JPS62142065A - Method and device for manufacturing metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a metal manufacturing method and apparatus (the term "metal" used in this text means both substantially pure metals and metal alloys).

BACKGROUND OF THE INVENTION Metals are traditionally made from liquid metals by casting. Common metal castings are associated with two major defects: segregation and undesirable coarse grain size.
These result in both significantly inferior mechanical properties for gold Ff4m products as well as difficulties in subsequent manufacturing steps when hot or cold working is required.

Although it has been known for many years that rapid solidification results in fine grain size and reduced segregation, attempts to achieve rapid solidification in large castings by conventional methods have not met with good results. It has also been known for many years that the formation of a large number of nucleation sites within a casting results in fine grain size and reduced segregation. This idea is exploited by inoculated castings with nucleation points by direct addition of nuclear material for this specific purpose.

We are currently developing metal manufacturing methods and equipment to solve the four points.
This allows both large and small metal silks to be produced with fine grain size and low segregation without the addition of special nucleating substances. Accordingly, the present invention directs a flow of pulverized molten metal onto a cooling surface to form a slurry of solidified metal in which the metal is partially solidified and suspended in the still molten metal; A metal manufacturing method is provided which includes pouring into a receiving vessel for post-processing under liquid flow conditions.

According to other features of the invention, there is provided a container for molten metal, a device for pulverizing the molten metal removed from the container, and a stream 1 of pulverized molten metal droplets obtained by the pulverizing device.
a device for directing the molten metal onto a cooling surface; a device for cooling this metal surface in such a way as to quench said molten metal and cause partial solidification of the nuclear bath molten metal; A metal manufacturing apparatus is provided having an apparatus for flowing metal under liquid flow conditions and a receiving vessel for receiving said partially solidified metal.

In the method according to the invention, the impact of the micronized droplets on the cooling surface causes a strong shearing effect, which damages the dendrites already present in the micronized particles in flight and the previous splash deposits upon impact. The dendrites formed in the remaining liquid film fracture and split. The fractured arms of the solidified metal are distributed throughout the solidification volume and act as nuclei for the subsequent solidification resulting in a fine grain size, while the split dendrite nuclei are distributed throughout the solidification volume (due to the influx of solutes). (preventing the formation of large liquid pockets that would otherwise be impossible), segregation is inhibited.

Although dendrite fragmentation has traditionally been utilized to produce fine grain sizes and low segregation castings, the practice has been accompanied by mechanical or magnetic stirring. Mechanical stirring is difficult to implement economically and often results in contamination of the product, while magnetic stirring produces less shear and less dendrite fragmentation. In the method according to the invention,
The idea of directing molten droplets in the form of a high-velocity spray onto a cooling surface is utilized so that cooling and shearing occur simultaneously through the formation of splattered deposits on the cooling surface.

According to the method according to the invention, an initial deposit forms a permanent thin skin or copper-shaving-like fully solidified metal on the cold surface, and a subsequent partially solidified metal deposit forms on the cooled surface. The step includes allowing the cooling to occur by the metal of its own composition adhering to the cooling surface without being in direct contact with the cooling surface.

In the process of the present invention, products with fine grain size and no segregation can be produced by atomizing the stream of bath molten metal to form atomized molten droplets which are directed onto a cooling surface and deposited onto the surface. is cooled to a temperature at which the flat deposit becomes layered and partially solidifies, and at the same time is subjected to intense shearing due to the flat deposition itself. Further shearing is caused by the bombardment of the micronized droplets onto the already partially solidified N layer. The partially solidified metal may be sent, for example, to a fully solidified mold or to a heated vessel and then recovered in a partially solidified state for further processing.

The term "partially solidified" means that the metal body described above has been cooled to a temperature such that it consists of metal crystals within a matrix of liquid metal. Such metal bodies exist in the equilibrium phase diagram at temperatures between the solid and liquid phases in the case of alloys and at the melting point in the case of pure metals.

