Annular weir

Abstract

An annular weir is fixed at a bottom of a tundish and just under a long nozzle of a ladle in a continuous casting apparatus. The annular weir includes a cavity which has a substantially circular shaped transverse section. The cavity includes: an upper side opening configured to receive a stream of molten metal from an upper side through the long nozzle; an inner protrusion which is annular in shape and which extends toward an inner side from an upper end of an inner wall of the cavity; a first space on an inner side of the inner protrusion; and a second space which communicates with the first space 13a and which is on a lower side of the first space.

Claims

1. An annular weir fixed at a bottom of a tundish and under a long nozzle of a ladle in a continuous casting apparatus, the annular weir comprising a cavity which has a substantially circular shaped transverse section, the cavity including: an upper side opening configured to receive a stream of molten metal from an upper side through said long nozzle; an inner protrusion which is annular in shape, the inner protrusion extending toward an inner side from an upper end of an inner wall of said cavity; a first space on an inner side of said inner protrusion; and a second space which communicates with said first space, the second space being on a lower side of said first space, wherein: an inside diameter of said first space is within a range of 4 times to 5 times a diameter of a discharge hole of said long nozzle, and an inside diameter of said second space is within a range of 1.2 times to 1.5 times the inside diameter of said first space; and a height of said annular weir is within a range of to of a height of a surface of a bath in the tundish during operation.

2. The annular weir as claimed in claim 1, wherein the cavity is a bore that bores in an upper and lower direction.

3. An annular weir fixed at a bottom of a tundish and under a long nozzle of a ladle in a continuous casting apparatus, the annular weir comprising a cavity which has a substantially circular shaped transverse section, the cavity including: an upper side opening configured to receive a stream of molten metal from an upper side through said long nozzle; an inner protrusion which is annular in shape, the inner protrusion extending toward an inner side from an inner wall of said cavity; a third space on an upper side of said inner protrusion; a first space which communicates with said third space, the first space being on a lower side of said third space and on an inner side of said inner protrusion; and a second space which communicates with said first space, the second space being on a lower side of said first space, wherein: an inside diameter of said first space is within a range of 4 times to 5 times a diameter of a discharge hole of said long nozzle, and an inside diameter of said second space is within a range of 1.2 times to 1.5 times the inside diameter of said first space; and a height of said annular weir is within a range of to of a height of a surface of a bath in the tundish during operation.

4. The annular weir as claimed in claim 3, wherein an inside diameter of said third space is within a range of 1 time to 1.1 times the inside diameter of said second space.

5. The annular weir as claimed in claim 3, wherein the cavity is a bore that bores in an upper and lower direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross section of a weir according to a prior art disposed on a tundish;

(2) FIG. 2 is an enlarged plan view of the weir of FIG. 1;

(3) FIG. 3 is a perspective view of an annular weir according to an embodiment of the present invention;

(4) FIG. 4 is a cross section of the annular weir of FIG. 3 disposed on a tundish;

(5) FIG. 5 is a diagram of results of operation performance with size of the annular weir of FIG. 3 changed;

(6) FIG. 6 is a perspective view of an annular weir according to an embodiment of the present invention;

(7) FIG. 7 is a cross section of the annular weir of FIG. 6 disposed on a tundish; and

(8) FIG. 8 is a diagram of results of operation performance with size of the annular weir of FIG. 6 changed.

MODE FOR CARRYING OUT THE INVENTION

(9) (Embodiment 1)

(10) Referring to FIG. 3 to FIG. 5, an annular weir 11 according to an embodiment of the present invention will be described.

(11) The annular weir 11 controls speed of molten metal delivered from a ladle within a tundish 12 in a continuous casting apparatus. The annular weir 11 includes a cavity 13, which has a substantially circular shaped transverse section (horizontal cross section).

(12) FIG. 3 is a perspective view of the annular weir 11 according to the present invention. FIG. 4 is a cross section of the annular weir 11 of FIG. 3 fixed on the tundish 12.

(13) The annular weir 11 includes refractory material and is prismatic in outward appearance. The annular weir 11 has the cavity 13 formed at a center thereof. The cavity 13 is a bore that bores in an upper and lower direction.

(14) An inner protrusion 13d is formed on an upper end of an inner wall of the cavity 13. The inner protrusion 13d is annular in shape and extends toward an inner side from the upper end.

(15) The cavity 13 includes: a first space 13a on an inner side of the inner protrusion 13d; and a second space 13b which communicates with the first space 13a and which is on a lower side of the first space 13a. The cavity 13 has a substantially convex-shaped longitudinal section.

