Salt spray test device and method for metal parts

Abstract

The invention relates to the technical field of salt spray tests, in particular to a salt spray test device and method for metal parts, the salt spray test device comprises a salt spray test box with a box door, the top end of the salt spray test box is fixedly connected with a liquid film thickness detection mechanism, and the interior of the salt spray test box is fixedly connected with a sprayer. When the liquid film on the upper surface of the metal part in the salt spray test box is not in the high-efficiency corrosion thickness, the spraying power of the sprayer is adjusted, so that the thickness of the liquid film is adjusted to the high-efficiency corrosion thickness, a relatively stable liquid film measurement mode can be provided in a non-stop high-salt and high-humidity environment, the liquid film can be not influenced by condensation and mist, and the measurement accuracy is improved. When the water absorption piece downwards touches the liquid film, water is rapidly absorbed under the action of capillarity, the pressure sensor can detect that the weight of the lower probe rod rapidly suddenly changes for the first time, and the capillarity occurs between a solid phase and a liquid phase, so that detection interference of condensation and mist is avoided, and non-stop detection in the salt spray test process is realized.

Description

Technical Field

[0001] This invention relates to the field of salt spray testing technology, specifically to a salt spray testing device and method for metal parts. Background Technology

[0002] During salt spray testing, changes in the thickness of the liquid film on the surface of metal materials can affect the dissolution and transport processes of corrosive media such as hygroscopic salts, thereby affecting the atmospheric corrosion rate.

[0003] The liquid film thickness range corresponding to the fastest atmospheric corrosion rate is approximately 2-100 micrometers. Therefore, controlling the liquid film thickness to ensure it is at an efficient experimental thickness can accelerate the experimental process. Thus, timely detection of the liquid film thickness on the surface of metal parts during salt spray testing is of great importance. The thickness of the liquid film is relatively thin, which requires high precision. Furthermore, in the salt spray test environment, the high humidity and high salt environment will limit many ways of measuring the thickness of the liquid film. If optical methods are used to measure the thickness of the liquid film, high humidity fog will severely interfere with the propagation of light, thus causing the detection to fail. If the conductivity probe method is used to measure the thickness of a liquid film, its core component is a platinum needle with good conductivity. The main principle of the conductivity probe method is that when the platinum needle contacts the upper and lower surfaces of the liquid film, the current in the measurement system will undergo two jumps. The vertical displacement of the platinum needle during these two jumps represents the thickness of the liquid film. However, in salt spray environments with high relative humidity, condensation easily forms on the surface of the metallic platinum needle, causing the conductive circuit of the conductivity probe method to appear prematurely, which will also affect the accuracy of the detection.

[0004] Therefore, a salt spray testing device and method for metal parts are proposed to address the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a salt spray testing device and method for metal parts, which can achieve accurate liquid level measurement in a low-cost manner without stopping the machine, without exposing conductive parts to the salt spray environment throughout the process, and provides a relatively stable liquid film measurement method in high-salt and high-humidity environments without stopping the machine.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a salt spray test device for metal parts, comprising a salt spray test chamber with a door, a liquid film thickness detection mechanism fixedly connected to the top of the salt spray test chamber, and a sprayer fixedly connected inside the salt spray test chamber. When the liquid film on the upper surface of the metal parts inside the salt spray test chamber is not at the high-efficiency corrosion thickness, the spraying power of the sprayer is adjusted to adjust the liquid film thickness to the high-efficiency corrosion thickness. The liquid film thickness detection mechanism includes a lower probe rod and a sliding assembly supporting the lower probe rod. A pressure sensor for detecting the weight of the lower probe rod is installed on the sliding assembly. A rotating cover is rotatably connected to the top of the salt spray test chamber. After the rotating cover is rotated open, the lower probe rod can extend downward into the inside of the salt spray test chamber. A water-absorbing component is detachably connected to the bottom of the lower probe rod by magnetic attraction or threaded connection. The water-absorbing component includes an outer shell and an inner water-absorbing cotton. The bottom of the shell and the bottom of the water-absorbing cotton are flush. This invention provides a relatively stable liquid film measurement method in high-salt and high-humidity environments without shutting down the system. It is unaffected by condensation and fog, avoiding the drawbacks of existing technologies using conductivity probes and optical thickness measurement methods. When the absorbent component touches the liquid film, it rapidly absorbs water due to capillary action. The pressure sensor detects the first rapid change in the weight of the lower probe. As the absorbent component continues to descend and touches the surface of the metal component, the weight of the lower probe is supported by the surface of the metal component, and the pressure sensor detects a second rapid change in the weight of the lower probe. The weight change of the absorbent component is amplified by the sliding component and detected by the pressure sensor, thus realizing the detection of the liquid film thickness. Furthermore, because capillary action occurs between the solid and liquid phases, it avoids interference from condensation and fog detection, enabling continuous detection during salt spray testing.

