The method comprises providing a cold-rolled sheet, with a composition containing: 0.15% ≤ C ≤ 0.23%, 1.4 % ≤ Mn ≤ 2.6%, 0.6% ≤ Si ≤ 1.3%, with C+Si/10 ≤ 0.30%, 0.4% ≤ Al ≤ 1.0%, with Al ≥ 6(C+Mn/10) – 2.5%, 0.010% ≤ Nb ≤ 0.035%, 0.1% ≤ Mo ≤ 0.5%, annealing the sheet at 860°C-900°C to obtain a structure consisting of at least 90% austenite and at least 2% intercritical ferrite, quenching to a temperature between Ms- 0°C and Ms-60°C at a rate Vc higher than 30°C/s, heating to a temperature PT between 410°C and 470°C for 60s to 130s, hot-dip coating the sheet, and cooling to room temperature. The microstructure comprises 45% to 68% of martensite, consisting of 85% to 95% partitioned martensite having a C content of at most 0.45%, and fresh martensite; 0% to 15% retained austenite; 2% to 10% intercritical ferrite; 20% to 30% lower bainite.