JPS63121628A - Manufacture of aluminum alloy powder - Google Patents

Abstract

PURPOSE:To easily manufacture an Al alloy powder free from the occurrence of defects such as blister, etc., by compacting an Al-type powder to a specific apparent density and by subjecting the resulting green compact to degasification by heating in the air and then to plastic working. CONSTITUTION:The Al-type powder is compacted so that an apparent density, by true density, of 65-94% is reached. The resulting powder green compact is heated at 300-500 deg.C in the air or in an inert-gas atmosphere of N2, Ar, He, etc., to undergo degasification treatment. Subsequently, plastic workings such as extrusion, forging, rolling, etc., are applied to the above, so that granular powder is formed into an alloy ingot of 100% density. In this way, the powdery Al alloy free from the growth of oxide film can be manufactured in high efficiency with reduced number of work processes.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for obtaining an AI-based powder alloy from an aluminum (AI)-based powder.

<Prior art> The method of manufacturing Aj gold alloy, also known as sintered A1 alloy, from powder containing Aj-based powder has been studied for a long time, but the surface of AI powder is covered with hard alumina (oxide coating). Therefore, sufficient strength could not be obtained by the conventional method of simply molding the powder and then sintering it at a temperature below the melting point.

Therefore, a method has been devised in which powder is solidified by extrusion. However, on the surface of AI powder, N20.0
2. Gases such as N2 (adsorbed gas) are adsorbed, and the adsorption occurs in the material during extrusion, in the heat treatment stage of the A1 alloy after solidification, or when the A1 alloy is used at high temperatures. Gas, especially N2°, is N20 gas or horse gas (3H20+2Aj-4A1203+3H2)
As a result, they expand under high temperatures, creating material defects commonly called blisters.

Therefore, when extruding powder, it is necessary to degas N20, and conventionally, H2O is degassed by heating in a vacuum.
, O was being degassed.

In addition, it was thought that sufficient Hρ could not be degassed unless heated in a vacuum (for example, human dvaneesin
Powder Technology P, 194)
.

Conventional degassing methods involve degassing in a heated vacuum. The molded powder or powder is directly placed in a hot press, degassed and pressure-molded under high-temperature vacuum, and made into a billet for extrusion, or into a can. A powder compact or powder was directly put into the can, the can was heated, and degassed by vacuuming. After completion, the can was sealed under vacuum to form a billet for extrusion.

<Problems to be solved by the invention> The method of obtaining AI-based powder alloys such as billets for extrusion as described above does not pose many problems for research purposes, but the process is too complicated for production. There were manufacturing and economic problems such as high costs.

The present invention was made in view of the above-mentioned conventional situation, and an object of the present invention is to make it possible to easily and economically obtain a blister-free AI-based powder alloy.

<Means and effects for solving the problems> The structure of the present invention to achieve the above object is to mold the aluminum powder so that the apparent density is 65 to 94% in terms of the true density ratio. The powder compact is heated to a temperature of 300°C or higher and 550°C or lower.
It is characterized by heating and degassing in the atmosphere and performing plastic working.

Each requirement of the above configuration is determined from the following considerations.

(1) Density of powder compact Aj-based powder adsorbs adsorbed gas, especially N20, on its surface. If this N20 gas is not sufficiently separated from the powder particles,
After solidification, material defects such as blisters occur.

Therefore, it is necessary to degas the powder compact in order to prevent material defects such as blisters.
The apparent density of the powder compact needs to be adjusted to a true density ratio in the range of 65% to 94%. When the density is lower than 65%, the strength of the powder compact is low and cracks occur during handling such as transportation, resulting in poor yield and difficulty in handling. When the density is 95% or more, the voids in the powder compact are closed from the outside, and if heating is continued during extrusion, the N20 gas in the closed space expands and destroys the powder compact. The limit at which such a closed space occurs is a density of 95% or more, so the density of the powder compact is 94%.
It is necessary to do the following.

More preferably, the density is preferably 70% to 90% to prevent cracking of the molded product or insufficient degassing.

(2) Degassing conditions for powder compacts Conventionally, degassing of gases adsorbed in powder has been done by predicting the degassing process from a thermodynamic point of view by determining the parallel gas pressure that is in equilibrium with the degree of vacuum and temperature. was common (
LEYBOLDHER EVSGMBH, Vacuum
Degassing of Metal Po
wders, by P, Fleehsrand R,
(see Ruthardt).

Furthermore, since oxidation generally progresses in the atmosphere, degassing in the atmosphere has not been considered in the past.

However, ■The actual degassing process is a time-related kinetic process; ■Moreover, it contains water, which cannot be predicted thermodynamically like adsorbed gas; and ■The AZAl powder solidifies. The oxidized film is difficult to reduce. However, the increase in the oxide film formed by actually heating in the atmosphere is slight.

From the above points, it is thought that dehydration (gas) is possible in the atmosphere.

