JP4227768B2 - Continuous casting mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a continuous casting mold in consideration of thermal deformation of a mold during casting.
[0002]
[Prior art]
Conventionally, a continuous casting mold (hereinafter, also simply referred to as a mold) 70 used in a continuous casting facility includes a pair of narrow cooling members 71 and 72 as shown in FIG. Long side members 73 and 74 which are a pair of wide cooling members disposed so as to sandwich the members 71 and 72, bolts 75 are attached to both ends of the long side members 73 and 74 facing each other, and springs (illustrated) No) is fixed by the nut 76.
The short side members 71 and 72 are mirror-symmetrical and have the same configuration, and are fixed to the short side copper plate 77 provided with a number of water guide grooves in the vertical direction on the back side and bolts on the back side of the short side copper plate 77. And a back plate 78 (also referred to as a cooling box). And the short side copper plate 77 is cooled by flowing the industrial water which is an example of a cooling water to a water guide groove through the drainage part and water supply part which were each provided in the upper end part and lower end part of the backplate 78. . On the other hand, the long side members 73 and 74 have substantially the same configuration, but the width of the long side copper plate 79 of the long side members 73 and 74 is longer than the width of the short side copper plate 77 of the short side members 71 and 72. The width of the back plate 80 fixed to the back side of the long side copper plate 79 is longer than the width of the long side copper plate 79.
The mold body 81 is constituted by the short side copper plate 77 of the short side members 71 and 72 and the long side copper plate 79 of the long side members 73 and 74. Further, the inner shape (cooling surface side) of the mold body 81 is a shape corresponding to the volume shrinkage of the cast slab to be manufactured, and the distance between the inner facing surface 82 of the long side copper plate 79 is as shown in FIG. As shown by the dotted line, the mold body 81 is narrowed from the upper end to the lower end.
[0003]
During the continuous casting operation, molten steel is poured from above the mold 70 (above the short side members 71 and 72 and the long side members 73 and 74), and initial casting of the slab as a product is performed by the mold 70, The solidified slab is continuously drawn from the lower part of the mold 70 at a constant speed. At this time, since the mold 70 is vibrated about 150 times / min in the vertical direction with respect to the slab, for example, in the range of 10 mm (also referred to as mold oscillation), the mold 70 moves relative to the slab. The mold 70 is lowered or raised from the slab. Thereby, when the mold 70 is lowered with respect to the slab, a cooling surface (a contact surface with the slab) constituted by the inner facing surface 83 of the short side copper plate 77 and the inner facing surface 82 of the long side copper plate 79, When a gap is generated between the slab and the solidified shell (solidified shell), and when it rises, the mold 70 is pressed against the slab.
Although the molten steel temperature poured into the mold 70 and the surface temperature of the slab at the outlet of the mold 70 differ depending on the operating conditions, the molten steel temperature is usually about 1500 ° C., and the surface temperature of the slab at the outlet of the mold 70 is 800 ˜1200 ° C. The inside of the slab here is in an unsolidified state, that is, in a liquid state.
[0004]
[Problems to be solved by the invention]
However, the above-described continuous casting mold 70 has the following problems.
The cooling surface of the mold body 81 is cooled to about 200 to 300 ° C., for example, but as shown in FIG. 7, a temperature distribution is generated from the upper end portion to the lower end portion of the mold body 81, The temperature is higher than the temperature of other parts. Therefore, as shown by the solid line in FIG. 6, the mold main body 81 is thermally expanded (thermally deformed) by the heat of the molten steel and the cast slab, and in particular, the inner upper part of the mold main body 81 is located on the cooling surface of the central part and the lower part. The main body 81 protrudes greatly inside and deforms.
As described above, the protrusion is generated at the upper part on the inner side of the mold body 81, so that the cooling surface of the mold body 81 and the surface of the slab are not substantially parallel. For this reason, as described above, when the mold 70 is moved relative to the slab, the protruding portion presses and deforms the solidified shell formed on the surface layer portion of the slab, so that the quality of the slab to be manufactured is deteriorated. There is a problem to make.
In addition, when the protruding portion presses the solidified shell, the solidified shell may be broken and repaired by cooling the mold 70 again, but at this time, a lap scratch or the like is generated on the surface of the slab, which deteriorates the product quality. There is also a problem. Further, there is a possibility that a slab breakout or the like resulting from this will be caused.
