JP5689423B2 - Manufacturing method of engine piston profile - Google Patents

Description

  The present invention relates to a method for producing an aluminum alloy engine piston shaped material excellent in wear resistance and high temperature characteristics, and an engine piston shaped material.

  Engine pistons used in engines mounted on vehicles such as automobiles are made of light weight, high temperature strength at the highest elevated temperature, durability at the highest elevated temperature, and thermal expansion to minimize the inertial force. Low thermal expansion is required to reduce clearance fluctuations, and wear resistance is required to reduce wear caused by ring groove wear due to piston ring sliding and wear caused by contact of the skirt with the cylinder surface.

  For this reason, in an engine piston manufactured by forging, an alloy having an Si addition amount equal to or higher than the eutectic point is used as an aluminum alloy constituting the piston when importance is placed on wear resistance (for example, Patent Document 1). On the other hand, when high temperature strength and high temperature fatigue strength are emphasized, alloys having an Si addition amount equal to or lower than the eutectic point have been used (see, for example, Patent Document 2).

JP-A-6-279904 JP 2001-181769 A

  However, in order to increase engine efficiency in an aluminum alloy engine piston, it is desirable to increase high temperature strength and high temperature fatigue strength while maintaining wear resistance.

  The present invention has been made in view of the above-described technical background, and an object of the present invention is to provide an aluminum alloy engine piston shaped material manufacturing method and engine piston shaped material excellent in wear resistance and high temperature characteristics. There is to do.

  Other objects and advantages of the present invention will become apparent from the following preferred embodiments.

  The present invention provides the following means.

[1] Si: 11.0 to 13.0 mass%, Fe: 0.6 to 1.0 mass%, Cu: 3.5 to 4.5 mass%, Mn: 0.25 mass% or less, Mg: 0.4 to 0.6 mass%, Cr: 0.15 mass% or less, Ni: 0.6 to {(-4/6) × [Cu mass%] + 5} mass%, Zr: 0.07 to 0 .15% by mass, P: 0.005 to 0.010% by mass, Ca: 0.002% by mass or less, and a molten metal having a balance composed of Al and inevitable impurities, the molten metal temperature before pouring the continuous casting mold A continuous casting step of obtaining a casting rod having a diameter of 85 mm or less by continuously casting at 720 ° C. or higher;
A forging step of obtaining a shaped material for an engine piston by forging a forging material obtained by homogenizing the cast rod at a temperature of 300 to 500 ° C .;
The manufacturing method of the shaped material for engine pistons characterized by including.

[2] The method for producing a shaped member for an engine piston according to claim 1, wherein in the composition of the molten metal, the amount of P added satisfies the following formula (1).
0.0025 × Si addition amount−0.025 ≦ P addition amount ≦ 0.0025 × Si addition amount−0.02 Formula (1)
However, the unit of P addition amount and Si addition amount: mass%, respectively.

[3] An engine piston shape material manufactured by the method for manufacturing an engine piston shape material according to item 1 or 2,
Primary crystal Si exists in at least the skirt portion corresponding portion and the piston ring groove portion corresponding portion in the shaped material,
In the entire raw material, there is no primary crystal Si having a maximum diameter of 50 μm or more, and no Al—Fe—Cr—Mn giant crystallized material having a maximum diameter of 50 μm or more.
A material for engine pistons.

[4] An engine piston shaped material manufactured by forging,
The composition of the base material is as follows: Si: 11.0 to 13.0 mass%, Fe: 0.6 to 1.0 mass%, Cu: 3.5 to 4.5 mass%, Mn: 0.25 mass% Hereinafter, Mg: 0.4 to 0.6 mass%, Cr: 0.15 mass% or less, Ni: 0.6 to {(−4/6) × [Cu mass%] + 5} mass%, Zr: 0 0.0-0.15 mass%, P: 0.005-0.010 mass%, Ca: 0.002 mass% or less, the balance being Al and unavoidable impurities Wood.

[5] The engine piston material according to claim 4, wherein in the composition of the material, the amount of P added satisfies the following formula (1).
0.0025 × Si addition amount−0.025 ≦ P addition amount ≦ 0.0025 × Si addition amount−0.02 Formula (1)
However, the unit of P addition amount and Si addition amount: mass%, respectively.

[6] Primary crystal Si exists in at least the skirt portion corresponding portion and the piston ring groove portion corresponding portion in the shaped material,
6. The engine piston according to 4 or 5 above, wherein no primary crystal Si having a maximum diameter of 50 μm or more and no Al—Fe—Cr—Mn-based giant crystallized material having a maximum diameter of 50 μm or more are present in the entire raw material. Shaped material.

  According to the present invention, the amount of the composition element of the molten metal is adjusted to a predetermined range, and the engine piston shape material is manufactured according to the manufacturing method of the present invention, so that it is made of an aluminum alloy excellent in wear resistance and high temperature characteristics. A material for engine piston can be obtained. Therefore, with the engine piston manufactured from the raw material, it is possible to improve the performance efficiency of the engine, and to reduce the amount of fuel used in automobiles, motorcycles, and the like.

  Further, since the raw material has primary Si at least in the skirt portion corresponding portion and the piston ring groove portion corresponding portion, at least these portions are excellent in wear resistance. Therefore, in an engine piston manufactured from the material, wear can be suppressed at least with respect to the skirt portion and the piston ring groove portion.

FIG. 1 is a bottom view of a shaped member for an engine piston according to an embodiment of the present invention. FIG. 2 is a front view of the allomorphic material. 3 is a cross-sectional view taken along line XX in FIG. FIG. 4 is a front view of an engine piston manufactured from an allomorphic material. FIG. 5 is a schematic cross-sectional view of a horizontal continuous casting apparatus. FIG. 6 is a schematic cross-sectional view of a hot top continuous casting apparatus. FIG. 7 is a cross-sectional view of a die of a forging device showing an example of a process for forging a forging material using the forging device. FIG. 8 is a cross-sectional view of the mold of the forging device showing another example of the process of forging the forging material using the forging device. FIG. 9 is a perspective view of an analytical sample of a molten aluminum alloy. FIG. 10 is a structural photograph of Example 1 taken by microstructural observation. FIG. 11 is a structure photograph of Comparative Example 3 imaged by microstructure observation. FIG. 12 is a diagram illustrating the relationship between the P addition amount and the Si addition amount in Examples 9 to 12 and Comparative Examples 17 to 24.

  Next, embodiments of the present invention will be described below with reference to the drawings.

  In the present embodiment, “excellent in high temperature characteristics” means excellent strength at 250 ° C., that is, fatigue strength (ie, high temperature fatigue strength) at 250 ° C. when the tensile strength (ie, high temperature tensile strength) is 120 MPa or more. Means 60 MPa or more.

  1-3, 11 is the aluminum alloy engine piston shaped material according to one embodiment of the present invention.

