JPH06279904A - Production of hyper-eutectic al-si alloy for forging and forging stock - Google Patents

Abstract

PURPOSE:To obtain a hyper-eutectic Al-Si alloy excellent in mechanical strength, wear resistance, and formability and capable of forging. CONSTITUTION:This hyper-eutectic Al-Si alloy has a composition which contains, by weight ratio, 13-21% Si, 0.5-5.0% Cu, 0.3-2.0% Mg, 6-120ppm Ca, and 40-130ppm P and where P/Ca is regulated to 0.6-6 by weight ratio. The component-regulated molten alloy is cast at a casting temp. not lower than (liquidus temp. + 70 deg.C), into an ingot of <=150mm diameter or thickness in the case of DC casting and into an ingot of =30mm diameter or thickness in the case of gravity die casting. In the cast structure, primary-crystal Si is micronized to <=20mum. Because the primary-crystal Si is micronized the occurrence of defects, such as crack, can be prevented even if high-degree forging is done and, as a result, a forged product excellent in shape characteristics can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hypereutectic Al-Si alloy for forging which is excellent in strength, wear resistance, workability and the like and a method for producing a forging material.

[0002]

2. Description of the Related Art A hypereutectic Al--Si alloy containing 12.6% by weight or more of silicon has a small coefficient of thermal expansion and is excellent in heat resistance. In addition, since high-hardness primary silicon crystallizes when the molten metal solidifies, it is used as a component for internal combustion engines such as pistons, crankcases, brake drums, and cylinder liners that require wear resistance. The hypereutectic Al-Si alloy exhibits excellent wear resistance due to the crystallization of hard primary crystal Si, but tends to have a cast structure in which primary crystal Si grows largely. If processing is performed in this state, cracks occur at the interface with the primary crystal Si or aluminum matrix, and not only the intended product cannot be obtained, but also the mechanical properties are not sufficient. Due to this cast structure, the hypereutectic Al-Si alloy was rarely used as a forging material that is highly processed. In addition, primary crystal Si
The structure with a large growth accelerates the wear of the tool due to the primary crystal Si during the cutting process and shortens the tool life.

Primary crystal Si is refined by rapid solidification. For example, a powder method is adopted, or Japanese Patent Laid-Open No. 52-12
As disclosed in Japanese Patent No. 9607, the molten aluminum alloy is rapidly solidified by the molten metal rolling method to refine the cast structure. In addition, Al-Cu can be added to molten aluminum alloy.
The primary crystal Si can also be made fine by adding P and Cu-P and performing P treatment. Further, in JP-A-1-298131 and JP-B-4-34621, both primary crystal Si and eutectic Si are refined by adding B such as Ti and B together with P treatment to improve mechanical properties and machinability. An improved hypereutectic Al-Si based alloy is disclosed. By the P treatment, the primary crystal Si is refined to improve workability and mechanical properties. It is considered that the added P forms an intermetallic compound AlP, and this intermetallic compound AlP acts on the refinement of primary crystal Si.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 52-153817, a fusion product of sodium hexametaphosphate and alumina is added to a molten aluminum alloy to suppress segregation of primary crystal Si to miniaturize a cast structure. Further, in JP-A-60-204843, Cu-P alloy, red phosphorus,
16 with phosphorus-containing substances such as sodium phosphate and calcium phosphate
~ Eutectic aluminum-Si containing ~ 25 wt% silicon
Processing alloys is introduced.

[0005]

However, hypereutectic Al--
Since the Si-based alloy requires special equipment and operating conditions in the rapid solidification method or the like, it is generally produced by die casting, DC casting or the like. In methods such as die casting and DC casting through ingots, it is often the case that the addition of P alone does not sufficiently refine the primary crystal Si. Especially when used as an extruded material, a forged material, etc. The crack caused by Si becomes a problem. The effect of P addition for refining primary crystal Si tends to be lost when the hypereutectic Al-Si alloy contains Na or Ca. In this regard, in pages 24 to 25 of "Development Research Report (I) of High Silicon-Aluminum Alloy Die Cast in 1984" edited by the foundation material, Na contained in the hypereutectic Al-Si alloy is described. And Ca react with P to form Na-P and Ca-P, which prevents the formation of AlP that acts on the refinement of primary crystal Si.

