JP2000000637A - METHOD FOR STIRRINGLY AND CONTINUOUSLY CASTING Al ALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stirringly and continuously casting an Al alloy, with which crystallized quantity of harmful α intermetallic compound is restrained to the inevitable quantity and simultaneously, crystallized quantity of helpful fine β intermetallic compound can be enhanced to the upper limit value in a point of the improvement of mechanical characteristics of an Al alloy member. SOLUTION: At the time of the stirringly continuous casting method while stirring the molten metal (m) having Al alloy composition in a spout 15, the molten metal is introduced into a cylindrical mold 13 disposed just below the spout 15. As the molten metal (m) having the Al alloy compound, the metal containing 0.75 wt.% to <2 wt.% Fe, and at the time of being 0.75 wt.%<=Fe<=1.5 wt.%, Mn<=[(Fe/5)+0.2] wt.% and at the time of being 1.5 wt.%<Fe<2 wt.%, Mn<=[-Fe+2] wt.% as the Mn content, is used. Further, cooling rate CR of the molten metal (m) at the upper peripheral part (c) of molten metal stirring range forming part (b) above the inner peripheral surface (a) of the spout, is set to 10 deg.C/s<=CR<=30 deg.C/s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agitated continuous casting method for an Al alloy, and more particularly, to an agitated continuous casting method in which a molten metal having an Al alloy composition is stirred in a spout and introduced into a cylindrical mold placed immediately below the spout. About.

[0002]

2. Description of the Related Art Conventionally, an Al alloy ingot obtained by a stirring continuous casting method has been used, for example, as a casting material for thixocasting. In the thixocasting method, molding is performed using the fluidity of a semi-solid casting material in which a solid phase and a liquid phase coexist. It is.

However, when a recycled material is used as a raw material due to a demand for resource saving, C in the recycled material is
If the content of u, Mn, Ti, etc. is increased, the high melting point acicular intermetallic compound crystallizes coarsely, and the problem that the coarse acicular intermetallic compound cannot be refined only by stirring power occurs. Was.

[0004] Therefore, the present inventors have proposed that a molten metal having an Al alloy composition has an Fe content of 0.75 wt% ≦ Fe <2 wt%.
By using a material which is as follows, at a high temperature equal to or higher than the crystallization temperature of primary crystal α, hard F
e-based intermetallic compound, that is, alpha intermetallic compound (hereinafter, referred to as
α-IMC) is crystallized, and the α-IMC is moved at random in the liquid phase by a stirring force to crush primary α and coarse acicular intermetallic compounds to make them finer. Developed a continuous casting method (Japanese Patent Application No. 10-
No. 103893 and drawings).

[0005]

As a result of further studies on the stirring continuous casting method, the present inventors have found that, depending on the Mn content in the molten metal, the crystallization amount of α-IMC increases and As it grows, it becomes a lump IMC, which allows fine beta intermetallic compounds (hereinafter β
-IMC) is suppressed. This massive α-IMC not only reduces the machinability of the Al alloy member, but also reduces the plating property and the fatigue strength.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a stirring continuous casting method capable of suppressing the crystallization amount of α-IMC to an unavoidable amount and increasing the crystallization amount of fine β-IMC to an upper limit. The purpose is to provide.

[0007] To achieve the above object, according to the present invention,
In a stirring continuous casting method in which a molten metal having an Al alloy composition is introduced into a cylindrical mold placed immediately below the spout while stirring the molten metal within the spout, the molten metal having the Al alloy composition has an Fe content of 0.75 wt% ≦ Fe <2 wt%, and M
When the n content is 0.75 wt% ≦ Fe ≦ 1.5 wt%, Mn ≦ [(Fe / 5) +0.2] wt%, while when 1.5 wt% <Fe <2 wt%, Mn ≦ [-F
e + 2] wt%, and an Al alloy which sets the cooling rate CR of the molten metal at the upper peripheral portion of the molten metal stirring area forming portion on the inner peripheral surface of the spout to 10 ° C./s≦CR≦30° C./s Is provided.

