Interval cooling control method based on runway type high-speed cooling platform

Abstract

An interval cooling control method based on a runway type high-speed cooling platform comprises the following steps that (1) a sample is placed on a sample bearing table on a trolley in the mode that an annular rail is combined with the trolley; at least one cooling device is arranged along the linear section track; the cooling jet flow ejected by the cooling device is directly jetted onto the sample to simultaneously perform double-sided cooling on the upper surface and the lower surface of the sample; 2) heating the sample according to cooling heat exchange research requirements, and synchronously measuring the temperature of the sample; (3) starting a cooling device after the sample reaches an initial cooling temperature T0 of 750-1000 DEG C, closing cooling water or moving the sample out of a cooling area when the temperature reaches a target temperature T1 of 500-800 DEG C after water cooling, and starting water cooling after continuous air cooling time t of 0-25 seconds; when the temperature reaches the final cooling temperature T2 = 0-700 DEG C, cooling water is closed or the trolley is moved out of the cooling area, and meanwhile the speed of the trolley is controlled to be reduced till the trolley is static; 4) testing the performance of the sample; and 5) repeating the step 2) to the step 4), and determining the cooling process test parameters of which the performance meets the requirements according to the measured data.

Description

Technical Field

[0001] The invention belongs to the technical field of metal heat treatment, and in particular relates to an interval cooling control method based on a runway-type high-speed cooling experimental platform. Background Art

[0002] The runway-type high-speed cooling test platform can operate at any speed, including low, medium, and high, and can particularly reach high strip speeds of approximately 25 m / s. Its layout and control methods differ significantly from existing test platforms and laminar cooling systems for hot rolling production lines.

[0003] The running speed and cooling time have a great influence on the cooling process. To simulate the production site conditions (the maximum speed can reach about 20m / s, and the cooling time is about 5s), a length of about 100m is required. Due to reasons such as laboratory space and economy, the maximum movement speed of the specimen (usually a metal plate) in cooling experimental research at home and abroad is currently about 1.6m / s. For example, the internationally renowned cooling experimental device of the University of British Columbia in Canada has a maximum speed of only 1m / s. Tata Motors has newly built a single-sided single-nozzle cooling experimental device with a maximum speed of 8m / s to conduct medium and low temperature heat exchange research, but the speed is still relatively low.

[0004] To ensure product performance, intermittent cooling—a combination of water and air cooling—is used on many types of steel, such as duplex steel and precipitation-hardened steel. Controlling the temperature after the first water cooldown, the air cooldown duration, and the temperature after the second water cooldown is crucial. Since this was the first application of a high-speed cooling test platform, intermittent cooling was not previously used.

[0005] Previous cooling studies typically observed and studied the heat transfer from the center of the jet outward after a fixed cooling jet impinged on the specimen's surface while the specimen was stationary. However, the cooling water flow on the specimen's surface at rest differs significantly from that on a moving specimen, and the resulting heat transfer behavior is also completely different.

[0006] Tata Motors has built a new single-sided, single-nozzle cooling device with a maximum speed of 8m / s, but this speed is still relatively low compared to the actual belt speed in hot rolling laminar cooling production. Single-sided cooling has great limitations for heat transfer research and cannot carry out segmented cooling research. In addition, the test device only uses a single nozzle and cannot simulate the complex water flow conditions in the actual production process.

[0007] In the past, water cooling and air cooling switching and time control were performed on linear motion, and there was no similar control method on the circulation device. Summary of the Invention

[0008] The purpose of the present invention is to provide an interval cooling control method based on a runway-type high-speed cooling platform. By adopting an annular cooling experimental platform, the metal specimens are loaded into the set process speed, heating and cooling states, which well simulates the actual state of on-site production, greatly reduces the test cost and improves the accuracy of laboratory simulation, and provides a strong reference and reference for product research and development, model development, and process improvement.

[0009] To achieve the above object, the technical solution of the present invention is:

[0010] The present invention adopts an annular cooling experimental device, which can quickly accelerate a metal sample heated to a specified process temperature (such as about 950°C) to a set process speed (maximum 25m / s), and then pass through the cooling zone, including the water cooling zone and the air cooling zone, at a constant speed or in an accelerated or decelerated state, and realize the temperature control of the water cooling zone, the air cooling time after water cooling, and then water cooling to the set temperature.

