JPH01309766A - Method and apparatus for producing cast billet - Google Patents

Abstract

PURPOSE:To produce a high quality cast billet at high casting speed by holding molten metal temp. to lower than liquidus temp., stirring and adding metal powder into the molten metal. CONSTITUTION:The molten metal temp. is held to lower than the liquidus temp. in slurry forming chamber 3 arranged at lower part of a tundish 2. The molten metal in the slurry forming chamber 3 is stirred with a rotator 8. Then, the metal powder 13 in a hopper 12 is added into the molten metal in the slurry forming chamber 3 through a passage 7 forming in the rotator 8. The metal powder is mixed with pressurized gas and supplied. By this method, the high quality cast billet can be produced at high casting speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for producing an ingot from a semi-molten metal slurry.

(Prior Art) Conventional methods for producing ingots from semi-molten metal slurry (hereinafter referred to as slurry) generally involve mechanically shearing dendrites that are formed in the solidification temperature range below the liquidus temperature of the metal. The product is manufactured from the slurry.

This will be explained with reference to FIG. 2, for example.

That is, there is a tundish (2) equipped with a heating element (1) for holding a metal melt field, and a tundish (2) with a melt 1 at the lower end.
A slurry forming chamber (3) equipped with a heating element (1) for maintaining the slurry (19) at a temperature suitable for slurry formation is provided, and below the slurry forming chamber (3), a water-cooled mold ( 5) is arranged, and the slurry forming chamber (
A rotor (8) whose outer periphery is provided with irregularities in the circumferential direction is inserted into the interior of the rotor (8) in order to mechanically shear the dendrites formed in the solidified region of the molten metal.

The molten g (19) is continuously transferred from a holding furnace (not shown) to the tundish (2), and is controlled by a control means (not shown) so that the height of the scene (20) is always constant. Furthermore, the temperature of the molten metal (19) in the tundish (2) is maintained at a temperature 5 to 10°C higher than the melting point of the cast metal, while the temperature in the slurry forming chamber (3) is maintained at the liquid phase of the cast metal. Since the temperature is maintained slightly below the line temperature, the temperature is maintained slightly lower than the line temperature, so that the temperature is
The melt 1 (19) introduced into is cooled to crystallize dendrites, which are immediately sheared by the rotation of the rotor (8) to form
Next, it becomes a solid particle, that is, a cell (solid phase) (21).

When the slurry reaches the vicinity of the insulating material (4) at the outlet of the slurry forming chamber (3), the number of slurries increases and slurry is produced.Subsequently, the slurry is fed into the water-cooled mold (5), where it is cooled and completely removed. It becomes solid and becomes an ingot (18) with a pinch roll (1
7) is continuously drawn out.

(Problems to be Solved by the Invention) However, the quality of conventional ingots obtained by the above method has the following drawbacks.

(1) The crystal has a structure in which cells in the slurry (in the same phase) and dendrites newly crystallized by the liquid phase are mixed.

(2) Added elements segregate.

B. There is a reverse segregation layer near the casting surface.

The concentration of alloying elements in the mouth and center increases.

These defects are due to the following causes.

That is, the solid phase fraction fs due to shearing at the molten metal temperature (2) at which a slurry is to be formed is determined by the following equation (1) from the equation of p fam and the equilibrium phase diagram.

TM: Melting point of pure metal (°K) TL: Liquidus line of alloy (°K) K: Partition coefficient Therefore, the solid phase fraction fs is determined by the temperature T of the molten metal in which the slurry is to be formed; The lower the in-phase rate fs
However, the fluidity of the slurry gradually deteriorates, so the actual molten metal temperature is set near the liquidus temperature. Therefore, in reality, a slurry containing a large amount of liquid and a low homophase ratio is used, and a large amount of latent heat of solidification is present in the slurry. Therefore, it is not possible to provide a sufficient cooling rate during solidification, resulting in low-speed casting, and as shown in Figure 2, the boundary line between slurry and completely solid (ingot) (hereinafter referred to as Zump) (22 ) is caused by the extremely concave shape of the center.

[Means to solve the problem]

In view of this, the present invention has been made as a result of various studies and has developed an ingot manufacturing method and apparatus that can eliminate all of these problems.

That is, the method of the present invention maintains a molten metal in a solidification temperature range below the liquidus temperature of the metal, and further mechanically stirs the molten metal to produce an ingot from a semi-molten metal slurry. It is characterized by adding metal powder to the molten metal being stirred, and it is effective to supply a mixture of pressurized gas and metal powder to the molten metal being stirred.

In addition, the apparatus of the present invention includes a rotor having a stirring section at the tip inside the slurry forming chamber equipped with a heating device that maintains the molten metal in a solidification temperature range below the liquidus temperature of the metal, and rotates the rotor. In an apparatus for producing an ingot from semi-molten metal slurry by rotating its tip stirring part to mechanically stir molten metal, a passage is formed in the rotor,
A hole is provided in the tip stirring section to communicate the passage with the outside, and a mixture of metal powder and pressurized gas is supplied into the passage from the other end of the passage, and the mixture is stirred through the hole. It is characterized by being released into molten metal.

[Function] The purpose of dispersing the metal powder into the molten metal in this way is to use the powder to crystallize the same phase, or to make the powder itself into a solid phase, which is caused by the shearing of the dendrites due to the rotation of the rotor. This is because a slurry with a high solid phase ratio can be formed, and the latent heat of solidification of the slurry can be significantly reduced compared to conventional methods, and the slurry can be solidified at a high cooling rate. have

That is, the in-phase ratio in the slurry can be increased by generating in-phase by shearing the dendrites due to the rotation of the rotor, and by adding metal powder to the slurry forming system to generate in-phase with the metal powder as a core. be.

