JP3976323B2 - Continuous casting alloy rod, continuous casting method and continuous casting apparatus - Google Patents

Description

The present invention relates to a continuous cast alloy rod and a continuous casting method that are optimal for forging.

Patent Document 1 discloses that a cast bar having a cross-sectional shape close to the shape of the final forged product is manufactured, and the cut surface of the cast bar cut in a direction crossing the longitudinal direction is pressed and forged.
Patent Document 2 discloses that as a continuous casting technique, the solidification interface position of a continuously cast alloy rod drawn from the mold is changed by changing the casting speed and the amount of cooling water.
In Patent Document 3, in continuous casting, another mold having a tapered surface that expands downward is provided on the mold, and when casting the rear end of the continuously cast alloy rod, the mold having the tapered surface is filled with molten metal. A technique for forming a tapered surface at the rear end of a continuously cast alloy bar is disclosed.
In addition, according to a conventionally known casting method using a sand mold, it is possible to manufacture a casting rod having at least one portion having a different cross-sectional area in the middle portion in the longitudinal direction in accordance with the cast product.
Moreover, after extruding a round bar, it is also possible to manufacture by cutting out at least one portion having a different cross-sectional area in the longitudinal intermediate portion in accordance with the cast product.

JP-A-6-73482 JP 2003-71546 A JP-A-2-307650

However, Patent Document 1 discloses that a segregated layer is removed by surface cutting before pressing (forging) a section cut in a direction intersecting with a longitudinal direction (drawing direction of a cast rod) or forging the segregated layer. Since it was removed as burrs, the yield was poor, and the segregation layer could not be contributed to improving the quality of the forged product.
Patent Document 2 only changes the position of the solidification interface in order to improve the quality of the cast bar, and does not change the cross-sectional area of the intermediate portion in the longitudinal direction of the continuous cast alloy bar.
Further, Patent Document 3 merely changes the shape of only the rear end of the continuously cast alloy rod, and does not change the cross-sectional area of the intermediate portion in the longitudinal direction (drawing direction).
And when a cast bar having a portion with a different cross-sectional area in the longitudinal intermediate portion is produced by casting using a sand mold, the segregation layer is contained in the internal granular layer due to the property that solidification occurs from multiple directions. Unnecessary entrapment quality is not stable, so it is not suitable for forging, and it cannot be manufactured as a long object of 5 m or longer like the continuous casting method, so the productivity is poor and the cost of the forged product cannot be reduced. . In addition, when the round bar was cut out, the yield was remarkably bad.
Therefore, the present invention can reduce the forging cost by forging the product cut in the longitudinal direction as it is, and improving the quality of the forged product by incorporating the segregation layer into the surface of the forged product. An object of the present invention is to provide a continuous cast alloy bar and a continuous casting method that are optimal for forging.

  The invention according to claim 1 is formed by spraying cooling water on a part drawn out from a mold having a tapered surface whose inner peripheral surface expands from the inlet side toward the outlet side. A large-diameter part and a small-diameter part are provided.The large-diameter part is formed by reducing the drawing speed from the mold and increasing the amount of cooling water, and the small-diameter part increases the drawing speed from the mold. In addition, it is formed by reducing the amount of cooling water, and has a segregation layer on the surface.

  The invention according to claim 2 is the invention according to claim 1, wherein the segregation layer formed on the surface is an aluminum alloy or a magnesium alloy and has a thickness of 5 mm or less.

  The invention according to claim 3 is the invention according to claim 1, wherein the invention is an aluminum alloy or a magnesium alloy, and the surface roughness of the surface is Ra35 or less.

  In the invention according to claim 4, the molten metal is poured into a mold having a tapered surface whose inner peripheral surface expands from the inlet side toward the outlet side, and cooling water is sprayed onto the continuous cast alloy rod drawn out from the outlet of the mold. The step of setting the solidification interface position of the continuous cast alloy rod in the mold to the tapered surface entrance side, and increasing the drawing speed and reducing the cooling water amount, the solidification interface position of the continuous cast alloy rod in the mold is set to the outlet of the taper surface. The process of making it to the side is repeated continuously, and a large diameter part and a small diameter part are formed in the middle part in the longitudinal direction.

