A bidirectional chain cooling bed and cooling control method

Abstract

The application provides a bidirectional chain type cooling bed and a cooling control method. The cooling bed comprises a plurality of forward chains and a plurality of reverse chains, the running direction of the forward chains is the same as the running direction of the steel material, and the running direction of the reverse chains is opposite to the running direction of the steel material; a forward chain motor, all the forward chains are connected with the forward chain motor; a reverse chain motor, all the reverse chains are connected with the reverse chain motor; a steel distribution disc located at the entrance of the cooling bed; and fans, a plurality of the fans are arranged on the two sides of the cooling bed. The cooling bed controls the cooling mode through temperature monitoring, cools the steel material on the cooling bed, the full-length temperature difference deviation of the steel material is small, the uniform cooling of the full length of the steel material is realized, the material performance fluctuation is small, the organization is stable, and the performance requirements of strength and toughness are met; the cooling uniformity of the two ends of the steel material is adjusted in real time by using the temperature, and the uniformity of the organization and the stability of the performance of the obtained steel material after cooling are ensured.

Description

Technical Field

[0001] This invention belongs to the field of special steel smelting and processing, and relates to a bidirectional chain cooling bed and a cooling control method. Background Technology

[0002] Engineering steel is widely used in industries such as petroleum, chemical, power plants, and boilers. Currently, most of the products produced in factories are delivered in the normalized state. However, the strength of some materials after normalizing does not meet national standards. Therefore, factories generally use convective heat transfer cooling for forced cooling, primarily reducing the temperature of the material from 900℃ to ≤150℃ through air cooling, wind cooling, and air mist cooling. The key equipment supporting the material is currently the cooling bed, which includes the worktable, mechanical transmission system, water cooling system, cooling bed worktable, and fixed support. Both air cooling and air mist cooling of the cooling bed use continuous operation, resulting in a difference in strength between the two ends of the material. This is mainly manifested in the lower strength and larger impact dispersion at the end farther from the air source, making it difficult to meet the national standards for engineering steel.

[0003] Furthermore, steel is typically subjected to rapid cooling after normalizing to improve its strength. Air cooling, wind cooling, or mist cooling are used to cool the material from the austenitizing temperature to room temperature. Without external forced cooling, the temperature drop caused by natural heat dissipation from the air is only 1% of the thermal radiation, which is negligible. Therefore, increasing the cooling rate after normalizing mainly relies on convection. Because the cooling bed operates continuously, the cooling process is unstable, easily leading to uneven cooling, resulting in material bending and inconsistent properties.

[0004] Therefore, how to solve the problem of uniform cooling during heat treatment is currently a technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a bidirectional chain cooling bed and a cooling control method, which uses a real-time temperature monitoring system to adjust the cooling uniformity at both ends of the steel, thereby ensuring the uniformity of the steel structure and the stability of its properties after cooling.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A bidirectional chain cooling bed is used for controlled cooling of steel after heat treatment. The cooling bed includes: multiple forward chains and multiple reverse chains, wherein the forward chains run in the same direction as the steel's travel direction, and the reverse chains run in the opposite direction to the steel's travel direction; a forward chain motor located at the entrance of the cooling bed, to which all the forward chains are connected; a reverse chain motor located at the exit of the cooling bed, to which all the reverse chains are connected; a steel distribution plate located at the entrance of the cooling bed, which pulls the steel onto the cooling bed; and fans, wherein several fans are respectively arranged on both sides of the cooling bed.

[0008] Furthermore, in the aforementioned bidirectional chain cooling bed, the forward chains and the reverse chains are alternately arranged; there are 6 to 9 forward chains, and all forward chains are connected to the same forward chain drive motor via a long shaft; the number of reverse chains is the same as the number of forward chains, and all reverse chains are connected to the same reverse chain drive motor via a long shaft; the distance between the forward chain and the axis of the cooling bed is less than the distance between the reverse chain and the axis of the cooling bed.

[0009] Furthermore, in the aforementioned bidirectional chain cooling bed, a loading platform is provided at the inlet of the cooling bed, and a unloading platform is provided at the outlet of the cooling bed; the steel is pipe or bar, the outer diameter of the pipe is 100mm-600mm and the wall thickness is 10mm-130mm, and the diameter of the bar is 60mm-350mm; the cooling rate of the fan is 5℃ / min-10℃ / min; the total cooling time t2 of the steel on the cooling bed is 3700s-4400s.

