JPH0243569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous casting method and apparatus for a metal ingot having a smooth and beautiful surface and a completely unidirectionally solidified structure as a whole.

[Conventional technology]

The conventional continuous casting method for ingots uses a hollow cooling mold with a through hole, and molten metal is supplied from one side of the mold.
A method of solidifying molten metal in a mold and continuously drawing out the ingot from the other end.
It has been widely used for casting ingots such as copper alloys.
However, in this method, the molten metal supplied into the mold forms a solidified shell along the casting wall surface, and the unsolidified molten metal inside the solidified shell is completely solidified by secondary cooling outside the mold. Therefore, there is a drawback that impurities are concentrated in the final solidified part at the center of the ingot, causing component segregation and defects such as bubbles.

In addition, in the conventional method, in order to prevent the occurrence of surface cracks due to friction between the mold and the surface of the ingot when the ingot is pulled out, and to prevent the breakout of the molten metal, a stable solidified shell of the ingot that comes out of the mold is grown. There has been a period of time when people have been forced to withdraw their resources. However, the oscillation marks formed on the surface of the ingot by this can cause cracks to occur during plastic working of the ingot. Prior to plastic working, maintenance such as removing surface scratches, chamfering, and melting was required.

In addition, for alloys with a wide solidification temperature range such as cast iron and phosphor bronze, if the molten metal is not pulled out intermittently from the mold after it has completely solidified in the mold, the ingot can be processed without surface cracks. I couldn't pull it out.

In the conventional continuous casting method, a solidified shell is formed on the inner wall surface of a cooling mold, so the crystals that make up the solidified shell tend to grow columnar in a direction almost perpendicular to the casting wall surface. When columnar crystal bands are formed on the surface layer of the ingot, cracks are likely to occur from the grain boundaries due to friction with the inner wall surface of the mold when the ingot is pulled out of the mold. Ingots that have surface cracks on the outer periphery are susceptible to surface cracks during plastic working, and in particular, metals and alloys with poor workability are difficult to form into plates or wires by further plastic working, even if the ingot is made by continuous casting. It has been considered difficult to process.

The present inventor has developed a structure that prevents the formation of such a surface solidified shell on the inner wall surface of the mold, has a completely unidirectional solidified structure in which crystals grow only in the casting direction, and is caused by friction between the ingot and the mold. In order to prevent the occurrence of surface defects and obtain a metal molded body with a smooth surface and an arbitrary cross-sectional shape, casting The temperature is maintained above the solidification temperature of the metal, and the molten metal supplied from the molten metal holding furnace does not form a solidified shell on the inner wall surface of the mold, and the unsolidified molten metal on the surface of the ingot starts solidifying outside the mold outlet. Invented a new continuous casting method called ``Continuous Casting'', and succeeded in continuously casting a long metal ingot with a smooth surface and a unidirectionally solidified structure (Patent No. 1049146).

[Problem that the invention seeks to solve]

However, when performing upward continuous casting of metal using the method described above, the most important thing is that the ingot does not shake or vibrate at the mold outlet, and that the surface is covered with a uniform thin layer of unsolidified molten metal. This means that the unsolidified molten metal in the surface layer solidifies as a free surface without any contact with anything outside the mold outlet end. If,
When the ingot shakes or vibrates at the mold outlet due to vibrations that occur when the ingot contacts the cooling water, the unsolidified molten metal on the surface of the ingot is affected by the shaking and vibrations, causing the surface to become uneven. present. In addition, when using this method to continuously cast metal downward or horizontally, the irregular shaking and vibration of the ingot significantly impairs the uniformity of the unsolidified molten metal film on the surface layer of the ingot, causing the ingot to flow at the mold outlet. Molten metal breakout is likely to occur.

Even if guide rolls for the ingot are provided near the mold outlet in order to prevent the shaking and vibration of the ingot, it is extremely difficult to prevent the shaking and vibration of the ingot at the mold outlet end. This is because minute differences in thickness and diameter at the joint between the ingot and the dummy bar cause vibrations when the joint passes through the guide roll, and the resulting unevenness on the surface of the ingot also causes vibration when the joint passes through the guide roll. It has become clear that this is because it causes irregular vibrations in the ingot.

