JPH05195108A - Production of agent for preparing micro- crystals - Google Patents

Abstract

PURPOSE: To produce a good crystal refining agent from a relatively simple starting material.

CONSTITUTION: This is a method for producing a crystal refining agent contained in an aluminum matrix including the obtainment of solid phase reaction products by homogeneously mixing at least one kind of reaction products of titanium and aluminum contained in an aluminum matrix and at least one kind of reaction products of boron and aluminum contained in the aluminum matrix and bringing the reaction products into solid phase reaction.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain refiner contained in an aluminum matrix, a grain refiner produced by the above method and a method for using the same.

[0002]

In the metal industry, semi-finished products and cast products
ings), the crystal size is
It is known to be an important factor to control because it affects many of the mechanical and chemical properties of aterial). Usually, the molten metal must have sufficient crystal nuclei in order for the cast product to have the desired crystal size. Often it is necessary to increase the number of crystal nuclei by adding them to the melt. Normal,
This is accomplished by adding to the melt a master alloy containing a large number of nucleating particles dispersed in the aluminum melt.

Titanium is the most common additive for refining aluminum crystals, and is also a very effective additive in this respect. At normal melting and casting temperatures
When the titanium concentration is 0.2% (m / m) or more, the intermetallic phase Al ₃ Ti is formed with aluminum, but even if the concentration is low, the crystal refining effect can be provided. In the preparation of master alloys containing 1-15% Ti in aluminum, Al ₃ Ti particles are formed according to the usual known phase diagram with some Ti in solution.
When boron is added to a master alloy containing Ti, in particular, Ti / B
It is generally known that when the ratio is between 2.2 and 25, the grain refining effect is greatly improved. Boron is TiB ₂ and
It has been made by some investigators with the inference that they form TiB ₁₂ -type particles and that these particles build up crystal nucleation sites, while others have found that in aluminum melts, boron Argues that it reduces the dissolution of Al ₃ Ti into Al and Ti, thus producing a more effective and durable grain refining effect when the intermetallic phase Al ₃ Ti is included.

In order to produce a suitable grain refiner or master alloy to be added to the aluminum melt, the former West German Patent Application No. 23 07 250 discloses that the aluminum melt should have an alkali fluoride titanium complex and an alkali fluoride. It is suggested to add fine particles of boron complex. Although such a method provides a suitable grain refiner, this method has several drawbacks.

First of all, the starting materials are relatively expensive, which makes the process economically disadvantageous. In addition to this, the reaction between the components is exothermic, which makes the reaction rather difficult to control. Further, the salt complex reduces the purity of the crystal grain refiner even in a small amount.

[0006]

The object of the present invention is to provide a process for the preparation of grain refiners from relatively simple starting materials which does not have the disadvantages of the prior art processes.

[0007]

According to the present invention, an excellent grain refiner is a reaction product of titanium and aluminum contained in at least one aluminum matrix,
It is based on the finding that it can be produced by solid state reaction of the reaction product of boron with aluminum.

Therefore, the present invention provides at least one of titanium and aluminum contained in the aluminum matrix.
A homogeneous reaction product of at least one reaction product of boron and aluminum contained in an aluminum matrix and subjecting the reaction product to a solid phase reaction to obtain a solid phase reaction product. , A method for producing a grain refiner contained in an aluminum matrix.

The reaction product of titanium and aluminum contained in the aluminum matrix is preferably Al ₃ Ti in aluminum, and the reaction product of boron and aluminum is preferably AlB ₂ and / or AlB ₁₂ . From the viewpoint of reactivity and efficiency, it is preferable to use AlB ₂ . However, in combination with AlB ₂ , Al
When formulating B _12, it can be a good grain refiner.

The solid phase reaction described above is initiated by combining and intimately mixing the solid reaction products [ie, Al ₃ Ti and AlB ₂ (and / or AlB ₁₂ ) contained in the aluminum matrix] and then the remainder. Is not only Al ₃ Ti,
It is defined as including the reaction steps that give the specified amount of TiB ₂ . However, how the reaction product reacts has not been completely elucidated. To date, the solid phase reaction decomposes at least a portion of the reaction product into its separate components, physically diffuses these components, and then chemically reacts Ti and B to produce TiB ₂ (or TiB ₂ ).
₁₂ ) and is considered to be included.

The reaction product of titanium and aluminum contained in the aluminum matrix and the reaction product of boron and aluminum contained in the aluminum matrix can be easily produced by methods known in the art. The method to be used may be the same as the method for producing the Al / Ti and Al / B master alloys. Usually, it is produced by adding a raw material containing titanium (eg, titanium sponge or titanium salt) and a raw material containing boron (eg, boron salt) to molten aluminum.