[0010] Furthermore, in the aforementioned bidirectional chain cooling bed, a temperature measuring instrument is installed above the outlet of the cooling bed. This instrument is connected to the control system and performs full-length temperature monitoring of the steel every 5 to 300 seconds. The control system records the temperature of the steel measured by the temperature measuring instrument. Both the forward chain motor and the reverse chain motor are connected to the control system, which can adjust the cooling rate of the steel based on the temperature difference between its two ends. The formula for calculating the cooling rate is:

[0011]

[0012] In Formula 1, Nu f For cooling rate; Re f The Reynolds number is 10. 4 ≤Re f ≤1.2×10 5 ;Pr fFor exchange capacity, 0.6 ≤ Pr f ≤120.

[0013] Furthermore, in the aforementioned bidirectional chain cooling bed, the fan includes a first fan, and a plurality of first fans are arranged on one side of the cooling bed, the first fans blowing air towards one end of the steel; a total of 8 first fans are arranged from the entrance of the cooling bed to the middle of the cooling bed; a first water pipe is provided on the first fan, the first water pipe being able to spray cooling water towards one end of the steel.

[0014] Furthermore, in the aforementioned bidirectional chain cooling bed, the fan includes a second fan, and several second fans are arranged on the other side of the cooling bed, with the second fans blowing air towards the other end of the steel; a total of 8 second fans are arranged from the middle of the cooling bed to the outlet of the cooling bed; a second water pipe is provided on the second fan, and the second water pipe can spray cooling water towards the other end of the steel.

[0015] Furthermore, in the above-mentioned bidirectional chain cooling bed, the distance between two adjacent forward and reverse chains is 18cm to 25cm; several columns are provided on the forward chain, and the columns are evenly arranged along the circumference of the forward chain, with the steel material located between two adjacent columns.

[0016] On the other hand, a cooling control method is provided, utilizing the aforementioned bidirectional chain cooling bed, wherein the running speed of the forward chain is controlled at a minimum frequency of 1Hz; the reverse chain controls the rotation speed of the steel material, which is placed on the reverse chain, and the operation of the reverse chain drives the steel material to rotate, thereby causing the steel material to uniformly contact the air for convection and uniform cooling; when the outer diameter of the steel material is ≤350mm, the running speed v of the reverse chain is 1mm / s to 3mm / s; when the outer diameter of the steel material is >350mm, the running speed v of the reverse chain is 3mm / s to 5mm / s; after cooling by the cooling bed, the surface temperature of the steel material is ≤150℃ and the temperature difference along its entire length is ≤50℃.

[0017] Furthermore, in the above-mentioned cooling control method, when the temperature difference between the two ends of the steel is ≥15℃, the fan at the low-temperature end of the steel is turned off; when the temperature difference between the two ends of the steel is <10℃, the fan at the low-temperature end of the steel is turned on.

[0018] Furthermore, in the above-mentioned cooling control method, the reverse chain runs continuously. When the temperature difference between the two ends of the steel is ≥15℃, the forward chain stops running. When the temperature difference between the two ends of the steel is <15℃, the forward chain starts running. The time between the stop and start of the forward chain is the intercept waiting time t1, which is 30s to 110s.

[0019] Analysis reveals that this invention discloses a bidirectional chain cooling bed and a cooling control method. This cooling bed uses temperature monitoring to control the cooling process, cooling steel (pipes or bars) on the bed. The temperature difference along the entire length of the steel is small, achieving uniform cooling throughout the steel, resulting in minimal fluctuations in material properties, stable microstructure, and simultaneously meeting the requirements for strength and toughness. This invention utilizes real-time temperature monitoring to adjust the cooling uniformity at both ends of the steel, ensuring the uniformity of the resulting steel microstructure and the stability of its properties. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a structure according to an embodiment of the present invention.

[0021] Figure 2 This is a top view of an embodiment of the present invention.

[0022] Figure 3 This is a cooling rate curve at both ends of the seamless steel pipe in Embodiment 1 of the present invention.

[0023] Figure 4 This is a cooling rate curve of both ends of the seamless steel pipe in Comparative Example 1 of the present invention.

[0024] Figure 5 The graph shows a comparison of the mechanical properties of the seamless steel pipes cooled in Example 1 and Comparative Example 1, respectively, according to the present invention.

