JP4748688B2 - Method for preparing semi-solid metal slurry - Google Patents

Description

  The present invention relates to a method for producing a semi-solid metal slurry.

  The metal slurry used in the semi-solid forming method (rheocast method) maintains primary crystals separated from each other by a liquid matrix, and the primary crystal particles are as fine and uniform non-dendritic as possible, preferably spherical It is desirable that By doing so, it becomes possible to mold (cast) in a semisolid state with a high solid phase ratio and a low viscosity, which can suppress the formation of shrinkage nests of the molded product and improve the mechanical strength of the molded product. Can do.

  The following are known as metal slurry production techniques.

  JP-A-8-325652   JP-A-11-138248   Japanese Patent No. 3520991

  The technique described in Patent Document 1 proposes a method for forming a semi-molten metal that can easily and easily produce a compact having a fine and spherical thixostructure at a low cost regardless of the mechanical stirring method or electromagnetic stirring method. A liquid state alloy having crystal nuclei above the liquidus temperature or a solid-liquid coexistence state having crystal nuclei above the forming temperature in a heat insulating container having a heat insulating effect in a predetermined liquid phase. By holding it for 5 seconds to 60 minutes while cooling to a forming temperature showing a rate, a fine primary crystal is crystallized in the alloy liquid, and the alloy is supplied to a molding die for pressure forming. To do.

  However, when a slurry is actually created using the technique described in Patent Document 1 and then molded, a molded product having a fine and uniform structure is not always obtained. In particular, the tendency is remarkable in alloy systems other than the JISAC4C alloy. In other words, a molded product having a fine and uniform structure cannot be obtained unless the alloy system has a wide solid-liquid temperature range. In addition, when pouring directly into the heat insulating container, there is a restriction that a crystal grain refining element must be added.

  On the other hand, the technology described in Patent Document 2 does not require a particularly complicated process, and can easily produce a semi-solid metal slurry having fine and almost uniform non-dendritic (spherical) primary crystal particles with simple equipment and facilities. This is a semi-solid molding method that can stably produce a semi-solid metal slurry, and can simply load the produced semi-solid metal slurry into a pressure sleeve of a molding machine and perform pressure molding. Applies a motion to the molten metal when the molten metal is being cooled and at least a portion of the molten metal is below the liquidus temperature, and then the molten metal is cooled and semi-solidified In the method for producing a semi-solid metal slurry, by pouring the molten metal into a slurry preparation container, a motion is applied to the molten metal while keeping at least a part of the molten metal below the liquidus temperature. It is obtained so as to load the pressure sleeve of the over produced container each molding machine.

  Regarding the technique described in Patent Document 2, when a slurry is actually prepared and then molded, a molded product having a fine and uniform structure is not always obtained. In particular, the tendency is remarkable except for JISAC4C alloy.

In Patent Document 3, an electromagnetic field that does not form an initial solidified layer on the molten metal poured into the container is applied to the container at the same time as the molten metal is poured into the container, and this electromagnetic field is applied. In a state where the molten metal is poured into the container, and a cooling step in which the molten metal poured into the container is cooled to form a solid-liquid coexisting metal material. A method for producing a solid-liquid coexisting metallic material is described.
However, the technique described in Patent Document 3 requires equipment for applying an electromagnetic field. This facility is large and requires cost and space. In addition, a time for applying the electromagnetic field is required, and the processing time becomes long.

The present invention has been made to eliminate the above problems.
The present invention provides a method for producing a semi-solid metal slurry capable of forming a molded product having a fine and homogeneous structure that can be processed in a short time without requiring a large facility. For the purpose.

The difference in height between the molten metal and the bottom of the cooling vessel is preferably at least 4 times the vessel diameter, and more preferably at least 5 times. If it is less than 3.5 times, a dendrite-like structure may be formed depending on conditions. By setting it to 4 times or more, an even finer and more uniform structure can be obtained.
The upper limit is preferably 10 times. If it exceeds 10 times, depending on the pouring conditions, the hot water may be blown out or air may be entrained, and the entrained air may suddenly expand and cause the hot water to dance. Moreover, it becomes difficult to cast the molten metal without spilling it.

