METAL STRIP MANUFACTURING METHOD AND NOZZLE THEREFOR

Abstract: In the continuous manufacturing of metal strip from molten alloy, the nozzle (1) from which the melt issues to form the continuous strip by rapid-cooling solidification has an orifice that is discontinuous in the width direction of the strip; i.e., it is a multiple orifice(2). This enables amorphous and crystalline continuous metal strip to be produced in much greater widths than has hitherto been possible, and the strip thus produced is more uniform in thickness.

Description: The present invention relates to a method of continuously manufacturing amorphous metal strip or crystalline metal strip by quench-solidification on the surface of a moving chill body of molten metal, according to the preamble of claim 1, and to a nozzle for the manufacture of metal strip according to the preamble of claim 6 and to an apparatus according to the preamble of claim 12. Various means have been disclosed relating to methods of continuously manufacturing strip from molten metal (continuous melt quenching method). In each case the molten alloy is ejected under a specific pressure from a nozzle having an orifice of a specific shape, and strikes a moving chill body that faces the nozzle orifice to be thereby solidified into continuous strip. The important manufacturing factors at this time are the shape of the nozzle orifice, the relative positional arrangement of the nozzle and the chill body, the pressure at which the molten alloy is ejected from the nozzle, and advancing the chill surface at a predetermined speed. With respect to these manufacturing factors, in general, conditions tend to become narrower and more stringent as the width of the strip increases. Japanese Patent Laid Open No. 53 (1978)-53525 is a representative example of means that have been disclosed for manufacturing wide strip, and in outline comprises a slotted nozzle positioned generally perpendicular to the direction of movement of a chill surface and located in close proximity to the chill surface to provide a gap of from about 0.03 to about 1 mm between the nozzle and the chill surface, molten alloy is ejected from the nozzle onto the chill surface at a velocity of 100 to 2,000 meters per minute for forming continuous strip by means of thermal-contact rapid-cooling solidification. In the above-mentioned conventional method, in principle there is no limitation on the width of the strip. That is, if the length of the rectangular orifice (the length of the orifice measured in a direction that is at right-angles to the direction of movement of the chill surface) is increased, the width of the strip could be increased. However, in practice, as the length of the rectangular orifice was increased it became difficult to maintain the parallelism of the orifice during the casting. Specifically, as shown in Figures 3a and 3b, convex or concave deformation of the nozzle portion caused by thermal expansion, deformation resulting from non-uniformity of the temperature and the like made it difficult to maintain the parallelism of the orifice. When the parallelism of the rectangular nozzle is thus lost, the thickness of the formed strip, especially in the direction of the width, becomes non-uniform. Accordingly, conventionally, the wider the strip became the more difficult it has been to produce strip having uniform thickness across its width. Also, strip that is of non-uniform thickness is undesirable because when such strip is laminated or coiled, for example, the space factor deteriorates. At present it is possible to keep thickness deviation in 25-mm-wide strip down to 5 to 10 per cent, but in the case of strip 150 mm in width it it difficult to keep the deviation to 10 per cent or less. Thus, with conventional methods the width of the strip is subject to a technical limitation. At present the width of the widest rapid-cooled strip is around 300 mm. However, strip of this width is being produced only on an experimental basis, and it is difficult to consider that production stability is such as to permit commercial mass-production. US-A-2 978 761 discloses a continuous casting apparatus having a nozzle for the manufacture of metal strip on a chill surface moving in a predetermined direction of movement, said nozzle comprising a plurality of orifices being arranged in a row at approximately a right-angle to said direction of movement of said chill surface. US-A-2 978 761 forms the basis for the preamble of