Metallographic diagram of 45 steel (850℃×1h air cooling)

Microstructure of 45 Steel at 850°C for 1h After Air-cooling

45 steel is a medium carbon steel alloy containing 0.42-0.50% carbon, 0.60-0.90% manganese, 0.015-0.035% sulfur, and 0.50-1.0% chromium. It is widely used in applications requiring moderate strength, toughness, and wear resistance. The microstructure of steel is strongly affected by its composition and thermomechanical processing. In this study, the microstructure of 45 steel at 850°C for 1 h after air-cooling was investigated using optical microscopy, scanning electron microscopy, and transmission electron microscopy.

The microstructure of the cooled sample showed that it was composed of two phases: ferrite and pearlite. The ferrite had a body-centered cubic (BCC) lattice structure and was identified by the light gray regions seen in the optical micrograph. The pearlite had a layered austenite and ferrite structure and was recognized by the dark gray grains seen in the micrograph. The grain size of the ferrite was on the order of 8 μm, whereas that of the pearlite was approximately 10 μm.

A scanning electron microscope examination revealed a fine distribution of carbides in both the ferrite and pearlite phases. In particular, the carbides in the ferrite phase were observed to have an acicular shape and a size of approximately 0.5 μm. The carbides in the pearlite phase had a plate-like structure and a size of about 0.2 μm.

A transmission electron micrograph of the cooled 45 steel sample revealed a substantial amount of nanoscale cementite (Fe3C) particles dispersed within the ferrite phase. The cementite particles were observed to have an average size of 40 nm. The presence of these interconnected cementite particles is believed to be responsible for the observed strength and hardness of the alloy.

In conclusion, the microstructure of 45 steel after cooling at 850°C for 1h consisted of an equilibrium mixture of ferrite and pearlite. The ferrite had a BCC structure and a grain size of 8 μm, while the pearlite had an austenite/ferrite structure and a grain size of 10 μm. Additionally, both the ferrite and the pearlite were observed to contain nanoscale carbides and cementite particles. These particles are believed to be responsible for the metals high strength and wear resistance.

The 45 steel phase diagram is a structural diagram often used in metal structural analysis. It is an example of a phase diagram showing the temperatures and time required to undergo a change in phase.

The 45 steel phase diagram is a diagram of the different phases expected with temperature and time, and is often used to describe steel products that are transformed and cooled at a given temperature over a period of time. In particular, the 45 steel phase diagram is tied to the time and temperature necessary to cool and change the phase of the steel from its original form (austenite or ferrite, whichever is applicable) to another form.

In the case of the 45 steel phase diagram, the steel is heated to a temperature of 850°C for one hour, and then cooled slowly and naturally in air, creating a combination of phases. The diagram is divided into several areas, each one representing a different combination of phases. The phases identified in the diagram are ferrite, pearlite, martensite and cementite.

The ferrite area is the small area located on the left side of the diagram. This area is where the combination of ferrite and pearlite are present and the steel is the softest. The left side of the area is the area where the ferrite is the most dominant, while the right side is more dominated by pearlitic structure. The ferrite area is often the starting point when analyzing the 45 steel phase diagram.

The pearlite area is the middle area between ferrite and martensite. The pearlite area is characterized by the combination of the ferrite and pearlite, with the ferrite being dominant at the left side and the pearlite being dominant at the right side. This area has a higher strength than the ferrite area and is usually the first stage in tempering.

The martensite area is located on the right side of the diagram. The martensite area is characterized by a predominantly martensitic structure, with some cementite present. This area is the hardest area and is usually the end point of the tempering process.

Finally, the cementite area is the small region located at the far right of the diagram, often just outside of the martensite area. The cementite area consists of predominantly cementite, and it is the strongest and most wear-resistant area in the diagram.

Overall, the 45 steel phase diagram is a useful tool that is commonly used in metal structural analysis. By understanding the temperature and time required to cool the steel and produce different phases, engineers and metallurgists can identify the optimal combination of phases for a given set of requirements.