Volume 8, Issue 7 (July 2011)
Duration of the Transient Nucleate Boiling Process and Its Use for the Development of New Technologies
In the paper a review of the transient nucleate boiling process duration is widely discussed. It has been established that duration of transient nucleate boiling process is directly proportional to square of the thickness of steel parts and inversely proportional to thermal diffusivity of a material, depends on the configuration of steel parts, liquid properties, and its velocity. The transient nucleate boiling (self-regulated thermal process) is followed by amazing regularities: The surface temperature during nucleate boiling is maintained at the level of the boiling point of the liquid, which is used as a quenchant. During this period, average effective heat transfer coefficients and average generalized Biot numbers and Kondratjev numbers can be found which significantly simplify core cooling time and cooling rate calculations. Using established characteristics of the transient nucleate boiling process, the new intensive quenching (IQ) technologies were developed: IQ-1; IQ-2: IQ-3. In the paper the steel super-strengthening phenomenon and optimal quenched layer, which provides maximal residual compressive stresses at the surface of steel parts, are discussed, which increase service life of products. Instead of oils, plain water is used as a quenchant, environmental conditions are significantly improved.