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- Title
Microcracking in multipass weld metal of alloy 690 Part 3 – Prevention of microcracking in reheated weld metal by addition of La to filler metal.
- Authors
Nishimoto, K.; Saida, K.; Okauchi, H.; Ohta, K.
- Abstract
The effect of addition of La to a filler metal on microcracking (ductility dip cracking) in the multipass weld metal of alloy 690 was investigated with the aim of improving its microcracking susceptibility. The susceptibility to ductility dip cracking in the reheated weld metal could be greatly improved by adding 0·01–0·02 wt-%La to the weld metal. Conversely, excessive La addition to the weld metal led to liquation and solidification cracking in the weld metal. Hot ductility of the weld metal at the cracking temperature was greatly improved by adding 0·01–0·02 wt-%La to the weld metal, implying that the ductility dip cracking susceptibility was decreased as a result of the desegregation of impurity elements of P and S to grain boundaries due to the scavenging effect of La. The liquation and solidification cracking resulting from excessive addition of La to the weld metal is attributed to the formation of liquefiable Ni–La intermetallic compound. A multipass welding test confirmed that microcracks in the multipass weldment were completely prevented by using a filler metal containing an addition of 0·01 wt-%La.
- Subjects
FILLER metal; DUCTILITY; CRYSTALLIZATION; MELTING points; CRYSTAL grain boundaries; INTERMETALLIC compounds
- Publication
Science & Technology of Welding & Joining, 2006, Vol 11, Issue 4, p471
- ISSN
1362-1718
- Publication type
Article
- DOI
10.1179/174329306X94318