JP2936695B2 - Aluminum alloy powder forging method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a high-performance aluminum alloy part by a powder forging method.

[Conventional technology]

In recent years, powder metallurgy alloys (P / M), which are formed by solidifying aluminum alloy powders such as Al-Si based on the rapid solidification method by powder metallurgy, have been put into practical use. Used in many fields such as automotive parts.

As a method for forming and solidifying the aluminum alloy powder, a powder extrusion method, a hot press method, a canned hot press method, a powder rolling method, and the like are known, and among them, the powder extrusion method is most commonly used. The reason is that the aluminum alloy powder has a stronger oxide film on the surface, but the extrusion method can destroy the oxide film by a large shear deformation to create a new surface, thereby obtaining a strong bond. However, the extrusion method has a drawback that it is limited to the production of a product having a constant cross-sectional shape because of the uniaxial extrusion.

On the other hand, the powder forging method has an advantage that a three-dimensional complex shape of a nano-shape product can be obtained, and has already been put to practical use in iron-based powder metallurgy. It was not used. However, according to the powder forging method disclosed in JP-A-62-224602, a solid having good mechanical strength characteristics can be produced from an aluminum alloy powder.

However, in practice, a solidified product having good mechanical strength cannot be obtained due to entrainment of a mold lubricant and humidification deterioration of the lubricant by a solvent, and the present situation is that it has not yet been put to practical use.

That is, in the powder forging, unlike the forging of a billet material by melting and casting without a true density and voids, the powder preform has porous and permeable voids, so that the mold lubricant passes through the voids during forging. Water or an organic solvent, which is a solvent for a lubricant, is vaporized by contact with a high-temperature mold or a preformed body, and is vaporized through pores into the preformed or solidified body. Absorbed. The confined components such as a lubricant and a solvent evaporate and expand in a later step such as solution heat treatment, and yield the surrounding material to form blisters and microvoids. For this reason, the surface layer of the solidified body usually has a defect layer to a depth of about 1.5 mm,
The strength of the solidified body was greatly reduced, resulting in a loss of reliability.

Therefore, it cannot be used as a reliable product unless this defective layer is removed.However, since the Al-based alloy powder produced by the rapid solidification method is expensive, making useless allowance increases the raw material cost, Since the cutting is performed, the cutting time is prolonged and the tool life is shortened, so that the processing cost is increased.

[Problems to be solved by the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a powder forging method capable of producing a high-strength and highly-reliable Al alloy part without the influence of a forging lubricant or a solvent.

[Means for solving the problem]

In order to achieve the above object, a method for forging an aluminum alloy powder of the present invention comprises the steps of: preheating a preformed body of a cold-formed aluminum alloy powder; After covering with a material, solidifying by hot forging, and performing solution heat treatment, the shielding material is removed.

The aluminum alloy powder that can be used in the method of the present invention is not limited, and may be a composite reinforcing material in which fibers such as ceramics are dispersed.

[Action]

In the method of the present invention, when the preform is placed in the forging die, the necessary surface of the preform is covered with a thin plate-shaped shielding material,
Since the shield between the preform and the mold and the lubricant is shielded, the lubricant or solvent applied to the mold is prevented from being caught or absorbed into the preform or the solidified body by forging. Even in the subsequent solution heat treatment, defects such as blisters are not formed at least on the surface covered with the shielding material.

The shielding material must be a material that does not cause a remarkable diffusion reaction or an intermetallic compound refining reaction with the preformed body of the Al alloy powder in the forging process, and that can be easily removed later by cutting or the like. The thickness is thinner such as a foil, and the later removal is easier. However, the thickness may be an appropriate thickness in consideration of handling properties and the like.

The surface of the preform to which the shielding material is applied is the surface of a part where a healthy surface layer component is required or a part where a defect layer is likely to be formed deeply. Therefore, it may be one surface of the preform, Any surface may be used.

When performing forward or backward extrusion by forging accompanied by plastic flow, a shielding material made of a metal having ductility, for example, steel or aluminum or an aluminum alloy is required.

That is, at least the surface of the preformed body orthogonal to the pressing direction with respect to the forging die is covered with a metal shielding material having ductility, and if forging is performed with a forging die having a complicated uneven shape, plastic flow parallel to the pressing direction is performed. Since the metal shielding material is easily deformed along with this, a complicated near-net shape product can be manufactured by forward or backward extrusion molding along the shape of the forging die.

The forging method and conditions are not particularly limited as long as the Al alloy powder can be solidified.
The method or conditions disclosed in JP-A-62-224602 may be used.

〔Example〕

Example 1 Al manufactured by the atomization method and having the following compositions A to H
An alloy powder was prepared.

A: 2024 B: 7090 C: 2024 + 17wt% Si + 5wt% Fe D: 2024 + 20wt% Si + 5wt% Fe E: 2024 + 25wt% Si + 0.5wt% Fe + 0.5wt% Mn F: 2024 + 35wt% Si + 2wt% Ni G: Al + 40wt% Si H: 2024 + 15vol% SiC Fiber Next, each powder is cold-formed at a pressure of 4 ton / cm ² to a diameter of 80
a preform mm and height 30 mm, 47 in N ₂ gas atmosphere
The mixture was preheated at 0 ° C. for 1 hour and placed in a heating mold spray-coated with a water-soluble graphite lubricant. At this time, the cylindrical preform was covered with a metal shielding material according to the following forging conditions.

