Micro-removal method suitable for micro-arc oxidation coating of magnesium-aluminum alloy part

Abstract

The invention relates to a trace removal method suitable for a magnesium-aluminum alloy micro-arc oxidation coating, which comprises the following steps: remaining machining allowance for the precise matching surface of a magnesium alloy part according to 0.3 mm of the end face and 0.6 mm of the diameter, and enabling other machining to meet the requirements of a drawing; the whole magnesium alloy part is subjected to micro-arc oxidation according to the standard; carrying out finish machining on the precision matching surface with the allowance by adopting a dry cutting method; wherein the size of the outer circle and the size of the plane are machined to have the median difference ranging from 0 mm to-0.02 mm, the size of the inner hole is machined to have the median difference ranging from 0 mm to + 0.02 mm, the planeness is smaller than or equal to 0.015 mm, and the cylindricity is smaller than or equal to 0.015 mm; after protection is arranged on the other surfaces, micro-arc oxidation is conducted on the machined precise matching surface, and the thickness of an oxidation layer is increased to 0.03-0.04 mm in a one-way mode; and machining the precision fit surface subjected to micro-arc oxidation by using a silicon carbide grinding wheel, so that the surface meets the precision requirement. According to the invention, high-precision matching surface controllable micro-arc oxidation modification is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of trace removal of electroplating layers, and in particular relates to a method for removing trace amounts of micro-arc oxidation coatings on magnesium-aluminum alloys. Background Art

[0002] Magnesium and magnesium alloys have the characteristics of low density and high strength. At the same time, the micro-arc oxidation surface modification technology successfully solves the poor corrosion resistance and wear resistance of magnesium alloys, making it widely used in aerospace, ship navigation, national defense weapons and other industries. However, due to the characteristics of the micro-arc oxidation electroplating layer, there are the following disadvantages:

[0003] 1. Since the thickness of the electroplating layer is affected by many complex factors such as power supply characteristics, current density, processing time, etc., and the electroplating layer has a bidirectional growth characteristic, it is difficult to control the thickness of the electroplating layer and it is difficult to meet the dimensional requirements of high-precision surfaces;

[0004] 2. The surface quality of the electroplating layer decreases with the increase of the coating thickness, and the surface roughness becomes worse with the increase of the coating thickness, which makes it impossible to ensure a thicker coating thickness while maintaining a high surface quality.

[0005] In summary, micro-arc oxidation of magnesium alloys cannot achieve controllable surface modification of magnesium alloys on mating surfaces with high roughness, and cannot meet the processing requirements of high-precision magnesium alloy parts in the current navigation field. Therefore, there is an urgent need for a method for removing a small amount of electroplated layer on the surface of magnesium alloys that can control the size of the electroplated layer and achieve a high roughness. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for removing a trace amount of micro-arc oxidation coating on magnesium-aluminum alloy.

[0007] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0008] A method for removing trace amounts of micro-arc oxidation coatings on magnesium-aluminum alloys, comprising the following steps:

[0009] Step 1: Precision fit the surface of the magnesium alloy parts to 0.3mm for the end face and 0.6mm for the diameter, leaving a machining allowance, and the rest of the machining shall meet the requirements of the drawing;

[0010] Step 2: Perform micro-arc oxidation on the entire magnesium alloy part according to the standard;

[0011] Step 3: Use dry cutting method to finish the precision matching surface with allowance; wherein, the outer circle and plane size are processed to have a mean difference of 0mm to -0.02mm, the inner hole size is processed to have a mean difference of 0mm to +0.02mm, the flatness is ≤0.015mm, and the cylindricity is ≤0.015mm;

[0012] Step 4: After setting protection for the remaining surfaces, micro-arc oxidation is performed on the processed precision matching surface, and the thickness of the oxide layer increases in one direction to 0.03-0.04mm;

[0013] Step 5: Use a silicon carbide grinding wheel to machine the precision matching surface after micro-arc oxidation to make the surface meet the precision requirements.

[0014] Furthermore, in step 4, the electrolyte for micro-arc oxidation is prepared by preparing the electrolyte with the following components per liter of solution:

[0015] Sodium silicate: 13g / L

[0016] Potassium fluoride: 12g / L

[0017] Sodium hydroxide: 4g / L

[0018] Glycerol: 15g / L

[0019] Hydrogen peroxide: 2ml / L

[0020] Triethanolamine: 15g / L

[0021] The electrical parameters for micro-arc oxidation are:

[0022] Temperature: 25℃

[0023] Pulse: 600-750Hz

[0024] Voltage: 100~150V

[0025] Current: 5-10A

[0026] Occupancy ratio: 20-30%

[0027] Processing time: 60~100min.

