JP2751080B2 - Manufacturing method of metal powder molding material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a metal powder molded material, and particularly to a method for producing a metal member by subjecting a metal powder to a pretreatment and then hot-forming. It is about.

[Related Art] In recent years, in the fields of automobiles, aircrafts, and the like, weight reduction, high performance, and high load of components have been actively studied. Above all, it is difficult to improve properties such as heat resistance, abrasion resistance, strength, and stress corrosion cracking by the conventional method combining the alloy composition, heat treatment and processing. Research is being actively conducted.

However, oxide, adsorbed water,
Crystallized water is present, which is hot-forming and hinders the compaction of powders, so that the mechanical properties of the powder molding material, especially toughness, the mechanical properties in the direction perpendicular to the molding direction are not sufficiently satisfactory. Absent. For this reason, it is necessary to remove these deposits before molding and solidifying the rapidly solidified powder.

For example, in rapidly solidified aluminum alloy powder,
Generally, as schematically shown in FIG. ₃ , a hydrated oxide layer 21 such as Al ₂ O ₃ .3H ₂ O and an Al ₂ O ₃
Is formed, and adsorbed water adheres. For this reason, before forming, a heating vacuum degassing process is usually performed in the following manner for the purpose of removing water and crystal water. That is, after the quenched and solidified powder is preformed, the preformed body is sealed in a metal can made of aluminum or the like, and heated at a high temperature (for example, 350
(−500 ° C.) at a vacuum of 10 ⁻² to 10 ⁻⁵ Torr, and then sealed. Further, in order to crush the oxide on the powder surface and join the powders together, the processing is performed at a relatively high extrusion ratio.

[Problems to be Solved by the Invention] In the conventional method for producing a molded material using such rapidly solidified powder, there are the following problems.

Due to the thermal influence during the degassing treatment, the steel is softened due to excessive annealing, and thus loses its properties as a rapidly solidified powder. For this reason, the degassing temperature cannot be sufficiently increased, and as a result, the amount of hydrogen gas in the molding material increases.

Even when hot forming, for example, hot forming at a high extrusion ratio, bonding of the powder interface may be insufficient due to insufficient crushing of the oxide on the powder surface. As a result, the fracture toughness of the obtained metal powder molding material decreases. In addition, anisotropy occurs in the mechanical properties of the molding material. (Mechanical properties are inferior in the direction perpendicular to the extrusion direction.) [Means for Solving the Problems] According to the invention of claim (1), the inside of the container has a reduced-pressure atmosphere or an inert gas atmosphere. In the step, the metal powder is vibrated by vibrating the container to modify the powder surface by contact between the powders; and then, the metal powder is heated and vacuum degassed and then hot-formed. Obtaining a molding material.

The invention of claim (2) is characterized in that, in claim (1), vibration is applied in a state where the metal powder is heated to a temperature lower than its melting point.

The invention according to claim (3) is the method according to claim (1) or (2), wherein the metal powder is vibrated before the metal powder is vibrated.
It is characterized by heating to 0 to 300 ° C.

The metal powder to be treated by the method of the present invention is mainly
It is a metal or alloy such as Al, Mg, Ti, Fe, Ni, W, and Mo obtained by rapid solidification. In this case, the cooling rate during powder solidification which can be used as metal powder, the metal may vary depending alloy, preferably 50~10 ⁶ ℃ / sec. Because
For example, in the case of an aluminum alloy, if the cooling rate is less than 50 ° C./sec, the intermetallic compounds such as Si and Fe contained in the aluminum alloy are coarsely crystallized, and the mechanical properties of the obtained member deteriorate. Therefore, the cooling rate is set to 50 ° C./sec or more.
On the other hand, even if the cooling rate is excessively high, there is no difference in the effect, the quenching technique becomes difficult, and the cost is increased.
Therefore, the cooling rate is preferably in the range of 50~10 ⁶ ℃ / sec.