[0007] This invention offers excellent economic benefits. The detection end that comes into contact with salt spray is only a water-absorbing component, which is inexpensive, replaceable, and unaffected by salt spray corrosion. The lower probe can be made of corrosion-resistant, non-conductive glass. Compared to conductive detection with electrode plates, which is susceptible to salt spray corrosion, and optical detection, which is expensive, this invention effectively reduces detection costs and subsequent maintenance costs.

[0008] Preferably, in a salt spray testing device for metal parts according to the present invention, the sliding assembly includes a mother plate, which is fixed to the top of the salt spray test chamber. A slider is slidably connected to the inner side of the mother plate, a slide block is fixedly connected to one side of the slider, a slide plate is slidably connected to the inner side of the slide block, a top plate is fixedly connected to the top of the slide plate, and a horizontal plate is rotatably connected to the top of the top plate via a rotating shaft. The inner side of the other end of the horizontal plate is slidably connected to the outer side of the lower probe rod, and a locking part is fixedly connected to the top of the lower probe rod. The locking part abuts against the top surface of the horizontal plate, and the locking part and the horizontal plate have a magnetic attraction structure.

[0009] The descent accuracy of the sliding component determines the detection accuracy of the liquid film thickness in this invention. The sliding component in this invention can achieve a micron-level descent, and because the descent rate is graded, it can achieve a rapid, large-stroke descent while ensuring descent accuracy, thus enabling accurate measurement of the liquid film thickness. Preferably, in this invention, a salt spray testing device for metal parts is provided, with a horizontal plate arranged horizontally, a protrusion fixedly connected to one side of the top plate, a stop block fixedly connected to the horizontal plate near the pivot point of the horizontal plate, and a pressure sensor installed between the stop block and the protrusion. The distance from the end of the horizontal plate to the pivot point of the horizontal plate is 100-300 times the distance from the top of the stop block to the pivot point of the horizontal plate, thereby amplifying slight changes in the weight of the absorbent component and making it more sensitive.

[0010] In this invention, since the water-absorbing component accounts for a small proportion of the total weight of the measurement system, the weight change of the entire system is not significant after the water-absorbing component absorbs water. This invention places the pressure sensor on the side with the shorter lever arm and the lower probe on the side with the longer lever arm, thereby realizing the torque amplification effect of the lever and ensuring that the pressure sensor can sensitively detect the weight change.

[0011] As a preferred embodiment of the salt spray testing device for metal parts according to the present invention, a stepper motor is fixedly connected to the top of the mother plate, and a precision screw is fixedly connected to the end of the main shaft of the stepper motor. The precision screw is rotatably connected to the inner side of the mother plate, and the inner side of the slider is helically connected to the outer side of the precision screw. The large stroke descent of the lower probe is achieved by the rotation of the stepper motor. A rotation sensor is provided on the shaft of the stepper motor, and the descent distance of the slide is obtained by the number of rotations of the stepper motor.

[0012] The stepper motor is used to achieve the first large-stroke descent, so that the lower probe reaches near the upper side of the liquid film; As a preferred embodiment of the salt spray testing device for metal parts according to the present invention, the pitch of the precision screw is 0.5mm, which ensures the descent accuracy of the lower probe while guaranteeing a large stroke descent.

[0013] The rotation unit of a stepper motor is half a revolution. For every half revolution of the stepper motor, the slide descends by 0.25mm. The descending distance of the slide is: the number of half revolutions multiplied by 0.25mm. Preferably, in a salt spray testing device for metal parts according to the present invention, a limiting rod is fixedly connected to the inner side of the slide, the outer side of the limiting rod is slidably connected to the inner side of the slide plate, a spring is provided on the outer side of the limiting rod, the two ends of the spring are fixedly connected to the inner side of the bottom end of the slide and the bottom end of the slide plate, a capacitive displacement sensor is fixedly connected to the inner side of the bottom end of the slide, and the bottom end of the slide plate is fixedly connected to the detection end of the capacitive displacement sensor, thereby realizing micron-level detection of the slide plate position movement through the capacitive displacement sensor.

