Welding Heat Affected Zone (HAZ)

Welding Heat Affected Zone (HAZ):

Welding Heat affected zone
Welding Heat Affected Zone (HAZ)

Heat Affected Zone (HAZ):

    
➦ The metal in this region has experienced the temperature below its melting point, but its high enough to change the micro-structure.

    ➦ This metal consists of the base metal which has undergone a heat treatment due to the welding temperatures, so that its properties have been altered.
    ➦ The amount of metallurgical damage in the heat affected zone (HAZ) depends on the amount of heat input, peak temp reached, distance from fusion zone, time at elevated temp, cooling rate, and the metal’s thermal properties. 
    ➦ The effect on the mechanical properties is usually negative, and it is most often the region of the weld joint where failure occurs.

Unaffected Base Metal Zone:

    ➦ Where no metallurgical change has occurred.
    ➦ The base metal surrounding the heat affected zone (HAZ) is likely to be in a state of high residual stress, due to the shrinkage in the fusion zone.

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