Temperature detection and cooling parameter determination method for hot continuous rolling direct quenched steel

Abstract

A hot continuous rolling direct quenched steel temperature detection and cooling parameter determination method comprises the following steps that (1) the mode that an annular track is combined with a trolley is adopted, the trolley bears a sample through a sample bearing table to do annular motion, and the annular track is an oval track comprising two parallel linear sections and two semicircular sections; at least one cooling spray box, a heating device and a temperature measuring device are arranged along the linear section track; (2) heating the sample, wherein the heating temperature required by the steel plate is set to be 830-950 DEG C according to a CCT curve; (3) the sample is cooled, the distance between the cooling spray boxes is kept consistent with the design of a production line, final cooling water parameters are determined according to the principle that the flow of the single spray nozzles is consistent, and the calculation method is that the flow of the single spray nozzles of the cooling spray boxes = the flow of the single spray boxes / the number of the spray nozzles on the spray boxes, and the flow of the single spray nozzles of the production line = the flow of the single header / the number of the spray nozzles on the header; the flow of a spraying box is set before cooling, the final cooling temperature is lower than 50 DEG C, and direct quenching is completed; recording temperature drop process data of the sample in real time in a cooling process, and calculating an average cooling speed; 4) performing mechanical property test on the sample, including strength and toughness; and (5) determining the finish rolling outlet temperature and cooling parameters according to the measured data including the mechanical property result and the cooling speed.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a method for detecting the temperature of hot-rolled direct quenched steel and determining cooling parameters. Background Art

[0002] Hot-rolled direct quenching steel is produced by adjusting the chemical composition of the strip, controlling the deformation rate of each rolling pass and the finishing exit temperature, and adjusting the cooling water flow rate during the hot rolling process to control the cooling rate, ultimately achieving high-strength steel plates. The development of this type of steel typically involves multiple tests on a hot rolling test machine after steelmaking and forging to determine the finishing exit temperature and water flow rate. This method has numerous drawbacks: 1) Each test involves at least 50 kg of steel plate, resulting in a utilization rate of less than 20%; 2) the equipment's cooling spray box differs significantly from actual production conditions, making the cooling parameters unavailable; 3) the lack of a temperature detection device prevents accurate detection of the steel plate temperature; and 4) poor cooling uniformity results in poor temperature and performance uniformity across the width and length of the steel plate, resulting in unreliable mechanical property data.

[0003] Because of the above-mentioned issues in current product development, the process parameters developed in pilot tests cannot be used in actual production. The only way to determine the target parameters and process window during production is to adjust the parameters at any time during the production process and based on the actual production performance. This not only prolongs the product development cycle and increases the trial production costs, but the parameters found are not necessarily the optimal parameters. Currently, there is no cooling spray box with an arbitrary operating speed and an infinite cooling zone for hot-rolled direct quenching steel temperature detection and cooling parameter determination. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for detecting the temperature and determining the cooling parameters of hot-rolled direct quenching steel. In a cooling zone with infinite length and at an arbitrary operating speed, the temperature drop curve and mechanical properties of the direct quenching steel at different flow rates are detected to determine the target parameters and process window required for the production of direct quenching steel. This method is consistent with the cooling conditions of actual production, can accurately detect important process parameters such as temperature and cooling rate, reduce the number of production trials, and improve product research and development efficiency.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] The present invention discloses a method for detecting the temperature of hot-rolled direct quenching steel and determining the cooling parameters based on an arbitrary speed and infinite length cooling platform. First, a device is placed on a device with an infinite length cooling zone at an arbitrary operating speed. After the temperature measuring device is loaded, the steel plate is heated to the target temperature. Different water flow rates and target operating speeds are set and the steel plate is cooled to room temperature to achieve the direct quenching effect. Finally, the cooling parameters, the temperature drop curve and the mechanical properties of the direct quenching steel are collected to determine the target parameters and process window required for the production of the direct quenching steel.

[0007] Specifically, the method for detecting the temperature of hot-rolled direct quenched steel and determining the cooling parameters of the hot-rolled direct quenched steel according to the present invention comprises the following steps:

[0008] 1) A circular track combined with a trolley is used. The trolley carries the sample through a sample carrier and moves in a circular motion. The circular track is an elliptical track consisting of two parallel straight segments and two semicircular segments. At least one cooling spray box and a heating device are arranged along the straight segments of the track. A temperature measuring device is installed on the trolley or the sample carrier to detect the sample temperature.

