In this paper, the critical points Ac1 and Ac3 of Q690D steels with different boron content were measured by Formastor-F automatic phase change meter, and the continuous cooling transformation curve of Q690D steel was drawn. The result shows that the addition of boron made the Ac3 and Ac1 of Q690D steel increased slightly, Ms point and Bs point reduced, the critical cooling rate of Q690D steel decreased, however the hardenability improved obviously. Boron in Q690D steel has different degrees of delayed effect on proeutectoid ferrite transformation and bainite transformation, which inhibits the precipitation of proeutectoid ferrite. The complete bainite structure can be obtained in a wide range of cooling rate.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |