JP3346186B2 - Aluminum alloy material for casting and forging with excellent wear resistance, castability and forgeability, and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy material having excellent forgeability and abrasion resistance used for automobile parts, home electric appliances, etc., which is cast by a die or die casting and then formed by forging. The present invention relates to a casting / forging alloy material and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum alloy materials for forging are commonly used as a continuously cast rod obtained by continuously solidifying a molten metal in a water-cooled mold, or a round bar extruded from a continuously cast rod. ing. However, when a product having a complicated shape is formed using these materials, the yield is low and the cost is high. Therefore, recently, a casting / forging method for forming a preformed body manufactured by a die or die casting by one-step forging has become widespread.
That is, in this casting / forging method, a preformed body is cast as close as possible to a final product at the time of casting, and the preformed body is hot forged without going through an extrusion step. In order to form the preformed body by one-step forging, it is important to obtain a sound preformed body in the pre-forging step, and development of an alloy having good castability is required. However, with the current aluminum alloy, a material satisfying all of castability, forgeability, and product strength has not been put to practical use. For example, aluminum alloys currently used for forging include Al-Mg-Si based alloys such as JIS A6061 and A6151 and JIS2017 and A70.
There is a high strength wrought material such as 75. However, since these materials use a continuously cast material or an extruded material as a forging material, when trying to obtain a three-dimensionally shaped preform by die casting, cracks during casting, poor fluidity, and the like are caused. As a result, casting defects are likely to occur, and the desired preformed body shape cannot be obtained. Further, since defects are likely to be present inside the material, it is not suitable as a forging material.

[0003]

SUMMARY OF THE INVENTION As an alloy material for extrusion and forging, the present inventors have proposed Si, Sb, Fe, Ti,
Japanese Patent Application No. 4-1 discloses an aluminum alloy material that balances the components among Mg, B, and Cu and has a tensile strength comparable to that of the wrought alloy.
No. 43405. This aluminum alloy is extrudable,
In order to ensure forgeability, the contents of Cr and Mg are kept low. However, since the Cr content is small, coarsening of recrystallized grains is sometimes observed in the solution treatment during the T6 treatment after forging. Further, in the casting / forging alloy introduced in Japanese Patent Application Laid-Open No. H8-3675, the Si content is adjusted to ensure the forgeability, but the castability is not sufficient because the Si content is low. Also, the wear resistance is not sufficient. The present invention is an improvement of the two types of alloys proposed above, and improves castability and forgeability by increasing the amount of Si and Cr in relation to other alloy components, thereby preforming a complex shape. To obtain an aluminum alloy material that suppresses coarsening of recrystallized grains during solution treatment, is excellent in wear resistance, and is excellent in forgeability by homogenizing the preformed body. Aim.

[0004]

Means for Solving the Problems The aluminum alloy material for casting and forging according to the present invention has a Si: 3.0 to achieve the object.
To 7.0% by weight, Mg: 0.6 to 1.5% by weight, Mn:
0.1 to 0.5% by weight, Cu: 0.3 to 0.9% by weight,
Cr: 0.35 to 0.5% by weight, Fe: 0.25% by weight
Hereinafter, Ti: 0.01 to 0.2% by weight, B: 0.001
~ 0.01% by weight, with the balance being substantially Al. This aluminum alloy material for casting / forging further contains Sr: 0.001 to 0.05% by weight, Sb:
It is preferable that one or two kinds of the eutectic Si are contained at 0.05 to 0.15% by weight, and the average length of eutectic Si at the time of casting is 3 to 6 μm. This aluminum alloy material for casting and forging is manufactured by melting, then producing a preformed body by die casting, performing a homogenizing treatment of heating the preformed body to 500 to 535 ° C. for 2 to 12 hours, and then forcibly cooling. And then the surface temperature of the forged material is 400-500 ° C
It is manufactured by hot forging under the following conditions, further performing T6 treatment, and machining. It is preferable that the gas content of the preformed body is restricted to 0.30 cc / 100 g or less. Further, at the time of melting, it is preferable to degas the molten alloy in an atmosphere of a mixed gas of argon or nitrogen and chlorine. When the preformed body has a simple shape and can be easily forged, the homogenization treatment and the forced cooling can be omitted. In addition, "for casting / forging" described in this specification means "a material for molding by forging after casting with a die or die casting or the like".