  In FIG. 4, reference numeral 1 denotes an aluminum alloy engine piston manufactured from the raw material 11.

  In the following description, the vertical direction toward the paper surface of FIG. 1 is referred to as “front-rear direction”, the horizontal direction is referred to as “left-right direction”, and the vertical direction toward the paper surface of FIGS. To do.

  As shown in FIG. 4, the engine piston 1 includes a crown surface portion 2 having a circular shape in plan view, a land portion 3 formed on the lower side, and a pair of skirt portions 4 disposed on the lower side so as to face each other. A pair of pin boss portions 5 and sidewall portions 6 are integrally provided. A plurality of piston ring groove portions 7 to which a plurality of piston rings (eg, pressure rings, oil rings) are attached are formed on the outer peripheral surface of the land portion 3.

  As shown in FIGS. 1 to 3, the engine piston blank 11 is manufactured by forging and, like the engine piston 1, a portion corresponding to the crown surface portion 2 (that is, the crown surface portion corresponding portion 12). And a land portion corresponding portion 13 formed on the lower side, a pair of skirt portion corresponding portions 14 and 14, a pair of pin boss portion corresponding portions 15 and 15 and a sidewall portion disposed on the lower side. Corresponding portions 16 and 16 are integrally provided. The outer peripheral surface of the land portion corresponding portion 13 and the vicinity of the inside thereof are portions where a plurality of piston ring groove portions 7 are formed at the time of final finishing, that is, constitute the piston ring groove portion corresponding portion 17.

  In this raw material 11, primary crystal Si exists at least in the skirt portion corresponding portion 14 and the piston ring groove portion corresponding portion 17. Furthermore, in the entire raw material, there is no primary crystal Si having a maximum diameter of 50 μm or more, and no Al—Fe—Cr—Mn-based giant crystallized material having a maximum diameter of 50 μm or more. Furthermore, there is no segregation of primary crystal Si in the whole raw material.

  In the present embodiment, “primary crystal Si is present” specifically means that, for example, when a sample is mirror-polished and then this mirror-polished surface is observed with a microstructure using a metal microscope, ash It indicates the presence of brown, block-like crystallization products.

  Here, the maximum diameter of primary Si is the diameter measured at the maximum primary Si. The maximum diameter of the Al—Fe—Cr—Mn-based giant crystallized product is a diameter measured at the maximum part of the giant crystallized product.

  As a specific method for measuring the maximum diameter of primary crystal Si, for example, when a sample is mirror-polished and then this mirror-polished surface is observed with a microstructure using a metal microscope, a grayish brown block-like crystallized product is obtained. The maximum diameter of the primary crystal Si can be obtained by setting the primary crystal Si and measuring the maximum length of the crystallized product using an image analyzer. As the image analysis device, for example, LUZEX manufactured by Nireco Corporation is used.

  As a specific method for measuring the maximum diameter of the Al-Fe-Cr-Mn giant crystallized product, for example, after the sample is mirror-polished, the surface of the mirror-polished surface is observed with a metal microscope, and a thin structure is obtained. The gray crystallized product is an Al-Fe-Cr-Mn-based giant crystallized product, and the maximum length of the giant crystallized product is measured using an image analyzer, thereby obtaining an Al-Fe-Cr-Mn-based giant crystallized product. The maximum diameter of the crystallized product can be obtained. As the image analysis device, for example, LUZEX manufactured by Nireco Corporation is used.

  Here, in the present embodiment, among the Al—Fe—Cr—Mn based crystals having various sizes, the Al—Fe—Cr—Mn based crystals having a maximum diameter of 50 μm or more are particularly Al—Fe—Cr. -This is called a Mn-based giant crystallized product. Note that the Al—Fe—Cr—Mn giant crystallized product is also called an Al—Fe—Cr—Mn giant intermetallic compound (giant compound).

  In the present invention, the criteria for determining whether or not there is segregation of primary crystal Si is not particularly limited. However, in this embodiment, with respect to this determination criterion, 5 or more (preferably 3 or more) primary crystal Si are formed and at least one interval between each primary crystal Si is larger than the grain size of primary crystal Si. It is assumed that there is segregation of primary Si when there is a short primary crystal Si aggregate, and there is no segregation of primary Si when there is no such primary crystal Si aggregate.

  Next, the manufacturing method of the above-mentioned shaped material 11 will be described below as a manufacturing method of a shaped material for engine pistons according to an embodiment of the present invention.

  The raw material 11 is manufactured by continuously casting a molten metal having a predetermined composition to obtain a cast bar, and forging a forging material obtained by homogenizing the cast bar, And a forging step for obtaining a profile.

  In the continuous casting process, it is necessary to continuously cast the molten metal at a temperature of 720 ° C. or more before pouring the continuous casting mold. Furthermore, the diameter of the cast bar obtained in this continuous casting process must be 85 mm or less.

  The composition of the molten metal is as follows: Si: 11.0 to 13.0 mass%, Fe: 0.6 to 1.0 mass%, Cu: 3.5 to 4.5 mass%, Mn: 0.25 mass% or less, Mg: 0.4 to 0.6 mass%, Cr: 0.15 mass% or less, Ni: 0.6 to {(−4/6) × [Cu mass%] + 5} mass%, Zr: 0.07 -0.15 mass%, P: 0.005-0.010 mass%, Ca: 0.002 mass% or less are included, and the remainder is Al and an unavoidable impurity.

  In the forging process, the forging material must be a homogenized treatment of a cast bar at a temperature of 300 to 500 ° C.

  Below, the addition significance of the composition element of the molten aluminum alloy, the reason for limiting the addition amount (addition concentration), and the reason for limiting the manufacturing conditions of the shaped material 11 will be described.

<About Si: 11.0 to 13.0% by mass>
Si is an element that suppresses the thermal expansion of the aluminum alloy and improves the wear resistance. That is, the wear resistance can be improved by controlling the crystallization of primary Si to an appropriate state.

Here, an appropriate coefficient of thermal expansion is determined by the material of the mating member for the engine piston 1, that is, the material of the cylinder block (iron, aluminum), but the cylinder block partially rises to a high temperature. As a whole, since the temperature does not become high (and it takes time to reach high temperature), it is advantageous that the coefficient of thermal expansion is as small as possible. In general, the design of the engine piston 1 and the selection of the piston ring are designed with dimensions when the engine reaches a high temperature. Therefore, if the thermal expansion is too large, the diameter of the skirt portion 4 becomes small at a low temperature, and the swing of the engine piston 1 is likely to occur at the start. Therefore, it is desirable that the amount of Si added is as large as possible because thermal expansion can be reduced. Preferred thermal expansion coefficient is ^{19 × 10 -6 / K~21 × 10} -6 / K in the range of 25 to 250 ° C., the addition amount of Si such thermal expansion coefficient is obtained from 11.0 to 13 0.0% by mass.

