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Method for molding aluminum and aluminum alloy powder

a technology of aluminum alloy and powder, which is applied in the direction of turbines, mechanical equipment, transportation and packaging, etc., can solve the problems of inconvenient powder injection molding method, difficult inability to manufacture high-density sintered bodies, etc., to achieve good corrosion and weathering resistance, low density, and high thermal conductivity and electrical conductivity

Inactive Publication Date: 2018-10-25
RES COOPERATION FOUND OF YEUNGNAM UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a powder injection molding technology for aluminum and aluminum alloys. This technology has advantages such as low density, high thermal conductivity and electrical conductivity, good corrosion and weathering resistance, and natural color, and also has excellent mechanical properties due to a high precipitation hardening effect depending on alloying. The method involves a single step in a same furnace using a single heating schedule, reducing the number of processes, energy consumption, and labor costs. The aluminum or aluminum alloy manufactured using the powder molding method may not necessarily include a sintering aid alloying element, resulting in a sintered body with enhanced mechanical properties. The powder molding method can be applied to various commercial aluminum alloys and can have a significant industrial effect in production of precision parts required for various purposes. Additionally, the invention provides a method of reinforcing an aluminum or aluminum alloy base with various materials to create a composite part.

Problems solved by technology

However, a powder injection molding technology has not yet been used industrially for aluminum and aluminum alloys.
The reason why the powder injection molding method is not industrially used for aluminum or aluminum alloys mainly is that it is difficult to manufacture a high-density sintered body.
Accordingly, due to the presence of such an oxide film that acts as an obstacle to material transfer between the adjacent particles in contact for densification, aluminum has been recognized as a material that is not suitable for the powder injection molding method.
However, the nitridation reaction may cause a big problem when a nitrogen gas is used as an atmospheric gas during a sintering process of a powder molded body according to the present invention, which is made of fine metal powder having a large specific surface area and a high reactivity, and having porosity of 50% to 10% after debinding.
That is, since the surface of aluminum powder is exposed to the nitrogen gas even before the onset of a sintering reaction between particles during debinding and further heating for a sintering, an aluminum nitride starts to form, and thus atomic migration across the interface between adjacent aluminum powders being in contact is inhibited, inter-particle bonding and densification during the sintering process are interfered.
Another reason why powder injection molding of aluminum is difficult compared to other metals is that a melting point of aluminum or a solidus temperature at which an aluminum alloy is liquefied and starts to melt is remarkably low compared to other metals, such as iron, stainless steel, nickel, copper, cobalt, titanium, etc., or alloys thereof.
Another problem to be solved during debinding and sintering of an aluminum molded body containing a large amount of an organic binder is formation of aluminum carbide (Al4C3) through a reaction between decomposed product of the organic binder and aluminum.
The aluminum carbide is brittle and is undesirable since it reacts with moisture by a reaction of Al4C3+6H2O=2Al2O3+3CH4.
As described above, various methods have been proposed for powder injection molding of aluminum and alloy thereof, but a method of precisely producing a complex-shaped product while properly realizing mechanical properties of aluminum alloys has not been provided yet.

Method used

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  • Method for molding aluminum and aluminum alloy powder
  • Method for molding aluminum and aluminum alloy powder
  • Method for molding aluminum and aluminum alloy powder

Examples

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example 1

[0088]A 300 g of feedstock having a solids loading of 62% was prepared by kneading aluminum powder having purity of 99.5% and an average particle size of about 6 μm (MEP 105, Ecka Granules, Germany) and an organic binder containing 70 wt % of paraffin wax, 16 wt % microcrystalline wax, 6 wt % maleic anhydride grafted polyethylene (DP-730, Hyundai EP, Korea) as a polyethylene copolymer having a carbonyl group, and 8 wt % polyethylene wax in a pressurized kneader at 140° C. for 2 hours. The resulting feedstock was crushed into about 6 mm sized granules, charged into an injection molding machine having clamping force of 80 tons, and injection-molded to produce an injection molded body of a tensile test specimen of ASTM subsize standard (ASTM E8).

