JPS6057418B2 - Method and device for producing unidirectionally solidified material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for producing unidirectionally solidified materials such as carbon steel, low alloy steel, alloy steel, and heat-resistant alloy, and particularly to a method and apparatus for producing unidirectionally solidified materials such as carbon steel, low alloy steel, alloy steel, and heat-resistant alloy. The present invention relates to a method and apparatus for producing directionally solidified materials.

Carbon steel, low-alloy steel, alloy steel, heat-resistant alloy, etc., are unidirectionally solidified to have particularly excellent mechanical properties in a specific direction, and are therefore used for special purposes.

The metallurgical requirements for obtaining a unidirectionally solidified material are to make the thermal gradient during solidification as large as possible [temperature gradient (temperature difference/distance) in the liquid phase-solid phase direction near the solidification interface], and to increase the solidification rate [ An example of this is to control the advancing speed (distance/time) of the solidification interface to be appropriately smaller than the thermal gradient.

Conventionally, in order to obtain a unidirectionally solidified material, a method has generally been adopted in which the above-mentioned metallurgical requirements are satisfied by adding a heating coil, a chill plate, and a metal bath for rapid cooling to the casting method. The casting method is extremely difficult and disadvantageous in principle, as it involves filling the mold with molten metal all at once and then rapidly solidifying and cooling the high-temperature liquid phase, and it is also difficult and disadvantageous in terms of equipment to obtain small-sized materials. Laboratory-scale furnaces and practical furnaces for producing medium-sized materials require an atmosphere chamber and are complicated to operate through the chamber.

By the way, in the normal electroslag remelting method, new high-temperature molten metal is always supplied from the electrode above the molten metal pool while the molten metal is solidifying below the molten metal pool in the metal for solidification and forming. It is theoretically advantageous to obtain a large thermal gradient and control the solidification rate, which are the metallurgical requirements for directional solidification, and if this is applied, it is possible to produce unidirectionally solidified materials of practical size using relatively simple equipment. 1. Easy to manufacture
It is thought that it can be done.

Therefore, the present inventors applied this ordinary electroslag remelting method to produce a long unidirectionally solidified material having the same cross-sectional shape in the length direction using a partial mold for ordinary molten metal solidification forming. We have separately developed a manufacturing method and equipment for use in the gate.

However, with this method and apparatus, it is not possible to produce a unidirectionally solidified material whose cross-sectional size and shape change in the length direction. As a result of further research, the present inventors found that by adding control of the molten metal solidification interface shape and increase of the thermal gradient using an electromagnetic induction heating coil to the conventional electroslag remelting method using a conventional full-form mold. , advantageously small to multiple cross-sectional shapes
Having obtained the knowledge that a medium-sized unidirectionally solidified material can be produced, the method of the present invention was developed.

That is, the method of the present invention is performed by heating the outer peripheral layer of the molten metal pool from the lateral direction using an electromagnetic induction coil in the conventional electroslag remelting method using a general mold for solidifying and forming molten metal. In this method, a unidirectionally solidified material having a cross-sectional dimension and shape that changes in the length direction is produced by making the molten metal solidification boundary surface flat and increasing the thermal gradient during solidification.

Figure 1 shows a general mold for solidifying and forming molten metal (hereinafter referred to as
1 is a schematic cross-sectional view showing a conventional electroslag remelting method performed using a full-form mold.

In FIG. 1, when an electrode material 1 having the same chemical composition as the product is fed into a slag bath 3 by an electrode supply device 2 and energized by a power source 4, the electrode material 1 becomes a droplet 5 due to the electroslag melting phenomenon and becomes a molten metal. The electroslag remelted material 8 dropped into the reservoir 6 and solidified along the solidification interface is sequentially moved into the water-cooled copper mold 1 starting from the starting base plate 9.
It is accumulated inside the 0 and manufactured.

Note that the line 20 indicates an inflow/outflow line for cooling water of the water-cooled copper mold 10. By the way, the water-cooled copper mold 10 shown in FIG. 1 cools not only the solidified electroslag remelted material 8 but also the molten metal pool 6, so that the molten metal in the molten metal pool 6 flows downward. The solidified electroslag remelted material 8 is passed through to the starting base plate 9.
It is cooled by heat transfer in two directions: heat transfer to and lateral heat transfer to the water-cooled copper mold 10, and as a result, the shape of the solidification interface 7 becomes V-shaped as shown in the figure. .

