Quenching device and non-oxidizing quenching method for pressure flat keys used in rotary drilling rigs

Abstract

This invention discloses a quenching device and an oxidation-free quenching method for a pressure key used in rotary drilling rigs. The device includes a sealed housing and an induction heating unit, a cooling tank, and a clamping transmission assembly built into it. The induction heating unit contains a copper tube induction coil, the shape of which matches the shape of the pressure key. One end of the pressure key extends into the copper tube induction coil. This invention, through the design and use of the medium-frequency induction heating unit and the copper tube induction coil, achieves localized heating of the pressure key, thus balancing its wear resistance and weldability. Furthermore, it improves the heating uniformity of the portion of the pressure key extending into the copper tube induction coil, thereby enhancing the quenching effect. The quenched pressure key of this invention meets the wear resistance requirements for mating with the drill bit, significantly reducing the frequency of downtime for maintenance due to pressure key wear and extending the service life of the rotary drilling rig.

Description

Technical Field

[0001] This invention relates to the field of metal quenching technology, and in particular to a quenching device and an oxidation-free quenching method for a pressure flat key used in rotary drilling rigs. Background Technology

[0002] Rotary drilling rigs are construction machines suitable for hole-forming operations in building foundation engineering, typically used for drilling in soil layers such as sand, cohesive soil, or silty soil. The pressure key is the transmission spline that drives the drill bit. One end is welded to a steel pipe and rotates with the pipe, while the other end is in contact with the rotating drill bit. In other words, the pressure key rotates under the drive of the steel pipe and simultaneously drives the drill bit to rotate and press down into the soil, serving to transmit rotational torque and compress the drill bit. It is a critical and easily damaged component of the rotary drilling rig.

[0003] In existing technologies, the end of the pressure flat key that contacts the drill bit is prone to wear and deformation, which affects the service life of the rotary drilling rig.

[0004] Quenching is a common method to improve the wear resistance of metal parts. However, the pressure-pressurized flat key treated by the existing quenching process cannot meet the performance requirements of steel pipe welding connection, and there is a large amount of oxide scale on the surface, so the quality stability after quenching cannot be guaranteed. Summary of the Invention

[0005] This invention provides a quenching device and an oxidation-free quenching method for pressure-pressurized flat keys used in rotary drilling rigs, thereby solving the technical problems existing in the prior art before and after quenching pressure-pressurized flat keys.

[0006] To solve the above-mentioned technical problems, the present invention provides a quenching device for a pressure flat key for a rotary drilling rig, comprising a sealed box and an induction heating unit, a cooling pool, and a clamping transmission assembly built into the sealed box; a feed door and a discharge door are provided on one side of the sealed box, and the heating inlet of the induction heating unit is collinear with the feed door; the clamping transmission assembly is installed at the inner top of the sealed box, and the cooling pool is located below the clamping transmission assembly; the induction heating unit contains a copper tube induction coil, the shape of which matches the shape of the pressure flat key; one end of the pressure flat key extends into the copper tube induction coil.

[0007] In a preferred embodiment of the present invention, the length of the pressure flat key extending into the copper tube induction coil is less than the total length of the pressure flat key.

[0008] In a preferred embodiment of the present invention, the distance between the portion of the pressure flat key extending into the copper tube coil and the inner wall surface of the copper tube induction coil is 4 to 10 mm.

[0009] In a preferred embodiment of the present invention, the distance between the portion of the pressure flat key extending into the copper tube coil and the inner wall surface of the copper tube induction coil is 5-8 mm.

[0010] In a preferred embodiment of the present invention, the clamping transmission assembly includes a support plate, a vertical slide rail, a vertical drive cylinder, a support plate, a horizontal slide rail, a horizontal drive cylinder, and a clamp; wherein, the support plate is vertically arranged inside the sealed box, and the vertical slide rail is vertically arranged on the support plate; the support plate is vertically arranged, and its back side is slidably connected to the vertical slide rail, while its front side is horizontally mounted with the horizontal slide rail; the clamp is slidably connected to the horizontal slide rail; the horizontal drive cylinder is mounted on the support plate, and its power output end is connected to the clamp; the vertical drive cylinder is mounted below the vertical slide rail, and its power output end is connected to the support plate, driving the support plate to move the clamp up and down in the vertical direction.

[0011] In a preferred embodiment of the present invention, a first transmission roller and a second transmission roller are respectively installed in the sealed box at the feed door and the discharge door.