the independent claims. However, the uniformity of metal strip produced with said casting apparatus is still not satisfactory. An object of the present invention is to remove constraints on width in the continuous manufacturing of metal strip from molten alloy by reducing the non-uniformity of the strip that with conventional methods often resulted from deformation of the nozzle portion during the manufacture of wide strip, and increasing the strength of the nozzle portion. This object is achieved by the method and nozzle according to the claims. The present invention attains the above object on the basis of new knowledge that, in contrast to the conventional method of manufacturing wide strip using a nozzle having a slot-shaped rectangular orifice, wide strip possessing the same flatness as strip produced according to the conventional method can be manufactured using a nozzle that is discontinuous in the width direction of the strip, and has a plurality of orifices that are elongated and are arranged in to 80 degrees with respect to the direction of movement of the chill surface. at least one row, the longitudinal centerline of each of said orifices being positioned at an angle of from 10 to 80 degrees with respect to the disection of movement of the chill surface. The method and nozzle according to the present invention do not have the drawbacks associated with conventional methods, and enable the width of the strip to be increased without limit. The invention will be described in detail in conjunction with the drawings in which Figures 1 and 2 are explanatory drawings showing the shape and arrangement of the nozzle orifices according to the present invention to be used in the method according to the present invention; Figure 3 is an explanatory drawing showing deformation of a slot-shaped nozzle caused by thermal expansion; Figure 4 illustrates a profile of a free surface in the width direction of strip produced according to an embodiment of the present invention- namely according to Example 1; Figure 5 illustrates a profile of a free surface in the width direction of strip produced according to another embodiment of the present invention- namely according to Example 3; Figure 6 illustrates a profile of a free surface in the width direction of strip produced according to still another embodiment of the present invention- namely according to Example 4; Figure 7 illustrates a profile of a free surface in the width direction of strip produced according to a conventional method (single-slot method); and Figure 8 is an explanatory drawing showing the shape and arrangement of nozzle orifices according to the present invention that may be used in the method according to the present invention. The nozzle used in the method of the present invention is for example the kind of multiple-orifice nozzle 1 illustrated in Figure 1. Orifices 2 are each a slender parallelogram in shape with the sides inclined in the direction of movement of a cooling surface 3 (indicated by the phantom line (single-dot chain line)). The orifices 2 are arrayed in a mutually parallel arrangement at right-angles to the direction of movement. The parameters defining the structure of the multiple-orifice nozzle 1 employed in the method of this invention as illustrated in Figure 1 are side d of the orifice 2 parallelogram; spaces b , c by which adjacent orifices are separated; angle of inclination α of each parallelogram relative to the direction of travel of the cooling plate 3; and the height a of the parallelograms. In general, a is larger than d and the shape is long and slender. With respect to the range of parameter dimensions, the orifice angle of inclination α,i.e the angle -the longitudinal centerline of the elongated orifice and the direction of movement of the chill surface, is 80 degrees, the length of the lower side d is 0.1 - 2.0 mm, the height a is 0.5 - 8.0 mm, and as the separation between adjacent orifices, preferably a distance b in the direction of the orifice array is within the range 0.2 - 3.0 mm and the distance c in the direction of travel of the cooling plate 3 is within the range 0.2 - 4.0 mm. Of the shape parameters, the distance c in the direction of movement of the chill surface 3 is important. It was found that if the said distance c exceeded 4.0 mm, strip having a good shape would not be formed. This is of special importance when it is amorphous alloy strip that is to be manufactured, wherein if 4.0 mm is exceeded the