In order to prevent the breakout of the molten metal at the mold outlet end due to such irregular swings and vibrations of the ingot, it is necessary to use metals such as copper, gold, or silver, which have large solidification shrinkage and do not react with the molten metal. In some cases, this is possible by finishing the solidification of the ingot surface inside the mold outlet. However, for many common metals and alloys, this method produces scratches while the ingot exits the mold, and the resulting ingot can be processed without surface grinding. It is difficult to turn it into a product. Also, this method cannot be applied to metals and alloys that undergo expansion during solidification.

The present invention aims to provide a method and apparatus that can continuously cast perfect unidirectionally solidified ingots with extremely smooth and beautiful surfaces without surface defects caused by irregular shaking or vibration of the ingots. This is the purpose.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention supplies molten metal from one end and solidifies the surface of the ingot immediately outside the outlet of the heating mold to obtain a metal ingot continuously from the other end to make the ingot smooth. A manufacturing method for continuously producing a metal ingot having a surface and a unidirectionally solidified structure, characterized in that the part of the metal ingot whose surface has been completely solidified is allowed to slide through a guide mold for preventing shaking. It is something.

The present invention also has a heating mold for supplying molten metal from one end and continuously obtaining a metal ingot from the other end, and solidifying the surface of the ingot immediately outside the outlet of the heating mold to form a smooth surface. In a manufacturing device that continuously produces metal ingots with a unidirectional solidification structure, a guide mold for preventing shaking is provided at the outlet end of the heating mold, through which the metal ingot whose surface has completely solidified slides through. The present invention provides a continuous casting device for metal ingots having a smooth surface.

[Effect]

That is, the present inventor has conducted intensive research on continuous casting of ingots with smooth surfaces using heated molds using tin, zinc, aluminum, and copper, and has completely eliminated the irregular shaking and vibrations of the ingots at the mold outlet. In order to obtain a unidirectionally solidified ingot with a smooth surface without fear of breakout of the molten metal and without the formation of a surface solidified shell, it is necessary to use graphite, refractory, Alternatively, a swing prevention guide mold made of metal is installed as close as possible to the mold outlet at a distance necessary for the unsolidified molten metal coming out of the mold to completely solidify, and the ingot is placed inside the mold. It has been found that by sliding the ingot, irregular shaking and vibration of the ingot at the mold outlet can be completely prevented, and an ingot with a smooth and beautiful surface can be easily obtained without breakout of the molten metal.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to configuration examples shown in the accompanying drawings.

FIG. 1 is a longitudinal sectional front view showing a main part of a structural example of a continuous casting apparatus for metal ingots according to the present invention.

Reference numeral 1 denotes a molten metal holding furnace, in which the level of the molten metal 2 is maintained as constant as possible by general means not shown. One end of the hollow heating mold 3 for forming is attached to the side wall of the molten metal holding furnace 1.
It is installed so that it opens inward. A heating element 4 is built in the peripheral wall of the hollow heating mold 3.
The hollow heating mold 3 is heated by the heat of the heating element 4. A guide mold 5 for preventing shaking of the metal ingot is located near the opening at the other end of the hollow heating mold 3 and is movable from side to side in the drawing. It has a hollow part with the same cross-sectional shape as . A metal ingot dummy 6 is placed from the hollow heating mold 3 on the exit side of the shaking prevention guide mold 5.
a cooling spray 8 that injects cooling water to cool the metal ingot 7 obtained by drawing it out;
A metal ingot dummy 6 and a pinch roll 9 for pulling out the metal ingot 7 drawn out by the dummy 6 are arranged. The anti-sway guide mold 5 provided just outside the exit of the hollow heating mold 3 is preferably one that does not cause scratches on the surface of the metal ingot 7 due to friction with the metal ingot 7, and has a mirror-like inner surface. They are made of refractories such as graphite, silicon carbide, boron nitride, alumina, and heat-resistant metals such as stainless steel or synthetic resins for low melting point metals such as tin.