  On the other hand, with such an added amount of Si, conventionally, crystallization of primary Si by continuous casting has become unstable as follows. That is, since the eutectic point of the Al—Si alloy is usually 11.7% by mass, primary crystal Si does not crystallize at 11.0% by mass or less. Therefore, when the amount of Si before and after the eutectic point is added, continuous casting cannot be performed so that the crystallization state of primary Si is stabilized. That is, when the addition amount of Si is within a range of, for example, 11.7 ± 0.5% by mass, crystallization of primary Si by continuous casting has been unstable conventionally.

  However, the inventors have specified alloy composition conditions that provide excellent high-temperature strength and high-temperature fatigue strength while maintaining wear resistance even when adding amounts of Si before and after sandwiching the eutectic point. Manufacturing conditions were found and the present invention was completed.

  That is, in the composition of the molten metal in the present invention, by adding Ca and P described later, the primary crystal Si is stably formed even when Si is added in amounts before and after the eutectic point due to the interaction with them. Since it crystallizes, the wear resistance can be improved. More preferably, the addition amount of Si should exceed 12.0% by mass.

  If the amount of Si added is less than 11.0% by mass, thermal expansion increases, and crystallization of primary Si is suppressed.

  On the other hand, if the added amount of Si exceeds 13% by mass, the crystallized primary crystal Si is segregated, which becomes the starting point of fatigue fracture and lowers the high temperature fatigue strength, which is not desirable.

  In particular, when a forging material obtained by homogenizing a forging rod at a predetermined temperature is forged into a shaped material for an engine piston, casting corresponding to the skirt portion 4 and the piston ring groove portion 7 of the engine piston 1 is performed. It is preferable that the distribution of primary crystal Si is uniform and the size of primary crystal Si is fine at the outer periphery of the rod.

<Fe: About 0.6 to 1.0 mass%>
Fe crystallizes as an Al—Fe—Cr—Mn intermetallic compound together with Cr, Mn, and the like, and this crystallized substance becomes a stable dispersion strengthening phase even at a high temperature and contributes to an improvement in high temperature strength.

  If the amount of Fe added is less than 0.6% by mass, the amount of the dispersion strengthening phase is small and the improvement in high temperature strength is small, which is not desirable.

  On the other hand, when the added amount of Fe exceeds 1.0% by mass, a needle-like Al—Fe—Cr—Mn giant crystallized product is crystallized, which serves as a starting point for fatigue fracture and reduces high temperature fatigue strength. Is not desirable.

  In general, when a large amount of Fe, Cr, and Mn is added, an Al—Fe—Cr—Mn-based giant crystallized product is crystallized, which may reduce high-temperature fatigue strength. Therefore, in the present invention, when the total addition amount of Fe, Cr, and Mn is large, it is particularly desirable to add the total addition amount of Cr and Mn to 40% or less with respect to the addition amount of Fe. By doing so, crystallization of the giant crystallized product can be suppressed even if the amount of Fe added is large.

  Fe, together with Al, Fe, and Ni, crystallizes an Al—Fe—Ni—Cu intermetallic compound that is stable even at high temperatures, and contributes to improving high temperature strength.

  Therefore, it is particularly preferable to add as much Fe as possible within a range in which no Al—Fe—Cr—Mn large crystallized product is generated.

<Cu: About 3.5 to 4.5% by mass>
Cu precipitates as an Al—Cu (—Mg) -based intermetallic compound, and its presence improves the strength and fatigue strength at 150 ° C. or lower (hereinafter abbreviated as normal temperature strength and normal temperature fatigue strength, respectively).

  Cu, together with Al, Fe, and Ni, crystallizes an Al—Fe—Ni—Cu intermetallic compound that is stable even at high temperatures, and contributes to the improvement of high temperature strength.

  If the amount of Cu added is less than 3.5% by mass, the amount of Al-Cu (-Mg) intermetallic compound precipitates is small, and the amount of Al-Fe-Ni-Cu intermetallic compound crystallized matter. Since there is little improvement in normal temperature strength and normal temperature fatigue strength, it is not desirable.

  Since Cu is a heavy element, if the amount of Cu added is large, the characteristic of lightness inherent in the aluminum alloy is hindered. However, the solid solubility limit of Cu is 5.65% by mass, but even if Cu is added in excess of 4.5% by mass, the effect of improving normal temperature strength and normal temperature fatigue strength is small. 4.5 mass% was set as the upper limit.

<Mn: About 0.25 mass% or less>
Mn crystallizes as an intermetallic compound together with Fe and Cr, becomes a dispersion strengthened phase, and is an element that contributes to the improvement of high-temperature strength. . Therefore, the amount of Mn added is set to 0.25% by mass or less. The amount of Mn added is desirably as small as possible, and particularly preferably below the detection limit. The most desirable amount of Mn added is 0% by mass.

<About Mg: 0.4 to 0.6% by mass>
Mg is an element that improves normal temperature strength and normal temperature fatigue strength by coexisting with Si and Cu. If the addition amount of Mg is less than 0.4% by mass, the above effect is poor, which is undesirable. Even if Mg is added in excess of 0.6% by mass, the above effect is saturated. Therefore, the amount of Mg added is set to 0.4 to 0.6% by mass.

<Cr: About 0.15 mass% or less>
Cr crystallizes as an intermetallic compound together with Fe and Mn, becomes a dispersion strengthened phase, and is an element that contributes to the improvement of high-temperature strength. . Therefore, the addition amount of Cr is set to 0.15% by mass or less. The addition amount of Cr is preferably as small as possible, and particularly preferably below the detection limit. The most desirable addition amount of Cr is 0% by mass.

<About Ni: 0.6 to {(−4/6) × [Cu Mass%] + 5} Mass%>
As described above, Ni crystallizes an Al—Fe—Ni—Cu intermetallic compound that is stable at high temperatures together with Cu, and improves high temperature strength and high temperature fatigue strength. It is desirable that there are as many such crystals as possible. However, if the amount of Ni added is less than 0.6% by mass, the above effect is poor, which is not desirable. Therefore, the addition amount of Ni is set to 0.6% by mass or more. On the other hand, if the additive amount of Ni increases and exceeds {(−4/6) × [Cu mass%] + 5} mass%, it is not desirable because cracks occur during forging. Therefore, the upper limit of the addition amount of Ni is set to {(−4/6) × [Cu mass%] + 5} mass%. Therefore, when the amount of Cu added is 3.5% by mass, which is the lower limit, the upper limit of the amount of Ni added is 2.7% by mass. Moreover, when the addition amount of Cu is the upper limit value of 4.5 mass%, the upper limit value of the addition amount of Ni is 2.0 mass%.

