JP2017078213A - Aluminum alloy powder for hot forging for slide component, method for producing the same, aluminum alloy forging for slide component, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy powder which makes it possible to obtain an aluminum alloy powder forging having excellent wear resistance and high-temperature strength, as a forging for a slide component used at high load, such as an automobile engine piston and others, and an aluminum alloy forging for slide components having excellent wear resistance and high-temperature strength, using the aluminum alloy powder.SOLUTION: An aluminum alloy powder for hot forging for slide components comprises Si: 10.0-19.0% and Mn: 3.0-10.0% with the balance being Al and inevitable impurities, with the average size of Si crystal grains of 15 μm or less. The aluminum alloy powder may comprise Cu: 0.5-10.0% and Mg: 0.2-3.0%. An aluminum alloy forging for slide components is obtained by hot forging the powdery extrusion material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an aluminum alloy forged product used as a part that slides at a high speed at high temperatures, such as an engine piston used in an internal combustion engine such as an automobile, and more particularly a forged product obtained by hot forging a powder extruded material. The present invention relates to an aluminum alloy powder suitable for the above, a method for producing the aluminum alloy powder, an aluminum alloy forged product for sliding parts using the aluminum alloy powder, and a method for producing the aluminum alloy forged product.

An engine piston of an internal combustion engine is a member that slides at a high speed with respect to a cylinder at a high temperature, and therefore requires excellent wear resistance, and is required to have excellent strength, particularly high temperature strength. It is necessary to have excellent seizure properties.
On the other hand, with respect to automobile parts, demands for weight reduction and higher functionality are increasing due to recent demands for improving fuel consumption in the automobile industry. Therefore, as a material for engine pistons for automobiles, there is an increasing tendency to use a light aluminum alloy instead of a conventional general steel material or cast iron material.

Among various aluminum alloys, an Al—Si based alloy containing about 10% by mass or more of Si, that is, an aluminum alloy having a high eutectic composition to a hypereutectic composition has a small thermal expansion coefficient and excellent resistance. Since it has abradability, it has been conventionally used as a material for automobile engines.
However, since this type of Al-Si alloy containing a large amount of Si is generally manufactured by a melting-casting method, it is difficult to completely prevent casting defects, and primary Si is coarse. In some cases, crystallization or segregation occurs, resulting in a decrease in strength and toughness, which is not satisfactory as a material for automobile engines. Further, since this type of high Si Al—Si alloy has limitations on the types and addition amounts of alloy elements, there has been a limit to the development of an alloy having dramatically improved characteristics.

Therefore, it is considered to use a material obtained by applying a so-called powder metallurgy method using a high-Si Al—Si alloy powder obtained by an atomizing method as a material for an automobile engine. According to the atomizing method, an aluminum alloy powder having a fine and uniform structure can be obtained by rapid solidification, and a large amount of alloy elements can be added. That is, in the atomization method, the molten aluminum alloy can be rapidly solidified at a high cooling rate of about 10 ³ to 10 ⁵ ° C./second, and therefore, diffusion of the alloy constituent elements during solidification can be suppressed, and crystal grains and precipitates can be obtained. In addition, by suppressing the appearance of equilibrium phase and metastable phase, it is possible to increase the solid solution amount of alloy elements, especially the transition element represented by Fe, Ni and Mn. Become.

  Conventionally, as one method for obtaining a material having high temperature and high strength required for a high-load engine piston or the like, eutectic composition to hypereutectic composition and high melting point metals such as Fe, Ni, Mn, etc. Forged products in which Al-Si-based high-Si aluminum alloy powders with a relatively large amount of transition elements are produced by the atomizing method, and rapidly solidified powders by the atomizing method are compression molded, extruded, and forged by powder metallurgy. Has been proposed by, for example, Patent Document 1 and the like as a wear-resistant material under a high load such as an automobile engine.

JP-A 63-266005

  According to the technique of the above-mentioned Patent Document 1, at least one of transition elements Fe, Ni, and Mn is added as an alloy element for improving the strength. For example, when using Fe or / and Ni among these transition elements, it has been found that sufficient wear resistance and high-temperature strength are not necessarily obtained as a sliding component after final forging. Of course, if the addition amount of Fe or / and Ni is increased, it is possible to increase the wear resistance and high temperature strength, but in that case, the material becomes brittle and there is a problem that cracking occurs in forging, Therefore, it is necessary to avoid increasing the amount of Fe or / and Ni added unnecessarily.

  In the case of the above-mentioned Patent Document 1, evaluation of characteristics is mainly performed with an extruded material, and evaluation of a forged product subjected to forging after extrusion is hardly performed. When engine pistons are manufactured from extruded materials, total cutting may be performed, but forged products that have a metal flow that follows the shape of the product have superior characteristics and are advantageous in terms of cost. Although the evaluation at this stage is an important factor, as described above, in Patent Document 1, since the evaluation at the forged product stage is hardly performed, it is unclear whether or not the engine piston is optimal as a forged product. .

  In addition, when a large amount of Fe or / and Ni is added, it has been confirmed that another problem such as the following also occurs.

  That is, since Ni is an expensive element, the addition of Ni causes an increase in material cost, while Fe may be mixed in the molten metal from an iron jig or the like during alloy melting for atomization. Therefore, if Fe is used as an alloy addition element for improving the characteristics, it is difficult to strictly control the amount of Fe in the alloy. Furthermore, since Fe and Ni have a high melting point, it is necessary to increase the melting temperature of the molten alloy for atomization, which tends to cause cost increases and refractory problems. Fe and Ni have a larger specific gravity than Al and Si. Therefore, if a large amount of Fe and Ni is added, it is disadvantageous for use in an automobile engine piston that requires light weight.

  The present invention has been made in the background of the above circumstances, and as a forged product for sliding parts used at high loads, such as engine pistons for automobiles, without causing the problems described above, wear resistance and To provide an aluminum alloy powder forged aluminum alloy powder with excellent high-temperature strength, and an aluminum alloy forged product for sliding parts with excellent wear resistance and high-temperature strength using the aluminum alloy powder. It is to be an issue.

  In order to solve the above-mentioned problems, the present inventors have made various incidents and examinations. As a result, the Al-Si alloy powder obtained by the atomization method is compression-molded, extruded, and hot forged. As characteristics, among the transition elements Fe, Ni, and Mn, when Mn is added, the wear resistance and high-temperature strength are much superior even when the same amount is added compared to the case where Fe and Ni are added. I found out that That is, it has been found that, as a sliding part used at a high load such as an engine piston for automobiles, when Mn is added as a transition element, it is significantly superior to the case where Fe and Ni are added. .

Furthermore, if Mn is used, the problem of an increase in material cost when Ni is added is avoided, and a problem due to Fe mixed in the molten metal from an iron jig or the like when Fe is added is also caused. Recognized that there was nothing. Further, since Mn has a lower melting point than Fe and Ni, it is not necessary to increase the melting temperature of the molten alloy for atomization, and Mn has a lower specific gravity than Fe and Ni. Therefore, it is advantageous for the application of an engine piston for automobiles that requires light weight.
Thus, as a high Si Al-Si based aluminum alloy powder of eutectic composition to hypereutectic composition for sliding parts such as automobile engine pistons, as an additive element (transition element) for improving characteristics, It has been found that it is advantageous to use Mn exclusively rather than Fe or / and Ni, and the present invention has been made.

Therefore, the aluminum alloy powder for hot forging for sliding parts according to the basic aspect of the present invention (first aspect) is:
% By mass
Si: 10.0 to 19.0%,
Mn: 3.0 to 10.0%
And the balance consists of Al and inevitable impurities,
In addition, the average size of the Si crystal grains is 15 μm or less.

Moreover, the aluminum alloy powder for hot forging for sliding parts according to the second aspect of the present invention,
1st aspect WHEREIN: Furthermore, Cu: 0.5-10.0% and Mg: 0.2-3.0% are contained by the mass%, It is characterized by the above-mentioned.

Furthermore, the aluminum alloy powder for hot forging for sliding parts according to the third aspect of the present invention is:
1st or 2nd aspect WHEREIN: Furthermore, 1 type (s) or 2 or more types in Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb are 0.01 to It is characterized by containing 5.0%.

The fourth aspect of the present invention is
A method of producing an aluminum alloy powder for hot forging for sliding parts according to any one of the first to third aspects,
A melt of the alloy having the component composition described in any one of the first to third aspects is melted, and the melt is rapidly solidified by an atomizing method to be pulverized.

Furthermore, the fifth aspect of the present invention provides
An aluminum alloy forged product for sliding parts formed by hot forging an extruded material of aluminum alloy powder,
% By mass
Si: 10.0 to 19.0%,
Mn: 3.0 to 10.0%
And the balance consists of Al and inevitable impurities,
In addition, the average size of the Si crystal grains is 15 μm or less.

Furthermore, the aluminum alloy forged product for sliding parts of the sixth aspect of the present invention is:
In the fifth aspect,
Furthermore, it is characterized by containing one or two of Cu: 0.5 to 10.0% and Mg: 0.2 to 3.0% by mass%.

The aluminum alloy forged product for sliding parts according to the seventh aspect of the present invention is
In any of the fifth and sixth aspects,
Furthermore, it is characterized by containing one or more of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb in 0.01% to 5.0% by mass. To do.

