Ferromagnetic metal corrosion test piece non-contact fixing device

Abstract

The invention belongs to the technical field of material corrosion testing, and particularly relates to a ferromagnetic metal corrosion test piece non-contact fixing device which mainly structurally comprises main magnet units arranged on the upper side and the lower side of a test piece, auxiliary magnet units arranged at the corners of the main magnet units and a laser displacement sensor arranged at the upper auxiliary magnet unit. The main magnet unit provides basic electromagnetic suspension force and balances the gravity of a test piece, the laser displacement sensor, the power amplifier and the PID controller are matched, and the auxiliary magnet unit performs electromagnetic force compensation and performs real-time fine adjustment on the position of the test piece, so that the test piece is kept in a stable suspension state; controllable electromagnetic force is applied to a ferromagnetic metal test piece through an electromagnet, so that the test piece is kept in a non-contact stable suspension state in a corrosion environment, the problems of galvanic corrosion, crevice corrosion and other abnormal local corrosion caused by a contact fixing mode are avoided, and the accuracy of material corrosion rate measurement is improved; the system has the advantages of high control precision, low power consumption and high environmental applicability.

Description

Technical field:

[0001] The present invention belongs to the technical field of material corrosion testing, and in particular relates to a device for non-contact fixing of ferromagnetic metal corrosion test pieces through active magnetic levitation technology, so as to simulate a gas phase environment or a liquid phase environment in a laboratory. Background technology:

