Anodizing of aluminium and aluminium alloys-Measurement of wear resistance and wear index of anodic oxidation coatings with an abrasive wheel wear test apparatus
Some standard content:
National Standard of the People's Republic of China
Anodizing of alurninium and aluminium alloys--Measurement of weartesistance and wear index of anodic oxidation coatingswith an ahrasive wheel wear test apparatusGB/T 12967.2 --91
This standard is equivalent to the international standard 1S08251-1987 "Measurement of wear resistance and wear index of anodic oxidation coatingswith an ahrasive wheel wear test apparatus for anodizing of aluminium and aluminium alloys".
The wear resistance of anodic oxidation film is closely related to the quality and use of the film. The wear resistance mainly depends on the metal composition, film thickness, anodizing conditions and sealing conditions. For example, when the anodizing temperature rises abnormally, its influence on the quality of the oxide film can be identified through wear tests. Therefore, wear resistance is an important quality index of aluminum and aluminum alloy anodized film. 1 Subject content and scope of application
This standard specifies a test method for measuring the wear resistance and wear coefficient of aluminum and aluminum alloy anodized film using a wheel wear tester.
This standard is applicable to the inspection of plate-shaped specimens with an anodized film thickness of not less than 5um. This method can be used to measure the wear resistance and wear coefficient of the entire layer thickness of the anodized film, the surface layer, or a layer of the arbitrarily selected oxide film. This standard is not applicable to the determination of anodized specimens with uneven surfaces. 2 Reference standards
GB4957 Determination of thickness of non-conductive covering layer on non-magnetic metal substrate Eddy current method GB8015.1 Test method for thickness of anodized film of aluminum and aluminum alloy Weight method 3 Definitions
The following definitions are used when applying this standard.
3.1 Standard specimen standard test specimen A specimen prepared under the conditions given in Appendix A.
3.2 Agreed reference specimen The specimen prepared according to the conditions agreed by both parties. 3.3 Test specimen
The specimen to be tested.
3.4 Double stroke (ds) Double stroke The complete reciprocating motion completed by the grinding wheel. 4 Principle
The anodized specimen shall be ground under the following conditions: the silicon carbide grinding paper belt is wound around the outer edge of the wheel, and the specimen performs a reciprocating grinding motion relative to the grinding paper belt. After each reciprocating motion [double stroke (ds), the grinding wheel rotates a small angle and rotates to a new part of the grinding belt, and this new part of the grinding belt continues to contact the surface to be tested. According to the reduction of the thickness or mass of the oxide film, its wear resistance or wear coefficient can be calculated. The results obtained should be compared with the test results of the special standard sample (see Appendix A) or the agreed reference sample. The overall wear resistance of the anodic oxide film can be tested by the layered test method. The principle is: wear layer by layer until the bare metal substrate is exposed. Then establish a relationship between the thickness of the worn film and the double stroke. 5 Apparatus
5.1 Wheel wear tester
5.1.1 The tester is mainly composed of a clamp for fastening the sample, a pressure plate and a wheel with a diameter of 50mm. The clamp and pressure plate keep the sample horizontal and fixed. The outer edge of the wheel is wrapped with a 12mm wide silicon carbide paper belt. The force between the wheel and the sample is variable, ranging from 0 to 4.9N (500gf) with an accuracy of ±0.05N.
5.1.2 There are two ways of grinding: one is to use a fixed grinding wheel, the sample reciprocates in the horizontal direction, and the wheel and the sample surface maintain horizontal contact; the other is to use a wheel reciprocating, and the sample is stationary. The wear marks should be 30mm long. 5.1.3 After the wheel slides relatively for a double stroke, it turns forward at a small angle, and the silicon carbide paper tape turns to a new surface. In the next stroke, the new paper tape surface contacts the surface to be ground again. After 400 times ds, the grinding wheel rotates for a week, and a new silicon carbide paper tape should be replaced at this time.
