JPH05261503A - Casting method of Al alloy casting - Google Patents

Abstract

(57) [Summary] [Purpose] Al- with excellent casting quality and mechanical properties.
Obtain a Si-based hypoeutectic alloy casting. [Structure] When casting Al-based alloy castings, Al-S
A melt of i-type hypoeutectic alloy composition is cooled to prepare a semi-solid material in which a solid phase and a liquid phase coexist, and then the semi-solid material is charged into a charging port 6, and the latter half solid material is pressurized with a plunger. By pressurizing by 9, the cavity 5 is passed through the gate 5 to successively fill the cavity 4 at high speed. The viscosity μ of the semi-solidified material when passing through the gate 5 is 0.1 Pa · sec ≦ μ ≦ 200
0 Pa · sec, and Reynolds number Re is Re ≦ 1
Each is set to 500. As a result, it is possible to prevent the entrainment of gas in the casting and the occurrence of a molten metal boundary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for casting an Al-based alloy casting, and in particular, to a casting material having an Al-based hypoeutectic alloy composition in which a solid phase and a liquid phase coexist, and then using the casting material. The present invention relates to a casting method for an Al-based alloy casting that is cast under pressure.

The term "casting material" as used herein means a semi-solid material prepared by cooling a molten metal having the above composition or a semi-molten material prepared by heating a solid material made of the alloy. Such a casting method was developed aiming at improving the casting quality of castings.

[0003]

2. Description of the Related Art Conventionally, as a casting method using the above-mentioned semi-solid material, a method disclosed in Japanese Patent Laid-Open No. 60-152358 is known.

[0004]

As a result of various investigations on this type of casting method, the present inventors have found that the characteristics of the casting material when passing through the gate, the pressure applied to the casting material filled in the cavity, and the casting material The average cooling rate of the molten metal at the time of preparing a certain semi-solid material, the area ratio of the primary crystal α-Al having a shape factor F of F ≧ 0.1 in the solid material used for preparing the semi-molten material, etc. And affecting the mechanical properties as well as the control of casting conditions,
Further, the pressing force also causes operational problems such as flash generation, and in addition, in order to improve the productivity without impairing the casting quality and mechanical characteristics of the casting, in order to improve the productivity, It was clarified that it is necessary to properly set the speed of the casting material.

The present invention was developed in view of the above facts, and its first purpose is to improve the casting quality and mechanical properties of castings by specifying the properties of the casting material when passing through the gate. An object of the present invention is to provide the above-mentioned casting method that can be performed.

A second object is to improve the productivity, casting quality and mechanical properties of the casting by specifying the speed of the casting material when passing through the gate and the pressure applied to the casting material filled in the cavity. It is an object of the present invention to provide the above-mentioned casting method that can avoid operational problems.

A third object of the present invention is to provide the above-mentioned casting method capable of improving the mechanical characteristics of the casting and facilitating the control of casting conditions by specifying the average cooling rate of the molten metal. ..

A fourth object is to improve the casting quality of castings by specifying the area ratio of primary crystal α-Al having a shape factor F of F ≧ 0.1 in a solid material. It is to provide the casting method.

[0009]

A method for casting an Al-based alloy casting according to the present invention comprises preparing a casting material having an Al-based hypoeutectic alloy composition in which a solid phase and a liquid phase coexist, and then casting the casting material. Casting is performed under pressure using a casting material having a viscosity μ of 0.1 Pa · sec ≦ μ ≦ 2000 P.
a · sec and Reynolds number Re of Re ≦ 1500 are passed through the mold gate.

In addition to the above conditions, the casting method of the Al type alloy casting according to the present invention has a velocity V of 0.5 m / sec ≦ V ≦ 20 m / s of the casting material when passing through the gate.
ec, and the pressing force P with respect to the casting material with which the cavity of the mold is filled is 10 MPa ≦ P ≦ 120
It is characterized by being MPa.

Further, in the casting method for an Al-based alloy casting according to the present invention, the casting material is a semi-solid material prepared by cooling a molten metal of an Al-based hypoeutectic alloy composition. In preparation, the average temperature drop rate Tv of the molten metal
Is set to 0.1 ° C./sec≦Tv≦10° C./sec.

Furthermore, in the casting method of an Al-based alloy casting according to the present invention, the casting material is a semi-molten material prepared by heating a solid material of an Al-based hypoeutectic alloy, and the solid material Is characterized in that the area ratio Ra of the primary crystal α-Al having the shape factor F of F ≧ 0.1 is set to Ra ≧ 80%.

[0013]

When the viscosity μ is set as described above, it is possible to prevent gas from being entrained by the casting material, and thus to prevent generation of pores in the casting, thereby improving the casting quality. However, when the viscosity μ of the casting material becomes μ <0.1 Pa · sec, it becomes turbulent as the viscosity of the material becomes low, and the gas is easily entrained. On the other hand, the viscosity μ is μ> 2000
At Pa · sec, as the viscosity of the casting material becomes higher, the pressure loss due to its deformation resistance increases, making it difficult for the casting material to pass through the gate, causing unfilled parts in the cavity, resulting in chipping of the casting. Occurs.