Moreover, the manufacturing method of the aluminum alloy forged product for sliding parts according to the eighth aspect of the present invention includes:
A compression molding step of compressing the aluminum alloy powder for hot forging for sliding parts of any one of the first to third aspects to obtain a green compact; and
Extrusion process to obtain extruded material by hot extrusion of the obtained green compact,
A hot forging of the extruded material to obtain a forged product having an average Si crystal grain size of 15 μm or less.

Furthermore, the method for producing an aluminum alloy forged product for sliding parts according to the ninth aspect of the present invention,
When the aluminum alloy powder contains, by mass%, Cu: 0.5 to 10.0% and Mg: 0.2 to 3.0%,
After the forging step, the forged product is further subjected to a solution treatment, quenched, and subjected to an aging treatment.

  ADVANTAGE OF THE INVENTION According to this invention, what is excellent in abrasion resistance and high temperature strength can be obtained as an aluminum alloy powder forging product for sliding parts used with high load like an automobile engine piston.

It is a flowchart which shows roughly the whole of an example of the manufacturing process of the forged product of this invention. It is a perspective view which shows the condition before and after forging in the Example of this invention.

  Hereinafter, embodiments of an aluminum alloy powder for hot forging for sliding parts and a method for producing the same, and an aluminum alloy forged product for sliding parts and a method for producing the same will be described in detail. Note that the embodiments described below are merely examples, and the present invention is of course not limited to these embodiments.

First, the component composition of the aluminum alloy powder will be described.
The aluminum alloy powder for hot forging for sliding parts of the present invention basically includes Si: 10.0 to 19.0% and Mn: 3.0 to 10.0% as essential alloy components. And the balance is made of Al and inevitable impurities. In addition to the above essential components, Cu: 0.5 to 10.0% and Mg: 0.2 to 3.0% may be included as necessary. Furthermore, in addition to the above-mentioned essential components or the above-described essential components and Cu and Mn, if necessary, one of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb Or 2 or more types may contain 0.01-5.0%, respectively. Then, the reason for limitation of these alloy elements is demonstrated next. Here, “%” for each component means mass%.

<Si: 10.0 to 19.0%>
Si is basically an important element in the aluminum alloy powder of the present invention. By containing Si in the Ai-Si eutectic to hypereutectic region, Si crystallized product (primary Si, co-crystal) is obtained. A large amount of crystal Si) is crystallized, and the fine Si crystallized product contributes to the improvement of wear resistance and the strength. If the amount of Si is less than 10%, the amount of Si crystallized product decreases, resulting in a decrease in wear resistance and strength, and if it exceeds 19%, coarse primary crystal Si crystallizes and causes a decrease in strength. The material becomes brittle and forgeability is reduced. Therefore, in order to obtain high wear resistance and strength, particularly high temperature strength, and at the same time achieve both forgeability, the Si content is set in the range of 10.0 to 19.0%. The amount of Si is particularly preferably in the range of 12% to 16%.

<Mn: 3.0 to 10.0%>
Mn generates an intermetallic compound as a transition metal, and contributes to improving wear resistance and high-temperature strength by dispersion strengthening. As already described, Fe and Ni may be added to improve the strength of a high-Si Al—Si alloy, but according to experiments and studies by the present inventors, Fe and Ni are added. It has been found that the effect of improving the wear resistance is much greater when Mn is added. In addition, it has been confirmed that the effect of improving the high temperature strength becomes more prominent than that of adding Fe and Ni when Mn is used. Furthermore, since Mn is inexpensive, there is no increase in material cost as in the case of adding expensive Ni, and Mn is rarely mixed during the melting of the alloy. Strict control of the amount of Mn becomes easy. Moreover, since Mn has a lower melting point than Fe and Ni, it is not necessary to increase the melting temperature of the molten alloy for atomization. Further, since Mn has a lower specific gravity than Fe and Ni, it is advantageous to add Mn to Fe and Ni for reducing the weight of the material, and an automobile engine piston that is particularly required to be lightweight. This is advantageous for applications. From these viewpoints, in the present invention, Fe and Ni are not positively added, but by adding Mn, wear resistance and high temperature strength are improved.

  Here, if the amount of Mn is less than 3.0%, the dispersion strengthening by the intermetallic compound cannot be sufficiently achieved. On the other hand, if the amount of Mn exceeds 10.0%, hardness and abrasion resistance are lowered, and the material tends to be brittle in the molded body. Therefore, the amount of Mn is set in the range of 3.0 to 10.0%. The amount of Mn is particularly preferably in the range of 6.0 to 8.0% even within the above range.

