GB/T 37789-2019 Metallic materials - Determination of microporosity - Fluorescence method
1 Scope
This standard specifies the preparation of specimen, microscope configuration, measurement, measurement accuracy and test report for determining the percentage of microporosity area in metallic materials by fluorescence method.
This standard is applicable to the determination of the percentage of microporosity area in as-cast metallic materials and 3D printed metallic materials. This standard may be used for reference for the determination of pore content in ceramics, powder metallurgy materials and other materials.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
GB/T 13298 Inspection methods of microstructure for metals
GB/T 15749-2008 Measuring method in quantitative metallography
GB/T 30067 Standard terminology relating to metallography
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 30067 and the following apply. For the convenience of application, some terms and definitions in GB/T 30067 are listed repeatedly as follows.
3.1
microporosity
extremely fine pores in castings
[GB/T 30067-2013, Definition 2.2.275]
Note: In the slow solidification area of castings, it is formed between dendrites due to the blockage of micro-feeding channels.
3.2
fluorescent infiltration
process where a kind of epoxy resin with low viscosity coefficient, low surface tension and low bubbles is mixed with a certain proportion of fluorescent agent, injected into the micro-pores of the material under a certain vacuum pressure and solidified
4 Preparation of specimen
4.1 Sampling position and specimen dimensions
Sampling position and specimen dimensions shall be determined according to relevant product standards or by agreement between the seller and the buyer. If not specified, sampling shall be conducted in accordance with GB/T 13298.
4.2 Pretreatment of specimen
After the deformation layer on the surface of the specimen is fully removed, the surface of the specimen shall be ground with sandpaper of 400# or less, then the specimen is subjected to ultrasonic cleaning with alcohol or acetone to remove the dirt remaining in microporosity or pores and edges, and finally blew drying for later use.
4.3 Fluorescent infiltration
4.3.1 Bisphenol A epoxy resin and aliphatic amine curing agent are mixed according to a certain proportion, and a certain proportion of fluorescent agent is added and fully stirred to prepare fluorescent infiltration agent.
Example:
The composition and proportion of fluorescent infiltration agent are: epoxy resin: curing agent: fluorescent agent = 100: 36: 7.
4.3.2 Vacuumize the specimen box containing the specimen in a vacuum injection device. When the vacuum degree reaches 10-1 Pa, and does not change any more, it means that the foreign matter such as gas in the microporosity has been basically pumped away. At this time, the fluorescent infiltration agent is introduced into the specimen box at a certain vacuum pressure for a certain time to ensure that the bubbles in the infiltration agent are pumped away. It is recommended that the vacuum pressure should be kept at 1.5 × 10-1 Pa for not shorter than 4.0 h.
4.4 Grinding and polishment
The fully solidified specimen is prepared according to GB/T 13298 and can be finely ground with sandpaper to 2000# or prepared into a polished metallographic specimen. Clean the surface of the specimen, and blow it dry for measurement.
5 Microscope configuration
The microscope imaging system selected shall be equipped with fluorescence imaging module for measuring the percentage of microporosity area.
6 Measurement
6.1 Measurement requirements
6.1.1 Magnification factor
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Preparation of specimen
5 Microscope configuration
6 Measurement
7 Measurement accuracy
8 Expression of results
Annex A (Information) Comparison of pictures before and after fluorescence infiltration
