Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1994-04-08
1996-05-07
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
164 61, 164 681, B22D 2300, B22D 2715
Patent
active
055136931
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method for casting low specific gravity metal with ultra-fine features using high differential pressure.
BACKGROUND ART
Low specific weight metals such as pure titanium and titanium alloy materials consisting mainly of titanium exhibit high heat resistance, excel in such mechanical properties as toughness and wear resistance, and being highly biocompatible, do not harm living organisms in which they are embedded. They therefore have the potential for extensive utility not only in industry but also in dental prosthetics, plastic surgery and other such surgical and medical fields.
However, since titanium materials are very active and are therefore exceedingly difficult to work, it has only been possible to process them in vacuo using special equipment and techniques. Because of this, it has not been possible to fabricate dentures and other complex, intricate articles from titanium.
Prior art casting methods for low specific gravity metals include the centrifugal casting method and the single chamber remelting plate bottom turn-open method. Since low specific gravity metals such as titanium have low mass and experience rapid solidification by cooling, however, they cannot easily be cast down to ultra-fine feature portions by the centrifugal casting method because the initial casting pressure at the start of rotation in this method is too small.
In the single chamber remelting plate bottom turn-open method, on the other hand, since the metal on the remelting plate is melted by an arc discharge from above, low-temperature molten metal is cast first. In addition, since the molten metal is deprived of heat as is passes through the drip hole of the remelting plate, the temperature of the cast metal is low and it thus solidifies rapidly with cooling. This makes it difficult to cast down to the ultra-fine feature portions.
Moreover, since the melting and casting chambers are not shut off from each other in the single chamber structure, it is impossible to establish a gas pressure differential between two vertically disposed chambers. This also makes it difficult to cast down to the ultra-fine feature portions.
This invention provides a high differential pressure, ultra-fine feature casting method for low specific gravity metal exhibiting an excellent unoxidized surface.
DISCLOSURE OF THE INVENTION
The present invention provides a method for casting low specific gravity metal with ultra-fine features using high differential pressure characterized in that it comprises a step of defining a melting chamber volume V.sub.1 and a casting chamber volume V.sub.2 such that V.sub.1 <V.sub.2 and melting fusible casting material with a melting plate under an inert gas atmosphere, a step of establishing high differential pressure between the melting chamber and the casting chamber by introducing compressed inert gas into the melting chamber simultaneously with pouring the melt into a mold of the casting chamber, and a step of holding the high differential pressure until the cast melt solidifies.
The present invention further provides a high differential pressure, ultra-fine feature casting method wherein V.sub.1 <V.sub.2 when the melting chamber volume
and the casting chamber volume
______________________________________ V.sub.1
Melting chamber volume
(l)
V.sub.2
Casting chamber volume
(l)
v.sub.0
Gas influx capability
(l/s)
T Solidification time (s)
v.sub.R
Gas leakage from mold
(l/s)
P.sub.R
Casting chamber pressure at time
(kg/cm.sup.2 abs)
of arc discharge
P.sub.C
Compressed gas pressure
(kg/cm.sup.2 abs)
P Casting chamber atmospheric
(kg/cm.sup.2 abs)
discharge pressure
______________________________________
defining the time, relative to the molten metal casting solidification
time T, at which the interior of the melting chamber is increased to
pressure P.sub.R.
The present invention can further melt the fusible casting material at a temperature equal to the melting point of the fusible casting material plus 50.degree. C. to 100.degree. C.
REFERENCES:
patent: 4762165 (1988-08-01), Ogina et al.
Matsuda Seijirou
Miyazaki Shouichirou
Lin Kuang Y.
U-WA Tech Corporation
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