JP2009084698A - Molding production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method by which a molding having a preferable structural state is produced using a 6,000 series aluminum alloy as the stock. <P>SOLUTION: The molding production method includes: a step of applying homogenizing treatment to a round rod obtained by casting 6,000 series aluminum alloy by a continuous casting method; a step of performing hot plastic working using the homogenizing-treated round rod as the stock to mold a shape stock; and steps of performing heat treatment including solution treatment after the plastic working, wherein the aluminum alloy has the components of, by mass, 0.3 to 1.0% Si, 0.2 to 0.6% Cu, 0.8 to 1.5% Mg, 0.05 to 0.5% Cr, 0.05 to 0.15% Mn and 0.18 to 0.40% Fe, and the balance Al with inevitable impurities, and temperature conditions that the temperature in the homogenizing treatment is 450 to 500°C and the stock temperature upon the hot plastic working is 460 to 530°C are satisfied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a molded product obtained by molding an aluminum alloy by plastic working to obtain a molded product and its production line. For example, the present invention relates to various vehicles such as automobiles, two-wheeled vehicles, and railway vehicles. The present invention relates to a method for producing a molded article made of an aluminum alloy, such as a universal joint yoke used.

  For automobile parts, iron-based materials have been exclusively used, but they are increasingly replaced with aluminum materials or aluminum alloy materials mainly for weight reduction. In these automobile parts, excellent corrosion resistance, high strength, and excellent workability are required. Therefore, an Al—Mg—Si based alloy called 6000 series alloy, particularly A6061, is frequently used as an aluminum alloy material. . Such automobile parts are manufactured by forging, which is one of plastic working, using an aluminum alloy material as a processing material in order to improve strength.

  In recent years, since it is necessary to reduce costs, suspension parts obtained by forging a cast member directly as a raw material without being extruded and then processed by T6 have begun to be put to practical use. In addition, development of a high-strength alloy that replaces the conventional A6061 alloy is underway (see, for example, Patent Documents 1, 2, and 3 below).

  These A6061 alloys and other high-strength alloys of Al-Mg-Si-based alloys cannot obtain sufficient high strength due to recrystallized processing structure and generation of coarse crystal grains in the forging and heat treatment processes. There was a problem. Therefore, as in Patent Documents 1 and 2, there are many examples in which recrystallization is prevented by adding Zr (zirconium) to prevent coarse recrystallization grains.

However, although the addition of Zr is effective in preventing recrystallization, it has the following problems.
(A) By adding Zr, the grain refinement effect of the Al-Ti (titanium) -B (boron) -based alloy is weakened, the crystal grains of the ingot itself become coarse, and conversely the processed product after plastic working It often causes a decrease in strength.
(B) Since the crystal grain refining effect of the ingot itself is weakened, ingot cracking easily occurs, internal defects increase, and yield deteriorates.
(C) Zr forms a compound with an Al-Ti-B alloy, and the compound is deposited on the bottom of the furnace storing molten alloy, contaminating the furnace, and these compounds are also in the ingot produced. Crystallizes coarsely to reduce the strength.
For this reason, although the addition of Zr is effective, it is difficult to maintain the stability of the strength, the quality of the product becomes unstable, and the material cost is increased.

  In addition, such an Al alloy forging material is disclosed in, for example, the following publications (1) to (4). In these publications, various Al alloy forging materials improved for the purpose of further improving the mechanical strength, toughness, etc. of automobile shock-absorbing members manufactured by hot forging cast bars without extrusion are proposed. (See Patent Documents 4, 5, and 6 below).

  (1) In Patent Document 4, Si: 0.6-3.0%, Mg: 0.2-2.0%, Cu: 0.3-1.0%, Ti: 0.01-0. 1%, B: 0.0001-0.01%, Mn: 0.1-0.5%, Cr: 0.1-0.5% and Fe: 0.05-0.5%, and After casting an Al alloy designed so that the Mg2Si amount converted from the alloy design value is 1.5% or more, or 0.5% or more, at a cooling rate of 200 ° C./second or less, it is set to 10 to 50%. An Al alloy forging material configured by forging at a filling rate is disclosed.

  (2) In Patent Document 5, Mg: 0.8 to 1.2 wt%, Si: 0.7 to 1.0 wt%, Cu: 0.3 to 0.6 wt%, Mn: 0.15 to 0. As a structure containing 3 wt%, Fe and Cr in total of 0.7 wt% or less, a dendrite secondary arm interval (DAS) of 40 μm or less, and an average grain size of crystallized material of 8 μm or less A constructed Al alloy forging material is disclosed.

  (3) Patent Document 6 includes Mg: 0.6 to 1.6%, Si: 0.6 to 1.8%, Cu: 0.05 to 1.0%, and Fe of 0.03. %, Including one or more of Mn: 0.15 to 0.6%, Cr: 0.1 to 0.2%, Zr: 0.05 to 0.2%, and hydrogen : 0.25 cc / 100 g Al or less, a material composed of the balance Al and inevitable impurities is cast at a cooling rate of 10 ° C./second or more, homogenized at 530 to 600 ° C., and then hot forged. As a forging material, the total area ratio of crystallized materials in the Mg2Si and Al-Fe-Si- (Mn, Cr, Zr) system in the Al alloy structure in this forging material is configured to be 1.5% or less per unit area. A forged Al alloy material is disclosed.

  These conventional methods for producing aluminum alloy forging materials disclosed in Patent Documents 4, 5, and 6 include a step of preparing an Al alloy molten metal by an ordinary melting method, followed by continuous casting of the Al alloy molten metal. Casting, while cooling at a cooling rate not within the range defined by the present invention by any of the so-called continuous casting methods such as the hot casting method, the semi-continuous casting method (DC casting method) and the hot top casting method. The process consisted of a process for producing an ingot of the alloy and a process for homogenizing the aluminum alloy crystal by subjecting the ingot to a homogenization heat treatment. In addition, an aluminum alloy forging material will be manufactured by forging to Al alloy forging raw material (the said ingot), and also performing T6 process.

