Crankshaft surface plasma heat treatment method and heat treatment system based on same

Abstract

The invention discloses a crankshaft surface heat treatment method and a heat treatment system based on the crankshaft surface heat treatment method. The crankshaft surface heat treatment method comprises the steps that a crankshaft is clamped on a rotary positioner; the surface of the crankshaft is sequentially divided into a plurality of stages of annular heat treatment areas from front to back in the axis direction, and each stage of annular heat treatment area is provided with a plurality of heat treatment sites avoiding holes in the surface of the crankshaft at intervals in the circumferential direction of the crankshaft; naturally sequencing the heat treatment sites; planning point position moving tracks of the crankshaft and the anode nozzle; and intermittent pulse voltage is applied between the crankshaft and the anode spray head, and heat cycle treatment is conducted on all the heat treatment sites on the crankshaft in sequence according to the sequence machining numbers of the heat treatment sites. The method has the beneficial effects that an electrolyte plasma surface heat treatment technology is combined with a plasma heat treatment method, heat treatment of a workpiece can be rapidly achieved under the condition of low energy consumption, crankshaft deformation is effectively reduced, secondary machining is avoided, recyclable electrolyte is adopted for cooling, and cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of surface heat treatment of metals and alloys, and relates to a crankshaft surface heat treatment method and a heat treatment system based on the method. Background Art

[0002] The crankshaft is one of the key components of the engine, and its performance directly affects the life and performance of the engine. The crankshaft is subjected to large loads and constantly changing bending moments and torques when working, so the crankshaft material is required to have high rigidity and fatigue strength as well as good wear resistance. There are usually two traditional crankshaft heat treatment processes. The first is: blank normalizing → machining → carburizing → quenching → straightening → grinding; the second is: blank normalizing → machining → carburizing → vacuum furnace gas quenching → grinding, among which carburizing and quenching processes are the most important links affecting the performance and deformation of the crankshaft. For example, a Chinese patent on a crankshaft heat treatment process and system (application number 202211311436.3) discloses a crankshaft heat treatment process, which includes: normalizing the workpiece; machining the workpiece; carburizing the surface of the workpiece; straightening the workpiece to eliminate the deformation generated during the carburizing process; tempering the workpiece to eliminate the deformation rebound generated after the straightening process; quenching the workpiece; grinding the surface of the workpiece. The application places the crankshaft in a tempering furnace for carburizing and quenching. Although the crankshaft prepared by this method can meet the heat treatment performance requirements, the crankshaft has severe runout after carburizing and quenching and cannot be directly ground. It needs to be straightened first and then ground. However, during the straightening process, due to the high surface hardness of the workpiece and the severe runout of the workpiece, high pressure and repeated straightening are required, which is very easy to produce cracks and cracks. The second method is to place the crankshaft in a heating furnace during the quenching stage to solve the deformation problem, and the cooling method is air cooling. For example, in a Chinese patent for a high-strength crankshaft processing process for a train drive mechanism (application number 201710627381.X), in order to prevent and reduce the bending deformation of the crankshaft, the patent adopts a vertical placement of the crankshaft during the heating and cooling process. Although the deformation of the crankshaft is reduced to a certain extent and the strength and hardness of the crankshaft are improved, this method uses air cooling for cooling. Due to the slow cooling speed of air cooling, the required cooling speed of the crankshaft cannot be reached, which easily causes insufficient cooling of the crankshaft, so that the surface hardness and hardening layer depth of the crankshaft do not meet the technical requirements, resulting in the wear resistance and fatigue strength of the crankshaft failing to meet the performance requirements. In addition, due to the slow cooling speed of air cooling, the processing efficiency of the crankshaft is low, the yield rate is reduced, and the energy consumption is high. Summary of the invention

[0003] In view of the shortcomings of the prior art described above, the purpose of the present application is to provide a method for heat treatment of the surface of a crankshaft and a plasma heat treatment system constructed based on the method, which are used to solve the problems of easy bending and deformation of the crankshaft during the current surface treatment of the crankshaft, complicated processing procedures, insufficient cooling of the crankshaft resulting in the crankshaft wear resistance and fatigue strength not meeting performance requirements, and high energy consumption. The present invention adopts electrolyte plasma surface heat treatment technology combined with a specific heat treatment method, which can quickly achieve heat treatment of workpieces under low energy consumption conditions, and is combined with a matching plasma heat treatment system to effectively reduce crankshaft deformation and avoid secondary processing. In addition, the present invention has the advantages of reducing material and energy costs, not generating polluting gases or substances, and being safe and environmentally friendly.

[0004] To solve the above problems, the technical solution adopted in this application is:

[0005] The present invention provides a crankshaft surface heat treatment method, which is characterized by comprising the following steps:

[0006] Clamp the formed crankshaft on the rotary positioner. During installation, the crankshaft is connected to the negative pole of the power supply, and the anode nozzle for spraying electrolyte is connected to the positive pole of the power supply, and a discharge gap is ensured between the surface of the crankshaft and the anode nozzle;

[0007] The surface of the crankshaft is divided into a plurality of annular heat treatment zones from front to back along the axial direction, and a plurality of heat treatment sites are arranged at intervals along the circumference of the crankshaft in each annular heat treatment zone to avoid the holes on the crankshaft surface;

[0008] Based on the position of the annular heat treatment zone and the position of the heat treatment sites in each level of the annular heat treatment zone, the numbers generated by the default rules for the several levels of annular heat treatment zones on the crankshaft surface and the several heat treatment sites in each level of the annular heat treatment zone are naturally sorted from small to large, and the obtained numbers are used as the sequential processing numbers of the heat treatment sites; in the annular heat treatment zones of the same level, every two heat treatment sites with adjacent sequential processing numbers are divided into a group, and any two heat treatment sites in the same group are symmetrically distributed on the surface of the crankshaft;

[0009] The control mechanism plans the point-to-point running trajectory of the crankshaft and the anode nozzle according to the sequential processing number of the heat treatment site and the predetermined requirements, and generates an operation instruction matching the point-to-point running trajectory;

[0010] An intermittent pulse voltage is applied between the crankshaft and the anode nozzle. The control mechanism controls the crankshaft and the anode nozzle to operate according to the operating instructions. The plasma heat treatment system performs heat cycle treatment on each heat treatment site on the crankshaft in sequence according to the processing number of the heat treatment site until the surface heat treatment depth of the crankshaft reaches the predetermined requirement.

