JPH02220739A - Heating mold for continuous casting - Google Patents

Abstract

PURPOSE:To manufacture a mold having excellent oxidizing resistant and wettable characteristics by using boron nitride to the mold material, using a binder and forming it with the use of a heating mold type continuous casting method. CONSTITUTION:The mold 2 is fitted on the wall face of the molten metal holding furnace 1 and heated at more than m.p. of casting metal with a heating device 3 and molten metal 4 is supplied in the mold 2 and drawn out from the outlet of the mold 2 with pinch rolls 5. A drawn cast billet 6 is water-cooled with a cooling device 7 arranged near the outlet of the mold 2 and the molten metal 4 in contact with the cast billet 6 in the mold 2 is continuously solidified. Then, the material of the mold 2 is made of the boron nitride and formed by using the binder (B2O3, CaO powder, etc.). By this method, the stable casting for long time is executed and the cast billet 6 having excellent quality is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heating mold for a continuous casting device, and particularly to one that can stably obtain high-quality ingots over a long period of time.

[Conventional technology]

Among continuous metal casting methods, heated mold continuous casting (hereinafter referred to as O
There is a law (abbreviated as CC).

As shown in Figure 1, this casting method involves attaching a mold (2) to the wall of a molten metal holding furnace (1), and then using a heating device (
3), the molten metal (hereinafter referred to as molten metal) (4) is heated above the melting point of the cast metal and supplied into the mold (2), and the ingot is pulled out from the outlet of the mold (2) by pinch rolls (5). (6) near the outlet of the cooling device (7)
) to continuously solidify the molten metal (4) in contact with the ingot (6) in the mold (2).

The feature of this method is that the solidification of the molten metal (4) does not proceed from the outer surface part as in the case of using a cooling mold, but starts from the inside and the final solidification part is the surface of the ingot (6). The purpose of this method is to obtain a unidirectionally solidified structure of excellent quality both inside and on the surface of the ingot.

[Problem to be solved by the invention]

In the above OCC method, the mold used is conventionally graphite or S.
Materials such as iC are used. Among these, graphite molds are difficult to wet with molten metal and have high lubricity, so even if the finished roughness of the mold's inner surface is around 124 obtained by general boring, the outer diameter is less than 0.5 ma1. It is possible to cast ingots with extremely small diameters, and the quality of the obtained ingots is also good.

However, since graphite is susceptible to oxidation loss, its lifespan as a mold is short at 20 to 30 hours.

On the other hand, SiC molds have very little oxidation wear (the mold life is sufficient, but due to poor wetting characteristics with the molten metal, the inside surface of the mold must be polished to 0.8 mm or less by lapping), which increases production costs. However, even with such precision finishing, the quality of the resulting ingot is slightly inferior to that of graphite molds.In addition, the inner diameter that can be lapped is 5 mm or more, so the outer diameter of It is impossible to cast an ingot of less than @1.

[Means for Solving the Problems] In view of this, the present invention has developed a heating mold for continuous casting that has excellent oxidation resistance and wetting properties as a result of various studies.

That is, in the present invention, into a mold heated above the melting point of the cast metal,
In heating molds, the molten metal is supplied from one end, the ingot is drawn out from the other end, and the molten metal in contact with the ingot is solidified continuously within the mold.
It is characterized by being molded using a binder.

[Effect]

The reason why we chose BN as the material for the heating mold is that BN has wetting properties equivalent to graphite, has oxidation resistance properties equivalent to SiC, and has low reactivity with molten metal, so it is stable for a long time. This is because ingots of excellent quality can be obtained.

Further, as the binder, B, 03 or CaO powder can be used.

〔Example〕

Next, the present invention will be explained in detail.

<Example! > B 203 and CaO powder as a binder were blended with BN powder, thoroughly kneaded, molded using a hot press method, and then sintered to obtain a mold material. Next, the outer diameter of the mold material is 23 mm.
! 1111. A heated mold for OCC was manufactured by molding to an inner diameter of 15 ma+ and a length of 150 mm.

The inner surface is finished by boring only, and its roughness is 12I.
It was a. Further, the BN content of this mold was 99%.

Using this mold and the continuous casting apparatus shown in Figure 1, oxygen-free copper (hereinafter abbreviated as OFC) with a diameter of 15 ffllll was cast.
The ingot was cast at a casting speed of 200IIIff1/set n, a molten metal temperature of 1150°C, a mold temperature of 1100°C, and a cooling water amount of 31°C.
Continuous casting was carried out under conditions of 7 ain.

For comparison, a graphite mold with the same shape as the above mold and an SI mold
A mold made of C was prepared and OFC was continuously cast under the same conditions. At this time, the inner surface of the graphite mold was finished to a roughness of 124 by boring only like the BN mold, while the inner surface of the SiC mold was lapped to a roughness of 0.7-.

For each of these molds, the life of the casting mold and the surface quality of the obtained ingot were investigated, and the results are shown in Table 1. The mold life is expressed as the time until the diameter of the ingot exceeds 15.2++u++, and the surface quality is measured by the roughness of the outer peripheral surface of the ingot.

