High-temperature plasticity of carbon steels

Conclusions

• 1. A relationship was found between the change in the plasticity and strength of carbon steels and the structure of divorced pearlite at subcritical and critical temperatures. Up to 600°C the plasticity changes little, while the strength decreases. Above 600°C the plasticity increases sharply, reaching a peak at Ac₁ (beginning of the transformation) and then decreases sharply, while the strength increases or remains unchanged. At Ac₃ in hypoeutectoid steel or Ac₁ (end of the transformation) in hypereutectoid steel the plasticity is minimal. With further increase in temperature the plasticity increases.

• 2. The increase in plasticity at 600–730°C is explained by recrystallization of α phase, and the reduction of the plasticity in the critical range is explained by the difference in the plasticity of the α and γ phases and the difference in recrystallization rates.

• 3. The plasticity of steels with lamellar pearlite has no extremal values and increases monotonically in the range of phase transformations, which results from the small difference in the properties of lamellar pearlite and austenite.

• 4. In alloys with austenitic and ferritic structures that do not undergo transformations no anomalous change in plasticity was observed.