Furthermore, in recent years, the casting speed has been increased in order to improve the efficiency of the continuous casting operation. In particular, the slab is about 1/3 to 1/2 of the slab thickness employed in many continuous casting facilities. With the advent of continuous casting machines equipped with thick molds, it has become possible to see casting speeds that are twice or three times higher than conventional casting machines. As the casting speed increases in this way, the amount of heat extracted into the mold body increases proportionally, and thermal deformation in the mold body has become more prominent.
The present invention has been made in view of such circumstances, and a continuous casting mold capable of producing a slab of good quality by making the shape of the cooling surface of the mold main body a predetermined shape when hot. The purpose is to provide.
[0005]
[Means for Solving the Problems]
The continuous casting mold according to the present invention that meets the above-mentioned object is a continuous casting mold in which molten steel put in an enclosed mold space is cooled and solidified to produce a slab. The mold space has a pair of narrow cooling. It is formed in the mold body consisting of the short side copper plate of the member and the long side copper plate of a pair of wide cooling members, considering the volume shrinkage of the slab from the upper end to the lower end of the short side copper plate and the long side copper plate The reference taper is a continuously inclined surface, and the mold body side is closer to the mold taper than the reference taper surface by a depth corresponding to the difference between the numerical value of the copper plate surface profile of the mold body that is thermally deformed and the value of the reference taper. in the lower position than the meniscus of the mold body having an elaborate's cooling surface shape cutting into, the inner portion of molten steel top is in contact, at the time of manufacture, the widening section is provided that substantially matches the expansion margin of the mold body, yet Further expand above the widened section The inner width and the same or wider expansion widened portion parts are provided. Thus, since the widened portion is provided in the inner part of the mold body during production, even if the mold body expands due to heat during hot, the cooling surface of the inner part of the mold body has a predetermined shape, for example, a substantially flat surface. It can be in a state (one step taper).
Further, on the upper side of the widened portion, further since providing internal width identical to or wider expansion widening section of the widening section, all of the cooling surface of the mold body, there is no need to process to a shape in consideration of the thermal deformation of the mold body .
[0006]
In the continuous casting mold according to the present invention, the expansion allowance is preferably obtained using a predicted calculation value. In this way, since the expansion allowance of the mold body during the hot state is obtained, the shape of the widened portion can be easily grasped.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
FIG. 1 is an explanatory diagram of a continuous casting mold according to an embodiment of the present invention, FIG. 2 is a graph showing predicted calculation values for obtaining the shape of the widened portion of the continuous casting mold, and FIG. FIG. 4A and FIG. 4B are explanatory diagrams of the mold main body according to the modified example.
[0008]
As shown in FIG. 1, a continuous casting mold 10 according to an embodiment of the present invention shows a shape for performing numerical analysis, and a molten steel 12 put into an enclosed mold space 11 is shown. It cools and solidifies and manufactures a slab (not shown). The continuous casting mold 10 is provided with a widened portion 15 which is located below the meniscus portion 13 and which is substantially coincident with the expansion allowance of the mold body 14 at the time of manufacture, at the inner portion of the mold body 14 where the upper part of the molten steel 12 contacts. It has been. Note that the widened portion 15 means a widened portion of the mold space 11 formed by the mold body 14. For the mold body 14, for example, 0. It is a hollow shape having a depth of about 1 to 0.5 mm. This will be described in detail below.
[0009]
As described above, the continuous casting mold 10 is manufactured by combining a short side member that is a pair of narrow cooling members and a long side member that is a pair of wide cooling members (FIG. 5). reference). Further, the long side member of the continuous casting mold 10 is made of copper which is an example of a metal having good thermal conductivity, and the long side copper plate 16 having a water flow portion provided on the back side, and the back side of the long side copper plate 16. A back plate (also referred to as a cooling box or a water box) that is an example of a support member fixed by a bolt that is an example of an attachment means is provided on the side, and water is passed through a water supply part and a drain part provided on the back plate. The long side copper plate 16 is cooled by flowing industrial water, which is an example of cooling water, to the part. Note that the short side member of the continuous casting mold 10 has substantially the same configuration as the long side member described above, and the mold main body 14 is configured by the long side copper plate 16 of the long side member and the short side copper plate of the short side member. ing. As a result, the mold space 11 is formed at the center of the mold body 14 in plan view.