<Cu: 0.5 to 10.0%>
Cu is an element effective in cooperating with Mg and imparting age hardening to the alloy. Accordingly, if Cu is added together with Mg, it effectively functions as a heat-treatable alloy to improve the normal temperature and high-temperature strength by subjecting the forging to solution treatment-quenching and age hardening treatment.
If the Cu content is less than 0.5%, sufficient age-curing property cannot be obtained, and therefore the effect of improving the strength is small. On the other hand, if the amount of Cu exceeds 10%, extrusion processability deteriorates. Therefore, the Cu content is set in the range of 0.5 to 10%. The Cu amount is particularly preferably within the range of 2.0 to 5.0% even within the above range.

<Mg: 0.2-3.0%>
As described above, Mg is an element effective for cooperating with Cu and imparting age hardening to the alloy. Therefore, if Mg is added together with Cu, it effectively functions as a heat-treatable alloy to improve the normal temperature and high-temperature strength by subjecting the forging to solution treatment-quenching and age hardening treatment.
If the Mg content is less than 0.2%, sufficient age-curing property cannot be obtained, so that the effect of improving the strength is small. On the other hand, if the amount of Mg exceeds 3.0%, the extrusion processability deteriorates. Therefore, the Cu content is set in the range of 0.2 to 3.0%. The Mg amount is particularly preferably in the range of 1.0 to 2.0% even within the above range.

<One or more of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb: 0.01 to 5.0%>
Since these elements all have a low diffusion rate in aluminum, they exhibit the effect of improving the heat resistance of the alloy and significantly increasing the high temperature strength. Here, if the content of any of these elements is less than 0.1, the above effect cannot be obtained sufficiently, while if it exceeds 0.5%, the material tends to become brittle. The total amount when two or more of these elements are contained is preferably 8.0% or less.

  In addition, Cu and Mg and Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb may be either one or two or more of them. May be contained at the same time.

  In addition to the above elements, basically, Al and inevitable impurities may be used. In the present invention, Fe and Ni are basically treated as impurities, and it is usually preferable to limit Fe to 1.0% or less and NI to 1.0% or less. However, depending on the case, it is permitted to contain either one or both of Fe and Ni within the range of Fe less than 3.0% and Ni less than 2.0%.

  Further, in the aluminum alloy powder for hot forging for sliding parts of the present invention, the Si crystal grains in the powder particles must be 15 μm or less on average. Here, the Si crystal grains in the powder particles are crystal grains of Si alone, and include both primary Si and eutectic Si. Of these Si crystal grains, primary Si is likely to be coarse, but by restricting to an average of 15 μm or less, as a material (forged product) after compression molding, extrusion, and hot forging as will be described later However, it becomes easy to suppress the Si crystal grains to fine particles having an average size of 15 μm or less, and as a result, it is possible to improve wear resistance, strength, and high-temperature strength. If the Si crystal grains in the powder particles exceed 15 μm on average, the Si crystal grains in the forged product after compression molding, extrusion, and hot forging become coarse, and the wear resistance, strength, and high temperature strength can be sufficiently improved. It becomes difficult.

  The particle diameter of the aluminum alloy powder particles is not particularly limited, but is usually preferably about 30 to 70 μm on average. If the average particle size is less than 30 μm, the yield is remarkably reduced, while if it exceeds 70 μm, coarse oxides and foreign substances may be mixed.

Here, as described above, it is a high Si Al—Si alloy and contains a relatively large amount of Fe as an alloy element, and the Si crystal grains are fine as an average of 15 μm or less, and the average particle diameter of the powder particles is 30. A fine alloy powder of about ˜70 μm can be reliably obtained by the atomizing method. That is, the atomizing method is a method in which molten aluminum alloy is sprayed from a nozzle together with gas, and fine alloy molten particles are rapidly cooled at a cooling rate of about 10 ² to 10 ⁵ ° C / second to obtain a solidified powder. By rapidly cooling the molten alloy particles, it suppresses the diffusion of alloy elements during solidification, suppresses coarsening of crystal grains and precipitates, and further suppresses the appearance of equilibrium and metastable phases. The solid solution amount of Mn, which is an element, can be increased.

  Next, an aluminum alloy forged product for sliding parts will be described as one aspect of the present invention.

  The aluminum alloy forged product for sliding parts according to one aspect of the present invention is manufactured by compression-molding the aluminum alloy powder for hot forging as described above, further extruding, and then hot forging. It is desirable. Therefore, the component composition of this forged product may be the same as that of the aforementioned alloy powder. That is, as essential alloy components, Si: 10.0 to 19.0% and Mn: 3.0 to 10.0% are contained, and the balance is made of Al and inevitable impurities. In addition to the above essential components, Cu: 0.5 to 10.0% and Mg: 0.2 to 3.0% may be included as necessary. Furthermore, in addition to the above-mentioned essential components or Cu and Mg, one type of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb, if necessary. Or 2 or more types may contain 0.01-5.0%, respectively. The reasons for limiting these alloy elements are the same as described above.