[0011] As a preference of the present application, the sequential processing numbers include but are not limited to Arabic numerals.

[0012] As a preference of the present application, the heat treatment sites in the annular heat treatment zone of the same level are divided into even groups, and the number of any heat treatment site is simultaneously greater than or simultaneously less than the numbers of two adjacent heat treatment sites.

[0013] As a preferred embodiment of the present application, in the two adjacent annular heat treatment zones, in addition to avoiding the holes on the crankshaft surface, the two heat treatment sites in the same position are aligned and partially overlapped in the axial direction of the crankshaft, together forming a continuous plasma hardening layer along the axial direction of the crankshaft.

[0014] As a preferred embodiment of the present application, the annular heat treatment zone is provided with eight heat treatment sites at equal intervals along the circumference of the crankshaft, and the eight heat treatment sites are divided into four groups according to the numbers from small to large, and the two heat treatment sites in the same group are symmetrically distributed on the surface of the crankshaft, the angle between the center diameter of the first heat treatment site and the center diameter of the second heat treatment site is 180°, the angle between the center diameter of the first heat treatment site and the center diameter of the third heat treatment site is 90°, the fifth heat treatment site is located between the first heat treatment site and the third heat treatment site, the seventh heat treatment site is located between the second heat treatment site and the third heat treatment site, and the angles between the center of the third heat treatment site and the center diameters of the fifth heat treatment site and the center diameters of the seventh heat treatment site are both 45°.

[0015] As a preferred embodiment of the present application, the intermittent pulse voltage includes a high-low voltage alternating step pulse voltage for heating the crankshaft surface and a cooling voltage for cooling the crankshaft surface.

[0016] As a preferred embodiment of the present application, the thermal cycle treatment is carried out according to the following steps:

[0017] heating the crankshaft surface during the step pulse voltage; and

[0018] The crankshaft surface is cooled during the cooling voltage period and the pulse repetition interval.

[0019] As a preferred embodiment of the present application, the high voltage range is 300-340V, and the low voltage range is 260-300V; the cooling voltage during the cooling treatment is 10-50V, and the total duration of the thermal cycle treatment is 25-50s.

[0020] As a preferred embodiment of the present application, the duration of the cooling voltage in each pulse cycle is 3 to 5 seconds.

[0021] As the preferred embodiment of the present application, the high voltage is 320V, the low voltage is 280V, the cooling voltage is 10V, and the total duration of the thermal cycle treatment is 25s.

[0022] As a preferred embodiment of the present application, the depth of the plasma hardened layer in its thickness direction (ie, radial direction of the crankshaft) is 1 to 10 mm.

[0023] As a preferred embodiment of the present application, the discharge gap between the surface of the crankshaft and the anode nozzle is controlled between 0.5 and 3 mm.

[0024] As a preferred embodiment of the present application, the distance between the anode nozzle and the workpiece is 2.5 mm.

[0025] As a preferred embodiment of the present application, the amplitude of the electrolyte sprayed by the anode nozzle near the surface of the workpiece to be processed is 1 to 3 mm.

[0026] As a preferred embodiment of the present application, the electrolyte is a sodium carbonate aqueous solution with a mass concentration of 12% to 16%.

[0027] The present invention also provides a heat treatment system based on the plasma heat treatment method of the crankshaft surface, characterized in that it comprises:

[0028] The rotary positioner is used to clamp the crankshaft and drive the crankshaft to rotate circumferentially around its own axis;

[0029] A plasma heat treatment unit, used to heat the surface of the crankshaft and cool the crankshaft;

[0030] a power supply for applying an intermittent pulse voltage between the crankshaft and the anode nozzle; and

[0031] The control mechanism is connected to the rotary positioner, the plasma heat treatment unit and the power supply, and is used to control the states of the rotary positioner, the plasma heat treatment unit and the power supply.

[0032] As a preferred embodiment of the present application, the rotary positioner includes a base, an end clamping mechanism arranged on the base for clamping the crankshaft in a horizontal state and driving the crankshaft to rotate circumferentially around its own axis, and a plurality of sliding support mechanisms slidably arranged on the base for supporting the crankshaft.

[0033] As a preferred embodiment of the present application, a slide rail is horizontally arranged on the base, and a plurality of sliders slidably matched with the slide rail are arranged on the slide rail.

[0034] As a preferred embodiment of the present application, the sliding support mechanism includes a lifting mechanism and / or a roller disposed on the top of the lifting mechanism. When the crankshaft needs to be supported, the top of the lifting mechanism is provided with a roller, and the horizontality of the crankshaft can be conveniently adjusted by adjusting the height of the roller of the lifting mechanism.

[0035] As a preferred embodiment of the present application, the lifting mechanism can be a hand-cranked screw lifter.