[0010]
The vertical length L from the upper end to the lower end of the long side copper plate 16 and the short side copper plate constituting the mold body 14 is, for example, about 700 to 1000 mm, and the thickness thereof is, for example, about 10 to 50 mm. Moreover, since the width | variety of the long side copper plate 16 (the width of a short side copper plate is also the same) is short from an upper end part to a lower end part, the inner side opposing surface 17 of the long side copper plate 16 of a pair of long side members, and The inner peripheral length formed by the inner facing surfaces of the short-side copper plates of the pair of short-side members is shorter at the lower end than at the upper end of the mold body 14. This is determined in consideration of the volume shrinkage of the slab such as solidification shrinkage and solid shrinkage, for example, and the numerical value is determined based on past performance data, the linear expansion amount and temperature of the slab. It is preferable.
[0011]
On the upper part of the long side copper plate 16 of the mold body 14, a widened portion 15 having a groove shape in the width direction of the long side copper plate 16 is provided. The widened portion 15 gradually widens from the lower side to the central portion of the upper side (upper region) of the long side copper plate 16 and gradually decreases from the central portion to the upper side. The same applies to the short side copper plate.
Here, how to obtain the shape of the widened portion 15 provided inside the mold body 14 will be described using the long-side copper plate 16.
First, when the inner side of the long side copper plate of the mold body at the time of production is assumed to be flat (also referred to as a one-step taper) (reference taper), the inner side of the long side copper plate is hot (when molten steel 12 is being charged). The shape is thermally deformed, for example, from the state of the two-dot chain line in FIG. 6 to the state of the solid line (shows expansion allowance). In addition, the predicted calculation value of the inner shape of the long side copper plate at this time is, for example, a conventionally known finite element method (FEM) using a drawing speed of a slab, a thickness of a mold body (long side copper plate), a cooling rate, and the like. Can be obtained. The result of this prediction calculation is shown in FIG. In addition, the position where the distance from the upper edge of the long side copper plate is 100 mm corresponds to the position of the molten steel surface (liquid surface).
As can be seen from the fact that the distance from the upper edge of the long side copper plate and the amount of displacement at each position in the height direction show a proportional relationship, this reference taper is applied from the upper end to the lower end of the long side copper plate and the volume shrinkage of the slab. In consideration of the continuous slope. However, the shape of the copper plate on the long side (copper plate surface profile) during the hot state has greatly increased the amount of displacement in the vicinity of the molten steel surface, so it can be predicted that significant thermal deformation will occur in the vicinity of the molten metal surface. .
[0012]
Moreover, the result of having calculated | required the inclination in each part of the height direction of a long side copper plate based on the data of FIG. 2 is shown in FIG. The inclination is the ratio of the change to the distance between the long side copper plates in each section when the long side copper plate is divided every 10 mm in the height direction, converted into a value per 1 m, and is shown by the following formula. It is.
Inclination [% / m] = (W1-W2) / W3 × 100 × (1000/10)
Here, W1 is the distance between the long side copper plates facing each other at the upper end position of each portion, W2 is the distance between the long side copper plates facing each other at the lower end position of each portion, and W3 is facing at the lower end position of the long side copper plate. This means the distance between the long side copper plates (see FIG. 6).
[0013]
Since the reference taper is continuously inclined in consideration of the volume shrinkage of the slab from the upper end to the lower end of the long side copper plate, as shown in FIG. 3, it extends from the upper end to the lower end of the long side copper plate. The inclination of each part is a substantially constant value (about 0.4% / m). However, since the long-side copper plate (copper plate surface profile) during hot time has greatly increased or decreased the inclination in the vicinity of the molten steel surface (liquid surface), it can be predicted that significant thermal deformation will occur in the vicinity of the molten metal surface. . In addition, in the position where the distance from a long side copper plate upper end is 450 mm, the inclination becomes a numerical value substantially near a reference | standard taper. Therefore, at the position where the distance from the upper end of the long side copper plate is 450 mm or more, it is preferable to mainly consider the influence of the volume shrinkage of the slab without considering the thermal deformation of the long side copper plate.
[0014]
As described above, the widened portion 15 is provided on the inner upper portion of the mold main body 14 that is most susceptible to the thermal influence of the molten steel 12, and the central portion and the lower portion are formed in a conventional shape, thereby taking into account the thermal deformation of the mold. The casting mold 10 can be manufactured.
