Aluminum-coated blank, manufacturing method thereof and apparatus for manufacturing aluminum-coated blank

An aluminum-coated blank comprising two or more aluminum-coated steel sheets connected together by a joint, wherein the aluminum-coated blank is a Tailor Welded Blank (TWB)

• each of the aluminum-coated steel sheets comprising:
• a base steel sheet comprising an amount of about 0.01 to 0.5 wt % of carbon (C), an amount of about 0.01 to 1.0 wt % of silicon (Si), an amount of about 0.5 to 3.0 wt % of manganese (Mn), an amount greater than 0 but not greater than about 0.05 wt % of phosphorus (P), an amount greater than 0 but not greater than about 0.01 wt % of sulfur(S), an amount greater than 0 but not greater than about 0.1 wt % of aluminum (Al), an amount greater than 0 but not greater than about 0.001 wt % of nitrogen (N), and the balance of iron (Fe) and other inevitable impurities, based on the total weight of the base steel sheet;
• and
• a coating layer comprising aluminum (Al) and formed on at least one surface of the base steel sheet in a coating weight of about 20 to 100 g/m2,
• wherein the joint comprises a composition comprising an amount of about 0.2 to 2.0 wt % of aluminum (Al) based on the total weight of the composition, the composition does not form ferrite at a temperature equal to or greater than the highest Ac3 temperature among the Ac3 temperatures of the two or more aluminum-coated steel sheets, and an average hardness of the joint is equal to or greater than an average hardness of the base steel sheet,
• wherein the coating layer comprises:
• a surface layer formed on the surface of the base steel sheet and comprising an amount of about 80 wt % or greater of aluminum (Al) based on the total weight of the surface layer;
• and an alloy layer formed between the surface layer and the base steel sheet and comprising aluminum-iron (Al—Fe), aluminum-iron-silicon (Al—Fe—Si) intermetallic compounds, and an amount of about 20 to 70 wt % of iron (Fe) based on the total weight of the alloy layer.