| 摘要 |
<p>A high-strength steel sheet with excellent low temperature toughness and low yield ratio property and a method for manufacturing the same are provided. The high-strength steel sheet with excellent low temperature toughness and low yield ratio property includes: 0.02-0.12 wt% of carbon (C), 0.05-0.5 wt% of silicon (Si), 0.5-2.0 wt% of manganese (Mn), 0.05-1.0 wt% of nickel (Ni), 0.005-0.25 wt% of molybdenum (Mo), 0.05-1.0 wt% of chrome (Cr), 0.005-0.1 wt% of titanium (Ti), 0.005-0.5 wt% of aluminum (Al), less than 0.015 wt% of phosphorus (P), less than 0.015 wt% of sulfur (S), the remainder consisting of iron (Fe) and inevitable impurities. The fine structure before SR treatment has more than 70% of ultrafine ferrite with an average grain size of less than 10μm and 10-30% of martensite/austenite composite structure (MA) with an average grain size of less than 5μm. According to the present invention, the high-strength steel sheet can have excellent low temperature toughness and low yield ratio property, and the steel sheet can have less deterioration of strength and toughness even after SR treatment.</p> |