[0011] Specifically, the interval cooling control method based on the runway-type high-speed cooling platform of the present invention comprises the following steps:

[0012] 1) A circular track combined with a trolley is adopted, wherein the circular track is an elliptical track comprising two parallel straight segments and two semicircular segments, and the sample is placed on the sample carrier on the trolley; at least one cooling device for cooling the sample is provided along the straight segment track; the sample carrier for fixing the sample is hollowed out in the middle, and when the sample is fixed to the sample carrier, the upper and lower surfaces of the sample are not blocked, and the cooling jet ejected by the cooling device is directly sprayed onto the sample, and the upper and lower surfaces of the sample are cooled on both sides at the same time; preferably, when the number of cooling devices is greater than or equal to 2, the distances between the cooling devices are equal; preferably, the cooling device adopts an offline design; during the process, the movement speed of the sample, the flow rate and pressure of the cooling medium of the cooling device, the total flow density, several instantaneous temperature values ​​of the sample measured by thermocouples embedded on the surface and inside of the sample during the entire cooling process, and the cooling time required from the start cooling temperature to the final cooling temperature are monitored and obtained in real time; water cooling is adopted for sample cooling;

[0013] 2) Heat the sample according to the requirements of cooling and heat transfer research, and measure the temperature of the sample simultaneously;

[0014] 3) After the sample reaches the cooling temperature T0 = 750 ~ 1000 ° C, the cooling device is turned on, and the temperature change of the sample during the experiment is monitored online in real time: when the temperature reaches the target temperature T1 = 500 ~ 800 ° C after water cooling

[0015] When the temperature reaches the final cooling temperature T2 = 0 ~ 700 ° C, immediately stop cooling by turning off the cooling water or moving out of the cooling zone, and at the same time control the trolley to slow down until it stops;

[0016] 4) Perform performance tests on the samples;

[0017] 5) Repeat steps 2) to 4) and determine the cooling process test parameters that meet the performance requirements based on the measured data.

[0018] Preferably, the trolley is driven by a motor or a traction drive.

[0019] Preferably, the circular motion speed of the sample, ie, the linear speed or angular speed, is monitored in real time, and the speed of the sample can be changed online according to the measured temperature data according to the predetermined cooling process, ie, the speed can be increased or decreased or kept constant.

[0020] Preferably, the sample is heated offline or online:

[0021] The offline heating method is as follows: after the sample is heated to the temperature required by the process, it is fixedly mounted on the sample carrier. When it approaches the predetermined cooling start temperature, the trolley is driven along the circular track, driving the sample to sequentially pass through the cooling device, that is, through a theoretically infinite cooling zone, to complete the cooling or heat treatment process;

[0022] The online heating method is as follows: the sample is first fixed on the sample carrier and then heated. When the temperature required by the process is reached, the heating device is separated from the circular track area, and then the trolley is driven along the circular track to complete the cooling or heat treatment process.

[0023] Preferably, the heating is performed by resistance heating, that is, electrodes are used to clamp both sides of the sample, and the sample is directly heated online as a resistor through a large current; or, induction heating is used.

[0024] Preferably, water cooling is used to cool the sample.

[0025] Preferably, the cooling jet has a fan-shaped, conical, cylindrical, slit-shaped or circumferentially porous shape.

[0026] Preferably, when water-cooled, the flow ratio of the upper and lower surfaces of the sample is 0.01 to 2, and the total flow density is 30 to 500 m 3 / h / m 2 , the water pressure is 0.01~2MPa.

[0027] Preferably, in step 1), the movement speed of the sample is less than 25 m / s.

[0028] Preferably, in step 1), the driving trolley drives the sample to reach a set process speed and maintains a constant speed; wherein,

[0029] Sample thickness h: 10mm<h≤25mm, running speed is 0~12m / s;

[0030] Sample thickness h: 5mm<h≤10mm, running speed is 2~14m / s;

[0031] Sample thickness h: 3mm<h≤5mm, running speed is 4~16m / s;

[0032] Sample thickness h: 2mm<h≤3mm, running speed is 6~18m / s;

[0033] Sample thickness h: 1~2mm, running speed is 8~20m / s.