  According to a fifth aspect of the present invention, in the invention of the fourth aspect, two cooling water jets are provided in the drawing direction of the continuous cast alloy rod, and when the solidification interface is on the inlet side, the cooling water is supplied from both jets. When the solidification interface is set to the outlet side, the cooling water is sprayed only at the one of the two outlets closer to the inlet side.

  According to the first aspect of the present invention, since at least one portion having a different cross-sectional area is provided in the longitudinal direction, the product cut in the longitudinal direction according to the shape and size of the forged product is left as it is. By forging, the segregation layer can also be incorporated and used on the surface of the forged product. By leaving the uneven lamination on the surface of the forged product, coarsening of recrystallization is suppressed, and high strength and high toughness characteristics are achieved. The forging material which has can be supplied. Moreover, since the optimal material distribution with respect to each part of a forged product can be reflected in the cross-sectional change of a cast bar, a burr | flash discharge amount is reduced, a yield is good, and a forged product can be obtained with few man-hours.

  The invention according to claim 2 can obtain the same effect as that of the invention according to claim 1, and since the thickness of the segregation layer is 5 mm or less, it is more effective when the continuously cast alloy bar is an aluminum alloy. Good surface appearance and fatigue strength can be obtained. In the case of magnesium alloy, better surface appearance, corrosion resistance and fatigue strength can be obtained, and a segregation layer of good quality covers the surface of the forged product. It can also be used for forged products that require elaborate and high quality (high strength, high toughness).

  The invention according to claim 3 can obtain the same effect as that of the invention according to claim 1, and since the surface roughness Ra is 35 or less, when the continuous cast alloy bar is an aluminum alloy, Better surface appearance and acid durability can be obtained, and in the case of magnesium alloy, better surface appearance, corrosion resistance and fatigue strength can be obtained, and sophisticated and high quality for automobile parts (high strength, high toughness) ) Can also be used for forged products.

  According to the fourth aspect of the invention, since the solidification interface position of the continuously cast alloy rod is changed between the inlet side and the outlet side of the taper surface in the mold, the position of the solidification interface on the taper surface is changed. By changing, the cross-sectional area of the part in the longitudinal direction of the continuous cast alloy rod can be easily changed, and the continuous cast alloy rod according to claim 1 can be obtained.

    The invention according to claim 5 can obtain the same effect as that of the invention according to claim 4, and the cooling water only controls the injection and stop of each of the two injection ports provided in the drawing direction. Therefore, the operation is easy, and a continuous cast alloy bar having a stable quality in the longitudinal direction can be obtained.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a mold and its peripheral part of a continuous casting apparatus according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a state when the position of a solidification interface is changed in FIG. FIG. 3 is a view of a mold, (a) is a top view, (b) is a longitudinal sectional view, FIG. 4 is a longitudinal sectional view of a continuous casting apparatus, and FIG. 5 is a casting speed (drawing speed) and cooling. FIG. 6 is a side view of a continuous cast alloy bar obtained by the continuous casting apparatus of FIG. 4, and FIG. 7 is a forging process diagram of the continuous cast alloy bar according to the present embodiment. is there.
As shown in FIG. 4, the continuous casting apparatus 1 according to the present invention includes a tundish 3 that stores the molten metal M, a mold 5, a cooling water jacket 7, and a bottom block 11 that moves up and down by a drawer 9. The molten metal M is drawn from the tundish 3 to the mold 5, the drawn molten metal M is cooled and solidified by the cooling water jacket 7, and then the continuously cast alloy rod Ma is led to the cooling water pit 13 by the bottom block 11. ing. The mold 5 is disposed on the inner periphery of the heat insulating mold 16 and is a heat insulating mold.
As shown in FIG. 1, the mold 5 includes a tapered surface 15 whose diameter is increased downward on the inner peripheral surface, and the tapered surface 15 is formed across the upper end and the lower end of the mold. The tapered surface 15 is a surface on which a solidification interface Mc, which will be described later, contacts and moves.
A cooling water jacket 7 is provided at the lower end of the mold 5, and the cooling water jacket 7 is provided with an outlet 17 for blowing cooling water to the continuous cast alloy rod M drawn vertically downward from the mold 5. .
The spout 17 can be controlled to change the amount of water sprayed.
The drawing machine 9 can control the lifting speed, and the drawing speed of the continuously cast alloy rod Ma is controlled by changing the lifting speed of the drawing machine 9.
In this embodiment, an aluminum alloy is used as an alloy for continuous casting. As a specific aluminum alloy, any alloy selected from the group consisting of 2000 series (JIS), 3000 series, 5000 series, 6000 series, and 7000 series is used. Or can be used in combination. Moreover, you may add metals, such as Ca and Be, to these aluminum alloys.

