JPS62131184A - Hearth for metallurgical device using eutectic metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a so-called cooling hearth for metallurgical equipment suitable for vacuum metallurgy equipment such as plasma melting furnaces and electron beam (EB) melting furnaces.

(Prior Art) In recent years, metallurgical equipment developed for high-purity melting of metal materials, such as vacuum metallurgical equipment such as plasma melting furnaces and EB melting furnaces, has a so-called cooling system that plays the role of melting and cleaning raw materials. A hearth is provided, which (i) adversely affects the vacuum, (ii) in the case of melting titanium or its alloys, etc.

Refractories such as ceramics cannot be used because they are active and contaminate the molten metal.

Therefore, in conventional hearths, an insert is provided in the part that comes into contact with the molten metal, a material with high thermal conductivity such as copper is used for this insert, and this is directly cooled with cooling water.

That is, for example, as shown in FIG. 3, such a hearth is composed of a copper insert 4 and a water cooling jacket 5. It has a structure in which cooling water is circulated through a conduit 7 for cooling. The reason why the hearth is cooled with cooling water in this way is to (i) maintain the high-temperature strength of the copper insert 4, and (it) maintain the temperature of the seal portion 6 below the operating limit temperature of the sealing material. This is because it is necessary to maintain the temperature below a certain level by considering two conditions. Generally, to meet the above two conditions, the maximum temperature of the hearth copper insert is 200°C.
The temperature is set to below ~300°C.

(Problem to be Solved by the Invention) However, in the hearth with the above structure, the copper insert and the hearth jacket must be assembled, and the structure must be such that water does not leak in that state and that cooling channels can be secured. Therefore, machining precision is required for manufacturing, which increases costs and also poses safety problems. Also, since it is necessary to keep the copper insert that comes into contact with the molten metal at a temperature considerably lower than the molten metal temperature (200 to 300°C), it is difficult to maintain the temperature during melting, etc. 8 The amount of heat lost from the hot water to the cooling water inevitably becomes large, which has the disadvantage of increasing energy costs and increasing unit consumption.

An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques and to ensure safety without requiring high machining accuracy.

In addition, the amount of heat removed during melting and other operations can be minimized,
The object of the present invention is to provide a hearth for metallurgical equipment that enables reduction of basic unit consumption.

(Means for Solving the Problems) In order to achieve the above object, the present inventor investigated a hearth structure that does not actively adopt a conventional forced cooling structure, and found that the material of the hearth is different from that of the molten metal. We have found that this is possible by making selections based on the following relationships. That is, the hearth is made into an integral structure consisting only of an insert made of the same or substantially the same material as the molten metal to be treated.

The present invention will be explained in detail below based on illustrated embodiments.

(Embodiment) FIG. 1 shows a hearth structure of an EB melting furnace according to an embodiment of the present invention, in which 1 is a hearth (insert), 2 is a hearth support, and 3 is a thermal lightning pair.

The hearth 1 has an integral structure consisting only of an insert, and is made of the same or almost the same material (common metal) as the molten metal M to be treated.
It consists of Here, the term "substantially the same material" does not mean that the composition of the molten metal to be treated and the content range of alloying elements or impurities must strictly match; This allows for inevitable variations in component composition during processing such as oxidation. The hearth 1 can have any suitable shape, and fins can be provided on its outer wall.

Although the hearth support 2 can be disposed on the hearth 1, it should be noted that the two are not connected. The hearth support 2 has a water-cooled pipe structure, and is provided to support the hearth 1, and the original purpose of making it water-cooled is to cool the hearth support itself and its mounting position.

Reference numeral 3 denotes thermal lightning pairs, which are embedded in the side walls, bottom, etc. from the outside at appropriate locations and numbers, as shown, for monitoring the temperature of the hearth 1. It can be used to detect and warn when the temperature of the hearth 1 exceeds a predetermined value due to abnormal operation, etc., and also to adjust the temperature of the hearth by increasing the amount of cooling water in the hearth support 2 for safety. is possible. Note that the predetermined temperature of the hearth 1 is determined from the melting point, high temperature strength, etc. of the hearth.

In the hearth with the above configuration, heat release to maintain the hearth temperature above its melting point during processing operations relies exclusively on radiant heat transfer from the hearth. The cooling water in the hearth support 2 only plays an auxiliary role.

Incidentally, it is clear from the following calculation example that in this common metal hearth, thermal equilibrium can be maintained only by thermal radiation from the outer wall of the hearth.

When the molten metal to be treated is pure Ti and the hearth is also made of pure Ti, the following equations (1), (2), and (3) hold true (see FIG. 2).

Q=t v (T, '-300') = 2.93 X 10-'' (T, '-300')...
...(1) Q=α1 (T r T x ) =500 (2023-T,) ...(2) Q
=λ(T,-T,)/(HX i O-3)=250(
T□-T2) ... (3) Here, Tr ("C]: 2023 ('K) at the molten Ti temperature a, (Kca Q / m thr + deg,):
The heat transfer coefficient between molten Ti and hearth is 50 from experimental results.
0 (Kca Q / m・hr・℃) T, same K]: Temperature on the molten metal side of the hearth wall T2 ('K): n Outside temperature E = emissivity, Q (Kca Q) as 0.6 : Radiant heat λ (Kca Q 1m-hr-deg, , ): Thermal conductivity of Ti (solid), set to 10 (Kca12/m-hr-' K): Boltzmann constant Equations (1) to (3) above Therefore, T1 and T2 are each Tyoi1809('K]=1536('C)//T2≠1
382jiK) = 1109 ('C)//, and T1
Since the melting point of is 1670°C, it can be seen that thermal equilibrium is established. In addition, in an actual metal hearth, the radiation area is larger than the contact area with the molten metal, so T1,
T2 tends to be lower than the above calculated value.

It should be noted that although this embodiment has been described with respect to an EB melting furnace, it goes without saying that the present invention can be similarly applied to a plasma melting furnace or other metallurgical equipment.

(Effects of the Invention) As described in detail above, according to the present invention, the hearth is made of the same or substantially the same material as the molten metal to be treated, and only the insert 1 does not have a forced cooling structure. Since it is an integral structure, since there is no sealing part, it does not require processing precision as much as a conventional hearth structure, which reduces manufacturing costs and is advantageous in terms of safety and maintenance. Additionally, although it depends on the hearth material, the temperature of the part of the hearth that is in contact with the molten metal, which is the highest temperature area, can be raised to near the melting point, which significantly reduces the amount of heat removed from the hearth compared to conventional hearths. Therefore, it is possible to reduce the basic unit. In particular, plasma melting furnace, EB
Suitable for vacuum metallurgy equipment such as melting furnaces.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the hearth structure of an EB melting furnace according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the thermal balance during molten metal processing in the above hearth structure, and Fig. 3 is a conventional cooling method. It is an explanatory sectional view showing a hearth and its cooling structure. 1... Hearth (insert), 2... Hearth support. 3.Thermocouple, 4.Copper insert, 5.
...Water cooling jacket, 6...Seal, 7...Cooling water conduit, M...Molten metal. Patent applicant Takashi Nakamura, Patent attorney representing Kobe Steel, Ltd. Figure 1 Figure 2 H = 40 (IvIffl)

Claims (1)

[Claims] A metallurgical device equipped with a hearth that receives molten metal for melting, cleaning, etc. of raw materials, characterized in that the hearth has an integral structure with only an insert made of the same or substantially the same material as the molten metal to be treated. Hearth for metallurgical equipment using common metal.