JP2003136174A - Method for manufacturing precast-forming billet of aluminum alloy for transport equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing precast-forming billets of aluminum for transport equipment, in which processes are simple to attain a low cost production, and obtained products are homogenous. SOLUTION: An aluminum alloy contains at least one kind of 0.15-1.5 wt.% Si, 0.20-2.0 wt.% Mg, at most 0.30 wt.% Zn, at most 1.2 wt.% Fe, and 0.001-0.5 wt.% Ti, and 0.0001-0.5 wt.% B, and at least one kind of 0.05-0.50 wt.% Cu, 0.10-1.0 wt.% Mn, and 0.03-0.50 wt.% Cr, and the rest of substantially Al composition. In the alloy, dendrite arm spacing is at most 200 μm. Work strain is induced by cold die-forging at 5-50% strain ratio, work-introduction ratio of at most 50 mm/sec., and at the recrystallization temperature. Thereafter, the temperature is raised to eutectic temperature or solidus temperature or above, and precast forming is performed by holding the temperature to give 20-80% liquid-phase ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a semi-molten molded billet of an aluminum alloy used for transportation equipment.

[0002]

2. Description of the Related Art The thixocasting method using a semi-molten billet has recently attracted attention because it has advantages such as less casting segregation / defects and longer die life than the conventional die casting method. As a billet casting method used for this, in order to make the primary α (Al) phase into a spherical shape at the billet stage known as the Pennesey Almax method, a method of performing electromagnetic / mechanical stirring in the semi-melting temperature range (method A) or a larger amount of Al-Ti- than is usually added during casting.
B was added, and the temperature was raised to the melting temperature range in the latter half and the primary crystal α (A
1) There is a method of making the phase spherical (method B). Further, a method (method C) in which the temperature is raised to spherical as in method B after introducing strain by extrusion / rolling is widely known.

[0003]

[Problems to be Solved by the Invention]
In case of method A, the process is very complicated and the manufacturing cost is high.
There was a problem of sticking. In the method B, a large amount of Al
-TiB in the melting furnace to add Ti-B _TwoFor settling
Quality instability occurs, and distortion occurs due to rolling of method C.
It is difficult to introduce uniform strain in the method of introducing
At room temperature extrusion, the work process is complicated, and the strain is uniform.
It is difficult to introduce only the product, and both strain introduction methods are product processing after processing
Is required, and mass production and cost reduction cannot be achieved.
There was a problem.

Japanese Patent No. 2976073 discloses an improved method. That is, there is a step in the first paragraph "a step of deforming a completely solidified metal or metal alloy material at a temperature lower than its recrystallization temperature, and heating the deformable material to cause recrystallization of the microstructure of the material. And partially melting the recrystallized structure to form free-standing particles in a liquid matrix that behaves thixotropically by raising the temperature of the material above its solidus temperature. A method including a step of
This method comprises heating a deformed material to cause recrystallization of the microstructure of the material, and raising the temperature of the material above its solidus temperature, so to speak 2.
The heating which should be called stepwise heating is performed. Although such a method can be said to be an improved technique as compared with the conventional technique, it still requires two steps of heating, and has a problem that the process is complicated and heating control is difficult.

The present invention solves the above-mentioned drawbacks of the prior art,
It is an object of the present invention to provide a method for manufacturing a semi-molten cast billet of an aluminum alloy for transportation equipment, which has a simple process, can promote cost reduction, and has a homogeneous product.

[0006]

In order to achieve the above object, a method for manufacturing a semi-molten cast billet of an aluminum alloy for transportation equipment according to the present invention is Si 0.15 to 1.5 wt%, M
g 0.20 to 2.0 wt%, Zn 0.30 wt% or less,
Fe 1.2 wt% or less and Ti 0.001 to 0.5 wt
% And B 0.0001 to 0.5 wt%, Cu 0.05 to 0.50 wt%, Mn 0.10
.About.1.0 wt% and Cr 0.03 to 0.50 wt% and at least one of them is composed substantially of Al, and the dendrite branch interval (DAS) is 200 .mu.m.
aluminum alloy having a strain rate of 5 to 50% and a processing introduction speed of 50 mm / sec. At a temperature below the recrystallization temperature, a working strain is introduced by cold mold forging, and thereafter, the temperature is raised to a temperature higher than the eutectic temperature or the solidus temperature, and the liquid phase ratio becomes 20 to 80%. It is a method of holding and semi-melt processing.

In this case, in order to homogenize the segregation of the components and release the casting stress, 450 to 450% before introducing the working strain.
It is preferable to perform homogenization treatment at a temperature of 600 ° C. for 1 to 10 hours.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Various reasons for limiting numerical values such as limiting the numerical values of the amounts of aluminum alloy components used in the present invention will be described in detail below.

