JP2878141B2 - Manufacturing method of superplastic molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a superplastic molded product utilizing heat generated by processing.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a molded product such as a rapidly solidified material (microcrystalline alloy material) exhibiting superplasticity, a heating temperature at the time of processing is increased, and a processing time at a high temperature is prolonged. In order to avoid formation, the material is formed slowly or in several steps from preliminary molding to finish molding to produce a final molded product. However, the problems in the series of processing steps as described above are that it takes a long time overall, that a large working force is required, and that several steps are required from preliminary forming to finish forming. For example, the number of processing dies increases. That is, since the work forming force is proportional to the pressure receiving area of the material, the forming cannot be performed in one step, and it is necessary to gradually perform the forming in several steps from preliminary forming to finish forming. As a result, there is a problem that the high-temperature exposure time of the material becomes longer, the crystal grain size becomes coarser, and the physical properties deteriorate. In addition, when molding is performed slowly in one mold, the material is placed in the mold and heated externally (from the mold) by induction heating, contact heating, and energization heating. Becomes longer, causing the above-mentioned coarsening of the crystal grain size and lowering of the physical properties, and the temperature of the mold itself is almost the same as or slightly higher than the material, so that the cooling of the molded product after the molding process is smooth. There is a problem that it cannot be performed.

On the other hand, as a method of manufacturing a molded product made of a rapidly solidified material in consideration of the heat generated by plastic working, a manufacturing method described in Japanese Patent Application Laid-Open No. 3-247706 is known. This publication discloses that plastic working is performed in the presence of a heat absorbing material that absorbs working heat generated in the material by plastic working in order to suppress the temperature rise of the material due to working heat. However, also in the method of manufacturing a molded product, the high-temperature exposure time is increased similarly to the above, and there is a problem that the crystal grain size is coarsened, and the physical properties are reduced. It is difficult to control or set the amount of heat-absorbing material added, the relative relationship with the material, etc., and if the material is processed with the heat-absorbing material, the molded product contains the heat-absorbing material. Therefore, there is also a problem that physical properties are deteriorated.

[0004]

Accordingly, the present invention provides a method for controlling a heating temperature by positively utilizing a temperature rise due to processing heat generated at the time of molding, and forming a final molded product in one process. It is an object of the present invention to provide a method for producing a molded product that can be easily produced with high productivity in a short time and that can maintain excellent properties as a rapidly solidified material in a final molded product.

[0005]

According to the present invention, there is provided, in accordance with the present invention, a supply section to which a material is supplied, a forming section to form the material into a desired shape, A material exhibiting superplasticity is loaded into the supply portion of the mold having a passage portion communicating with the portion, and the material is supplied to the molding portion through the passage portion and compressed to perform molding. This is a method for producing a superplastic molded product, wherein a heating temperature (T ₁ ) applied to a material in a supply section is determined from a temperature (T ₂ ) at which the material exhibits superplasticity and the following formulas (1) and (2). Asked,
T ₁ = T ₂ due to the temperature rise (ΔT) due to processing heat generated when the material is extruded from the supply unit to the passage and deformed.
-Set to △ T and the heating temperature (T ₁ ) indicates superplasticity
To be lower than the crystalline coarsening starting temperature to the material (T _X)
Method for producing a superplastic forming workpiece and controlling the is provided.

[0006]

(Equation 2)

[0007]

According to the method described in the above-mentioned Japanese Patent Application Laid-Open No. 3-247706, the processing heat generated in the material by plastic working is efficiently absorbed by, for example, a heat absorbing material disposed around the material, and the heat generated by the processing is generated. It is to suppress the temperature rise of the material, and in this case, since the heat generated by processing is not used for plastic working of the material, a large waste is generated in terms of thermal efficiency,
Also, the high temperature exposure time becomes longer. On the other hand, the method of the present invention positively utilizes the temperature rise due to the heat generated during processing in forming the material, and attempts to perform the forming in a short time with high productivity in one process. That is, in the method of manufacturing a superplastic molded product of the present invention, the heating temperature (T ₁ ) applied to the material of the supply unit is changed to the temperature (T ₂ ) at which the material is superplastic, and the material is supplied from the supply unit to the passage. It is characterized in that it is controlled by the temperature rise (ΔT) due to the heat generated during processing when it is extruded and deformed. More specifically, the temperature rise (ΔT) due to the processing heat is obtained from the above equations (1) and (2), and the heating temperature (T ₁ ) is set by T ₁ = T ₂ −ΔT.

[0008] Temperature rise (ΔT) due to heat generation during material processing
Is obtained by the above equation (2). By setting the strain rate, the stress σ is obtained from the above equation (1), and the temperature rise (ΔT) can be calculated by substituting this into the equation (2). The temperature range in which the material used for processing exhibits superplasticity can be determined by measuring in advance, and an appropriate temperature within the temperature range is set as the temperature (T ₂ ) indicating superplasticity. The heating temperature (T ₁ ) is set to the temperature obtained by subtracting the rise (ΔT) due to the heat generated by the processing from the temperature (T ₂ ) indicating the superplasticity, and the material is in a structurally stable temperature range by the external heating means. Heat to temperature (T ₁ ). By performing the forming process continuously, the material is rapidly heated to the temperature showing superplasticity due to the heat generated by the process, and the process is completed when the temperature reaches the superplastic temperature range, and the mold temperature is lower than the superplastic temperature. Therefore, it is rapidly cooled by contact heat transfer, and is cooled to a temperature range that is systematically stable.

[0009] In plastic working of a material that undergoes a structural change at a certain temperature, such as an amorphous alloy or a microcrystalline material, rapid heating, working and cooling are essential conditions. By adopting it, superplastic working of bulk material, solidification molding of powder material, and superplastic diffusion bonding become possible. In addition, according to the method of the present invention, heating, processing, and cooling are performed in one step, and the cycle time is shortened, and solidification molding can be performed in a short time. Changes in the structure of the product (such as coarsening of crystal grains) and the accompanying deterioration in physical properties are minimized. As a result, a superplastic molded product can be manufactured without impairing the properties of the material.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically while describing embodiments of the present invention with reference to the accompanying drawings.

FIG. 1 shows a main part of an embodiment of an apparatus for producing a superplastic molded product according to the present invention.
In the figure, reference numeral 1 denotes a mold, and the mold 1 is made of a material 7 (bulk material,
It has a supply section 2 to which the powder material is supplied, a forming section 4 in which the material 7 is formed into a desired shape, and a passage section 3 communicating between the supply section 2 and the forming section 4. A heating unit 6 is provided on the side of the supply unit 2 of the mold 1. Further, a punch 5 having a cross-sectional shape corresponding to the hole of the supply unit 2 is provided above and below the supply unit 2 so as to be slidable in the hole of the supply unit 2.

[0012] In molding, first, loaded with material 7 of superplastic material supply section 2 of the mold 1, the temperature rise due to working heat generation from the temperature (T ₂₎ showing a superplastic (△ T)
Is heated by the heating means 6 to the heating temperature (T ₁ ) obtained by subtracting When the heating temperature (T ₁ ) is reached, a pressure is applied at once by a punch 5 arranged immediately above the supply unit 2. The raw material 7 is extruded through the passage portion 3 to the molded portion 4 and is compressed, and is rapidly heated to a temperature range showing superplasticity due to heat generated by processing. Subsequently, it is rapidly cooled by a temperature difference between the molding portion 4 and the mold 1, and is solidified into a desired shape. As the heating means, any conventionally known heating means such as induction heating, contact heating, and electric heating can be used. By performing the forming process by such a method, heating can be performed with a lower electric power than in the case of rapidly heating from room temperature to a predetermined temperature in the superplastic development temperature range at the same time, and cooling after forming is also performed in the superplastic development temperature range. And a supply unit 2 provided with a heating means 6
Because the cooling by contact heat transfer with the low temperature of the forming part 4 itself which is separated from the passage part 3 by narrowing the passage part 3 is used, not only is it economical, but also the time of exposure to high temperature is short, so that the structural change (crystal (E.g., coarsening of grains) and the accompanying deterioration in physical properties are minimized, and plastic working can be performed reliably and easily without impairing the properties of the material.

The basic structure of the manufacturing apparatus shown in FIG. 2 is the same as that of FIG. 1, except that the passage 3 and the forming section 4 are located on the side of the supply section 2 in the apparatus of FIG. On the other hand, in the apparatus of FIG. 2, the passage 3a and the molding 4a of the mold 1a are located below the supply unit 2. When molding is performed using such an apparatus as shown in FIG. 2, that is, an apparatus in which the direction in which the material is extruded is the same as the direction in which the punch 5 is moved up and down, depressions are likely to occur in the center of the bottom surface of the molded article. In order to prevent this, a cutout forming portion 8 is provided at the center of the bottom surface of the forming portion 4. As a result, the center of the bottom surface of the molded product becomes convex, and is similarly cut after being molded together with the convex portion formed in the passage portion.

As a material to which the manufacturing method of the present invention is applied, any material having a large deformability such as superplasticity to be subjected to plastic working can be applied.
The following superplastic metal material or rapidly solidified alloy powder solidified material described in No. 7178 can be advantageously used. The superplastic aluminum-based alloy described in JP-A-6-17178 is prepared by rapidly cooling an alloy material having a specific composition to form an amorphous phase, a mixed phase of amorphous and fine crystalline or a fine crystalline phase. An aluminum-based alloy is prepared, which is heat-treated at a predetermined temperature for a predetermined time, and subjected to a working heat treatment to adjust the crystal grain size and the intermetallic compound particle size. 0.005 to 1 μm in diameter
In the matrix of aluminum or a supersaturated solid solution of aluminum, a mean particle of a stable phase or a metastable phase of an intermetallic compound of the matrix element (A1) and another alloy element or an intermetallic compound of other alloy elements is included. It is a superplastic aluminum-based alloy material in which particles having a size of 0.001 to 0.1 μm are uniformly dispersed, and its alloy system includes those having the following compositions.

[0015] ^{_{(A) Al a M 1 b}} X e ( where, M ^1: M
at least one element selected from n, Fe, Co, Ni and Mo; X: Nb, Hf, Ta, Y, Zr, Ti,
At least one element selected from the group consisting of rare earth elements and aggregates of rare earth elements (Mm: misch metal), a, b, and e
Is an atomic percentage of 75 ≦ a ≦ 97, 0.5 ≦ b ≦ 1
5, a superplastic aluminum-based alloy material having a composition represented by 0.5 ≦ e ≦ 10), (B) Al _a M ¹ _(bc) M ² _c X
_e (where, M ¹ : at least one element selected from Mn, Fe, Co, Ni, and Mo; M ² : at least one element selected from V, Cr, and W; X: Nb, H
f, Ta, Y, Zr, Ti, at least one element selected from the group consisting of rare earth elements and rare earth elements (Mm; misch metal), a, b, c, and e are 7 atomic percent.
5 ≦ a ≦ 97, 0.5 ≦ b ≦ 15, 0.1 ≦ c ≦ 5,
(C) Al _a M ¹ _(bd) M ³ _d X _{e, a} superplastic aluminum-based alloy material having a composition represented by 0.5 ≦ e ≦ 10)
(However, M ¹ : at least one element selected from Mn, Fe, Co, Ni, and Mo; M ³ : Li, Ca, M
g, at least one element selected from Si, Cu, and Zn; X: Nb, Hf, Ta, Y, Zr, Ti, a rare earth element, and an aggregate of rare earth elements (Mm; misch metal)
At least one element selected from the group consisting of a, b, d, and e is, in atomic percent, 75 ≦ a ≦ 97, 0.5 ≦ b ≦ 15,
A superplastic aluminum-based alloy material having a composition represented by 0.5 ≦ d ≦ 5, 0.5 ≦ e ≦ 10), and (D) Al
_a M ¹ _(bcd) M ² _c M ³ _d X _e (where M ¹ : Mn, F
e, at least one element selected from Co, Ni and Mo, M ² : at least one element selected from V, Cr and W, M ³ : Li, Ca, Mg, Si, Cu and Z
at least one element selected from n, X: Nb, H
f, Ta, Y, Zr, Ti, a rare earth element and at least one element selected from the group of rare earth elements (Mm; misch metal), a, b, c, d, and e are 75 ≦ a ≦ 97 in atomic percent. , 0.5 ≦ b ≦ 15, 0.1 ≦ c ≦
5, a superplastic aluminum-based alloy material having a composition represented by 0.5 ≦ d ≦ 5, 0.5 ≦ e ≦ 10).

The alloy material having the above composition has excellent heat resistance, does not cause grain growth even at a high temperature, and can provide fine crystal grains and intermetallic compounds after working heat treatment, and have high strength at a high temperature. Has characteristics. Further, the alloy having the above composition is subjected to heat treatment and thermomechanical treatment (Thermo-Mechanical Trea
tment: rolling, extrusion, etc.), a superplastic material having a fine crystal structure in which smooth grain boundary movement or slip occurs is obtained, which exhibits large elongation at a relatively high strain rate. The superplastic aluminum-based alloy can also be produced by adjusting a fine crystalline material having an average crystal grain size of 1 μm or less to the average crystal grain size and the average particle size of the intermetallic compound.
When forming using the superplastic aluminum-based alloy as a raw material, the heating temperature during the forming process is 350 to 600
C. and a strain rate of 10 ^-2 s ^-1 or more, preferably 10 ^-1 s ^-1 or more, and the flow stress at that time is about 20-17.
0 MPa.

FIG. 3 shows Al ₈₈ Ni ₈ Mm _3.5 Zr _0.5
FIG. 4 is a graph showing the relationship between the strain rate and the breaking elongation at various temperatures for the solidified material of the rapidly solidified alloy powder having a composition of (atomic%), and FIG. 4 is a graph showing the relationship between the strain rate and the stress. The material was prepared as follows. A1 ₈₈ N
An alloy having a composition of i ₈ Mm _3.5 Zr _0.5 (at%) was subjected to gas atomization to obtain a powder having a center particle diameter of 10 μm. These powders consisted of a fine A1 matrix phase and an intermetallic compound phase. The powder was placed in a metal capsule (made of copper) having an outer diameter of 50 mm (thickness of 1 mm) and heat-treated at 400 ° C. for 3 hours. Then 200
Pressing was performed at MPa to prepare an extruded billet. At this stage, crystallization progressed, and it was adjusted to an A1 matrix phase having an average crystal grain size of 0.1 to 0.3 μm and an intermetallic compound phase of 0.05 μm or less. This was extruded at an extrusion ratio of 10, 360 ° C to obtain an extruded rod. At this stage, the crystal grain size and the grain size of the intermetallic compound were not changed from those of the extruded billet. An induction coil was attached to the obtained extrusion rod, and the extrusion rod was heated by induction heating. FIG. 3 shows the relationship between the strain rate and the elongation at break at various temperatures.
FIG. 4 shows the relationship between the strain rate and the stress at various temperatures.

As is clear from FIGS. 3 and 4, the extruded aluminum alloy exhibits superplasticity at a high temperature of 673 K (400 ° C.) or more, and has a strain rate of 10 ⁻² s ⁻¹ or more, especially 10 ⁻¹ to 10 ⁻¹ .
It can be seen that a large elongation is exhibited in the range of 10 s ^-1 , and the elongation increases as the temperature increases, but the elongation tends to decrease at a certain temperature or higher. 600 ° C
It can be seen that elongation of 600% can be obtained if the strain rate is 1 s ^-1 at (873K). When heating a material having superplastic properties and performing forming processing using the superplastic phenomenon, the temperature range in which the material exhibits the superplastic phenomenon, generally 75 to
It is necessary to heat to a temperature of about 95%, preferably 80-95%, optimally about 90%. In the strain rate-stress curve shown in FIG. 4, superplasticity is exhibited when m = 0.3 or more.

FIG. 5 is a graph showing the relationship between the temperature exposure time and the hardness and tensile strength of the extruded aluminum alloy, and FIG. 6 is a graph showing the relationship between the temperature and the allowable temperature exposure time. As is clear from FIG. 5, the hardness is closely related to the tensile strength, and an almost proportional relationship is seen. The horizontal straight line at the upper left in FIG. 5 shows the hardness and tensile strength at room temperature.
Also, from FIG. 6, when exposed to a temperature of, for example, 550 ° C., the allowable exposure time for maintaining the tensile strength σ _B at 850 MPa is about 0.15 second or less, and the allowable exposure for maintaining the tensile strength σ _B at 800 MPa. Time is less than about 1.2 seconds, 750M
It can be seen that in the case of Pa, it is 10 seconds or less, and in the case of 700 MPa, it is about 12 seconds or less. That is, from FIGS. 5 and 6, it is understood that if the required physical property values and processing temperatures are determined, the time allowed for them is regulated by itself.

Generally, molding is performed in a temperature range of 500 ° C. or higher. On the other hand, the allowable temperature exposure time for maintaining the required strength is the area on the left side of each curve in FIG. Therefore, the temperature at which processing can be performed while maintaining the required strength-
The time area is an upper left area surrounded by the 500 ° C. line and each curve of the required intensity in FIG. Then, when heating to a temperature (T ₂ ) showing superplasticity only by external heating in t seconds or less, the rate of temperature rise is T ₂ / t at a minimum. On the other hand, according to the method of the present invention, the temperature (T
_The temperature obtained by subtracting the temperature rise (ΔT) due to processing heat from ₂ ) is set as the heating temperature (T ₁ ), and heating is performed to this temperature (T ₁ ) by the external heating means. Since the heating temperature (T ₁ ) is in a temperature range where the material is systematically stable, the heating rate may be slower than in the above case, and the heating power capacity can be greatly reduced. By performing the forming process continuously, it is rapidly heated to the temperature that shows superplasticity due to the heat generated by the process, and the process is completed when the temperature reaches the superplastic expression temperature range, and the mold temperature is lower than the superplastic expression temperature, It is quenched by contact heat transfer and cooled to a temperature range that is systematically stable.

Next, the aforementioned Al ₈₈ Ni ₈ Mm _3.5 Zr _0.5
The solidification material of the rapidly solidified alloy powder having the composition of
The initial heating temperature (T ₁ ) was set to 400 ° C. under the condition that the billet of FIG. 1 was compressed from the supply part 2 having the same inner diameter of the mold shown in FIG. The following shows the temperature rise due to the heat generated during the forming process performed in Example 1 and the predicted value obtained by calculation. First, when a trial calculation is made of the temperature rise (ΔT) due to the heat generated by processing, the value of m in the above equation (1) is set to m = 0.3 from the data shown in FIG. Next, when the strain is calculated, the strain due to the reduction in cross section (extrusion ratio R = 10)
Is calculated from the following equation (3), and the shear strain due to the angle is calculated as 3.23 and 1, respectively, from the equation (4), and the overall strain is 4.23.

(Equation 3)

On the other hand, if the initial heating temperature is set to 400 ° C., the K value in the above formula (1) is K = 20 at 400 ° C.
It is. Then, when these values are substituted into the above equation (2) to obtain ΔT, ΔT = 331 ° C. as shown in the following Expression 4.
And the maximum temperature will exceed 600 ° C.

