AU6074498A - Billet for molding aluminum - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATfION STANDARD PATENT 1 Applicant: YASUDA METAL INDUSTRIES.,

LTD.

invention Title: BILLET FOR MOLDING ALUMINUM The following statement is a full description of this invention, including the best method of performing it known to me/us: t

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BILLET FOR HOLDING

ALUMINUM

BACKGROUND OF THE INVENTION This invention relates to a billet for molding aluminum by extrusion which is formed with vent grooves to prevent air trapped near the front end (end near the die of the container) of the billet from mixing into the aluminum material.

Aluminum extrusion molding methods are roughly classified into "direct extrusion", "indirect extrusion", "hydrostatic extrusion" and "conform extrusion". Figs. and 6 show the mechanism of the former two methods, and their load-extrusion curves Y and flow patterns F. As i 15 shown in Fig. 5B, the load decreases during extrusion.

The flow patterns F are markedly disturbed near the die (Figs. 5C). In the indirect extrusion, the load increases at the beginning of the load-extrusion curve 1, but stays substantially flat thereafter (Fig. 6B). The flow pattern is disturbed (Fig. 6C), though not so markedly as in a direct extrusion.

Hydrostatic extrusion is a method in which material Sis extrusion-molded with a high-pressure liquid film t. formed at a container-billet interface. As the name suggests, conform extrusion method is a method in which Smaterial is molded between a rotary wheel and a fixed

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shoe. These methods, having none of such problems as the former two methods have, make it possible to extrude material extremely smoothly- But these methods are complicated in mechanism and need large and thus costly equipment. The former two methods are thus much more popular. The latter two methods are mainly used only in rather rare and special applications.

In direct or indirect extrusion method, a billet 1 is placed in a container 3, the billet is pressed by a 0 ram 4 to extrude an aluminum article 5 from a die 8x. At the beginning of extrusion, the billet 1 buckles as shown in Fig. 3, creating air pockets at the front and rear ends 6f and 6r of the container 3. As explained above Swith reference to the flow patterns of Figs. 5C and 6C, when the flow of aluminum is disturbed at the front end 6f of the container 3, air in the air pockets 7 tends to mixed into the flow of aluminum. This phenomenon is most remarkable at the beginning of extrusion. Thus, the end product inevitably has a portion containing air bubbles and other impurities. Such a portion has to be cut off or otherwise removed after molding.

SSuch a portion has to be removed. Thus, the yield or productivity was low.

SOne solution to this problem is proposed in 25 unexamined Japanese patent publication 8-257633, in which, as shown n ig. 4, vacuum pumps 12 are connected to 2 1.p i 3 pipes 11 connected to vent holes 10 formed in the front and rear ends 6f and 6r of the container 3 to discharge air trapped in the air pockets 7.

Although this proposed arrangement can prevent the mixing of air into material, this arrangement needs a large, complicated and costly equipment.

An object of this invention is to provide an aluminum billet which can discharge air in an air pocket formed in the container near its front and rear ends to 10 the rear of the container, and a method of manufacturing such a billet.

SUMMARY OF THE INVENTION According to this invention, there is provided a billet for extrusion-molding aluminum, the billet comprising an aluminum body having an outer peripheral surface in which is formed a groove extending continuously from one end to the other end of the aluminum body.

With this arrangement, air is prevented from being trapped into the billet at initial stage of extrusion molding. Thus the end products have no portions containing air bubbles.

Also provided is a method of manufacturing a billet for extrusion-molding, aluminum, the method comprising the .3.

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a r r step of passing a billet through a casting die of a continuous casting machine formed with a rib on inner periphery thereof to form a continuous groove in the outer periphery of the billet by the rib.

With this arrangement, a long billet formed with a longitudinal groove in its outer periphery can be manufactured by a continuous casting machine and the long billet can be cut to suitable lengths according to the capacity of the container.

Further provided is a method of manufacturing a billet for extrusion-molding aluminum, the method comprising arranging a billet guide means and a die coaxially with each other, the die having on its inner periphery a convex blade protruding inwardly, and pushing 15 a billet with a press through the guide means and then through the die to form a continuous groove in the outer periphery of the billet.

With this arrangement, a groove can be formed on the surface of a cylindrical billet by use of a press.

