JP2007118040A - Forging-formed article, producing method therefor and forging-formed apparatus, and producing system for forging article and preliminary formed article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a forging-formed article with which even in the case of being a material having difficulty to work, this material can be forged. <P>SOLUTION: In the method for producing the forging-formed article having thick portions at both sides in the forging direction of the center portion; after performing a first forging process for obtaining a preliminary formed article formed to almost finish shape at one side of the thick portion by using an aluminum alloy-made material having difficulty to work as a blank for forging, since a second forging process for forming to the finish shape at the other side of the thick portion while keeping the contacting state over the whole range of the one side of the preliminary formed article and a die, even in the case of using the material having difficulty to work as the blank for forging, since the forging-formed article can be formed under state of no developing of the free forging surface at the one side of the thick portion, the formed article having no crack can be obtained. Further, since the excess thickness for preparing the development of crack is not needed, there is no necessity for removing the excess thickness portion by machining, and thus, good yield of the material is obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a forged product having a thick portion on both sides in the forging direction of a central portion using a difficult-to-work material, a manufacturing method thereof, a forging apparatus, a forged product manufacturing system, and a preformed product.

  An example of the molded product having a thick part on both sides in the forging direction of the central part is an engine piston. The engine piston is required to have a mechanical strength with a high temperature strength characteristic on the head surface. For this purpose, an aluminum alloy that has high strength at high temperatures and can be reduced in weight is used.

A molded product obtained by simply casting such an alloy may have a “nest” inside, and a stable quality cannot be obtained even if the mechanical strength requirement is satisfied. In addition, due to the casting surface, the appearance quality is poor, the dimensional accuracy is rough, and there are many problems such as thickening to achieve stable quality, and weight reduction cannot be achieved, so the quality is more reliable than casting. High forging is being studied.

In particular, a method has been studied in which a preformed product is further forged to obtain a final shaped product.
For example, in Japanese Patent Laid-Open No. 6-190493, a metal casting material having a surplus part formed on the edge of a product part is formed, and when the metal casting material is forged, the surplus part is used as a material. By restricting the flow of material at the edge by preventing the occurrence of cracks, high compressive stress is generated inside the product, and the structure is refined by plastic deformation. For the purpose of improving mechanical strength, a first step of forming a metal casting material in which a surplus portion is formed at the edge of the product portion that approximates the product shape, and after the first step, the product Forming a forging part by die forging, and a second step of compression-molding the product part while suppressing plastic flow of the material by pressurizing the surplus part. A method is disclosed.

Japanese Patent Laid-Open No. 10-80761 has the following disclosure. Providing a casting and forging method that can prevent the occurrence of rib cracking even when using an aluminum alloy that is inferior in castability, with an emphasis on forgeability, and can provide forged parts with excellent mechanical properties and appearance quality. Therefore, when preforming the roughing material for forging by casting, the ratio A / L of the cross-sectional area A (mm ² ) of the rib E to the circumferential length L (mm) of the rib E is 2 or more. Casting roughing material for forging.

Moreover, the method of shape | molding with aluminum alloy powder has the following indication in Unexamined-Japanese-Patent No. 2003-96524, for example. In order to make a cup-shaped molded product that is lighter and more excellent in heat resistance properties by hot forging using the rapidly solidified Al alloy powder, Si: 10 to 40 mass%, Fe, Co, Ni, Cr, Mn, A rapid solidified Al alloy powder consisting of 3 to 11 mass% in total of at least two elements selected from Ti and V and the balance substantially consisting of Al is prepared by an atomizing method, and then cold preformed, The time of exposure to a temperature of 430 ° C. or higher is limited to 5 hours and heated to 430 ° C. to 530 ° C. to hot plastically process the preform into a dense body having a relative density of 99% or higher. Hot forging into a rough shape of the cup-shaped molded product is performed, and the forged product is machined to obtain a finished cup-shaped molded product.
JP-A-6-190493 Japanese Patent Laid-Open No. 10-80761 JP 2003-96524 A

Conventionally, in the case of an engine piston, the shape has been obtained by performing forging once in the main forming by hermetic forging. However, cracking occurred in the forged product once it was formed once using a difficult-to-extend material that has high temperature strength but is difficult to stretch. Moreover, in order to suppress the occurrence of cracks, there is a method to improve the formability by raising the forging temperature and the like, and to improve the cracks. Cracking occurred. Specifically, there is an example as shown in FIG. FIG. 15 is an explanatory view schematically showing an example of a conventional forging process. The forging material 1 obtained by cutting the rod-shaped material into a predetermined length in the step (E) is upset in the step (F), and the diameter is increased to be close to the diameter of the molded product.
Thereafter, in the second steps (G) and (H), forging is performed into a final shape. If it is a raw material for forging having a normal alloy composition, the final molded product can be manufactured by this method. However, in the case of the alloy used in the present invention, a crack occurs at the GG site in the step (G) during the molding of the second step. The broken mouth undergoes a process of closing again when the thick part is completely filled. The defect is observed by appearance inspection and ink check of the final molded product. When the longitudinal section is observed, the depth reaches about 3 to 10 mm from the surface.

Similarly, in the conventional forging process shown in FIG. 16, the forging material 2 obtained by cutting the rod-shaped material into a predetermined length in the step (E) is upset in the step (F), and the diameter of the molded product is obtained. Increase the diameter to near. Thereafter, in the second steps (G) and (H), forging is performed into a final shape. However, in the case of the alloy used in the present invention, a crack occurs at the GG site in the step (G) during the molding of the second step. The broken mouth undergoes a process of closing again when the thick part is completely filled. In this example, the shape formed in the first step is a shape having a plurality of irregularities.
In this way, cracks cannot be improved if a difficult-to-process material is used to make a shape backward while pushing forward. In particular, in the case of an engine piston, three-point bending acts at the core portion on the pin boss side, and cracks occur on the crown surface side.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2000-213812, even if a crack occurs, it can be removed by machining. It is being considered to avoid this. However, with this method, the material yield is poor because the surplus portion is removed.
On the other hand, as described above, a method of performing main forming after obtaining a forged material by preliminary forming has been studied, but sufficient results have not been obtained.
For example, in the methods disclosed in JP-A-10-80761 and JP-A-6-190493, a method for forging a forging material after molding by casting is disclosed. Therefore, even if it has sufficient high-temperature strength, a high-quality molded product cannot be obtained.

In addition, the method disclosed in Japanese Patent Application Laid-Open No. 2003-96524 only describes a preforming process for making an aluminum alloy powder into a dense body, and does not disclose crack prevention during actual forging.
The present invention has been proposed in view of the above, and provides a product in which cracking does not occur in the final product using difficult-to-process materials, a manufacturing method thereof, a forging device that stably produces the product, and a forging production system The purpose is to do.

