Ductile brittle transition temperature

Ductile brittle transition temperature: it is mainly aimed at the change of internal crystal structure of steel with the change of temperature, so that the toughness and brittleness of steel change correspondingly.

1. Low temperature: when the temperature drops to a lower level (depending on the type of steel), the steel with good toughness loses its toughness and becomes as brittle and flexible as a glass bar. Therefore, the steel used in cold areas (such as Siberia in winter, North and south poles) must be selected to adapt to cold conditions. The low temperature brittleness is affected by the displacement force of dislocation, which makes it difficult to move at low temperature, resulting in a sharp increase in the yield strength of the material, which is equal to the fracture strength at a certain temperature. This temperature is the ductile brittle transition temperature. As the temperature continues to drop, the yield strength continues to increase, which is greater than the fracture strength, so brittle fracture has occurred in the material at low temperature without plastic deformation. The fracture strength of the material is less affected by temperature.

2. Hot steel: steel is basically crystal structure. When the temperature rises to 200 ~ 300 ℃, the bond breaks because of the increase of internal energy. At this time, the steel is still a hard solid state, so it becomes brittle and easy to fold.

3. Ductile brittle transition temperature: when the temperature is lower than a certain temperature TK, the material changes from ductile state to brittle state, and the temperature is ductile brittle transition temperature.

Ductile brittle transition temperature refers to the temperature (TK) of transition from ductile state to brittle state, also known as ductile brittle transition temperature or plastic brittle transition temperature, or brittle transition temperature for short. The magnitude of this tendency is generally determined by impact test.

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