When the contents of Fe and Mn are set as described above, the crystallization amount of α-IMC can be suppressed to an unavoidable amount. Further, the upper peripheral portion is a position where the cooling rate of the molten metal is the slowest. When the cooling rate CR of the molten metal in the upper peripheral portion is set as described above, α-IMC
Growth can be suppressed. This allows fine β
-The crystallization amount of IMC can be increased to the upper limit. The cooling rate determines a cooling curve in the upper peripheral portion,
It is calculated from the cooling curve. The α-IMC contributes to crushing and refinement of the coarse acicular intermetallic compound and the primary crystal α.

However, when the Fe content and the Mn content deviate from the above ranges, the crystallization amount of α-IMC tends to increase. When the cooling rate CR is CR <10 ° C./s, α
-The growth of IMC progresses, and fine β-IMC hardly crystallizes or does not crystallize. On the other hand, CR> 30 ° C
At / s, the cooling rate is too high, so that the primary crystal α in the ingot is not sufficiently refined, and the rheological properties of the ingot are also reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Continuous casting apparatus 1 shown in FIGS.
Has a body 2 whose axis is oriented vertically. The body 2 includes an inner peripheral wall 3, an outer peripheral wall 4 arranged at a predetermined interval on the outer peripheral side, an annular upper end wall 5 on the upper end side of the two walls 3, 4, And an annular lower end wall 6 located at the lower end side.

The inner peripheral wall 3 is composed of an upper cylindrical body 7 and a lower cylindrical body 8, and an inward annular portion 10 of an annular rubber seal 9 fitted to a lower outer peripheral surface of the upper cylindrical body 7 is provided between the two cylindrical bodies 7, 8. It is sandwiched and seals between them. In the upper cylindrical body 7, the lower half thereof is formed to be thicker than the upper half 12 so as to form the annular step portion 11 on the inner side, and forms a cylindrical water-cooled mold 13. The water-cooled mold 13 is made of an Al alloy (for example, A505
2).

A spout 15 is fitted into the upper half 12 through a thin cylindrical body 14 so as to be located coaxially with the water-cooled mold 13, and an annular lower end surface 17 forming a downwardly directed molten metal outlet 16. Abuts on the annular step portion 11. Also spout 1
An annular retaining plate 18 is fitted to a portion of the projection 5 protruding from the upper end wall 5, and the retaining plate 18 is fixed to the upper end wall 5.
The spout 15 is made of calcium silicate having adiabatic fire resistance. Alumina as spout constituent material,
Silica or the like is also used. A molten metal supply gutter 19 for performing horizontal pouring is disposed above the spout 15, and its downwardly-facing water supply port 20 is connected to the upwardly-facing molten metal receiving port 2 of the spout 15.
Communicate with 1.

In the torso body 2, the outer peripheral wall 3,
An electromagnetic induction type stirrer 23 is provided in the cylindrical closed space 22 between the four, and the stirrer 23 applies an electromagnetic stirring force to the molten metal m in the spout 15. The stirrer 23 includes a cylindrical core 24 and a plurality of coils 2 wound around the core 24.
5 As shown in FIG. 3, the laminated iron core 24 includes a cylindrical portion 26 and a plurality of ridges 27 arranged on the inner peripheral surface thereof at equal circumferential intervals and extending in the generatrix direction. Each coil 25 includes two coils 25 on one ridge 27.
Are wound around the adjacent ridges 27 so that a part of the ridges overlap each other.

A thin-walled coil stopping cylinder 28 is fitted inside the laminated iron core 24 so that the tips of the ridges 27 are in close contact with each other. 9 and is fixed in the cylindrical closed space 22. The stratified iron core 24 is mounted on an annular support member 29 of the lower end wall 6 and a plurality of bolts 30 and nuts 3
Fixed by 1. A plurality of connecting tools 32 are prepared in two ratios for one coil 25, and each connecting tool 32 is attached to the lower end wall 6 by watertight means through the lower end wall 6.