(1) In order to achieve the above object, according to a first aspect of the present invention, in a method for producing a forged product having thick portions on both sides in the forging direction of a central portion, an aluminum alloy difficult-to-work material is used as a forging material. Then, after the first step forging to obtain a pre-formed product in which one thick part is formed to almost the final shape, the one thick part of the pre-formed product and the mold are in contact with each other over almost the entire region. It has a second process forging in which the other thick part is formed to the final shape while maintaining it.

(2) Moreover, in this invention, ratio (L / D) of the average thickness (L) of the center site | part of the said forge molded product and the maximum thickness (D) of a thick-wall site | part is 1 / 2-1 / The method for producing a forged product according to item (1), wherein the forged product is 20.

(3) In the present invention, the substantially final shape of the thick part is 97% by volume or more of the final shape, and the minute gap is 3% by volume or less. It is a manufacturing method of the forge molded product as described in (2).

(4) In the present invention, the mechanical properties of the aluminum alloy difficult-to-work material at (material temperature during molding × 0.7) ° C. are tensile stress of 70 to 120 MPa, 0.2% proof stress. Is a method for producing a forged product according to any one of the above (1) to (3), wherein the elongation is 15 to 25%, the fatigue strength is 45 to 85 MPa.

(5) In the present invention, the difficult-to-work material made of aluminum alloy includes Si: 10.5 to 13.5% by mass, Cu: 3 to 5% by mass, Ni: 1 to 3% by mass, and Fe: 0. The forged molded product according to any one of the above (1) to (4), which is a rapid-quenching continuous cast rod of an aluminum alloy containing 1 to 0.5% by mass and Mg: 0.8 to 1.2% by mass It is a manufacturing method.

(6) Moreover, in this invention, the said difficult-to-work material made from an aluminum alloy is Si: 11-12 mass%, Cu: 3-5 mass%, Mg: 1-1.4 mass%, Fe: 4-6 Any one of the above (1) to (4), wherein an aluminum alloy containing mass% is powdered by an atmospheric atomization method, then compression molded into a billet shape, and then shaped and cut into a round bar shape by hot extrusion 1. A method for producing a forged molded product according to 1.

(7) Further, in the present invention, the tensile stress at the time of molding one thick portion of the preform is not more than the value of the tensile stress at (material temperature at molding × 0.7) ° C. ( It is a manufacturing method of the forge molded product of any one of 1)-(6).

(8) Moreover, in this invention, it shape | molds so that the elongation at the time of shaping | molding of one thick part of the said preform may not exceed the value of elongation in (material temperature at the time of shaping | molding x0.7) degreeC. It is a manufacturing method of the forge molded product of any one of said (1)-(7) which is what.

(9) In the present invention, the mold temperature used for the first process forging (preliminary molding) is 100 to 400 ° C., and the material temperature used for the second process forging (main molding) is 350 to 500 ° C. It is each hold | maintained, It is a manufacturing method of the forge molded product of any one of said (1)-(8) characterized by the above-mentioned.

(10) Further, in the present invention, the forging material formed by the first process forging (preliminary molding) is lubricated before the second process forging (main molding), and then the main molding is performed. (1) It is a manufacturing method of the forge molded product of any one of (9).

(11) Further, in the present invention, it is made of a difficult-to-work material made of aluminum alloy used in a method for manufacturing a forged product having thick portions on both sides in the forging direction of the central portion, and the final shape 97 of one thick portion is formed. It is a preformed product having a molded shape of volume% or more.

(12) Further, in the present invention, the present invention is a forged molded product obtained by subjecting the preformed product described in (11) above.

(13) In the present invention, the forged molded product according to (12), wherein the central portion is a ceiling portion of the engine piston and the thick portion is a pin boss portion.

(14) Further, in the present invention, the mold is used in a method for producing a forged product having a thick portion on both sides in the forging direction of the central portion, and 97% by volume or more of the final shape of one thick portion. It is a forging apparatus having a preform mold for molding and a mold for molding the preform into a final shape.

(15) Further, in the present invention, there is provided a forged product manufacturing system including the forging device described in (14) described above.

  Since this invention consists of an above-described structure, there can exist an effect which is demonstrated below.

  The present invention relates to a method for manufacturing a forged molded product having thick portions on both sides in the forging direction of the central portion, and using one of the hard-working materials made of aluminum alloy as a forging material, molding one thick portion to a final shape. After the first step forging to obtain a preformed product, one thick part of the preform and the mold are molded to the final shape while maintaining a state where the mold is in contact with almost the entire region. Since the second process forging is performed, even when a difficult-to-work material made of aluminum alloy is used as a forging material, the thick part of one side is always in contact with the mold, Since the portion can be molded, the forged molded product can be molded in a state where a free forged surface does not occur in one thick-walled portion, so that a molded product without cracks can be formed. In addition, since it is possible to suppress the occurrence of cracks, there is no need to implement a workaround in which a surplus is provided in preparation for the occurrence of cracks and the parts are removed by machining after the cracks have occurred. , Material yield is improved.

  In the present invention, the ratio (L / D) between the average thickness (L) of the central portion of the forged product and the maximum thickness (D) of the thick portion is 1/2 to 1/20. By setting it as such a shape, the effect of this invention can be achieved more reliably. Further, since a product having no crack at the central portion can be formed, it is not necessary to increase the thickness of the central portion in consideration of the crack, the central portion can be thinned, and the forged product can be reduced in weight.

In the present invention, the substantially final shape of the thick portion is 97% by volume or more of the final shape and the minute gap is 3% by volume or less, so that the effects of the present invention can be achieved more reliably.
In the present invention, the mechanical properties of the aluminum alloy difficult-to-work material at a high temperature (for example, 300 ° C. which is a raw material temperature × 0.7 ° C.) are tensile stresses of 70 to 120 MPa, Since the 0.2% proof stress is 40 to 80 MPa, the elongation is 15 to 25%, and the fatigue strength is 45 to 85 MPa, the high temperature fatigue strength of the material is high. It can be used for an engine piston. In addition, the molded product becomes a forged molded product that does not break even when used severely in an environment of high output and high temperature.

 In the present invention, the difficult-to-work material made of aluminum alloy includes Si: 10.5 to 13.5% by mass, Cu: 3 to 5% by mass, Ni: 1 to 3% by mass, and Fe: 0.1 to 0.1%. 0.5% by mass, Mg: Rapidly quenched continuously cast rod of aluminum alloy containing 0.8 to 1.2% by mass. Therefore, when the content of Cu and Ni is increased, high-temperature tensile strength, 0.2% proof stress, High temperature fatigue strength becomes high, and it can be used for forged molded products (for example, engine pistons) that require high temperature strength characteristics.