Further, this aluminum alloy forged product for sliding parts needs to have an average Si crystal grain of 15 μm or less in the same manner as described above for the alloy powder. Here, the Si crystal grain is a crystal grain of a simple substance of Si and includes both primary crystal Si and eutectic Si. Of these Si crystal grains, primary Si is likely to be coarse, but by controlling to an average of 15 μm or less, it is possible to improve wear resistance and strength as a material for sliding parts such as automobile engine pistons. It is possible to improve the high temperature strength. If the Si crystal grains are coarser than 15 μm on average, it is difficult to sufficiently improve the wear resistance, strength, and high-temperature strength.
Here, in the process of compression molding, extruding and hot forging the alloy powder, the average size of the Si crystal grains hardly changes, so that the average Si crystal grains in the particles as the alloy powder is 15 μm as described above. If the following are used, the Si crystal grains in the forged product after compression molding, extrusion, and hot forging can be reduced to 15 μm or less on average.

  Next, an example of a process for manufacturing the aluminum alloy forged product for sliding parts of one embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the overall concept of the process for producing an aluminum alloy forged product for sliding parts is as follows. As shown in FIG. 1, a powder production stage P1 in which an aluminum alloy is melted to produce an alloy powder by an atomizing method, Forging product production stage P2 in which the alloy powder obtained in the powder production stage P1 is compressed into a predetermined shape (for example, a cylindrical shape), extruded and hot forged to obtain a forged product, and heat treatment containing Cu and Mg In the case of a mold alloy, it comprises a heat treatment stage P3 in which the forged finished material is subjected to solution treatment-quenching and aging treatment (preferably overaging stabilization treatment in practice). Each of these steps will be described in more detail.

<Powder production stage P1>
First, the molten aluminum alloy whose components are adjusted as described above is melted by a normal melting method (S11). The obtained molten aluminum alloy is pulverized by an atomizing method (S12). The atomization method is a method in which fine droplets of molten alloy are misted and sprayed from a spray nozzle with a gas flow such as nitrogen gas, and the fine droplets are rapidly solidified to obtain fine alloy powder. However, the type is not particularly limited as long as it is a method capable of obtaining a cooling rate of about 10 ³ to 10 ⁵ ° C / second and obtaining an alloy having a fine particle size of about 30 to 70 µm or less on average. . The alloy powder obtained by the atomization method is classified by a sieve as necessary (S13), and only the alloy powder under 150 μm, for example, is sent to the next step. The alloy powder to be sent to the next process at this stage must have the component composition as described above, and the Si crystal grains in the alloy powder particles should be 15 μm or less on average.

<Forging production stage P2>
[Compression molding]
The alloy powder obtained as described above is heated to, for example, about 250 to 300 ° C. (S21), filled in a mold preheated to, for example, about 230 to 270 ° C., and compressed into a predetermined shape. (S22) A green compact is obtained. Although the pressure of compression molding is not particularly limited, it is usually preferable to use a pressure of about 0.5 to 3.0 ton / cm ² and a green compact with a relative density of about 60 to 90%. The shape of the green compact is not particularly limited, but usually it is preferably a cylindrical shape or a disk shape in consideration of the extrusion process.

[Extrusion]
The green compact is subjected to machining such as chamfering as necessary, and then subjected to degassing (S23), heated (S24), and subjected to an extrusion step (S25). The heating temperature (preheating temperature) before extrusion is preferably about 300 to 450 ° C., for example. In the extrusion, the green compact is charged into an extrusion container, applied with an extrusion ram, and extruded from an extrusion die into, for example, a round bar shape. It is desirable to heat it. Thus, by extruding hotly, the plastic deformation of the green compact proceeds, and the alloy powder particles are bonded together to obtain an integrated extruded body.
Here, the extrusion pressure is preferably about 10 to 25 MPa, the extrusion ratio (outer diameter ratio before and after extrusion) is about 5.0 to 50, and the density of the extruded body is preferably about 2.80 to 2.90.

[Hot forging]
For example, a round bar-shaped extruded body is cut to a predetermined length as required (S26), and then heated to a temperature suitable for hot forging (S27) and hot forged (S28). This hot forging is preferably closed die forging or semi-sealed die forging so that the forged material (forged product) has a shape close to the product shape (for example, engine piston shape), but it is free depending on the product shape. Forging may be used. In the case of the alloy targeted by the present invention, the hot forging temperature is preferably about 300 to 450 ° C.
In some cases, after hot forging, cold forging may be applied to finish the product closer to the product shape.

