The name of the invention: the immersion nozzle

Technical field

[0001]

　The present invention relates to a submerged nozzle for continuous casting of pouring the molten steel into the mold from a tundish, in particular, thin slabs, such as those used for the thick slabs like medium, lateral near the discharge hole of the immersion nozzle (vertical perpendicular) cross section direction is flat (true circle, other than a square, about immersion nozzle of the length of one side and the other side is referred to a different shape).

Background technique

[0002]

　Molten steel and continuously cooled to solidify in a continuous casting process for forming a cast piece having a predetermined shape, has been continuous casting immersion nozzle (hereinafter, simply referred to as "submerged nozzle".) Placed on the bottom of the tundish through the molten steel is poured into the mold Te.

[0003]

　Generally, the immersion nozzle, upper end is an inlet for molten steel, molten steel flow path extending downward from the molten steel inlet (inner hole) formed therein, consist tube having a bottom, the bottom of the tube the side surface, a pair of discharge holes communicating with the molten steel flow path (inner hole) is formed to face. Immersion nozzle is used with its lower while being immersed in the molten steel in the mold. Thus, it is possible to prevent the scattering of pouring has been molten steel, to prevent oxidation by blocking the contact between the molten steel and the atmosphere. Further, the molten steel in the mold is rectified by the use of the immersion nozzle, impurities such as slag and non-metallic inclusions which float the molten metal surface is prevented involved into the molten steel.

[0004]

　Recently, thin slab during continuous casting, such as medium-thickness slabs, are increasingly thick to produce a thin cast strip. Such immersion nozzle to accommodate thin mold of the continuous casting should be a flat shape. For example, Patent Document 1 flat immersion nozzle installed an ejection hole in the shorter-side side wall is, in Patent Document 2 is shown more flat immersion nozzle also provided the discharge hole to the bottom surface. Typically in these flat immersion nozzle, so that to expand the width of the inner bore between a molten steel inlet of the discharge hole of the mold.

[0005]

　However, if the shape and flat shape width of such inner hole is enlarged, it tends disordered molten steel flow in the immersion nozzle, disturbed even discharge flow to the mold. Fluctuations increase in the molten metal surface of the molten steel flow turbulence within the mold (surface of molten steel), inclusion of the slab of powder oxide as an impurity-inclusions, temperature nonuniformity, etc., slab poor quality and operation of the also it causes to cause the increased risk, or the like. Therefore it is necessary to stabilize the within the submerged nozzle and the discharge to the molten steel flow.

[0006]

　To stabilize these molten steel flows, for example, Patent Document 3, the immersion nozzle disclosed forming at least two bending facets towards the lower edge of the discharge holes from the point in the plane of the lower bore (center) It is. Further in Patent Document 3, the immersion nozzle is disclosed comprising a diverter for diverting the flow of molten steel into two streams. When this flat immersion nozzle shown in Patent Document 3, compared to the immersion nozzle having no means for changing the flow direction, forms the internal space, such as in Patent Document 1 and Patent Document 2, the molten steel flow in the immersion nozzle stability increases of.

[0007]

　However, if the means to divert such lateral direction of the flow of molten steel, still, variation of molten steel discharge flow between the left and right discharge holes is increased, variations in mold molten steel surface by that increase it is there.

CITATION

Patent Literature

[0008]

Patent Document 1: JP-A-11-5145 JP
Patent Document 2: JP-A 11-47897 discloses
Patent Document 3: JP-T 2001-501132 Patent Publication

Summary of the Invention

Problems that the Invention is to Solve

[0009]

　An object of the present invention is to provide, in flat immersion nozzle, to stabilize the molten steel discharge flow, to stabilize the mold molten steel surface, that is to provide a submerged nozzle to reduce the variation. And thus for the purpose of improvement of the slab quality.

