JPS60130449A - Continuous casting device for hollow billet - Google Patents

Abstract

PURPOSE:To prevent the breakage of a solidified shell, cracking of a core, etc. by providing many gas ejecting holes in the outside circumferential part of the core and disposing independently paths for supplying the ejecting gas and passages for cooling fluid in the core. CONSTITUTION:A core 7 consists of a hollow cylindrical outside body 11 and an inside body 12 which is concentrical with said body and has an open top end. Paths 16 for supplying an ejecting gas and passages 14 for cooling fluid are independently provided in the body 12. The pressure and flow rate of the gas ejected from gas ejecting holes 13 are adjusted to optimum values separately and independently from the pressure and flow rate of the cooling fluid of the core. The holes 13 are further made gradually larger in the drawing direction of a billet and the compressive stress to be exerted from a shell to the core is adequately decreased. The compressive force to the core 7 is decreased by the pressure of the ejecting as in the above-mentioned method, by which the drawing of the billet is made easy and the breakage of the shell, etc. are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for continuously casting hollow pipe-shaped slabs.

An apparatus for continuous casting of hollow pieces is such that a core having a cylindrical outer surface is placed in the center of a hollow cylindrical mold having a cylindrical inner surface, and molten steel or the like is poured from one side of the mold. An apparatus is known in which metal is injected, a solidified shell is generated from a portion in contact with the inner surface of the mold and a portion in contact with the outer surface of the core, and the solidified slab is intermittently or continuously pulled out from the other side of the mold. However, when continuously casting hollow slabs using a core as described above, there are the following problems.

In other words, since the solidified shell generated around the core contracts during the cooling process by the core, compressive stress acts on the core, and as a result, the gap between the inner wall surface of the hollow slab and the surface of the core is Frictional resistance increases, and when the slab is pulled out, the solidified shell on the inner wall side of the slab may break, making it difficult to manufacture a hollow slab with a beautiful inner wall surface. Conversely, due to the above-mentioned frictional resistance, cracks may occur in the core when the slab is pulled out, making it impossible to continue the casting operation itself.

Conventionally, a method to deal with the above-mentioned problems is to use a core that is tapered so that the outer diameter of the core gradually decreases toward the mold outlet by an amount corresponding to the amount of shrinkage of the solidified shell. or a method using a core whose surface is covered with a cushioning material as described in JP-A-54-25222 so that the compressive stress from the solidified shell does not directly act on the core surface. etc. have been proposed. However, these methods also have the following problems. In other words, the amount of shrinkage of the solidified shell varies depending on casting conditions such as the type of molten metal being cast, the drawing speed, and the cooling capacity of the core, but when a tapered core is used as described above, the same core Since there are restrictions on the range of variation in the solidified shell that can be accommodated, there is a narrow range of casting conditions that can be cast without replacing the core, resulting in the problem of reduced productivity due to the troublesome work of replacing the core. .

In addition, when using a core covered with cushioning material, the growth of the solidified shell on the inner wall side of the slab tends to be delayed because the cushioning material generally has high heat insulation properties, so the cushioning material cannot be made too thick. There are restrictions on the range of variation in the solidified shell that can be accommodated, and the range of casting conditions that can be cast without replacing the cushioning material is narrow, similar to the case where a taper is provided, resulting in a problem of reduced productivity.

Therefore, the inventors of the present invention have already proposed in Japanese Patent Application No. 163706 (1978) that a large number of gas ejection holes are provided on the outer peripheral surface of the core, and cooling gas is supplied from the cooling gas passage to cool the inside of the core. A hollow casting system in which the cooling gas is guided to an injection hole, and is ejected from the gas injection hole toward the solidified shell on the inner wall side of the slab, thereby reducing the compressive stress applied from the solidified shell on the inner wall side to the outer peripheral surface of the core. We are proposing a continuous piece casting device. According to the proposed casting apparatus, the compressive stress applied to the outer circumferential surface of the core due to the stress of the gas ejected from the gas injection holes on the outer circumferential surface of the core is reduced. The frictional resistance is reduced, and it is possible to effectively prevent cracks from occurring in the core where the solidified shell on the inner wall side is broken when the slab is pulled out. In addition, in this proposed device, fluctuations in the amount of solidification shrinkage can be dealt with by adjusting the ejected gas pressure.
The same core can accommodate a wide range of changes in casting conditions.

However, the above proposed device had another new problem. In other words, in the device proposed above, gas is guided from the cooling gas passage provided inside the core to the gas ejection hole in order to cool the core. the pressure of the cooling gas supplied to the
As a result, the cooling conditions for the core will also change, and there is a risk that appropriate cooling conditions will not be obtained.

