JP2011177785A - Forged billet, wheel made from light metal, and processes for production of those products - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forged billet from which forged products such as a wheel made from a light alloy excellent and uniform in mechanical strength can be manufactured, a wheel made from a light alloy obtained from the forged billet, and a process for manufacturing the wheel made from a light alloy. <P>SOLUTION: A cast billet 4 is produced by casting a light metal alloy, and the forged billet 10 is obtained by pressurization and compression of the cast billet 4. The forged billet 10 has the Charpy impact value of 15 J/cm<SP>2</SP>or more by the Charpy impact test in accordance with JIS (Japanese Industrial Standards) -Z2242. The forged billet 10 is used suitably as various industrial members. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a forged billet, a light metal wheel and a method for producing the same, and more specifically, a forged billet capable of producing a forged product (wheel or the like) having excellent mechanical strength and uniform mechanical strength, The present invention relates to a method for producing the forged billet, a light alloy wheel obtained from the forged billet, and a method for producing the light alloy wheel.

The vehicle wheel is equipped with tires. The road surface on which the automobile travels is not necessarily flat. When a wheel rides on an uneven road surface or curbstone, the wheel may receive shock stress locally.
Such stress is generally absorbed by a tire, which is an elastic body, and does not reach the wheel directly. However, since the flange portion of the rim of the wheel is exposed from the tire, there is a high probability that the wheel rim directly contacts an obstacle during traveling.

  In recent wheels, the caliber has become larger and the rim width has increased with the flattening of the tire. For this reason, the cylindrical rim has a structure that is easily bent. In order to maintain this cylindrical structure, it is required to improve the rigidity of the rim flange such as tensile strength, proof stress, and elongation. And it must be lightweight.

  On the other hand, a wheel having excellent impact resistance while improving the tensile strength, proof stress, and elongation of the wheel disk portion and rim portion using a precipitation hardening type Al alloy (see, for example, Patent Document 1), casting A method of manufacturing a wheel by forging a billet obtained by cutting a round bar made of an aluminum alloy manufactured in step 1 with a die (see, for example, Patent Document 2), and straining a cast magnesium alloy A vehicle wheel made of a recrystallized magnesium alloy (see, for example, Patent Document 3), a vehicle wheel in which a protruding portion is formed in the inner diameter portion of the wheel rim flange toward the center of the rim diameter (for example, see Patent Document 4), etc. It has been known.

The wheels described in Patent Documents 1 to 4 are all obtained by forging from a cast billet (hereinafter referred to as “cast billet”). In addition, the wheel described in Patent Document 1 increases the Si component ratio and reduces the average area of the eutectic structure, thereby reducing the structure. After the solution heat treatment, the wheel is rapidly cooled and then subjected to an aging treatment to obtain mechanical characteristics. It is improving. The wheels described in Patent Documents 2 and 3 improve the heat treatment process for preventing recrystallization due to spinning. In the wheel described in Patent Document 4, a protrusion is formed in the radial center direction of the rim flange in order to increase the rigidity of the inner rim flange.
These patent documents do not disclose the idea of forging a cast billet to refine the metal structure.

JP 2002-60879 A Japanese Patent Laid-Open No. 2007-2110017 JP 2007-308780 A JP 2008-137562 A

  However, in the wheels described in Patent Documents 1 to 4, since the cast billet is formed into a complicated shape by forging, it is stretched only partially rather than entirely, resulting in a metallographic structure. In view of this, a portion having weak impact and toughness (hereinafter referred to as “mechanical strength”) is unevenly distributed. That is, the obtained wheel has non-uniform mechanical strength.

  In a conventional wheel, when a cylindrical cast billet is installed in a press machine for forging and pressed in the axial direction by a pair of molds, the cast billet extends in the radial direction. At this time, since the raw material for forming the hub portion does not receive large displacement, the hub portion has a particularly large crystal grain size of the metal crystal particles of the conventional wheel.

  On the other hand, in an integrated wheel, when a spinning process is performed to mold a rim, recrystallization occurs partially and the crystal grain size becomes coarse, which may reduce mechanical strength. The spinning process only spreads the material, and almost no forging effect can be obtained.

  The present invention has been made in view of the above circumstances, and is obtained from a forged billet capable of producing a forged product (wheel or the like) having excellent mechanical strength and uniform mechanical strength, and the forged billet. It is an object of the present invention to provide a light alloy wheel and a method for producing the light alloy wheel.

The inventors of the present invention have intensively studied to solve the above-mentioned problem. Instead of forging the conventional cast billet, the cast billet is temporarily compressed to a predetermined size and the Charpy impact value is set to 15 J / The inventors have found that the above-mentioned problems can be solved by setting it to cm ² or more, and have completed the present invention. By the way, in view of the Hall-Petch relationship represented by the following formula, the strength and impact resistance (Charpy impact value) of the material are increased by reducing the crystal grain size.
σ = σ ₀ + kd ^−1/2
In the formula, σ represents yield stress or deformation stress, d represents average grain size, and σ ₀ and k represent constants determined by the material.

That is, the present invention relates to (1) a forged billet obtained by casting a light metal alloy into a cast billet and pressurizing and compressing the cast billet, wherein the Charpy impact value is 15 J / cm ² or more. Exist.

This invention exists in the forge billet of the said (1) description which satisfies the following formula | equation (2).
H1 / H2 ≧ 4.0
(In the formula, H1 indicates the length in the direction in which the cast billet is compressed and compressed, and H2 indicates the length in the direction in which the forged billet is compressed and compressed.)

The present invention resides in (3) a method for producing a forged billet obtained by casting a light metal alloy to form a cast billet, pressurizing and compressing the cast billet, and satisfying the following formula.
H1 / H2 ≧ 4.0
(In the formula, H1 indicates the length in the direction in which the cast billet is compressed and compressed, and H2 indicates the length in the direction in which the forged billet is compressed and compressed.)

  The present invention resides in (4) the method for producing a forged billet according to the above (3), wherein the pressure compression is performed by closed forging, swing forging, hammer forging or section forging.

  The present invention (5) is obtained by compressing and compressing a cast billet in one direction to obtain a pre-forged billet, and further compressing and compressing the pre-forged billet in a direction different from the direction in which the pre-forged billet is compressed and compressed. Or it exists in the manufacturing method of the forge billet as described in (4).

  The present invention is (6) press-compressing the cast billet in one direction to obtain a pre-forged billet, further compressing and compressing the pre-forged billet in a direction different from the direction in which the pre-forged billet is compressed, The method for producing a forged billet according to the above (3) or (4), wherein pressure compression is performed to deform only the outer portion.

  The present invention is (7) the above (3) to (6), which is for flying parts, for transport equipment parts, for industrial equipment parts, for building materials, for optical equipment parts, or for manufacturing members for these applications. The method for producing a forged billet according to any one of the above.

The present invention is (8) a light alloy wheel forged using a forged billet obtained by the method for producing a forged billet according to any one of (3) to (6) above, wherein the disk portion Further, the present invention resides in a light alloy wheel having a Charpy impact value of 15 J / cm ² or more at the spoke portion, the outer flange portion, the inner rim portion, and the inner flange portion.

  The present invention is (9) a light alloy wheel forged using a forged billet obtained by the method for producing a forged billet according to any one of (3) to (6) above, wherein the spoke portion In the light alloy wheel, the elongation ratio of the outer flange portion, the inner rim portion, and the inner flange portion is 16% or more.

  The present invention is (10) a light alloy wheel forged using a forged billet obtained by the method for producing a forged billet according to any one of (3) to (6) above, comprising an inner rim A light alloy wheel having an average particle diameter of 5 to 20 μm of metal crystal particles based on a cutting method based on JIS-H0542 of at least one portion selected from the group consisting of a portion and an inner flange portion.

  The present invention provides (11) any one of the above (8) to (10), wherein the average particle size excluding the recrystallized portion of the metal crystal particles of the inner rim portion based on the cutting method based on JIS-H0542 is 20 μm or less. The light alloy wheel described in 1.

  The present invention is (12) a method for producing a light alloy wheel forged using a forged billet obtained by the method for producing a forged billet according to any one of (3) to (6) above. The present invention resides in a light alloy wheel manufacturing method for forming an outer rim portion and an inner rim portion by an extrusion method.

  The present invention is (13) a milling machine including a lathe or a machining center, forging a pre-wheel using a forged billet obtained by the method for producing a forged billet according to any one of (3) to (6) above. It exists in the manufacturing method of the wheel made from a light alloy which carries out the machining of the disk part pattern.

  In the present invention, (14) a pre-rim portion is formed by forging a forged billet obtained by the method for producing a forged billet according to any one of (3) to (6) above with a die. Is a light alloy wheel manufacturing method in which an inner rim portion is formed by spinning, and the spinning is pressed with a rolling roller from an oblique direction in a state where a gap is provided between the pre-rim portion and the mold. And a light alloy wheel manufacturing method for forming an inner rim portion.

