Medium and high frequency ion nitriding heat treatment pulse power supply and its control system

Abstract

The present invention provides a medium-high frequency ion nitriding heat treatment pulse power supply and its control system, the pulse power supply comprises: a first rectifier circuit, a current conversion circuit, a chopper circuit and a control circuit; the current conversion circuit comprises a full-bridge inverter circuit, a boost circuit and a second rectifier circuit; the input end of the first rectifier circuit is used to receive three-phase alternating current, the output end of the first rectifier circuit is connected to the input end of the full-bridge inverter circuit; the output end of the full-bridge inverter circuit is connected to the input end of the boost circuit, the output end of the boost circuit is connected to the input end of the second rectifier circuit; the output end of the second rectifier circuit is connected to the input end of the chopper circuit, the output end of the chopper circuit is connected to the furnace body and the workpiece in sequence; wherein the furnace body is used as an anode and the workpiece is used as a cathode. The pulse power supply is used to perform nitriding heat treatment on the workpiece, which improves the wear resistance, hardness and qualified rate of the workpiece.

Description

Technical Field

[0001] The invention relates to the field of nitriding heat treatment, and in particular to a medium-high frequency ion nitriding heat treatment pulse power supply and a control system thereof. Background Art

[0002] The development of power supply technology has seriously affected the development of ion desalination treatment process. Domestic nitriding heat treatment is still at the level of the 1980s. In the development of the heat treatment industry, the degree of popularization is far less than that of foreign countries. In the early 1990s, the heat treatment power supply mainly used DC power supply, but this type of power supply has poor arc extinguishing effect. The existing nitriding heat treatment process uses low-frequency power supply to process parts, but the qualified rate of workpieces is still low. Summary of the invention

[0003] The embodiment of the present invention provides a medium-high frequency ion nitriding heat treatment pulse power supply and its control system to solve the technical problem that the existing nitriding heat treatment process uses the existing power supply to process the workpiece, and the workpiece qualification rate is low. The power supply provided by the embodiment of the present invention can improve the workpiece qualification rate.

[0004] The embodiment of the present invention provides a medium-high frequency ion nitridation heat treatment pulse power supply, comprising:

[0005] A first rectifier circuit, a current conversion circuit, a chopper circuit and a control circuit; the current conversion circuit includes a full-bridge inverter circuit, a boost circuit and a second rectifier circuit; the input end of the first rectifier circuit is used to receive three-phase alternating current, and the output end of the first rectifier circuit is connected to the input end of the full-bridge inverter circuit; the output end of the full-bridge inverter circuit is connected to the input end of the boost circuit, and the output end of the boost circuit is connected to the input end of the second rectifier circuit; the output end of the second rectifier circuit is connected to the input end of the chopper circuit, and the output end of the chopper circuit is connected to the furnace body and the workpiece in sequence; wherein the furnace body serves as an anode and the workpiece serves as a cathode; the output end of the chopper circuit is also connected to the input end of the control circuit; the first control end of the control circuit is connected to the controlled end of the chopper circuit, and the second control end of the control circuit is connected to the controlled end of the current conversion circuit.

[0006] Preferably, the first rectifier circuit is a three-phase uncontrolled rectifier circuit, and the three-phase uncontrolled rectifier circuit includes:

[0007] A first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a first capacitor, a second capacitor, a first resistor, and a second resistor;

[0008] The anode of the first diode is connected to the cathode of the fourth diode;

[0009] The anode of the third diode is connected to the cathode of the sixth diode;

[0010] The anode of the fifth diode is connected to the cathode of the second diode;

[0011] The negative electrode of the first capacitor is connected to the positive electrode of the second capacitor, and the second end of the first resistor is connected to the first end of the second resistor;

[0012] The cathode of the first diode is connected to the cathode of the third diode, the cathode of the third diode is connected to the cathode of the fifth diode, the cathode of the fifth diode is connected to the positive electrode of the first capacitor, the positive electrode of the first capacitor is connected to the first end of the first resistor, and the first end of the first resistor is the first output end of the three-phase uncontrolled rectifier circuit;

[0013] The anode of the fourth diode is connected to the anode of the sixth diode, the anode of the sixth diode is connected to the anode of the second diode, the anode of the second diode is connected to the negative electrode of the second capacitor, the negative electrode of the second capacitor is connected to the second end of the second resistor, and the second end of the second resistor is the second output end of the three-phase uncontrolled rectifier circuit.

[0014] Preferably, the full-bridge inverter circuit adopts a single-phase full-bridge inverter circuit, and the single-phase full-bridge inverter circuit includes:

[0015] a third capacitor, a fourth capacitor, a seventh diode, an eighth diode, a ninth diode, a tenth diode, a first N-type insulated gate bipolar transistor, a second N-type insulated gate bipolar transistor, a third N-type insulated gate bipolar transistor, and a fourth N-type insulated gate bipolar transistor;

[0016] The second end of the third capacitor is connected to the first end of the fourth capacitor;

[0017] The anode of the seventh diode is connected to the cathode of the eighth diode, the emitter of the first N-type insulated gate bipolar transistor is connected to the collector of the second N-type insulated gate bipolar transistor and connected to the anode of the seventh diode, which is the first output terminal of the inverter circuit;

[0018] The emitter of the third N-type insulated gate bipolar transistor is connected to the collector of the fourth N-type insulated gate bipolar transistor; the anode of the ninth diode is connected to the cathode of the tenth diode and connected to the emitter of the third N-type insulated gate bipolar transistor, which is the second output terminal of the inverter circuit;

[0019] The cathode of the ninth diode is connected to the collector of the third N-type insulated gate bipolar transistor, the collector of the third N-type insulated gate bipolar transistor is connected to the cathode of the seventh diode, the cathode of the seventh diode is connected to the collector of the first N-type insulated gate bipolar transistor, the collector of the first N-type insulated gate bipolar transistor is connected to the first end of the third capacitor, and is the first input end of the single-phase full-bridge inverter circuit;

[0020] The anode of the tenth diode is connected to the emitter of the fourth N-type insulated gate bipolar transistor, the emitter of the fourth N-type insulated gate bipolar transistor is connected to the anode of the eighth diode, the anode of the eighth diode is connected to the emitter of the second N-type insulated gate bipolar transistor, the emitter of the second N-type insulated gate bipolar transistor is connected to the second end of the fourth capacitor, and is the second input end of the single-phase full-bridge inverter circuit.

[0021] Preferably, the boost circuit comprises: a first high-frequency transformer, a second high-frequency transformer and a fifth capacitor;

[0022] The first end of the primary coil of the first high-frequency transformer is connected to two ends of a fifth capacitor, and the first end of the fifth capacitor is a first input end of the boost circuit;

[0023] The first end of the primary coil of the first high-frequency transformer is also connected to the second end of the primary coil of the second high-frequency transformer; the second end of the first high-frequency transformer is connected to the first end of the second high-frequency transformer, and serves as the second input end of the boost circuit;

[0024] The first end of the secondary coil of the first high-frequency transformer is connected to the first input end of the first rectifying unit of the second rectifying circuit, and the second end of the secondary coil of the first high-frequency transformer is connected to the second input end of the first rectifying unit of the second rectifying circuit;

[0025] The first end of the secondary coil of the second high-frequency transformer is connected to the first input end of the second rectifying unit of the second rectifying circuit, and the second end of the secondary coil of the second high-frequency transformer is connected to the second input end of the second rectifying unit of the second rectifying circuit.

[0026] Preferably, the second rectifier circuit is a dual single-phase full-bridge rectifier circuit, and the dual single-phase full-bridge rectifier circuit includes:

[0027] A first rectifying unit and a second rectifying unit, wherein the first rectifying unit and the second rectifying unit are connected in series;

[0028] The first rectifying unit comprises:

[0029] a sixth capacitor, a third resistor, an eleventh diode, a seventh capacitor, a fourth resistor, a twelfth diode, an eighth capacitor, a fifth resistor, a thirteenth diode, a ninth capacitor, a sixth resistor, and a fourteenth diode;

[0030] The sixth capacitor and the third resistor are connected in series and then connected in parallel with the eleventh diode;

[0031] The eighth capacitor and the fifth resistor are connected in series and then connected in parallel with the thirteenth diode;

[0032] A first end of the sixth capacitor is connected to a cathode of an eleventh diode, a cathode of the eleventh diode is connected to a first end of an eighth capacitor, and one end of the eighth capacitor is connected to a cathode of the thirteenth diode, which is a first output end of the rectifier circuit;

[0033] The seventh capacitor is connected in series with the fourth resistor, the ninth capacitor is connected in series with the sixth resistor, the first end of the seventh capacitor is connected to the cathode of the twelfth diode, the cathode of the twelfth diode is connected to the first end of the ninth capacitor, and the first end of the ninth capacitor is connected to the cathode of the fourteenth diode; the second end of the fourth resistor is connected to the anode of the twelfth diode, the anode of the tenth diode is connected to the second end of the sixth resistor, and the second end of the sixth resistor is connected to the anode of the fourteenth diode;

[0034] The anode of the eleventh diode is the first input terminal of the first rectifying unit, connected to the cathode of the twelfth diode; the anode of the thirteenth diode is the second input terminal of the first rectifying unit, connected to the cathode of the fourteenth diode;

[0035] The second rectifying unit comprises:

[0036] a tenth capacitor, a seventh resistor, a fifteenth diode, an eleventh capacitor, an eighth resistor, a sixteenth diode, a twelfth capacitor, a ninth resistor, a seventeenth diode, a thirteenth capacitor, a tenth resistor, and an eighteenth diode;

[0037] The tenth capacitor and the seventh resistor are connected in series and then connected in parallel with the fifteenth diode;

[0038] The twelfth capacitor and the ninth resistor are connected in series and then connected in parallel with the seventeenth diode;

[0039] The first end of the tenth capacitor is connected to the cathode of the fifteenth diode, the cathode of the fifteenth diode is connected to the first end of the twelfth capacitor, and the first end of the twelfth capacitor is connected to the cathode of the seventeenth diode;

[0040] The eleventh capacitor is connected in series with the eighth resistor, the thirteenth capacitor is connected in series with the tenth resistor, the first end of the eleventh capacitor is connected to the cathode of the sixteenth diode, the cathode of the sixteenth diode is connected to the first end of the thirteenth capacitor, and the first end of the thirteenth capacitor is connected to the cathode of the eighteenth diode;

[0041] The second end of the eighth resistor is connected to the anode of the sixteenth diode, the anode of the sixteenth diode is connected to the second end of the tenth resistor, the second end of the tenth resistor is connected to the anode of the eighteenth diode, and is the second output end of the rectifier circuit;

[0042] The anode of the fifteenth diode is the first input terminal of the second rectifying unit, connected to the cathode of the sixteenth diode; the anode of the seventeenth diode is the second input terminal of the second rectifying unit, connected to the cathode of the eighteenth diode;

[0043] The anode of the twelfth diode is connected to the cathode of the fifteenth diode.