Therefore, the addition of P for the purpose of refining the primary crystal Si is a hypereutectic Al-Si containing as little Na and Ca as possible.
The applicable objects were limited to alloys. Ca is an effective alloying element that exhibits the effect of improving eutectic Si and improves the properties such as tensile properties and impact value of the hypoeutectic alloy. However, in the hypereutectic Al-Si alloy, Ca inhibits the action of P added for refining the primary crystal Si, and conversely P
Inhibits the improving effect of Ca on the eutectic structure,
Ca was not added to the hypereutectic Al-Si alloy. Therefore, in an alloy of this system, when it is attempted to improve workability by further refining the primary crystal Si,
The P treatment alone is not sufficient, and there is no choice but to rely on a rapid solidification method such as a melt rolling method that requires special equipment.

As a result of investigating and studying P treatment in the presence of Ca, the inventors of the present invention have made it possible to make primary crystals of Si by coexisting appropriate amounts of P and Ca under certain specific conditions, as compared with the case of only P. It was found that the miniaturization of No. 1 was further advanced, and it was proposed in Japanese Patent Application No. 4-244259. That is,
P: 40-13 under the condition that the P / Ca weight ratio is 0.6-6.
0ppm and Ca: 6-120ppm hypereutectic Al-S
1-B-C-D-E- of FIG.
When casting the molten metal maintained in the A region, a product having a cast structure in which primary crystal Si is refined is obtained. The present invention further develops the condition of P / Ca = 0.6 to 6 which is effective for refining primary crystal Si, and performs rapid solidification by adjusting the composition with other alloy compositions. Hypereutectic A for forging which is excellent in workability and mechanical properties suitable as a forging material because the primary crystal Si is sufficiently miniaturized even in die casting, DC casting, etc.
An object is to provide an l-Si alloy.

[0008]

Means for Solving the Problems Hypereutectic A for forging of the present invention
In order to achieve the purpose, the 1-Si alloy has Si: 1
3 to 21% by weight, Cu: 0.5 to 5.0% by weight, Mg:
0.3 to 2.0 wt%, Ca: 6 to 120 ppm and P: 40 to 130 ppm are included, and P / Ca is characterized by being in a range of 0.6 to 6 by weight ratio. The hypereutectic Al-Si alloy melt having this composition is (liquidus line +70
DC casting or die casting is performed at a casting temperature of ℃) or higher.
When using DC casting, it is cast into an ingot having a diameter or thickness of 150 mm or less. In the case of die casting, it is cast into an ingot having a diameter or thickness of 30 mm or less. The obtained ingot is
The average grain size of primary crystal Si (hereinafter simply referred to as grain size) is 20μ
It is a forging material with a casting structure of m or less. The forging material is forged into a scroll at a ram speed of 50 mm / sec or less, for example. Alternatively, it is extruded into a pipe with a bottom by backward extrusion, and then cut and cut to produce a cylinder liner.

[0009]

When P is added to the hypereutectic Al-Si alloy, A
An IP compound is formed. The AlP compound acts as a nucleus of primary crystal Si, and the cast structure is refined. At this time,
When Ca coexists, a large number of Ca-P compounds are formed in addition to AlP, and when the Ca-P compound is in a preferable state, it serves as an effective nucleus by crystallization of primary crystal Si. Ca-
It is speculated that the P compound acts as an effective crystal nucleus when the primary crystal Si crystallizes, and further refines the primary crystal Si, as compared with AlP. In order for the Ca-P compound to act as the nucleus of primary crystal Si, it is necessary to adjust the weight ratio P / Ca in the molten aluminum alloy immediately before casting to a range of 0.6 to 6. The weight ratio P / Ca immediately before casting is 0.
As long as it is maintained at 6 to 6, no matter which of the following methods is adopted or a combination of these methods is adopted, a cast structure which is further refined as compared with the conventional P treatment can be obtained. .

A method of preliminarily blending a predetermined amount of Ca and P with a melting raw material in consideration of consumption of Ca and P in the process from the start of melting to casting. A method of adding Ca after melting a hypereutectic Al-Si alloy in a step of melting and casting a hypereutectic Al-Si alloy containing a predetermined amount of P to obtain an ingot. A method in which a hypereutectic Al-Si-based alloy containing no Ca and P is melted, and then predetermined amounts of Ca and P are added simultaneously or in tandem. A method of analyzing the composition of a hypereutectic Al-Si alloy containing Ca and P according to any one of the above items immediately before casting, and adding Ca and P when the Ca and P are insufficient. The composition of a hypereutectic Al-Si alloy containing Ca and P in any of the above-mentioned items is analyzed immediately before casting. If the Ca content is excessive, either raise the melt temperature or increase the holding time. The method of reducing Ca content by doing.

Up to now, the reason why Ca has been considered to be detrimental to the refining effect of P treatment and harmful to the refining of primary crystal Si is that P / Ca ratio, Ca and P relative to Si content.
It is considered that this was due to insufficient studies on the content (different from the amount added), the time from melting to casting, the casting temperature, the cooling rate in the primary Si crystallization temperature range, and the like. That is, either condition is not appropriate, and Ca-
The reason is that the P compound did not work as an effective nucleus. Therefore, the present inventors conducted a detailed study on these conditions, as introduced in Japanese Patent Application No. 4-244259. The following conditions are Cu and M
The same holds true for a hypereutectic Al-Si alloy containing g.

Addition of Ca Ca is contained in the hypereutectic Al—Si alloy by either preliminarily containing it in the molten raw material or by adding it to the melted hypereutectic Al—Si alloy. be able to. In any case, since Ca is highly worn in the melting and holding processes, it is necessary to grasp the content not by the amount added but by the content. It should be noted that Ca is added in the form of lumps, rods, wires, powders, granules, melts, etc. as a Ca-containing Al-Ca-based mother alloy, compound, mixture, and the like. In order to control the Ca content with high accuracy, a predetermined amount of Ca should be added to the hypereutectic Al-Si alloy after melting.
Is preferably added. That is, if Ca is blended before melting, C is added in the steps such as melting, holding at high temperature, and degassing.
a is worn, and it becomes difficult to accurately control the Ca content in the ingot. In particular, when handling a large amount of metal as in continuous casting, the target Ca content cannot be obtained, and the probability of failure increases. Further, since the yield of Ca transferred to the ingot is low, it is necessary to add a larger amount of Ca in consideration of the amount of wear.

When Ca is added to the hypereutectic Al--Si alloy after melting, the Ca content in the ingot can be controlled relatively accurately, and the primary crystal Si can be refined as desired. For example, when Ca is mixed as a cold material into a melting raw material and cast immediately after melting, the yield of Ca is 45
There was a large variation in the range of ~ 85%. On the other hand, when Ca is added to the hypereutectic Al-Si alloy after melting and immediately cast, the yield of Ca is improved to 76 to 94%, and the Ca content of the ingot does not vary greatly. It was When the weight ratio P / Ca in the hypereutectic Al-Si alloy just before casting is in the range of 0.6 to 6.0, Ca-P
The miniaturization effect of the compound is effectively exhibited. But C
The a content gradually decreases when the hypereutectic Al-Si alloy is held in a molten state, and P / Ca increases accordingly. Further, the reduction rate of the Ca content increases as the temperature of the hypereutectic Al-Si alloy melt increases. Therefore, it is preferable to adjust the Ca content to a predetermined range prior to casting and then perform casting without a long holding time.

The Ca content is reduced, and the weight ratio P / C
When a exceeds 6.0, the Ca-P compound does not have a sufficient refining effect. Also, if the weight ratio P / Ca is less than 0.6, the miniaturization effect cannot be obtained. When the Ca content further increases and P / Ca decreases, the primary crystal Si becomes coarser than that in the case where no Ca is added. When the weight ratio P / Ca is less than 0.6, it is considered that the Ca concentration in the Ca-P compound also rises, which is not preferable because it does not work as crystal nuclei of primary Si. As a result, the miniaturization effect of P treatment is impaired, as reported previously. Also,
If the Ca content exceeds 120 ppm, the weight ratio P / Ca
Is less than 0.6, the primary crystal Si becomes finer, but the fluidity of the molten metal is remarkably reduced, and casting defects such as the boundary of the molten metal are likely to occur. From this point, the upper limit of Ca content is 120 pp
set to m. On the other hand, the lower limit of Ca content is P = 6C
6 from the value at the intersection B of a and P = 40 (see FIG. 1)
It was set to ppm.

Addition of P, P is less reactive than Ca. Therefore, even if P is added to the dissolution raw material in advance, or if P is added after the dissolution, the effect of P addition does not substantially change.
Therefore, the addition timing of P may be any of the following. Further, a hypereutectic Al containing a predetermined amount of P in advance
After melting the -Si alloy or the melting raw material, the remaining P can be added before or after the addition of Ca. P is added to the P-containing mother alloy, compound, mixture, etc. in the form of a lump, rod, wire, powder, granule, melt or the like.

Preparation of hypereutectic Al-Si alloy containing P or melting raw material → melting → Ca addition → casting Preparation of hypereutectic Al-Si alloy containing P-free or melting raw material → melting → Ca and P Simultaneous addition →
Casting Preparation of hypereutectic Al-Si alloy containing no P or molten raw material → Addition of molten P → Addition of Ca →
Casting Preparation of hypereutectic Al-Si-based alloy or P-free P-containing alloy → Melting → Ca addition → P addition
→ casting

The P content is the primary crystal S due to the Ca-P compound.
In order to promote the miniaturization of i, it is necessary to maintain it in the range of 40 to 130 ppm. Unlike the Ca content, the P content is not significantly affected by the holding time even when the hypereutectic Al-Si alloy is held in the molten state, and the decrease amount is small. If the P content is less than 40 ppm, the effect of refining the primary crystal Si is insufficient. However, if the P content exceeds 130 ppm, although there is an effect of refining the primary crystal Si, the fluidity of the molten alloy is reduced, and casting defects such as a molten metal boundary are likely to occur. Further, when the concentration of P is high, the melting yield is extremely reduced.
It is very difficult to contain P of 30 ppm or more.

P / Ca ratio The P / Ca ratio is a factor that has a great influence on the miniaturization effect. It is presumed that by maintaining P / Ca in the range of 0.6 to 6 by weight, a Ca-P compound effective for refining primary crystal Si is produced. That is, the generated Ca
The -P compound is uniformly dispersed in the alloy as fine nuclei, and primary crystals of Si crystallize from these nuclei. As a result, a fine cast structure can be obtained. If the P / Ca weight ratio is less than 0.6, Ca-P having a high Ca concentration that does not act as a crystal nucleus of primary Si is formed, and Ca in the Ca-P compound is retained by the molten metal for a long time. It is considered that when the amount decreases, it becomes a preferable state and exhibits an action as a crystal nucleus.
On the other hand, if the P / Ca weight ratio exceeds 6, Ca will run short,
The number of Ca-P compounds formed is insufficient.

The phenomenon that primary crystal Si is refined by the Si contents Ca and P is a hypereutectic Al—Si having a Si content in the range of 13 to 21% by weight.
Found in alloys. As the Si content increases, it is necessary to contain a larger amount of Ca and P, and it is also necessary to strictly control the casting conditions. Moreover, the miniaturization effect decreases depending on the Si content. Therefore, the upper limit of the Si content is set to 21% by weight. Further, in order to obtain the characteristics of a hypereutectic Al-Si alloy,
The lower limit of Si content was set to 13% by weight.

Cu content Cu forms an intermetallic compound CuAl ₂ and forms a hypereutectic Al
-It is an important alloying element that improves the strength and altitude of the Si-based alloy. In order to obtain this effect, Cu content of 0.5% by weight or more is required. However, even if a large amount of Cu exceeding 5% by weight is contained, the action of Cu is saturated and the strength cannot be improved in proportion to the increase in the amount. Therefore, in the present invention, the Cu content is set in the range of 0.5 to 5% by weight.

Mg Content Mg is an alloying element that contributes to the improvement of strength in the coexistence with Si, and when it is contained in an amount of 0.3% by weight or more, the action of Mg remarkably appears. However, when a large amount of Mg exceeding 2.0% by weight is contained, the elongation rate decreases as the Mg content increases, and the workability deteriorates. Therefore,
In the present invention, the Mg content is 0.3 to 2.0% by weight.
Set to the range of. Particle size primary crystal Si primary crystal Si is, P content, by adjusting the Ca content and P / Ca ratio, being finely divided in the following average particle size 20 [mu] m. If the grain size of the primary crystal Si exceeds 20 μm, the machinability deteriorates. Further, when forging an ingot in which large primary crystal Si is crystallized, defects such as cracks are likely to occur in the structure after forging due to the difference in deformation resistance between the matrix and primary crystal Si. Become. Therefore, in the present invention, the grain size of the primary crystal Si is restricted to 20 μm or less in consideration of forgeability, workability and the like.