[0014] When the cam rotates, it presses the slide plate down, and the spring is always in a stored state to achieve the lower limit of the slide plate; Preferably, in the salt spray testing device for metal parts according to the present invention, the detection stroke of the capacitive displacement sensor is 0.25 mm.

[0015] As a preferred embodiment of the salt spray testing device for metal parts according to the present invention, a cam is rotatably connected to the inner side of the top of the slide block, and the bottom end of the cam is slidably connected to the top of the slide block, so that the slide block can be lowered at a low stroke by rotating the cam.

[0016] As a preferred embodiment of the salt spray testing device for metal parts according to the present invention, a worm gear is rotatably connected to the inner side of the slide, the worm gear is coaxial with the cam, a geared motor is fixedly connected to the top of the slide, a worm is fixedly connected to the end of the main shaft of the geared motor, the worm meshes with the worm gear, and the rotation of the cam is realized by the rotation of the geared motor.

[0017] Under the above settings, when the probe descends for the second time, it is driven by a geared motor. The capacitive displacement sensor has a small detection stroke but high accuracy, which is existing technology and will not be elaborated on here. The detection stroke of the capacitive displacement sensor is 0.25mm, which, in conjunction with the descent method of the precision screw, achieves a micron-level descent. In order to ensure the stability of the slide's descent, the rotation of the cam in this invention is achieved by the geared motor driving the worm gear. This setting can provide sufficient speed redundancy, prevent the slide from descending excessively, and provide sufficient detection time for the detection system.

[0018] A salt spray test method for metal parts, comprising the following steps: Step 1: Open the chamber door, place the metal parts to be tested inside the salt spray test chamber, and then close the door; Step 2: Open the cover and use a laser rangefinder to obtain the surface height of the metal parts at a fixed height. Because the accuracy of the laser rangefinder cannot reach the micrometer level, the surface height of the metal parts obtained by the laser rangefinder can only be used as a reference for the first descent of the first-generation lower probe. Step 3: The sprayer operates to generate salt mist for a simulated test; Step 4: As the liquid film forms, its thickness is measured. Based on the insufficient accuracy of the metal component surface height obtained in Step 2, and assuming an upper limit for the laser rangefinder's error on the metal component surface height, the liquid film thickness is set at 110 μm. The lower probe is lowered for the first time, and the stepper motor operates, causing the slide to descend with a large stroke, lowering the suction component to the set height. The set height is: the upper limit of the laser rangefinder's error on the metal component surface height plus the set liquid film thickness of 110 μm, ultimately positioning the suction component near the top surface of the liquid film. If the pressure sensor reading suddenly increases during the first descent, it is determined that the liquid film thickness exceeds the high-efficiency corrosion thickness, and the sprayer power is reduced in subsequent operations. Step 5: The geared motor operates and the lower probe is precisely lowered according to the reading of the capacitive displacement sensor. As the descent proceeds, when the water suction component touches the liquid film, it quickly absorbs water under the action of capillary action. The pressure sensor can detect the first sudden change in the weight of the lower probe and record the descent distance d1 at this time. When the water suction component continues to descend and touches the surface of the metal parts, the weight of the lower probe is supported by the surface of the metal parts. The pressure sensor detects the second sudden change in the weight of the lower probe. If the suction element fails to contact the liquid film during the second descent, reset the slide plate, then rotate the precision screw half a turn again, and perform a second descent. Repeat this cycle until the thickness of the liquid film is detected. The total descent distance of the liquid film thickness detection mechanism is the sum of the descent distance of the slider and the descent distance of the slide plate; Record the descent distance d2 at this time, and the liquid film thickness is the absolute value of d2-d1, so as to avoid interference from condensation and fog detection and achieve uninterrupted detection during the salt spray test.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a salt spray testing device for metal parts, offering a relatively stable liquid film measurement method in high-salt and high-humidity environments without shutdown. It is unaffected by condensation and fog, avoiding the drawbacks of existing technologies using conductivity probes and optical thickness measurement methods. When the absorbent component touches the liquid film, it rapidly absorbs water due to capillary action. The pressure sensor detects the first rapid change in the weight of the lower probe. As the absorbent component continues to descend and touches the surface of the metal part, the weight of the lower probe is supported by the surface of the metal part, and the pressure sensor detects a second rapid change in the weight of the lower probe. This weight change of the absorbent component is amplified by the sliding component and detected by the pressure sensor, thus achieving liquid film thickness detection. Because capillary action occurs between the solid and liquid phases, it avoids interference from condensation and fog detection, enabling continuous testing during the salt spray test.