[0036] As a preferred embodiment of the present application, the end clamping mechanism includes a rotary drive device, a chuck and a plurality of claws, the rotary drive device is arranged on a base, the chuck is installed on an output shaft of the rotary drive device, a plurality of claws are respectively vertically connected to the chuck and arranged at equal intervals, and the claws are driven by the claw drive device to jointly clamp the end of the crankshaft.

[0037] As a preferred embodiment of the present application, the electrolyte circulation injection mechanism includes a box body and an electrolyte circulation injection mechanism arranged in the box body, the box body can be slidably installed on the base, and through holes for the crankshaft to pass through are respectively arranged at the same position of the front box wall and the rear box wall of the box body, and the through holes are provided with fixing clamps for clamping the crankshaft; the electrolyte circulation injection mechanism includes a fixed bracket, an anode nozzle, and a cooling nozzle, the fixed bracket is movably arranged in the box body, and a driving device for controlling the movement of the fixed bracket is arranged, and the driving device is connected to the control mechanism; the anode nozzle and the cooling nozzle are installed on the fixed bracket; the anode nozzle and the cooling nozzle are connected to the outside of the box body through an electrolyte delivery pipe.

[0038] As a preferred embodiment of the present application, the anode nozzle includes a metal conductive shell, a nozzle body, an insulating protective cover and a metal anode mesh, the metal conductive shell is adjustably mounted on a fixed bracket, and the nozzle body is assembled in the metal conductive shell; an electrolyte input channel is provided at the bottom of the metal conductive shell, and the electrolyte is fed into the electrolyte input channel through an electrolyte delivery pipe; an electrolyte output channel is provided inside the nozzle body, and the electrolyte output channel is connected to the electrolyte input channel through a liquid inlet hole opened at the bottom of the nozzle body; the insulating protective cover is installed on the top of the nozzle body, and the two are in sealing contact; the insulating protective cover has a conical cavity which is small at the top and large at the bottom and open at the top, and the top of the insulating protective cover is provided with a spray port connected to the conical cavity; the metal anode mesh is assembled in the nozzle body and is electrically connected to the positive pole of the power supply.

[0039] As a preference of the present application, the liquid outlet of the cooling nozzle and the injection port of the anode nozzle are arranged opposite to each other up and down.

[0040] As a preferred embodiment of the present application, the electrolyte output channel is divided into an upper expansion section and a lower conveying section. The upper expansion section is a conical cavity that is larger at the top and smaller at the bottom, and its top opening is adapted to the bottom of the insulating protective cover. The upper expansion section and the insulating protective cover are combined to form a spray chamber for spraying electrolyte.

[0041] Compared with the prior art, the beneficial effects of this application are:

[0042] 1. The heat treatment method of the present invention can realize heat treatment of the surface of a crankshaft, especially a porous crankshaft. The target treatment position is accurate during the treatment process, which effectively avoids the ablation of the holes of the crankshaft, increases the rigidity of the porous crankshaft and reduces the secondary processing of the porous crankshaft.

[0043] 2. The distance between the anode nozzle and the cooling nozzle is adjusted according to the size of the crankshaft, and the position is adjusted by the driving device. Then, the fixing clamp is used in conjunction with the rotary positioner to greatly limit and reduce the heat treatment deformation of the workpiece.

[0044] 3. For the surface hardening of a porous crankshaft, the method of the present invention performs a high and low voltage alternating treatment process with a suitable number of pulse segments, and sprays electrolyte on the crankshaft surface for cooling during the cooling voltage period and the pulse repetition interval. The voltage between the electrodes during the cooling process is 10 to 50V to prevent the occurrence of quenching cracks. At the same time, combined with the heat treatment method of alternating high and low voltage cycles, the workpiece surface can obtain the maximum hardening effect.

[0045] 4. During the heat treatment process of the method described in the present invention, the running trajectories of the crankshaft and the anode nozzle are set based on the processing order of the heat treatment sites on the crankshaft surface and the predetermined requirements, the movement of the crankshaft and the anode nozzle is controlled, and the crankshaft is subjected to surface heat treatment in a high-low voltage alternating cycle, thereby ensuring multiple refinement and homogenization of the austenite grains before quenching, and ultimately achieving the alternating appearance of the surface hard structure and the soft structure in the hardened layer, as well as the uniform distribution of deep fine grains, thereby reducing stress and improving the impact toughness of the workpiece under high hardness.

[0046] 5. The method of the present invention adjusts the electrolyte flow rate to control the amplitude of the electrolyte near the surface of the workpiece to be processed to 1-3 mm, and at the same time controls the distance between the anode nozzle and the surface of the workpiece to be processed to 0.5-3 mm, thereby finally achieving the stability of plasma discharge between the anode nozzle and the workpiece to be processed, so that a stable plasma hardening layer is formed near the surface of the workpiece, ensuring the controllability of the current intensity of the plasma layer in the electrode gap.

[0047] 6. In the electrolytic plasma surface heat treatment process of the method described in the present invention, the high voltage range is 300-340V, the high voltage discharge density is high, the surface heating rate of the workpiece to be treated is fast, and the heating rate can reach 500℃ / s. The rapid heating leads to a large temperature gradient in the surface layer of the workpiece. The voltage is adjusted and switched to a low voltage in the range of 260-300V to reduce the discharge energy density, so that the heat is transferred to a deeper level, thereby forming a sufficient hardened layer depth, reducing stress, improving toughness, and improving the heat treatment efficiency of the workpiece surface.

[0048] 7. The electrolytic plasma equipment and method described in the present invention adopts a recyclable electrolyte, and uses the electrolyte as a coolant during the operation of the equipment. The cooling can be completed without immersing the workpiece in the electrolyte, and no additional coolant is required. The amount of electrolyte used is reduced, liquid doping is reduced, cooling is fast and energy consumption is low. Applying this method in the industrial field can reduce material and resource costs, reduce pollution, and protect the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The present invention is a flow chart of the method for heat treatment of the crankshaft surface.

