DEVICE FOR CASTING STRANDS OF METAL

Abstract

The invention is directed to a device for casting strands of metal, in particular steel, with a material supply vessel, the liquid metal being delivered to the carrying side of a circulating conveyor belt by means of the pouring nozzle of the material supply vessel. The conveyor belt comprises a thin, heat-resistant belt which circulates between a first deflection roller and a second deflection roller and which is shaped after the first deflection roller and in the region of the outlet nozzle to form a trough for receiving the liquid metal and resumes the shape of a flat belt in proximity to the second deflection roller. In order to reduce stresses on the belt, it is proposed that at least one of the deflection rollers is cambered in a convex manner.

Description

PRIORITY CLAIM

This is a U.S. national stage of Application No. PCT/DE2008/000031, filed on 8 Jan. 2008, which claims Priority to the German Application No.: 10 2007 010 578.0, filed: 26 Feb. 2007 the contents of both being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to a device for casting strands of metal, in particular steel, with a material supply vessel, the liquid metal being delivered to the carrying side of a circulating conveyor belt by a pouring nozzle of the material supply vessel, wherein the conveyor belt comprises a thin, heat-resistant belt that circulates between a first deflection roller and a second deflection roller, the conveyor belt is shaped after the first deflection roller in a region of the pouring nozzle to form a trough for receiving the liquid metal and the conveyor belt resumes a flat shape in proximity to the second deflection roller.

2. Prior Art

A device of the type mentioned above is known from Japanese Publication 59147755 A, in which the trough shape of the belt is achieved by vertical and horizontal conveying rollers arranged along the conveying path between the two deflection rollers and act on the belt.

SUMMARY OF THE INVENTION

Due to the relatively large differences in temperature along a width of the belt that act on the belt through the liquid metal and because of the deformation of the belt from a flat shape to the trough shape and then back again into the flat belt shape, there are widely varying changes in length along the width of the belt resulting in critical stresses on the belt material, particularly in the edge area.

Although the belt—usually a steel belt for this purpose—has an elasticity corresponding to the belt material that is used, a cost-effective lifetime cannot be achieved as a result of the different stresses on the belt along the width.

Therefore, it is an object of the invention to design the device such that the stresses on the belt are reduced and evened out. Further, new materials are used for the belt material because of the reduced, more uniform stress on the belt. Further, the entry length and exit length are adapted to the geometry of the trough profile for specific adjustment of the degree of camber. This increases the cost effectiveness of the casting process appreciably.

The above-stated object is met according to one embodiment of the invention in that at least one of the deflection rollers is cambered in a convex manner.

Owing to a deliberate cambering of at least one of the deflection rollers, by which the shortening of the belt resulting from the formation of the trough profile is at least partially compensated and because the different temperature distribution along the width of the belt is also taken into consideration in the camber, the stress on the belt is made homogeneous, which has a positive impact on the life of the belt.

It is advantageous when the camber of at least one of the deflection rollers is varied by a pressure medium to compensate for the change in length, e.g., due to modified casting parameters. To this end, a profiled cavity is provided in the roller shell. In this connection, it can also be advantageous when the camber of the first deflection roller, is smaller than that of the second deflection roller.

The camber can be calculated based on the geometry of the trough profile. The average trough profile is used for the calculation when the trough profile varies over the length of the trough to adapt to the shrinkage of the casting profile.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic side view of the belt with the deflection rollers in a side view;

FIG. 2 is a cross section through the trough shape

FIG. 3 is a calculation model with a simplified trough shape as a rectangular shape for the calculation and cambering of the deflection roller; and

FIG. 4 is a trough cross section for calculating the influence of temperature.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a belt 10 and deflection rollers 12 and 14. As shown, pouring nozzle 16 is configured to supply liquid metal to the belt 10 in an area between rollers 12 and 14. The belt 10 is shaped such that a portion of the area between the rollers 12 and 14 is trough-shaped. At least one of the rollers 12, 14 is convexly cambered.

The camber of the rollers 12, 14 is a function of the respective entry belt length Le and exit belt length La between the deflection roller and the trough profile (FIG. 1) or, conversely, of the belt width B_B, trough width B_T, trough height H_T and trough profile (FIG. 2), where a rectangular longitudinal shape is assumed for purposes of the calculation.

The camber is yielded by: f(Le or La,B_B,B_T,H_T, trough profile).

The calculation of the camber is preferably carried out for every point of the deflection roller between points A and B of the trough profile with coordinates X and Y and length Le (a) for half of the belt width B_B between points C and D, shown in FIG. 3. The calculation of the camber is carried out for the entry side and the exit side.

The calculation of the different belt length owing to the varying temperature distribution over the width of the belt is carried out in a simplified manner according to the indicated formula. For an exact calculation, the temperature profile over the width of the belt is calculated corresponding to the casting parameters.

