CN100457332C

CN100457332C - Injection molding process of AZ91 Mg alloy

Info

Publication number: CN100457332C
Application number: CNB2007100640968A
Authority: CN
Inventors: 何新波; 曲选辉; 姜海; 祝丽叶
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2007-02-28
Filing date: 2007-02-28
Publication date: 2009-02-04
Anticipated expiration: 2027-02-28
Also published as: CN101020241A

Abstract

The injection molding process of AZ91 magnesium alloy belongs to the field of magnesium alloy forming technology. The injection molding process includes the following steps: mixing AZ91 magnesium alloy powder in size of 47 micron and water soluble adhesive of PEG and PMMA in certain ratio, pelletizing, injection molding, solvent defatting and heat defatting to eliminate adhesive, and sintering at 580-620 deg.c under inert gas protection to obtain the product. The present invention has the advantages of low cost and capacity of producing magnesium alloy of complicated shape and excellent performance.

Description

A kind of ejection forming method of AZ91 magnesium alloy

Technical field

The invention belongs to Mg alloy formed technical field, a kind of AZ91 (the magnesium alloy model is a kind of, wherein contains the about 9wt.% of Al, and it is about 1% to contain Zn, and other is magnesium and small amount of impurities) particularly is provided the magnesium alloy ejection forming method.Be applicable to preparation high-performance, high dimensional accuracy, the magnesium alloy parts of complicated shape.

Background technology

Magnesium alloy is a lightest present structural metallic materials, has very high specific strength and specific stiffness, physical properties such as good heat radiation, electromagnetic shielding, damping shock absorption, high strain rate energy absorption characteristics, shock resistance, and it is easy to be recycled that product satisfies environmental requirement.Since the nineties in 20th century, breakthrough along with technology and price two big bottleneck problems, whole world magnesium alloy consumption sharp increase, magnesium alloy obtains people's attention gradually with its particular performances, emergence becomes the third-largest engineering metal material after iron and steel and aluminium rapidly, be described as " 21 century green engineering material ", be expected to become important commercial lightweight structural material.

The method for preparing at present AZ91 magnesium alloy parts mainly contains: technologies such as die casting, extrusion forging.The copper alloy part of the method for hot investment casting or casting+machining preparation component segregation occurs, tissue odds spares, is mingled with defectives such as more easily, and these two explained hereafter efficient are low, and the production cost height is difficult to realize producing in batches.Machining after the die casting also can cause raw-material a large amount of waste.Extrusion forging technology can be prepared the magnesium alloy of superior performance, but shortcomings such as this method also exists, and forging temperature is wayward, molding procedure is many, mould design complexity, and adopt this method can't produce complex-shaped part, thereby influence being extensive use of of this manufacturing process.

Metal injection moulding technology is prior powder metallurgy to be combined with plastic injection-moulded forming technique and a kind of new parts process technology that forms, compare with traditional technology, adopt injection molding process to prepare the AZ91 magnesium alloy parts and have following advantage: 1) can be according to using needs, make the magnesium alloy parts of various complicated shapes easily, as camera, phone housing etc.; 2) can guarantee the uniformity of part interior tissue and composition, make magnesium alloy obtain favorable conductive and heat conductivility; 3) technology is simple, the production efficiency height, and product size precision height, and stock utilization can reduce production costs effectively near 100%.

Summary of the invention

The objective of the invention is to, a kind of AZ91 magnesium alloy ejection forming method is provided, can realize producing magnesium alloy parts complex-shaped, function admirable in batches with lower cost.

The present invention adopts ejection forming method to prepare the shaping base, prepares magnesium alloy parts by degreasing and sintering then.Concrete technology is:

1, the preparation of binding agent: in whole binding agent, polyethylene glycol PEG accounts for 70～80% of mass percent, and polymetylmethacrylate accounts for 20～25% of mass percent, and stearic acid SA accounts for 2～5% of mass percent.Wherein, because the difference of water-soluble, the shrinkage of the PEG of different molecular weight, intensity aspect, the solid PEG prescription that adopts is 10%PEG600+30%PEG1000+60%PEG1500.Consider PEG and PMMA mixed effect, mix effects such as back intensity, swelling, selecting molecular weight for use is 98.4 * 10 ⁴PMMA have better effect.To carry out blend in PEG, PMMA, SA constituent element adding torque rheometer or the double helix extruder, and it is even to reach composition;

2, mixing: is 58～66vol% on rubber mixing machine mixing 1～1.5 hour with selected magnesium alloy powder and the binding agent prepared according to the powder useful load, melting temperature is 70 ℃, granulate on mixing extruder, make feeding further even, the powder useful load is 58～66vol%;

3, injection moulding: the back of granulating is 80 ℃ in injection temperature, and injection pressure is to inject under the condition of 80～100MPa, obtains the magnesium alloy preform of required form;

4, degreasing: the degreasing process of solvent degreasing+subsequent thermal degreasing is adopted in the degreasing of shaping base, at first preform is dipped in and carries out solvent degreasing 4～8 hours in the deionized water, and skimming temp is 3040 ℃, takes out blank after degreasing is finished, then oven dry; Hot degreasing is carried out between 30～410 ℃, needs 6～10 hours altogether;

5, sintering:, be incubated 0.5～1 hour, the high-purity argon gas atmosphere protection with 580～620 ℃ the sintering temperature in sintering furnace of base after the degreasing.

The selected copper alloy powder of the present invention is an aerosolization AZ91 magnesium alloy powder, and the particle diameter of powder is 6～50 μ m.

The invention has the advantages that: adopt the AZ91 magnesium alloy alloy of the method preparation, relative density is greater than 95%, and hot strength is greater than 90MPa, and dimensional accuracy is within ± 0.5%.

The specific embodiment

Embodiment 1:

Raw material: binding agent is that 78%PEG, 20%PMMA, 2%SA form by mass percent, and AZ91 magnesium alloy powder average grain diameter is 47 μ m, and the powder useful load is 66vol%.

With powder and the binding agent for preparing on opening rubber mixing machine mixing 1.5 hours, melting temperature was 70 ℃, granulates on mixing extruder again, and feeding is mixed.Feeding after the granulation is 80 ℃ in injection temperature; injection pressure is to inject under the condition of 100MPa; obtain the magnesium alloy preform of required form; then preform was immersed in the deionized water degreasing 6 hours; skimming temp is 30 ℃; taking out blank after degreasing is finished dries in thermostatic drying chamber; hot degreasing is carried out between 30～400 ℃; degreasing is 10 hours altogether; after the degreasing degreasing base is heated to 630 ℃ and carried out sintering 1 hour, protective atmosphere is a high-purity argon gas, promptly gets relative density 95%; tensile strength 91MPa, the copper alloy element of dimensional accuracy within ± 0.3%.

Embodiment 2:

Raw material: binding agent is that 70%PEG, 25%PMMA, 5%SA form by mass percent, and AZ91 magnesium alloy powder particle diameter is 47 μ m, and the powder useful load is 60vol%.

With powder and the binding agent for preparing on opening rubber mixing machine mixing 1.5 hours, melting temperature was 70 ℃, granulates on mixing extruder again, and feeding is mixed.Feeding after the granulation is 75 ℃ in injection temperature; injection pressure is to inject under the condition of 90MPa; obtain the copper alloy preform of required form; then preform was immersed in the deionized water degreasing 7 hours, skimming temp is 30 ℃, takes out blank after degreasing is finished and dries in thermostatic drying chamber; hot degreasing is carried out between 30～410 ℃; degreasing is 12 hours altogether, after the degreasing degreasing base is heated to 610 ℃ of sintered heat insulatings 1 hour, and protective atmosphere is a high-purity argon gas.Promptly get relative density 97%, hot strength 101MPa, the magnesium alloy parts of dimensional accuracy within ± 0.4%.

Embodiment 3:

Raw material: binding agent is that 75%PEG, 22%PMMA, 3%SA form by mass percent, and AZ91 magnesium dust particle diameter is 32 μ m, and the powder useful load is 64vol%.

With powder and the binding agent for preparing on opening rubber mixing machine mixing 1 hour, melting temperature was 70 ℃, granulates on mixing extruder again, and feeding is mixed.Feeding after the granulation is 85 ℃ in injection temperature; injection pressure is to inject under the condition of 95MPa; obtain the copper alloy preform of required form, then preform was immersed in the deionized water degreasing 6 hours, skimming temp is 40 ℃; taking out blank after degreasing is finished dries in thermostatic drying chamber; hot degreasing is carried out between 30～420 ℃, and degreasing is 8 hours altogether, after the degreasing degreasing base is heated to 600 ℃ and carries out sintering; sintering time is 0.5 hour, and protective atmosphere is a high-purity argon gas.Promptly get relative density 96%, hot strength 89MPa, the magnesium alloy parts of dimensional accuracy within ± 0.2%.

Claims

1, a kind of ejection forming method of AZ91 magnesium alloy is characterized in that, technology is:

The preparation of a, binding agent: in whole binding agent, polyethylene glycol PEG accounts for 70～78% of mass percent, and polymetylmethacrylate accounts for 20～25% of mass percent, and stearic acid SA accounts for 2～5% of mass percent; The PEG prescription that adopts is 10%PEG600+30%PEG1000+60%PEG1500; Selecting molecular weight for use is 98.4 * 10 ⁴PMMA, will PEG, PMMA, the SA constituent element adds in torque rheometer or the double helix extruder and carry out blend, and it is even to reach composition;

B, mixing: is 58～66vol% on opening rubber mixing machine mixing 1～1.5 hour with selected magnesium alloy powder and the binding agent prepared according to the powder useful load, and melting temperature is 70～80 ℃, granulates on mixing extruder again, makes feeding further even;

C, injection moulding: the back of granulating is 80～90 ℃ in injection temperature, and injection pressure is to inject under the condition of 90～100MPa, obtains the magnesium alloy preform of required form;

D, degreasing: the degreasing of shaping base adopts solvent degreasing to add the degreasing process of subsequent thermal degreasing, at first preform is dipped in and carries out solvent degreasing 4～8 hours in the deionized water, and skimming temp is 30～40 ℃, takes out blank after degreasing is finished, then oven dry; Hot degreasing was carried out between 30～410 ℃ 6～14 hours;

E, sintering: with 580～620 ℃ the sintering temperature in sintering furnace of briquet after the degreasing, be incubated 0.5～1 hour, adopt the high-purity argon gas atmosphere protection in the sintering process.

2, method according to claim 1 is characterized in that: selected magnesium alloy powder manufacturing process is the injection moulding processing technology, and used powder is an aerosolization AZ91 magnesium alloy powder, and the particle diameter of powder is 6～50 μ m.