JP2004074172A - Casting mold for continuously casting and continuous casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a casting mold for continuously casting which can prevent a surface of an ingot from cracking due to occurrence of an air gap, a structure from being coarsely grown or heterogenized or grain boundary cracked or the like due to them and to provide a continuous casting method. <P>SOLUTION: In the casting mold 1A for continuously casting, its long side 5 is projected to an inside so that an element 20 of a solidified shell 16 on a surface of the ingot 10 corresponding to a central part a of the side 5 becomes a stress of a direction for pressing a composite vector 22a of a stress vector 21a to be applied by a contraction to an inner surface 13 of the mold. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuous casting mold and a continuous casting method for an ingot having a rectangular cross section, and in particular, cracks on the surface of the ingot due to the generation of an air gap, coarsening and unevenness of the structure, and grain boundary cracking due to these. TECHNICAL FIELD The present invention relates to a continuous casting mold and a continuous casting method capable of preventing such problems.
[0002]
[Prior art]
FIG. 7 schematically shows a conventional vertical continuous casting apparatus. This continuous casting apparatus is provided with a continuous casting mold 1C for pouring a molten metal 15 of a predetermined metal compounded to be copper or a copper alloy in a predetermined ratio and solidifying the molten metal 15, and disposed below the continuous casting mold 1C. And a secondary cooler 2 for cooling the ingot 10 solidified with copper or a predetermined metal taken out from the continuous casting mold 1C by discharging water in a shower or spray form, and taken out from the continuous casting mold 1C. A water tank 3 for further cooling the ingot 10 is provided. In the continuous casting mold 1C, a hollow portion 12 having an opening 11 is formed by long sides 5 and 5 as side walls and short sides 6 and 6 as side walls.
[0003]
FIG. 8 shows a cross section (hereinafter, referred to as “cross section”) in a direction perpendicular to the casting direction of a conventional continuous casting mold used in a vertical continuous casting apparatus. The continuous casting mold 1C has a hollow rectangular cross section, and includes short sides 6 and 6 as side walls and long sides 5 and 5 as side walls.
[0004]
FIG. 9 shows a cross section of the continuous casting mold during operation of the continuous casting apparatus.
[0005]
This continuous casting apparatus operates as follows. A molten metal 15 in which copper or a predetermined metal compounded to be a copper alloy in a predetermined ratio is melted is poured into the hollow portion 12 from the opening 11 above the continuous casting mold 1C to form a solidified shell having a sufficient thickness. This is pulled out downward, cooled by a secondary cooler disposed immediately below the mold 1C, further cooled through the water tank 3, and a solidified ingot 10 is formed.
[0006]
At this time, an air gap 7 is generated between the inner surface 13 of the mold and the surface 10a of the ingot due to shrinkage accompanying cooling of the ingot 10. In the ingot 10 having a rectangular cross section, as shown in FIG. 9, the shrinkage near the center of the long side 5 is large, and the air gap 7 is easily generated in this portion.
[0007]
The heat transfer at the portion where the air gap 7 occurs becomes radiant heat transfer, and the heat flux is greatly reduced as compared with the heat transfer at other contacting portions. When the outflow of heat is smaller than the inflow of heat supplied from the molten metal, the temperature of the solidified shell rises and reheats. Then, in a severe case, the solidified shell dissolves again, comes into contact with the inner surface 13 of the mold, and starts solidifying again. For this reason, in the portion where the air gap 7 occurs, surface cracking, coarsening and non-uniformity of the structure, and grain boundary cracking due to these cracks occur.
[0008]
In order to solve this problem, conventionally, a taper of an angle in consideration of the shrinkage amount of the ingot in the casting direction in the mold, optimization of the amount of cooling water, and cooling after cooling as shown in FIGS. In order to approximate the cross-sectional shape of the ingot 10 to a rectangle, measures such as solidification using a mold having a central portion of the long side 5 projecting outward in anticipation of shrinkage in advance have been taken.