[0050] Figure 2 It is a schematic structural diagram of the plasma heat treatment system of the present invention.

[0051] Figure 3 Schematic diagram of a plasma heat treatment unit of the present invention.

[0052] Figure 4 is a schematic diagram of the intermittent pulse voltage of the present invention;

[0053] Figure 5 It is one of the point operation schematic diagrams of the plasma heat treatment system of the present invention.

[0054] Figure 6 This is the second schematic diagram of the point operation of the plasma heat treatment system of the present invention.

[0055] In the accompanying description:

[0056] 1-rotating positioner; 11-base; 111-slide rail; 112-slider; 113-foot; 12-end clamping mechanism; 121-rotating drive device; 122-chuck; 123-claw; 13-sliding support mechanism; 131-lifting mechanism; 132-roller; 133-roller adjustment frame;

[0057] 2-plasma heat treatment unit; 21-box; 211-fixing clamp; 22-electrolyte circulation injection mechanism; 221-fixing bracket; 222-anode nozzle; 2221-metal conductive shell; 2222-nozzle body; 2223-metal anode net; 2224-insulating protective cover; 223-cooling nozzle; 224-electrolyte delivery pipe;

[0058] 3- Power supply;

[0059] 4- Control mechanism;

[0060] 5- Crankshaft. DETAILED DESCRIPTION

[0061] The following describes the implementation of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application.

[0062] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0063] In addition, it should be understood that one or more method steps mentioned in this application do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in this application does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these two explicitly mentioned devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of implementation of this application. Changes or adjustments in their relative relationships shall also be regarded as the scope of implementation of this application without substantial changes in the technical content.

[0064] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0065] In the description of the present application, it should be understood that the terms "upper", "lower", "left", "right", "inner", "outer", "axial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, "multiple" means two or more.

[0066] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0068] The present application is further described below in conjunction with specific embodiments, but the protection scope of the present application is not limited thereto.

[0069] Example 1

[0070] like Figure 1 As shown, the present invention provides a crankshaft surface heat treatment method, comprising the following steps:

[0071] S1: Clamp the formed crankshaft on the rotary positioner. During installation, the crankshaft is connected to the negative pole of the power supply, and the anode nozzle for spraying electrolyte is connected to the positive pole of the power supply, and a discharge gap is ensured between the surface of the crankshaft and the anode nozzle;

[0072] S2: dividing the surface of the crankshaft from front to back in the axial direction into a plurality of annular heat treatment zones, wherein each annular heat treatment zone is provided with a plurality of heat treatment sites that are spaced apart along the circumference of the crankshaft and avoid the holes on the surface of the crankshaft;

[0073] S3 Based on the position of the annular heat treatment zone and the position of the heat treatment sites in each level of the annular heat treatment zone, the numbers generated by the default rules for the several levels of annular heat treatment zones and the several heat treatment sites in each level of the annular heat treatment zone on the crankshaft surface are naturally sorted from small to large, and the obtained numbers are used as the sequential processing numbers of the heat treatment sites; in the annular heat treatment zones of the same level, the heat treatment sites are sorted from small to large according to the numbers and every two adjacent numbered heat treatment sites are a group, and any two heat treatment sites in the same group are symmetrically distributed on the surface of the crankshaft;

[0074] S4 determines the point-to-point running trajectory of the crankshaft and the anode nozzle based on the processing order and predetermined requirements of each heat treatment site on the crankshaft surface, and generates an operation instruction matching the point-to-point running trajectory;

[0075] S5 applies intermittent pulse voltage between the crankshaft and the anode nozzle. The crankshaft and the anode nozzle move according to the operation instructions. The plasma heat treatment system performs heat cycle treatment on the heat treatment sites on the crankshaft in sequence until the surface heat treatment depth of the crankshaft reaches the predetermined requirement.

[0076] In some embodiments of the present application, the sequential processing numbers include but are not limited to Arabic numerals. The heat treatment sites of each level of the annular heat treatment zone are sequenced and numbered in the same manner.

[0077] In some embodiments of the present application, the heat treatment sites in the annular heat treatment zone of the same level are divided into even groups, and the number of any heat treatment site is simultaneously greater than or simultaneously less than the numbers of two adjacent heat treatment sites.

[0078] In some embodiments of the present application, in the two adjacent annular heat treatment zones, two heat treatment sites at the same position are aligned and partially overlapped in the axial direction of the crankshaft, together forming a continuous plasma hardening layer along the axial direction of the crankshaft.

[0079] In some embodiments of the present application, the annular heat treatment zone is provided with eight heat treatment sites at equal intervals along the circumference of the crankshaft, and the eight heat treatment sites are divided into four groups according to the numbers from small to large, and the two heat treatment sites in the same group are symmetrically distributed on the surface of the crankshaft, and the angle between the diameter of the center of the first heat treatment site and the diameter of the center of the second heat treatment site is 180°, and the angle between the diameter of the center of the first heat treatment site and the diameter of the center of the third heat treatment site is 90°, the fifth heat treatment site is located between the first heat treatment site and the third heat treatment site, and the seventh heat treatment site is located between the second heat treatment site and the third heat treatment site, and the angle between the center of the third heat treatment site and the diameter of the center of the fifth heat treatment site and the diameter of the center of the seventh heat treatment site are all 45°. The processing order of the heat treatment sites of the annular heat treatment zones of each level of the present application is not limited to the above situation.