[0028] Moreover, in step five, the grain size of the silicon carbide grinding wheel used is 100# to 160#.

[0029] The advantages and positive effects of the present invention are:

[0030] 1. The present invention is realized by thickening the substrate coating in the early stage and removing it by mechanical processing in the later stage, which has simple steps and wide application range;

[0031] 2. The coating removal method of the present invention adopts a traditional mechanical processing method and realizes a trace amount of uniform removal of the coating by optimizing the tool and cutting parameters, thereby avoiding peeling and damage of the coating.

[0032] 3. The present invention adopts a method for micro-removal of the coating on the finely machined surface, which can achieve high-precision matching of the navigator magnesium alloy and controllable micro-arc oxidation modification of the surface. It can be used in precision machining industries such as aerospace, aviation, shipbuilding, and precision instruments, and has a very broad prospect for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a structural diagram of application example 1 of the trace removal method of the present invention;

[0034] Figure 2 is a structural diagram of application example 2 of the trace removal method of the present invention;

[0035] Figure 3 It is a structural diagram of application example 3 of the trace removal method of the present invention. DETAILED DESCRIPTION

[0036] The structure of the present invention is further described below with reference to the accompanying drawings and by way of examples. It should be noted that the present examples are descriptive rather than restrictive.

[0037] A method for removing a trace amount of micro-arc oxidation coating on magnesium-aluminum alloy parts, the invention point is that it comprises the following steps:

[0038] Step 1: According to the conventional process steps, the magnesium alloy parts are precisely matched with the surface, leaving a processing allowance of 0.3mm for the end face and 0.6mm for the diameter, and the rest of the processing meets the requirements of the drawing.

[0039] Step 2: Perform micro-arc oxidation on the entire magnesium alloy part according to the standard to ensure that all surfaces other than the precision matching surface are fully oxidized.

[0040] Step 3: Finish the precision matching surface with allowance. To ensure the quality of other oxidized surfaces, dry cutting is used for processing. The outer circle and plane dimensions are processed to a range of 0mm to -0.02mm, and the inner hole dimensions are processed to a range of 0mm to +0.02mm. The flatness is ≤0.015mm, and the cylindricity is ≤0.015mm. The purpose of finishing the precision matching surface is to achieve better shape and position accuracy through static processing before coating the precision matching surface, so as to facilitate the implementation of subsequent coating.

[0041] Step 4: Use electroplating protective peelable glue to apply protection to the remaining surfaces, and at the same time, micro-arc oxidation is performed on the processed precision matching surface to make the coating thickness reach the set value. Each liter of solution contains the following components to prepare the electrolyte:

[0042] Sodium silicate: 13g / L

[0043] Potassium fluoride: 12g / L

[0044] Sodium hydroxide: 4g / L

[0045] Glycerol: 15g / L

[0046] Hydrogen peroxide: 2ml / L

[0047] Triethanolamine: 15g / L

[0048] Micro-arc oxidation was performed with the following parameters. When the pulse, voltage and current were lower, the processing time was appropriately increased:

[0049] Temperature: 25℃

[0050] Pulse: 600-750Hz

[0051] Voltage: 100~150V

[0052] Current: 5-10A

[0053] Occupancy ratio: 20-30%

[0054] Processing time: 60-100 minutes

[0055] In the present invention, the unidirectional growth of the oxide layer thickness is preferably 0.03-0.04 mm.

[0056] The electrical parameters are as follows:

[0057] Electroplating parameters Influence pulse When the frequency is less than 600 Hz, the film forming rate gradually increases, reaches a peak at 600-750 Hz, and gradually decreases when the frequency is greater than 750 Hz. Voltage The film forming rate is low when the voltage is less than 100V, the film quality is good when the voltage is between 100 and 150V, and the film quality gradually decreases when the voltage is greater than 150V. Current <5A film forming rate is low, 5-10A rate is appropriate and film quality is good, >10A film quality gradually decreases Processing time With the above electrical parameters, the film layer is too thin for subsequent processing when the coating is less than 60 minutes; the surface quality of the coating deteriorates when the coating is more than 100 minutes.

