HU185540B - Method and apparatus for degasing metal melts and/or removing their non-metallic contaminations - Google Patents

Abstract

According to the invention flushing gases are fed into lower end (13) of a duct (2) containing static mixing element(s) and/or spin elements (3). In operation the duct is located in the melt, and so the duct contains molten metal. The duct may contain space-filling bodies and the metal melt is optionally caused to flow or the streaming velocity thereof is changed by means of the gas stream streaming through the duct (2) or by the static mixing elements and/or by means of an inductive heating current. In a modification molten metal flows continuously through the apparatus, which may have more than one duct. It is stated that efficient mixing of gas and metal is obtained without mechanical agitation. <IMAGE>

Description

Several methods are known for degassing metal melts which, in the gauze atmosphere in contact with the melt, reduce the partial pressure of the gases to be removed and thereby facilitate their removal from the melt by altering the equilibrium. thus removing eg. oxygen from the melt of metals in Group VIII of the Periodic Table, etc. The partial pressure can be reduced e.g. by reducing the atmospheric pressure, i.e. by applying a vacuum or by flowing inert gas. The latter is feasible e.g. by bubbling the inert gas.

When using inert gas, the removal efficiency depends on the size of the phase contact surface and the contact time of the phases, i.e. contact time. In order to achieve maximum efficiency and thus a minimum use of inert gas, it must be ensured that the gas to be removed is in equilibrium or very close to the equilibrium in the melt and surrounding inert gas atmosphere. The smallest amount of inert gas added is also necessary because the added gas, if not preheated, can cool the melt.

A gas contacting process and apparatus providing a large contact area is described, e.g. 3.227.547, 3.743.263, and 3.870.511, supra; U.S. Pat. According to the first description, a compressed inert gas (argon, xenon, helium, nitrogen or krypton) is introduced under the surface of a molten metal at a rate of 0.3 m ³ / h. at a velocity greater than 0, through an orifice smaller than 0 = 20 mm, while providing a relative movement of at least 0.9 m / s and no more than 9 m / s between the gas exiting the orifice and the resulting molten gas. It is distributed in bubbles with a diameter of 1 mm and moves upward in the melt. The latter two patents describe an apparatus for carrying out the process discussed above, and a similar method, in which a rotary shaft is fixedly connected to a rotatable shaft in a closed pressurized container. This rotor has a plurality of vertical channels between the number paddles. The inert gas pressed from the top of the rotary shaft passes through the vertical channels of the submersible rotor into the metal melt in the form of small bubbles, while rotating the rotor to achieve the above relative velocity of 0.9 to 9 m / s between the blades on the rotor create an intense flow in the molten metal so that substantially all of its mass comes into contact with the gas bubbles. With the methods and apparatus described, the specific gas demand is 0.3 to 2.5 Nm ³ / t metal melt.

Preferably, the rotor is made of a stainless material or a heat-resistant material such as graphite or silicon urea. A rotor made of stainless material is generally quite resistant under industrial conditions. More commonly, however, chemically active gases reactive with impurities, e.g. also chlorine gas. In this case, at the temperature of the metal melts, the stainless material can no longer be used as a structural material. It is not opposed to the chlorine atomic sphere, corrodes, breaks down and corrosion products can also contaminate the molten metal. A rotor made of graphite or other heat-resistant material is resistant to the chlorine atmosphere, but it has the great disadvantage that it is difficult to withstand the extreme conditions (sudden high temperature fluctuations, etc.) resulting from the industrial practice and eg. the graphite rotor is likely to fail in a matter of weeks or months.

It is an object of the present invention to provide a method and apparatus for its realization that eliminates these disadvantages.

The development of the method and apparatus of the present invention is based on the discovery that the flushing gas introduced into the melt underneath the known statilois mixing elements or insertion tubes containing fluttering elements causes the gas to pass through and to trap the metal melt upwards. Surprisingly, the resulting metal melt flow is so intense that the mechanical mixing methods described above can be omitted. The flow of the metal melt is otherwise promoted without the use of mechanical stirrers, e.g. and inductive currents in the metal melt can also be generated. Due to the turbulent movement of the bubbles, the sputtering elements increase the metabolism between the active gas and the metal melt so that a surprisingly smaller amount of gas can be used to achieve a mixing and cleaning effect.