On the other hand, the crystallographic direction of the solidified material is generally perpendicular to the solidified interface. Therefore, in the conventional electroslag remelting method using the general mold shown in FIG. 1, crystallization occurs in the direction indicated by 15 in the figure, making it impossible to obtain a unidirectionally solidified material. Therefore, in the present invention, an electromagnetic induction heating coil is provided in contact with a general mold (that is, equivalent to the water-cooled copper mold 10 in FIG. 1), and a current-carrying connection terminal is arranged for each turn of the coil. Furthermore, by providing a current-carrying brush that slides on the current-carrying connection terminal, the part of the solidified electroslag remelted material is heated, and the outer peripheral layer of only the molten metal pool part is heated from the lateral direction. , we have developed an apparatus for manufacturing a unidirectionally solidified material having a flat solidification interface shape, a large thermal gradient during solidification, and a cross-sectional shape that changes in the length direction.

FIG. 2 is a schematic sectional view showing an example of an embodiment of the apparatus of the present invention and an aspect of the method of the present invention when carried out using the apparatus.

In FIG. 2, the same reference numerals as in FIG. 1 indicate the same parts as in FIG. A connecting terminal 12 is disposed, and the energizing connecting terminal 12 is further provided with an energizing brush 13 that sequentially slides upward as the electroslag remelting process progresses. The heating current is communicated only to the portion of the electromagnetic induction heating coil 11 that is in contact with the current-carrying brush 13.

In FIG. 2, only the electromagnetic induction heating coils 11 in the horizontally adjacent portions of the molten metal pool 6 are energized by the electromagnetic induction heating power supply 14 of an appropriate frequency to heat the outer peripheral layer of the molten metal pool 6. Therefore, the heat of the molten metal in the molten metal reservoir 6 is transferred to the starting table 9 through the solidified electroslag reprocessed material 8 below, and a portion is also transferred to the water-cooled copper mold 10 below. Although it is cooled by heat transfer,
Nevertheless, the shape of the solidification boundary surface 7 is flat as shown in the figure, and the crystallization direction of the solidified material is generally perpendicular to the solidification boundary surface, so that the solidification material crystallizes in the solidification direction indicated by 15 in the figure.

In this way, the molten metal reservoir 6 is not only heated by the energy from the power source 4 through the electrode material 1, but also
Since it is also heated by the electromagnetic induction heating coil 11, it is maintained at a high temperature, and therefore the thermal gradient near the solidification interface 7 becomes large, resulting in an ideal unidirectionally solidified material. This is because the solidified material 8 is formed as a small triangular lump with a small heat capacity near the solidification interface 7 in FIG. This is in contrast to the case where the thermal gradient becomes smaller. The directionally solidified materials of carbon steel, low alloy steel, alloy steel, and heat-resistant alloy produced by the method and apparatus of the present invention explained above are as follows:
Used for gas turbine stationary blades and moving blades, steam turbine blades, tension bolts for steam turbine casings, etc.

EXAMPLE The present invention was applied to a gas turbine blade material in the following manner.

Material: SUS3O4 Solidified material dimensions: Plate width 7c) Tlrln x thickness 10~2h x length 300Tn1n (gas turbine blade section assumption)
(The test was conducted with a constant cross-sectional shape in the length direction to facilitate mold production.) Mold: Water-cooled copper general mold Electroslag remelting conditions
: Melting power: approx. 500A x 45V (weakly basic slag) Solidification rate: approx. 25-50m/Min Electromagnetic induction heating conditions: 4.8K pressure, approx. 100A x 300cm
(Total efficiency approximately 20%) The cross-sectional structure of the unidirectionally solidified material obtained in the above manner is as shown in the photograph in Figure 4.
As a result, it can be seen that the direction is approximately the solidification direction as shown by 15 in FIG.

Note that FIG. 4 shows the cross-sectional structure of the shaded area in FIG. 3, and FIG. 4A shows a solidification rate of approximately 25Tfn/Min.
, Figure 4B shows a solidification rate of about 30W! &/MinlFigure 4C
These are the results obtained at a solidification rate of about 50 m/min.

Further, for reference, SUS3O was manufactured by a conventional electroslag remelting method at a solidification rate of about 30 mm/min, which is similar to the above.

This result is as shown in the photograph of the cross-sectional structure in FIG. The figure is the third
This figure shows a cross-sectional tissue surface of the shaded area in the figure.・
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic sectional view showing a normal electroslag remelting method carried out using a general mold, and Fig. 2 shows an example of an embodiment of the device of the present invention and an example of the method carried out using the same. FIG. 2 is a schematic cross-sectional view showing an embodiment of the method of the present invention when

Claims (1)

[Claims] 1. In the ordinary electroslag remelting method using a general mold for solidifying and forming molten metal, the outer circumferential layer of the molten metal pool is laterally heated by an electromagnetic induction heating coil. A method for producing a unidirectionally solidified material. 2. An electromagnetic induction heating coil is provided in contact with a general mold for solidifying and forming molten metal used in the ordinary electroslag remelting method, and a current-carrying connection terminal is arranged for each turn of the coil, and the current-carrying connection terminal is arranged for each turn of the coil. A device for producing a unidirectional solidifying material, characterized in that it is provided with an energized brush that slides on a terminal.