RU2323990C1 - Producing method of ligature aluminium-refractory, metal for melting casting aluminum alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes melting of aluminium and processing of melted aluminum by punching it through the layer of halogenide granules of refractory metal, under the influence of nanosecond electromagnetic pulse with the power 600-900 Mwt /m³. Simultaneously with punching the melt is revolved and sprayed. The punching of melted aluminium through the layer of halogenide of refractory metal is produced by pressure of rare gas to the mirror of the melt in limits (1.5 - 3)-10⁵ Pa. The spraying of the melt is produced under the residual pressure of environmental air 2-8 kPa.

EFFECT: generated ligatures have the increased characteristics under the heightened temperatures.

3 cl, 3 tbl, 3 ex

Description

The invention relates to the field of foundry and can be used in the preparation of aluminum alloys - refractory metals for the smelting of cast aluminum alloys and obtaining from them accurate castings.

Currently, aluminum alloys are widely used in casting processes silumin. Given that these alloys are eutectic, they have sufficiently high casting properties (increased fluidity, a tendency to form a concentrated shrink shell, etc.). However, they are characterized by relatively low strength characteristics, especially at elevated operating temperatures of cast parts in modern engineering, the development of which objectively increases the requirements for precision casting.

One of the effective ways of creating high-strength silumins is their alloying with refractory metals (elements of transition groups: molybdenum, tungsten, scandium, titanium, copper, zirconium, etc.) / Kolobnev I.O., Krymov V.V., Melnikov A.V. Handbook of a caster. Color casting of light alloys. - M.: Mechanical Engineering, 1974. - S. 16 ... 17 /. This process is complicated by the low solubility of the alloying elements, their high melting points. In the well-known high-strength foundry aluminum alloys, titanium, zirconium, and scandium are most widely used. The use of more refractory metals, such as molybdenum, tungsten, seems to be problematic. Therefore, they go along the path of preliminary preparation of ligatures using chemical compounds of refractory metals. However, in this case as well, the preparation of the aluminum – refractory metal alloy is characterized by a high superheat temperature, low solubility, and uneven distribution of alloying elements.

A known method of preparing alloys aluminum - refractory metal, including the processing of aluminum melt with a refractory metal halide / Destruction of aluminum alloys under tensile stresses. Collective Monograph, ed. M.E. Dritza. - M .: Nauka, 1973. - P.85 ... 87 /. The disadvantage of this method is similar to the above method.

The closest in technical essence is the method of preparing the aluminum - refractory metal alloys for smelting cast aluminum alloys, including the melting of aluminum and the processing of molten aluminum with refractory metal halide when exposed to electromagnetic pulses / RF Patent No. 2232827. Method of preparing the aluminum alloy - refractory metal. Znamensky L.G. Bulletin of inventions No. 20, 2004 /.

The known technical solution provides the possibility of alloying aluminum with scandium, titanium, zirconium, etc., with lower temperatures and the duration of the preparation of the corresponding ligatures. However, the prototype has the following significant disadvantages:

- the impossibility of electropulse activation of large volumes of metal due to the local nature of the impact of NEMI;

- insufficient efficiency of "assimilation" of refractory metals when they are introduced into the melt by the "bell" method;

- the impossibility of creating nanostructures from the resulting intermetallic compounds when casting liquid ligatures in air (at low cooling rates of the melt;

- insufficient uniformity of distribution of refractory alloying elements in a metal matrix.

In addition, the phenomena of the inheritance of the ligature structure by working aluminum alloys obtained from their use are insufficiently expressed, which significantly hinders the achievement of a potential level of improvement in the properties of alloys and castings.

The basis of the invention is the task of creating such a method for preparing aluminum-refractory metal alloys, which would ensure a high degree of uniformity in the distribution of refractory metals in an aluminum matrix and the creation of nanostructures from the resulting intermetallic compounds, as well as the inheritance of their structure and properties by working aluminum alloys to achieve their increased physical - mechanical characteristics.