Means for Solving the Problems

[0010]

　The present invention is a flat immersion nozzle from the next 1 7.
1. In the immersion nozzle is inside width Wn of holes bore thickness Tn larger flat, provided with a portion protruding wall central portion in the width direction of the flat portion (hereinafter referred to as "central projecting portion".), The central the ratio Wp / Wn with respect to the Wn length Wp of the width direction of the protruding portion is 0.2 to 0.7, wherein the central protrusion is arranged in pairs symmetrically, the pair of central projecting portion the total length Tp in the thickness direction of 0.15 to 0.75 of the Tn, submerged nozzle. (Claim
1) 2. The central projecting portion is inclined discharge hole downward in the vertex center of the width direction, the immersion nozzle according to the 1. (Claim
2) 3. It said top surface of the central protrusion immersion nozzle according to the boundary portion between the immersion nozzle wall in the width direction are inclined to the thickness direction and downward the to the apex, in the 1 or the 2. (Claim
3) 4. The projecting length of the upper surface of the central projecting portion, the central portion is the largest of the Wp, gradually decreases toward both ends from the central portion, the immersion nozzle according to any one of the three from the 1. (Claim
4) 5. The upwardly projecting portion of the central projecting portion (hereinafter referred to as "upper projecting portion".) Was 1 or more provided a submerged nozzle according to any one of 4 from the 1. (Claim
5) 6. The upwardly projecting portion is inclined discharge hole direction, the immersion nozzle according to the 5. (Claim
6) 7. Wherein it is wide and the ratio Wn / Tn of the thickness of 5 or more, the immersion nozzle according to any one of the 6 from the 1. (Claim 7)

[0011]

　The width Wn of the inner hole in the present invention, the thickness Tn, the width of the bore at the upper end position of the pair of discharge holes provided in the short-side side wall portion of the immersion nozzle (length in the long side direction) refers to the thickness (length in the short side direction).

Effect of the invention

[0012]

　The flat immersion nozzle of the present invention, without fixing or complete separation of the molten steel flow, it is possible to control the direction of flow of molten steel in a continuous state, an appropriate balance of the molten steel flow in the nozzle it can be ensured. Thereby stabilizing the molten steel discharge flow, by reducing the variation of the mold molten steel surface can be stabilized to the molten steel in the mold flow. It is possible to turn improve the slab quality.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]

An image diagram illustrating an example of the immersion nozzle of FIG. 1 the invention was installed central projecting portion, (a) shows the cross section through a short side side center, (b) is a sectional view through the long side side center (vision A -A) there.
An image diagram illustrating an example of the immersion nozzle of FIG. 2 in addition to the central projecting portion present invention was installed upwardly projecting portion, (a) shows the through cross-section through a short side-side center, the (b) is a long side-side center it is a cross-sectional view (view a-a).
FIG. 3 is a conceptual view seen downward from the central projecting portion upper section B-B of FIG.
[Figure 4] shows a portion C of FIG. 1 (immersion nozzle bottom), and an image view of a cross-section showing an example in which the central protruding portion is inclined in the discharge hole direction.
[5] In another example of FIG. 4 similar cross section, Wp Gayori large and is an image diagram showing an example in which also established the discharge hole in the bottom.
[6] A sectional view of the immersion nozzle width direction center (A-A position of FIG. 3 or the like), an image view showing an example in which the upper surface of the central projecting portion is inclined bore center direction.
[7] a view as viewed from above a section of the A-A position of FIG. 4, an image view showing an example in which the projecting length of the bore center direction of the central projecting portion gradually decreases in the bore width direction from the center is there.
Is a schematic diagram showing a lower portion of the immersion nozzle (2) in FIG. 8 in addition to the central projecting portion present invention was installed upwardly projecting portion.
[Figure 9] the immersion nozzle according to the prior art, example no protrusion (others Figure 1 the same) is an image diagram showing a.

DESCRIPTION OF THE INVENTION

[0014]

　Molten steel flow falling from a narrow hole of the upper end center portion of the immersion nozzle molten steel inlet tends to concentrate in the center. If there is no obstacle in particular the bore, the molten steel flow velocity in the vicinity of the center and near the end of the flat portion width direction of the immersion nozzle is greatly different trend.