[0002] Fixing metal corrosion test specimens is a core component of industrial corrosion monitoring and material performance evaluation. Conventional methods currently employ mechanical fixtures or brackets to secure test specimens within industrial equipment or laboratory testing devices using non-metallic screws, coated steel bolts, non-metallic hangers, or specialized brackets. These include the salt spray test specimen brackets and insulation material hangers specified in GB / T 10125, the glass brackets or hooks for full immersion testing specified in JB / T 7901, and the disc-type specimen clamps specified in NACE SP0775-2013. For example, Chinese patent 202221018634.6 discloses a glass container for a full immersion test of uniform corrosion of metal materials, which consists of six parts: a condenser, a glass cover, a cylindrical glass liner, a cylindrical glass bottle, a thermometer and a glass stopper. The condenser, the glass cover, the cylindrical glass liner and the cylindrical glass bottle are connected from top to bottom; the lower end of the condenser contains a rubber stopper 1, and the thermometer is inserted into the rubber stopper 2; the outer wall edges of both sides of the glass stopper are rough, and the lower end contains a glass hook for hanging a stainless steel sheet to prevent the stainless steel sheet from contacting the inner wall of the container, and each set of glass containers for a full immersion test of uniform corrosion of metal materials contains 3 glass stoppers, the glass cover is umbrella-shaped, and there are 5 openings on the top, wherein the condenser The inner walls of the opening and the temperature control opening are smooth and are connected to rubber stopper 1 and rubber stopper 2 respectively; the inner walls of sample opening 1, sample opening 2 and sample opening 3 are rough and are connected to three glass stoppers respectively; the edge of the lower end of the glass cover is frosted and connected to the frosted mouth of the cylindrical glass bottle, the edge of the mouth of the cylindrical glass liner extends outward, and the lower end of the extended edge is a frosted layer; the inner diameter of the cylindrical glass liner is 10 cm and the height is 10 cm, the edge of the mouth of the cylindrical glass bottle extends outward, and the upper end of the extended edge is frosted and connected to the glass cover; there is a card groove on the inner wall of the cylindrical glass bottle 1 cm away from the bottle mouth, and the upper surface of the card groove is a frosted layer for fixing the cylindrical glass liner; the inner diameter of the cylindrical glass bottle is 15 cm and the height is 15 cm.Chinese Patent 202411682470.0 discloses an irregular sample fixture for salt spray test, comprising a bracket, an angle adjustment plate, at least one contoured flexible clamping seat and at least one auxiliary clamping assembly, wherein the angle adjustment plate is arranged on the bracket, the angle adjustment plate can be adjusted by flipping, a plurality of positioning holes are provided on the angle adjustment plate, the auxiliary clamping assembly comprises a clamping base, a telescopic adjustment rod and a pressing plate, the contoured flexible clamping seat and the clamping base can be connected to the angle adjustment plate through the positioning holes, a plurality of protruding elastic top columns are provided on the side of the contoured flexible clamping seat, the elastic top columns can be pressed into the contoured flexible clamping seat and have an outward rebound force, the elastic top columns are used to press against the curved surface of the sample, one end of the clamping base is provided with a clamping portion for pressing against the side of the sample, the telescopic adjustment rod is vertically connected to the clamping base, the pressing plate is connected to the upper end of the telescopic adjustment rod, one end of the pressing plate is provided with a pressing portion, the pressing portion extends to the side of the pressing plate, the pressing portion is used to press on the top of the sample, the pressing portion The cam is provided with a plurality of support members, each of which is provided with a plurality of support members, and the support members are provided with a plurality of support members, each of which is provided with a plurality of support members.Chinese Patent 202420164989.9 discloses a tool for salt spray test, comprising a sample mounting plate, a first angle disk and a fixed plate parallel to the first angle disk; a channel for the sample mounting plate to pass through is provided between the first angle disk and the fixed plate; the test tool also comprises a rotating assembly for driving the sample mounting plate to rotate axially in the channel, and a positioning assembly for fixing the sample mounting plate at any angle of the first angle disk, the fixed plate is a second angle disk, and the first angle disk and the fixed plate are provided with arc-shaped guide grooves respectively; the two arc-shaped guide grooves are provided with a plurality of positioning holes for the connecting rod to pass through along their length directions; the connecting rod and the arc-shaped guide groove are both located on the rotation trajectory of the sample mounting plate; the arc-shaped guide groove and the connecting rod constitute a positioning assembly; the plurality of positioning holes on the first angle disk correspond to different scale values respectively; the two opposite positioning holes constitute a group of positioning hole units; the connecting rod is fixed in any positioning hole unit, the connecting rod is a cylindrical structure, and the positioning hole is circular; the connecting rod The outer surface of the cam is provided with an external thread; the inner wall of the positioning hole is provided with an internal thread threadedly connected to the external thread, and the connecting rod is a flat rod-shaped structure; the positioning hole is a rectangular structure adapted to the cross-section of the connecting rod; the positioning hole is arranged vertically with the arc guide groove; the connecting rod is interference-connected with the positioning hole, and the tooling also includes a base plate; the first angle disk and the fixed plate are both placed sideways on the base plate; the sample mounting plate is rotatably connected to the base plate through a rotating assembly, and the rotating assembly includes a rotating shaft perpendicular to the first angle disk or the fixed plate, and a bearing sleeved on the rotating shaft; the inner ring of the bearing is fixedly connected to the rotating shaft, and the outer ring of the bearing is fixedly installed on the base plate, and both sides of the sample mounting plate facing the rotating assembly are provided with outwardly extending connecting parts; the two connecting parts are respectively fixedly connected to the two ends of the rotating shaft, and the sample mounting plate is fixedly installed on the surface of the side facing away from the connecting rod; the lower end face of the sample is flush with the lower surface of the sample mounting plate, and the rotation angle range of the sample mounting plate is 0°-180°. However, the above-mentioned contact fixation has the following significant problems: (1) When metal fixings are used, the pre-applied anti-corrosion insulation coating may fail in a long-term harsh corrosive environment, causing the contact area between the fixing (such as bolts) and the test piece to be exposed to the corrosive environment, thereby causing galvanic corrosion; (2) Whether it is non-metallic or metallic material, it is inevitable that a gap will form between the mechanical clamping support point or fixture and the contact surface of the test piece, resulting in crevice corrosion, which makes the corrosion rate test value of corrosion-resistant metal materials such as stainless steel too large; (3) Bolt fixing or hanging methods often require drilling fixing holes or hanging holes on the specimen, which destroys the structural integrity of the specimen and increases the edge effect of corrosion; (4) Bolts, brackets and other fixings are difficult to make flush with the surface of the specimen. Especially in fluid corrosion tests, the sudden change in the geometric structure of the fixing will cause turbulence and other flow changes, which promotes the occurrence of local corrosion.

