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The isothermal kinetics of the recrystallization processes of vanadium microalloyed high carbon steels has been measured and modelled. The overall softening data were obtained by double hit compression tests performed at temperatures between 900 to 1 050°C, strain rates of 0.01 to 1 s Ϫ1, and inter-pass times of 0.1 to 30 s. The recrystallization behavior above and below and the critical strain for dynamic recrystallization was investigated. The results show that there is a transition strain region between where both static and metadynamic recrystallization take place during the inter-pass time. The results also revealed that V and Si have a strong solute drag effect, on the kinetics of metadynamic recrystallization. A kinetic model is proposed which takes the V and Si concentrations into account.

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The metadynamic and static recrystallization behavior in hypereutectoid steel containing 1 % carbon was determined by hot compression testing. Compression tests were performed using double hit schedules at temperatures between 900 to 1 050°C, strain rates of 0.01 to 1sϪ1 and recrystallization times of 0.1 to 500 s. The characteristics of static and metadynamic recrystallization are distinctly different. Results show that the metadynamic kinetics was twice as fast as the static kinetics. These data were used to generate equations to predict the kinetics of static and metadynamic recrystallization, as well as the evolution of grain size, after recrystallization.KEY WORDS: hot rolling; metadynamic and static recrystallization; hypereutectoid steel; grain size; mathematical model. As shown in Fig. 1(a), to determine the dynamic recrystallization characteristics, the specimens were heated at a constant rate of 1.5°C/s to 1 200°C for 20 min. Then the temperature was decreased at a rate of 1°C/s to the test temperature (900, 950, 1 000, 1 050°C) and held for 5 min to homogenize the temperature within the specimen. The specimens were deformed isothermally at a strain rate of 0.01, 0.1 or 1/s and the specimens were then water quenched. Double-hit Compression TestsTo study the progress of static and metadynamic recrystallization, several sets of double hit compression tests were performed ( Fig. 1(b)). The tests were performed in a radiant furnace using mica sheets lubricated with boron nitride, which were positioned between the anvils the specimen, in order to reduce frictional effects. The specimens were austenitized at 1 200°C for 20 min, and then slowly cooled (1°C/s) to the test temperature. After holding at the test temperature for 5 min the first deformation was applied.For the metadynamic recrystallization tests, the first strain had to be at high enough to at least initiate dynamic recrystallization. Testing was conducted using a strain rate range of between 0.01 to 1 s Ϫ1 and a temperature range from 900 to 1 050°C to generate a number of different dynamically recrystallized conditions. At the peak strain of dynamic recrystallization, the specimen was unloaded and held at the test temperature for times between 0.1 to 50 s to allow metadynamic recrystallization to occur. Then the specimen was reloaded to measure the level of metadynamic softening that had occurred and the specimens were then water quenched.In the case of static recrystallization, testing was first interrupted at a strain below the critical strain for nucleation of dynamic recrystallization using the same strain rate and temperature ranges that were used for the metadynamic investigations. In this case the kinetics were followed from 1 to 500 s and the specimens were then water quenched. Quantifying the SofteningThe interrupted deformation method is based on the principle that the yield stress at high temperatures is a sensitive measure of structural changes. In this work, the 0.2 % offset yield strength was used to determine the softening due to ...

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