Patent Application
20090255644
The present invention relates to a twin roll caster.
Known as one of techniques for directly producing a strip from molten metal is twin-roll continuous casting where molten metal is supplied to between a pair of rotated rolls to deliver a solidified metal strip therefrom.
The chilled rolls 1 are constructed such that cooling water passes through the rolls and a nip G between the rolls may be expanded/contracted depending on thickness of the strip 3 to be produced.
The rotated speed and direction of the chilled rolls 1 are set such that outer circumferential surfaces of the respective rolls move from above to the nip G between the rolls at the same speed.
One of the side weirs 2 surface-contact one ends of the respective chilled rolls 1 and the other side weir 2, the other ends of the rolls 1. In a space defined by the chilled rolls 1 and the side weirs 2, a molten-metal delivery nozzle 4 made from refractory material is arranged just above the nip G between the rolls.
The delivery nozzle 4 has a top with an elongated nozzle trough 6 for receiving molten metal 5 and has longitudinal side walls formed with openings 7 from the trough 6 toward the outer circumferential surfaces of the chilled rolls 1, the openings 7 being formed on the side walls adjacent to lower ends thereof and being aligned along axes of the rolls 1. When the molten metal is poured into the nozzle trough 6, a casting pool 8 is formed above the nip G between the rolls 1 and in contact with the outer circumferential surfaces of the rolls 1.
Thus, with the casting pool 8 being formed, the rolls 1 are rotated while being cooled by circulation of cooling water, so that the molten metal 5 is solidified on the outer circumferential surfaces of the rolls 1 to deliver a strip 3 downwardly from the nip G.
In so-called triple point regions where the rolls 1, the side weirs 2 and the casting pool 8 meet, the solidified shells may be produced abnormally.
If such solidified shells at the triple point regions were drawn and peeled away by the solidified shells on the outer circumferential surfaces of the rolls 1, they might be drawn into the nip G between the rolls 1, resulting in not only defective shape in the form of locally thickened strip 3, but also deteriorated cooling efficiency due to the flared nip G by the locally thickened strip, breakage of the strip 3 due to thermal recuperation from the molten metal 5 and/or impair of the side weirs 2 upon drop of the solidified shells.
Thus, a twin roll caster has been proposed which directs molten metal 5 to side weirs 2 and especially positively in a direction tangent to chilled rolls 1 so as to suppress formation of undesired solidified shell (see, for example, Patent Literature 1).
[Patent Literature 1] JP62-45456A
However, in the twin roll caster according to the Patent Literature 1, the hot molten metal 5 just after the pouring streams along the side weirs 2 to reach the nip G within an extremely short time, so that the solidified shells are produced belatedly at regions adjacent to edges of the outer circumferential surfaces of the chilled rolls 1.
As a result, the strip 3 delivered from the nip G tends to have reduced thickness at its lateral ends or edges, resulting in difficulty of having uniform thickness throughout the width of the strip 3.
The invention was made in view of the above and has its object to provide a twin roll caster which can suppress reduction in thickness of a strip at lateral edges thereof.
In order to attain the above object, the invention is directed to a twin roll caster with chilled rolls, side weirs and a molten-metal delivery nozzle, comprising baffles capable of suppressing stream of molten metal along the side weirs into a nip between the rolls.
More specifically, the baffles are projected from bottoms of end faces of the nozzle in a casting pool toward the side weirs, respectively; alternatively, the baffles are projected from the side weirs in the casting pool toward the bottoms of the end faces of the nozzle, respectively.
Alternatively, ends of the nozzle extend to the side weirs, respectively, the baffles being projected from intermediate portions on a bottom of the nozzle toward said side weirs so as to form voids between the baffles and the bottom of the nozzle, respectively.
According to the invention, in order that the hot molten metal just after the pouring does not stream along the side weirs to instantly reach the nip, the baffles suppress stream of the molten metal toward the nip to eliminate belated formation of the solidified shells at and adjacent to the edges of the outer circumferential surfaces of the chilled rolls.
Extension of the ends of the nozzle to the side weirs prevents the hot molten metal from being poured directly into just above the nip at regions adjacent to the side weirs and reduces a contact area of the molten metal to the side weirs.
A twin roll caster according to the invention exhibits excellent effects and advantages mentioned below.
(1) The baffles suppress stream of the molten metal toward the nip and eliminate belated formation of the solidified shells at and adjacent to the edges of the outer circumferential surfaces of the chilled rolls, so that the strip delivered from the nip between the rolls has no reduced thickness at regions adjacent to lateral edges of the strip and the strip can be obtained which has uniform thickness throughout the width of the strip.