strip thus produced is often crystallized. Other shape parameters shown are the preferred ranges for embodiments in practising of the present invention. For example, height a is a parameter related to the strip thickness and is preferably within the range 0.5 - 8.0 mm; the lower limit is set at a value that eliminates difficulties in the manufacture of the nozzle. The major fear in the method according to the present invention is whether there will appear in the formed strip longitudinal strand-shaped hollows or open portions, or protrusions. Such strip is regarded as a product of low commercial value, tending as it does to produce a lowering of the space factor when it is utilized as a core material. Unexpectedly, however, tests confirmed that selection of correct combinations within the parameter ranges proposed for the method of the present invention enabled strip to be obtained which substantially was free of the aforementioned strand-shaped hollows or protrusions, and therefore there was almost no lowering of the space factor. The method according to the present invention goes beyond the conventional state of knowledge of the art as recited in columns 2 to 3 of the Official Gazette entry for Japanese Laid Open Publication No. 53 (1978)-53525 in the point that the thickness of strip formed by the ejection of the molten alloy from a nozzle having a plurality of orifices in the width direction of the strip is substantially uniform. In addition, it was found that as, if the method of the present invention is adopted, there are none of the drawbacks associated with the conventional method, constraints on the width of the strip are removed and the strip can be made wider. The method used according to the present invention, as already described, is what is referred to as the single-roll rapid-cooling method, a variation of the melt rapid-cooling method, wherein molten metal is forced onto the chill surface 3 under the pressure by means of nozzle 1 for thermal-contact rapid-cooling solidification. It goes without saying that this also includes centrifugal cooling type methods in which the inner wall of a drum is utilized, as well as improvements thereto such as, for example, methods using auxiliary rolls or attachments such as a roll-surface-temperature control means, or casting under reduced pressure or in a vacuum, or in an inert gas. Casting conditions employed with the method of the present invention will now be described. The distance between the nozzle tip and the chill surface is in the range of about 0.05 - about 3.0 mm. The molten metal ejection pressure is 0.01 - 2.0 kg/cm² and the travel speed of the chill surface is 5 - 50 m/sec. The optimum value of the above mentioned distance and travel speed within this range will be selected according to the structure of the nozzle. With respect to the shape of the nozzle orifices, there are a number of possible variations within the range of the basic concept that has been described. For example, an orifice may be trapezoidal in shape, as shown in Figure 2. In this case, the angle of inclination α of the orifice with respect to the direction of movement of the chill surface is 10 - 80 degrees, the lengths d 1 and d 2 of the upper and lower sides are each 0.1 - 6.0 mm and as the separation between adjacent orifices, preferably distances b 1 and b 2 in the direction of the orifice array are within the range 0.2 - 6.0 mm and the distance c in the direction of travel of the chill surface 3 is within the range 0.2 - 7.0 mm, and the height a within the range 0.5 - 8.0 mm. Here, the angle of inclination α of the orifice with respect to the direction of movement of the chill surface, as shown in Figure 2, is the angle formed between a line joining the respective midpoints of the upper and lower sides of the trapezoidal orifices and the direction of movement of the chill surface 3. In Figure 2, with regard to the lengths d 1 and d 2 of the upper and lower sides of the trapezoidal orifice, d 1 is shown as smaller than d 2 , but if it is within the aforementioned range, d 1 may be larger than d 2 . The nozzle orifices may also be ellipsoidal in shape as shown in Figure 8. In this case, preferably the angle of inclination α of the orifices relative to the direction of movement of the chill surface 3 is 10 - 80 degrees, the length of the short axis is 0.1 - 3.0 mm, the length of the long axis is 0.5 - 10.0 mm and the narrowest distance between adjacent orifices is in the order