WO1992008560A1

WO1992008560A1 - Method of making pressure-molded product from aluminum powder

Info

Publication number: WO1992008560A1
Application number: PCT/JP1991/001599
Authority: WO
Inventors: Akira Yoshino; Haruo Senbokuya; Masaaki Tahara
Original assignee: Daidousanso Co., Ltd.
Priority date: 1990-11-20
Filing date: 1991-11-20
Publication date: 1992-05-29
Also published as: JP2868889B2; JPH04187704A

Abstract

A method of making a pressure-molded product from aluminum powder according to this invention consists in a fluoridizing process performed prior to nitriding process. Thus, a passive film such as an oxide film on the surface of aluminum powder turns into a fluoridized film to protect the surface of aluminum powder. Therefore, even with the lapse of time between formation of the fluoridized film and nitriding process, the fluoridized film formed on the surface of aluminum powder protects said surface in satisfactory condition and prevents an oxide film form from being formed again. Since the fluoridized film is decomposed at the time of subsequent nitriding process, N atoms acting during the nitriding process are dispersed evenly and deeply into the surface layer of aluminum powder to form a uniform hard nitride layer.

Description

Specification

Manufacturing method of aluminum powder molded product technology fer field

The present invention relates to a method for producing an aluminum powder press molded article.

if view

Recently, in order to increase the strength, toughness, etc. of the chassis of automobile parts, aluminum powder formed by hot isostatic pressing has been used. This thermal isostatic pressing method is performed using a hip (HIP) device 20 shown as a conceptual diagram in FIG. That is, a thin metal container 26 having a desired shape (for example, a shape of a chassis of an automobile part or the like) is arranged in the furnace body 21. Aluminum powder 11 containing titanium powder, magnesium powder and the like is vacuum-sealed in the metal container 26. Then, an inert gas such as an argon gas is injected into the above-mentioned metal container 26 by pressing the inert gas such as argon gas at a temperature of 100 or more by the heater 25 to apply a pressure of 10 O MPa or more. The internal aluminum powder 11 is pressed into the same shape as the metal container 26 to obtain an aluminum alloy product. 2 2 is the upper side, and 2 3 is the lower lid.

However, it is necessary to remove the oxide film formed on the surface of the aluminum powder 11 before vacuum-sealing the aluminum powder 11 mixed with various powders in the metal container 26. Heating of the mixed aluminum powder 11 has been performed. However, when a powder having a low melting temperature is used as the powder to be mixed with the aluminum powder 11, the powder having a low melting temperature is melted by the above heating and adheres to the surface of the aluminum powder 11. However, the oxide film cannot be removed, and the HIP equipment In view of such circumstances, the present invention has been made in consideration of the problem that aluminum alloy products are inferior in strength, toughness, etc., and is an aluminum powder press-formed product capable of obtaining an aluminum alloy product having excellent strength and toughness. Its purpose is to provide a manufacturing method.

Disclosure of the invention

In order to achieve the above object, a method of manufacturing an aluminum powder press-molded product of the present invention comprises contacting aluminum powder with a fluorine-based gas in a heated state, and then contacting the aluminum powder with a nitriding gas in a heated state. Then, hard nitrided β is formed on the surface layer of the aluminum powder, and the aluminum powder on which the nitrided layer is formed is directly pressed and formed into a pressed product.

That is, the method for producing an aluminum powder press-molded article of the present invention comprises: before press-forming the aluminum powder, contacting the aluminum powder with a fluorine-based gas in a heated state to form fluoride on the surface thereof. At the same time, the upper sa-fluoride film is removed by being brought into contact with a nitriding gas in a heated state, and at the same time, the removal layer (the surface layer of the aluminum powder) is formed into a hard nitride). According to this method, the surface of the aluminum powder is purified and activated by performing fluoridation prior to nitriding, so that the nitriding layer can be formed evenly and deeply. This makes it possible to make the thickness of the hard honey layer rich in properties uniform and thick. In this way, since no oxide film is formed on the surface of the aluminum powder at the time of E-forming and a hard nitrided layer is formed, the obtained press-formed product has excellent toughness, particularly excellent strength. It will be worthwhile.

Next, the present invention will be described in detail.

