Analisa Perbandingan Nilai Kekerasan Pada Perlakuan Panas Baja Polos dan Baja Ulir

Heat treatment is an essential process for improving the mechanical properties of metals, particularly hardness, through stages of heating, holding at a certain temperature, and cooling. This study aims to compare the changes in hardness values of plain steel (ST 55) and deformed steel (ST 60) after undergoing heat treatment at 920°C with a holding time of one hour. The cooling process was carried out using three different media: water, oil, and air, each of which provides a different cooling rate and influences the final hardness.Hardness testing using the Rockwell method showed an overall increase in hardness across all specimens. Deformed steel exhibited the highest hardness increase when cooled in water (54.1%), followed by oil (41.9%) and air (7.3%). Meanwhile, plain steel showed increases of 38.7% (water), 30.9% (oil), and 21.1% (air). These results confirm that the choice of cooling medium significantly affects the effectiveness of heat treatment, with water being the most optimal medium for enhancing hardness.