When the Si component coexists with the Mg component, it precipitates Mg ₂ Si by heat treatment and contributes to the improvement of mechanical properties, but if it is less than 0.15 wt%, its effect is small, while 1.5 wt%. %, The cold forgeability deteriorates, so the content was made 0.15 to 1.5 wt%.

The Mg component contributes to the improvement of mechanical properties by coexisting with the Si component, but if it is less than 0.20 wt%, its effect is small, and if it exceeds 2.0 wt%, cold forgeability is poor. 0.20 to 2.0 wt because it gets worse
%.

Since the Zn component lowers the corrosion resistance,
It was set to 0.30 wt% or less.

The Fe component forms an intermetallic compound with Al, and if contained in a large amount, becomes an Al-Fe-Si based compound, which adversely affects elongation, toughness and corrosion resistance.
% Or less.

The Ti component refines the structure of the ingot and prevents the occurrence of ingot cracking, but if it is less than 0.001 wt%, its effect is small, while if it exceeds 0.5 wt%, TiA is produced.
to promote the formation of huge crystallized substance of l _3, since lowering the mechanical properties of the cracks and transportation equipment components during cold forging, and the 0.001~0.5wt%.

The B component, together with the Ti component, also refines the structure of the ingot and prevents the occurrence of ingot cracking.
If it is less than 0.5% by weight, the effect is small, and if it exceeds 0.5% by weight, cracking during cold forging and deterioration of mechanical properties of parts for transportation equipment may occur, so the content was made 0.0001 to 0.5% by weight.

The Cu component serves to improve the mechanical properties, but if it is less than 0.05% by weight, its effect is small and 0.5
If it exceeds 0 wt%, cracking during cold forging and deterioration of corrosion resistance will occur, so the content was made 0.05 to 0.50 wt%.

The Mn component contributes to the improvement of strength and elongation by suppressing recrystallization and refining recrystallized grains.
If it is less than wt%, its effect is small, and if it exceeds 1.0 wt%, ductility is deteriorated, so 0.10 to 1.0 wt%
And

The Cr component, like the Mn component, suppresses the refinement or recrystallization of the recrystallized grains and improves the strength, elongation and toughness, but if it is less than 0.03 wt%, its effect is small and 0.50 wt%. %, The ductility is adversely affected, so the content was made 0.03 to 0.50 wt%.

The dendrite branch spacing (DAS) is 200μ
Although a billet having a diameter of m or less is cast, if the dendrite branch spacing (DAS) exceeds 200 μm, it becomes difficult to obtain uniform fine spheroidization of the primary crystal α (Al) phase when heated to a semi-melting temperature range, and it is uniform. Since it takes time to perform the homogenization treatment when performing the deoxidization treatment, the dendrite branch interval (DAS) is set to 200.
It was set to not more than μm.

By subjecting the billet obtained by casting to homogenization treatment, Al ₂ Cu crystallized at the grain boundaries during casting,
Crystallized substances such as Mg ₂ Si dissolve in the matrix. When the homogenization treatment temperature is less than 450 ° C. or the heating time does not reach 1 hour, solid solution is not sufficiently obtained and casting strain is not sufficiently removed. However, at a processing temperature exceeding 600 ° C., partial melting occurs and the workability during forging is impaired. Further, when the heating time exceeds 10 hours, the effect of homogenization commensurate with the long heating time is not increased and the heating energy is lost. For this reason, the homogenization treatment conditions were heating at a temperature of 450 to 600 ° C. for 1 to 10 hours.

Next, the working strain is introduced by cold forging so that the process can be simplified and the strain can be effectively introduced with a small working rate, and the strain is uniformly introduced to the entire forging billet. The frame is forged so that The distortion rate is
If it is less than 5%, the introduction of strain is small, and even if the temperature is raised to the semi-melting temperature range, the primary spheroidal α (Al) phase cannot be made uniform spheroidization, while if it exceeds 50%, the primary crystal α (Al) is spheroidized. The change in phase size was not observed, and cracking occurred during cold forging, so the content was made 5 to 50%. The strain rate here is (L ₁ −L ₂ ) / L ₁ × 100, where L ₁ is the original length of the forging billet and L ₂ is the length of the billet after forging.
It was defined by (%).

The processing introduction speed can be greatly increased by adding crystal grain refining and homogenizing treatment to the billet ingot. From the viewpoint of productivity, it is preferable that the processing introduction speed is as fast as possible. However, 50 mm / sec. If it exceeds 50 mm / sec., Cracks may occur during forging, or forging dead zones may occur, and strain may not be uniformly introduced.
Below. Also, the billet temperature during cold formwork forging is
Above the recrystallization temperature, the introduction of strain for a predetermined processing rate was insufficient, and the primary crystal α (Al) phase did not have a granular structure even when the temperature was raised to the semi-melting temperature, so the temperature was set below the recrystallization temperature.