5.1.4 The relative speed of the double stroke is 40 ± 2 sliding times per minute. The number of double strokes is recorded by a counter, and the machine should be able to stop automatically after reaching the predetermined double stroke (maximum 400 times ds). During the grinding test, the surface of the sample should remain free of powder or grinding debris. 5.2 Abrasive paper tape
5.2.1 The width of the abrasive paper tape is 12 mm, and the particle size of silicon carbide is 45 μm (320 mesh). Its length should just wrap around the grinding wheel, without any joints. The paper tape can be glued or fixed mechanically. 5.3 Eddy current instrument
5.3.1 During the inspection, an eddy current instrument with a probe diameter not greater than 12 mm should be used to measure the thickness. The thickness can also be measured by the weight loss method. 6 Test steps
6.1 Inspection of ordinary sulfuric acid anodized film
6.1.1 Standard specimen
The specimen is prepared according to the conditions given in Appendix A.
6.1.2 Specimen
6.1.2.1 According to the needs and possibilities, cut the sample to be inspected of appropriate size according to the test terms. However, the inspection surface of the specimen shall not be damaged. 6.1.2.2 The size of the specimen is usually selected as l×, mm: 50×50 (see 6.1.4). 6.1.3 Instrument calibration
6.1.3.1 Select the surface to be worn of the standard sample and mark it. According to the method specified in GB4957, measure the oxide film thickness at more than one point along the test surface with an eddy current meter and calculate its average value. 6.1.3.2 Fix the standard sample at the detection position of the instrument. 6.1.3.3 Wrap a circle of new silicon carbide paper tape around the outer edge of the grinding wheel. According to the instructions for use of the instrument, adjust the grinding wheel to ensure that the wear amount of the test surface is uniform within the specified grinding width. The force between the grinding wheel and the test surface should be adjusted to 3.92N. 6.1.3.4 The instrument should run 400 times. Use suction, blowing or brushing with fine soft hair. Keep the test surface of the standard sample free of any grinding debris at all times.
6.1.3.5 Remove the standard sample from the instrument, clean it carefully to remove the loose oxides, and then according to 6.1.3.! Measure the average film thickness (d2) on the test surface using the method in the above clause. 6.1.3.6 Due to the continuous rotation of the grinding wheel, the area 3 mm away from the end point of the grinding mark on the test surface is often the most worn area. Therefore, this area should be avoided when measuring the film thickness.
GB/T 12967.2-91
6.1.3.7 According to the steps specified in clauses 6.1.3.1 to 6.1.3.5, at least two more measurements are made on the non-overlapping test areas of the standard specimen.
6.1.3.8 Based on the measured average value, calculate the wear rate of the standard specimen (see clause 6.3). 6.1.4 Measurement
6.1.4.1 Test the specimen to be tested (6.1.2) according to the procedure specified in clause 6.1.3. The grinding paper tape used should be from the same batch as the paper tape used for calibration.
6.1.4.2 If the sample is too thin, it can be firmly glued to the surface of a flat metal and then tested. The minimum size of the sample to be tested is l×b, mm: 50×20.
6.2 Inspection of colored anodized film or hard anodized film 6.2.1 Carry out the initial test in accordance with the provisions of 6.1.3. 6.2.2 If the film thickness loss on the test surface is less than 3μm, grinding can be carried out by adjusting the grinding conditions, such as: increasing the force between the grinding wheel and the test surface; using a coarser silicon carbide paper belt; increasing the number of double strokes, etc. 6.2.3 In addition to the layered inspection method (see 6.4), the grinding conditions should be adjusted to the film wear thickness of 5±3μm after running 400 times ds
6.2.4 If the weight loss method is used, the equivalent mass of ±3um should be known. The calculation method of the equivalent mass can be carried out in accordance with the regulations of GB8015.1.
6.2.5 Calculate the relative wear rate in accordance with the provisions of Article 7.5. 6.3 Relative wear test
6.3.1 Overview
When testing the wear resistance of the anodic oxide film, the test method used should be agreed upon by the supplier and the buyer. The test results should be compared with the results of the standard sample or the agreed reference sample. The comparison method is usually relative thickness loss or relative mass loss. The relative wear rate is expressed as a percentage of the agreed reference sample.