[0044] Preferably, the chopper circuit comprises:

[0045] a first inductor, a fifth N-type insulated gate bipolar transistor, a nineteenth diode, an eleventh resistor, a fifteenth capacitor, a twentieth diode, a fourteenth capacitor, a sixth N-type insulated gate bipolar transistor, a twenty-first diode, a sixteenth capacitor, and a twelfth resistor;

[0046] The eleventh resistor and the fifteenth capacitor are connected in series and then connected in parallel with the nineteenth diode, the cathode of the nineteenth diode is connected to the collector of the fifth N-type insulated gate bipolar transistor, and the anode of the nineteenth diode is connected to the emitter of the fifth N-type insulated gate bipolar transistor;

[0047] The sixteenth capacitor and the twelfth resistor are connected in series and then connected in parallel with the twenty-first diode, the anode of the twenty-first diode is connected to the collector of the sixth N-type insulated gate bipolar transistor, and the cathode of the twenty-first diode is connected to the emitter of the sixth N-type insulated gate bipolar transistor;

[0048] The second end of the first inductor is respectively connected to the collector of the fifth N-type insulated gate bipolar transistor and the anode of the twentieth diode, and the cathode of the twentieth diode is respectively connected to the collector of the sixth N-type insulated gate bipolar transistor and the first end of the fourteenth capacitor; the emitter of the sixth N-type insulated gate bipolar transistor is connected to the first end of the second inductor, and the second end of the second inductor is the first output end of the chopper circuit, which is used to be connected to the nitriding furnace; the emitter of the fifth N-type insulated gate bipolar transistor is connected to the second end of the fourteenth capacitor, which is the second output end of the chopper circuit, which is used to be connected to the workpiece; wherein the furnace body serves as the anode and the workpiece serves as the cathode.

[0049] In the second aspect, an embodiment of the present invention provides a control system for a medium-high frequency ion nitriding heat treatment pulse power supply, comprising: the pulse power supply and the control circuit described above; the first control end of the control circuit is connected to the controlled end of the chopper circuit, the second control end of the control circuit is connected to the controlled end of the converter circuit, and the input end of the control circuit is connected to the first output end of the chopper circuit for receiving the output signal of the output end of the chopper circuit.

[0050] Preferably, the control system of the medium and high frequency ion nitriding heat treatment pulse power supply also includes:

[0051] A display circuit is connected to the control circuit.

[0052] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0053] The present invention provides a medium-high frequency ion nitriding heat treatment pulse power supply, including: a first rectifier circuit, a current conversion circuit, a chopper circuit and a control circuit; the current conversion circuit includes a full-bridge inverter circuit, a boost circuit and a second rectifier circuit; the input end of the first rectifier circuit is used to receive three-phase alternating current, and the output end of the first rectifier circuit is connected to the input end of the full-bridge inverter circuit; the output end of the full-bridge inverter circuit is connected to the input end of the boost circuit, and the output end of the boost circuit is connected to the input end of the second rectifier circuit; the output end of the second rectifier circuit is connected to the input end of the chopper circuit, and the output end of the chopper circuit is connected to the furnace body and the workpiece in sequence; wherein the furnace body is used as an anode and the workpiece is used as a cathode. The pulse power supply provided by the embodiment of the present invention is used to perform nitriding heat treatment on the workpiece, and the nitriding effect is significantly improved, the wear resistance and hardness of the workpiece are improved, and the qualified rate of the workpiece is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of the ion nitridation process;

[0055] Figure 2It is the volt-ampere characteristic curve of gas DC discharge;

[0056] Figure 3 It is a structural diagram of a medium-high frequency ion nitridation heat treatment pulse power supply provided by an embodiment of the present invention;

[0057] Figure 4 is a circuit diagram of a first rectifier circuit provided by an embodiment of the present invention;

[0058] Figure 5 is a circuit diagram of a full-bridge inverter circuit provided by an embodiment of the present invention;

[0059] Figure 6 is an output voltage waveform diagram of a full-bridge inverter circuit provided by an embodiment of the present invention;

[0060] Figure 7 is a circuit diagram of a boost circuit provided by an embodiment of the present invention;

[0061] Figure 8 is a circuit diagram of a second rectifier circuit provided in an embodiment of the present invention;

[0062] Fig. 9 is a circuit diagram of a chopper circuit provided by an embodiment of the present invention;

[0063] Fig.10 is a waveform diagram of an output voltage of a chopper circuit provided by an embodiment of the present invention;

[0064] Fig.11 is a waveform corresponding diagram of the current i and the current change rate di / dt provided by an embodiment of the present invention;

[0065] Fig.12 It is a schematic diagram of the structure of a control system for a medium-high frequency ion nitriding heat treatment pulse power supply provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] Ion nitriding is a method of heat treatment of metal materials, which can improve the hardness, wear resistance and fatigue resistance of the material. Therefore, it is often used in the heat treatment process of gears, cutting tools, molds, spindles, handles and other devices.

[0068] Ion nitriding heat treatment is mainly a process of heat treating the material surface by using anode and cathode electrodes to generate glow discharge to ionize nitrogen-containing gas to generate N ions under high temperature and low pressure conditions. Figure 1 Ion nitriding needs to be carried out in a closed space, with the furnace body as the anode and the workpiece as the cathode. In a vacuum state, N2 or NH3 is injected into the furnace until the pressure reaches between 13 and 133 Pa. When the workpiece is heated to about 500°C under power, the low-pressure gas inside will be ionized, decomposing N ions that penetrate into the surface of the workpiece, thereby achieving the purpose of nitriding.

[0069] The ion nitriding process is divided into three periods: N atom generation, penetration and diffusion. During the nitriding process, the furnace body is first vacuumed. After reaching the required pressure of 6.7Pa, the power is turned on and NH3 is injected into the furnace body, and the temperature in the furnace body begins to rise. Entering the first stage: NH3 is relatively active and undergoes ionization and decomposition under high temperature and high pressure conditions. The decomposition equation is: NH3→[N]+3[H]. The decomposed N atoms bombard the surface of the workpiece under the action of the electric field to produce a glow. The second stage: The workpiece is bombarded by N atoms and emits Fe atoms. The N atoms combine with Fe atoms to adsorb on the surface of the workpiece to form a nitride layer, which improves the hardness and wear resistance of the workpiece surface. The third stage: The glow generated will heat the furnace body again, which can promote the diffusion of N atoms into the workpiece. Therefore, the length of the heating time is directly related to the thickness of the nitriding layer and the nitriding effect, and ultimately achieve the purpose of improving the surface hardness of the workpiece.