The fluorinated gas used for the fluorination treatment of the present invention is NF ₃ , B F,, CF ₄ , HF, SF,, Fi At least one fluorine source component selected from inert gas such as N ₂ . Among these fluorine瀛成content, reactivity, surface in NF _S such as handling properties is practical and best.

As described above, the manufacturing method of the present invention comprises, as described above, aluminum powder (a mixture of aluminum alone or other metal powder such as titanium powder and magnesium powder) with the above-mentioned fluorine-based gas, for example, NF _In the case of _S , the surface of the aluminum powder is fluorinated by contacting at a temperature of 250 to 400, and then nitriding (or nitriding) is performed using a known nitriding gas such as ammonia. The concentration of a fluorine source component such as NF in such a fluorine-based gas is, for example, from 1,000 to 10,000 ppm, preferably from 20,000 to 70,000 ppm, and more preferably from 30,000 to 50,000 ppm. The time of contact with such a fluorine-based gas may be selected from an appropriate time according to the type of aluminum powder, the type of powder mixed with the aluminum powder, the heating temperature, etc., and is usually several minutes. .

To explain the production method of the present invention more specifically, aluminum powder is introduced into, for example, a gas treatment chamber 9 provided in the heat treatment furnace 1 shown in FIG. 1 and brought into contact with a fluorine-based gas. The above furnace 1 is a bit furnace in which an inner vessel 4 is placed inside a heater 3 provided in an outer shell 2, and an exhaust pipe 6 is inserted into the inner vessel 4 from outside the furnace 1, and a gas inlet pipe 5 is provided. The powder outlet pipe 8 is inserted into the room from the upper side of the gas processing chamber 9 through the inner container 4, passing through the inner container 4 from the lower side of the gas processing chamber 9. Gas is supplied to the gas introduction pipe 5 from the cylinders 15 and 16 via the flowmeter 17 and the valve 18. In the figure, reference numeral 13 denotes a vacuum bomb and reference numeral 14 denotes an abatement system S.

In this configuration, the gas processing chamber 9 內 is heated to a predetermined reaction temperature. Then, a fluorine-based gas, for example, a mixed gas of NF, and N ₂ gas is blown up from the gas outlet 5a opened at the top of the gas introduction pipe 50. In addition, the on-off valve (not shown) provided in the powder storage tank 7 is opened to supply the aluminum powder 11 in the powder storage tank 7 to the powder outlet pipe 8, and the powder outlet 8a at the lower end thereof is provided. From the gas treatment chamber 9. Above I5NF, generates fluorine as an active group at a temperature of 250-400, and removes organic and inorganic contamination on the surface of aluminum powder 11 by collision with aluminum powder. Reacts with oxides such as Ajg ₂ Oa, A £ (OH), etc. on the surface of powder 11 as shown in the following formula to form ultra-thin fluoride AjgF, on the surface of aluminum powder 11 I do.

Α £ ι 0, + 6 F → 2 A Fa +3/20 _t

A £ (OH) t + 3F- »AjeF _a + 3 / 2H, 0

By this reaction, the oxide film on the surface of the aluminum powder 11 is converted into a fluoride film, and the 0, adsorbed on the surface is also removed. And, in the absence of 0 _¾ , Η,, Η, 0, the fluorinated aluminum is stable at the following temperature at 600, and the aluminum powder before the subsequent nitriding treatment is 1 1 to prevent the adsorption of formation and 0 ₂ of the oxide film to the fabric. In such a fluoridation treatment, a fluoride film is formed on the surface of the furnace material in the first stage, and the film is used to form a fluorine-based gas on the surface of the furnace material thereafter. Damage will be prevented. These fluorinated aluminum powders 11 are stored in a powder storage box 10 arranged at the bottom of the gas processing chamber 9.

After that, the aluminum powder 11 stored in the powder storage box 10 is nitrided using the same heat treatment furnace as the heat treatment furnace 1. Ie, heating the gas treatment chamber provided in the heat treatment furnace to nitrided temperature at 450 to 550, have a Nyuita ₃ or NH _S and a carbon source, in this state A mixed gas with the gas to be blown (eg, RX gas) is blown up from the gas outlet at the end of the gas inlet tube, and the aluminum powder 11 is dropped from the powder outlet tube to bring them into contact. As a result, the above-mentioned fluoride film is reduced or destroyed by H or a trace amount of water, for example, as shown in the following formula, whereby the active aluminum powder 11 is exposed and formed.

