Metal founding – Process – With measuring – testing – inspecting – or condition determination
Reexamination Certificate
2001-03-23
2002-12-10
Lin, Kuang Y. (Department: 1725)
Metal founding
Process
With measuring, testing, inspecting, or condition determination
C164S476000, C164S484000
Reexamination Certificate
active
06491088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and a device for continuously casting thin metal strips in a continuous casting device with an oscillating, water-cooled casting mold, a vertical strip guide arranged underneath it with devices for supporting and cooling the strand up to the point of solidification, one or more driver roll pairs which are pressed against the strand for supporting and conveying the strand, a device for bending the strand, and a device for bending the strand back.
2. Description of the Related Art
In the known prior art for continuously casting metal strips of minimal thickness (up to approximately 80 mm), the minimal strand thickness is achieved by a special shaping of the continuous cast plates and/or by squeezing the strand while the core is still liquid. Such a continuous casting device, as can also be taken from the company brochure “CSP/Compact Strip Production/Das neue Gie&bgr;- und Walzverfahren fur die wirtschaftliche Bandherstellung” (The new casting and rolling method for economical strip manufacture), No. W4+9/319/company SMS Schloemann-Siemag Aktiengesellschaft/4000/8/87, is comprised typically of an oscillating casting mold, a vertical strand guide arranged underneath thereof and provided with water jets for cooling the strand to the point of complete solidification, and one or more driven roll pairs for conveying the strand out. In order for the casting device to be able to transport the strand out, the driver rolls are pressed with a certain pressure against the strand which prevents their slipping. A special feature of these continuous casting devices is the arrangement of the driver rolls for conveying the strand below the point of complete solidification wherein The absence of the liquid core in the strand ensures that the strand will not yield to the driver roll pressure and a sufficiently large tension force is produced on the strand.
In this connection, it is known to press the driver rolls with hydraulic cylinders against the strand wherein the pressure during the casting process is invariable. This solution has been successfully employed for casting low-carbon and austenitic stainless steel. However, when casting steels which are very soft at the temperature of 1100° C. , such as, for example, Si-alloyed steels, stainless ferritic steels, high carbon-contents steels, the pressure of the rolls for generating the Conveying force results; in a thickness reduction of the strand. Moreover, the required advancing pressure of the driver rolls in practice is adjusted substantially higher than would actually be sufficient in order to exclude with certainty the risk of slipping of the driver rolls, which is identical to the standstill of the strand. With this increased pressure, the strand is actually rolled in an uncontrolled fashion by means of the driver rolls with a thickness reduction of, for example, up to 8 mm for a 60 mm strand thickness.
Since the strength of the strand continuously and constantly changes as a function of all casting parameters which affect the strand temperature (e.g., parameters such as temperature of the melt, casting speed, intensity of secondary cooling), the thickness reduction of the strand is a variable parameter that cannot be influenced in the case of an invariable driver roll pressure. For controlling the forces which are exerted by the oppositely arranged guide rolls of a strand casting machine onto a strand passing therebetween, it is proposed according to DE 27 47 000 A1 to measure these forces and, in the case of deviations from a standard value, to readjust the size of the roll gap by a simple rotation of a nut or of a bolt. Such a readjustment or correction can be carried out quickly between individual casting runs. However, during the casting runs, the disadvantage of an uncontrolled rolling action remains.
The disadvantages of the uncontrolled and variable rolling of the strand by driver rolls are as follows:
splitting of the edges of the strand
irregular thickness reduction of the strand
difficulties in regard to the synchronization of the motor drives of the strand casting device because of the unknown length change of the strand
difficulties in regard to maintaining the preset coil weight.
In order to avoid the undesirable uncontrolled rolling of the strand by the driver rolls, the roll pressure cannot surpass a certain limit.
The required conveying force can be achieved by increasing the number of roll pairs, by increasing the roll diameter, and by driving all rolls.
The disadvantages of all these measures are increased investment costs for the device technology and the additional production cost resulting from the increased service expenditure. The smaller the strand thickness, the greater the aforementioned disadvantages, because the strand weight, which supports the conveying force, is correspondingly smaller as a result of the reduced cross-section and, additionally, the shorter device height.
SUMMARY OF THE INVENTION
It is an object of the invention to develop a continuous cast device as well as a method for continuously casting thin metal strips with which the driver rolls for conveying the strand cause a predetermined thickness reduction of the strand with greatest possible constancy and maintain it during the entire casting process by means of a device-technological expenditure as minimal as possible.
The above object is inventively solved for a method of continuously casting thin metal strips in a casting device comprising an oscillating, water-cooled casting mold and a vertical strand guide positioned underneath it in that, for a defined thickness reduction of the strand of at least 2%, relative to the strand thickness at the point of complete solidification of the strand, and for maintaining constant a previously adjusted nominal strand thickness, at least one driver roll pair is pressed against the strand continuously during the entire casting process with a variable, defined pressure.
Advantageous embodiments of the invention are provided in the dependent claims wherein the aforementioned object is solved with respect to the device with at least one driver roll pair arranged below the point of complete solidification of the strand, which is connected to means for detecting the driver roll gap width and to means for generating and transmitting a variable pressure of the drive roll pair onto the strand.
When casting thin strands of soft steels, it is unavoidable that a rolling of the completely solidified strand occurs between the driver roll pairs when the number of driven driver roll pairs with large diameter is not to be increased and a standstill of the strand is to be avoided with certainty. Accordingly, in accordance with the method of the invention this rolling is carried out in a controlled fashion with a total strand thickness reduction, which is at least 2%. In this context, the thickness reduction of at least 2% is so great that the slipping of the driven rolls is prevented; it can be so great that the advantages of an increased strand thickness do have an effect in the area of the casting mold and the secondary cooling.
According to the invention, this controlled thickness reduction of the strand by means of at least one driver roll pair, while simultaneously keeping a previously adjusted nominal strand thickness constant, is achieved in that at least one driver roll pair conveying the strand out is pressed with a variable defined pressure continuously against the strand directly after its complete solidification. Accordingly, the actual roll spacing which corresponds to the strand thickness is continuously measured and is compared in a measuring and control device with the previously adjusted nominal strand thickness. Based on the measuring data comparison, the pressure with which the driver roll pair is pressed against the strand is controlled online by means of a hydraulic pump which is connected with the measuring and control device such that at all times the predetermined nominal strand thickness is obtained and m
Capotosti Romeo
Sucker Jürgen
Kueffner Friedrich
Lin Kuang Y.
SMS Schloemann--Siemag Aktiengesellschaft
LandOfFree
Method and device for continuously casting thin metal strips does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for continuously casting thin metal strips, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for continuously casting thin metal strips will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2931369