[0005]

In the aluminum alloy material of the present invention, a preform having a complicated shape is manufactured by casting, and is formed into a final shape by forging without going through an extrusion process. Has adopted. Above all, an increase in the Si content effectively improves the fluidity, casting cracks, sink marks and the like, and enables the production of a preformed body having a complicated shape. Increasing the Si content is also effective in improving wear resistance. In addition, due to the increase in the Cr content, coarsening of recrystallized grains is suppressed in the solution treatment during the T6 treatment after forging, and elongation is given to the material. Deterioration of the forgeability due to an increase in the amount of Si and Cr can be eliminated by homogenizing the preform at a high temperature when the preform has a complicated shape and poor forgeability. Although the homogenization treatment is not performed on the preformed body used in the conventional casting / forging method, the extrusion step can be omitted, thereby contributing to cost reduction.

Hereinafter, alloy components, contents, and the like contained in the aluminum alloy material of the present invention will be described. Si: 3.0 to 7.0% by weight The function of improving the flow of molten metal to the mold when casting a complicated preform, improving the casting cracking and sinking properties, and casting a sound preform. . It also has the effect of improving the wear resistance of the product. Such an effect becomes remarkable when the content of Si is 3.0% by weight or more. However, when a large amount of Si exceeding 7.0% by weight is contained, elongation and toughness are deteriorated, and forgeability is deteriorated. Mg: 0.6 to 1.5% by weight An alloy component that exhibits an effect of improving the material strength by precipitating fine Mg ₂ Si into a matrix by T6 treatment. If the Mg content is less than 0.6% by weight, the effect of improving the strength is small, and if it exceeds 1.5% by weight, the workability during forging is deteriorated.

Mn: 0.1 to 0.5% by weight An alloy component which has the effect of suppressing the coarsening of recrystallized grains and improving the strength, elongation and toughness in the solution treatment at the time of T6 treatment. The effect of Mn becomes significant at a content of 0.1% by weight or more. However, a large amount of Mn exceeding 0.5% by weight
Is contained, the precipitation amount of a hard and brittle intermetallic compound such as an Al—Si—Fe—Mn system increases, which adversely affects workability. In this regard, when the Mn content is maintained in the range of 0.1 to 0.5% by weight, the Al-Fe-Si-based compound changes from acicular to massive, thereby improving toughness. Cu: 0.3 to 0.9% by weight Al-Cu based material such as CuAl ₂ during aging treatment of T6 treatment,
It becomes an Al-Cu-Mg precipitate or the like and exhibits an effect of improving the material strength. The effect of Cu becomes significant at a content of 0.3% by weight or more. However, when a large amount of Cu exceeding 0.9% by weight is included, the corrosion resistance deteriorates.

Cr: 0.35 to 0.5% by weight Like Mn, it has the effect of suppressing the coarsening of recrystallized grains and improving the strength, elongation and toughness in the solution treatment during the T6 treatment. The effect of Cr becomes remarkable at 0.35% by weight or more, and a greater effect can be obtained by adding it in combination with Mn. However, when a large amount of Cr exceeding 0.5% by weight is contained, workability is deteriorated. Fe: 0.25% by weight or less Fe is a component mixed into the aluminum alloy as an impurity.
It becomes an Fe—Si-based compound and is dispersed in the matrix, which has an adverse effect on elongation, toughness, corrosion resistance, and the like. Therefore, Fe
The lower the content, the better, but excessively lowering the Fe content makes it difficult to melt the alloy. Therefore, in the present invention, the upper limit of the Fe content is set to 0.25% by weight where no substantial adverse effect is observed.