According to the present invention, the metal ingot dummy 6 is heated into the mold 3.
When the metal ingot dummy 6 is placed at the outlet end and brought into contact with the molten metal 2, solidification starts from the tip of the metal ingot dummy 6, avoiding the inner wall surface of the heating mold 3 which is kept above the solidification temperature.
Next, the metal ingot dummy 6 is pulled out to the right by the pinch rolls 9 to obtain the metal ingot 7. The solidified interface of the metal ingot 7 protrudes into the heated mold 3 when the cooling rate is high. At that time, heating mold 3
To prevent crystal nucleation on the inner wall surface of
By controlling the temperature of the inner wall of the heating mold 3 by the current sent to the built-in heating element 4, the metal ingot can be drawn out without friction with the inner wall of the heating mold 3. An unsolidified molten metal film 10 is present on the surface of the metal ingot 7 exiting the outlet end of the heating mold 3, but this solidifies immediately outside the heating mold 3. As soon as the surface of the metal ingot 7 completes solidification, it moves to the right through the anti-sway guide mold 5.

Since the tip of the metal ingot 7 is completely prevented from irregular shaking or vibration by the shaking prevention guide mold 5, breakout of the molten metal at the outlet end of the heating mold 3 can be prevented. It is desirable that the shaking prevention guide mold 5 be installed as close as possible to the exit end of the heating mold.In order to set it at a position where the surface of the metal ingot 7 has completely solidified, it can be moved from side to side by general means not shown in the figure. It is now possible to move to

Next, specific examples will be described.

Example 1 Using a horizontal continuous casting device as shown in Fig. 1, a graphite hollow mold with an outer diameter of 16 mm, an inner diameter of 8 mm, and a length of 60 mm, with a nichrome wire heating element wrapped around the outer circumference, was installed on the side wall of a molten metal holding container. While maintaining the temperature of the mold inner wall at 670℃,
Molten aluminum was supplied into the mold, and cooling water was sprayed onto the aluminum casting wire drawn out from the mold outlet by pinch rolls at a position 20 mm from the mold outlet end, and continuous casting of aluminum wire with a diameter of 8 mm was carried out at a speed of 200 mm/min. I went. At that time, when no guide was provided directly outside the mold, the surface of the wire became uneven and the wire diameter became uneven;
A graphite guide with a hole of 10 mm in length and 9 mm in inner diameter with a gap of 1.5 mm was installed between the mold outlet and the water cooling device, and an aluminum cast wire was slid inside the through hole. We were able to obtain an aluminum wire with an extremely smooth mirror surface.

Example 2 Outer diameter 16 with nichrome resistance heating element wrapped around the outer circumference
Using a horizontal continuous casting machine as shown in Figure 1, in which a graphite hollow mold with a diameter of 6 mm, an inner diameter of 6 mm, and a length of 100 mm is installed on the side wall of a molten metal holding container, molten magnesium is poured into the mold while maintaining the temperature of the inner wall of the mold at 665°C. Supplied into the mold,
Cooling water was sprayed onto the magnesium casting wire pulled out from the mold outlet by pinch rolls at a position 40 mm from the mold outlet end, and continuous casting of a magnesium wire with a diameter of 6 mm was performed at a speed of 100 mm/min. At that time, when no guide was provided outside the mold, the surface of the magnesium wire was uneven and the inner diameter became uneven. When a cast magnesium wire was slid along the grooves of a synthetic resin guide, a magnesium wire with an extremely smooth and beautiful surface was obtained.

Although the horizontal continuous casting of metal ingots of the present invention was explained in FIG. 1, the present invention also applies to upward continuous casting and downward continuous casting.
By providing a guide mold just outside the heating mold outlet and preventing shaking and vibration of the metal ingot at the heating mold exit, a metal molded body with a smooth surface can be obtained.