<About Zr: 0.07 to 0.15 mass%>
Zr is an element that precipitates an Al—Zr intermetallic compound at a temperature of 350 ° C. or higher and improves the high-temperature strength of the alloy material. If the amount of Zr added is less than 0.07% by mass, the above effect is poor and undesirable. Even if Zr is added in an amount exceeding 0.15% by mass, the above effect is saturated. Therefore, the amount of Zr added is set to 0.07 to 0.15% by mass.

<About P: 0.005 to 0.010 mass%>
P is an element that shifts the lower limit of the amount of Si added to crystallize primary Si to the low Si content side and further refines the grain size of the crystallized product of primary Si. In the case where the Si addition amount is high, the primary crystal Si becomes coarse unless P is added. If the addition amount of P is less than 0.005% by mass, the above effect is poor, which is not desirable. On the other hand, if the addition amount of P exceeds 0.010% by mass, the above effect is saturated, and further, the needle-like formation of eutectic Si is promoted and the toughness is lowered. Therefore, the addition amount of P is set to 0.005 to 0.010% by mass. By doing in this way, the maximum diameter of primary crystal Si can be 50 micrometers or less.

  In particular, it is desirable that the addition amount of P satisfies the following formula (1). By doing so, crystallization of primary Si by continuous casting can be reliably stabilized. As a result, primary Si can be surely present throughout the entire shape material, segregation of primary Si can be reliably prevented, and eutectic Si can be spheroidized reliably. Can do. As a result, it is possible to reliably obtain an engine piston shaped material that is extremely excellent in wear resistance and high temperature characteristics.

0.0025 × Si addition amount−0.025 ≦ P addition amount ≦ 0.0025 × Si addition amount−0.02 Formula (1)
However, the unit of P addition amount and Si addition amount: mass%, respectively.

  Note that P has a small amount of P dissolved in the molten metal (that is, the amount of P added), and handling is troublesome. Therefore, in order to increase the amount of addition of P and facilitate handling, it is preferable to add P to the molten metal in the form of a P—Cu alloy (a master alloy of 8 mass% P and 92 mass% Cu).

<About Ca: 0.002 mass% or less>
Ca is an element that inhibits the refinement and hardening of primary Si by P. Therefore, a flux containing magnesium chloride (MgCl ₂ ) is charged into the molten metal and stirred, so that the amount of Ca in the molten metal is decreased and the amount of Ca added is controlled to be 0.002% by mass or less. More preferably, by defining the addition amount of Ca and P (unit: mass%) as P> 6 × Ca, even when adding Si before and after the eutectic point, P is consumed by Ca. Not. As a result, AlP is generated, and this AlP effectively functions as a nucleus for heterogeneous nucleation of primary Si, whereby primary Si can be crystallized finely and uniformly. Thereby, abrasion resistance can be improved. The addition amount of Ca is preferably as small as possible, and particularly preferably below the detection limit. The most desirable addition amount of Ca is 0% by mass.

  The reason why the molten metal temperature is set to 720 ° C. or higher in the continuous casting process is as follows.

  Casting while maintaining the molten metal before the start of solidification at a high temperature suppresses the formation of Al-Fe-Cr-Mn-based giant crystals in the solidification process, and further, the primary crystal Si crystallizes in the casting rod. It contributes to miniaturization and uniform distribution. Therefore, casting temperature shall be 720 degreeC or more. This can be realized by setting the melt temperature before pouring the continuous casting mold to 720 ° C. or higher. A particularly preferable molten metal temperature is 740 ° C. or higher. When the forging material obtained by homogenizing the casting rod is forged into the shaped material for the engine piston by setting the molten metal temperature to 720 ° C. or higher, the skirt portion 4 and the piston ring groove portion of the engine piston 1 In the outer peripheral portion of the casting rod corresponding to 7, the crystallization state of primary Si can be made fine and uniform. In addition, the upper limit of molten metal temperature is not specifically limited, For example, it is 850 degreeC (preferably 750 degreeC).

  The reason why the diameter of the casting rod is set to 85 mm or less in the continuous casting process is as follows.

  As the diameter of the cast bar (ie, the cast diameter) increases, the cooling rate at the center of the ingot slows down, so that an Al-Fe-Cr-Mn-based giant crystallized product is likely to be generated, and further at the center of the cast bar. The refinement and uniform distribution of primary Si are hindered. When the diameter of the casting rod is 85 mm or less, the difference in cooling rate between the center portion and the outer peripheral portion of the casting rod can be kept small, and preferably this cooling rate difference can be made 200 ° C./s or less. Thereby, the production | generation of an Al-Fe-Cr-Mn type giant crystallized product can be suppressed. For this reason, the diameter of the cast bar is regulated to 85 mm or less. In this way, when the forging material obtained by homogenizing the casting rod is forged into the shaped material for the engine piston, Al is formed at the center of the casting rod corresponding to the crown surface portion 2 of the engine piston 1. The —Fe—Cr—Mn-based giant crystallized product does not exist, and the crystallized state of the primary crystal Si can be made fine and uniform with a maximum diameter of less than 50 μm. In addition, the lower limit of the diameter of a casting rod is not specifically limited, For example, it is 20 mm.

  The reason for homogenizing the cast bar at 300 to 500 ° C. is as follows.

  The larger the area of the interface between the Al-Si crystallized product or Al-Fe-Cr-Mn crystallized product and the aluminum base, the more the Al-Fe-Cr-Mn crystallized product becomes Since it becomes resistance, plastic deformation at high temperatures is difficult. As a result, high temperature strength and high temperature fatigue strength are improved.

  However, the homogenization treatment just under the solidus temperature generally performed for improving forgeability has a high treatment temperature, and Al-Si-based crystals and Al-Fe-Cr-Mn-based crystals. To spheroidize and reduce the area of the interface. Therefore, in the present invention, the upper limit of the treatment temperature is set to a temperature at which the Al—Si based crystallized product and the Al—Fe—Cr—Mn based crystallized product are not divided and are not spheroidized. However, if the homogenization temperature is too low, the deformability is insufficient during forging, and defects such as cracks occur. Therefore, the homogenization temperature is set to 300 to 500 ° C., and more preferably, the temperature is set as low as possible within a range in which the material does not break during forging in accordance with the shape of the engine piston. The homogenization time is preferably 4 hours or longer. By homogenizing the cast rod under such processing conditions, it is possible to reliably maintain an Al-Si-based crystallized product and an Al-Fe-Cr-Mn-based crystallized product that are not divided or spheroidized. . In addition, the upper limit of the holding time of the homogenization processing time is not particularly limited, and is, for example, within 24 hours.

  Next, the continuous casting apparatus used when continuously casting the molten metal will be described below.

  The continuous casting apparatus is not limited to that method as long as it can obtain a casting rod having a diameter of 85 mm or less while maintaining the molten metal temperature at 720 ° C. or higher. For example, a vertical semi-continuous casting apparatus. A hot top continuous casting apparatus, a horizontal continuous casting apparatus, and a gas pressure type continuous casting apparatus can be used.