Ti: 0.01 to 0.2% by weight The structure of the ingot is made fine to prevent cracking of the ingot, and rough surface such as orange peel occurs on the surface of the forged product due to plastic working. This is an alloy component that has the effect of preventing Such an effect is obtained when 0.01% by weight or more of Ti
It becomes remarkable in the content. However, a large content of Ti exceeding 0.2% by weight promotes the generation of giant crystallized substances such as TiB ₂ and TiAl ₃ and causes cracks during forging and surface flaws during cutting. Becomes B: 0.001 to 0.01% by weight Like Ti, it is an alloy component effective for refining crystal grains at the time of casting. The effect is exhibited at 0.001% by weight or more. However, when Ti is contained in a large amount exceeding 0.01% by weight, crystallized substances such as huge TiB ₂ are easily generated,
Workability such as forging and cutting decreases.

Sr: 0.001 to 0.05% by weight An alloy component added as necessary, and has an effect of refining eutectic Si at the time of casting and improving impact value and elongation. Also, since excessive miniaturization does not occur unlike Na, wear resistance is not impaired. The effect of Sr is
It becomes remarkable at a content of 0.001% by weight or more. But,
A large content exceeding 0.05% by weight causes a reduction in workability due to the generation of intermetallic compounds and promotes intervention of gas, inclusions, and the like in the molten aluminum. Sb: 0.05 to 0.15% by weight An alloy component that is added as needed, and has an effect of refining eutectic Si at the time of casting similarly to Sr.
Forging alloys improve elongation. Also, since excessive miniaturization does not occur unlike Na, wear resistance is not impaired. The refining effect by the addition of Sb is 0.
It becomes remarkable at a content of 05% by weight or more. However, 0.1
A large content exceeding 5% by weight promotes generation of an intermetallic compound such as Sb ₂ Mg ₃ and deteriorates forgeability.

Casting In smelting / casting an aluminum alloy whose composition is designed as described above, it is important to control the manufacturing conditions to a higher degree than in the casting of a normal Al-Si alloy. Specifically, an aluminum alloy is melted at 700 to 750 ° C., and the gas content of the molten alloy is particularly strictly controlled. If the manufacturing conditions at this time are inappropriate, cracks are likely to occur during forging, and blisters are likely to occur in the product even in the homogenization treatment and the T6 treatment. For example, melting at a high temperature exceeding 750 ° C. increases the gas content, which causes cracking during forging and causes blistering of the product. The molten alloy melt is sufficiently degassed in a mixed gas atmosphere of argon or nitrogen and chlorine gas as compared with a normal casting. The gas content of a normal Al-Si based casting is 0.30 to 0.35 cc / 100 g, but at most 0.25 in the aluminum alloy material according to the present invention.
Reduce gas content to the order of 0.30 cc / 100 g. This prevents the occurrence of blisters during the homogenization process.

An ordinary method is employed for miniaturization, but the casting temperature is set at 700 to 750 ° C. As the casting method, gravity casting, molten metal forging, and the like are preferable, and the die casting method is not preferable because the gas content increases. The material of the mold includes metal, graphite, and the like. Mold temperature is from room temperature
The temperature is set in the range of 450 ° C., but it is important that the temperature is always constant. If the temperature varies, the casting structure fluctuates, making it difficult to control in the subsequent process. The cooling rate of the molten metal at the time of casting is set to 0.3 ° C./second or more to prevent generation of coarse crystals. At a cooling rate lower than 0.3 ° C./sec, coarse crystallized substances are crystallized at crystal grain boundaries, which adversely affects workability during forging.

The preformed body thus obtained has no casting defects, and is a material that can be hot forged without going through an extrusion step. When the average length of the eutectic Si in the preformed body is adjusted to 3 to 6 μm, the metal flows smoothly during forging, and forging defects such as cracks and orange peel do not occur. On the other hand, if the average length of eutectic Si is less than 3 μm, the number of Si particles effective for abrasion resistance is reduced by homogenization treatment or heat treatment because the average length is too small. Conversely, in the case of eutectic Si having an average length exceeding 6 μm, the eutectic Si particles are broken during hot forging, and metal flow is not performed smoothly due to the large size, and casting defects are likely to occur.

