The mechanical properties of ferritic and martensitic cast steel at ambient and sub-zero temperatures
Abstract
This paper focuses on the analysis of the mechanical properties of ferritic and martensitic cast steel at ambient temperatures and sub-zero temperatures. Results indicate that both steels exhibit an increase in strength and hardness with decreasing temperature, which may increase the wear resistance of the material. This paper also evaluates the effects of the alloying elements on both ferritic and martensitic cast steel. It is observed that by increasing the alloy content, the strength and hardness of the material increases, while ductility and toughness decreases. Furthermore, the paper discusses different processing methods of both steels and the impact of these processes on the mechanical properties. It is concluded that enhancing strength and hardness of ferritic and martensitic cast steel can be achieved by proper heat treatment methods.
1. Introduction
Ferritic and martensitic cast steels are extensively used in different industrial applications due to their superior mechanical properties such as high strength, hardness and wear resistance. These steels are high-alloy steels and contain a variety of alloying elements like chromium, nickel etc. which enhance their mechanical properties. In the automotive industry, these steels are often used for crankshafts and other engine components that require high strength, but also need to retain their ductility under operating temperature conditions. Similarly, in the power generation industry, these steels are often used for turbine components due to their superior strength and wear resistance.
The mechanical properties of ferritic and martensitic cast steels are determined by their chemical composition and their heat treatment methods. The mechanical properties of ferritic and martensitic cast steels may also be affected by ambient and sub-zero temperatures. In sub-zero temperatures, these steels exhibit an increase in strength and hardness, due to the formation of martensite and its associated precipitation strengthening. These changes in microstructure and mechanical properties can be used to optimize the performance of the steels for specific applications. In this paper, the mechanical properties of ferritic and martensitic cast steels at ambient and sub-zero temperatures are critically evaluated.
2. Mechanical properties at ambient temperatures
At ambient temperatures, ferritic and martensitic cast steels exhibit exceptional strength and hardness due to the presence of various alloying elements. The microstructure of these steels consists of a large amount of ferrite and some carbon-enriched martensite. The addition of alloying elements enhances the mechanical properties of these steels.
For instance, chromium and nickel are essential alloying elements in ferritic and martensitic cast steels, and the presence of these elements increases the strength and hardness of steels due to their effect on microstructure. It is observed that by increasing the alloying elements, there is a higher amount of ferrite and less carbon-enriched martensite in the microstructure, which increases the strength and hardness at ambient temperatures. Furthermore, these steels exhibit excellent corrosion resistance due to the presence of these alloying elements.
3. Mechanical properties at sub-zero temperatures
At sub-zero temperatures, ferritic and martensitic cast steels exhibit an increase in strength and hardness compared to their ambient temperature properties. This increase in strength and hardness is due to a phenomenon known as “cold work”, wherein the microstructure of the steel changes due to the presence of sub-zero temperatures.
At temperatures below 0°C, steel undergoes a phenomenon known as transformation toughening, wherein the ferrite in the microstructure is converted to martensite and carbon-rich martensite. This transformation toughening increases the strength, hardness and wear resistance of the steel.
Moreover, the presence of alloying elements like chromium and nickel also increases the strength and hardness, as these elements increase the amount of martensite in the microstructure. The presence of other alloying elements like manganese, vanadium and molybdenum also increases the strength and hardness of the steel by forming carbides which strengthen the steel. Hence, the presence of alloying elements in ferritic and martensitic cast steels affects the microstructure and enhances the mechanical properties of the steel.
4. Processing methods
Ferritic and martensitic cast steels are processed through different methods to enhance their mechanical properties, such as heat treatment methods. Different heat treatment methods, such as quenching and tempering, can be used to increase the hardness and strength of these steels. Quenching is the process of rapidly cooling the steel to a low temperature, and tempering is the process of reheating the steel in order to reduce the hardness.
Also, austempering is a heat treatment process in which the steel is held at a constant temperature for a period of time in order to obtain a uniform distribution of martensite in the microstructure. This process increases the ductility and toughness of the steel.
Furthermore, martempering is a heat treatment process in which the steel is heated to a temperature above the transformation temperature, held for a certain period of time and then cooled in quenching oil. The process of martempering eliminates the chances of cracking due to sudden quenching and results in a uniform distribution of martensite in the microstructure, thereby increasing the strength and hardness of the steel.
5. Conclusion
This paper has discussed the mechanical properties of ferritic and martensitic cast steels at ambient and sub-zero temperatures. It is observed that both steels exhibit an increase in strength and hardness with decreasing temperature, due to the presence of alloying elements and the formation of martensite. Furthermore, different processing methods have been discussed, and it is concluded that proper heat treatment methods can be used to enhance the hardness and strength of these steels.
