JPS6340853B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of molten metals or alloys, and more particularly to apparatus and methods for producing molten metals to form metal composites containing initial solids that are not dendritized. This is related to.

The invention also relates to solid magnesium metal containing particles for improving the fatigue strength of metals or alloys, especially magnesium.

Molten metals containing up to about 65% by weight solids consisting of degenerated dendrite or dendritic structures are known to exhibit thixotropic properties. Metal composites containing such degenerated dendrites are described, for example, in US Pat. No. 3,902,544, issued September 2, 1975, and US Pat. As the molten metal cools, dendrites form. It is therefore necessary to vigorously agitate the solidifying metal in order to prevent the formation of an interconnected dendrite structure and to substantially eliminate or reduce the already formed dendrite branches. The devices of the two aforementioned US patents are useful for obtaining the desired metals.

The incorporation of solid additives into various metals to improve their properties is described, for example, in US Pat. No. 3,583,471 for carbide-loaded welding rods. Furthermore, US Pat. No. 3,936,298 states that metal mixtures of base metals containing metal and/or non-metal particles exhibit thixotropic properties.

Certain metal composites containing abrasive particles have heretofore been considered unsuitable for conventional machining. This is because the cutting tools fatigue prematurely or because cutting tools and cutting edges hard enough to cut the abrasive are not available. Although such composites could be polished, polishing complex shapes was often difficult and time consuming. Accordingly, there is a need for castable metal composites that are more resistant to fatigue and wear than base metals that can be machined with commonly available equipment.

A solid composite having a matrix of magnesium or a magnesium alloy having degenerated dendrites, in which substantially insoluble metal carbide or oxide particles are dispersed and mixed up to about 30% by weight. has been found to exhibit improved fatigue resistance than base metal magnesium or magnesium alloys. Such magnesium compositions are suitable for example for rollers, pulleys, cylinder liners, cylinders, pistons, hoses, etc. Magnesium or magnesium alloys, e.g.
Lightweight composites of alloys such as Mg-Al-Zn, Mg-Al, Mg-Zn with metal carbides or oxides mixed therein are surprisingly resistant to fatigue and wear. Furthermore, it can be machined using well-known techniques. The present invention will now be described using a magnesium alloy as a preferred example, but it should be understood that unless otherwise specified, this term also includes what is commercially treated as pure magnesium. The carbides or oxides that are mixed with the magnesium or magnesium alloy are preferably moistened with molten magnesium, as they are harder than magnesium and generally do not react with the magnesium at the temperatures at which they are added. The oxide suitable for mixing with the magnesium alloy is preferably magnesium oxide, aluminum oxide, or a mixture thereof. Carbides suitable for mixing with the magnesium alloy include carbides such as hafnium, iron, lanthanum, manganese, molybdenum, nickel, neodymium, niobium, praseodymium, samarium, uranium, vanadium, yttrium, zirconium, silicon, and the like. As silicon carbide, SiC and Si ₂ C can be used. It is surprising that silicon carbide is suitable for addition to the magnesium alloys of the invention. This is because, thermodynamically, it is believed that silicon carbide reacts with the molten magnesium alloy.

The apparatus of the present invention is an apparatus for producing metal or metal alloy containing degenerated dendrites, which comprises: a molten metal storage container having a metal supply port and a metal discharge port; a holding member for holding the molten metal during stirring and cooling; a control means for controlling the temperature of the molten metal in cooperation with the holding member; and a control means disposed generally in the axial direction inside the holding member. The rotating member includes a rotating member and a member for removing solid metal adhering to an inner wall of the holding member, and the rotating member extends generally outward from the rotating member and toward the inner wall of the holding member. The apparatus includes spaced apart molten metal stirring members, the stirring members being spaced apart from the inner wall.

The present invention further relates to a method for treating a molten metal or alloy to form a metal composite containing an initial solid that is not dendritized, the method comprising: controlling the temperature of the molten metal to be between the liquidus temperature and the solidus temperature; stirring the molten metal to minimize the formation of interconnected dendrites; and continuously removing the metal deposited on the inner wall of the holding member. and solidifying the metal.

Embodiments will be described below with reference to embodiments shown in the accompanying drawings. FIG. 1 shows an embodiment of the manufacturing apparatus of the present invention, and FIG. 2 is a sectional view thereof. In the figure, 1
0 represents the molten metal manufacturing apparatus of the present invention. The manufacturing apparatus 10 includes a container 12 for storing molten metal.
The storage container 12 is a suitable container capable of withstanding molten metal. The materials of construction used for the container or other parts of the device may be well known to those skilled in the art. For example, steel, ceramic, graphite, etc. can be used with molten metal. The storage container has a supply inlet for supplying solid, preferably molten metal. In FIG. 1, this inlet is designed to minimize heat loss from storage container 12 and to
In order to reduce oxidation of the molten metal 16 in 2,
It is sealed with a cover device 14.

