The various metallographic tests are another way to obtain information about the properties of the metal or weld. These tests are essentially in the excision and subsequent careful polishing of the sample from the metal or welded seam. After such processing of the sample, it is possible to evaluate the metal with the naked eye or with the help of magnifying optics.
The metallographic tests usually refer to the macroscopic or microscopic group. The difference is the magnification used. The macrostructure tests are carried out with the increase of 10 and lower, while in microstructure tests much larger increase, usually 100 and higher, is used.
On the typical section with the macrostructure, many characteristic elements can be distinguished. In the cross section of the welded seam, it is possible to obtain the section with the macrostructure that allows to determine a number of parameters: the penetration depth, the penetration fusion, the actual thickness of the seam, the absence of defects in the seam, the degree of fusion, the presence of discontinuities in the seam, the profile of the seam, the number of superimposed layers and other parameters. The photographic image of the macrosection is called macrographs.
The microstructure with thin sections can also be used to determine various characteristics, including the components of the microstructure, presence of inclusions, and the presence of microscopic defects and cracking character etc. Similarly, the microstructure images are called micrographs.
Both types of the metallographic tests are very useful in the analysis of destruction, certification of technology and welders, as well as in the implementation of tests to monitor the process. These two tests differ in the degree of necessary preparation of the samples. Some macrosections can be ground with abrasive material, microsections require very fine abrasive grinding and subsequent mirror polishing. For the disclosure of the structure of the material, the etching is provided in both methods. It is carried out with the help of reagents for etching. The conducting simple macro- and micro-investigations can give a large amount of information about the properties of the metals.