[0025] Figure 6 The graph shows a comparison of the mechanical properties of the seamless steel pipes cooled in Example 2 and Comparative Example 2, respectively, according to the present invention.

[0026] Figure 7 The diagram shows a comparison of the impact performance of seamless steel pipes cooled in Example 1 and Comparative Example 1, respectively, according to the present invention.

[0027] Figure 8 The graph shows a comparison of the impact performance of seamless steel pipes cooled in Example 2 and Comparative Example 2, respectively, according to the present invention.

[0028] Figure 9 This is a diagram showing the microstructure of the seamless steel pipe near the fan during operation of the cooling bed in Embodiment 1 of the present invention.

[0029] Figure 10 This is a diagram showing the structure of the seamless steel tube away from the fan during operation of the cooling bed in Embodiment 1 of the present invention.

[0030] Figure 11 This is a microstructure diagram of the seamless steel pipe near the fan during operation of the cooling bed in Comparative Example 1 of the present invention.

[0031] Figure 12 This is a microstructure diagram of the end of the seamless steel tube away from the fan during operation of the cooling bed in Comparative Example 1 of the present invention.

[0032] Explanation of reference numerals in the attached diagram: 1 Forward chain; 2 Reverse chain; 3 Temperature measuring instrument; 4 Steel material; 5 First fan; 6 Second fan; 7 Column; 8 Steel disc; 9 Long shaft; 10 Forward chain motor; 11 Reverse chain motor; 12 Loading platform; 13 Unloading platform. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. Indeed, those skilled in the art will recognize that modifications and variations can be made to the invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the invention encompass such modifications and variations falling within the scope of the appended claims and their equivalents.

[0034] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected," "linked," and "set up" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; a wired connection, a radio connection, or a wireless communication signal connection. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0035] The accompanying drawings illustrate one or more examples of the invention. The detailed description uses numerals and letters to refer to features in the drawings. Similar or analogous reference numerals in the drawings and description have been used to refer to similar or analogous parts of the invention. As used herein, the terms “first,” “second,” and “third,” etc., are used interchangeably to distinguish one component from another and are not intended to indicate the location or importance of individual components.

[0036] like Figures 1 to 12As shown, according to an embodiment of the present invention, a bidirectional chain cooling bed is provided for controlled cooling of steel 4 after heat treatment, such as... Figure 1 and Figure 2 As shown, the cooling bed includes: multiple forward chains 1 and multiple reverse chains 2. The forward chains 1 run in the same direction as the steel 4, driving the steel 4 to move on the cooling bed. The reverse chains 2 run in the opposite direction to the steel 4, driving the steel 4 to rotate continuously on the cooling bed. A forward chain motor 10 is located at the entrance of the cooling bed, and all forward chains 1 are connected to it. A reverse chain motor 11 is located at the exit of the cooling bed, and all reverse chains 2 are connected to it. A steel distribution plate 8 is located at the entrance of the cooling bed, and it pulls the steel 4 onto the cooling bed. Several fans are respectively arranged on both sides of the cooling bed. This cooling bed can cool steel 4 by air, wind, and water. By using the cooling bed to cool steel 4, the cooling rate at both ends of steel 4 can be controlled, achieving uniform cooling of the entire length of steel 4. This results in steel 4 with uniform structure and properties, small performance fluctuations, stable structure, and meets the performance requirements of strength and toughness. It effectively solves the technical problem of uniform cooling during heat treatment.

[0037] Furthermore, forward chains 1 and reverse chains 2 are alternately arranged. There are 6 to 9 forward chains 1, all of which are connected to the same forward chain 1 drive motor via a long shaft 9. The number of reverse chains 2 is the same as the number of forward chains 1, and all of which are connected to the same reverse chain 2 drive motor via a long shaft 9. The distance between the forward chain 1 and the axis of the cooling bed is less than the distance between the reverse chain 2 and the axis of the cooling bed. One forward chain 1 and one reverse chain 2 constitute a chain group, and 6 to 9 chains are evenly arranged on the cooling bed. During the operation of the cooling bed, the forward chains 1 can be stopped and started, while the reverse chains 2 drive the steel 4 to rotate continuously. The continuous rotation of the steel 4 prevents the steel 4 from bending due to prolonged suspension at both ends, and also allows the surface of the steel 4 to contact the air for uniform convection cooling, resulting in uniform cooling of the steel 4.

