A continuous casting billet heating device and method

Abstract

The application discloses a continuous casting billet heating device and method, which comprises a first induction heating unit and a second induction heating unit; the first induction heating unit comprises a first induction coil arranged around the length and width direction of the continuous casting billet; the second induction heating unit comprises a second induction coil arranged around the length and thickness direction of the continuous casting billet, and a temperature detector used for detecting the surface temperature of the continuous casting billet. The application effectively solves the induction heating needs under two working conditions in the prior art, fully meets the requirements of products and processes on the heating temperature and the uniformity of the continuous casting billet temperature, and finally can realize the technical requirement that the overall temperature difference of the continuous casting billet is within ±10℃.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic induction heating technology for hot rolling production lines, and more specifically, to a heating device and method for continuous casting billets. Background Technology

[0002] In modern steel production, there is a certain distance between the continuous casting and hot rolling processes. Furthermore, due to the frequent surface treatment of continuously cast billets, the temperature drop is generally significant. Before entering the rolling mill, the billets must be heated in a furnace to ensure they meet the technical requirements for hot rolling. Under traditional production processes, the average temperature of the billets entering the furnace is typically between 300 and 400°C. With process improvements, this temperature can be increased to over 800°C. However, traditional gas-fired furnaces have high fuel consumption, generally between 30 and 50 kgce / t, making them a major source of carbon emissions at the casting-rolling interface in steel production.

[0003] On the other hand, induction heating technology has been widely used in industrial production due to its advantages such as being green, low-carbon, pollution-free, fast heating speed, and easy automation. Based on the relationship between the magnetic field direction and the steel plate surface, it can generally be divided into transverse magnetic field induction heating and longitudinal magnetic field induction heating. In the former, the magnetic field direction is perpendicular to the steel plate surface, while in the latter, the magnetic field direction is parallel to the steel plate surface. Compared with traditional heating methods, induction heating technology, in addition to the aforementioned advantages, also suffers from poor temperature uniformity. These problems depend on specific operating conditions, and relevant technical experts have proposed corresponding solutions and ideas. Chinese patent CN100488324C proposes a device and method for flexibly controlling two layers of staggered transverse magnetic coils with an iron core. The long side of the lower coil is perpendicular to the direction of steel plate movement, while the long side of the upper coil is parallel to the direction of steel plate movement. This idea essentially does not help improve the overall temperature uniformity of the steel plate because, when using transverse magnetic induction heating technology, due to the end effect, the temperature distribution at the edge of the steel plate is non-linear. Especially when the coil length is greater than the width of the steel plate, the temperature at the edge of the steel plate will be much higher than the temperature in the middle. While this method theoretically can effectively reduce the temperature at the edge of the steel plate by changing the eddy current distribution, the superposition of coils generates multiple small local eddy currents, resulting in low induction heating efficiency and a grid-like heating effect. Therefore, it has little practical industrial application value. US Patent 5403994A proposes using a pair of paired J-type coils for heating. Depending on the specifications of the steel plate, the J-type coils can be adjusted by sliding to control the heating range. This method has two major problems: due to sliding contact, long-term heating, especially under high power conditions, inevitably leads to poor contact or arcing, affecting coil lifespan and production; secondly, this design cannot solve the problems of excessively high edge temperature and overall temperature unevenness of the steel plate. US Patent 20170002438A1 proposes a method of installing a shielding plate between the induction coil and the heated steel plate to control the problem of excessively high edge temperature. This method can improve temperature uniformity to some extent; however, adjusting the shielding plate alone cannot meet the process requirements for uniform temperature across the plate surface.

