Adjustable differential temperature induction quenching device and method for forged steel backup roll

Abstract

The application discloses a kind of adjustable differential temperature induction quenching device and method for forged steel backup roll, it is related to quenching device technical field, two ways of power heating and intermediate frequency heating in the conventional quenching process are improved, the application includes endpoint temperature rising action and intermediate frequency temperature rising action, two actions can be carried out simultaneously and do not interfere with each other, but the key is: the influence key between two parameters of temperature and current in metal structural member, on the basis of not changing intermediate frequency temperature rising action, the current value in endpoint temperature rising action is used as the basis to calculate the temperature-electricity cooperation order, the linear movement action of intermediate frequency temperature rising action in forged steel backup roll is carried out with temperature-electricity cooperation order, its essence is to drive winding coil in intermediate frequency temperature rising action to move in the length direction of forged steel backup roll in the same direction or opposite direction, and the purpose is to maintain the quenching temperature of forged steel backup roll itself, and to "reserve" quenching holding time or temperature rising time.

Description

Technical Field

[0001] This invention relates to the field of quenching equipment technology, specifically to an adjustable differential temperature induction quenching device and method for forged steel support rollers. Background Technology

[0002] The formulation of quenching process involves determining multiple parameters, including furnace loading temperature, heating rate, holding time, quenching temperature, and soaking time. Especially for large forgings such as support rollers, medium / high frequency heating methods are often used. The heating process proceeds from the outside to the inside, specifically, the surface temperature of the forging gradually increases and is conducted to its interior. It should be noted that during the quenching process of support rollers, there may be uneven temperature distribution between the inside and outside of the forging. For example, the surface temperature may be higher than the critical quenching temperature, while the internal temperature may be lower than the quenching process temperature. Such phenomena will lead to poor quenching effect of the forging, such as insufficient hardness or even deformation and cracks.

[0003] It is particularly important to note that forgings such as support rollers have varying diameters, which can be understood as differences in the "heat conduction distance." This can exacerbate problems caused by uneven heat distribution, such as excessively fast temperature conduction in small-diameter areas and slower temperature conduction in large-diameter areas.

[0004] This application proposes a solution to this problem. Summary of the Invention

[0005] The purpose of this invention is to provide an adjustable differential temperature induction hardening device and method for forged steel support rollers, which addresses the temperature distribution problem in conventional hardening processes. This is because the essence of conventional medium-frequency heating is the conduction of surface temperature to the interior. However, forgings such as support rollers have varying diameters, resulting in uneven temperatures between the inside and outside of the forgings in actual conditions, which affects the hardening effect.

[0006] The objective of this invention can be achieved through the following technical solution: an adjustable differential temperature induction quenching method for forged steel support rollers, applied in a quenching device, the quenching method including an end electrode heating process and a medium frequency heating process, and equipped with a temperature control module associated with the end electrode heating process and the medium frequency heating process, the temperature control module consisting of a data integration unit, an action crosslinking analysis unit and an action response unit, and performing temperature acquisition actions through a temperature detection component during the end electrode heating process and the medium frequency heating process;

[0007] The endpoint electrode heating process uses the two ends of the forged steel support roller as the energized positions and heats the forged steel support roller by resistance heating. The medium frequency heating process heats the outer surface of the forged steel support roller.

[0008] The endpoint electrode heating process and the intermediate frequency heating process are respectively equipped with endpoint heating action and intermediate frequency heating action, and the endpoint electrode heating process and the intermediate frequency heating process are carried out simultaneously. The intermediate frequency heating action also includes a linear movement action, in which the forged steel support roller moves in the same direction or in opposite directions along its length.

[0009] Further configured as follows: the data integration unit is used to record dynamic temperature parameters during the heating process of the endpoint electrode and the intermediate frequency heating process, and inputs the dynamic temperature parameters into the action crosslinking analysis unit;

[0010] The action crosslinking analysis unit is set with endpoint heating action and intermediate frequency heating action related to the endpoint electrode heating process and intermediate frequency heating process. The dynamic temperature parameters include the first-order temperature group and the second-order temperature group in the endpoint heating action and intermediate frequency heating action.