[0012] In a preferred embodiment of the present invention, a first infrared sensor switch is installed at the end of the first transmission roller facing the induction heating unit, and a second infrared sensor switch is installed between the second transmission roller and the discharge gate. The quenching device further includes a program controller, and the motor, the first infrared sensor switch and the second infrared sensor switch are signal connected to the program controller.

[0013] To solve the above-mentioned technical problems, the present invention provides a quenching method for a pressure flat key used in rotary drilling rigs, comprising the following steps:

[0014] (1) Expel all the air from the sealed box and inject nitrogen into it;

[0015] (2) Pressurized flat key feeding: After the pressurized flat key to be quenched enters from the feed door of the sealed box, it is clamped by the clamping and transmission assembly and horizontally transported to the copper tube induction coil of the induction heating unit.

[0016] (3) Heating treatment: The induction heating unit is started, and the first stage of heating treatment is carried out first, then the temperature is kept constant for 15-30 seconds, and then the second stage of heating treatment is carried out.

[0017] (4) Cooling treatment: After the heating treatment in step (3), the clamping transmission assembly clamps and removes the pressurized flat key, and then quickly sends it into the cooling pool for cooling treatment;

[0018] (5) Tempering treatment: After the cooling treatment in step (4), the clamping transmission assembly clamps and removes the pressurized flat key, and puts it back into the induction heating unit for tempering treatment.

[0019] (6) Discharge: After the tempering process is completed, the clamping and transmission assembly clamps and removes the pressure flat key, so that it is transported out of the sealed box through the discharge door to complete the quenching process.

[0020] In a preferred embodiment of the present invention, in step (3), the process conditions for the first stage of heating treatment are: heating power 1-3.5KHz, heating time 30-50s, and heating temperature 550-650℃; the process conditions for the second stage of heating treatment are: heating power 1-3.5KHz, heating time 35-45s, and heating temperature 800-880℃.

[0021] In a preferred embodiment of the present invention, in step (4), the cooling process conditions are: coolant temperature of 10-16°C and cooling time of 100-150s; in step (5), the tempering process conditions are: heating power of 1-3.5KHz, temperature of 280-300°C and time of 10-20s.

[0022] The beneficial effects of this invention are:

[0023] Because the rotary drill rod transmits torque and bears considerable impact loads, its key component, the pressure key 50, needs to be made of wear-resistant steel. This steel is easy to weld and possesses certain strength, rigidity, hardness, and impact toughness, thereby improving the overall equipment lifespan, reducing maintenance downtime, minimizing capital investment, and increasing efficiency. Furthermore, localized quenching is performed at the contact points between the pressure key and other transmission components, significantly improving the metal's tensile strength, toughness, and fatigue strength, resulting in superior comprehensive mechanical properties and extending the workpiece's service life.

[0024] The specific effects of this invention are as follows: This invention provides a quenching device and method for a pressure key used in rotary drilling rigs. Through the design and use of a medium-frequency induction heating unit and a copper tube induction coil, on the one hand, the heating range of the pressure key is controllable, achieving localized heating treatment. This allows the pressure key to maintain both wear resistance and weldability, solving the problem in the prior art where quenched pressure keys cannot be used due to reduced weldability. On the other hand, the distance from the portion of the pressure key extending into the copper tube induction coil to the inner wall of the coil is equal, effectively improving the uniformity of heating in different parts. Through two-stage heating treatment, the surface and interior of the pressure key are heated more uniformly, further improving the uniformity and stability of the microstructure, thereby enhancing the quenching effect. The quenched pressure key of this invention has a high grain size at the quenched end, exhibiting excellent tensile strength, yield strength, and hardness, as well as high wear resistance, meeting the wear resistance requirements for mating with the drill bit. This significantly reduces the frequency of downtime for maintenance due to pressure key wear, thus extending the service life of the rotary drilling rig. Attached Figure Description

[0025] Figure 1 This is a three-dimensional structural diagram of a preferred embodiment of a quenching device for a pressure flat key used in a rotary drilling rig according to the present invention, wherein only the clamping transmission component is shown.

[0026] Figure 2 This is a schematic diagram of the structure in which one end of the pressure flat key extends into the copper tube induction coil.

[0027] Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure in the AA direction;

[0028] Figure 4 yes Figure 2 Schematic diagram of the cross-sectional structure in the middle BB direction;

[0029] Figure 5 This is a schematic diagram of the clamping transmission assembly shown.

