Variable-thickness pre-coated steel sheet for hot forming, production method thereof, part hot formed by using same, and manufacturing method thereof

The invention provides a thickness-variable pre-coated steel plate for hot forming, a production method, a part hot-formed by using the thickness-variable pre-coated steel plate and a manufacturing method of the part. According to the method, the thickness of the pre-coating layer is controlled to be 13-20 microns, the continuous variable cross-section rolling reduction rate is smaller than or equal to 30%, and further, optional Ti and Sr are added into the pre-coating layer, so that the defect that large and dense cavities appear in the coating layer after the aluminum-silicon coating steel plate is subjected to continuous variable cross-section rolling hot forming can be effectively inhibited. The thickness of the pre-coating after continuous variable cross-section rolling is smaller than or equal to 14 microns, a part with more excellent cold bending toughness can be obtained after the prepared thickness-variable aluminum-silicon pre-coating steel plate is subjected to hot stamping quenching forming, the c