During the entire micronization process using molten metal, some of the micronized particles remain completely liquid even when their temperature drops below the liquid phase. This is a well-known phenomenon called "supercooling." Such subcooling is usually applied to some of the small particles at temperatures within the range of 50'C to 200C. The nuclei crystallize as soon as the particles, such as dendrites, are deposited on the deposited layer before they have formed or partially solidified. Therefore, subcooling has little effect on the method of the invention.

Micronization can be achieved by various methods such as gas micronization, pressure shedding,
This can be achieved by mechanical or centrifugal pulverization. Typically, it is necessary to maintain an entirely inert or reducing atmosphere within the pulverizing chamber to prevent oxidation of the metal during pulverization, and this makes pulverization of certain metals possible with mixtures of hydrocarbons and steam. Water atomization is generally excluded. Although the following description refers to gas-based pulverization, it should be understood that other pulverization processes such as those mentioned above (particularly centrifugal pulverization) can also be used.

When using gaseous atomization in the method of the invention, some of the cooling of the molten metal droplets is caused by the gas, and some of the smaller droplets freeze partially or completely during flight;
The main cooling effect generally occurs when the droplet hits the cooling surface.

At the beginning of the process, such a surface is usually a water-cooled solid metal surface having the same or a different composition of metal than the injected metal. The first few deposited layers formed on such a cooling surface are those that completely solidify and do not pass into the receiving vessel. In fact, the first few deposited layers, when examined in cross-section, show clear deposit boundaries, indicating that the previous deposited layer has completely solidified before the arrival of the next counterfeiting droplet.

As the number of deposited layers increases and the thickness of the deposit increases, the rate of heat dissipated from the cooling surface decreases. From simple solidification theory, it can be assumed that the solidification rate is inversely proportional to the thickness of the underlying sediment.

All this takes place rapidly and within a short time, usually within a few seconds, a steady state is reached in which the last deposited layer is only partially solidified. These partially solidified metal-containing deposits are in the form of a slurry containing crushed dendrites, for example moved into a receiving vessel under the influence of gravity and/or by the impact of the droplets and the pressure of the pulverized gas. can be poured into.

On reaching a stable f-fish, the jet droplet imparts an impact gA on the surface consisting of a partially solidified metal pattern. This film contains small dendrites in a matrix of liquid metal. When the newly arriving droplets partially solidify and form an adhesion layer, the impact occurs! The bowl of 7-dendritic crystals is fractured and split and distributed within the membrane.

Any droplet that partially solidifies in flight due to the cooling action of the atomized gas causes shearing and splitting of the dendrite arms within the droplet that strike the partially solidified layer and form the adherent layer.

As a result of the shearing action of the intense adhesion phenomenon, the partially solidified Kasa film consists of a single fragment of dendrites in a liquid matrix.

Such contaminants are slurry! I have had it once. An armless mixture of also crushed dendrites with the same composition and liquid proportions (as occurs during solidification of 4i castings)
It has a much lower viscosity and flows much more easily.

The difference in viscosity is significant. For example, 50% under relatively quiet conditions and relatively low cooling rate of ordinary castings.
The viscosity of the solidifying metal mass is so high that it does not flow under gravity because of the network of large, intertwined dendrites that surround the remaining liquid sludge. In contrast, a metal mass of the same composition produced by adhesion layer formation produces much smaller dendrites (due to the higher cooling rate), all the dendrite arms are fractured. There is no dendrite network and at 50% solids the metal content has a low viscosity and flows easily.

For a more complete understanding of the present invention, embodiments thereof will now be described with reference to the accompanying drawings.

2. Example In FIG. 1, the flow of hot water from the molten brass funnel 1 is sent perpendicularly to the gas atomization device 3, which directs a focused high-pressure jet N2 onto the flow of the molten brass. . This stream is atomized to form atomized melt@brass droplets, which are oriented at 60° to their axis.
oriented onto a water-cooled steel surface inclined at an angle of . A thin layer 6 of solidified adhesion (copper chips) is quickly formed on this water-cooled steel surface,
The layer of copper chips increases in thickness until the heat dissipated from the newly arriving droplets is no longer sufficient for complete solidification. A partially solidified brass film is then formed at the interface between the deposit and the gas, consisting of a slurry of crushed dendrites in a matrix of molten metal. This partially solidified brass has a low viscosity and flows away from the underlying solid copper scraps, enters the mold γ, and solidifies there.