In addition, by supplying the metal powder mixed with pressurized gas to disperse it in the molten metal, when the gas floats in the form of bubbles in the molten metal, degassing from the molten metal is promoted. ! It has the advantage of having an X-physical effect. Note that the gas may be an inert gas such as N gas or an active gas such as C12 gas. And the gas pressure is FgtA
Set the pressure to be slightly larger than the hydrostatic pressure.

〔Example〕

Next, examples of the present invention will be described.

As shown in Fig. 1, as in the past, a tundish (2) equipped with a heating element (1) and a slurry forming chamber (3) equipped with a heating element (1°) are provided at its lower end, and roughly below it. In an apparatus in which a water-cooled mold (5) is disposed through a heat insulating material (4), a tip stirring part (6) having irregularities formed in the circumferential direction on the outer periphery of the tip is provided from above in the slurry forming chamber (3). ,
A rotor (8) with a hollow passageway (7) formed therein was inserted. One end of the passageway (7) communicates with the external slurry forming chamber (3) through radial horizontal holes (9) provided in each concave portion of the tip stirring section (6), and the other end communicates with the rotor (8). It was connected to the gas supply port (11) in the rotary joint (10) supported at the upper end. There is also a rotary joint (1
0), metal powder (
13) is fed by a spiral shaft (14) and mixed with a pressurized gas (15). Note that (17) indicates a pinch roll for pulling out the cooled ingot (18).

An ingot having an outer diameter of 25 m was continuously produced from a semi-molten slurry of A1-5% Cu alloy using the grooved apparatus as described above.

The inner diameter of the slurry forming chamber (3) was 25 m, the outer diameter of the rotor was 20 m, and the clearance between them was 2.5#. The temperature of the molten metal (19) in the tundish (2) is A1-5
651° 5°C higher than the liquidus temperature (TL) of the %Cu alloy
C, and the melt field temperature in the slurry forming chamber (3) is 635°C.
was held at Then, the rotor (8) is rotated at 300 rpm, and N gas is fed at a rate of 11/min. The dendrites crystallized in this state are sheared to form a slurry with a homomorphic ratio of about 50%. This slurry was introduced into a water-cooled mold (5), and an ingot (18) was drawn out at a casting speed of 50 m/min. When the casting became stable, Shun started the spiral shaft (14) and started the hopper (1).
2) Pure A1 powder of 1 to 50 μm stored in 'l'9/
Continuous addition was started at a rate of min. This direct temperature in the slurry forming chamber (3) decreased by 1-2°C, but
The temperature was restored and kept constant by the action of the temperature controller. Its q17
The casting speed was gradually increased to 0 m/min, and constant speed casting was performed. At this time, the shape of the jumper (22) is formed into a smooth curved surface.

The amount of powder added is 3xlO per minute of casting amount.
-3%, and the influence of alloy composition is negligible.

Diameter 2 obtained by continuous casting using the method of the present invention
The structure of 5M A1-5% OL + alloy ingot is 0.2-0.
4. Degenerate and rounded dendrites were formed. In addition, it has a uniform composition with no segregation of Cu, and such high quality ingots can be cast at a conventional casting speed of 140
% casting speed.

On the other hand, the structure of an ingot produced from a conventional slurry having the same composition was a mixed structure of sheared and degenerated dendrites and dendrites crystallized from the liquid phase.

In the above examples, the A1-5% CLI alloy was explained, but the method of the present invention can also be applied to other metals.

Furthermore, the injection holes for the metal powder provided in the stirring part at the tip of the rotor were provided laterally and radially in this example, but they may also be provided directly below.Although pure Al was used as the metal powder added, cast metal The same kind of powder may also be used.

Although a cooling mold was used as the casting method, the method is not limited to this.

〔Effect of the invention〕

As described above, according to the present invention, an ingot having a uniform dendrite casting structure can be obtained from a slurry with a high solid phase ratio and good fluidity, and furthermore, the ingot has no segregation of solute elements, which is industrially remarkable. This has the following effects.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing one embodiment of the device of the present invention, and FIG. 2 is a side sectional view showing a conventional device. 1.1゛...Heating element 2...Tundish 3...Slurry forming chamber 4...Insulating material 5...・・・・・・Water cooling mold 6・・・・・・・ Tip @ Stirring part 7・・・・・・Passage 8・・・・・・Rotor 9・・・・・・・Side Hole 10...Rotary joint 11...
..... Gas supply port 12 ..... Hopper 13 ..... Metal powder 14 ..... Spiral shaft 15 ....
・・・・Pressure to gas 16・・・・・・・Mixing 17・・・・・・・Pinch roll 18・・・・・・・Ingot 19・・・・・・・・・Molten metal 20...Mold surface 21...Cell (solid phase) 22...Zump Figure 1

Claims (3)

[Claims] (1) In a method of producing an ingot from a semi-molten metal slurry by maintaining the molten metal in a solidification temperature range below the liquidus temperature of the metal and mechanically stirring the molten metal,
A method for producing an ingot, characterized by adding metal powder to molten metal being stirred. (2) The method for producing an ingot according to claim (1), wherein a mixture of pressurized gas and metal powder is supplied to the stirred molten metal. (3) By providing a rotor with a stirring section at the tip inside a slurry forming chamber equipped with a heating device that maintains the molten metal in a solidification temperature range below the liquidus temperature of the metal, and rotating the rotor. , a device that mechanically stirs molten metal by rotating its tip stirring section to produce an ingot from semi-molten metal slurry, in which a passage is formed in the rotor and the passage is communicated with the outside in the tip stirring section. A hole is provided, a mixture of metal powder and pressurized gas is supplied into the passage from the other end of the passage, and the mixture is discharged from the hole into the molten metal being stirred. Ingot manufacturing equipment.