[0009] 2) Heating the sample: setting the required heating temperature of the steel plate at 830-950°C according to the CCT curve, simulating the finishing rolling exit temperature at this temperature; heating the sample at the heating temperature;

[0010] 3) Sample cooling: The spacing between the cooling spray boxes is consistent with the production line design. Therefore, the final cooling water parameters are determined based on the principle of consistent single nozzle flow. The calculation method is: single nozzle flow of the cooling spray box = single spray box flow / number of nozzles on the spray box; single nozzle flow of the production line = single manifold flow / number of nozzles on the manifold. The spray box flow is set before cooling, and the final cooling temperature is below 50°C to complete direct quenching. The temperature change of the sample is recorded in real time using a temperature measuring device during the cooling process.

[0011] 4) Perform performance tests on the specimens, including strength and toughness;

[0012] 5) Determine the finishing rolling outlet temperature and cooling parameters based on the measured data, including mechanical property results and cooling rate.

[0013] Preferably, the trolley is driven by a motor or a traction drive.

[0014] Preferably, the sample is heated offline or online;

[0015] The offline heating method is as follows: after the sample is heated to the temperature required by the process, it is fixed on the sample carrier. When it approaches the predetermined cooling temperature, the trolley is driven along the circular track to drive the sample to pass through the cooling spray box in sequence, that is, through the theoretically infinite cooling zone, to complete the cooling or heat treatment process;

[0016] 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.

[0017] 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.

[0018] Preferably, the sample is cooled by water cooling or air cooling.

[0019] Preferably, the temperature measuring device includes a wireless temperature measuring module and a temperature measuring host; the wireless temperature measuring module uses a pre-buried thermocouple wire, is connected to the sample to measure the sample temperature, and transmits the signal wirelessly to the temperature measuring host, and the temperature measuring host is connected to the controller by wire.

[0020] Beneficial effects of the present invention:

[0021] This invention utilizes a circular track test platform, capable of operating at any speed and with an infinite cooling zone, essentially aligning with actual production conditions. This platform allows for temperature detection and cooling rate calculation to determine target process parameters and process windows. This allows for precise measurement of key process parameters such as temperature and cooling rate, reducing production trial runs, improving product development efficiency, and lowering production line trial costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0024] See also Figure 1 The method for detecting the temperature of hot-rolled direct quenched steel and determining the cooling parameters of the hot-rolled direct quenched steel according to the present invention comprises the following steps:

[0025] 1) A circular track 1 is combined with a trolley 2. The trolley 2 carries the sample 100 through the sample carrier 3 and performs circular motion. The circular track 1 is an elliptical track comprising two parallel straight segments and two semicircular segments. At least one cooling spray box 4, 4' is provided along the straight segments, and a heating device 5 is provided across the circular track 1 or on the trolley 2. A temperature measuring device 6 is provided on the trolley 2 or the sample carrier 3.

[0026] 2) Heating the sample: setting the required heating temperature of the steel plate to 830-950°C according to the CCT curve, simulating the finishing rolling outlet temperature at this temperature; heating the sample at the heating temperature;

[0027] 3) Sample cooling: The spacing between the cooling spray boxes is consistent with the production line design. Therefore, the final cooling water parameters are determined based on the principle of consistent single nozzle flow. The calculation method is: single nozzle flow of the cooling spray box = single spray box flow / number of nozzles on the spray box; single nozzle flow of the production line = single manifold flow / number of nozzles on the manifold. The spray box flow is set before cooling, and the final cooling temperature is below 50°C to complete direct quenching. During the cooling process, the temperature change of the sample is recorded in real time using a temperature measuring device to calculate the average cooling rate.

[0028] 4) Perform performance tests on the specimens, including strength and toughness;

[0029] 5) Determine the finishing rolling outlet temperature and cooling parameters based on the measured data, including mechanical property results and cooling rate.

[0030] Preferably, the trolley is driven by a motor or a traction drive.

[0031] Preferably, the sample is heated offline or online.

[0032] 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 temperature, the trolley is driven along the circular track to drive the sample to pass through the cooling spray box in sequence, that is, through a theoretically infinitely long cooling zone to complete the cooling or heat treatment process.

[0033] 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.

[0034] 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.

[0035] Preferably, the sample is cooled by water cooling or air cooling.

[0036] In this embodiment, the temperature measuring device 6 includes a wireless temperature measuring module 61 and a temperature measuring host 62; the wireless temperature measuring module 61 uses a pre-buried thermocouple wire, is connected to the sample 100 to test the sample temperature, and wirelessly transmits the signal to the temperature measuring host 62, and the temperature measuring host 62 is wired to the controller 7.

[0037] Example

[0038] The embodiment of the present invention adopts direct quenching steel with a size of 5×300×400 mm, and its chemical composition by mass percentage is as follows: C 0.08-0.22%, Si 0.1-0.55%, Mn 0.8-1.5%, P≤0.012%, S≤0.005%, Als 0.01-0.055%, Ti 0.005-0.019%, and N≤0.007%.