[0009]
[Problems to be solved by the invention]
However, depending on the type of the alloy to be cast, for example, a copper alloy, an air gap is remarkably generated, so that it is not possible to cope with only measures such as taper, and even if the cooling water amount is optimized, it is not a sufficient measure. . In addition, the measure for expanding the center portion outward in anticipation of shrinkage also promotes the air gap 7 between the inner surface 13 of the mold and the ingot 10, causing cracks on the surface of the ingot and coarsening of the structure. There is a problem that unevenness and grain boundary cracking due to these are likely to occur.
[0010]
Accordingly, an object of the present invention is to provide a continuous casting mold and a continuous casting method capable of preventing cracks on the surface of an ingot, coarsening and non-uniform structure of the ingot due to generation of an air gap, and grain boundary cracking due to the cracks. Is to provide.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a hollow portion formed by a pair of side walls having a length of a first side and a pair of side walls having a length of a second side. Wherein the metal is cooled and solidified while the metal flows in the hollow portion, and the solidified metal is continuously taken out. A pair of side walls having a longer side of the length of the side has a shape protruding inside the hollow portion.
[0012]
According to this configuration, when the molten metal is solidified in the hollow portion of the continuous casting mold, the combined vector of the stress vectors due to the shrinkage of the solidified shell formed on the surface of the continuous casting mold has a stress in the direction of pressing the side wall. Thus, the molten metal solidifies toward the surface of the continuous casting mold.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically shows a vertical continuous casting apparatus to which a continuous casting mold according to a first embodiment of the present invention is applied. This continuous casting apparatus includes a continuous casting mold 1A for pouring and solidifying a molten metal 15 of a predetermined metal compounded to be copper or a copper alloy of a predetermined ratio, and a water disperser disposed below the continuous casting mold 1A to shower water. A secondary cooler 2 for cooling an ingot 10 in which copper or a predetermined metal has been solidified by discharging water or a spray from the continuous casting mold 1A, and an ingot 10 removed from the continuous casting mold 1A. Further, a water tank 3 for cooling is provided. The continuous casting mold 1A is made of copper, a copper alloy or carbon, and has a hollow portion 12 having an opening 11 formed by long sides 5 and 5 as side walls and short sides 6 and 6 as side walls.
[0014]
FIG. 2 shows a continuous casting mold according to the first embodiment, and shows a cross section. The continuous casting mold 1A of the present invention includes short sides 6 and 6 serving as side walls facing each other and long sides 5 and 5 serving as side walls facing each other. The cross-sectional shape is a horizontally long rectangle whose aspect ratio (length-to-width ratio) is based on 1.5 or more, and a curved surface shape in which the mold inner surface 13 projects into the hollow portion 12 over the entire long sides 5 facing each other. Is presented.
[0015]
This continuous casting apparatus operates as follows. A molten metal 15 in which copper or a predetermined metal compounded to have a predetermined ratio of copper alloy is melted is poured into the hollow portion 12 from the opening 11 above the continuous casting mold 1A. The poured molten metal 15 is cooled by the mold inner surface 13 to form a solidified shell 16 solidified to an appropriate thickness.
[0016]
FIG. 3 shows the tensile stress component of the ingot in the cross section of the continuous casting mold. This is a simplified explanation of the force applied by the shrinkage of the solidified shell 16 formed on the mold inner surface 13 in the cross section where solidification has started by the contact between the inner surface 13 of the mold and the melt 15. First, the molten metal 15 supplied to the hollow portion 12 is cooled by being deprived of heat from the inner surface 13 of the mold, starts solidifying at a contact portion with the inner surface 13 of the mold, and forms a solidified shell 16. Due to the large shrinkage at this time, a stress vector 21 a is generated in the solidified shell 16 in parallel with the mold inner surface 13.
