Introduction
Steel containing 0.65 percent to Si is a common low-carbon steel alloy used for various applications for different grades. It is most commonly used for electric body equipment, car parts such as springs, bearings, and transmissions, and for electric welding materials. It is also used in the production of tools and propellers. In this article, we will investigate the microstructure of a 0.65 percent silicon alloy after it has undergone heat treatment at 1100℃ for 20 minutes followed by a cooling in water at 350℃ for 4 seconds.
Experiment
The experiment was conducted on a sample of steel with 0.65Si2MnV (1100℃x20min+350℃x4s water cooling). The sample was cut into thin slices and prepared for the experiment by grinding and polishing with emery paper up to 1000 grits. The heat treatment was performed using an electric furnace. The temperature of the furnace was preheated to 1100°C and the sample was placed in the furnace. The furnace was then heated to 1100°C and held for 20 minutes. After the 20 minutes, the sample was removed and quenched for 4 seconds in cold water. The microstructure of the sample was then examined using an optical microscope.
Results
The results of the investigation indicate that the 0.65Si2MnV sample displayed a microstructure consisting of a combination of ferrite and pearlite. The pearlite first completely replaced the ferrite and then the ferrite re-appeared as the second phase in the microstructure. There was a particularly large amount of pearlite filling the grain boundaries. The ferrite present was mainly in the form of small grains and islands surrounded by the pearlite. The size of the pearlite and ferrite grains differed significantly depending on the part of the sample examined. The pearlite grains were generally larger than the ferrite grains in size, with the pearlite grains having an average size of 8µm and the ferrite grains having an average size of 2µm.
Discussion
The results indicate that the 0.65Si2MnV sample displayed a pearlite and ferrite microstructure as a result of the thermal treatment. The rate of cooling is an important factor in determining the microstructure of steel alloys. In this case, the sample was quenched for 4 seconds, much slower than is typical for steel alloys as the rate of cooling increases. Therefore, the slower cooling rate allowed more time for pearlite and ferrite to form in the sample, leading to a higher content of pearlite in the sample.
Conclusion
After undergoing a heat treatment of 1100℃ for 20 minutes followed by a cooling in water of 350℃ for 4 seconds, the 0.65Si2MnV sample displayed a pearlite and ferrite microstructure. The pearlite was present in much higher quantities than the ferrite, with the pearlite generally in the form of larger grains than the ferrite and surrounded by the ferrite grains. The size of the pearlite and ferrite grains varied, but the pearlite grains generally had an average size of 8µm and the ferrite grains had an average size of 2µm. This experiment demonstrates that controlling the cooling rate can have a large effect on the microstructure of steel alloys.