  Moreover, in this invention, the said difficult-to-work material made from an aluminum alloy is Si: 11-12 mass%, Cu: 3-5 mass%, Mg: 1-1.4 mass%, Fe: 4-6 mass%. The aluminum alloy contained is powdered by the atmospheric atomization method, then compression molded into a billet, and then molded and cut into a round bar by hot extrusion, so when the Cu and Ni contents increase, the high temperature tensile strength, 0 .2% proof stress, high temperature fatigue strength is high, and can be suitably used for forged products (for example, engine pistons) that require high temperature strength characteristics.

 In the present invention, since the tensile stress at the time of molding one thick part of the preformed product is equal to or less than the value of the tensile stress at (material temperature at molding × 0.7) ° C., By applying an appropriate compressive stress to the one thick part, cracking can be suppressed even at a temperature at which the plastic workability can be maintained. Further, the preform can be formed without cracking with a stress equal to or lower than the high temperature tensile stress in the preforming, and cracking can be suppressed even in the main molding. For example, the tensile stress value at (material temperature during molding × 0.7) ° C. can include a tensile stress value at 300 ° C., for example, 70 MPa. In addition, stress cannot be measured with an actual press, but cracks can be predicted by conducting a simulation in advance and designing in this way. Simulation eliminates the need for unnecessary test cycles and forging materials, thereby reducing development speed and costs.

 Further, in the present invention, since the elongation at the time of molding of one thick part of the preformed product is molded so as not to exceed the value of elongation at (material temperature at molding × 0.7) ° C. In molding, a preform can be molded without cracking at a strain value not exceeding the high temperature elongation, and cracking can be suppressed even in the main molding. For example, the elongation value at (material temperature during molding × 0.7) ° C. includes an elongation value at 300 ° C., for example, 15%. In addition, the actual press cannot measure the strain, but it is possible to predict cracks by conducting a simulation in advance and designing in this way. In addition, simulation eliminates the need for unnecessary test times and forging materials, thereby reducing development speed and reducing costs.

  In the present invention, the mold temperature used for the first process forging (preliminary molding) is maintained at 100 to 400 ° C., and the material temperature used for the second process forging (main molding) is maintained at 350 to 500 ° C., respectively. The If the mold temperature is lower than this range, the material temperature is lowered, and cracks are likely to occur. Since the mold temperature can be maintained at a high temperature, the forging material will not be deprived of heat by the mold (it will be difficult to cool), and cracking will be difficult to occur.

  Further, in the present invention, the forging material formed by the first process forging (preliminary molding) is subjected to lubrication before the second process forging (main molding), and then the main molding is performed. By performing lubrication treatment (preliminary lubrication) on the product, the moldability is improved and the molding load is reduced. There are merits such as reducing the amount of lubricant applied to the mold (cost reduction).

  Further, in the present invention, it is made of an aluminum alloy difficult-to-work material used in a method for manufacturing a forged molded product having thick portions on both sides in the forging direction of the central portion, and is 97 vol% or more of the final shape of one thick portion. Since this is a preformed product with the following shape, one thick part can be molded in the state where one thick part is always in contact with the mold at the time of the main molding. Since a forged molded product can be molded in a state in which no crack occurs, it is preferable that a molded product made of a difficult-to-work material without cracking can be formed.

  Further, in the present invention, since the above-described preformed product is a forged molded product, the other thick part can be molded in a state where one thick part is always in contact with the mold during the main molding, Since a forged molded product is formed in a state where a free forged surface does not occur in one thick part, it is preferable because it is a molded product made of a difficult-to-work material without cracking.

  Further, in the present invention, the center part is the engine piston ceiling part and the thick part part is the pin boss part. In molding, the pin boss part is molded while the shape is in contact with the mold. Therefore, an engine piston which is a forged product made of a difficult-to-process material with no crack on the crown surface (piston head) can be obtained.

  Further, in the present invention, a mold used in a method for manufacturing a forged molded product having a thick portion on both sides in the forging direction of the central portion, and a preliminary shape for forming 97% by volume or more of the final shape of one thick portion. Since it has a mold for molding a molded product and a mold for molding a preformed product into a final shape, a forged molded product with thick parts on both sides in the forging direction of the central part using difficult-to-work materials is cracked. It can be stably molded without generating.

  Further, in the present invention, since the forging apparatus described above is included, the forged molded product having thick portions on both sides in the forging direction of the central portion using the difficult-to-work material without causing crack defects. Can be molded stably.

An example of the embodiment of the present invention will be described below. FIG. 1 is an explanatory view schematically showing the forging process of the present invention, and FIG. 2 is a cross-sectional view showing an example of a molded product having thick parts on both sides in the forging direction of the central part manufactured by the method of the present invention. is there.
In FIG. 1, a forging material 10 obtained by cutting a rod-shaped material into a predetermined length in step (A) is prepared, and 97% by volume or more of the final shape of the thick portion 11 is formed in step (B). Here, 97% by volume means that the shape of the thick part 11 which is almost the same as the final shape is formed by the first process forging, and in reality, between the upper mold used for the main molding and the thick part. This means that there is a slight clearance.

These (A) + (B) processes are called first process forging (preliminary molding). As a result, it is considered that compressive stress remains in the thick portion 11 of the primary molded product.
Next, the primary molded product (preliminary molded product) Y is put into steps (C) and (D) which are the main molding, and the thick portion 12 is molded to obtain a final molded product Z. As a result, no tensile stress is generated and cracking can be suppressed. In general, the tensile strength tends to decrease as the temperature rises and tends to crack, and the plastic workability becomes worse as the temperature falls. In the present invention, an appropriate compressive stress is applied by forming 97% by volume or more of the final shape of the thick-walled portion 11 by preforming, and cracking is suppressed even at a temperature at which plastic workability can be maintained in the second step. Can do.

<Description of final molded product>
FIG. 2 is a longitudinal sectional view of the piston head 13 of the engine which is a forged product of the present invention. As shown in FIG. 2, the molded product manufactured by the method for manufacturing a forged molded product of the present invention includes a central portion M and thick portions S and T on both front and rear sides in the forging direction. Here, the ratio (L / D) between the average thickness (L) of the central portion M and the maximum thickness (D) of the thick portion is 1/2 to 1/20. For example, in the case of an engine piston, the ratio of the volume of the central part M to the volume of the thick part T is 0.7 to 1.2. The plastic working rate is 75% or more.

  Here, the center portion is a portion where the volume of the molded product is concentrated. Specifically, in the case of an engine piston, it corresponds to the portion of the center portion M (ceiling thickness) in FIG. The thick portion means a portion whose thickness is larger than the thickness of the central portion. Specifically, in the case of an engine piston, the thick portion T (pin boss portion) shown in FIG. It corresponds to the part S.

