Quality Improvement of Low Carbon Reinforcing Steel by Rapid Heat Treatment

In this paper the authors report the results of a series of experiments on two types of concrete steels subjected to rapid heat treatment (RHT). The results show that mechanical properties can be improved dramatically by the RHT. RHT involves a process whereby samples are heated up by their Joule heat. Because of this the steels composed of ferrite and pearlite transform to austenite in a short time (0.001-5 sec) depending on the current density. Austenite grains formed this way are much smaller than in the normally treated steels. The ferrite, pearlite and martensite originating from this austenite also have a very small grain size. Therefore the RHT procedure, in compliance with the Hall-Petch equation, produces higher strengths. The following are the results of a research program involving the quality improvement of two types of steels, often used for concrete reinforcement, by rapid heat treatment (RHT). The two types of steels treated were an unalloyed low carbon steel and a HSLA steel