Therefore, the shape of the widened portion 15 is, for example, from the surface of the reference taper to the mold body 14 side by a depth corresponding to the difference between the value of the copper plate surface profile and the value of the reference taper at each distance from the upper end of the long side copper plate. The widened portion 15 can be provided inside the long side copper plate 16 by cutting. That is, in FIG. 2, the line of the copper plate surface profile that is symmetrical with respect to the solid line of the reference taper is the shape of the widened portion 15 to be obtained (solid line in FIG. 1).
Based on this data, the long side copper plate 16 provided with the widened portion 15 is manufactured by processing the long side copper plate using an NC machine tool. In addition, this process can also be performed with respect to the long side copper plate 16 continuously or intermittently at predetermined intervals (for example, about 1 to 10 mm).
[0015]
Thereby, when the continuous casting operation is hot, the continuous casting mold 10 is expanded by the heat of the molten steel 12, so that the shape of the long side copper plate 16 is thermally deformed from the solid line in FIG. 1 to the two-dot chain line. . Accordingly, during the hot state, the widened portion 15 of the long side copper plate 16 expands by the expansion allowance due to the thermal effect of the molten steel 12, so that the inner shape of the mold body 14 is substantially the predetermined shape (1 Step taper). Thereby, the cooling surface of the mold main body 14 and the surface of the slab can be made substantially parallel.
In addition, in each distance from the upper end of the long side copper plate 16, when providing the widened portion 15 having a depth corresponding to the difference between the numerical value of the copper plate surface profile and the numerical value of the reference taper, the portion of the long side copper plate 16 where the widened portion 15 is provided. The thickness changes. Thereby, the expansion allowance of the mold body 14 also changes. Therefore, the long side copper plate 16 is provided with the widened portion 15 corresponding to thermal deformation by predicting and calculating using the finite element method in consideration of this thickness and determining the inner shape of the long side copper plate 16. Can do.
[0016]
Next, a modified example of the continuous casting mold 10 will be described using the long side copper plate of the mold body. The same applies to the short side copper plate, and the size and material of the mold main body are the same as those of the continuous casting mold described above. Since it is the same as 10, detailed description is omitted.
As shown in FIG. 4A, the mold body 20 is provided with an enlarged widened portion 23 that is the same as the inner width of the widened portion 22 on the upper side of the widened portion 22 provided on the upper part of the long side copper plate 21 at the time of manufacture. It is a thing. Therefore, from the position X where the inner width of the widened portion 22 provided on the long side copper plate 21 is the widest to the upper end 24 of the long side copper plate 21, the same inner width is obtained. The widened portion 22 is substantially the same as the widened portion 15 except that the shape on the upper side of the widened portion 15 is different.
[0017]
Moreover, the shape of the long side copper plate 21 from the position X to the lower end 25 of the long side copper plate 21 is the same shape as the continuous casting mold 10. Accordingly, it is possible to reliably prevent the portion of the long side copper plate 21 that is most susceptible to heat from protruding near the molten metal surface, and to prevent all the cooling surfaces of the long side copper plate 21 from being moved to the long side copper plate 21. It is not necessary to process into a shape that takes into account the thermal deformation of 21.
It is also possible to provide an enlarged widened portion 26 that gradually becomes wider than the inner width of the widened portion 22 on the upper side of the widened portion 22 toward the upper end 24 of the long side copper plate 21 (in FIG. 4A). Two-dot chain line). Thereby, the process of the wide part 22 with respect to the long side copper plate 21 becomes easy, and workability | operativity becomes still more favorable.
[0018]
As shown in FIG. 4 (B), the mold body 30 is provided with an enlarged widened portion 34 that is the same as the inner width of the molten metal surface position Y of the widened portion 33 on the upper side of the meniscus portion 32 of the long side copper plate 31 at the time of manufacture. It is provided. Therefore, the inner width is the same from the surface Y of the long side copper plate 31 to the upper end 35 of the long side copper plate 31. The widened portion 33 is substantially the same as the widened portion 15 except that the shape on the upper side of the widened portion 15 is different.
Moreover, the shape of the long side copper plate 31 from the molten metal surface position Y to the lower end 36 of the long side copper plate 31 is the same shape as the continuous casting mold 10. Thereby, since the shape of the cooling surface of the part which does not contact molten steel can be simplified, the process of the long side copper plate 31 can be made easy.
In addition, it is also possible to provide the enlarged widening part 37 which becomes gradually wider than the inner width of the molten metal surface position Y toward the upper end 35 of the long side copper plate 31 on the upper side of the meniscus part 32 (FIG. 4B). Middle two-dot chain line).