[0011] The action response unit has control authority over the endpoint electrode heating process and the intermediate frequency heating process. It inputs first-order and second-order operating parameters into the endpoint electrode heating process and the intermediate frequency heating process through the data integration unit. It integrates and analyzes the first-order temperature group, the second-order temperature group, the first-order operating parameters, and the second-order operating parameters to obtain the temperature-electric coordination level. It uses the temperature-electric coordination level to interactively control the endpoint electrode heating process and the intermediate frequency heating process.

[0012] Further configuration: During the endpoint heating action, a closed-loop circuit is provided with an associated forged steel support roller, the forged steel support roller serving as a conductor in the closed-loop circuit, and the closed-loop circuit includes a power supply component and a current detection structure.

[0013] Further settings include: the first-order temperature group includes temperature parameters at two end points of the forged steel support roller, which are set as TdS and TdX respectively; the second-order temperature group is used to represent the temperature parameters on the surface of the forged steel support roller, which is set as TdM; the first-order operating parameters include the current value It during the end-point heating action; and the second-order operating parameters include the medium-frequency power supply power Pd during the medium-frequency heating action.

[0014] Further settings include: subdividing the current value It in the first-order operating parameters into an output current value I1 and a return current value I2. The output current value I1 represents the actual current output in the power supply component, and I2 is less than or equal to I1.

[0015] Further settings include: setting the critical temperature To during the quenching process of the forged steel support roll in the data integration unit; ensuring that TdS / TdX / TdM is less than or equal to To during the end-point heating action and the intermediate-frequency heating action; and setting the following settings through the action response unit:

[0016] When one or both values ​​of TdS and TdX are greater than or equal to To, the endpoint heating action stops running, while the intermediate frequency heating action continues to run.

[0017] When TdS and TdX are both less than To, and TdM is greater than or equal to To, the endpoint heating action and the intermediate frequency heating action continue to run, and the linear movement action command is generated through the action crosslinking analysis unit in the endpoint heating action.

[0018] When TdS and TdX are both less than To, and TdM is less than To, the endpoint heating action and the intermediate frequency heating action continue to run, and the linear movement action is not executed.

[0019] Further defined as: Let Md represent the thermoelectric synergistic series, ,when equal When the time is up, it indicates that the quenching process is complete.

[0020] An adjustable differential temperature induction hardening device for forged steel support rollers includes a work frame, a lower end seat installed at the bottom of the work frame, the forged steel support rollers placed vertically on the lower end seat, and an upper end seat provided at the upper end of the forged steel support rollers.

[0021] The work frame is vertically equipped with an upper intermediate frequency heating component and a lower intermediate frequency heating component corresponding to the upper and lower ends of the forged steel support roller, and the work frame is equipped with vertical motion components corresponding to the upper end seat, the upper intermediate frequency heating component and the lower intermediate frequency heating component.

[0022] The present invention has the following beneficial effects:

[0023] 1. An improvement is made to the quenching process of large structural components such as forged steel support rollers. The conventional medium-frequency heating and electric heating processes are integrated, and the two processes can be carried out simultaneously without interference. In order to ensure the normal operation of the two processes, a linear movement action is added to the medium-frequency heating action. The essence of this action is that, based on the winding coils of the two medium-frequency heating components, the coils move in the same or opposite directions along the length of the forged steel support roller. The purpose is that after one of the medium-frequency heating components completes the local heating of the forged steel support roller, the linear movement action can "retain" the quenching holding time or the recovery time of that local heating position, mainly to avoid insufficient or excessive quenching temperature.

[0024] 2. In conjunction with the above, it is explained that the overall invention utilizes the key influence between the temperature and current parameters in the metal structural components. Without changing the medium-frequency heating action, the temperature-electric synergy level is calculated based on the current value in the end-point heating action. The essence is that when the overall forged steel support roller is heated to the quenching temperature in all directions, its resistance value tends to stabilize. Therefore, the linear movement action can be controlled based on the current value in the closed-loop current in the end-point heating action. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of an adjustable differential temperature induction hardening device and method for forged steel support rollers proposed in this invention.