After that, the billet is heated to a temperature higher than the eutectic temperature or the solidus temperature, and is held at a temperature at which the liquid phase ratio is 20 to 80% for semi-melt molding, but if the liquid phase ratio is less than 20%. Uniform spheroidization of the primary crystal α (Al) phase cannot be achieved, and the deformation resistance of semi-molten molding is large, making pressure molding difficult. Further, if it exceeds 80%, a molded product having a uniform structure cannot be obtained. Therefore, the liquid phase ratio in the semi-melting temperature range above the eutectic temperature or solidus temperature is set to 20 to 80%.

[0023]

EXAMPLES Specific examples of the present invention will be described below. FIG. 1 is a schematic view of cold die forging used in the method of the present invention. In the figure, reference numeral 1 is a forging die, 2 is a forging die punch, and 3 is an aluminum alloy billet.

Si, Mg, Zn, Fe, Ti, B, C
A molten metal was prepared so that u, Mn, and Cr each had a composition shown in Table 1 below, and an aluminum alloy billet was cast by continuous casting.

[0025]

[Table 1]

The aluminum alloy billets shown in Table 1 were treated under the conditions shown in Table 2 to evaluate the moldability of semi-melt molding and the shape of the primary crystal α (Al) phase after semi-melt molding. Also described in.

[0027]

[Table 2]

As for the moldability shown in Table 2 when the processing strain was introduced, the moldability that did not cause cracks when molded under the molding conditions shown in Table 2 was good, and the moldability was evaluated as ×, and the cracks were found. It was judged by. Regarding the moldability of the semi-melt molding, the good one was evaluated as ◯, and the poor moldability was evaluated as x. Primary crystal α after semi-melt molding
The shape of the (Al) phase was evaluated as ◯ when spheroidization was recognized, and as x when spheroidization was insufficient. In the homogenization of the primary crystal α (Al) phase after semi-melt molding,
If the (Al) phase size is 100 μm or less, it is set to 100 μ
Those having a size exceeding m were judged as x.

FIG. 2 shows a photograph of a representative example in which the fine homogenization of the primary crystal α (Al) phase was evaluated as ◯.

[0030]

As described above, according to the method of the present invention, the process can be simplified and the cost can be reduced as compared with the conventional semi-molten billet. Further, the obtained structure is also primary crystal α (Al).
Phase size average 100μm or less and primary crystal α (Al)
It has a uniform spheroidized structure with a phase area ratio of 50% and can be used for transportation equipment such as automobile parts.

[Brief description of drawings]

FIG. 1 is a schematic view of cold formwork forging.

FIG. 2 is a photomicrograph of a typical example in which fine homogenization of primary crystal α (Al) phase is evaluated as ◯, and the magnification is 50 times.

[Explanation of symbols]

1 Forging die 2 Forging die punch 3 Aluminum alloy billet

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B22D 17/00 B22D 17/00 Z C22C 21/02 C22C 21/02 21/06 21/06 C22F 1/05 C22F 1/05 // C22F 1/00 681 1/00 681 682 682 685 685 695 A 691 691B 691C 694 694A (72) Inventor Yasuyuki Murayama 80 Kyushu Mitsui Aluminum Industry Co., Ltd. ) Inventor Tsunaki Iwashita 80 Yoyama-cho, Omuta City, Fukuoka Prefecture F-term in Kyushu Mitsui Aluminum Industry Co., Ltd. (Reference) 4E087 AA01 BA04 BA14 CB03 DB15 DB22 GA07 HB17

Claims (2)

[Claims] 1. Si 0.15 to 1.5 wt%, Mg 0.
20-2.0 wt%, Zn 0.30 wt% or less, Fe
1.2 wt% or less, at least one or more of Ti 0.001 to 0.5 wt% and B 0.0001 to 0.5 wt%, Cu 0.05 to 0.50 wt%, Mn 0.10 to
An aluminum alloy containing at least one of 1.0 wt% and Cr 0.03 to 0.50 wt%, the balance being substantially composed of Al, and having a dendrite branch interval of 200 μm or less is produced, and then strained. Rate 5-50%,
Processing introduction speed 50 mm / sec. Below, a working strain is introduced by cold mold forging at a temperature lower than the recrystallization temperature, then the temperature is raised to a temperature higher than the eutectic temperature or the solidus temperature, and the liquid phase ratio is 20 to
A method for producing a semi-molten cast billet of an aluminum alloy for transportation equipment, characterized by holding at a temperature of 80% and performing semi-melt processing. 2. The aluminum for transportation equipment according to claim 1, wherein the aluminum alloy is manufactured and subjected to a homogenizing treatment at a temperature of 450 to 600 ° C. for 1 to 10 hours before introducing a working strain. A method for producing a semi-molten cast billet of an alloy.