[0058] Step 5: Use a silicon carbide grinding wheel with a grit of 100# to 160# to machine the precision matching surface after micro-arc oxidation with specific parameters to make the surface meet the accuracy requirements.

[0059] Embodiment 1:

[0060] See also Figure 1 , aluminum-magnesium alloy inner shell of a navigation instrument, The inner hole is a precision matching surface with a dimensional tolerance of 0 to +0.009 mm, a roughness of Ra0.8, and a cylindricity of 0.003 mm. The inner hole needs to be subjected to micro-arc oxidation modification treatment and precision machining to achieve a certain accuracy. The purpose of the invention is achieved through the following technical solutions:

[0061] (1) According to the conventional process steps, The inner hole allowance is 0.6mm, and the processing is In addition, the rest of the surface processing meets the requirements of the drawings;

[0062] (2) Perform micro-arc oxidation on the parts as a whole to meet the requirements of the drawings;

[0063] (3) For the remaining The inner hole is finely machined and turned by dry cutting. The inner hole size is Range, ensure the cylindricity ≤ 0.015mm.

[0064] (4) Protection All surfaces outside the inner hole are calibrated using the following parameters The inner hole is subjected to micro-arc oxidation to increase the coating inward by 0.04 mm. The inner hole size is about

[0065] Sodium silicate: 13g / L

[0066] Potassium fluoride: 12g / L

[0067] Sodium hydroxide: 4g / L

[0068] Glycerol: 15g / L

[0069] Hydrogen peroxide: 2ml / L

[0070] Triethanolamine: 15g / L

[0071] Temperature: 25℃

[0072] Pulse: 750Hz

[0073] Voltage: 130V

[0074] Current: 10A

[0075] Occupancy ratio: 30%

[0076] Processing time: 60min;

[0077] (5) Install the workpiece, protect the corresponding surface, use a 120# silicon carbide grinding wheel, and use dry cutting method to The inner hole is processed using the following cutting parameters to achieve the dimensional accuracy required by the drawing:

[0078] Grinding wheel linear speed: 1400-1600m / min

[0079] Cutting depth: 0.004mm;

[0080] Feed rate: 50mm / min.

[0081] Embodiment 2:

[0082] See also Figure 2 , Aluminum-magnesium alloy guide column of a navigation instrument ( Figure 2 ), The outer circle is a precision matching surface with a dimensional tolerance of -0.009 to 0 mm, a roughness of Ra0.8, and a cylindricality of 0.003 mm. The outer circle needs to be subjected to micro-arc oxidation modification treatment and precision machining to achieve a certain accuracy. The purpose of the invention is achieved through the following technical solutions:

[0083] (1) According to the conventional process steps, The outer circle allowance is 0.6mm, and the processing is In addition, the rest of the surface processing meets the requirements of the drawings;

[0084] (2) Perform micro-arc oxidation on the parts as a whole to meet the requirements of the drawings;

[0085] (3) For the remaining The outer circle is finely machined and turned by dry cutting. The outer circle size is Range, ensure the cylindricity ≤ 0.015mm.

[0086] (4) Protection For all surfaces outside the outer circle, use the following parameters The outer circle is subjected to micro-arc oxidation to increase the coating by 0.04mm. The outer circle size is about

[0087] Sodium silicate: 13g / L

[0088] Potassium fluoride: 12g / L

[0089] Sodium hydroxide: 4g / L

[0090] Glycerol: 15g / L

[0091] Hydrogen peroxide: 2ml / L

[0092] Triethanolamine: 15g / L

[0093] Temperature: 25℃

[0094] Pulse: 750Hz

[0095] Voltage: 130V

[0096] Current: 10A

[0097] Occupancy ratio: 30%

[0098] Processing time: 60min;

[0099] (5) Install the workpiece, protect the corresponding surface, use a 120# silicon carbide grinding wheel, and dry cutting The outer circle is processed using the following cutting parameters to achieve the dimensional accuracy required by the drawing.

[0100] Grinding wheel linear speed: 1400-1600m / min

[0101] Cutting depth: 0.004mm

[0102] Feed rate: 50mm / min.