[0038] Furthermore, a loading platform 12 is provided at the inlet of the cooling bed, and a unloading platform 13 is provided at the outlet of the cooling bed. The steel material 4 is pipe or bar, with an outer diameter of 100mm-600mm (e.g., 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm) and a wall thickness of 10mm-130mm (e.g., 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm). The diameter of the bar stock is 60mm-350mm (e.g., 60mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm), and the cooling rate of the fan is 5℃ / min-10℃ / min (e.g., 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min). The total cooling time t2 of steel 4 on the cooling bed is 3700s-4400s (e.g., 3700s, 3800s, 3900s, 4000s, 4100s, 4200s, 4300s, 4400s). The total cooling time of steel 4 on the cooling bed is mainly determined by the outer diameter and wall thickness of steel 4. A larger outer diameter results in a larger heat exchange area and a faster cooling rate, while a thicker wall accumulates more heat internally, requiring greater cooling intensity and a longer total cooling time.

[0039] Furthermore, a temperature measuring instrument 3 is installed above the outlet of the cooling bed. The temperature measuring instrument 3 is connected to the control system. The temperature measuring instrument 3 performs full-length temperature detection on the steel 4 every 5s to 300s (e.g., 5s, 30s, 60s, 90s, 120s, 150s, 180s, 210s, 240s, 270s, 300s). The more frequently the temperature measuring instrument 3 refreshes, the more accurate the detection. In one embodiment of the present invention, the temperature measuring instrument 3 performs full-length temperature detection on the steel 4 every 60s. The temperature measuring instrument 3 detects 5 points along the length of each steel pipe. Finally, the difference between the two ends is used as the control factor for control. The monitoring system adjusts the operation and stop of the forward chain 1 according to the temperature difference between the two ends of the steel 4. The control system records the temperature of the steel 4 measured by the temperature measuring instrument 3 and calculates the cooling rate curves at both ends of the steel 4. Both the forward chain motor 10 and the reverse chain motor 11 are connected to the control system. The control system can adjust the cooling rate of the steel 4 according to the temperature difference between its two ends. The formula for calculating the cooling rate is:

[0040]

[0041] In Formula 1, Nu f Re is the cooling rate; f Reynolds number (Re fThe Reynolds number in the empirical formula for heat exchange refers to a transitional flow around a pipe (a flow state between laminar and turbulent flow), 10 4 ≤Re f ≤1.2×10 5 ;Pr f For air exchange capacity, 0.6 ≤ Pr f ≤120.

[0042] Furthermore, the fan includes a first fan 5, such as Figure 2 As shown, a plurality of first fans 5 are arranged on one side of the cooling bed, blowing air onto one end of the steel 4. There are eight first fans 5 in total, arranged from the entrance to the middle of the cooling bed. Each first fan 5 has a first water pipe that sprays cooling water onto one end of the steel 4. A plurality of second fans 6 are arranged on the other side of the cooling bed, blowing air onto the other end of the steel 4. There are eight second fans 6 in total, arranged from the middle to the exit of the cooling bed. Each second fan 6 has a second water pipe that sprays cooling water onto the other end of the steel 4. The first fans 5 and second fans 6 provide air cooling for the steel 4, while the first and second water pipes provide water cooling. Different cooling methods are formulated according to the composition and requirements of different steel grades. One process is used for steel of one composition. The process is set in advance. When steel 4 enters the cooling bed, it is cooled according to the requirements. When steel 4 requires air cooling, the first and second water pipes are turned on when steel 4 enters the cooling bed. The first fan 5 and the second fan 6 are staggered on both sides of the cooling bed to improve the heat exchange efficiency between steel 4 and air.

[0043] Furthermore, the spacing between two adjacent forward chains 1 and reverse chains 2 is 18cm to 25cm, such as... Figure 1 As shown, a plurality of columns 7 are arranged on the forward chain 1, and the columns 7 are evenly arranged along the circumference of the forward chain 1. The steel 4 is located between two adjacent columns 7.

