Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Patent
1996-07-29
2000-06-06
Batten, Jr., J. Reed
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
164448, B22D 11041, B22D 11128
Patent
active
060706465
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a roll for a strand guide stand which prevents a weaving motion of the cast strand.
2. Description of the Prior Art
Strand guide stands in which the rolls have curved rather than straight surface lines are known from the prior art, e.g., DE 36 27 991 C2. Such rolls are used whenever the mold outlet cross section produces a strand cross section substantially deviating from a rectangular form.
Generally, for rectangular strands with strand thicknesses greater than 60 to 80 mm, rolls with straight surface lines are used in the strand guide stand directly below the continuous casting mold (segment 0) and the surface lines of rolls located opposite one another in pairs lie parallel to one another.
In strand guide stands having such rolls, the casting speed is limited by a weaving motion of the strands so that the following values are conventionally applied:
SUMMARY AND DESCRIPTION OF THE INVENTION
FIG. 1a is a schematic view of the rectangular mold and cast strand of the instant invention;
FIG. 1b is a schematic side view of FIG. 1a;
FIG. 2 is a partial cross-sectional view of the cast strand permitted to expand due to the concave surface line of the guide rolls;
FIG. 3 is a schematic view of the guide rolls of the instant invention in parallel position;
FIG. 3b is a view of the guide rolls in concave position.
The object of the present invention is to provide rolls for the strand guide stands for rectangular strands in which the rolls are designed so that a weaving or wobbling motion of the strands is prevented.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a roll for a guide stand for rectangular strands, which guide stand has guide rolls and driving rolls located opposite one another in pairs. The roll is provided with a cambered slightly concave surface line, at least when loaded so that the strand can be accurately guided without weaving. The slightly concave surface line allows the strand to expand spherically upon exiting from the continuous casting mold.
In another embodiment of the invention, the concave surface line only extends over part of the strand width, preferably 40%, thereof.
In yet another embodiment of the invention, the maximum concave surface line does not exceed 8%, and is preferably 2-4%, of the strand thickness.
In still another embodiment of the invention, the camber of the strand is achieved by correspondingly arranged split rolls. The camber of the strand can also be obtained by a corresponding bending of the rolls in a range of elasticity under casting loading.
Surprisingly, it has been shown that when using continuous casting molds with a rectangular cross section and cylindrical guide rolls, which is presently the case in the majority of continuous casting installations throughout the world, the casting speed may not exceed specified maximum values because, otherwise, the number of breakout defects in the strand increases disproportionately. This due to the fact that the strand begins to weave, that is, to move back and forth between the guide rolls, if a determined casting speed is exceeded. This leads to tilting and an uneven transfer of heat at the strand in the vicinity of the mold outlet cross section which, in turn, results in stress cracks and breakout.
FIG. 1 is a schematic view of the rectangular mold of the present invention with its narrow side 1 and broad side 2 and height D. The strand 3 cast with such rectangular mold has a length A, width B and thickness C. FIG. 2 is a partial cross-sectional and partially elevational view of the concavely shaped guide rolls 5 of the present invention, wherein 1 is the lenght of the roll for permitting the shell of the cast strand to assume a convex shape in accordance with the invention. FIGS. 3a and 3b show schematic views of the guide rolls 5' of the present invention whereby the concavity of the rolls has been achieved by bending of the rolls in the elasticity range und
REFERENCES:
patent: 4955428 (1990-09-01), Schrewe
patent: 5188167 (1993-02-01), Perry et al.
patent: 5460220 (1995-10-01), Coassin
Batten, Jr. J. Reed
Mannesmann Aktiengesellschaft
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