JPH0410557Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Industrial application field] With the recent development of new materials and new functional materials, high purity,
Demand for high quality metals is increasing.

By the way, carbon crucibles used in vacuum induction melting furnaces contain significantly fewer impurities than natural graphite crucibles, making them ideal for melting high-quality, high-purity metals.

For this reason, vacuum induction melting furnaces have recently come into the spotlight as melting furnaces for processing these high-quality, high-purity metals, and new demand for them is on the rise.

The present invention relates to a vacuum induction melting furnace suitable for such uses.

[Prior Art] A conventional vacuum induction melting furnace, as shown in FIG.
Mold 6, induction coil 7, furnace tilting mechanism 8, material addition bucket 9, gate valve 10, bucket lifting mechanism 1
1. Material insertion door 12. Vacuum pump (not shown)
connecting portions 13, 13' communicating with evacuation paths such as
It was comprised of a vacuum chamber 14 and a door 14'.

The gate valve 10 has a through hole 10a through which the material addition bucket can pass, as shown in FIG.
Although this through hole 10a is normally closed, it can be moved to a course position for vertical movement of the bucket when necessary.

In addition, a gate valve 10, a bucket lifting mechanism 11,
A material addition device 15 was constituted by the material insertion door 12 and the connecting portion 13' of the evacuation system.

The working steps performed using a conventional vacuum melting furnace are as follows.

Inserting the material to be melted into the crucible.

Exhaust the vacuum chamber (usually to about 0.1Pa).

Turn on the high frequency inverter switch and start heating.

melted to a given temperature (e.g., for copper alloys)
After heating (1100°C to 1500°C), a predetermined metallurgical treatment (for example, addition of a trace amount of alloying material) is performed.

The melting furnace is tilted and tapped, and the melt is cast into a mold.

Leave it as is and wait until the temperature of the crucible drops below 400℃.

Air is introduced into the vacuum chamber to create atmospheric pressure, and the vacuum chamber door is opened. Remove the casting and prepare the mold.

Return below.

[Problems that the invention aims to solve] Two engineering problems have been pointed out with conventional vacuum induction melting furnaces: it is difficult to dispose of floating slag, which has low productivity, and slag gets into the product during casting. There is. This is due to the following reason.

That is, as shown in Fig. 2B, even if solid materials are fully loaded into the crucible 1 of the induction furnace, voids occur between each material, so the bulk specific gravity of the material is 30 to 60% larger than the true specific gravity. It can be said to be a void part. Therefore, even if the material is melted in the state shown in (B), the level of the material after melting down becomes the level B as shown in (c), resulting in a shortage of molten metal by B-A with respect to the rated capacity level A.

In the conventional vacuum induction melting furnace, in order to add this insufficient amount after the material burns through, it is equipped with an addition device 15 and performs the following operations.

That is, the material to be added is added to the bucket 9 located in the upper position indicated by the two-dot chain line, the door 12 is closed, and the inside of the addition device 15 is evacuated to the same vacuum condition as the inside of the vacuum chamber 14. After that, the gate valve 10 was opened and the bucket 9 was lowered from the upper position by the lifting mechanism 11, and the bottom was opened at a position directly above the crucible 1 to charge the material.

For this reason, an additional addition device 15 is required, and this addition process requires time, which is a factor in reducing productivity.

Next, the floating slag generated during melting will be described. This slag is caused by non-metal inclusions contained in the material itself, impurities in the crucible with an oxidized surface layer, residue of the previous melt that adhered to the inner surface of the crucible and oxidized, and metals with a strong tendency to oxidize react with residual oxygen in the vacuum chamber. This occurs due to oxide film, etc.

By the way, the molten metal 2 induced and melted in the crucible 1
When pouring molten metal into the mold 6 by the tilting mechanism 8 for casting, as shown in FIG. 2D, the floating slag 16
can get mixed into the product, causing problems. Therefore, even if an attempt was made to remove the floating slag 16 before tilting, it was extremely difficult to manually remove the floating slag 16 because the crucible 1, the tilting mechanism 8, and other devices are all located within the vacuum chamber 14.

The object of the present invention is to provide a vacuum melting furnace that solves these problems.

[Means for Solving the Problems] An embodiment of the present invention shown in FIG. 1 will be described below. In the same figure, components equivalent to those in FIG. 2 are designated by the same reference numerals.

In the present invention, the structure of the crucible 1 constituting the induction furnace is modified as follows, and the other structure may be the same as that in FIG. 2 except for the addition device 15 .

That is, as shown in Fig. 1A, the crucible 1 of the present invention extends its side wall by a length L above the molten metal surface level B of the rated capacity (longer by △L compared to the conventional crucible). , hot water outlet hole 1 on the side wall of the crucible
7 is provided so that when the crucible 1 is tilted to tap the hot water, the tap hole 17 is located below the level of the hot water during most of the time of the tap process.

Note that this tapping hole 17 is usually circular as shown in (B), but it may have a shape other than this, for example,
Various shapes such as rectangle, diamond, triangle, etc. can be substituted.