[0070] The volt-ampere characteristic curve of gas DC discharge is as follows Figure 2 As shown, the nitriding process occurs in the DE zone, which can ensure that the surface of the workpiece is evenly covered by the glow. As the current increases, it will transition to the EF zone and generate an arc. The arc will not only terminate the ion nitriding process, but may also damage the surface of the workpiece and the power supply itself. Therefore, it is necessary to quickly shut down the current in the arc discharge zone to protect the corresponding equipment and workpiece from secondary damage. However, the workpiece needs to be cleaned before the nitriding heat treatment. Physical cleaning is difficult to meet the requirements. At this time, the workpiece needs to be cleaned by arc. Therefore, some arc is necessary before the ion nitriding treatment. Therefore, it is necessary to introduce NH3 after the arc discharge completes the cleaning of the workpiece. The subsequent heat treatment process should try to make the current and voltage in the DE section so that the surface of the workpiece can be evenly covered by the glow. At this time, the nitriding effect is better.

[0071] See also Figure 3 The embodiment of the present invention provides a medium-high frequency ion nitriding heat treatment pulse power supply, comprising:

[0072] A first rectifier circuit, a current conversion circuit, a chopper circuit and a control circuit; the current conversion circuit includes a full-bridge inverter circuit, a boost circuit and a second rectifier circuit; the input end of the first rectifier circuit is used to receive three-phase alternating current, and the output end of the first rectifier circuit is connected to the input end of the full-bridge inverter circuit; the output end of the full-bridge inverter circuit is connected to the input end of the boost circuit, and the output end of the boost circuit is connected to the input end of the second rectifier circuit; the output end of the second rectifier circuit is connected to the input end of the chopper circuit, and the output end of the chopper circuit is connected to a furnace body and a workpiece in sequence; wherein the furnace body serves as an anode and the workpiece serves as a cathode.

[0073] In the embodiment of the present invention, please refer to Figure 4 , the first rectifier circuit is a three-phase uncontrolled rectifier circuit, and the three-phase uncontrolled rectifier circuit includes:

[0074] A first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a first capacitor, a second capacitor, a first resistor, and a second resistor;

[0075] The anode of the first diode is connected to the cathode of the fourth diode;

[0076] The anode of the third diode is connected to the cathode of the sixth diode;

[0077] The anode of the fifth diode is connected to the cathode of the second diode;

[0078] The negative electrode of the first capacitor is connected to the positive electrode of the second capacitor, and the second end of the first resistor is connected to the first end of the second resistor;

[0079] The cathode of the first diode is connected to the cathode of the third diode, the cathode of the third diode is connected to the cathode of the fifth diode, the cathode of the fifth diode is connected to the positive electrode of the first capacitor, the positive electrode of the first capacitor is connected to the first end of the first resistor, and the first end of the first resistor is the first output end of the three-phase uncontrolled rectifier circuit;

[0080] The anode of the fourth diode is connected to the anode of the sixth diode, the anode of the sixth diode is connected to the anode of the second diode, the anode of the second diode is connected to the negative electrode of the second capacitor, the negative electrode of the second capacitor is connected to the second end of the second resistor, and the second end of the second resistor is the second output end of the three-phase uncontrolled rectifier circuit.

[0081] In the embodiment of the present invention, the first rectifier circuit uses six diodes to complete the rectification; among them, the first diode VD1, the third diode VD3, and the fifth diode VD5 are a common cathode group; the second diode VD2, the fourth diode VD4, and the sixth diode VD6 are a common anode group. To achieve rectification, only one diode in each of the common cathode group and the common anode group is in a conducting state at each moment, and they cannot be on the same bridge arm. Therefore, each diode is turned on for 120° in one cycle, and the conduction sequence is VD1→VD2→VD3→VD4→VD5→VD6. In addition, compared with the single-phase rectifier bridge, the pulsating frequency of the DC output by the six-pulse rectifier circuit reaches 300Hz when the three-phase AC is input. Connecting an RC filter circuit after the rectifier bridge can make the output rectified power more stable.

[0082] according to Figure 4 The connection method in the figure is:

[0083]

[0084] Among them, U2 = 220V, after rectification, the average output voltage is U d =2.34U2.

[0085] In the embodiment of the present invention, please refer to Figure 5 The full-bridge inverter circuit adopts a single-phase full-bridge inverter circuit, and the single-phase full-bridge inverter circuit includes:

[0086] a third capacitor, a fourth capacitor, a seventh diode, an eighth diode, a ninth diode, a tenth diode, a first N-type insulated gate bipolar transistor, a second N-type insulated gate bipolar transistor, a third N-type insulated gate bipolar transistor, and a fourth N-type insulated gate bipolar transistor;

[0087] The second end of the third capacitor is connected to the first end of the fourth capacitor;

[0088] The anode of the seventh diode is connected to the cathode of the eighth diode, the emitter of the first N-type insulated gate bipolar transistor is connected to the collector of the second N-type insulated gate bipolar transistor and connected to the anode of the seventh diode, which is the first output terminal of the inverter circuit;

[0089] The emitter of the third N-type insulated gate bipolar transistor is connected to the collector of the fourth N-type insulated gate bipolar transistor; the anode of the ninth diode is connected to the cathode of the tenth diode and connected to the emitter of the third N-type insulated gate bipolar transistor, which is the second output terminal of the inverter circuit;

[0090] The cathode of the ninth diode is connected to the collector of the third N-type insulated gate bipolar transistor, the collector of the third N-type insulated gate bipolar transistor is connected to the cathode of the seventh diode, the cathode of the seventh diode is connected to the collector of the first N-type insulated gate bipolar transistor, the collector of the first N-type insulated gate bipolar transistor is connected to the first end of the third capacitor, and is the first input end of the single-phase full-bridge inverter circuit;

[0091] The anode of the tenth diode is connected to the emitter of the fourth N-type insulated gate bipolar transistor, the emitter of the fourth N-type insulated gate bipolar transistor is connected to the anode of the eighth diode, the anode of the eighth diode is connected to the emitter of the second N-type insulated gate bipolar transistor, the emitter of the second N-type insulated gate bipolar transistor is connected to the second end of the fourth capacitor, and is the second input end of the single-phase full-bridge inverter circuit.