  FIG. 5 is a cross-sectional view illustrating an example of a horizontal continuous casting apparatus that performs horizontal continuous casting. The continuous casting apparatus 20A includes a molten metal receiving part 21 for storing a molten aluminum alloy 30 and a solidification continuous casting water cooling mold (water cooling mold) 22 having a molten metal passage 22a. And the mold 22 is arrange | positioned in the molten state through the molten metal injection | pouring opening | mouth 23 in the molten metal receiving part 21, and is arrange | positioned horizontally. Reference numeral 24 denotes a cooling water passage formed in the mold 22. The mold 22 and the casting rod 31 drawn from the mold 22 are cooled by the cooling water 25 discharged from the cooling water passage 24.

  FIG. 6 is a cross-sectional view showing an example of a hot top continuous casting apparatus. The continuous casting apparatus 20B includes a molten metal receiving portion 21 and a continuous casting water-cooling mold 22 for solidification that is disposed below the molten metal receiving portion 21 and has a molten metal passage 22a. And the mold 22 is arranged in the molten state through the molten metal inlet 23 through the molten metal receiving portion 21 and the outlet of the molten metal passage 22a is directed downward. In the continuous casting apparatus 20B, the molten aluminum alloy 30 in the molten metal receiving portion 21 is introduced into the cooled mold 22 through the molten metal inlet 23 from above. The molten metal 30 introduced into the mold 22 is drawn downward from the mold 22 while forming a strong shell (solidified shell) at a portion in contact with the mold 22. The casting rod 31 drawn out from the mold 22 is cooled by the cooling water 25 discharged from the cooling water passage 24.

  In the present invention, in each of the continuous casting apparatuses 20A and 20B as described above, preferably, the temperature at the position C immediately before the molten metal 30 is poured into the mold 22 is the molten metal temperature, and this temperature is 720 ° C. or higher. Is good. In the [Example] column described later, the temperature at this position C in the molten metal 30 is set as the molten metal temperature.

  Next, the homogenization furnace used when homogenizing the forged bar will be described below.

  Any homogenization heat treatment furnace may be used as long as it can accommodate a casting rod and can perform a homogenization process at a processing temperature of 300 to 500 ° C., for example, a hot air circulation type furnace. In the case of a furnace, either a direct furnace or a radiant tube furnace may be used, and in the case of a transfer type furnace, either a continuous furnace or a batch furnace may be used.

  Next, a forging apparatus used when forging a forging material will be described below.

  Any forging device may be used as long as it has a forging die for forging a forging material into an engine piston-shaped material, and in particular, a forging device further provided with a preheating treatment device and a lubricant coating device. desirable. Further, the forging die is desirably a closed forging die. Specifically, a knuckle press, a crank press, a friction press, a hydraulic press, and a servo press can be used as the forging device.

  Therefore, the manufacturing method of the shaped member in the present embodiment is performed as follows.

  Using a continuous casting apparatus, a molten metal having a predetermined composition is continuously cast into a casting rod having a molten metal temperature of 720 ° C. or more and a diameter of 85 mm or less [continuous casting process]. The cross-sectional shape of the cast bar is preferably circular, that is, the cast bar is preferably round.

  Next, the forging material is obtained by homogenizing the cast bar at a temperature of 300 to 500 ° C. And as for this raw material, the outer peripheral surface of a raw material is peel-processed (peripheral surface cutting process) as needed after the homogenization process. Thereafter, the material is cut into a predetermined length (thickness) in the length direction of the material, thereby forming a disk shape or a cylindrical shape. Here, the cut surface of the cast bar becomes the upper surface and the lower surface of the material, and the outer peripheral surface of the cast bar or the vicinity thereof becomes the outer peripheral surface of the material. Furthermore, this material is subjected to upsetting, lubricating, and preheating as necessary.

  Next, the material is forged into an engine piston-shaped material by a forging device [forging process].

  7 and 8 are diagrams illustrating a forging process in which a material is forged using a forging device.

  A die 41 of the forging device 40 shown in FIGS. 7 and 8 is composed of an upper die 42 and a lower die 43, and the upper and lower dies 42, 43 are fitted together to form a sealed molding space 44. The disk-shaped or columnar material 32 is forged inside, and the raw material 11 for the engine piston is obtained.

  In FIG. 7, 32A is a long forging bar-shaped material 32A obtained by homogenizing the casting bar 31. The disc-shaped or columnar material 32 obtained by cutting the rod-shaped material 32A into a predetermined length (thickness) is disposed in the lower mold 43 of the forging device 40 and then fitted into the lower mold 43. When the upper die 42 is pressed in the axial direction of the raw material 32, the raw material 32 is forged into a predetermined shape in the sealed molding space 44, and the shaped material 11 for the engine piston is obtained. A die 41 of the forging device 40 shown in FIG. 7 is configured such that a skirt portion corresponding portion (not shown) and pin boss portion corresponding portions 15 and 15 are forward-extruded.

  In FIG. 8, the raw material 32 is forged in the same manner as the forging method shown in FIG. The die 41 of the forging device 40 shown in FIG. 8 is configured such that a skirt portion corresponding portion (not shown) and pin boss portion corresponding portions 15 and 15 are rearwardly extruded.

  As shown in FIGS. 7 and 8, the material 32 is such that the upper surface or the lower surface of the material 32 becomes the crown surface corresponding portion 12 of the base material 11, and the outer peripheral portion of the material 32 is the piston ring groove corresponding portion 17. And it arrange | positions in the lower mold | type 43 so that it may become a skirt part corresponding | compatible part (not shown).

  The treatment temperature of the preheating treatment performed immediately before forging and the material temperature during forging are desirably 470 ° C. or less and as short as possible, and particularly preferably lower than the homogenization treatment temperature. Further, the heating time may be the shortest time during which the material temperature can be raised to the processing temperature (ie, 470 ° C. or lower). Thus, by processing in a low temperature for a short time, the state of the Al-Si-based crystallized product and the Al-Fe-Cr-Mn-based crystallized product after homogenization can be maintained even after forging.

  The raw material 11 thus obtained is subjected to solution treatment and aging treatment as necessary.

  It is desirable that the solution treatment temperature is not higher than the solidus temperature. The reason is that the state of the Al—Si based crystallized product or the Al—Fe—Cr—Mn based crystallized product after the homogenization treatment can be maintained.

  As for the aging temperature and the aging time, it is desirable that the aging temperature and the aging time are slightly overaged by adjusting the temperature and time. By doing so, dimensional growth due to aging during product use can be suppressed.

  The base material 11 is subjected to a final finishing process by machining or the like, and then other parts such as a piston ring are attached to form an engine piston.

