JPS588941B2 - Renzokuchiyuuzouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves forming a mold with a rotating casting ring with grooves on its circumferential surface and an endless metal belt that is in contact with the circumferential surface of the rotating ring, and continuously pouring molten metal into the mold. The molten metal is cooled and solidified by cooling water applied around the mold to continuously obtain ingots. In a so-called belt-wheel type continuous casting device, high-quality and high-grade ingots are produced. This invention relates to a continuous casting method aimed at achieving high efficiency and continuous casting, and in particular to improvements to its endless belt.

A casting mold is continuously formed using a rotary casting wheel (hereinafter referred to as the wheel) having grooves on its circumferential surface and a metal endless belt made of, for example, low carbon steel (hereinafter referred to as the belt) that is in contact with this circumferential surface. In a continuous casting device that continuously obtains ingots by injecting and cooling molten metal, the wheel rotates using an electric motor as a drive source, and the wheel has a wall thickness of 2 to 31 rLrIL whose tension is adjusted by one or more belt tension wheels. Since the belt must be rotated and the ingot poured into the mold and subsequently solidified must be sent to the rolling process, the wheel must be made strong and its wall thickness should be approximately IQ mm. ing.

A large number of cooling water injection nozzle groups are arranged around the mold constructed in this way, and the cooling water injected from these cools and solidifies the molten metal poured into the mold to continuously obtain an ingot.

In this way, the belt is thin (2~31n11L), and the wheel is thick (about 10mm), so the cooling efficiency of the cooling water is thicker on the belt side than on the wheel side.Therefore, a belt with a metal skin as obtained is used. The poured molten metal is cooled and solidified unevenly.

Non-uniform solidification as described above promotes the formation of solidification shrinkage pores in the center of the ingot, resulting in cracks in the ingot and non-uniform solidification structure, making it impossible to obtain a high-quality ingot. .

One way to counter this is to reduce the amount of cooling water on the belt side to equalize the cooling capacity, but in this case, the belt will undergo an intense heat cycle due to the poured molten metal and cooling water, which will shorten the belt's lifespan. This is not preferable as it significantly reduces the amount of water.

On the other hand, as shown in Figures 1 and 2, the cross-sectional shape of the mold has an angle θ of 90° or less at the two corners A on the left and right where the belt and wheel contact, in order to facilitate the release of the ingot. The angle is relatively acute, so if you use a belt with a metal skin as obtained, the cooling ability from that surface will be large, so the poured molten metal will cool before it reaches corner A, and a thin solidified film will form. Since the molten metal is not supplied any more, its shape is rounded due to the surface tension of the molten metal, as shown in FIG.

Therefore, there is a gap B between the solidified film and the mold, and the solidified film is cooled through the air, resulting in slow cooling, and cooling is significantly delayed compared to other molds, resulting in a drop in the center of the ingot. Solidification in the opposite direction is delayed, and the temperature gradient with other parts is large, so the thermal stress is also large, and micro-cracks occur continuously or intermittently in the longitudinal direction in the ingot part corresponding to mold corner A. .

In order to improve this, rust or soot with a low thermal conductivity is generated and adhered to at least the mold forming surface of the belt, which has a metal skin, to reduce the cooling ability of the belt and allow the molten metal to flow to the corners. Measures are also being taken.

In this case, the fluidity of the molten metal to the corner A is improved and the microcracks at the corner of the ingot are reduced, but since the cooling ability from the belt side is reduced, this also results in non-uniform cooling. Prone to defects in lumps.

Furthermore, approximately % of the solidification of the molten metal depends on cooling from the belt side, and if rust or soot adheres to the entire surface of the belt, the amount of heat extracted from the entire mold will be reduced, and the solidification of the entire mold will be delayed, making it necessary to cast at a low speed. Therefore, the ingot production performance will be low.

The present invention eliminates the above-mentioned drawbacks and provides a method for continuously and highly efficiently manufacturing high-quality and high-grade ingots, and in particular, provides a belt for the same. The central part of the contact surface is polished continuously or intermittently to remove rust in this part, change the thermal conductivity in the width direction of the belt, maintain the fluidity of the molten metal to the corners of the mold, and cool it. The desired purpose was achieved by increasing the performance and making the amount of heat extracted from each side of the mold uniform.

In other words, both sides of the belt or the surface in contact with the molten metal (mold forming surface)
During the break-in operation, which is always performed before casting, the central part of the belt is polished to remove the adhering rust and expose the metal skin. After that, casting begins.

Incidentally, the polishing of the central portion of the belt is continued because the belt becomes high in temperature due to the heat of the molten metal and rust is formed.

A case will be described below in which an embodiment of the present invention is applied to aluminum casting. At this time, the temperature at which the molten metal is poured into the mold is 700°C, and the number of rotations of the wheel (casting speed) is 2.5.
r. p, m, , the amount of cooling water was 37 d/H, and the thickness of rust was 30 μ.

Further, as shown in FIG. 2, wedges were attached to both sides of the belt, and polishing of the central portion of the belt was performed only on the mold forming surface that was in contact with the molten metal.

Therefore, in FIG. 3, the molten metal is melted in a melting furnace and a holding furnace (not shown), is led to the sump 4 through the molten metal transfer path, flows through the hole of the pouring nozzle 5, and is injected into the mold. .

