High-strength hot-rolled steel sheet for automotive applications and method for manufacturing the same

摘要

The present invention relates to a high-strength hot-rolled steel sheet with a minimum tensile strength of 540 MPa and method of manufacturing the same. The high-strength hot-rolled steel sheet of the current invention finds use in automotive applications like wheel rims. The method of manufacturing the hot-rolled steel sheet includes the steps of casting a steel slab in either a conventional or a thin slab caster and then reheating the cast slab to a temperature greater than 1100°C, hot rolling the slab such that finish rolling is done at a temperature (TFRT), such that TFRT varies in the range Ae3 - 50 (°C) to Ae3 + 50 (°C), where Ae3 is the temperature at which the transformation of austenite to ferrite starts at equilibrium, and then cooling at a cooling rate of 50 - 70°C/s till an intermediate temperature (TINT = Ae3 - 320 (°C) to Ae3 - 300 (°C)) is reached, followed by performing natural cooling till the coiling temperature (TCT) is reached, and then coiling the steel sheet at TCT.