The process according to the invention thus comprises passing the flushing gases under the lower opening of one or more insertion tubes containing a static mixing element (s) and / or perforating elements filled with a resting or flowing metal melt and optionally at least partially filling elements, and optionally the metal melt. or by changing the flow rate of the gas in an inlet pipe or on static mixing elements with upward flow of gas and / or induction current.

In a preferred embodiment of the process of the invention, the upward gas stream is dispersed in bubbles.

In one embodiment of the process of the invention, the gas stream is introduced through one or more orifices <10 mm in diameter.

In a preferred embodiment of the process according to the invention, the upward flow of gas is alternately passed through static mixing elements forming a narrowing and expanding space, or through an insertion tube containing fluttering elements,

In a further preferred embodiment of the process according to the invention, the upward flow of gas is passed through an insertion tube provided with a converging part at the bottom and / or a diffuser part at the top.

The process according to the invention may also be carried out by flowing the metal melt in countercurrent flow with the introduced gases.

The apparatus according to the invention comprises at least a portion of the one or more static mixer elements and / or insertion tubes containing the static mixer elements and / or the static mixer elements located above the gas inlet (s) in the resting or flowing metal melt. having filled-in fills and, where appropriate, means for generating an induction current.

In an embodiment of the device according to the invention, the insert tube is preferably vertical or deviating from it by <5 °.

In a preferred embodiment of the device according to the invention there are alternatingly narrowing or expanding spaces between the insert tube and the baffles therein.

In another preferred embodiment of the apparatus according to the invention, the insertion tube containing the flutter elements comprises a tapered confluent portion and / or an expandable diffuser portion.

185,540

In a further preferred embodiment of the device according to the invention, the static mixing elements and the device (s) are alternately narrowing or expanding.

In an embodiment of the device according to the invention, the material of the space-filling elements is preferably the same as the material of a static mixing element or a transfer element or a metal or metal alloy or ceramic material which is resistant to molten metal.

The process and apparatus of the invention will now be described with reference to the drawings.

Figure 1 Schematic of a batch metal melt cleaning device with a confluent tube and a diffuser insert with alternating taper static mixing elements.

2-3. Fig. 3A is a schematic diagram of a continuously operating metal melt purifier with static mixing elements alternating between narrowing and expanding spaces and the space filling elements of Fig. 3.

Figure 4 Schematic diagram of a continuous operation metal melt purifier with two inlet tubes provided with flushing elements with a confluent part and a diffuser part in the same flow of metal melt and purifier gas.

In the open metal melt cleaning apparatus of batch operation shown in Figure 1, a metal melt 6 is filled in the tank 1 at the metal melt inlet 4. In the center of the container there is a vertical insertion tube 2 with a confluent portion 13 and a diffuser portion 14 filled with static mixing elements 3. This liner may be in a position <50 from the vertical position. Below the lower opening of the liner is a flushing gas inlet 5. Optionally, an induction coil 12 is provided on the outside of the container 1.

In Figure 2, a metal melt 6 is divided into two parts by a partition wall 9 in a container 1 of a continuous metal melt cleaning device. The container 1 has a closure 7. The container is provided with a metal melt inlet 4 and a purified metal melt outlet 8. On one side of the partition 9 there are static mixing elements 3 and below the flushing gas inlet 5.

In Figure 3, the container 1 is a U-shaped open container having a narrower and wider shaft. In the narrower shaft there is a metal melt inlet 4 at the top of the shaft and there are static mixing elements 3 therebetween, and there is a flushing gas inlet 5 below the static mixing elements 3. The wider shaft of the container 1 has a purified metal melt drain 8.

In Figure 4, a container 1 is provided on each side of the wall 9 in a container 1 with a lid 7 and divided by a partition wall 9. Above one of the insertion tubes 2 is the metal melt inlet 4, which is provided with a diffuser 14 at the top and is filled with axial fluttering elements II which are identical to the insertion tube axis. The other insertion tube 2 has a configurator portion 13 and has actuating members 10 with an angled axis at the insertion tube 2, above which is a cleaned metal melt outlet 8. Under each of the liners 2 there is a flushing gas inlet 5. The compartments 1 of the container 1 are separated by a partition 9 and contain a metal melt 6.