  (4) On the other hand, in the following Patent Document 7, as a method for producing an Al alloy forging material that omits the homogenization heat treatment, Mg: 0.6-1.2%, Si: 0.6- 1.5%, Cu: 0.3-1.1%, Ti: 0.005-0.1%, B: 0.0001-0.004% one or two, Mn : Al alloy containing one or more of 0.2 to 0.8%, Cr: 0.05 to 0.3%, Zr: 0.05 to 0.25%, and the remainder consisting of Al and inevitable impurities The ingot is subjected to extrusion processing at a temperature of 450 to 520 ° C. without being subjected to a homogenization heat treatment before extrusion processing, and this extruded material is subjected to a precipitation treatment at a temperature of 490 to 570 ° C. for 1 hour or more. A forged Al alloy material is disclosed.

  (5) In Patent Document 8 below, Mg is 0.8 wt% to 1.2 wt%, Si is 0.7 wt% to 1.0 wt%, Cu is 0.3 wt% to 0.6 wt%, and Mn is 0.14 wt% to 0.3 wt%, Cr 0.14 wt% to 0.3 wt%, Fe 0.5 wt% or less, Ti 0.01 wt% to 0.15 wt%, and B 0.0001 wt% to 0 An aluminum alloy ingot for plastic working having a structure containing 0.03 wt%, having an average grain size of 8 μm or less, a dendrite secondary arm interval of 40 μm or less, and a crystal grain size of 300 μm or less, A method for producing an aluminum alloy ingot for plastic working that continuously casts an ingot, casting at a casting temperature of (750 ± 50) ° C., casting speed of (240 ± 50) mm / min, and homogenizing after casting Do not give this casting There is a disclosure of [430 + plastic working rate (%)] when heated to 550 ° C. or lower and solution treatment at 520 ° C. to 550 ° C. when performing plastic processing on the lump.

(6) Further, in Patent Document 9 below, a continuous casting method including a semi-continuous casting method of an aluminum alloy having a component standard of a JIS 6000 series alloy in which the Ti content is regulated to 0.01 to 0.1% by mass. Is cast at a cooling rate of 10 ° C./second or more to form an ingot, and a forging material is obtained without subjecting the ingot to a homogenization heat treatment and without undergoing extrusion processing. There is a disclosure that a manufacturing method of an aluminum alloy forging material and that the forging material has an average value of dendrite arm spacing calculated using an intersection method at the center of a cross section of 23 μm or less.
Japanese Patent Laid-Open No. 5-59477 JP-A-5-247574 JP-A-6-256880 JP-A-8-3675 JP-A-6-256880 Japanese Patent Application No. 11-2224024 JP-A-7-150312 JP 2002-294383 A JP 2002-254143 A

  There is a universal joint yoke (hereinafter sometimes referred to as a yoke) as a molded article having a bottomed thin cylindrical portion and a convex portion extending to the opposite side of the bottom cylindrical shape.

  In the case of yokes, there is a cold forging method as a conventional technique. In the case of cold forging, unlike hot forging, the solution treatment is performed with a sufficient amount of processing strain remaining, so a molded product with a fine structure. Can be obtained. However, since the burden on the mold is large, the mold life is shortened, resulting in low productivity and high cost. In order to reduce the burden on the mold, it was necessary to add extra space to the molded product or to perform molding in two steps. Thus, a highly productive manufacturing method has been required.

  On the other hand, each of the above-mentioned patent documents 1 to 9 discloses the composition of the aluminum alloy, the temperature of the homogenization treatment, the material temperature during hot plastic working, and the temperature of the solution treatment for obtaining mechanical strength. Yes. However, in actual production, temperature control considering heat removal from the mold according to the shape of the molded product, setting of conditions to reduce the temperature difference for each product part, and processing rate due to back pressure load Although it is necessary to suppress non-uniformity, those specific conditions are not shown.

  Particularly in the case of a molded product having a thick part (ear part (pin boss part) in the yoke) and a thin part (cup part (cylindrical part) in the yoke), the processing rate is large between the thick part and the thin part. Will be different. As a result, a cooling difference due to a difference in heat extraction from the mold and a heating difference due to a processing heat generation difference are induced, and as a result, a temperature difference between the parts occurs. For this reason, it has been difficult to make a molded article into a preferable fine structure state only by the technique based on the material composition that has been effective in the conventional hot working such as rolling and extrusion and the conventional technique based on the heat treatment temperature. In the conventional method, coarse recrystallization occurs, and it is difficult to obtain a product having a homogeneous fine structure.

  For this reason, at present, the design has been designed with safety in mind, for example, by designing the whole to be thick so as to have a preferable strength even in an insufficient microstructure.

  There has been a demand for a production method for obtaining a preferable microstructure state that can sufficiently exhibit the strength potential of the material.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the molded article which manufactures the molded article which has a preferable structure | tissue state.

  The present inventor has conducted intensive research on the relationship between forging formability and product shape, and has completed the present invention based on the findings.

  As a result of examining the relationship between the molding conditions and the state of the metal flow to the cup part and the microstructure, a molded article having a preferable microstructure is controlled by controlling the heat treatment temperature and the forging material temperature according to the shape of the molded article. Succeeded in getting. The mechanism is estimated as follows. The homogenization temperature is preferably low. In particular, when Fe and Mn are added, the addition effect is reduced at a high temperature, for example, at 560 ° C. or higher. The forging temperature must be controlled for the purpose of releasing residual strain. The solution temperature is preferably low because it acts in the direction of promoting particle coarsening due to residual strain. Moreover, the lower one is good also from the point of bond growth of fine grains. Therefore, when the forging (forging material) temperature is low and the solution temperature is high, the particles are likely to become coarse.