[0004] In current continuous casting production, on the one hand, the thickness of traditional continuous casting billets is typically between 150 and 300 mm. The surface temperature of the billet exiting the casting machine is >800℃, and the core temperature is around 1000℃. There is a significant temperature drop, particularly at the edges and corners, and at the beginning and end of the billet, with the corner temperature being more than 150℃ lower than the center temperature. On the other hand, hot rolling temperatures are typically required to be between 1100 and 1200℃, and the overall temperature difference of the billet must be within ±10℃. To achieve this target heating temperature and temperature uniformity, the continuous casting billet must be heated. Simultaneously, to meet production requirements such as capacity matching, rapid heating methods such as induction heating must be used to heat the billet to the target temperature in a short time. Summary of the Invention

[0005] In view of the above-mentioned defects in the prior art, the purpose of the present invention is to provide a continuous casting billet heating device and method, which effectively solves the induction heating needs under two working conditions in the prior art, and fully meets the requirements of product and process for heating temperature and continuous casting billet temperature uniformity, and can ultimately achieve the technical requirement of the overall temperature difference of continuous casting billet within ±10℃.

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

[0007] On the one hand, a continuous casting billet heating device includes a first induction heating unit and a second induction heating unit;

[0008] The first induction heating unit includes a first induction coil arranged around the length and width of the continuous casting billet;

[0009] The second induction heating unit includes a second induction coil arranged around the length and thickness of the continuous casting billet, and a thermometer for detecting the surface temperature of the continuous casting billet.

[0010] Preferably, the first induction coil is made of one or more turns of copper tubing.

[0011] The center line of the magnetic field generated by the first induction coil is perpendicular to the wide surface of the continuous casting billet;

[0012] The second induction coil is made of a multi-turn copper tube;

[0013] The center line of the magnetic field generated by the second induction coil is parallel to the wide surface of the continuously cast billet.

[0014] Preferably, the thermometer is an infrared thermometer, and at least one set is provided.

[0015] Preferably, the heating frequency f1 of the first induction heating unit needs to satisfy: 50Hz≤f1≤500Hz;

[0016] The heating frequency f2 of the second induction heating unit must satisfy: 100Hz≤f2≤1000Hz.

[0017] On the other hand, a method for heating a continuously cast billet involves using a continuously cast billet heating device to heat the same billet in two stages, rather than at the same time.

[0018] Preferably, after the first induction heating unit heats the continuous casting billet, the temperature T1 at the midpoint of the surface in the thickness direction of the continuous casting billet and the heating target temperature T0 must satisfy: -10℃≤T1-T0≤10℃, and the total heating time t1≤3min.

[0019] Preferably, when the continuously cast billet enters the first induction heating unit, the core temperature Tc, the surface center temperature Tb, and the target heating temperature T0 of the continuously cast billet must satisfy the following:

[0020] T0-Tc < 100℃

[0021] T0-Tb < 350℃.

[0022] Preferably, the second induction heating unit heats the continuous casting billet in two stages: the first stage is a rapid heating stage, and the second stage is a heat preservation stage.

[0023] During the rapid heating phase, the second induction heating unit heats the surface temperature of the continuous casting billet to the target heating temperature T0±10℃, and then reduces the heating power of the second induction heating unit to enter the heat preservation phase.

[0024] The heat preservation stage employs oscillating heating with heating power varying over time, resulting in a wave curve corresponding to the heating time and heating power.

[0025] Preferably, the wave curve should satisfy:

[0026] There are one or more power values ​​Pn on the wave curve, where n is an odd number and is the minimum power within any segment of the wave curve. The segment contains the power value Pn and the time does not exceed 3 minutes, and Pn < 10% × P0, where P0 is the average heating power of the rapid heating stage.

[0027] There are one or more power values ​​Pm on the wave curve, where m is an odd number and is the maximum power within any segment of the wave curve. The segment contains the power value Pm and the time does not exceed 3 minutes, and Pm > 30% × P0, where P0 is the average heating power of the rapid heating stage.

[0028] The power values ​​Pn and Pm are distributed alternately on the wave curve.

[0029] Preferably, the height Wc of the energized portion on the second induction coil of the second induction heating unit needs to satisfy:

[0030] 200mm≤Wc-W≤600mm, unit mm, where W is the width of the continuously cast billet.

[0031] Preferably, the width W of the continuously cast billet is 850mm≤W≤2050mm, the thickness H is 150mm≤H≤300mm, and the length L is 4000mm≤L≤12000mm.

[0032] Preferably, when the first induction heating unit heats the continuous casting billet, the wide surface of the continuous casting billet is parallel to the horizontal plane;

[0033] When the second induction heating unit heats the continuous casting billet, the wide side of the continuous casting billet is perpendicular to the horizontal plane.