Homogenization treatment: 500-535 ° C. × 2-12
Time heating By pre-homogenizing the preformed body obtained by casting,
Crystallized substances such as Al ₂ Cu, Mg ₂ Si, etc. crystallized at the crystal grain boundaries during casting dissolve in the matrix. Further, by the homogenization treatment, Al—Fe—Si—Cr, Al—Fe—Mn
A crystallized product of an intermetallic compound such as a Si system is dissolved in a matrix as much as possible. Thereby, deformation resistance at the time of hot forging is small, and workability is improved. In addition, eutectic Si having an average length of 3 to 6 μm becomes spherical, and the deformation resistance during hot forging decreases. Regarding the conditions of the homogenization treatment, if the treatment temperature is less than 500 ° C. or the heating time does not reach 2 hours, the solution is not sufficiently dissolved and the casting distortion is not sufficiently removed. But 5
At processing temperatures above 35 ° C., partial melting of the preform occurs. When the heating time exceeds 12 hours, the effect of homogenization corresponding to the prolongation of the heat treatment does not increase. The homogenized preform is forcibly cooled after the homogenization to maintain its structure. The cooling rate at this time needs to be 200 ° C./hour or more, and forced air cooling, cooling in oil, cooling in water, or the like is employed. In addition, if the shape of the preformed body manufactured by casting is simple, casting defects do not occur,
Since the flow of metal is simple even during hot forging, hot forging is possible without performing homogenization treatment.

Hot forging: Material surface temperature after forging is 40
0 to 500 ° C. Prior to hot forging of the preformed body, the preformed body is heated to 400 to 500 ° C. in order to dissolve the alloy element as much as possible. On the other hand, the hot forging die is required to be 3 in consideration of the material size and the working ratio.
It is preheated to 00 to 450 ° C. and hot forged at a working ratio of 30 to 80%. At this time, the material surface temperature after forging is 4
It is important to select the heating conditions so as to be from 00 to 500 ° C, preferably from 450 to 500 ° C. By setting the hot forging to the high-temperature condition, the deformation resistance during forging is reduced, the forgeability is improved, and the Cr and Mn-based compounds can be finely and uniformly distributed. As a result, coarsening of the recrystallized grains is prevented in the solution treatment during the next T6 treatment. On the other hand, if the heating temperature of the preformed body exceeds 500 ° C., the alloy material may be partially melted by the temperature rise during forging. Below 400 ° C, deformation resistance increases,
Further, since the Cr and Mn-based compounds do not precipitate finely,
6 Recrystallization grains may be coarsened by the solution treatment during the treatment.

T6 treatment: The hot-forged aluminum alloy material is subjected to solution treatment to form a solid solution of Cu, Mg, Si, etc., quenched with water, and then subjected to aging treatment. In the solution treatment, for example, a hot forged product is heated to 500 to 530 ° C. for 2 to 6 hours. In the aging treatment, heating is performed at 150 to 200 ° C. for 4 to 12 hours. Al ₂ Cu, Mg ₂ Si by aging treatment
Etc. precipitate, and the material strength increases. Further, Al-Si-Fe-Cr-based, Al-Mn solid solution
The intermetallic compound such as an Fe-based compound is also finely precipitated by the aging treatment, though in a small amount, and improves the strength of the material. The aging-treated Al alloy material is then machined and, if necessary, subjected to a surface treatment to become a final product.

[0017]

EXAMPLES Various aluminum alloys having the compositions shown in Table 1 were melted at 720 ° C. as aluminum alloys used for various tests.

[0018]

Example 1 Approximately 10 kg of the molten aluminum alloy of Sample No. 3 was degassed under the conditions shown in Table 2, poured into a mold heated and maintained at 400 ° C., and cooled at 0.4 ° C./sec. The mold used was a cast iron block-shaped mold having a size of 31 mm in height, 70 mm in width, and 130 mm in length. A sample was cut out from the obtained block-shaped ingot, and the gas content was measured. Table 2 also shows the measurement results. As is clear from Table 2, the gas content of the ingot is large in the degassing treatment using only nitrogen, but the gas content is 0.30 cc in the degassing using argon or a mixed gas of chlorine-nitrogen.
/ 100 g or less. Therefore, 530 ℃ × 6
When the soaking process was performed for a long time, swelling did not occur in ingots A and B, whereas swelling occurred in ingot C.