[0027] Figure 2 The present invention provides an adjustable differential temperature induction hardening device for forged steel support rollers. Figure 1 The front view;

[0028] Figure 3 This is a schematic diagram of the closed-loop circuit in an adjustable differential temperature induction hardening method for forged steel support rollers proposed in this invention.

[0029] Figure 4 This is a block diagram of the operation of the temperature control module in an adjustable differential temperature induction quenching method for forged steel support rollers proposed in this invention.

[0030] In the diagram: 1. Work frame; 2. Upper intermediate frequency heating component; 3. Vertical motion component; 4. Upper end seat; 5. Lower intermediate frequency heating component; 6. Lower end seat. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1:

[0033] For the quenching process of large structures such as forged steel support rollers, conventional quenching methods, such as medium-frequency heating and electrode heating, essentially involve the heat transfer from the surface of the forging to the inside. However, due to the varying diameters of these structures, the heat transfer distance differs, exacerbating the uneven heat distribution and affecting the quenching effect. The following technical solution is proposed to address this issue:

[0034] Reference Figure 3 and Figure 4 This embodiment describes an adjustable differential temperature induction hardening method for forged steel support rollers, applied in a hardening device. The hardening method includes an end electrode heating process and a medium frequency heating process, and is equipped with a temperature control module associated with the end electrode heating process and the medium frequency heating process. The temperature control module consists of a data integration unit, an action cross-linking analysis unit, and an action response unit, and performs temperature acquisition actions through a temperature detection component during the end electrode heating process and the medium frequency heating process.

[0035] The endpoint electrode heating process uses the two ends of the forged steel support roller as the energized positions and heats the forged steel support roller by resistance heating. The medium frequency heating process heats the outer surface of the forged steel support roller.

[0036] The data integration unit is used to record the dynamic temperature parameters during the heating process of the endpoint electrode and the intermediate frequency heating process, and input the dynamic temperature parameters into the action crosslinking analysis unit;

[0037] The action crosslinking analysis unit is set with endpoint heating action and intermediate frequency heating action related to the endpoint electrode heating process and intermediate frequency heating process. The dynamic temperature parameters include the first-order temperature group and the second-order temperature group in the endpoint heating action and intermediate frequency heating action.

[0038] The action response unit has control authority over the endpoint electrode heating process and the intermediate frequency heating process. It inputs first-order and second-order operating parameters into the endpoint electrode heating process and the intermediate frequency heating process through the data integration unit. It integrates and analyzes the first-order temperature group, the second-order temperature group, the first-order operating parameters, and the second-order operating parameters to obtain the temperature-electric coordination level. It uses the temperature-electric coordination level to interactively control the endpoint electrode heating process and the intermediate frequency heating process.

[0039] Working principle: The end electrode heating process and the medium frequency heating process are explained as follows: The essence of the end electrode heating process is to use the forged steel support roller as a "large resistance element" to heat up when energized. However, this heating process is mainly concentrated at both ends of the structural component (forged steel support roller). Therefore, during the end electrode heating process, the temperature "transfer direction" of the structural component is from the end position to the center position.

[0040] The essence of the intermediate frequency heating process is to utilize the phenomenon of electromagnetic induction. When the magnetic flux surrounding the conductor loop changes, an induced electromotive force is generated in the loop. The structural component in the alternating magnetic field generates an induced current (eddy current). The induced current overcomes the resistance of the conductor itself and generates Joule heat. This heat is used to heat the conductor itself and raise its temperature. However, in this process, the "direction of temperature transfer" of the structural component is from the outer surface of the structural component to the inside. To explain this in conjunction with the above two processes, the end electrode heating process and the intermediate frequency heating process are carried out simultaneously, and the heating positions of the two processes correspond to the end position and the surface position of the structural component, respectively.

[0041] It should also be noted that a linear movement action is also set in the medium-frequency heating process, in which the forged steel support roller moves in the same or opposite directions along the length of the roller.