<Manufacturing method of rod by rapid cooling continuous casting>
The material used in the present invention may be produced by any method such as continuous casting, extrusion, and rolling. In the case of aluminum or an aluminum alloy, a continuously cast round bar is preferable because it is inexpensive. For example, SHOTTIC material (registered trademark) manufactured by Showa Denko KK can be used. In aluminum alloys, round bars continuously cast by the gas pressure hot top casting method have excellent internal soundness, fine crystal grains, and no crystal grain anisotropy due to plastic working Therefore, it is preferable because the resistance effect of the frictional resistance portion can be obtained stably.

<Description of material (powder)>
As the material of the composition shape material, an Al—Si based powder metallurgy alloy using a rapidly solidified powder can be used as an Al—Si based alloy that is difficult to be plastically processed by forging. An aluminum alloy containing Si: 11 to 12%, Cu: 3 to 5%, Mg: 1 to 1.4%, and Fe: 4 to 6% is preferable.
Si is added to improve wear resistance. The preferable content of Si is 11-12. Cu, Fe, and Mg are added in order to improve high temperature tensile strength and high temperature fatigue strength. Preferred content ranges are Cu: 3 to 5, Fe: 4 to 6, and Mg: 1 to 1.4.
When the high temperature fatigue strength is increased, it is preferable that the high temperature fatigue strength can be used for a forged molded product (for example, an engine piston) requiring high temperature strength characteristics.
<Manufacturing method of stick from powder material>
The molten metal adjusted to the above-mentioned composition is solidified by rapid cooling by the atmospheric atomization method to form a powder. After mixing the powder, it is compression-molded into a billet shape (for example, 200 mm in diameter), and then formed into a round bar shape (for example, 84 mm in diameter) as a powder extruded material having a uniform structure without gaps by, for example, hot extrusion.
The alloy thus obtained is a fine structure containing primary crystals and eutectic Si whose atomized powder has a structure of 10 μm or less, and a metal containing X formed by the addition of transition elements X (Fe, Ni, Mn) Since the intermetallic compound is also fractured by the extrusion process to have a fine and uniform structure, it is preferable because the high temperature tensile stress and high temperature fatigue strength characteristics are enhanced.

<Description of upper and lower molds for first process forging>
FIG. 3 is a cross-sectional view showing an example of upper and lower molds used for the first step forging in the method for producing a forged molded product of the present invention.
In the present embodiment, the molding hole 15 of the upper mold 14 has a shape that molds 97% by volume or more of the final shape of the thick portion S formed above the central portion M.
Here, 97% by volume or more of the final shape of the thick portion S matches the “contour shape of the final shape” and the “contour shape of the preformed product” of the thick portion S shown in FIG. This means that the range to be formed is 97% or more (almost the same shape is formed). Moreover, the shape of the shaping | molding hole 15 can also be provided so that the site | part which shape | molded 97% or more of the final shape of the thick-walled site | part S may be shape | molded by free forging.
The lower die 16 is formed with a molding hole 17 in which the forging material 10 is accommodated in an almost intact form, and is provided with a knockout pin 18 for discharging the product.

<Description of upper and lower molds for second process forging>
FIG. 4 is a cross-sectional view showing an example of upper and lower molds used in the second step forging in the method for producing a forged molded product of the present invention.
In the present embodiment, the gap between the molding hole 20 of the upper mold 19 and the one thick portion 22 of the preform Y is 3% by volume or less.
Here, the gap between one thick part 22 of the preform Y and the upper mold 19 is 3% by volume or less means that the final contour of the thick part 22 and the molding hole 20 of the upper mold This means that the non-matching range is 3% by volume or less, and the molding is performed with almost no gap.
The lower mold 23 is formed with a molding hole 24 for forming the thick portion T, and a knockout pin 25 for discharging the product is provided.

<Description of forging equipment>
The forging used in the present invention is die forging, and an example of the configuration of the forging apparatus used in the present invention will be described with reference to the drawings. FIG. 5 is a schematic configuration diagram of a forging device showing an embodiment of the present invention. Here, the forging device includes a forging machine 50, an upper mold 19 attached to the upper bolster 51, and a lower mold 23 attached to the lower bolster 52. An example of a mold used in the present apparatus is the same as that shown in FIG. The mold includes an upper mold 19, a lower mold 23, and a knockout pin 53. In this figure, one thick part S (the crown part in the case of an engine piston) of the molded product is the upper mold 19, and the other thick part T (the pin boss part in the case of an engine piston) is the bottom. This is a combination of molds formed by the mold 23. The upper die 19 for molding one thick portion S has a forming hole 20 for forming a protrusion at the center of the bottom surface.
Further, as another embodiment (not shown), one thick portion S (in the case of an engine piston, a crown surface portion) uses a lower mold, and another thick portion T (engine piston of the engine piston). In this case, the pin boss portion may be a combination of dies formed using an upper die.

<Description of the first step>
In the first step, forging is performed using, for example, the forging device shown in FIG. 5 and the forging die shown in FIG. FIG. 6 is an explanatory view schematically showing a forging process when the shape to be formed by the first process forging has a plurality of irregularities. In FIG. 6, a forging material 10 obtained by cutting a rod-shaped material into a predetermined length in the step (A) is prepared, and 97% by volume or more of the final shape of the thick portion 26 is formed in the step (B). In the present embodiment, the thick portion 26 has a plurality of irregularities. The forging material 10 is prepared by cutting a round bar into a predetermined length according to the molded product. The forging material 10 is preheated before forging. The temperature condition for the preheating treatment is preferably in the range of 350 ° C. to (solidus temperature of aluminum alloy−10) ° C. The processing time is set until the temperature of the entire forging material reaches the preheating temperature range, and then the forging process is started. If it is less than 350 ° C, sufficient plastic flow cannot be obtained when the forging material 10 is hot forged, and if it exceeds (solidus temperature of aluminum alloy -10) ° C, burning (local melting) occurs in the forging material. There is a risk. When burning occurs, the strength of the forged product is severely deteriorated, or the product may cause defects due to local dissolution such as swelling and micro-shrinkage. More preferably, it is 420 degreeC-480 degreeC, More preferably, it is 460 +/- 20 degreeC.

Since forging is normally performed hot, not only preheating the forging material 10 but also the mold is heated. The heating temperature can be 100 to 400 ° C. The heating temperature is selected depending on the shape to be forged, the type of forging equipment, the type of alloy of the forging material used, and other forging factors. If the temperature is too low, heat removal from the forging material increases, resulting in poor workability and insufficient plastic flow of the forging material. If the temperature is too high, the strength of the mold is reduced, and damage such as wear and chipping tends to occur, which is not preferable from the viewpoint of the mold life.
More preferably, the mold temperature is 150 ° C to 250 ° C, and more preferably 250 ° C to 350 ° C.