Further, in the above embodiment, the crucible 1 is a carbon crucible using so-called artificial graphite, but the present invention is not limited to this. However, it is preferable to use a carbon crucible for the following reasons. In other words, in the case of a carbon crucible, because it is electrically conductive, the crucible itself heats up and reaches a high temperature, melting the point of contact with the melted material, which often occurs in a vacuum induction furnace using a general ceramic non-conductive crucible. This is because the problematic shelf-hanging phenomenon (a phenomenon in which the upper material bridges due to frictional force with the wall and prevents it from falling naturally) does not occur. This is advantageous in the case of the preferred method of initially charging a large amount of undissolved material corresponding to the total dissolved amount, which will be described later.

In the above embodiment, the case where the crucible 1 is constructed integrally has been explained, but the crucible 1 is divided into two parts, the lower crucible which has relatively high wear and the upper extension part which has relatively little wear. It is also possible to replace only the lower crucible when the crucible becomes unusable due to wear and tear.

[Function] As mentioned above, since the vacuum induction melting furnace of the present invention is longer than the conventional one by an amount L above the molten metal level B of the rated capacity, the material that can be initially stored in the crucible 1 is also as shown in C. can do more than traditional ones.

Therefore, by setting the length L of the above-mentioned extension to an appropriate value, it is possible to make the molten metal level A after burn-through coincide with the level B, as shown in d. Therefore, the addition device 15 , which was necessary in conventional devices of this type, is no longer necessary.

In addition, in the present invention, since the tapping hole 17 is arranged on the side wall of the crucible as described above, when the tilting mechanism 12 is operated to tap the melt from the crucible 1 into the mold 6, in most cases, the tapping hole 17 is placed as shown in E. is located below the molten metal level, so that only molten metal can be supplied into the mold 6, and floating slag can be prevented from entering.

In addition, in the final step of the above hot water tapping process, the hot water tap hole 1
7 and the molten metal surface level, the floating slag is mixed into the molten metal and supplied, but at this stage, it is a problem because it corresponds to the feeder part and not the product part for the mold 6 side. No.

In addition, in the vacuum induction melting furnace of the present invention, the crucible 1
At first glance, the side walls of the
The vacuum chamber 15 becomes larger, giving the impression that equipment costs will increase. However, for the following reasons, this does not lead to an increase in the size of the vacuum chamber.

That is, in the present invention, the upper and lower (right end) positions P and Q of the induction furnace that rotates around the tilting shaft 5 are
is displaced as shown by the broken line in FIG. However, as shown in Figure A, the trajectory radius of Q falls within the volume of the vacuum chamber even if the size of the vacuum chamber is the same as the conventional one, so there is no need to expand the vacuum chamber. It is.

From a practical standpoint, the desirable crucible extension dimensions are as follows.

That is, if we calculate the desired value of the hot water level of the rated capacity mentioned above B and the length L of the crucible to be extended, then when L and B are set in the range of L/B = 0.43 to 1.5, this is the value of the solid material. Considering that it corresponds to 30 to 60%, it can be said that L/B=0.5 to 2.0 is a desirable range.

[Effects of the invention] Since the present invention has modified the structure of the crucible of the vacuum induction melting furnace as described above, the vacuum induction melting furnace of the present invention has the following features compared to the conventional one.

Since the side wall of the crucible is extended by a length L above the rated capacity hot water level B to compensate for the level caused by melting of the melted material, the conventional addition device and addition process are no longer necessary.

As a result, equipment costs have been reduced and productivity has been significantly improved.

The existence of the above-mentioned upper length L makes it possible to tilt and tap the hot water while maintaining the hot water level at a position above the hot water tap, and during most of the time of the tapping process, the hot water tap is kept above the hot water level. Since it is set in the lower position, it is possible to prevent floating slag from being mixed in when the product portion is tapped into the mold.

This has made it possible to significantly improve product quality.

Additional charging of undissolved materials during melting is no longer required, reducing melting work time.
Productivity has improved.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the present invention, in which A is a longitudinal front view, B is a side view of the extended part of the crucible, C and D are longitudinal front views drawn with only the crucible taken out, and H is a longitudinal front view of the crucible. FIG. Figure 2 is a vertical front view showing the conventional one, of which A shows the entire vacuum induction melting furnace, B and C show only the crucible taken out, and D shows the relationship between the crucible and the mold. It is something. Moreover, FIG. 3 is a perspective view of the gate valve in FIG. 2 taken out. 1... Crucible, 2... Molten metal, 5... Tilting axis, 6
...Mold, 7...Induction coil, 16...Floating slag, 17...Tap hole.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In a vacuum induction melting furnace in which molten metal is stored in a crucible placed in a vacuum chamber and nonferrous metals, etc. are melted by induction heating of the crucible in a vacuum atmosphere, During most of the process of extending the side wall of the crucible of the induction melting furnace by a length L above the molten metal surface level B of the rated capacity, forming a tap hole in the side wall of the crucible, and tilting the crucible to tap the hot water, A vacuum induction melting furnace characterized in that the outlet is configured to be located below the level of the molten metal. 2 Utility model registration claim 1 in which the side wall of the crucible is extended so that L/B is in the range of 0.5 to 2.0
Vacuum induction melting furnace as described in . 3 Claim No. 1 for utility model registration in which the crucible is configured to be divisible into the extended portion and the lower crucible.
Vacuum induction melting furnace as described in .