In the open-ended metal melt cleaning apparatus of Fig. 1, the metal melt to be cleaned is filled into the container 1 through the metal melt filler opening 4 to be cleaned. Inert gas and / or submerged gas is introduced into the metal melt 6 via a flushing gas port 5 located below the lower opening of the liner 2. The flushing gas passes upwardly through the static mixing elements 3 in the liner 2 and is distributed in a small bubble. The upward bubble current also captures the metal melt and thus flows upwardly in the liner 2. Outside the liner 2, a slower downward flow of metal melt is formed which can carry small bubbles. The resulting metal melt flow can be increased by the flow generated by the induction coil 12 into the metal melt. Due to the narrowing and expanding spaces, the accelerating and slowing flow develops in the insertion tube 2, resulting in a very strong turbulence at the junction of the currents, which causes the bubbles to burst and exert a very strong rinsing effect. From the melt current flowing downward with the tiny bubbles, non-metallic impurities settle or the tiny bubbles float to the surface. The flow of the metal melt can also be maintained by stopping the flushing gas flow by using the current in the induction coil 12. This can facilitate the floating of non-metallic contaminants.

2, the metal melt to enter the tank 1 to be cleaned through the septum 9 through the septum 9 is initially countercurrently downstream of the upstream and downstream gas stream 5 through the static mixer elements. The metal melt 6 then enters the other space of the container 1 separated by the partition wall 9 and flows slowly upwards. Meanwhile, non-metallic contaminants float to the top of the melt. The purified metal melt is discharged to the purified metal melt outlet 8. Drainage of flushing gas is not indicated in the figure.

In the open continuous metal melt cleaning apparatus shown in Fig. 3, there are spacer elements between the static elements 3, on which non-metallic impurities of the metal melt may surface. Otherwise, the apparatus operates in a manner similar to that described in the second figure.

4, the metal melt flowing down one of the insertion tubes 2 into the closed continuous metal melt cleaning device through the opening of the metal melt filler 4 to be cleaned into one half of the container 1 separated by the partition wall 9. The flushing gas inlet 5 into the liner 2 flows upwardly through the flushing elements 11, causing very strong gas bubble bursting. Slower metal melt flow occurs in the liner than with direct current, thus extending the contact time and this, together with the large gas-metal interface formed by the tiny gas bubbles, produces a very intense and rapid metal-melt degassing effect. On the other side of the partition 9, the metal melt 6 slowly moves upwards. The flushing gas thus results in a faster metal melt flow velocity in the liner 2 in this space. The resulting lower contact time is offset by the fact that the flutter elements 10 cause greater turbulence already due to their geometric arrangement. This is accompanied by increased turbulence due to the higher flow rate of the metal melt. Thus, very good degassing can be achieved. The downward flow around the liner 2 is almost completely neutralized by the upward movement of the metal melt in this space, which results in a very good float of non-metallic impurities.

The use of the method and apparatus of the invention is illustrated by the following examples.

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Example 1

One continuous operation, closed, with two configurator sections at the bottom and a diffuser section at the top, e.g. With a 50 mm inner 0-tube as mixing element, the contaminant content of the parent metal (99.5 E AI) was reduced as follows in a purification plant operating at a flow rate of 4 t / h at a flow rate of 650 kg molten metal:

Na from 0.005% to 0.0001%

Li from 0.006% to less than 00,0001%

H ₂ 0,28 cm ^3/100 g fémről 0.05-0.1 cm ^3/100 g of metal

The purification was carried out at 700-800 ° C with 1 m ³ / ton 99.995% nitrogen gas - in which the chlorine content was changed to 0 + 3% vol. The addition of the calculated amount of chlorine and the suction of the enclosed space allowed no harmful gases to be found in the work hall.

Each pair of gas conducting tubes and pads can clean 4-5,000 tons of metal. In a known process, when using a graphite mixer, 1000 to 1500 tons of metallic metal can be cleaned with a mixer. Other known methods use ceramic filler and can be used to clean -30001 metallurgical aluminum. The use of flushing gas in the known processes is from 3 to 5 m ³ / t of metallic metal. The reduction of gas consumption to 1/3 and the high lifetime of the mixing elements have made it possible to reduce the specific costs of metal cleaning by 30-40% compared to the direct cost of a metal cleaner with mechanical agitators of the above degree of purification. .