By means of the two formulas, the optimum camber of the deflection rollers for homogenized tensile stress over the width of the belt can be calculated for a given trough profile (casting format) and temperature profile by superposition:

B_B/2=X_B+X+X_T  (1)

ΔL_XB=L−L_V=√{square root over (L²+X²+Y²)}  (2)

Δl_Temp=L_Troughα(T_M−T_R)  (3)

where

• • B_B is the width of the belt (FIG. 3)
  • B_T is the width of the trough (FIG. 3)
  • H_T is the height of the trough (FIG. 3)
  • L is the length of the (final) trough profile between the entry and exit (FIG. 1)
  • Le is the entry length from the center of the first deflection roller to the final trough profile (FIG. 1)
  • La is the exit length from the final trough profile to the center of the second deflection roller (FIG. 1)
  • L_V is the length of the space diagonal in longitudinal direction of the trough (FIG. 3)
  • X is the X coordinate for calculating L_V (FIG. 3)
  • X_T is the distance from the center of the belt or trough to the side of the trough (FIG. 3)
  • X_B is the distance from point C to X_L+x from the center of the belt (FIG. 3)
  • Y is the Y coordinate for calculating L_V (FIG. 3)
  • T_M is the temperature in the center of the belt (FIG. 4)
  • T_R is the temperature at the edge area of the belt (FIG. 4)
  • α is the coefficient of expansion of the belt material
  • β is the angular deviation from the vertical (FIG. 2)

The camber of the first deflection roller 14 is preferably smaller than that of the second deflection roller 12.

The camber should be changeable, e.g., by a pressure medium, in at least one of the deflection rollers 12, 14. To this end, a profiled cavity can be provided at the roller shell for applying pressure.

The entry length and exit length, respectively, should preferably be greater than 500 MM.

The maximum entry length or exit length is selected in such a way that the camber due to the trough profile is not greater than 2%.

The belt is preferably shaped by the deflection roller continuously over the distance Le or La to form the trough profile or flat belt.

A particularly suitable belt material is a thermal shock-resistant alloy based on CuNi, Fe.

The belt material can be made of a single-phase or multiple-phase Cu alloy or a nickel-based alloy.

The belt 10 preferably has a thickness from about 0.5 mm to about 2.0 mm.

The trough profile should have the shape of an arc and is preferably symmetrical.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

1-21. (canceled)

22. A device for casting strands of metal, the device comprising:

an outlet nozzle configured to supply liquid metal from a material supply vessel;

a circulating conveyor belt assembly being configured to receive the liquid metal from the outlet nozzle on a carrying side, the conveyor belt assembly comprising: a first deflection roller; a second deflection roller; and a thin, heat-resistant belt that circulates between the first deflection roller and the second deflection roller, the belt being shaped to form a trough for receiving the liquid metal between the first deflection roller and the second deflection roller in a region of the outlet nozzle, the circulating conveyor belt resuming the shape of a flat belt proximate to the second deflection roller,

wherein at least one of the first deflection roller and the second deflection roller is convexly cambered.

23. The device according to claim 22, wherein the camber is selected such that a shortening of the belt resulting from the formation of the trough profile is at least partially compensated.

24. The device according to claim 22, wherein the camber is calculated according to the following formulae: wherein

BB/2=XB+X+XT  (1)

ΔLXB=L−LV=√{square root over (L2+X2+Y2)},  (2)

BB is a width of the belt

BT is a width of the trough,

L is a length of a final trough profile between an entry and exit,

LV is a length of a space diagonal in longitudinal direction of the trough,

X is an X coordinate for calculating LV,

XB is a distance from point C,

XT is a distance from a center of the belt or trough,

Y is a Y coordinate for calculating LV.

25. The device according to claim 24, wherein a change in belt length due to varying temperature distribution over a width of the belt is taken into account in the camber and is calculated according to the following formula: wherein

ΔlTemp=LTroughα(TM−TR),  (3)

LTrough is a length of the trough,

TM is a temperature in a center of the belt

TR is a temperature at an edge area of the belt, and

α is a coefficient of expansion of a belt material.

26. The device according to claim 25, wherein the camber of the deflection rollers for a homogenized tensile stress over the width of the belt is calculated for a given trough profile and temperature profile by superposition.

27. The device according to claim 26, wherein a first deflection roller camber is smaller than a second deflection roller camber.

28. The device according to claim 22, wherein the camber is changable by a pressure medium in at least one of the deflection rollers.

29. The device according to claim 28, wherein a profiled cavity is provided at a roller shell for applying pressure.

30. The device according to claim 22, wherein each of a belt entry length and a belt exit length is at least 500 mm.

31. The device according to claim 30, wherein at least one of a maximum belt entry length and a maximum belt exit length is selected such that the camber due to the trough profile is not greater than 2%.

32. The device according to claim 22, wherein the belt is shaped by the deflection roller continuously over a distance to form at least one of the trough profile and flat belt.

33. The device according to claim 22, wherein the belt material comprises a thermal shock-resistant alloy comprising at least one of CuNi and Fe.

34. The device according to claim 22, wherein the belt material comprises a single-phase or multiple-phase Cu alloy.

35. The device according to claim 22, wherein the belt material comprises a nickel-based alloy.

36. The device according to claim 22, wherein the belt has a thickness greater than about 0.5 mm and less than about 2.0 mm.

37. The device according to claim 32, wherein the trough profile is arc-shaped.

38. The device according to claim 32, wherein the trough profile is symmetrical.

39. The device according to claim 32, wherein the trough profile has substantially straight-line regions at both ends.

40. The device according to claim 32, wherein sides of the trough profile are higher than the casting profile by about 10 mm.

41. The device according to claim 40, wherein the sides have an angular deviation of +/−25 degrees relative to a perpendicular of the belt when flat.

42. The device according to claim 32, wherein the trough profile is adapted to shrinkage of a casting cross section by an adjustment of the rollers in casting direction over the length of the trough.

43. The device according to claim 22, wherein a change in belt length due to varying temperature distribution over a width of the belt is taken into account in the camber and is calculated according to the following formula: wherein

ΔlTemp=LTroughα(TM−TR),  (3)

LTrough is a length of the trough,

TM is a temperature in a center of the belt

TR is a temperature at an edge area of the belt, and

α is a coefficient of expansion of a belt material.