6.3.2 Relative thickness loss
6.3.2.1 Carry out the test in accordance with the provisions of 6.1.3, and then determine the thickness loss value on the sample and the standard sample or the agreed reference sample. 6.3.2.2 Calculate the relative wear rate in accordance with the provisions of 7.3. 6.3.3 Relative weight loss
6.3.3.1 Select the worn surface of the sample and mark it. Weigh the sample weight (ml) to the nearest 0.0001g. Carry out the test in accordance with the steps specified in 6.1.3.1~6.1.3.4. 6.3.3.2 Remove the sample from the instrument, brush off the loose oxide on the surface, and weigh it again (m2) to the nearest 0.0001g. 6.3.3.3 Measure the test surface of the sample at least twice, but the measuring points cannot be repeated. 6.3.3.4 Repeat the test of the standard sample or the agreed reference sample in accordance with the provisions of 6.3.3.1~~6.3.3.2. Calculate the relative wear rate in accordance with the provisions of 7.4.
Note: The newly exposed oxide film easily absorbs water vapor, which is manifested in the increase of the weight of the sample. Therefore, when the atmospheric humidity changes, it will cause a certain error in each test result.
6.4 Layered test for wear resistance
6.4.1 Overview
In some cases, it is necessary to test the wear resistance of each layer of the anodic oxide film along the thickness direction, so the layered test method must be used for testing.
6.4.2 Testing
6.4.2.1 Measure the average thickness of the film according to the provisions of 6.1.3.1. Use a positioning device to accurately fix the sample on the test table of the instrument so that the wear test is ensured to be ground on the same test surface. 6.4.2.2 According to the provisions of 6.1.3.3 and 6.1.3.4, the first grinding only uses 20 to 50 double strokes (depending on the estimated hardness). Remove the sample and measure the average film thickness on the test surface according to the provisions of 6.1.3.1. 451
GB/T12967.2
6.4.2.3 Accurately reposition the sample on the instrument, follow the steps specified in 6.4.2.2, and then select a certain number of double strokes to grind (see Note (1)). Similarly, use an appropriate number of double strokes, repeat the wear and thickness measurement layer by layer, until the base metal is just exposed.
Note: () The interval conditions of a typical grinding test are: 50-~100~200~~400800 and 1200 times. ② Repositioning the sample is a difficult task, even unbelievable. However, as long as the cumulative wear test is carried out on adjacent tests, the same daily results can be achieved. Therefore, this test takes a longer time. 6.4.2.4 For the oxide film tested, calculate the relationship between the film thickness and the change in wear resistance, as well as the wear resistance coefficient and the wear coefficient. If necessary, a relationship diagram between the film thickness and the double stroke can also be drawn. 6.4.2.5 When necessary, the results of the layered test can be compared with the results of the standard test specimen. Result Expression
7.1 Abrasiveness
Wear resistance WR is expressed by the number of double strokes required to wear each micron of the oxide film. The calculation formula is as follows: WR
dr — dz
Where: t—-average thickness before wear, um (see 6.1.3.1); d-average thickness after 400 wears ds, um (see 6.1.3.5). 7.2 Wear coefficient
The wear coefficient is expressed as WRC and is calculated as follows:WRt dis - tas
d,t — dzt
The wear resistance of the specimen is expressed as the number of double strokes per micron; The wear resistance of the standard specimen is expressed as the number of double strokes per micron; di The average film thickness of the standard specimen before wear, um (see 6.1.3.1); d2s
The average thickness of the standard specimen after 400 wears ds, um (see 6.1.3.5); The average film thickness of the specimen before wear, um (see 6.1.3.1); The average film thickness of the specimen after 400 wears ds, μm (see 6.1.3.5). f
Note: The wear coefficient is the reciprocal of the wear coefficient and is a measure of wear resistance. A coefficient greater than 1 indicates that the degree of wear is less than that of the standard specimen, and a coefficient less than 1 indicates that the degree of wear is greater than that of the standard specimen.