This problem is solved in such a way that in the method of preparing the ligature, aluminum is a refractory metal, including melting aluminum and treating the molten aluminum with a refractory metal halide when exposed to electromagnetic pulses, according to the invention, the processing of molten aluminum is carried out by forcing a refractory metal halide through a layer of granules when exposed to nanosecond electromagnetic pulses by power 600 ... 900 MW / m ^3, while at the same time forcing the melt spun and aspylyayut. The molten aluminum is pushed through the refractory metal halide layer by inert gas pressure on the melt mirror in the range (1.5 ... 3) · 10 ⁵ Pa, and the melt is sprayed at a residual ambient pressure of 2 ... 8 kPa.

Squeezing molten aluminum through a layer of refractory metal halide in the field of nanosecond electromagnetic pulses provides a high specific (per unit volume) power of the effect of the latter on the occurrence of reactions of reduction of refractory metal with liquid aluminum at the atomic level. The use of nanosecond electromagnetic pulses with a power of 600 ... 900 MW / m ³ creates the conditions for the maximum absorption of this atomic refractory metal and its uniform distribution in the aluminum matrix.

Spraying the melt provides a high cooling rate of aluminum alloyed with refractory metals (10 ⁷ ... 10 ¹⁰ ° C / s). As a result of this, intermetallic compounds (aluminum is a refractory metal) are formed on a nanometer scale, the structure of which is inherited when working alloys are obtained using alloys. These nanostructures act as effective crystallization centers and provide a powerful modifying effect. Spraying the melt in vacuum at a residual pressure of ambient air of 2 ... 8 kPa seems to be the most effective, since it blocks the undesired oxidation of aluminum. As a result of all this, significant hardening of working aluminum alloys is achieved and the quality of castings is improved.

The processing of an aluminum melt by a refractory metal halide with simultaneous exposure to it by nanosecond electromagnetic pulses provides the electrophysical activation of the interaction of these components, which leads to accelerated isolation of the reaction product, an atomic refractory metal at lower aluminum superheating temperatures. The “transfer” of excess energy to refractory metal atoms in the NEMI field creates the conditions for a sharp increase in its solubility and uniform distribution in aluminum.

The proposed method for the preparation of alloys aluminum - refractory metal is as follows.

Technical aluminum is melted in a melting and casting plant and overheated to temperatures of 750 ... 800 ° C. Aluminum melt is forced through a layer of refractory metal halide, which can be used chlorides or fluorides of molybdenum, tungsten, titanium, zirconium, chromium (metals of transition groups of the chemical elements table of D.I. Mendeleev). In this case, the refractory metal halide is located in a conductive, for example, graphite, perforated glass, pre-connected to a NEMI generator with a capacity of 600 ... 900 MW / m ³ / RF Patent No. 2030097, MKI N03K 3/33, 3/45. Shaper of nanosecond electromagnetic pulses. Belkin BC, Shulzhenko G.I. Claim 1/17/92 /. Punching is carried out by acting on a mirror of liquid aluminum with an inert gas, for example argon, under pressure (1.5 ... 3) · 10 ⁵ Pa. Simultaneously with the filtration of the melt through a layer of refractory metal halide, a perforated cup is rotated and alloyed aluminum is sprayed at a residual air pressure of 2 ... 8 kPa. Prepared ligature aluminum - refractory metal in the form of granules is used to obtain silumins and precision casting.

The optimality of NEMI power values of 600 ... 900 MW / m ³ is dictated by the possibility of effectively influencing the rate of interaction of liquid aluminum with a refractory metal halide and achieving, with these parameters, a significant increase in the solubility and uniformity of the distribution of refractory alloying elements in the matrix, and refinement of its structure to a nanolevel, ensuring An improved set of properties of ligatures and silumins and precision castings obtained with their use.

When the power of NEMI is less than 600 MW / m ^{3, the} change in the properties of the aluminum – refractory metal alloy is insignificant. Therefore, the positive effects of its use in the precision casting of silumins are weakly expressed. The impact of NEMI with a capacity of more than 900 MW / m ^{3 is} impractical due to the increase in energy costs.

