JPH05208243A - Mold device for continuously casting metallic tube - Google Patents

Abstract

PURPOSE:To prevent the breakage of a casting tube without lowering the productivity. CONSTITUTION:A tube forming passage 25 having a mold 19 and a core 20 is formed between the mold 19 and the core 20 and the molten metal introduced from the casting side of the tube forming passage 25 is cooled to form the casting tube. in the mold device 13 for continuously casting the metallic tube capable of drawing the casting tube from the drawing side of the tube forming passage 25, the mold 19A at the casting side consists of a low thermal conductivity material and a mold 19B at the drawing side consists of a high thermal conductivity material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting mold apparatus for continuous casting of metal tubes.

[0002]

2. Description of the Related Art Conventionally, there is a casting mold apparatus for continuous casting of metal tubes as described in JP-A 1-177048. This mold device has a mold and a core to form a pipe forming passage between the mold and the core, and forms a casting pipe by cooling the molten metal introduced from the casting side of the pipe forming passage, This casting pipe can be drawn from the drawing side of the pipe forming passage, and the entire mold is made of graphite (see FIG. 4 (B)).

[0003]

However, in the prior art, since the entire mold is made of graphite, which is a material having high thermal conductivity, cooling means such as a water cooling jacket provided on the outer peripheral portion of the mold on the drawing side. The heat removal function of the mold easily spreads to the casting side of the mold, and the temperature gradient of the mold (temperature drop rate per length of the pipe forming passage in the unit of the mold) becomes small, resulting in solid-liquid coexistence in the pipe forming passage. The area becomes longer. The longer solid-liquid coexistence region means that the surface solidification shell that prevents the molten metal from flowing out is longer in the initial stage of solidification, and the solidification front where unsolidified melt must be inserted becomes deeper and narrower. It means that it is difficult to insert smoothly and the fracture of the cast pipe easily occurs.

Particularly, in a thin-walled tube, the surface solidified shell is unstable and it is difficult to supply the molten metal to the solidification front, so that the cast tube is easily broken.

For this reason, in the prior art, even if the solid-liquid coexisting region in the pipe forming passage of the mold is long, the unsolidified molten metal is surely inserted into the solidification front so as not to break the casting pipe. Since the withdrawal speed is slowed, the productivity is unavoidable.

An object of the present invention is to prevent breakage of a cast pipe without lowering productivity.

[0007]

The present invention according to claim 1 has a mold and a core to form a pipe forming passage between the mold and the core, and the casting side of the pipe forming passage. A casting pipe is formed by cooling the molten metal introduced from, and the casting pipe is made of a low thermal conductivity material in a casting device for continuous casting of a metal pipe that allows the casting pipe to be drawn from the drawing side of the pipe forming passage. The mold on the drawing side is made of a material having high thermal conductivity.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, the low thermal conductivity material is Si ₃ N.
_4- BN or BN, wherein the high thermal conductivity material is graphite or metal.

According to a third aspect of the present invention, in addition to the first or second aspect of the present invention, cooling means is provided on the outer peripheral portion of the mold on the drawing side.

[0010]

FIG. 5 is a schematic diagram showing the relationship between the temperature gradient of the mold and the length of the solid-liquid coexistence region. (A) shows the SKIN solidification state of ordinary cast iron when the temperature gradient is small, and (B) shows when the temperature gradient is small. Mussy solidified state of FCD (ductile cast iron),
(C) is a Mussy solidification state of FCD at a large temperature gradient.

When the temperature gradient of the mold is small, the solid-liquid coexistence region is present in both the SKIN solidification type ordinary cast iron and the Mussy solidification type FCD, as shown in FIGS. 5 (A) and 5 (B). It is recognized that the solidification front becomes longer and the solidification front where the unsolidified molten metal has to be inserted becomes deeper and narrower, so that the fracture is likely to occur.

Since the FCD is Mussy solidified as shown in FIG. 5B, it is recognized that the surface strength in the solid-liquid coexistence region is small and the fracture is more likely to occur due to casting stress. ..

However, in the present invention, the casting side mold is made of a low thermal conductivity material such as Si ₃ N ₄ -BN or BN, and the drawing side mold is high thermal conductivity such as graphite or copper. Since it is made of a material, the temperature gradient in the mold can be increased and the solid-liquid coexistence region can be shortened. Therefore, in both SKIN solidification type ordinary cast iron and Mussy solidification type FCD, the solid-liquid coexistence region is shortened, and as a result, the solidification front where the unsolidified molten metal has to be inserted is made shallow and fracture occurs. Can be suppressed. Also,
In FCD, in particular, the solid-liquid coexistence region of Mussy solidification can be shortened, the range in which the surface strength becomes small due to Mussy solidification can be reduced, and the occurrence of fracture can be suppressed. Therefore, even in the case of a thin-walled tube in which the surface solidified shell is unstable and it is difficult to supply the molten metal to the solidification front, breakage of the cast pipe can be suppressed, and the drawing speed of the cast pipe is slowed to prevent the breakage of the cast pipe. It is not necessary to do so, and by increasing the drawing speed, it is possible to prevent breakage of the cast pipe without lowering productivity.