In this way, the active aluminum powder 11 is formed into the dough, and at the same time, the active N atoms penetrate and diffuse into the aluminum powder 11 and, as a result, contain AN on the surface of the dough. A compound layer (nitriding) is formed.

The formation of such a nitrided layer is the same in the conventional nitridation method, but in the conventional method, the oxide film formed on the surface rising from the room temperature to the honey temperature, Since the activity of the surface is reduced by the amount, the degree of surface adsorption of N atoms is low and non-uniform. Such non-uniformity is also magnified by the fact that it is practically difficult to keep the degree of decomposition of NH, uniformly in the reactor. According to the production method of the present invention, the adsorption of N atoms on the surface of the aluminum powder 11 is performed uniformly and quickly, so that the above-mentioned problem does not occur. As shown in FIG. 2, the aluminum powder 11 thus obtained has a surface layer formed of hard and uniform hard nitride A, as shown in FIG. Thereafter, the aluminum powder 11 is press-formed into an aluminum alloy product having a desired shape using a known HIP device 20.

As described above, in the manufacturing method of the present invention, since the oxide film on the surface of the aluminum powder 11 is removed before being applied to the HIP device 20, it is necessary to heat the aluminum powder 11 mixed with various powders. Powder with low melting temperature as powder to be mixed with aluminum powder 1 Even when β is used, the resulting molded product has excellent mechanical properties such as strength and toughness. Moreover, since the surface calendar of the aluminum powder 11 is formed of hard nitrided shoes, it is particularly excellent in strength.

As described above, in the method for producing an aluminum powder press-formed product of the present invention, fluorination is performed prior to nitriding. As a result, an erroneous film such as an oxide film on the surface of the aluminum powder is changed to a fluoride film, and the surface of the aluminum powder is protected. Therefore, even if there is a time passage between the formation of the fluoride film and the nitriding treatment, the fluoride film formed on the surface of the aluminum powder can protect the surface of the aluminum powder in good condition. As a result, the formation of the oxide film again on the surface of the aluminum powder is prevented. This fluoride film is decomposed and removed during the subsequent nitriding treatment, thereby exposing the surface of the aluminum powder. Since the surface of the exposed aluminum powder is in an active state, the Ν atom in the nitriding treatment spreads in the surface layer of the aluminum powder, and the Ν atom diffuses deeply and uniformly. Thereby, the surface layer of the aluminum powder is formed into a thick and uniform hard nitrided layer. Therefore, the resulting molded product has excellent mechanical properties such as strength and toughness.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view of a heat treatment furnace used in one embodiment of the present invention, FIG. 2 is a cross-sectional view showing a state of a nitride layer of aluminum powder, and FIG. 3 is a conceptual diagram of a Η.Ι.Ρ. .

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention will be described based on embodiments.

〔Example〕

After the trichloroethane π ethane washed Aruminiumu powder, the NF ₃ in the heat treatment furnace 1 as shown in FIG. 1 5 0 0 O ppm content to N ₂ gas Kiri囲 Contact at 300 ° C for several minutes. Thereafter, nitriding treatment was performed in the above heat treatment furnace 1 at 530 with a mixed gas of 50% NK15QHNi for several minutes, and then, the mixture was air-cooled and taken out. The obtained aluminum powder had a nitride thickness of 5 to 10 m and a surface hardness of 190 to 210 OHv. This surface hardness is much higher than that obtained by nitriding by a conventionally known method. After that, an aluminum alloy product having a desired shape was obtained by using the HI device as described above. This aluminum alloy product had much higher strength and toughness than the conventional aluminum alloy product.

Claims

The scope of the claims

1. The aluminum powder is brought into contact with the fluorine-based gas in a heated state, and then the aluminum powder is brought into contact with the nitriding gas in a heated state to form a hard nitride on the surface layer of the aluminum powder. A method for producing an aluminum powder press-formed product, wherein the aluminum powder having the nitrided layer formed thereon is directly press-formed into a press-formed product.