The forged billet of the present invention is obtained by pressure-compressing a cast billet, and by setting the Charpy impact value to 15 J / cm ² or more, as a result, a forged product having a fine crystal grain size (light alloy wheel, etc.) Is obtained. That is, by pressing and compressing a cast billet to form a forged billet, when it is installed in a press machine for forging and pressed with a pair of molds, even if it is a portion that does not show a large displacement, Since the metal crystal particles of the metal structure have already been refined, the forged product obtained has a fine crystal grain size of the metal crystal particles.
Therefore, according to the forged billet, a forged product having excellent mechanical strength and uniform mechanical strength can be produced. In addition, it is preferable that the average particle diameter based on the cutting method of JIS-H0542 of the metal crystal particle of a forge billet is 30 micrometers or less.

  Further, the light alloy wheel using the forged billet of the present invention has extremely high toughness, so even if the rim or the disk portion of the light alloy wheel is cracked for some reason during vehicle running, Does not grow at a stretch. In this case, the tire pressure gradually decreases and the operator notices abnormally, so that it does not lead to a major accident. Therefore, safety can be ensured by using such a light alloy wheel.

  The forging billet preferably has a forging ratio (H1 / H2) of 4 or more. By setting it as such a forging ratio, the crystal grain diameter of a forge billet can be rapidly atomized.

In the method for producing a forged billet according to the present invention, when the cast billet is obtained by pressure compression by closed forging, swing forging, hammer forging or section forging, a shape in which the periphery of the middle abdomen swells (so-called (Taiko shape) can be reliably suppressed. Incidentally, the pressure compression, temperature of 300 to 550 ° C., is preferably performed under pressure conditions of ^{9.8 × 10 3 kN~88.2 × 10 3} kN.

  In the forged billet manufacturing method, the cast billet is pressure-compressed in one direction to form a pre-forged billet, and is further pressure-compressed in a direction different from the pressure-compressed direction of the pre-forged billet. In this case, the proportion of the structure having a small crystal grain size in the entire metal crystal particles of the forged billet becomes large. For this reason, it is possible to produce a forged product having better mechanical strength and more uniform mechanical strength.

  Furthermore, the material flow of the outer portion of the forged billet can be positively performed by compressing the pressure to deform only the outer portion. As a result, the obtained forged billet has the same particle size of the metal crystal particles in the central portion as that of the metal crystal particles in the other portions, and can be uniformly refined.

  As a result, it is possible to greatly improve the material yield when almost all of the cast billet that has been used is made of forged billets, and the forged products that have passed through the pre-forged billet exhibit a uniform mechanical strength and impact resistance. It will be expensive.

Since the light alloy wheel of the present invention uses the forged billet described above, the mechanical strength is excellent and the mechanical strength is uniform.
In addition, the Charpy impact value of the disk portion, spoke portion, outer flange portion, inner rim portion and inner flange portion is 15 J / cm ² or more, and the elongation rate of the spoke portion, outer flange portion, inner rim portion and inner flange portion Is an average particle diameter of metal crystal particles based on a cutting method in accordance with JIS-H0542 of at least one portion selected from the group consisting of a disk portion, a spoke portion, an outer flange portion, and an inner flange portion. It is preferable that it is 5-20 micrometers. In these cases, the light alloy wheel is unlikely to be damaged when an unexpected situation occurs when the vehicle travels and an impact stress is applied to the rim. In addition, it is more preferable that the average particle diameter excluding the recrystallized portion of the metal crystal particles in the inner rim portion based on the cutting method based on JIS-H0542 is 20 μm or less.

In the light alloy wheel manufacturing method of the present invention, when the outer rim portion and the inner rim portion are formed by an extrusion method, recrystallization is generated between the hump portion and the well portion and the inner rim flange. Almost uniform crystal grain size can be formed. In this case, the Charpy impact value of the inner rim flange portion exceeds 29 J / cm ² and the elongation is 16% or more.

  In the light alloy wheel manufacturing method of the present invention, the above-described forged billet is forged with a die, and the disk portion pattern is machined by a lathe or a milling machine including a machining center. There is a method in which an inner rim portion is formed by forging with a die and spinning the pre-rim portion.

  Among these, when performing the spinning process, it is preferable to form the inner rim portion by pressing with a rolling roller from the oblique direction in a state where a gap is provided between the pre-rim portion and the mold. When spinning is performed using a forged billet with a refined crystal grain size, if a forged billet with high mechanical strength is used, the pressing force of the rolling roller increases and recrystallization tends to occur. On the other hand, in the above-described case, since the gap is provided and the rolling roller is pressed from the oblique direction, recrystallization of the inner rim portion can be suppressed.

FIG. 1 is a perspective view showing a first embodiment of a forged billet according to the present invention. FIG. 2 is a cross-sectional view showing a forged billet according to the first embodiment and a cast billet before pressure compression. FIGS. 3A and 3B are cross-sectional views showing a state where the cast billet before pressure compression is a forged billet according to the first embodiment by closed forging. 4A to 4D are cross-sectional views showing an example in which a cast billet is compressed and compressed a plurality of times to obtain a forged billet according to the present invention. FIG. 5A is a front view showing a light alloy wheel according to this embodiment, and FIG. 5B is a cross-sectional view taken along the line I-I ′ of FIG. FIG. 6 is a schematic view showing a manufacturing process from the forged billet to the light alloy wheel according to the first embodiment. (A) of FIG. 7 is sectional drawing which shows the 1st spinning process in the manufacturing method of the wheel made from a light alloy which concerns on this embodiment, (b) And (c) is sectional drawing which shows a 2nd spinning process. . FIG. 8 is a perspective view showing a second embodiment of the forged billet according to the present invention. (A)-(d) of FIG. 9 is the top view and side view which show the manufacturing process of the forge billet which concerns on 2nd Embodiment. (A)-(e) of FIG. 10 is the schematic for demonstrating the effect at the time of compressing and compressing a casting billet in one direction, and then further compressing and compressing in a different direction. (A)-(f) of FIG. 11 is the top view and side view which show the manufacturing process of the forge billet which concerns on 3rd Embodiment. 12 (a) and 12 (b) are cross-sectional views showing forward extrusion in a light alloy wheel manufacturing method according to another embodiment. (A) And (b) of Drawing 13 is a sectional view showing back extrusion processing in a manufacturing method of a light alloy wheel concerning other embodiments. 14A and 14B are cross-sectional views showing a flaring process in the wheel manufacturing method according to the present embodiment. FIG. 15 is a graph showing the results of tensile strength evaluation in Examples. FIG. 16 is a graph showing the results of proof stress evaluation in the examples. FIG. 17 is a graph showing the results of elongation evaluation in the examples. FIG. 18 is a graph showing the results of Brinell hardness evaluation in Examples. FIG. 19 is a graph showing the result of the Charpy impact value in the example. 20A is a macro photograph of the cross section of the forged billet obtained in Example 1, and FIG. 20B is a micrograph thereof. FIG. 21A is a macro photograph of the cross section of the forged billet obtained in Example 2, and FIG. 21B is a micrograph thereof. (A) of FIG. 22 is a macro photograph of the cross section of the forged billet obtained in Example 3, and (b) is a micrograph thereof. FIG. 23A is a macro photograph of the cross section of the forged billet obtained in Example 4, and FIG. 23B is a micrograph thereof. FIG. 24A is a schematic cross-sectional view showing sampling positions A to I of the test pieces of the forged billet in evaluation 7 of the example. FIG.24 (b) is a microscope picture which shows the result of evaluation 7 of an Example. (A) of FIG. 25 is a figure which shows the sampling position of the test piece in evaluation 8-11 of an Example, (b) is a figure which shows the shape of a tensile test piece, (c) is a Charpy impact. It is a figure which shows the shape of a test piece. FIG. 26 is a macro photograph of the cross section of the wheel obtained in Example 6. FIG. 27A is a schematic cross-sectional view showing sampling positions A to E of test pieces of a prewheel obtained by forward extrusion processing in Evaluation 13 of the example. FIG. 27B is a schematic cross-sectional view showing sampling positions A to E of pre-wheel test pieces obtained by backward extrusion in evaluation 13 of the example. FIG. 27C is a schematic cross-sectional view showing sampling positions A to E of wheel test pieces obtained by flaring in Evaluation 13 of the example. FIG. 27D is a photomicrograph showing the results of the evaluation 13 of the example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[First Embodiment]
FIG. 1 is a perspective view showing a first embodiment of a forged billet according to the present invention.
A forged billet 10 according to the first embodiment shown in FIG. 1 includes a cylindrical main body 1.

The average particle diameter of the metal crystal particles of the forged billet 10 is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.
When the average particle diameter exceeds 30 μm, the mechanical strength may be insufficient as compared with the case where the average particle diameter is within the above range. In the present specification, the “average particle diameter” is a value measured based on the cutting method of JIS-H0542. Further, the measurement site is the forged billet and each part of the light alloy wheel, both near the center.