Further, in the present invention, by providing a cooling means such as a water cooling jacket body or an air cooling zone on the outer periphery of the drawing side of the mold, the temperature of the mold made of the high thermal conductivity material on the drawing side is made as low as possible. The temperature gradient between the mold and the mold made of the low thermal conductivity material on the casting side can be surely increased, and the solid-liquid coexistence region can be surely shortened.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing a casting mold apparatus according to one embodiment of the present invention, FIG. 2 is a schematic view showing a casting side end surface of the casting mold apparatus,
3 is a schematic diagram showing a continuous casting apparatus, FIG. 4 is a schematic diagram showing a modified example of the present invention and a conventional example, and FIG. 5 is a schematic diagram showing the relationship between the temperature gradient of the mold and the length of the solid-liquid coexisting region. is there.

As shown in FIG. 3, the continuous casting apparatus 10 is provided with a casting mold apparatus 13 attached to a casting port 12 formed in a lower portion of a side surface of a molten metal holding furnace 11. The continuous casting device 10 is
The molten metal is cooled by the casting mold device 13 to form a casting pipe 14, which is drawn and cast.

The continuous casting apparatus 10 comprises a guide roller 15 for supporting the casting pipe 14 on the outlet side of the casting mold device 13 and a drawing device 16 for intermittently drawing the casting pipe 14. The drawing device 16 includes a pinch roller 17 and a pressing roller 18.

As shown in FIGS. 1 and 2, the casting mold device 13 has a
It is composed of a mold 19 and a core 20.

The mold 19 is hollow and has a core holding inner diameter portion 21 at the end on the casting side, and a pipe outer surface forming inner diameter portion around the center axis of the mold over substantially the entire length excluding the core holding inner diameter portion 21. 22 is provided.

The core 20 is equipped with a flange portion 23 which is inserted into the mold 19 and which is fitted to the core holding inner diameter portion 21 of the mold 19 at the end of the casting side. A pipe inner surface forming outer diameter portion 24 is provided around the center axis of the mold and forms a pipe forming passage 25 with the pipe outer surface forming inner diameter portion 22 of the mold 19. Further, the core 20 is provided with a molten metal injection passage 26 communicating with the pipe forming passage 25 at each of a plurality of positions (four positions in this embodiment) around the center axis of the mold in the flange portion 23. Each molten metal injection passage 26
The cross-sectional shape of the passage is arc-shaped. In addition, it is preferable that the thickness g of the joint portion 27 sandwiched between the adjacent molten metal injection passages 26 is as small as possible in terms of strength, and the passage area of each molten metal injection passage 26 is larger.

That is, in the casting mold device 13, the flange portion 23 of the core 20 is fitted and fixed to the core holding inner diameter portion 21 of the mold 19, and the molten metal injection passage 26 and the pipe forming passage 25 are communicated in a straight manner. ..

In the casting mold device 13, the water cooling jacket 30 made of copper is fitted to the outer peripheral portion of the casting mold 19 on the pulling side, and the insert ring 31 made of brick is fitted to the outer circumferential portion of the casting mold 19 on the casting side. I am trying. As a result, in the casting mold device 13, the portion of the water cooling jacket body 30 is used as a cooling portion for solidifying the molten metal, the portion of the insert ring 31 is used as a non-cooling portion, and the holding furnace 11 is attached to the furnace wall 11A.

Further, the continuous casting apparatus 10 of this embodiment is
A hole-shaped recess 20A is provided at the end of the core 20 on the casting side so that the molten metal that has flowed into the mold 13 is not overcooled.

However, in the casting mold device 13, the casting mold 1
9 is divided into a casting side mold 19A and a drawing side mold 19B, and the casting side mold 19A is made of Si ₃ as a low thermal conductivity material.
It is made of N ₄ -BN, and the drawing-side mold 19B is made of graphite as a high thermal conductivity material. Where mold 1
The boundary between 9A and the mold 19B is aligned with the position corresponding to the end of the water-cooling jacket body 30 on the insert ring 31 side, and the water-cooling jacket body 30 is attached to the outer peripheral portion of the mold 19B on the pull-out side.

In the practice of the present invention, FIG.
As shown in, the casting side mold 19A and the drawing side mold 19B
The boundary of the insert ring 3 of the water cooling jacket body 30
It may be set at a position corresponding to the intermediate portion, which is close to 1.

