METHOD OF HARDENING LARGE-SIZED STEEL ARTICLES Russian patent published in 2003 - IPC

FIELD: metallurgy; particularly, thermal treatment of steels and alloys; possibly, hardening of steel articles of large diameter, for instance, with nominal diameter of 150-700 mm. SUBSTANCE: this method incorporates steps of heating up to austenization temperature, holding, controlled cooling which is carried out in several steps with various concentration of water-and-air mixture at different stages. Duration of the first cooling stage is also an innovation. Duration of this stage is determined by value of nominal diameter of article, factor of hardness penetration, distance to semimartensite zone. Realization of this method allows a complex of mechanical properties to be enhanced in required points of cross-section by means of creation of most favorable structure which is provided by optimum relationship among parameters of cooling process, that is concentration of water-and-air mixture and duration of cooling. EFFECT: enhanced quality of products. 1 tbl