JPS6039459B2 - Bumping prevention method during continuous or semi-continuous casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing bumping during continuous or semi-continuous casting.

A widely used method for continuous or semi-continuous casting (hereinafter simply referred to as continuous casting) of molten metals such as AI and Cu is the method shown in FIG. 1 (schematic vertical cross-sectional view).

That is, at the start of casting, a metal block called a bottom metal (or dummy bar) 2 is inserted into the mold 1, and a metal melt M is cast into this through a nozzle 4 from a casting gutter 3 to form an appropriate solidified shell. While doing so, the bottom metal 2 is lowered at a predetermined speed. In particular, in the DC casting method, a hole (or slit) la is bored in the lower end of the mold 1, and mold cooling water is directly applied to the surface of the solidified coin coin to promote cooling of the coin coin. In addition, the upper surface of the base metal 2 is generally formed into a concave shape as shown in the figure, in order to make it easier for the molten metal to accumulate in the early stages of damage and to form a solidified shell, as well as to make it easier to extract the Zentama from the mold 1. It is true. However, when such a concave bottom plate is used, the following problems occur.
That is, the solidified shell solidified at the top of the bottom metal 2 immediately after the start of rare production warps upward due to contraction (hereinafter simply referred to as contraction) due to solidification and cooling, as shown in Figure 2, and forms a part between the bottom metal 2 and the bottom of the hoko castle. A gap S is created. For this reason, the cooling water released from the mold 1 flows along the surface of the coin coin or the float block and flows into this gap S, but at this point, the lower surface of the coin coin and the surface of the waist metal 2 have not been sufficiently cooled, and the cooling water flows into the gap S. rapidly boils or vaporizes within the narrow gap S, causing explosive volumetric expansion. As a result of this continuous firing phenomenon, the coin coin vibrates up and down, left and right, and in extreme cases, it appears to bounce. Such a phenomenon is called bumpisog, and the thin, brittle solidified shell that is being formed within the mold 1 is mechanically destroyed, which may lead to serious accidents such as leakage. In addition, the relative positions of the mirror block and the base metal are misaligned, making it impossible to obtain a straight coin coin, and this becomes a major cause of a decrease in walking speed in the subsequent cutting and shaving processes. Moreover, the coagulation structure of the coin coin changes due to vibrations, etc., and the quality of the coin coin itself is significantly deteriorated, such as cracking of the coin coin or entrainment of oxide due to fall of oxide near the scar or meniscus. In order to avoid such problems, conventional methods mainly controlled casting conditions, such as reducing the amount of cooling water and slowing down the casting speed, but this resulted in a decrease in productivity and it was difficult to completely prevent the bumping phenomenon. I couldn't do it either. There is also a known method, as disclosed in Japanese Patent Publication No. 51-9168, in which the bottom metal is provided with a drainage drain to extract the cooling water and steam that have flowed into the gap, but this method requires a complicated shape of the bottom metal. There are some difficulties. In addition, when casting relatively small diameter billets, dovetail grooves or bolt-like protrusions are formed on the surface of the bottom metal and cast into the coin coin, and the mirror block and bottom metal are fixed to each other. Efforts are also being made to prevent gaps from forming.

However, in this method, the shrinkage force during cooling and solidification is restrained by the coin holder, so if residual stress occurs, cracks may occur starting from the coin holder, or the coin may not be pulled out smoothly from the mold. It can be difficult. Moreover, there are problems such as it takes time and effort to separate the coin coins from the bottom coins after the coin is minted, and the bottom coins may have to be shaped each time. The inventors of the present invention have focused on the above-mentioned circumstances, and have established a technique that uses a bottom metal with a smooth surface without dovetail grooves or protrusions, and that can reliably prevent the bumping phenomenon described above. I have been conducting research.

The present invention was completed as a result of such research, and its configuration is such that, when starting vertical continuous casting, an annular metal part is placed on the contact surface of the bottom metal with the casting material, and the bottom metal surface is The cast material in contact with the annular metal member solidifies after being fused with a part of the metal member, and as the cast material solidifies and shrinks, the unfused portion of the annular metal member is pulled up toward the cast material, causing the unfused portion to stand up. The key point is to form a cooling water inflow prevention wall between the cast material and the bottom metal, which is effective in reliably preventing the bumping phenomenon. The configuration and effects of the present invention will be explained below based on drawings showing examples, but the following are representative examples and do not limit the present invention.
All changes in the shape, structure, etc. of the mold and the bottom metal are included within the scope of the present invention to the extent that the purpose described below is met.