[0034] The present invention provides a continuous casting billet heating device and method. Based on the temperature distribution characteristics of the continuous casting billet during induction heating, it proposes a targeted approach combining two sets of induction heating methods to simultaneously address the heating of the billet's edges and corners as well as overall heating, thereby achieving the target temperature requirements set by the process. Using the continuous casting billet heating device and method of the present invention not only effectively solves the problem of uneven temperature distribution commonly found in the induction heating process of continuous casting billets, but also allows for flexible adjustment of heating process parameters according to changes in billet specifications and incoming material temperature, adapting to heating requirements under various operating conditions and achieving high heating efficiency while ensuring temperature uniformity. Attached Figure Description

[0035] Figure 1 This is a top view schematic diagram of the first induction heating unit in the continuous casting billet heating device of the present invention;

[0036] Figure 2 This is a side view schematic diagram of the first induction heating unit in the continuous casting billet heating device of the present invention;

[0037] Figure 3 This is a side view of the narrow face of the second induction heating unit corresponding to the second induction coil in the continuous casting billet heating device of the present invention.

[0038] Figure 4 This is a side view of the second induction heating unit corresponding to the wide surface of the second induction coil in the continuous casting billet heating device of the present invention;

[0039] Figure 5This is a schematic diagram of the heating power curve of the continuous casting billet entering the second induction heating unit in an embodiment of the continuous casting billet heating method of the present invention, after the rapid heating stage and the surface reaching the target temperature, and then entering the heat preservation stage.

[0040] Figure 6 This is a schematic diagram of the heating curve in an embodiment of the continuous casting billet heating method of the present invention. Detailed Implementation

[0041] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] The present invention provides a continuous casting billet heating device, comprising a first induction heating unit 100 and a second induction heating unit 200.

[0043] Combination Figure 1 and Figure 2 As shown, the heating frequency f1 of the first induction heating unit 100 must satisfy: 50Hz≤f1≤500Hz. The first induction heating unit 100 includes a first induction coil 101 arranged around the length and width of the continuous casting billet 300. The first induction coil 101 is a copper tube with one or more turns. The center line of the magnetic field generated by the first induction coil 101 is perpendicular to the wide surface of the continuous casting billet 300.

[0044] Combination Figure 3 and Figure 4 As shown, the heating frequency f2 of the second induction heating unit 200 must satisfy: 100Hz≤f2≤1000Hz. The second induction heating unit 200 includes a second induction coil 201 arranged around the length and thickness of the continuous casting billet 300. The second induction coil 201 is a multi-turn copper tube. The center line of the magnetic field generated by the second induction coil 201 is parallel to the wide surface of the continuous casting billet 300.

[0045] The second induction heating unit 200 also includes a temperature measuring instrument 202 for detecting the surface temperature of the continuously cast billet 300. The temperature measuring instrument 202 is an infrared temperature measuring instrument, and at least one (e.g., Figure 3 Two temperature measuring instruments 202 are set up as shown. The surface temperature value of the continuous casting billet 300 detected by the temperature measuring instruments 202 is used to correct the heating power of the second induction heating unit 200.

[0046] The present invention also provides a method for heating a continuous casting billet. In order to achieve the requirement of uniform heating temperature set in the process, the continuous casting billet heating device of the present invention heats the same continuous casting billet 300 at different times. The first induction heating unit 100 and the second induction heating unit 200 are independently controllable, so as to realize the heating of the continuous casting billet in two stages.

[0047] After the first induction heating unit 100 heats the continuous casting billet 300, the temperature T1 at the midpoint of the surface of the continuous casting billet 300 in the thickness direction and the heating target temperature T0 must satisfy: -10℃≤T1-T0≤10℃, and the total heating time t1≤3min.

[0048] When the continuous casting billet 300 enters the first induction heating unit 100, the core temperature Tc, the surface center temperature Tb, and the heating target temperature T0 of the continuous casting billet 300 must satisfy the following:

[0049] T0-Tc < 100℃

[0050] T0-Tb < 350℃.