Next, a continuous casting method using the continuous casting apparatus 1 will be described.
The molten metal M is poured into the mold 5, and the continuous casting alloy rod Ma is pulled out vertically from the casting mold 5 by the drawing machine 9, and cooling water is blown from the jet port 17 to the continuous casting alloy rod Ma to be cooled.
Although the molten metal M is solidified by cooling, the amount of water sprayed from the ejection port 17 and the drawing speed are controlled so that the solidification interface Mc is located in the mold 5. The solidification interface Mc moves in contact with the tapered surface 15 of the mold 5.
As shown in FIG. 1, when the solidification interface Mc is formed on the upper part of the mold 5, the cross-sectional area is small. When the solidification interface Mc is formed on the lower part of the mold 5 as shown in FIG. 2, It becomes a part with a larger cross-sectional area than the case shown in FIG.
That is, when the drawing speed is increased or the amount of cooling water is reduced as compared with the case shown in FIG. 1, the solidification interface Mc moves down the tapered surface 15 to a position below the position shown in FIG. When the solidification interface moves and the drawing speed is made slower than in the case shown in FIG. 2 or the amount of cooling water is increased, the solidification interface Mc moves upward on the tapered surface 15, and the position shown in FIG. The solidification interface moves to the upper position.
In this way, by continuously changing the drawing speed (casting speed) and the amount of cooling water (see FIG. 5), a continuous casting alloy bar for forging having portions Me and Ms having different cross-sectional areas in the middle in the longitudinal direction ( Billet) Ma was obtained (see FIG. 6). The portions Me and Ms having different cross-sectional areas (diameters) are formed in accordance with the shape of the forged product and each forging process performed step by step. The degree of change can be set in various ways.
The billet Ma in the present embodiment has a length of about 5.5 m, and a plurality of portions (L = 400 to 500 mm, φ = 50 to 80 mm) having at least one portion having a different cross-sectional area therein as a unit. The unit U (see FIG. 6) formed continuously is cast, and is cut for each unit U and shipped to the forging process. The thickness of the segregation layer is changed by fine adjustment of the drawing speed and the amount of cooling water, and it is effective to use a heat insulating mold when the surface roughness Ra is 35 or less.

  Next, forging using the continuous casting alloy bar Ma for forging will be described with reference to FIG. In this embodiment, the continuous casting alloy bar Ma for forging cut at a predetermined position in the longitudinal direction is placed horizontally and the side surface of the continuous casting alloy bar Ma for forging is pressed, bent, crushed, and roughened. Forging (product) was made by performing forging in four stages of punching and finishing.

Further, the continuous casting alloy rod Ma for forging of the present invention is adjusted so that the thickness of the segregation layer and the surface roughness Ra of the segregation layer are different, and a plurality of continuous casting alloy rods Ma for forging are manufactured by the continuous casting apparatus described above. , Tensile strength, yield strength, elongation, surface appearance (smoothness) of forged products, durability of boiling chromic acid (existence of appearance changes such as occurrence of cracks in boiling chromic acid corrosion test), fatigue Since it measured about intensity | strength (breakage probability), the result is shown in Table 1.
Examples 1 to 7 and Comparative Example 1 are continuous casting alloy bars Ma for forging manufactured by a heat insulating mold continuous casting method, and Comparative Examples 2 and 3 are continuous casting for forging manufactured by a DC casting method. Alloy rod.
In Table 1, if the surface appearance, boiling chromic acid durability, and fatigue strength in the case of a forged product are △ or more, the general required quality of building materials, etc. is satisfied. The strict required quality of parts etc. was fully satisfied.
As can be seen from Table 1, when the segregation layer is remarkably thick (Comparative Example 1) or the surface roughness is remarkably large (Comparative Example 3), the surface appearance of the forged product, boiling chromic acid durability, fatigue strength when forged as it is. Becomes worse.

