Hot dipping and high-temperature austenitizing technologies-based zinc-aluminum-magnesium coated steel sheet to be stamped, preparation method therefor and use thereof

A zinc-aluminum-magnesium coated steel sheet to be stamped based on hot dipping and high-temperature austenitizing technologies, wherein the zinc-aluminum-magnesium coated steel sheet to be stamped is prepared by subjecting a steel substrate to hot dipping and austenitizing under high-temperature conditions, wherein

• a plating bath for the hot dipping is a Zn—Al—Mg plating bath, with a composition by mass percentage as follows:
• Al content of 4.5-8.5 wt. %, Mg content of 1-4.5 wt. %, and the balance of Zn and inevitable impurities;
• the steel substrate after the hot dipping becomes a zinc-aluminum-magnesium coated steel sheet based on hot dipping comprising a steel substrate, a zinc-aluminum-magnesium coating-2, and an intermediate compound layer between the steel substrate and the coating-2, wherein
• the zinc-aluminum-magnesium coating-2 comprises Zn, Al, and MgZn2 phases;
• the zinc-aluminum-magnesium coating-2 comprises Zn—Al two-phase eutectic and Zn—Al—MgZn2 three-phase eutectic, wherein a total eutectic content of the Zn—Al two-phase eutectic and the Zn—Al—MgZn2 three-phase eutectic is 50-95%, and a lamellar spacing of the eutectic structure is less than 1 μm;
• the intermediate compound layer between the steel sheet and the coating, referred to as an intermediate compound layer, is Fe—Al or Fe—Al—Zn intermetallic compounds;
• after having undergoing austenitizing at 900-920° C., the zinc-aluminum-magnesium coated steel sheet based on hot dipping technology is changed into a zinc-aluminum-magnesium coated steel sheet to be stamped based on hot dipping and austenitizing technologies, wherein
• the zinc-aluminum-magnesium coated steel sheet to be stamped based on hot dipping and austenitizing technologies comprises a steel substrate and a zinc-aluminum-magnesium coating-3, wherein the zinc-aluminum-magnesium coating-3 comprises an α-Fe(Zn, Al) single-layer structure, in which Fe, Zn, Al, and Mg elements are uniformly distributed, with a Zn content of 3.5-10.3 wt. %, a Al content of 0.5-12.2 wt. %, a Mg content of 0-0.2 wt. %, and a O content of 0.5-8.2 wt. %.