The optimum range of the viscosity μ in the casting material is 1P
a · sec ≦ μ ≦ 1000 Pa · sec. The reason is that such a viscosity range can be easily realized by a pressure casting apparatus having a conventional mold temperature control mechanism. However, when the viscosity μ is low such as μ <1 Pa · sec, the speed of the casting material when passing through the gate must be controlled at a low speed and precisely, and such control is performed in the conventional pressure casting apparatus. Then it becomes difficult. On the other hand, when the viscosity μ is high such that μ> 1000 Pa · sec, the casting material may be cooled by the mold and the viscosity may be rapidly increased. However, in order to prevent this, the temperature of the mold must be controlled high. Of course, such control is difficult with the conventional pressure casting apparatus.

Further, when the Reynolds number Re of the casting material is set as described above, it is possible to prevent the gas from being entrained and the occurrence of cold shuts in a laminar flow state of the casting material. However, Reynolds number Re is Re> 15
At 00, the casting material becomes in a turbulent state, and it becomes easy to entrain gas.

The optimum range of Reynolds number Re is Re ≦ 10.
It is 0. The reason is that the Reynolds number Re in such a casting material can be easily realized by a conventional pressure casting apparatus. However, Reynolds number Re is Re>
At 100, the influence of the inertial force becomes large depending on the shape of the cavity and the shape of the gate, so that the casting material cannot be smoothly filled into the cavity, and gas entrainment, molten metal level, etc. may occur.

Further, by setting the speed V and the pressing force P as described above, it is possible to improve the productivity and the casting quality of the casting and to avoid the operational trouble. However, when the speed V becomes V <0.5 m / sec,
Since the filling time of the casting material in the cavity becomes long, the viscosity of the casting material increases as the temperature of the casting material decreases, and an unfilled portion occurs in the cavity. On the other hand, the speed V is V> 20m /
At sec, the casting material is injected into the cavity as a jet flow from the gate, and the filling order of the casting material in the cavity is the innermost area and the next to the inlet side area. ..

Regarding the pressing force P, when the pressing force P becomes P <10 MPa, it becomes impossible to sufficiently press the high-viscosity casting material, so that an unfilled portion occurs in the cavity. On the other hand, when the applied pressure P becomes P> 120 MPa, a large amount of flash is generated on the divided surfaces of the mold, and a casting material enters between the sleeve and the pressure plunger, which causes operational problems.

When the average temperature lowering rate Tv of the molten metal is set as described above, it is possible to relatively easily control the casting conditions and obtain a casting having good casting quality and excellent mechanical properties. However, the average cooling rate Tv of the molten metal is Tv <
When the temperature is 0.1 ° C./sec, it takes a long time to prepare and cast the casting material, resulting in coarsening of the structure and casting defects such as chipping of the casting. Further, the primary crystal α-Al is coarsened and the mechanical properties of the casting are impaired. On the other hand, when the average temperature lowering rate Tv is Tv> 10 ° C./sec, the time width for maintaining the required viscosity μ of the molten metal becomes narrow, so that it becomes difficult to control the casting conditions and the practicality is lost.

The shape factor F is the cross-sectional area of the primary crystal α-Al which is A
(Measured value) and F = 4 when the perimeter is L (measured value)
It is defined as πA / L ^2, and indicates the ratio of the cross-sectional area A of the primary crystal α-Al to the area L ² / 4π of the perfect circle having the peripheral length L, that is, the circularity of the primary crystal α-Al. Therefore, the shape factor F has a maximum value of 1.0 in a perfect circle, and the primary crystal α-Al
The smaller the flattened cross-sectional shape or the more uneven the shape, the smaller the value.

When the shape factor F of the primary crystal α-Al and the area ratio Ra thereof are specified as described above, the viscosity μ of the casting material obtained from the solid material at the time of passing through the gate can be matched with the required viscosity μ. This makes it possible to obtain a casting with good casting quality. However, the area ratio Ra of the primary crystal α-Al having the shape factor F of F <0.1 is Ra.
When it becomes> 20%, the viscosity of the casting material at the time of passing through the gate becomes higher than the required viscosity μ, and as a result, the casting quality of the casting is deteriorated.

[0022]

EXAMPLE FIG. 1 schematically shows a pressure casting apparatus used for casting an Al-based alloy casting. Mold 1 of the pressure casting device
Is composed of a fixed mold 2 and a movable mold 3 which faces the fixed mold 2. The molds 2 and 3 form a molding cavity 4 having a circular cross section and a gate 5 communicating with one end thereof. It communicates with the casting material charging opening 6 of the mold 2. The fixed mold 2 is provided with a sleeve 8 that communicates with the loading port 6, and a pressure plunger 9 that is inserted into and removed from the loading port 6 is slidably fitted into the sleeve 8. The cavity 4 has an inlet-side region 4a having a relatively large capacity, which communicates with the gate 5, and an intermediate region 4 having a relatively small capacity, which communicates with the region 4a.
b and the inner region 4c having a relatively large capacity that communicates with the region 4b.