[0051] The second induction heating unit 200 heats the continuous casting billet 300 in two stages: the first stage is the rapid heating stage, and the second stage is the heat preservation stage.

[0052] During the rapid heating phase, the second induction heating unit 200 heats the surface temperature of the continuous casting billet 300 to the target heating temperature T0±10℃, and then reduces the heating power of the second induction heating unit 200 to enter the heat preservation phase.

[0053] During the heat preservation stage, oscillating heating is performed using heating power that varies over time, resulting in a wave curve corresponding to the heating time and heating power.

[0054] The wave curve must meet the following requirements:

[0055] 1) There are one or more power values ​​Pn on the wave curve, where n is an odd number and is the minimum power within any segment of the wave curve. This segment contains the power value Pn and the time does not exceed 3 minutes, and Pn < 10% × P0, where P0 is the average heating power during the rapid heating phase.

[0056] 2) There are one or more power values ​​Pm on the wave curve, where m is an odd number and is the maximum power within any segment of the wave curve. This segment contains the power value Pm and the time does not exceed 3 minutes, and Pm > 30% × P0, where P0 is the average heating power during the rapid heating phase.

[0057] 3) The power values ​​Pn and Pm are distributed alternately on the wave curve.

[0058] The height Wc of the energized portion of the second induction coil 201 of the second induction heating unit 200 must meet the following requirements:

[0059] 200mm≤Wc-W≤600mm, unit mm, where W is the width of the continuously cast billet 300.

[0060] The width W of the continuously cast billet 300 is 850mm≤W≤2050mm, the thickness H is 150mm≤H≤300mm, and the length L is 4000mm≤L≤12000mm.

[0061] When the first induction heating unit 100 heats the continuous casting billet 300, the wide surface of the continuous casting billet 300 is parallel to the horizontal plane.

[0062] When the second induction heating unit 200 heats the continuous casting billet 300, the wide surface of the continuous casting billet 300 is perpendicular to the horizontal plane.

[0063] Continuously cast billets commonly experience temperature drops during production, necessitating reheating before entering the rolling process. Traditional heating methods are time-consuming, energy-intensive, and cause severe surface burn-off, failing to meet the energy conservation and emission reduction requirements of modern steel production. To achieve the ±10℃ temperature uniformity requirement for continuously cast billets in the hot rolling process, using only longitudinal magnetic coils or scanning induction heating is insufficient for engineering purposes. In particular, continuously cast billets inherently experience heat loss at their corners, with corner temperatures typically exceeding 150℃ in temperature compared to the center. Longitudinal magnetic coils or scanning induction heating methods cannot effectively compensate for this low-temperature region. Even after using longitudinal magnetic coils or scanning induction heating, the corner low-temperature region remains more than 100℃ lower than the center region.

[0064] The present invention provides a continuous casting billet heating device and method. Based on the temperature distribution characteristics of the continuous casting billet during induction heating, it proposes a targeted approach combining two sets of induction heating methods to simultaneously address the heating of the billet's edges and corners as well as overall heating, thereby achieving the target temperature requirements set by the process. Using the continuous casting billet heating device and method of the present invention not only effectively solves the common problem of uneven temperature distribution during the induction heating process of continuous casting billets, but also allows for flexible adjustment of heating process parameters according to changes in billet specifications and incoming material temperature, adapting to heating requirements under various operating conditions. While ensuring temperature uniformity, it achieves high heating efficiency, and after implementation, it can meet the technical requirement of an overall temperature difference of the continuous casting billet within ±10℃.

[0065] Example

[0066] The dimensions of the continuously cast billet 300 to be heated are 10000mm × 1450mm × 230mm. When it enters the first induction heating unit 100, the core temperature of the billet 300 is approximately 1060℃, the surface center temperature is approximately 880℃, and the head, tail, and edge temperatures are approximately 700℃. The target heating temperature is 1130℃. The billet 300 is placed horizontally and conveyed to the heating station via roller conveyors. First, a mechanical moving mechanism positions the first induction heating unit 100 corresponding to the first heating coil 101. After the system checks for errors, it is energized for heating. Figure 1 and Figure 2 As shown. The heating setting frequency of the first induction heating unit 100 is 50Hz. By controlling the heating power, it can heat the temperature of the center point of the narrow face of the continuous casting billet 300 to within 1130±10℃ within 3 minutes.