of 0.2 mm. Here, α refers to the angle between the long axis and the direction of movement of the chill surface. Moreover, orifices may be polygonal in shape, such as hexagonal. The provision at the edge portions of additional small triangular parallelogram or trapezoid orifices such as are shown in Figures 1 and 2 as A is an effective way of ensuring that the strip does not become thinner at the edge portions. The shapes and dimensions of these small orifices will be selected according to the shapes and positioning of adjacent orifices. The height will be in the range of 0.5 - 7.0 mm. The length of the lower side thereof will be about the same as the length of the lower side of adjacent orifices. However if the angle α should exceed 60 degrees, making the length of the lower side longer than the length of the lower side of the adjacent orifice, or adding a plurality of small orifices, is effective. The various conditions described in the foregoing are mutually interrelated, not independent. Accordingly, what constitutes an optimum combination is determined by experiment. Desirable parameter combinations are shown below in the form of examples. The advantages are particularly marked when the method of this invention is applied to alloys which readily become amorphous and to metals which are difficult to be rolled or otherwise processed, but the method is not limited to such applications. Table 1 shows data relating to shape, magnetic properties, 180-degree bend-testing, tensile strength testing, corrosion-resistance and other such properties of examples of strip of various alloys manufactured using the nozzle according to the present invention. Strip thickness ratio is the ratio of the thickness calculated according to weight to the thickness measured using a micrometer. Data magnetic properties are figures obtained after annealing. For amorphous strip, annealing conditions were 60 minutes at 380°C in an N₂ atmosphere and a field strength of 40 Oe(3.183A/m). Crystalline strip was annealed at 1,100°C for 60 minutes in a vacuum (down to 10⁻⁴ torr (1.33 10- 2 'Pa). Mi is initial permeability, M5 is the permeability at 5 mOe (0.40 A/m) and M50 at 50 mOe(3.98A/m). The corrosion-resistance test was according to the method of JIS Z-23711 (Salt Water Exposure Method; equivalent to the U.S. Salt Spray Test). All strips were subjected to x-ray diffraction and differential scanning calorimetry to confirm amorphosity. Thickness ratios were high, all over 90%. These figures are on a par with those for strip manufactured according to the conventional method. The surface (free surface) characteristics of strip obtained in Examples 1, 3 and 4 are shown in Figures 4, 5 and 6, respectively. These data are equivalent to those for the surface characteristics of strip produced by the conventional method shown in Figure 7. Thickness deviation in the width direction was examined with respect to strip obtained in the Examples 1, 6, 9, and 10. It was found that even when strip width was increased, there were virtually no differences in thickness deviation, in each case the figure not exceeding 10%. Also, while flume-shaped warping was often seen in the width direction of wide trip manufactured according to a conventional method, such flume-shaped warps were almost entirely absent in strip manufactured according to the method of the present invention. Thus, as has been described in the above, adoption of the method of this invention enables metal strip of a desired large width to be manufactured, and substantially without any lowering of the space factor. As the method according to this invention allows the production of, for example, wide Fe amorphous alloy strip, it can be applied to large wound or laminated core transformers. It is also well suited for use with magnetic shielding materials, decorative and other building materials and, if plated with copper or other such high-conductivity metal, as electromagnetic-frequency shielding material, especially as a material for the blinds used in electromagnetic dark-rooms. At present the widest amorphous alloy strip that can be obtained is around 10 cm wide. The method according to the present invention eliminates the conventional necessity to resort to brazing or the like in order to increase the width of the available strip. Also, the strip can be cut into thin slices to form composite reinforced material which can be copper-plated and made into spirals for use as coaxial cable shielding.