  In addition, although the shape of a container etc. is set in consideration of a thermal balance etc., as an internal diameter, 10 mm-200 mm are preferable and 40 mm-120 mm are more preferable. With such dimensions, a finer and more homogeneous structure can be obtained. When the inner diameter D increases, the poured hot water cannot move in the horizontal direction, and it becomes difficult to sufficiently perform the thermal stirring. As a result, it is difficult to obtain a finer or uniform particle size.

Incidentally, from the bottom of the container or the like to the head height (internal height) When it is h, for example, be designed with h ≒ _{3H in} ~10H in. In this case, pouring can be performed from the vicinity of the head of the container, and spillage during pouring can be reduced. On the other hand, for example, if h <H _in is designed, h / D can be reduced, so that gas entrainment during pouring can be reduced.

It is preferable to place the container or the like vertically without inclining and to pour hot water from the center without being along the side inner wall of the container or the like. In the past, pouring was performed gently by tilting the container or the like along the inner wall of the side. However, in the present invention, it is preferable to pour hot water at once without being along the side inner wall. This tends to cause self-stirring.
The molten metal is preferably poured directly into the container or the like without using a cooling member or the like.

  The pouring time is also an important factor. The pouring time is preferably 1 to 10 seconds, although it depends on the amount of pouring. 3 to 8 seconds is more preferable. 3 to 5 seconds is more preferable. In consideration of mass productivity, it is preferable that the pouring time is short, but if it is less than 1 second, there is a case where the desired structure cannot be obtained because the hot water is not stirred in the container. If it exceeds 10 seconds, workability deteriorates. Moreover, when time is taken, new hot water will be poured into the place where the whole became a semi-solidified state, and it will become difficult to produce self-stirring. The amount of pouring is generally 200 cc to 3000 cc (for example, 540 to 8100 g in the case of an aluminum alloy).

  The bottom of the container or the like has a concave curved surface shape when viewed from the pouring side.

It is preferable that the bottom portion of the cooling container has a concave curved shape when viewed from the side where the molten metal is poured. Although it is set as this curved surface shape, the molten metal containing the nucleus produced | generated by contacting the bottom part of a cooling vessel flows along a curved surface. That is, when the molten metal is poured into the center of the bottom of the container, the molten metal that has reached the bottom flows to the outside of the container over the curved surface of the bottom. When the molten metal that flows to the outside hits the wall of the container, it flows again into the container. Thereby, since the convection of a molten metal arises easily, self-stirring is performed better. As a result, a large number of the nuclei are also present inside, and a more uniform and fine crystal structure can be obtained.
The curvature of the curved surface is preferably 0.5D to 3D, and more preferably 0.6D to 1D, where D is the inner diameter of the container. By setting it within this range, convection is better generated, self-stirring is performed vigorously, and temperature uniformity is better caused throughout the container.

The molten metal is pressurized to perform pouring.
T _c <(T _L +100) is preferable for the initial temperature of the molten metal.
T _L : Liquidus temperature of metal (° C)
T _c : initial temperature of molten metal (° C.)

After the pouring, the pouring is performed so as to satisfy the following formula.
T _S <T _eq <T _I
T _S : Liquidus temperature of the metal T _L : _Solidus temperature of the metal T _eq : Temperature when the temperature of the container and the metal is the same after pouring

The container or the like is kept in a heat insulating state.
The pouring is performed by setting the heat capacity of the container or the like to a predetermined value in accordance with the amount of heat of the molten metal.
When the inner diameter, height, and material of the container or the like are constant, pouring is performed with the wall thickness set to a predetermined value.
The container is made of a nonmagnetic material or a magnetic material. In the present invention, electromagnetic stirring is not performed. Therefore, the degree of freedom in selecting materials such as containers is expanded .
The container or the like is made of stainless steel or copper. In particular, a material having a thermal conductivity larger than that of stainless steel is preferable.
The casting time varies depending on the shape of the container and the casting amount, but is preferably 1 to 10 seconds. 3 to 5 seconds is more preferable. If the casting time is too short, self-stirring is difficult to occur. On the other hand, the casting time is not too long and it is difficult to become homogeneous.
In addition, you may hold | maintain the said container etc. in the heat insulation state.

Molding method of the present invention is characterized by molding the semi-solid metal slurry prepared by the method for manufacturing a semi-solid metal slurry above follow.

Molded article of the invention features that it has been molded by the molding method.