U: Preformed body only (no metal shielding material) V: Cover the upper surface of the preformed body with a pure Al plate with a diameter of 80mm x 1mm VV: Cover both upper and lower surfaces with the above pure Al plate W: Diameter of 80mm x thickness Cover the upper surface with a 5052Al alloy plate of 0.5mm WW: Cover both upper and lower surfaces with the 5052Al alloy plate above X: Cover the upper surface with a mild steel plate of diameter 80mm x 0.5mm XX: Cover both upper and lower surfaces with the above mild steel plate Y: Diameter Cover the lower and side surfaces with an 80 mm × 30 mm deep Al alloy concave container Z: Cover the lower surface and side surfaces with a household Al foil cup container WZ: Lower surface and side surfaces with a household Al foil cup container and 505 above
Then, the upper surface was covered with a 2Al alloy plate. Thereafter, the solidified body was manufactured by hot forging at a pressure of 6 ton / cm ^{2 in} the vertical direction, and a T6 heat treatment was performed.

For each of the obtained products, the blisters were observed on the top, bottom and side surfaces.In each case, the blisters were generated on the surface not covered with the metal shielding material up to a depth of 5 mm. Therefore, no blisters were generated on the surface portion covered with the metal shielding material.

Further, the hardness distribution (micro Vickers hardness) of the upper surface was measured for the solidified body of the example of the present invention in which the powder E was forged under the forging condition W and the solidified body of the comparative example in which the powder E was forged under the forging condition U. As shown in FIG.

Example 2 Powders C, D, E and H of Example 1 were prepared, and
Cold-formed at a pressure of 4 ton / cm ² to obtain a cylindrical preform having a diameter of 80 mm and a height of 30 mm, and preheated at 490 ° C. for 1 hour in a N ₂ gas atmosphere. Fig. 1 to 3
As shown in (a) of the figure, forging conditions U, W and X in Example 1 were covered with a metal shielding material 2 and placed in a heating mold spray-coated with a water-soluble graphite lubricant, and a pressure of 6 ton / cm ² was applied. The front and rear extrusion molding was performed by hot forging accompanied by plastic flow in the above, and the solidified body 3 shown in each (b) of FIGS. Heat treatment was applied.

For each of the obtained products, the upper boss side surface of FIG. 1 (b), the ring side surface of the double ring of the upper boss side surface and the lower surface of FIG. 2 (b), the upper hole side surface and the lower side of FIG. 3 (b) The occurrence of blisters on the inner surface of the skirt was investigated. As a result, under the forging condition U which was not covered with the metal shielding material, blisters were generated in a portion from the surface to a depth of 2 mm regardless of the powder and the shape. However, under the forging conditions W and X covered with the metal shielding material, no blister was generated on the surface of any of the products.

After the powder E of the present invention was forged under forging conditions W and heat-treated, the upper boss side surface of the product having the shape shown in FIG. 1 (b) and the powder E of the comparative example were forged under forging conditions U and heat-treated. The hardness distribution of the upper boss side surface of the product having the shape shown in FIG. 1 (b) was measured and is shown in FIG. Further, FIGS. 6 and 7 show micrographs (× 50) of cross sections of the side surfaces of the upper boss showing the state of blistering of the same products of the present invention and the comparative example, respectively. The light gray part in FIG. 6 is a metal shielding material on the surface, and the black part in FIG. 7 is a blister.

〔The invention's effect〕

According to the present invention, a high-strength and highly reliable Al alloy part can be manufactured from an Al alloy powder without being affected by a forging lubricant or a solvent by the powder forging method.

[Brief description of the drawings]

1 to 3 are schematic cross-sectional views of specific examples showing the positional relationship of a shielding material according to the method of the present invention, wherein (a) shows a positional relationship with a preform and (b) shows a solidification after forging. The positional relationship with the body is shown. FIG. 4 is a graph showing the hardness distribution of the product surface obtained by the present invention example of Example 1 and FIG. 5 by Comparative Example. FIG. 6 is a photomicrograph of a metal structure of a product according to the present invention of Example 2 and FIG. 1 ... pre-formed body, 2 ... metal shielding material 5 ... solidified body

Continued on the front page (72) Inventor Yusuke Kotani 1-1-1, Koyokita, Itami-shi, Hyogo Pref. Within Itami Works, Sumitomo Electric Industries, Ltd. (72) Inventor Kiyoaki Akechi 1-1-1-1, Koyokita, Itami-shi, Hyogo No. Sumitomo Electric Industries, Ltd. Itami Works (56) References JP-A-3-219001 (JP, A) JP-A-1-270210 (JP, A) JP-A-2-117800 (JP, A) (58 ) Field surveyed (Int. Cl. ⁶ , DB name) B22F 3/02 B30B 11/00

Claims (2)

(57) [Claims] 1. A pre-formed body of cold-formed aluminum alloy powder is pre-heated, and at least one surface of the pre-formed body is covered with a thin plate-like shielding material in a mold, and is solidified by hot forging. A powder forging method of an aluminum alloy, wherein the shielding material is removed after heat treatment. 2. A forward or rearward extrusion molding by covering a surface of a preform at least orthogonal to a pressing direction with respect to a forging die with a shielding material made of a metal having ductility and forging with a plastic flow parallel to the pressing direction. The powder forging method for an aluminum alloy according to claim 1, wherein the method is forging.