20 Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which; BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view ;of an aluminum billet 4 .i S.2w

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U for extrusion molding embodying this invention; Fig. 2 is a view of the aluminum billet of Fig. 1 as inserted in a container; Fig. 3 is a view of a conventional aluminum billet as inserted in a container; Fig. 4 is a view of a device having means for expelling air trapped in the container near its front and rear ends; Figs- 5A 5C are views showing a direct extrusion method; Figs. 6A 6C are views showing an indirect 'extrusion method; Fig. 7 is a perspective view of a continuous casting die for manufacturing the aluminum billet S according to this invention; and Fig. 8 is a view of a press having a means for forming grooves in the outer periphery of an aluminum billet.

DETAILED DESCRIPTION OF THE PREFERRED

EMBODIMENT

Now referring to the drawings, description is made of a billet for molding aluminum by extrusion according to this invention and a method of manufacturing such a billet.

Fig. 1 is a perspective view of such a billet. Six "l axial grooves 2 are formed in the outer periphery of the billet 1. The grooves 2 shown have a square section. But instead, the grooves may have a semicircular section.

Also, the grooves may be straight grooves as shown or oblique or curved ones. In any case, the grooves have to extend continuously from the front to rear end.

Fig. 2 shows a state at the beginning of extrusion with the aluminum extruding billet 1 inserted in the container 3. An article 5 is extruded with the billet 1 buckled under the pressure of the ram 4. Air trapped in the air pocket 7 near the front end 6f of the container 3 is discharged through the grooves 2 formed in the outer periphery of the billet 1 and small gaps present between the container 3 and the ram 4 (though not seen in the figure) to the rear of the container 3.

One may think that the presence of the grooves 2 may result in the formation of similar marks on end products. But we have found out that no such marks are impressed on the end products by properly determining the width a and depth 4 of the grooves 2 based on the experimental data.

For example, when four grooves 0.5-1-0 mm deep and mm wide were formed on aluminum billets 179 mm and 152 mm in outer diameter, the results were good. When four grooves with 0.7-0.8 mm depth and 2.5 mm width were formed, the results were even better.

l: now two methods for Mauatrn the billet according to the invention are described with reference to Figs. 7 and S.

Fig. -j shows a continuous casting method,

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plurality Of ribs 9 are formed Onl the inner Periphery of a die Sc of a k~nown continuous casting machine near its outet-~Ibn n eongtebillet 1' is formed by casting, grooves 2 are formed in its outer periphery bY the ribS9 The billet V. is cut into a pljuralitY of billets I eachi having a length c 0 rrepoding to the volme Oof the container 3 of an extrulsion molding machine- Fig- 8 showS a method in which the grooves 2 are formed by cutting with a press- An anvil 13 ofthe press is formed with an axial bore 14 through which a billet 1 can pass. Also, the anvil 13 has a die 16 as a groove f .orming eascarrying a plurality of convexI bl-ades 15 on its inner periphery, and a guide means 17, forcetrn the billbet I with respect to th e die 16 as groove forming mean Wth abillet 1 inlserted in the guide means17 I the jram IS is advaured to push the billtit h i 6 As the billet is pushed through the die 16, greoves 2 are cutw by the convex blades 15.1 As described above, according to this invention, whe a rodct s etruion-molded from a billet by a A 2 direct or indireect extrusion method, air trapped jn the container near its front arid rear ends will never mix into the billet. Thus, end prodlucts have no portions containing air bubbles or other impurities, so that there is no need -to remove any portion of end products.- This improves productivity. Al!so it is possible to prevent the formation of any marks on end products due to -the grooves of the billet by selecting a proper groove width and depth.

Such a billet can be manufactured easily using a continuous casting machine having ribs on the inner per-iphery of the die near its outlet, or with a press having a die formed with blades in its inner periphery- I4

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Claims (2)

1. A billet for extr 5 ion-iwldIng alum1~lnum, said billet comprising an aluminum body having an outer surface in wbich is foxred a groove extending continuouSly froma one end to the other end of said aluiiiifn body-

2- A method of manufacturng a billet for extrulsionl- 1 moldinug alunint3m, said method comprising the step Of *passing a billet through a castin~g die of a continuous casting machine formed with a rib on inner periphery thereof to forn a continuous groove in the outer periphery of the billet by said rib. A Method of jjanafactu1ring a billet for extrusionl- molding aluminlum, said method comprising arranging a billet guide means and a die coaxially with each other, said die having on its inner periphery a convex blade protruding5 inwardly, and pushing a billet with a press through said oui-de means and then through said die to formn a continulous groove in the outer periphery of the billet- DATED THIS 0!9TH- DAY OF APRIL 1998 YASUDA METAL INDUSTRIES, LTD.. 3y. its Patent AttorneyS: GRIFFITH BACK Fellows institute of Patent AttzeiIys. of Australia 9