[0015]

　The present inventors have found that turbulence of the molten steel discharge flow from such flat immersion nozzle was found that concentration of the molten steel flow to the inner hole center is great factor of influence. Accordingly, the present invention subtracts the molten steel flow into the inner hole center, and be provided with an appropriate balance between the flow rate of the discharge hole direction.

[0016]

　The even some extent by installing a shunt means such as references 3, is forming a molten steel flow in the width direction end portion side can be. However, when performing such a fixed or complete shunt, resulting a portion i.e. molten steel flow separated for each single narrow range of the inner bore, a portion of flow direction and flow rate are different for each location of the bore likely to occur. In particular molten steel flow when there is a variation rate and direction of by molten steel flow control, etc. are biased to either, which may cause significant turbulence in the nozzle or the discharge flow.

[0017]

　The present invention is not a fixed-complete diversion of the molten steel flow in the bore, means for gradually control the flow direction and the flow rate of the portion of molten steel flow passes, namely in the inner hole space side from the bore wall while protrudes, placing the projecting portion of the state of maintaining the release portion of the bore space in the protruding portion. This protrusion, or its location, length, by adjusting the direction or the like, dispersed in the width direction end portion side, that the discharge hole side while avoiding to concentrate the flow of molten steel in the vicinity of the center, appropriate balance it can be provided with. Moreover not only dispersed, the space in established a projected area is communicated, not in a state of complete dividing the flow of molten steel, the flow of dispersed with uniform are gently mixed. As a result, it is possible to contribute to obtaining a uniform discharge flow without the discharge region is divided into a narrow area resulting in portions of different directions, flow rates. Protrusions having such feature is installed in a wall central portion in the width direction of the flat portion of the immersion nozzle to the first (long side) (central projecting portion).

[0018]

　The upper surface of the central projecting portion of the may also be inclined to the central portion of the protruding long side side to the immersion nozzle width direction and downward i.e. discharge hole direction at the vertex. Such tilting, further changing the flow rate and flowing form molten steel, it can also be optimized.

[0019]

　The upper surface of the central projecting portion of the may also be inclined toward the center or spatial side and lower side of the immersion nozzle thickness direction boundary with the top of the immersion nozzle width direction (long side) wall. Such tilting, further changing the flow rate and flowing form molten steel, it can also be optimized.

[0020]

　Further protruding length of the upper surface of the central projecting portion of the may also be inclined so that the center portion of the immersion nozzle width direction (long side) is gradually reduced toward the immersion nozzle widthwise ends as the largest vertex. Such tilting, further changing the flow rate and flowing form molten steel, it can also be optimized.

[0021]

　Since the form in which discharge holes of the short side side wall portion is opened longer in the longitudinal direction in the flat of the immersion nozzle, the in discharge holes tend to discharge flow rate as the upper side is reduced, especially in the immersion nozzle in the vicinity of the upper end backflow draw also often seen. Therefore, it is possible in the present invention in addition to the central projecting portion of the aforementioned installing the one or more protrusions on its upper (upper protrusion). The upper projecting portion may be the same structure as the central projection of the above, it can also be installed in a pair in symmetrical positions placed any distance from the central longitudinal axis of the immersion nozzle.

[0022]

　The upper projecting portion, a reduction in flow velocity in the discharge hole upwards particular, or to suppress the backflow in the vicinity of the upper end portion, to supplement the function of equalizing the flow velocity distribution for each vertical position of the discharge hole. Again the upper projecting portions, without cutting the inner pore space like the central projecting portion of the lower, the protruding length and angle, width, etc., individual immersion nozzle structure, be optimized according to operating conditions it can. Then, the inclination in the width direction and below the upper surface of the central projecting portion of the lower, inclined etc. to the immersion nozzle thickness direction and downward can be applied to the upwardly projecting portion. By applying such inclined upward protrusion, likewise further changing the flow rate and flowing form molten steel, it can also be optimized.

[0023]

　The projections (central projecting portion and the upper protruding portion) can be obtained the effect be provided on a flat portion where the variation of the flow of molten steel is increased as described above. Its position in the height direction in the immersion nozzle is not required to match the height direction position of the discharge hole, operating conditions, structure of the immersion nozzle bore, a relative relationship between the structure and the like of the discharge holes it may be installed at an optimum position.