Furthermore, by using a groove-shaped or hollow guide mold with an open top to prevent shaking in horizontal continuous casting, it is possible to easily obtain a metal ingot with a smooth surface in the shape of a line, rod, or plate.

For continuous casting of metals with a high melting point, a vibration-preventing guide mold can be cooled by providing a copper cooling box on its outer circumferential surface. Furthermore, by forming the guide mold with a plurality of split molds, installation and removal operations can be facilitated.
While sliding through the guide mold, friction with the inner wall surface of the guide mold may cause scratches parallel to the casting direction on the surface of the metal ingot, but these scratches have already been removed when the ingot has completely solidified. It was created after
This method does not involve the formation of a surface solidified shell due to the nucleation of new crystals, and does not cause surface cracking due to plastic working caused by the formation of a surface solidified shell. In order to prevent such scratches, it is extremely effective to add an oil-based lubricant to the inner wall surface of the guide mold.

〔Effect of the invention〕

As described above, according to the continuous casting method of metal ingots having a smooth surface according to the present invention, an ingot with a smooth and beautiful surface, less center segregation and gas bubbles can be obtained without fear of surface cracks, and also , metal ingots of metals and alloys with a unidirectional solidification structure of any cross-sectional shape can be continuously produced. The ingot having an arbitrary cross-sectional shape obtained by the method of the present invention can not only be used as a final product without any surface treatment, but also be used for rolling into ultra-thin plates and ultra-fine wire. This method is extremely suitable for producing processed materials for wire drawing. In other words, it is possible to obtain a mirror-finished ingot with a perfect unidirectional solidification structure that has excellent workability and has no surface structure that would cause cracks during processing, and can be plastic processed without any surface grinding. The present invention is revolutionary in that an ingot can be obtained that can be given the following properties. Furthermore, the continuous casting equipment for metal ingots that implements this method has a simple structure in which a guide mold for preventing shaking, through which the ingot slides through a guide passage, is installed just outside or near the exit of the heating mold, but it is not reliable. It is possible to obtain a mirror-finished ingot with a perfect unidirectional solidification structure and excellent workability.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional front view of a main part showing an example of the configuration of a horizontal continuous casting apparatus provided with a guide mold for preventing shaking according to the present invention. In the drawing, 1 is a molten metal holding furnace, 2 is a molten metal, and 3 is a molten metal holding furnace.
4 is a heating mold, 4 is a heating element, 5 is a guide mold for preventing shaking, 6 is a metal ingot dummy, 7 is a metal ingot, 8 is a cooling spray, 9 is a pinch roll, and 10 is an unsolidified molten metal film.

Claims (1)

[Scope of Claims] 1. Molten metal is supplied from one end and the surface of the ingot is solidified just outside the outlet of a heating mold to obtain a metal ingot continuously from the other end, so that the ingot has a smooth surface and is unidirectional. A manufacturing method for continuously producing a metal ingot with a solidified structure, characterized in that a solidified part of the surface of the metal ingot is allowed to slide through a shaking prevention guide mold. Continuous casting of ingots. 2. A heating mold for supplying molten metal from one end and continuously obtaining a metal ingot from the other end, solidifying the surface of the ingot just outside the outlet of the heating mold to have a smooth surface and a uniform In a manufacturing apparatus that continuously produces metal ingots having a directionally solidified structure, an anti-swaying guide mold is provided at the outlet end of the heating mold, and the guide mold is provided with a guide groove through which the metal ingot whose surface has completely solidified slides. A continuous casting device for metal ingots having a smooth surface, characterized in that: 3. The metal ingot having a smooth surface according to claim 2, wherein the shaking prevention guide mold is movable in parallel to the casting direction of the ingot in order to adjust its installation position. Continuous casting equipment. 4. The continuous casting apparatus for metal ingots having a smooth surface according to claim 2, wherein the guide mold for preventing shaking is composed of a plurality of split molds.