[0044] This invention also discloses a method for cooling control using the aforementioned bidirectional chain cooling bed. The running speed of the forward chain 1 is controlled at a minimum frequency of 1Hz (approximately 100mm / s), and the reverse chain 2 controls the rotation speed of the steel 4. The steel 4 is placed on the reverse chain 2, and the operation of the reverse chain 2 drives the steel 4 to rotate. The rotation of the steel 4 causes it to uniformly contact the air for convection and uniform cooling. When the outer diameter of the steel 4 is ≤350mm, the running speed v of the reverse chain 2 is 1mm / s to 3mm / s (e.g., 1mm / s, 2mm / s, 3mm / s). When the outer diameter of the steel 4 is >350mm, the running speed v of the reverse chain 2 is 3mm / s to 5mm / s (e.g., 3mm / s, 4mm / s, 5mm / s). After cooling by the cooling bed, the surface temperature of the steel 4 is ≤150℃ and the temperature difference along its entire length is ≤50℃. When the temperature difference between the two ends of steel 4 is ≥15℃, the fan at the low-temperature end of steel 4 is turned off; when the temperature difference between the two ends of steel 4 is <10℃, the fan at the low-temperature end of steel 4 is turned on. Reverse chain 2 runs continuously, while forward chain 1 operates in a stop-and-go mode. When the temperature difference between the two ends of steel 4 is ≥15℃, forward chain 1 stops running; when the temperature difference between the two ends of steel 4 is <15℃, forward chain 1 starts running. The time between the stop and start of forward chain 1 is the stop-and-go waiting time t1, which is 30s to 110s (e.g., 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s).

[0045] Because the first fan 5 and the second fan 6 are located on opposite sides of the cooling bed and are staggered, the air heat exchange area of ​​steel 4 varies depending on its specifications, resulting in inconsistent cooling rates at both ends of the steel 4. This leads to a temperature difference between the two ends of the steel 4 during the cooling process. After the steel 4 is placed on the cooling bed, temperature data is received by the thermometer 3. The control system controls the stopping and starting time of the forward chain 1 based on the temperature difference measured by the thermometer 3, thereby controlling the cooling bed's cutoff waiting time t1 and the operation of the fans. The system also controls the running speed v of the reverse chain 2 according to the specifications of the steel 4, thus controlling the rotational speed of the steel 4. The cooling bed cutoff waiting time t1 and the running speed v of the reverse chain 2 together determine the uniformity of cooling along the entire length of the steel 4. The thicker the steel 4, the longer the waiting time; that is, the cooling rate of the steel 4 is directly proportional to its thickness. By adjusting the running speed of the reverse chain 2, the rotational speed v of the steel 4 is adjusted, thus fine-tuning the cooling rate of the steel 4 to ensure uniform cooling. By adjusting the cooling rate of steel 4, uniform cooling of steel 4 is achieved, preventing the performance of steel 4 from being affected by uneven cooling at both ends. This method can uniformly control the cooling rate of steel 4 throughout the entire length of the cooling bed, achieving efficient, precise, and uniform control of the cooling rate of steel 4 throughout its entire length, ensuring that the cooling rates at both ends are nearly uniform, and obtaining steel 4 with uniform microstructure and properties.

[0046] Example 1

[0047] Seamless steel pipes with a low-carbon steel composition of 16Mn and a specification of 298.5×36mm (outer diameter×wall thickness) were used as experimental materials. The main components of the seamless steel pipes are shown in Table 1. After complete austenitization at 900-940℃, forced cooling was performed using a sectionalized waiting-type air-cooling method on a cooling bed to complete the entire normalizing cooling process. The cooling parameters are shown in Table 2. The cooling rate curves at both ends of the seamless steel pipe are shown in the figure. Figure 3 As shown.

[0048] Example 2

[0049] The difference between this embodiment and Embodiment 1 is that a seamless steel pipe with a low-carbon steel composition of 16Mn and a specification of 298.5×60mm (outer diameter×wall thickness) is used as the test material. The cooling bed adopts a truncated waiting type air mist cooling for forced cooling. The main components of the seamless steel pipe are shown in Table 1, and the cooling parameters in the experiment are shown in Table 2.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 1 is that the cooling bed uses continuous air cooling (forward chain 1 runs continuously) to force-cool the seamless steel pipe. The cooling parameters are shown in Table 2. The cooling rate curves at both ends of the seamless steel pipe are shown in the figure. Figure 4 As shown.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 2 is that the seamless steel pipe is forcibly cooled by a continuous air-cooling system (forward chain 1 runs continuously) using a cooling bed, and the cooling parameters are shown in Table 2.