[0024]

　Incidentally, the bottom of the inner immersion nozzle 1, 2, without forming a discharge hole near the center as shown in FIG. 4, may be a wall with a simple diversion function, provided the discharge holes as shown in Figure 5 it may be. In relation to the structure and the mold of the immersion nozzle for individual operating condition, when the total discharge amount of the mold (speed) is not enough discharge hole of the side wall portion, or lateral or upward molten steel in the mold etc. If desired reduced relative to the flow velocity, it is preferable to provide a discharge hole in the bottom.

[0025]

　Flat extent of the flat dipping the bore space in the nozzle (i.e., the long side length magnitude of the ratio of the short side length) by the flow rate of each fluid form and part of the molten steel or the form of the discharge flow-, the flow rate also changes. Therefore, the relationship between the degree and structure and individual operation conditions of the flat, are preferably optimized. Incidentally, the experience, the immersion nozzle ratio Wn / Tn of the width and thickness of the inner hole is approximately 5 or more, the difference in flow rate between the center and near the widthwise ends of the immersion nozzle becomes significant, the discharge hole such fluctuations in differences and flow velocity distribution of the flowing form tends to be noticeable. Accordingly, the present invention is particularly suitable for the immersion nozzle Wn / Tn is approximately 5 or more.

[0026]

　Next the invention will be described in conjunction with examples.
Example 1

[0027]

　Example 1 (hereinafter also referred to simply as "first embodiment".) Form was placed only central projecting portion as the first embodiment i.e. protrusions of the present invention shown in Figure 1 per immersion nozzle, the width of the central projecting portion the width of the immersion nozzle bore of Wp (the long side direction of the length) ratio Wp / Wn and mold molten steel surface about variation with respect to Wn, and the projecting length in the spatial direction of the central projecting portion (length of a pair of total) Tp It shows the thickness of the immersion nozzle bore (short side direction of the length) ratio Tp / Tn and mold molten steel surface about variation to Tn, a water model experiment results.

[0028]

　Comparative Examples were the structure shown in FIG. 9, i.e. the immersion nozzle structure obtained by removing the protruding portion from the immersion nozzle in the form of FIG.

[0029]

Specifications of the immersion nozzle is as follows.
Total length: 1165Mm
-molten steel inlet: Fai86mm
-discharge hole upper end position of the inner hole width (Wn): 255 mm
· discharge hole upper end position the inner bore thickness (Tn): 34 mm
- discharge hole upper end position of the nozzle the lower end surface of the height: 146.5Mm
-central projecting portion of the height (height from the nozzle lower end surface): 155mm
the length of the - central projecting portion (the left-right length from the center): 80 mm
in-immersion nozzle wall thickness: about 25mm
thickness of the bottom portion of the-immersion nozzle (vertex): height 100mm

[0030]

Molds, fluid conditions are as follows.
· Mold Width: 1650 mm
, thickness of the mold: 65 mm (central upper portion 185 mm)
, immersion depth (from the discharge hole the upper end to the water surface): 180 mm
feed rate of & Fluid: 3.5t / min
　※ value converted into molten steel

[0031]

　Mold molten steel surface about variation considers molten metal surface in the mold in the continuous casting water and (molten steel surface), to measure the distance to the water surface by using the ultrasonic sensor from the upward direction, and calculates the change height. The measurement was performed in a total of four places of 50mm position and 1/4 width from the width end portion of the lateral width direction sides around the immersion nozzle, and a value obtained by calculating the maximum and minimum difference between the change height.

[0032]

　Incidentally, the specifications of the immersion nozzle of the mold, the fluid conditions are the same for all examples below Example 2.

[0033]

　To any direction of the central projecting portion, the inclination angle is 0 ° (no tilt), the projecting thickness of the widthwise central projection constant (top view rectangle), and an inclination is not the structure of the inner hole center direction .