The forging is preferably performed after applying a lubricant to the mold. A water-soluble lubricant that is resistant to contamination, is environmentally friendly, is relatively inexpensive, and has low flammability is preferable. However, in some cases, an oil-based lubricant may be used in combination in order to improve the mold life or improve the moldability of the product.
Basically, it is preferable that the forging material is not subjected to a lubricant treatment. This is because material lubrication increases the number of processes and increases costs. Also, it is better for the environment to use no lubricant. However, depending on the shape of the molded product, the lubricant treatment may be performed for the purpose of improving the moldability, reducing the load, and reducing the amount of lubrication of the mold.

  As shown in FIG. 3, the prepared forging material 10 is pushed into a space (forming hole) formed by the upper die 14 and the lower die 16 and forged into a preform Y. The molding load is, for example, 150 to 300 tons when a molded product having a diameter of about 100 mm is obtained. The formed forging material is taken out from the lower mold 16 by the knockout pin 18 and becomes a preform Y.

<Description of the first processed finished product>
The preform Y obtained here is a preform Y obtained by molding 97% by volume or more of the final shape of one thick portion 26.
By the above, the stress of the shape part which shape | molded 97 volume% or more of the final shape of one thick-walled part 26 is below the tensile stress value in the (material temperature at the time of pre-forming x0.7) degreeC, for example, the tensile stress of 70 MPa or less A preform Y can be obtained. Further, the elongation at the time of molding of one thick part of the preform is set to a value that does not exceed the value of elongation at (material temperature at molding × 0.7) ° C.
Moreover, although the site | part (it shows with the code | symbol 22 in FIG. 4) which shape | molded 97 volume% or more of the final shape of one thick part 26 can be shape | molded by free forging, the metal mold | die 19 used at a 1st process. The molding hole 20 of (usually the upper mold) has a shape in which 97% by volume or more of the final shape of one thick part is molded, and the molding hole 20 having the shape of the forging material in the first step. It is preferable to be filled.
As a result, during the secondary molding, the thick part of the maximum thickness of the secondary mold (lower mold) is ensured while the preform Y and the secondary molding mold (upper mold) are in contact with each other. This is because the final product can be molded while compressive stress is applied to one thick portion of the upper mold shape, and a sound molded product can be obtained.

<Description of the second step>
Next, the second process forging is performed using the forging device shown in FIG. 5 and the forging die shown in FIG. First, the preform Y is preheated before forging. The temperature condition for the preheating treatment is preferably in the range of 350 ° C. to (solidus temperature of aluminum alloy−10) ° C. The processing time is set until the temperature of the entire forging material reaches the preheating temperature range, and then the forging process is started. If it is less than 350 ° C., sufficient plastic flow cannot be obtained when the preform Y is hot forged, and if it exceeds (solidus temperature of aluminum alloy −10) ° C., burning (local dissolution) occurs in the preform Y. May occur. When burning occurs, the strength of the forged product is severely deteriorated, or the product may cause defects due to local dissolution such as swelling and micro-shrinkage. More preferably, it is 420 degreeC-480 degreeC, More preferably, it is 460 +/- 20 degreeC.

Since forging is usually performed hot, not only preheating the preform Y but also the mold is heated. The heating temperature is 100 to 400 ° C. The heating temperature is selected depending on the shape to be forged, the type of forging equipment, the type of alloy of the preform Y to be used, and other forging factors. If the temperature is too low, the heat removal from the preform Y increases, the workability is inferior, and the plastic flow of the preform Y becomes insufficient. On the other hand, when the temperature is too high, the strength of the mold is lowered, and damage such as wear and chipping is likely to occur, which is not preferable from the viewpoint of the mold life.
More preferably, the mold temperature is 150 ° C to 250 ° C, and more preferably 250 ° C to 350 ° C.
Forging is preferably carried out after applying a lubricant to the mold. A water-soluble lubricant is preferred because the product is less soiled, environmentally friendly and relatively inexpensive. However, in some cases, an oil-based lubricant may be used in combination in order to improve the mold life or improve the moldability of the product.

  The preform Y is preferably subjected to a lubrication treatment (albonde treatment, sodium stearate treatment, water-soluble graphite film treatment, shot blast treatment, etc.). By performing the lubrication treatment, the moldability is improved, the load is reduced, the mold life is improved, and the mold lubrication amount can be reduced.

  As shown in FIG. 4, the prepared preform Y is pushed into a space forming hole formed by the upper mold 19 and the lower mold 23, and forged to the final molded product. When obtaining a molded article having a diameter of about 100 mm, the molding load can be set to 350 to 600 tons, for example.

In the second step, it is important to form the final shape while maintaining a state where the gap between one thick portion 22 of the preform Y and the upper mold 19 is 3% by volume or less. By using the above-described mold, it is possible to maintain a state where the gap between one thick portion 22 of the preform Y and the mold is 3% by volume or less. In addition, by placing the preform Y in the center of the mold, it is possible to more accurately maintain a state where the gap between one thick portion of the preform Y and the mold is 3% by volume or less. Further, when the preform Y is introduced using a robot or the like, it becomes more accurate.
The formed final molded product is taken out from the lower mold 23 by the knockout pin 25.

<Description of molded product after second process>
The final molded product Z obtained in the present invention is excellent in high-temperature tensile strength and high-temperature fatigue strength, and has no crack defects on the surface.
The second-processed molded product obtained by forging can be used as it is, but in an alloy to which Cu, Mg, etc. are added, the mechanical properties of the material are improved by heat treatment, so artificial aging treatment is performed as heat treatment. It is preferable to apply. The artificial aging treatment is, for example, a solution treatment performed by immersing the molded article material in water immediately after performing a holding time of 1 to 10 hours at a heating temperature of 400 to 550 ° C, and then 1 to 20 at 150 to 250 ° C. Time tempering is preferably performed. Thereby, mechanical properties (for example, tensile strength, 0.2% proof stress) and fatigue strength can be enhanced including hardness.

  After that, the final molded product Z is subjected to a machining process and subjected to machining, for example, finished in the shape of the final product by performing drilling, chamfering, grooving, and other processes.

