JPH0511003Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application This invention relates to a nozzle for supplying molten metal in a continuous casting and rolling apparatus for directly manufacturing thin plates from molten metal such as aluminum by a twin roll method.

Conventional technology As continuous casting and rolling methods, the twin roll method, such as the 3C method, is known, in which molten metal is guided between a pair of rolls rotating from a nozzle and cooled and solidified by the heat removal action of the rolls. A rotating belt method, for example, the Hesley method, is known in which molten metal is guided from a nozzle between a pair of rotating belts, heat is removed by the belts, and the metal is cooled and solidified. Among these, a conventional example of a nozzle for supplying molten metal between the rolls in the twin roll method is shown in FIG.

In FIG. 3, the nozzle 1 is usually made of refractory material, and the tip surface 3 forming the tap hole 2 of the nozzle 1 forms an angle of θ=90° with respect to the tapping direction. That is, it is made to form an angle θ=90° with respect to a plane 6 perpendicular to a straight line 5 connecting the rotation centers O and O' of the rolls 4 and 4'. In FIG. 3, 8 is a molten metal, and 9 is a cast plate in which the molten metal 8 has solidified.

Problems to be solved by the invention When metals such as aluminum are continuously cast and rolled by the conventional twin roll method, the obtained cast plate 9 has stripes perpendicular to the casting and rolling method, as shown in Fig. 4. A similar pattern 7 often appears. This striped pattern is called a ripple mark or a level line (hereinafter referred to as "ripple mark" for convenience), and usually exists not only on the surface of the cast plate but also deep inside. Therefore, if ripple marks occur on a cast plate, even if heat treatments such as soaking or rolling methods are devised in the process of rolling the cast plate to the final thickness, the ripple marks will remain until the final plate, resulting in poor appearance, for example. A problem arises that makes it unusable for alumite applications. Furthermore, when ripple marks are formed on the cast plate in this manner, there is a risk that cracks may occur at the ripple mark portion during the subsequent rolling process.

This invention was made against the background of the above-mentioned circumstances, and its purpose is to prevent ripple marks from occurring during continuous casting and rolling using the twin roll method.

Means for Solving the Problems In order to eliminate the occurrence of ripple marks in continuous casting and rolling using the twin roll method, the inventors of the present invention have taken the following steps:
When investigating the cause of the ripple marks, the following findings were obtained.

In the conventional continuous casting and rolling apparatus, as shown in FIG.
is in contact with rolls 4 and 4' (contact start position)
moves from point Pa to Pb as the roll rotates,
Next, the process of returning from point Pb to Pa due to surface tension is repeated, resulting in a kind of pulsation phenomenon, and as a result, the contact status of the molten metal with the roll fluctuates periodically, resulting in the periodicity of the solidification rate at the time of initial solidification shell formation. It was found that some fluctuations were occurring. Such periodic fluctuations in the solidification rate during the initial solidification shell formation result in periodic fluctuations in the amount of crystallized intermetallic compounds and periodic fluctuations in the gap between the dendrite arms, which appear as patterns on the cast plate. It was found that this caused the occurrence of ripple marks.

Based on this knowledge, it is considered that the occurrence of ripple marks can be prevented if the contact start position of the molten metal discharged from the nozzle with the roll is not changed. Therefore, as a result of further investigation into the variation in the contact start position of the molten metal with the roll as described above, the following facts were found.
That is, in the case of the conventional nozzle, the nozzle outlet end surface 3 is at an angle θ (perpendicular to the straight line 5 connecting the rotation centers O and O' of the rolls 4 and 4', and the nozzle 1 was 90°, a gap G was created between the outer edge surface 11 of the flow of molten metal 8 flowing out from the nozzle tip and the nozzle tip surface 3, The existence of this gap G allows the position of the outer edge surface 11 of the molten metal outflow to fluctuate, and the position where the molten metal 8 contacts the rolls 4, 4' fluctuates due to the pulsation phenomenon described above. be. Therefore, the present inventors changed the angle of the tip surface of the nozzle from the conventional one and gave it an inclination, thereby preventing the generation of the gap G as described above and suppressing the fluctuation of the outer edge surface 11 of the molten metal outflow. We thought that it would be possible to prevent the occurrence of ripple marks by suppressing fluctuations in the starting position of molten metal contact with the rolls, and as a result of conducting experiments, we found that by setting the aforementioned angle θ to 75° or less, the occurrence of ripple marks could actually be prevented. They found that it could be suppressed and came up with this idea.

In other words, this invention supplies molten metal between a pair of rotating rolls in a molten metal supply nozzle in a twin-roll continuous casting and rolling machine that supplies molten metal between a pair of rotating rolls and casts the molten metal into a thin plate. The two long sides of the tip of the tap opening of the nozzle are at an angle of 75° or less with respect to a plane that is perpendicular to the straight line connecting the rotation centers of the pair of rolls and passes through the central axis of the nozzle. The sloping surface is inclined at an angle, thereby suppressing fluctuations in the contact start position of the molten metal with the roll.

