Steel sheet for hot press forming, method of producing steel sheet for hot press forming, and method of producing hot pressed member

A steel sheet for hot press forming, comprising a base steel sheet and a coated layer on both sides of the base steel sheet, wherein

• the coated layer comprises a chemical composition containing
• Si:
• 7 mass % to 11 mass %,
• Mg:
• 0.6 mass % to 1.9 mass %,
• one or both of Ca and Sr:
• in total, 1.0% to 10% of Mg in atomic concentration,
• Fe:
• 0 mass % to 30 mass %, and
• at least one selected from the group consisting of Mn, V, Cr, Mo, Ti, Ni, Co, Sb, Zr, and B, in total, more than 0 mass % and 2 mass % or less,
• with the balance being Al and inevitable impurity, wherein
• concentration of Mg solute in Al phase in the coated layer is less than 1 mass %, and
• average thickness of the coated layer is 10 μm or more and 30 μm or less on each side of the base steel sheet.

A method of producing a hot pressed member, the method comprising:

• heating a steel sheet for hot press forming;
• and
• hot press forming the steel sheet for hot press forming heated in the heating, wherein
• the steel sheet for hot press forming comprises a base steel sheet and a coated layer on both sides of the base steel sheet,
• the coated layer comprises a chemical composition containing
• Si:
• 7 mass % to 11 mass %,
• Mg:
• 0.6 mass % to 1.9 mass %,
• one or both of Ca and Sr:
• in total, 1.0% to 10% of Mg in atomic concentration, and
• Fe:
• 0 mass % to 30 mass %,
• with the balance being Al and inevitable impurity, wherein
• concentration of Mg solute in Al phase in the coated layer is less than 1 mass %, and
• average thickness of the coated layer is 10 μm or more and 30 μm or less on each side of the base steel sheet, and
• in the heating,
• temperature is increased from a heating start temperature of 50° C. or less to a heating temperature that is from the Ac3 transformation temperature of the base steel sheet to 1000° C.