<Description of modification>
FIGS. 7-11 is explanatory drawing which shows the other modification of the upper-and-lower metal mold | die used by the 1st process forge, and the upper-lower metal mold | die used by the 2nd process forge. FIG. 7A shows an upper die 70 and a lower die 71 used in the first process forging to obtain a preform Y having a thick portion 26 having a plurality of irregularities shown in FIG. FIG. 7B shows an upper die 72 and a lower die 73 used in the second process forging for obtaining the final molded product Z.
8 (a) and 8 (b) are for obtaining a preform Y having a thick portion 27 having a simple convex shape on the upper side and a final molded product Z having a thick portion having an asymmetrical left and lower side. An upper mold 80 and a lower mold 81 used in the first process forging, and an upper mold 82 and a lower mold 83 used in the second process forging are shown.
9 (a) and 9 (b) show a preform Y having a thick portion 28 having a large convex shape on the top and a final molded product Z having a symmetrical thick portion below. The upper die 90 and the lower die 91 used in the first step forging, and the upper die 92 and the lower die 93 used in the second step forging are shown.
10 (a) and 10 (b) are for obtaining a preform Y having a thick portion 29 having an asymmetrical uneven shape on the upper side and a final molded product Z having a symmetrical thick portion on the lower side. The upper die 100 and the lower die 101 used in the first step forging, and the upper die 102 and the lower die 103 used in the second step forging are shown.
11 (a) and 11 (b) are for obtaining a preform Y having a thick portion 30 having an asymmetric convex shape on the upper side and a final molded product Z having a thick portion having an asymmetric shape on the lower side. The upper die 111 and the lower die 112 used in the first step forging, and the upper die 113 and the lower die 114 used in the second step forging are shown.

  FIG. 12 is a flowchart showing a manufacturing process using a continuous cast material. In the conventional manufacturing process shown in FIG. 12 (a), a continuous cast material is cut and chamfered, and then pre-lubricated, heated to a raw material, formed into a main body, and inspected after heat treatment. On the other hand, in this invention shown in FIG.12 (b), after cutting a continuous cast material and chamfering, raw material heating is performed and preform shape forging is performed. Thereafter, preliminary lubrication, material heating, main forming, heat treatment, and inspection are performed.

  FIG. 13 is a flowchart showing a manufacturing process using a powder material. In the conventional manufacturing process shown in FIG. 13 (a), a powder atomized manufacturing material was cut to a predetermined length, chamfered, pre-lubricated, heated with raw material, formed into a main body, and subjected to inspection after heat treatment. . On the other hand, in the present invention shown in FIG. 13 (b), the powder atomized manufacturing material is cut to a predetermined length, face-cut, and then the material is heated to perform preform shape forging. Thereafter, preliminary lubrication, material heating, main forming, heat treatment, and inspection are performed.

<Description of forging line>
FIG. 14 is a schematic configuration diagram showing an example of a forged product manufacturing system of the present invention. The forging production system includes a continuous casting apparatus 701, a homogenization processing apparatus 702, a correction apparatus 703, a peeling apparatus 704, a material cutting apparatus 705, a preliminary lubrication processing apparatus 707, a material heating processing apparatus 708, and a forging apparatus (forging machine) 709. Composed. The forging device 709 includes the forging die described above.
When there is one forging device, the molds in the first process (1F process) / second process (2F process) are replaced. Or you may provide the forge apparatus for each of a 1st process and a 2nd process.
Moreover, you may provide the solution heating apparatus 710, the quenching apparatus 711, and the aging treatment apparatus 712 in the back | latter stage of the forging apparatus 709 as needed. In addition, a melt treatment apparatus (not shown) for improving the purity of the melt may be provided in the front stage of the continuous casting apparatus 701.
Further, if necessary, a device for preheating the forging material and further performing a lubrication treatment can be provided before the forging devices in the first step and the second step.
And an integrated production line can be comprised by providing an automatic conveyance apparatus for conveyance between each apparatus. Furthermore, an integrated automatic production system including a raw material supply device (not shown), a raw material conveyance device (not shown), and a molded product discharge device (not shown) is a more preferable system.

Among the above devices, the material cutting device 705 is for cutting the forging material into a predetermined length. The material supply device is for holding a certain amount of forging material in the hopper and supplying the forging material to the next process. The material conveying device is for conveying a forging material to a mold.
The homogenizer 702 is for homogenizing the material and can be omitted. The forging device 709 is for forging a forging material. The molded product carry-out device is for discharging the molded product from the mold by a knockout pin mechanism and transporting it to the next process. The material heating device 708 is for heating the forging material to a recrystallization temperature or higher to improve forging workability. The aging treatment device 712 is for heat treatment for continuously solution-treating and aging treatment of the taken-out molded product.

Hereinafter, although a specific example is shown and the effect of this invention is clarified, this invention is not limited to this. The engine piston having the shape shown in FIG. 2 was molded using the materials shown in Table 1 under the conditions shown in Table 2. For example, difficult-to-process material A has Si of 12.8 mass%, Fe of 0.49 mass%, Cu of 3.8 mass%, Mn of 0.23 mass%, Mg of 1.09 mass%, and Ni of The composition is 2.0% by mass, Ti is 0.1% by mass, and P is 0.009% by mass. In difficult-to-process material B, Si is 12.8 mass%, Fe is 0.45 mass%, Cu is 3.8 mass%, Mn is 0.25 mass%, Mg is 0.9 mass%, and Ni is 2. The composition is 1% by mass and P is 0.01% by mass.
The material strength was measured by cutting out a sample after performing the homogenization treatment, upsetting process, and T6 treatment (solution treatment: 495 ° C. × 1 hour, water quenching, aging: 200 ° C. × 6 hours) shown in Table 1. .
The strength of the molded product was measured by aging the molded engine piston and then collecting a sample from the head portion of the engine piston. The results of crack generation, formability, mechanical strength, quality, and the overall evaluation results are shown in the table.

  The appearance of cracks is visually observed, x indicates that the frequency of occurrence of cracks is severe, ◎ indicates that the frequency of occurrence of cracks is 5% or less, ◎ △, ◎ ○ decreases in frequency, ◎◎ There is almost no cracking. Formability is visually observed for appearance, x indicates cracks, ○ indicates poor dimensional accuracy, ◎ indicates dimensional accuracy, ◎ △, ◎ ○ Is small, and ◎ means that there is almost no loss of thickness.

Mechanical properties were measured by measuring high-temperature fatigue strength. X was less than 45 MPa, ◯ was 45 MPa or more, ４８ was 48 MPa or more, ○ was 50 MPa or more, and ◎ was 55 MPa or more.
The quality was evaluated by observing the cross section of the test piece, “X” when the “nest” or the roughening of the crystal grains was observed, and “A” when the roughness was not observed.

<Comparative Example 1>
In the case of using the conventional material, the engine piston was molded by one-time molding by forging once in the main molding by closed forging to obtain the shape. In the case of a conventional material, the moldability is good, and defects such as cracks do not occur in the final molded product. However, the conventional material does not satisfy the high temperature fatigue strength requirement, which has been demanding severe conditions in recent years. Therefore, it is indicated that it is necessary to use a difficult-to-work material that can provide high high temperature fatigue strength.