A plurality of water supply ports 33 are formed in the outer peripheral wall 4,
Cooling water w is supplied into the closed space 22 through each water supply port 33. A plurality of through holes 34 are formed in the cylindrical body 28 inside the laminated iron core 24 near the upper end thereof, so that a cooling water reservoir 35 exists above the annular rubber seal 9. The water-cooled mold 13 is cooled by the cooling water sump 35 and has a plurality of jet holes 36 for jetting the cooling water w of the cooling water sump 35 obliquely downward. The through hole 34 is also formed on the lower side of the cylindrical body 28.

In order to supply lubricating oil between the water-cooled mold 13 and the molten metal m, there are the following lubricating oil passages around the spout 15. In the inner peripheral wall 3, a lower plate 37 of the upper end wall 5 is integrally provided at an upper end of the upper cylindrical body 7.
An annular path 39 surrounding the spout 15 and a plurality of straight paths 40 extending radially from the annular path 39 are provided between the upper plate 38 and the lower plate 37 of the upper end wall 5. An inlet 41 formed in the upper plate 38 communicates with an end of each straight path 40, and the inlet 41 is connected to a refueling pump. As clearly shown in FIG. 2, a cylindrical path 42 is formed between the inner peripheral surface of the upper half 12 of the upper cylindrical body 7 and the outer peripheral surface of the cylindrical body 14.
In addition, a plurality of obliquely downward facing through holes 43 communicating between the annular passages 39 are formed in a continuous portion between the upper half portion 12 and the lower plate 37. The lower end of the cylindrical path 42 communicates with a plurality of V-shaped outlets 44 radially arranged between the annular step 11 and the annular lower end face 17 of the spout 15.

The molten metal stirring area A in the spout 15
Is a space surrounded by a group of coils 25 having a substantially cylindrical shape, that is, an intermediate portion in the spout 15 located at the same height position as the upper end surface of the group of coils 25, and a melt outlet 16.
The molten metal stirring area forming portion b on the spout inner peripheral surface a forms a curved surface. Furthermore, the inner radius of the molten metal outlet 16 of the spout 15 and r _1, whereas, the inner radius of the water-cooled mold 13 when the r _2, between the two within a radius r _1, r _2, r ₁
<R ₂ and r ₂ −r ₁ = Δr (where Δr is the overhang amount of the spout 15). That is, spout 1
5 has an annular overhang 15a around the melt outlet 16 thereof.

In FIG. 1, when a molten metal m having an Al alloy composition is supplied into a spout 15 through a water supply port 20 of a molten metal supply gutter 19, the molten metal m is stirred in the spout 15 by a stirrer 23.
While being electromagnetically stirred by, the water is introduced into a water-cooled mold 13 disposed immediately below the spout 15, where it is cooled to obtain an ingot I.

As the molten alloy m of the Al alloy composition, the Fe content is 0.75 wt% ≦ Fe <2 wt%, and Mn is
When the content is 0.75 wt% ≦ Fe ≦ 1.5 wt%, Mn ≦ [(Fe / 5) +0.2] wt%.
When 1.5 wt% <Fe <2 wt%, Mn ≦ [−Fe +
2] wt% is used. Further, the cooling rate CR of the molten metal m at the upper peripheral portion c of the molten metal stirring region forming portion b on the inner peripheral surface a of the spout is 10 ° C./s≦CR≦30° C. /
s.