A molten metal holding member 18 having a generally cylindrical inner wall portion 19 is attached to the storage vessel 12 and allows molten metal to flow from within the vessel 12 through an outlet 20 and into a stirring chamber 22 located within the holding member 18. . A rotating member, such as an elongate support member or shaft 24, extends through the cover device 14, the storage container 12 and the outlet 20 and defines the axis of the inner wall 19 of the retaining member 18. The lower end of the shaft 24 extends into and is sealed into an outlet 26 which can advantageously eject metal from the retaining member 18. The shaft 24 is, for example, a blade 28
A plurality of stirring members, such as , are connected to the shaft and extend outwardly, preferably radially, from the shaft 24 toward the inner wall portion 19 . The blade 28 is spaced from the inner wall 19 to prevent it from contacting, catching on, and wearing out the inner wall during operation. Two sets of blades 28 mounted oppositely on opposite sides of the shaft 24
Approximately equal weights are desirable so that the parts 4 rotate more evenly, ie with little vibration. The total weight of the metal removal member, including shear plate 30 and pivot member 32, and blade 28 must be considered with blade 28, shear plate 30, and pivot member 32 weight balanced about axis 24. No. Blade 28 in FIG. 1 is mounted at an angle of about 30 degrees from horizontal to create a shear-type stirring motion during rotation of shaft 24. It is sufficient that the angle of the other parts of the blade position and the cross-sectional shape of the blade provide a stirring motion that destroys and removes the dendrites that form as the molten metal cools.

The shear plate 30 is adapted to move outwardly from the shaft into contact with the inner wall 19 during clockwise rotation of the shaft. In the figure, this outward movement is caused by centrifugal force, which scrapes off solid metal such as dendrites adhering to the inner wall 19 as the molten metal cools. Press the shear plate 30 toward the inner wall 19 so as to do so. The pivot member 32 may have other shapes, such as a hinge. Similarly, any means of bringing shear plate 30 into constant contact with inner wall 19, with or without centrifugal force, is within the scope of the invention.

Instead of the short shear plate 30, only one elongated shear plate (not shown) can also be used. Also, the arrangement and number of blades 28 and shear plates 30 mounted about shaft 24 can be varied. However, it is desirable that the entire shaft, blade, pivot member, and shear plate be axially balanced to minimize vibration during operation.

If possible, shear plates 30 or blades 28 should be used to avoid a situation in which the plates pivot toward the shaft 24 when the shaft 24 is not rotating, and thus do not come into contact with the inner wall 19 when the shaft 24 rotates. may be provided with suitable members or protrusions.

The operation of the metal manufacturing apparatus 10 is described in the aforementioned U.S. Pat.
It is carried out in the same manner as described in No. 3902544. Metals suitable to be produced in the apparatus described therein are, for example, aluminium, copper, iron, nickel, cobalt, lead, zinc and preferably magnesium and alloys thereof. In the following description, magnesium and magnesium alloys will be described as examples, but it should be understood that the invention can of course be similarly applied to other metals and alloys.

Commercially available magnesium alloys e.g.
Mg-Al-Zn alloy is poured into the container 12 after removing the cover 14. If the magnesium alloy is molten during injection, it is only necessary to maintain the metal in the container at a predetermined temperature. If desired, the metal may be poured in solid form and melted within the container. Any suitable commercially available means (not shown) can be used for heating and melting, etc. The shaft 24 has a metal partition plate 34 . During operation, the partition plate 34
2 and the stirring chamber 22, further helping to more accurately control the temperature of the metal.

In the preferred embodiment, shaft 24 is tubular and has a generally axially disposed metal drain plug 35 therein. Drain plug 35 extends through the center of shaft 24 and operates independently of shaft 24 .

Plug 35 is moved downwardly to seal outlet 26, causing stirring chamber 22 to fill with molten metal. The temperature of the metal within chamber 22 is controlled by suitable heating and cooling means 36. The metal is cooled until some of it solidifies. During such solidification, the molten magnesium is agitated by shaft 24 at a rate sufficient to minimize, and desirably prevent, the formation of interconnected solid dendrites within the molten metal. The shear plate 30 continuously removes metal adhering to the inner wall and minimizes the buildup of solid magnesium on the inner wall portion. shear plate 30 to blade 2
8, heating and cooling means 36
The agitation or mixing of the molten metal reduces the formation of interconnected dendrites, leaving the desired degenerated or fractured dendrites with the metal in the stirring chamber 22. Helps to distribute it generally evenly throughout.