[0042] Example 2:

[0043] This embodiment explains the temperature control module in Embodiment 2:

[0044] The first-order temperature group includes temperature parameters at two endpoints of the forged steel support roller, which are set as TdS and TdX respectively. The second-order temperature group is used to represent the temperature parameters on the surface of the forged steel support roller, which are set as TdM. TdS, TdX and TdM can all be detected by temperature detection components such as temperature sensors. In this embodiment, they are represented as relative variables. The first-order operating parameters include the current value It in the endpoint heating action, and the second-order operating parameters include the medium-frequency power supply power Pd in ​​the medium-frequency heating action.

[0045] In conjunction with the above, when the endpoint heating action occurs independently, the heating formula is: TdS / TdX = (It) 2 *Ro*t, where Ro and t represent the resistance of the forged steel support roller and the action time in the end-point heating action, respectively; when the medium frequency heating action is performed independently, the heating formula is t=(D*ρ*C*TdM) / (Pd*f*η), where t is the action time in the medium frequency heating action, D is the diameter of the structural component, ρ is the density of the structural component, C is the specific heat capacity of the structural component, f is the frequency in the medium frequency heating action, and η is the heating efficiency. It should be noted that D, ρ, C, f, and η are treated as relative constants, so the heating formula in the medium frequency heating action is optimized to: t=(A*TdM) / (Pd*B), where A and B are constants between D, ρ, C, f, and η.

[0046] In this embodiment, it should be noted that the intermediate frequency heating action and the endpoint heating action need to be simultaneous. However, the intermediate frequency heating action will cause the structural component temperature to rise. Since the structural component temperature rise causes a change in the structural component resistance, it will also affect the endpoint heating action. This part is the basic technical point of the present invention, and the working process is set as follows:

[0047] S1: This section explains the endpoint heating action. The endpoint heating action is equipped with a closed-loop circuit. The forged steel support roller is the conductor in the closed-loop circuit, which includes a power supply component and a current detection structure. The current value It in the first-order operating parameter is further subdivided into the output current value I1 and the return current value I2. This part mainly explains the endpoint heating action. The output current value I1 is used to represent the actual current output by the power supply component. It should be noted that when the current is continuously output, the current does work and the forged steel support roller heats up, so I2 is less than or equal to I1.

[0048] S2: Set the critical temperature To during the quenching process of the forged steel support roll in the data integration unit, so that TdS / TdX / TdM is less than or equal to To during the end-point heating action and the medium-frequency heating action. The action response unit sets the following settings for this:

[0049] S2-1: When one or both values ​​of TdS and TdX are greater than or equal to To, the endpoint heating action stops running, while the intermediate frequency heating action continues to run.

[0050] S2-2: When TdS and TdX are both less than To, and TdM is greater than or equal to To, the endpoint heating action and the intermediate frequency heating action continue to run, and the linear movement action command is generated through the action crosslinking analysis unit in the endpoint heating action.

[0051] S2-3: When TdS and TdX are both less than To, and TdM is less than To, the endpoint heating action and the intermediate frequency heating action continue to run, and the linear movement action is not executed.

[0052] Example 3:

[0053] This embodiment provides supplementary explanation of the action response unit in Embodiment 2:

[0054] The action response unit is based on the action cross-linking analysis unit, and the relevant content in S2-2 of Example 2 is explained. The integrated analysis action is explained as follows:

[0055] S3: During the end-point heating action, when TdS and TdX are both less than To and TdM is greater than or equal to To, a linear movement action is performed along the length direction of the forged steel support roller, so that TdM at the full surface position of the forged steel support roller is greater than or equal to To.