[0020]

Example 2 In order to investigate the effect of Sr and Sb on the eutectic Si size, the melts of Sample Nos. 3, 7 to 9 were degassed at 720 ° C. using an N ₂ —Cl ₂ mixed gas. The casting was cast into the same mold as in Example 1, and the casting structure of the obtained ingot was examined. As shown in Table 3, the average length of the eutectic Si, which is the result of the investigation, shows that the eutectic Si is refined by the addition of Sr and Sb.

[0022]

The present inventors have found that the average length of eutectic Si is 3 to
It has already been found that a thickness of 6 μm does not impair the abrasion resistance and has good toughness.
260462). Sample Nos. 3 and 7 according to the invention
All of the ingots No. to No. 9 satisfy the requirement of the average length of eutectic Si of 3 to 6 μm, and can be said to have good wear resistance and toughness.

Example 3 The melts of Sample Nos. 1 to 5 were degassed at 720 ° C. using an N ₂ —Cl ₂ mixed gas,
It was cast into a block mold made of cast iron that was heated and maintained at 0 ° C. A sample having a diameter of 14 mm and a height of 21 mm was cut out from the obtained ingot to prepare an As Cast material and a material (HO material) which was forcibly air-cooled after soaking at 530 ° C. for 6 hours.
Each material was heated to 350 ° C., 400 ° C., and 450 ° C., and hot deformation resistance was examined by a compression test method. Figure 1 shows the compression test method.
As shown in the figure, an As Cast material or HO is placed between the upper mold 1 and the lower mold 2 heated and maintained at 350 ° C, 400 ° C or 450 ° C.
The As Cast material or the HO material 3 was compressed at a compression speed of 100 mm / sec. Then, the load-displacement curve shown in FIG. 2 is obtained for each material, and the processing rate 5
The required load at 0% was read, and the hot deformation resistance was calculated by dividing by the ideal cross-sectional area obtained by the calculation. Table 4 shows the survey results. Note that the material surface temperature immediately after the compression test was a value close to the mold temperature because the sample was small.

[0025]

As is clear from the results of the investigation in Table 4, As C
The deformation resistance of the HO material is smaller than that of the ast material, and the deformation resistance decreases as the test temperature increases. Also,
As the Si content increases, the deformation resistance also increases. From the results of this investigation, it is found that it is effective to set the preheating temperature and the temperature after forging of the HO material to 400 ° C. or more as the evaluation of the forgeability (workability) in hot forging. Also, when the forging temperature is as high as 450 ° C., the hot deformation resistance is small even with an As Cast material, which indicates that a forging product having a simple shape can be forged without a homogenization treatment. However, a high temperature exceeding 500 ° C. is not preferable because the material partially melts.

Example 4: As Cas having the composition of Sample No. 3
The homogenization treatment was performed on t-materials under various conditions, and the effect of the homogenization treatment conditions on the hot deformation resistance was investigated. The shape and test method of the sample used in this example were the same as those in Example 3. The hot test conditions were as follows:
And hot forging at a mold temperature of 450 ° C. and a working ratio of 50%. As can be seen from Table 5 showing the test results, the preformed body subjected to the homogenization treatment according to the present invention has a low hot deformation resistance value and has good forgeability. However, when the temperature of the homogenization treatment was less than 500 ° C. and the treatment time was about 1 hour, the hot deformation resistance of the preformed body was almost the same as that of the As Cast material. Although the temperature at the time of forging has the greatest effect on the hot deformation resistance value, it can be seen that when the forging temperature is kept constant, the forgeability is further improved by the homogenizing treatment of the preformed body. As a result, it was confirmed that, even in a preformed body having a complicated shape, the hot deformation resistance value was reduced by the homogenization treatment and forging could be performed smoothly.