This exemplary method has some M4J characteristics as described below.

1) Since the copper chips of the solidified brass separate from the water-cooled copper surface from the colliding liquid droplets, there is no contamination or dilution of the brass, and there is no corrosion of the copper.

(11) High pressure gas (5 MPa in this case) is used in low volumes (for example at a rate of 10% of the weight of the brass) to save on expensive raw materials. Cooling of the particles in flight by the gas is minimal compared to cooling by water-cooled surfaces.

(iii) The copper shavings are thickest at the top 8 of the water-cooled surface and thinner at the bottom 9 where the brass, subject to more intense atomization flow and partially solidified, flows continuously over the surface. The thickness of the copper scraps can be automatically adjusted to some extent at any point. This is because if the spray rate increases slightly and the copper scrap at that point becomes unduly thin, heat transfer will increase, more liquid will clear the ice, and the layer will stabilize at a slightly reduced thickness. be. Similarly, a situation of self-adjustment can also be found if the copper shavings become thicker at any point for any reason, eg as a result of a reduction in the spray rate.

(The partially solidified metal flowing into the 1φ mold is in the form of fractured dendrites #14, containing a constant number of nuclei, and completely solidifies to produce a portion of the 9 o'clock fine grain size.

(v) Since some of the latent heat of solidification has already been removed by the surface, the metal solidifies more rapidly and requires less mold cooling. Also, since there is no large liquid container that would reject solutes, the product has reduced segregation.

Although the simple apparatus of FIG. 1 illustrates the principles of the invention, a more preferred embodiment will now be described which ensures continuous operation and good economy on a production scale. In FIG. 2, the molten m10 is allowed to fall vertically downward from the funnel 11 through a gas pulverizer 12 in a flow-like track (usually with a diameter of 1 crn). Directed to 14. This stream forms a spray of molten steel droplets that are pulverized, water-cooled, and directed onto the copper surface. In the example shown, the device is axially symmetrical and has a water-cooled copper surface 16.
forms the bottom of the chamber and has the shape of an inverted truncated cone with an included angle of 100°.

An exit orifice 17 is formed at the free end of face 16 and is configured to allow partially solidified metal and gas to enter the continuous mold. The top of the chamber is provided with a refractory lining 19 to seal it against the atomization device 12, which is connected to the funnel 1.
The bottom of 1 is sealed.

During operation, the gas is at a pressure of 4 MPa and 7% of the metal weight.
supplied at a rate of The atomizer operates such that the conical spray rotates rapidly about the atomizer axis (as shown in Figure 2). This conical spray of micronized droplets is directed onto an inclined water-cooled steel surface 16. The included angle of 90% of the spray is 10° in the example shown, and it is arranged such that only a small portion of the spray reaches the outlet orifice 1γ of the refractory lining 19, i.e. only the outer periphery of the conical spray. The small amount of spray that enters the mold without impinging on the surfaces is not critical and is simply incorporated into the casting. In fact, further dendrite fragmentation occurs due to metal droplets striking directly on the partially solidifying metal in the mold. Similarly, a small portion of the spray deposited on the refractory lining 19 will not completely solidify due to low heat dissipation from the deposited layered droplets by the refractory lining. The liquid or partially solidified metal flows downward and finally reaches the mold, joining the flow of the partially solidified metal. If necessary, part or all of the refractory wall can be heated to reduce the possibility of complete solidification and metal deposition in high areas.

Rotation of the atomizing spray cone about the device axis as shown in FIG. 2 is advantageous because the point of maximum droplet delivery, or center of the spray, is constantly moving.

As a result, the local thinning of the copper shavings continues, and an increase in thickness above and below the plane of the paper in FIG. 2 is prevented. If desired, the spray can be kept stationary and the other side moved or rotated, with the same advantageous effects.

However, it is more advantageous to move the spray body than the surface. If both the surface and the spray are moved, the shearing action will be increased, and if the movements of both are in opposite directions, the beneficial effects will be further enhanced.

In both of the above examples, pulverization is used to decompose the molten metal body. In these cases, some of the gas may be mixed into the gas slurry, resulting in a porous casting. Therefore, precautions must be taken to ensure that the gas velocity at the point of impact on the cooling surface is minimized and suitably configured to provide a slow gas exit flow over the metal surface. One way to reduce porosity is to lower the device until the next water-cooled section 16 touches the top of the mold 18.

Next, a gas outlet is provided at the top of the metal refractory lining 19. This method provides minimal porosity with the minor drawback that when gas atomization is used, large amounts of small metal particles escape and yields are slightly reduced.

This difficulty can also be largely overcome in an alternative embodiment of the invention in which the molten metal is arranged to fall in a vertical curve onto the disk or impeller of a centrifugal atomizer, which is preferably arranged.

- An example is shown in FIG. The molten metal 20 is transferred from the funnel 21 to the annular water-cooled bearing 23, and the electric motor (
The flow can flow to a rotary driven impeller 22 driven by a boot 24 and a belt 25 (not shown), and the impeller made of water-cooled metal or ceramic coated metal or ceramic rotates at a speed of, for example, 1000 rpm to 400 rpm. do.

The molten metal is pulverized by the impeller 22 to form a spray on a horizontal surface. This pulverized molten metal is splash deposited in the form of a truncated cone onto the inclined water-cooled cooling surface 26, resulting in simultaneous cooling, shearing and fracturing of the dendrite bowl to form copper shavings 21, which form copper shavings 21. Slurry dendrites and molten metal 28 descend down the side of refractory cone 29 and flow into base 32 through outlet opening 31 to form casting 33.

Particular advantages of the device include the use of minimal gas, i.e., the use of minimal gas to expel the atmosphere within the device and maintain a protective atmosphere, yet generates intense spatter and shearing, resulting in dendrite fragmentation and the advantages of the present invention. The point is that it can be used sufficiently to achieve this goal. Due to this minimal use of gas, porosity is less likely to occur in the casting.

In another embodiment of the invention, a very severe shearing action directs the atomized metal onto the cloth of a rapidly rotating cooling drum or disk, where it partially solidifies and is then thrown off by the action of a remote force. can be caused by

Such a system would produce similar products and have the same economics in terms of gas usage as the system of FIG. The main objection is that with such devices it is difficult to accurately direct the partially solidified metal of the cascading stream into the mold or container, with the result that metal recovery is reduced.

In each of the examples described above, the sheared and partially solidified metal stream consisting of slurry dendrites within a molten matrix forms either a simple bit or ingot or a shaped casting. Shows appropriate fluidity. It is not necessarily necessary to have a high percentage of solidification, it is only necessary to have a large number of dendrites or crushed dendrites in the mold to ensure a large number of nucleated FgT and therefore fine grain sizes. This metal stream solidifies to form a fine-grained casting with very little segregation. The room temperature mechanical properties of such castings can be improved compared to those obtained using similar compositions and conventional casting techniques. The products obtained by the process of the invention also exhibit improved hot and cold working properties due to their low segregation and fine grain size.

The method of the invention is applicable to all metals or alloys used in melting and casting. It is desirable, but not essential, to use an inert or reducing gas during the gas atomization step, which provides an atmosphere to suitably protect the solidifying metal within the mold.

In the case of alloys, the manufacturing process can be controlled by measuring the temperature of the alloy as it flows away from the surface and enters the mold or container. As the system tends to approach equilibrium, a comparison with the equilibrium diagram indicates the approximate proportion of solids present between the solid and liquid phases.