[0017]
Here, when considering the contracted shape, in the cross section of the ingot 10, a portion in contact with the central portion 5a and the corner portions 5b, 5b is considered to be a fixed point. The part in contact with the corner 5b is considered as a fixing point because the vicinity of the corner 5b has the highest cooling in the same cross section and the ingot 10 is thicker, and is hardly deformed. It is because it is considered that it is done. In the cross-sectional shape according to the embodiment of the present invention, since the stress vector 21a is applied to the element 20a on the surface of the ingot 10 corresponding to the central portion 5a of the long side 5 of the continuous casting mold by shrinkage, the resultant vector 22a Is a stress that presses the mold inner surface 13.
[0018]
FIG. 4 shows the tensile stress component of the ingot in the cross section of the conventional continuous casting mold 1C shown in FIG. In the element 20b of the solidified shell 16 corresponding to the central portion 5e of the long side 5, when the molten metal 15 is cooled by the mold inner surface 13 and solidification is started, a stress vector 21b is formed in the solidified shell 16 in parallel with the mold inner surface 13. Occurs. The composite vector is “0”. However, in actuality, an air gap 7 is generated at the center of the long side 5 due to the cooling conditions (the temperature of the mold inner surface 13, the temperature of the molten metal, etc.) by the mold inner surface 13.
[0019]
FIG. 5 shows a tensile stress component of a solidified shell in a cross section of the conventional continuous casting mold 1D shown in FIG. When the molten metal 15 is cooled by the mold inner surface 13 and solidification is started, a stress vector is formed in the solidified shell 16 in parallel with the mold inner surface 13 in the element 20 c on the surface of the ingot 10 corresponding to the central portion 5 f of the long side 5. 21c results. The resultant vector 22c of the stress vectors 21c, 21c due to the contraction of the solidified shell 16 becomes a stress in a direction away from the inner surface 13 of the mold. Therefore, the air gap 7 between the inner surface 13 of the mold and the ingot 10 is promoted, and cracks on the surface of the ingot, grain boundary cracks due to coarsening and uneven structure of the ingot, and the like occur.
[0020]
Next, while the ingot 10 is continuously taken out from below the continuous casting mold 1A, water is discharged to the ingot 10 by the secondary cooler 2 in a shower shape or a spray shape, and the ingot 10 is cooled. The ingot 10 cooled by the secondary cooler 2 is sent to a water tank 3 containing cooling water (not shown) and cooled.
[0021]
As described above, according to the casting mold 1A for continuous casting according to this embodiment, when the molten metal 15 solidifies, the combined vector 22a of the stress 21a of the solidified shell 16 applied to the central portion 5a of the long side 5 is formed in the mold. Since a curved surface shape which becomes a stress in the direction of pressing the surface 13 is formed to prevent the generation of an air gap, the surface of the ingot 10 is cracked, and the structure of the ingot 10 is coarsened or uneven. Generation of grain boundary cracks and the like can be prevented. The same effect can be obtained even if the curved shape is a multi-plane approximation.
[0022]
FIG. 6 is a cross-sectional view of a continuous casting mold according to a second embodiment of the present invention. In the continuous casting mold 1B, the central portion 5c of the long side 5 projects into the hollow portion 12. Even in the continuous casting mold 1B, the combined vector of the stress of the solidified shell 16 applied to the central portion 5c of the long side 5 when the molten metal 15 solidifies becomes the stress in the direction of pressing the inner surface 13 of the mold. -Gap is less likely to occur.
[0023]
【Example】
<Example 1>
A molten metal 15 of a Cu-Fe-P-based copper alloy was supplied from a downcomer to the hollow portion 12 of the continuous casting mold 1A of the continuous casting apparatus shown in FIG. 1, and vertical continuous casting was performed at a casting speed of 100 mm / min. The ingot is a copper alloy to which Cr and Zr are added, and has a cross-sectional size of 180 mm × 480 mm and a length of 300 mm. In the casting direction, 10 'is tapered on the long side and 15' on the short side. The molten metal surface was 50 mm from the upper end of the mold, and the molten metal surface was coated to prevent oxidation of the molten metal.