Once the desired concentration of solids within the molten magnesium has been achieved, the shaft is lifted and the stirring chamber 22
An outlet 26 is opened to remove metal from the metal. Subsequent rotation of shaft 24 causes chamber 22
The removal of metals from The produced solid and liquid mixture is cast into a suitable shape by well known means. If desired, solid metallic and/or non-metallic substances may be mixed with the molten metal in stirring chamber 22.

Examples of the present invention include the following.

EXAMPLE 1 This example is a metal manufacturing apparatus substantially similar to that illustrated. 9% Al, 0.7% Zn, 0.2 by weight
A standard magnesium-based alloy (AZ91B) consisting of % Mn, and equilibrium magnesium is melted in a melting vessel separate from the metal manufacturing equipment. Approximately 9 kg of molten magnesium alloy, container 1
2 and into the stirring chamber 22. Argon gas is included in the device to prevent the magnesium alloy from burning. The temperature of the molten metal injected into the device is approximately 615°C.

Initially, the metal within the stirring chamber is heated by heating coils placed around the outer circumference of the chamber. The stirring member, including the shaft, stirring blade and shear plate,
The total diameter is approximately 10cm. As the agitator rotates at a speed of approximately 300 revolutions per minute, the heat provided by the coils is turned off and the metal in the chamber is exposed to air flowing through three tubular coils surrounding the chamber's perimeter. It is then cooled down. Therefore, the molten magnesium alloy is simultaneously cooled and sheared.

The metal inside the stirring chamber is maintained at 580°C during stirring. At this temperature, which is below the liquidus temperature of the AZ91B alloy, the rapidly mixed solid portion of the metal accounts for approximately 27% of the weight of the metal in the chamber. The agitation based on this example apparatus was sufficient to break and separate the interconnected dendrites and minimize the formation of dendrite structures. The shear blades continuously scraped over the interior walls of the stirring chamber to minimize solid metal buildup on the interior walls of the chamber, even as heat was removed from the interior walls by the cooling coils.

A homogeneous mixture of generally uniformly mixed solids and liquid is formed at 580° and exits the chamber through an opening in the lower part of the stirring chamber. This evacuation is accomplished by lifting an axially disposed metal evacuation plug and rotating the shaft and plug to assist evacuation from the opening. Once the approximately 0.3Kg chamber has been drained, the metal drain plug is returned to its original position to seal the drain and prevent metal leakage therefrom. Approximately 0.3 kg of molten metal is automatically transferred from the storage container to the stirring chamber. Since the metal held at the top of the storage container is maintained at 610°C to 620°C, the temperature of the metal in the stirring chamber increases by 1°C to 2°C when molten metal is injected. On average, the cooling coil takes approximately
Requires 0.6 minutes.

The above method is repeated until the predetermined quantity is produced. In order to keep the temperature of the molten metal in the upper part of the storage container uniform, the molten metal is injected through the hole in the cover after about 1.8Kg is produced.

The material discharged from the stirring chamber is cast into a predetermined shape by pressure die casting. The solid liquid metal produced by this process was found to have thixotropic properties.

Example 2 To make a metal or metal composite, such as a molten magnesium alloy, the alloy is cooled within a range between the liquidus and solidus temperatures of the alloy and the dendrites that form upon cooling of the metal are crushed. and are thoroughly mixed in the apparatus described below in order to separate them. The metal is kept within this temperature range at all times during mixing.

Preferably, carbide or oxide particles are added to the partially solidified magnesium alloy after solidification of the magnesium alloy in a weight proportion of 15% to 40%, preferably 20% to 30%.
As the carbide is added and mixed with the partially solidified magnesium alloy, the melting temperature is increased sufficiently to increase the fluidity of the magnesium alloy;
This continues stirring the mixture. At these elevated temperatures, sufficient agitation must be provided to minimize the amount of carbide or oxide precipitation from the magnesium alloy. If possible, this temperature increase should be sufficient to maintain the total solids content of the magnesium alloy carbide mixture between 15% and 40% by weight of the total mixture. The final temperature of the mixture can be higher or lower than the liquidus temperature of the alloy.

