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Ultrasonic testing is used for the detection of material faults by ultrasound, i.e. with sound vibrations of over 20,000 Hz. The frequencies used lie between 0.05 MHz and 25 MHz. In practice, cast-part testing typically uses frequencies of 0.5 to 5 MHz. The coarser the grain structure, the lower the frequency must be chosen, because the grain boundaries scatter the sound and reduce penetration depth.

A tipping point of a crucible furnace refers to the pivot point of the crucible furnace, around which the furnace is tipped. The casting spout length and the relevant tipping point must be optimised, depending on the use of the furnace and the device employed to accept the melt. An optimum pivot point for all applications is the “lower lip” of the casting spout with a relatively long casting spout, in order to provide clearance for ladles in front of the furnace. This arrangement means that the casting stream can be directed accurately, and produces the lowest possible height differences between casting and total emptying.

Tipping cylinders are as a rule designed in the form of “plunger cylinders”, i.e. the piston rod, without its own sealing elements, acts simultaneously as the “piston”. Lowering takes place due to the counter-pressure of the furnace being raised. In most cases, the 2 tipping cylinders are arranged laterally in the front area of the furnaces. The lever arm has a length of 250 mm for small furnaces and a length of up to approx. 1,000 mm for a 70-t furnace. Wherever possible, the arrangement should be such that in the basic position, the tipping cylinders are standing either vertically, or inclined up to 3° to the rear. In the end position, the tipping cylinders should be either vertical, or inclined a maximum of 3° toward the front or rear. For furnaces from approx. 10 t, the tipping cylinders are equipped with “end-position damping”, which is achieved due to the piston rod design at the bottom. This is done to avoid sudden, jerky lowering into the basic position and any associated shocks when positioning the crucible.. In order to prevent any unforeseen “tipping errors”, the cylinders should be bled every 6 months.

A throat is the term for the upper section of a shaft furnace, such as a cupola furnace. The
furnace is charged through the throat, and the furnace exhaust gases are also
drawn off through the throat.

References

1. Herbert H. Netzel: Induktionsofenhandbuch. 3rd edition, Eigenverlag IES, Witten 2003, p. 65.

See also

• Gicht (German version)

A throat platform is the platform or working stage for charging the furnace with the material or charge to be melted.

A thermoelement is an electrical element which generates a voltage when heated. It consists of 2 different wires, which due to the voltage, cause a current to flow. These are used up to a maximum of 1,600 °C. The voltage generated is in the mV-range.

Thermal storage heating furnaces are used as holding and storage vessels in continuous and non-continuous foundry operations. Unforeseeable problems can also occur in continuous casting operations, which can then be rectified with the aid of storage furnaces. Storage furnaces are designed as channel furnaces or crucible furnaces with good heat insulation. A crucible storage furnace has the advantage of total emptying over a channel furnace, which must always be operated with a sump. The heat losses are as follows for 40-t furnaces:

a) normal crucible melting furnace                            approx. 400 kW
b) crucible storage furnace                                           approx. 300 kW
c) channel furnace 40 t usable capacity/12 t sump  approx. 250 kW

Temperature change or temperature change resistance refer as a rule in induction furnaces to the properties of the ceramic materials at different temperatures. An acidic lining is less temperature-sensitive, and thus more resistant to temperature change than basic or neutral compounds.

Temperature difference in relation to the distance between 2 points. The unit of measure of the temperature gradient is K/m or K/cm.

Temperature is the heat level of a material, measured in Kelvin (K) or degrees Celsius (°C). K is the SI unit of measure. The Kelvin scale begins at absolute zero, which corresponds to –273.15 °C. Conversion between k and °C:

K = °C + 273.15

°C = K – 273.15

Temperature differences are expressed in Kelvin, although they can also be specified in degrees Celsius.
In some countries, Fahrenheit is still commonly used as a unit. In this case, the conversion is as follows:

°C = (°F-32) x 5/9

°F = °C x 9/5 + 32