| 摘要 |
<p>This invention provides a method for quenching a steel product such as a high-strength boron steel, which method can prevent the formation of a slack hardened structure of a steel product surface layer after quenching to provide an even structure and thus to improve mechanical properties of the steel product. In quenching of a high-strength boron steel, a vapor film breaking time, which is an elapse time from a cooling start point to a treating material temperature sharp drop point, is regarded as a control item for determining the properties of a quenching oil, and quenching is carried out in a quenching oil which has been regulated so thatthe vapor film breaking time is a predetermined time or less (2.1 sec or less as determined by a cooling property testing method specified in JIS K 2242). The vapor film breaking time is regulated by preparing a quenching oil comprising a mineral oil as a base oil and various polymers with a high molecular weight mixed, into the base oil, as an additive for vapor film breaking time shortening purposes.</p> |
