| 摘要 |
PURPOSE: An ultra-high strength plate with excellent fatigue crack arrest ability and a manufacturing method thereof are provided to reduce fatigue crack generated when continuous stress is applied and improve yield strength and tensile strength. CONSTITUTION: An ultra-high strength plate with excellent fatigue crack arrest ability contains carbon of 0.02~0.10%, silicon of 0.01~0.6%, manganese of 1.8~2.5%, aluminum of 0.005~0.5%, niobium of 0.005~0.10%, boron of 5~40ppm, titanium of 0.005~0.1%, nitrogen of 15~150ppm, phosphorus of less than 0.02%, sulfur of less than 0.01%, residual iron, and other inevitable impurities. A micro-structure includes bainitic ferrite which has a column shape, constitutes the grain boundary azimuth difference of 55~65 degrees and Σ 3 grain boundary fraction of 20~40%. The yield strength is over 690MPa. |
