KR20150108248A - Outside densification method for aluminum alloy sintered parts - Google Patents

Abstract

The present invention provides a method to produce a product using aluminum alloy powder to increase strength and durability which can be applied to a variety of industrial areas including automobiles which require a lightweight and durable material. The surface densification method of the present invention comprises: a mixing process to add aluminum alloy powder, which is a mixture of silicone (Si), copper (Cu), magnesium (Mg), and zinc (Zn), and a solid lubricant easy for shape formation and easy detachment of a mold to an aluminum (Al) powder, which is a material for sintering, and mixing them; a molding process to supply the mixed aluminum alloy powder into the mold of the desired shape, providing pressure and making it into the intended shape; a sintering process to provide heat and provide properties to the molded shape body for a chemical combination to be conducted by a movement of atom diffusion between the powder particles; a densification process which increases a surface density and a hardness of the part connected to the other parts combined by improving a degree of precision in the sintering process; and a heat treatment process for going through a film treatment or a heat treatment to improve a quality and a durability of the product after densification.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of densifying a surface of an aluminum alloy sintered product,

The present invention relates to a method of densifying a surface of an aluminum alloy sintered product, and more particularly, to a method of densifying a surface of an aluminum alloy sintered product, and more particularly to a method of densifying a surface of an aluminum alloy sintered product It is one thing.

Compared with conventional techniques such as casting and roll forming, molding sintering using metal powder is a technique widely used in recent years due to its simplicity of process, improvement of precision, weight and cost reduction.

Such a sintering process is a mixing process in which a solid lubricant is added to various metal powders such as iron (Fe) powder, copper (Cu) powder and alloy powder to be used for sintering, ;

A shaping step of premixing the mixed powder into a mold having a desired shape and applying pressure to form the shape;

A sintering process for imparting physical properties by applying heat so that chemical bonds are formed by atomic diffusion between powder particles formed in the molding process;

A squeezing step of squeezing deformation due to dimensional deformation or warping or the like which may occur in the sintering step so as to improve overall accuracy;

And a post-treatment process through heat treatment, finishing and coating treatment for improving the quality and durability of the product after the shaping process.

Patent No. 10 - 2011 - 0104287 Patent No. 10 - 2012 - 0017964

When various kinds of industrial parts are completed by the sintering method as described above, high precision can be obtained, and not only the quality can be improved, but the overall manufacturing cost can be reduced. However, In the case of products, the durability of the interlocking parts is weak, so a shaping process is added to densify the tissue.

Since the sintered product to which the prior art is applied is formed by sintering a metal powder of iron (Fe) system, the sintering condition for maintaining the shape in the molding step or the molded state before the sintering step is a high- After the sintering is completed, the shaping process is performed to densify the structure.

Efforts have been made to obtain products by molding and sintering aluminum-based alloy powder materials in which silicon, zinc, copper, and magnesium are mixed while taking out aluminum from the iron-based metal powders in recent years. In the case of such aluminum alloys, It has high durability and is used in automobile and other industrial fields.

When the process of shaping and sintering an iron-based metal powder as such is applied to an aluminum alloy as it is, not only normal molding is performed, but also aluminum can not be maintained in a sintering process A mischief occurs.

In addition, aluminum alloy is lightweight and can provide ease of molding and processing. However, since it is practically difficult to perform heat treatment at a high temperature such as metal in order to increase hardness and strength, It is a technical problem to densify the surface texture of the outer surface or the inner surface which is connected or interlocked with other products, which is essentially a sintered product.

In order to densify the surface texture of the product sintered with the aluminum alloy as described above, if the sintering process is performed under the same conditions as the metal powder, it is difficult to obtain a normal product in the sintering process. Even if it is obtained, cracks are generated in the molded or sintered product due to excessive pressure in the densification process, or in case of severe damage, the product of the desired shape is not obtained.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems and it is an object of the present invention to provide a method of manufacturing a sintered aluminum (Al) powder, which comprises mixing silicon (Si), copper (Cu), magnesium (Mg) Alloy powders and shapes are easily mixed and added with solid lubricant for ease of mold release. Mixed aluminum alloy powder is supplied to a mold of desired shape and pressure is applied to make the shape of the desired bar. A sintering process for imparting physical properties by applying heat so that chemical bonding by atomic diffusion between the powdered particles is performed between the molded body and the sintered body; And a densification step of densifying the densification by increasing the hardness, and a densification step of densifying the product to improve the quality and durability of the product, And a heat treatment step through a process such as a heat treatment;

It is possible to produce products which can increase strength and durability by using aluminum alloy powder, which can be applied to various industrial fields such as automobiles in light weight and durability.