[0067] After the heating process is completed, the continuous casting billet is moved into the second induction heating unit 200 corresponding to the second induction coil 201 via a mechanical transmission and flipping mechanism, so that the continuous casting billet 300 is placed perpendicular to the horizontal plane and aligned with the second induction coil 201. Figure 3 and Figure 4 As shown. The height of the energized portion of the second induction coil 201 is 1850mm, meaning that the upper and lower sides of the second induction coil 201 are each 200mm higher than the continuous casting billet 300. Simultaneously, the continuous casting billet 300 is properly fixed, and the second induction coil 201 is properly sealed at the top and bottom. The second induction heating unit 200 is set to a heating frequency of 250Hz. After all modules of the system have been checked and found to be working correctly, it is energized for heating. The heating process is divided into two stages. The first stage is a rapid heating stage, with a heating power P0 of approximately 10MW and a heating time of approximately t. 21 Approximately 3 minutes. The surface temperature of the continuous casting billet 300 is continuously monitored by a temperature measuring instrument 202 located in the middle of the second induction coil 201. When the surface temperature of the continuous casting billet 300 reaches 1130℃, the heating power is reduced to enter the second stage of heat preservation. The heating time of the heat preservation stage is t. 22 Approximately 12 minutes. The power curve for the heat preservation stage is as follows: Figure 5 As shown in Table 1, the heating power initially decreases rapidly, dropping to 6.9% of P0 within one minute, then increases to 57.4% of P0 within another minute, followed by a decrease to 3.9% of P0, and so on until heating ends. The specific Pn and Pm setting ratios are shown in Table 1. By continuously adjusting the heating power setting, the heating power exhibits a fluctuating curve that changes over time.

[0068] Table 1

[0069] No TIME(s) Power / P0 P0 0 100.0％ P1 60 6.9％ P2 120 57.4％ P3 180 3.9％ P4 240 39.2％ P5 300 3.9％ P6 360 36.8％ P7 420 1.7％ P8 480 35.3％ P9 540 1.7％ P10 600 31.5％ P11 660 3.9％ P12 720 10.9％

[0070] Temperature detection points were set at different locations on the continuously cast billet 300 mm. The corresponding locations of each point are as follows:

[0071] SENSOR_1: Center of continuously cast billet

[0072] SENSOR_2: Center of the wide surface of the continuously cast billet

[0073] SENSOR_3: 20mm below the center of the wide surface of the continuously cast billet

[0074] SENSOR_4: 20mm from the narrow face of the continuously cast billet and 20mm below the surface of the wide face.

[0075] SENSOR_5: 20mm from the narrow face of the continuously cast billet and 115mm below the surface of the wide face.

[0076] As can be seen from the heating curves displayed at each point, after heating, the temperature at each point is basically between 1120℃ and 1140℃, which meets the temperature uniformity requirement of 1130±10℃ set in the process. Figure 6 As shown.

[0077] Under current requirements for carbon peaking and carbon neutrality, the steel industry is increasingly stringent in controlling carbon emissions throughout the entire production process and placing greater emphasis on energy conservation and consumption reduction in each stage. Induction heating technology, due to its significant advantages such as being green and low-carbon, and having a fast heating speed, has become an indispensable metallurgical technology in the steel production process. The combined induction heating device and method designed in this invention are ingeniously designed, functionally flexible, and relatively easy to process and manufacture. They balance both heating temperature uniformity and heating efficiency, and are convenient to install and replace, and are expected to have broad application prospects.