At the temperature T (K) of various powders, the equilibrium partial pressure (mbnr) for reaching a water vapor content of 1 ppm, which is considered to be sufficient degassing, is given by:

On the other hand, the saturated water vapor pressure in the atmosphere is as shown in FIG. In other words, from this figure, during the rainy season, the hottest and humid season in Japan, if the temperature is 30°C and the relative humidity is 100%, the saturated water vapor pressure is 42 mbar, and even in this case, according to equation (1), if the temperature is 408°C or higher, the powder It can be seen that the amount of water vapor can be reduced to 1 ppm or less. Furthermore, at a winter temperature of 5°C, if the relative humidity is 30%, the water vapor pressure in the atmosphere is about 3 mbar, and from equation (1) it is possible to reduce the amount of water vapor in the powder to 1 ppm or less by heating it at about 320°C or higher. I understand.

Therefore, the degassing temperature needs to be 300° C. or higher. At temperatures above 550° C., water or other gases adsorbed on the powder are almost completely separated from the powder particles, so there is no need to increase the temperature above this temperature.

(3) Heating atmosphere Previously, it was thought that heating Al powder in the atmosphere would cause an oxide film to grow, so it was impossible to heat it in the atmosphere. Although the oxygen content of the Al powder before heating was about 0.15 to 0.25 wt%, it was found that even after heating, the oxygen content remained almost the same at 0.17 to 0.25 wt%.

Therefore, even if the heated gas is heated in the atmosphere, no oxidation effects will be a problem. However, since the atmosphere contains water vapor, there is some H20 partial pressure, but when degassing is performed in an inert gas atmosphere such as N2, Ar, He, etc., this partial pressure becomes even smaller9. Degassing becomes easier.

(4) Plastic processing method Plastic processing of powder is a method for turning powder into an alloy lump with a density of IO%, and generally extrusion is the most commonly used (although it is also possible to use methods such as forging and rolling). .

(5) Raw material powder The AI-based powder targeted by the present invention is any powder containing Al powder, that is, Al powder or 11 alloy powder or A
It is a mixed powder of 1 powder and A1 alloy powder, or a mixed powder of Al powder or 11 alloy powder, or a mixed powder of these powders and other metal powder or nonmetal powder.

Implementation example>At' -20wt%Si-5wt%Fe-4wt%C
u-1wt%Mg 11 alloy powder (-100 mesh)
molded with a density of approximately 70%, 90%, and 96%, respectively,
The resulting powder compact was heated in the air at temperatures of 300°C, 400°C, and 500°C for 7 hours, and then extruded at the same temperature at an extrusion ratio of 10:1.

The obtained extruded material was heated at 500° C., and the presence or absence of blisters generated at this time was investigated. The results are shown in Table 1.

0... No occurrence within 5 hours ○... Occurrence within 5 hours Δ... Blistering occurs during extrusion ×... Molded product cracks during heating As shown in Table 1, the true density ratio is 96 %, the powder compact sometimes cracked during heating before extrusion.

Furthermore, in the case of heating at 300°C, none of the densities cracked during heating, but blisters occurred during extrusion or after heating at 500°C for a short time.

However, in the case of heating at 400°C or higher, no blisters were observed even after heating at 500°C for 5 hours.

<Effects of the Invention> According to the method for producing an AI-based powder alloy according to the present invention, AI
Degassing the powder in the atmosphere at atmospheric pressure or in N2, Ar, He
Since the process is carried out in an inert gas such as, the number of steps is smaller than conventional degassing treatment in a vacuum, the equipment is simple, and the process can be carried out with high efficiency.

Furthermore, the Aj-based powder alloy obtained in this way has almost the same quality as that obtained by the conventional method, and there is no increase in oxide film despite heat treatment in air, and powder A1
Extremely suitable for manufacturing alloys.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between temperature and saturated water vapor pressure in the atmosphere. Patent application agent Sumitomo Electric Industries Co., Ltd.

Claims (5)

[Claims] (1) Apparent density of aluminum powder is 6 as true density ratio
5 to 94%, and the powder compact is 30%
A method for producing an aluminum-based powder alloy, which comprises heating and degassing in the atmosphere at a temperature of 0°C or more and 550°C or less, and subjecting it to plastic working. (2) The apparent density of the powder compact is 70 to 90 in terms of true density ratio.
% of the aluminum-based powder alloy according to claim 1. (3) N_2 gas or Ar, H as degassing atmosphere gas
The method for producing an aluminum-based powder alloy according to claim 1 or 2, using an inert gas such as e. (4) As aluminum-based powder, aluminum powder, aluminum alloy powder, mixed powder of aluminum powder and aluminum alloy powder, or mixed powder of aluminum powder or aluminum alloy powder, or mixed powder of these and other metal powder or non-metal powder. A method for producing an aluminum-based powder alloy according to any one of claims 1 to 3, using the method. (5) The method for producing an aluminum-based powder alloy according to any one of claims 1 to 4, in which extrusion, forging, and rolling are used as the plastic working method.