  As described above, the base material 11 manufactured according to the base material manufacturing method of the present embodiment does not generate cracks in the crown surface corresponding part 12 during forging, and at least the skirt part corresponding part 14 and the piston ring groove part corresponding part. In FIG. 17, primary Si is appropriately present, there is no primary crystal Si having a maximum diameter of 50 μm or more, no segregation of primary crystal Si is present, and Al—Fe—Cr—Mn giant crystallization having a maximum diameter of 50 μm or more Things do not exist. Therefore, the engine piston 1 manufactured using this shaped material 11 is excellent in wear resistance and further excellent in normal temperature tensile characteristics and high temperature characteristics (that is, high temperature tensile characteristics and high temperature fatigue characteristics).

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  Next, specific examples and comparative examples of the present invention will be shown. However, the present invention is not limited to the following examples.

  <Examples 1-8, Comparative Examples 1-16>

  Here, in Table 1, the unit of the composition element is “mass%”. In the Ni column of Table 1, A means {(−4/6) × [Cu mass%] + 5} mass%.

  A round bar-shaped casting rod was obtained by continuously casting a molten Al alloy having the composition shown in Table 1 using a hot top continuous casting apparatus (see FIG. 6). In this continuous casting, the melt temperature before pouring the continuous casting mold is as described in the “melt temperature” column of Table 2. The diameter of the obtained cast bar is as described in the column “Diameter of cast bar” in Table 2.

  In casting, an approximately disk-shaped analysis sample 50 as shown in FIG. 9 is collected by casting a molten metal into a mold in accordance with JIS Z 2611. This analysis sample 50 is used to comply with JIS H 1305. Then, the constituent elements of the molten metal were quantitatively analyzed by emission spectroscopic analysis. In FIG. 9, reference numeral 51 denotes an analysis unit for the analysis sample 50. The analysis unit 51 was subjected to analysis after being cut by a milling machine by about 0.5 mm (0.3 to 0.6 mm). About the dimension of each site | part of the analysis sample 50, they are A = 50mm, B = 30mm, C = 18mm, D = 5mm, E = 5mm, F = 35mm.

  The cast bar was then cut to a length of 6000 mm. Next, the cut cast bar was homogenized. In this homogenization treatment, the treatment temperature is as described in the “homogenization treatment temperature” column in Table 2. Further, the processing time is 7 hours.

  Thereafter, the outer circumference of the cast bar was cut to a diameter of 50 mm, and the cast bar was cut to a length of 60 mm to obtain a cylindrical forging material.

  Next, after preheating the material at 420 ° C., the material was axially pressed from its end face to upset the material to a thickness of 10 mm. This upset forging corresponds to the forging in the forging process of the present invention, and was carried out at a forging rate corresponding to the forging rate when the material was actually forged into an engine piston blank.

  Thereafter, the upset forged product was subjected to T6 heat treatment. That is, the upset forged product was solution-treated at 495 ° C., and then artificially aged under the conditions of an aging temperature of 200 ° C. and an aging time of 6 hours.

  With respect to the upset forged product thus subjected to the T6 heat treatment, the presence of cracks and hole defects on the surface of the upset forged product was examined by a solvent-removable penetration test (color check). Thereafter, the upset forged product is cut, the cross section is mirror-polished, and the mirror-polished surface is observed with a metal microscope to observe the microstructure from the center to the outer periphery of the upset forged product. Existence / absence, presence / absence of primary crystal Si having a maximum diameter of 50 μm or more, presence / absence of Al—Fe—Cr—Mn giant crystallized substances, and segregation of primary crystal Si were examined. The results are shown in the “Presence / absence of primary Si” column, “Presence / absence of primary crystal of 50 μm or more” column, “Presence / absence of giant crystal” column and “Presence / absence of segregation of primary crystal Si” column in Table 2. Respectively. In each of Examples 1 to 8, primary Si was present throughout the upset forged product. In addition, the upset forged product thus subjected to the T6 heat treatment was evaluated for normal temperature tensile properties, high temperature tensile properties, and high temperature fatigue properties.

  The structure photograph of Example 1 is shown in FIG. 10 as a typical example among the structure photographs of Examples 1-8 imaged by microstructure observation. Moreover, the structure photograph of the comparative example 3 is shown in FIG. 11 as a representative example among the structure photographs of the comparative examples 1-16 imaged by micro structure observation. Moreover, LUZEX manufactured by Nireco Co., Ltd. was used as an image analysis apparatus for analyzing the image of the tissue photograph.

  In the structure photograph, the Al—Fe—Cr—Mn crystallized product is a light gray crystallized product, the primary crystal Si is a grayish brown and block crystallized product, and the eutectic Si is more than the primary crystal Si. It is a grayish brown crystallization product with a small average particle size of about 5 μm. In addition, when Al-Fe-Ni-Cu-based crystals are present in the upset forged product, the structure photograph shows that the Al-Fe-Ni-Cu-based crystals are Al-Fe-Cr-Mn-based crystals. It is observed as a gray crystallized product that is lighter than the product.

  In FIG. 10 (Example 1), a large number of eutectic Si are present in a dispersed state, and the average particle size is about 5 μm. A plurality of primary crystal Si are present in a dispersed state, the maximum diameter is about 25 μm, and the average particle diameter is about 20 μm, but there is no primary crystal Si having a maximum diameter of 50 μm or more. A large number of Al-Fe-Cr-Mn crystals are dispersed and the average particle diameter is about 5 μm, but the Al—Fe—Cr—Mn giant crystal having a maximum diameter of 50 μm or more. There are no artifacts. In addition, a large number of Al-Fe-Ni-Cu-based crystallized substances are present in a dispersed state, and the average particle size is about 5 μm.

  In FIG. 11 (Comparative Example 3), a large amount of eutectic Si is present in a dispersed state, and the average particle size is about 5 μm. Primary crystal Si is unevenly distributed, its maximum diameter is about 35 μm, and its average particle size is about 20 μm. There are two types of Al-Fe-Cr-Mn crystallization products. Among them, one type is a crystallized substance having an average particle diameter of about 5 μm, and many are present in a dispersed state. The other one is a block-like crystallized product having an average particle size of about 60 μm, and Al—Fe—Cr—Mn giant crystallized product having a maximum diameter of 50 μm or more exists.

  The evaluation method of the room temperature tensile properties is as follows.

  A JIS 14A proportional test piece was collected from the upset forged product subjected to T6 heat treatment, and the tensile strength at 25 ° C. was measured with this test piece. And the tensile strength of 350 MPa or more was considered good, and less than 350 MPa was judged as defective. The results are shown in the “room temperature tensile properties” column of Table 2.

  The evaluation method of the high temperature tensile property is as follows.