[0092] In the embodiment of the present invention, in order to convert the rectified direct current into alternating current for use in subsequent circuits, a passive inverter circuit is used as the inverter circuit. Since the rectified direct current is equivalent to a voltage source with a stable voltage, a voltage-type inverter circuit is required to complete the conversion of direct current into alternating current, that is, a passive voltage-type inverter circuit is required as the inverter circuit. In the inverter circuit, each inverter bridge arm needs to be connected in parallel with a diode to play the role of freewheeling and feedback energy.

[0093] like Figure 5 As shown, a single-phase full-bridge voltage-type inverter circuit uses four IGBTs (insulated gate bipolar transistors) to form four bridge arms. The first N-type insulated gate bipolar transistor V1 and the fourth N-type insulated gate bipolar transistor V4 are group A, the second N-type insulated gate bipolar transistor V2 and the third N-type insulated gate bipolar transistor V3 are group B, and C1 and C2 are connected in series to the DC input terminal, which mainly buffers the reactive energy and stabilizes the voltage. During the operation of the inverter circuit, group A and group B are alternately turned on, and each is turned on for 180° in a cycle, so that direct current can be converted into alternating current. The control end of the control circuit of the control system of the pulse power supply is connected to the gate of the N-type insulated gate bipolar crystal, and the frequency of the output alternating current can be adjusted by changing the frequency of the IGBT exchange. The controlled end of the inverter circuit is the gate of each N-type insulated gate bipolar crystal in the inverter circuit, and the control end of the control circuit is connected to the gate of each N-type insulated gate bipolar crystal in the inverter circuit.

[0094] The embodiment of the present invention specifically uses two IGBT modules, each module has two IGBTs, and the specific model is: Infineon IGBT FF300R12KS4. In this module, a diode is anti-parallel connected to each IGBT. V1, V2, VD5, and VD6 belong to the same module; V3, V4, VD7, and VD8 belong to the same module. The output voltage waveform is as follows: Figure 6 As shown, the output voltage Uo is a rectangular wave with an amplitude of Ud, which is expanded into a Fourier series.

[0095]

[0096] The amplitude of the first harmonic (or fundamental wave) is

[0097]

[0098] For the inverter circuit, it is necessary to avoid the two thyristors on the same half bridge arm being turned on at the same time, so the conduction angle of each IGBT is as small as possible to be less than 180°. In addition, in order to avoid the generation of DC components that affect the subsequent transformer primary winding and cause magnetic circuit saturation, it is necessary to ensure that the conduction time of group A IGBT and group B IGBT reaches saturation.

[0099] In the embodiment of the present invention, please refer to Figure 7 , the boost circuit comprises: a first high-frequency transformer, a second high-frequency transformer and a fifth capacitor;

[0100] The first end of the primary coil of the first high-frequency transformer is connected to two ends of a fifth capacitor, and the first end of the fifth capacitor is a first input end of the boost circuit;

[0101] The first end of the primary coil of the first high-frequency transformer is also connected to the second end of the primary coil of the second high-frequency transformer; the second end of the first high-frequency transformer is connected to the first end of the second high-frequency transformer, and serves as the second input end of the boost circuit;

[0102] The first end of the secondary coil of the first high-frequency transformer is connected to the first input end of the first rectifying unit of the second rectifying circuit, and the second end of the secondary coil of the first high-frequency transformer is connected to the second input end of the first rectifying unit of the second rectifying circuit;

[0103] The first end of the secondary coil of the second high-frequency transformer is connected to the first input end of the second rectifying unit of the second rectifying circuit, and the second end of the secondary coil of the second high-frequency transformer is connected to the second input end of the second rectifying unit of the second rectifying circuit.

[0104] Since the voltage output by the inverter circuit contains odd harmonics, which will affect the subsequent circuits, the embodiment of the present invention adopts an LC filter circuit, such as Figure 7 As shown, the primary coil of the high-frequency transformer is used as an inductor coil and connected in series with capacitor C5 to form a filter circuit to suppress harmonics. The embodiment of the present invention uses two high-frequency transformers to achieve voltage boosting. The high-frequency transformer can achieve isolation and voltage boosting. The capacitor C5 connected in series at the front end can isolate DC and avoid saturation caused by magnetization of the transformer core.

[0105] In the embodiment of the present invention, please refer to Figure 8 , the second rectifier circuit is a dual unidirectional full-bridge rectifier circuit, and the dual unidirectional full-bridge rectifier circuit includes:

[0106] A first rectifying unit and a second rectifying unit, wherein the first rectifying unit and the second rectifying unit are connected in series;

[0107] The first rectifying unit comprises:

[0108] In an embodiment of the present invention, the chopper circuit comprises:

[0109] a first inductor, a fifth N-type insulated gate bipolar transistor, a nineteenth diode, an eleventh resistor, a fifteenth capacitor, a twentieth diode, a fourteenth capacitor, a sixth N-type insulated gate bipolar transistor, a twenty-first diode, a sixteenth capacitor, and a twelfth resistor;

[0110] The eleventh resistor and the fifteenth capacitor are connected in series and then connected in parallel with the nineteenth diode, the cathode of the nineteenth diode is connected to the collector of the fifth N-type insulated gate bipolar transistor, and the anode of the nineteenth diode is connected to the emitter of the fifth N-type insulated gate bipolar transistor;

[0111] The sixteenth capacitor and the twelfth resistor are connected in series and then connected in parallel with the twenty-first diode, the anode of the twenty-first diode is connected to the collector of the sixth N-type insulated gate bipolar transistor, and the cathode of the twenty-first diode is connected to the emitter of the sixth N-type insulated gate bipolar transistor;

[0112] The second end of the first inductor is respectively connected to the collector of the fifth N-type insulated gate bipolar transistor and the anode of the twentieth diode, and the cathode of the twentieth diode is respectively connected to the collector of the sixth N-type insulated gate bipolar transistor and the first end of the fourteenth capacitor; the emitter of the sixth N-type insulated gate bipolar transistor is connected to the first end of the second inductor, and the second end of the second inductor is the first output end of the chopper circuit, which is used to be connected to the nitriding furnace, and the nitriding furnace serves as the anode; the emitter of the fifth N-type insulated gate bipolar transistor is connected to the second end of the fourteenth capacitor, which is the second output end of the chopper circuit, which is used to be connected to a workpiece, and the workpiece serves as a cathode.