In order to solve the above-mentioned problems, the present invention provides a step of homogenizing a round bar obtained by casting an alloy made of a 6000 series aluminum alloy by a continuous casting method, and performing hot plastic working using the homogenized material as a raw material. In a method for producing a molded article including a step of forming a raw material, and a step of heat treatment including solution treatment after plastic working, the component of the 6000 series aluminum alloy is 0.3% to 1.0% by mass%. Si, 0.2% to 0.6% Cu, 0.8% to 1.5% Mg, 0.05% to 0.5% Cr, 0.05% to 0.15% Mn, Fe of 0.18% to 0.40%, the balance being Al and inevitable impurities, the temperature of homogenization treatment is 450 ° C to 500 ° C, and the material temperature during hot plastic working is 460 ° C to 530 ° C A method for producing a molded product characterized by satisfying a temperature condition A.
In addition, 1) the first invention for solving the above problems is a process of homogenizing a round bar made of an alloy made of a 6000 series aluminum alloy by a continuous casting method. In a method of manufacturing a molded article including a step of forming a shaped material by hot plastic working and a heat treatment including solution treatment after plastic working, the temperature of the homogenization treatment is 450 ° C. to 500 ° C. or hot plastic working The material temperature at the time satisfies the temperature condition of 460 ° C to 530 ° C.

  2) A second invention for solving the above-mentioned problems is the method for producing a molded article according to 1), wherein the temperature of the solution treatment satisfies 430 ° C. to 530 ° C.

  3) A third invention for solving the above problems is a process of homogenizing a round bar made of an alloy made of a 6000 series aluminum alloy by a continuous casting method. The temperature of homogenization treatment in the manufacturing method of a molded article including the step of forming a shaped material by plastic working, the step of heat treatment including solution treatment after plastic working, and the step of machining and surface treatment of the shaped material. Is a method for producing a molded product, wherein the material temperature is 450 ° C. to 500 ° C., the material temperature during hot plastic working is 460 ° C. to 530 ° C., and the temperature of the solution treatment is 430 ° C. to 530 ° C.

  4) A fourth invention for solving the above-mentioned problem is that the composition of a 6000 series aluminum alloy is 0.3% to 1.0% Si, 0.2% to 0.6% Cu in mass%, 0.8% to 1.5% Mg, 0.05% to 0.5% Cr, 0.05% to 0.15% Mn, 0.18% to 0.40% Fe, and the balance Is a method for producing a molded product according to any one of 1) to 3), wherein Al is an unavoidable impurity.

  5) A fifth invention for solving the above-mentioned problems is characterized in that the molded product has a bottomed thin cylindrical portion and a convex portion extending to the opposite side of the bottom cylindrical shape. The method for producing a molded article according to any one of items 4) to 4).

  6) A sixth invention for solving the above-mentioned problem is a forging process in which the hot plastic working uses an upper die of a lower die, and the back of the tip is formed when the cylindrical portion is formed by the lower die. In any one of 1) to 5), forging is performed by applying pressure, and the back pressure condition is an initial back pressure of 5 to 20 MPa and a stroke end back pressure of 10% to 180% of the initial back pressure. It is a manufacturing method of the described molded article.

  7) A seventh invention for solving the above-mentioned problems is the method for producing a molded article according to 6), wherein forging is performed at a mold temperature of a lower mold of 150 ° C to 350 ° C.

  8) An eighth invention for solving the above-mentioned problems is the method for manufacturing a molded product according to any one of 1) to 7), wherein the molded product is a universal joint yoke.

  9) A ninth invention for solving the above-described problem is a homogenization heat treatment apparatus for performing a homogenization treatment or a hot plastic working, which is used in the method for manufacturing a molded article according to any one of 1) to 8). It is a production line including at least a material heating device that heats the shaped material.

  Since the production method of the present invention is a production method that satisfies the temperature conditions of a homogenization temperature of 450 ° C. to 500 ° C. or a material temperature of 460 ° C. to 530 ° C. during hot plastic working, a uniform fine structure It is possible to manufacture a molded product having high strength and high strength with high productivity.

  The mechanism is that the transition metal element that becomes the recrystallization nucleus of the material is not coarsely precipitated and can be made into a material with a fine uniform distribution, or the residual strain scattered during hot plastic working is a solution. This is presumably because coarse recrystallization nuclei can be formed at the time of the temperature increase, but since the material temperature is a high temperature of 460 ° C. or higher, residual strain is released and coarse recrystallization can be prevented.

  An example of an embodiment of the present invention will be described.

  FIG. 2 shows an example of a universal joint yoke as an example of a molded product after machining the base material. The universal joint yoke includes at least a joint (cup-shaped portion) (95) to the shaft, a pin boss portion (43), pin holes (94a, 94b), and a plate portion (42). Each part is further processed into a final product by machining as necessary.

  FIG. 1 shows an example of a universal joint yoke body according to the present invention. The base material is composed of at least a joint (cup-shaped part) (41) to the shaft, a pin boss part (43), and a plate part (42).

  FIGS. 3A and 3B are schematic views of another example of the universal joint yoke element used for the propeller shaft. The universal joint yoke element 10 includes a cylindrical portion 11, a bottom 12 that closes one end of the cylindrical portion 11, and two pin boss portions 13 that extend opposite to the cylindrical portion 11 of the bottom 12. Has been. The cup-shaped part (bottomed cylindrical part) is composed of a cylindrical part 11 and a bottom 12 and functions as a connection part.