In the practice of the present invention, Si ₃ N ₄ -is used as the low thermal conductivity material for the casting mold 19A.
Other than BN, BN or the like may be used. Further, as the high thermal conductivity material forming the drawing-side mold 19B, in addition to graphite,
A metal such as copper may be used. The thermal conductivity of each material (ca
l / cm ℃ sec), Si ₃ N ₄ -BN is 0.034
, BN is 0.083 and graphite is 0.28.

Further, in the casting mold device 13, the core 20 is used.
Is composed of Si ₃ N ₄ -BN. The core 20 is S
The material is not limited to i ₃ N ₄ -BN and may be made of metal such as BN, graphite, and copper.

In the practice of the present invention, the cooling means provided on the outer peripheral portion of the drawing side of the mold is the mold 19B on the drawing side.
It is also possible to have a cooling medium flow path built in, or to provide an air cooling zone around the mold.

Next, the operation of this embodiment will be described. Since the casting-side mold 19A is made of a low thermal conductivity material such as Si ₃ N ₄ -BN or BN, the drawing-side mold 19B is made of a high thermal conductivity material such as graphite or copper. The temperature gradient in the mold 19 can be increased to shorten the solid-liquid coexistence region. Therefore, in both SKIN solidification type ordinary cast iron and Mussy solidification type FCD, the solid-liquid coexistence region is shortened, and as a result, the solidification front where the unsolidified molten metal has to be inserted is made shallow and fracture occurs. Can be suppressed. Further, in FCD, in particular, the solid-liquid coexistence region of Mussy coagulation is shortened, and
The range in which the surface strength is low due to solidification can be reduced, and the occurrence of fracture can be suppressed. Therefore, the surface solidified shell is unstable,
And even for thin-walled pipes where it is difficult to supply molten metal to the solidification front,
It is possible to suppress the rupture of the casting pipe, it is not necessary to slow down the drawing speed of the casting pipe so as not to cause the rupture of the casting pipe, and by increasing the drawing speed, the rupture of the casting pipe can be prevented without lowering the productivity Can be prevented.

By providing a cooling means such as a water cooling jacket 30 and an air cooling zone on the outer periphery of the mold 19 on the drawing side, the temperature of the mold 19B made of the photothermal conductivity material on the drawing side is made as low as possible, and the cooling of this cooling means is performed. The effect is difficult to reach,
The temperature gradient between the casting side and the mold 19A made of the low thermal conductivity material can be surely increased, and the solid-liquid coexistence region can be surely shortened.

Table 1 shows the concrete results of the casting mold of the present invention shown in FIG. 1 (C) and the conventional casting mold shown in FIG. 4 (B). According to Table 1, it is recognized that the temperature gradient in the solid-liquid coexistence region becomes significantly large by the present invention.

[0032]

[Table 1]

[0033]

As described above, according to the present invention, it is possible to prevent breakage of a cast pipe without lowering productivity.

[Brief description of drawings]

FIG. 1 is a schematic view showing a casting mold apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view showing an end face on a casting side of a casting mold device.

FIG. 3 is a schematic view showing a continuous casting device.

FIG. 4 is a schematic diagram showing a modified example of the present invention and a conventional example.

FIG. 5 is a schematic diagram showing the relationship between the temperature gradient of the template and the length of the solid-liquid coexisting region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Continuous casting apparatus 13 Mold apparatus 14 Casting pipe 19 Mold 19A Casting side mold 19B Extraction side mold 20 Core 25 Tube forming passage

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Saito 1-1, Kawasaki-cho, Handa-shi, Aichi Kawasaki Steel Co., Ltd. Chita Works (72) Inventor Akira Sogabe 1-1-chome, Kawasaki-cho, Handa-shi, Aichi Kawasaki (72) Inventor Kenji Ichino, 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.Technical Research Division (72) Inventor Yuichiro Sato 1-93, Shimoshinnisocho, Toyama-shi, Toyama Ohira (72) Inventor, Yuzuru Watanabe 1-93 Shimoshin Nissocho, Toyama City, Toyama Prefecture Daihei Yoyo Steel Co., Ltd., Toyama Works

Claims (3)

[Claims] 1. A pipe forming passage is formed between the mold and the core having a mold and a core, and a molten metal introduced from a casting side of the pipe forming passage is cooled to form a cast pipe. In a casting machine for continuous casting of metal pipes that allows this casting pipe to be drawn from the drawing side of the pipe forming passage, the casting side mold is made of a low thermal conductivity material, and the drawing side mold is made of a high thermal conductivity material. A mold device for continuous casting of a metal tube, which is configured as follows. 2. The mold apparatus for continuous casting of a metal tube according to claim 1, wherein the low thermal conductivity material is Si ₃ N ₄ -BN or BN, and the high thermal conductivity material is graphite or metal. 3. The mold apparatus for continuous casting of a metal tube according to claim 1, wherein a cooling means is provided on an outer peripheral portion of the mold on a drawing side.