JPH01127608A - Manufacture of aluminum based alloy rapidly cooled solidified powder - Google Patents

Abstract

PURPOSE:To manufacture Al based alloy powder improving strength of molded form and forged form by using mixed gas composing of the specific ratio of air and nitrogen as cooling gas at the time of manufacturing Al based alloy rapidly cooled solidified powder. CONSTITUTION:The molten Al based alloy is dropped through nozzle part 3 in a ladle 2 and allowed to collide against stainless steel-made rotating disk 4 rotating at about 20000-30000rpm. By this method, the molten metal comes to droplet 5 and the cooling gas is blown to the droplet 5 from an injecting nozzle 6 at about 0.75MPa pressure and the droplet is rapidly solidified to make the powder. Then, the cooling gas uses the mixed gas having composition of 15-95vol.% air and the balance substantially at least one kind among helium, argon and nitrogen. The Al series alloy rapidly cooled solidified powder improving the tensile strength in the molded form and the forged form of the compacting state is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing rapidly solidified aluminum alloy powder that can improve the strength of molded bodies and forged bodies.

[Prior Art] Conventionally, air atomization methods, inert gas atomization methods, rotating disk methods, twin roll methods, and the like have been provided as methods for producing rapidly solidified aluminum-based alloy powders. The air atomization method is a method in which molten aluminum alloy is supplied to air ejected from a nozzle, thereby obtaining aluminum alloy particles. In addition, the inert gas atomization method is a method in which molten aluminum alloy is supplied to an inert gas ejected from a nozzle, thereby obtaining aluminum alloy particles. The rotating disk method is a method in which molten aluminum alloy is collided with a disk rotating at high speed, thereby obtaining aluminum alloy particles. The twin roll method is a method in which molten aluminum alloy is collided with a pair of high speed rotating rolls to obtain particles of aluminum alloy powder.

In the above-mentioned air atomization method, the cooling rate is relatively low, so the properties of the resulting rapidly solidified powder particles are poor.

Further, in the twin roll method, only thin or ribbon-shaped particles can be obtained, and powder particles are difficult to obtain. Furthermore, the rotating disk method yields only spherical powder particles.

Therefore, the strength of compacts produced by compression molding powders and foils manufactured by the above-described method, and forged bodies obtained by powder forging the compacts, was not necessarily sufficient for use as high-strength members.

Therefore, in recent years, as disclosed in Japanese Unexamined Patent Application Publication No. 177304/1984, molten aluminum alloy is collided with a high-speed rotating disk to pulverize the molten metal, and cooling gas is applied to the pulverized aluminum particles. A method for producing a rapidly solidified aluminum-based alloy powder that is ejected to accelerate cooling of aluminum particles has been published in W#. Also, JP-A-59-211506 and JP-A-55-504
As disclosed in Publication No. 07, the molten metal is made to collide with a cup that rotates at high speed to pulverize the molten metal, and
A method for producing rapidly solidified powder has been developed in which powdered metal particles are fed into a moving water layer to promote cooling of the metal particles.

[Problems to be Solved by the Invention] By the way, the strength of a molded body obtained by compression molding the powder produced by the above-mentioned manufacturing method, and the strength of a forged body obtained by hot powder forging the molded body, are not necessarily sufficient (, Further improvement in strength was desired.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a rapidly solidified aluminum alloy that can improve the strength of compacts obtained by compression molding powder and forged products obtained by hot powder forging of compacts. An object of the present invention is to provide a rotating disk type manufacturing method capable of manufacturing powder.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventor has conducted intensive research on a rotating disk method that uses the above-mentioned cooling gas to accelerate cooling of aluminum-based alloy powder particles. As a result, by adjusting the composition of the cooling gas, the volume ratio of the cooling gas is
If the mixed gas has a composition of 15 to 95% air and the remainder substantially at least one of helium, argon, and nitrogen, the strength of the compact and the strength of the forged body obtained by forging the compact can be improved. This discovery led to the completion of the present invention.