Example 2

By carrying out the above purification operation with A1 MgSi 1 grade aluminum alloy, the contaminant contents were reduced as follows:

Na from 0.0092% to 0.0001%

Li from 0.0005% to 0.0001%

Diluting 0.42 cm ^3/100 g fémről 0.12 to 0.16 cm ^3/100 g of metal.

Purification was carried out at 700-800 ° C with 1.3 m ³ / ton 99.995% nitrogen gas containing 2.5% vol. Chlorine.

In both cases, coarse wire was formed from refined metal, and the number of wire breaks and cracks during self-rolling was completely eliminated. During the production of fine wires from the product thus obtained, the former 0.8 tens per tonne coarse wire was reduced to 0.2 tens per tonne coarse wire.

The improved casting properties of the alloyed aluminum, purified by this method, made it possible to abandon the previous refining operations.

The examples illustrate how to use the method and apparatus of the invention. The mode of application and the field of application are very varied, of course, and are not at all limited to the few cases illustrated in the examples and figures.

The examples illustrate the advantages of our process and equipment: Abandoning the preparation operations and reducing the amount of gas used, the high lifetime of the mixing elements and the lower production cost of the alloyed aluminum reduced the cost of cleaning and treatment operations by 50-55% and .

Claims (12)

PATENT CLAIMS 1. A process for the degassing of metal melts by intermittent or continuous degassing and removal of their non-metallic impurities, optionally by melting the metal in an open or closed vessel, introducing an inhaled and / or chemically active gas under the surface of the metal melt in the vessel; removing non-metallic impurities on the surface of the metal melt, characterized in that the gases are introduced under the lower orifice of one or more liner tubes containing static mixing element (s) and / or swirling elements filled with dormant or melting metal melt and optionally at least partially space-filling fittings; introducing or changing the flow rate of the gas in the liner or static mixing elements with upward flow of gas and / or induction current. 2. The method of claim 1, wherein the upstream gas stream is dispersed in bubbles. 3. A method according to claim 1 or 2, characterized in that the gas stream is introduced through one or more openings with a diameter of <10 mm. A method according to any one of the preceding claims, characterized in that the upward flow of gas is passed alternately through static mixing elements or a liner pipe containing fluttering elements. 5. A method according to any one of the preceding claims, characterized in that the upward gas flow is passed through a liner having a bottom tapering cone section and / or a top expanding diffuser section. 6. A process according to any one of the preceding claims, characterized in that the metal melt is flowed in countercurrent with the introduced gases. 7. Equipment according to claims 1-5. A method according to any one of claims 1 to 4, having an open or closed batch fill or flow container or tube section (s) having a metal melt and an inert and / or chemically active gas resistant liner, metal melt inlet and outlet means, gas inlet and outlet. gas discharge means, means for removing non-metallic contaminants from the surface of the metal melt and temperature control, characterized in that one or more static mixing elements and / or insertion tubes are provided in the resting or flowing metal melt above the gas inlet opening (s); the insertion tubes containing static mixing elements and / or fluttering elements have at least partially filled space filling elements and, if necessary, means for generating an induction current. 8. The device of claim 7, wherein the axis of the liner is preferably vertical or deviating from it by <50. An embodiment of the apparatus as defined in claims 7 and 8, characterized in that there is a narrowing or expanding space alternately between the insert tube and the flapping elements disposed therein. 10. 7-9. An embodiment of the apparatus as defined in any one of claims 1 to 4, characterized in that the insertion tube comprising the flutter elements comprises a tapered portion of a configurator and / or a diffuser portion extending above. 185,540 11. The apparatus of claim 7, wherein the static mixing elements and the apparatus have alternately tapering or expanding spaces between the bowl (s). 12. An embodiment of the apparatus as defined in any one of claims 1 to 6, wherein the material of the space-filling elements is a metal or metal alloy or a ceramic material which is identical to the material of the static mixing elements or fluttering elements.