Charpy impact value of the forged billet 10 is at 15 J / cm ² or more, preferably 20 J / cm ² or more, and more preferably 22~31.3J / cm ^2. The Charpy impact value is a value measured according to JIS-Z2242. Further, the Charpy impact value is one of the materials for judging whether the impact resistance is superior or inferior, and indicates the possibility of absorbing impact energy.
By setting the Charpy impact value to 15 J / cm ² or more, a wheel having a fine crystal grain size can be obtained. That is, when a forging billet is installed in a forging press as a starting material and pressed with a pair of molds, the metal crystal particles of the metal structure of the forged billet are already present even in a portion that does not show a large displacement. Since it is refined, the forged product obtained has a fine crystal grain size of the metal crystal particles.

The tensile strength of the forged billet 10 is preferably 250 MPa or more. The tensile strength is a value measured according to JIS-Z2241.
The yield strength of the forged billet 10 is preferably 150 MPa or more. The proof stress is a value measured according to JIS-Z2241.
The elongation of the forged billet 10 is preferably 8% or more. The elongation is a value measured according to JIS-Z2241. The elongation is the rate at which the material stretches in the tensile test of the material. When the starting point distance of the test piece is L ₀ and the breaking point distance is L ₁ , the elongation is expressed by the following formula. It is.
δ = [(L ₁ −L ₀ ) / L ₀ ] × 100
This shows the elongation rate until breakage, and shows the range in which the shape of the light alloy wheel is maintained.
The forged billet 10 preferably has a Brinell hardness of 65 HB or more. The Brinell hardness is a value measured according to JIS-Z2243.

The forged billet 10 preferably has forged lines.
Here, the forging line means a state of a flow of metal crystal particles generated in a forged product in a metal structure and having a crystal grain size of at least 12 μm. In this forged streamline, the flow of the metal structure becomes clearer when the crystal grain size of the metal crystal particles becomes finer than 9 μm by pressure compression.
In the forged billet 10, it is preferable that forged lines extend radially from the center of the cylinder.

  When the forged billet 10 has a forged line, the forged product to be obtained has a forged line even if forging is performed based on a known method. As a result, the forged product has a uniform mechanical strength. In addition, since the said forge billet 10 has a forge flow line even if it is a part which is not compression-forged, mechanical strength improves reliably.

Examples of the light metal alloy include an aluminum alloy or a magnesium alloy. Moreover, the hybrid alloy which consists of an aluminum alloy and a magnesium alloy may be sufficient.
In these cases, a lightweight wheel is obtained. Further, in order to improve the performance of such a light metal alloy, an additive metal can be added.

  When the main metal is aluminum, the additive metal is preferably at least one selected from the group consisting of Ca, Cr, Cu, Fe, Mg, Mn, Si, and Y. When the main metal is magnesium, it is preferably at least one selected from the group consisting of Al, Ca, Cr, Cu, Fe, Mn, Si and Y. In this case, the performance of the light alloy wheel itself can be improved based on the physical properties of the added metal added.

For example, the additive metal is preferably calcium (Ca). In particular, when the added amount of calcium is 4 to 8% by mass, the heat resistance of the obtained light alloy wheel is improved.
Therefore, it is preferable that the light metal alloy contains 4 to 8% by mass of calcium.
When the content ratio of calcium is less than 4%, recrystallization is difficult to proceed and fine crystals tend not to be obtained as compared with the case where the content ratio is in the above range, and the content ratio of calcium is 8%. If the content exceeds the above range, a homogeneous alloy of calcium added tends not to be obtained as compared with the case where the content ratio is in the above range.

Specific examples of the light metal alloy include aluminum (1000 series), magnesium, Al-Mn series (3000 series), Al-Si series (4000 series), Al-Mg series (5000 series), and Al-Mg-Si series. (6000 series), Al-Zn-Mg series (7000 series), Al-Cu-Mg series (2000 series), Al-Cu-Si series, Al-Cu-Mg-Si series and the like.
Among these, from the viewpoint of versatility, an Al—Mg—Si system (6000 system) is preferable.

FIG. 2 is a cross-sectional view showing a forged billet according to the first embodiment and a cast billet before pressure compression.
As shown in FIG. 2, the forged billet 10 is obtained by compressing and compressing the cast billet 4 in the axial direction (one direction).

  The cast billet 4 is obtained by heating and melting a light metal alloy at, for example, 800 ° C. or more and casting it under an inert gas atmosphere.

  Examples of the inert gas include nitrogen and argon. That is, by removing oxygen, it is possible to prevent the molten raw material (hereinafter referred to as “molten raw material”) from being oxidized.

The casting method is not particularly limited, and examples thereof include a sand casting method, a gypsum casting method, a precision casting method, a die casting method, a centrifugal casting method, and a continuous casting method.
Among these, the casting method is preferably a continuous casting method. In this case, the forged billet 10 having a more uniform crystal grain size of the metal crystal particles can be obtained.

In casting, a molten raw material is poured into a casting machine at a speed of 65 to 90 mm / min, for example.
When the casting speed is less than 65 mm / min, the crystal grain size of the metal crystal particles tends to be non-uniform compared to the case where the speed is within the above range, and the casting speed is 90 mm / min. When it exceeds, there exists a possibility that it may be damaged at the time of casting billet manufacture compared with the case where speed exists in the said range.

The molten raw material poured into the casting machine is homogenized, for example, by being heated at 550 ° C. or higher for 6 hours or longer.
And it cools after that and the cylindrical cast billet 4 is obtained.
Here, the cooling is preferably rapid cooling. In this case, there is an advantage that crystal grains become fine. In addition, you may cut | disconnect the obtained cylindrical cast billet 4 in the orthogonal | vertical direction with respect to an axial direction as needed.

  The size of the resulting cast billet 4 is preferably such that the length / diameter ratio is 2.0 to 2.5. In this case, when the cylindrical cast billet 4 is pressed in the axial direction, it is possible to suppress the occurrence of a buckling phenomenon in which the cast billet 4 is bent suddenly.

  Since the forged billet 10 is obtained by compressing the cast billet 4 in the axial direction, the crystal grain size of the metal crystal particles is refined at the stage of the forged billet 10. For this reason, the light alloy wheel which has become a product using this as a starting material also maintains the crystal grain size, and at least the crystal grain size of the metal crystal particles becomes finer.

Here, examples of the method for compressing and compressing the cast billet 4 include free forging, die forging, swing forging, extrusion forging, rotary forging, closed forging, and section forging. Note that die forging includes press forging and hammer forging. Also, partial forging can be used in which a casting billet is rotated by a certain angle and a part of pressure is repeatedly applied.
Among these, it is preferable that pressure compression is based on closed forging, swing forging, hammer forging or section forging.

FIGS. 3A and 3B are cross-sectional views showing a state where the cast billet before pressure compression is a forged billet according to the first embodiment by closed forging.
As shown in FIGS. 3A and 3B, in closed forging, when the casting billet 4 is compressed in the axial direction, the metal structure can be prevented from spreading in the lateral direction. That is, by adding the lateral restraining force P, the forged billet 10 can be prevented from becoming a drum shape swelled in the middle part, and the crystal grain size of the metal crystal particles can be refined.

The processing conditions at this time may be any of hot forging, warm forging, cold forging, and isothermal forging.
Among these, the processing conditions are preferably hot forging. Specifically, the pressure compression temperature of 300 to 550 ° C., it is preferably carried out under pressure conditions of ^{9.8 × 10 3 kN~88.2 × 10 3} kN. The pressure of ^{9.8 × 10 3 kN~88.2 × 10 3} kN when converted to thrust scale forging machine (press machine), the 1000 to 9000 tons.

  Thus, the cast billet 4 is pressurized and compressed, and then cooled to obtain a cylindrical forged billet 10. The cooling is preferably rapid cooling.

The forging billet 10 according to the first embodiment preferably has a forging ratio satisfying the following formula in the pressure compression.
H1 / H2 ≧ 4.0
In the formula, H1 means the length in the direction in which the cast billet 4 is compressed and compressed, that is, the height in the axial direction of the cast billet 4, and H2 is the length in the direction in which the forged billet 10 is compressed and compressed. That is, it means the height of the forged billet 10 in the axial direction (see FIG. 2). In addition, when pressurizing and compressing a plurality of times, H1 means the length of the cast billet 4 in the direction before being compressed and compressed, and H2 is the final forged billet 10 that has been compressed and compressed a plurality of times. It means the length in the direction of pressure compression at the end.

When the light metal alloy is an aluminum alloy, the particle size of the metal crystal particles is extremely refined as the H1 / H2 (forging ratio) by pressure compression increases from 3.5.
The H1 / H2 (forging ratio) is preferably 4.0 or more, more preferably 4 to 12 because it is surely refined, and 4 to 6 from the viewpoint of practicality. More preferably. Since the forged billet 10 is an intermediate product, it is expected that the forging ratio further increases when the forged product is forged using the forged billet 10.

Here, when it is set as the forge billet of a high forging ratio, it is preferable to compress and compress several times. If trying to make a forged billet with a high forging ratio in one stage, buckling may occur.
4A to 4D are cross-sectional views showing an example in which a cast billet is compressed and compressed a plurality of times to obtain a forged billet according to the present invention.
First, as shown in FIG. 4 (a), when the casting billet 4 is closed and forged, a mold 51 having a cylindrical hole 51a that covers at least half the height of the casting billet 4 and preferably covers the entire height. Closed forging is performed using Next, as shown in FIG. 4B, closed forging is performed using a mold 52 in which a cylindrical hole 52a covering the half or more of the pre-forged billet 12a is formed in the same manner. As shown in the figure, closed forging is performed using a mold 53 in which a cylindrical hole 53a that covers more than half of the pre-forged billet 12b is formed in the same manner as shown in FIG. Closed forging is performed using a mold 54 in which a cylindrical hole 54a that covers more than half of the billet 12c is formed. Thus, the forged billet 10 is obtained.

  The forged billet 10 is suitably used for manufacturing a light alloy wheel for a vehicle. Besides, it is suitably used for flying parts, transportation equipment parts, industrial equipment parts, equipment for building materials including sashes, and members for these uses. Specifically, aircraft It is suitably used for light alloy wheel manufacturing of aircraft wheels, flying objects such as airplanes and helicopters, transportation equipment parts such as trucks, industrial equipment parts such as machine tools and electrical appliances.

Next, an embodiment of a light alloy wheel according to the present invention will be described.
FIG. 5A is a front view showing a light alloy wheel according to this embodiment, and FIG. 5B is a cross-sectional view taken along the line II ′ of FIG.
The light alloy wheel 3 (multi-piece) according to the present embodiment includes a disc portion 6, and an outer rim portion 7 and an inner rim portion 8 provided on the periphery of the disc portion. That is, the light alloy wheel 3 includes a disk portion 6, an outer rim portion 7 connected to the periphery of the disk portion 6 and extending in the surface direction of the disk portion 6, and a disk portion connected to the periphery of the disk portion 6. 6 is provided with an inner rim portion 8 erected in the vertical direction.

The disk portion 6 includes a disk-shaped hub portion 6a and a spoke portion 11 extending from the hub portion 6a in a radial Y shape. That is, in the light alloy wheel 3, the outer rim portion 7 and the inner rim portion 8 are connected to the tip of the spoke portion 11. The hub portion 6a is preferably a gently curved surface. In this case, since the flow of the raw material at the time of pressing becomes uniform, the training ratio is more equalized.
The hub portion 6a has a disk shape having a curved surface whose surface is gently curved, and is provided with a bolt insertion hole 6b for inserting a bolt when the light alloy wheel 3 is fixed to the axle with the bolt. .
In addition, an empty portion 9 is provided between the adjacent spoke portions 11.
The inner rim portion 8 has an inner flange portion 8a formed at the tip, and the outer rim portion 7 has an outer flange portion 7a formed at the tip.

The forging ratio of the light alloy wheel 3 to the cast billet 4 (hereinafter referred to as “total forging ratio” for convenience) is preferably 4.0 or more, and 5.5 or more when the light metal alloy is a magnesium alloy. It is preferable that
Here, the total forging ratio is obtained by multiplying the forging ratio of the forged billet 10 with respect to the above-described casting billet 4 by the forging ratio of the light alloy wheel 3 with respect to the forging billet 10. That is, the total training ratio is a value represented by “the height H1 of the cast billet 4” ÷ “the height H3 of the light alloy wheel 3”. The height H3 of the light alloy wheel 3 is shown in FIG. The height H3 of the light alloy wheel is calculated as the average of the heights of the respective parts of the light alloy wheel in the forged direction.

In the light alloy wheel 3, since the starting material is the forged billet 10 described above, when the average particle size of the metal crystal particles of the forged billet 10 is 30 μm or less, the inner rim portion 8 and the inner flange portion 8 a The average particle diameter of the metal crystal particles based on the cutting method based on JIS-H0542 of at least one portion selected from the group becomes 30 μm or less. In addition, it is more preferable that this average particle diameter shall be 5-20 micrometers, and it is still more preferable to set it as 5-15 micrometers.
Moreover, it is preferable that the average particle diameter except the recrystallized part of the metal crystal particle of the inner rim part 8 based on the cutting method based on JIS-H0542 is 20 μm or less.
In these cases, the light alloy wheel 3 is unlikely to be damaged when an unexpected situation occurs during traveling of the vehicle and an impact stress is applied to the rim.

In the light alloy wheel 3, the Charpy impact value of the disk portion 6, the spoke portion 11, the outer flange portion 7a, the inner rim portion 8 and the inner flange portion 8a is preferably 15 J / cm ² or more.
Moreover, it is preferable that the elongation rate of the spoke part 11, the outer flange part 7a, the inner rim part 8, and the inner flange part 8a is 16% or more.

  The light alloy wheel 3 is manufactured by forging the above-described forged billet 10 as a starting material, so that the mechanical strength is excellent and the mechanical strength is uniform. In addition, since the disk part 6, the outer rim part 7, and the inner rim part 8 are integrated (one piece), the light alloy wheel 3 has better mechanical strength and more uniform mechanical strength. It becomes.

Next, an example of a method for manufacturing the light alloy wheel 3 will be described.
FIG. 6 is a schematic view showing a manufacturing process from the forged billet to the light alloy wheel according to the first embodiment.
As shown in FIG. 6, the manufacturing process from the forged billet to the light alloy wheel includes a forging process, a heat treatment process, and a finishing process.

  The forging process includes a first forging molding 21, a second forging molding 22, and a third forging molding 23. That is, the forged billet 10 becomes the light alloy wheel 3 through the first forging molding 21, the second forging molding 22, the third forging molding 23, and a finishing process (not shown).

Specific methods of the first forging molding 21, the second forging molding 22, and the third forging molding 23 include free forging, die forging, swing forging, extrusion forging, rotary forging, and closed forging. Note that die forging includes press forging and hammer forging. Also, partial forging can be used in which the forging billet 10 is rotated by a certain angle and the operation of pressurizing a part thereof is repeated.
Among these, it is preferable that the first forging molding 21, the second forging molding 22, and the third forging molding 23 are all closed forging. In this case, the light alloy wheel 3 having a more uniform mechanical strength can be manufactured.

The processing conditions at this time may be any of hot forging, warm forging, cold forging, and isothermal forging. These forged molding, 300 ° C. or higher, preferably is preferably performed at a pressure at a temperature of ^{300~550 ℃, 9.8 × 10 3 kN~88.2} × 10 3 kN.

  By performing the forging as described above, the forged billet 10 is forged and then cooled to obtain the prewheel 3a.

The heat treatment step is a step of heat treating the pre-wheel 3a. When the light metal alloy is an aluminum alloy, the heat treatment is performed under T6 conditions based on JIS-H0001. Specifically, solution treatment is performed at 500 to 580 ° C. for 3 to 5 hours, quenching is performed for 3 to 7 minutes, and artificial aging treatment is performed at 150 to 200 ° C. for 7 to 9 hours.
Moreover, when a light metal alloy is a magnesium alloy, it carries out on T5 conditions based on JIS-H0001. Specifically, artificial aging treatment is performed at 300 to 380 ° C. for 1 to 3 hours.

In the light alloy wheel manufacturing method according to the present embodiment, as shown in FIG. 6, the pre-wheel 3a (light alloy wheel) is obtained by the forging process described above. The pre-wheel 3a includes a pre-rim portion 5 provided upright on the periphery, and a finishing process described later is performed.
Here, examples of the finishing process include machining such as spinning, drilling, cutting, and milling. That is, the disk portion pattern is machined and machined by a milling machine including a lathe or machining center on the pre-wheel 3a.
The spinning process is a process for forming the rim part by narrowing down the pre-rim part 5 of the pre-wheel 3a, and the drilling process is a process for forming a spoke part 11 and a pattern in the machining center by making a hole in the pre-wheel 3a. The cutting process is a process in which the periphery of the pre-wheel 3a is cut by a lathe to form a rim portion, and the milling process is a process in which almost the entire light alloy wheel is cut and molded.

  As a finishing process, first, a spinning process is performed. That is, in the spinning process, the outer rim portion 7 and the outer flange portion 7a extending in the surface direction of the pre-wheel 3a and the pre-wheel 3a are narrowed by spinning a part of the pre-rim portion 5 while spinning. An inner rim portion 8 and an inner flange portion 8a which are erected in the vertical direction on the peripheral edge of the rim are formed. At this time, a finishing margin may be formed at the same time.

