MANUFACTURING AND EQUIPMENT
USE OF ULTRASOUND IN ORDER TO INTENSIFY MOLDING
OF HIGH-TEMPERATURE THERMOCOUPLE SHEATHS
S. A. Shakhov
Translated from Novye Ogneupory, No. 6, pp. 25 – 28, June 2008.
Original article submitted February 4, 2008.
The possibility is demonstrated of intensifying molding of sheaths made of beryllium oxide for thermocouples
by means of ultrasound. Use of ultrasound during molding improves the production properties of
thermoplastic slips and structural and mechanical properties of molded castings. The efficiency of casting
structure formation under ultrasound conditions is determined by the cumulative effect of the main production
Recently continuous casting of thermoplastic slips has
become the main method of molding long, multichannel
ceramic sheaths, providing reliable protection for thermo-
couples during high-temperature firing of refractories.
The essence of the method involves filling under pressure
the molding cavity of a die with thermoplastic slip and
subsequent fixing of the shape acquired by changing the
aggregate state of the slip during cooling . The technology
is characterized by relatively simple implementation, and it
is very important in organizing mass production of objects.
However, alongside the advantages of the method there are
some disadvantages, giving rise low solid-phase impregna
tion with slip and its uneven distribution throughout the
volume of casting. As a result of this there is deformation
and scrap of objects.
Currently the possibility is being studied of intensifying
the continuous casting process for thermocouple sheaths by
means of ultrasound. The main direction of the research is
establishment of the effect of ultrasonic action intensity on
castings and the structural and mechanical characteristics of
castings. Experiments were carried out using a continuous
casting ultrasonic device (Fig. 1). In order to provide ultra
sonic activation of the slip during casting the device was
fitted with a special acoustic-technological circuit (ATC).
A feature of this ATC is its use in the form of a die, the
shape of whose cavity consists of two zones: a preliminary
treatment zone, in which the slip as a result of a heated
surface is held in the liquid state, and a molding zone in
which there is molding of a casting with slip cooling .
The potential of the device make it possible to prescribe
both precise pressure control P(0.1 – 10 at.
) and rate v
(0.0001 – 0.03 m/sec) of casting, heat exchange conditions
during slip solidification (temperature 18 – 20°C, cooling
agent consumption 0.01 – 0.5 m
/h), and ultrasonic vibration
intensity N (0.1 – 1.6 kW).
Thermoplastic slips were used for casting prepared on
the basis of beryllium oxide powder grade N4 (specific
Refractories and Industrial Ceramics Vol. 49, No. 4, 2008
1083-4877/08/4904-0261 © 2008 Springer Science+Business Media, Inc.
Novosibirsk State Academy of Water Transport, Russia.
Fig. 1. Layout of the experimental device for continuous casting
with ultrasound: 1) working tank; 2) die-waveguide; 3) ultrasonic
generator; 4) thermostat; 5) mixing mechanism; 6) control cabinet.
1 at = 0.1 MPa.