When the contents of Fe and Mn are set as described above, the crystallization amount of α-IMC can be suppressed to an unavoidable amount. Further, the upper peripheral portion c is a position where the cooling rate of the molten metal m is the slowest. When the cooling rate CR of the molten metal m in the upper peripheral portion c is set as described above, α
-It is possible to suppress the growth of IMC. Thereby, the crystallization amount of fine β-IMC can be increased to the upper limit. The crystallized α-IMC contributes to crushing and refinement of the coarse acicular intermetallic compound and the primary crystal α. Example 1 Table 1 shows the compositions of Al alloys (1) to (12) and the upper limit of Mn. The upper limit is 0.75wt
% ≦ Fe ≦ 1.5 wt%, Mn = [(Fe / 5) +
0.2] wt%, whereas 1.5 wt% <Fe <2
When wt%, Mn = [− Fe + 2] wt%.

[0021]

[Table 1]

An ingot I was cast from each of the Al alloys (1) to (12) by the stirring continuous casting apparatus 1. Casting conditions were as follows: melting temperature: 730 ° C .; molten metal temperature immediately above spout 15: 650 ° C .; casting withdrawal speed: 150 mm / min;
Projecting amount Δr of spout 15: 2 mm; diameter of ingot I: 152.4 mm; magnetic flux density in molten metal stirring region forming portion b: 360 Gs (4-pole coil, 50 Hz); cooling speed CR of molten metal m in upper peripheral portion c: 15 .5 ° C /
s;

When the existence of α-IMC and fine β-IMC was examined for each ingot I, Al alloys (1), (3), (4), (7), (10), (11)
A large amount of fine β-IM
Although the presence of C was recognized, Al alloys (2), (5),
In each ingot I consisting of (6), (8), (9) and (12), a large amount of α-IMC was observed.

FIG. 4 shows the Al alloys (1) to (1) with the Fe content on the horizontal axis and the Mn content on the vertical axis.
2) is expressed by its Fe and Mn contents. In the figure, points (1) to (12) correspond to Al alloys (1) to (1).
This corresponds to 2).

From the casting results, the point (0.
75, 0), point (1), point (3), point (7), point (1
0), the point (11), and the inside of the quadrilateral obtained by connecting the points (2.0, 0) can be said to be a region where a large amount of fine β-IMC can be crystallized. In this case, a line Fe =
0.75, line Mn = (Fe / 5) +0.2 and line Mn
= −Fe + 2 is included, but the line Mn = 0 is not included. Example 2 Table 2 shows the composition of the Al alloy and the upper limit of Mn. The upper limit is 0.75 wt% ≦ Fe ≦ 1.5
wt%, Mn = [(Fe / 5) +0.2] wt
%.

[0026]

[Table 2]

The stirring continuous casting apparatus 1 using an Al alloy
Ingot I was cast. The casting conditions were as follows: melting temperature: 730 ° C .; molten metal temperature immediately above spout 15: 650
° C; casting withdrawal speed: 150 to 270 mm / min; overhang amount of spout 15 Δr: 2 to 36 mm; diameter of ingot I: 152.4 mm; magnetic flux density in molten metal stirring area forming part b: 360 Gs (4-pole coil, 50 Hz) ; The cooling rate CR of the molten metal m in the upper peripheral portion c is:
The casting withdrawal speed and the overhang amount Δr of the spout 15 were changed by changing each in the above range.

For each ingot I, the existence ratio and rheological properties of α-IMC and fine β-IMC were examined, and the results shown in Table 3 were obtained.

Α-IMC abundance D ₁ and fine β-I
Prevalence D ₂ of the MC is the area ratio of the alpha-IMC in metallurgical microscope 100 times viewing and d _1, when the area ratio of the beta-IMC was _{d 2, D 1 = {d} 1 / (d 1 + d 2 )｝ × 1
00, D ₂ = {d ₂ / (d ₁ + d ₂ )} × 100.

Regarding rheological properties, each ingot I
, A test piece having a diameter of 3 mm and a thickness of 2 mm was cut out from the sample, a 20 g separating cylinder 47 was placed on one plate 46 of a balance 45, and a test piece 49 was fitted into the other container 48 as shown in FIG. The piece 49 is heated by the heater 50 and a pin 51 having a diameter of 1 mm and a length of 2 mm is pressed against the test piece 49, and the temperature at which the pin 51 pierces the test piece 49 with a pressing force balanced with the 20 g separating cylinder 47. That is, the TMA temperature was measured.