(A) of FIG. 7 is sectional drawing which shows the 1st spinning process in the manufacturing method of the wheel made from a light alloy which concerns on this embodiment, (b) And (c) is sectional drawing which shows a 2nd spinning process. .
As shown in FIGS. 7A, 7 </ b> B, and 7 </ b> C, in the light alloy wheel manufacturing method according to this embodiment, the spinning process includes a first spinning process and a second spinning process.
The pre-wheel 3a uses a forged billet having a high forging ratio, and has a high toughness because the tensile strength, Charpy impact value, elongation, and the like are significantly improved. For this reason, in the light alloy wheel manufacturing method according to the present embodiment, the first spinning process and the second spinning process are provided in order to avoid imposing a considerable burden on the rolling roller due to plastic deformation caused by the spinning process. Yes.

As shown to (a) of FIG. 7, in the 1st spinning process, the 1st spinning apparatus 31 is the some rolling which narrows the inner rim 31a and the outer die 31b which can clamp the prewheel 3a, and the pre-rim part 5. A roller 35.
In the first spinning process, the pre-wheel 3a is pinched between the inner mold 31a and the outer mold 31b, so that they are securely fixed and rotate together. At this time, by pressing a plurality of rolling rollers 35 against the pre-rim portion 5, the pre-rim portion 5 is rolled and becomes a rough shape of the inner rim portion 8.

As shown in FIG. 7B, in the second spinning process, the second spinning device 32 includes a plurality of inner molds 32a and outer molds 32b that can support the pre-wheel 3a, and a plurality of pre-rim portions 5 that are further narrowed down. A rolling roller (not shown).
In the second spinning process, the prewheel 3a is attached to the outer mold 32b, and the tip of the prerim portion 5 of the prewheel 3a is supported by the inner mold 32a. That is, a gap 38a is provided between the pre-wheel 3a and the inner mold 32a, and a gap 38b is provided between the pre-rim portion 5 and the inner mold 32a. In the second spinning process, the inner mold 32a is an assembled mold.

  Then, in the state of FIG. 7B, as shown in FIG. 7C, the pre-rim portion 5 is pressed by the rolling roller 35 from the oblique direction (for example, the direction of 45 °), and the inner flange portion 8a is moved. Mold. At this time, it is preferable that the gaps 38a and 38b are maintained.

  In the method for manufacturing the light alloy wheel 3, since the gaps 38a and 38b are provided, there is an advantage that no stress is pushed up from below even when pressed by a rolling roller. In addition to this, as described above, since pressing is performed by the rolling roller 35 from the oblique direction, recrystallization of the inner rim portion 8 can be reliably suppressed. That is, when spinning is performed using the forged billet 10 having a refined crystal grain size, if the forged billet 10 having a high mechanical strength is used, the pressing force of the rolling roller 35 is increased and recrystallization is likely to occur. However, recrystallization of the inner rim portion 8 can be suppressed by providing a gap and pressing with the rolling roller 35 from an oblique direction. The number of rolling rollers 35 is not particularly limited. If there are a plurality of them, one of them may be pressed from the oblique direction.

Next, with respect to the prewheel 3a formed with the outer rim portion 7 and the inner rim portion 8, the pattern of the disk portion 6 is formed by drilling, and the periphery of the prewheel 3a is cut by cutting. A light alloy wheel 3 is obtained.
According to the manufacturing method of the light alloy wheel 3 according to the present embodiment, the light alloy wheel 3 is reduced in weight and is excellent in design by forming irregularities and voids. If necessary, chemical surface treatment, plating, shots, painting, and the like may be performed.

  The light alloy wheel 3 is suitably used for applications such as vehicles and aircraft wheels, for example. In particular, when used for a vehicle, the automobile can be reduced in weight, so that the environmental load caused by gasoline or the like can be reduced and the cost can be reduced.

[Second Embodiment]
FIG. 8 is a perspective view showing a second embodiment of the forged billet according to the present invention.
A forged billet 10a according to the second embodiment shown in FIG. 8 is different from the forged billet 10 according to the first embodiment in that the forged billet 10a includes a polygonal column, that is, a hexagonal columnar main body 1 here. The light alloy wheel and the light alloy wheel manufacturing method are the same as described above.

  When the forged billet 10a has a hexagonal column shape, the forged billet can be accurately positioned when the forged billet is processed, so that the flow of the metal crystal particles can be made constant.

(A)-(d) of FIG. 9 is the top view and side view which show the manufacturing process of the forge billet which concerns on 2nd Embodiment.
As shown in FIG. 9 (a), the forged billet 10a is formed by first casting a light metal alloy into a cylindrical cast billet 4, and this cast billet 4 is closed by forging using a hexagonal column mold. A pre-forged billet 12 shown in FIG. 9B is compressed by pressing in the direction P1.
Next, as shown in FIG. 9C, the obtained pre-forged billet 12 is erected with its side face down. Then, the pre-forged billet 12 is again pressed and compressed from the direction P2, which is different from the axis, that is, the vertical direction, by closed forging using a hexagonal column mold to obtain a forged billet 10a shown in FIG. At this time, since the pre-forged billet 12 has a hexagonal column shape, it is easy to position the pre-forged billet 12 with one side face down. That is, it is easy to compress and compress in a direction different from the direction in which it is compressed.

  Thus, in the production of the forged billet 10a according to the second embodiment, the forged billet 10a as a starting material pressurizes and compresses the cast billet 4 in one direction to form the pre-forged billet 12, and the pre-forged billet 12 Since it is obtained with a history of further pressing and compressing in a direction different from the direction in which the metal is pressed and compressed, the proportion of the structure having a small crystal grain size in the entire metal crystal particles of the forged billet 10a increases. That is, the forged billet obtained by pressure-compressing the cast billet has a smaller crystal grain size due to the flow of the metal structure. In addition to this, in the forged billet 10a, the metal structure moves in different directions because it is compressed and compressed a plurality of times in different directions, and the crystal grain size becomes smaller. For this reason, it is possible to manufacture a light alloy wheel having better mechanical strength and more uniform mechanical strength.

Here, when pressure-compressed in one direction, the metal crystal particles in the middle portion (so-called central portion) are refined (hereinafter referred to as “fine regions”), and the upper and lower ends are made fine in metal crystal particles. Region (hereinafter referred to as “NG region”) occurs. In addition, a forge line is generated in the finely divided region in the middle part.
On the other hand, as described above, by further compressing and compressing the pre-forged billet in a direction different from the direction in which the pre-forged billet is compressed and compressed, a part of the NG region is further miniaturized, so that the NG region is reduced as a whole. be able to.

(A)-(e) of FIG. 10 is the schematic for demonstrating the effect at the time of compressing and compressing a casting billet in one direction, and then further compressing and compressing in a different direction.
First, as shown in FIG. 10A, when the cast billet 4 is compressed and compressed, the middle portion becomes the fine region A and the upper and lower ends become the NG region B.
Then, when the side of this is stood down and pressed and compressed from above again, as shown in FIG. 10 (b), the middle part becomes the fine region A, and the fine region A in FIG. Remains. That is, the corners in the four directions become the NG region B.
Further, when the side face is stood down and pressed and compressed again from above, as shown in FIG. 10 (c), the middle part becomes the fine region A, and (a) in FIG. The fine area A of b) remains. That is, the corners in the eight directions become the NG region B.
Further, when the side of this is stood down and pressed and compressed again from above, the result is as shown in FIG. 10 (d). Furthermore, the side of this is stood down and pressed again from above. When compressed, the result is as shown in FIG. That is, the NG region B can be reduced stepwise by repeating the pressure compression from different directions.
Thus, after compressing and compressing the cast billet in one direction and then compressing and compressing in a different direction, the proportion of the fine region A increases, and by repeating this, the proportion of the fine region A increases stepwise. To go. By utilizing this phenomenon, the effective use area of the forged billet can be increased, and the yield of the material can be greatly improved. In practice, 95% becomes the fine region A and 5% becomes the NG region B by at least five pressurizations and compressions.

[Third Embodiment]
(A)-(f) of FIG. 11 is the top view and side view which show the manufacturing process of the forge billet which concerns on 3rd Embodiment.
The forged billet 10b according to the third embodiment is different from the forged billet 10a according to the second embodiment in that the pre-forged billet has a hexagonal truncated cone shape or a truncated cone shape. The light alloy wheel and the light alloy wheel manufacturing method are the same as described above.

  As shown in FIG. 11 (a), the forged billet 10b is a cylindrical pre-forged billet 13a obtained by first compressing and compressing a cylindrical cast billet 4 in the axial direction by flat-pressing closed forging. .