  The forged material may be subjected to cutting or surface polishing as appropriate, and immediately used as a sliding part of the product (for example, an engine piston). However, the aluminum alloy is an alloy element that imparts age hardening and Cu and In the case of a heat treatment type alloy containing Mg, it is subjected to the next heat treatment stage P3.

<Heat treatment stage P3>
[Solution Treatment (S31)]
The solution treatment is a treatment in which Cu, Mg, and the like contributing to age hardening are dissolved in supersaturation, and the heating temperature of the solution treatment is preferably 480 to 500 ° C. If the temperature is lower than 480 ° C, a supersaturated solid solution cannot be sufficiently obtained, and the age-hardening ability is lowered. On the other hand, if the temperature is higher than 500 ° C, crystal grains and eutectic Si are coarsened, leading to a decrease in strength, The problem of prompting occurs. The heating time for the solution treatment is preferably 2 hr to 4 hr. If it is less than 2 hr, a supersaturated solid solution cannot be obtained sufficiently, and if it exceeds 4 hr, crystal grains and eutectic Si are coarsened.

[Hardening (S32)]
After heating for solution treatment, quenching is performed by quenching with water or the like (quenching) to obtain a material (supersaturated solid solution) in which Cu, Mg, etc. are supersaturated in excess of the solid solution limit at room temperature. The quenching temperature is preferably 0 to 50 ° C. If the temperature is lower than 0 ° C., cracks may occur due to rapid thermal shrinkage, leading to cracks. On the other hand, if it exceeds 50 ° C., a sufficient supersaturated solid solution cannot be obtained, and sufficient strength cannot be obtained.

[Aging treatment (S33)]
Solution treatment-After quenching, perform aging treatment. By this aging treatment, an intermetallic compound containing Cu, Mg and the like can be finely precipitated, and the strength and wear resistance can be greatly improved. However, in the case of the present invention, the present invention is applied to the manufacture of sliding parts represented by engine pistons, and such sliding parts are desired to have good dimensional stability. For example, in an engine piston, it is desired to maintain a stable clearance with the cylinder inner peripheral surface. Therefore, in the case of the present invention, the aging process is advanced to the stabilization process in the so-called T7 process, which exceeds the aging process condition (aging process condition for obtaining the maximum strength) in the general T6 process and is over-aged. Is desirable.

  From the above viewpoint, it is desirable that the conditions for the aging treatment be 1 hr to 4 hr at a temperature in the range of 180 ° C. to 280 ° C. If the aging treatment temperature is lower than 180 ° C, aging is required for a long time and the production efficiency is lowered. On the other hand, if it exceeds 280 ° C, coarsening of crystal grains and eutectic Si occurs in a short time, and the strength May decrease. On the other hand, if the aging time is less than 1 hr, overaging does not occur and the stabilization becomes insufficient and sufficient dimensional stability cannot be obtained. On the other hand, if the aging time exceeds 4 hr, crystal grains and eutectic Si due to excessive overaging. There is a possibility that the coarsening of the material occurs and the strength is reduced.

  The forged product after the aging treatment as described above is subjected to machining such as cutting or surface polishing as appropriate, and finished to a sliding part such as an engine piston for automobiles.

  Examples of the present invention will be described below. The following examples are for clarifying the operation and effects of the present invention, and it is needless to say that the conditions described in the examples do not limit the technical scope of the present invention.

[Example 1]
No. in Table 1 1-No. The high Si aluminum alloy melt having the composition shown in No. 12 was atomized with gas to be powdered, and classified with a sieve to obtain a powder of −100 mesh. The size of the Si crystal grains in the powder particles is estimated to be 15 μm or less from the measurement result of the size of the Si crystal grains for the test material (forged product) described later.
Next, the powder was preheated to a temperature of 280 ° C., filled in a mold heated and held at the same temperature, and compression-molded at a pressure of 1.5 ton / cm ² to form a cylindrical shape having a diameter of 210 mm and a length of 250 mm. A green compact was obtained. Next, the green compact was chamfered to a diameter of 203 mm with a lathe to obtain a green compact billet. Next, the green compact billet was heated to 350 ° C., inserted into an extrusion container having an inner diameter of 210 mm that was heated and maintained at 350 ° C., and extruded with a die having an inner diameter of 75 mm at an extrusion ratio of 7.8. The obtained extruded material was cut to a length of 30 mm and then heated to 450 ° C. to perform hot free forging to obtain a test material (forged product) of φ107.5 × L15 mm. In the actual manufacturing of sliding parts, die forging is often performed, but here, for the purpose of evaluating characteristics only, free forging was applied. FIG. 2 shows the extruded material 10 before forging and the forged product 20 after forging.

