Hydrogen induced cracks, also known as cold, delayed or under-bead/toe cracking, primarily occur in the heat-affected zone (HAZ) and result from specific metallurgical conditions and constraints. Four key factors contribute to the formation of these cracks, including deposit composition and residual tensile stress, while prevention strategies involve managing preheat, inter-pass temperature, and cleaning to reduce hydrogen contamination. Techniques such as post-heating and selecting appropriate welding processes also play a critical role in mitigating these cracks.

1. Hydrogen Induced Cracks
Also known as cold, delayed or under-bead/toe cracking.
Root (underbead) crack Toe crack

2. Hydrogen Induced Cracks
Occurs primarily in the grain
coarsened region of the HAZ
Its path is usually a combination of inter and
transgranular cracking.
Lies parallel to the fusion boundary
Also known as cold, delayed or under-bead/toe cracking.

3. Hydrogen Induced Cracks
When this happens, the
crack growth rate decreases
and eventually arrests.
The principal residual tensile stress in toe cracks grow
progressively away from the fusion boundary towards a
region of lower sensitivity to hydrogen cracking.

4. Hydrogen Induced Cracks
Four factors are necessary to cause HAZ hydrogen cracking:
> 15ml/100g of weld metal
deposited
> 0.5 of the yield stress
< 300°C
> 400HV hardness

5. Hydrogen Induced Cracks
PREVENTIONS
Susceptible Microstructures Preventions
 Apply preheat to slow down the cooling rate
 Maintain a specific inter-pass temperature
 Use a multi-run instead of a single run technique
 Use a temper bead or hot pass technique

6. Hydrogen Induced Cracks
PREVENTIONS
 Hydrogen and Residual Stresses Preventions
 Apply Postheat / multi-run/ hot pass technique to diffuse hydrogen from
the weld area.
 Clean rust from joint to avoid hydrogen contamination
 Blend the weld profile to reduce stress concentration at the toes of the
weld
 Use dry shielding gases to reduce hydrogen content.
 Reduce weld metal hydrogen by proper selection of welding process or
consumable (eg use TIG welding instead of MMA, basic covered electrodes
instead of cellulose).