  After holding the upset forged product subjected to the T6 heat treatment at 250 ° C. for 100 hours, a flanged JIS14A proportional test piece was collected from the upset forged product. And at the time of a strength test, after hold | maintaining a test piece again at 250 degreeC for 15 minutes, tensile strength was measured at 250 degreeC with this test piece. And the tensile strength of 120 MPa or more was considered good, and less than 120 MPa was judged as defective. The results are shown in the “High temperature tensile properties” column of Table 2.

  The evaluation method of the high temperature fatigue characteristics is as follows.

  After holding the upset forged product subjected to the T6 heat treatment at 250 ° C. for 100 hours, a fatigue test piece was collected from the upset forged product. Then, a fatigue test was performed on the test piece at a temperature of 250 ° C. using an Ono type rotating bending fatigue tester, and a stress value that did not break even at 10000000 cycles was defined as a fatigue strength. A stress value of 60 MPa or more was considered good, and a stress value of less than 60 MPa was judged as bad. The results are shown in the “High-temperature fatigue characteristics” column of Table 2.

  Since Examples 1 to 8 satisfy all the requirements of the present invention, cracks do not occur, primary Si exists throughout the upset forged product, and primary Si having a maximum diameter of 50 μm or more does not exist. In addition, there was no Al—Fe—Cr—Mn giant crystallized product having a maximum diameter of 50 μm or more, and no segregation of primary Si was present. Furthermore, it was excellent in normal temperature tensile properties, high temperature tensile properties, and high temperature fatigue properties.

  In Comparative Example 1, since the addition amount of Si was small, primary Si was not present.

  In Comparative Example 2, since the amount of Si added was too large, primary crystal Si segregated and the primary crystal Si had a large particle size, and cracking occurred during upsetting forging starting from this primary crystal Si.

  In Comparative Example 3, since the amount of Fe added was too large, an Al—Fe—Cr—Mn-based giant crystallized product was generated, and cracks occurred during upsetting forging starting from the giant crystallized product.

  In Comparative Example 4, since the amount of Mn and Cr added was too large, an Al—Fe—Cr—Mn-based giant crystallized product was generated, and cracks occurred during upsetting forging starting from this giant crystallized product.

  Since the comparative example 5 had too few Cu and Mg addition amount, the normal temperature tensile characteristic fell.

  In Comparative Example 6, since the Zr addition amount was too small, the high temperature tensile properties and the high temperature fatigue properties were deteriorated.

  Since the comparative example 7 had too little Fe addition amount, the high temperature tensile characteristic and the high temperature fatigue characteristic fell.

  In Comparative Example 8, the amount of Si added was small, and P was not added, so primary crystal Si was not present.

  In Comparative Example 9, since the amount of Si added was large and P was not added, the primary crystal Si was coarsened.

  Since the comparative example 10 did not reduce Ca addition amount with a flux, primary crystal Si coarsened.

  In Comparative Example 11, since the molten metal temperature was too low, segregation of primary crystal Si occurred.

  In Comparative Example 12, since the diameter of the cast bar was too large, the primary crystal Si in the center of the upset forged product was coarsened.

  In Comparative Example 13, since the homogenization temperature was too low, the spheroidization of eutectic Si or the like was insufficient, and cracks occurred during upsetting forging.

  In Comparative Example 14, since the homogenization treatment temperature was too high, eutectic melting was caused by preheating before upsetting forging, and cracks were generated starting from the melting portion during upsetting forging.

  In Comparative Example 15, since the amount of Ni added was too small, there were few stable crystallized substances even at high temperatures, so that the high-temperature tensile properties deteriorated.

  In Comparative Example 16, since the amount of Ni added was too large and exceeded {(−4/6) × [Cu mass%] + 5} mass%, cracks occurred during upsetting forging.

  <Examples 9 to 12, Comparative Examples 17 to 24>

  Here, in Table 3, the unit of the composition element is “mass%”. In the Ni column of Table 3, A means {(−4/6) × [Cu mass%] + 5} mass%.

  FIG. 12 is a diagram illustrating the relationship between the P addition amount and the Si addition amount in Examples 9 to 12 and Comparative Examples 17 to 24. In the formulas in the figure, [P] means the amount of P added (unit: mass%), and [Si] means the amount of Si added (unit: mass%).

  A round bar-shaped cast bar was obtained by continuously casting a molten Al alloy having the composition shown in Table 3 using a hot top continuous casting apparatus (see FIG. 6). In this continuous casting, the molten metal temperature before pouring the continuous casting mold was 750 ° C., and the diameter of the casting rod was 55 mm.

  In casting, an approximately disk-shaped analysis sample 50 as shown in FIG. 9 is collected by casting a molten metal into a mold in accordance with JIS Z 2611. This analysis sample 50 is used to comply with JIS H 1305. Then, the constituent elements of the molten metal were quantitatively analyzed by emission spectroscopic analysis.

  The cast bar was then cut to a length of 6000 mm. Next, the cut cast bar was homogenized under the conditions of a processing temperature of 470 ° C. and a holding time of 7 hours.

  Thereafter, the outer circumference of the cast bar was cut to a diameter of 50 mm, and the cast bar was cut to a length of 60 mm to obtain a cylindrical forging material.

  Next, after preheating the material at 420 ° C., the material was axially pressed from its end face to upset the material to a thickness of 10 mm. This upset forging corresponds to the forging in the forging process of the present invention, and was carried out at a forging rate corresponding to the forging rate when the material was actually forged into an engine piston blank.

  Thereafter, the upset forged product was subjected to T6 heat treatment. That is, the upset forged product was solution-treated at 495 ° C., and then artificially aged under the conditions of an aging temperature of 200 ° C. and an aging time of 6 hours.

  By cutting the upset forged product that has been subjected to T6 heat treatment, the cross section is mirror-polished, and the microstructure of the mirror-polished surface is observed from the center to the outer periphery of the upset forged product using a metal microscope. The presence or absence of primary Si, the presence or absence of segregation of primary Si, and the shape of eutectic Si were examined in the center and outer periphery of upset forged products.

  The presence or absence of primary Si was judged by the presence or absence of grayish brown block-like crystallization products when the microstructure was observed.

  As for the presence or absence of segregation of primary Si, there are primary Si aggregates formed by gathering 3 or more primary Si and having at least one interval between the primary Si shorter than the grain size of primary Si. In this case, segregation of primary Si was allowed, and when there was no such primary crystal Si aggregate, segregation of primary Si was absent.

  Eutectic Si is a grayish brown crystallization product that is smaller than primary Si. When the size of this crystallized product was measured, if “maximum length” / “minimum length” was 3 or more, it was determined that eutectic Si was acicular, and if it was less than 3, It was judged that crystal Si was spheroidized.

  In the [judgment] column in FIG. 12, “◯” means that it is suitable as a material for engine piston, and “x” means that it is not suitable.