The action of the present invention will be described together with the knowledge obtained in making the present invention.
The inventor has sought the reason why a fine and uniform composition cannot always be obtained in the techniques of Patent Documents 1 and 2.

In Patent Documents 1 and 2, generation of crystal nuclei is recognized due to a supercooling phenomenon. However, after pouring into the container, the molten metal is not stirred in the container, and the temperature remains in a gradient. That is, the molten metal is poured into the container and the movement of the molten metal stops. As a result, the temperature on the container side is low, and even if many nuclei are generated, the slurry is in a state where the temperature is high on the inside and the number of nuclei is small.

In particular, in Patent Document 1, this tendency is remarkable because pouring is performed gently for the purpose of preventing air entrainment (and thus preventing the formation of a gas nest in a molded product).

On the other hand, in the present invention, by controlling the drop start height, as shown in FIG. 4, the particle size is as fine as 100 μm or less (30 to 50 μm) and uniform (there is no variation in particle size). ) Get the organization.
Therefore, a predetermined kinetic energy is given to the molten metal to generate nuclei without generating an initial solidified layer. Numerous nuclei generated at the bottom of the container due to pouring are distributed throughout the container by self-stirring. That is, since the initial pouring metal having a large number of nuclei moves in the container, the nuclei are uniformly distributed throughout.

  Eventually, the molten metal is poured into the cooling container from a certain height and brought into contact with the bottom of the cooling container to generate nuclei without generating an initial solidified layer using the supercooling phenomenon. By dropping from a certain height, potential energy is converted into kinetic energy. In the container, if the kinetic energy of the molten metal is large, the molten metal moves around in the container until the kinetic energy disappears. Therefore, self-stirring is performed in the container. When the molten metal self-stirs, the temperature gradient of the molten metal in the container disappears, and the entire molten metal is in a semi-solid state. As a result, a slurry in which a large number of nuclei are uniformly distributed is obtained.

However, in order to generate self-stirring by giving potential energy and converting it into kinetic energy, it is not necessary to simply pour hot water from a high position. The present inventor found that there was a factor other than the height and searched for it, and found that the ratio with the diameter of the container was important. That is, it has been found that self-stirring occurs favorably when the ratio of diameter to height is 3 or more.

  The temperature of the container or the like is generally preferably from room temperature to 100 ° C., but varies depending on the type of metal, the temperature of the molten metal, and the like. The temperature may be a temperature at which a cooling phenomenon occurs when poured. What is necessary is just to investigate beforehand according to the metal used by experiment etc.

In the present invention, for example, BN spray may be applied to the surface of the container in order to generate nuclei.
Conventionally, BN spray is sometimes applied to a container in order to enhance the releasability, but in the present invention, it is applied to generate nuclei.

  When molten metal is poured into the container, nuclei are also generated on the surface of the hot water in the container. In that case, if new hot water is poured so as to pour onto the hot water surface, the core of the hot water surface is mixed into the entire container by the energy of the newly poured hot water (kinetic energy of the molten metal).

  In the present invention, the molten metal temperature is kept substantially uniform by forced convection during filling. Further, since the inner surface of the cup is constantly washed with molten metal, it utilizes the fact that many nuclei are generated and grow into a spherical shape. In order to make the molten metal temperature uniform, it is important to control the temperature in a thermal equilibrium state after pouring. Hereinafter, this point will be described in detail with reference to FIG.

When the molten metal 1 is poured into the cup (container or the like) 2 (FIG. 1A), the heat of the molten metal 1 starts to move to the cup 2 (FIG. 1B). Accordingly, the molten metal initial temperature _{Tc is} decreased, and the cup initial temperature _Tm is increased. When the temperature of the molten metal and the cup eventually becomes the same, the heat transfer stops and the temperature does not change any more) (FIG. 1 (c)).
The temperature T _{eq at} this time (hereinafter referred to as the equilibrium temperature) is given by the following equation.

Here, T _c is the melt initial temperature, T _m is a cup initial temperature, those are H _`f obtained by dividing the latent heat of solidification in the specific heat, f _s is the solid fraction. Further, γ is obtained by dividing the amount of heat necessary for increasing the temperature of the cup by 1K by the amount of heat necessary for increasing the temperature of the molten metal by 1K, and is given by the following equation.
_{γ = (ρ m c m V} m) / (ρ c c c V c) - (2)
Here, ρ is density, c is specific heat, V is volume, subscript c indicates the molten metal, and subscript m indicates that of the cup.