[0020] 2. This invention provides a salt spray testing device for metal parts. It offers excellent economic benefits. The detection end that comes into contact with the salt spray is only a water-absorbing component, which is inexpensive, replaceable, and not subject to corrosion by the salt spray. The lower probe can be made of corrosion-resistant, non-conductive glass. Compared to conductive detection using electrode sheets, which is susceptible to corrosion by the salt spray, and optical detection, which is expensive, this invention effectively reduces testing costs and subsequent maintenance costs.

[0021] 3. In this salt spray test device for metal parts, the descent accuracy of the sliding component determines the detection accuracy of the liquid film thickness. The sliding component in this invention can achieve a micron-level descent, and because the descent rate is graded, it can achieve rapid large-stroke descent while ensuring descent accuracy, thus enabling accurate measurement of the liquid film thickness.

[0022] 4. In this invention, a salt spray test device for metal parts is provided. Since the weight of the water-absorbing component in the entire measurement system is not large, the weight change in the entire system is not significant after the water-absorbing component absorbs water. The invention places the pressure sensor on the side with the shorter lever arm and the lower probe on the side with the larger lever arm, thereby realizing the torque amplification effect of the lever and ensuring that the pressure sensor can sensitively detect the weight change.

[0023] 5. In this salt spray testing device for metal parts, the second descent of the lower probe is driven by a geared motor. The capacitive displacement sensor has a small detection stroke but high accuracy. The detection stroke of the capacitive displacement sensor is 0.25mm. In conjunction with the descent method of the precision screw, a micron-level descent is achieved. To ensure the stability of the slide plate descent, the rotation of the cam in this invention is achieved by the geared motor driving the worm gear. This setting can provide sufficient speed redundancy, prevent the slide plate from descending excessively, and provide sufficient detection time for the detection system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the liquid film thickness detection mechanism of the present invention; Figure 2 This is a cross-sectional view of the liquid film thickness detection mechanism of the present invention. Figure 3 For the present invention Figure 2 A magnified structural diagram at point A; Figure 4 For the present invention Figure 2 A magnified structural diagram at point B; Figure 5 This is a pressure sensor diagram showing the pressure changes when the probe of the present invention contacts the liquid film surface and the surface of the metal parts during the descent process; Figure 6 This is a schematic diagram of the external structure of the cam in this invention; Figure 7 This is a schematic diagram of the connection structure of the worm gear and worm shaft in this invention; Figure 8 This is a schematic diagram of the external structure of the liquid film thickness detection mechanism and the salt spray test chamber of the present invention; Figure 9 This is a cross-sectional structural diagram of the liquid film thickness detection mechanism and the salt spray test chamber of the present invention.