The pressure of inert gases on the mirror of the aluminum melt in the range of (1.5 ... 3) · 10 ⁵ Pa provides the necessary filtration rate and the interaction between the aluminum melt and the refractory metal halide.

Spraying the metal at a residual pressure of 2 ... 8 kPa blocks the oxidation of aluminum and minimizes the number of non-metallic inclusions.

The proposed method for the preparation of alloys aluminum - refractory metal is illustrated by the following examples.

Example 1. The melting is carried out in a melting and casting plant, for example, the brand “Lin Electronics” (Germany) or “Modular” (Italy) / Magnitsky ON, Pirainen V.Yu. Art casting. - St. Petersburg: Polytechnic, 1996. - P.179 ... 180 /. Technical grade A85 aluminum is melted with a mass of 15 kg and overheated to 750 ° C. The temperature is controlled by the readings of a platinum-platinum-rhodium thermocouple integrated in the furnace. Granular MoCl ₅ powder is poured into a perforated graphite glass with a height and a diameter of 50 mm installed in the filling chamber of the installation. The stopper in the melting chamber and the glass in the pouring chamber of the installation are connected to the generator NEMI / RF Patent No. 2030097, MKI N03K 3/33, 3/45. Shaper of nanosecond electromagnetic pulses. Belkin BC, Shulzhenko G.I. Claim 1/17/92 /. Create argon pressure on the mirror of molten aluminum in the melting chamber of the installation and push it through a layer of refractory metal halide (MoCl ₅ ) with the NEMI generator turned on with a capacity of 800 MW / m ³ while rotating the beaker at a speed of 240 rpm and spraying the alloyed aluminum in vacuum at residual air pressure in the filling chamber of the installation 5 kPa. During the tests, the argon pressure varies: (1.5; 2; 3) · 10 ⁵ Pa.

The shape, average size and distribution of intermetallic inclusions in the aluminum matrix were recorded using a JEOL JSM 6460LV scanning electron microscope with wave and energy dispersive analyzers.

Ligatures prepared in this way are used for smelting AK12ch working aluminum alloy, additionally alloyed with 0.2 ... 0.4 wt.% Mo. The influence of the methods for the preparation of Al-Mo ligatures (prototype and developed version at different inert gas pressures) on their properties and characteristics of silumins is presented in Table 1.

Table 1 The influence of methods for preparing Al-Mo ligatures on the properties of ligatures and working aluminum alloy The properties Prototype Inert gas pressure × 10 ⁵ Pa 1,5 2 3 1. The degree of assimilation of the refractory metal in the matrix,% 20 ... 25 65 58 49 2. The duration of the preparation of the ligature, min 20 ... 40 fifteen 12 10 3. The average size of the intermetallic compounds in the ligature, microns 5 ... 8 0.4 0.2 0.1 4. The degree of mastering of the ligature,% 30 ... 40 68 70 75 5. The average size of the intermetallic compounds in the working alloy, microns 8 ... 20 0.5 0.3 0.2 6. The grain size in the working alloy, microns 70 ... 100 12 eleven 10 7. Strength, MPa at temperatures: a) 20 ° C 490 510 550 560 b) 300 ° C 184 240 270 280 8. Hardness, HB 124 170 185 190 Note. Similar results were obtained in the treatment of molten aluminum with tungsten chloride.