The present invention is also a method applicable to curved continuous casting, and the term "vertical continuous casting" in this specification should be understood in a broad sense to include curved continuous casting. 3 to 5 are schematic vertical cross-sectional explanatory views showing an embodiment of the present invention, and the structure of the mold 1 and the bottom metal 2 and the procedure for extracting the coin coins are substantially the same as the examples shown in FIGS. 1 and 2.

However, in this example, the cylindrical metal foil 5 is covered so as to surround the outer periphery of the upper part of the bottom plate 2, and the upper part of the metal foil 5 is extended at least above the upper edge of the bottom plate 2. Start injection with the tube folded toward the edge (Figure 3). The material of the metal foil 5 is not particularly limited, but when using a material with a melting point similar to or slightly lower than the melting point of the metal scar M,
When the molten metal from which casting has started enters the bottom metal 2, the metal foil 5 on the periphery of the bottom metal is fused to the metal molten moat M, and then transferred to the metal molten metal M.
It also coagulates (Fig. 4). If a material having a higher melting point than the metal tower M is used as the metal foil 5, the molten metal M solidifies with the upper end of the metal foil 5 remaining loose. Next, when the bottom metal 2 is lowered at a predetermined speed and the twill lump is extracted,
As mentioned above, the coin coin shrinks and there is a gap S between it and the surface of the bottom coin 2.
However, as shown in FIG. 5, the unmelted part of the cylindrical metal foil 5 hanging down on the outer circumference of the bottom plate 2 slides upward in response to the deflection of the ingot, and the unfused part hangs down on the outer circumference of the gap S. Forms a skirt-like barrier membrane. Therefore, even if the cooling water is spouted to the outer circumferential side of the coin coin, there is no fear that the cooling water will be blocked by the metal foil 5 and flow into the gap S, and the bumping phenomenon can be completely prevented. By the way, with the above method, it is possible to prevent the cooling water from flowing into the gap S, and the purpose of preventing bumping is achieved, but in reality, the gap between the mold 1 and the bottom metal 2 is narrow, so the wall is quite thin. metal foil 5 must be used,
When the metal foil 5 is applied to the bottom metal 2 or when the cooling water collides with it, the metal foil 5 may be torn and the cooling water blocking effect may become insufficient.
Figures 6 to 8 are schematic longitudinal sectional views showing an embodiment that does not cause such problems, in which an annular vertical groove 6 is formed on the periphery of the upper surface of the bottom plate 2, and a rut-shaped blocking plate 7 is inserted into the groove. At the same time, the upper end is made to protrude above the surface of the bottom plate 2 (FIG. 6).

The material of the shielding plate 7 is the same as that of the metal foil 5 used in FIGS. 6-8. When this bottom metal 2 is inserted into the mold 1 and the metal flaw M is cast, the upper end protrusion of the bottom metal 2 is once fused with the metal flaw M and solidified as one, or the metal flaw M is solidifies while encircling the upper protrusion of the bottom metal 2 (Fig. 7). Next, the bottom coin 2 is lowered at a predetermined speed to pull out the coin coin, but at this time, as shown in FIG. is the gap S
As it expands, it slides upward in the annular groove 6 and forms a blocking wall on the outer circumferential side of the gap S, which prevents cooling water from flowing into the gap S and prevents bumping. In this case, since the shielding plate 7 is made of a fairly thick material, there is no fear that it will be torn during installation or by the jet pressure of cooling water, unlike when metal foil is used, and bumping can be reliably prevented. Furthermore, the annular groove 6 and the cylindrical blocking plate 7
It is necessary to have an iron fitting that allows the shielding plate 7 to easily slide upward during key making, but if the gap between the two is too large, cooling water will go around the annular groove 6 and flow into the gap S. To prevent this, it is better to use the loose iron with as much clearance as possible. It goes without saying that the depth of the annular groove 6 and the height of the blocking plate 7 should be slightly longer than the maximum length of the gap S caused by the contraction of the coin coin. In Fig. 9, a downwardly sloping slope 2' is formed on the outer peripheral edge side of the connecting part of the shielding plate 7 in the bottom metal 2 to prevent cooling water from collecting in this part, and the cooling water circulates around the annular female 6. This is effective in preventing the liquid from flowing into the gap S.