The metal powder obtained in this manner is a fine powder that can generally take various shapes such as a sphere, a flake, and a thread depending on the manufacturing conditions.

As a powder alloy suitable for the present invention, for example, an aluminum alloy, specifically, an Al-Si-based alloy, an Al-Si-Cu-based alloy, an Al-Zn-based alloy, an Al-Fe-based alloy and the like can be mentioned. Further, these alloys may contain Mg, and may further contain transition metals such as Ni and Fe. The content of other metal components contained in these aluminum alloys is generally in the following range.

Si: 10 to 30 wt% Mg: 0.2 to 10.0 wt% Cu: 0.5 to 8.0 wt% Fe: 0.5 to 10.0 wt% Zn: 0.01 to 10.0 wt% Of course, the present invention starts with various aluminum alloy powders other than the above. It can be applied to pretreatment of various metals and alloys.

In the present invention, in order to impart vibration to the metal powder, for example, a container filled with the metal powder obtained by rapid cooling and solidification is placed on a vibrating device, and the container is exposed to a reduced-pressure atmosphere or In an active gas atmosphere, for example, vibration is performed for about 1 to 2 hours.

As the hot forming process in the present invention, processes such as extrusion forming, forging, HIP, hot pressing, and rolling are performed.

[Action] According to the treatment method of the present invention, since the surface layer of the metal powder is modified, the amount of hydrogen gas is easily reduced, and the generation of blisters is small. Need not be performed, and excessive annealing can be avoided. As a result, coarsening of the metal structure obtained by rapid solidification is suppressed, and fracture toughness is improved.

Since the oxide layer on the surface of the powder is crushed to form an active surface, bonding between the powders proceeds effectively during hot compaction. As a result, the fracture toughness is improved, and the anisotropy of the mechanical properties of the hot-formed material is small.

In the case of Al alloy powder containing Mg, the oxide layer is effectively removed by the coexistence of Mg oxide in the Al oxide on the surface. As a result, the effect becomes more prominent.

By the way, the pretreatment method of the present invention is intended to destroy or peel off the particle surface layer by the contact of the particles only, and to use a modified medium (for example, metal or ceramic ball).
Stirring with an attrition mill using a ball mill,
Different from mechanical alloying. That is, although the surface of the powder can be modified to some extent by an attrition mill, a ball mill, or the like, moisture such as crystallization water on the powder surface or oxidation due to the impact when the reforming medium collides with the surface of the powder. There is a possibility that substances, hydroxides, minute fragments of the reforming medium, moisture or impurities attached to the container may be taken into the alloy particles. On the other hand, in the present invention, the surface layer is destroyed or peeled off only by the contact between the particles, so that hydroxides, moisture and the like are not taken into the alloy particles.

Further, when the vibration is applied, a combination of preheating and heat treatment is expected to remove the influence of the moisture adsorbed on the powder surface and the container and promote the modification of the powder surface.

Incidentally, usually, oxides and the like generated on the surface of the metal powder are 10
Although it is 0 to 200 mm thick, almost 0
Becomes Å. Further, by performing vacuum degassing under heating before molding, the adhered moisture is almost completely removed.

When molding such as extrusion molding is performed as it is after the vibration imparting process, no new oxide is generated. After performing the vibration imparting treatment, it was exposed to the air for about 30 minutes to 1 hour, and then the thickness of the oxide layer on the surface of the metal powder was measured. The thickness was only about 10 to 20 °. For this reason, if the molding is performed as soon as possible after performing the above-described mechanical energy applying treatment, a good effect can be obtained even if the molding is temporarily exposed to the atmosphere. It should be noted that the moisture can be kept at zero if the dry state is continuously formed.

EXAMPLES The present invention will be described below in more detail with reference to the drawings.

FIGS. 1 and 2 show a vibration device suitable for carrying out the present invention, and FIG. 1 shows that a metal powder is vibrated in a closed container so as not to come into contact with the atmosphere at all until the completion of vacuum degassing. FIG. 2 is a partial vertical sectional view of a vibration processing apparatus for performing powder reforming, and FIG. 2 shows a vibration processing apparatus which is once exposed to the atmosphere when transferring metal powder to a container for deaeration processing. Partial longitudinal sectional views are shown.