In casting an Al-based alloy casting, the following steps are sequentially carried out. (A) A casting material having an Al-based hypoeutectic alloy composition in which a solid phase and a liquid phase coexist is prepared. (B) The casting material is charged into the charging port 6. (C) The pressurizing plunger 9 is inserted into the charging port 6, and the pressurizing plunger 9 sequentially and rapidly fills the cavity 4 with the casting material through the gate 5. (D) By holding the pressure plunger 9 at the end of the stroke, a pressure is applied to the casting material filled in the cavity 4, and the casting material is solidified under the pressure to obtain a casting.

In the casting method, the Al-based hypoeutectic alloy includes Al-Si-based, Al-Mg-based, Al-Cu-based, and A-based.
Hypoeutectic alloys such as 1-Ca type and Al-Ga type correspond.

For example, as the Al-Si-based hypoeutectic alloy, an alloy having a Si content of less than 11.7% by weight is used. This Al-Si-based hypoeutectic alloy is, for example, 6.5% by weight. ≤ Si ≤ 7.5 wt%, Fe ≤ 0.20 wt%, C
u ≦ 0.20% by weight, Mn ≦ 0.10% by weight, 0.40
% By weight ≦ Mg ≦ 0.70% by weight, 0.04% by weight ≦ Ti
≦ 0.20% by weight.

Among the above chemical components, Si contributes to the strength improvement of the casting by precipitating Mg ₂ Si by heat treatment.
However, when the Si content is Si <6.5% by weight, the strength improving effect is small, while when Si> 7.5% by weight, the impact value and the toughness of the casting are lowered.

Fe is used to improve the high temperature strength of castings and molds.
In particular, it contributes to the prevention of seizure of the casting material on the mold. This high temperature strength improvement mechanism is due to the dispersion strengthening of the AlFeMn intermetallic compound. However, if the Fe content is Fe> 0.20
If the content is wt%, the elongation and toughness of the casting will be reduced.

Cu contributes to improving the strength of the casting by precipitating Al ₂ Cu by heat treatment. However, if the Cu content is Cu> 0.20% by weight, the corrosion resistance of the casting decreases.

Mn contributes to the improvement of the high temperature strength of the casting and has the function of agglomerating the AlFe intermetallic compound. However, when the Mn content is Mn> 0.10% by weight, the elongation and toughness of the casting decrease.

As described above, Mg cooperates with Si to contribute to the improvement of the strength of the casting. However, if the content of Mg is Mg <
When the content is 0.40% by weight, the strength improving effect is small, and on the other hand, Mg
When it is> 0.70% by weight, the elongation and toughness of the casting are lowered.

Ti contributes to the refinement of crystal grains in the above content.

First, the case where a semi-solid material obtained from molten metal is used as the casting material will be described.

Under the cooling conditions for preparing the semi-solidified material from the molten metal, the average temperature decrease rate Tv of the molten metal is 0.1 ° C./sec≦Tv≦10° C./sec as described above, and the semi-solidified material Viscosity μ is 0.1 Pa · sec ≦ μ ≦ 200
Each is set to 0 Pa · sec. By setting the cooling conditions in this way, it is possible to relatively easily control the casting conditions and to obtain a casting having good casting quality and excellent mechanical properties.

The viscosity μ of the semi-solidified material is set to be the same as that at the time of casting. Its viscosity μ is μ <0.1Pa
When it becomes sec, the handleability of the semi-solidified material deteriorates, while when the viscosity μ becomes μ> 2000 Pa · sec, the casting quality of the casting deteriorates as described above.

The property of the semi-solidified material when passing through the gate 5 at the time of casting, that is, the viscosity μ of the semi-solidified material is 0.1 Pa · sec ≦ μ ≦ 2000 Pa · sec as described above.
And the Reynolds number Re is Re ≦ 15 as described above.
00, respectively.

In order to improve the casting quality of the casting, the Reynolds number Re of the semi-solid material as well as the cross-sectional area expansion ratio Rs in the mold 1 become a problem. Here, as for the cross-sectional area expansion ratio Rs, the cross-sectional area of the gate 5 is S ₀ in FIG. 1, and the cross-sectional area of the inlet side region 4 a in the cavity 4 is S ₁
Then, Rs = S ₁ / S ₀ is expressed.

The cross-sectional area enlargement ratio Rs is set to Rs ≦ 10. By setting the cross-sectional area enlargement ratio Rs in this way, it is possible to prevent the entrainment of gas by the semi-solidified material and the occurrence of a molten boundary. However, the cross-sectional area expansion rate Rs is Rs> 10
Then, the semi-solidified material becomes a jet flow from the gate 5 and is injected into the cavity 4, and the filling order is the inner region 4c,
Since it is next to the entrance side area 4a, a hot water boundary occurs.