In order to effectively exert the refining effect of the melting temperatures Ca and P, Si
It is preferable to melt the hypereutectic Al-Si alloy melt in the temperature range of 760 to 850 ° C so that The molten metal temperature is set high in proportion to the Si content. However, melting at an excessively high temperature not only causes energy loss for melting, but also tends to change conditions in the process up to casting. Therefore, the upper limit of the melting temperature is set to 850 ° C.

The refining effect by the molten metal holding time Ca is Ca in the hypereutectic Al-Si alloy containing Ca whose weight ratio P / Ca exceeds 0.6.
Appears immediately after addition. This refinement action disappears when the molten alloy is held for a long time. The time when the action of Ca disappears is
Approximately 60 to 60, depending on Ca content and holding temperature
0 minutes. In this respect, it is preferable to adjust the Ca content to a setting range in which the weight ratio P / Ca is 0.6 to 6.0 and then enter the casting process without the holding process for a long time. On the other hand, in the hypereutectic Al-Si based alloy containing excess Ca such that the weight ratio P / Ca is less than 0.6, Ca
The refining action due to does not appear immediately after the addition of Ca, but appears after holding the molten alloy for a certain period of time. There is a so-called incubation period. The incubation period becomes longer as the Ca content immediately after addition increases. For example, 61 ppm P and 1
When the hypereutectic Al-Si alloy containing 80 ppm of Ca is held at 760 ° C, the refining action of Ca is exhibited after about 100 minutes.

The latent period observed when a large amount of Ca is contained is derived from the fact that Ca is reduced while holding the molten alloy, and as a result, the weight ratio P / Ca is increased to 0.6 or more. it is conceivable that. That is, when the weight ratio P / Ca becomes 0.6 or more, the refining effect of Ca is exhibited for the first time. If the molten alloy is held for a long time, Ca
When the weight ratio P / Ca exceeds 6.0 as the content decreases, the refining effect disappears. This means that as the amount of Ca decreases, Ca- that acts as an effective nucleus for crystallization of primary Si
It suggests that the number of P compounds is insufficient.

When the Ca content is high, the molten metal holding time becomes long until the weight ratio P / Ca becomes 0.6 or more.
Generally, it becomes difficult to control the Ca content within the set range. However, when a large amount of alloy is produced using a large melting furnace, preparation and casting take a long time. In such a case, the latent period and the period during which the Ca decreases and the weight ratio P / Ca exceeds 6.0 after the latent period is effective can be used for a long miniaturization. That is,
If the time until casting is long, Ca is excessively added, and the weight ratio P / Ca is adjusted to fall within the range of 0.6 to 6.0 at the time of casting.

[0026] In terms of refining the primary Si by casting temperatures higher cooling rate, it is preferable to set the casting temperature as high as possible. However, as the molten alloy temperature becomes higher, the wear of Ca becomes more severe, and it becomes difficult to control the Ca content during casting.
Therefore, it is preferable that the casting temperature is as low as possible within a range in which the refining effect can be obtained by the high cooling rate.
Specifically, it depends on the composition and content of the hypereutectic Al-Si alloy such as Si content, but it is (liquidus line + 70 ° C) or more, preferably (liquid phase) in the Al-Si binary system phase diagram. Phase line + 70 ℃
The casting temperature is set in the temperature range of 170 to 170 ° C. For example, a hypereutectic Al-Si alloy containing 15% by weight of Si has a casting temperature of 680 ° C or higher, and a hypereutectic Al-Si alloy containing 17% by weight of Si has a casting temperature of 710 ° C or more. For a hypereutectic Al-Si alloy containing 20% by weight of Si, the casting temperature is set to 760 ° C or higher.

The Ca content also changes depending on other manufacturing conditions. In particular, the Ca content is greatly reduced by the degassing treatment. The decrease in the Ca content at this time shows different tendencies depending on the type of gas used for degassing, the degassing time, and the like. Therefore, it is preferable to previously obtain the change rate of the Ca content corresponding to the degassing condition and control the Ca content based on this change rate.

Size of Ingot When DC casting is performed, in order to reduce the grain size of primary crystal Si to 20 μm or less, the ingot is cast into an ingot having a diameter or thickness of 150 mm or less. When the diameter or the thickness of the ingot exceeds 150 mm, the cooling rate of the central portion of the ingot becomes small, and the action and effect of P and Ca for refining the primary crystal Si become small. The ingot can also be obtained by die casting. However, since the mass effect is further increased in die casting, it is necessary to regulate the diameter or thickness of the ingot to 30 mm or less and to secure the cooling rate of the central portion of the ingot.