  As shown in Table 4 and FIG. 12, Examples 9-12 have Si addition amount in the range of 11.0-13.0 mass%, P addition amount is 0.005-0.010 mass%. Further, the P addition amount satisfies the above formula (1). Therefore, the crystallization of primary Si by continuous casting became stable. As a result, primary Si was present from the center to the outer periphery of the upset forged product, and there was no segregation of primary Si. Further, eutectic Si was spheroidized. Therefore, it had a good microstructure.

  In Comparative Examples 17, 23, and 24, since the Si content was too small, primary Si was partially present in the upset forged product, that is, it was not present throughout the upset forged product.

  In Comparative Example 18, although the Si content was within the range of the present invention, the amount of P added was small, so that primary Si was present only at the center of the upset forged product, and primary Si was present at the outer periphery. Did not exist.

  In Comparative Examples 19, 20, and 21, since the amount of Si added was too large, segregation of primary Si occurred.

  In Comparative Example 22, although the Si content was within the range of the present invention, the amount of added P was too large, so that eutectic Si became needle-like. Therefore, the toughness of upsetting forged products was low.

  This application is accompanied by the priority claim of Japanese Patent Application No. 2009-250278 filed on Oct. 30, 2009, the disclosure of which constitutes a part of the present application as it is. .

  The terms and expressions used herein are for illustrative purposes and are not to be construed as limiting, but represent any equivalent of the features shown and described herein. It should be recognized that various modifications within the claimed scope of the present invention are permissible.

  While this invention may be embodied in many different forms, this disclosure is to be considered as providing examples of the principles of the invention, which examples are hereby incorporated by reference. Many illustrated embodiments are described herein with the understanding that they are not intended to be limited to the preferred embodiments described and / or illustrated.

  Although several illustrated embodiments of the present invention have been described herein, the present invention is not limited to the various preferred embodiments described herein, and is equivalent to what may be recognized by those skilled in the art based on this disclosure. Any and all embodiments having various elements, modifications, deletions, combinations (eg, combinations of features across the various embodiments), improvements and / or changes are encompassed. Claim limitations should be construed broadly based on the terms used in the claims, and should not be limited to the embodiments described herein or in the process of this application, as such The examples should be construed as non-exclusive. For example, in this disclosure, the term “preferably” is non-exclusive and means “preferably but not limited to”. In this disclosure and in the process of this application, means plus function or step plus function limitations are clearly stated as a) “means for” or “step for” with respect to the limitations of a particular claim. And b) the corresponding function is clearly described, and c) all the conditions that the configuration, material or action supporting the configuration are not mentioned are present in the limitation. Applied. In this disclosure and in the process of this application, the term “present invention” or “invention” may be used to refer to one or more aspects within the scope of this disclosure. The term present invention or inventory should not be construed inappropriately as identifying criticality, nor should it be construed inappropriately as applied across all aspects or all embodiments ( That is, it should be understood that the present invention has numerous aspects and embodiments) and should not be construed inappropriately to limit the scope of the present application or the claims. In this disclosure and in the process of this application, the term “embodiment” is also used to describe any aspect, feature, process or step, any combination thereof, and / or any part thereof. It is done. In some examples, various embodiments may include overlapping features. In this disclosure and in the process of the present application, the abbreviations “e.g.,” and “NB” may be used, meaning “for example” and “careful” respectively.

  INDUSTRIAL APPLICABILITY The present invention can be used for a manufacturing method of a shape material for manufacturing an engine piston used for an engine mounted on a vehicle such as an automobile or a motorcycle, and a material for an engine piston.

1: Engine piston 2: Crown surface portion 4: Skirt portion 7: Piston ring groove portion 11: Engine piston shaped material 12: Crown surface portion corresponding portion 14: Skirt portion corresponding portion 17: Piston ring portion corresponding portion 20A: Horizontal continuous casting apparatus 20B: Hot Top Continuous Casting Device 22: Continuous Casting Mold 30: Molten Metal 31: Casting Rod 32: Forging Material 40: Forging Device

Claims (5)

Si: 11.0-13.0% by mass, Fe: 0.6-1.0% by mass, Cu: 3.5-4.5% by mass, Mn: 0.25% by mass or less, Mg: 0.4 -0.6 mass%, Cr: 0.15 mass% or less, Ni: 0.6-{(-4/6) x [Cu mass%] + 5} mass%, Zr: 0.07-0.15 mass %, P: 0.005 to 0.010% by mass, Ca: 0.002% by mass or less, with the balance consisting of Al and inevitable impurities, the melt temperature before pouring the continuous casting mold is 720 ° C. or higher. A continuous casting process to obtain a cast rod having a diameter of 85 mm or less by continuous casting with setting to
A forging step of obtaining a shaped material for an engine piston by forging a forging material obtained by homogenizing the cast rod at a temperature of 300 to 500 ° C .;
The manufacturing method of the shaped material for engine pistons characterized by including. The method for producing a shaped material for an engine piston according to claim 1, wherein in the composition of the molten metal, the amount of P added satisfies the following formula (1).
0.0025 × Si addition amount−0.025 ≦ P addition amount ≦ 0.0025 × Si addition amount−0.02 Formula (1)
However, the unit of P addition amount and Si addition amount: mass%, respectively. An engine piston shaped material produced by the method for producing an engine piston shaped material according to claim 1 or 2,
Primary crystal Si exists in at least the skirt portion corresponding portion and the piston ring groove portion corresponding portion in the shaped material,
In the entire raw material, there is no primary crystal Si having a maximum diameter of 50 μm or more, and no Al—Fe—Cr—Mn giant crystallized material having a maximum diameter of 50 μm or more.
A material for engine pistons. An engine piston shaped material manufactured by forging,
The composition of the base material is as follows: Si: 11.0 to 13.0 mass%, Fe: 0.6 to 1.0 mass%, Cu: 3.5 to 4.5 mass%, Mn: 0.25 mass% Hereinafter, Mg: 0.4 to 0.6 mass%, Cr: 0.15 mass% or less, Ni: 0.6 to {(−4/6) × [Cu mass%] + 5} mass%, Zr: 0 .07～0.15 wt%, P: 0.005 to 0.010 mass%, Ca: includes 0.002 wt% or less, Ri balance Al and inevitable impurities der,
Primary crystal Si exists in at least the skirt portion corresponding portion and the piston ring groove portion corresponding portion in the shaped material,
In the entire raw material, there is no primary crystal Si having a maximum diameter of 50 μm or more, no Al—Fe—Cr—Mn giant crystallites having a maximum diameter of 50 μm or more , and eutectic Si is spherical. A shaped material for an engine piston, characterized in that 5. The engine piston shape material according to claim 4, wherein in the composition of the shape material, the amount of P added satisfies the following formula (1).
0.0025 × Si addition amount−0.025 ≦ P addition amount ≦ 0.0025 × Si addition amount−0.02 Formula (1)
However, the unit of P addition amount and Si addition amount: mass%, respectively.

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