[0028]

Example 5: A molten metal having the composition of Sample Nos. 1 to 9 was degassed using a N ₂ -Cl ₂ mixed gas,
And then cast into a block mold made of cast iron which was heated and maintained at 400 ° C. The obtained ingot was subjected to a soaking treatment at 520 ° C. for 6 hours, and then was forcedly cooled. Then 450
C., and hot forging was performed at a working rate of 60% using a mold that was also heated and maintained at 450.degree. 520 ℃ × 2 for forged products
175 ° C × after solution treatment of time and quenching with water
The aging treatment was performed for 6 hours. A test piece was cut out of the material after the aging treatment in a direction perpendicular to the forging direction, and mechanical properties and wear resistance were investigated. The abrasion resistance was evaluated by using FC28 as a mating material and using a friction speed of 1.21 without using a lubricant.
It was slid at a friction distance of 600 m at a rate of m / sec, and evaluated by the specific wear amount. Tensile strength 400N / mm ² or more, 0.2% proof stress 3
50N / mm ² or more, elongation 10% or more, specific wear 9 × 1
A product with a value of 0 ^-7 mm ² / kg or less is judged to be acceptable. As can be seen from the survey results in Table 6, the forged product obtained according to the present invention was subjected to T6 treatment, and the tensile strength, 0.2% proof stress,
Both elongation and wear resistance were good. In addition, the microstructure of the T6 treated material except for Sample No. 6 having a small Cr content,
All were fine recrystallized grains. On the other hand, in the T6 treated material of Sample No. 6 with a small Cr content, coarse recrystallized grains were detected.

[0030]

[0031]

As described above, according to the present invention, an alloy in which the castability is improved by increasing the amount of Si and Cr and the coarsening of recrystallized grains is suppressed by solution treatment during T6 treatment after forging. Adopt design. When this aluminum alloy material is homogenized at a relatively high temperature, deterioration of forgeability due to an increase in the amount of Si and Cr is suppressed. In this way, the aluminum alloy material of the present invention can be formed into a product shape by a casting / forging method that does not go through an extrusion step, and is a material having excellent wear resistance and mechanical properties. It is used in a wide range of fields such as home appliances.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a hot deformation resistance test

FIG. 2 is a graph showing a load-displacement curve.

[Explanation of symbols]

1: Upper mold 2: Lower mold 3: As Cast material or HO material

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C22F 1/00 682 C22F 1/00 682 683 683 691 691B 691C 694 694B (56) References JP-A-7-109537 (JP, A) JP-A-7-109536 (JP, A) JP-A-7-48643 (JP, A) JP-A-9-125181 (JP, A) International publication 95/34691 (WO, A1) West German patent 1,952,564 (DE, B) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 21/00-21/18 C22F 1/04-1/057

Claims (5)

(57) [Claims] 1. Si: 3.0 to 7.0% by weight, Mg:
0.6 to 1.5% by weight, Mn: 0.1 to 0.5% by weight,
Cu: 0.3 to 0.9% by weight, Cr: 0.35 to 0.5
% By weight, Fe: 0.25% by weight or less, Ti: 0.01 to
0.2% by weight, B: 0.001 to 0.01% by weight, the balance being substantially an Al composition, and an aluminum alloy material for casting and forging having excellent wear resistance, castability and forgeability. 2. The composition according to claim 1, further comprising one or two kinds of Sr: 0.001 to 0.05% by weight and Sb: 0.05 to 0.15% by weight, wherein the average length of the eutectic Si at the time of casting is 3%. 2. The aluminum alloy material for casting and forging according to claim 1, which has an excellent wear resistance, castability and forgeability. 3. After melting the alloy having the composition according to claim 1 or 2, a preformed body is manufactured by die casting, and
After performing a homogenization treatment of heating to 00 to 535 ° C for 2 to 12 hours, forcible cooling is performed, and then hot forging is performed under the condition that the surface temperature of the forged material is 400 to 500 ° C.
Abrasion resistance characterized by processing and machining,
A method of manufacturing aluminum alloy materials for casting and forging with excellent castability and forgeability. 4. The production of an aluminum alloy material for casting / forging having excellent wear resistance, castability and forgeability according to claim 3, wherein a preformed body whose gas content is regulated to 0.30 cc / 100 g or less is used. Method. 5. An aluminum alloy material for casting and forging having excellent wear resistance, castability and forgeability according to claim 3, wherein the molten alloy is degassed during melting in an atmosphere of a mixed gas of argon or nitrogen and chlorine. Manufacturing method.