<Comparative Example 2>
Using the difficult-to-process material A, the final molded product was cracked as a result of performing one-time molding by forging once in the main molding without pre-molding under the same conditions as the conventional material. No matter how high the high-temperature tensile strength or high-temperature fatigue strength is, the product is cracked and cannot be used. This is because the cracked part is the starting point, and repeated use will lead to destruction. The reason why cracking occurs is that difficult-to-work material A has a higher tensile strength than conventional materials, but has low elongation (about 1/2), so that the formability is poor and cracking is considered to occur.

<Comparative Example 3>
In the forging of the main forming once, it was considered that the processing rate became too high and cracking occurred, so that the forging material was formed by pre-forming by upsetting, and an attempt was made to form at a processing rate of twice. However, cracks occurred in the final molded product, and as a result, there was no significant difference from Comparative Example 2.

<Comparative example 4>
In order to suppress the generation of cracks, a method for improving the formability by raising the forging temperature and improving the crack generation was considered, and forging was carried out by raising the temperature during pre-forming by upsetting and the second molding. . Although the moldability was improved, cracks occurred in the molded product for the difficult-to-work material A used in the present invention.

<Comparative Example 5>
Forging was attempted in which the temperature during the second molding was further increased to improve the moldability. The material temperature was a temperature near the limit where burning (local melting) occurred in the preform. As a result, the formability was improved as compared with Comparative Example 4, but the occurrence of cracks was further deteriorated.

<Comparative Example 6>
A molded product obtained by simply casting a difficult-to-work alloy cannot obtain stable quality even if it satisfies the mechanical strength requirements (high temperature tensile strength, high temperature fatigue strength). Moreover, the appearance quality is not good due to the casting surface, and the dimensional accuracy is also rough. Furthermore, many internal defects occur, and there are many problems such that the molded product becomes thick in order to ensure stable quality, and the weight cannot be reduced.

<Example 1>
The result of the Example of this invention is demonstrated.
As described above, cracks occurred in the preform Y in a flat state, that is, in the preform Y having a larger material diameter. Therefore, in order to improve the above-mentioned problem, in the embodiment of the present invention, a method of pre-molding one thick part at the time of final molding was performed at the stage of preliminary molding. The first step forging was performed to obtain a preform Y that was formed by 97% by volume or more of the final shape of one thick part. Then, the 2nd process forging which shape | molds in a final shape was implemented, maintaining the state where the clearance gap between one thick part of the preform Y and a metal mold | die is 3 volume% or less. As a result, the cracks that have occurred have been improved.
Therefore, the final molded product was not cracked, and a molded product satisfying mechanical properties (high temperature strength, high temperature fatigue strength) could be obtained.

<Example 2>
In this example, forging was performed by raising the mold temperature in order to further suppress cracking. As a result, cracking could be further suppressed. If the mold temperature is low, the temperature of the forging material is removed by the mold, the moldability is deteriorated, and cracking may occur. Therefore, it was thought that cracking could be further suppressed by increasing the mold temperature.

<Example 3>
In this example, forging was performed by raising the material temperature of the difficult-to-process material A. As a result of increasing the temperature and forging the final molded product, the moldability improved. As a result, it was confirmed that forging was possible by raising the temperature range, and the operation management range was increased, and it was confirmed that stable production could be carried out.

<Example 4>
In this example, in order to improve the forgeability of the difficult-to-work material B, the heat treatment temperature of the continuous cast bar was changed. The treatment temperature was changed from 370 ° C to 470 ° C. As a result, the moldability became very good and there was no concern about cracking. However, mechanical properties such as high temperature tensile strength and high temperature fatigue strength were slightly reduced. Depending on the durability requirements of the molded product, it is preferable to select a processing condition of 470 ° C. with good moldability.

<Example 5>
In this example, forging was performed using a forging material cast at the upper limit of the composition of difficult-to-work material components. The heat treatment condition was 370 ° C. High-temperature tensile strength and high-temperature fatigue strength were the best, and very good ones could be formed. However, since the strength was high, the elongation decreased and the moldability deteriorated.

<Example 6>
In this example, forging was performed using a forging material which was the upper limit material of the difficult-to-work material component and the heat treatment conditions were performed at 470 ° C. As a result, it was possible to obtain an excellent molded product having good moldability and good mechanical properties (high temperature tensile strength, high temperature fatigue strength).

<Example 7>
In this example, forging was performed using a forging material cast at the lower limit of the difficult-to-work material component. The heat treatment condition was 370 ° C. The mechanical properties were inferior to the central composition material and the upper limit composition material, but the moldability was greatly improved. Even in the lower limit component, it was confirmed that the molded product may be used depending on the durability requirements of the molded product because it has better mechanical properties than the conventional material.

<Example 8>
In this example, forging was performed using a forging material which was the lower limit material of the difficult-to-work material component and the heat treatment conditions were performed at 470 ° C. The mechanical properties were inferior to the central composition material and the upper limit composition material, but the moldability was greatly improved. Even in the lower limit component, it was confirmed that the molded product may be used depending on the durability strength requirement of the molded product because it has superior mechanical properties than the conventional material.

<Example 9>
In this example, forging was performed using a rod-like material obtained from an atomized powder material instead of a continuous cast material. Since the powder material has a very dense structure, the high temperature tensile strength and high temperature fatigue strength are very high. Even if a powder material was used, the present invention could obtain a final molded product having no mechanical cracks and high mechanical properties.

<Comparative Example 7>
In the case of this comparative example, in which the preformed product Y was molded after molding less than 95% by volume of the final shape of one thick part, cracking occurred in the final molded product Z. The formability, mechanical properties, etc. were ◎.

<Comparative Example 8>
This is a comparative example in which the gap between one thick portion of the preform Y and the final molding die exceeds 5% by volume, and the final molded product Z was cracked.

<Prediction of crack>
In addition, a forging simulation was performed before actual molding, and the actual molding results were compared with the simulation results to confirm that the presence or absence of cracks in the molded product was the same. The forging simulation software used was a general-purpose software (DEFFORM). The simulation conditions were the same as the actual forging conditions. Moreover, the physical property value data of the difficult-to-work material used in the calculation was also calculated based on the data obtained by experiments.
The tensile stress cannot be measured with an actual press, but was confirmed by numerical simulation in advance. As a result of simulation, the result of forging into a final molded product using a forging material that does not preform the thick part formed according to the conventional method, the maximum tensile stress occurs in one thick part 75-80MPa I was able to confirm that This difficult-to-work material with a tensile stress in the high temperature range of 70 to 80 MPa exceeds the tensile stress value at (material temperature x 0.7) ° C at the time of molding, so there is a possibility that cracking may occur. Was confirmed.
In the case of forging into a final molded product using a preform material with the shape of one thick part molded according to the method of the present invention transferred to 97% by volume or more, the one thick part is always compressed. It was confirmed that stress was generated, no tensile stress was generated, and there was no possibility of cracking.

