How to weld > Welding thermal cycle
The t₈⁄₅ value
The thermal cycle of welding can be defined by the cooling time in the HAZ between +800°C and +500°C.
This parameter is called the t8/5 value. It is illustrated in the graph below.
Schematic diagram for a thermal heat treatment in the part of the HAZ situated closest to the weld metal.
The t8/5 value is mainly calculated. Evaluations of the t8/5 value show that it is close to constant throughout different parts of the joint. That is true as long as the peak temperature in the joint reaches above +900°C during the welding performance.
The formulas for the calculation of the t8/5 value is explained in the SSAB Welding Handbook.
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