JPS644573B2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an arc melting method.

The arc melting method is used to melt steel and alloys that require a high level of quality.
The remelting method is generally widely used.

In this VAR method, as shown in FIG. 1, a consumable electrode 50 is inserted into a water-cooled copper mold 51, and the electrode
0 and the bottom of the mold 51,
This is a method of melting the electrode 50 and refining the metal.

However, in the case of this method, since the temperature of the melting pool is high and the mold 51 is water-cooled, there is a large temperature gradient inside the cast metal, resulting in the formation of coarse granular crystals, which significantly impairs subsequent workability. There were flaws that damaged it. Also, when making alloys of high-melting point metals such as Nb-Ti, there was a drawback that manufacturing the electrodes was expensive. Furthermore, side arcs are likely to occur between the electrode 50 and the side wall of the water-cooled copper mold 51 due to warping of the electrode 50 due to thermal stress, and there is a risk of burnout of the mold 51 and explosion due to reaction between cooling water and molten metal. Furthermore, because the shape of the mold 51 is limited to a cylindrical shape due to the characteristics of the arc, only cylindrical ingots can be obtained, which has the drawback of significantly lowering the yield when making slabs.

On the other hand, as shown in FIG. 2, a pair of consumable electrodes 52, 52 are placed horizontally opposite each other on a non-water-cooled mold 53, and an arc A is generated between the electrodes in a vacuum, and the heat causes the electrodes to VADER to dissolve
(Vacuum Arc Double Electrode Remelting)
The law is known. In this method, the above VAR
Compared to the method, there is no risk of arcing between the ingot and the mold, and there is no restriction on the shape of the mold, which has the advantage that ingots of arbitrary shapes can be obtained. In addition, when the electrode melts, droplets fall immediately, so it solidifies with a low degree of superheating. Therefore, the crystal structure is fine and workability is good, but metals with a high melting point may not melt sufficiently, and there is a risk of leaving a pock-like shape. There is. In addition, there are drawbacks such as difficulty in controlling the temperature of the droplets and molten pool.

Note that this VADER uses two electrodes, so if different metals are used for each electrode, separate droplets will be generated, and in principle it is possible to alloy them in a pool, but depending on the temperature of the pool Because of the low metallurgy, uniform alloying is difficult, and in reality, VADER is only a method of remelting metals with the same composition.

The present invention has been made to improve the above-mentioned drawbacks of the conventional technology, and allows for uniform melting without the need for complicated pretreatment, the ability to arbitrarily control the temperature of the melt pool, and the ability to freely control the crystal structure. The purpose of this project is to provide an arc melting method that allows accurate control of alloy composition.

For this purpose, the present invention arranges a plurality of consumable electrodes horizontally or downwardly facing each other on a mold so that their extension lines intersect, and connects each electrode to the mold and the mold in a vacuum or an inert gas atmosphere. The basic feature is that an arc is generated between the remelted ingots.

The method of the present invention will be explained in detail with reference to FIG.

1 and 2 are consumable electrodes, respectively, which are placed on a water-cooled copper mold 3. The electrodes 1 and 2 are placed obliquely downward and facing each other so that their extension lines intersect with each other. In this example, there are two electrodes, but the number may be increased to three or four if necessary. This electrode 1,
2 can be slid in its longitudinal direction,
It is constructed so that the tip of the electrode can be drawn out as it melts and the gap between the electrodes can be adjusted. Further, the electrodes 1 and 2 are movable in the vertical direction, so that the gap between them and the bottom 30 of the mold 3 or the remelted ingot 4 can be adjusted.

Further, in this embodiment, a pull-out mechanism 5 is provided at the bottom 30 of the mold 3, so that the ingot 4 is gradually pulled out from the bottom as melting progresses. This is because the method of the present invention uses a plurality of electrodes, and the electrodes are not inserted into the mold 3 but placed above it. This is because it is preferable to configure it as follows.

In the above arrangement, an arc is generated between the electrodes and between the electrodes and the ingot 4 in a vacuum or an inert gas atmosphere to melt the ingot. At this time, the temperature of the melting pool, etc. is controlled by adjusting the gap between the electrodes 1 and 2 or the gap between the electrodes 1 and 2 and the ingot 4, as well as the voltage and current between the electrodes or between the electrodes and the ingot.

For example, if the arc between electrodes 1 and 2 and the arc between the electrodes and the ingot are controlled separately, the droplet temperature and pool temperature can be controlled, which is different from conventional VAR and
The shortcomings of VADER can be improved.

Needless to say, it is also possible to perform the same function as VAR by generating an arc only between electrodes and ingots, or it is possible to perform the same function as VADER by generating an arc only between multiple electrodes. is also possible.

As described above, in the method of the present invention, the melting temperature can be optimally controlled, and as a result, the crystal structure can be easily controlled and voids within the ingot can be prevented. In addition, you can obtain ingots with healthy structure and internal quality.

Furthermore, the method of the present invention also allows the production of alloys of high melting point metals. In other words, when making an alloy of two or more metals, each metal usually does not have the same melting point; for example, Nb-
In case of Ti alloy, melting point is Nb: 2500℃, Ti: 1700℃
There is a difference of 800℃. These dissimilar metals can be
When dissolved as a consumable electrode using VADER, Ti dissolves faster and in larger amounts, making it difficult to form the required alloy component. In the method of the present invention, by shortening the gap between the Nb electrode and the ingot 4 or by increasing the current voltage therebetween, Nb, which has a high melting point, can be melted quickly, making it possible to precisely adjust the alloy composition. . Furthermore, since the temperature of the molten pool can be maintained at a high temperature, a uniform alloy can be obtained. Note that during alloy production, the molten pool may be maintained at a high temperature and metal of the same type or different type as the electrode may be added in the form of powder or wire.

Note that in the present invention, the shape of the remelted ingot does not have to be round, but can be square, hollow, etc.
Shape) Can be cast. Furthermore, there is no risk of contact between the mold 3 and the electrodes 1 and 2, and the drawbacks of the VAR method, such as no side arcs, are eliminated.

FIG. 4 is a wiring diagram of electrodes and ingots when carrying out the present invention. In the figure, A, B and C indicate the terminals of the electrodes 1 and 2 and the ingot 4 in FIG. Figure 4A uses a DC power supply, and switches SW ₁ and SW ₂ , which are made up of switching elements such as transistors, are operated in conjunction to alternately apply voltage between E and Lo and between E and H or LO. It is configured to be used. The operating speed of the switches SW ₁ and SW ₂ shall be such that the arc can be easily ignited when it is extinguished and then re-ignited. Note that VR ₁ and VR ₂ are variable resistors.

FIGS. 4B and 4C show the case where three-phase alternating current is used; B is the case where a star connection transformer is used, and FIG. 4C is a case where a delta connection transformer is used. WT is a variable reactor,
This allows the current to be adjusted independently. In addition, Figure 4 is an example of wiring,
It is not limited to this. Also, circuit a,
It is also possible to use B and C by connecting them to three electrodes.

As described above, according to the arc melting method of the present invention, the drawbacks of VAR and VADER can be overcome, and uniform melting, free control of crystal structure, precise control of alloy components, etc. are possible.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of the prior art, FIG. 3 is an explanatory diagram of the method of the present invention, and FIG. 4 is a wiring diagram of a power supply when implementing the method of the present invention.

Claims (1)

[Claims] 1. Arranging multiple consumable electrodes horizontally or downwardly facing each other on a mold so that their extension lines intersect, and generating an arc between each electrode and between each electrode and the remelted ingot in a vacuum or inert gas atmosphere. Arc melting method characterized by: