US3700026A

US3700026A - Ingot casting apparatus

Info

Publication number: US3700026A
Application number: US100713A
Authority: US
Inventors: Toshio Adachi; Kiyohide Hayashi; Yukio Okura
Original assignee: Daido Steel Co Ltd
Current assignee: Daido Steel Co Ltd; Daido Seiko KK
Priority date: 1969-12-25
Filing date: 1970-12-22
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24

Abstract

An ingot casting apparatus in which protecting gases used in melting metals are introduced into a sealed casting vessel through a specially design sealed ladle or tundish connected with the vessel and through a spout of the remelting furnace which is also connected with the ladle or tundish in a completely gassealed condition, and molten metal is cast under an evacuated or inert gas atmosphere.

Description

United States Patent Adachi et al.

[ 51 Oct. 24, 1972 [54] INGOT CASTING APPARATUS [72] Inventors: Toshio Adachi; Kiyohide l-layashi;

Ynkio Okura, all of Nagoya, Japan [73] Assignee: Daido Seiko Kabushiki .;Kaisha,

[30] Foreign Application Priority Data I Dec. 25, 1969 Japan ..44/l22378 [52] US. Cl ..164/256, 164/259, 266/34 V [51] Int. Cl. ..B22d 27/16 [58] Field of Search ..l64/256, 258, 259; 266/34 V ated or inert gas atmosphere.

[56] References Cited UNITED STATES P TENTS eta] .26 6 /34 v x 3,554,268 1/1971 Ta'fibr'a 164/258 x Primary Examiner-J. Spencer Overholser Assistant Examiner-John E. Roethel Attorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT An ingot casting apparatus in which protecting gases used in melting metals are introduced into a sealed casting vessel through a specially design sealed ladle or tundish connected with the vessel and through a spout of the remelting furnace which is also connected with the ladle or tundish in a completely gas-sealed condition, and molten metal is cast under an evacu- 4 Claims, 2 Drawing Figures INGOT CASTING APPARATUS This invention relates to a ingot castingapparatus employing a furnace gas which is generated in the refining period as protecting gas in the .casting.

The apparatus consists of a specially designedtundish or ladle equipped with a gas-sealed cover connected with a furnace spout and a gas sealed-vesselin which an ingot mold is installed.

This vessel is used under conditions when it is full of an inert gas atmosphere or a vacuum, introduced through a specially designed tundish or ladle.

Many reports or inventionshave been'published on the various methods and apparatus which have been used for ingot casting in neutral or inert gas atmospheres.

Especially for obtaining lower undesirable inclusions, the following methods and apparatus are used:

1. A method which prevents the molten steel'from oxidizing by blowing inert gas along with the streamof molten steel being teemed,

2. A method which prevents molten steel .from segregation by blowing inert gas into the molten steel with or without slag and stirring the steel by aninduction coil;

3. A method which keeps a certain pressure in'the mold by means of blowing a neutral or inert gas into the molten steel in the mold, thereby to obtain ,a roundin- 4. method of casting the metal in agas-curtain along the bottom and inner surfaces of mold in order to prevent the surface defectsin the ingot;

5. An apparatus in which an innergasconduit-extends nearly to the bottom of the ingot mold in order to reduce splashing in the metal casting in the inert gas atmosphere.

The apparatus of the present invention is quite different from the above mentioned methods and apparatus.

This invention relates to ingot casting apparatus which comprises a specially designed tundish or ladle equipped with a gas sealed cover which is connected with a spout of the special remelting furnace,(for example, a plasma arc furnace) which is enclosed by an inert or neutral atmosphere gas and can be freely adjustable, those gases being for example, Ar or N gas, and a gas sealed vessel in which an ingot mold is installed.

Therefore, according to the apparatus of the'present invention, the atmospheric gas used in the remelting furnace is introduced through the spout and, covered tundish or ladle into the sealed vessel. This vessel can be used under vacuum.

The purpose of this invention is to resolve the following problems of conventional metal casting by using a special atmosphere in a remelting furnace gas and protecting gas. Those problems in conventional castings are:

1. Increased inclusions or gases in the high purity metal because of teeming in the air.

2. In general, the protected gas casting cost is somewhat higher than ordinary casting in the air, because much high cost inert gas is used.

Detailed structure of the present apparatus is explained hereunder in accordance with the drawings.

In F IG. 1, the spout FA of the plasma arc furnace F and the cover of the tundish 1 are connected and sealed by bellows 3b and the tundish 1, teeming tube 7, and

the casting vessel6 are connected and'sealed by he]- lows 5.