[0080] In some embodiments of the present application, the intermittent pulse voltage includes a high-low voltage alternating step pulse voltage and a cooling voltage. Figure 4 As shown, section A is the step pulse voltage, and section B is the cooling voltage. The cycle and pulse width of the high and low voltages in the step pulse voltage are adjusted according to the material, size and preset requirements of the crankshaft to be processed.

[0081] In some embodiments of the present application, the thermal cycle treatment is performed according to the following steps:

[0082] heating the crankshaft surface during the step pulse voltage; and

[0083] The crankshaft surface is cooled during the cooling voltage period and the pulse repetition interval.

[0084] In some embodiments of the present application, the intermittent pulse voltage includes a high-low voltage alternating step pulse voltage for heating the crankshaft surface and a cooling voltage for cooling the crankshaft surface, wherein the high voltage range is 300-340V, the low voltage range is 260-300V; the cooling voltage is 10-50V, and the total duration of the thermal cycle treatment is 25-50s. Specifically: high voltage 320V, low voltage 280V, cooling voltage 10V, and the total duration of the thermal cycle treatment is 25s.

[0085] In some embodiments of the present application, the duration of the cooling voltage in each pulse cycle is 3 to 5 seconds.

[0086] Specifically, during heat treatment under high pressure, when the surface temperature of the crankshaft reaches the melting point, the control mechanism controls the power supply to reduce the voltage to low voltage, thereby reducing the discharge energy density. After the set time, the control mechanism controls the power supply to increase the voltage to high voltage, and cyclically increases and decreases the voltage. After the depth of the hardened layer on the crankshaft surface reaches the predetermined requirement, the control mechanism controls the power supply to reduce the voltage to the cooling voltage, and the cooling nozzle sprays electrolyte onto the crankshaft surface until the cooling voltage lasts for 3 to 5 seconds. The power supply is then cut off and the pulse repetition interval period begins. During this period, the cooling nozzle continuously sprays electrolyte onto the crankshaft surface to cool the crankshaft. The crankshaft runs to the next heat treatment site, and the next intermittent pulse starts, and the above operation is repeated to complete the processing of the crankshaft surface.

[0087] In some embodiments of the present application, the depth of the plasma hardened layer in the thickness direction is 1 to 10 mm.

[0088] In some embodiments of the present application, the discharge gap between the surface of the crankshaft and the anode nozzle is controlled to be between 0.5 and 3 mm, preferably 2.5 mm.

[0089] In some embodiments of the present application, the amplitude of the electrolyte sprayed by the anode nozzle near the surface of the workpiece to be processed is 1 to 3 mm.

[0090] Example 2

[0091] like Figure 2 and Figure 3 As shown, the present application also provides a heat treatment system based on the plasma heat treatment method of the crankshaft surface, comprising:

[0092] The rotary positioner 1 is used to clamp the crankshaft and drive the crankshaft to rotate circumferentially around its own axis;

[0093] The plasma heat treatment unit 2 is movably arranged on the rotary positioner 1, and is used to spray electrolyte onto the surface of the crankshaft and perform heat treatment and cooling treatment on the surface of the crankshaft;

[0094] A power supply 3, used for applying an intermittent pulse voltage between the crankshaft and the anode nozzle; and

[0095] The control mechanism 4 is connected to the rotary positioner 1, the plasma heat treatment unit 2 and the power supply 3, and is used to control the states of the rotary positioner 1, the plasma heat treatment unit 2 and the power supply.

[0096] In some embodiments of the present application, the rotary positioner 1 includes a base 11, an end clamping mechanism 12 arranged on the base 11 for clamping the crankshaft in a horizontal state and driving the crankshaft to rotate circumferentially around its own axis, and a plurality of sliding support mechanisms 13 slidably arranged on the base 11 for supporting the crankshaft.

[0097] In some embodiments of the present application, the plasma heat treatment unit 2 includes a box body 21 and an electrolyte circulation injection mechanism 22 arranged in the box body 21, the box body 21 can be slidably installed on the base 11, and through holes for the crankshaft to pass through are respectively arranged at the same position of the front box wall and the rear box wall of the box body 21, and the through holes are provided with fixing clamps 211 for clamping the crankshaft; the electrolyte circulation injection mechanism 22 includes a fixed bracket 221, an anode nozzle 222, and a cooling nozzle 223, and the fixed bracket 222 and the cooling nozzle 223 are installed in the box body 21 through the fixed bracket 221; the anode nozzle 222 and the cooling nozzle 223 are connected to the outside of the box through an electrolyte delivery pipe 224.

[0098] In some embodiments of the present application, the plasma heat treatment unit 2 also includes an electrolyte supply mechanism, which is connected to the anode nozzle 222 and the cooling nozzle 223 through an electrolyte delivery pipe 224 to form an electrolyte circulation. The circulatory electrolyte can not only form an electric current between the anode nozzle and the crankshaft surface, but also be used for cooling during the interval of local heat treatment of the crankshaft. It can save the amount of electrolyte and replace air cooling to achieve a fast processing process and lower energy supply. Applying this method to the industrial field can reduce material and resource costs, reduce pollution, and protect the environment.

[0099] In some embodiments of the present application, an electrolyte convergence port is further provided on the box body 21, and the electrolyte convergence port is connected to the electrolyte supply mechanism, and is used to re-send the electrolyte in the box body into the electrolyte supply mechanism to complete the recycling of the electrolyte.

[0100] In some embodiments of the present application, a cooling device may be provided on the electrolyte delivery pipe 224 between the electrolyte supply mechanism and the cooling nozzle 223 to facilitate cooling of the electrolyte.

[0101] In some embodiments of the present application, the rotary positioner 1 includes a base 11, an end clamping mechanism 12 arranged on the base for clamping the crankshaft in a horizontal state and driving the crankshaft to rotate circumferentially around its own axis, and a plurality of sliding support mechanisms 13 slidably arranged on the base.