[0019]
As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, the present invention is also applied to the case where the continuous casting mold of the present invention is configured by combining some or all of the above-described embodiments and modifications.
In the above embodiment, the case of using a continuous casting mold having a mold body having a rectangular opening in a plan view is described. However, the shape of the opening in a plan view is manufactured. Of course, it may be polygonal (for example, convex, concave, hexagonal, octagonal, etc.) corresponding to the cross-sectional shape of the slab.
[0020]
In the above-described embodiment, the case where the shape of the cooling surface inside the mold body is a one-step taper has been described. However, other shapes may be used, for example, a conventionally known two-step taper, multi-taper, or the like. Is also possible.
[0021]
【The invention's effect】
The continuous casting mold according to claim 1 or 2 , wherein the widened portion is provided in the inner portion of the mold body at the time of production, so that the cooling surface of the inner portion of the mold body is expanded even when the mold body is expanded by heat during the hot process. Can be in a predetermined shape, eg, substantially planar. Thereby, since generation | occurrence | production of the protrusion part to the molten steel side which arises in a part of cooling surface with the heat | fever of molten steel can be prevented, the contact with the conventional protrusion part and the solidification shell of a slab can be prevented. Therefore, it is possible to improve the surface condition of the slab to be manufactured, improve the product quality, and reduce the possibility of occurrence of breakout of the slab. In addition, even when the casting speed is increased, by obtaining the shape when the mold body is thermally deformed in advance, a widened portion can be provided according to the expansion allowance of the mold body. A continuous casting mold can be provided.
In addition , since an enlarged widened portion that is the same as or wider than the inner width of the widened portion is provided above the widened portion, it is not necessary to process all of the cooling surface of the mold body into a shape that takes into account the thermal deformation of the mold body. The workability during the production of the mold body is improved.
[0022]
In the continuous casting mold according to claim 2 , since the expansion allowance is obtained using the predicted calculation value, the shape of the widened portion can be easily grasped. Therefore, at the time of production of a continuous casting mold, the work of the widened portion of the mold main body considering the thermal deformation of the mold main body can be easily performed, so that the workability is good.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a continuous casting mold according to an embodiment of the present invention.
FIG. 2 is a graph showing predicted calculation values for obtaining the shape of the widened portion of the continuous casting mold.
FIG. 3 is an explanatory diagram obtained by processing the predicted calculation value.
4A and 4B are explanatory views of a mold body according to a modification.
FIG. 5 is a plan view of a continuous casting mold according to a conventional example.
FIG. 6 is an explanatory view of the shape during production and hot production of the mold body of the continuous casting mold.
FIG. 7 is an explanatory view of a temperature distribution of a long-side copper plate constituting a mold body of the continuous casting mold.
[Explanation of symbols]
10: mold for continuous casting, 11: mold space, 12: molten steel, 13: meniscus part, 14: mold body, 15: widened part, 16: long side copper plate, 17: inner facing surface, 20: mold body, 21: Long side copper plate, 22: widened portion, 23: enlarged widened portion, 24: upper end, 25: lower end, 26: enlarged widened portion, 30: mold body, 31: long side copper plate, 32: meniscus portion, 33: widened portion, 34: enlarged widened portion, 35: upper end, 36: lower end, 37: enlarged widened portion

Claims (2)

In a continuous casting mold for producing a slab by cooling and solidifying molten steel put in an enclosed mold space,
The mold space is formed in a mold body constituted by a short side copper plate of a pair of narrow cooling members and a long side copper plate of a pair of wide cooling members,
The copper plate surface of the mold main body that is thermally deformed when hot is used as a reference taper with a continuously inclined surface taking into account volume shrinkage of the slab from the upper end to the lower end of the short side copper plate and the long side copper plate A depth corresponding to the difference between the numerical value of the profile and the numerical value of the reference taper is lower than the meniscus portion of the mold body having a cooling surface shape cut from the surface of the reference taper to the mold body side. In addition, a widened portion that substantially coincides with the expansion allowance of the mold main body is provided at the inner portion where the molten steel upper portion is in contact, and the upper portion of the widened portion is further equal to or wider than the inner width of the widened portion. A continuous casting mold characterized in that an enlarged widened portion is provided .   The continuous casting mold according to claim 1, wherein the expansion allowance is obtained by using a predicted calculation value.

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