7.3 Wear coefficient
The wear coefficient is represented by WI and is calculated as follows: WI
Wear rate of the specimen, um/100ds;
Formula: Wt-
dit - dzt
dis des
Wt dit = da
Wear rate of the standard specimen, um/100ds; dis - das
Note: The wear coefficient is a dimensionless ratio, which is a representation of relative wear rate. When its value is greater than 1, it means that the degree of wear is greater than the standard specimen, and when its value is less than 1, it means that the degree of wear is less than the standard specimen. 7.4 Mass wear coefficient
Mass burnout coefficient is expressed by MWI and is calculated as follows: MWI
mit. mnat
ms - m2s
Wu Zhong: MWt-
MWs --
12967.2-91
-mass wear rate of the sample, mg/100ds; MWt = mit.- m2t
mass wear rate of the standard sample, mg/100ds; MWs =- mis - ms
mlt—-average mass of the specimen before wear, mg (see 6.3.3.1); mzt.----average mass of the specimen after 400 wears, mg (see 6.3.3.2); mi8-~-average mass of the standard specimen before wear, mg (see 6.3.3.1); mss--average mass of the standard specimen after 400 wears, mg (see 6.3.3.2). The mass wear coefficient of the standard specimen is 1.
Note: The mass wear coefficient is a dimensionless ratio, which is a way of expressing relative wear rate. When its value is greater than 1, it means that the degree of wear is greater than that of the standard specimen. When its value is less than ", it means that the degree of wear is less than that of the standard push sample. 7.5 Relative wear rate
Wa×100=
Wherein: Wa
wear rate of the protocol reference sample, μm/100ds; dia
wear rate of the sample, μm/100ds.;
dia dza
dit - d2t
dit d2t
dia-average film thickness of the protocol reference sample before wear, um; dza-average film thickness of the protocol reference sample after 400 ds of wear, um. 7.6 Relative mass wear rate
Relative mass wear rate cWRm is expressed in percentage, and the calculation formula is as follows: MW×100
mia - mza
CWRm -
mit --- mzt
mass wear rate of the protocol reference sample, mg/100ds, where MWo
mja --
8Test Report
mya - m2a
Average mass of the protocol reference specimen before grinding, mg (6.3.3.1) Average mass of the protocol reference specimen after 400 wears ds, mg (see 6.3.3.2). The test report shall include the following:
Selection of specimens and protocol reference specimens;bzxz.net
Number of this standard:
Specify the special instrument used;
The force between the grinding wheel and the test surface and the grinding medium used; The number of test points and the test position on the specimen surface;·(5)
(6)
Calculate the wear resistance, wear resistance coefficient, wear coefficient, mass wear coefficient, relative wear rate or relative mass wear rate as required: record the relevant test process, the characteristics of the specimen and the test surface. GB/T 12967.2 --- 91
Appendix A
Preparation of standard specimens
(reference)
The standard specimens for wear resistance test shall be prepared from polished aluminum plates or bright rolled aluminum plates. Al
Aluminum grade: A199.5 (13);
Hardening state: Y2;
Standard specimen size: 140mm×70mm;
Standard specimen thickness: 1.0~~1.6mm.
A3After degreasing, it can also be polished by chemical or electrochemical methods. Oxidation tank liquid composition
Sulfuric acid concentration: 180±2g/L;
Aluminum ion concentration: 510g/L;
Other: water.
A5Anodizing conditions
Temperature: 20±0.5℃;
Current density: 1.5±0.1A/dm2;
Stirring method: compressed air;
Time: 45min;
Film thickness: 20±2μm;
Sealing requirements: In deionized water containing 1g ammonium acetate per liter (pH 5.5-6.5), seal the holes for 60min under boiling conditions. When the A6 standard sample is oxidized in the tank, it should be placed horizontally and vertically. The anode surface should be stirred vigorously, and the current should be stable with fluctuations not exceeding 5%. No more than 20 standard samples are oxidized each time, and the volume of the electrolyte is not less than 10L for each sample. Note: ① When the anodic oxidation conditions are strictly controlled, very accurate samples can be prepared, and they also have good reproducibility. ② According to the provisions of this Appendix A, the deviation of the standard sample is ±10%. Additional notes:
This standard was proposed by China Nonferrous Metals Industry Corporation. This standard was drafted by Northeast Light Alloy Processing Plant. The main drafters of this standard are Gao Kangzhi and Wang Ziyi. 457
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