Similarly, the elongation was confirmed in the same manner.
There is no possibility of cracking by molding so that the elongation at molding of one thick part of the preform Y does not exceed the elongation at (material temperature at molding x 0.7) ° C. Was confirmed.
From these results, it is possible to predict cracks before actual trial molding by confirming stress and elongation by performing numerical simulation. As a result, useless prototypes can be reduced, so that development speed can be increased and development costs can be reduced.

FIG. 1 is an explanatory view schematically showing a forging process of the present invention. FIG. 2 is a longitudinal sectional view showing an example of a forged product manufactured by the method for manufacturing a forged molded product of the present invention. FIG. 3: is sectional drawing which shows an example of the up-and-down metal mold | die used for the 1st process forging of the manufacturing method of the same forge molded product. FIG. 4 is a cross-sectional view showing an example of upper and lower molds used in the second step forging of the method for producing the forged molded product. FIG. 5 is a schematic configuration diagram of a forging device showing an embodiment of the present invention. FIG. 6 is an explanatory view schematically showing a forging process when the shape to be formed by the first process forging has a plurality of irregularities. FIG. 7A is an explanatory view showing the upper and lower molds used in the first process forging, and FIG. 7B is an explanatory view showing the upper and lower molds used in the second process forging. FIG. 8A is an explanatory view showing another upper and lower mold used in the first process forging, and FIG. 8B is an explanatory view showing another upper and lower mold used in the second process forging. FIG. 9A is an explanatory view showing another upper and lower mold used in the first process forging, and FIG. 9B is an explanatory view showing another upper and lower mold used in the second process forging. FIG. 10A is an explanatory view showing another upper and lower mold used in the first process forging, and FIG. 10B is an explanatory view showing another upper and lower mold used in the second process forging. FIG. 11A is an explanatory view showing another upper and lower mold used in the first process forging, and FIG. 11B is an explanatory view showing another upper and lower mold used in the second process forging. FIG. 12 is a flowchart showing a manufacturing process using a continuous cast material. FIG. 13 is a flowchart showing a manufacturing process using a powder material. FIG. 14 is a schematic configuration diagram showing an example of a forged product manufacturing system of the present invention. FIG. 15 is an explanatory view schematically showing an example of a conventional forging process. FIG. 16 is an explanatory view schematically showing another conventional forging process.

Explanation of symbols

Y Pre-formed product Z Final molded product 10 Forging material 11 Thick part 12 Thick part 13 Piston head 14 Upper die 15 Molding hole 16 Lower die 17 Molding hole 18 Knockout pin 19 Upper die 20 Molding hole 22 Thick wall Part 23 Lower mold 24 Molding hole 25 Knockout pin 26 Thick part 50 Forging machine 51 Upper bolster 52 Lower bolster 53 Knockout pin

Claims (15)

In the method for producing a forged molded product having thick parts on both sides in the forging direction of the central part,
After the first process forging to obtain a preformed product in which one thick-walled part is formed to almost the final shape, using an aluminum alloy difficult-to-work material as a forging material,
A second step forging for forming the other thick part to the final shape while maintaining a state in which the one thick part of the preform and the mold are in contact with each other over almost the entire region. Manufacturing method for forged products.   The ratio (L / D) of the average thickness (L) of the central portion of the forged product to the maximum thickness (D) of the thick portion is 1/2 to 1/20. A method for producing a forged molded product according to 1.   3. The method for producing a forged product according to claim 1, wherein the substantially final shape of the thick portion is 97% by volume or more of the final shape, and the minute gap is 3% by volume or less. .   The mechanical properties of the aluminum alloy difficult-to-work material at (material temperature during molding × 0.7) ° C. are as follows: tensile stress is 70 to 120 MPa, 0.2% proof stress is 40 to 80 MPa, and elongation is 15 to The method for producing a forged product according to any one of claims 1 to 3, wherein 25% and the fatigue strength are 45 to 85 MPa.   The difficult-to-work material made of aluminum alloy is Si: 10.5 to 13.5% by mass, Cu: 3 to 5% by mass, Ni: 1 to 3% by mass, Fe: 0.1 to 0.5% by mass, The method for producing a forged molded product according to any one of claims 1 to 4, which is an aluminum alloy rapid-quenched continuous cast rod containing Mg: 0.8 to 1.2% by mass.   The difficult-to-work material made of aluminum alloy is an aluminum alloy containing Si: 11 to 12% by mass, Cu: 3 to 5% by mass, Mg: 1 to 1.4% by mass, and Fe: 4 to 6% by mass. The method for producing a forged molded product according to any one of claims 1 to 4, wherein the forged molded product is formed into a powder by the atomizing method, compression-molded into a billet, and then molded into a round bar by hot extrusion and cut.   The tensile stress at the time of shaping | molding of one thick part of the said preform is below the value of the tensile stress in (material temperature at the time of shaping | molding x0.7) degreeC, The any one of Claims 1-6 Manufacturing method for forged products.   8. The molding according to claim 1, wherein one of the thick-walled portions of the preform is molded so that the elongation at the time of molding does not exceed the value of elongation at (material temperature at molding × 0.7) ° C. 8. The manufacturing method of the forge molded product as described in 2.   The mold temperature used for the first process forging (preliminary molding) is maintained at 100 to 400 ° C, and the material temperature used for the second process forging (main molding) is maintained at 350 to 500 ° C, respectively. Item 9. The method for producing a forged product according to any one of Items 1 to 8.   The material for forging according to any one of claims 1 to 9, wherein the forging material formed by the first step forging (preliminary forming) is subjected to a lubrication treatment before the second step forging (main forming) is introduced, and then subjected to the main forming. Manufacturing method for forged products.   It is made of an aluminum alloy difficult-to-work material used in the method for manufacturing a forged molded product having thick portions on both sides in the forging direction of the central portion, and has a molded shape of 97% by volume or more of the final shape of one thick portion. Pre-formed product.   A forged molded article obtained by subjecting the preform according to claim 11 to a final molding.   The forged molded product according to claim 12, wherein the central portion is a ceiling portion of the engine piston and the thick portion is a pin boss portion.   Mold for use in a method of manufacturing a forged molded product having thick portions on both sides in the forging direction of the central portion, and a preform molding die that molds 97% by volume or more of the final shape of one thick portion And a forging apparatus having a mold for forming the preform into a final shape.   A forged product manufacturing system comprising the forging device according to claim 14.

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