This standard specifies the method for non-destructive measurement of the thickness of non-magnetic coatings (including glaze and enamel layers) on magnetic base metals using a magnetic thickness gauge. This method is only applicable to measurements on appropriately flat specimens. The method specified in GB/T 13744 is preferred for measuring the thickness of nickel coatings on non-magnetic substrates. GB/T 4956-2003 Magnetic method for measuring the thickness of non-magnetic coatings on magnetic substrates GB/T4956-2003 Standard download decompression password: www.bzxz.net
This standard specifies the method for non-destructive measurement of the thickness of non-magnetic coatings (including glaze and enamel layers) on magnetic base metals using a magnetic thickness gauge. This method is only applicable to measurements on appropriately flat specimens. The method specified in GB/T 13744 is preferred for measuring the thickness of nickel coatings on non-magnetic substrates.

GB/T4956—2003/1S02178:1982
This standard is equivalent to 1S2178:1982. Non-magnetic coating on magnetic substrate
Except the standard GB/T4956
The second standard is modified as follows according to 1S0217H::332: a) "This standard" replaces "this international standard"; b) The predecessor of the international standard is cancelled;
For the purpose of convenience, the international standard is quoted and adopted To the national standard: d) Add "normative reference documents".
This standard is issued by China Machinery Industry Association. This standard is issued by the National Metal and Non-metallic Chemical Technology Committee. The drafting person in charge of this standard is: Institute of Material Protection. The drafting unit of this standard is: Sijiang Lexiao City New Ten Enterprise Co., Ltd. The main contributors are: Xiang Zhen, You Lichang, Feng Yongchun, Jue Duxin, Zheng Xiulin. The previous versions of the standards replaced by this standard are as follows: GT/T 195F—198.1.
Magnetic transport method.
1 Scope
Gl/T4956—2003/1902178;19B2
Non-magnetic covering layer on magnetic substrate
Magnetic method for measuring the thickness of covering layer
This standard specifies the method for measuring the thickness of non-magnetic covering layer (including ceramic layer) on magnetic substrate metal by using magnetic thickness gauge
This method is applicable to the For the measurement of the flat surface, the method specified in GB/T13744 shall be used first for the measurement of the non-elastic surface.
2 Normative Reference Documents
The following documents may become the technical terms of this standard through the introduction of this standard. All the subsequent revisions (excluding the revised version) or versions of the referenced documents of the society are not applicable to this standard. However, it is encouraged that the relevant parties reach an agreement based on the industry law of this standard to make the latest version of this document available. The applicable documents and their updated versions apply to this standard, (B12334 Definition of general rules for the measurement of thickness of metallic and other non-metallic coatings (IDTS) 2551) CB/13744 Transient and non-transient single layer energy (E0V1) 2351) 3 Principle
The magnetic thickness gauge uses the attraction between a permanent magnet and the base metal. The attraction is changed to the magnetic resistance of the layer. The magnetic flux passing through the layer and the base metal is slightly different. 4 Factors affecting the measurement accuracy ||tt ||The following factors may affect the accuracy of the thickness measurement before and after the cover: 4.1 The thickness of the coating
The accuracy of the measurement varies with the coating thickness. It depends on the design of the instrument. For the coating of the process, the measurement accuracy is independent of the thickness change of the coating and is a constant. For the coating of the process, the measurement accuracy falls below a certain fraction of the test thickness and the product of the test pressure. 2.2 Properties of the base metal
The changes in the properties of the base metal can affect the inductive method of measurement. For practical purposes, it is considered that the changes of low-temperature steel are not important. In order to avoid the influence of uneven or local heat treatment and cold treatment, the instrument should be calibrated with a calibration standard with the same properties as the test base metal. If possible, the old parts to be tested should be used as the standard sample to eliminate the instrument process. 4.3 Thickness of the base metal screen
Each instrument has a different base metal screen. Above this critical thickness, the measurement will not be affected by the increase in base metal thickness. The critical value depends on the mass of the instrument head and the metal thickness of the point. Unless otherwise specified by the manufacturer, the size of the critical value should be determined by experiment.
4.4 Edge Effects
This method is sensitive to discontinuities. Therefore, measurements too close to these discontinuities or indirections will not be acceptable unless the instrument is specially calibrated for such measurements: this reverse effect may extend forward from the discontinuity to about 20 m. The method depends on the instrument.
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GB/T4956-2003/TSO217B:13824.5 curvature
of the sample, the curvature of the sample varies greatly with the different manufacture and type of the receiver, but the overall curvature is more obvious when the curvature is reduced.
If you use a bipolar tester, match the two poles in a plane parallel to the axial direction of the filter or match them in a plane parallel to the axial direction of the body, you may also get different readings. If the reverse or the probe is worn, the same result can be obtained. Note that the test may not be effective on curved specimens, unless the instrument is specially calibrated for this type of specimen. 4.6 Surface roughness If the range of the coefficient values ​​obtained on the same surface (see GR/T 1234) exceeds the required reproducibility, the number of measurements required shall be increased to at least 5. 4.7 Measurement of machining direction Use a bipolar probe or a single-pole probe that has been reported for measurement. It may be necessary to use a single-pole probe to measure the surface. 4.8 The difference between the two magnetic materials may affect the required value of the fixed magnetic field, but the effect on the magnetic type instruments using alternating magnetic fields is very small (see 6.7). 4.9 Magnetic fields are short-frequency, such as those produced by strong chemicals and electrolytic equipment, which may interfere with the work of using fixed fields (see 6.7). 4.10 Foreign dust The instrument probe must be in close contact with the surface of the coating because these instruments are affected by foreign matter that is in contact with the coating surface. 4.11 Conductivity of the film
The operating frequency of some dielectric testers is between 200[1z-235IIz. In this frequency range, eddy currents generated in the high conductivity chamber may affect the readings.