The optimum range of the cross-sectional area enlargement ratio Rs is 1 ≦ Rs ≦
It is 5. The reason is that such a cross-sectional area enlargement ratio Rs can be easily realized by a conventional pressure casting device. However, when the cross-sectional area expansion ratio Rs is Rs> 5, the cross-sectional area of the gate 5 is substantially reduced, so that the solidification of the semi-solidified material in the gate 5 precedes the final solidification of the semi-solidified material in the cavity 4, As a result, the feeder effect cannot be obtained, and the inlet side region 4a and the inner region 4 are
There is a risk of shrinkage occurring in both thick-walled parts of the casting corresponding to c. On the other hand, when the cross-sectional area expansion ratio Rs becomes Rs <1, the cross-sectional area of the gate 5 becomes substantially equal to the cross-sectional area of the inlet side region 4a of the cavity 4, so that the yield of the casting increases as the scrap portion corresponding to the gate 5 increases. Results in operational problems such as a decrease in

The velocity V of the semi-solidified material when passing through the gate 5 is 0.5 m / sec≤V≤20 m / s as described above.
ec, and the pressure P applied to the semi-solid material filled in the cavity 4 is 10 MPa ≦ P ≦ 12 as described above.
Each is set to 0 MPa.

In the Al-based alloy castings obtained under the above-mentioned conditions, the semi-solid material is subjected to a shearing force while passing through the gate 5, and the primary crystal α-Al is spheroidized,
Area ratio R of primary crystal α-Al having a shape factor F of F ≧ 0.1
It has a metal structure in which a is set to Ra ≧ 80% and the maximum grain size d of primary α-Al is set to d ≦ 300 μm, and has excellent elongation, toughness, fatigue strength and the like. However,
Area ratio R of primary crystal α-Al having a shape factor F of F ≧ 0.1
When a is Ra <80%, the spheroidization of the primary crystal α-Al is insufficient, so that the fatigue strength, elongation and toughness of the casting decrease. Also, when the maximum grain size d of the primary crystal α-Al is d> 300 μm, the fatigue strength of the casting is lowered. One kind of additional element selected from Sr, Sb, and Na may be added to the molten metal having the Al-Si-based hypoeutectic alloy composition in order to make the primary crystal α-Al spherical.

Specific examples will be described below.

As the molten metal of the Al-Si-based hypoeutectic alloy composition, one having the composition shown in Table 1 was prepared using a control furnace equipped with a heating and cooling mechanism.

[0043]

[Table 1] In the mold 1, the cross-sectional area expansion ratio Rs (S ₁ / S ₀ ) established between the cross-sectional area S ₀ of the gate 5 and the cross-sectional area S ₁ of the inlet side region 4a of the cavity 4 is set to Rs = 4. ..

First, the molten metal is cooled in a controlled furnace with the average cooling rate Tv set to Tv = 1 ° C./sec, whereby a semi-solid material having a solid phase volume fraction Vf of Vf = 70% is prepared. did.

The above semi-solidified material was charged into the charging port 6 of the mold 1, and then the semi-solidified material was charged into the cavity 4 through the gate 5 at a high speed by the pressure plunger 9. In this case, the moving speed of the pressure plunger 9 is set to about 78 mm / sec, and the speed V of the semi-solidified material when passing through the gate 5 is V.
Is V = 3 m / sec, viscosity μ is μ = 300 Pa · se
c, Reynolds number Re was Re = 0.21.

Further, as shown in FIG. 1, the lower position G of the gate 5 in the mold 1, the upper position U1 and lower position L1 of the inlet side region 4a of the cavity 4 and the inner region 4c.
When the filling behavior of the semi-solidified material was investigated by measuring the temperature rising start points of the upper position U2 and the lower position L2 of the, the filling sequence was G → L1 → U1 → L2 and U2 at approximately the same time, It was confirmed to be ideal for avoiding the occurrence of casting defects.

While holding the pressure plunger 9 at the end of the stroke, a pressure is applied to the semi-solid material filled in the cavity 4, and the semi-solid material is solidified under the pressure to cast the casting A ₁
Got In this case, the pressure P applied to the semi-solid material is P =
It was 30 MPa, and it was confirmed that the flash generated on the dividing surface 10 of the mold 1 was extremely small.

FIG. 2 shows the relationship between the time in the casting operation and the stroke of the pressure plunger and the pressure applied to the semi-solid material. In the figure, the line a indicates the stroke,
Lines b correspond to the pressing force. From Figure 2,
It can be seen that the pressure applied to the semi-solid material rises rapidly near the end of the stroke of the pressure plunger 9. The pressing force at the start of this rise is 10 MPa, which is the minimum pressing force for obtaining the casting A ₁ .

