The present invention relates to the extraction of castings from a mold for horizontal continuous casting of metal, particularly steel, whereby particularly the casting is extracted in steps, each extraction step being succeeded by a slight retraction step and holding periods are respectively interposed in between. A retraction step and the next extraction step together may last from about 0.01 sec to a maximum duration of about half a second for the holding period.
Generally speaking, horizontal continuous casting of this kind is known through the Rexroth Information Quarterly, June issue 1985, pages 32 and 33. Such horizontal casting of metal, e.g. of steel, in this name requires that the casting strand be extracted, i.e. pulled out of the mold, because the process of casting withdrawal is not aided by gravity. During and following each extraction step, molten metal flows into that part of the mold which has just been vacated by a portion of the stepwise extracted and (partially) solidified casting. This flow of molten metal is dependent upon the extraction generally but in addition, the flow is determined by the inertia, viscosity and other parameters of the flowing metal itself. In particular then, a fast extraction of the casting does not immediately and directly entail a fast flow of molten metal into the vacated space, but inertia and viscosity impart a certain sluggishness upon the molten metal. It has been observed that cavities, for example, may form between, so to speak, the end of that portion of the casting that is being extracted, and the following metal as it flows into the mold. Therefore, it was the practice in the past that the extraction process during horizontal continuous casting had to match flow dynamics of the molten metal so the speed of an extraction stroke and so the cycle time of extraction in order to avoid the formation of cavities.
Specific extraction strokes and/or speeds attained by an extraction device can be provided with certainty only if at the same time the clamping force exerted upon the casting strand by the extraction device through clamping brackets or the like is appropriately determined. An adjustment of the clamping force is required, so as to inter alia match the operation of the clamping device to the format of the strand. In addition, in the case of an impending danger of interference a maximum clamping force can be exerted, for example, independent from the adjustment and from any matching of clamping to normal extracting conditions.