**4.2 Processes of construction and arrangement of the weldment**

The authors [64] highlight the need to establish in advance the meanings of the welding sequence and the deposition sequence used in the construction of a structure. The welding sequence is closely linked to the assembly sequence, which must be established during construction planning, observing the manufacturing feasibility in order to minimize residual stresses and distortions. The manufacture of a structure formed by several unions, must follow some basic rules. In summary, the welding process must be performed symmetrically in relation to the neutral axis of the structural set, in order to counterbalance the forces arising from the contraction of the weld beads. However, it is not always possible to follow welding procedures determined in the project, in practice, these procedures will be decided when the construction inconveniences are observed in the field.

The deposition sequence refers to the progression of the formation of the beads during the execution of the welding, being able to use several types of progression that can be combined in different ways. As examples of sequences and progressions one can mention: continuous sequence (continuous pass); symmetric sequence; sequence with guided passes; progression by continuous passes and sequence of backwards passes.

The researchers [69, 70] developed studies on welding sequences, in order to promote the reduction of deformations in stiffened panels. The authors [69] used the robotic FCAW welding process in T joints of ASTM 131 grade AH32 stiffened steel panels. **Figure 5** shows examples of welding sequences used. After welding, they observed that sequence 3 (S3) presented the lowest global distortions value. In addition to the deformation analysis, he quantified the RS values using a portable X-ray diffraction equipment. **Figure 6** presents the 3D representation of the mean RS values in the longitudinal σy and transversal σx directions along the X axis. As the RS is closely linked to the behavior of the distortions, the panel that presented the lowest RS values was the sequence S3, with 59 and 86% for longitudinal and transverse compression stresses, respectively.

The influence of direction, welding sequence and reverse pass welding were analyzed by [70] on the distortions levels. The author uses in his work the GMAW process in short circuit mode, in T-joints of low carbon steel stiffened panels, where five welding sequences were used. Six welds of the same length were deposited in each panel to fix the reinforcements, obeying the order and sequence of welding.

**247**

**Figure 6.**

**Figure 5.**

**Figure 7.**

The welding sequences and directions for fixing the stiffeners can be seen in **Figure 7**. In the fifth sequence, the reverse pass was used, since the weld was divided into three

*TR's values in the 3D perspective for (a) reference plate; (b) sequence 1; (c) sequence 2; (d) sequence 3 in the longitudinal direction; (e) sequence 1; (f) sequence 2; and (g) sequence 3 in the transverse direction.*

The taking of the values of distortions of the panels was carried out in the four corners of each panel, adding the values of the distortions to obtain the global distortion of the panel. The average global distortion values measured, **Figure 8**, show that the lowest distortion values are obtained from the pass in the central direction to the ends (Exp. 2) and to the reverse pass (Exp. 5). For Exp. 2, the sequence used

equal segments. The arrow indicates the welding direction.

*Examples of welding sequences and directions in the union of hardened panels.*

*Schematics of welding sequences and directions for the stiffened panels.*

*Welding Residual Stresses to the Electric Arc DOI: http://dx.doi.org/10.5772/intechopen.93533* *Welding Residual Stresses to the Electric Arc DOI: http://dx.doi.org/10.5772/intechopen.93533*

**Figure 5.**

*Welding - Modern Topics*

the GMAW process.

backwards passes.

intermediate thickness correspond to the highest angular distortion value [64–66]. However, for plates with great thickness the value of angular deformation became low, due to its greater rigidity. **Figure 4b** shows, in a qualitative way, the angular deformation as a function of the thickness of the plate and the heat input, qw [67]. The increase in heat delivered to the plate can be represented using different welding parameters, such as increasing the feed value, in the case of the GMAW process, using the welding torch manipulation, weaving, and reducing the welding speed. The variation of these parameters generates an increase in material deposited per unit of length, consequently greater heat input, which shifts the curve to the right (**Figure 4b**). The authors [68] observed in their study that by applying a variant of the GMAW process to the CW-GMAW process, a reduction in the width of HAZ was obtained. This trend would be consistent with faster cooling rates produced using the CW-GMAW process, which suppresses ferrite nucleation at the grain boundaries. This reduction in the cooling rate resulted in less misalignment of the welded joint in the CW-GMAW process, compared to welding performed by

**4.2 Processes of construction and arrangement of the weldment**

construction inconveniences are observed in the field.

transverse compression stresses, respectively.