Claims: A method for manufacturing metal strip comprising rapid solidification of molten metal ejected onto a chill surface moving in a predetermined direction of movement from a plurality of orifices arranged in at least one row at approximately a right-angle to said direction of movement of said chill surface, characterized in that said molten metal is ejected from elongated orifices, each of said elongated orifices having a longitudinal centerline, and each of said centerlines being positioned at an angle of from 10 to 80 degrees with respect to said direction of movement of said chill surface. A method according to claim 1 wherein each orifice has a discharge end being spaced at a distance of from about 0.05 to about 3.0 mm from said chill surface. A method according to claim 1 or 2 wherein said chill surface moves at a speed of from 5 to 50 m/sec. A method according to any of claims 1 to 3 wherein said rapidly solidified metal strip is an amorphous metal strip. A method according to any of claims 1 to 3 wherein said rapidly solidified metal strip is a crystalline metal strip. A nozzle for the manufacture of metal strip on a chill surface (3) moving in a predetermined direction of movement, said nozzle (1) comprising a plurality of orifices (2) being arranged in at least one row at approximately a right-angle to said direction of movement of said chill surface (3), characterized in that said orifices (2) are elongated, and each of said elongated orifices (2) has a longitudinal centerline, each of said centerlines forming an angle of from 10 to 80 degrees with respect to said direction of movement of said chill surface (3). A nozzle according to claim 6 wherein the geometric shape of said elongated orifices (2) is a parallelogram, trapezoid or ellipsoid. A nozzle according to claim 6 or 7 wherein the edge portions of said nozzle (1) are each provided with an orifice (A) smaller in area than said elongated orifices (2), and the geometric shape of said orifices (A) smaller in area is a triangle, parallelogram or trapezoid. A nozzle according to claim 7 or 8 wherein said elongated orifices (2) have the geometric shape of a parallelogram, wherein for each elongated orifice (2) the parallelogram has a base (d) having a dimension of from 0.1 to 2.0 mm, a height (a) having a dimension of from 0.5 to 8.0 mm, a separation distance (b) between sides of adjacent parallelograms in the direction of said at least one row having a dimension of from 0.2 to 3.0 mm and a distance (c) between sides of adjacent parallelograms in the direction of movement of said chill surface (3) having a dimension of from 0.2 to 4.0 mm. A nozzle according to claim 7 or 8 wherein said elongated orifices (2) have the geometric shape of a trapezoid, wherein for each elongated orifice (2) the trapezoid has an upper side (d₁) and a lower side (d₂), each side (d₁, d₂) having a dimension of from 0.1 to 6.0 mm, a height (a) having a dimension of from 0.5 to 8.0 mm, a separation distance (b 1 ,b 2 ) between sides of adjacent trapezoids in the direction of said at least one row having a dimension of from 0.2 to 6.0 mm, and a distance (c) between sides of adjacent trapezoids in the direction of movement of said chill surface (3) having a dimension of from 0.2 to 4.0 mm. A nozzle according to claim 7 or 8 wherein said elongated orifices (2) have the geometric shape of an ellipsoid, wherein for each elongated orifice (2) the ellipsoid has a short axis of from 0.1 to 3.0 mm and a long axis of from 0.5 to 10 mm, and between sides of adjacent ellipsoids there is a narrowest separation distance of 0.2 mm. An apparatus for manufacturing metal strip by depositing molten metal on a chill surface (3) moving in a predetermined direction of movement, said apparatus comprising means providing said moving chill surface (3) for movement in said predetermined direction of movement, and a nozzle (1) having a discharge end disposed above said chill surface (3) with said nozzle discharge end facing said chill surface (3), said nozzle discharge end having a plurality of orifices (2) being arranged in at least one row at approximately a right angle to said direction of movement of said chill surface (3), characterized in that said orifices (2) are elongated, and each of said elongated orifices (2) has a longitudinal centerline positioned at an angle of from 10 to 80 degrees with respect to said direction of movement of said chill surface (3). An apparatus according to claim 12 wherein said nozzle discharge end is spaced at a distance from about 0.05 to 3.0 mm from said chill surface (3). An apparatus according to claim 12 or 13 wherein the geometric shape of said elongated orifices (2) is a parallelogram, trapezoid or ellipsoid. An apparatus according to any of claims 12 to 14 wherein said nozzle discharge end has a first edge portion and an opposite second edge portion with said first edge portion and said second edge portion each being provided with an orifice (A) smaller in area than said elongated orifices (2), the geometric shape of said orifices (A) smaller in area being a triangle, parallelogram or trapezoid.

Inventors: SATO, TAKASHI NIPPON STEEL CORP., SATO, YUICHI NIPPON STEEL CORP., YAMADA, TOSHIO NIPPON STEEL CORP.
Applicants: NIPPON STEEL CORPORATION
Application year: 1987
Main classification: B22D11
IPC codes: B22D11