[0056] S4: Regarding the content of S3, it should be noted that: Md represents the thermoelectric synergy series, and the thermoelectric synergy series is calculated as follows: It should be noted that the temperature-electric synergy level is calculated only during the endpoint heating action. Conversely, when the endpoint heating action stops, the temperature-electric synergy level is not calculated. The calculation method for the temperature-electric synergy level is explained as follows: It mainly represents the temperature difference during the end-point heating process, and It is not used as a calculation factor in the formula for the thermoelectric synergistic series, but rather as a judgment factor in the formula. The compensation constant for the calculation formula is explained in conjunction with the endpoint heating action and the intermediate frequency heating action: when TdM at the full surface position of the forged steel support roll is greater than or equal to To, a linear movement action is continuously performed during the intermediate frequency heating action. equal When the time is up, it indicates that the quenching process is complete.

[0057] Example 4:

[0058] This embodiment provides supplementary explanation of an adjustable differential temperature induction hardening device for forged steel support rollers, based on the relevant content in Embodiments 1 to 3:

[0059] Reference Figure 1 and Figure 2 An adjustable differential temperature induction hardening device for forged steel support rollers includes a work frame 1, a lower end seat 6 installed at the bottom of the work frame 1, a forged steel support roller placed vertically on the lower end seat 6, and an upper end seat 4 provided at the upper end of the forged steel support roller.

[0060] The work frame 1 is vertically equipped with an upper intermediate frequency heating component 2 and a lower intermediate frequency heating component 5, which are located at the upper and lower ends of the forged steel support roller. The work frame 1 is also equipped with a vertical motion component 3, which corresponds to the upper end seat 4, the upper intermediate frequency heating component 2 and the lower intermediate frequency heating component 5.

[0061] Working principle: It should be noted that the upper intermediate frequency heating component 2 and the lower intermediate frequency heating component 5 in the overall device are structural components for the intermediate frequency heating action in Embodiment 1 to Embodiment 3, while the upper end seat 4 and the lower end seat 6 are structural components for the end heating action in Embodiment 1 to Embodiment 3, and the upper end seat 4 and the lower end seat 6 play a role in fixing the forged steel support roller.

[0062] A brief explanation of the endpoint heating action is as follows: the upper end seat 4, in conjunction with the lower end seat, energizes the forged steel support roller. The upper intermediate frequency heating component 2 and the lower intermediate frequency heating component 5 are essentially two sets of winding coils. The forged steel support roller is located at the center of the winding coils. It should also be noted that, regarding the linear movement action in Embodiments 1 to 3, in the initial state, the two sets of winding coils are located at the middle section of the forged steel support roller. If the length of the forged steel support roller is L, and the width of the winding coil is h, and the linear movement action includes the following two actions:

[0063] Z1: The two winding coils are located in the middle of the forged steel support roller, and move away from each other by a distance of h in a single operation;

[0064] Z2: When the two winding coils are located at the two ends of the forged steel support roller, they continue to move closer to each other by a distance of h.

[0065] In summary, this invention improves upon conventional quenching processes using both electrical heating and medium-frequency heating. It includes both endpoint heating and medium-frequency heating actions, which can be performed simultaneously without interference. The key lies in utilizing the relationship between temperature and current parameters in the metal structure. Without altering the medium-frequency heating action, a temperature-electricity synergy level is calculated based on the current value in the endpoint heating action. This synergy level, combined with the medium-frequency heating action in the forged steel support roller, enables linear movement. Essentially, it drives the winding coil in the medium-frequency heating action to move in the same or opposite direction along the length of the forged steel support roller. The purpose is to maintain the quenching temperature of the forged steel support roller itself and "retain" the quenching holding time or reheating time.