  An example of the configuration of the universal John yoke of the present invention and a powertrain system incorporating the universal yoke will be described with reference to FIG. Reference numerals 112a, 112b, and 112c are yokes, and as shown in FIG. 2, the yoke has pin holes (94a and 94b) that serve as connecting portions with a cross shaft provided by machining in the pin boss portion (43). Yes. The pin holes are connected to a pair of yokes via cross shafts (113a, 113b, 113c). On the other hand, the cup-shaped portion (95) is finished by machining to match the diameter of the shafts (114a, 114b), and MIG (Metal Inert Gas arc welding), TIG (Tungsten) It is fixed to the shaft (114a, 114b) by welding such as Inert Gas arc welding), friction welding, friction stir welding or the like.

  In the universal joint yoke and its shape member, reference numerals 41 and 11 correspond to thin cylindrical portions having a bottom, and reference numerals 43 and 13 correspond to convex portions extending to the opposite side of the cylindrical shape of the bottom portion. The universal joint yoke and its shaped material are molded products having a thick part (ear part (pin boss part)) and a thin part (cup-shaped part (cylindrical part)).

  A process of subjecting a round bar, which is an alloy made of a 6000 series aluminum alloy included in the present invention, by a continuous casting method to homogenization will be described.

  First, a molten aluminum alloy is prepared, and the molten aluminum alloy is cast by any one of so-called continuous casting methods such as a continuous casting method, a semi-continuous casting method (DC casting method), and a hot top casting method. Get a bar.

  There is no particular limitation as long as it is a continuously cast round bar material, but it is preferable that a transition metal element contained in a trace amount is finely and uniformly precipitated in the structure of the continuous cast bar. For example, it can be realized by increasing the molten metal temperature under casting conditions, for example, 700 ° C. or more, or by reducing the casting diameter to φ90 or less.

  The alloy composition of the cast continuous cast bar (round bar) was 0.3% to 1.0% Si, 0.2% to 0.6% Cu, 0.8% to 1.% by mass. It is preferable that 5% Mg, 0.05% to 0.5% Cr, 0.05% to 0.15% Mn, 0.18% to 0.40% Fe and the balance are Al and inevitable impurities.

  Fe serves as fine recrystallization nuclei, prevents coarse recrystallization, and has a function of forming a fine and uniform structure. Therefore, the effect of addition of a small amount on corrosion resistance is reduced, which is preferable from the viewpoint of balance between strength and corrosion resistance. More preferably, it is 0.2 mass%-0.3 mass%.

  Mn serves as a fine recrystallized nucleus and has the effect of preventing coarse recrystallization and forming a fine and uniform structure. Therefore, the addition of a small amount has less influence on the corrosion resistance, and is preferable from the viewpoint of the balance between strength and corrosion resistance. More preferably, it is 0.06 mass%-0.1 mass%.

  It is preferable to manage the total amount of Fe and Mn, for example, 0.23 to 0.55% by mass.

  Thereafter, the ingot is subjected to homogenization heat treatment to homogenize the aluminum alloy crystal. In the present invention, the homogenization temperature (atmosphere temperature) is 450 ° C. to 500 ° C. (preferably 460 ° C. to 480 ° C.). Within this range, the effect of homogenizing segregation during casting can be obtained, and the transition metal element that becomes a recrystallization nucleus does not become coarse, which is preferable from the viewpoint of preventing coarse recrystallization. If it is less than this range, it becomes difficult to obtain the effect of homogenizing segregation during casting, and if it exceeds this range, the precipitation of transition metal elements becomes coarse, and the effect of preventing coarse recrystallization becomes small. In particular, when Fe and Mn are added, this range is preferable in order to obtain a higher effect.

  The holding time is preferably 5 to 8 hours.

  The homogenized round bar is cut into a predetermined length as necessary. At this time, it is preferable to cut the material while cooling so that the material is not overheated because the homogenized state can be maintained.

  Next, a step of forming a shaped material by hot plastic working using a homogenized material included in the present invention will be described.

  An example of the structure of the forging apparatus used for the forging process which is an example of the plastic working of this invention is demonstrated based on FIG.

  The forging device includes a forging machine (221), an upper mold (103), and a lower mold (105). A gas cushion (300) is built in the lower mold as an example of back pressure generating means. The lower die is provided with a knockout pin (107) for discharging a forged product. Reference numeral 108 denotes a spray moving device, reference numeral 109 denotes a spray rotating device, and reference numeral 110 denotes a spray shaft. The spray nozzle (104) is attached by a spray rotating device and a spray moving device via a spray shaft, and discharges the lubricant in a spray form to apply the lubricant to the mold.

  The forging die of the present invention will be described in detail.

  FIG. 6 shows a schematic cross-sectional view of an example of an upper mold and a lower mold used in the manufacturing method of the present invention. The lower mold has a back pressure and a center bush (203) that forms the inside of the cup-shaped portion, a lower mold (201) that forms the outside, a ring knock (67) that forms the cup-shaped tip while applying back pressure. As a means for generating, a gas cushion, a lower pressure receiving plate (204), a knockout pin (107), a lower bolster (205) for supporting these, an upper bolster (211) for supporting a punch (202) as an upper mold, etc. It is composed of As the gas cushion, for example, one constituted by a pneumatic cylinder pressure transmission shaft (68), a pneumatic cylinder (71), and a pneumatic cylinder gas sealing part (72) can be used. The ring knock receives the back pressure generated from the pneumatic cylinder via the pneumatic cylinder pressure transmission shaft. For this reason, the ring knock can be moved rearward relative to the upper mold by receiving a force larger than the pneumatic cylinder pressure.

  It is also possible to adopt a structure in which a knockout pin is incorporated in the ring knock.