As is clear from Table 1, the life of the mold No. 1 of the present invention is equivalent to that of conventional mold No. 3 made of SIC, and the surface quality is equivalent to that of conventional mold No. 2 made of graphite mold. . This is because the mold of the present invention has excellent oxidation resistance, so it has a long life, and also has excellent wetting characteristics, so the surface quality of the ingot is also good. As a matter of course, the internal quality was also excellent.

<Example 2> In recent years, small-diameter ingots with a diameter of around 1 mm have come to be used as signal transmission cables for AV without performing diameter reduction processing after continuous casting.

Therefore, the mold material containing 99% BN, which was molded in the same manner as in Example 1, was bored to a mold inner surface roughness of 12.
A mold was formed into a shape of 1 m, outer diameter 10 wm, inner diameter 0.5 m+@, and length 50 cm.

Using this mold and the apparatus shown in Figure 1, a mold with a diameter of 0.5
A mm thick OFC ingot was continuously cast under the same conditions as in Example 1.

At this time, for comparison, a graphite mold and a SiC mold of the same shape were manufactured and the same <OFC was cast. Note that both of these inner diameter holes were bored and the roughness of the inner diameter of the graphite mold was set to 12-, but on the other hand, since lapping cannot be applied to the SiC mold, boring was performed using a diamond tool. Its inner surface roughness was io.

For each of these molds, the lifespan of the casting mold, the surface quality of the obtained ingot, and whether or not continuous casting was possible were investigated, and the results are shown in Table 2.

The mold life was expressed as the time until the diameter of the ingot exceeded 0.5211 In.

Casting such small-diameter ingots requires even higher wetting characteristics between the molten metal and the mold, and the quality of the wetting characteristics determines whether or not continuous casting is possible. Therefore, as is clear from Table 2, molds made of graphite and BN have a diameter of 0.
Casting of 5 mm ingots was easily possible.

However, SIC has poor wetting properties and no self-lubricating properties.
In mold making, the solid phase in the initial stage of solidification breaks due to friction between the molten metal and the ingot within the mold and the mold, making it impossible to continuously draw out the ingot.

Furthermore, the mold life of mold No. 094 of the present invention was 100 hours or more, and the surface roughness of the ingot was 0.2p, both of which were excellent.

<Example 3> As described in <Example 2> above, by casting a small-diameter ingot, it is possible to clearly judge whether the mold material characteristics are good or bad.

Therefore, the content of BN was set to 20.40.60.80 and 9.
Using mold materials variously changed to 9%, <Example 2
), and ingots with a diameter of 0.51 mm were continuously cast for each mold in the same manner as in Example 2.

As a result, continuous casting was possible regardless of the BN content. However, the surface quality of the obtained ingot was proportional to the BN content, and the mold containing 20% BN was the worst. It has also been found that if the mold has a BN content of 40% or more, an ingot can be obtained with almost the same surface quality as a mold with a BN content of 99%.

The reason for this is that by reducing the BN content, the
This is because the amount of powder increases and the wetting properties and self-lubricating properties deteriorate.

<Example 4> In the above examples, continuous casting of OFC, which is pure copper, was described. Next, an example in which a BN mold is applied to continuous casting of copper alloy will be described.

It is known that graphite usually reacts with some metals to form carbides. Therefore, OCC using a graphite mold
In this method, the mold is kept at a high temperature, so this reaction occurs significantly, resulting in the formation of a carbide layer on the inner surface of the mold, which loses its wettability and self-lubricating properties, and when the initial solidification phase ruptures and the degree of reaction increases. It becomes impossible to even pull out the ingot.

For this reason, when a graphite mold is used to cast 65/35 brass containing Aff, which is known as wire-cutting electrode wire, for example, the reaction occurs in a relatively short time after AO is added to the molten 65/35 brass. Aluminum carbide (1
/3AO,C is formed and the mold loses its self-lubricating properties,
It becomes impossible to pull out the ingot.

Therefore, this AO gold-containing 65735 brass was cast using a mold made of BN and the casting apparatus shown in FIG. That is, 65/35 brass having a diameter of 51I1m and containing 1.2% 8% was continuously cast under the conditions of a molten metal temperature of 1000°C, a mold temperature of 950°C, a casting speed of 10 shafts @/sin, and a cooling water amount of 3/min. As a result, no formation of 1/3AOscz was observed, and an ingot of high quality could be obtained stably for a long period of time.

Although copper and copper alloys have been described in the above embodiments, the present invention is not limited to these and can be applied to other metals, and the BN content of the mold of the present invention is determined most appropriately depending on the cast metal. Just choose the appropriate amount.

〔Effect of the invention〕

As described above, according to the present invention, not only is it possible to cast ingots of various sizes using the OCC method, but also stable casting for a long time is possible, and furthermore, conventional graphite molds generate carbides and cannot be cast. This has significant industrial effects, such as making it possible to cast alloys of different types.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing a heating mold continuous casting apparatus. 1.- Molten metal holding furnace 2.-Mold 3. Heating device 4.--molten metal 5- Pinch roll 6- Ingot 7-・Cooling device

Claims (1)

[Claims] (1) A heating mold that supplies molten metal from one end into the mold heated above the melting point of the cast metal, cools the ingot that is pulled out from the other end, and continuously solidifies the molten metal that comes into contact with the ingot within the mold. A heating mold for continuous casting, characterized in that the mold is made of boron nitride and molded using a binder.