Several Key Points in Metallographic Microscopy Inspection of Metal Materials
The main aspects that require metallographic examination (metallographic microscope) for metal materials are as follows:
1. In the past, in the production, maintenance, heat treatment and other processes of steel and components, changes in metal materials were often caused by improper process equipment or heat treatment operations, resulting in products not meeting quality standards. If metallographic inspection is used to guide production and supervise product quality, such defects can be avoided.
2. After a certain period of use or under alternating loads and high temperature changes, steel components and large castings and forgings will gradually deteriorate, and the microstructure of the material will undergo varying degrees of changes. When this change reaches a certain limit, it may cause accidents such as leakage, deformation, or sudden fracture of the components, seriously affecting * * production. At this time, regular metallographic inspection can be conducted, Check and monitor the changes in materials, take timely and reasonable measures to avoid accidents.
3. Metallographic inspection is a very important task in the failure analysis of metal materials, including macroscopic and microscopic inspections, which often include the following aspects:
(1) Low magnification acid etching test. Check the internal segregation, looseness, inclusions, porosity and other defects of the material; Defects such as surface folding, sand inclusion, and scars; Internal cracks, white spots, overburning, etc; Forging streamline, welding quality, grinding, etc.
(2) Use sulfur and phosphorus printing methods to inspect the segregation of sulfur and phosphorus in steel.
(3) Explicit dimensional organizational analysis is used to determine whether the heat treatment or cold working process of the failed component is normal.
(4) Analyze the corrosion, wear, oxidation, and surface work hardening of failed components under working conditions.
(5) Determine the nature of the crack based on the characteristics of the crack on the failed part and the microstructure on both sides of the crack.
(6) Determine whether the material is qualified by analyzing the non-metallic inclusions inside the failed component material.
