On the Hardenability of an Intercritically Heat Treated Microalloyed Steel

Abstract

& Dual phase steel has become an important engineering material to be used in structural and automotive applications due to its good combination of strength, ductility, and formability. In this study, hardenability of a low carbon and microalloyed steel was investigated by using the standard Jominy End Quench Test at four different quenching temperatures. Three steel specimens were quenched from the intercritical region at 737 C, 754 C, and 779 C separately, whereas one of them was tested at 900 C, in the fully austenitic region. After finishing the Jominy test, metallographic examination of the samples was carried out to see the variation in the microstructure through the length of the steel. And also, hardness measurements were made through the length of the samples. Results brought out that there was a strong decrease in the hardness of the tested samples after a depth of 5 mm from the quenched end.

Low-carbon cast microalloyed steel intercritically heat-treated at different temperatures: microstructure and mechanical properties

“…It can be realized from these results that the hardness of the IHT750 sample is similar to the hardness level obtained for IHT800 sample. This seems to contradict the previous reports [8,42] which show that the hardness increases with martensite volume fraction; their view had taken no account of the austenite carbon content which is reduced when the IHT temperature is elevated, reducing the martensite hardness. In this investigation, the hardness value obtained could be explained based on the results of microhardness measurements (Table 5) together with the volume fractions obtained for each phase (Table 3).…”

Effects of Heat Treatment on the Microstructure and Mechanical Properties of Low-carbon Microalloyed Steels

“…In these steels, the microstructural studies suggest that the increasing in the cooling rate is related to the change in the microstructure from predominantly ferrite-pearlite to predominantly bainitic ferrite [6,9]. On the other hand, it has been found that higher hardness values were obtained in microalloyed steel by cooling rate due to phases [10]. Although many papers about the cooling rate effect on tensile behaviours of steels have been published in steels and alloys [11][12][13][14], there are few studies on the effects of cooling rate on the microstructure and microhardness [15][16][17].…”