In FIG. 1, an aluminum can closed container 2 containing a metal powder 4 is mounted on a vibrating device 6 having a vibration motor 5 so as to be immovably fixed. 7, a pipe from the cock 7 to the vacuum pump 1 is provided, and a pipe (not shown) for introducing an inert gas is connected to the aluminum can sealed container 2.

In the device configured as described above, the vibrating device 6 and the vacuum pump 1 are started, the cock 7 is opened, and the metal powder 4 loaded in the aluminum can closed container 2 is opened under a reduced pressure atmosphere or an inert gas atmosphere. For example, vibration is applied for about 0.2 to 20 hours, preferably about 0.5 to 5 hours, particularly preferably about 1 to 2 hours.

In FIG. 2, an open top container containing a metal powder 4 is shown.
11 is placed on a vibration device 6 having a built-in vibration motor 5 and fixed so as not to be movable. Then, the whole is put into a closed box 8 having a lid 12, and further inserted and connected to the lid 12. Two pipes are provided. One of the two pipes is connected to the valve 10 and has a function of releasing the inert gas introduced into the closed box 8 and returning the gas to the atmospheric pressure. One of the other pipes is connected to the inert gas supply source 7 via the three-way valve 9, and the other is connected to the vacuum pump 1 when no inert gas is introduced. .

In the apparatus thus configured, the vibrating device 6 and the vacuum pump 1 were started, and the three-way valve 9 was switched to make the inside of the closed box 8 under a reduced-pressure atmosphere or an inert gas atmosphere. Vibration is applied to the metal powder 4.

In this case, in FIG. 1 and FIG. 2, the degree of the vibration intensity is appropriately selected according to the type and particle size of the powder, since a sufficient effect cannot be obtained if the frequency or amplitude is too small. .

The metal powder pretreated by the method of the present invention is subjected to vacuum degassing according to a conventional method, and is then subjected to hot extrusion to form a metal member.

However, according to the method of FIG. 1, there is no exposure to the atmosphere until the completion of vacuum degassing, but according to the method of FIG.
When the powder is transferred to a degassing container, the powder must be exposed to the atmosphere once, so it must be processed promptly.

In addition, the deaeration process for the purpose of removing water from the powder surface is
It is desirable to perform the process in a high vacuum of 100 torr or less.

In the present invention, in the step of applying vibration to the powder, a composite material can be obtained by mixing reinforcing fibers such as SiC.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Examples 1-3 were obtained by rapid solidification at a cooling rate of Comparative Example ^{1,2 10 3 ~10 4 ℃ / sec} , the particle size
Aluminum alloy powder (Al-17% Si-4.5% Cu-0.6% Mg-6% Fe) by nitrogen gas atomization method of 149-44μm
Was subjected to vacuum degassing under the conditions shown in Table 1, and the obtained preform was extruded at an extrusion ratio of 5.7, an extrusion speed of 2.8 mm / sec, and a temperature of 40.
Hot extrusion was performed at 0 ° C.

The obtained extruded product was examined for the presence or absence of blisters, the amount of hydrogen gas, and the impact value. The results are shown in Table 1.

As is clear from Table 1, the molded body of the metal powder produced by the method of the present invention has no blister and shows a high impact value.

Example 4, Comparative Example 3 Particle size obtained by rapid solidification at a cooling rate of 10 ³ to 10 ⁴ ° C./sec.
Aluminum alloy powder (7091 alloy; Al-6.7% Zn-2.6% Mg-1.7% Cu-
0.4% Co) by using the apparatus shown in FIG.
After performing the pretreatment under the conditions shown in the column, degassing treatment (520
Extrusion (extrusion ratio 10, extrusion speed 3mm / sec, temperature)
420 ° C.). As a comparative example, deaeration treatment was performed under the conditions of Comparative Example 3 in Table 2 without performing this pretreatment, and then extrusion molding was performed.

