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Introduction
Steel is an alloy consisting primarily of iron and carbon, with several additional elements. Steel hardness is increased through a process known as hardening and tempering. One of the common forms of hardening and tempering is quenching and tempering, which involves heating the steel past its critical temperature and then cooling it in a bath of water or oil. This method of hardening is used for steels such as 52100, 5160, and 1095. R5 is a type of steel produced through a hardening and tempering process known as hardening and tempering with oil.
Forging
The forging process is used to make certain types of steel, such as R5, tougher and stronger. Forging is the process of forcing a metal, such as steel, into shape, and the shape it takes on will depend on the mold used, which is typically a hammer and anvil. During forging, the steel is compressed and heated in an anvil, causing it to become malleable and high-carbon molecules are mixed into the steel. This causes the steel to become harder and more ductile.
Heat Treatment
Heat treatment is used to harden and strengthen steels, such as R5, and to change their metallurgical structure. Heat treatment involves heating the steel to temperatures above its critical temperature, so the steel can form martensite, a type of hardened steel. For R5, the heat treatment process is further divided into two parts.
Quenching
Quenching is the first stage of heat treatment, in which the steel is heated above its critical temperature and then cooled in a bath of oil or water. This causes carbides, strengthened particles within the steel, to form. This added hardness makes it possible for steels, such as R5, to have higher strength and wear resistance.
Tempering
The second stage of the heat treatment process is tempering. Tempering involves reheating the steel below its critical temperature and allowing it to cool slowly. This helps to reduce the hardness of the steel by allowing the steel to relax and redistribute the variants of microstructures, increasing its toughness and ductility.
Microstructure
The microstructure of a steel gives insight into its performance. The microstructure of R5 consists mainly of a mixture of ferrite, pearlite, and martensite. Ferrite is the softest of the three and provides ductility. Martensite is the hardest and provides strength and abrasion resistance. Pearlite is the intermediate of the two and provides good strength and ductility.
Conclusion
Hardening and tempering with oil is a process used to harden and strengthen steels, such as R5. This process involves heating the steel past its critical temperature and then cooling it in a bath of oil or water. Forging helps to increase the steel’s tensile strength and wear resistance, and the heat treatment process further increases the steel’s strength and wear resistance. The microstructure of R5 consists mainly of a mixture of ferrite, pearlite, and martensite.
References
1. Leo L. Schrom, Metallurgy of Heat Treatable Steels, ArcelorMittal Steel South Africa, 3rd Edition, 2020.
2. J.M. Iturbide, Y. Liu, P. Collares-Pereira, et al., “Influence of Oil-Quenching on the Microstructure of a 52100 Bearing Steel”, International Journal of Advanced Manufacturing Technology. 63(2010): 13–20.
3. D. Schaeffler, D.T. Midgley, “Heat Treatment of 52100 Bearing Steel”, ASM Specialty Handbook: Heat Treating, 1984, pp. 467-472.
4. Carlos F. Canet and Alfredo Plazas-Ochoa, “Heat Treatment of Steels: Principles and Processes”, Elsevier B.V, 2021.
