1. Subject and Aspects Covered
This standard specifies the sample preparation, sample grinding, and sample erosion, inspection of microstructure, micrography and test data sheet for inspection of metal microstructure.
This standard is applicable to the operating procedure of inspecting metal structure with metalloscope.
2. Sample Preparations
2.1 Sample selection
The cutting direction, location and quantity of sample shall be carried out according to the metalworking method, inspection purpose, technical condition or the provisions of mutual agreement.
The cross section which is perpendicular to the forging rolling direction may be used for study of the following items: structure of metal material from surface layer to the center, state of microstructure, level of grain fineness, network of carbonide, depth of deficiency in surface layer, depth of oxide layer, depth of decarburized layer, depth of corrosion layer, chemical heat treatment for the surface and thickness of coating.
The longitudinal section which is parallel with the forging rolling direction may be used for the studies of the following items: deformation degree of non-metallic inclusions, distortion degree of grains, degree of plastic deformation, pattern of all structures after deformation, overall conditions of heat treatment.
It is allowed to sample at the breakage or to sample nearby normal section for comparison when inspecting causes of metallic damage.
2.2 Sample size
The proper sample should be 15~20 in height and less than 400mm2 in surface grinding area.
2.3 Sample interception
The sample may be taken through shearing, sawing, plane, turning and milling with handsaw, abrasive wheel cutting machine, microtome, chemical cut-off unit and spark cutting machine, and the oxyacetylene cutting method also may be adopted if necessary. Stamping method may be adopted for hard and fragile metals. No matter which method is adopted for sampling, the interception effects on the structure like deformation and superheating shall be prevented. These effects shall be reduced according to different methods, and preventive measures like water cooling also may be adopted while cutting.
2.4 Sample cleaning
The sample may be cleaned through ultrasonic cleaning. Samples with oil stains, dirt or rust stains may be cleaned with proper resolvent. Coating metal that can disturb corrosion of base metal shall be removed before polishing.
2.5 Sample inlaying
As for excessively fine and thin samples (such as thin plate, thin wire stock and thin tubular goods), soft and fragile samples, samples requiring inspection on fringe structure, or those being convenient for automatic polishing and grinding on buffing machine, one of the following methods may be adopted for inlaying the sample. The selected inlaying method must not change the prior structure.
2.5.1 Mechanical setting method
The sample shall be embedded in steel ring or steel clip as showed in figure 1, figure 2 and figure 3.
Contents
1. Subject and Aspects Covered
2. Sample Preparations
3. Sample Grinding
4. Sample Erosion
5. Microstructure examinations
6. Microphotography
7. Test records
Additional Explanation