The amount of hydrogen gas, tensile strength, and impact value of the obtained molded body were examined, and the results shown in Table 2 were obtained.

As is apparent from Table 2, according to the method of the present invention,
A molded article having almost no anisotropy of mechanical properties in the material and having a high impact value can be obtained. As a result of observing the fracture surface of the 7091 alloy in the impact test, when the powder was mechanically treated and the powder surface was modified as shown in FIG. 4A, the powder was modified as shown in FIG. 4B. It was confirmed that the fracture from the powder interface was significantly reduced as compared with the case where no dimple was present, and that a dimple fracture surface showing ductile fracture was observed.

Example 5, Comparative Example 4,5 Particle size obtained by rapid solidification at a cooling rate of 10 ³ to 10 ⁴ ° C./sec.
Aluminum alloy powder (Al-8% Fe-1.5% Zr-1.5% Cr- (0.1
%) Mg (however, Mg content is as shown in Table 3))
After pre-treatment was performed with the apparatus shown in FIG. 1 under the conditions shown in Table 3 (however, no pre-treatment was performed in Comparative Examples 4 and 5), at a degree of vacuum of 10 ^-5 torr, 400 ° C. × 1 h, vacuum After degassing, the obtained preform was extruded at an extrusion ratio of 7, an extrusion speed of 2.8 mm / sec, and a temperature of 440.
Hot extrusion molding was carried out at ℃.

A tensile test was performed on the obtained molded body, and the results are shown in Table 3.

From Table 3, the following is clear.

In Comparative Examples 4 and 5, the difference between the tensile strength in the extrusion direction (L direction) and the tensile strength in the direction perpendicular to the extrusion (T direction) is large, and the impact value is low. On the other hand, in Example 5, there was no large difference in the tensile strength between the L direction and the T direction, and the impact value was high. Furthermore, there is almost no generation of blisters.

[Effects of the Invention] As described in detail above, according to the method for manufacturing a metal powder molded material of the present invention, the following effects are exerted.

Since the amount of hydrogen gas is easily reduced and the generation of blisters is small, it is not necessary to perform a high-temperature and long-time degassing treatment, and excessive annealing can be avoided. As a result, coarsening of the metal structure obtained by rapid solidification is suppressed, and fracture toughness is improved.

Since the oxide layer on the surface of the powder is crushed to form an active surface, bonding between the powders proceeds effectively during hot compaction. As a result, the fracture toughness is improved, and the anisotropy of the mechanical properties of the hot-formed material is small.

[Brief description of the drawings]

1 and 2 are longitudinal sectional views showing different embodiments for carrying out the present invention, and FIG. 3 is a schematic sectional view of an aluminum alloy particle portion. Figures 4A and 4B
The figure is a schematic view of a micrograph of a fracture surface of the alloy. DESCRIPTION OF SYMBOLS 1 ... Vacuum pump, 2 ... Can closed container, 4 ... Alloy powder, 6 ... Vibration device, 8 ... Closed box, 11 ... Open top type container.

 ────────────────────────────────────────────────── ─── Continuing from the front page Judge Hideyuki Ono Judge Katsuyoshi Yamagishi Judge Susumu Ogawa (56) References JP-A-2-243701 (JP, A)

Claims (3)

(57) [Claims] 1. A process in which a metal powder is vibrated by vibrating a container in a container having a reduced-pressure atmosphere or an inert gas atmosphere inside, and the powder surface is modified by contact between the powders; and A step of subjecting the metal powder to heat vacuum degassing and then hot forming to obtain a formed material. 2. The method according to claim 1, wherein the metal powder is vibrated while being heated to a temperature equal to or lower than its melting point. 3. The method according to claim 1, wherein the metal powder is heated to 100 to 300 ° C. before applying vibration to the metal powder.