FIG. 3 is a micrograph (100 times) showing the metal structure of the casting A ₁ obtained by the casting method.
In the figure, it can be seen that the light gray granular portion occupying most of the region is the primary crystal α-Al and the maximum grain size d is d = 300 μm. The casting A ₁ having such a fine primary crystal α-Al has an excellent fatigue strength. This seed metallographic structure is subjected to shearing force when the semi-solidified material passes through the gate 5 and solidified under pressure. It is obtained by doing. Further, the area ratio Ra of the primary crystal α-Al having a shape factor F of F ≧ 0.1 is Ra = 98%, and the fatigue strength, elongation and toughness of the casting A ₁ are improved by setting the area ratio Ra in this way. You can Further, as is clear from FIG. 3, the casting A ₁ has no molten metal boundary, no porosity due to gas entrainment, and no chipping due to unfilling of the semi-solid material in the cavity 4. None, and thus this casting A ₁ was found to have excellent casting quality.

Next, by changing the moving speed of the pressure plunger 9, the speed V and the Reynolds number Re of the semi-solidified material when passing through the gate 5 are changed, and the other conditions are set the same as in the casting method. Castings A ₂ and A ₃ according to the example and castings B ₁ and B _{2 according} to the comparative example were cast.

Table 2 shows the relationship between the castings A _{1 to} A ₃ according to the examples and the castings B ₁ and B ₂ according to the comparative examples, and the speed V and the Reynolds number Re.

[0052]

[Table 2] FIG. 4 shows the velocity V of the semi-solidified material when passing through the gate 5.
And the viscosity μ of the semi-solidified material when passing through the gate. In the figure, the line c corresponds to the case where the Reynolds number Re when passing through the gate 5 is Re = 1500. Therefore, the region including the line c and above the line c is the laminar flow region, and the line c The region below is the turbulent flow region.

FIG. 5 shows the relationship between the velocity V of the semi-solid material passing through the gate 5 and the pressure P applied to the semi-solid material filled in the cavity 4.

As described above, from the viewpoint of improving casting quality, the speed V is 0.5 m / sec ≦ V ≦ 20 m / se.
c, the viscosity μ is 0.1 Pa · sec ≦ μ ≦ 2000P
It is desirable that a · sec, Reynolds number Re be Re ≦ 1500, and the pressing force P be 10 MPa ≦ P ≦ 120 MPa. Casting A according to the example from Table 2, FIG. 4 and FIG.
It can be seen that the above conditions are satisfied in _{1 to} A ₃ .

In the casting B ₁ according to the comparative example, the speed V is lower than the lower limit value (0.5 m / sec). Therefore, the filling sequence of the semi-solidified material into the cavity 4 is G → L1 in FIG. → U1 → L2 → U2, and as a result, the upper position U2 in the inner region 4c of the cavity 4
There was an unfilled portion of the semi-solidified material on the surface, and correspondingly, the casting B ₁ was chipped. In the casting B ₂ according to the comparative example, since the speed V exceeds the upper limit value (20 m / sec), the filling order of the semi-solidified material into the cavity 4 is G → U2 → L2 → L1 → in FIG. The result is U1, and as a result, the semi-solidified material partially solidifies early in the inlet side region 4a and the inner region 4c of the cavity 4, and correspondingly, the casting B ₂ has a molten boundary. In addition, since the semi-solidified material was injected into the cavity 4 as a jet flow, it was confirmed that gas was entrained in the casting B ₂ to generate pores.

For comparison, castings B ₃ and B ₄ were cast by the above casting method except that the conditions shown in Table 3 were changed. Both castings B ₃ and B ₄ are also shown in FIG.

[0057]

[Table 3] In the casting B ₃ according to the comparative example, the occurrence of chipping was recognized due to the increased viscosity of the semi-solidified material. Further, in the casting B ₄ according to the comparative example, gas entrainment due to turbulent flow due to the lowering of the viscosity of the semi-solidified material, and therefore generation of pores were observed.

For comparison, the pressure P is set to P = 90MP.
a, and other conditions are set in the same manner as described above, and by the casting method, castings A _{4 to} A ₆ corresponding to the castings A _{1 to} A _{3 according} to the example and castings B ₁ and B according to the comparative example.
Castings B ₅ and B ₆ corresponding to No. ₂ were cast. Those castings A
_{4 to} A ₆ and B ₅ and B ₆ are shown in FIGS. 4 and 5, and it was confirmed that they have casting quality corresponding to the castings A _{1 to} A ₃ and B ₁ and B ₂ , respectively. That is, castings A _{4 to} A ₆ do not have casting defects, while castings B ₅
Was found, and cast metal B ₆ was found to have molten metal boundaries and porosity.

Table 4 shows various conditions and types of casting defects when casting castings B _{7 to} B ₉ according to the comparative example. Under these conditions, only the average cooling rate Tv of the molten metal deviates from the above range.