[0031]

[Table 3]

As is clear from Table 3, when the cooling rate CR is set to 10 ° C./s≦CR≦30° C./s, Examples 8 to 1
2, the a-IMC abundance was 5%, that is, the amount of crystallization was suppressed to an unavoidable amount, and the abundance of fine β-IMC was 9%.
5%, that is, the crystallization amount can be increased to the upper limit.

The TMA temperature of an ingot obtained by using an Al alloy having the same composition as in Table 2 without stirring was 600 ° C., which was inferior in rheology and could not be used as a casting material for thixocasting. The TMA temperature of Examples 8 to 12 cast in the range of the cooling rate CR is less than 600 ° C., and thus has good rheological properties.

Next, thixocasting was performed using Examples 5 and 8 to cast two types of Al alloy members. The casting conditions were as follows: the temperature of the casting material was 580 ° C., and the injection speed was 2.0 m / m.
s, the mold temperature was set to 250 ° C.

Test pieces were prepared from each of the Al alloy members, and subjected to a tensile compression fatigue test. The results shown in FIG. 6 were obtained. In the figure, examples 5 and 8 respectively correspond to examples 5 and 8 of the ingot. As is clear from FIG. 6, using Example 8 having a large amount of fine β-IMC,
-An Al alloy member having excellent fatigue strength can be obtained as compared with the case of using Example 5 having only IMC.

[0036]

According to the present invention, by employing the above-described means, the amount of harmful α-IMC crystallized can be reduced to an unavoidable amount while improving the mechanical properties of the Al alloy member. It is possible to provide an agitated continuous casting method of an Al alloy capable of increasing the amount of fine β-IMC crystallized to the upper limit.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a continuous casting apparatus.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a plan view of a main part showing a relationship between a laminated core and a coil.

FIG. 4 is a graph showing Fe contents and Mn contents of various Al alloys.

FIG. 5 is an explanatory diagram showing a TMA temperature measuring method.

FIG. 6 is a graph showing the results of a fatigue test.

[Explanation of symbols]

 13 Water-cooled mold 15 Spout a Spout inner peripheral surface b Melt stirring area forming part c Upper peripheral part m Melt A Melt stirring area

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[Procedure amendment]

[Submission date] April 20, 1999 (1999.4.2
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

As a result of further studies on the stirring continuous casting method, the present inventors have found that, depending on the Mn content in the molten metal, the crystallization amount of α-IMC increases and As it grows, the mass α- IM
C, thereby suppressing crystallization of a fine beta intermetallic compound (hereinafter referred to as β-IMC). This massive α-IMC not only reduces the machinability of the Al alloy member, but also reduces the plating property and the fatigue strength.

Continued on the front page (72) Inventor Teruyuki Otani 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 4E004 AA09 KA12 MC05 NC08

Claims (1)

[Claims] 1. A stirring continuous casting method in which a molten metal (m) having an Al alloy composition is stirred in a spout (15) and introduced into a cylindrical mold (13) disposed immediately below the spout (15). As the molten alloy (m) of the Al alloy composition, Fe
When the content is 0.75 wt% ≦ Fe <2 wt%, and when the Mn content is 0.75 wt% ≦ Fe ≦ 1.5 wt%, Mn ≦ [(Fe / 5) +0.2] wt%. On the other hand, when 1.5 wt% <Fe <2 wt%, Mn ≦ [−F
e + 2] wt%, and the cooling rate CR of the molten metal (m) at the upper peripheral portion (c) of the molten metal stirring region forming portion (b) on the inner peripheral surface (a) of the spout is set at 10 ° C.
/ A ≦ CR ≦ 30 ° C./s
Continuous stirring method for 1 alloy.