And cooling water injection nozzle group 6 arranged around the mold,
The ingot 3 is cooled and solidified through the mold by the cooling water injected from the ingot 7, and as the wheel 2 rotates, the ingot 3 is released from the mold near the release point 8 and guided to the rolling process.

At this time, the belt 1 rotates in the same direction due to friction with the wheel 2, and further rotates the pulley 9.

And about 50crrLO behind the mold release point 8 of the ingot 3
The central part of the belt 1 is continuously polished by a polishing machine 10, which is installed around the belt and rotated at high speed by a drive source such as an electric motor, to maintain a metal surface at all times.

The cross section of the belt 1 at this time is shown in Figure 2, where 1-1 and 1-2 are the rust that has been deposited, and 1-3 is the exposed metal surface that has been polished by the above method. be.

In this example, only the surface in contact with the molten metal was continuously polished, but the present invention is not limited to this. Both surfaces in contact with the cooling water may be polished continuously or intermittently in the same manner.

The polishing machine may be installed at a location that takes functionality and casting workability into consideration.

On the other hand, the rust to be attached to the belt may be naturally formed by exposing it to the atmosphere, or it may be left in or passed through a corrosive gas, liquid, or spray to accelerate rust formation. A rust preventive agent or anticorrosive tape may be applied to the surface to which it is not attached, and the surface may be removed after rust treatment.

Incidentally, the thickness at which rust occurs is not limited to 30μ as shown in the example.

FIG. 4 shows the ratio of the width 1 of the polished part at the center of the belt to the width L of the surface of the belt in contact with the molten metal, that is, 1.
Experiments were conducted by varying /L, and the effects of 1/L on the ingot are shown.

Figure A shows the temperature difference between the belt contact surface and wheel contact surface of the ingot, which was measured simultaneously and continuously at a point approximately 50 cm after the ingot was released, and l/L = 0. ．．
It can be seen that the temperature difference is relatively small in the range of 1 to 0.9, and therefore uniform cooling occurs.

The diagram of the mouth is a measurement of the radius of curvature of the corner of the ingot, which is a parameter of the degree of molten metal supply at the corner, and is 1 / L = O
In the range of ~08, the gap is small <<, indicating that the gap between the solidified film and the mold is relatively small, and beyond this, the gap increases rapidly.

Figure C shows the number of solidification shrinkage holes per unit length in the center of the ingot due to uneven solidification, and the number is proportional to the temperature difference between each part of the ingot shown in Figure A. ing.

That is, the temperature difference is relatively small 1/L=0. 1~
The range of 0.9 indicates a small number of solidification shrinkage pores per unit length.

The second figure shows the crack length per unit length of the longitudinal micro-crank that occurs at the corner of the ingot, where 1/L=0.
It can be seen that microcracks do not occur in the range of 1 to 0.8.

The figure E shows the number of external defects such as cracks that occur in places other than the corners of the ingot per unit length, and l/L = 0.
．． It can be seen that it is small in the range of 1 to 0.8.

To summarize the above results, as shown in FIG. 5, it is recognized that l/L = 0.1 to 0.8 is optimal in order to obtain a good quality and high quality ingot.

As described above, according to the method of the present invention, the cooling ability of the entire ingot is increased,
Moreover, since the temperature difference between the cross section and the longitudinal direction of the ingot is extremely small, and uniform cooling is achieved, no solidification shrinkage holes are generated in the center of the ingot, and therefore, no cracks are generated and the solidification structure is uniform.

Furthermore, since the molten metal is completely supplied to the corners of the mold, the gap between the corners of the mold and the corners of the ingot is small, which increases the cooling capacity inside the ingot, reducing the temperature gradient in the ingot.
In turn, there is no thermal stress, so no microcracks occur at the corners of the ingot.

Therefore, according to the method of the present invention, it is possible to improve the cooling ability of the ingot, exhibit a uniform temperature distribution, and continuously produce a healthy ingot with no internal or external defects with high efficiency. This made it possible.

[Brief explanation of drawings]

Figure 1 is a cross-sectional explanatory diagram of a mold in the conventional continuous casting method.
FIG. 2 is a cross-sectional explanatory diagram of a mold in the continuous casting method of the present invention, FIG. 3 is an explanatory diagram showing an embodiment of the continuous casting method of the present invention,
Figures 4A to 4E are graphs showing the relationship between l/L and the influence on the ingot, and Figure 5 is a table summarizing the results of Figure 4I to H. A... Mold corner, B... Gap above, 1... Belt, 2... Wheel, 3... Ingot, 4... Hot water reservoir, 5...
...Pouring nozzle, 6,7...Injection nozzle group, 8...Mold release point, 9...Hooley, 1
0... Polishing machine.

Claims (1)

[Claims] 1. A casting mold is formed by a rotating casting wheel with grooves on its circumferential surface and an endless metal belt that is in contact with the circumferential surface of the rotating wheel,
In this method, the molten metal is continuously poured into the mold, and the molten metal is cooled and solidified by cooling water applied to the circumferential surface of the mold to continuously obtain an ingot. A continuous casting method characterized by continuously or intermittently polishing the center portion of the mold forming surface or both surfaces of the generated belt, and then bringing the mold forming surface of the belt into contact with molten metal. 2 When the width of the surface of the belt in contact with the molten metal is L, and the width of the polishing part at the center of the belt is 1, the range of l/L is 0.1 to 1.
The continuous casting method according to claim 1, wherein the continuous casting method is set to 0.8.