JPS623866A - Spray casting method - Google Patents

Abstract

PURPOSE:To improve casting productivity, etc. by dropping the flow of a molten metal in a thin film state and blowing a high-pressure gas thereto to form liquid drops. CONSTITUTION:A slit nozzle 3 is formed to the bottom of a tundish 2 to drop the molten metal 1 thereby forming metallic flow 4. The high-pressure gas such as nitrogen or argon is blown to the metal flow 4 from slit nozzles 5A, 5B. The molten metal 4 is sprayed to form the liquid drops in this stage. The liquid drops 6 are dropped and stucked into a mold 7. The flow rate of the molten metal is made considerably higher than in the molten metal is made considerably higher than in the case of the conventional cylindrical nozzle by the above-mentioned method, by which the casting speed is increased. The liquid drops 6 solidify only on the surface and the inside in the unsolidified state is accumulated into the mold 7. The casting productivity is thus improved and the quality of the casting ingot is made uniform.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is a spray method that sprays high-pressure gas onto a flow of molten metal such as molten steel to atomize it into droplets, and collects the droplets in a mold to form an ingot. It concerns casting methods.

Conventional technology The conventional methods for producing ingots and slabs of steel, etc. are as follows:
An ingot casting method in which molten metal such as molten steel is cast into an ingot case, and a continuous casting method using a vibration mold or the like are widely used. However, these conventional general casting methods inevitably cause macroscopic component segregation. That is, in ingot casting, V segregation, reverse V segregation, etc. occur, and although segregation is less in continuous casting compared to ingot casting, center segregation, etc. inevitably occur.

As a method for manufacturing slabs that eliminates such macroscopic component segregation, a so-called spray casting method has already been proposed in Japanese Patent Application Laid-Open No. 58-86969.

This proposed method is melting! The molten steel is sprayed and turned into droplets by blowing liquefied inert gas into the flow, and only the surface of the molten steel is solidified before it falls into the mold, leaving the inside unsolidified and semi-solidified. If the molten steel is turned into droplets and accumulated in the mold with only the surface solidified, there will be almost no movement of components within the mold, and the As a result, an ingot with almost no macro segregation can be obtained.

A similar spray casting method has also been proposed in Japanese Patent Publication No. 54-29985, and this proposed method also injects inert gas to turn the via metal flow into droplets, producing precision molded metal parts without macro segregation. It is said that it can be obtained.

Furthermore, as a method that improves the above-mentioned Japanese Patent Application Laid-Open No. 58-86969, Japanese Patent Application Laid-Open No. 58-163565 discloses a nozzle for discharging the melt #A stream from a tundish. ! A method has been proposed in which several nozzles are provided and a liquefied inert gas is individually sprayed onto the solution flow flowing down from each nozzle to form droplets.

Problems to be Solved by the Invention In the spray casting method described in gR Publication No. 58-86969 and the spray casting method described in Japanese Patent Publication No. 54-29985, a cylindrical nozzle is used as a nozzle for flowing molten steel from a tundish. In this case, the flow rate of 101 from the nozzle is determined by
-20~ as described in Publication No. 163565
1000)t.

It is limited to a range of /-. In other words, the molten steel flow rate is 2
Below 0kl/1Il11, the nozzle diameter becomes extremely small and molten steel nozzle clogging occurs;
If - is exceeded, the droplet formation efficiency will deteriorate and the proportion of oversized particles mixed in the droplets will increase, making it impossible to achieve the original purpose of the spray casting method of preventing macro segregation, as well as reducing the inertness required for droplet formation. The amount of gas increases, leading to increased costs.

In this way, in the conventional spray casting method using a cylindrical nozzle, the flow rate of the melt, and therefore the casting speed, is 1000 kO.
/m or less, and as a result, productivity has been significantly inferior compared to conventional general ingot casting methods and continuous casting methods.

Therefore, in the method described in Japanese Patent Application Laid-Open No. 58-163563, a plurality of nozzles are used. Although the casting speed is increased by providing this, another new problem arises in this case. In other words, in this case, it is necessary to provide multiple nozzles and to provide an injection gas line for each nozzle, which complicates the overall equipment configuration, leading to high costs and complicated maintenance and inspection. In addition, the 5w1m of each nozzle varies, and the amount of injection gas for the molten steel flow flowing down from each nozzle varies, resulting in a cold 1fll.
As a result, the amount of collected droplets may vary depending on the location within the mold, and the droplet diameter may also be uneven or the degree of surface solidification before reaching the mold. There is a problem that uniformity occurs and the quality of the ingot becomes non-uniform.

