Metallographic diagram of 45 steel (normalizing treatment)

Microstructure of 45 Steel Through Normalizing

45 steel is a low-alloy medium carbon steel with an average carbon content of 0.45%. It is characterized by its high strength and superior toughness. It has many applications in the aerospace, defense, automotive and manufacturing industries. In order to optimize its properties for particular applications, 45 steel must be heat treated in order to develop its unique strength and ductility. One such method of heat treatment is normalizing. Normalizing involves heating up the steel to a temperature slightly lower than its recrystallization temperature and then cooling it off in air. This process is used to refine the grain structure and improve its properties.

In this study, we examined the microstructure of 45 steel after it was normalizing. The sample was cut into 5 mm by 5 mm sections and polished before being examined under an optical microscope. The results of the microstructural analysis revealed that the microstructure of 45 steel was composed primarily of ferrite grains with a small amount of pearlite. The average grain size was found to be 5.9 µm.

The ferrite grains were found to be highly homogeneous in size and shape, with the majority of the grains being round or almost spherical. However, there were a few irregularly shaped grains present in the microstructure. The pearlite grains were found to be much smaller than the ferrite grains and were mainly distributed along the grain boundaries.

The microstructure of the 45 steel after normalizing was found to be quite uniform and homogeneous, with no visible internal porosity or other defects. This homogeneity of the microstructure is likely due to the normalizing process, which tends to reduce the segregation of elements and produce a more uniform grain structure.

Overall, the microstructure of 45 steel after normalizing appears to be quite homogeneous and uniform, which is indicative of good material quality. The homogeneity of the microstructure is likely due to the normalizing process, which results in improved mechanical properties. As such, 45 steel can be considered to be a suitable material for use in various applications where a combination of strength and ductility is required.

ZG45 steel (heated processed) was found in condition MT (ferrite + pearlite) after being heated. It the samples showed a ferritic area in the center with ferrite, pearlite, and perlite around it. In the center area one can notice two zones where the two ferrite grains, one on each side, touch each other. On the outer layer, the ferrite was predominant among pearlite, granular, and perlite colonies, forming a diffuse boundary zone.

At the boundary zone, the boundary ferrite was surrounded by thinner colonies of pearlite, granular, and perlite. It is possible for the ferrite to interpenetrate the colonies of pearlite and the compounds to form in different shapes. In some areas, rows of ferrite were visible on the ferrite side, but not so on the other side.

The oracle ferrite was generally surrounded by a thin layer of pearlite and granular-containing perlite. On the oracle side, one can see that the pearlite was less in volume and scattered than it was on the other side of the ferrite grain. On the oracle side, the pearlite was either almost or completely replaced by granular-containing perlite. 

The sample of ZG45 steel was characterized by a coarse grain structure with small ferrite colonies and large pearlitic colonies. The fine pearlite represented a large fraction of the inter-site area. The ferrite/pearlite phase area ratio can be estimated at 1.7/1. At certain locations, one could observe some signs of carbide precipitation in the form of bands or random distortions of the ferrite-pearlite grain boundaries. The carbides appeared to be second phase particles which were located on the ferrite grain boundaries.

Generally, the ZG45 steel showed a uniform microstructure with no visible segregation. The microstructure consisting of large ferrite grains, pearlite grain and a few small carbides was in agreement with the properties required for the desired purpose.