[0030] The components in the attached diagram are labeled as follows:

[0031] 10. Sealed housing; 11. Feed door; 12. Discharge door; 13. First drive roller; 14. Second drive roller; 15. First infrared sensor switch; 16. Second infrared sensor switch;

[0032] 20. Induction heating unit; 21. Copper tube induction coil;

[0033] 30. Cooling pool;

[0034] 40. Clamping transmission assembly; 41. Support plate; 42. Vertical slide rail; 43. Vertical drive cylinder; 44. Support plate; 45. Horizontal slide rail; 46. Horizontal drive cylinder; 47. Fixture;

[0035] 50. Pressurized flat key. Detailed Implementation

[0036] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0037] Please see Figure 1-5 The embodiments of the present invention include:

[0038] Example 1

[0039] like Figure 1 As shown, the present invention discloses a quenching device for a pressure flat key for a rotary drilling rig, comprising a sealed housing 10, an induction heating unit 20, a cooling pool 30, a clamping transmission assembly 40, and a program controller. The program controller is a PLC controller, and the induction heating unit 20 and the clamping transmission assembly 40 are signal-connected to the PLC controller.

[0040] The sealed housing 10 is a cuboid structure made of sheet metal with a thickness of 16mm. It has an inlet door 11 and an outlet door 12 arranged vertically on one side. It has 42 nitrogen injection ports with a diameter of 4mm evenly distributed on its top edge, bottom edge and the side opposite to the inlet door 11. A one-way valve is installed on each nitrogen injection port to evenly inject nitrogen into each area inside the sealed housing 10, so as to isolate air and ensure that the working pressure of nitrogen in the entire sealed housing 10 is greater than or equal to 50kPa.

[0041] Inside the sealed housing 10, a first drive roller 13 and a second drive roller 14 are respectively installed at the inlet gate 11 and the outlet gate 12. A first infrared sensor switch 15 (denoted as position a) is installed at the end of the first drive roller 13 facing the induction heating unit 20. A second infrared sensor switch 16 is installed between the second drive roller 14 and the outlet gate 12. The first and second infrared sensors 15 are connected to the PLC controller. The first infrared sensor switch 15 detects that the pressurized flat key 50 has been fed and reached position a, and sends a signal to the program controller to activate the clamping transmission assembly 40. Upon receiving the signal, the clamping transmission assembly 40 activates, clamps the pressurized flat key 50, and transports it horizontally to the induction heating unit 20. The second infrared sensor switch 16 activates the outlet gate 12 via the program controller, allowing the quenched pressurized flat key 50 to leave the sealed housing 10.

[0042] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the induction heating unit 20 is installed inside the sealed housing 10, with its heating inlet facing the feed door 11. The heating inlet and feed door 11 are collinear, ensuring that the pressurized flat key 50 entering the sealed housing 10 from the feed door 11 can be horizontally transported into the induction heating unit 20. Specifically, the induction heating unit 20 is a medium-frequency induction unit, model LW-200, with an input power of 200KVA, a frequency of 1-5KHz, and a cooling water pressure greater than or equal to 0.3kPa. The induction heating coil inside the induction heating unit 20 is a copper tube induction coil 21. The copper tube induction coil 21 is formed by bending a 2mm thick, rectangular copper tube. The shape of the bent copper tube induction coil 21 matches the shape of the pressure key to be heated, ensuring that the distance from different parts of the pressure key to the inner wall of the copper tube induction coil 21 is equal. This improves the uniformity of heating, thereby enhancing the uniformity and stability of the internal structure of the pressure key 50 after quenching and extending its service life. One end of the copper tube induction coil 21 is a cooling water inlet, and the other end is a cooling water outlet. A pressure sensor is also installed at the cooling water outlet, which is connected to the PLC controller to automatically regulate the cooling water flow rate within the copper tube induction coil 21. This ensures effective cooling and prevents the copper tube induction coil 21 from burning out due to insufficient cooling water flow.

[0043] The pressure-pressurized flat key 50 is made of NM450 wear-resistant steel, which comprises the following components by mass percentage: C≤0.26%, Si≤0.70%, Nb≤1.6%, P≤0.025%, S≤0.010%, Mo≤0.50%, Cr≤1.50%, Ni≤0.80%, and B≤0.004%.