[0003] Active magnetic levitation technology utilizes controllable electromagnetic forces to generate attractive or repulsive forces by real-time adjustment of the current in an electromagnet, enabling objects to levitate stably without contact. This technology offers advantages such as zero friction, zero wear, high rigidity, and high precision. It is widely used in power generation, petroleum refining, and high-speed rotating machinery, and is particularly well-suited for highly corrosive environments such as high temperature, high pressure, humidity, and salt spray. Therefore, the development and design of a non-contact fixture for ferromagnetic metal corrosion specimens ensures accurate corrosion rate measurements and avoids distortion of corrosion test data, demonstrating positive social and economic benefits. Summary of the invention:

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and seek to design a non-contact fixing device for ferromagnetic metal corrosion test pieces to provide technical support for the evaluation of the corrosion resistance of materials in gas or liquid environments.

[0005] In order to achieve the above-mentioned purpose, the main structure of the non-contact fixing device for ferromagnetic metal corrosion test strips involved in the present invention includes main magnet units arranged on the upper and lower sides of the test strip, auxiliary magnet units arranged at the corners of the main magnet units, and a laser displacement sensor arranged at the upper auxiliary magnet units. The main magnet units are connected in series and connected to the power amplifier to form a closed loop so as to control the electromagnetic force as a whole. Each auxiliary magnet unit is connected to the power amplifier to form a closed loop so as to control the electromagnetic force individually and fine-tune the posture of the test strip in real time to keep it in a stable suspended state. The power amplifier is also connected to the PID controller.

[0006] The main structure of the main magnet unit of the present invention includes a plurality of cubic electromagnets connected in series to form a strip-shaped Halbach array to generate a unilateral strong magnetic field gradient. The upper main magnet unit and the lower main magnet unit are positioned relative to each other and have opposite magnetic pole directions. The number of turns of the coil of each electromagnet in the upper main magnet unit is n times the number of turns of the coil of each electromagnet in the lower main magnet unit (n>1).

[0007] The main structure of the auxiliary magnetic unit includes at least one electromagnet. The positions of the auxiliary magnetic units correspond to the four corner points of the test piece in a stable suspension state. The magnetic poles of the auxiliary magnetic units on the same side are in the same direction, while the magnetic poles of the auxiliary magnetic units on the opposite sides are in opposite directions.

[0008] Furthermore, the electromagnet is composed of a central iron core and a coil surrounding it, and is encapsulated in a slot in a shell of an inert material (such as PTFE). It is protected from corrosion by the test environment without affecting the electromagnetic force. The slot is used to fix and separate the electromagnets. The number of electromagnets in the main magnet unit is greater than or equal to 1, and is adjusted according to the size of the test piece. The number of electromagnets in the auxiliary magnet unit is 1.

[0009] When the non-contact fixing device for ferromagnetic metal corrosion test pieces according to the present invention is used:

[0010] When the coil is energized, the main magnet unit generates a net upward magnetic force on the test piece. By adjusting the current, the electromagnetic force of the main magnet unit is gradually increased to balance the gravity of the test piece and make it levitate.