Here, in the rotating disk method, when the cooling gas is a mixed gas having a composition consisting of 15 to 95% air in terms of volume ratio and the remainder substantially consisting of at least 1111 of helium, argon, and nitrogen, The reason why the strength and the strength of the forged body obtained by forging the formed body can be improved is presumed to be as follows.

In other words, when the amount of air in the cold IJ3 gas is less than 15%, the cooling rate is high, so the powder particles become true spherical, and when they become true spherical, there is almost no entanglement of the powder particles when molded. As a result, it becomes difficult to mold with a die, and even if it is molded, the strength of the molded product obtained by compression molding the powder and furthermore the strength of the forged product obtained by hot forging the compact is considerably reduced.

Furthermore, if the amount of air in the cooling gas exceeds 95%, too much oxide film will be generated on the surface of the powder particles, making it difficult for the sintering phenomenon to proceed, reducing the strength of the forged body, and
When the amount of air in the cooling gas exceeds 95%, the cooling rate slows down and the quenching effect decreases. In the manufacturing method according to the present invention, the cooling gas is a mixed gas having a composition of 15 to 95% air by volume and the remainder substantially consisting of at least one of helium, argon, and nitrogen. The rapidly solidified alloy powder remains fine and becomes teardrop-shaped with a complicated shape. Therefore, when the powder is compression molded, the powder particles are well entangled with each other and the bonding strength is increased.
Therefore, the strength of the molded body and the strength of the forged body obtained by forging the molded body can be improved.

That is, in the method for producing a rapidly solidified aluminum alloy powder according to the present invention, a molten aluminum alloy is placed in a disk rotating at high speed! I will strike you and turn my thirst into dust,
In a method for producing rapidly solidified aluminum alloy powder in which a cooling gas is ejected onto powdered aluminum particles to promote cooling of the aluminum particles, the cooling gas has a volume ratio of:
15-95% air and the remainder substantially helium, argon and nitrogen! It is characterized by being a mixed gas having a composition consisting of.

As the molten aluminum alloy, for example, pure aluminum, aluminum-magnesium alloy, or aluminum-copper alloy can be used. In this case, the contents of the components are appropriately selected as necessary, and for example, the content of magnesium can be 0 to 60%, and the content of copper can be 0 to 20%.

The aluminum-based alloy rapidly solidified powder produced according to the present invention is compression-molded in a mold to form a compact.

After that, the molded body is hot forged at 500 to 600°C,
It is considered to be a forged body with a product shape.

The rapidly solidified powder produced by the present invention has a cooling W speed of 10'
~104/sec, the alloying elements are dissolved in supersaturation.

In the IIJ manufacturing method of the present invention, the cooling gas is used to promote cooling of the pulverized powder particles. The gas pressure of the cooling gas can be about 0.5 to 1.1 MPa. Cooling gas can be sprayed onto the powdered particles using a nozzle. In the manufacturing method of the present invention, the rotation speed of the rotating disk is 20,000 to 300
00 rpm. It is desirable that the material of the rotating disk has good cold section performance, and may be made of copper or stainless steel, for example.

Incidentally, the average particle size of the rapidly solidified powder obtained by the normal atomization method is usually about 140 μm, but with the manufacturing method according to the present invention, the average particle size of the rapidly solidified powder is about 140 μm. ! The average particle size of the rapidly solidified powder is
It is 10 to 60 μm, for example about 40 μm, and can be made into a fine powder by a normal atomization method. The reason for this is that in the atomization method, only gas pressure is used as the energy for pulverization, whereas in the rotating disk method, the energy from the collision between the molten metal and the disk, the friction between the molten metal and the disk, and the energy from the rotation of the disk are used. This is thought to be because the present invention, which uses a rotating disk method, requires more energy for powdering than the normal 7tomizing method.

Air m in the cooling gas used in the present invention has a volume ratio of 1
5 to 95%, and the remainder of the cooling gas is essentially one of helium (He), argon (Ar), and nitrogen (N2). Among helium, argon, and nitrogen, nitrogen is preferred for reasons of safety and low cost. The temperature of the cooling gas is usually room temperature.