(2) Extension of the ends of the nozzle to the side weirs prevents the molten metal from being poured into just above the nip between rolls at regions adjacent to the side weirs and eliminates belated formation of the solidified shells at and adjacent to the edges of the outer circumferential surfaces of the chilled rolls, so that the strip delivered from the nip between the rolls has no reduced thickness at regions adjacent to lateral edges of the strip and the strip can be obtained which has uniform thickness throughout the width of the strip.
(3) Extension of the ends of the nozzle to the side weirs reduces the contact area of the molten metal to the side weirs, which suppresses formation of undesired solidified shell.
Embodiments of the invention will be described in conjunction with the drawings.
In a twin roll caster with chilled rolls 1, side weirs 2 and a molten-metal delivery nozzle 4, baffles 11 are provided which are contiguous with bottoms of end faces of the delivery nozzle 4 and are projected in a casting pool 8 toward the side weirs 2.
Tip ends of the baffles 11 may abut on the side weirs 2 or may be spaced apart from the side weirs 2 by minimum gaps, the baffles 11 being also spaced apart from the outer circumferential surfaces of the chilled rolls 1 by minimum gaps.
In the twin roll caster, the baffles 11 suppress stream S of the molten metal just adjacent to the side weirs 2 directly into the nip G between the rolls and guide the same in less resistive directions, i.e., toward longitudinally intermediate portions of the chilled rolls 1, so that the hot molten metal just after the pouring does not reach the nip G along the side weirs 2; the molten metal considerably lowered in temperature with lapse of time after the pouring is guided into the nip G between the rolls 1 with the rotation of the rolls.
Thus, eliminated is the belated formation of the solidified shells at and adjacent to the edges of the outer circumferential surfaces of the chilled rolls adjacent to the side weirs 2; as a result, the strip 3 delivered from the nip G between the rolls has no reduced thickness at regions adjacent to lateral edges of the strip and the strip 3 can be obtained which has uniform thickness throughout the width of the strip.
The baffle 11 may be contiguous with the side weirs 2 to be projected in the casting pool 8 toward the bottoms of the end faces of the delivery nozzle 4. When the baffle 11 is grooved at its top into gutter shape as shown in two-dotted chain line in
In a twin roll caster with chilled rolls 1, side weirs 2 and a molten-metal delivery nozzle 4, ends of the delivery nozzle 4 extend to side weirs 2, respectively, guttered baffles 13 being projected from intermediate portions on a bottom of the nozzle 4 toward the side weirs 2 to form voids 12 between the baffles and the bottom of the nozzle, respectively.
Tip ends of the baffles 13 may abut on the side weirs 2 or may be spaced apart from the side weirs 2 by minimum gaps, the baffles 13 being also spaced apart from the outer circumferential surfaces of the chilled rolls 1 by minimum gaps.
In the twin roll caster, the ends of the nozzle 4 extend to the side weirs 2, which prevents the molten metal from being directly poured into just above the nip G just adjacent to the side weirs. It reduces the contact area of the molten metal to the side weirs 2, which can suppress formation of undesired solidified shell.
The steam S of the molten metal from the voids 12 adjacent to the side weirs 2 to outside is prevented by the baffle 13 from being directly directed to the nip G between the rolls, and is guided in less resistive directions, i.e., toward longitudinally intermediate portions of the chilled rolls 1, so that the molten metal lowered in temperature with lapse of time after the pouring is guided into the nip G between the rolls with the rotation of the rolls 1.
The steam S of the molten metal introduced into the gutter on the baffles 13 is partly redirected upward.
Thus, eliminated is the belated formation of the solidified shells at and adjacent to the edges of the outer circumferential surfaces of the chilled rolls 1 adjacent to the side weirs 2; as a result, the strip 3 delivered from the nip G between the rolls has no reduced thickness at regions adjacent to lateral edges of the strip and the strip 3 can be obtained which has uniform thickness throughout the width of the strip.
Alternatively, the baffles 13 contiguous with the side weirs 2 may be projected in the casting pool 8 toward the bottom end faces of the molten-metal delivery nozzle 4; the tops of the baffles 13 may not always be grooved.
It is to be understood that a twin roll caster according to the invention is not limited to the above embodiments and that various changes and modifications may be made without departing from the scope of the invention.
A twin roll caster according to the invention is applicable for production of steel and other various strips.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/314843 | 7/27/2006 | WO | 00 | 1/9/2009 |