[0044] One end of the pressure-pressurizing flat key 50 (the end that needs to contact other rotating parts, such as a drill bit) extends into the copper tube induction coil 21 for localized heating and quenching. The extension length is less than the total length of the pressure-pressurizing flat key 50, typically 30mm. Through the design of the copper tube induction coil 21, localized heating and quenching of the pressure-pressurizing flat key 50 is achieved. This locally improves the microstructure and grain size of the end in contact with other rotating parts, enabling it to achieve the required hardness and fracture strength, while not affecting the weldability of the other end. Furthermore, the distance between the perimeter of the extended end of the pressure-pressurizing flat key 50 and the inner wall of the copper tube induction coil 21 is 5–8mm.

[0045] like Figure 1As shown, the top of the cooling pool 30 is open, and it contains coolant, which can be either cooling water or cooling oil. The temperature of the coolant in the cooling pool is controlled at 14°C by a refrigerator (not shown) to ensure the cooling effect. The coolant contains a temperature sensor (not shown), and both the refrigerator and the temperature sensor are connected to the programmable controller. The cooling pool 30 is specifically located below the area where the feed gate 11 is connected to the induction heating unit 20.

[0046] like Figure 1 and Figure 5 As shown, the clamping transmission assembly 40 is installed on the inner top of the sealed housing and includes a support plate 41, a vertical slide rail 42, a vertical drive cylinder 43, a support plate 44, a horizontal slide rail 45, a horizontal drive cylinder 46, and a clamp 47. The support plate 41 is vertically fixed to the wall surface inside the sealed housing 10 to provide support for the entire clamping transmission assembly 40. There are two or more vertical slide rails 42, vertically arranged at both ends of the support plate 41; the support plate 44 is vertically arranged, and its back is slidably connected to the vertical slide rails 42, allowing it to slide up and down along the vertical slide rails 42, while its front is horizontally mounted with the horizontal slide rails 45; the clamp 47 is a cantilevered recessed clamp, slidably connected to the horizontal slide rails 45, used to clamp the pressure flat key 50 to be processed and move it back and forth along the horizontal slide rails 45; the horizontal drive cylinder 46 is mounted on the support plate 41, and its power output end is connected to the clamp 47; the vertical drive cylinder 43 is mounted below the vertical slide rails 42, and its power output end is connected to the support plate 44, driving the support plate 44 to move the clamp 47 up and down in the vertical direction, thereby immersing the pressure flat key into the coolant of the cooling pool 30, or removing it from the cooling pool 30. The horizontal drive cylinder 46 and the vertical drive cylinder 43 are signal-connected to the program controller.

[0047] This invention also discloses a quenching method for a pressure flat key used in rotary drilling rigs, specifically including the following steps:

[0048] (1) Since nitrogen is less dense than air under normal pressure, it is necessary to first use a vacuum pump to remove the air from the sealed box 10, then turn off the vacuum pump and slowly inject nitrogen into the sealed box 10 through 42 nitrogen injection ports at the same time. When the nitrogen pressure in the entire sealed box 10 reaches 50 kPa, the corresponding operation is carried out to prevent the pressurized flat key 50 from being oxidized at high temperature during quenching.

[0049] (2) Pressurized flat key feeding: After the pressurized flat key 50 to be quenched enters from the feed door 11 of the sealed box 10, it is conveyed to position a by the first transmission roller 13. After the first infrared sensor switch 15 senses the pressurized flat key 50, it sends a signal to the PLC controller. After receiving the signal, the PLC controller sends a signal to start the clamping transmission assembly 40. The clamp 47 of the clamping transmission assembly grabs the pressurized flat key 50 and slides horizontally to the left along the horizontal slide rail 45 under the drive of the horizontal drive cylinder 46, so that the left end of the pressurized flat key 50 extends into the copper tube induction coil 21 of the induction heating unit 20 for heating treatment.

[0050] (3) Heating treatment: When the induction heating unit 20 is started, the copper tube induction coil 21 first heats the extended end of the pressure flat key 50. Under the conditions of heating frequency of 3.5KHz and DC current of 100A, it heats for 46s to about 600℃. Then the heating is stopped and the temperature is kept constant for 20s to make the pressure flat key 50 transfer heat evenly to improve the uniformity of heating and prevent uneven heating inside and outside. Then the copper tube induction coil 21 performs the second heating treatment. Under the conditions of heating frequency of 3.5KHz and DC current of 100A, it heats for 40s to heat the left end of the pressure flat key 50 to 865℃.

[0051] The two-stage heating process design helps to improve the uniformity of the microstructure at the heating end of the pressurized flat key 10 and improve the grain size grade.