[0034]

　The mold molten steel surface about variation, Table 1 shows the results expressed in Comparative Example index to 100 the value of (the structure of FIG. 9) (hereinafter simply referred to as "fluctuation index".).

[0035]

　When based on the fluctuation index, degradation of the slab above about 40 in actual operation of the continuous casting it is found to exceed about permissible. Therefore, in the present invention can solve the problems of the present invention, i.e. the variation index of the target is 40 or less.

[0036]

　As a result, the installation structure of the central projecting portion to the comparative example of FIG. 9, Wp / Wn ratio of 0.2 to 0.7, and Tp / Tn ratio is 0.15 to 0.75 Example it can be seen that it is possible to obtain a target of 40 or less in the case of. Moreover, Wp / Wn ratio Tp / Tn ratio of 0.5 to obtain the highest effect may 0.5, it can be seen that preferred.

[0037]

[Table 1]

Example 2

[0038]

　Example 2 In the immersion nozzle of the first embodiment of the present invention shown in FIG. 1, showing a mold molten steel surface about variations in the structure are inclined from the center of the central projecting portion to the discharge hole side and the lower, water model experiment results it is.

[0039]

　Wp / Wn ratio 0.1,0.5,0.8, Tp / Tn ratio at the center protrusion structure of 0.1,0.5,0.9, with respect to the lateral (horizontal) direction of the immersion nozzle 30 ° angle of inclination of the central projecting portion, were studied case of a 45-degree. For comparison, it was not inclined to the various elements as the same condition (inclination angle of 0 °) Again experiment.

[0040]

　The results are shown in Table 2. As a result, in either case the inclination angle increases as the mold molten steel surface about variation it can be seen that the smaller. Incidentally, during this condition, Wp / Wn ratio of 0.5, in the case of Tp / Tn ratio 0.5, it can be seen that it is possible to obtain the goal of less than 40 at any angle.

[0041]

[Table 2]

Example 3

[0042]

　In the immersion nozzle of the first embodiment of the third embodiment the present invention shown in FIG. 1, the upper surface of the central projecting portion, the boundary between the central projecting portion and the wall surface (long side) of the immersion nozzle width direction of the upper surface It shows the effect of tilting the central projecting portion structure which is inclined to the central direction and downward in the thickness direction of the immersion nozzle to the vertex (see FIG. 6), a water model experiment results.

[0043]

　Wp / Wn ratio 0.1,0.5,0.8, Tp / Tn ratio 0.5, the inclination angle is 45 degrees to the discharge port side, 30 degrees inclination angle of the the thickness center direction, the case of a 45-degree and experiment.
For comparison, it was not inclined to the various elements as the same condition (inclination angle of 0 °) Again experiment.

[0044]

　The results are shown in Table 3. As a result, in either case the inclination angle increases as the mold molten steel surface about variation it can be seen that the smaller. Incidentally, Wp / Wn ratio of 0.5, in the case of Tp / Tn ratio 0.5, it can be seen that it is possible to obtain a target of 40 or less at any angle.

[0045]

[table 3]

Example 4

[0046]

　In the immersion nozzle of the first embodiment of the third embodiment the present invention shown in FIG. 1, the width of the immersion nozzle from the center of the central projecting portion (end portion) progressively shorter projecting length in the direction, the upper surface of the central projecting portion It shows a mold molten steel surface about fluctuations in the case of a pentagonal structure (see FIG. 7) provided angle view, a water model experiment results.

[0047]

　Wp / Wn ratio 0.1,0.5,0.8, Tp / Tn ratio 0.5, the inclination angle is 45 degrees in the width direction discharge hole side, the inclination angle of the the thickness center direction 0 degrees (without inclination), were studied case of the 8mm length of the central protrusion central vertex. For comparison, it was also experiments For not provided an angle above the elements as same conditions (top rectangle).