While an evacuation system is operated, the air in the tundish 1 and vessel 6 is evacuated.

In a meantime, inert gas'is supplied'from the plasma jet torchintothe plasma arcfumace F,:therefore this inert gas is introduced into the vessel 7 6 through the spout FA, tundish .1, tundish nozzlel 2 and evacuated to the outerside through anevacuation system.

'After checking the displacement of the air in the vessel with'the inert gas, valve 1'0is shut and the vessel .6

' remains filledzwith the inert gas.

:tundish 1 through the spoutFA- and introduced into the nozzle 2, teeming tube 7 and-finallyto the ingot mold 8 which is complete protected 'by the inert gas at- .mosphere.

As the metals are cast in the-"above process, clean ingots are obtained withoutnon-metallic inclusions and also without increments of gases in'the. metals.

The lower casting cost-are obtained'by the inventive method rather than by conventional inert gas protected castingmethods. When vacuum .casting is desired, just as shown in FIG. 2, the tundish l and the vessel 6 are closed, byinserting a meltable metalplate, which is a little larger than the inner diameter of the nozzle 2, into the bottom of the nozzle 2'and fastening it by bolts 12b.

Thereafter, the air in the vessel 6 is evacuated by operation of an evacuationsystem and the desired pressure in the vessel 6 is confirmed bylthe safety valve 9.

In the meantime, the air in-theitundish lis converted by continuously supplying inert gas from the plasma jet torch through plasma arc'furnace-F, the spout FA and tundish l,'therefore the tundish l is filled with the inert gas and the pressure in the tandish increases.

But as soon as thepressure reaches a set pressure on the safety valve 4, the-valve is opened and the mixture of the air and inert gas is discharged.

Hence, the displacement of theair in the tundish l by inert gas is confirmed.

After that, the remelting furnace is tilted just in direction by the arrow mark and the molten metal refined and alloyed in the furnace 'is teemed into the tundish l which is filled with inert gas and the pressure is maintained below a set value.

The hot metal melts the metallic plate 12 and is introduced into the vessel 6 becoming fine droplets in the vacuum therein, and finally filling the ingot mold 8 through teeming tube 7.

As a result of the above mentioned process, the purity of the metal is increased and gas volume in the metal is minimized. These casting operations in the inert gas or vacuum are inspected through a inspection hole 11 mounted on the upper side of the vessel 6.

Moreover, by high temperature gas supplied from the remelting furnace, tundish 1 is preheated up to about 500 600 C and ingot mold 8 is heated to about 300 400 C. That preheating improves ingot casting.

This apparatus is intended to be used for atmosphere remelting and for re-circulating the inert gas which is discharged from the remelt zone.

Even the comparably simple structure of this apparatus can prevent contamination of the molten metal by the air and at the same time can preheat the tundish l and ingot mold 8, and moreover this apparatus has characteristics which can produce clean ingots at lower COSt.

What we claim is as follows:

1. An ingot casting apparatus, comprising:

a plasma arc melting furnace,

a tundish associated with the output spout of said furnace,

a casting vessel enclosing a casting mold associated with the tundish,

first bellows connecting and sealing the spout of said furnace and the cover of said tundish, second bellows connecting and sealing the outlet of said tundish and the top of said casting vessel, the output spout providing means for tapping molten 5 metal from the furnace to the tundish and also providing means for circulating the inert gas from the furnace into the tundish and the casting vessel, and means for evacuating said casting vessel. 2. The apparatus of claim 1 wherein said furnace is rotatably mounted so that it may be tilted to tap molten metal from said furnace into said tundish.

3. The apparatus of claim 1 additionally comprising a meltable metal plate closing the outlet of the tundish.

4. The apparatus of claim 1 wherein said casting mold additionally comprises a teeming tube aligned below the tundish outlet.

Claims

1. An ingot casting apparatus, comprising: a plasma arc melting furnace, a tundish associated with the output spout of said furnace, a casting vessel enclosing a casting mold associated with the tundish, first bellows connecting and sealing the spout of said furnace and the cover of said tundish, second bellows connecting and sealing the outlet of said tundish and the top of said casting vessel, the output spout providing means for tapping molten metal from the furnace to the tundish and also providing means for circulating the inert gas from the furnace into the tundish and the casting vessel, and means for evacuating said casting vessel.

2. The apparatus of claim 1 wherein said furnace is rotatably mounted so that it may be tilted to tap molten metal from said furnace into said tundish.