Duration of the Transient Nucleate Boiling Process and Its Use for the Development of New Technologies

Abstract

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.

Uniform and Intense Cooling During Hardening Steel in Low Concentration of Water Polymer Solutions

“…Transient nucleate boiling process during quenching of steel parts in water and water solutions is very intensive by itself due to high frequency and intense acting of thousands vapor bubbles [4,5]. The new characteristics of transient nucleate boiling process, discovered by author [17,18], were used for designing new technology. Engineers in heat treating industry, as a rule, considered effective heat transfer coefficients during nucleate boiling which can differ from real HTCs almost ten times showing always slow cooling [15].…”

“…As known, when initial austenitizing temperature is fixed at 850°C and bath temperature at 20°C, the duration of transient nucleate boiling process can be calculated by simplified Eq. (9) [17,18]:…”

Uniform and Intense Cooling During Hardening Steel in Low Concentration of Water Polymer Solutions

“…As known, when initial austenitizing temperature is fixed at 850 o C and bath temperature at 20 o C, then duration of transient nucleate boiling process can be presented by simplified Eq. (7) [17,18]:…”

“…[4,5]. New characteristics of transient nucleate boiling process were discovered by author [17,18] which were also used for designing new technology. Engineers in heat treating industry, as a rule, considered effective heat transfer coefficients during nucleate boiling which can differ from real HTCs ten times showing always slow cooling [15].…”

Designing of Advanced and Original Austempering Processes Based on Thermal Science and Engineering Physics Approaches

“…Here nb τ is the duration of the transient nucleate boiling process in seconds; Ω is characteristic of a quenchant when the austenitizing temperature is fixed at 850 o C; F k is coefficient responsible for a geometrical form of a steel part; D is the size (thickness or diameter) in m; a is the thermal diffusivity of a material in m 2 /s [13].…”