Page 26 - SSAB Welding Handbook Edition 2

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4.0 Hydrogen cracks Welding handbook

The two latter steel grades require both stainless measurement of preheat temperature can be carried
austenitic consumables and the use of preheating out after a soaking period of at least 2 min/25 mm of
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during welding of certain plate thicknesses, in the single plate thickness.
accordance with the section titled 4.5 Preheat
temperatures during Welding of the Hardox and
Strenx grades. Measure the preheat
temperature here
AWS 307 consumables are preferred, if possible,
since they have a higher resistance to hot cracks
than AWS 309. 75 mm

4.7 The preheat performance Intended
weld joint
The use of preheating elements, shown in fig. 4.6 is
often the best method for preheating since it facilitates
uniform heating of the area in and around the joint.
An alternative method is to heat the area with a gas Fig. 4.7: Measure the temperature of the thickest plate in the joint. If
torch. However, extra care must be taken with the the plate is 25 mm thick, measure the temperature 2 minutes after
heating. If the plate is 12.5 mm thick, measure the temperature after
latter method since it tends to give a more unevenly 1 minute, etc. The interpass temperature can be measured in the
distributed preheat temperature in the joint. weld metal or in the immediately adjacent parent metal.

4.8 Interpass temperatures

The requirements for the interpass temperature of
multi-pass joints is the same as for the preheat
temperature. The interpass temperature is
measured in the weld metal or the immediately
adjacent parent metal. The previous welding
sequence may, in this case, produce an elevated
temperature that fulfils the preheat requirements.
If so, the next weld pass can be made directly after
the temperature measurement.

When additional preheating is needed between weld
sequences, it is carried out in the same way as for
preheating prior to the first weld pass.

Fig. 4.6: Preheating elements.

Preheating is performed on each side of the joint,
covering an area of at least 100 mm from the
center of the joint. The preheat temperature is
assessed 75 mm from the midpoint of the joint,
illustrated in fig. 4.7, in order to achieve an even heat
distribution throughout the plate thicknesses. The

26 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.
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.