  Next, as shown in FIG. 11 (b), the pre-forged billet 13a is pressure-compressed in the axial direction by closed forging using a hexagonal prism lens-shaped die to form a pre-forged billet 13b. The pre-forged billet 13b has a hexagonal prism lens shape in which the upper and lower bases of the hexagonal column are convex and the center is slightly flat. That is, the end surface orthogonal to the central axis of the hexagonal column is formed as a bulging curved surface whose center is slightly flat. By forming the pre-forged billet 13c into a hexagonal prism lens shape, forging defects due to buckling can be prevented, and as a result, the yield can be improved. Moreover, the generation | occurrence | production of the wrinkle damage | wound by forging can be suppressed by giving roundness to the corner | angular of the pre forge billet 13c. It is preferable to apply a small R to the ridge line where the bulging surface and the hexagonal column side surface intersect. Furthermore, the thickness of the side surface of the hexagonal column portion is thin at the corner portion, and gradually increases between the corners. Thereby, when covering the hexagonal surface with the curvature radius of the curved surface being constant, it is possible to prevent a gap from being generated between the corners when the corner portions contact each other.

  Next, as shown in FIG. 11C, the obtained pre-forged billet 13b is erected with its side face down. Then, the pre-forged billet 13b is pressure-compressed from a direction different from the axis, that is, the vertical direction, by closed forging using a hexagonal column lens-shaped die again to obtain a pre-forged billet 13c. At this time, since the pre-forged billet 13b has a hexagonal columnar lens shape, the pre-forged billet 13b can be easily positioned with one side face down. That is, it is easy to press and compress in a direction different from the direction in which the pressure is compressed.

  Next, as shown in FIG. 11D, the obtained pre-forged billet 13c is erected with its side face down. Then, the pre-forged billet 13c is pressure-compressed from a direction different from the axis, that is, the vertical direction by closed forging using a truncated cone-shaped die to obtain a pre-forged billet 13d. The pre-forged billet 13d has a truncated cone shape in which the peripheral surface (side surface) is tapered.

  Next, as shown in FIG. 11 (e), the obtained pre-forged billet 13d is inverted and placed on the lower mold 20 so that the bottom surface with the larger area faces down. At this time, the pre-forged billet 13d is locked to the middle of the inner peripheral surface of the lower mold 20. That is, an air gap is generated below the bottom surface. Then, by closed forging using a frustoconical mold, the pre-forged billet 13e is compressed and compressed from the same direction as the shaft. The pre-forged billet 13e has a truncated cone shape whose peripheral surface (side surface) is tapered. In addition, generation | occurrence | production of the flaw at the time of forging is suppressed by eliminating the angle | corner of a taper surface.

  Next, as shown in FIG. 11 (f), the obtained pre-forged billet 13e is pressed and compressed in the axial direction by flat-pressed closed forging to form a cylindrical forged billet 10b. Instead of the cylindrical forged billet 10b, the pre-forged billet 13e may be used as it is as the forged billet.

Thus, in the manufacture of the forged billet 10b according to the third embodiment, as described above, since it is obtained with a history of sequentially pressing and compressing in different directions, the crystal grains in the entire metal crystal particles of the forged billet 10b. The proportion of the tissue having a small diameter increases (see the principle of FIG. 10).
Further, by compressing and compressing the pre-forged billet 13d into a truncated cone shape, and then reversing and compressing and compressing again, only the outer portion Q of the pre-forged billet 13d is deformed. That is, the material flow of the outer portion Q can be positively performed. As a result, the obtained forged billet 10b has the same crystal grain size in the central portion as that of the other portions, and the entire crystal grain size can be made uniform. In addition, when the fatigue strength test of the forge billet which passed through the pre forge billet was done and the tension and compression were repeatedly performed with the test frequency of 20 Hz, it did not reach a fracture | rupture in 1 * 10 < ⁷ > cycles.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in the forged billet according to the first embodiment, the cast billet is manufactured by pressing and compressing in the axial direction, but the pressing and compressing is not limited to the axial direction. For example, the horizontal direction may be used. That is, H1 / H2 (forging ratio) indicates the length in the direction in which the cast billet is pressed (lateral direction), and H2 indicates the length in the direction in which the forged billet is pressed (lateral direction). It will be.

In the forged billet according to the second embodiment, the cast billet is compressed and compressed into a hexagonal column-shaped pre-forged billet, and then compressed and compressed from the lateral direction to obtain the final hexagonal column-shaped forged billet. A cast billet that has been compressed into a hexagonal column may be used as the final forged billet.
Further, the forged billet and the pre-forged billet may have a polygonal column shape with many corners such as a hexagonal column shape, an octagonal column shape, or a dodecagon column shape.

In the forged billet according to the second embodiment, the cast billet is pressure-compressed to form a pre-forged billet, which is further compressed in a vertical direction different from the direction in which the pre-forged billet is compressed. The number of compressions is not limited to two, and may be performed three or more times.
Similarly, in the forged billet according to the third embodiment, the flat forged pre-forged billet is pressure-compressed twice from different vertical directions, but may be performed three or more times, and the hexagonal frustum-shaped pre-forged The billet may be inverted and compressed under pressure a plurality of times.
Further, the hexagonal columnar pre-forged billet may be a polygonal columnar lens shape including a cylindrical lens shape, and the hexagonal frustum-shaped preforged billet may be a polygonal truncated cone shape including a truncated cone shape. Good.

  In the embodiment of the light alloy wheel according to the present invention, the shape of the spoke portion 11 is Y-shaped, but is not limited thereto. It may be fan-shaped or X-shaped.

In the light alloy wheel described above, the forging for producing the light alloy wheel includes three times of the first forging molding 21, the second forging molding 22, and the third forging molding 23. The number of times may be one time or a plurality of times.
Alternatively, the light billet wheel 10 may be manufactured by forging the forged billet 10 with a die and machining the disk portion pattern with a lathe or a milling machine including a machining center.

In the light alloy wheel described above, forging when the light alloy wheel is manufactured may be performed by a forward extrusion method and a backward extrusion method. The final adjustment of the inner rim 8 is preferably performed by a flaring method.
12 (a) and 12 (b) are cross-sectional views showing forward extrusion in a light alloy wheel manufacturing method according to another embodiment. The forward extrusion process is a process of performing the forward extrusion process on the forged billet 10 to form the pre-wheel 3b.
As shown in FIG. 12A, in the forward extrusion process, first, the forged billet 10 is placed between the upper die 16 and the lower die 17 provided with the knockout portion 17a. Here, the knockout part 17a is for pushing up and taking out the pre-wheel 3b after forward extrusion.

As shown in FIG. 12B, the upper die 16 is lowered, and a part of the forged billet 10 is pushed into the gap between the knockout portion 17 a and the lower die 17. Thereby, the outer rim precursor 7b, the inner rim precursor 8b, and the disk portion precursor 13 are formed.
And the prewheel 3b is obtained by raising the knockout part 17a.

(A) And (b) of Drawing 13 is a sectional view showing back extrusion processing in a manufacturing method of a light alloy wheel concerning other embodiments. Such backward extrusion processing is processing for forming the inner rim portion 8 by performing backward extrusion processing on the pre-wheel 3b.
As shown in FIG. 13 (a), in the backward extrusion process, first, the pre-wheel 3b is placed between the upper mold 18 and the lower mold 19 provided with the knockout portion 19a. Here, the knockout part 19a is for pushing up and taking out the pre-wheel 3c after back extrusion.

As shown in FIG. 13B, the upper mold 18 is lowered, and a part of the pre-wheel 3 b is pushed into the gap between the upper mold 18 and the lower mold 19. As a result, the disk portion 13a having a design surface including irregularities such as spokes is formed, and at the same time, the inner rim portion 8 is formed. The inner rim portion 8 is formed by extending the excess material of the disk portion precursor 13 by extrusion.
And the prewheel 3c is obtained by raising the knockout part 19a.

  Here, in the backward extrusion, since the traveling direction of the upper mold 18 and the extending direction of the inner rim portion 8 are opposite to each other, the resistance due to friction is large. For this reason, it is preferable to extend the inner rim 8 linearly at a predetermined inclination angle because further pressing force is required. Then, a part of recrystallization can be prevented.

  14A and 14B are cross-sectional views showing a flaring process in the wheel manufacturing method according to the present embodiment. Such a flaring process is a process of flaring the outer rim precursor 7 b to form the outer rim portion 7.

  As shown in FIG. 14A, in the flaring process, first, the pre-wheel 3c is placed between the upper mold 25 and the lower mold 26 provided with the knockout portion 26a. Here, the knockout part 26a is for pushing up and taking out the pre-wheel 3d after a flaring process.

As shown in FIG. 14B, the upper mold 25 is lowered, the outer rim precursor 7 b of the pre-wheel 3 c is pressed, and flared (expanded) outward to form the outer rim portion 7. At this time, the inner rim portion 8 is expanded around the inner flange portion 8a to form a final shape.
Thereby, the prewheel 3d is obtained. In addition, a light alloy wheel is obtained by performing turning machining after heat treatment and aging treatment after processing.