[0025] In the diagram: 1. Mother plate; 2. Stepper motor; 3. Slide; 4. Gear motor; 5. Cam; 6. Slide plate; 7. Top plate; 8. Protrusion; 9. Pressure sensor; 10. Stop block; 11. Horizontal plate; 12. Locking part; 13. Lower probe rod; 14. Water suction part; 15. Slider; 16. Precision screw; 17. Limiting rod; 18. Spring; 19. Capacitive displacement sensor; 20. Worm gear; 21. Worm wheel; 22. Salt spray test chamber; 23. Turning cover; 24. Chamber door; 25. Sprayer; 26. Metal parts; 27. Liquid film; Figure 5 In this context, d represents the descent distance, and p represents the pressure from the pressure sensor. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figures 1-9 The present invention provides a technical solution: a salt spray test device for metal parts, including a salt spray test chamber 22 with a door 24, a liquid film thickness detection mechanism fixedly connected to the top of the salt spray test chamber 22, and a sprayer 25 fixedly connected inside the salt spray test chamber 22. When the liquid film 27 on the surface of the metal parts 26 inside the salt spray test chamber 22 is not at the high-efficiency corrosion thickness, the spraying power of the sprayer 25 is adjusted so that the thickness of the liquid film 27 is adjusted to the high-efficiency corrosion thickness. The liquid film thickness detection mechanism includes a lower probe 13 and a sliding assembly supporting the lower probe 13. A pressure sensor 9 for detecting the weight of the lower probe 13 is installed on the sliding assembly. A rotating cover 23 is rotatably connected to the top of the salt spray test chamber 22. After the rotating cover 23 is rotated open, the lower probe 13 can extend downward into the inside of the salt spray test chamber 22. A water-absorbing component 14 is detachably connected to the bottom of the lower probe 13 by magnetic attraction or threaded connection. The water-absorbing component 14 includes an outer shell and an inner water-absorbing cotton. The bottom of the shell and the bottom of the water-absorbing cotton are flush. This invention provides a relatively stable liquid film measurement method in high-salt and high-humidity environments without shutdown. It is unaffected by condensation and fog, avoiding the drawbacks of existing technologies using conductivity probes and optical thickness measurement methods. When the water-absorbing component 14 touches the liquid film 27, it rapidly absorbs water under capillary action. The pressure sensor 9 can detect the first rapid change in the weight of the lower probe 13. When the water-absorbing component 14 continues to descend and touches the surface of the metal component 26, the weight of the lower probe 13 is supported by the surface of the metal component 26. The pressure sensor 9 detects a second change in the weight of the lower probe 13. The weight change of the water-absorbing component 14 is amplified by the sliding component and detected by the pressure sensor 9, thus realizing the detection of the thickness of the liquid film 27. Because the capillary action occurs between the solid and liquid phases, it avoids interference from condensation and fog detection, enabling continuous detection during the salt spray test.

[0028] This invention offers excellent economic benefits. The detection end that comes into contact with salt spray is only the water-absorbing element 14, which is inexpensive, replaceable, and not subject to salt spray corrosion. The lower probe 13 can be made of corrosion-resistant, non-conductive glass. Compared to the conductive detection of electrode sheets, which is susceptible to salt spray corrosion, and the expensive cost of optical detection, this invention effectively reduces detection costs and subsequent maintenance costs.

[0029] Specifically, the sliding assembly includes a mother plate 1, which is fixed to the top of the salt spray test chamber 22. A slider 15 is slidably connected to the inner side of the mother plate 1. A slide block 3 is fixedly connected to one side of the slider 15. A slide plate 6 is slidably connected to the inner side of the slide block 3. A top plate 7 is fixedly connected to the top of the slide plate 6. A horizontal plate 11 is rotatably connected to the top of the top plate 7 via a rotating shaft. The inner side of the other end of the horizontal plate 11 is slidably connected to the outer side of the lower probe rod 13. A locking part 12 is fixedly connected to the top of the lower probe rod 13. The locking part 12 abuts against the top surface of the horizontal plate 11. The locking part 12 and the horizontal plate 11 have a magnetic attraction structure.

[0030] The descent accuracy of the sliding component determines the detection accuracy of the liquid film thickness in this invention. The sliding component in this invention can achieve a micron-level descent, and because the descent rate is graded, it can achieve a fast, large-stroke descent while ensuring descent accuracy, thus enabling accurate measurement of the liquid film thickness. Specifically, the horizontal plate 11 is set horizontally, and a protrusion 8 is fixedly connected to one side of the top plate 7. A stop block 10 is fixedly connected to the horizontal plate 11 near the pivot of the horizontal plate 11. A pressure sensor 9 is installed between the stop block 10 and the protrusion 8. The distance from the end of the horizontal plate 11 to the pivot of the horizontal plate 11 is 100-300 times the distance from the top of the stop block 10 to the pivot of the horizontal plate 11, so that slight changes in the weight of the water-absorbing component 14 are amplified and become sensitive.

[0031] In this invention, since the water-absorbing component 14 accounts for a small proportion of the total weight of the measurement system, the weight change of the entire system is not significant after the water-absorbing component 14 absorbs water. This invention places the pressure sensor 9 on the side with the shorter lever arm and the lower probe 13 on the side with the longer lever arm, thereby achieving the torque amplification effect of the lever and ensuring that the pressure sensor 9 can sensitively detect the weight change.