This invention has been made in view of the above circumstances, and by further improving the device proposed above, the gas pressure ejected from the core of the chamber for pressurizing the inner wall surface of the hollow slab can be easily and easily controlled according to casting conditions, etc. It is an object of the present invention to provide a continuous casting device for hollow slabs that can be appropriately adjusted.

That is, the present invention provides an apparatus for continuously casting hollow slabs by injecting molten metal from one side of a mold with a core arranged in the center and pulling out the solidified slab from the other side (5). A large number of gas jet holes are formed radially on the outer circumferential surface of the core, which open along the radial direction from the inside to the outside, and inside the core, there is a gas jet hole for guiding the gas to the gas jet holes. It is characterized in that the supply passage and the cooling fluid passage for cooling the core are formed separately and independently.By providing the jetting gas supply passage and the cooling fluid passage independently in this way, the jetting gas is This made it possible to easily adjust the gas pressure without affecting the core cooling conditions.

Furthermore, in the apparatus of the present invention, the diameter (cross-sectional area) of the gas jet hole is set to increase from the molten metal injection side toward the slab withdrawal direction. By setting these settings, it is possible to appropriately respond to slabs that show a tendency for solidification shrinkage to gradually increase from the molten metal injection side to the slab withdrawal direction, and prevent breakage of the solidified slab shell or cracking of the core. This makes it possible to prevent this even more reliably.

(6) Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the overall configuration of a casting apparatus according to an embodiment in which the present invention is applied to horizontal drawing casting (horizontal casting), and FIGS. 2 to 4 show the core used in the casting apparatus of FIG. 1. It is shown enlarged.

In Fig. 1, a mold l having a cylindrical shape as a whole is arranged so that its axis is horizontal, and its -blade side (
The molten metal injection side) is connected to a molten metal holding container 3 by a connecting bolt 2.

The mold is cooled from the inside by fluid, as is the case with known molds. Further, the molten metal holding container 3 is one into which molten metal 5 such as molten steel is injected from a ladle or the like (not shown) through a nozzle 4, and a molten metal injection port 6 is formed in the upper part. A core 7 is disposed at the center of the mold 1, passing through the molten metal holding container. This core is made to have a cylindrical shape as a whole, and is positioned so that its center axis coincides with the axis of the mold l, and its base end 7A is on the opposite side with respect to the mold l. It protrudes from the outer surface of the holding container 3 and is fastened and fixed to the wire ring 8, and the distal end 7B on the opposite side to the base end 7A is attached to the mold l.
It is set to extend to the inside of the Further, a refractory ring 9 is provided between the molten metal injection side end of the core 7 and the molten metal holding container 3, and the refractory ring 9 has an annular shape as a whole and surrounds the core 7. A refractory ring 10 is also provided between the molten metal injection side end of the inner circumferential surface of the holding container 3 and the holding container 3, and the refractory ring 10 has an annular shape as a whole and extends along the inner circumferential surface of the holding container 3.

As particularly shown in FIGS. 2 to 4, the core 7 includes a hollow cylindrical external body 11 with a closed tip, and an open tip that is fitted concentrically inside the external body l. The inner body 12 has a hollow cylindrical shape. A large number of gas ejection holes 13 are radially formed along the radial direction of the core in the peripheral wall portion near the tip of the core outer body 11.

On the other hand, the internal space of the core internal body 12 serves as the return path 14B of the cooling fluid passage 14, and on the outer peripheral side of the core internal body 12, there are a plurality of recesses m that serve as the outward path 14A of the cooling fluid passage 14.
15, and a plurality of recesses #1117 that become the ejected gas supply path 16.
are formed parallel to the core axis so as to be alternately located at predetermined intervals in the circumferential direction. Here, 40117 constituting the ejection gas passage 16 is connected to each gas ejection hole 1.
It is formed at a position corresponding to 3. Also, gas jet hole 1
3 is from the core base end side (molten metal injection side) to the core tip side (
The cross-sectional area (hole diameter) is set to gradually increase toward the slab drawing side).

In FIG. 1, 18 is a hollow slab cast by the mold 1 and core 7, 19 is a solidified shell on the outer wall side thereof, and 20 is a solidified shell on the inner wall side.

Further, the hollow slab 18 pulled out from the mold 1 is
1 for secondary cooling.

When continuously casting hollow slabs using the above-described continuous casting apparatus, as described above,
Molten metal [5] is injected into the container 3, and while the molten metal is maintained at a predetermined temperature by a heater (not shown) in the holding container 3, solidification is caused from the inner surface of the mold 1 and the portion that contacts the outer surface of the mold (9) and the outer surface of the mold 7. advance to form an outer wall-side solidified shell 19 and an inner wall-side solidified shell 20,
Finally, a pipe-shaped hollow slab 18 is formed, and while the hollow slab 18 is cooled by a shower 21, it is intermittently pulled out in the horizontal direction by an intermittent drive device (not shown).

