Method of restrained-quenching of annular member

A method of restrained-quenching of an annular member, comprising the steps of:

• heating an annular member made of steel to a temperature not lower than an A1 point;
• cooling said annular member heated to the temperature not lower than the A1 point, from the temperature not lower than the A1 point to a first cooling temperature which is a temperature not higher than an MS point;
• restraining said annular member cooled to said first cooling temperature with a restraint member;
• and
• cooling said annular member restrained with said restraint member to a second cooling temperature which is a temperature lower than a restraint start temperature at which restraint with said restraint member is started and not higher than the MS point, while said annular member remains restrained with said restraint member, and
• in said step of restraining said annular member and said step of cooling said annular member to said second cooling temperature, said annular member being restrained such that said restraint member and said annular member are in contact with each other at a ridgeline portion which is a portion where an outer circumferential surface and at least one end surface out of one end surface and the other end surface of said annular member intersect with each other, without said annular member and said restraint member being in contact with each other at said at least one end surface and at said outer circumferential surface of said annular member.