[0034] The invention is designed on a track similar to the shape of a stadium runway, on which a trolley carrying a sample is arranged. The sample is placed on the carrying platform of the trolley, and the trolley drives the sample to move along a closed curve.

[0035] Beneficial effects of the present invention:

[0036] The present invention adopts a runway-type high-speed cooling experimental platform, which can drive the heated metal sample to any specified speed (low, medium or high speed), and pass through a theoretically infinite cooling zone in a moving state to ensure that the sample is cooled from a high temperature state to room temperature in one go according to a given temperature curve within the "uninterrupted cooling zone". The present invention is particularly suitable for simulating "high belt speed" working conditions of about 15m / s, such as hot rolling laminar cooling, and can reach a maximum of 25m / s.

[0037] The present invention provides a method for realizing intermittent cooling on an annular cooling experimental device, which can drive the heated metal sample to any specified speed, so that the metal sample can be switched between water cooling and air cooling on the running track. By controlling the corresponding cooling temperature and air cooling time, dynamic cooling process simulation research at various speeds is realized, so as to develop and optimize the cooling process required by certain specific steel grades and improve product quality.

[0038] At the same time, through the test platform, the method of the present invention has the following advantages:

[0039] 1. It can achieve more accurate control of the outlet water temperature (can be measured). Actual production relies solely on calculation and cannot predict deviations. The intermediate temperature measurement point cannot fully represent the outlet water temperature.

[0040] 2. It can realize flexible and accurate configuration of process parameters such as cooling start temperature T0, target temperature T1, final cooling temperature T2, air cooling time t, etc. For example, it can control longer air cooling time and theoretically design the air cooling time under extreme process conditions;

[0041] 3. It is possible to realize multi-stage interval cooling process design based on more reasonable boundary conditions (speed, etc.) to verify the performance of the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the layout diagram of the annular cooling experimental device for the interval cooling control method described in the present invention.

[0043] Figure 2 This is a schematic diagram of the interval cooling control method of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0045] See also Figure 1 、 Figure 2 The interval cooling control method based on the runway-type high-speed cooling platform of the present invention comprises the following steps:

[0046] 1) A circular track combined with a trolley is adopted, wherein the circular track 1 is an elliptical track comprising two parallel straight segments and two semicircular segments, and the sample 100 is placed on a sample carrier 3 on the trolley 2; at least one cooling device 4 for cooling the sample is provided along the straight segment track; the sample carrier for fixing the sample is hollowed out in the middle, and when the sample is fixed to the sample carrier, the upper and lower surfaces of the sample are not blocked, and the cooling jet ejected by the cooling device 4 is directly sprayed onto the sample, and the upper and lower surfaces of the sample are cooled on both sides at the same time; preferably, when the number of cooling devices is greater than or equal to 2, the distances between the cooling devices are equal; preferably, the cooling device adopts an offline design; during the process, the movement speed of the sample, the flow rate and pressure of the cooling medium of the cooling device, the total flow density, several instantaneous temperature values ​​of the sample measured by thermocouples embedded on the surface and inside of the sample during the entire cooling process, and the cooling time required from the start cooling temperature to the final cooling temperature are monitored and obtained in real time; water cooling is adopted for sample cooling;

[0047] 2) Heat the sample according to the requirements of cooling and heat transfer research, and measure the temperature of the sample simultaneously;

[0048] 3) After the sample reaches the start-cooling temperature T0 = 750-1000°C, the cooling device 4 is turned on, and the temperature change of the sample during the experiment is monitored online in real time: when the temperature after water cooling reaches the target temperature T1 = 500-800°C, the cooling is immediately stopped by turning off the cooling water or moving out of the cooling zone. After the air cooling time t = 0-25s, water cooling is immediately started again. When the temperature reaches the final cooling temperature T2 = 0-700°C, the cooling water is immediately turned off or the cooling is stopped by moving out of the cooling zone. At the same time, the speed of the trolley is controlled to decrease until it stops.

[0049] 4) Perform performance tests on the samples;

[0050] 5) Repeat steps 2) to 4) and determine the cooling process test parameters that meet the performance requirements based on the measured data.

[0051] Preferably, the trolley is driven by a motor or a traction drive.

[0052] Preferably, the circular motion speed of the sample, ie, the linear speed or angular speed, is monitored in real time, and the speed of the sample can be changed online according to the measured temperature data according to the predetermined cooling process, ie, the speed can be increased or decreased or kept constant.