[0048]

　The results are shown in Table 4. As a result, mold molten steel surface about change when the length of the end portion in either case of Wp / Wn ratio of 4mm is found to be smaller. Incidentally, Wp / Wn ratio of 0.5, Tp / Tn ratio 0.5, when a 45-degree angle of inclination of the central projecting portion with respect to the lateral (horizontal) direction of the immersion nozzle, in any case the upper surface shape having an angle it can be seen that it is possible to obtain a target of 40 or less.

[0049]

[Table 4]

Example 5

[0050]

　Example 5 a second aspect of the present invention shown in FIG. 8, i.e. in addition to the central projecting portion of the lower, (hereinafter also referred to simply as "the second embodiment".) Form was installed upwardly projecting portion in its upwardly, It shows a mold molten steel surface about variations in the immersion nozzle installed in a pair of upwardly projecting portions at a position symmetrical to put any distance from the longitudinal central axis of the immersion nozzle, a water model experiment results.

[0051]

　Central projecting portion of the downward, from the immersion nozzle bottom surface (outer surface) and the apex a central position of 150 mm, the discharge hole direction length of the left and right respectively 80 mm, Wp / Wn ratio 0.1,0.5,0. 8, Tp / Tn ratio 0.5, the inclination angle is 45 degrees in the width direction discharge hole side, the inclination angle of the thickness center direction 0 ° (no tilt), the upper surface shape is rectangular (no angle) , the upwardly projecting portion is provided above the central projecting portion of the lower, and starting from the position of the left and right from the immersion nozzle width direction center 50 mm, inclination angle 45 degrees to the discharge hole side, the length to its discharge port direction 60mm, it was studied case of a 40mm. For comparison, it was also experiments if not installed an upwardly projecting portion as the same condition above the elements.

[0052]

　The results are shown in Table 5. As a result, when also disposed an upper protrusion cases mold molten steel surface about variation it can be seen that the smaller. Incidentally, Wp / Wn ratio of 0.5, in the case of Tp / Tn ratio 0.5, it can be seen that it is possible to obtain a target of 40 or less at any of the upwardly projecting portion length.

[0053]

[table 5]

[0054]

　Having described embodiments with examples of the present invention, the present invention is no not limited to the above embodiments, other embodiments within the scope of matters described in the claims and modifications are intended to include.

DESCRIPTION OF SYMBOLS

[0055]

　10: immersing Techno DANGER Hikaru
　1: projecting portion
　1a: the central projection
　1b: the upper projection
　2: molten steel inlet
　3: hole (molten steel flow
　passage) 4: discharge hole (short vicinities sideのwall
　portion) 5: bottom
　6: ejection hole (bottom)

The scope of the claims

[Claim 1]

　In the immersion nozzle is inside width Wn of holes bore thickness Tn larger flat, provided with a portion protruding wall central portion in the width direction of the flat portion (hereinafter referred to as "central projecting portion".), The central the ratio Wp / Wn with respect to the Wn length Wp of the width direction of the protruding portion is 0.2 to 0.7, wherein the central protrusion is arranged in pairs symmetrically, the pair of central projecting portion the total length Tp in the thickness direction of 0.15 to 0.75 of the Tn, submerged nozzle.

[Claim 2]

　The central projecting portion is inclined discharge hole downward in the vertex center of the width direction, the immersion nozzle according to claim 1.

[Claim 3]

　Said top surface of the central protrusion, in the vertex boundary portion between the immersion nozzle wall in the width direction are inclined in the thickness direction and downward above, submerged nozzle according to claim 1 or claim 2.

[Claim 4]

　The projecting length of the upper surface of the central projecting portion, a central portion of the Wp is the largest, gradually decreases toward both ends from the central portion, the immersion nozzle according to any one of claims 1 to 3.

[Claim 5]

　The upwardly projecting portion of the central projecting portion comprising one or a plurality of (. Hereinafter referred to as "upwardly projecting portion"), the immersion nozzle according to any one of claims 1 to 4.

[Claim 6]

　The upwardly projecting portion is inclined discharge hole direction, the immersion nozzle according to claim 5.

[Claim 7]

　Wherein it is wide and the ratio Wn / Tn of the thickness is 5 or more, the immersion nozzle according to any one of claims 1 to 6.