[0052] (4) Cooling treatment: After the heating treatment in step (3), the clamp 47 moves the pressurized flat key 50 horizontally to the right under the drive of the horizontal drive cylinder 46 to the top of the cooling pool 30 (marked as position b). Then the vertical drive cylinder 43 is started, driving the support plate 44 to move downward along the vertical slide rail 42. Since the clamp 47 is a cantilever sinking clamp, it can quickly send the pressurized flat key 50 it holds downward into the cooling pool 30, so that the pressurized flat key 50 is immersed in the 14°C coolant for 120s. It should be noted that the time for the pressurized flat key 50 to be moved out of the induction heating unit 20 and sent into the cooling pool 30 should be controlled within 0.5s to ensure that the temperature of the pressurized flat key 50 when it is immersed in the cooling oil is not lower than 850°C.

[0053] (5) Tempering treatment: After the cooling treatment in step (4), the vertical drive cylinder 43 drives the support plate 44 to move upward along the vertical slide rail 42, and the clamp 47 pulls the pressure flat key 50 out of the cooling pool 30 and returns it to position b. Then, under the drive of the horizontal drive cylinder 46, it moves horizontally to the left and inserts the left end of the pressure flat key into the copper tube induction coil 21 of the induction heating unit 20 for tempering treatment. The insertion depth is controlled to be the same as the depth during the heating treatment in step (3). The tempering process conditions are: heating frequency 3.5KHz, DC current 100A, tempering to 290℃.

[0054] (6) Discharge: After the tempering process is completed, the horizontal drive cylinder 46 drives the clamp to move the pressure flat key 50 horizontally to the right to the position above the second transmission roller 14, which is marked as position c. Then the vertical drive cylinder 43 is started, driving the support plate 44 to move downward along the vertical slide rail 42. The clamp 47 places the tempered pressure flat key 50 on the second transmission roller 14. The second transmission roller 14 moves the pressure flat key 50 toward the discharge gate 12. After the second infrared sensor switch 16 senses the pressure flat key 50, it sends a signal to the PLC controller to start the discharge gate 12. Finally, the pressure flat key 50 is transported out from the discharge gate, completing the quenching process.

[0055] Comparative Example 1

[0056] Compared with Example 1, the heating process is carried out by heating to 865°C in one go under the conditions of heating frequency of 3.5KHz and DC current of 100A.

[0057] Comparative Example 2

[0058] Compared with Example 1, the heat treatment process of the pressurized flat key 50 adopts a box-type heating furnace. During heating, the pressurized flat key 50 is completely placed in the box-type heating furnace and heated to the same temperature in two stages.

[0059] Performance testing:

[0060] The pressure flat keys 50 prepared in Examples 1, 1, and 2 above were tested for tensile strength, yield strength, hardness, and grain size according to GB NM450. The test results are as follows.

[0061]

[0062] The data comparison above shows that the pressure key prepared using the quenching process of this invention not only possesses excellent mechanical strength but also maintains good weldability, solving the problem of the inability to simultaneously achieve both mechanical and weldability. Furthermore, the quenched pressure key exhibits high mechanical strength and excellent impact toughness, significantly improving the wear resistance of the mating end between the pressure key and the drill bit. This greatly reduces the frequency of downtime for maintenance due to pressure key wear, thereby extending the service life of the rotary drilling rig.

[0063] Because the rotary drill rod transmits torque and bears considerable impact loads, its key component, the pressure key 50, needs to be made of wear-resistant steel. This steel is easy to weld and possesses certain strength, rigidity, hardness, and impact toughness, thereby improving the overall equipment lifespan, reducing maintenance downtime, minimizing capital investment, and increasing efficiency. Furthermore, localized quenching is performed at the contact points between the pressure key and other transmission components, significantly improving the metal's tensile strength, toughness, and fatigue strength, resulting in superior comprehensive mechanical properties and extending the workpiece's service life.

[0064] The specific effects of this invention are as follows:

[0065] 1. The process is carried out in a closed nitrogen atmosphere, which effectively avoids the high-temperature oxidation of the heated flat bond;

[0066] 2. By designing and using a medium-frequency induction heating unit and a copper tube induction coil, the heating range of the pressure key is controllable, achieving the goal of local heating treatment only on the wear-resistant end of the pressure key. This allows the pressure key to have both wear resistance and weldability, solving the problem in the prior art where the pressure key cannot be used after quenching due to reduced weldability.