(16) The inner wall of the cavity 13 and an end surface of the inner protrusion 13d extend vertically. The first space 13a and the second space 13b are formed on an uneven base with a step therebetween.

(17) An inside diameter D.sub.1 of the first space 13a is within a range of 4 times to 5 times a diameter of a discharge hole 15a of a long nozzle 15. In the present embodiment, D.sub.1 of the first space 13a is 400 mm, and an inside diameter D.sub.2 of the second space 13b is 500 mm which is 1.25 times the inside diameter D.sub.1 of the first space 13a. The diameter of the discharge hole 15a of the long nozzle 15 is 95 mm.

(18) Height of a surface of a bath in operation is 1000 mm from a bottom of the tundish 12. Height H of the annular weir 11 is (200 mm) of height of the surface of the bath in operation in the tundish 12. Heights H1, H2 of the first space 13a and the second space 13b meet H1=H2=H.

(19) As shown in FIG. 4, the annular weir 11 is fixed at the bottom of the tundish 12 in such a manner that the cavity 13 is just under the long nozzle 15 of a ladle not shown. While the cavity 13 does not include a bottom, the bottom of the tundish 12 substitutes for the bottom. The annular weir 11 is fixed by the same ways as ordinary weirs, by mortar for example.

(20) In FIG. 3 and FIG. 4, a body of the annular weir 11 is prismatic. But the outward appearance of the body of the annular weir 11 is not strictly limited. Examples of the outward appearance include a columnar shape in accordance with an inner part of the cavity 13 and a pyramidal trapezoid which spreads upward in accordance with a shape inside the tundish 12.

(21) With this configuration of the annular weir 11, the stream of molten metal, which is directed by the long nozzle 15 into the cavity 13 of the annular weir 11, impacts the bottom of the tundish 12, and rebounds upward. As a result, this configuration prevents short circuiting of the molten metal to immersion nozzles 16 immersed in a mold.

(22) The inner protrusion 13d tightens up the upward stream and the upward stream interferes the downward stream from the long nozzle 15. This configuration slows the opposing upward and downward streams each other and increases time for the molten metal to reach the immersion nozzles 16.

(23) In addition, with the configuration that the height H of the annular weir 11 is of the height of the surface of the bath in operation, possibility of surface turbulence in the bath caused by the upward stream is low and therefore, slag entrainment on the surface of the bath is minimized.

(24) This configuration promotes float and separation of the non-metal inclusions in the molten metal, thereby improving quality of the cast products.

(25) In addition, above-described conditions prevent erosion on a top end of the long nozzle 15 (see FIG. 5).

(26) In addition, with the configuration that the cavity 13 is the bore that bores in the upper and lower direction, the annular weir 11 is simply manufactured at a low cost. The bore does not cause any structural disadvantage for a bottom of the tundish 12 substitutes for the bottom of the annular weir 11.

(27) (Embodiment 2)

(28) Conditions for Embodiment 2 will be described.

(29) In the present embodiment, the inside diameter D.sub.1 of the first space 13a was 450 mm and the inside diameter D.sub.2 of the second space 13b was 550 mm.

(30) The height H of the annular weir 11, the height H.sub.1 of the first space 13a, and the height H.sub.2 of the second space 13b remain unchanged from Embodiment 1.

(31) (Embodiment 3)

(32) In Embodiment 3, the inside diameter D.sub.1 of the first space 13a and the inside diameter D.sub.2 of the second space 13b remain unchanged from Embodiment 1. The height H of the annular weir 11 was 250 mm, the height H.sub.1 of the first space 13a was 150 mm, and the height H.sub.2 of the second space was 100 mm.

(33) As shown in FIG. 5, in Embodiment 2 and Embodiment 3, entrainment of the surface of the bath was slight, and therefore, resultant molten steel was high in purity. In addition, the long nozzle 15 was not eroded.

(34) The results show that the inside diameter D.sub.1 of the first space 13a is preferably within the range of 4 times to 5 times the diameter of the discharge hole 15a of the long nozzle.

(35) (Comparative Examples 1 to 4)

(36) In Comparative Example 1, the diameter D.sub.1 of the first space 13a was larger. As a result, as shown in FIG. 5, slag entrainment on the surface of the bath was promoted and the resultant molten steel was slightly inferior to the Embodiment in purity.

(37) In Comparative Example 2, the diameter D.sub.1 of the first space 13a was smaller. As a result, entrainment of the surface of the bath was not observed, but the resultant molten steel was considerably inferior in purity.