Once a predetermined amount of carbide or oxide has been dispersed throughout the melt, the partially molten magnesium containing carbide or oxide is allowed to cool and completely solidify. Fatigue-resistant magnesium alloys can be made from carbide- or oxide-containing magnesium alloys, such as by sand casting, permanent molding, centrifugal casting,
Manufactured by well known techniques such as pressure die casting. Generally and desirably, the metal carbide or oxide is uniformly distributed throughout the solid casting, but in centrifugal casting castings, by having more carbide or oxide at the outer periphery than at the center, The fatigue resistance of the part is increased.

Carbide grains are nominally 0.5 inch (1.3 cm)
The following sizes were added to the magnesium alloy, smaller than the 8 mesh size of the US standard sieve. The machinability of the solidified composite is determined by particle sizes ranging from 0.1 microns to 30 microns in average diameter;
The improvement is preferably from 5 microns to 30 microns. Fatigue resistance of composite castings is achieved when the carbide content is between 1% and 20% by weight. 2% to 10% carbide generally provides improvements in machinability and tensile strength over higher carbide additions.

Oxide particles nominally less than 0.5 inches (1.3 cm) in size and smaller than the 4 mesh size of a US standard sieve were added to the magnesium alloy.
The machinability of the solidified composite is improved when the particle size is from 0.1 microns to 200 microns in average diameter, preferably from 5 microns to 50 microns. The fatigue resistance of composite castings is 1% by weight of oxide.
% to 30%. Oxide starting from 1%
10% generally improves machinability and tensile strength over higher oxide additions.

Castings made of magnesium alloy carbide composites can be the basis for conventional wear wheels, and surprisingly, the castings can be made from 1% to 10% carbides or oxides. It can be processed using well-known machining equipment and techniques. It has been found that during machining removal or cutting, it is desirable for the amount of work on the composite surface to be approximately equal to the average diameter of the carbide particles in the composite in each machining bath.

Example 3 Approximately 1.8 kg of a standard magnesium-based alloy (AZ91B) of the same composition as the alloy in Example 1 was melted and
Injected into the dendrite shear device in the present invention. The device is equipped with a rotatable shearing blade approximately 10 cm in diameter suitable for shearing and breaking off dendrites formed in the alloy during cooling. U.S. Patent Nos. 3902544 and 3936298
No. 1 describes other means of shearing dendrites in metal melts.

The top surface of the molten alloy AZ91B is slightly above the top of the rotating shear blade. Protective argon gas prevents the top surface of the molten alloy from burning. The shear blade rotates at 300 revolutions per minute and the AZ91B alloy is cooled to 579°C. It is sufficient that this temperature is within 570°C to 585°C. Approximately 30% of the AZ91B alloy was solidified at this temperature. Partially solidified metal is directed to shear blades with nominal diameter
15 micron SiC powder is added to the melt at a rate of approximately 0.018 Kg per minute. This rate corresponds to an addition of 1% per minute. From about 300℃ to remove moisture
The addition of SiC, which has been preheated to 400°C,
This was continued until the weight reached 0.091Kg, and the weight was partially solidified.
Mixed into AZ91B alloy. Agitation with shear blades is continued during the addition of SiC. However, the blade is moved up and down every 5 minutes after the SiC has been added generally evenly distributed in the magnesium.

The metal thus prepared is cast into approximately 1 pound (0.45 Kg) cylindrical shapes in graphite molds. This composite was found to be fatigue resistant and has good machinability. The tensile strengths of the two composite samples are as follows:

1st sample: tensile strength 22.3Ksi, yield point
22.3Ksi, elongation 0.25%.

2nd sample: tensile strength 26.8Ksi, yield point
24.3Ksi, elongation 0.25%.

Example 4 Using the same method as Example 3, 10 micron particles were
%, 5-10% 5 micron particles, alloy AZ91B
added to. Castings made from such composites were found to be more fatigue resistant and more machinable than AZ91B alloy.

Example 5 Magnesium-based alloy AM60A was obtained in a manner generally similar to Example 3, except that the temperature of the metal was maintained at 600°C to 609°C. This alloy is Al
6% Mn, 0.5% Mn, and equilibrium magnesium, with a nominal particle size of 23 microns in diameter.
25% SiC is mixed. Castings made from this mixture in graphite molds are wear resistant.

EXAMPLE 6 Approximately 1.8 Kg of a standard magnesium base alloy (AZ91B) of the same composition as the alloy of Example 1 was melted and poured into a dendrite shearing device in the present invention. The device is equipped with a rotatable shearing blade approximately 10 cm in diameter suitable for shearing and breaking off dendrites formed in the alloy during cooling.