[0032] Specifically, a stepper motor 2 is fixedly connected to the top of the mother plate 1, and a precision screw 16 is fixedly connected to the end of the main shaft of the stepper motor 2. The precision screw 16 is rotatably connected to the inner side of the mother plate 1, and the inner side of the slider 15 is helically connected to the outer side of the precision screw 16. The large stroke descent of the lower probe 13 is achieved by the rotation of the stepper motor 2. A rotation sensor is provided on the shaft of the stepper motor 2, and the descent distance of the slide block 3 is obtained by the number of rotations of the stepper motor 2.

[0033] The stepper motor is used to achieve the first large stroke descent, so that the lower probe 13 reaches the vicinity of the upper side of the liquid film 27; Specifically, the pitch of the precision screw 16 is 0.5mm, which ensures the descent accuracy of the lower probe 13 while guaranteeing a large stroke descent.

[0034] The rotation unit of stepper motor 2 is half a revolution. For every half revolution of stepper motor 2, slide 3 descends by 0.25mm. The descending distance of slide 3 is: the number of half revolutions multiplied by 0.25mm. Specifically, a limiting rod 17 is fixedly connected to the inner side of the slide block 3, and the outer side of the limiting rod 17 is slidably connected to the inner side of the slide plate 6. A spring 18 is provided on the outer side of the limiting rod 17, and the two ends of the spring 18 are fixedly connected to the inner side of the bottom end of the slide block 3 and the bottom end of the slide plate 6. A capacitive displacement sensor 19 is fixedly connected to the inner side of the bottom end of the slide block 3, and the bottom end of the slide plate 6 is fixedly connected to the detection end of the capacitive displacement sensor 19. The micron-level detection of the position movement of the slide plate 6 is achieved through the capacitive displacement sensor 19.

[0035] When the cam 5 rotates, it presses the slide plate 6 down, and the spring 18 is always in a stored state, thus achieving the lower limit of the slide plate 6; Specifically, the detection stroke of the capacitive displacement sensor 19 is 0.25 mm.

[0036] Specifically, a cam 5 is rotatably connected to the inner side of the top of the slide block 3. The bottom end of the cam 5 is slidably connected to the top of the slide plate 6. The slide plate 6 is lowered by a low stroke through the rotation of the cam 5.

[0037] Specifically, a worm gear 21 is rotatably connected to the inner side of the slide block 3. The worm gear 21 is coaxial with the cam 5. A geared motor 4 is fixedly connected to the top of the slide block 3. A worm 20 is fixedly connected to the end of the main shaft of the geared motor 4. The worm 20 meshes with the worm gear 21. The rotation of the cam 5 is achieved by the rotation of the geared motor 4.

[0038] Under the above settings, when the lower probe 13 descends for the second time, it is driven by a geared motor. The capacitive displacement sensor 19 has a small detection stroke but high accuracy, which is existing technology and will not be elaborated further here. The detection stroke of the capacitive displacement sensor 19 is 0.25mm, which, in conjunction with the descent method of the precision screw 16, achieves a micron-level descent. In order to ensure the stability of the slide plate 6 descent, the rotation of the cam 5 of this invention is achieved by the geared motor 4 driving the worm gear. This setting can provide sufficient speed redundancy to prevent the slide plate 6 from descending excessively and to provide sufficient detection time for the detection system.