As is clear from the equations (1) and (2), the equilibrium temperature T _eq (or the obtained solid phase ratio) is determined by the value of γ, which is the ratio of the initial temperature of the cup and molten metal to the heat capacity of the cup and molten metal. However, the relationship between the solid phase ratio and temperature needs to be examined in advance. Further, from the equation (2), it is understood that if the material of the cup and the molten metal is specified, γ is determined only by the volume of the cup and the molten metal.
Now, when T _eq satisfies the following equation:
T _s <T _{eq TL} − (3)
The molten metal in the cup is kept in a semi-solid state.
Actually, the heat escapes from the cup surface and hot water surface to the atmosphere, so the temperature should be lower than T _eq obtained by equation (1), but by insulating the outer surface of the cup (1) A temperature close to T _eq given by the equation is reached.

The heat insulation may be performed by covering the outside of the cup with a heat insulating material.
The actual reached temperature is expressed by the following equation.
αT _eq (0 <α <1) − (4)
α is a correction coefficient obtained from an experiment, and may be obtained in advance by an experiment in accordance with an actual implementation condition.
For example, if the cup shape is a cylinder with an inner diameter: D, an inner height: H, and a wall thickness: t (constant)
V _c = π (D / 2) ² h − (5)
V _m = π (D / 2 + t) ² (h + t) −V _{c
^{∴ V m / V c = (}} 1 + 2t / D) 2 (1 + t / h) -1 - (6)

From equations (1) and (6), if the inner diameter D and the internal height h of the cup are constant, the equilibrium temperature T _eq can be _{calculated as} follows: It is determined only by the initial temperature.
From the above, given the initial temperature of the molten metal and the cup, and the material, amount, solid phase ratio and temperature T corresponding to the semi-solid body to be produced, (1), (2), (3), (4), (6 The required cup thickness can be obtained from the formula (1).

The semi-solid body having the desired solid fraction can be created by the above, but the pouring height must be sufficient to crystallize a fine crystal with a uniform solid fraction in the cup. is important.
That is, the molten metal is sufficiently stirred in the cup so that there is no temperature difference between the cup wall surface and the center of the cup, nucleation occurs sufficiently on the cup wall surface and the molten metal surface, and growth is suppressed. Can be realized.

In addition, as a material of the container or the like, it is preferable to use a material having good thermal conductivity such as stainless steel or copper.
In addition, as described above, the shape of the container or the like is set in consideration of thermal equilibrium and the like, and the inner diameter is preferably 10 mm to 200 mm, more preferably 40 mm to 120 mm. With such dimensions, a finer and more homogeneous structure can be obtained.

ここで，温度と固相率の関係を次式で評価すると，

In the following, specific examples of changes in fs when the superheat degree of the molten metal is constant and when the wall thickness t of the cup is constant will be shown. However, α in the formula (4) was set to 1.
(conditions)
Molten metal: AC4C
ρ = 2710 kg / m ³
C = 963J / kg · k
T _L = 612 ° C
T _s = 555 ° C
H _f = 398000 J / kg
∴H _f '= H _f / C
= 413 / K
Cup: Stainless steel wall thickness t
Cylindrical cup inner diameter D
Cup height h
ρ _m = 7700 kg / m ³
C _m = 500 J · kg · k
T _m = 25 ° C
(Ρ _m · C _m ) / (ρ _c · C _c )
= 7700 × 500/2710 × 963
≒ 1.48

Here, when the relationship between temperature and solid fraction is evaluated by the following equation:

Substituting the above results into equation (1), f _s is given by the following equation.
f _s = (587 · γ−δT) / (413+ (1 + γ) · 57) − (8)
Here, a δT ₌ T c -T _L, a superheat.

An example of calculation with D, t, h, etc. as specific values is shown below.
○ When overheating is constant D = 60mm
h = 150mm
δT = 50 (K)
t (mm) fs (%)
1 3
2 17
3 31
4 45
5 60
6 74

○ D = 60mm when the wall thickness is constant
t = 4mm
δT (k) fs (%)
0 56
10 54
20 52
50 45
100 35

According to the present invention, the following numerous effects are achieved.
Does not require large equipment.
It is possible to create a semi-solid slurry in a short time.
A molded article having a fine and homogeneous structure can be formed.
A semi-solid metal slurry can be produced without being limited to the type and composition of the target metal.
That is, the material selectivity can be expanded. It can be applied to iron alloys, aluminum alloys, magne alloys and other alloys. In the case of an aluminum alloy, conventionally, only an AC4C alloy can be semi-solidified, but in the present invention, it can also be applied to an ADC10 alloy that is conventionally considered to be substantially unapplicable. For example, even an alloy having a composition near the eutectic point can be semi-solidified.