[0113] In the embodiment of the present invention, please refer to Fig. 9 , the chopper circuit comprises:

[0114] a first inductor, a fifth N-type insulated gate bipolar transistor, a nineteenth diode, an eleventh resistor, a fifteenth capacitor, a twentieth diode, a fourteenth capacitor, a sixth N-type insulated gate bipolar transistor, a twenty-first diode, a sixteenth capacitor, and a twelfth resistor;

[0115] The eleventh resistor and the fifteenth capacitor are connected in series and then connected in parallel with the nineteenth diode, the cathode of the nineteenth diode is connected to the collector of the fifth N-type insulated gate bipolar transistor, and the anode of the nineteenth diode is connected to the emitter of the fifth N-type insulated gate bipolar transistor;

[0116] The sixteenth capacitor and the twelfth resistor are connected in series and then connected in parallel with the twenty-first diode, the anode of the twenty-first diode is connected to the collector of the sixth N-type insulated gate bipolar transistor, and the cathode of the twenty-first diode is connected to the emitter of the sixth N-type insulated gate bipolar transistor;

[0117] The second end of the first inductor is respectively connected to the collector of the fifth N-type insulated gate bipolar transistor and the anode of the twentieth diode, and the cathode of the twentieth diode is respectively connected to the collector of the sixth N-type insulated gate bipolar transistor and the first end of the fourteenth capacitor; the emitter of the sixth N-type insulated gate bipolar transistor is connected to the first end of the second inductor, and the second end of the second inductor is the first output end of the chopper circuit, which is used to be connected to the nitriding furnace; the emitter of the fifth N-type insulated gate bipolar transistor is connected to the second end of the fourteenth capacitor, which is the second output end of the chopper circuit, which is used to be connected to the workpiece; wherein the furnace body serves as the anode and the workpiece serves as the cathode.

[0118] In an embodiment of the present invention, the control circuit of the control system of the pulse power supply can realize the adjustable duty cycle α or frequency f of the output pulse power supply by switching control of different IGBTs (insulated gate bipolar transistors) in the chopper circuit. The first inductor L1 increases the output voltage value in the process of storing and releasing energy, and the voltage across C4 will not change suddenly. The two work together to achieve an output voltage greater than the input voltage. In specific operation, f (or pulse period T) is first determined, and this is achieved by changing the switching state of the fifth N-type insulated gate bipolar transistor V5. Then, under the set f, adjustable α is achieved by adjusting V6, and PWM control modulation technology is used to achieve the conversion of the output pulse power supply. The output voltage waveform of the chopper circuit is as follows: Fig.10 As shown, where T on There is voltage output during the time period, T off There is no voltage output during the time period, so the calculation formula for the duty cycle α is:

[0119]

[0120] Before the pulse power is output to the nitriding furnace body, a second inductor L2 is required to prevent current mutation and damage to the device. out for

[0121]

[0122] The controlled end of the chopper circuit is the gate level of each N-type insulated gate bipolar transistor. The control end of the control circuit is connected to the gate level of the N-type insulated gate bipolar transistor (IGBT) of the chopper circuit, so that it can judge whether it is arc discharge or glow discharge according to the current change rate di / dt collected at the output end of the chopper circuit to control the IGBT on / off, and then the arc extinguishing speed can be controlled by controlling the IGBT on / off speed. Based on the pulse power supply provided by the embodiment of the present invention, the arc can be extinguished quickly and reliably within 2μs. In addition, since the influence of parasitic capacitance and inductance in the chopper circuit will cause surge current or transient overvoltage, which may affect the normal operation of the IGBT, an RC absorption circuit needs to be set in the chopper circuit.

[0123] In summary, by using the pulse power supply provided in the embodiment of the present invention to perform nitriding heat treatment on the workpiece, the nitriding effect is significantly improved, the wear resistance and hardness of the workpiece are improved, and the qualified rate of the workpiece is improved.

[0124] An embodiment of the present invention also provides a control system for a medium-high frequency ion nitriding heat treatment pulse power supply, comprising the pulse power supply and a control circuit as described above; the first control end of the control circuit is connected to the controlled end of the chopper circuit, and the second control end of the control circuit is connected to the controlled end of the converter circuit; the input end of the control circuit is connected to the first output end of the chopper circuit, for receiving an output signal from the output end of the chopper circuit.

[0125] In an embodiment of the present invention, the input end of the control circuit is connected to the first output end of the chopper circuit, which means that the control circuit receives an output signal from the output end of the chopper circuit, and the control circuit performs comprehensive control on the converter and chopper circuits according to the received output signal to achieve controllable output.

[0126] In an embodiment of the present invention, the control circuit includes: a PWM control circuit, a current sharing circuit, a protection circuit and an auxiliary power supply circuit.

[0127] In one preferred embodiment, a display circuit is further included, wherein the display circuit is connected to the control circuit and is used to display the operation status of the pulse power supply.