  Due to the back pressure generated from the pneumatic cylinder, it is preferable that the front end of the ring knock is on the same plane as the front end of the center bush (203) forming the cup inner diameter portion or a position protruding from the front before the start of molding. This is because the expected back pressure effect cannot be obtained sufficiently when the tip of the ring knock enters the tip of the center bush (203).

  It is preferable that the internal pressure of the pneumatic cylinder or the number of cylinders is adjusted so that the back pressure from the pneumatic cylinder applied to the ring knock is an initial back pressure of 5 to 20 MPa.

  A gas cushion, which is an example of means for generating back pressure, is built in the lower mold. Furthermore, in the mold configuration of the present invention, the gas cushion is disposed with the lower pressure receiving plate as a fixed end, and transmits the stress to the ring knock via the pressure transmission shaft. Examples of the pressure transmission shaft include a knock pin and a top in addition to the pneumatic cylinder pressure transmission shaft.

  The means for generating the back pressure only needs to have a function of generating pressure over the entire length of the stroke in which the mold moves during molding.

  When the gas cushion is used as the back pressure generating means, a sufficient back pressure can be obtained without receiving pressure supply from the outside, so that it can be incorporated in the mold. As a result, the generator attached to the press machine can be omitted, and a die set having a dedicated pressure transmission pipe is not necessary, so that it can be easily attached to a general-purpose press and a die set.

  It is preferable to use a gas cushion as a device for generating back pressure because it has excellent durability against repeated expansion and contraction and has a wide variety of sizes and stroke lengths, which can be selected according to the application.

  Examples of the material of the ring knock include die steel and powdered high-speed steel. Other examples of the material constituting the mold include die steel, powdered high-speed steel, and cemented carbide. In order to ensure the sliding between the ring knock and the lower mold 201 or the center bush 203 of the lower mold, each surface of the mold on which the ring knock slides, for example, the inner diameter and the outer diameter of the cup-shaped portion are formed. It is preferable to perform nitriding treatment, molybdenum coating treatment, etc. on the surface of each mold. The gap between the ring knock and the lower mold 201 or the center bush 203 of the lower mold is preferably about 0.05 to 0.3 mm. Less than 0.05mm, it is difficult to slide and difficult to apply lubricant. If it is 0.3 mm or more, sliding and lubricant application are good, but gap burrs that need to be removed are generated.

  The operation of the molding process will be described.

  The forging material is put into the lower mold. The upper mold is lowered, and the material is sandwiched in the closed space formed by the lower mold and the upper mold. In the initial state of molding, plastic flow of the material mainly to the pin boss occurs, and since the back pressure from the pneumatic cylinder is applied to the ring knock of the lower mold, the plastic flow of the material to the cup is suppressed. The At this time, an initial back pressure of 5 to 20 Mpa is applied to the tip of the cup-shaped molded part via a ring knock.

  As the material filling the pin boss shape progresses, the ring knock moves backward. At this time, the pressure of the pneumatic cylinder balances the molding load (upper die lowering direction pressure) and the pressure, while the ring knock advances in the moving direction of the upper die while applying the back pressure to the material. At the stroke end, the back pressure is preferably 10% to 180% (more preferably 50 to 110%) of the initial back pressure.

  In the case of back pressure by a pneumatic cylinder, the initial pressure when the ring knock comes into contact with the material and starts to be loaded can be set by the internal pressure. Thereafter, the internal pressure increases due to the contraction of the cylinder, and the load pressure increases toward the end of the stroke of the cylinder. As the pressure increases, the height of the cup end can be adjusted uniformly, which is preferable.

  The position of the stroke end of the cylinder of the back pressure generator is preferably set so that the cylinder does not fully contract even at the bottom dead center of the press. This is because there is no risk of damaging the cylinder.

  When the filling of the material is completed and the molding is completed, when the upper die is raised, the tip of the forged product cup is pushed up through the ring knock by the pressure from the pneumatic cylinder provided in the lower die at the same time. The forged product comes off from the lower die. A ring knock having a mechanism for generating back pressure also has a function of discharging a molded product.

  After the upper mold is raised, the knock pin is further raised from the lower part of the lower mold, the forged product is pushed up to the upper surface of the lower mold, and the forged product is discharged out of the mold.

  An embodiment will be described in which the initial back pressure is increased to increase the filling ratio of the pin boss portion, and then molding is performed with a back pressure lower than the initial pressure. Since the initial back pressure is increased and the filling ratio of the pin boss is increased, molding is performed at a lower back pressure than the initial pressure, so the molding load during molding of the cup can be reduced, and as a result, the mold life is improved. Is preferable.

  As an example, an embodiment using a hydraulic cushion as a back pressure generating means will be described. For example, the hydraulic cushion may have the same configuration as the air cylinder described above, and may be oil-filled instead of air.

  In this case, it is preferable that the initial value of the back pressure is 5 to 20 MPa, and then a value lower than the initial value, for example, 1.2 to 5 MPa.

  If the back pressure is due to hydraulic pressure, the back pressure is high when the ring knock comes into contact with the material and the load starts to be applied (when the hydraulic cylinder starts to shrink), and then the back pressure depends on the stroke length of the hydraulic cylinder. Since the pressure is not affected, a predetermined pressure can be applied from the beginning of shrinkage to the end of molding, so that the molding ability is increased. For example, the setting so that the ring knock does not fall until the filling on the pin boss side is completely completed is possible (for example, preferably it does not drop until the filling rate is 90% or more), and the pin boss side lack of thickness is less likely to occur. Because the ring knock descends at a constant pressure, irregularities in the cup do not occur.