In the rotating disk method, if the amount of air in the cooling gas is less than 15% and the remainder is essentially nitrogen, if a cooling gas with this composition is used, IS! !
Since the cold part gas is relatively clean, it is pulverized by a rotating disk, and the solidification of the liquid occurs through natural solidification, which reduces the powder surface. A solidified powder is obtained.When this perfectly spherical rapidly solidified powder is molded into a mold, there is almost no entanglement of the rapidly solidified powder particles during molding, so mold forming is virtually impossible.Therefore, when this perfectly spherical rapidly solidified powder is solidified, The method of bonding is not the molding method, but the extrusion method or the hot isostatic pressure method (
Instead of a molding method such as the HIP method (HIP method), an expensive method must be used. Therefore, the manufacturing cost of the forged body increases.

Therefore, in order to form a compact by molding, which is a low-cost consolidation method, the amount of air in the cooling gas must be 15% by volume.
The above is necessary. On the other hand, the amount of air in the cooling gas is 95%
If the value exceeds 1g, the amount of oxygen contained in the rapidly solidified aluminum alloy powder will increase considerably, that is, the amount of lI oxide formed on the surface of the powder particles will increase, and as a result, the rapidly solidified powder will be Neck growth during sintering is inhibited. Therefore, the strength of the forged body does not improve. Therefore, the amount of air in the cooling gas needs to be 15 to 95% so as not to exceed 95% by volume.

[Example 1 (Example 1) Fig. 1 shows an apparatus used in Example 1. In the ordinary aluminum melting furnace 1 shown in FIG. 1, at 11 fi%,
Aluminum alloy m't consisting of 8% zinc, 2% magnesium, 2% copper, and the balance substantially aluminum
Q was manufactured. The molten aluminum alloy produced in this manner was transferred to ladle 2 and fell downward through nozzle portion 3. This fallen hot water was made to collide with a stainless steel rotary disk 4 rotating at 2500 rpm.

The size of the rotating disk 4 is φ70 mm.

Due to this collision, the hot water turns into a fine liquid wI45.

A cooling gas consisting of 95% air and the remainder substantially nitrogen by volume is sprayed onto the droplets 5 from the jet nozzle 6 at a gas pressure of 0.7 MPa, thereby causing the droplets 5 to rapidly The mixture was solidified to obtain a rapidly solidified powder. The obtained rapidly solidified powder was sieved through a 100-mesh screen.

Thereafter, the above powder was put into a JSPM standard tensile test mold and compression molded at a surface pressure of 200 MPa, thereby forming a green compact. The molded body is a JSPM standard tensile test piece, and its length is 96°, 5 mm, thickness 5 mm, and the width at the center is 5.7 mm.

At this time, in order to prevent the rapidly solidified powder from galling in the mold, wax was applied to the cavity wall of the mold. This green compact was set in a 2-ton autograph, and a tensile test was conducted at a crosshead speed of 1 am per minute. The tensile strength of the green compact is 120M.
It was Pa.

On the other hand, the green compact was stored in a furnace and heated to 540℃ for 6 hours.
Heating was maintained in a nitrogen atmosphere for 0 minutes.

After that, the molded body is taken out from the furnace and immediately set in the mold cavity, and the height dimension variation of the molded body is reduced by 30%.
It was hot powder forged to give the following.

This results in a forged body (7).The forged body is the same as the JPSM standard tensile test piece, but the height is 30% smaller.

This forged body was set in a 2-ton autograph, and a tensile test was conducted at a crosshead speed of 11111 per minute. The tensile strength of the forged body was 590M Table 1 Pa. The test results are shown in Table 1.

(Example 2) The manufacturing method according to Example 2 is basically the same as that of Example 1. However, by reducing the amount of air in the cooling gas,
The composition of the cooling gas was 20% air by volume and the remainder substantially argon gas.

Then, in the same manner as in Example 1, a tensile test was conducted on the molded body and the forged body.

