PSI - Issue 30

A.A. Antonov et al. / Procedia Structural Integrity 30 (2020) 6–10 A.A. Antonov et al. / Structural Integrity Procedia 00 (2020) 000–000

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3. Results and discussion Field hardness measurements showed that the hardness of the metal from the outside at a distance of 5 mm from the fusion line is 56 HRB, 10 mm - 59 HRB, 15 mm - 64 HRB. On the inner side, it is 70 HRB at a distance of 5 mm; 10 mm - 72 HRB; 15 mm - 69 HRB. Table 1 presents the measurement data. Their distribution along the fusion line and HAZ is demonstrated in Fig. 1. The hardness measurements results show that the hardness in the root weld to the fusion line reaches its maximum value (~ 239 HB), and it is 215 HV in the superheated area (HAZ). As pointed out by Seyffarth et al. (1992), this hardness value corresponds to a structural composition of approximately 72% bainite and 28% ferrite. Further, with an increase in the number of passes and, correspondingly, the volume of deposited metal in the weld (W), the hardness values of the HAZ and fusion lines gradually decrease and reach 140 HB in the filling seam. Such a decrease in hardness in the HAZ in multilayer welding indicates a decrease in the cooling rate and a shift in structural transformations to the area of ferrite-pearlite transformations. Therefore, the strength characteristics significantly decrease with an increase in the number of passes in the superheated area of the welded joint. The softening of the metal near the HAZ of the fusion line reaches its maximum at the last two filling welds (FW), where the hardness is ~ 150 HB (Table 1). In the HAZ of the root weld, the maximum softening occurs at a distance of ~ 27 mm from the center of the weld, where the hardness drops to 132 HB, and the hardness of the cap weld (CW) remains within 150 ... 154 HB (Table 1, Fig. 1).

Fig 1. Distribution of hardness in the welded joint.

Table 1. Hardness measurement data, HB Distance, mm line 8 line 7

line 6

line 5

line 4

line 3

line 2

line 1

0 3 6 9

144 171 239 215 206 137 127 123 129 132

170 168 164 138 139 134 134 140 139 134

153 154 170 152 143 140 138 138 137 134

163 168 161 158 135 141 141 141 147 132

158 171 170 170 139 137 141 138 139 141

144 158 139 125 129 127 132 126 129 129

147 147 152 153 134 129 141 133 126 134

153 152 153 154 150

12 15 18 21 24 27

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