A more practical and convenient means of control is to observe the condition 7 as the processed metal flows out of the outlet opening 17 in FIG. 2 and the outlet 31 in FIG. 3. If too much solids enters the process metal stream, it will luml. A more accurate test is to inject a small amount into a fluid or spiral car. This gives an immediate indication of the viscosity of the treated metal.

It is desirable to use a degree of fluidity that is minimally consistent with producing fine grain size, segregation-free castings.

If the slurry used in the process according to the invention is too fluid, i.e. has too few nuclei, the pressure of the atomization gas and/or the cooling of the cooling surface may be increased in the case of a gas atomization step. The viscosity and proportion of the solid can thereby be increased.

In some cases, it may be necessary to further process the slurry while it is only partially solidifying. This can be achieved by using a heating vessel maintained at a suitable temperature between the solid phase and the temperature. Although the product remains usable for some time at a constant temperature, it is advisable not to delay post-processing for longer than the limit, since gradual deterioration will occur.

[Brief explanation of drawings]

Fig. 1 is a side view of a very simple device according to the invention, Fig. 2 is a side view of a slightly more complicated device of the invention, and Fig. 3 is a side view of another embodiment of the device of the invention, in which the pot is is pulverized. 1... Funnel, 2... Molten metal flow, 3... Micronization device, 5... Cooling surface, 6... Adhesion/i# (steel scrap), 1
...Mold, container, 8...Top, 9...Bottom, 13
... High pressure jet, 14... Molten steel flow, 16... Water-cooled steel surface, 17... Orifice, 19... Refractory lining, 22... Impeller, 27... Steel scrap, 28...
・・Slurry bath melting metal, 29・・Refractory material

Claims (17)

[Claims] (1) directing a stream of pulverized molten metal onto a cooling surface to form a slurry containing solidified metal suspended in the molten metal, with the metal partially solidified; A method of manufacturing metals comprising the step of entering a liquid in a flowing state into a receiving vessel for processing. (2) A method according to claim 1, wherein the cooling surface is inclined with respect to the centerline of the spray. 3. A method according to claim 1 or 2, wherein a stream of micronized droplets is directed onto a completely solidifying layer of metal on the cooling surface. (4) A method according to any one of claims 1 to 3, wherein the cooling surface is a water-cooled metal. (5) A method according to any one of claims 1 to 4, in which the flow falls onto the cooling surface under the action of gravity. (6) A method according to any one of claims 1 to 5, wherein the molten metal is pulverized by gas pulverization using an inert gas or a reducing gas. (7) A method according to any one of claims 1 to 4, wherein the molten metal is pulverized by centrifugal force. (8) A method according to any one of claims 1 to 7, in which the slurry flows off the cooling surface and directly into the receiving vessel. 9. A method according to claim 8, wherein the cooling surface has the form of an inverted truncated cone and the flow is rotated about the axis of the truncated cone. (10) A storage tank for molten metal, a device for pulverizing the molten metal taken out from the storage tank, and a device for directing the flow of the pulverized molten metal produced by the pulverization device onto the metal surface. and an apparatus for the metal surface to cool the molten metal and cause partial solidification of the molten metal;
A metal manufacturing apparatus comprising: a device for flowing a partially solidified metal from said surface in a liquid flow state; and a receiving container for receiving said partially solidified metal. (11) Claim 10: The cooling device is a water-cooled type.
Device according to section. (12) The metal surface is inclined with respect to the horizontal plane, and the device for flowing the partially solidified metal is configured so that the metal flows under the influence of gravity. Method according to paragraph 11. (13) The method according to claim 12, wherein the metal surface has the shape of an inverted truncated cone. 14. Apparatus according to claim 13, further comprising means for rotating the stream of micronized droplets about the axis of the truncated cone. (15) A device according to any one of claims 10 to 14, wherein the pulverization device includes a pulverization device using an inert gas or a reducing gas. (16) The device according to any one of claims 10 to 14, wherein the pulverization device includes a centrifugal pulverizer. (17) An apparatus according to claim 16, wherein the centrifugal atomizer has a horizontally arranged rotationally driven impeller.