Heat treatment process for ultra-high-strength steel blind hole structural member

The invention relates to the technical field of heat treatment processes, and discloses a heat treatment process for an ultrahigh-strength steel blind hole structural member, which comprises the following steps: S1, normalizing: heating the blind hole structural member to 30-50 DEG C above Ac3, preserving heat, and cooling after preserving heat; s2, quenching is conducted, specifically, the cooled blind hole structural part is reheated to Ac3 or above, so that the blind hole structural part is austenitized, and then the blind hole structural part is put into a quenching medium to be subjected to staged cooling so as to be subjected to martensite transformation; s3, cold treatment is conducted, specifically, the quenched blind hole structural part is cooled to 0 DEG C or below so that the retained austenite in the blind hole structural part can be continuously converted into martensite; and S4, tempering is conducted, specifically, the blind hole structural part is reheated to the tempering temperature interva