[0039] The specific method includes the following steps:

[0040] 1) A circular track 1 is combined with a trolley 2. The trolley 2 carries the sample 100 through the sample carrier 3 and performs circular motion. The circular track 1 is an elliptical track comprising two parallel straight segments and two semicircular segments. At least one cooling spray box 4, 4' is provided along the straight segments, and a heating device 5 is provided across the circular track 1 or on the trolley 2. A temperature measuring device 6 is provided on the trolley 2 or the sample carrier 3.

[0041] 2) Sample heating: The required heating temperature of the steel plate is set at 830-950°C according to the CCT curve, which is used to simulate the finishing rolling exit temperature. The heating temperature is divided into five levels: 830, 860, 890, 920, and 950°C, with each level being 30°C.

[0042] 3) Sample cooling: The number of nozzles of a single cooling spray box is 20, and the number of nozzles calculated for layer cooling of a hot rolling production line is 76; the flow rate of a single nozzle of the cooling spray box = the flow rate of a single spray box / 20, and the flow rate of a single nozzle of the production line = the flow rate of a single header / 76; the flow rate of the spray box is set before cooling to 10, 20, 30, and 40 m 3 / h, the final cooling temperature is lower than 50℃, and direct quenching is completed; the temperature change of the sample is recorded in real time using a temperature measuring device during the cooling process, and the average cooling rate is calculated, as shown in Table 1;

[0043] 4) Perform performance tests on the specimens, including strength and toughness, as shown in Table 1;

[0044] 5) Determine the finishing rolling outlet temperature and cooling parameters based on the measured data, including mechanical property results and cooling rate.

[0045] The performance requirements of the direct quenching steel in the embodiment are: strength greater than 1300 MPa, impact greater than 20J at -40°C; typical strength is 1480 MPa, and typical impact is 40J.

[0046] Analyzing the performance and cooling rate under various process parameters in Table 1, numbers 3-21 all meet the minimum requirements; however, only numbers 7, 8, 11, 12, 15, 16, and 21 meet the typical value requirements. Combining the product performance requirements and process parameters, the target value of the finishing outlet is determined to be 890℃, and the flow rate of a single nozzle is not less than 1.25m3 / h, the cooling rate is not less than 50℃ / s, and the target value for finishing rolling outlet is 890±30℃.

[0047] Table 1

[0048]

Claims

1. A method for detecting temperature and determining cooling parameters of hot-rolled direct quenched steel, characterized in that: The steps include: 1) A circular track combined with a trolley is used. The trolley carries the sample through a sample carrier and moves in a circular motion. The circular track is an elliptical track consisting of two parallel straight segments and two semicircular segments. At least one cooling spray box and a heating device are arranged along the straight segments of the track. A temperature measuring device is installed on the trolley or the sample carrier to detect the sample temperature. 2) Heating the sample: setting the required heating temperature of the steel plate to 830-950°C according to the CCT curve, simulating the finishing rolling outlet temperature at this temperature; heating the sample at the heating temperature; 3) Sample cooling: The spacing between the cooling spray boxes is consistent with the production line design. Therefore, the final cooling water parameters are determined based on the principle of consistent single nozzle flow. The calculation method is: single nozzle flow of the cooling spray box = single spray box flow / number of nozzles on the spray box; single nozzle flow of the production line = single manifold flow / number of nozzles on the manifold; the spray box flow is set before cooling, and the final cooling temperature is below 50°C to complete direct quenching; During the cooling process, the temperature change of the sample is recorded in real time using a temperature measuring device to calculate the average cooling rate; 4) Perform performance tests on the specimens, including strength and toughness; 5) Determine the finishing rolling outlet temperature and cooling parameters based on the measured data, including mechanical property results and cooling rate.

2. The method for detecting temperature and determining cooling parameters of hot-rolled direct quenched steel according to claim 1, wherein: 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 fixed on the sample carrier. When it approaches the predetermined cooling temperature, the trolley is driven along the circular track to drive the sample to pass through the cooling spray box in sequence, that is, through the 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.

3. The method for detecting temperature and determining cooling parameters of hot-rolled direct quenched steel according to claim 1 or 2, 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.

4. The method for detecting temperature and determining cooling parameters of hot-rolled direct quenched steel according to claim 1, wherein: The sample is cooled by water or air.

5. The method for detecting temperature and determining cooling parameters of hot-rolled direct quenched steel according to claim 1, wherein: The temperature measuring device includes a wireless temperature measuring module and a temperature measuring host; the wireless temperature measuring module uses a pre-buried thermocouple wire, is connected to the sample to test the sample temperature, and wirelessly transmits the signal to the temperature measuring host, which is connected to the controller by wire.

6. The method for detecting temperature and determining cooling parameters of hot-rolled direct quenched steel according to claim 1, wherein: The trolley is driven by motor or traction.

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