[0128] See also Fig.12 , a pulse power supply is constructed with the specific circuits of the above-mentioned three-phase uncontrolled rectifier circuit, single-phase full-bridge inverter circuit, boost circuit, dual single-phase full-bridge rectifier circuit and chopper circuit, the output of the pulse power supply is controlled by the control circuit, and the display circuit is used to display the operation of the pulse power supply. The parameter requirements for the power supply are: the working voltage is continuously adjustable at 300-750V; the working current is continuously adjustable at 0-150A; the output is 500-20KHz near-rectangular square wave, and the average power can be adjusted by adjusting the duty cycle, and the duty cycle can be adjusted in the range of 0-95%; the arc can be extinguished automatically, and the arc extinguishing time td≤2μs. The ion nitriding furnace body used is a bell-shaped nitriding furnace, and the workpieces are stacked inside the furnace body. The furnace body adopts a hot arm structure to complete the heating of the workpiece. The pulse power supply has been put into trial use in Guangzhou A heat treatment processing plant, and nitriding treatment is carried out for 38CrMoAl material as an example. Before being placed in the nitriding furnace, it is necessary to perform tempering and cleaning treatment, remove oil stains as much as possible and dry it. The results of spot checks on multiple batches of workpieces after nitriding treatment using the pulse power supply are shown in Table 1:

[0129] Table 1 Comparison table of heat treatment conditions before and after using the pulse power supply provided by the embodiment of the present invention

[0130]

[0131] It can be seen that by using the pulse power supply of the embodiment of the present invention to perform nitriding heat treatment on the workpiece, the wear resistance and hardness of the workpiece are greatly improved, and the workpiece qualification rate is increased from the original 80.2% to 99.1%, which greatly reduces the scrap rate and saves processing costs.

[0132] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A medium-high frequency ion nitriding heat treatment pulse power supply, characterized in that: include: A first rectifier circuit, a current conversion circuit, a chopper circuit and a control circuit; the current conversion circuit includes a full-bridge inverter circuit, a boost circuit and a second rectifier circuit; the input end of the first rectifier circuit is used to receive three-phase AC power, and the output end of the first rectifier circuit is connected to the input end of the full-bridge inverter circuit; the output end of the full-bridge inverter circuit is connected to the input end of the boost circuit, and the output end of the boost circuit is connected to the input end of the second rectifier circuit; the output end of the second rectifier circuit is connected to the input end of the chopper circuit, and the output end of the chopper circuit is connected to the furnace body and the workpiece in sequence; wherein the furnace body serves as an anode and the workpiece serves as a cathode; The full-bridge inverter circuit adopts a single-phase full-bridge inverter circuit, and the single-phase full-bridge inverter circuit comprises: a third capacitor, a fourth capacitor, a seventh diode, an eighth diode, a ninth diode, a tenth diode, a first N-type insulated gate bipolar transistor, a second N-type insulated gate bipolar transistor, a third N-type insulated gate bipolar transistor, and a fourth N-type insulated gate bipolar transistor; the second end of the third capacitor is connected to the first end of the fourth capacitor; the anode of the seventh diode is connected to the cathode of the eighth diode, the emitter of the first N-type insulated gate bipolar transistor is connected to the collector of the second N-type insulated gate bipolar transistor and is connected to the anode of the seventh diode, which is the first output end of the inverter circuit; the emitter of the third N-type insulated gate bipolar transistor is connected to the collector of the fourth N-type insulated gate bipolar transistor; the anode of the ninth diode is connected to the cathode of the tenth diode and is connected to the emitter of the third N-type insulated gate bipolar transistor, which is the inverter circuit the second output terminal of the single-phase full-bridge inverter circuit; the cathode of the ninth diode is connected to the collector of the third N-type insulated gate bipolar transistor, the collector of the third N-type insulated gate bipolar transistor is connected to the cathode of the seventh diode, the cathode of the seventh diode is connected to the collector of the first N-type insulated gate bipolar transistor, the collector of the first N-type insulated gate bipolar transistor is connected to the first end of the third capacitor, which is the first input terminal of the single-phase full-bridge inverter circuit; the anode of the tenth diode is connected to the emitter of the fourth N-type insulated gate bipolar transistor, the emitter of the fourth N-type insulated gate bipolar transistor is connected to the anode of the eighth diode, the anode of the eighth diode is connected to the emitter of the second N-type insulated gate bipolar transistor, the emitter of the second N-type insulated gate bipolar transistor is connected to the second end of the fourth capacitor, which is the second input terminal of the single-phase full-bridge inverter circuit; The boost circuit comprises: A first high-frequency transformer, a second high-frequency transformer and a fifth capacitor; the first end of the primary coil of the first high-frequency transformer is connected to the two ends of the fifth capacitor, and the first end of the fifth capacitor is the first input end of the boost circuit; the first end of the primary coil of the first high-frequency transformer is also connected to the second end of the primary coil of the second high-frequency transformer; the second end of the first high-frequency transformer is connected to the first end of the second high-frequency transformer, and is the second input end of the boost circuit; the first end of the secondary coil of the first high-frequency transformer is connected to the first input end of the first rectifying unit of the second rectifying circuit, and the second end of the secondary coil of the first high-frequency transformer is connected to the second input end of the first rectifying unit of the second rectifying circuit; the first end of the secondary coil of the second high-frequency transformer is connected to the first input end of the second rectifying unit of the second rectifying circuit, and the second end of the secondary coil of the second high-frequency transformer is connected to the second input end of the second rectifying unit of the second rectifying circuit; The chopper circuit comprises: a first inductor, a second inductor, a fifth N-type insulated gate bipolar transistor, a nineteenth diode, an eleventh resistor, a fifteenth capacitor, a twentieth diode, a fourteenth capacitor, a sixth N-type insulated gate bipolar transistor, a twenty-first diode, a sixteenth capacitor, and a twelfth resistor; the eleventh resistor and the fifteenth capacitor are connected in series and then connected in parallel with the nineteenth diode, the cathode of the nineteenth diode is connected to the collector of the fifth N-type insulated gate bipolar transistor, and the anode of the nineteenth diode is connected to the emitter of the fifth N-type insulated gate bipolar transistor; the sixteenth capacitor and the twelfth resistor are connected in series and then connected in parallel with the twenty-first diode, the anode of the twenty-first diode is connected to the collector of the sixth N-type insulated gate bipolar transistor, and the twenty-first The cathode of the diode is connected to the emitter of the sixth N-type insulated gate bipolar transistor; the second end of the first inductor is respectively connected to the collector of the fifth N-type insulated gate bipolar transistor and the anode of the twentieth diode, and the cathode of the twentieth diode is respectively connected to the collector of the sixth N-type insulated gate bipolar transistor and the first end of the fourteenth capacitor; the emitter of the sixth N-type insulated gate bipolar transistor is connected to the first end of the second inductor, and the second end of the second inductor is the first output end of the chopper circuit, which is used to be connected to the nitriding furnace; the emitter of the fifth N-type insulated gate bipolar transistor is connected to the second end of the fourteenth capacitor, which is the second output end of the chopper circuit, which is used to be connected to the workpiece; wherein the furnace body serves as the anode and the workpiece serves as the cathode.