Function If continuous casting and rolling is performed using the nozzle of this invention, the outer edge surface of the flow of molten metal flowing out from the nozzle outlet (molten metal outflow flow), especially the outer edge surface on the long side of the nozzle outlet, will almost always be Inclination angle of nozzle tip
It will be along a slope of 75° or less. In other words,
Of the flow of molten metal flowing out from the nozzle tip,
The outer edge of the flow toward the roll surface almost always follows the inclined surface. This means that there is almost no room for a gap to form between the outer edge surface of the molten metal outflow toward the roll and the nozzle tip.
Therefore, fluctuations in the outer edge surface of the molten metal outflow are suppressed by the inclined surface, and fluctuations in the contact start position of the molten metal with the roll are suppressed, and as a result, the solidification rate of the initially solidified shell also hardly changes. gone,
As a result, the occurrence of ripple marks is prevented. Here, if the angle of the slope exceeds 75°, the above-mentioned effects will hardly be obtained, so the slope angle needs to be 75° or less. Note that even if the angle of inclination is 75° or less, the above effect can be obtained more reliably by setting the inclination angle to 45° or less.

Embodiment FIG. 1 shows an example of the molten metal supply nozzle 1 of this invention, and FIG. 2 shows a situation in which the nozzle 1 of FIG. 1 is used for continuous casting and rolling by a twin roll method.

The nozzle 1 is made of refractory material, and its outlet 2 has a long and short cross-section with a width approximately equal to the width of the casting plate 9 to be cast. Two surfaces 10A and 10B on the long side of the nozzle tip surface forming the outlet 2 of the nozzle 1 are perpendicular to the straight line 5 connecting the rotation centers O and O' of the rolls 4 and 4', and are at the center of the nozzle 1. It is an inclined surface having an inclination angle θ of 75° or less with respect to a plane 6 passing through the axis.

When performing continuous casting and rolling using the nozzle 1 as described above, for example, by the twin roll method as shown in FIG. The outer edge surface 11 of the flow of the molten metal 8 flowing out from the sprue 2 is the inclined surface 1 at the tip of the nozzle.
It flows along 0A and 10B. Therefore, fluctuations in the position of the outer edge surface 11 of the molten metal outflow, and thus fluctuations in the position (contact start position) P where the molten metal 8 contacts the rolls 4, 4', are suppressed, and the occurrence of ripple marks is suppressed.

Next, the results of continuous casting and rolling experiments of aluminum were conducted while varying the angles of the inclined surfaces 10A and 10B at the tips of the nozzles.

A twin-roll casting machine with a roll diameter of 300 mm was used as the continuous casting and rolling equipment, and the casting was carried out on JIS1100 aluminum alloy. The rotation speed of the rolls is 1 rpm, and the surface spacing between upper and lower rolls 4 and 4' is 5.2
mm, distance between straight line 5 connecting the rotation centers of rolls 4 and 4' and the exit of nozzle 1 (setback distance)
was set to 25mm. The inclined surface 10A at the tip of the nozzle 1,
The inclination angle θ of 10B is 90°, 75°, 60°, 45°, 27°
，
When we investigated the occurrence of ripple marks on the cast plate by casting with the angle changed to 15°, we found that θ = 90°.
Strong ripple marks were observed at 75°,
As the angle θ decreased to 60° and 45°, the ripple mark became weaker, and in particular, at 45° or less, almost no ripple mark was observed.

Effects of the invention If continuous casting and rolling is performed by the twin roll method using the molten metal supply nozzle of this invention, the occurrence of ripple marks on the cast plate can be effectively prevented.
Therefore, it is possible to achieve remarkable effects such as preventing appearance defects caused by the ripple marks on the final product board or cracks from occurring due to the ripple marks during the rolling process.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of the molten metal supply nozzle of this invention, and Fig. 2 is a schematic longitudinal section showing an example of a situation in which continuous casting and rolling is performed using the molten metal supply nozzle of this invention. Figure 3 is a schematic vertical cross-sectional view showing an example of continuous casting and rolling using a conventional molten metal supply nozzle, and Figure 4 is a schematic longitudinal sectional view showing an example of continuous casting and rolling using a conventional molten metal supply nozzle. FIG. 3 is a plan view showing the occurrence of ripple marks on a cast plate when rolling is performed. 1... Nozzle, 2... Tap, 4, 4'... Roll, 8... Molten metal, 10A, 10B... Inclined surface, θ... Incline angle.

Claims (1)

[Scope of Claim for Utility Model Registration] In a molten metal supply nozzle in a twin-roll type continuous casting and rolling machine that supplies molten metal between a pair of rotating rolls and casts the molten metal into a thin plate, Of the tip surfaces of the outlet of the molten metal supply nozzle for supplying molten metal, the two long side surfaces are aligned with a plane that is perpendicular to the straight line connecting the rotation centers of the pair of rolls and that passes through the center axis of the nozzle. 1. A molten metal supply nozzle for a continuous casting and rolling apparatus, characterized in that the molten metal has an inclined surface inclined at an angle of 75° or less, thereby suppressing fluctuations in the contact start position of the molten metal with the roll.