  A sample of about 10 mm x 10 mm was cut out from the obtained specimen (forged product), filled with resin, then coarsely polished with emery paper and finished with buffing, and observed with an optical microscope. As a result of measuring the diameter, it was confirmed that the size of the Si crystal grains was 15 μm or less in any of the test materials.

  The obtained test material was heated to 490 ° C. and held for 3 hours as a solution treatment, and then quenched in water at 20 ° C. Thereafter, as an aging treatment (over-aging stabilization treatment), heating was performed at 220 ° C. for 1 hr to obtain a T7-treated product. The obtained T7 treated product was processed into a normal temperature tensile test piece with a distance between gauge points of 25.4 mm and a parallel part diameter of 2.85 mm and a high temperature tensile test piece with a flange with a distance between gauge points of 20 mm and a parallel part diameter of 4 mm. Tensile tests were performed at room temperature, 150, and 300 ° C. The tensile test was carried out at each test temperature after holding for 100 hours. Here, the test material No. 1-No5, No.1. 8, no. 11, no. 12 is a comparative example. 6, no. 7No. 9, no. 10 is an example of the present invention. These results are shown in Table 2.

  As is apparent from Table 2, the comparative example No. In comparison with Nos. 6 and no. The forged product No. 7 has high tensile strength and yield strength at high temperatures.

  No. which is a comparative example. No. 5 is excellent in high-temperature strength, but cracks were generated during forging, and it was confirmed that the forgeability was extremely poor, with the ratio of forging without cracks being 20%.

  Moreover, No. which is a comparative example. No. 8 could be forged with almost no cracking, but cracking occurred due to water quenching after solution treatment. In order to prevent this quenching cracking, hot water quenching at 60 ° C. was attempted, but the crack generation rate was not significantly improved, and the strength was lowered, resulting in a failure to obtain high strength. .

  No. of the example of the present invention. No. 7 and No. 7 in which the amount of Mn was distributed with a constant amount of Si. No. 9 to No. 12 in the example of the present invention are compared. Nos. 9 and 10 have sufficient wear resistance and high-temperature strength. No. 11 is not excellent in high temperature strength because sufficient dispersion strengthening of the Al—Mn—Si intermetallic compound cannot be obtained. The comparative example No. In No. 12, toughness decreased due to excess Mn and forgeability decreased, and cracks occurred during quenching after solution treatment.

Next, the forged product after the heat treatment as described above was cut to obtain an evaluation material (fixed piece) of 5 × 25 × 40 mm, and the Ogoshi type abrasion test was performed. Using SS400 as a mating member (rotating disk), the rotating disk was pressed against the fixed piece and rubbed, and the wear amount and specific wear amount were calculated from the wear marks on the surface of the fixed piece. Table 2 shows the calculation results of the specific wear amount. The amount of wear was determined using an approximate expression based on the diameter and thickness of the rotating disk and the width of the wear scar, and the specific amount of wear was calculated based on the determined amount of wear, the friction distance, and the final load. The wear amount is the amount of wear of the evaluation material, and the specific wear amount is a value representing the amount of wear of the SS400 of the counterpart material. The smaller the specific wear amount, the better the wear resistance.
The conversion formula for specific wear is shown below.

^{W = B × b 3/12} × r
^{Ws = B × b 3/8} × r × P × L
= 3 x W / 2 x P x L
here,
W: Wear amount (mm ³ )
Ws: specific wear amount (mm ² / kgf)
r: Rotating disc radius (mm)
B: Rotating disc thickness (mm)
b: Wear scar width (mm)
P: Final load (kgf)
L: Friction distance (mm)

  No. which is a comparative example. 1, 2, and 5 are compared, No. having the maximum Si amount of 20%. 5 shows that the specific wear amount is the smallest and the wearability is good. No. 5 and No. of the present invention example. 7 shows that the specific wear amount is almost the same, and it can be seen that the material of the present invention has good wear properties.

  In addition, No. of the present invention example. Nos. 9 and 10 have a specific wear amount of no. It can be seen that all of the materials of the present invention have excellent wear resistance.