2. The medium-high frequency ion nitriding heat treatment pulse power supply according to claim 1 is characterized in that: The first rectifier circuit is a three-phase uncontrolled rectifier circuit, and the three-phase uncontrolled rectifier circuit includes: A first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a first capacitor, a second capacitor, a first resistor, and a second resistor; The anode of the first diode is connected to the cathode of the fourth diode; The anode of the third diode is connected to the cathode of the sixth diode; The anode of the fifth diode is connected to the cathode of the second diode; The negative electrode of the first capacitor is connected to the positive electrode of the second capacitor, and the second end of the first resistor is connected to the first end of the second resistor; The cathode of the first diode is connected to the cathode of the third diode, the cathode of the third diode is connected to the cathode of the fifth diode, the cathode of the fifth diode is connected to the positive electrode of the first capacitor, the positive electrode of the first capacitor is connected to the first end of the first resistor, and the first end of the first resistor is the first output end of the three-phase uncontrolled rectifier circuit; The anode of the fourth diode is connected to the anode of the sixth diode, the anode of the sixth diode is connected to the anode of the second diode, the anode of the second diode is connected to the negative electrode of the second capacitor, the negative electrode of the second capacitor is connected to the second end of the second resistor, and the second end of the second resistor is the second output end of the three-phase uncontrolled rectifier circuit.

3. The medium-high frequency ion nitriding heat treatment pulse power supply according to claim 1 is characterized in that: The second rectifier circuit is a dual single-phase full-bridge rectifier circuit, and the dual single-phase full-bridge rectifier circuit includes: A first rectifying unit and a second rectifying unit, wherein the first rectifying unit and the second rectifying unit are connected in series; The first rectifying unit comprises: a sixth capacitor, a third resistor, an eleventh diode, a seventh capacitor, a fourth resistor, a twelfth diode, an eighth capacitor, a fifth resistor, a thirteenth diode, a ninth capacitor, a sixth resistor, and a fourteenth diode; The sixth capacitor and the third resistor are connected in series and then connected in parallel with the eleventh diode; The eighth capacitor and the fifth resistor are connected in series and then connected in parallel with the thirteenth diode; A first end of the sixth capacitor is connected to a cathode of an eleventh diode, a cathode of the eleventh diode is connected to a first end of an eighth capacitor, and one end of the eighth capacitor is connected to a cathode of the thirteenth diode, which is a first output end of the rectifier circuit; The seventh capacitor is connected in series with the fourth resistor, the ninth capacitor is connected in series with the sixth resistor, the first end of the seventh capacitor is connected to the cathode of the twelfth diode, the cathode of the twelfth diode is connected to the first end of the ninth capacitor, and the first end of the ninth capacitor is connected to the cathode of the fourteenth diode; the second end of the fourth resistor is connected to the anode of the twelfth diode, the anode of the tenth diode is connected to the second end of the sixth resistor, and the second end of the sixth resistor is connected to the anode of the fourteenth diode; The anode of the eleventh diode is the first input terminal of the first rectifying unit, connected to the cathode of the twelfth diode; the anode of the thirteenth diode is the second input terminal of the first rectifying unit, connected to the cathode of the fourteenth diode; The second rectifying unit comprises: a tenth capacitor, a seventh resistor, a fifteenth diode, an eleventh capacitor, an eighth resistor, a sixteenth diode, a twelfth capacitor, a ninth resistor, a seventeenth diode, a thirteenth capacitor, a tenth resistor, and an eighteenth diode; The tenth capacitor and the seventh resistor are connected in series and then connected in parallel with the fifteenth diode; The twelfth capacitor and the ninth resistor are connected in series and then connected in parallel with the seventeenth diode; The first end of the tenth capacitor is connected to the cathode of the fifteenth diode, the cathode of the fifteenth diode is connected to the first end of the twelfth capacitor, and the first end of the twelfth capacitor is connected to the cathode of the seventeenth diode; The eleventh capacitor is connected in series with the eighth resistor, the thirteenth capacitor is connected in series with the tenth resistor, the first end of the eleventh capacitor is connected to the cathode of the sixteenth diode, the cathode of the sixteenth diode is connected to the first end of the thirteenth capacitor, and the first end of the thirteenth capacitor is connected to the cathode of the eighteenth diode; The second end of the eighth resistor is connected to the anode of the sixteenth diode, the anode of the sixteenth diode is connected to the second end of the tenth resistor, the second end of the tenth resistor is connected to the anode of the eighteenth diode, and is the second output end of the rectifier circuit; The anode of the fifteenth diode is the first input terminal of the second rectifying unit, connected to the cathode of the sixteenth diode; the anode of the seventeenth diode is the second input terminal of the second rectifying unit, connected to the cathode of the eighteenth diode; The anode of the twelfth diode is connected to the cathode of the fifteenth diode.

4. A control system for a medium-high frequency ion nitriding heat treatment pulse power supply, characterized in that: include: A pulse power supply and a control circuit as claimed in any one of claims 1 to 3; a first control end of the control circuit is connected to a controlled end of the chopper circuit, a second control end of the control circuit is connected to a controlled end of the converter circuit, an input end of the control circuit is connected to a first output end of the chopper circuit, and is used to receive an output signal of an output end of the chopper circuit.

5. The control system of the medium-high frequency ion nitriding heat treatment pulse power supply according to claim 4 is characterized in that: Also includes: A display circuit is connected to the control circuit.

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