(Equation 4) However, the above calculation is performed on the assumption that the K value at the initial heating temperature (extrusion start temperature) is constant as it is. However, in actuality, the temperature rises due to processing heat, so the K value decreases (σ decreases). The calorific value of processing decreases (K value at 600 ° C. becomes 1/10 of K value at 400 ° C. at K = 2). 400
It has been experimentally determined that the work amount corresponding to the heat generated during processing when the temperature rises from ℃ to 600 ° C. becomes １ ／ of the work amount at the time of the initial heating temperature. Therefore, the temperature rising from 400 ° C. to 600 ° C. is 331/2 ≒ 165
° C. Therefore, it is expected that the maximum temperature will reach 565 ° C. due to the heat generated during processing. On the other hand, after the billet (φ8 mm) was actually loaded into the material supply section 2 of the mold 1 shown in FIG.
C. and pressurized at an initial strain rate of 1S ^-1 by a punch 5 installed directly above the supply unit.
The temperature rose to ° C. and was extruded to the molding section 4 to complete the molding. Although the temperature rise of 140 ° C. due to the heat generated by the processing slightly differs from the calculated value, in any case, the temperature reaches the superplasticity manifestation temperature range of the material, and the initial heating temperature is calculated from the value predicted by the calculation as described above. It can be seen that the molding process can be performed sufficiently even if is set.

[0023]

As described above, according to the method of manufacturing a superplastically formed product of the present invention, the heat generated during processing is used to heat, process, and cool in a single mold to perform the forming. Therefore, the following effects and advantages can be obtained. (A) The material is heated to an organically stable temperature range by an external heating means, then rapidly heated to a temperature showing superplasticity due to the heat generated during the forming process, and reached a superplasticity manifestation temperature range. At the same time as the processing is completed, it is rapidly cooled to a structurally stable temperature range due to the temperature difference with the mold, so that the time of exposure to high temperature is short. Coarsening) and the accompanying deterioration in physical properties are minimized. As a result, a superplastic molded product can be manufactured without impairing the properties of the material. (B) Heating, processing, and cooling can be performed in a single mold in one step, shortening the processing cycle time, and performing superplastic processing at high speed. Molding can be performed in a short time. (C) Temperature at which superplasticity is exhibited by utilizing the heat generated during processing (T ₂ )
Since the temperature is raised to a minimum, there is almost no extra heating, the thermal efficiency is extremely high, and the heating temperature (T ₁ )
Since heating can be performed at a gradual heating rate up to this point, heating can be performed with lower power than in the case of rapid heating at once, and manufacturing costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of an example of an apparatus for performing a method of the present invention.

FIG. 2 is a cross-sectional view of a main part of another example of an apparatus for performing the method of the present invention.

FIG. 3 is a graph showing the relationship between the strain rate at various temperatures and the elongation at break of a rapidly solidified alloy powder solidified material having a composition of Al ₈₈ Ni ₈ Mm _3.5 Zr _0.5 (at%).

FIG. 4 is a graph showing the relationship between strain rate and stress at various temperatures of a rapidly solidified alloy powder solidified material having a composition of Al ₈₈ Ni ₈ Mm _3.5 Zr _0.5 (at%).

FIG. 5 is a graph showing the relationship between the temperature exposure time, hardness and tensile strength of a rapidly solidified alloy powder solidified material having a composition of Al ₈₈ Ni ₈ Mm _3.5 Zr _0.5 (at%).

FIG. 6 is a graph showing the relationship between the temperature of the rapidly solidified alloy powder solidified material having a composition of Al ₈₈ Ni ₈ Mm _3.5 Zr _0.5 (at%) and the allowable temperature exposure time.

[Explanation of symbols]

1 mold, 2 supply section, 3 passage section, 4 molding section, 5
Punch, 6 heating means, 7 material, 8 cut-out molding

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22K 3:00

Claims (1)

(57) [Claims] 1. A supply section of a mold having a supply section to which a material is supplied, a molding section in which the material is molded into a desired shape, and a passage communicating between the supply section and the molding section. Is a method of manufacturing a superplastic molded product in which a material exhibiting superplasticity is charged, supplied to a molding portion through a passage portion, and compressed to perform molding, and is added to the material of the supply portion. the heating temperature (T _1), the material is a temperature (T ₂₎ that shows superplasticity,
The △ T - determined from the following formula (1) and _{(2), T 1 = T} 2 by the supply unit increase in temperature due to processing heat generated during the material is extruded deformed into the passage section and (△ T) Setting
And a crystal of a material whose heating temperature (T ₁ ) is superplastic
Method for producing a superplastic forming workpiece and controlling so as to be lower than the coarser starting temperature (T _X). (Equation 1)