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Rewetting Behaviour During Immersion Quenching

Thomas LÜBBEN ; Institut für Werkstofftechnik, Bremen, Germany
Friedhelm FRERICHS ; Institut für Werkstofftechnik, Bremen, Germany
Hans-Werner ZOCH ; Institut für Werkstofftechnik, Bremen, Germany

Puni tekst: engleski pdf 1.874 Kb

str. 45-52

preuzimanja: 735



Immersion quenching is a widely used technique in heat treatment, because
this technique provides higher heat transfer coefficients than the most
alternative gas quenching techniques. The disadvantage of immersion
quenching in evaporating fluids is the complex heat transfer mechanism
which consists of three phases, namely film boiling, nucleate boiling and
convective cooling. Especially the transition from film to nucleate boiling
– the rewetting of the sample surface – is a complicated process which
leads to an extreme local dependence of the heat transfer coefficient.
Therefore immersion quenching is very difficult to control and often leads
to distortion of the quenched workpieces.
In the present paper the rewetting behaviour was investigated by means
of hollow and solid cylinders. These workpieces offer the possibility to
investigate different distributions of surface temperatures of samples
with the same outer geometry/curvature. The observation of the rewetting
process was done by means of video films. Additionally, the cooling curves
at two positions near the surface were measured. From these data, heat
transfer for the quenching simulation by the Finite Element Method was
estimated and rewetting curves were calculated.

Ključne riječi

Immersion quenching; Oil; Rewetting behaviour; Simulation

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