| 摘要 |
<p>Provided is a high-strength cold-rolled steel sheet that combines aging resistance with bake hardenability. By mass, said steel sheet contains 0.0010-0.0080% carbon, up to 1.0% silicon, 0.1-1.8% manganese, up to 0.100% phosphorus, 0.01-0.5% soluble aluminum, up to 0.0050% nitrogen, 0.005-0.050% niobium such that C* = C - (12/92.9)Nb > 0, and either 0.01-0.10% chromium such that Cr > 60C* - 0.03 or 0.010-0.050% copper such that Cu > 42.8C* + 0.018. This makes it possible to obtain a high-strength cold-rolled steel sheet that exhibits the following: high strength, with a tensile strength in the 340-440 MPa range; excellent bake hardenability, with at least 30 MPa of bake hardening after the application of a 2% prestrain followed by a 20 minute paint-bake hardening process at 170°C; and excellent aging resistance, with a yield elongation of no more than 0.5% in a tensile test after 60 days of natural aging at 70°C.</p> |