Furthermore, when a plurality of nozzles are provided in this way, the jet II
There is also the problem of increased gas consumption for forming droplets.

This invention was made against the background of the above circumstances, and includes:
Spray casting can be performed without causing uneven ingot quality due to complex zones, uneven flow of molten metal such as molten steel, uneven cooling capacity, etc., and with relatively low gas consumption. The aim is to significantly improve legal productivity compared to the past.

Means for Solving the Problems This invention sprays high-pressure gas such as an inert gas onto an in-metal flow of molten steel, thereby atomizing the molten metal into droplets, and placing the generated droplets in a mold. The spray casting method in which the molten metal is collected is characterized by dropping the molten metal flow in the shape of Nm (film shape), and spraying high-pressure gas onto this one-seismic molten metal flow to form droplets.

Function: As mentioned above, since the molten metal flow falls in a single channel, the molten metal flow rate can be significantly increased compared to the case of using a conventional cylindrical nozzle, and therefore the casting speed can be increased compared to the conventional method. can also be dramatically increased. In other words, when using a conventional cylindrical nozzle, in order to increase the flow rate of molten metal in one nozzle, the inner diameter must be increased, and in this case, as mentioned above, the droplet formation efficiency is poor (
However, when a molten metal flow is dropped in a thin pattern using a slit, etc., the molten metal flow rate can be increased by the width without increasing the thickness (therefore, the length of the short side of the molten metal outlet). Therefore, a large outflow of molten metal can be simultaneously turned into droplets with a smaller injection high-pressure gas flow m than in the past, without reducing the droplet formation efficiency and reducing the droplet formation efficiency. Even when the molten metal flow is made into a thin film, its thickness (
The inventors have confirmed through experiments that by making the length of the short side of the molten metal outlet equal to or smaller than the inner diameter of a conventional cylindrical nozzle, it is possible to sufficiently form droplets by high-pressure gas injection. There is. Note that the term "roll-shaped molten metal flow" here means a molten metal WA flow whose width is sufficiently large relative to its thickness, and although the ratio of thickness to width is not particularly limited, the width is usually several times the thickness. Above, specifically, about 5 times or more is desirable.

In addition, when the molten metal flow is dropped in a shape of 2 m, as in the case where a plurality of cylindrical nozzles are individually provided, jl
There is little risk of variation in the amount of N or variation in cooling capacity, and it becomes easy to keep the flow rate of molten steel substantially constant in each portion in the width direction and to keep the cooling capacity constant. Furthermore, in terms of equipment, it is sufficient to have a single molten metal outlet such as a slit for allowing the thin film-like +11FM metal flow to flow down, and the thin film-like molten metal fi falling from the outlet is sufficient.
&The injection of high pressure gas against the flow is 'WIJ1! Since it is sufficient to simply spray from both sides of the molten gold stream, the high-pressure gas line does not need to be particularly complicated.

Incidentally, the droplets generated by spraying and forming droplets by spraying high-pressure gas against the thin film-like molten metal flow are accumulated in the mold and finally become an ingot, as in the conventional method. In this case, only the surface of the droplet solidifies before it reaches the mold,
Therefore, the ingot finally obtained by f% is free from macro segregation as in the case of the conventional method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show an example of a situation in which the method of the invention is implemented.

In this case, a slit-shaped nozzle 3 as a molten metal yh outlet is formed at the bottom of a tundish 2 containing a clear metal 1 such as molten steel, and the molten metal 1 flows down from this slit-shaped nozzle 3. A thin film-like molten metal stream 4 is formed by this. Slit nozzles 5A and 5B for injecting high-pressure gas are arranged at positions sandwiching the thin film-like molten metal flow 4 flowing down from the slit-like nozzle 3 from both sides. The slit nozzles 5A, 5B are configured so that their lengths are equal to or longer than the width of the thin film-like molten metal flow 4. This slit nozzle 5A, 5B
From thin film 1! ! ! Nitrogen, argon and other i in fi19I4 now! Molten metal G by spraying % pressure gas
j! The liquid droplets 6 fall and accumulate in the mold 7. Here, by making the length of the short side of the slit-shaped nozzle 3 equal to or less than the inner diameter of the cylindrical nozzle used in the conventional spray casting method, a thin film can be melted by spraying high-pressure gas. Based on the actual situation of the present inventors, it is possible to sufficiently convert the metal flow 4 to v1.
(See Figure 5 below). By increasing the width of the slit nozzle 3 (long side length: therefore the width of the WJ film-like molten metal Ft4), even if the short side length is short, it can be compared with the case using a conventional cylindrical nozzle. By doing so, the flow rate of molten gold I can be significantly increased and the casting speed can be increased. Note that the gas for spraying and forming droplets is usually an inert gas such as nitrogen or argon, but is not necessarily limited to these.