[0039] This invention also discloses a salt spray test method for metal parts, the steps of which are: Step 1: Open the chamber door 24, place the metal parts 26 to be tested inside the salt spray test chamber 22 and then close it; Step 2: Open the rotating cover 23 and use a laser rangefinder to obtain the surface height of the metal part 26 at a fixed height. Because the accuracy of the laser rangefinder cannot reach the micrometer level, the surface height of the metal part obtained by the laser rangefinder can only be used as a reference for the first descent of the first-generation lower probe 13. Step 3: Sprayer 25 operates to generate salt mist for a simulation test; Step 4: As the liquid film 27 forms, its thickness is measured. Based on the insufficient accuracy of the surface height of the metal component 26 obtained in Step 2, and assuming an upper limit for the laser rangefinder's error on the surface height of the metal component 26, the liquid film thickness is set at 110 μm. The lower probe 13 is lowered for the first time, and the stepper motor 2 operates, causing the slide 3 to descend with a large stroke, lowering the water-absorbing component 14 to the set height. The set height is: the upper limit of the laser rangefinder's error on the surface height of the metal component 26 plus the set liquid film thickness of 110 μm. Finally, the water-absorbing component 14 is positioned near the top surface of the liquid film 27. If the reading of the pressure sensor 9 suddenly increases during the first descent, it is determined that the liquid film thickness exceeds the high-efficiency corrosion thickness, and the power of the sprayer 25 is reduced in subsequent operations. Step 5: The reduction motor 4 operates and, with reference to the reading of the capacitive displacement sensor 19, precisely lowers the probe rod 13. As the descent continues, when the water-absorbing component 14 touches the liquid film 27, it rapidly absorbs water under the action of capillary action. The pressure sensor 9 can detect the first sudden change in the weight of the probe rod 13 and records the descent distance d1 at this time. When the water-absorbing component 14 continues to descend and touches the surface of the metal component 26, the weight of the probe rod 13 is now supported by the surface of the metal component 26. The pressure sensor 9 detects the second sudden change in the weight of the probe rod 13. If the suction element 14 fails to contact the liquid film 27 during the second descent, the slide plate 6 is reset, and then the precision screw 16 is rotated half a turn again for a second descent. This cycle is repeated until the thickness of the liquid film 27 is detected. The overall descent distance of the liquid film thickness detection mechanism is the sum of the descent distance of slider 15 and the descent distance of slide plate 6; Record the descent distance d2 at this time, and the liquid film thickness is the absolute value of d2-d1, so as to avoid interference from condensation and fog detection and achieve uninterrupted detection during the salt spray test.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A salt spray test device for metal parts, comprising a salt spray test chamber (22) with a chamber door (24), characterized in that: The top end of the salt spray test box (22) is fixedly connected with a liquid film thickness detection mechanism, the inside of the salt spray test box (22) is fixedly connected with a sprayer (25), when the liquid film (27) on the surface of the metal part (26) in the salt spray test box (22) is not at the efficient corrosion thickness, the spray power of the sprayer (25) is adjusted, and the thickness of the liquid film (27) is adjusted to the efficient corrosion thickness; The liquid film thickness detection mechanism comprises a down rod (13) and a sliding assembly supporting the down rod (13), the sliding assembly is provided with a pressure sensor (9) for detecting the weight of the down rod (13), the top end of the salt spray test box (22) is rotatably connected with a rotating cover (23), after the rotating cover (23) is rotated and opened, the down rod (13) can be deeply inserted into the inside of the salt spray test box (22), the bottom end of the down rod (13) is detachably connected with a water absorbing part (14) through magnetic attraction or threaded connection, when the water absorbing part (14) touches the liquid film (27) downwards, the water absorbing part (14) rapidly absorbs water under the action of capillary phenomenon, the pressure sensor (9) can detect that the weight of the down rod (13) rapidly changes for the first time, when the water absorbing part (14) continues to touch the surface of the metal part (26) downwards, the weight of the down rod (13) is supported by the surface of the metal part (26), the pressure sensor (9) detects that the weight of the down rod (13) changes for the second time, the weight change of the water absorbing part (14) is amplified through the sliding assembly and then detected by the pressure sensor (9), the thickness of the liquid film (27) is detected, so that the detection interference of condensation and mist is avoided, and non-stop detection during the salt spray test process is realized.

2. A salt spray testing apparatus for metal parts as claimed in claim 1 wherein: The sliding assembly comprises a mother plate (1), the mother plate (1) is fixed at the top end of the salt spray test box (22), the inside of the mother plate (1) is slidably connected with a sliding block (15), one side of the sliding block (15) is fixedly connected with a sliding seat (3), the inside of the sliding seat (3) is slidably connected with a sliding plate (6), the top end of the sliding plate (6) is fixedly connected with a top plate (7), the top end of the top plate (7) is rotatably connected with a horizontal plate (11) through a rotating shaft, the inside of the other end of the horizontal plate (11) is slidably connected with the outside of a down rod (13), the top end of the down rod (13) is fixedly connected with a clamping part (12), and the clamping part (12) abuts against the top surface of the horizontal plate (11).

3. A salt spray testing apparatus for metal parts as claimed in claim 2 wherein: The horizontal plate (11) is horizontally arranged, one side of the top plate (7) is fixedly connected with a protruding part (8), the position of the horizontal plate (11) close to the rotating shaft of the horizontal plate (11) is fixedly connected with an abutting block (10), the pressure sensor (9) is mounted between the abutting block (10) and the protruding part (8), and the distance from the end of the horizontal plate (11) to the rotating shaft of the horizontal plate (11) is 100-300 times the distance from the top end of the abutting block (10) to the rotating shaft of the horizontal plate (11), so that the slight change of the weight of the water absorbing part (14) is amplified and becomes sensitive.