Here, the gas supplied through the jet gas supply path 16 is strongly blown from the gas jet holes 13 onto the inner surface of the solidified shell 20 on the inner wall side of the hollow slab 18 . This ejected gas pressure reduces the compressive stress on the core due to solidification shrinkage of the inner wall side solidified shell 20, and as a result, the slab is pulled out due to the frictional resistance between the core surface and the inner wall side solidified shell surface, which has been a problem in the past. This makes it possible to prevent the dangers such as difficulty in solidification, rupture of the L, and cracking of the core. The ejected gas supply path 16 includes an outgoing path 14A and an incoming path 14B of the cooling fluid path 14 for cooling the core.
Since it is provided separately from the pressure of the gas ejected from the gas ejection hole 13.

The flow rate is independent from the pressure and flow rate of the core cooling fluid (10
) can be adjusted. In other words, the inner wall side solidified shell 2
Since the amount of solidification shrinkage of 0 varies depending on casting conditions such as the type and composition of the metal to be cast, casting speed (withdrawal speed), and cooling conditions, the compressive stress of the inner wall side solidified shell 20 relative to the core also depends on those casting conditions. Therefore, the pressure and flow rate of the ejected gas must be adjusted to appropriate values according to the casting conditions. However, with the above configuration, the pressure and flow rate of the ejected gas can be adjusted without changing the core cooling conditions. , the flow rate can be easily adjusted to an appropriate value.

On the other hand, since the surface temperature of the solidified shell 20 on the inner wall side gradually decreases and the shell thickness increases in the drawing direction, the compressive stress applied to the core gradually increases. is set so that it gradually increases in the slab drawing direction, and therefore the force applied to the inner wall side solidified shell 20 by the gas jetted from the gas jetting hole 13 also increases, reducing the compressive stress on the core. This effect also gradually increases in the pulling direction. That is, the compressive stress reducing effect of the ejected gas changes appropriately in response to the change in the compressive stress on the core in the drawing direction, thereby making it possible to more appropriately deal with the compressive stress on the core.

In the above-described embodiments, the case of horizontal pultrusion casting is shown, but it goes without saying that the core can be constructed in the same manner as described above also in vertical pull-down continuous casting or vertical pull-up continuous casting.

As is clear from the above description, in the continuous hollow slab casting apparatus of the present invention, compressive force is applied to the core from the solidified shell on the inner wall side by the gas pressure blown out from the gas jet holes formed on the outer periphery of the core. As a result, the slab can be easily pulled out, effectively preventing breakage of the solidified shell on the inner wall side and cracking of the core. Since the supply channel is formed separately from the cooling fluid passage that cools the core from inside, the ejected gas pressure and flow rate can be adjusted to the optimal value according to the casting conditions without affecting the core cooling conditions. Effects that can be easily adjusted and set can be obtained.

In particular, in embodiments in which the cross-sectional area of the gas injection hole is set to be larger on the side where the slab is pulled out, the blowout exerted on the inner wall side solidified shell in response to changes in the compressive force by the inner wall side solidified shell in the drawing direction. Since the force from the gas changes, breakage of the solidified shell on the inner wall side and cracks in the core due to compressive force can be more reliably prevented.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing an embodiment of the invention applied to a horizontal drawing type continuous casting apparatus, and FIG. 2 is a longitudinal sectional side view showing an example of a core used in the continuous casting apparatus of the invention.
Figure 3 is a vertical cross-sectional view taken along the lI[-1 line in Figure 2;
The figure is a longitudinal sectional view taken along the line IV-1V in FIG. 2. 1... Mold, 5... Molten metal, 7... Core, 13
...Gas outlet, 14...Cooling fluid passage, 16...
・Blowout gas passage. (13) Figure 2 Figure 3 Figure 4 l 1617 12 ・・・・／＋１乎手

Claims (2)

[Claims] (1) In an apparatus for continuously casting hollow slabs by injecting molten metal from one side of a mold with a core arranged in the center and pulling out solidified slabs from the other side intermittently or continuously, A large number of gas ejection holes are formed radially on the outer periphery of the child, opening along the radial direction from the inside to the outside.
A continuous casting apparatus for hollow slabs, characterized in that, inside the core, a blowout gas supply path for guiding gas to the gas blowout hole and a cooling fluid path for cooling the core are independently provided. . (2) The continuous casting apparatus for hollow slabs according to claim 1, wherein the cross-sectional area of the gas jet holes formed in the core increases from the molten metal injection side toward the slab withdrawal direction. .