[0060]

[Table 4] Table 5 shows the relationship between the area ratio Ra of the primary crystal α-Al with F ≧ 0.1 and the fatigue strength of the casting A ₁ (FIG. 3) according to the example and the castings B ₁₀ and B ₁₁ according to the comparative example. Show. Castings B ₁₀ , B ₁₁
Has the same composition as the casting A ₁ , but the casting B ₁₀ is cast by the gravity die casting method, and the casting B ₁₁ is cast by the molten metal forging method. The primary crystal α-Al in the castings B ₁₀ and B ₁₁ has a substantially dendrite shape. In the table, stress amplitude δ
a shows the value when the number of breaks is 10 ⁸ . Damage probability 0.
5 means that 5 out of 10 test pieces are broken, and 0.1 means that 1 out of 10 test pieces breaks.

[0061]

[Table 5] From Table 5, it is clear that the casting A _{1 according} to the example has a better fatigue strength than the castings B ₁₀ and B _{11 according} to the comparative example.

Table 6 shows casting A ₁ (FIG. 3) and castings B ₁₀ and B.
₁₁ shows the relationship between the area ratio Ra of primary α-Al having F ≧ 0.1 and other mechanical properties.

[0063]

[Table 6] From Table 6, it is clear that the casting A _{1 according} to the example has excellent elongation and toughness as compared with the castings B ₁₀ and B _{11 according} to the comparative example.

Next, the case where a semi-molten material obtained from a solid material is used as the casting material will be described.

In the metallic structure of the solid material, the shape factor F
The area ratio Ra of the primary crystal α-Al in which F ≧ 0.1 is set to Ra ≧ 80% as described above, and the primary crystal α-Al is
The maximum particle size d of is set to d ≦ 300 μm. By setting the maximum grain size d of the primary crystal α-Al in this way, the fatigue strength of the casting can be improved. However, if the maximum particle size d is d> 300 μm, the above effect cannot be obtained.

When a semi-molten material is obtained from a solid material, the heating conditions are set as follows.

The average heating rate Tv of the solid material is Tv ≧ 0.
2 ° C / sec, soaking degree between inside and outside of semi-molten material Δ
T is ΔT ≦ ± 10 ° C., the viscosity μ of the semi-molten material is 0.1 Pa
・ Sec ≦ μ ≦ 2000 Pa · sec. By setting the heating conditions in this manner, the semi-molten material can be efficiently prepared and handled, and the casting quality of the casting can be improved. However, the average heating rate Tv of the solid material is T
When v <0.2 ° C./sec, it takes a long time to prepare the semi-molten material, which causes coarsening of the primary crystal α-Al and impairs the mechanical properties of the casting. The optimum range of the average heating rate Tv is Tv ≧ 1.0 ° C./sec. The reason is that when the average heating rate Tv is Tv <1.0 ° C./sec, the productivity is likely to decrease, the metal structure is coarsened, and the surface oxidation is likely to occur.

When the soaking degree ΔT between the inside and the outside of the semi-molten material is ΔT> ± 10 ° C., the viscosity μ of the semi-molten material is partially different, so that a melted-out portion is generated or the cavity 4 does not have a melted portion. This leads to the occurrence of chipping in the filling location and thus in the casting. The optimum range of the soaking degree is ΔT ≦ ± 3 ° C. The reason is that the semi-molten material can be automatically handled in such a range, which can improve the productivity of the casting.

The viscosity μ of the semi-molten material is set to be the same as that at the time of casting. Its viscosity μ is μ <0.1Pa
At sec, a melted-out portion is generated and the handling property of the semi-molten material is deteriorated, while the viscosity μ is μ> 2000 Pa.
At sec, the casting quality of the casting deteriorates as described above.

The property of the semi-molten material at the time of passing through the gate 5 at the time of casting, that is, the viscosity μ of the semi-molten material is 0.1 Pa · sec ≦ μ ≦ 2000 Pa · sec as described above.
And the Reynolds number Re is Re ≦ 1 as described above.
It is set to 500. Cross-sectional area expansion ratio Rs in mold 1
Is set to Rs ≦ 10 similarly to the above. Further, the velocity V of the semi-molten material when passing through the gate 5 is 0.5 m / sec ≦ V ≦ 20 m / sec as described above, and the pressure P applied to the semi-molten material filled in the cavity 4 is
As described above, 10 MPa ≦ P ≦ 120 MPa is set.

Specific examples will be described below. In this example, the same pressure casting device as that using the semi-solid material was used.

As the solid material made of Al-Si type hypoeutectic alloy, one having the same composition as in Table 1 was selected. In the metallic structure of this material, the shape factor F is F ≧
The area ratio Ra of the primary crystal α-Al that is 0.1 is Ra = 80%.
And the maximum grain size d of primary α-Al is d = 200μ.
It was m.

First, the solid material is placed in a heating furnace, and then the average heating rate Tv is set to Tv = 1.3 ° C./sec for heating, whereby the soaking degree ΔT between the inside and outside is ΔT.
= 6 ° C., a semi-molten material having a solid phase volume fraction Vf of Vf = 70% was prepared. This solid phase possessed the same metallic texture as the solid material.