In addition, in some cases, as shown by the broken line in FIG.
It is also effective to form an extraction hole 8 in the lower surface of the groove 6 and discharge the cooling water that has flowed into the groove 6 to the outside. The blocking plate 7 is most commonly molded as a single piece as shown in FIG. 10, but the blocking plate 7 may also be formed by assembling a set of divided pieces as shown in FIGS. 11 and 12. In this case, it is desirable to insert a corner plate 7' as shown in the figure in order to prevent cooling water from entering from the assembly portion of the divided Kataokashi. In addition, when the shielding plate 7 as shown in the figure is installed at a considerable height from the top surface of the base plate 2, the metal weld moat M is dammed by the shielding plate 7 at the start of casting, and the metal melting moat M is dammed over the entire area inside the mold. There is a risk of inconvenience caused by a delay in the time it takes for the
, 14, if a through hole 7a, a notch 7b, etc. are formed above the blocking plate 7, such inconveniences can be easily solved. FIG. 15 shows still another embodiment of the present invention. FIG. 16 is a partially cutaway diagram showing the bottom metal part, and FIG. A frame body 9 is arranged with an appropriate gap S' on the outer circumferential side, and is integrally fixed to the bottom metal 2 with a connecting lip 10, thereby forming the bottom metal as a whole.

Then, the blocking plate 7 is inserted into the gap S'. In this case, if there is a gap between the shielding plate 7 and the frame material 9 or the bottom metal 2, there is a risk that the molten metal moat M will leak from this gap, so the upper part of the gap S1 is sealed with a heat-resistant sealing material 11. should be kept. With such a configuration, even if the cooling water enters into the gap S', it will flow out from the lower entrance, so there is no fear that the cooling water will enter the inside of the shielding plate 7. In addition, although the above-mentioned examples show cases in which rectangular slabs are continuously cast, the present invention is of course not limited to this, and can similarly be applied to cases in which circular or elliptical billets are continuously cast. I can do it. The present invention is roughly constructed as described above, and can prevent the bathoping phenomenon with relatively simple operations, and can eliminate accidents such as melt leakage that occur at the start of casting.

Furthermore, since there is almost no vibration caused by the rising sun inside the mold, surface defects such as hot water boundaries, contamination of oxides, uneven solidification structure, etc. are eliminated, and furthermore, the shrinkage of the gun mass during solidification is not restricted at all. There is no fear that the pot mass will crack, and since the warping and bending during solidification and shrinkage are almost uniform, many effects can be obtained, such as an improved double-cutting yield.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic vertical cross-sectional views showing the continuous casting method of the secondary tank, Figures 3 to 8 are schematic vertical cross-sectional views showing embodiments of the present invention, and Figure 9 is a preferred example of the bottom plate and the annular caster. 1st cross-sectional view of main parts showing
Figures 0 to 12 are sketch diagrams illustrating the blocking plate, 13th and 14th
FIG. 15 is a side view showing another example of the blocking plate; FIG. 15 is a partially cutaway sketch showing another embodiment of the present invention;
FIG. 16 is a cross-sectional view showing a state in which a blocking plate is placed loosely on the bottom plate of FIG. 15. 1... Mold, 2... Bottom metal, 3... Casting gutter, 4... Pouring nozzle, 5... Metal foil, 6... ...Annular groove, 7...Block plate, M.
...Molten metal, S...Gap. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16-

Claims (1)

[Claims] 1. When starting vertical continuous or semi-continuous casting, an annular metal member is placed on the contact surface of the bottom metal with the casting material, and the casting material in contact with the bottom metal surface fuses with a part of the metal member. After solidification, as the cast material solidifies and shrinks, the unfused part of the annular metal member is pulled up toward the cast material, so that the unfused part stands up and creates a cooling water inflow prevention wall between the cast material and the bottom metal. A method for preventing bumping during continuous or semi-continuous casting, characterized by forming.