[0102] In some embodiments of the present application, a slide rail 111 is horizontally disposed on the base 11 , and a plurality of sliders 112 slidably matched with the slide rail are disposed on the slide rail 111 .

[0103] In some embodiments of the present application, a plurality of feet 113 are installed at the bottom of the base 11 to facilitate leveling the base.

[0104] In some embodiments of the present application, the sliding support mechanism 13 includes a lifting mechanism 131 and / or a roller 132 disposed on the top of the lifting mechanism. When the crankshaft needs to be supported, a roller mounting frame 133 is configured on the top of the lifting mechanism, and rollers 132 are configured on the roller mounting frame 133. By adjusting the height of the roller mounting frame 133 and the lifting mechanism to adjust the rollers, the horizontality of the crankshaft can be conveniently adjusted. When the plasma heat treatment unit needs to be supported, there is no need to configure rollers on the top of the lifting mechanism, and the top of the lifting mechanism can be directly fixed to the plasma heat treatment unit.

[0105] In some embodiments of the present application, the lifting mechanism 131 may be a hand-cranked screw lifter.

[0106] In some embodiments of the present application, the end clamping mechanism 12 includes a rotation driving device 121, a chuck 122 and a plurality of claws 123, the rotation driving device 121 is arranged on a base, the chuck 122 is installed on the output shaft of the rotation driving device 121, and the plurality of claws 123 are respectively vertically connected to the chuck and arranged at equal intervals, and the claws 123 are driven by the claw driving device to jointly clamp the end of the crankshaft.

[0107] In some embodiments of the present application, the anode nozzle 222 includes a metal conductive shell 2221, a nozzle body 2222, an insulating protective cover 2224 and a metal anode mesh 2223, the metal conductive shell is adjustably mounted on a fixed bracket, and the nozzle body 2222 is inserted into the metal conductive shell 2221; an electrolyte input channel is provided at the bottom of the metal conductive shell 2221, and the electrolyte is fed into the electrolyte input channel through an electrolyte delivery pipe; an electrolyte output channel is provided inside the nozzle body 2222, and the electrolyte output channel is connected to the electrolyte input channel through a liquid inlet hole opened at the bottom of the nozzle body 2222; the insulating protective cover 2224 is installed on the top of the nozzle body 2222, and the two are in sealed contact; the insulating protective cover 2224 has a conical cavity with a small top and a large bottom and an open top, and a spray port connected to the conical cavity is provided on the top of the insulating protective cover 2224; the metal anode mesh is assembled in the nozzle body 2222 and is electrically connected to the positive electrode of the power supply.

[0108] In some embodiments of the present application, a control valve for controlling the flow of electrolyte is arranged at the liquid inlet hole opened at the bottom of the nozzle body 2222, and the control valve is electrically connected to the control mechanism, thereby controlling the flow of electrolyte by controlling the control valve.

[0109] In some embodiments of the present application, the liquid outlet of the cooling nozzle 223 and the nozzle of the fixed bracket 222 are arranged opposite to each other up and down, that is, the cooling nozzle 223 is arranged on the back of the local heat treatment site of the crankshaft. When operating the heat treatment site of the crankshaft, the remaining surface of the crankshaft can be cooled according to the set program. Usually, the crankshaft surface is cooled within the pulse repetition interval. The cooling nozzle 223 sprays electrolyte onto the crankshaft surface. After the electrolyte is gathered, it is sent into the electrolyte supply mechanism from the electrolyte discharge port of the box to complete the circulation of the electrolyte.

[0110] In some embodiments of the present application, the electrolyte output channel is divided into an upper expansion section and a lower conveying section. The upper expansion section is a conical cavity that is larger at the top and smaller at the bottom and is adapted to the insulating protective cover 2224, and its top opening is adapted to the bottom of the insulating protective cover.

[0111] The energy distribution in the heat treatment system is calculated as Q k =U ak I ak -Q p -Q d , where: Q k is the energy consumed by heating the plasma layer and the workpiece; Q p is the energy consumed by the evaporation of the electrolyte to form the plasma; Q d is the radiation energy of the plasma layer; I ak is the current between cathode and anode; U akis the voltage between the cathode and the anode. Since the thickness of the plasma layer (h = 2-3 mm) is relatively large relative to the diameter of the plasma layer (D k =30-50mm) is very small, so the radiation (Q d ) can be ignored. In addition, experiments show that the energy loss Q due to electrolyte evaporation is p It accounts for 5-10% of the total power consumption. Therefore, in the heat treatment system proposed by the present invention, Q k It is the main energy consumption and is used for the formation of the plasma layer and heating of the workpiece surface.

[0112] To test this method, a plasma heat treatment system was designed and manufactured. Figure 2 , 3 The following are schematic diagrams of the device for testing the present invention. The present application uses a porous crankshaft as an example for the experiment.

[0113] For the operation process of the electrolytic plasma surface heat treatment system, such as Figure 3 . The crankshaft 5 is mounted and fixed above the anode nozzle 222 and below the cooling nozzle 223, and the surface of the crankshaft 5 is kept from contacting the top of the anode nozzle 222 and the cooling nozzle 223. The top of the anode nozzle 222 and the cooling nozzle 223 are bound by a fixed bracket 221 so that they are in a relatively vertical position, so as to treat the same cross section of the crankshaft 5. During treatment, the electrolyte is ejected from the anode nozzle 222 through the electrolyte delivery pipeline, and forms effective contact with the crankshaft surface after passing through the discharge gap between the surface of the crankshaft and the anode nozzle, and an intermittent pulse voltage is applied between the crankshaft and the anode nozzle, thereby forming a current in the electrolyte between the anode nozzle and the crankshaft, and forming a thin steam layer and local high pressure at the boundary between the crankshaft 5 and the electrolyte jet, and finally inducing plasma discharge at the surface to be treated of the crankshaft, so as to achieve heating of the surface to be treated of the workpiece until the workpiece treatment is completed. During the electrolytic plasma surface heat treatment process, electrolyte is sprayed on the back of the crankshaft to be treated to quickly cool the crankshaft surface until the treatment is completed, completing the surface heat treatment of the entire workpiece.