The semi-molten material was charged into the charging port 6 of the mold 1, and then the semi-molten material was successively filled into the cavity 4 at high speed through the gate 5 by the pressure plunger 9. In this case, the moving speed of the pressure plunger 9 is set to about 78 mm / sec, and the speed V of the semi-molten material when passing through the gate 5 is V.
Is V = 3 m / sec, viscosity μ is μ = 300 Pa · se
c, Reynolds number Re was Re = 0.21.

Further, as shown in FIG. 1, the lower position G of the gate 5 in the mold 1, the upper position U1 and the lower position L1 of the inlet side region 4a of the cavity 4, and the inner region 4c.
When the filling behavior of the semi-molten material was examined by measuring the temperature rising start points of the upper position U2 and the lower position L2 of, the filling sequence was G → L1 → U1 → L2 and U2 at approximately the same time, It was confirmed to be ideal for avoiding the occurrence of casting defects.

While holding the pressure plunger 9 at the end of the stroke, a pressure is applied to the semi-molten material filled in the cavity 4, and the semi-molten material is solidified under the pressure so that the casting A ₇
Got In this case, the pressure P applied to the semi-molten material is P =
It was 30 MPa, and it was confirmed that the flash generated on the dividing surface 10 of the mold 1 was extremely small. The relationship between the time in this casting operation and the stroke of the pressure plunger and the pressure applied to the semi-molten material is the same as in FIG.

FIG. 6 is a micrograph (100 times) showing the metal structure of the casting A ₇ obtained by the casting method.
In the figure, it is understood that the light gray granular portion occupying most of the area is primary crystal α-Al and the maximum grain size d is d = 200 μm. The reason why such a metallographic structure is obtained is that the maximum grain size d of the primary crystal α-Al in the solid phase of the semi-molten material is d = 200 μm, and the primary crystal α-Al crystallized from the liquid phase is This is because the phase is subjected to shearing force when passing through the gate 5 and is solidified under pressure, so that the refinement is achieved. Further, the area ratio Ra of the primary crystal α-Al having the shape factor F of F ≧ 0.1 is Ra = 98%, and the elongation and the toughness of the casting A ₇ can be improved by setting in this way. Further, as is clear from FIG. 6, the casting A ₇ has no molten metal boundary, no pores due to gas entrainment, and no chipping due to unfilling of the semi-molten material into the cavity 4. None, and therefore this casting A ₇ was found to have excellent casting quality.

Next, by changing the moving speed of the pressure plunger 9, the speed V and the Reynolds number Re of the semi-molten material when passing through the gate 5 are changed, and the other conditions are set to be the same as those of the casting method. Castings A ₈ and A ₉ according to the example and castings B ₁₂ and B _{13 according} to the comparative example were cast.

Table 7 shows the relationship between the castings A _{7 to} A ₉ according to the examples and the castings B ₁₂ and B ₁₃ according to the comparative example, and the speed V and the Reynolds number Re.

[0080]

[Table 7] FIG. 7 shows the velocity V of the semi-molten material when passing through the gate 5.
And the viscosity μ of the semi-molten material when passing through the gate. In the figure, the line c corresponds to the case where the Reynolds number Re when passing through the gate 5 is Re = 1500. Therefore, the region including the line c and above the line c is the laminar flow region, and the line c The region below is the turbulent flow region.

FIG. 8 shows the relationship between the velocity V of the semi-molten material when passing through the gate 5 and the pressure P applied to the semi-molten material filled in the cavity 4.

From the viewpoint of improving the casting quality as described above, the speed V is 0.5 m / sec ≦ V ≦ 20 m / se.
c, the viscosity μ is 0.1 Pa · sec ≦ μ ≦ 2000P
It is desirable that a · sec, Reynolds number Re be Re ≦ 1500, and the pressing force P be 10 MPa ≦ P ≦ 120 MPa. From Table 7, FIG. 7 and FIG. 8, casting A according to the example
It is understood that the above-mentioned conditions are satisfied in _{7 to} A ₉ .

In the casting B ₁₂ according to the comparative example, the speed V is below the lower limit value (0.5 m / sec), so that the order of filling the semi-molten material into the cavity 4 is G → L1 in FIG. → U1 → L2 → U2, and as a result, the upper position U2 in the inner region 4c of the cavity 4
There was an unfilled portion of the semi-molten material at the same time, and the chip B ₁₂ was chipped correspondingly. In the casting B ₁₃ according to the comparative example, since the speed V exceeds the upper limit value (20 m / sec), the filling sequence of the semi-molten material into the cavity 4 is G → U2 → L2 → L1 → in FIG. The result was U1, and as a result, the semi-molten material partially solidified early in the inlet side region 4a and the inner region 4c of the cavity 4, and correspondingly, the casting B ₁₃ had a molten boundary. Further, since the semi-molten material was injected into the cavity 4 as a jet flow, generation of pores due to gas entrainment in the casting B ₁₃ was observed.

For comparison, castings B ₁₄ and B ₁₅ were cast by the above casting method except that the conditions shown in Table 8 were changed. Both castings B ₁₄ and B ₁₅ are also shown in FIG.