The light alloy wheel is provided with a pre-rim portion 5 erected on the periphery of the light alloy wheel 3 and processed into an outer rim portion 7 and an inner rim portion 8. That is, in the light alloy wheel described above, a disc part 6 and a pre-rim part 5 are integrated, but a rim is separately provided in a two-piece light alloy wheel other than a one-piece light alloy wheel. It is also possible to provide a mounting seat on the peripheral edge of the disk portion and attach the outer rim and / or inner rim to the mounting portion by screwing, friction welding, caulking means such as rivets.
When the pre-rim part is manufactured separately, the forging pressure can be reduced. In this case, since only the disk part or the disk part and the outer rim part are forged, the average height after forging becomes small. For this reason, there is also an advantage that the training ratio can be increased.

Specifically, the following production methods can be mentioned.
(A) A disk part is made by using a forged billet, and a rim part in which an outer rim part and an inner rim part are integrally formed is made alone, and an annular mounting seat is provided for each of them. Connect with bolts and nuts.
(B) Using a forged billet, a disk part is made alone, and an outer rim part and an inner rim part are made separately and integrated in the same manner as described above.
(C) When the disk portion is made using the forged billet, the outer rim portion is integrally formed, and the separately created inner rim portion is coupled with a plurality of bolts and nuts.
(D) When making a disk portion using a forged billet, the inner rim portion is integrally formed, and the separately created outer rim portion is joined with a plurality of bolts and nuts.
(E) When making a disk part using a forged billet, an outer rim part and an inner rim part are integrally formed as a pre-rim part.

  In addition to a bolt and a nut, a hack bolt or the like provided with friction welding, screwing, rivet fastening, or a caulking member can be used as a coupling method.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
An aluminum alloy having a weight of 19.8 kg was prepared as a light metal alloy. This was melted to obtain a molten raw material.
Under an argon gas atmosphere, a continuous casting method was used to pour into a casting machine, heat, and then cool to obtain a cylindrical casting billet (standard number: A61512) having a diameter of 254 mm and a height of 145 mm.

The cast billet was subjected to pressure compression by closed forging. That is, a cast billet was placed on a press machine, and hot forging was performed at a pressure of 63700 kN under a temperature condition of 350 to 400 ° C.
Then, by cooling with a fan, a cylindrical forged billet having a height of 36.2 mm was obtained. The forging billet has a forging ratio of 4.

(Example 2)
A forged billet was obtained in the same manner as in Example 1 except that the cast billet was compressed under pressure to obtain a forged billet having a height of 24.2 mm. The forging billet has a training ratio of 6.

(Example 3)
A forged billet was obtained in the same manner as in Example 1 except that the cast billet was compressed under pressure to obtain a forged billet having a height of 12.1 mm. The forging billet has a training ratio of 12.

Example 4
A forged billet was obtained in the same manner as in Example 1 except that the cast billet was compressed under pressure to obtain a forged billet having a height of 7.3 mm. The forging billet has a forging ratio of 20.

(Example 5)
An aluminum alloy having a weight of 54 kg was prepared as a light metal alloy. This was melted to obtain a molten raw material.
Under an argon gas atmosphere, by a continuous casting method, it was poured into a casting machine, heated, and then cooled to form a cylindrical casting billet (standard number: A61512) having a diameter of 204 mm and a height of 612 mm.

Based on the method shown in FIG. 11, the cast billet was subjected to flat press forging at a press pressure of 100 tons and a billet temperature of 480 ° C., and the swollen outer portion was turned to form a cylindrical pre-forged billet.
Next, pressure compression was performed by closed forging. That is, a pre-forged billet was placed on a press and hot forged at a pressure of 63700 kN under a temperature condition of 350 to 400 ° C. to obtain a hexagonal columnar pre-forged billet.
Next, the pre-forged billet is raised 90 degrees so that the side faces downwards, and is vertically set. The pressure is 5000 tons, the workpiece temperature is 480 ° C., and pressure compression is performed again by hermetic forging, and the height is 145.5 mm. A hexagonal columnar pre-forged billet was used. At this stage, the training ratio is 4.2.

And this was raised 90 degree | times so that a side might be turned down, it stood | emitted vertically, and pressure compression was performed again by the closed forging under the same conditions, and it was set as the hexagonal frustum-shaped pre forge billet.
Next, this was inverted, and pressure compression was performed again by hermetic forging under the same conditions to obtain a forged billet having a diameter of 474 mm, a height of 142 mm, and a weight of 50 kg. Note that the forging ratio of the forged billet is 4.3.

(Comparative Example 1)
A cast billet (standard number: A6151) made of an aluminum alloy was used as Comparative Example 1. Forging ratio: 0 is the value of the cast billet.

[Evaluation 1]
The tensile strength was measured according to JIS-Z2241 for the forged billet obtained in Examples 1 to 4 and the cast billet of Comparative Example 1. The obtained values are shown in Table 1, and the graph is shown in FIG.

[Evaluation 2]
The 0.2% proof stress was measured according to JIS-Z2241 with respect to the forged billet obtained in Examples 1 to 4 and the cast billet of Comparative Example 1. The obtained values are shown in Table 1, and the graph is shown in FIG.

[Evaluation 3]
With respect to the forged billet obtained in Examples 1 to 4 and the cast billet of Comparative Example 1, the elongation was measured according to JIS-Z2241. The obtained values are shown in Table 1, and the graph is shown in FIG.

[Evaluation 4]
The Brinell hardness was measured according to JIS-Z2243 for the forged billet obtained in Examples 1 to 4 and the cast billet of Comparative Example 1. The obtained values are shown in Table 1, and the graph is shown in FIG.

[Evaluation 5]
The Charpy impact value was measured according to JIS-Z2242 for the forged billet obtained in Examples 1 to 4 and the cast billet of Comparative Example 1. The obtained values are shown in Table 1, and the graph is shown in FIG.

[Table 1]

[Evaluation 6]
The forged billets obtained in Examples 1 to 4 were observed according to the cutting method of JIS-H0542, and the number of metal crystal particles and the average particle size of the metal crystal particles were measured. The obtained results are shown in Table 2. In the table, “−” means that the crystal grain was too fine to be measured.
Moreover, the macro photograph of the cross section of the forged billet obtained in Example 1 is shown in FIG. 20 (a), the micrograph is shown in FIG. 20 (b), and the cross section of the forged billet obtained in Example 2 is shown. A macro photograph is shown in FIG. 21 (a), a micrograph thereof is shown in FIG. 21 (b), a macro photograph of a cross section of the forged billet obtained in Example 3 is shown in FIG. 22 (b), a macro photograph of the cross section of the forged billet obtained in Example 4 is shown in FIG. 23 (a), and a micrograph thereof is shown in FIG. 23 (b).

[Table 2]

From the results shown in Table 1, it was found that the forged billets obtained in Examples 1 to 4 have excellent Charpy impact values compared to the cast billets shown in the comparative examples, and particularly have a remarkable effect on elongation. .
Moreover, from the result of Table 2, the particle diameter of the metal crystal particle became fine in the forge billet obtained in Examples 1-4. This has shown that the light alloy wheel using the forge billet obtained in Examples 1-4 is fully refined | miniaturized.

[Evaluation 7]
With respect to the sampling positions A to I of the forged billet specimens obtained in Example 5 (see FIG. 24 (a)), observation was performed according to the cutting method of JIS-H0542, and the average particle diameter of the metal crystal particles was determined. It was measured. Sampling positions A to I in the cross section of the forged billet are shown in FIG. 24A, and the obtained average particle diameter and micrograph are shown in FIG.

  From the results shown in FIG. 24 (b), although the average particle diameter of 28 μm was observed in a part of the forged billet, the average particle diameter was in the range of 11 to 17 μm as a whole. From this, it was found that the forged billet of Example 5 was excellent in mechanical strength and uniform in mechanical strength.

(Example 6)
Based on the method shown in FIG. 12, the forged billet obtained in Example 1 was subjected to forward extrusion at a pressure of 78.4 × 10 ³ kN under a temperature condition of 350 ° C. to 500 ° C. On the basis of the method shown in Fig. 5, a rear wheel was extruded at a pressure of 78.4 x 10 ³ kN under a temperature condition of 350 ° C to 500 ° C to obtain a prewheel.
Next, the pre-wheel was subjected to flaring processing at a pressure of 4.9 × 10 ³ kN under the temperature condition of 350 ° C. to 500 ° C. based on the method shown in FIG. A wheel having the shape shown in FIG.

(Comparative Example 2)
The cast billet of Comparative Example 1 was subjected to the forging process, the heat treatment process, and the finishing process described above to obtain a wheel having the same shape as Example 6.