[0114] In order to improve the efficiency of the crankshaft electrolytic plasma surface heat treatment and reduce the deformation caused by the heat treatment process, the crankshaft is horizontally installed on the fixed fixture and the rotary positioner 1, as shown in FIG. Figure 2 The crankshaft 5 passes through the housing 21 to fix one end of the crankshaft 5 at the claw 123 of the rotary positioner 1, and the two ends of the crankshaft 5 are fixed at the same level through the sliding support mechanism 13, and then fastened through 211. After the crankshaft 5 to be processed is installed, the plasma heat treatment system can be turned on for plasma heat treatment, and the angle can be adjusted through the chuck 122 during the treatment process. In addition, the bottom of the sliding support mechanism 13 is installed on the slide rail 111 through 112, and the support and fixing position can be adjusted to process different positions of the crankshaft.

[0115] Example 3

[0116] The plasma heat treatment system of Example 2 and the method of Example 1 were used to perform plasma heat treatment on the crankshaft. The parameters of the intermittent pulse voltage applied between the crankshaft and the anode nozzle and the distance between the anode nozzle and the crankshaft surface on the treatment effect during the plasma heat treatment were measured. The intermittent pulse voltage changes were as follows: Figure 4 shown.

[0117] A) Under the premise that other conditions remain unchanged, change the low voltage value;

[0118] B) Under the premise that other conditions remain unchanged, change the high voltage value;

[0119] C) Under the premise that other conditions remain unchanged, change the cooling voltage value;

[0120] D) Change the processing time while other conditions remain unchanged;

[0121] E) Under the premise that other conditions remain unchanged, change the distance between the anode nozzle and the workpiece to be processed;

[0122] According to the test results, the cooling voltage value and the distance between the anode nozzle and the workpiece to be processed have little effect on the product performance, while the high voltage value, low voltage value and processing time have a greater impact. In most test results, the surface hardness can reach above 55HRC, and the depth is internally controlled at 1 to 10mm. The parameters can be adjusted according to product requirements. The recommended parameters are high voltage 320V, low voltage 280V, cooling voltage 10V, total time 25s, and the distance between the anode nozzle and the workpiece is 2.5mm. Under this parameter, there is no ablation on the surface, the time is short, and it has a certain surface hardness and hardened layer depth.

[0123] Table 1 Example experimental results

[0124]

[0125]

[0126] Example 4

[0127] The crankshaft was subjected to plasma heat treatment using the heat treatment system of Example 2 and the method of Example 1, and the fixing method and point operation trajectory (such as Figure 5 and Figure 6 The influence of the running track shown in the figure on the crankshaft deformation. Tests were carried out under different fixing methods and processing tracks:

[0128] Fixing method:

[0129] A) After the workpiece to be processed is fixed on the rotary positioner, it is supported only on the side near the clamping claw;

[0130] B) After the workpiece to be processed is fixed on the rotary positioner, it is supported at both ends of the workpiece and fastened by fixing clamps;

[0131] Point running track:

[0132] a) First proceed along the axial direction of the workpiece, and then proceed along the circumferential direction after processing a certain length, from ① radial direction to ⑧ radial direction;

[0133] b) First process along the circumference of the workpiece (from ① to ⑧), and then process along the axial direction after completing one circle.

[0134] Under the two fixing modes A and B, two different point operation modes a and b are carried out respectively. By comparing the test results, it can be obtained that the deformation variables under each condition are Aa>Ab>Ba>Bb. Under the two conditions of B and b, the porous crankshaft has almost no deformation and can be put into use directly if there is no requirement for surface roughness.

[0135] In summary, the total operation time and point operation mode of thermal cycle treatment are important influencing parameters of surface hardness and hardening depth. Controlling the total operation time of thermal cycle treatment according to demand can increase the hardening depth of workpiece surface heat treatment to 1 to 10 mm. The processing method of this application can achieve precise processing of the target processing position during the surface heat treatment of porous crankshafts, avoid ablation of holes, increase the rigidity of porous crankshafts and reduce secondary processing of porous crankshafts. Through the restrictions of fixed fixtures and rotary positioners, the deformation of workpiece heat treatment is further reduced. While reducing material and energy costs, efficient surface heat treatment can be completed through simple operation, so that the porous crankshaft can obtain sufficient surface hardness and hardened layer depth, and improve its wear resistance and fatigue strength.

[0136] The above examples are for the purpose of illustrating the embodiments disclosed in the present application and should not be construed as limiting the present application. In addition, the various modifications listed herein and the variations of methods and compositions in the invention are obvious to those skilled in the art without departing from the scope and spirit of the present application. Although the present application has been specifically described in conjunction with various specific preferred embodiments of the present application, it should be understood that the present application should not be limited to these specific embodiments. In fact, various modifications obvious to those skilled in the art as described above to obtain inventions should be included within the scope of the present application.

