چكيده به لاتين
The aim of this research is to simulate the effect of cooling environments on the hardness of rebar produced using the thermex method. In this study, Deform 3D software was utilized to simulate the effects of various cooling environments (water, air, compressed air, and oil) on the hardness of bars with diameters of 10, 12, 14, and 16 mm. The austenitizing temperature was measured using dilatometry. The rebars were subjected to heat treatment, including cooling and tempering, after being heated to an austenitizing temperature of 880 °C. To assess hardness, Rockwell C and Brinell hardness tests were conducted at three regions: surface, middle, and core of the rebars. The hardness values at the surface of the 10, 12, 14, and 16 mm rebars were found to be 41, 30, 38, and 40 HRC, respectively. Ultimate tensile strength was determined through tensile testing, yielding values of 1744, 543, 569, and 701 MPa for the rebars, respectively. To obtain the heat transfer coefficient (HTC) between the sample and water, Jominy's test was employed. The HTC for the water environment was found to be 0.9. Metallographic analysis was conducted on the surfaces of all four samples. The metallographic results indicated that the depth of the martensite layer in the water-cooled sample (1000 micrometers) was the highest compared to other cooling environments. Parameters such as the austenitizing temperature and HTC were input into the software. Based on the comparison of experimental and simulation results, the highest hardness obtained was for the water environment. In the simulation, the surface hardness of samples cooled in water was recorded as 44 HRC, the middle section as 30 HRC, and the core as 20 HRC. The surface hardness of samples cooled in air, compressed air, and oil was measured at 31, 38, and 43 HRC, respectively, with core hardness values of 12, 14, and 24 HRC. Overall, this research demonstrates that selecting an appropriate cooling environment is crucial for improving the hardness of thermex bars and can lead to significant optimizations in the mechanical properties of the final products.