[0085]

[Table 8] In casting B ₁₄ according to the comparative example, chipping was observed due to the high viscosity of the semi-molten material. Further, in the casting B ₁₅ according to the comparative example, gas entrainment due to turbulent flow due to the decrease in viscosity of the semi-molten material, and therefore generation of pores, were observed.

For comparison, the pressure P is set to P = 90MP.
a, and other conditions are set in the same manner as described above, and by the casting method, castings A _{10 to} A ₁₂ corresponding to castings A _{7 to} A _{9 according} to the example and castings B ₁₂ and B according to the comparative example.
Castings B ₁₆ and B ₁₇ corresponding to No. ₁₃ were cast. Those castings A
_{10 to} A ₁₂ and B ₁₆ and B ₁₇ are shown in FIG. 7 and FIG. 8, and it was confirmed that they have casting quality corresponding to the castings A _{7 to} A ₉ and B ₁₂ and B ₁₃ , respectively. That is, castings A _{10 to} A ₁₂ have no casting defects, while castings B ₁₆
Was found, and casting B ₁₇ was found to have molten metal boundaries and porosity.

Table 9 shows various conditions and types of casting defects when casting castings B _{18 to} B ₂₀ according to the comparative example. Under these conditions, the area ratio Ra of the primary crystal α-Al having a shape number F of F ≧ 0.1 and the viscosity μ of the semi-molten material of the solid material deviate from the scope of the present invention.

[0088]

[Table 9]

[0089]

According to the invention of claim 1, the viscosity μ and Reynolds number Re of the casting material when passing through the gate
By specifying the above as described above, it is possible to obtain an Al-based alloy casting having high quality without generation of pores and molten metal boundaries and excellent mechanical properties.

According to the second aspect of the invention, by specifying the velocity V and the pressure P of the casting material when passing through the gate as described above, in addition to the above-mentioned effects, the productivity and operation of the Al-based alloy casting can be improved. The above trouble can be avoided.

According to the third aspect of the invention, the casting having excellent mechanical properties can be obtained by specifying the average cooling rate Tv of the molten metal in the preparation of the semi-solidified material as described above. Also, the management of casting conditions can be facilitated.

According to the invention described in claim 4, by using the solid material specified as described above, a casting having excellent casting quality can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a pressure casting device.

FIG. 2 is a graph showing a relationship between time and a stroke of a pressure plunger and a pressing force applied to a semi-solid material.

FIG. 3 is a micrograph showing an example of a metal structure of a casting.

FIG. 4 is a graph showing a relationship between a velocity V and a viscosity μ of a semi-solidified material when passing through a gate.

FIG. 5 is a velocity V of the semi-solidified material when passing through the gate,
It is a graph which shows the relationship with the pressing force P with respect to a semi-solid material.

FIG. 6 is a micrograph showing another example of the metal structure of a casting.

FIG. 7 is a graph showing the relationship between the velocity V and the viscosity μ of the semi-molten material when passing through the gate.

FIG. 8 shows the velocity V of the semi-molten material when passing through the gate,
It is a graph which shows the relationship with the pressing force P with respect to a semi-molten material.

[Explanation of symbols]

 1 Mold 4 Cavity 5 Gate 6 Loading Port 9 Pressurizing Plunger

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction content]

Table 4 shows various conditions and types of casting defects in casting castings B _{7 to} B ₉ according to the comparative examples. Under these conditions, the average temperature decrease rate Tv of the molten metal and the semi-solidified material
The viscosity μ is outside the above range.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0060

[Correction method] Change

[Correction content]

[0060]

[Table 4]

Claims (4)

[Claims] 1. A casting material having an Al-based hypoeutectic alloy composition in which a solid phase and a liquid phase coexist, is prepared, and then casting is performed under pressure using the casting material. The viscosity μ is 0.1 Pa · sec ≦ μ ≦ 2000 Pa · s
ec, and a method of casting an Al-based alloy casting, which is characterized in that it passes through the gate of the mold under the condition that Reynolds number Re is Re ≦ 1500. 2. The velocity V of the casting material when passing through the gate is 0.5 m / sec ≦ V ≦ 20 m / sec, and the pressure P applied to the casting material filled in the mold cavity is 10 MPa ≦. The casting method for an Al-based alloy casting according to claim 1, wherein P ≦ 120 MPa. 3. The casting material is a semi-solid material prepared by cooling a molten metal of Al-based hypoeutectic alloy composition, and the average cooling rate Tv of the molten metal is 0 when preparing the semi-solid material. .1 ° C./sec≦Tv≦10° C./sec,
The casting method of the Al-based alloy casting according to claim 1. 4. The casting material is a semi-molten material prepared by heating a solid material composed of an Al-based hypoeutectic alloy,
The Al-based alloy casting according to claim 1 or 2, wherein as the solid material, an area ratio Ra of primary crystal α-Al having a shape factor F of F ≧ 0.1 is set to Ra ≧ 80%. Casting method.