Introduction
Ferritic steel is a type of alloy steel containing chromium as its major alloying element. It is an iron-chromium alloy with a low carbon content and ferritic structure. It is often used as an alternative to austenitic stainless steel and is known for its corrosion resistance and strength. Ferritic steel is widely used in a variety of applications including automotive parts, domestic appliances, and industrial equipment. The present work sought to analyze the microstructure of a ferritic steel (70 # steel) to determine its mechanical properties.
Background
Ferritic steel is an iron-chromium alloy with a low carbon content. The main characteristic of ferritic steel is its relatively low malleability which allows for its use in applications where malleability is not required such as vehicle frames and industrial equipment. The alloy is normally supplied in the form of plates or bars and can be cold-rolled or hot-rolled to produce a wide range of final products. Due to its low malleability, ferritic steel can only be drawn or bent into particular shapes by specialized equipment.
Methods and Sample
The sample used in this study was a 70 # steel plate obtained from a local source. The plate was subjected to a tempering process to improve its properties and then drawn into a plate with a thickness of 2 mm using a drawing press. The plate was then subjected to various metallographic techniques to investigate its microstructure.
Results
The metallographic investigation of the 70 # steel plate revealed a ferritic microstructure consisting primarily of ferrite (85%). There was also a small amount of martensite present (5%), as well as some other forms of iron such as pearlite (7%) and graphite (3%). The amount of free carbon present in the sample was found to be 0.1%. There were no significant inclusions or segregations present in the sample.
The hardness of the sample was measured using the Vickers hardness tester and found to be around 205 (HV 1/1000). The ultimate tensile strength of the sample was measured to be 450 MPa, indicating the high strength of the ferritic microstructure. The ductility of the sample was measured using the strain hardening rate test, where it was found to have a strain hardening rate of 1.3 GPa.
Discussion
The ferritic microstructure of the 70 # steel revealed by the metallographic investigation revealed that it was composed mainly of ferrite (85%) along with a small amount of martensite (5%), pearlite (7%), and graphite (3%). The small amount of free carbon present in the sample (0.1%) suggests that it is suitable for fabrication using a variety of welding processes. The hardness of the sample, measured by the Vickers hardness tester was 205 (HV 1/1000), which is relatively low for a steel alloy. The ultimate tensile strength was measured to be 450 MPa, which is quite high and indicates that this ferritic steel is quite strong. The strain hardening rate of the sample was measured to be 1.3 GPa, which is relatively low indicating that the steel has low ductility.
Conclusion
The 70 # steel plate was found to have a ferritic microstructure consisting mainly of ferrite with a small amount of martensite and other forms of iron such as pearlite and graphite. The sample was also found to have a low amount of free carbon (0.1%). The hardness of the steel was measured to be 205 (HV 1/1000) and its ultimate tensile strength was found to be 450 MPa. Additionally, the strain hardening rate of the sample was measured to be 1.3 GPa, indicating that it has low ductility. Overall, the results of this study indicated that the 70 # steel plate has good strength and is suitable for use in applications where malleability is not required.