Forging Forging is performed using an ingot in which primary crystal Si is refined to 20 μm or less. Because of the refined primary Si, primary S
Cracks due to i do not occur during forging, and tool wear is reduced. In addition, when the Al-Si alloy after forging is cut and finished into a predetermined product, the cutting is also facilitated. When forging an ingot to make a scroll, 50 mm /
Forging is preferably carried out at a ram speed of less than or equal to seconds. When the ram speed exceeds 50 mm / sec, cracks are likely to occur in the lap portion, and the rise of meat in the lap portion becomes uneven. When manufacturing a cylinder liner from an ingot,
Forging by backward extrusion is preferred, using a small-diameter ingot that makes it easy to refine the primary crystal Si. When trying to manufacture a cylinder liner by normal extrusion, the diameter is 100 mm.
In order to manufacture the above pipe, a large billet in which it is difficult to reduce the primary crystal Si is required.

[0030]

【Example】

Example 1: 3 kg of a hypereutectic Al-Si alloy having various contents of Si, Cu and Mg was melted in a crucible, and
Ca was added using 1-5% Ca. After adding Ca, the molten metal is kept at 760 ° C for 30 minutes, and the diameter is 1 by die casting.
An ingot of 8 mm and a height of 90 mm was obtained. The cross section of the ingot was observed with an optical microscope to measure the grain size of primary crystal Si. The measurement results are shown in Table 1 together with the components and compositions.

[Table 1]

As is clear from Table 1, Si: 13-2
1% by weight, P: 40 to 140 ppm, Ca: 6 to 120
ppm and P / Ca: In test numbers 2 to 4, 6 and 7 satisfying the conditions of 0.6 to 6, even if the contents of Si, Cu and Mg are slightly changed, the primary crystal Si is fine to 20 μm or less. Has been converted. On the other hand, in Test Nos. 1 and 5 in which Ca is not added, and Test No. 8 in which the Si content exceeds 21% by weight, the primary crystal Si is larger than 20 μm and it is understood that the Si is not refined.

Example 2: Si: 15% by weight, Cu: 3.
An alloy having a composition of 5% by weight, Mg: 0.5% by weight, P: 70 ppm and the balance Al, Si: 17% by weight, Cu:
An alloy having a composition of 4.5% by weight, Mg: 0.6% by weight, P: 70 ppm and the balance Al was melted in a crucible of 50 kg each, and the hot top was cast at a temperature of 780 ° C. and a speed of 150 m / min. An ingot having a diameter of 98 mm was manufactured by the casting method. In addition, for each molten alloy, A
A target value of 50 ppm Ca was continuously added in a gutter using an 1-5% Ca alloy, and the diameter was 98 mm under the same casting conditions.
The ingot was obtained. For each ingot, P and Ca were analyzed, and the grain size of primary crystal Si was measured at a position corresponding to 1/2 of the radius of the ingot. As is clear from Table 2 showing the measurement results, in comparison with test numbers 9 and 11 in which Ca was not added,
In the ingots of test numbers 10 and 12 to which Ca was added, the primary crystal S
It can be seen that the miniaturization of i is progressing.

[Table 2]

The four kinds of ingots shown in Table 2 were heated at 500 ° C. for 5 hours.
After homogenizing for a period of time, it was cut into blocks having a length of 90 mm. A round bar having a diameter of 20 mm was extruded from each block under the conditions of a temperature of 480 ° C., a ram speed of 5 cm / min, and an extrusion condition of one-piece feeding. A test piece having a diameter of 14 mm and a length of 21 mm was cut out from the ingot after the homogenization treatment and the round bar obtained by the extrusion, and the temperature was 450 ° C. using a 400 ton press.
Was subjected to the hot upsetting test. Boron nitride was used as a lubricant. The other conditions were in accordance with the Japan Plasticity Society Cold Forging Subcommittee Cold Forging Test Standard [Plasticity and Working Volume 22 No. 241 (1981-2) p. 139].