4.12 Measuring pressure
The force applied to the probe tip must be appropriate and constant so that the soft film does not deform. On the other hand, the front layer can be completely covered and then the thickness of the metal film can be subtracted from the measured value. This is also necessary when measuring broken films. 4.13 The actual measurement
is related to the earth's field and should be used! The reading of the thickness measurement may vary with the body orientation: therefore, the measurement point of the instrument in the horizontal or inverted position may need to be calibrated separately or it may not be possible. 5.1 General
Before the instrument is brought to the surface, it shall be calibrated using appropriate calibration standards in accordance with the manufacturer's instructions: or by the optical method. From these standards one shall be selected and the thickness shall be measured using the force method specified in the relevant international standard for the particular layer. The measured data shall be compared with the nominal value. For instruments that cannot be calibrated, the difference from the nominal value shall be determined by comparison with non-standard films. All the measured values ​​shall be recorded. It is expected that calibration shall be carried out at regular intervals during use. Due attention shall be paid to the factors listed in Chapter 4 and the procedures specified in Chapter 5.
5.2 Calibration standards
The appropriate standard may be in the form of optical standards or nominal films. 5.2. 1. The standard of oil is not in the United States. "Standard" refers to non-medical or non-full-quality. 2. CB/T4956-2003/1SO2178:1982 Because it is difficult to ensure good contact, it is usually not suitable to calibrate the thickness gauge based on the magnetic attraction principle without a box: but in some cases where the necessary preparatory measures for Cui Rong are stipulated, the box is still applicable. Other types of instruments can usually be used for calibration. For the calibration surface, the standard sheet with a covering layer is suitable for the customer. In order to avoid measurement errors, it should be ensured that the box has never contacted with the substrate if possible, and avoid using strong sieves. Calibration push foil pictogram change indentation, 5.2.2 Coated Standards
The base metal of the standard with the coating is known to be firmly bonded to the base metal and has a uniform coating. 5.3 Calibration
5.3. The base metal thickness of the calibration standard should have similar surface stability and magnetic properties to the base metal of the sample. It is recommended that the readings obtained on the base metal of the uncoated standard be compared with the readings obtained on the uncoated sample to confirm the suitability of the calibration standard.
5.3.2 In some cases, the instrument must be rotated ↓0 to verify the calibration of the instrument (see 4.7 and 4.8]): 5.3.3 If the thickness of the base metal of the specimen varies by more than 4.3, the thickness of the base metal of the specimen and the reference standard must be the same.
The base metal of the reference standard or specimen may be padded with an intermetallic layer of sufficient thickness to make the data independent of the base metal thickness.
5.3.4 If the bending state of the cover is such that it cannot be accurately measured in a flat manner, the curvature of the reference standard or the base metal of the reference box shall be the same as the curvature of the test column. 6 TESTING PROCEDURE
6.1 General
Each instrument shall be selected in accordance with the manufacturer's instructions, with the appropriate precautions listed in Section 4, and shall be tested on the test surface before each use and at regular intervals during use to ensure that the instrument is functioning properly. The following precautions must be observed.
6.2 Thickness of the body
Check whether the thickness of the base metal exceeds the critical value. If not, the method described in 3.3 should be adopted, or the instrument should be trained with a calibration sheet. 6.3 Edge effect
Do not measure near edges, corners, etc. unless the validity of the calibration for such measurements has been confirmed.
6.4 Curvature
Do not measure on the curve of the test column unless the validity of the calibration for such measurements has been confirmed. 6.5 Number of readingsbzxZ.net
To show the correctness of the instrument, it is necessary to take several readings on each measuring surface (see also GB/T 12331). Since the thickness of the layer may also require the measurement to be carried out in the same plane, the gravitational instrument is sensitive to vibration and should avoid the reading. 6.6 Machining direction
If the machining direction obviously affects the reading, care should be taken when measuring on the specimen that the direction of the probe is consistent with the direction taken by the probe when pressing. If this is not the case, make a measurement every 91\ of the probe rotation in the same measuring disk plane, for a total of 10 times. 6.7 Magnetic Field
When using a bipolar detector with a fixed field, if the base metal is magnetic, the measurement must be carried out in two directions at 180 degrees.
CB/T4956--2003/IS0>2175:1982 In order to obtain reliable results, it may be necessary to eliminate the properties of the sample. 6.8 Surface Cleanliness
In the creation, any foreign substances on the test piece should be removed, such as paint, grease and separation products; but any thin layer of material should not be removed. When measuring, obvious product defects that are difficult to remove, such as welding or soldering, acid spots, clear or oxide areas should be selected. 6.9 Platinum Cover
If a magnetic field type design is used, lead may be adhered to the product! , except for a very small area of ​​the tear film, the measurement will be extremely important; but when using a tension type tester, the test should be greatly reduced so that the display is actually in a state of tension. Except for the test layer, all other test layers should be small.
6.10 Techniques
The measurement results may depend on the skill of the user. For example, the pressure applied to the probe or the speed of the flat plate on the body will vary from person to person. 6.11 Probe Positioning
The probe of the instrument should be placed vertically on the measuring point of the modified surface. For some instruments, it is required to tilt the probe slightly to the side and select the most effective tilting cloth. When the results obtained change significantly with the blood flow, the tester may be damaged and needs to be replaced. If the magnetic device is used in a horizontal or inverted position, and the measuring device is supported at the center of gravity, it should be calibrated in the horizontal or inverted position respectively. The accuracy requirement is that the calibration and operation of the device should be able to accurately measure the actual thickness within 10 or 5F, whichever is greater (the first 5th value). The method has good control accuracy.
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