[0103] Example 3

[0104] See also Figure 3 , aluminum-magnesium alloy platform of a navigation instrument ( Figure 3 ), A (h1 = 40.0), B (h2 = 240.0) surfaces are precision matching surfaces, with a dimensional tolerance of 0 ~ + 0.006mm, a roughness of Ra0.8, and a flatness of 0.002mm. The plane needs to be modified by micro-arc oxidation, and precision machining is required to achieve a certain accuracy. The purpose of the invention is achieved through the following technical solutions:

[0105] (1) According to the conventional process steps, except for the A and B surfaces with a reserve of 0.3mm, the rest of the surfaces are processed to meet the requirements of the drawings;

[0106] (2) Perform micro-arc oxidation on the parts as a whole to meet the requirements of the drawings;

[0107] (3) Using the bottom surface for positioning, the A and B surfaces with allowances are finely machined by dry cutting. The plane height dimensions are processed to the range of h1 = 39.98 ~ 40.0 and h2 = 239.98 ~ 240.0, respectively, to ensure that the flatness is ≤ 0.015 mm.

[0108] (4) Protect all surfaces except A and B. Micro-arc oxidation is performed on A and B surfaces using the following parameters to increase the coating by 0.04 mm. The plane dimensions are approximately h1 = 40.04 mm and h2 = 240.04 mm.

[0109] Sodium silicate: 13g / L

[0110] Potassium fluoride: 12g / L

[0111] Sodium hydroxide: 4g / L

[0112] Glycerol: 15g / L

[0113] Hydrogen peroxide: 2ml / L

[0114] Triethanolamine: 15g / L

[0115] Temperature: 25℃

[0116] Pulse: 750Hz

[0117] Voltage: 130V

[0118] Current: 10A

[0119] Occupancy ratio: 30%

[0120] Processing time: 60min;

[0121] (5) Install the workpiece, protect the corresponding surface, use a 120# silicon carbide grinding wheel, and use dry cutting to process the A and B surfaces. Use the following cutting parameters to achieve the dimensional accuracy required by the drawing.

[0122] Grinding wheel linear speed: 1400-1600m / min

[0123] Cutting depth: 0.004mm

[0124] Feed rate: 50mm / min.

[0125] The cutting test was carried out according to the above embodiment. The single variable method was adopted in the cutting test. Except for the different cutting surfaces, the other parameters were the same. The sample was aluminum-magnesium alloy (AZ91D). The cutting parameters were grinding wheel linear speed 1400-1600m / min, cutting depth 0.004mm, feed rate 50mm / min. After the cutting test was completed, the test piece was cleaned and the roughness of the machined surface of the test piece in each cutting test was measured using a portable roughness meter, and the dimensional accuracy was measured using three coordinates.

[0126] The following table shows the cutting test results of the embodiments.

[0127]

[0128]

[0129] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for removing trace amounts of micro-arc oxidation coatings on magnesium-aluminum alloys, characterized in that: The steps include: Step 1: Precision fit the surface of the magnesium alloy parts to 0.3mm for the end face and 0.6mm for the diameter, leaving a machining allowance, and the rest of the machining shall meet the requirements of the drawing; Step 2: Perform micro-arc oxidation on the entire magnesium alloy part according to the standard; Step 3: Use dry cutting method to finish the precision matching surface with allowance; wherein, the outer circle and plane size are processed to have a mean difference of 0mm to -0.02mm, the inner hole size is processed to have a mean difference of 0mm to +0.02mm, the flatness is ≤0.015mm, and the cylindricity is ≤0.015mm; Step 4: After setting protection for the remaining surfaces, micro-arc oxidation is performed on the processed precision matching surface, and the thickness of the oxide layer increases in one direction to 0.03-0.04mm; Step 5: Use a silicon carbide grinding wheel to machine the precision matching surface after micro-arc oxidation to make the surface meet the precision requirements.

2. The method for removing trace amounts of micro-arc oxidation coatings on magnesium-aluminum alloys according to claim 1, characterized in that: In step 4, the electrolyte for micro-arc oxidation is prepared by preparing the electrolyte with the following components per liter of solution: Sodium silicate: 13g / L Potassium fluoride: 12g / L Sodium hydroxide: 4g / L Glycerol: 15g / L Hydrogen peroxide: 2ml / L Triethanolamine: 15g / L The electrical parameters for micro-arc oxidation are: Temperature: 25℃ Pulse: 600-750Hz Voltage: 100~150V Current: 5-10A Occupancy ratio: 20-30% Processing time: 60~100min.

3. The method for removing trace amounts of micro-arc oxidation coatings on magnesium-aluminum alloys according to claim 1, characterized in that: In step five, the grain size of the silicon carbide grinding wheel used is 100# to 160#.

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