Page 57 - SSAB Welding Handbook Edition 2

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Welding handbook 10.0 Joint preparations

10.0 Joint preparations
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A sound welded joint requires proper joint preparation Therefore, the proper joint geometry for a given
prior to and during welding. Accurately preparing the situation is for the user to decide.
joint can counteract several types of discontinuities.
4 Keep the joint preparation area clean from
General issues to consider during joint preparation contaminants such as moisture, grease, rust and
are to: oil prior to each weld pass. If these substances are

4 Take measures to minimize the risk for hydrogen not removed, discontinuities may occur such as:
cracks in the cut edge and its surroundings from - Hydrogen cracks in the joint
the cutting performance by following our - Lack of root penetration
recommendations for avoidance of cracks. If - Lack of fusion
hydrogen cracks develop, leaving the cracks in the
plate can impair the mechanical properties of the - Porosity
structure. Normal measures to remove these cracks - Slag inclusion
include repair welding or removing the section that
includes the cracks by a separate cutting operation. 4 After thermal cutting, the joint contains an oxide
4 Choose a suitable joint geometry. It should be or a nitrite layer and a carbonized layer. The total
sufficiently wide to facilitate proper welding thickness of these layers is typically around 0.2 mm.
conditions and minimize the risk for discontinuities These layers are removed before welding, usually
in the joint. On the other hand, a joint geometry by grinding.
that is too wide and large causes negative effects.
The most common issues in this respect are that:
- Additional weld passes may be required in More information regarding hydrogen cracks can
be found in chapter 4, the mentioned discontinuities
the joint
in chapter 14 and suitable proceedings for repair
- The amount of weld passes may remain the same welding in chapter 17.
as for a narrower joint, but each weld pass may
need to be executed with a reduced welding
speed in order to produce the required amount
of weld metal.
- A higher degree of distortions in the structure
is promoted, due to the increase of the volume
of weld metal.

The choice of a suitable joint geometry depends on
the specific welding process and the present welding
situation.

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. 57
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.