3.2 Hardness and strength of SZ
The hardness distribution of the original joint and rolled joints is
shown in Fig. 3 (a). It was observed that the hardness of the as-welded
SZ was approximately 68.4 HV and was lower than that of BM
(approximately 108 HV). After rolling process, the hardness of the SZ
was gradually increased to 151.6 HV (2 mm) as shown in Fig. 3 (b).