[0024]
In Example 1, no cracks or deep dents were found on the surface of the ingot 10, and the wrinkles were shallow, and the appearance was good. No cracks were seen inside, and the microstructure of the cross section was fine, uniform and good.
[0025]
<Comparative Example 1>
Under the same conditions as in Example 1, vertical continuous casting of a Cu-Fe-P-based copper alloy was performed using the continuous casting mold 1C of the conventional continuous casting apparatus shown in FIG.
[0026]
In Comparative Example 1, deep dents and cracks having a period of about 300 mm were found in the surface of the ingot 10 in the casting direction. On the other hand, no cracks were found inside, and the microstructure of the cross section was fine, uniform and good.
[0027]
<Example 2>
A molten metal of a Cu-Zr-based copper alloy was supplied from the downcomer to the hollow portion 12 of the continuous casting mold 1A of the continuous casting apparatus shown in FIG. 1, and vertical continuous casting was performed at a casting speed of 200 mm / min. The ingot is a copper alloy to which Cr and Zr are added, and has a sectional size of 180 mm × 480 mm and a length of 350 mm. In the casting direction, a taper processing of 10 'on the long side and 30' on the short side is performed. The molten metal surface was 50 mm from the upper end of the mold, and the molten metal surface was coated to prevent oxidation of the molten metal.
[0028]
In Example 2, no cracks or dents were found on the surface of the ingot 10, and the wrinkles were shallow, and the appearance was good. No cracks were seen inside, and the microstructure of the cross section was fine, uniform and good.
[0029]
<Comparative Example 2>
Under the same conditions as in the example, a vertical continuous casting of a Cu-Zr-based copper alloy was performed using a continuous casting mold 1C of a conventional continuous casting apparatus having a cross section shown in FIG.
[0030]
In Example 2, no dents or cracks were found on the surface of the ingot 10 and the appearance was good, but the structure of the cross section was coarse near the center of the long side, and cracks were generated at the grain boundaries in this part. It was observed.
[0031]
As described above, in each of the examples using the continuous casting mold according to the embodiment of the present invention, no cracks or dents were found on the surface of the ingot, and the wrinkles were shallow, and the appearance was good. Furthermore, no cracks were seen inside, and the structure of the cross section was fine, uniform and favorable. Therefore, it is considered that no air gap occurred along the long side of the hollow portion.
[0032]
However, in each of the comparative examples, deep dents and cracks were found on the surface of the ingot, and the structure of the cross section near the center of the long side was coarse, and cracks were seen at the grain boundaries in this portion. This seems to be due to the formation of an air gap near the center of the long side of the continuous casting mold, which caused pits, cracks, and grain boundary cracks on the surface of the ingot.
[0033]
The continuous casting mold can be modified without being limited to the above embodiments and examples. An appropriate amount of taper can be provided in anticipation of shrinkage of the ingot in the casting direction. That is, the hollow portion is slightly narrowed in the casting direction. Thereby, the effect of preventing the generation of the air gap is further increased.
[0034]
In the continuous casting mold, the case where the long side is formed with a curved surface has been described. However, not only the curved surface but also a straight line may protrude inside the hollow portion. Further, the long side may be formed by a straight line and a curve.
[0035]
Even when the inner surface 13 of the mold is plated with metal, the combined vector of the stress of the solidified shell 16 applied to the central portion 5a of the long side 5 when the molten metal 15 solidifies is the stress in the direction of pressing the inner surface 13 of the mold. Therefore, generation of an air gap can be prevented. Similar effects can be expected even when the short sides 6, 6 and the long sides 5, 5 as the side walls are formed of copper, a copper alloy or carbon.
[0036]
In the present invention, the hollow portion is described as having an aspect ratio of 1.5 or more, but if the length of the long side is equal to or more than a certain value, the solidified shell formed at the center of the side shrinks. It is desirable to protrude inside the hollow portion.