Claims

1. A crankshaft surface plasma heat treatment method, characterized in that: The following steps are involved: Clamp the formed crankshaft on the rotary positioner. During installation, the crankshaft is connected to the negative pole of the power supply, and the anode nozzle for spraying electrolyte is connected to the positive pole of the power supply, and a discharge gap is ensured between the surface of the crankshaft and the anode nozzle; The surface of the crankshaft is divided into a plurality of annular heat treatment zones from front to back along the axial direction, and each annular heat treatment zone is provided with a plurality of heat treatment sites which are spaced apart along the circumference of the crankshaft and avoid the holes on the surface of the crankshaft; Based on the position of the annular heat treatment zone and the position of the heat treatment sites in each level of the annular heat treatment zone, the numbers generated by the default rules for the several levels of annular heat treatment zones on the crankshaft surface and the several heat treatment sites in each level of the annular heat treatment zone are naturally sorted from small to large, and the obtained numbers are used as the sequential processing numbers of the heat treatment sites; in the annular heat treatment zones of the same level, every two adjacent numbered heat treatment sites form a group, and any two heat treatment sites in the same group are symmetrically distributed on the surface of the crankshaft; The control mechanism plans the point-to-point running trajectory of the crankshaft and the anode nozzle according to the sequential processing number of the heat treatment site and the predetermined requirements, and generates an operation instruction matching the point-to-point running trajectory; An intermittent pulse voltage is applied between the crankshaft and the anode nozzle. The control mechanism controls the crankshaft and the anode nozzle to move according to the operating instructions. The plasma heat treatment system performs thermal cycle treatment on the heat treatment sites on the crankshaft in sequence until the surface heat treatment depth of the crankshaft reaches the predetermined requirement.

2. The crankshaft surface plasma heat treatment method according to claim 1, characterized in that: The heat treatment sites in the annular heat treatment zone of the same level are divided into even groups, and the number of any heat treatment site is simultaneously greater than or less than the numbers of two adjacent heat treatment sites.

3. The crankshaft surface plasma heat treatment method according to claim 1, characterized in that: In the two adjacent annular heat treatment zones, two heat treatment sites at the same position are aligned and partially overlapped in the axial direction of the crankshaft, and together form a continuous plasma hardening layer along the axial direction of the crankshaft.

4. The crankshaft surface plasma heat treatment method according to claim 2, characterized in that: The annular heat treatment zone is provided with eight heat treatment sites at equal intervals along the circumference of the crankshaft. The eight heat treatment sites are divided into four groups according to the numbers from small to large. The two heat treatment sites in the same group are symmetrically distributed on the surface of the crankshaft. The angle between the center diameter of the first heat treatment site and the center diameter of the second heat treatment site is 180°, the angle between the center diameter of the first heat treatment site and the center diameter of the third heat treatment site is 90°, the fifth heat treatment site is located between the first heat treatment site and the third heat treatment site, the seventh heat treatment site is located between the second heat treatment site and the third heat treatment site, and the angles between the center of the third heat treatment site and the center diameters of the fifth heat treatment site and the center diameters of the seventh heat treatment site are both 45°.

5. The crankshaft surface plasma heat treatment method according to claim 1, characterized in that: The intermittent pulse voltage includes a high-low voltage alternating step pulse voltage for heating the crankshaft surface and a cooling voltage for cooling the crankshaft surface, wherein the high voltage range is 300-340V, the low voltage range is 260-300V, and the cooling voltage during cooling treatment is 10-50V; the total duration of the thermal cycle treatment is 25-50s.

6. The crankshaft surface plasma heat treatment method according to claim 5, characterized in that: The thermal cycle treatment is carried out according to the following steps: heating the crankshaft surface during the step pulse voltage; and The crankshaft surface is cooled during the cooling voltage period and the pulse repetition interval.

7. The crankshaft surface plasma heat treatment method according to claim 3, characterized in that: The plasma hardened layer has a depth of 1 to 10 mm in the thickness direction.

8. A heat treatment system based on the plasma heat treatment method for the crankshaft surface according to any one of claims 1 to 7, characterized in that: include: A rotary positioner (1) is used to clamp the crankshaft and drive the crankshaft to rotate circumferentially around its own axis; A plasma heat treatment unit (2) is used to perform heat treatment on the surface of the crankshaft and to cool the crankshaft; A power supply (3) for applying an intermittent pulse voltage between the crankshaft and the anode nozzle; as well as A control mechanism (4) is connected to the rotary positioner (1), the plasma heat treatment unit (2) and the power supply (3) and is used to control the states of the rotary positioner (1), the plasma heat treatment unit (2) and the power supply.

9. The heat treatment system according to claim 8, characterized in that: The rotary positioner (1) comprises a base (11), an end clamping mechanism (12) arranged on the base (11) for clamping a crankshaft in a horizontal state and driving the crankshaft to rotate circumferentially around its own axis, and a plurality of sliding support mechanisms (13) slidably arranged on the base (11).

10. The heat treatment system according to claim 9, characterized in that: The plasma heat treatment unit (2) comprises a box body (21) and an electrolyte circulation injection mechanism (22) arranged in the box body (21); the box body (21) is slidably mounted on the base (11); through holes for the crankshaft to pass through are respectively arranged at the same position of the front box wall and the rear box wall of the box body (21); a fixing clamp (211) for clamping the crankshaft is arranged at the through hole; the electrolyte circulation injection mechanism (22) comprises a fixing bracket (221), an anode nozzle (222) and a cooling nozzle (223); the fixing bracket (221) is movably arranged in the box body (21); a driving device for controlling the movement of the fixing bracket (221) is arranged, and the driving device is connected to the control mechanism; the anode nozzle (222) and the cooling nozzle (223) are mounted on the fixing bracket (221); the anode nozzle (222) and the cooling nozzle (223) are connected to the outside of the box body through an electrolyte delivery pipe (224).

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