  Furthermore, in the comparative example No. 1 containing 7.0% Fe with 12.0% Si. No. 1 and Comparative Example No. 1 containing Si of 12.0% and 7.0% Ni. No. 3 of the present invention containing 7.0% Mn with a Si amount of 12.0%. 6 is compared with Example No. 6 of the present invention containing 7.0% Mn. It can be seen that No. 6 has better wear resistance. Further, in the comparative example No. 1 containing 7.0% Fe with an Si amount of 16.0%. No. 2 and Comparative Example No. 1 containing 7.0% Ni with a Si content of 16.0%. No. 4 of the present invention containing 7.0% of Mn with Si amount of 16.0%. 7 is compared with Example No. 7 of the present invention containing 7.0% Mn. It can be seen that No. 7 has better wear resistance. From these results, the superiority in the case of using Mn instead of Fe and Ni is clear.

[Example 2]
No. in Table 1 13-No. The high Si aluminum alloy melt having the composition shown in FIG. 17, that is, the non-heat-treatable alloy composition was powdered by the atomization method in the same manner as in Example 1 and classified to obtain a powder of −100 mesh. This powder is also estimated that the Si crystal grains in the powder particles are 15 μm or less.
Next, compression molding and chamfering were carried out in the same manner as in Example 1, the obtained green compact billet was hot extruded, the resulting extruded body was cut, and hot forged in the same manner as in Example 1.
When the size of the Si crystal grains in the obtained specimen (forged product) was examined in the same manner as in Example 1, it was confirmed that all were 15 μm or less.
In the case of Example 2, heat treatment (solution treatment, quenching, aging treatment) was not performed on the specimen (forged product).

In addition, from the obtained specimen (forged product), a room temperature tensile test piece and a high temperature tensile test piece with the same dimensions and shape as in Example 1 were cut out, and a tensile test was performed at room temperature, 150, and 300 ° C. It was. The tensile test was conducted at each test temperature after holding for 100 hours.
Furthermore, the Ogoshi type abrasion test was conducted in the same manner as in Example 1.
These No. 13-No. The test results for 17 are shown in Table 2.

  No. of the example of the present invention. In Nos. 13 to 15, sufficient abrasion resistance and high-temperature strength were obtained without heat treatment. No. 16, the dispersion strengthening of the Al—Mn—Si intermetallic compound is insufficient, and high high-temperature strength cannot be obtained. In No. 17, toughness decreased due to excess Mn and forgeability decreased, and cracks occurred during quenching after solution treatment.

  From the above examples, the material of the present invention has high temperature strength, wear resistance, and forgeability, and it is clear that the material of the present invention is suitable for sliding members used at high loads such as automobile engine pistons. .

  10 ... extruded material, 20 ... forged product.

Claims (9)

% By mass
Si: 10.0 to 19.0%,
Mn: 3.0 to 10.0%
And the balance consists of Al and inevitable impurities,
An aluminum alloy powder for hot forging for sliding parts, wherein the average size of the Si crystal grains is 15 μm or less.   The aluminum alloy for hot forging for sliding parts according to claim 1, further comprising Cu: 0.5 to 10.0% and Mg: 0.2 to 3.0% by mass%. Powder.   Furthermore, it is characterized by containing one or more of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb in 0.01% to 5.0% by mass. The aluminum alloy powder for hot forging for sliding parts according to any one of claims 1 and 2. A method for producing an aluminum alloy powder for hot forging for sliding parts according to any one of claims 1 to 3,
For a sliding part characterized by melting a molten alloy of the component composition described in any one of claims 1 to 3 and rapidly solidifying the molten metal by an atomizing method. Manufacturing method of aluminum alloy powder for hot forging. An aluminum alloy forged product for sliding parts formed by hot forging an extruded material of aluminum alloy powder,
% By mass
Si: 10.0 to 19.0%,
Mn: 3.0 to 10.0%
And the balance consists of Al and inevitable impurities,
An aluminum alloy forged product for sliding parts, wherein the average size of the Si crystal grains is 15 μm or less.   The sliding according to claim 5, further comprising one or two of Cu: 0.5 to 10.0% and Mg: 0.2 to 3.0% by mass%. Aluminum alloy forgings for parts.   Furthermore, it is characterized by containing one or more of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb in 0.01% to 5.0% by mass. The aluminum alloy forged product for sliding parts according to any one of claims 5 and 6. A compression molding step of compressing the aluminum alloy powder for hot forging for sliding parts according to any one of claims 1 to 3 to obtain a green compact;
Extrusion process to obtain extruded material by hot extrusion of the obtained green compact,
A method for producing an aluminum alloy forged product for sliding parts, comprising: forging a hot forged product of the extruded material to obtain a forged product having an average Si crystal grain size of 15 μm or less. When the aluminum alloy powder contains, by mass%, Cu: 0.5 to 10.0% and Mg: 0.2 to 3.0%,
The method for producing an aluminum alloy forged product for sliding parts according to claim 8, wherein after the forging step, the forged product is further subjected to a solution treatment, quenched and subjected to an aging treatment.

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