JPH07148551A - Method for continuously casting half-solidified al alloy - Google Patents

Abstract

PURPOSE:To facilitate the continuous casting of a half-solidified Al alloy excellent in profitability and workability and to obtain an Al alloy cast billet having good quality as the billet for thixotropical work, forging and the other work. CONSTITUTION:At the time of continuously casting the half-solidified Al alloy slurry, the casting is started after preheating a passage of the half-solidified metal, and the drawing speed of the cast billet at the initial stage is controlled to <=100mm/min to avoid the trouble at the initial stage of casting. Further, the height from the solidified position in the cast billet center to the surface of molten metal or the half-solidified metal is held to >=100mm and the drawing speed of the cast billet is controlled into the range of 50-200mm/min to execute the stable operation.

Description

Detailed Description of the Invention

[0001]

This invention relates to a material for thixo-processing,
The present invention relates to the production of Al alloy slabs suitable as casting materials and other processing materials, and proposes a continuous casting method for semi-solidified Al alloys which is excellent in economic efficiency and workability.

[0002]

2. Description of the Related Art A technique for continuously casting a slab using a semi-solid metal of an Al alloy has not been established so far, and trial and error is performed by using a continuous casting technique for a slab using a molten Al alloy. It was being done. Therefore, there are many troubles such as the slab not pulling out at the initial stage of continuous casting, the slab is fragmented,
Further, the cast slab has problems in quality such as coarsening of the structure and segregation of components.

[0003]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems in an advantageous manner, and enables stable continuous casting from the initial stage of casting. It is an object of the present invention to propose a continuous casting method for a semi-solidified Al alloy that can obtain a slab with excellent quality as a raw material.

[0004]

The present invention has been achieved as a result of repeated experiments on continuous casting of semi-solidified Al alloys, and its gist is as follows.

The semi-solidified metal producing device or the semi-solidified metal holding device is used as a semi-solidified metal supply device, and the semi-solidified metal slurry is continuously supplied from the bottom of the supply device to a continuous casting mold provided at the bottom. When continuously casting a solidified Al alloy, the casting is started after preheating the bottom of the feeder and the passage of the semi-solidified metal slurry at the upper part of the continuous casting mold connected to this, and the initial drawing speed of the slab is set to 100 mm / min or less. After controlling and avoiding initial casting troubles, while maintaining the height from the solidification position at the center of the slab to the bath surface of the molten metal or semi-solidified metal in the feeder to 100 mm or more, the slab drawing speed is 50 mm.
It is a continuous casting method for semi-solidified Al alloys, which is characterized by stable operation by controlling in the range of / min to 200 mm / min.

[0006]

The operation of the present invention will be described below. This invention
When continuously casting semi-solidified Al alloy by continuously supplying the semi-solidified metal slurry to the continuous casting mold provided at the bottom of the semi-solidified metal feeder as described above, the bottom of the feeder and this Preheating the passage of the semi-solidified metal at the top of the continuous continuous casting mold and then starting casting, and setting the initial drawing speed of the slab to 100 mm / min or less, and further, from the solidification position at the slab center during casting. The height of the molten metal or semi-solidified slurry in the feeder to the bath surface (hereinafter simply referred to as the molten metal head height) is maintained at 100 mm or more, and the slab drawing speed is controlled within the range of 50 mm / min to 200 mm / min. The main idea is to operate in a stable manner.

With respect to the above, the details of the action and effect are listed below. First, at the start of casting, the bottom of the feeder and the passage of the semi-solidified metal at the upper part of the continuous casting mold connected to this are preheated, but the preheating suppresses the progress of solidification in the preheated portion, and the slabs produced by early solidification Eliminate the trouble of being unable to pull out. The preheating method may be any method such as heating with a heater embedded in the apparatus or heating with a gas burner or the like from the outside, and the preheating temperature may be selected at an appropriate temperature below the temperature of the semi-solid metal.

The initial drawing speed of the slab is 100 mm / min.
If it exceeds, the slab will be broken and continuous casting will not be possible.
Therefore, in order to avoid this trouble, the initial drawing speed should be 100 mm / min or less. Since the microstructure of the obtained slab becomes coarse when the drawing speed is too slow, in order to produce a good slab with a good microstructure in good yield, the lower limit of the initial drawing speed may be 50 mm / min. preferable.

Next, during stable operation, the molten metal or semi-solidified metal is fed to the feeder to raise the molten metal head height to 100 m.
Hold it above m, but this is 100mm
If it does not meet the requirement, the slab is broken and continuous casting cannot be performed.

Further, the drawing speed of the slab during stable operation is
If it is less than 50 mm / min, the macrostructure of the obtained slab becomes coarse and the quality deteriorates, and if it exceeds 200 mm / min, a concentrated phase of the alloy component, that is, segregation occurs in the obtained slab. Therefore, the drawing speed of the slab during stable operation is 50 mm / min to 200 m.
The range is m / min.

Thus, according to the present invention, semi-solid Al
Continuous casting of alloy, stable operation is possible without causing troubles from the beginning of casting, the obtained slab does not cause coarsening of the microstructure, segregation, etc., thixotropic material, casting material, etc. It is a good quality material for processing.

