The use of so-called electromagnetic stirrers for the purpose of stirring a melt in a mould in a continuous casting device forms contemporary technique well known to the person skilled in the art. Preferably, a part of the melt including the region of the meniscus thereof is to be stirred by means of such an electromagnetic stirrer. However, in certain cases, in which there is a risk of having inclusions brought down into the melt due to the presence of stirring at the meniscus, prior art suggests the use of a screen impermeable to the electromagnetic field of the stirrer, in order to suppress stirring in the region of the meniscus.
In order to control the casting process it is also well known to use an inductive sensor in order to monitor the level of the meniscus of the melt. Typically, such a sensor comprises two coils, one for inducing an eddy current in the melt and another one for sensing said eddy current. The sensor may, typically, be supplied with current high frequent current, for example alternating current of 800 Hz.
Also for reasons well known to the person skilled in the art, frequency converters have become widely used for supplying electromagnetic stirrers with the alternating current with which they are to operate, normally 0.5-10 Hz. However, frequency converters will result in the supply of harmonics, i.e. current of high frequency, on top of the base frequency with which they supply the stirrer. The applicant has realised that the electromagnetic field generated by said harmonics may disturb the operation of inductive sensors used for monitoring the height of the meniscus.
The problem to be solved by the invention is to provide a continuous casting device that permits an effective stirring of a melt in a mould thereof while at the same time permitting a correct measurement of the height of a meniscus by means of an inductive measurement sensor arranged at the mould.
In particular, stirring in the region of the meniscus of a melt in the mould of the device by means of the electromagnetic stirrer should be permitted.
USPTO Backgrounds
USPTO Backgrounds