The a? of the molten metal sprayed and turned into droplets as described above? i
Only the surface of I6 solidifies before it reaches the mold 7. In other words, the inside of the mold 7 remains in an unsolidified state. It is accumulated. At the time of this accumulation, since the inside is unsolidified, the whole has a certain degree of fluidity (easiness of deformation), so it is accumulated without forming any voids in each mum, and each of the 11 surfaces is U-hardened. As a result, there is no movement of components (therefore, it is possible to obtain an ingot free of macrodeposition.Also, since the droplets obtained by simultaneously turning the thin film-like molten metal flow into droplets are 111fi,
Unlike the case where multiple cylindrical nozzles are used, the collection WAm may vary depending on the location within the mold, the droplet diameter may vary, and the solidity of the droplets may vary due to variations in cooling capacity. Therefore, there is little risk of variations in final ingot quality.

FIGS. 3 and 4 show other examples of situations in which the spray casting method of the present invention is implemented.

In this example, a pair of parallel rotating rolls 11A, IIB are arranged below a normal cylindrical nozzle 10 provided at the bottom of the tundish 2, and in this case, the molten metal member 1 is connected to the rolls 11A, 11B. The molten metal 1 is injected into the gate and flows down from the gap between the rolls 11A and 11B, thereby forming a thin film-like molten metal stream 4.

In the example of FIG. 3 and m42I, one film of molten metal ff1. The thickness of t4 is r1! It can be adjusted to i11. Here, by setting the roll interval to be the same as or smaller than the internal diameter of a conventional cylindrical nozzle, it is possible to form droplets by spraying high-pressure gas, as in the case of FIGS. 1 and 2. In addition, when rolls 11A and 11B are used, rolls 11A and i
By rotating IB, it is possible to make the roll surface temperature uniform, and it is also possible to prevent narrowing of the roll interval due to adhesion 3i of molten metal to the roll surface. Therefore, when it is desired to make the film-like molten metal flow 4 thinner. It is possible to stably generate a thin film-like molten metal flow.

Although it is not impossible to use gold aUO-ru for the rolls 11A and 11B, in one case it is necessary to cool the rolls to protect the rolls.

If the gold JO-roll is cooled in this way, the molten gold 5 will solidify and adhere on the roll surface even if the roll is rotated as described above.
As time passes, the distance between the rolls becomes narrower and stable casting becomes difficult, and a situation may occur where both rolls come into contact and casting becomes impossible. In order to prevent this, O-ru IIA and IIB materials should be used.
It is desirable to select a material that has excellent heat insulation properties and does not form a solidified shell on the roll surface. For example, it is desirable to use a refractory material such as boron nitride < BN) or magnesia (N.1go) for the roll. Of course, the entire roll does not need to be made of such a refractory material, and only the surface layer of the roll may be made of such a refractory material.

Note that the examples shown in FIGS. 1 and 2, and FIG. 3.

In any of the examples shown in FIG. 4, by reducing the thickness of the thin film-like molten metal flow 4, ? 1m shaped molten gold II
By reducing the amount of gas required to atomize and turn stream 4 into droplets,
It has been confirmed through practice by the inventors that gas consumption can be reduced. That is, FIG. 5 shows a method in which molten steel is used as the metal, argon gas is used as the injection gas, and slit nozzles with substantially the same width as the width of the molten steel flow are installed on both sides of a thin film-like molten steel flow having a constant width. NII! The argon gas flow was carried out with various changes for I-state melt f[! The presence or absence of two drops was investigated, and from this figure, when the thickness of the thin film molten steel flow was 201, it was 100N.
However, if the thickness is reduced to 5111Il, it is possible to form droplets of 3ONr+t'/ with a small amount of gas or more.