The surface roughness Ra was measured with a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd .: Surfcom 550AD (trade name)).
The method for measuring the thickness of the segregation layer is that the cut surface cut perpendicular to the casting direction is polished to a mirror surface, and then immersed in an etching solution so that the texture becomes clear, A structural photograph of the cut surface was taken with a metal microscope, and the thickness of the segregation layer was measured on a scale.
The segregation layer refers to the range from the surface layer until the crystal grain size settles to a certain level.
The boiling chromic acid durability was 5 in a boiling chromic acid corrosion test and boiling CrO: 36 g / l (liter) -K ₂ CrO ₇ : 30 g / l (liter) -NaCl: 3 g / l (liter). It was soaked for a long time and measured after confirming changes in appearance such as the occurrence of cracks.
The fatigue strength was measured by preparing a plane bending test piece, performing a plane bending fatigue test, and determining the failure probability.

  Other embodiments of the present invention will be described below. In the following description, the same parts as those of the above-described embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. Differences from the above-described first embodiment will be mainly described.

FIG. 8 shows a second embodiment. In the second embodiment, the taper surface 15 of the mold 5 has a linear taper surface 15a in which the longitudinal section is linear, and a curved taper surface in which the longitudinal section continuous below the linear taper surface is curved. 15b, and the curved tapered surface 15b is convex toward the inner peripheral side.
According to the second embodiment, by changing the position of the solidification interface Mc within the curved tapered surface 15b (indicated by a two-dot chain line in FIG. 8), the same as compared with the linear tapered surface 15a. When obtaining a change in the diameter of the cross-sectional area, the amount of movement in the vertical direction is small, and a continuous casting alloy bar for forging with stable quality can be obtained.
Moreover, the linear taper surface 15a functions as a run-up portion from which the molten metal is drawn out. With the linear tapered surface 15a, for example, when the drawing speed changes, the molten metal hardly leaks and the drawing speed can be easily controlled.

  FIG. 9 shows a third embodiment. In this third embodiment, the cooling water jacket 7 is provided with cooling water jets 17a and 17b on the upper and lower sides (in the direction of pulling out the continuous cast alloy rod Ma), and when the solidification interface Mc is on the upper side (inlet side). When cooling water is sprayed at the upper and lower jet outlets 17a and 17b and the solidification interface Mc is lowered (outlet side), the upper jet outlet 17a is stopped and cooling water is blown only at the lower jet outlet 17b. It is. According to the third embodiment, the amount of the cooling water sprayed onto the continuous cast alloy rod Ma can be adjusted by the ON / OFF control of the upper and lower cooling water jets 17a, 17b, so that the operation is easy and simple. The position of the solidification interface can be controlled with a simple configuration.

In the present invention, the forging continuous having at least one portion having a continuously different cross-sectional area in the middle portion in the longitudinal direction by moving the solidification interface position in the vertical direction on the mold taper surface by controlling the casting speed and the cooling water amount. A method for producing a cast alloy bar. Although it can be solidified under appropriate cooling conditions when forming the large diameter part, it acts in the slow cooling direction and reduces the position of the solidification interface and the cooling point (cooling water into the billet) when forming the small diameter part. Since the distance of the collision position is increased, the cooling capacity is insufficient. This problem causes a difference in internal quality between the large-diameter portion and the small-diameter portion. In particular, in the small-diameter portion, the segregation layer is enlarged and the internal crystal grains are coarsened. The point to solve this quality problem is to make the cooling capacity uniform by narrowing the difference in casting speed at the time of forming the large diameter part and the small diameter part or the vertical movement amount of the solidification interface.
By using the second embodiment and the third embodiment in combination, the cross-sectional area of the large-diameter portion and the cross-sectional area of the small-diameter portion can be made more different than before, and the above-mentioned quality problems can be reduced. Quality can be improved.