[0037]
Although the above description has been made on the continuous casting mold used in the vertical continuous casting apparatus, the present invention can be similarly applied to a continuous casting mold used in the horizontal continuous casting apparatus.
[0038]
【The invention's effect】
As described above, according to the present invention, when the molten metal is solidified in the hollow portion of the continuous casting mold, the resultant vector of the stress vector accompanying the shrinkage of the solidified shell formed on the surface of the continuous casting mold presses the side wall. Therefore, it is possible to prevent cracks on the surface of the ingot due to the generation of the air gap, coarsening and unevenness of the structure, and grain boundary cracks due to these.
[Brief description of the drawings]
FIG. 1 shows a continuous casting apparatus to which a continuous casting mold according to a first embodiment of the present invention is applied.
FIG. 2 shows a cross section of the continuous casting mold according to the first embodiment of the present invention.
FIG. 3 shows a tensile stress component of an ingot in a cross section of a continuous casting mold.
FIG. 4 shows a tensile stress component of an ingot in a cross section of a conventional continuous casting mold.
FIG. 5 shows a tensile stress component of an ingot in a cross section of another conventional continuous casting mold.
FIG. 6 shows a cross section of a modified example of the continuous casting mold of the present invention.
FIG. 7 shows a continuous casting apparatus to which a conventional continuous casting mold is applied.
FIG. 8 shows an example of a conventional continuous casting mold.
FIG. 9 shows a cross section of a continuous casting mold during operation of a conventional continuous casting apparatus.
FIG. 10 shows another example of a conventional continuous casting mold.
FIG. 11 shows still another example of a conventional continuous casting mold.
FIG. 12 shows still another example of a conventional continuous casting mold.
[Explanation of symbols]
1A Continuous casting mold 1B Continuous casting mold 1C Continuous casting mold 1D Continuous casting mold 2 Secondary cooler 3 Water tank 5 Long side 5a Central part 5b Corner part 6 Short side 7 Air gap 10 Ingot 10a Ingot surface 11 Opening 12 Hollow part 13 Mold inner surface 15 Melt 16 Solidified shell 20a Element 21a Stress vector 21b Stress vector 21c Stress vector 22a Synthetic vector 22b Synthetic vector

Claims (8)

A hollow portion formed by a pair of side walls having a length of a first side and a pair of side walls having a length of a second side, wherein a metal melted in the hollow portion is supplied; Cooling and solidifying the metal while the metal flows, in a continuous casting mold from which the solidified metal is continuously taken out,
A continuous casting mold, wherein a pair of longer side walls of the first and second sides have a shape protruding inside the hollow portion. The continuous casting mold according to claim 1, wherein the pair of longer side walls of the side has a whole curved surface. The mold for continuous casting according to claim 1, wherein the pair of longer side walls of the side has a curved surface only at the center of the side. The aspect ratio of the pair of side walls having a length of the first side and the pair of side walls having a length of the second side of the hollow portion is 1.5 or more. 2. The continuous casting mold according to 1. A pair of side walls having a length of the first side and a pair of side walls having a length of the second side are provided with metal plating on a surface forming the hollow portion. The continuous casting mold according to claim 1. 2. The continuous casting mold according to claim 1, wherein the pair of longer side walls has a taper in a direction in which the metal flows. The continuous casting mold according to claim 1, wherein the pair of longer side walls is formed of one of copper, a copper alloy, and carbon. Supplying a molten metal to a continuous casting mold having a hollow portion, a first step of cooling and solidifying the metal while the metal flows in the hollow portion,
In a continuous casting and melting method including a second step of continuously taking out the solidified metal,
In the continuous casting mold used in the first step, the hollow portion is formed by a pair of side walls having a length of a first side and a pair of side walls having a length of a second side, The pair of side walls having a longer side of the lengths of the first and second sides protrude inward, and a resultant force accompanying shrinkage when the molten metal is cooled and solidified has a resultant force of the longer side. A continuous casting and melting method, wherein the method is configured so as to face a pair of tail side walls.

Images