Investigation of the microstructure, machinability and hole quality of AISI 1045 steel forged at different temperatures

Abstract

In this study, AISI 1045 steel material was hot forged at 1100, 1150, 1200 and 1250°C temperatures. The microstructure and hardness of the test specimens after forging were investigated. The non-forged samples and forged samples were drilled with 6.8 mm diameter solid tungsten carbide drills. Drilling tests were performed in 80 and 120 m/min cutting speed combinations and 0.15, 0.20 and 0.3 mm/rev feed rate. After drilling operations progress forces, surface roughness, roundness deviation, the deviation from cylindricity and taper were investigated. It has been determined that AISI 1045 steel consists of ferrite + pearlitic microstructure and its hardness increases due to the removal of microvoids and pores by forging. It was also determined that the hardness of the samples decreased due to the coarsening in grain size depending on the cooling time with the increase of the forging temperature. It was observed that the feed force obtained during the drilling of the untreated sample in the perforation process was less than the values obtained during the drilling of the hot forging process samples. However, it was found that the measured surface roughness, roundness, cylindricity and conicity values of an untreated sample were more than the hot forging treated sample. It was observed that this situation was caused by the difficulties experienced in sawdust evacuation due to the longer hole length of the untreated sample. Feed rates, surface roughness, roundness, cylindricity and taper values decreased with increasing forging temperature. This situation arises from the decrease in the feed rate due to the decrease in the hardness of the samples, which occurs with the increase in the forging temperature. With the hot forging process applied to the untreated A sample, the hardness values of the forged samples increased between about 8.7 and 10%. The increase in feed force was between 11 and 20%. Surface roughness, Circularity, Cylindricity and Taper values decreased between 40 and 98% compared to the untreated A sample.