pressure for two descaling processes, combined with a descaling process that reduces the roll gap by 0.2~0.4mm, to thoroughly clean the iron oxide scale on the billet surface, reduce the amount of iron oxide scale pressed into the billet, improve the surface smoothness of the wire rod, and optimize the basic surface quality of the wire rod. Furthermore, this method combines gradient temperature control with twistless rolling and online uniform temperature control in finishing rolling. It uses U-shaped rolls to control the roll gap accuracy to ≤±0.05mm, and four-level gradient temperature control to reduce the final rolling temperature fluctuation to ≤±15℃. Combined with 45° water-cooled nozzles and air-cooled uniform temperature section, it ensures uniform wire deformation and stable temperature transition, reduces surface scratches and subcutaneous micro-cracks, and controls local decarburization on the surface. Furthermore, this method combines closed-loop control of the wire-spinning temperature with Stellmore segmented cooling to stabilize the wire-spinning temperature at 880~920℃ with fluctuations ≤±10℃. Combined with the segmented cooling process of weak cooling in the front section and slow cooling in the back section, the coiling is regular and the cooling is uniform, reducing the difference in internal structure, inhibiting the expansion of original defects in the billet, and reducing the probability of surface cracks. Furthermore, this method employs surface protection measures throughout the entire coil bundling process. Through flexible clamping, uniform bundling pressure of 7 to 13 tons, and the use of protective pads and rubber pads, it avoids bumps, indentations, and scratches on the coils during transportation, forming, and bundling, thus maintaining the integrity of the finished product surface and improving the stability of the finished product's appearance quality. Furthermore, this method forms a closed-loop quality control system by conducting full online surface defect inspection. It scans and identifies surface defects one by one and rejects defective parts with a depth > 0.1 mm. It also uses pickling to verify shallow defects, promptly screens out unqualified products, improves the consistency of finished product surface quality, and makes the wire better suited to the needs of downstream cold heading processing with large deformation.

[0023] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A controlled rolling and cooling method for improving the surface quality of SAE10B33A steel, comprising the following steps: Step 1: slow cooling pretreatment of the billet; Step 2: three-stage step heating of the billet; Step 3: multi-stage high-pressure water descaling; Step 4: gradient temperature-controlled twist-free rolling; Step 5: online uniform temperature control after finishing rolling; Step 6: closed-loop control of wire drawing temperature; Step 7: Stellmore segmented controlled cooling; Step 8: surface protection for coiling and bundling; Step 9: online full inspection of surface defects, characterized in that: Step 1: Slow cooling pretreatment of the billet; Use an overhead crane to smoothly lift qualified continuous casting billets to the slow cooling pit, and stack them neatly according to the furnace number, leaving a 60-90mm ventilation gap between the billets to ensure uniform slow cooling temperature. After all the billets are put into the pit, the pit is completely covered and sealed with high-temperature resistant insulation cotton. The sealing edges are compacted to prevent air leakage, and the temperature inside the slow cooling pit is controlled to be stable at 600~750℃. Strictly control the slow cooling time to ≥30h, and check the temperature inside the pit every 8h during this period to ensure that the temperature fluctuation is ≤±30℃; After slow cooling, the surface temperature of the billet is detected by an infrared thermometer. Once the overall temperature drops to ≤200℃, it is then smoothly transferred to the heating furnace loading platform by an overhead crane. High-temperature billets are prohibited from being directly loaded into the furnace.

2. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 2: Three-stage step heating of the billet; Before feeding the heating furnace, clean the residual iron oxide scale and debris inside the furnace, turn on the furnace circulation fan, and adjust the walking beam to a horizontal state; A single-row loading method is adopted, in which billets are placed stably on the walking beam, with the billet spacing controlled at 90~110mm, and stacking or tilting during loading is avoided.

3. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 2: Three-stage step heating of the billet; Performs three-stage precise temperature control heating: Preheating section: Set furnace temperature ≤680℃, move the walking beam at a constant speed, and heat for 26~32 minutes. Slowly increase the temperature to avoid rapid surface oxidation. Heating section: Set furnace temperature to 1100~1140℃, heating time to 32~38min, to ensure that the core and surface of the billet are heated simultaneously; The heat soaking section is set at a furnace temperature of 1080~1120℃ and a heat soaking time of 32~42min to eliminate the temperature difference between the inside and outside of the billet. The billet is in the furnace for a total time of ≥90 minutes. Before exiting the furnace, it is tested with a multi-point infrared thermometer to ensure that the overall temperature difference of the billet is ≤±25℃. After the standard is met, the furnace door is opened to discharge the billet.

4. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 3: Multi-stage high-pressure water descaling; First descaling before rough rolling: After the billet exits the furnace, it is immediately transported to the descaling box at the rough rolling inlet. The sealing door of the descaling box is closed, the high-pressure water pump is turned on, the descaling pressure is adjusted to 19~25MPa, the billet running speed is controlled to 1.0~1.6m / s, and the descaling is repeated 2~3 times to completely remove the primary iron oxide scale. Secondary descaling before intermediate rolling: After rough rolling, the billet is transported to the descaling box at the entrance of the intermediate rolling mill. The descaling pressure is maintained at 19~25MPa. The descaling covers the entire surface of the billet in one pass, with no areas missed. Descaling rolling auxiliary treatment: After secondary descaling, the roll gap of the intermediate rolling mill is adjusted to be 0.2~0.4mm smaller than that of conventional rolling mill. The residual iron oxide scale is broken by rolling pressure to prevent the iron oxide scale from being pressed into the billet and forming surface defects.

5. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 4: Gradient temperature controlled twist-free rolling; Replace all U-shaped rolls before rolling, use a feeler gauge to adjust the roll gap accuracy to ≤ ±0.05mm, and check that the roll surface is free of scratches and wear to avoid scratching the wire surface during rolling. The process employs a twist-free high-speed rolling technique with four-stage gradient temperature control. Roughing mill: Control the initial rolling temperature to 1060~1090℃, set a large reduction, and ensure uniform deformation of the billet surface; Intermediate rolling mill: Control the rolling temperature to 980~1020℃, stabilize the mill speed, and avoid excessively rapid temperature drop of the billet; Pre-finishing mill: Control the rolling temperature to 930~970℃, gradually reduce the amount of deformation, and optimize the wire forming accuracy; Finishing mill: Real-time monitoring of the final rolling temperature, and by adjusting the mill speed and the water volume in the water cooling section, the final rolling temperature is stabilized at 870~930℃, with temperature fluctuation ≤±15℃; During the rolling process, the condition of the rolls and the roll gap accuracy are checked every 30 minutes, and the iron oxide scale adhering to the roll surface is cleaned in a timely manner.

6. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 5: Online temperature control after finishing rolling; A segmented water-cooling device is installed at the outlet of the finishing mill, and the angle of the water-cooling nozzles is adjusted to 45° to ensure that the water-cooling covers the entire circumference of the wire. The water flow rate in the water-cooling section is automatically adjusted to 12~18m based on the real-time temperature at the finishing mill exit. 3 / h, to avoid stress concentration on the wire surface caused by rapid cooling; After water cooling, a uniform temperature section is set up, and the wire is air-cooled for 8~12m to make the surface and core temperatures tend to be consistent, and smoothly transition to the spinning temperature range.

7. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 6: Closed-loop control of silk spinning temperature; Before the wire enters the spinning machine, a dual-point infrared thermometer is installed to monitor the wire temperature in real time, and the data is transmitted synchronously to the central control system. The central control system automatically adjusts the spinning machine speed and water cooling intensity based on temperature measurement data to stabilize the spinning temperature at 880~920℃, with temperature fluctuation ≤±10℃. During the spinning process, observe the coiling state and adjust the spinning tube angle in a timely manner to ensure that the coiled shape is regular, without sticking, and without dragging or scratches.

8. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 7: Stello segmented cooling; After the coils enter the Stellmore cooling line, they undergo a segmented cooling process of weak cooling at the front and slow cooling at the back. Front cooling zone: Set the roller conveyor speed to 0.13~0.17m / s, turn on the fan air volume to 55%~75%, and slowly control the phase change rhythm to avoid uneven cooling and cracks. Rear cooling zone: Keep the roller conveyor speed constant, reduce the fan air volume to 25%~45%, extend the cooling time, refine the internal structure, and reduce the strip structure level; The temperature of the coil is monitored throughout the cooling process. After cooling is complete, the coil is transported to the air-cooling area and allowed to cool naturally to room temperature. Forced air cooling is prohibited.

9. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 8: Surface protection during coiling and bundling; After the coil cools to room temperature, turn on the winding equipment and use a flexible clamping device to grab the coil with moderate clamping force to avoid surface damage caused by bumps and drags. After the coil is assembled, the bundling operation is carried out. The bundling pressure is controlled at 7 to 13 tons and the pressure is evenly distributed around the coil. A flexible protective pad is placed between the bundling tape and the coil to prevent indentations and abrasions. After bundling, the coils are hoisted smoothly to the finished product stacking area. Rubber mats are placed on the coils during stacking to prevent them from coming into direct contact with the hard ground.

10. The controlled rolling and controlled cooling method for improving the surface quality of SAE10B33A steel according to claim 1, characterized in that: Step 9: Online full inspection of surface defects; Before the finished products are bundled, the entire surface of each wire is scanned by an online thermal inspection device to automatically identify defects such as cracks, scars, pits, and iron oxide scale indentation, and the location of the defects is marked in real time. Defect judgment: Wires with surface defect depth > 0.1mm are directly cut and rejected; wires with short and shallow defects are sampled for acid washing verification. Wires that pass the pickling verification are classified and stored in the warehouse according to furnace number and specifications; unqualified wires are isolated separately, properly labeled, and returned for processing. Record the detection data, defect type and treatment results for each furnace to form a complete surface quality control file.