Next, a fourth embodiment will be described with reference to FIG. In the fourth embodiment, the continuous casting alloy rod Ma for forging is made of a magnesium alloy, and the molten metal is a magnesium alloy. Further, since the molten metal is made of a magnesium alloy, a flameproof gas is blown from the flameproof gas outlet 31 onto the molten metal surface to seal it from the outside air. Other configurations of the continuous casting apparatus 1 are substantially the same as those in the first embodiment described above.
Moreover, AZ61 (JIS) was used for the magnesium alloy.
The drawing speed and the amount of cooling water in continuous casting are continuously changed as shown in FIG. 11, but the magnesium alloy has a smaller heat capacity than the aluminum alloy, and the molten metal cools and solidifies faster. Compared to the embodiment of the aluminum alloy (FIG. 5), the amount of cooling water is reduced by about 20% in the large diameter portion Me of the continuously cast alloy rod Ma. Further, since it is necessary to suppress the rapid increase in the amount of cooling water in the small-diameter portion Ms, the variation in the amount of cooling water (variable water amount region) and the variation in the drawing speed (variable speed region) are also reduced compared to the aluminum alloy. .
Also in the fourth embodiment, as in the first embodiment, the obtained continuous casting alloy rod Ma for forging has tensile strength, yield strength, elongation, surface appearance (smoothness) of the forged product, boiling chromic acid. Table 2 shows the results measured for durability (existence of appearance change such as occurrence of cracks by boiling chromic acid corrosion test) and fatigue strength (failure probability).
Examples 8 to 14 are continuous casting alloy bars Ma for forging manufactured by the heat-insulating mold continuous casting method, and Comparative Examples 4 and 5 are continuous casting alloy bars for forging manufactured by the DC casting method.
In Table 2, symbols ◯, Δ, and X are used in the same meaning as in Table 1. Further, the corrosion resistance in Table 2 is an evaluation of corrosion weight loss (mg / cm ² ) after 24 hours of salt spray, and other measurements were performed in the same manner as in the first embodiment. As can be seen from Table 2, when the segregation layer is extremely thick and the surface roughness is extremely large (Comparative Examples 4 and 5), forging as it is, the surface appearance, boiling chromic acid durability, and fatigue strength of the forged product deteriorate.

  A fifth embodiment will be described with reference to FIG. In the fifth embodiment, the continuous cast alloy bar Ma is drawn out in the horizontal direction by the horizontal continuous casting method. The continuous cast alloy rod Ma is a magnesium alloy as in the fourth embodiment, and a flameproof gas is injected toward the surface of the molten metal M of the magnesium alloy. Further, the inner peripheral surface of the mold 5 is a curved tapered surface 15a having a diameter increasing from the inlet side toward the outlet side and a projecting shape on the inner peripheral side, and the solidified interface Mc contacts the curved tapered surface 15a. And move as a surface. In the fifth embodiment, the same effect as that of the fourth embodiment described above can be obtained, and by changing the position of the solidification interface Mc in the curved tapered surface 15b, the same cross-sectional area can be obtained. When obtaining a change in diameter, the amount of movement of the solidification interface Mc is small, and a continuous casting alloy bar for forging with stable quality can be obtained.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.
For example, by using the continuous casting apparatus 1 and performing continuous casting without changing the position of the solidification interface Mc in the mold 5 during continuous casting, forging with a cylindrical shape having the same cross-sectional area in the longitudinal direction. It is also possible to cast a continuous casting alloy bar Ma (round bar). In this case, the diameter of the round bar can be easily set by changing the position of the solidification interface Mc.
As shown in FIG. 10, the mold 5 may have a substantially rectangular cross section on the inner peripheral surface thereof. Thus, by making the inner periphery of the mold 5 have a rectangular cross section, a continuous casting alloy bar for forging having a substantially rectangular cross section can be obtained as shown in FIG. Moreover, the casting_mold | template 5 may cast the continuous casting alloy rod for forging whose cross section ellipse diameter makes the internal peripheral surface an elliptical cross section.
The continuous casting alloy bar Ma for forging may be a zinc alloy.
In 1st Embodiment, it is good also considering the taper surface 15 whole as the curved taper surface 15b which made the inner peripheral side protrusion shape like 5th Embodiment. Further, the curved tapered surface 15b may be curved such that the inner peripheral side of the mold 5 is concave.
In the second embodiment, the curved tapered surface 15b may be curved such that the inner peripheral side of the mold 5 is concave.
In the fifth embodiment, the curved tapered surface 15b may be curved so that the inner peripheral side of the mold 5 is concave, or the vertical surface of the tapered surface 15 of the mold is linear as in the first embodiment. Alternatively, as in the second embodiment, the linear taper surface 15a and a continuous curved taper surface 15b may be used.
In the fifth embodiment, as in the fourth embodiment, the cooling water jacket 7 is provided with cooling water jets 17a and 17b in the horizontal direction (in the drawing direction of the continuous cast alloy rod Ma), and the solidification interface is provided. When Mc is set to the inlet side, cooling water is sprayed at both jet outlets 17a and 17b, and when the solidification interface Mc is set to the outlet side, spraying of the inlet side jet outlet 17a is stopped and only the outlet side jet outlet 17b is applied. You may make it spray cooling water.
In the fifth embodiment, a continuous casting alloy rod Ma for forging made of aluminum alloy may be manufactured by continuously casting an aluminum alloy in the molten metal, but the continuous casting alloy for forging is an aluminum alloy. For this purpose, it is not necessary to spray flameproof gas.