[Evaluation 8]
Tensile strength was measured according to JIS-Z2241 for the spoke part, outer flange part, and inner flange part of each wheel obtained in Example 6 and Comparative Example 2. The obtained values are shown in Table 3. The sampling position of the test piece is shown in FIG. 25 (a), and (b) shows the shape of the tensile test piece. As shown in (b) of FIG. 25, the dimension of the parallel portion is set to 27 mm smaller than the standard value (31.3 mm to 35.6 mm) in order to improve the off-point breakage.

[Evaluation 9]
The 0.2% proof stress was measured according to JIS-Z2241 with respect to the spoke part, the outer flange part, and the inner flange part of each wheel obtained in Example 6 and Comparative Example 2. The obtained values are shown in Table 3. In addition, the collection position of a test piece is shown to (a) of FIG.

[Evaluation 10]
The elongation was measured according to JIS-Z2241 with respect to the spoke part, outer flange part and inner flange part of each wheel obtained in Example 6 and Comparative Example 2. The obtained values are shown in Table 3. In addition, the collection position of a test piece is shown to (a) of FIG.

[Evaluation 11]
Charpy impact values were measured in accordance with JIS-Z2242 for the spoke portions, outer flange portions, and inner flange portions of the wheels obtained in Example 6 and Comparative Example 2. The obtained values are shown in Table 3. Note that the sampling position of the test piece is shown in FIG. 25A, and the shape of the Charpy impact test piece is shown in FIG. Since the Charpy impact test is mainly applied to steel materials, the test piece is required to be 10 mm square and 55 mm long. On the other hand, in order to measure the impact values of the inner flange portion, the outer flange portion and the spoke portion of the wheel, it is necessary to set a separate rule for the convenience of the volume at the sampling position, and therefore, as shown in FIG. As described above, the test piece has a shape that can be sampled from each part of the rim flange and the spoke, has a cross section of 4 mm × 10 mm, a length of 55 mm, and a U-shaped notch in the center part set to a depth of 2 mm. In addition, the Charpy impact tester uses non-ferrous resin for improving the accuracy of the reading scale.

[Table 3]

[Evaluation 12]
The cross section of the wheel obtained in Example 6 was observed. A macro photograph of the cross section of the wheel is shown in FIG.

  From the results shown in FIG. 26, no recrystallization was observed between the wheel hump part, the well part, and the inner rim flange part, and a homogeneous structure could be confirmed.

[Evaluation 13]
In Example 6, the pre-wheel obtained by the forward extrusion process, the pre-wheel obtained by the backward extrusion process, and the sampling positions A to E of the test pieces of the wheel obtained by the flaring process [from FIG. 27 (a)] With reference to FIG. 27 (c)], observation was performed according to the cutting method of JIS-H0542, and the average particle diameter of the metal crystal particles was measured. The outline of the cross section of the prewheel obtained by the forward extrusion process and the measured parts A to E are shown in FIG. 27A, the outline of the cross section of the pre wheel obtained by the backward extrusion process and the measured parts A to E. FIG. 27 (b) shows the outline of the cross section of the wheel obtained by the flaring process and the measured portions A to E in FIG. 27 (c), and the obtained average particle diameter and photomicrograph. Is shown in FIG.

  From the result shown in FIG. 27D, the obtained wheel was in the range of 10 to 24 μm as a whole. From this, it was found that the wheel of Example 6 was excellent in mechanical strength and uniform in mechanical strength.

  According to the forged billet of the present invention, a light alloy wheel having excellent mechanical strength and uniform mechanical strength can be produced. The obtained light alloy wheel is suitably used for applications such as vehicles and aircraft wheels. In particular, when it is used for a vehicle, the weight of the automobile can be reduced, so that the environmental load caused by gasoline or the like can be reduced, and the cost can be reduced. More importantly, the forged light alloy wheel using the forged billet of the present invention has an extremely high Charpy impact value and elongation when the rim or the disk part cracks for some reason during running in a vehicle or the like. Therefore, the cracks do not increase at a stretch, and a safer light alloy wheel can be provided, for example, the tire air pressure gradually decreases and the driver notices abnormalities so that no serious accidents occur.

DESCRIPTION OF SYMBOLS 1 ... Main-body part 3 ... Light alloy wheel 3a, 3b, 3c, 3d ... Pre wheel 4 ... Cast billet 5 ... Pre rim part 6, 13a ... Disk part 6a ... Hub part 6b ... Bolt insertion hole 7 ... Outer rim part 7a ... Outer flange part 7b ... Outer rim precursor 8 ... Inner rim part 8a ... Inner flange part 8b ... Inner part Rim precursor 9 ... Empty part 10, 10a, 10b ... Forged billet 11 ... Spoke part 12, 12a, 12b, 12c, 13a, 13b, 13c, 13d, 13e ... Pre-forged billet 13. .. Disk portion precursors 13a, 13b, 13c, 13d, 13e ... Pre-forged billets 16, 18, 25 ... Upper mold 17, 19, 20, 26 ... Lower mold 17a, 19a, 26a ... knockout portion 21 ... first forging 22 ... second forging 23 ... third forging 31 ... first spinning device 31a ... inner mold 31b ... -Outer die 35 ... Rolling roller 32 ... Second spinning device 32a ... Inner die 32b ... Outer die 38a, 38b ... Gaps 51, 52, 53, 54 ... Mold Mold 51a, 52a, 53a, 54a ... cylindrical hole A ... fine region B ... NG region H1, H2, H3 ... height P ... restraining force P1, P2 ... direction Q ... Outside part

Claims (14)

A forged billet obtained by casting a light metal alloy into a cast billet, and compressing and compressing the cast billet,
A forged billet with a Charpy impact value of 15 J / cm ² or more. The forged billet according to claim 1 satisfying the following formula.
H1 / H2 ≧ 4.0
(In the formula, H1 indicates the length in the direction in which the cast billet is compressed and compressed, and H2 indicates the length in the direction in which the forged billet is compressed and compressed.) A light metal alloy is cast into a cast billet, obtained by compressing and compressing the cast billet,
A method for producing a forged billet satisfying the following formula.
H1 / H2 ≧ 4.0
(In the formula, H1 indicates the length in the direction in which the cast billet is compressed and compressed, and H2 indicates the length in the direction in which the forged billet is compressed and compressed.)   The forging billet manufacturing method according to claim 3, wherein the pressure compression is performed by closed forging, swing forging, hammer forging, or section forging.   The forged billet according to claim 3 or 4 obtained by compressing and compressing the cast billet in one direction to obtain a pre-forged billet, and further compressing and compressing the pre-forged billet in a direction different from the direction in which the pre-forged billet is compressed. Manufacturing method.   The cast billet is pressure-compressed in one direction to form a pre-forged billet, further compressed and compressed in a direction different from the direction in which the pre-forged billet is compressed and compressed into a truncated cone shape, and only the outer portion is deformed. The method for producing a forged billet according to claim 3 or 4, wherein the forged billet is compressed under pressure.   The forged billet according to any one of claims 3 to 6, wherein the forged billet is for flying parts, for transportation equipment parts, for industrial equipment parts, for building materials, for optical equipment parts, or for manufacturing members for these uses. Manufacturing method. A light alloy wheel forged using a forged billet obtained by the method for producing a forged billet according to any one of claims 3 to 6,
A light alloy wheel having a Charpy impact value of 15 J / cm ² or more at the disk portion, the spoke portion, the outer flange portion, the inner rim portion, and the inner flange portion. A light alloy wheel forged using a forged billet obtained by the method for producing a forged billet according to any one of claims 3 to 6,
A light alloy wheel having a spoke portion, outer flange portion, inner rim portion, and inner flange portion with an elongation of 16% or more. A light alloy wheel forged using a forged billet obtained by the method for producing a forged billet according to any one of claims 3 to 6,
A light alloy wheel in which an average particle diameter of metal crystal particles based on a cutting method based on JIS-H0542 of at least one portion selected from the group consisting of an inner rim portion and an inner flange portion is 5 to 20 μm.   The light alloy wheel according to any one of claims 8 to 10, wherein an average particle diameter excluding a recrystallized portion of the metal crystal particles of the inner rim portion based on a cutting method based on JIS-H0542 is 20 µm or less. It is a manufacturing method of the wheel made from a light alloy forged using the forge billet obtained by the manufacturing method of the forge billet as described in any one of Claims 3-6,
A light alloy wheel manufacturing method for forming an outer rim portion and an inner rim portion by an extrusion method.   A pre-wheel is forged using the forged billet obtained by the method for producing a forged billet according to any one of claims 3 to 6, and a disk portion pattern is machined by a milling machine including a lathe or a machining center. A light alloy wheel manufacturing method. A forged billet obtained by the method for producing a forged billet according to any one of claims 3 to 6 is forged with a die to form a pre-rim portion, and the pre-rim portion is spun to form an inner rim portion. A light alloy wheel manufacturing method comprising:
A method of manufacturing a light alloy wheel in which the spinning process is performed by pressing with a rolling roller from an oblique direction in a state where a gap is provided between the pre-rim part and a mold, and the inner rim part is formed.

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