Page 19 - SSAB Welding Handbook Edition 2

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Welding handbook 4.0 Hydrogen cracks

4.0 Hydrogen cracks
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Each type of steel has its own unique characteristics able to form at lower tensile stresses. Different models
regarding its resistance to different kinds of weld exist on how these three parameters interact with each
discontinuities in joints. Hydrogen cracks can form other. However, no exact proven mechanism for the
in different kinds of steels but they are emphasized initiation of hydrogen cracks exists.
in high strength steels including the Hardox and
Strenx grades. The risk for this type of crack in Hydrogen cracks can be surface breaking or exist as
joints of Hardox and Strenx grades is minimized by enclosed cracks in the joint. Examples of small
following the welding recommendations put forth hydrogen cracks are shown in fig. 4.1.
by SSAB.

Another name for a hydrogen crack is a cold crack.
As both names indicate, this type of crack is
influenced by hydrogen and is formed at relatively Transverse
low temperatures. Hydrogen cracks can be initiated crack
in the HAZ and in the weld metal.

Root crack
4.1 Description of crack appearance

A hydrogen crack is a delayed crack that
normally forms after the welding process when the
temperature in the joint drops below +200°C. A Underbead
crack can initiate and develop hours after welding is Toe crack crack
finalized. Detection of potential cracks is normally Fig. 4.1: Examples of where hydrogen cracks can form in a joint.
made 16-48 hours after the completion of welding.
The actual time depends on standard requirements or
a separate agreement.
If a hydrogen crack is formed, it can propagate
perpendicularly to the direction of the main stress
Three conditions must be present at the same
time in order for hydrogen cracks to form: that is present in the joint. A crack that is initiated
in the HAZ will normally grow into the unaffected
1) A relatively high content of alloy elements in the parent metal; an example is illustrated in fig. 4.2.
steel and/or in the consumable
2) A rather high quantity of hydrogen in the joint

3) High levels of tensile stresses in the joint.

These three factors interact with each other. For
example, if the hydrogen content is increased in the
joint for a specific welding situation, the cracks are

This handbook contains general suggestions and information without any expressed or implied warranty of any kind. SSAB hereby expressly disclaims
all liability of any kind, including any damages, in connection with the use of the information and for their suitability for individual applications. 19
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.