It is sectional drawing which shows the casting_mold | template and its peripheral part of the continuous casting apparatus concerning 1st Embodiment of this invention. It is sectional drawing which shows the casting_mold | template and its peripheral part of a continuous casting apparatus when the position of the solidification interface is changed from the state shown in FIG. It is a figure of a casting_mold | template, (a) is a top view, (b) is a longitudinal cross-sectional view. It is a longitudinal cross-sectional view of a continuous casting apparatus. It is a graph which shows control of casting speed (drawing speed) and the amount of cooling water. It is a side view of the continuous casting alloy bar for forging. It is a forging process figure of the continuous casting alloy bar for forging by this Embodiment. It is sectional drawing which shows the casting_mold | template and peripheral part of the continuous casting apparatus concerning 2nd Embodiment of this invention. It is sectional drawing which shows the casting_mold | template and its peripheral part of the continuous casting apparatus concerning 3rd Embodiment of this invention. It is a perspective view which shows the other example of the continuous casting alloy rod manufactured with the continuous casting apparatus of this invention. It is sectional drawing which shows the casting_mold | template and peripheral part of the continuous casting apparatus concerning 4th Embodiment of this invention. It is a graph which shows control of the casting speed (drawing speed) and the amount of cooling water in 4th Embodiment. It is sectional drawing which shows the casting_mold | template and its peripheral part of the continuous casting apparatus concerning 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Continuous casting apparatus 5 Mold 7 Cooling water jacket 9 Drawer 15 Tapered surface 15a Linear taper surface 15b Curved taper surface 17, 17a, 17b Outlet Ma Continuous casting alloy rod Mc Solidification interface Me, Ms Cutting of longitudinal intermediate portion Parts with different areas

Claims (5)

  The inner peripheral surface is formed by blowing cooling water to a part drawn from a mold having a tapered surface whose diameter increases from the inlet side toward the outlet side, and a large diameter portion and a small diameter portion are formed in the middle portion in the longitudinal direction. The large diameter part is formed by reducing the drawing speed from the mold and increasing the amount of cooling water, and the small diameter part is formed by increasing the drawing speed from the mold and reducing the cooling water quantity. A continuous cast alloy bar characterized by having a segregation layer on the surface.   The continuous cast alloy bar according to claim 1, which is an aluminum alloy or a magnesium alloy, and the segregation layer has a thickness of 5 mm or less.   The continuous cast alloy bar according to claim 1, wherein the continuous cast alloy bar is an aluminum alloy or a magnesium alloy and has a surface roughness of Ra35 or less.   The molten steel is poured into a mold having a tapered surface whose inner peripheral surface expands from the inlet side toward the outlet side, and cooling water is sprayed onto the continuous cast alloy rod drawn from the mold outlet to solidify the continuous cast alloy rod in the mold. The process of making the interface position the inlet side of the tapered surface and the process of increasing the drawing speed and reducing the cooling water amount to make the solidified interface position of the continuously cast alloy rod in the mold the outlet side of the tapered surface are continuously repeated. A continuous casting method characterized in that a large diameter portion and a small diameter portion are formed in the middle portion in the longitudinal direction.   Two cooling water outlets are provided in the direction of drawing out the continuously cast alloy rod. When the solidification interface is set to the inlet side, cooling water is sprayed from both outlets, and when the solidification interface is set to the outlet side, two of the two jet outlets are provided. 5. The continuous casting method according to claim 4, wherein the cooling water is sprayed only at a jet outlet that is closer to the inlet side.

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