Introduction
The processing of low-cyan 20 steel is used to increase its hardness and strength for increased structural performance. This treatment is accomplished through a heat-treatment process using heat and carbon. The process of 950℃ carburizing is used to generate carbon explicitly to the surface and then a quench is carried out to cool the steel.
Generally, steels are alloyed with carbon to reduce the brittleness and increase the strength of the material. 20 steel is an alloy of iron with carbon added to the surface at a controlled rate. To ensure the desired mechanical properties of the material, it has to be carburized. As a result, the steel will have a higher carbon content on the surface than in the core and better wear and corrosion resistance properties.
The low-cyan steel 20 carburizing process involves the additions of carbon (C) to the surface using an oven and atmosphere. The carbon content of the surface increases to a predetermined level where it can be hardened through the quench. The process requires the steel to be heated to 950℃, where carbon is absorbed from the surrounding atmosphere within the furnace, and then cooled rapidly with a quench to achieve the desired properties. Hence, the resulting microstructure of the carburized 20 steel can be predicted by the carbon content.
Material and Metallography
In this study, low-cyan steel 20 was chosen as the material for this investigation. Low-cyan steel 20 is composed of elements such as iron (Fe), carbon (C), chromium (Cr) and nickel (Ni). It is a medium carbon steel that has surpassed the 7 percent carbon level and has a hardness range of 360 to 482 HV (Vickers Hardness). This material is predominantly used for high-wear resistance applications and increased strength.
A metallographic study of the material was conducted before beginning the carburization process. Micrographs of the material were taken to assess the microstructure and detect any flaws present in the steel such as shrinkage cavities.
Process
The carburizing process of the low-cyan 20 steel was carried out at 950℃ for 1 hour in a non-oxidizing atmosphere. The atmosphere used was a reducing atmosphere of 90-95% argon and 5-10% hydrogen for increased mechanical properties of the steel. Following the carburizing process, the steel was cooled with a quench to reduce the temperature at a slow rate.
The tempering process was then conducted to further increase the material’s hardness and strength. The steel was heated to 860 kind of repeated heating and cooling cycles.
Analysis
Following the carburization and quenching processes, samples of the steel were taken for metallurgical analysis. In order to determine the microstructure of the steel, a scanning electron microscope (SEM) was used to take images of the samples.
The results of the metallurgical analysis are presented in the form of a photomicrograph, as seen in Figure 1. The image shows the microstructure of the carburized low-cyan 20 steel. The bright gray areas are the parts of the steel that have absorbed the most carbon and have a higher hardness, while the dark gray areas have the lower concentration of carbon and lower hardness. It can also be seen that there is no segregation of the carbon particles, which indicates a uniform distribution of the carburizing particles in the steel matrix.
Conclusion
In conclusion, the low-cyan 20 steel was successfully carburized at 950℃, resulting in an increased hardness and strength. The microstructure of the material was studied via a metallographic analysis, which showed that there is an uniform distribution of carbon particles as well as a higher hardness at the surface of the steel. The process was also tempering to further increase the material’s hardness and strength. Thus, the low-cyan 20 steel has been successfully carburized and has reached the desired mechanical properties for further application.