In the present invention, by densifying a molded and sintered body made of an aluminum alloy and sintering it, the densification and hardness of the surface texture at the position where it is connected to other parts are increased to improve durability, It is possible to maintain the uniformity while increasing the quality.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram showing an example of a surface densification method of an aluminum alloy sintered product to which the technique of the present invention is applied; FIG.
2 is a process diagram of two examples showing a method of densifying a surface of an aluminum alloy sintered product to which the technique of the present invention is applied.
3 is a graph showing the depth variation obtained by the surface densification method of an aluminum alloy sintered product to which the technique of the present invention is applied.
4 is a graph showing a change in density obtained by a method of surface densification of an aluminum alloy sintered product to which the technique of the present invention is applied.
5 is a graph showing changes in surface hardness according to a surface densification method of an aluminum alloy sintered product to which the technique of the present invention is applied.
6 is a graph showing changes in core portion hardness according to a surface densification method of an aluminum alloy sintered product to which the technique of the present invention is applied.
7 is a process diagram showing the sintering and surface densification process to which the prior art is applied.

Hereinafter, a preferred surface densification process according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a process chart showing an example of a surface densification method of an aluminum alloy sintered product to which the technique of the present invention is applied, FIG. 2 is a process drawing showing two methods of densifying a surface of an aluminum alloy sintered product to which the technique of the present invention is applied, FIG. 3 is a graph showing the depth variation obtained by the surface densification method of the aluminum alloy sintered product to which the technique of the present invention is applied, FIG. 4 is a graph showing the density variation obtained by the surface densification method of the aluminum alloy sintered product, FIG. 5 is a graph showing surface hardness variation according to the surface densification method of an aluminum alloy sintered product to which the technique of the present invention is applied, and FIG. 6 is a graph showing the surface densification of an aluminum alloy sintered product to which the technique of the present invention is applied. As a graph showing the change in deep portion hardness according to the present invention.

A method of densifying a surface of an aluminum alloy sintered product to which the technique of the present invention is applied is a method of densifying the surface of an aluminum alloy sintered product to which aluminum (Al) powder as a material for sintering is mixed with silicon (Si), copper (Cu), magnesium (S100) in which a solid lubricant is added and mixed for ease of alloy mold powder and shape release as well as ease of mold release;

A forming step S200 of supplying a mixed aluminum alloy powder to a metal mold having a desired shape and forming a desired bar shape while applying pressure;

A sintering step (S300) of applying a heat to the shaped body formed in the forming step (S200) so as to cause chemical bonding by atomic diffusion between the powder particles, thereby imparting physical properties;

A densification step (S400) of correcting the deformation due to dimensional deformation or warpage or the like which may occur in the sintering process (S300) to improve the overall precision and densifying the surface density and hardness of the part connected to other parts to be joined to increase densification;

After the densification step (S400), the molding and sintering is completed in a heat treatment step (S500) through a process such as coating or heat treatment for improving the quality and durability of the product.

As another example of the present invention, an aluminum alloy powder obtained by mixing silicon (Si), copper (Cu), magnesium (Mg) and lead (Zn) with aluminum (Al) powder to be a sintering material, (S100) in which a solid lubricant is added and mixed for ease of use;

A forming step S200 of supplying a mixed aluminum alloy powder to a metal mold having a desired shape and forming a desired bar shape while applying pressure;

A sintering step (S300) of applying a heat to the shaped body formed in the forming step (S200) so as to cause chemical bonding by atomic diffusion between the powder particles, thereby imparting physical properties;

A heat treatment step (S500) of passing through processes such as coating or heat treatment for improving the quality and durability of the product through the sintering process (S300);

In the densification step (S400) of increasing the surface density and hardness of the parts connected to the other parts to be combined while correcting the deformation due to dimensional deformation, warping, etc. occurring in the heat treatment step (S500) And the densification process may be changed and completed.

In the forming step (S200), it is preferable that aluminum alloy powder is supplied to a metal mold processed to a desired shape and then pressed at a pressure of 5 ton / cm2 or more. If the pressure is 5 ton / The shape can be maintained at the initial stage of molding. However, when an impact or vibration is transmitted from the outside in the process of moving for sintering or when the sintering process is exposed to a high temperature, deformation or damage, It is not preferable.

In the sintering process (S300), sintering is performed for 1 hour at a temperature of 550 to 610 ° C in a mesh belt (Mesh Belt Furnace) or a pusher furnace in a nitrogen gas (N ₂ gas) atmosphere, The sintered relative density is set to 96%.

The sintering temperature should be within a range of ± 3 ° C. This is to ensure that the aluminum alloy powder is not in a solid state or in a liquid state but in the form of a gel which covers the surface of other alloy powders If the temperature is low, gelation does not occur. If the temperature is high, it is in a completely liquefied state, so that the relative density after sintering becomes remarkably low.

It is preferable that the distribution of oxygen (O ₂ ) in the nitrogen gas in the sintering process is 3 ppm or less because if the oxygen content is 3 ppm or more, the surface of the aluminum alloy powder is oxidized during the sintering process.

In the densification step (S400), the surface of the sintered product is densified by being connected to a rolling die that is engaged with the surface of the product after sintering. When the feed density is 96%, the product may crack or break Therefore, the feed amount of the sintered product is preferably from 0.3 to 0.7 mm / min and the rotation speed is preferably from 50 to 100 rpm as a condition for densification to a depth of 0.3 to 1.2 mm on the surface of the sintered product.

In a state satisfying the above condition

A specimen of a circular plate having a diameter of 1.5 cm and a diameter of 2.0 cm and a diameter of 10 cm is subjected to the dipping step S400 after completing the mixing step S100 and the forming step S200 and then the sintering step S300, The densification of the outer surface of the test piece was performed under the same conditions as those of FIGS. 3 to 6.

As the amount of precursor increases, the densification depth increases and the density becomes higher and the surface hardness becomes higher. As a result, the desired sintered product is formed by using the aluminum alloy powder, and then densified to densify the surface to obtain strength and durability It has various applications such as parts and equipments in general industry as well as automobile field.

Claims (6)

Aluminum alloy powder in which silicon (Si), copper (Cu), magnesium (Mg) and zinc (Zn) are mixed with aluminum (Al) powder to be a material of sintering, A mixing step (SlOO) of adding and mixing lubricating oil;
A forming step S200 of supplying a mixed aluminum alloy powder to a metal mold having a desired shape and forming a desired bar shape while applying pressure;
A sintering step (S300) of applying a heat to the shaped body formed in the forming step (S200) so as to cause chemical bonding by atomic diffusion between the powder particles, thereby imparting physical properties;
A densification step (S400) of correcting the deformation due to dimensional deformation or warpage or the like which may occur in the sintering process (S300) to improve the overall precision and densifying the surface density and hardness of the part connected to other parts to be joined to increase densification;
And a heat treatment step (S500) of passing the densification step (S400) through a coating process or a heat treatment process for improving the quality and durability of the product. The method for densifying a surface of an aluminum alloy sintered product according to claim 1, The method of claim 1, further comprising:
Wherein the aluminum alloy powder is supplied to the metal mold so as to maintain the desired shape and then pressed at a pressure of 5 ton / cm2 or more to form the aluminum alloy sintered product in the molding step (S200). The method of claim 1, further comprising:
The sintering step (S300) in a nitrogen gas (N ₂ Gas) sintering at a temperature of 550 ℃ in an atmosphere with a relative density of the aluminum alloy sintering product characterized in that sintering for one hour so that 96% of the surface densification methods. The method of claim 1, further comprising:
Wherein the temperature variation during sintering in the sintering step (S300) is +/- 3 DEG C. The method of claim 1, further comprising:
Wherein the oxygen (O ₂ ) distribution in the furnace in the nitrogen gas atmosphere in the sintering step (S300) is set to 3 ppm or less so as to prevent the surface of the aluminum alloy powder from being oxidized. The method of claim 1, further comprising:
In the densification step (S400), when the rolling dies that are in contact with the surface of the sintered product are densified by sintering, the feed amount of the sintered product is 0.3 to 0.7 mm / min, the rotation speed is 50 to 100 rpm, Wherein the surface of the product is densified to a depth of 0.3 to 1.2 mm.

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