To provide a welded joint in which the occurrence of fatigue cracks starting from microcracks in a boundary between a weld metal and a base material (steel plate), so far considered to be difficult to inhibit, can be inhibited and HAZ toughness can also be improved as much as possible.
The welded joint is formed by joining high tensile strength steel plates with high yield ratio by welding. The structure of the weld heat-affected zone of the high tensile strength steel plates is characterized as follows: the average grain size of old austenite is 200 m; the fraction of bainite is 90 area%; and, when a region surrounded by high angle grain boundaries having 15 orientation difference between two crystals is defined as a crystal grain, the average circle-equivalent diameter of the crystal grain is 9 m.
OGAKI SEIICHI
| JP2005320624A | 2005-11-17 | |||
| JPH0762489A | 1995-03-07 | |||
| JP2007177327A | 2007-07-12 |
| WO2000075388A1 | 2000-12-14 |
Tadashi Sugakawa
Osamu Futakuchi
Hiroaki Ito