The authors [64] highlight the need to establish in advance the meanings of the welding sequence and the deposition sequence used in the construction of a structure. The welding sequence is closely linked to the assembly sequence, which must be established during construction planning, observing the manufacturing feasibility in order to minimize residual stresses and distortions. The manufacture of a structure formed by several unions, must follow some basic rules. In summary, the welding process must be performed symmetrically in relation to the neutral axis of the structural set, in order to counterbalance the forces arising from the contraction of the weld beads. However, it is not always possible to follow welding procedures determined in the project, in practice, these procedures will be decided when the

The deposition sequence refers to the progression of the formation of the beads during the execution of the welding, being able to use several types of progression that can be combined in different ways. As examples of sequences and progressions one can mention: continuous sequence (continuous pass); symmetric sequence; sequence with guided passes; progression by continuous passes and sequence of

The researchers [69, 70] developed studies on welding sequences, in order to promote the reduction of deformations in stiffened panels. The authors [69] used the robotic FCAW welding process in T joints of ASTM 131 grade AH32 stiffened steel panels. **Figure 5** shows examples of welding sequences used. After welding, they observed that sequence 3 (S3) presented the lowest global distortions value. In addition to the deformation analysis, he quantified the RS values using a portable X-ray diffraction equipment. **Figure 6** presents the 3D representation of the mean RS values in the longitudinal σy and transversal σx directions along the X axis. As the RS is closely linked to the behavior of the distortions, the panel that presented the lowest RS values was the sequence S3, with 59 and 86% for longitudinal and

The influence of direction, welding sequence and reverse pass welding were analyzed by [70] on the distortions levels. The author uses in his work the GMAW process in short circuit mode, in T-joints of low carbon steel stiffened panels, where five welding sequences were used. Six welds of the same length were deposited in each panel to fix the reinforcements, obeying the order and sequence of welding.

**246**

*Examples of welding sequences and directions in the union of hardened panels.*

#### **Figure 6.**

*TR's values in the 3D perspective for (a) reference plate; (b) sequence 1; (c) sequence 2; (d) sequence 3 in the longitudinal direction; (e) sequence 1; (f) sequence 2; and (g) sequence 3 in the transverse direction.*

#### **Figure 7.**

*Schematics of welding sequences and directions for the stiffened panels.*

The welding sequences and directions for fixing the stiffeners can be seen in **Figure 7**. In the fifth sequence, the reverse pass was used, since the weld was divided into three equal segments. The arrow indicates the welding direction.

The taking of the values of distortions of the panels was carried out in the four corners of each panel, adding the values of the distortions to obtain the global distortion of the panel. The average global distortion values measured, **Figure 8**, show that the lowest distortion values are obtained from the pass in the central direction to the ends (Exp. 2) and to the reverse pass (Exp. 5). For Exp. 2, the sequence used

**Figure 8.** *Overall distortion of the experiments.*

generated values consistent with those found in numerical studies [71–73]. Similarly, the results are corroborated by the work of [69], where it was observed that the welding sequence that provided the lowest distortion value must be performed from a more rigid point (central part) to one of less rigidity (extremities), resulting in less flexion of the panel and consequently lower values of RS. Exp. 5 obtained values very close to Exp. 2, due to the greater control of the temperature differential applied to the welded sheet and to a more uniform distribution of residual stresses [71]. However, this gain in the distortion values must be well considered, since a longer time was used to make the stiffener joint.