Example 2. The preparation of the aluminum alloy molybdenum is carried out analogously to example 1, but during the preparation vary. During the tests, the power of the NEMI is varied: 600, 800, 900 MW / m ³ . The influence of this treatment parameter on the properties of Al - Mo alloys and working aluminum alloy is presented in Table 2. The values of the indicators according to the developed method are given at an inert gas (Ar) pressure on the molten aluminum mirror of 2 · 10 ⁵ Pa.

table 2 The effect of NEMI power on the properties of Al-Mo ligatures and working aluminum alloy The properties Power of NEMI, MW / m ³ 600 800 900 1. The degree of assimilation of the refractory metal in the matrix,% 46 58 61 2. The duration of the preparation of the ligature, min 12 12 12 3. The average size of the intermetallic compounds in the ligature, microns 0.4 0.2 0.1 4. The degree of mastering of the ligature,% 55 70 73 5. The average size of the intermetallic compounds in the working alloy, microns 0.5 0.3 0.2 6. The grain size in the working alloy, microns eighteen eleven 9 7. Strength, MPa at temperatures: a) 20 ° C 520 550 560 b) 300 ° C 195 270 290 8. Hardness, HB 163 185 190

Example 3. The method of preparing the aluminum – refractory metal alloys in this case is similar to that shown in Example 1, but the residual air pressure in the casting chamber of the unit varies when the alloyed aluminum is sprayed during rotation. The effect of this indicator on the properties of the ligature and working aluminum alloy is given in table 3. The values of the indicators according to the developed method are given at an inert gas (Ar) pressure on the molten aluminum mirror of 2 · 10 ⁵ Pa and a NEMI power of 800 MW / m ³ .

Table 3 Effect of residual pressure in the casting chamber on the properties of Al-Mo alloys and working aluminum alloy The properties Residual air pressure, kPa 2 5 8 1. The average size of the intermetallic compounds in the ligature, microns 0.1 0.2 0.6 2. The degree of mastering of the ligature,% 78 70 64 3. The average size of the intermetallic compounds in the working alloy, microns 0.2 0.3 0.8 4. The grain size in the working alloy, microns 10 eleven fifteen 5. Strength, MPa at temperatures: a) 20 ° C 560 550 530 b) 300 ° C 280 270 230 6. Hardness, HB 195 185 180

The results of these tests show that, in comparison with the prototype, the claimed method provides a transition from intermetallic compounds of sizes 5 ... 8 μm, penetrating the grains of the aluminum matrix and "weakening" it, to highly dispersed compact inclusions with an average size of 0.1 ... 0, 5 microns. Such a structure, practically on a nanometer scale, is characterized by a high degree of uniformity in the distribution of refractory alloying elements in an aluminum matrix and creates the conditions for the effective inheritance of its properties in a working alloy and for enhancing the modifying effect when sulumines are melted using ligatures prepared according to the developed method. The result is an increase in almost 2 ... 3 times the degree of assimilation of the refractory alloying element in the matrix, the ligature itself in the working aluminum alloy. In general, a high quality of preparation of the modifying ligature and an increase of 30 ... 40% in the strength characteristics of these aluminum alloys, especially at elevated temperatures, are achieved.

The claimed method was tested in the manufacture of die-casting rubber models in highly porous forms on a gypsum binder of aluminum wheels of compressors of internal combustion engines. There has been an improvement in the quality of these precision castings for critical applications.

Given that the claimed method of preparing the aluminum – refractory metal alloys, in fact, is the basis of nanotechnology, it can be used in precision casting from aluminum alloys for the needs of mechanical engineering, instrument making, and the aerospace complex.

Claims (3)

1. The method of preparation of the ligature aluminum - refractory metal for the smelting of cast aluminum alloys, including the melting of aluminum and the processing of molten aluminum with a refractory metal halide when exposed to electromagnetic pulses, characterized in that the processing of molten aluminum is carried out by forcing through a layer of granules of a refractory metal halide when exposed to nanosecond electromagnetic pulses power of 600-900 mW / m ^3, while simultaneously forcing the melt and rotated disintegrations lyayut. 2. The method according to claim 1, characterized in that the extrusion of molten aluminum through a layer of refractory metal halide is carried out by the pressure of an inert gas on the melt mirror in the range of (1.5-3) · 10 ⁵ Pa. 3. The method according to claim 1 or 2, characterized in that the spraying of the melt is carried out at a residual pressure of ambient air of 2-8 kPa.