[0053] Preferably, the sample is heated offline or online;

[0054] Preferably, the offline heating method is as follows: after the sample is heated to the temperature required by the process, it is fixedly mounted on the sample carrier, and when it approaches the predetermined cooling start temperature, the trolley is driven along the circular track to drive the sample to pass through the cooling device in sequence, that is, through a theoretically infinite cooling zone, to complete the cooling or heat treatment process;

[0055] The online heating method is as follows: the sample 100 is first fixed on the sample carrier 3 and then heated. When the temperature reaches the required process temperature, the heating device 5 is separated from the circular track area, and the trolley 2 is driven to move along the circular track 1 to complete the cooling or heat treatment process;

[0056] Preferably, the heating is carried out by resistance heating, i.e., electrodes are clamped on both sides of the sample and a large current is passed through the sample to directly heat it online as a resistor; or, induction heating is used;

[0057] Preferably, the cooling jet has a fan-shaped, conical, cylindrical, slit-shaped or circumferentially porous shape.

[0058] Preferably, when water-cooled, the flow ratio of the upper and lower surfaces of the sample is 0.01 to 2, and the total flow density is 30 to 500 m 3 / h / m 2 , the water pressure is 0.01~2MPa.

[0059] Preferably, in step 1), the movement speed of the sample is less than 25 m / s.

[0060] Preferably, in step 1), 10mm<h≤25mm, the running speed is 0~12m / s; 5mm<h≤10mm, the running speed is 2~14m / s; 3mm<h≤5mm, the running speed is 4~16m / s; 2mm<h≤3mm, the running speed is 6~18m / s; h=1~2mm, the running speed is 8~20m / s; h is the sample thickness.

[0061] In this embodiment, the temperature measurement device includes a wireless temperature measurement module 61 and a temperature measurement host 62. The wireless temperature measurement module 61 uses pre-buried thermocouple wires to connect to the sample 100 to measure the sample temperature and wirelessly transmits the signal to the temperature measurement host 62. The temperature measurement host 62 is connected to the controller 7 via a wired connection. During movement, the wireless temperature measurement module 61 and the sample 100 remain relatively stationary to ensure that the thermocouple wires are not broken, thereby ensuring real-time and synchronous temperature measurement.

[0062] Example 1

[0063] Steel type X1, sample specification is 3×1500mm.

[0064] The cooling device uses a columnar jet spray box, the upper and lower flow ratio is set to 0.8, and the flow density is set to 130m 3 / h / m 2 , water pressure is set to 0.07MPa.

[0065] After the sample is heated to the process-required cooling temperature of 860°C through online heating, the heating device is separated from the track area and the trolley is driven to move along the track; the trolley is driven to drive the sample to reach the specified process speed of 8m / s and maintain a constant speed; after the sample is heated to the process-required cooling temperature T0 of 860°C, the cooling device is turned on and the sample is temperature measured synchronously; when the target temperature T1 reaches 680°C after water cooling, the trolley is immediately moved out of the cooling zone to stop cooling for 8s, and then the trolley is immediately moved back to the cooling zone to continue water cooling. When the final cooling temperature T2 reaches 520°C, the trolley is immediately moved out of the cooling zone again to stop cooling, and the trolley is controlled to slow down until it stops.

[0066] Example 2

[0067] Steel type X2, sample specification is 5×1600mm.

[0068] Select a columnar jet spray box, set the flow ratio of the upper and lower tables to 0.9, and the flow density to 130m 3 / h / m 2 , water pressure is set to 0.07MPa.

[0069] After the sample is heated to the process-required cooling temperature of 830°C through online heating, the heating device is separated from the track area and the trolley is driven to move along the track; the trolley is driven to move the sample to reach the specified process speed of 6m / s and maintain a constant speed; after the sample is heated to the process-required cooling temperature T0=830°C, the cooling device is turned on; the sample is synchronously temperature measured, and when the target temperature T1 reaches 650°C after water cooling, the cooling water is immediately turned off to stop cooling, and the air cooling time is continued for 10s, and then the cooling water is immediately turned on to continue water cooling. When the final cooling temperature T2 reaches 480°C, the cooling water is turned off again to stop cooling, and the trolley is controlled to slow down until it stops.

