Tundish and method for production of a metal strip of high purity
View Patent ↗To achieve the highest possible separation rate for foreign particles in a tundish combined, at the same time, with a minimized level of inclusions, the refractory-lined interior space of the tundish, as a function of an operating bath level (h), satisfies the condition that a dimensionless ratio (κ) of the refractory-lined surface area (A ref ) to the filling volume (V) which is delimited by this refractory-lined surface area and the bath-level-dependent exposed surface area (A Top ) and results from the relationship κ = A ref ( V ) 2 3 be between 3.83 and 4.39.
1. A tundish for producing and transferring high-purity metal melt from a casting ladle into a permanent mold of a continuous-casting installation, the tundish having a refractory lining which defines a refractory-lined interior space of the tundish, the lining having a refractory-lined surface area which, as a function of an operating bath level (h), satisfies the condition that a dimensionless ratio (κ) of the refractory-lined surface area (A ref ) which is wetted by the metal melt to the filling volume (V) which is delimited by the refractory-lined surface area (A ref ) and the bath-level-dependent exposed surface area (A Top ) and results from a relationship
κ
=
A
ref
(
V
)
2
3
be between 3.83 and 4.39.
2. The tundish as claimed in claim 1 , wherein the dimensionless ratio (κ) is between 3.83 and 4.20.
3. The tundish as claimed in claim 1 , wherein as a function of the operating bath level (h), the refractory-lined interior space of the tundish satisfies the condition that the ratio (ζ) of the exposed surface area (A Top ) to the refractory-lined surface area (A ref ) which is wetted by the metal melt is between 0.4 and 1.0.
4. The tundish as claimed in claim 3 , wherein the ratio (ζ) is between 0.5 and 0.8.
5. The tundish as claimed in claim 1 , wherein the operating bath level (h) in the tundish is between 0.5 m and 1.5 m.
6. The tundish as claimed in claim 1 , wherein the filling volume (V) of the interior space of the tundish is at least 0.75 m 3 .
7. The tundish as claimed in claim 1 , wherein the filling volume (V) of the interior space of the tundish contains at least 5 times the quantity of metal melt which is cast each minute in normal operation.
8. The tundish as claimed in claim 1 , wherein the refractory-lined interior space of the tundish is shaped as substantially formed by a generatrix which rotates about a vertical tundish axis.
9. The tundish as claimed in claim 1 , wherein the refractory-lined interior space of the tundish is shaped as substantially formed by a generatrix which rotates about a vertical tundish axis at a distance (r) from a vertical tundish axis that varies as a function of the rotation angle of the generatrix.
10. The tundish as claimed in claim 1 , wherein at least in sections thereof, the interior space of the tundish is in the shape of one of a hemisphere, a truncated cone, a paraboloid of revolution or a cylinder.
11. The tundish as claimed in claim 9 , wherein the cross section of the interior space of the tundish, in a section plane taken normally to a vertical tundish axis, at least in sections, is circular or elliptical in form.
12. The tundish as claimed in claim 1 , further comprising a submerged pipe which projects into the tundish to supply the melt there a flow diverter arranged on the tundish base and beneath the submerged pipe, an outlet opening arranged at a location of the tundish base which is spaced apart from the flow diverter by at least half the diameter (d) of the base.
13. The tundish as claimed in claim 1 , further comprising a melt feed tank and at least one melt discharge tank, each melt discharge tank is separated from the melt feed tank, a transfer passage between the melt discharge and feed tanks, and each melt discharge tank delimits an interior space of the tundish.
14. The tundish as claimed in claim 13 , wherein the melt feed tank delimits an interior space of the tundish.
15. The tundish as claimed in claim 13 , further comprising a flow diverter in the melt feed tank and an outlet opening from the melt discharge tank.
16. The tundish as claimed in claim 1 , further comprising a distributor carriage supporting the tundish, the carriage having at least one of a lifting device and a tilting device, and having a movement drive, the carriage being displaceable on a movement path between an operating position and a waiting position.
17. The tundish as claimed in claim 6 , wherein the filling volume of the interior space is at least 1.0 m 3 .
18. The tundish as claimed in claim 7 , wherein the filling volume of the interior space contains at least 7 times quantity of melt.
19. The tundish as claimed in claim 9 , wherein the distance (r) form the vertical axis is harmonically pulsating.
20. The turnish as claimed in claim 13 , wherein the transfer passage is an overflow.
21. A process for producing a high-purity metal strand using a continuous casting installation, comprising passing metal melt from a casting ladle into a tundish and from the tundish into a continuous-casting permanent mold, setting a melt volume (V) of a metal melt contained in the refractory-lined interior space of a tundish, as a function of a respective operating bath level (h), such that a dimensionless ratio (κ) of the contact surface area (A ref ) formed by the metal melt to the melt volume (V) which is delimited by the contact surface area (A ref ) formed by the metal melt and the bath-level-dependent exposed surface area (A Top ) and which results from the relationship
κ
=
A
ref
(
V
)
2
3
is between 3.83 and 4.39.
22. The process as claimed in claim 21 , wherein the dimensionless ratio (κ) is between 3.83 and 4.2.
23. The process as claimed in claim 21 , further comprising setting a melt volume (V) of the metal melt contained in the interior space such that a ratio (ζ) of the exposed surface area (A Top ) formed by the metal melt to the contact surface area (A ref ) formed by the metal melt is between 0.45 and 1.0.
24. The process as claimed in claim 23 , wherein the ratio (ζ) is between 0.5 and 0.8.
25. The process as claimed in claim 21 , further comprising setting the operating bath level (h) to between 0.5 m and 1.5 m.
26. The process as claimed in claim 21 , further comprising setting the melt volume (V) to at least 0.75 m 3 .
27. The process as claimed in claim 21 , further comprising setting the melt volume (V) to at least 5 times the quantity of metal melt which is cast each minute during a normal operation of the process.
28. The process as claimed claim 21 , wherein the metal melt substantially takes up an interior space formed by a generatrix (E) which rotates about a vertical tundish axis.
29. The process as claimed in claim 21 , wherein the metal melt substantially takes up an interior space which is formed by a generatrix (E) which rotates about a vertical tundish axis at a fluctuating distance (r) from the vertical tundish axis that varies as a function of the rotation angle of the generatrix.
30. The process as claimed in claim 21 , further comprising supplying the melt below a metal bath level and guiding the metal bath flow in a controlled manner to a melt outlet.
31. The process as claimed in claim 21 , comprising setting a horizontal distance (H) between a jet of metal melt which enters the melt volume (V) substantially vertically and a jet of metal melt which exits from the melt volume (V) substantially vertically, the horizontal distance being set to less than half a base diameter (d) of the interior space.
32. The process as claimed in claim 26 , wherein the melt volume is set to at least 1.0 m 3 .
33. The process as claimed in claim 29 , wherein the distance (r) from the vertical axis is harmonically pulsating.
34. The process as claimed in claim 27 , wherein the melt volume is set to at least 7 times the quantity of the metal melt.