[0054] Table 1. Main chemical composition (%) of the experimental steel grades

[0055]

[0056] Table 2. Main Cooling Parameters of Experimental Steel Grades

[0057]

[0058] Notes: 1. Intercept waiting time t1 is the waiting time of the seamless steel pipe on the cooling bed; v is the running speed of the reverse chain 2; t2 is the total cooling time of the steel 4 on the cooling bed; T is the temperature difference between the two ends of the seamless steel pipe after it leaves the cooling bed.

[0059] Analysis of the experimental results of Example 1, Example 2, Comparative Example 1 and Comparative Example 2

[0060] 1. Mechanical property analysis

[0061] After testing two specifications of 16Mn steel pipes under different cooling methods (intercept-waiting air cooling and continuous air cooling), the distribution of yield strength and impact toughness results is shown in the figure. Figures 5-8 .from Figure 5 , Figure 6 It can be seen that both ends of the steel controlled by the intercept-waiting air cooling process can meet the performance requirements of yield strength > 335MPa and V-notch impact energy > 130J at -20℃, and the strength difference between the two ends of steel 4 is only 15MPa, and the difference in impact value between the two ends of steel 4 is only 50J. From Figure 7 , Figure 8 It can be seen that when continuous air cooling is used, there is a significant difference in strength between the two ends of steel 4, with insufficient wind strength at the end far from the air source, resulting in a large dispersion in impact energy and making it very difficult to control the uniformity of performance. In contrast, the performance of steel 4 cooled by the intercept-waiting air cooling process is significantly better than that of steel 4 cooled by the continuous air cooling process. This is because the intercept-waiting cooling rate is more uniform than that of continuous cooling, and the cooling rate along the entire length of the material can be controlled by controlling the operation, pause, and restart of the cooling bed, thereby improving the uniformity of strength and toughness indicators.

[0062] 2. Brinell Hardness Analysis and Discussion

[0063] To further verify the uniformity of performance, full-length, full-wall-thickness hardness analysis was performed on the two specifications (for steel pipes controlled by different cooling methods, the four-quadrant Brinell hardness test was performed on the head, middle, and tail of the pipe, as shown in Table 3). From the cross-sectional hardness values, it can be seen that the hardness values ​​and range values ​​of the control method with the interval waiting cooling are quite similar, while the hardness values ​​with the continuous cooling control method have a large range. This is because the interval waiting cooling can achieve uniform control of the cooling rate of the entire length of the steel pipe, thereby obtaining uniform microstructure and mechanical properties.

[0064] Table 3. Comparison of Hardness of 16MnC under Different Cooling Methods

[0065]

[0066] 3. Microstructural Analysis and Discussion

[0067] Figure 9 This is a diagram showing the microstructure of the seamless steel pipe near the fan in Example 1. Figure 10 This is a microstructure diagram of the end of the seamless steel pipe away from the fan in Example 1. Figure 11 This is a microstructure diagram of the seamless steel pipe near the fan in Comparative Example 1. Figure 12 This is a microstructure diagram of the seamless steel tube from Comparative Example 1, located away from the fan. Figures 9-12It can be seen that when continuous cooling is used, the cooling speed is faster at the end near the air source, and mixed crystal phenomenon occurs with a grain size of 7-3. The structure at the end far from the air source is better with no coarse structure and a grain size of 6. However, when intercept-waiting cooling is used, the structure at both ends is uniform with no obvious difference, and the grain size at both ends is 6.

[0068] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0069] (1) By controlling the cooling method through temperature monitoring, the steel 4 (pipe or bar) is cooled on the cooling bed. The temperature difference deviation of the entire length of the steel 4 is small, and the uniform cooling of the entire length of the steel 4 is achieved. The material properties fluctuate little, the structure is stable, and the performance requirements of strength and toughness are met at the same time.