  It is preferable to add hydraulic control so that the pressure setting can be changed for each product. For example, it is possible to control the pressure of the external hydraulic unit with a molding slide signal, or to simply adjust the pressure with a pressure reducing valve using a hydraulic cylinder with the same pressure setting.

  By combining with the back pressure generating means described above, the pressure pattern can be changed, and the load pattern required for each product can be selected.

  It is preferable to use a hydraulic cushion as a device for generating the back pressure because an initial pressure higher than the oil filling pressure can be generated due to the flow resistance of the oil. Further, it is preferable because it has excellent durability against repeated expansion and contraction and has a wide variety of sizes and cushion stroke lengths, and can be selected according to the application. It is preferable because it is small and easy to place in the mold.

  This mold is used to forge the shape of the universal joint yoke, and the back pressure is applied to the upper mold, the lower mold, the ring knock, the knockout pin, and the ring knock that form a closed space. Forging die including a pressure receiving plate for disposing a means for generating a forging machine, when the stroke of the forging machine is short, the interval between the die sets is narrow, and a conventional large-scale back pressure device cannot be arranged It can also be applied to. Moreover, since it can be applied to a small forging device, the equipment cost can be reduced.

  The mold according to the present invention has a small back pressure generating mechanism and is built in the lower mold. Therefore, the conventional die set is used as it is, and only the mold is replaced with the above-described mold. In addition, a forged product having a uniform cup-shaped portion can be obtained by a mechanism that applies a stress opposite to the main molding direction.

  Next, an embodiment of the yoke manufacturing method of the present invention using the apparatus of FIG. 5 will be described.

  The manufacturing method of the present invention includes a step of casting an alloy made of an aluminum alloy into a round bar by a continuous casting method, a step of homogenizing the round bar, a step of cutting the round bar material into a predetermined length, A step of applying a lubricant to the material, a step of preheating the material to a predetermined temperature, a step of feeding the material into a forging device, a step of applying a lubricant to a mold, and a step of forging the material. The manufacturing method includes a step of discharging a forged product (yoke blank) by a knockout mechanism, a heat treatment step, and a step of machining the forged product.

  The step of obtaining the material for upsetting forging by cutting the round bar may be provided after the cutting step.

  In the present invention, the material is heated to 460 ° C. to 530 ° C. (preferably 480 ° C. to 510 ° C.) at the time of upsetting which is a part of plastic working. If it is less than this range, processing strain that causes coarse recrystallization remains even after molding, and a coarse recrystallized structure is formed during solution formation, which may reduce the strength. If this range is exceeded, there is a concern that local melting will occur at a site with a high processing rate due to heat generated by plastic processing, and if local melting occurs, there is a risk of strength reduction.

  In the present invention, by controlling the temperature management as described above, it is possible to control the microstructure of the molded product and manufacture a product having favorable mechanical strength.

  The forging material is put into the lower die of the forging device in which the aforementioned die is arranged. For example, a material obtained by cutting a continuous casting rod into a predetermined length can be used. For example, the material is subjected to a bonding treatment as a material lubrication and a lubricant coating treatment by immersion in a graphite-based aqueous lubricant as necessary. Bonding is preferable from the viewpoint of preventing lubrication loss when molding is carried out at a high plastic working rate that is strongly plastically processed and an aluminum ground inside the material is formed on the surface layer and a new surface having a silver metallic luster is generated. When the outer diameter of the product is as large as 90 mm or more, a preforming material whose diameter has been increased by upsetting in advance can be used.

  In the present invention, the raw material is heated to 460 ° C. to 530 ° C. (preferably 480 ° C. to 510 ° C.) when it is put into a die during forging, which is a part of plastic working. If it is less than this range, deformation resistance of the material will be large, leading to defects such as lack of product shape, residual strain that causes coarse recrystallization will remain, and after solution treatment will result in a coarse recrystallized structure, leading to strength reduction. If the range is exceeded, local melting occurs due to plastic processing heat generation, which leads to strength reduction.

  When the raw material is charged after being heated by the preheating device, it is preferable to manage the charging time to the die after heating within 20 seconds or so that the temperature does not decrease so that the material temperature does not decrease.

  In particular, in the case of a molded product with a thin cylindrical shape such as a yoke, in order to maintain a balance between the fluidity of the material and the back pressure, the temperature setting is increased in anticipation of the temperature decrease of the material, or the temperature inside the material. In order to make the distribution uniform, it is preferable to add control during heating, such as providing a holding time.

  Apply lubricant to mold. Examples of the lubricant to be used include an aqueous graphite lubricant and an oily graphite lubricant. Since the lubricant is applied to the mold in a state in which the ring knock of the upper mold is housed in the mold, an oily graphite lubricant is more preferable due to the permeability to the gap. The amount of lubricant applied to the mold is preferably 1 g to 10 g (concentration is 0.5 to 25% by mass).

  Next, the forging process will be described.

  First, main forging is performed. The upper die is lowered and restrained between the upper and lower dies, and the material first flows into the pin boss shape portion carved into the lower die, and the approximate shape of the pin boss portion is formed. At this stage, the material flow mainly occurs in the pin boss portion, and the material flow to the cup portion hardly occurs because the pressure from the pneumatic cylinder is applied to the ring knock on the cup portion on the lower mold side. At this stage, the details of the pin boss are not full.

  Furthermore, the upper mold continues to descend after fitting into the inner diameter part of the lower mold, and the filling of the pin boss part is completed. At this position, the molding load exceeds the pressure of the pneumatic cylinder provided in the lower mold, the ring knock descends, the material flow to the cup portion occurs, and the cup portion is also filled with metal.

  Forging conditions can be optimized according to the product shape. For example, the press speed is 10 to 40 spm and the press load is 120 to 450 tons.