  Semi-solid forming is possible without being limited by the temperature of the molten metal. Conventionally, a precise temperature is required, and thus a complicated control system is required. However, the present invention does not need to provide such a complicated control system, and therefore the system can be simplified.

  Conventionally, in order to refine the crystal, a refinement material (for example, Ti, B, etc.) has been added, but the crystal can be refined without using such a refinement material. Of course, in the present invention, a finer material may be added, and in that case, further miniaturization is achieved. Furthermore, the solid phase ratio can be easily controlled by performing heat balance.

  It is a conceptual diagram for showing a thermal equilibrium state.   2 is a perspective view of a container used in Example 1. FIG.   3 is a graph showing a temperature measurement result in Example 1.   2 is a photomicrograph of a molded article using the semi-solid body produced in Example 1. FIG.   6 is a side view showing a pouring method according to Embodiment 2. FIG. It is a graph showing the relationship between the particle diameter and H _{in / D} of the crystal in Example 3.   Test No. 3 in Example 3 3 is a photomicrograph of 3.   Test No. 3 in Example 3 4 is a photomicrograph of 4.

Explanation of symbols

1 Molten metal 2 Container (cup)
10 Plunger

In the embodiment of the present invention, the molten metal poured into a container or the like is stirred so as not to form an initial solidified layer without applying an electromagnetic field from the outside, and the molten metal is poured into the container or the like. Is. The molten metal poured into the container is cooled to form a solid-liquid coexisting metal material to produce a semi-solid metal slurry.
An embodiment of the present invention will be described below with reference to the drawings.

Using the container shown in FIG. 2, pouring was performed under the following conditions.
Melt material: AC4CH
T _L = 610-612 ° C
T _S = 555 ° C
Molten metal initial temperature: 670 ° C
Cup thickness t: 3 mm
Cup material: SUS304
Cup inner diameter D: 60 mm
Cup height h: 150 mm
Initial cup temperature: 5 ° C
Pouring height H _in : 550mm (pour from 400mm above the cup)
H _in /D=9.1
Casting time: 8 seconds Cup insulation: Existence (not shown)
Pouring time: 5 seconds

The temperature change in each part was measured from the straightness of pouring. The result is shown in FIG. As can be seen from FIG. 3, the equilibrium temperature is about 590 ° C., which is kept between T _s and T _L.
FIG. 4 shows a photomicrograph of a molded product formed using the semi-solid body obtained in this example. As can be seen from FIG. 4, in the structure of the molded product obtained in this example, it can be seen that minute primary crystals exist uniformly throughout.

In FIG. 5, the bottom plunger tip 10 of the container 2 is arranged and a curved surface having a curvature at the tip of the plunger tip. The curved surface has a concave shape when viewed from the pouring side.
The curved surface had a curvature of R = 70 mm.
Hot water was poured into this container.
The pouring conditions were the same as in Example 1.
When molding was performed using the semi-solidified slurry obtained in this example and the structure of the molded product was observed, a finer and more uniform structure than that in Example 1 was obtained.

  Although the example of the aluminum alloy is shown in the above embodiment, other molten metal may be used, and the same effect as the above embodiment is achieved.

In this example, pouring was performed by changing H _in / D.
H _in: pouring height D: the container having an inner diameter of the other points were the same as in Example 1.
Test No. H _in / D crystal grain size ^*
1 1 3
2 2 2.8
3 3 2.7
4 3.5 2.3
5 4 1.5
6 5 1.2
7 7 1.1
8 8 1
9 9 1
10 10 0.9
11 11 **
*: The crystal grain size (spherical primary crystal size) The relative value of the crystal grain size is shown with 9 as the reference (1).
*: Air entrainment occurred.
FIG. 6 shows the relationship between the crystal grain size and H _in / D. In addition, Test No. 4 and test no. The micrographs of 5 are shown in FIGS. 7 and 8, respectively.
As can be seen from each of them, when H _in / D is 4 or more, an extremely excellent structure is shown.