Claims

1. A method for controlling interval cooling based on a runway-type high-speed cooling platform, characterized in that: The steps include: 1) A circular track combined with a trolley is adopted, wherein the circular track is an elliptical track comprising two parallel straight segments and two semicircular segments, and the sample is placed on the sample carrier on the trolley; at least one cooling device for cooling the sample is provided along the straight segment track; the sample carrier for fixing the sample is hollowed out in the middle, and when the sample is fixed to the sample carrier, the upper and lower surfaces of the sample are not blocked, and the cooling jet ejected by the cooling device is directly sprayed onto the sample, and the upper and lower surfaces of the sample are cooled on both sides at the same time; preferably, when the number of cooling devices is greater than or equal to 2, the distances between the cooling devices are equal; preferably, the cooling device adopts an offline design; during the process, the movement speed of the sample, the flow rate and pressure of the cooling medium of the cooling device, the total flow density, several instantaneous temperature values ​​of the sample measured by thermocouples embedded on the surface and inside of the sample during the entire cooling process, and the cooling time required from the start cooling temperature to the final cooling temperature are monitored and obtained in real time; water cooling is adopted for sample cooling; 2) Heat the sample according to the requirements of cooling and heat transfer research, and measure the temperature of the sample simultaneously; 3) After the sample reaches the start-cooling temperature T0 = 750 ~ 1000 ° C, the cooling device is turned on, and the temperature change of the sample during the experiment is monitored online in real time: when the temperature after water cooling reaches the target temperature T1 = 500 ~ 800 ° C, the cooling is immediately stopped by turning off the cooling water or moving out of the cooling zone. After the air cooling time t = 0 ~ 25s, water cooling is immediately started again. When the temperature reaches the final cooling temperature T2 = 0 ~ 700 ° C, the cooling water is immediately turned off or the cooling is stopped by moving out of the cooling zone. At the same time, the speed of the trolley is controlled to decrease until it stops. 4) Perform performance tests on the samples; 5) Repeat steps 2) to 4) and determine the cooling process test parameters that meet the performance requirements based on the measured data.

2. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 1 is characterized in that: The trolley is driven by motor or traction.

3. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 1 is characterized in that: The circular motion speed of the sample, i.e. the linear speed or angular speed, is monitored in real time, and the speed of the sample can be changed online according to the measured temperature data according to the predetermined cooling process, i.e. the speed can be increased or decreased or kept constant.

4. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 1, Its characteristics are: In step 2), the sample is heated offline or online: The offline heating method is as follows: after the sample is heated to the temperature required by the process, it is fixedly mounted on the sample carrier. When it approaches the predetermined cooling start temperature, the trolley is driven along the circular track, driving the sample to sequentially pass through the cooling device, that is, through a theoretically infinite cooling zone, to complete the cooling or heat treatment process; The online heating method is as follows: the sample is first fixed on the sample carrier and then heated. When the temperature required by the process is reached, the heating device is separated from the circular track area, and then the trolley is driven along the circular track to complete the cooling or heat treatment process.

5. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 1 is characterized in that: The cooling jet shape is fan-shaped, conical, cylindrical, slit-shaped or circumferentially porous.

6. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 1 is characterized in that: When water-cooled, the flow ratio of the upper and lower surfaces of the sample is 0.01 to 2, and the total flow density is 30 to 500 m 3 / h / m 2 , the water pressure is 0.01~2MPa.

7. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 1 is characterized in that: In step 1), the moving speed of the sample is less than 25 m / s.

8. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 1 is characterized in that: In step 1), the driving carriage drives the sample to reach the set process speed and maintains a constant speed; wherein, Sample thickness h: 10mm<h≤25mm, running speed is 0~12m / s; Sample thickness h: 5mm<h≤10mm, running speed is 2~14m / s; Sample thickness h: 3mm<h≤5mm, running speed is 4~16m / s; Sample thickness h: 2mm<h≤3mm, running speed is 6~18m / s; Sample thickness h: 1~2mm, running speed is 8~20m / s.

9. The interval cooling control method based on the runway-type high-speed cooling platform according to claim 4, characterized in that: Heating adopts resistance heating method, that is, electrodes are clamped on both sides of the sample, and the sample is directly heated online as a resistor through a large current; or, induction heating method is adopted.

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