4. A salt spray testing apparatus for metal parts as claimed in claim 2 wherein: The top end of the mother plate (1) is fixedly connected with a stepping motor (2), the main shaft end of the stepping motor (2) is fixedly connected with a precision screw rod (16), the precision screw rod (16) is rotatably connected to the inner side of the mother plate (1), the inner side of the sliding block (15) is screw-connected with the outer side of the precision screw rod (16), and the large-stroke descent of the down rod (13) is realized through the rotation of the stepping motor (2).

5. A salt spray testing apparatus for metal parts as claimed in claim 4 wherein: The pitch of the precision screw rod (16) is 0.5 mm, which ensures the large-stroke descent and the descending precision of the down rod (13).

6. A salt spray testing apparatus for metal parts as claimed in claim 4 wherein: The inner side of the sliding seat (3) is fixedly connected with a limiting rod (17), the outer side of the limiting rod (17) is slidingly connected with the inner side of the sliding plate (6), the outer side of the limiting rod (17) is provided with a spring (18), the two ends of the spring (18) are fixedly connected with the inner side of the bottom end of the sliding seat (3) and the bottom end of the sliding plate (6), the inner side of the bottom end of the sliding seat (3) is fixedly connected with a capacitive displacement sensor (19), and the bottom end of the sliding plate (6) is fixedly connected with the detection end of the capacitive displacement sensor (19). The micron-level detection of the position movement of the sliding plate (6) is realized through the capacitive displacement sensor (19).

7. A salt spray testing apparatus for metal parts as claimed in claim 6 wherein: The detection stroke of the capacitive displacement sensor (19) is 0.25 mm.

8. A salt spray testing apparatus for metal parts as claimed in claim 6 wherein: The inner side of the top end of the sliding seat (3) is rotatably connected with a cam (5), the bottom end of the cam (5) is slidingly connected with the top end of the sliding plate (6), and the low-stroke descent of the sliding plate (6) is realized through the rotation of the cam (5).

9. A salt spray testing apparatus for metal parts as claimed in claim 8, wherein: The inner side of the sliding seat (3) is rotatably connected with a worm wheel (21), the worm wheel (21) is coaxial with the cam (5), the top end of the sliding seat (3) is fixedly connected with a speed reducer motor (4), the main shaft end of the speed reducer motor (4) is fixedly connected with a worm (20), the worm (20) is engaged with the worm wheel (21), and the rotation of the cam (5) is realized through the rotation of the speed reducer motor (4).

10. A salt spray test method for metal parts using the salt spray test device according to claim 9, characterized by, The steps are as follows: Step one: open the box door (24), put the metal parts (26) to be tested into the inner side of the salt spray test box (22) and close it; Step two: open the rotating cover (23), and use a laser range finder to obtain the surface height of the metal parts (26); Step three: the sprayer (25) works to generate salt-containing mist for simulation test; Step four: with the formation of the liquid film (27), the thickness of the liquid film (27) is detected, based on the surface height of the metal parts (26) with insufficient accuracy obtained in step two, assuming a surface height of the metal parts (26) with an error upper limit, the liquid film thickness is set to 110 μm, the down rod (13) is lowered for the first time, the stepping motor (2) works, the sliding seat (3) is lowered for a large stroke, and finally the water absorption part (14) is near the top surface of the liquid film (27). Step five; the deceleration motor (4) works, and the reading of the capacitive displacement sensor (19) is referred to for the accurate lowering of the probe rod (13), and as the lowering proceeds, when the water absorption part (14) touches the liquid film (27) downward, it rapidly absorbs water under the action of capillary phenomenon, the pressure sensor (9) can detect the first mutation of the weight of the probe rod (13), and record the lowering distance d1 at this time, and when the water absorption part (14) continues to touch the surface of the metal part (26), the weight of the probe rod (13) is supported by the surface of the metal part (26), the pressure sensor (9) detects the second mutation of the weight of the probe rod (13), and records the lowering distance d2 at this time, and the thickness of the liquid film is the absolute value of d2-d1, thereby avoiding the detection interference of condensation and mist, and realizing the non-stop detection in the salt spray test process.

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