As shown in FIG. 2, the limit upsetting rate when hot-upsetting the test piece cut out from the ingot is 60.5% in the test number 9 (Si: 15%) without Ca addition, It was 58.4% in test number 11 (Si: 17%). On the other hand,
The critical upsetting ratios of Test Nos. 10 and 12 with Si added were 74.0% and 70.2%, respectively. From this, the ingot test pieces of Test Nos. 10 and 12 have an upsetting limit improved by 10% or more as compared with Test Nos. 9 and 11, that is, Ca addition, and the forgeability is improved. It is understood that there is. As shown in FIG. 3, the critical upsetting rate of the test piece cut out from the extruded round bar was 75.4% in the test number 9 (Si: 11%) without Ca addition, and the test number 11 (Si: 17%). Was 67.4%,
Test Nos. 10 and 12 with Si added 82.
5% and 81.8%. From this, it is understood that good extrudability is ensured even in the extruded material.

Example 3: Diameter of 98 m obtained in Example 2
m ingot, homogenized, diameter 96 mm and thickness 55 m
A large number of m forging materials were cut out. Using 200 ton press, material heating temperature 450 ℃, upper mold temperature 300-320
℃, lower mold temperature 270-320 ℃, ram speed 20mm /
Each forging material is extruded backwards under the condition of sec.
A bottomed cylinder having a diameter of 0 mm, an outer diameter of 98 mm and an inner diameter of 82 mm was molded. The upper and lower ends of the obtained cylindrical body were cut off to obtain a cylinder liner member.

When the internal structure of the cylinder liner member was observed, in the members obtained from Test Nos. 9 and 11 which did not contain Ca, coarse primary crystal Si was generated, and the inside of the primary crystal Si and primary crystal Si were found. Many cracks were detected between the matrix. On the other hand, in the members obtained from Test Nos. 10 and 12 to which Ca was added, a healthy structure in which the primary crystal Si was sufficiently refined was observed, and cracks were substantially formed inside and in the vicinity of the primary crystal Si. Could not be detected. C6 liner member treated with T6 (500 ° C x 6
After time → water cooling → 170 ° C × 10 hours), a JIS No. 4B test piece was cut out and subjected to a tensile test. Table 3 shows the mechanical properties obtained. As is clear from Table 3, there is no difference in Brinell hardness, but the addition of Ca causes the primary S
It can be seen that in the examples in which i is miniaturized, the strength and elongation are higher than those in the comparative examples.

[Table 3]

The surface of the same cylinder liner member was chamfered and then subjected to a cutting test. Since the cylinder liner member is as thin as about 16 mm, many test pieces were prepared and tested. Carbide dies (SPMN12030)
8) is used as a tool, the cutting edge inclination angle is 0 degree, the vertical scooping angle is 5 degrees, the cutting edge angle is 15 degrees, the cutting speed is 300 mm / min, and the feed rate is 0.2 mm / rev. , Depth of cut 0.5mm,
The maximum cutting distance is 18000m depending on the type of alloy,
The condition without lubricant was adopted. Then, the machinability was evaluated by measuring the amount of wear of the tool flank for each appropriate chamfering distance. As is clear from FIG. 5 showing the results of the cutting test, it is understood that the wear of the tool is reduced to less than half in the case where the primary crystal Si is refined by adding Ca as compared with the case where the Ca treatment is not performed.

Example 4: The same Si as in Example 2, 5% of each of two alloys containing 15% by weight and 17% by weight of Si, respectively.
Dissolves in 0 kg of crucible, temperature 780 ℃ and speed 150
Diameter 8 by hot top casting under casting conditions of m / min
A 1 mm ingot was produced. Also, for each alloy melt, the target value is 50ppm using Al-5% Ca alloy.
Ca was continuously added with a gutter, and an ingot having a diameter of 81 mm was obtained under the same casting conditions. For each ingot, P and Ca were analyzed, and the grain size of primary crystal Si was measured at a position corresponding to 1/2 of the radius of the ingot. As is clear from Table 4 showing the measurement results, in the ingots of test numbers 14 and 16 to which Ca was added, as compared with test numbers 13 and 15 to which Ca was not added, the refinement of primary crystal Si proceeded. You can see that

[Table 4]

The four kinds of ingots shown in Table 4 were heated at 500 ° C. for 5 hours.
After time homogenization treatment, diameter 80mm and length 20mm
I cut it out into blocks. Using a 350 ton hydraulic forging machine, the scroll shown in FIG. 4 was forged from each block under the extrusion conditions of a material temperature of 480 ° C., a pressing force of 300 tons, a ram speed of 20 mm / sec and a mold temperature of 250 ° C. This scroll comprises a flange 1 having a diameter of 80 mm and a wrap portion 2 having a thickness of 10 mm and a height of 18 mm. When the shape of the obtained scroll was observed, the scrolls of test numbers 14 and 16 to which Ca was added had a height of 20 m.
The m-shaped spiral wrap portion 2 had a normal shape in which it was completely filled. On the other hand, it was found that the materials of Test Nos. 13 and 15 which did not contain Ca were inferior in formability because the lap winding start portion 2s did not rise completely.