[0067] 3. By designing the copper tube induction coil to match the shape of the pressure flat key, the end of the pressure flat key to be processed is inserted into the pressure flat key for local heating, so that the pressure flat key and the inner wall surface of the copper tube induction coil are equidistant, which effectively improves the uniformity of heating in different parts.

[0068] 4. Through two-stage heating treatment, the surface and interior of the pressurized flat key are heated more evenly, which further improves the uniformity and stability of the microstructure, thereby improving the quenching effect.

[0069] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A quenching device for a pressure flat key used in a rotary drilling rig, characterized in that, It includes a sealed enclosure and an induction heating unit, a cooling pool, and a clamping transmission assembly built into the sealed enclosure; The sealed box has an inlet and an outlet on one side, and is filled with nitrogen. The working pressure of nitrogen in the entire sealed box is greater than or equal to 50 kPa. The heating inlet of the induction heating unit is collinear with the feed gate; The clamping and transmission assembly is installed on the inner top of the sealed box and includes a support plate, a vertical slide rail, a vertical drive cylinder, a support plate, a horizontal slide rail, a horizontal drive cylinder, and a clamp. The support plate is vertically arranged inside the sealed box, and the vertical slide rail is vertically arranged on the support plate. The support plate is vertically arranged, with its back side slidably connected to the vertical slide rail, and its front side horizontally mounted with the horizontal slide rail. The clamp is slidably connected to the horizontal slide rail. The horizontal drive cylinder is mounted on the support plate, with its power output end connected to the clamp. The vertical drive cylinder is installed below the vertical slide rail, with its power output end connected to the support plate, driving the support plate to move the clamp up and down in the vertical direction. The cooling pool is located below the clamping transmission assembly; The induction heating unit contains a copper tube induction coil, the shape of which matches the shape of the pressure flat key; one end of the pressure flat key extends into the copper tube induction coil; the distance between the part of the pressure flat key extending into the copper tube coil and the inner wall surface of the copper tube induction coil is 4-10mm. The sealed box is equipped with a first drive roller and a second drive roller at the inlet and outlet gates, respectively. A first infrared sensor switch is installed at the end of the first drive roller facing the induction heating unit, and a second infrared sensor switch is installed between the second drive roller and the discharge gate. The quenching device also includes a program controller, and the vertical drive cylinder, the horizontal drive cylinder, the first infrared sensor switch and the second infrared sensor switch are signal connected to the program controller.

2. The quenching device for the pressure flat key for rotary drilling rigs according to claim 1, characterized in that, The length of the pressure flat key extending into the copper tube induction coil is less than the total length of the pressure flat key.

3. The quenching device for the pressure flat key for rotary drilling rigs according to claim 1, characterized in that, The distance between the portion of the pressure flat key that extends into the copper tube coil and the inner wall of the copper tube induction coil is 5-8 mm.

4. A non-oxidizing quenching method, characterized in that, The use of the pressure flat key for rotary drilling rigs as described in any one of claims 1-3 includes the following steps: (1) Expel all the air from the sealed box and inject nitrogen into it; (2) Pressurized flat key feeding: After the pressurized flat key to be quenched enters from the feed door of the sealed box, it is clamped by the clamping and transmission assembly and horizontally transported to the copper tube induction coil of the induction heating unit. (3) Heating treatment: The induction heating unit is started, and the first stage of heating treatment is carried out first, then the temperature is kept constant for 15-30 seconds, and then the second stage of heating treatment is carried out. The process conditions for the first stage of heating treatment are: heating power 1-3.5KHz, heating time 30-50s, and heating temperature 550-650℃; the process conditions for the second stage of heating treatment are: heating power 1-3.5KHz, heating time 35-45s, and heating temperature 800-880℃. (4) Cooling treatment: After the heating treatment in step (3), the clamping transmission assembly clamps and removes the pressurized flat key, and then quickly sends it into the cooling pool for cooling treatment; (5) Tempering treatment: After the cooling treatment in step (4), the clamping transmission assembly clamps and removes the pressurized flat key, and puts it back into the induction heating unit for tempering treatment. (6) Discharge: After the tempering process is completed, the clamping and transmission assembly clamps and removes the pressure flat key, so that it is transported out of the sealed box through the discharge door to complete the quenching process.

5. The non-oxidizing quenching method according to claim 4, characterized in that, In step (4), the cooling process conditions are: coolant temperature of 10-16℃ and cooling time of 100-150s; in step (5), the tempering process conditions are: heating power of 1-3.5KHz, temperature of 280-300℃ and time of 10-20s.

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