Several types of steel can be sensitive to brittle breakage at low temperatures.
In order to be able to indicate the toughness (being the opposite of brittleness) of a steel grade, the impact value of the material is measured at different temperatures.
Several types of steel can be sensitive to brittle breakage at low temperatures.
In order to be able to indicate the toughness (being the opposite of brittleness) of a steel grade, the impact value of the material is measured at different temperatures.
When determining the toughness, a notch impact test is done (according to NEN-EN-ISO 148-1). To do this, a normalised test piece fitted with a notch is broken with a drop hammer in a pendulum. The energy required for this can be read/calculated. The impact value is expressed in Joules (Nm), measured at standardised temperatures of 20°C, 0°C, -20 °C, -40 °C, and -60 °C.
An example: Structural steel S355 J2+N
The normalised designation 'J2' indicates that the impact value of this material is 27 Joules at a temperature of -20 °C. (+N idicates that the matarial is normalized).