[0066] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0067] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An adjustable differential temperature induction hardening method for a forged steel backup roll, characterized by, The quenching method is applied to a quenching device, and comprises an end-point electrode heating process, a medium-frequency heating process, and a temperature control module associated with the end-point electrode heating process and the medium-frequency heating process, which comprises a data integration unit, an action cross-linking analysis unit and an action response unit, and performs temperature collection actions through a temperature detection assembly during the end-point electrode heating process and the medium-frequency heating process; The end-point electrode heating process is to heat the forged steel supporting roller by resistance heating, with the positions of the two ends of the forged steel supporting roller as the power supply positions, and the medium-frequency heating process is to heat the forged steel supporting roller from the outer surface of the forged steel supporting roller; The end-point electrode heating process and the medium-frequency heating process are provided with end-point temperature rising actions and medium-frequency temperature rising actions respectively, and the end-point electrode heating process and the medium-frequency heating process are performed simultaneously, and the medium-frequency temperature rising action further comprises a linear movement action, which is to move the forged steel supporting roller in the length direction in the same direction or in the opposite direction; The data integration unit is used to record dynamic temperature parameters in the end-point electrode heating process and the medium-frequency heating process, and input the dynamic temperature parameters into the action cross-linking analysis unit; The end-point temperature rising actions and the medium-frequency temperature rising actions associated with the end-point electrode heating process and the medium-frequency heating process are provided in the action cross-linking analysis unit, the dynamic temperature parameters comprise a first-order temperature group and a second-order temperature group in the end-point temperature rising actions and the medium-frequency temperature rising actions, the action response unit has the control authority of the end-point electrode heating process and the medium-frequency heating process, and inputs first-order working parameters and second-order working parameters into the end-point electrode heating process and the medium-frequency heating process through the data integration unit, integrates and analyzes the first-order temperature group, the second-order temperature group, the first-order working parameters and the second-order working parameters, and obtains a temperature-electricity coordination order, so as to interactively control the end-point electrode heating process and the medium-frequency heating process according to the temperature-electricity coordination order, the first-order temperature group comprises temperature parameters of two end-point positions in the forged steel supporting roller, and is set as TdS and TdX respectively, the second-order temperature group is used to represent the temperature parameter of the surface of the forged steel supporting roller, and is set as TdM, the first-order working parameters comprise a current value It in the end-point temperature rising action, the second-order working parameters comprise a medium-frequency power Pd in the medium-frequency temperature rising action, the current value It in the first-order working parameters is further subdivided into an output current value I1 and a return current value I2, the output current value I1 is used to represent the actual current output by the power assembly, and I2 is less than or equal to I1; A critical temperature To in the forged steel supporting roller quenching process is provided in the data integration unit, TdS / TdX / TdM is less than or equal to To in the end-point temperature rising action and the medium-frequency temperature rising action, and the following contents are provided through the action response unit: When one or both of TdS and TdX are greater than or equal to To, the end-point temperature rising action stops running, and the medium-frequency temperature rising action maintains running; When TdS and TdX are both less than To, and TdM is greater than or equal to To, the end-point temperature rising action and the medium-frequency temperature rising action maintain running, and the action command of the linear movement action is generated by the action cross-linking analysis unit in the end-point temperature rising action. When TdS, TdX are all less than To, and TdM is less than To, the endpoint temperature rising action and the intermediate frequency temperature rising action are maintained to run, and the linear movement action is not executed, and the temperature-power cooperative order is expressed by Md, When is equal to , it indicates that the quenching process is completed.

2. The adjustable differential temperature induction quenching method for a forged steel backup roll according to claim 1, characterized by, In the endpoint temperature rising action, a closed loop circuit related to the forged steel supporting roller is arranged, the forged steel supporting roller is used as a conductor in the closed loop circuit, and the closed loop circuit comprises a power supply assembly and a current detection structure.

3. A temperature-adjustable differential induction quenching device for a forged steel backup roll, which is used in a temperature-adjustable differential induction quenching method for a forged steel backup roll according to any one of claims 1 to 2, characterized by The work frame (1) is provided with a lower end seat (6) at the bottom end position, and the forged steel supporting roller is placed on the lower end seat (6) in a vertical state, and an upper end seat (4) is arranged at the upper end position of the forged steel supporting roller. The work frame (1) is provided with an upper-positioned medium-frequency heating assembly (2) and a lower-positioned medium-frequency heating assembly (5) corresponding to the upper and lower end positions of the forged steel supporting roller in the vertical direction, and the work frame (1) is provided with a vertical movement assembly (3) corresponding to the upper end seat (4), the upper-positioned medium-frequency heating assembly (2) and the lower-positioned medium-frequency heating assembly (5).

Images