In this example, the influence of the initial temperature of the molten metal was examined.
In this example, AC4CH was also used. However, the liquidus temperature of the material of this example is 617 ° C.
The casting temperature was 610 (−7), 620 (+3), 640 (+23), 655 (+38), 670 (+53), 680 (+63), 700 (+83), 720 (+103), 730 (+113) ° C. The experiment was conducted with various changes. The value in parentheses is the difference from the liquidus temperature.
Other conditions were the same as in Example 1.
The crystal grain size decreased with increasing temperature.
However, with a peak at 700 ° C., it showed a tendency of saturation or a slight decrease at higher temperatures.

In this example, the pouring time was changed.
The other points were the same as in Example 1.
No. Pouring time (seconds) Crystal grain size ^* Structure uniformity ^**
4-1 0.5 2.0 △
4-2 1 1.3 ○
4-3 2 1 ○
4-4 3 1 ◎
4-5 4 1 ◎
4-6 5 1 ◎
4-7 6 1 ◎
4-8 7 1 ○
4-9 8 1 ○
4-10 9 1 ○
4-11 10 1.4 ○
4-12 11 1.5 △
4-13 12 1.6 △
*: The crystal grain size (spherical primary crystal size) The relative value of the crystal grain size is shown with 4-6 as the reference (1).
**: The homogeneity of the tissue is the sample No. With 4-6 as the reference (◎), the case where the non-uniformity including segregation is large is indicated by ◯, and the case where it is considerably large is indicated by △.

In this example, in Example 1, the ratio (t / D) between the thickness of the container and the inner diameter D was changed.
When t / D was 0.01 to 0.08, a finer and more uniform crystal structure was obtained than in other cases.
In particular, the tendency was remarkable when the diameter D of the container was 40 to 120 mm.

Claims (10)

A method for producing a semi-solid slurry having a desired fixed solid fraction without pouring molten metal set to a predetermined heat capacity and initial temperature into a container made of a single cup and cooling from the outside Because
A method for producing a semi-solid metal slurry, characterized in that the heat capacity and initial temperature of the container are set so that the temperature T _eq is obtained so as to satisfy the following formula and obtain the desired constant solid phase ratio: .
T _S <T _eq <T _I
T _L : Liquidus temperature of the metal T _S : _Solidus temperature of the metal T _eq : A constant temperature (“equilibrium temperature”) when the temperature of the container and the temperature of the metal are equal after pouring Called.) The method for producing a semi-solid metal slurry according to claim 1, wherein the molten metal is poured into the container so that self-stirring occurs. The method for producing a semi-solid slurry according to claim 1 or 2, wherein T _C <(T _L +100).
T _C : Initial temperature of molten metal (° C.) A molten metal set to a predetermined heat capacity and initial temperature is poured into a container consisting of a single cup set to the initial temperature, and a semi-solidified state having a certain solid phase ratio desired without external cooling. A container for producing a slurry of
The temperature T that satisfies the following formula and obtains the desired constant solid phase ratio: _eq The container for preparing a semi-solid metal slurry is characterized in that the heat capacity of the container is set so that
T _S <T _eq <T _I
T _L : Liquidus temperature of the metal
T _S : Solidus temperature of the metal
T _eq : After pouring, a constant temperature when the temperature of the container and the temperature of the metal are the same (referred to as "equilibrium temperature") The container for producing a semi-solid metal slurry according to claim 4, wherein the molten metal is poured into the container so that self-stirring occurs. Difference in height between molten metal and bottom of container (H _in 6) The molten metal is poured into the container in the range of 3.5 times to less than 11 times the diameter (D) of the container. The diameter of the said container is 10-200 mm, The container for preparation of the semi-solidified slurry of any one of the Claims 4 thru | or 6 characterized by the above-mentioned. The container for producing a semi-solid slurry according to any one of claims 4 to 7, wherein t / D = 0.01 to 0.08.
t is the thickness of the container, and D is the inner diameter of the container. The container for preparing a semi-solid metal slurry according to claim 8, wherein t> 1 (mm). The container for producing a semi-solid slurry according to any one of claims 4 to 9, wherein the container is made of stainless steel or copper.

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