Welded joint of high fatigue strength
AssigneeNippon Steel Corporation
InventorsKatsumi Kurebayashi, Syuji Aihara, Hidesato Mabuchi, Naoki Saito
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Abstract
A propagation speed of a fatigue crack in a HAZ is restricted, and a fatigue strength of an as-welded joint can be improved, by limiting an area ratio of a ferrite micro-structure in the HAZ of the welded joint to 20 to 100% and the balance to one of a bainite, a martensite, a pearlite and a residual austenite micro-structure, or limiting a carbon equivalent of a steel plate used for the welded joint to not greater than 0.275.
Claims6
A welded joint having an excellent fatigue strength characterized in that an area of a ferrite micro-structure in a heat affected zone of the welded joint is from 20 to 100% of the area of the heat affected zone, and the balance comprises at least one of a bainite, a martensite, a pearlite and a residual austenite micro-structure;
- said welded joint being produced by using a steel plate containing 0.06 to 2.0 wt. % Si, and
- having a carbon equivalent (Ceg) of not greater than 0.275:
- Ceg=C+Mn/6+(Cu+Ni)/15+(Cr+Mo+V)/5+Nb/3.
A welded joint having an excellent fatigue strength characterized in that an area of a ferrite micro-structure in a heat affected zone of the welded joint is from 20 to 1000 of the area of the heat affected zone, and the balance comprises at least one of a bainite, a martensite, a pearlite and a residual austenite micro-structure;
- said welded joint being produced by using a steel plate containing, in terms of percent by weight:
- C:
- 0.015 to 0.15%,
- Si:
- 0.06 to 2.0%,
- Mn:
- 0.2 to 1.5%,
- P:
- not greater than 0.05%,
- S:
- not greater than 0.05%,
- Al:
- 0.001 to 0.08%,
- N:
- 0.002 to 0.015%, and
- the balance of Fe and unavoidable impurities;
- and having a carbon equivalent (Ceq) of not greater than 0.275:
- Ceq=C+Mn/6+(Cu+Ni)/15+(Cr+Mo+V)/5+Nb/3.
- 3.
Dependencies are inferred from the claim text.