[0089]The injection molded body was cut and inspected visually to examine presence of an internal defect and also through an X-ray non-destructive test, and it was confirmed that the injection molded body was defect-free.

[0090]After placing the...

example 2

[0093]About 50 g of feedstock having a solids loading of 65% was prepared at 135° C. for 2 hours by kneading, in a twin-cam mixer (Rheocord 90, Haake, Germany), gas-atomized 99.8% purity aluminum powder (Aluminum powder company, U.K.) having an average particle size of about 6 pm and an organic binder containing 60 wt % paraffin wax, 26 wt % microcrystalline wax, 8 wt % maleic anhydride grafted polyethylene (DP-730, Hyundai EP, Korea) as the polyolefin copolymer having a carbonyl group, and 6 wt % polyethylene wax.

[0094]The feedstock was crushed into about 3 mm granules by using a steel mortar and pestle, charged into a steel mold preheated to 120° C., and then compression-molded under pressure of 20 MPa to manufacture an molded body of a small and non-standard tensile test specimen having a total length of 50 mm, a length of a parallel section of 20 mm, a width of a grip section of 16 mm, and a width of the parallel section of 5 mm.

[0095]After placing the molded body of the tensile...

example 3

[0096]A 500 g of feedstock having a solids loading of 67% was prepared by kneading gas-atomized AA6061 aluminum alloy powder (Al-0.91 wt % Mg-0.70 wt % Si-0.26 wt % Cu, Aluminum powder company, U.K.) having an average particle size of about 6 μm with an organic binder containing 58 wt % paraffin wax, 26 wt % microcrystalline wax, 10 wt % maleic anhydride grafted polyethylene (DP 730, Hyundai EP, Korea) as a polyolefin copolymer containing a carbonyl group, and 6 wt % polyethylene wax, in a double-blade planetary mixer at 140° C. for 2 hours. The resulting feedstock was crushed into granules, charged into a hopper of an injection molding machine, and injection-molded to form a defect-free injection molded body of a tensile test specimen without any internal defect. In addition, another specimen having a disc shape with a diameter of 20 mm and a height of 4 mm was prepared via warm compression molding using a steel mold preheated to 118° C.

[0097]The tensile test specimen was placed on...

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Abstract

A powder molding method of aluminum and aluminum alloy includes: preparing a feedstock by kneading aluminum powder, aluminum alloy powder, or aluminum composite powder containing a reinforcing material with a thermoplastic organic binder; molding the feedstock to a product having a complex shape via powder injection molding, compression molding, or extrusion molding; and then producing a high-density sintered body having relative density of at least 96% by performing debinding and sintering in a single heating process under an argon gas atmosphere.

Description

TECHNICAL FIELD[0001]The present invention relates to a precision part manufacturing technology, whereby a product having a complex and precise shape is manufactured to a near net shape via a powder molding method, such as powder injection molding, warm compression molding, warm powder extrusion, or the like by using metal powder of aluminum or aluminum alloy as a raw material.[0002]Further, the present invention relates to a precision part manufacturing technology, whereby a precision part is manufactured by a composite material, in which aluminum or aluminum alloy is reinforced with a ceramic or another inorganic reinforcing material.BACKGROUND ART[0003]Various precise shape manufacturing technologies are available as powder molding processes, such as powder injection molding, warm compression molding, warm powder extrusion, etc., whereby a complex shape is formed by using a feedstock including a powder material and a sufficient amount of an organic binder. In particular, as alrea...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B22F7/00B22F1/00B22F3/10B22F3/22B22F3/12B22F5/04B22F5/10B22F9/08B22F1/102
CPCB22F7/008B22F1/0062B22F3/1021B22F3/225B22F3/1007B22F3/12B22F5/04B22F5/10B22F9/082B22F2201/11B22F2301/052B22F2302/10B22F2302/20B22F2302/25B22F9/04B22F2009/043C22C21/08B22F3/20B22F3/1025B22F3/227B22F5/009C22C1/0416B22F2003/145B22F2003/208B22F2998/10B22F2999/00B22F1/102
Inventor HAN, KWAN HEELEE, HAN-SOL
Owner RES COOPERATION FOUND OF YEUNGNAM UNIV
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