Page 204 - Handbook of Structural Steel Connection Design and Details

Welded Joint Design and Production

Welded Joint Design and Production 189

prevent underbead cracking. In order for postheat operations to be
effective, they must be applied before the weldment is allowed to cool
to room temperature. Failure to do so could result in heat-affected
zone cracking prior to the application of the postheat treatment.

3.2.3 Transverse cracking
Transverse cracking, also called cross-cracking, is characterized as a
crack within the weld metal perpendicular to the longitudinal direc-
tion (Fig. 3.6). This is the least frequently encountered type of crack-
ing, and is generally associated with weld metal that is higher in
strength, significantly overmatching the base material. Transverse
cracking is also hydrogen assisted, and like heat-affected zone crack-
ing, is also a factor of excessive hydrogen, residual stresses, and a
sensitive microstructure. The primary difference is that transverse
cracking occurs in the weld metal as a result of the longitudinal
residual stress.
As the weld bead shrinks longitudinally, the surrounding base
material resists this force by going into compression. The high
strength of the surrounding steel in compression restricts the
required shrinkage of the weld material. Due to the restraint of the
surrounding base material, the weld metal develops longitudinal
stresses which may facilitate cracking in the transverse direction.
When transverse cracking is encountered, a review of the low-
hydrogen practice is warranted. Electrode storage conditions should
be carefully reviewed. If these are proper, a reduction in the strength
of the weld metal will usually solve transverse cracking problems. Of
course, design requirements must still be met, although most trans-
verse cracking results from weld metal overmatch conditions.
Emphasis is placed upon the weld metal because the filler metal
may deposit lower-strength, highly ductile metal under normal condi-
tions. However, with the influence of alloy pickup, it is possible for
the weld metal to exhibit extremely high strengths with reduced duc-
tility. Using lower-strength weld metal is an effective solution, but
caution should be taken to ensure that the required joint strength is
attained.

Figure 3.6 Transverse cracking. (Courtesy of The Lincoln Electric
Company.)

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