[0012]

Example Using the semi-solid metal continuous casting apparatus shown in Fig. 1, AC4C Al alloy (solidus temperature: 558 ° C, liquidus temperature:
613 ℃) and AC7A Al alloy (solidus temperature: 599 ℃, liquidus temperature: 640 ℃) semi-solid metal casting experiments were conducted.

FIG. 1 is an explanatory view of a semi-solid metal continuous casting apparatus, in which a heat-meltable semi-solid metal producing apparatus and a semi-solid metal holding apparatus are arranged in the upper portion, and a continuous casting mold and a cooling apparatus are provided in the lower portion. We have a continuous mold casting machine.

In FIG. 1, an upper semi-solidifying metal producing apparatus and a semi-solidifying metal holding apparatus are a crucible 1 made of graphite, a stirrer 2 made of graphite arranged in the crucible 1, and a high frequency wave arranged on the outer periphery of the crucible 1. The lower vertical continuous casting machine composed of an induction heating coil 3 is a continuous casting mold 4 made of graphite which fits into a bottom outlet of the crucible 1, a bottom of the crucible 1 and a continuous casting mold 4.
Refractory wall 5 for preheating the upper part of the furnace, a heater 6 embedded in the refractory wall 5, a water cooling jacket 7 made of copper for cooling the continuous casting mold 4, and a cooling water spray for directly cooling the continuous casting slab 9 8. Dummy bar 10 to adjust the initial drawing speed,
It is composed of a pinch roll 11 for pulling out the continuous cast slab 9.

In the experiment, an Al alloy piece was placed in the crucible 1,
The Al alloy is heated by the high frequency induction heating coil 3 and completely melted, and then the solid-liquid mixed phase temperature range, that is, the temperature in the case of the AC4C Al alloy, while stirring with the stirrer 2:
594 ° C (solid phase ratio: 0.15), temperature for AC7A Al alloy:
A semi-solidified metal slurry was obtained by cooling and holding it at 633 ° C. (solid phase ratio: 0.15), and continuous casting was performed by pulling out the dummy bar 10 to obtain a cast ingot round bar (diameter: 60 mm).

In the above, first, the initial casting situation was investigated for those with and without the preheating of the bottom of the crucible 1 and the upper portion of the continuous casting mold 4 by the heater 6 and the initial drawing speed of the slab.

The results of these investigations are summarized in Table 1.

[Table 1]

As is apparent from Table 1, when preheated by the heater 6, the initial drawing speed is 100 mm / min or less and the drawing is possible. The initial drawing speed at which drawing is possible without preheating is 50 mm / min.

Next, the pinch roll 11 was used to investigate the metallographic structure of the slab obtained when the drawing speed during stable operation was changed.

The results of those investigations are summarized in Table 2.

[Table 2]

As is clear from Table 2, the drawing speed is 50
If it is less than mm / min, the microstructure becomes coarse, and conversely, if the drawing speed exceeds 200 mm / min, segregation occurs. Therefore, in order to obtain a slab with no microstructure coarsening and no segregation, it is preferable to continuously cast at a drawing speed of 50 mm / min to 200 mm / min.

Further, when the drawing speed was changed, the continuous casting was continued while the amount of semi-solidified metal in the crucible 1 was reduced, and the height of the molten metal head when the slab was cut was measured. The solidification position at the center of the slab was the cutting position of the slab.

The results of these measurements are summarized in Table 3.

[Table 3]

As is apparent from Table 3, the height of the molten head at which the slab breaks is in the range of 80 to 100 mm, and if the height of the molten head is kept at 100 mm or more, the slab will remain stable without breaking. It shows that continuous casting is possible.

[0025]

The present invention avoids the initial trouble of casting by specifying the preheating of the equipment and the initial drawing speed of the slab during the continuous casting of the semi-solidified Al alloy slurry, and the molten head height and the slab drawing speed To achieve stable operation and obtain a good quality slab with no coarse microstructure and segregation.The slab obtained by the present invention has excellent economical efficiency and is a material for thixotropic processing, for forging. It can be advantageously applied as a material and other processing materials, and improves the quality of processed products.

[Brief description of drawings]

FIG. 1 is an explanatory view of a semi-solid metal continuous casting device.

[Explanation of symbols]

 1 crucible 2 stirrer 3 high frequency induction heating coil 4 continuous casting mold 5 refractory wall 6 heater 7 water cooling jacket 8 cooling water spray 9 continuous casting slab 10 Tammy bar 11 pinch roll

Claims (1)

[Claims] 1. A semi-solid metal production device or a semi-solid metal holding device is used as a semi-solid metal supply device, and the semi-solid metal slurry is continuously supplied from the bottom of the supply device to a continuous casting mold provided at the bottom. When continuously casting a semi-solidified Al alloy, preheating the passage of the semi-solidified metal slurry at the bottom of the feeder and the upper part of the continuous casting mold connected to it, then starts casting,
After controlling the initial drawing speed of the slab to 100 mm / min or less to avoid initial casting troubles, the height from the solidification position at the center of the slab to the bath surface of the molten metal or semi-solidified metal in the feeder is 100 mm or more. A continuous casting method for semi-solidified Al alloy, which is characterized by controlling the drawing speed of the slab while maintaining the temperature to a range of 50 mm / min to 200 mm / min for stable operation.