(38) In Comparative Example 3, the height H of the annular weir 11 was of the height of the surface of the bath. As a result, the resultant molten steel was equivalent in purity but entrainment of the surface of the bath was considerable, thereby hampering steady operations.

(39) In Comparative Example 4, the diameter D.sub.2 of the second space 13b was 1.1 times the diameter D.sub.1 of the first space 13a. As a result, entrainment of the surface of the bath was slightly observed and the erosion on the top end of the long nozzle 15 after casting was so considerable that the long nozzle 15 became ineffective approximately at half number of heating.

(40) (Embodiment 4)

(41) Referring to FIG. 6 to FIG. 8, the annular weir 11 according to another embodiment of the present invention will be described.

(42) The annular weir 11 controls speed of molten metal delivered from the ladle within the tundish 12 in the continuous casting apparatus. The annular weir 11 includes the cavity 13, which has the substantially circular shaped transverse section (horizontal cross section).

(43) FIG. 6 is a perspective view of the annular weir 11 according to the present invention. FIG. 7 is a cross section of the annular weir 11 of FIG. 6 fixed on the tundish 12.

(44) The annular weir 11 includes refractory material and is prismatic in outward appearance. The annular weir 11 has the cavity 13 formed at the center thereof. The cavity 13 is the bore that bores between the upper end and the lower end.

(45) The inner protrusion 13d is formed at a substantial center in an upper and lower direction of the inner wall of the cavity 13. The inner protrusion 13d is annular in shape and extends toward the inner side from the substantial center.

(46) The cavity 13 includes: a third space 13c on an upper side of the inner protrusion 13d; the first space 13a on the inner side of the inner protrusion 13d; and the second space 13b which communicates with the first space 13a and which is on the lower side of the first space 13a.

(47) The inner wall of the cavity 13 and an end surface of the inner protrusion 13d extend vertically. The third space 13c and the first space 13a, and the first space 13a and the second space 13b are formed on an uneven base with a step therebetween.

(48) An inside diameter D.sub.a of the first space 13a is within the range of 4 times to 5 times the diameter of the discharge hole 15a of the long nozzle 15. In the present embodiment, D.sub.a of the first space 13a is 400 mm, and an inside diameter D.sub.c of the third space 13c and an inside diameter D.sub.b of the second space 13b are 500 mm, respectively, which is 1.25 times the inside diameter D.sub.a of the first space 13a. The diameter of the discharge hole 15a of the long nozzle 15 is 95 mm.

(49) The height of the surface of the bath in operation is 1000 mm from the bottom of the tundish 12. The height H of the annular weir 11 is (250 mm) of the height of the surface of the bath in operation in the tundish 12. Heights H.sub.c, H.sub.a, H.sub.b of the third space 13c, the first space 13a, and the second space 13b meet H.sub.c= H, H.sub.a=H.sub.b= H.

(50) As shown in FIG. 7, the annular weir 11 is fixed at the bottom of the tundish 12 in such a manner that the cavity 13 is just under the long nozzle 15 of the ladle not shown. While the cavity 13 does not include the bottom, the bottom of the tundish 12 substitutes for the bottom. The annular weir 11 is fixed by the same ways as ordinary weirs, by mortar for example.

(51) In FIG. 6 and FIG. 7, the body of the annular weir 11 is prismatic. But the outward appearance of the body of the annular weir 11 is not strictly limited. Examples of the outward appearance include the columnar shape in accordance with the inner part of the cavity 13 and the pyramidal trapezoid which spreads upward in accordance with the shape inside the tundish 12.

(52) With this configuration of the annular weir 11, the stream of molten metal, which is directed by the long nozzle 15 into the cavity 13 of the annular weir 11, impacts the bottom of the tundish 12, and rebounds upward. As a result, this configuration prevents short circuiting of the molten metal to the immersion nozzles 16, immersed in the mold.

(53) The inner protrusion 13d tightens up the upward stream and the upward stream interferes the downward stream from the long nozzle 15. This configuration slows the opposing upward and downward streams each other and increases time for the molten metal to reach the immersions nozzles 16.

(54) In addition, with the configuration that the height H of the annular weir 11 is of the height of the surface of the bath in operation, possibility of surface turbulence in the bath caused by the upward stream is low and therefore, slag entrainment on the surface of the bath is minimized.

(55) This configuration promotes float and separation of the non-metal inclusions in the molten metal, thereby improving quality of the cast products.

(56) In addition, above-described conditions prevent erosion on the top end of the long nozzle 15 (see FIG. 8).