  In the present invention, it is important to control the mold temperature, and the temperature is maintained at, for example, 150 ° C to 350 ° C. In particular, in the thin cylindrical portion, the temperature is preferably in the range of 200 ° C. to 300 ° C. so that the thin cylindrical portion does not have a coarse recrystallized structure. The thin cylindrical part has a large plastic working rate, and the corresponding residual strain increases. If the temperature of this part decreases during plastic working due to heat removal from the mold, the residual strain that becomes the core of coarse recrystallization remains. Is completed. For this reason, it is necessary to dispose the mold heater in the vicinity of the portion where the thin cylindrical portion is molded, and to control the mold temperature so as to minimize the heat removal from the product to the mold. If the mold temperature becomes too high (over 350 ° C), the mold life will be shortened due to a decrease in the strength of the mold itself, the lubricant applied to the mold will be repelled, and the material will stick to the mold. cause.

  In the construction method using back pressure, if the mold temperature and the forging material temperature are set too high, the strength of the material may be lowered, and the thin cup portion may be deformed by the back pressure. In addition, the mold surface and the material surface are in close contact with each other, and there is a risk of occurrence of seizure defects. From such a viewpoint, the combination of (back pressure, mold temperature, material temperature) is preferably controlled as a set.

  After the forging is completed, the forged product is discharged with a knockout pin.

  The forged product is preferably heat treated. The heat treatment is aimed at improving the mechanical strength of the forged material, and the conditions are a solution treatment temperature (atmosphere temperature) of 430 ° C. to 530 ° C. (preferably 510 ° C. to 530 ° C.), Hold for 1 to 5 hours and immediately immerse in a refrigerant bath (for example, water temperature of 10 to 70 ° C.). When the solution temperature is less than this range, solid solution strengthening elements such as Cu due to solution cannot be sufficiently dissolved, and the hardness after aging treatment becomes insufficient. During holding, finely recrystallized crystal grains once bond and grow to form a coarse recrystallized structure, resulting in a decrease in strength. Examples of the refrigerant include cold water, hot water, oil, and water with an additive (such as ethylene glycol). Water is preferable because it is inexpensive, has a high cooling capacity, and is rapidly cooled.

  An example of a production line that realizes the above manufacturing process is shown in FIG.

  In FIG. 7, the forged product production system includes a continuous casting apparatus 81 that casts a continuous casting rod from a molten metal and cuts it to a predetermined length, and heat treatment (homogenization) on the continuous casting rod cast by the continuous casting apparatus 81. Heat treatment device (homogenization heat treatment device) 82 for performing the treatment), a straightening device 83 for correcting the bending of the continuous cast bar that is bent by the heat treatment device 82, and the straightening device 83 corrects the bending. The peeling device 84 for removing the outer peripheral portion of the continuous cast bar, and the cutting device 85 for cutting the continuous cast bar from which the outer peripheral portion has been removed by the peeling device 84 into a cut piece having a length necessary for forging the product. A pre-lubricating device 86 for pre-heating the cut piece cut by the cutting device 85 and adhering a water-soluble lubricant that is easy to become familiar with the cut piece; and a lubricant heated by the pre-heating device 87. A forging device 88 forging a forged product (original material) from the cut pieces, a solution heating device 89 for subjecting the forged product forged by the forging device 88 to a solution treatment, and heating by the solution heating device 89 A quenching device 90 for quenching the forged product and an aging treatment device 91 for subjecting the forged product quenched with the quenching device 90 to an aging treatment. The peeling device 84 can be omitted. Moreover, the conveyance between each apparatus can be performed by an automatic conveyance apparatus.

  Here, the heat processing apparatus 82 has a function which makes material temperature 450 to 500 degreeC. The preheating device 87 has a function of setting the material temperature to 460 ° C to 530 ° C. The solution heating apparatus 89 has a function of setting the raw material temperature to 430 ° C. to 530 ° C.

  The forging device 88 has the above-described back pressure application function.

  The production line of the present invention is a process of homogenizing a round bar made of an alloy made of 6000 series aluminum alloy by a continuous casting method, and forming a shaped material by hot plastic working using the homogenized material as a raw material. And a heat treatment including a solution treatment after plastic working, wherein the temperature of the homogenization treatment is 450 ° C. to 500 ° C. or the material temperature during hot plastic working is 460 ° C. Since the temperature control that satisfies the temperature condition of 530 ° C. is performed and the molded product is consistently manufactured including the respective heat treatment steps from the casting process, the molded product having a preferable fine structure can be stably manufactured.

  Forged products that have undergone the heat treatment process are finished by drilling the pin holes by machining using a machining center, and machining the attachment to the shaft by an NC lathe machine to finish the final product yoke.

  Although the case of forging as plastic working has been described, the production method of the present invention can be rolled as long as it satisfies the conditions of homogenization temperature, material temperature during hot plastic working, and solution treatment temperature. It can also be an extrusion process. In any case, the transition metal element that becomes the fine recrystallization nucleus at the time of solution treatment is maintained in a finely precipitated state, and the processing strain that becomes the coarse recrystallization nucleus at the time of plastic working can be recovered, and the crystal grains at the time of solution treatment can be recovered. This is because growth can be suppressed, and as a result, a coarse recrystallized structure can be prevented.

  As an example of the molded product, the yoke has been described, but if it is a molded product having a bottomed thin cylindrical part, a convex part extending to the opposite side of the cylindrical part of the bottom, the object of the present invention is For example, the case of a hydraulic cylinder or a damper can be mentioned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

3 was produced using the forging device shown in FIG.
<Production conditions>

  A round bar material of φ85 mm was cast by a hot top continuous casting machine.

  In the homogenization treatment, the holding time was 12 hours (treatment temperature is shown in the table).