[0070] (2) The present invention utilizes real-time temperature monitoring and adjusts the cooling uniformity at both ends of the steel 4 to ensure the uniformity of the structure and the stability of the properties of the steel 4 obtained after cooling.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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 bidirectional chain cooling bed for controlled cooling of steel after heat treatment, characterized in that, The cooling bed includes: Multiple forward chains and multiple reverse chains, wherein the forward chains run in the same direction as the steel material's direction of travel, and the reverse chains run in the opposite direction to the steel material's direction of travel. A forward chain motor is located at the entrance of the cooling bed, and all the forward chains are connected to the forward chain motor; A reverse chain motor is located at the outlet of the cooling bed, and all the reverse chains are connected to the reverse chain motor. The reverse chains control the rotation speed of the steel. A steel distribution tray, located at the entrance of the cooling bed, is used to distribute the steel onto the cooling bed. Fans, several of the aforementioned fans are respectively arranged on both sides of the cooling bed. The fan includes a first fan, and a plurality of the first fans are arranged on one side of the cooling bed. The first fans blow air toward one end of the steel. The first fans are arranged from the entrance of the cooling bed to the middle of the cooling bed. The fan includes a second fan, and several second fans are arranged on the other side of the cooling bed, with the second fans blowing air towards the other end of the steel. The second fans are arranged from the middle of the cooling bed to the outlet of the cooling bed. The first fan and the second fan are staggered and positioned on opposite sides of the cooling bed. A temperature measuring instrument is installed above the outlet of the cooling bed. The temperature measuring instrument is connected to the control system. The temperature measuring instrument performs full-length temperature detection on the steel every 5s to 300s. The control system records the temperature of the steel measured by the temperature measuring instrument. Both the forward chain motor and the reverse chain motor are connected to a control system, which can adjust the cooling rate of the steel based on the temperature difference between the two ends of the steel. The control system controls the stopping and starting time of the forward chain based on the temperature difference between the two ends of the steel measured by the thermometer, and controls the running speed of the reverse chain based on the specifications of the steel, thereby controlling the rotation speed of the steel.

2. The bidirectional chain cooling bed according to claim 1, characterized in that, The forward chain and the reverse chain are alternately arranged; There are 6 to 9 forward chains, and all of the forward chains are connected to the same forward chain motor via a long shaft; The number of reverse chains is the same as the number of forward chains, and all the reverse chains are connected to the same reverse chain motor via a long shaft.

3. The bidirectional chain cooling bed according to claim 1, characterized in that, A loading platform is provided at the entrance of the cooling bed, and a unloading platform is provided at the exit of the cooling bed. The steel material is a pipe or a bar, the outer diameter of the pipe is 100mm-600mm and the wall thickness is 10mm-130mm, and the diameter of the bar is 60mm-350mm. The cooling rate of the fan is 5℃ / min-10℃ / min; The total cooling time t2 of the steel on the cooling bed is 3700s-4400s.

4. The bidirectional chain cooling bed according to claim 1, characterized in that, The first fan has a total of 8 units; The first fan is equipped with a first water pipe, which can spray cooling water to one end of the steel.

5. The bidirectional chain cooling bed according to claim 1, characterized in that, The second fan has a total of 8 units; The second fan is equipped with a second water pipe, which can spray cooling water to the other end of the steel.

6. The bidirectional chain cooling bed according to claim 1, characterized in that, The spacing between two adjacent forward and reverse chains is 18cm to 25cm; The forward chain is provided with a number of columns, which are evenly arranged along the circumference of the forward chain, and the steel is located between two adjacent columns.

7. A cooling control method, utilizing the bidirectional chain cooling bed according to any one of claims 1-6, characterized in that, The operating speed of the forward chain is controlled at a minimum frequency of 1Hz; The steel is placed on the reverse chain, and the operation of the reverse chain drives the steel to rotate. The rotation of the steel causes it to come into uniform contact with the air, resulting in uniform cooling. The steel material is pipe. When the outer diameter of the steel is ≤350mm, the running speed v of the reverse chain is 1mm / s~3mm / s; When the outer diameter of the steel is greater than 350mm, the running speed v of the reverse chain is 3mm / s to 5mm / s; After being cooled by the cooling bed, the surface temperature of the steel is ≤150℃ and the temperature difference along its entire length is ≤50℃.

8. The cooling control method according to claim 7, characterized in that, When the temperature difference between the two ends of the steel is ≥15℃, the fan at the low-temperature end of the steel is turned off. When the temperature difference between the two ends of the steel is less than 10°C, the fan at the low-temperature end of the steel is turned on.

9. The cooling control method according to claim 7, characterized in that, The reverse chain continues to run. When the temperature difference between the two ends of the steel is ≥15℃, the forward chain stops operating. When the temperature difference between the two ends of the steel is less than 15°C, the forward chain starts operating. The time between the start and stop of the forward chain is the intercept waiting time t1, which is 30s to 110s.

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