As shown in Table 11, the tensile strength of the green compact according to Example 2 is 108 MPa, and the a
The tensile strength of the solution was 570 MPa.

(Comparative Example 1) Comparative Example 1 was basically carried out in the same manner as in Example 1. However, in Comparative Example 1, the composition of the cooling gas was 10% air and the remainder substantially nitrogen in terms of volume ratio. Comparative example 1
The powder was perfectly spherical.

The powder of Comparative Example 1 could not be molded with a mold under a molding load of 220 MPa, and peeled off near the center of the test piece in the thickness direction.

Therefore, the molding load was set to 200 MPa, but molding was not possible at this time as well, and the product remained in a powder state. Therefore, forged bodies could not be manufactured either. The test results related to Comparative Example 1 are
Shown in the table.

(Comparative Example 2) Comparative Example 2 is an air atomization method that does not use a rotating disk. That is, in the aluminum melting furnace 11 shown in FIG.
In the same manner as in Example 1 described above, a molten aluminum alloy containing fflfi% of 8% zinc, 2% magnesium, 2% copper, and the remainder substantially aluminum was produced. This molten metal was transferred to a ladle 12 and dropped downward through a nozzle 13. The composition of this fallen molten metal is % by volume.
A cooling gas consisting of 95% air and the balance substantially nitrogen was blown at a gas pressure of 0.9 MPa, thereby rapidly solidifying the molten metal to obtain a rapidly solidified aluminum alloy powder.

The quenched rapidly solidified powder according to Comparative Example 2 was sieved using a 100-mesh screen in the same manner as in Example 1.
In the same way as in the case of , a green compact and a forged body were produced by IFJ. Tensile tests were also conducted on the molded bodies and the Wi-shaped bodies under the same conditions. The tensile strength of the green compact in Comparative Example 2 is 50 MPa, and the tensile strength of the forged body is 3.
It was 90 MPa. As is clear from Table 1, in the case of Comparative Example 2, the strength of the molded body and the strength of the forged body are lower than those of Examples 1 and 2.

(Comparative Example 3) The method of Comparative Example 3 is basically the same as that of Example 1. However, in Comparative Example 3, the composition of the cooling gas was 100% air by volume. The cold solidified powder according to Comparative 1M3 was sieved using a 100-mesh screen in the same manner as in Example 1, and then similarly as in Example 1, compacted powder-like compacts,
A forged body was manufactured. The molded body and forged body of Comparative Example 3 were also subjected to a tensile test under the same conditions. The tensile strength of the compacted compact according to Comparative Example 3 was 98 MPa, and the tensile strength of the forged body was 320 MPa.

As is clear from Table 1, in the case of Comparative Example 3, the strength of the molded body and the strength of the forged body are lower than those of Examples 1 and 2.

[Effects of the Invention] According to the method for producing a rapidly solidified aluminum alloy powder according to the present invention, the tensile strength of a green compact and the strength of a forged body are improved compared to rapidly solidified powder produced by a conventional method. Tensile strength can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of the device, and FIG. 2 is a schematic side view of the device used in Comparative Example 2. In the figure, 1 indicates a melting furnace, and 4 indicates a rotating disk.

Claims (3)

[Claims] (1) Rapid solidification of aluminum alloy in which molten aluminum alloy is collided with a disk rotating at high speed to pulverize the molten metal, and cooling gas is ejected to the pulverized aluminum particles to accelerate cooling of the aluminum particles. In the powder manufacturing method, the cooling gas has a volume ratio of 15
A method for producing rapidly solidified aluminum alloy powder, characterized in that the mixed gas has a composition of ~95% air and the remainder substantially consists of at least one of helium, argon, and nitrogen. (2) The cooling gas is a mixed gas consisting of 95% air and the remainder substantially nitrogen in terms of volume ratio, and the gas pressure is 0.7 MPa. A method for producing rapidly solidified alloy powder. (3) The method for producing rapidly solidified aluminum alloy powder according to claim 1, wherein the cooling gas is a mixed gas consisting of 20% air and the remainder substantially argon in terms of volume ratio.