Keywords: representativeness, inspection surface, appropriate size.


Choosing suitable and representative samples is an extremely important step in conducting metallographic microanalysis, including selecting the sampling location, inspection surface, determining the cutting method, sample size, etc. So, today, the editor of Kemai will share with you the precautions for sampling. The details are as follows:


1、 Selection of sampling location and inspection surface


The selection of sampling locations and inspection surfaces should be based on the inspection purpose, and representative locations should be selected. For example, when analyzing the causes of metal defects and damages, samples should be taken from the areas where the defects and damages occur, and also from intact areas for comparison.


The transverse section should be taken for detecting decarburization layer, chemical heat treatment layer, quenching layer, grain size, etc; When studying the deformation of banded structure and cold plastic deformation workpieces, the longitudinal section should be taken.


2、 Method of sampling


The method of sampling can vary depending on the properties of metal materials. For soft materials, methods such as sawing, turning, and planing can be used; For hard materials, methods such as grinding wheel slicing machine cutting or electric spark cutting can be used; For hard and brittle materials, such as white cast iron


Strike method; Sampling on large workpieces can be done using methods such as oxygen cutting.


When using grinding wheels or electric spark cutting, cooling measures should be taken to reduce the structural changes of the sample caused by heating. The deformation layer or burnt layer caused by cutting on the sample must be removed in subsequent processes.


3、 Sample size and shape


The size and shape of the metallographic specimen are based on ease of grip and grinding, usually using diameter ф A cylinder with a length of 15-20mm and a height of 15-20mm or a cube with a side length of 15-20mm.


Alright, the above are the relevant precautions for metallographic sampling. If you have any other questions related to metallographic sample preparation, please log in to the official website www.qmaxis.cn for technical exchange with the engineers of Kemai, or visit Kemai Testing Nanjing Laboratory for on-site testing.