[0078] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A continuous casting billet heating device, characterized by: The first induction heating unit and the second induction heating unit are included. The first induction heating unit includes a first induction coil arranged around the length and width of the continuously cast billet. The second induction heating unit includes a second induction coil arranged around the length and thickness of the continuously cast billet, and a temperature detector for detecting the surface temperature of the continuously cast billet. The center line of the magnetic field generated by the first induction coil is perpendicular to the wide surface of the continuously cast billet. The center line of the magnetic field generated by the second induction coil is parallel to the wide surface of the continuously cast billet. The heating frequency f1 of the first induction heating unit needs to satisfy 50Hz≤f1≤500Hz. The heating frequency f2 of the second induction heating unit needs to satisfy 100Hz≤f2≤1000Hz. The height Wc of the energized part of the second induction coil of the second induction heating unit needs to satisfy: 200mm≤Wc-W≤600mm, unit: mm, where W is the width of the continuously cast billet. The continuously cast billet heating device does not heat the same continuously cast billet at the same time, and realizes heating the continuously cast billet in two stages. After the first induction heating unit heats the continuously cast billet, the thickness direction surface midpoint temperature T1 of the continuously cast billet and the heating target temperature T0 need to satisfy -10℃≤T1-T0≤10℃, and the total heating time t1≤3min. When the continuously cast billet enters the first induction heating unit, the core temperature Tc, the surface center temperature Tb of the continuously cast billet and the heating target temperature T0 need to satisfy: T0-Tc<100℃ T0-Tb<350℃. The second induction heating unit heats the continuously cast billet in two stages, the first stage is a rapid heating stage, and the second stage is a holding stage. The second induction heating unit heats the surface temperature of the continuously cast billet to the heating target temperature T0±10℃ in the rapid heating stage, and then reduces the heating power of the second induction heating unit to enter the holding stage. The holding stage adopts oscillating heating with time-varying heating power, and forms a wave curve corresponding to the heating time and the heating power.

2. The continuously cast billet heating device according to claim 1, characterized by: The first induction coil is wound by one or more turns of copper pipe. The second induction coil is wound by multiple turns of copper pipe.

3. The continuous casting billet heating device according to claim 1, characterized by: The temperature detector is an infrared temperature detector, and at least one group is provided.

4. A continuous casting billet heating method, characterized by: The continuously cast billet heating device does not heat the same continuously cast billet at the same time, and realizes heating the continuously cast billet in two stages, After the first induction heating unit heats the continuously cast billet, the thickness direction surface midpoint temperature T1 of the continuously cast billet and the heating target temperature T0 need to satisfy -10℃≤T1-T0≤10℃, and the total heating time t1≤3min, When the continuously cast billet enters the first induction heating unit, the core temperature Tc, the surface center temperature Tb of the continuously cast billet and the heating target temperature T0 need to satisfy: T0-Tc<100℃ T0-Tb<350℃, The second induction heating unit heats the continuous casting billet in two stages, a first stage being a rapid heating stage and a second stage being a holding stage; The second induction heating unit heats the surface temperature of the continuous casting billet to a heating target temperature T0±10℃ in the rapid heating stage, and then reduces the heating power of the second induction heating unit to enter the holding stage; The holding stage adopts oscillating heating with time-varying heating power, and forms a wave curve corresponding to the heating time and the heating power.

5. The continuous casting billet heating method according to claim 4, characterized by, The wave curve needs to satisfy: There is one or more power values Pn on the wave curve, n is an odd number, is the minimum power in the curve segment of the wave curve, the curve segment contains the power value Pn and the time is not more than 3 min, and Pn<10%×P0, P0 is the average value of the heating power in the rapid heating stage; There is one or more power values Pm on the wave curve, m is an odd number, is the maximum power in the curve segment of the wave curve, the curve segment contains the power value Pm and the time is not more than 3 min, and Pm>30%×P0, P0 is the average value of the heating power in the rapid heating stage; The power value Pn and the power value Pm are staggered and spaced apart on the wave curve.

6. The continuous casting billet heating method according to claim 4, characterized in that: The width W of the continuous casting billet is 850mm≤W≤2050mm, the thickness H is 150mm≤H≤300mm, and the length L is 4000mm≤L≤12000mm.

7. The continuous casting billet heating method according to claim 4, characterized by: When the first induction heating unit heats the continuous casting billet, the wide surface of the continuous casting billet is parallel to the horizontal plane; When the second induction heating unit heats the continuous casting billet, the wide surface of the continuous casting billet is perpendicular to the horizontal plane.

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