| 摘要 |
<p>PURPOSE: An ultra-high strength twip steel sheet and a manufacturing method thereof are provided to manufacture vehicle body parts of complex shape without crack or burst and obtain a lightweight vehicle body. CONSTITUTION: An ultra-high strength twip steel sheet of austenite matrix tissue including manganese 15~25 weight% is characterized as follows. The brass orientation is restricted in a thermal treatment process after cold rolling. In the recrystallization texture, {352}<221> is developed as main orientation. The average plastic deformation ratio is 1.2 or greater. The composition includes, in weight percentage, carbon 0.15~0.30%, silicon 0.01~0.03%, manganese 15~25%, aluminum 1.2~3.0%, phosphorus 0.020% or less, sulfur 0.001~0.002%, and the rest iron. TheΣ3 grain boundary fraction of misorientation angle of 60°is 10% or less. The grain boundary fraction of misorientation angle less than 5°is 50% or greater. The grain boundary fraction of misorientation angle over 15°is 40% or less.</p> |