[0011] The laser displacement sensor measures the distance between the corner point of the suspended test piece and the corresponding auxiliary magnet unit above it, records the initial position of the test piece, monitors the displacement of the test piece from the initial position, and feeds the displacement data of the test piece back to the PID controller in real time;

[0012] The PID controller calculates the distributed current value of the auxiliary magnet unit based on the displacement data of the test piece fed back by the laser displacement sensor;

[0013] The power amplifier calls the distributed current value calculated by the PID controller and applies current to the corresponding auxiliary magnet units: when the test piece translates, the compensation current of the auxiliary magnet units corresponding to the four corner points is calculated; when the test piece rotates, the differential current of the auxiliary magnet units corresponding to the diagonal points of rotation is calculated; the power amplifier calls the distributed current value calculated by the PID controller and distributes compensation current or differential current to the corresponding auxiliary magnet units, and pulls the displaced corner points of the test piece back to the initial position under the action of electromagnetic force, and fine-tunes the suspension posture of the test piece; when the test piece loses weight due to corrosion and the four auxiliary magnet units at the bottom generate compensating electromagnetic force, the PID controller calculates the distributed current value and current attenuation coefficient of the main magnet unit, and the power amplifier calls the data calculated by the PID controller, and simultaneously reduces the distributed current of the main magnet unit and the compensation current of the auxiliary magnet unit, reduces the output power, and keeps the test piece in the initial position.

[0014] Compared with the prior art, the main structure of the present invention includes main magnet units arranged on the upper and lower sides of the test piece, auxiliary magnet units arranged at the corners of the main magnet units, and a laser displacement sensor arranged at the upper auxiliary magnet unit. The main magnet unit provides basic electromagnetic suspension force to balance the gravity of the test piece. The laser displacement sensor, power amplifier and PID controller cooperate with the auxiliary magnet unit to perform electromagnetic force compensation and make real-time fine-tuning of the position of the test piece to keep it in a stable suspension state. The structure is simple, and a controllable electromagnetic force is applied to the ferromagnetic metal test piece by an electromagnet, so that the test piece maintains a non-contact stable suspension state in a corrosive environment, avoiding abnormal local corrosion problems such as galvanic corrosion and crevice corrosion caused by contact fixing methods, improving the accuracy of material corrosion rate measurement, and having the advantages of high control precision, low power consumption and strong environmental applicability. It can be used in a variety of gas or liquid phase application scenarios, and is particularly suitable for highly corrosive environments such as high temperature, high pressure, humidity and heat, and salt spray. Description of the drawings:

[0015] Figure 1It is a schematic diagram of the main structural principle of the present invention.

[0016] Figure 2 This is a schematic diagram of the magnetic pole direction of the upper main magnet unit involved in the present invention.

[0017] Figure 3 This is a schematic diagram of the magnetic pole direction of the lower main magnet unit involved in the present invention.

[0018] Figure 4 This is a schematic diagram of the magnetic pole direction of the auxiliary magnet unit involved in the present invention.

[0019] Figure 5 This is a schematic diagram of the working process of the PID controller involved in the present invention. Specific implementation method:

[0020] The present invention will be further described below through implementation examples in conjunction with the accompanying drawings.

[0021] Example 1:

[0022] The main structure of the non-contact fixing device for ferromagnetic metal corrosion test strip involved in this embodiment includes a test strip 1, a main magnet unit 2, an auxiliary magnet unit 3, a laser displacement sensor 4, a wire 5, a power amplifier 6 and a PID controller 7; main magnet units 2 (upper main magnet unit and lower main magnet unit) are provided on the upper and lower sides of the test strip 1, auxiliary magnet units 3 are provided at the corners of the two main magnet units 2, and laser displacement sensors 4 are provided at the upper four auxiliary magnet units 3. The main magnet unit 2 is connected in series with the power amplifier 6 through the wire 5 to form a closed loop, and the auxiliary magnet units 3 are respectively connected to the power amplifier 6 to form a closed loop. The power amplifier 6 is connected to the PID controller 7, wherein the wires aa, bb, cc are connected to each other, and the wires d, e, f, g, h are respectively connected to the wire j.

[0023] The main magnet unit 2 and the auxiliary magnet unit 3 involved in this embodiment have similar main structures, both including a housing 11, slots 12, and an electromagnet 15. Five slots 12 are provided inside the housing 11 of the main magnet unit 2, and one slot 12 is provided inside the housing 11 of the auxiliary magnet unit 3. An electromagnet 15 consisting of an iron core 13 and a coil 14 is placed in the slot 12, and each slot 12 corresponds to the electromagnet 15 one-to-one.

[0024] The non-contact fixing device for a ferromagnetic metal corrosion test piece involved in this embodiment fixes a rectangular test piece 1 made of ordinary carbon steel Q235 to perform a corrosion test;

[0025] Place the test piece 1 horizontally between the upper and lower main magnet units 2. Apply current through the power amplifier 6, causing the main magnet unit 2 to generate a net upward magnetic force on the test piece 1. Gradually increase the input current until the net magnetic force balances the weight of the test piece 1, causing it to levitate. Use the laser displacement sensor 4 to record the initial position of the four corner points of the test piece 1, that is, the distance between each corner point of the test piece 1 and the auxiliary magnet unit 3 on the same side of the upper main magnet unit 2.

[0026] Adjust the simulated environmental parameters and start the simulated environmental corrosion test;

[0027] The position deviation of the test piece 1 is monitored by the laser displacement sensor 4. When the test piece 1 deviates from the initial position due to geometric changes caused by corrosion or impact of the test environment, such as translation or rotation, the laser displacement sensor 4 feeds back the monitored displacement data to the PID controller 7.

[0028] The PID controller 7 calculates the current distribution scheme based on the displacement data of the test piece 1 fed back by the laser displacement sensor 6: when the test piece 1 is translated, the compensation current of the auxiliary magnet unit 3 corresponding to the four corner points is calculated; when the test piece 1 is rotated, the differential current of the auxiliary magnet unit 3 corresponding to the rotating diagonal point is calculated;

[0029] The power amplifier 6 calls the distributed current value calculated by the PID controller 7 to distribute the compensation current or differential current to the corresponding auxiliary magnet unit 4. Under the action of the generated electromagnetic force, the displaced corner point of the test piece 1 is pulled back to the initial position, thereby achieving fine adjustment of the suspension posture of the test piece 1;

[0030] When the test piece 1 loses weight due to corrosion, and the four auxiliary magnetic units 3 on one side of the main magnetic unit 2 below it generate a compensating electromagnetic force, the PID controller 7 calculates the distributed current value and the current attenuation coefficient of the main magnetic unit 2. The power amplifier 6 calls the data calculated by the PID controller 7 and simultaneously reduces the distributed current of the main magnetic unit 2 and the compensating current of the auxiliary magnetic units 3, thereby reducing the output power and keeping the test piece 1 in the initial position.

[0031] The size of the test piece 1 is 100 mm × 50 mm × 2 mm;

[0032] The dimensions of the main magnet unit 2 are 108 mm × 20 mm × 20 mm. The number of turns of the coil 14 of each electromagnet 15 in the upper main magnet unit 2 is twice the number of turns of the coil 14 of each electromagnet 15 in the lower main magnet unit 2. When power is supplied to the coil 14, the upper main magnet unit 2 will generate an electromagnetic force twice that of the lower main magnet unit 2. The magnetic pole directions 16 of the electromagnets 15 in the upper main magnet unit 2 are, from left to right, right, bottom, left, top, and right. The magnetic pole directions 16 of the electromagnets 15 in the lower main magnet unit 2 are, from left to right, left, bottom, right, top, and left. A strong magnetic field gradient is generated between the opposing surfaces of the two main magnet units 2. When power is supplied to the coil 14, a magnetic field in a fixed direction is generated, generating an electromagnetic attraction force on the test piece 1.

[0033] The auxiliary magnet unit 3 is a cube with a side length of 10 mm. The magnetic pole direction 16 of the auxiliary magnet unit 3 on the upper main magnet unit 2 side is downward, and the magnetic pole direction 16 of the auxiliary magnet unit 3 on the lower main magnet unit 2 side is upward.

[0034] The electromagnet 15 is a cube with a side length of 20 mm.