Practical Examples When pouring molten steel, an actual flow example in which spray casting was performed according to the five steps of the present invention, and a comparative example in which spray casting was performed using a conventional cylindrical nozzle will be described below.

Example 1: As shown in Figs.
A slit-shaped nozzle (slightly longer than the width of the thin film-like molten steel flow) for injection forms a thin film-like molten steel flow 4 by flowing down 1, and VM is applied to both sides of the thin-like molten steel flow 4. Melt from 5! l! ! Argon gas was sprayed onto both sides of the flow to turn mtR into droplets, and the droplets 6 were collected in a mold 7 to create an ingot. Casting speed It<molten steel flow! Table 1 shows the argon gas flow [1 (total), argon gas jet pressure, and tundish nozzle dimensions.

Embodiment 2: As shown in FIGS. 3 and 4, a normal cylindrical tundish nozzle 10 is used, and a pair of parallel rolls 11A and 11 made of boron nitride are arranged below the tundish nozzle 10.
By supplying molten steel 1 between the rolls and letting the molten steel flow down from the gap between the rolls, a thin film of Wii Gold! A stream 4 was produced. Then, as in Example 1, argon gas was injected to form droplets, which were collected in a mold. Detailed conditions are shown in Table 1.

Comparative Example 1: Molten steel was flowed down through a cylindrical nozzle with an inner diameter of 181+11 attached to the bottom of a tundish, and argon gas was injected into it to form droplets, which were collected in a mold. Detailed conditions are shown in Table 1.

Comparative Example 2: Molten steel was flowed down through a cylindrical nozzle with an inner diameter of 5 Qma+ attached to the bottom of a tundish, and argon gas was injected into the molten steel flow. Detailed conditions are shown in Table 1.

The presence or absence of macroscopic analysis of the finally obtained ingots in each of the above Examples and Comparative Examples was investigated, and the results are also shown in Table 1.

As is clear from Table 1, in the cases of Example 1, Example 2, and Comparative Example 1, almost no macro-segregation was observed in the ingots, and it was confirmed that they had the same quality. In particular, in the case of Example 1 and Example 2 of this invention, compared to the case of Comparative Example 1 using a cylindrical nozzle,
Approximately 10 times the casting speed (150
I was able to obtain 0kM spear).

On the other hand, in Comparative Example 2, the diameter of the cylindrical nozzle attached to the bottom of the tundish was increased to 50Q11 and the casting speed was increased to 1000 klJ/m+. Even if it was increased to /-, the molten PA flow was too thick to form droplets sufficiently, and macroscopic wind bending occurred in the ingot. Therefore, it can be seen that in the case of the conventional method, it is not possible to obtain a high quality ingot without macroscopic dust precipitation at a high pouring speed.

Effects of the Invention As is clear from the above explanation, according to the spray casting method of the present invention, a high-quality ingot free of macro-segregation can be obtained at a much higher casting speed than before. The productivity of spray casting can be dramatically increased. Furthermore, according to the spray casting method of this invention,
Unlike when multiple cylindrical nozzles are used in the past, there is no unevenness in the quality of the ingot due to uneven flow rates of molten metal or uneven cooling capacity between the nozzles, and equipment In general, there is no need to double the number of windows, so maintenance and inspection are easy, and gas consumption for spraying and turning molten metal into droplets can be reduced.
A significant effect can be obtained.

[Brief explanation of drawings]

Figure M1 is a partially cutaway front view schematically showing an example of a situation in which the method of the present invention is implemented, Figure 2 is a vertical view of the flange of Figure 1, and Figure 3 is a diagram showing the situation in which the method of the present invention is implemented. Fig. 5 is a partially cutaway front view schematically showing an example of a pond in a situation where the method of the present invention is applied.
It is a graph showing the wJ relationship between the thickness of a film-like molten steel flow and the flow rate of injection gas (argon gas) for spraying and forming droplets. 1...Full melting, 2...Kunditshu,
4... 3 streams of thin film-like molten gold, 6... Droplets, 7...
·mold.

Claims (1)

[Claims] In the spray casting method, the molten metal is sprayed and turned into droplets by spraying high-pressure gas onto the molten metal flow, and the generated droplets are collected in a mold. A spray casting method characterized by spraying high-pressure gas onto a thin film of molten metal to form droplets.