The top surface of the molten alloy AZ91B is slightly above the top of the rotating shear blade. Protective argon gas prevents the top surface of the molten alloy from burning.
The shear blade rotates at 300 revolutions per minute.
AZ91B is cooled to 583℃. This temperature is 570℃
It is sufficient if the temperature is within 585℃. At this temperature approx.
23% AZ91B alloy was solidified. The partially solidified metal is directed to a shear blade and nominal particle size minus 100, and 200 meshes of Al ₂ O ₃ are added to the melt at a rate of 0.018 Kg per minute. This rate corresponds to an addition of 1% per minute. Addition of Al ₂ O ₃ , which has been preheated to about 300° C. to remove moisture, continues until 0.09 Kg is mixed into the partially solidified AZ91B alloy. Stirring with shear blades was continued during the addition _{of Al2O3} ;
Continue for 5 minutes after all Al ₂ O ₃ has been added. After the Al ₂ O ₃ is added, the blade is alternately moved up and down during a final 5 minute stirring period to generally evenly disperse the Al ₂ O ₃ in the magnesium. The metal thus prepared is cast into approximately 1 pound (0.45 Kg) cylindrical shapes in graphite molds. This composite was found to be fatigue resistant and has good machinability.

Example 7 In the same manner as described in Example 6, Al ₂ O ₃ is
9% for AZ91B alloy with 200 micron particles;
They were added at a rate of 16.7%, 23%, and 28%. Castings made from such composites were found to have better fatigue resistance and machinability than AZ91B alloy.

Example 8 Magnesium-based alloy AM60A was obtained in substantially the same manner as in Example 5, except that the temperature of the metal was changed from 600°C to 609°C. The alloy contains 6% Al, 0.4% Mn, and balanced magnesium, with a nominal particle size of 44 microns in diameter.
25% MgO is mixed. Castings made from this mixture in graphite molds are wear resistant. The tensile strength of the cast composite is 1870Kg/cm ² ,
The yield strength is 1370Kg/cm ² and the elongation is 0.5%.

As will be apparent from the foregoing description, the apparatus of the present invention is susceptible to various changes and modifications.
Accordingly, it should be understood that the embodiments described above are merely illustrative and not limiting.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a metal manufacturing apparatus according to the present invention, and FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1. 10... Manufacturing equipment, 12... Storage container, 14...
... Cover, 16 ... Molten metal, 18 ... Holding member, 19 ... Inner wall, 20 ... Discharge port, 22 ... Stirring chamber, 24 ... Shaft, 28 ... Stirring member, 30 ...
Shear plate, 36...Heating and cooling means.

Claims (1)

[Scope of Claims] 1. An apparatus for producing a metal or metal alloy containing degenerated dendrites, comprising: a molten metal storage container having a metal supply port and a metal discharge port; a holding member for holding the molten metal during stirring and cooling of the metal; a control means for controlling the temperature of the molten metal in cooperation with the holding member; and a control means disposed generally in the axial direction inside the holding member. and a member for removing solid metal adhering to the inner wall of the holding member,
The rotating member has spaced apart molten metal stirring members extending generally outwardly from the rotating member and toward an inner wall of the retaining member, the stirring members having a space between them. A production device for degenerated dendrite metal characterized by being arranged in an open manner. 2. The apparatus according to claim 1, wherein the solid metal removing member is pivotally supported by the stirring member. 3. The apparatus according to claim 1 or 2, wherein the solid metal removing member is capable of rotating while fully contacting the inner wall during rotation of the rotating member. 4. The device according to any one of claims 1 to 3, wherein the inner wall of the holding member has a generally cylindrical shape. 5. The stirring member has a plurality of blades positioned at an angle with respect to a horizontal plane and arranged around the rotating member so as to maintain weight balance, and the solid metal removing member is arranged between the stirring blades. 4. Apparatus according to any one of claims 1 to 3, comprising a plurality of shear plates pivoted on and moved outwardly into contact with said inner wall by centrifugal force. 6. A device according to any one of claims 1 to 5, wherein the holding member has an outlet suitable for ejecting metal from the holding member. 7 A method of processing a molten metal or alloy to form a metal composite containing an initial solid that is not dendritized, the method comprising: controlling the temperature of the molten metal in a molten metal holding member to be between the liquidus temperature and the solidus temperature; agitating the molten metal to minimize the formation of interconnected dendrites; and continuously removing metal deposited on the inner wall of the holding member to accumulate solid metal on the inner wall. 1. A method of treating a metal, comprising the steps of: minimizing the amount of metal; and solidifying the metal. 8 The metal is magnesium, aluminum,
The processing method according to claim 7, wherein the material is selected from copper, iron, nickel, cobalt, lead, zinc, and alloys thereof.