  The outer diameter of the cast rod was peeled to φ80 mm and cut and sliced to a thickness of 68 mm.

The cut material was heated to a predetermined material temperature in a heating furnace, and upset formed into a cylindrical shape of φ110 × 36 mm. The mold temperature during installation was 180 ° C. The installed material was heated to 180 ° C. and immersed in an aqueous solution in which 15% graphite and a dispersant were added and dispersed to form a preliminary lubricating film. The pre-lubricated material was forged by heating to a predetermined material temperature in a heating furnace. The temperature of the forging die was 250 ° C. in the thin cylindrical portion. The back pressure was 12 MPa. As a lubricant for the mold, an oil-based graphite lubricant was applied with a 2 g spray gun, and then an aqueous graphite lubricant was applied with a 10 g spray gun. Molding was performed at a press speed of 25 spm and a molding load of 200 t. The molded product was heated and heated to a predetermined solution temperature in 2 hours, held for 2 hours, and then quenched in a water bath at a water temperature of 20 ° C. In the aging treatment, the temperature was raised to 180 ° C. in 1 hour and held for 6 hours to obtain a forged material. Other conditions are shown in Table 1.
<Evaluation method>

  Structure: The test piece was processed by cutting a forged shaped material at a cross section including the center of the ear and the cup, and processing the cut surface with a milling machine or a lathe to have a cutting surface roughness of 5S or less. The finished processed surface is polished with # 320 to # 800 polishing paper. The polished surface is immersed in a 10% to 25% sodium hydroxide aqueous solution heated to 40 ° C. to 60 ° C. for 1 to 5 minutes and etched. Immediately thereafter, the etched surface was washed with running water and dried to complete the treatment. The evaluation of the structure is ◎ if the entire surface is fine structure by visual observation, ◯ if only the vicinity of the surface is coarse recrystallized structure, ◯ if only the central part is fine and the surface layer is coarse recrystallized structure, △, the whole surface is coarse A recrystallized structure was marked as x.

  Strength: A round bar tensile test piece was manufactured by machining from the center of the ear, and a tensile test was performed using a universal material testing machine.

  The above evaluation results are also shown in the table.

  Table 1 shows the following. When the homogenization temperature is in a predetermined temperature range or the plastic working temperature (upsetting temperature, forging temperature) is in a predetermined temperature range, the macro structure and the tensile strength are preferable. It can be seen that the homogenization temperature is preferably 470 ° C rather than 530 ° C. The upsetting temperature and forging temperature are preferably 475 ° C. or higher. It can be seen that the solution temperature is preferably 530 ° C rather than 560 ° C. What satisfy | filled all of these is more preferable. Further, as a component, it is preferable to contain 0.24% rather than 0.15% Fe. It is preferable to contain 0.09 to 0.10% of Mn rather than 0.03%.

  The present invention can be used for manufacturing a molded article made of an aluminum alloy.

It is a sketch of an example of the raw material of the yoke before machining. It is a sketch of an example of the yoke after machining. It is a sketch of another example of the raw material of the yoke before machining. It is a schematic block diagram of a propeller shaft. It is a schematic block diagram of the forging apparatus which is an example of the plastic processing apparatus used for this invention. It is sectional drawing of an example of the metal mold | die structure used for this invention. It is the schematic of an example of the production line of this invention.

Explanation of symbols

10: York shape material 11: Cylindrical portion 12: Bottom 13: Pin boss portion 41: Cup shape portion 42: Plate portion 43: Pin boss portion 67: Ring knock (movable ram)
68: Pneumatic cylinder pressure transmission shaft 71: Pneumatic cylinder 72: Pneumatic cylinder gas sealing part 81: Continuous casting device 82: Heat treatment device 83: Correction device 84: Peeling device 85: Cutting device 86: Pre-lubricating device 87: Preheating device 88: Forging device 89: Solution heating device 90: Quenching device 91: Aging device 95: Shaft connecting portion 94a, 94b: Pin hole 103: Upper die 104: Spray nozzle 105: Lower die 107: Knockout pin 108 : Spray moving device 109: Spray rotating device 110: Spray shaft 111a, 111b, 111c: Transmission rear end 112a, 112b, 112c: Yoke parts 113a, 113b, 113c: Cross shaft 114a, 114b: Shaft 115: Center bearing 116: Mount Insi Aerator 117: body (body)
118a, 118b: welded portion 119: final drive 201: lower mold 202: upper mold 203: center bush 204: pressure plate 205: lower bolster 210: forging material 211: upper bolster 221: forging machine 300: gas cushion

Claims (4)

A step of homogenizing a round bar made of a 6000 series aluminum alloy by a continuous casting method, a step of forming a shaped material by hot plastic processing using the homogenized material as a raw material, and a solution after plastic processing In a method for producing a molded article including a step of heat treatment including crystallization treatment,
The components of the 6000 series aluminum alloy are 0.3% to 1.0% Si, 0.2% to 0.6% Cu, 0.8% to 1.5% Mg, 0.05% by mass. % To 0.5% Cr, 0.05% to 0.15% Mn, 0.18% to 0.40% Fe, and the balance is Al and inevitable impurities,
Satisfying temperature conditions of a homogenization treatment temperature of 450 ° C. to 500 ° C. and a material temperature during hot plastic working of 460 ° C. to 530 ° C.,
A method for producing a molded product characterized by the above.   The method for producing a molded article according to claim 1, wherein the temperature of the solution treatment satisfies 430 ° C to 530 ° C.   2. The molded product according to claim 1, wherein the hot plastic working is a forging process using an upper mold of a lower mold, and the mold temperature of the lower mold is set to 150 ° C. to 350 ° C. Production method.   The method for producing a molded product according to any one of claims 1 to 3, wherein the molded product is a universal joint yoke.

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