(57) In addition, with the configuration that the cavity 13 is the bore that bores in the upper and lower direction, the annular weir 11 is simply manufactured at the low cost. The bore does not cause any structural disadvantage for the bottom of the tundish 12 substitutes for the bottom of the annular weir 11.

(58) (Embodiment 5)

(59) Conditions for Embodiment 5 will be described.

(60) In the present embodiment, the inside diameter D.sub.c of the third space 13c was 550 mm, the inside diameter D.sub.a of the first space 13a was 450 mm, and the inside diameter D.sub.b of the second space 13b was 550 mm.

(61) The height H of the annular weir 11, the height H.sub.c of the third space 13c, the height H.sub.a of the first space 13a, and the height H.sub.b of the second space 13b remain unchanged from Embodiment 4.

(62) (Embodiment 6)

(63) In Embodiment 6, the inside diameter D.sub.c of the third space 13c, the inside diameter D.sub.a of the first space 13a, and the inside diameter D.sub.b of the second space 13b remain unchanged from

(64) Embodiment 4. The height H of the annular weir 11 was 200 mm, the height H.sub.c of the third space 13c was 50 mm, the height H.sub.a of the first space 13a was 50 mm, and the height H.sub.b of the second space 13b was 100 mm.

(65) As shown in FIG. 8, in Embodiment 5 and Embodiment 6, entrainment of the surface of the bath was slight, and therefore, resultant molten steel was high in purity. In addition, the long nozzle 15 was not eroded.

(66) The results show that the inside diameter D.sub.a of the first space 13a is preferably within the range of 4 times to 5 times the diameter of the discharge hole 15a of the long nozzle.

(67) (Comparative Examples 5 to 9)

(68) In Comparative Example 5, the diameter D.sub.c of the third space 13a was larger. As a result, as shown in FIG. 8, the resultant molten steel was slightly inferior to the Embodiment in purity.

(69) In Comparative Example 6, the diameter D.sub.a of the first space 13a was smaller. As a result, the resultant molten steel was considerably inferior in purity.

(70) In Comparative Example 7, the height H of the annular weir 11 was of the height of the surface of the bath. As a result, the resultant molten steel was equivalent in purity but entrainment of the surface of the bath was considerable, thereby hampering steady operations.

(71) In Comparative Example 8, the diameter D.sub.b of the second space 13b was 1.1 times the diameter D.sub.a of the first space 13a. As a result, entrainment of the surface of the bath was observed, which was substantially of the same degree as Comparative Example 7.

(72) In Comparative Example 9, the diameter D.sub.c of the third space 13c was smaller than the diameter D.sub.b of the second space 13b. As a result, entrainment of the surface of the bath was observed, which was substantially of the same degree as Comparative Example 8. Also, erosion on the top end of the long nozzle 15 after casting was so considerable that the long nozzle 15 became ineffective approximately at half number of heating.

(73) In the present embodiment, the inside diameter D.sub.2, D.sub.b of the second space 13b may be within a range of 1.2 times to 1.5 times the inside diameter D.sub.1, D.sub.a of the first space 13a.

(74) In addition, the height H of the annular weir 11 may be within a range of to of the height of the surface of the bath.

(75) In addition, the inside diameter D.sub.c of the third space 13c may be within a range of 1 time to 1.1 times the inside diameter D.sub.b of the second space 13b.

(76) While the cavity 13 of the present embodiment is the bore, shape of the cavity 13 is not strictly limited. That is, the cavity 13 may include a bottom such that the cavity 13 does not bore the annular weir 11.

(77) In addition, the inside diameter of the third space 13c may be gradually increased from a lower side toward an upper side. In this configuration, a diameter on a lower end of the third space 13c equals to a diameter on an upper end of the first space 13a.

(78) In addition, a plurality of inner protrusions 13d may be formed in the upper and lower direction. In this configuration, the plurality of inner protrusions 13d divide the cavity 13 into more spaces than the singular inner protrusion 13d.

DESCRIPTION OF NUMERALS

(79) 1 inner circumferential surface 2 opening 3 concave shaped opening 4 weir 5 long nozzle 6 tundish 11 annular weir 12 tundish 13 cavity 13a first space 13b second space 13c third space 13d inner protrusion 15 long nozzle 15a discharge hole 16 immersion nozzle D.sub.1 inside diameter of first space D.sub.2 inside diameter of second space D.sub.a inside diameter of first space D.sub.b inside diameter of second space D.sub.c inside diameter of third space H height of annular weir H.sub.1 height of first space H.sub.2 height of second space H.sub.a height of first space H.sub.b height of second space H.sub.c height of third space