Claims

1. A non-contact fixing device for a ferromagnetic metal corrosion test piece, characterized in that: The main structure includes main magnet units arranged on the upper and lower sides of the test piece, auxiliary magnet units arranged at the corners of the main magnet units, the main magnet units are connected in series and connected to the power amplifier to form a closed loop, and each auxiliary magnet unit is connected to the power amplifier to form a closed loop.

2. The non-contact fixing device for a ferromagnetic metal corrosion test piece according to claim 1, characterized in that: The main structure of the main magnet unit includes several cubic electromagnets connected in series to form a strip Halbach array to generate a unilateral magnetic field gradient.

3. The non-contact fixing device for a ferromagnetic metal corrosion test piece according to claim 2, characterized in that: The main magnet units on the upper and lower sides are positioned relative to each other and have opposite magnetic pole directions.

4. The method for preparing a non-contact fixing device for a ferromagnetic metal corrosion test piece according to claim 2, characterized in that: The main structure of the auxiliary magnet unit includes at least one electromagnet.

5. The method for preparing a non-contact fixing device for a ferromagnetic metal corrosion test piece according to claim 4, characterized in that: The positions of the auxiliary magnetic units correspond to the four corner points of the test piece in a stable suspension state. The magnetic pole directions of the auxiliary magnetic units on the same side are the same, and the magnetic pole directions of the auxiliary magnetic units on the opposite sides are opposite.

6. The method for preparing a non-contact fixing device for a ferromagnetic metal corrosion test piece according to claim 4, characterized in that: The electromagnet consists of a central iron core and a coil surrounding it, which is encapsulated in a slot in an inert material shell. The slot fixes and separates the electromagnet. The number of electromagnets in the main magnet unit is greater than or equal to 1, which is adjusted according to the size of the test piece. The number of electromagnets in the auxiliary magnet unit is 1.

7. The method for preparing a non-contact fixing device for a ferromagnetic metal corrosion test piece according to claim 6, characterized in that: The number of turns of the coil of each electromagnet in the upper main magnet unit is n times the number of turns of the coil of each electromagnet in the lower main magnet unit.

8. A method for preparing a non-contact fixing device for a ferromagnetic metal corrosion test piece according to any one of claims 1 to 7, characterized in that: The laser displacement sensor and the power amplifier provided at the upper auxiliary magnet unit are connected to the PID controller.

9. The method for preparing a non-contact fixing device for a ferromagnetic metal corrosion test piece according to claim 8, characterized in that: When using: When the coil is energized, the main magnet unit generates a net upward magnetic force on the test piece. By adjusting the current, the electromagnetic force of the main magnet unit is increased to balance the gravity of the test piece and make it levitate. The laser displacement sensor measures the distance between the corner point of the suspended test piece and the corresponding auxiliary magnet unit above it, records the initial position of the test piece, monitors the displacement of the test piece from the initial position, and feeds the displacement data of the test piece back to the PID controller in real time; The PID controller calculates the distributed current value of the auxiliary magnet unit based on the displacement data of the test piece fed back by the laser displacement sensor; The power amplifier uses the distributed current value calculated by the PID controller to apply current to the corresponding auxiliary magnet units: when the test piece translates, the compensation current of the auxiliary magnet units corresponding to the four corner points is calculated; when the test piece rotates, the differential current of the auxiliary magnet units corresponding to the rotating diagonal points is calculated; the power amplifier uses the distributed current value calculated by the PID controller to distribute compensation current or differential current to the corresponding auxiliary magnet units, and under the action of electromagnetic force, the displaced corner points of the test piece are pulled back to the initial position, and the suspension posture of the test piece is fine-tuned; When the test piece loses weight due to corrosion, causing the four auxiliary magnet units at the bottom to generate compensating electromagnetic force, the PID controller calculates the distributed current value and current attenuation coefficient of the main magnet unit. The power amplifier calls the data calculated by the PID controller and simultaneously reduces the distributed current of the main magnet unit and the compensation current of the auxiliary magnet unit, reducing the output power and keeping the test piece in its initial position.

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