Scroll flange portion 1 to JIS14B
The test piece was cut out, subjected to T6 treatment (500 ° C. × 6 hours → water cooling → 170 ° C. × 10 hours), and then subjected to a normal temperature tensile test. As is clear from Table 5 showing the results, Test No. 14 and Test No. 16 containing Ca have improved tensile strength and elongation as compared with Test No. 13 and Test No. 15 without addition, respectively.

[Table 5]

[0041]

As described above, according to the present invention, in the Al-Si-Cu-Mg alloy, the P / Ca weight ratio is 0.6 to 6, and 6 to 120 ppm of Ca and 40 are contained.
By including P of ~ 130 ppm, primary crystal Si
To obtain a hypereutectic Al-Si alloy having excellent forgeability. In this hypereutectic Al-Si alloy, since the primary crystal Si is refined to 20 μm or less, defects such as cracks do not occur even when forged into a product having a complicated shape. Also, the tool life can be extended during cutting. Moreover, it exhibits excellent mechanical properties in combination with alloy elements such as Si, Cu and Mg. Therefore, it can be used as various parts for which strength, wear resistance, formability, etc. are required, including parts for internal combustion engines.

[Brief description of drawings]

FIG. 1 Relationship between Ca content, P content, P / Ca weight ratio and grain size of primary Si

FIG. 2 Effect of Ca treatment on forgeability of ingot

FIG. 3 Effect of Ca treatment on forgeability of extruded material

FIG. 4 Scroll forged in Example 4

[Fig. 5] Cylinder liner cutting test results

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsu Yamada 1-34-1 Kambara, Kambara-cho, Awara-gun, Shizuoka Nipparu Giken Co., Ltd. (72) Kenji Tsuchiya 1-chome, Kambara-cho, Anbara-gun, Shizuoka No. 1 within Nikkei Giken Co., Ltd. (72) Inventor Yamaharu Kitaoka 3-13-12 Mita, Minato-ku, Tokyo Within Japan Light Metals Co., Ltd.

Claims (8)

[Claims] 1. Si: 13 to 21% by weight, Cu: 0.5
~ 5.0 wt%, Mg: 0.3-2.0 wt%, Ca:
6 to 120 ppm and P: 40 to 130 ppm,
A hypereutectic Al-Si alloy for forging, wherein P / Ca is in a range of 0.6 to 6 by weight. 2. The hypereutectic Al—Si alloy for forging according to claim 1, wherein the grain size of the primary crystal Si is 20 μm or less. 3. The hypereutectic Al—Si according to claim 1 or 2.
A DC casting material for forging having a diameter or a thickness of 150 mm or less, which is made of a system alloy. 4. The hypereutectic Al—S according to claim 1.
A scroll member made of an i-based alloy. 5. The hypereutectic Al—S according to claim 1.
A cylinder liner member made of an i-based alloy. 6. Si: 13 to 21% by weight, Cu: 0.5
~ 5.0 wt%, Mg: 0.3-2.0 wt%, Ca:
6 to 120 ppm and P: 40 to 130 ppm,
Hypereutectic Al with P / Ca in the range of 0.6 to 6 by weight
A method for producing a forging material, which comprises DC-casting a Si-based alloy into a ingot having a diameter or a thickness of 150 mm or less at a casting temperature of (liquidus line + 70 ° C.) or more. 7. Si: 13 to 21% by weight, Cu: 0.5
~ 5.0 wt%, Mg: 0.3-2.0 wt%, Ca:
6 to 120 ppm and P: 40 to 130 ppm,
Hypereutectic Al with P / Ca in the range of 0.6 to 6 by weight
A method for producing a forging material, which comprises casting a Si-based alloy into an ingot having a diameter or a thickness of 30 mm or less at a casting temperature of (liquidus line + 70 ° C.) or more. 8. A forged product obtained by forging the ingot produced by the method of claim 7.