According to the invention, the titanium component, Al ₃ Ti and the boron component, AlB ₂ and / or AlB ₁₂ are in the form of alloys with aluminum (ie Al ₃ Ti in aluminum and AlB ₂ and / or AlB in aluminum). ₁₂ shapes) are preferably used. These alloys are then homogenously mixed in the solid phase and the material is heated to the temperature required for the solid phase reaction during or after mixing.

The intimate mixing step can be carried out in various ways. In one embodiment, particles of two materials, for example granules, powders, flakes, needles or similar shaped fine particles, are homogenized and the resulting mixture is heated. This heating may be carried out by compressing or extruding the mixture with sufficient shear stress or force and raising the temperature to the desired level. However, annealing the material after compression or extrusion is preferred as it allows for better control of the process and results in a more reproducible product. Alternatively, it can be carried out by heating the material during extrusion.

In another embodiment, the material is coextruded at a temperature below the melting point of the material, optionally with heating.
If desired, this method may be repeated several times until a sufficient mixture is obtained. The materials will react depending on the temperature used, but it is usually preferred to heat the mixture after mixing to react the materials.

When making a powder mixture of alloys, the particle size and state of the powder should promote diffusion in the solid phase and allow the reaction to occur. In the case of oxide powders, the particle size should not be too small as it has been found that the effect is diminished, probably because the oxygen concentration becomes too high when the surface area is large. Therefore, the preferred particle size is 50 μm.
~ 1 mm.

The heating or annealing of the material should also be carried out so that the solid state reaction as defined above proceeds to a suitable degree. The preferred temperature is 400 ° C or higher. Upper limit (temperature)
Is determined by the melting point of the material. The temperature also depends on the length of time and must be low for long heating times. The heating time is usually 0.1 to 5 hours. Although it is not particularly effective even if it is carried out for a long time, the lower limit (time) is usually the time required to obtain a sufficient reaction.

The amount of titanium in the grain refiner is 0.2 to 15
Weight% is preferred, but the amount of boron in the grain refiner is
0.02 to 10% by weight is preferable. Titanium to boron ratio (m / m)
Is 1 to 80, especially 2.5 to 35.

It should be noted that the amounts of boron and titanium depend on the effect of the grain refiner and the amount of grain refiner to be used in the final product.

Although the mechanism for refining the alloy crystals with respect to the composition of the active reaction components obtained by the solid phase reaction is not completely clear, the solid phase reaction product containing the components is
At least Al ₃ T with a particle size of 30 μm or more and 5 μm or less
i and TiB ₂ . Preferred solid phase reaction products include fine and many phase particles. Preferred particle sizes are 10 to 30 μm and 0.5 to 5 μm, respectively. The particle size of the component products is measured by microscopy and means that at least 80% of the particles detected are of said size.

It has been observed that when the above-mentioned two components have such a grain size, an optimum grain refining effect is obtained. It has been found that a minimum amount of the grain refiner of the present invention can be conveniently used in aluminum. Usually, these amounts are 5 kg or less per 1000 kg of aluminum, preferably 0.1 to 5 kg. Furthermore, Ti content of 5% by weight and B
Compared to the case of using 2 kg of the conventional crystal refining agent having a content of 1% by weight, the Ti content was only 3% by weight and the B content was slightly lower when 2 kg of the crystal refining agent of the present invention was used.
It turned out that 0.5% by weight is sufficient. Note that for the sake of clarity, the amount of grain refiner (kg) was calculated on the basis of the total amount of grain refiner and not on the amount of titanium and boron.

The crystal grain refiner of the present invention can be used in various shapes such as powder, needles, flakes and granules. The grain refiner is preferably manufactured in the form of a wire, as is conventional in the prior art for aluminum castings.

The grain refiner can be used to make aluminum intermediate products such as ingots, but can also be used in cast products.

The invention will be further illustrated by the following examples, which are provided as an illustration of the invention.

[0024]

EXAMPLES Examples 1-3 Granules of the reaction product of titanium and aluminum contained in an aluminum matrix containing approximately 3.4 to 3.6% (m / m) of titanium in the form of Al ₃ Ti, mainly AlB _12. (2.2
%) Or AlB ₂ (1.2 and 0.4%) in the form of boron 2.
Boron contained in an aluminum matrix containing 2, 1.2 and 0.4% (m / m) and granules of the reaction product of aluminum and aluminum were mixed.

The mixture of granules was first compressed into extruded billets and subsequently extruded. 640 extruded material
It was annealed at 0 ° C for the time shown in the table. Grain refinement response (grain
Various products were tested for refining response) [ie, the crystal size (μm) of aluminum with grain refiner included]. So-called Kawecki-Billiton crystal refinement test or ring test [Vadar et al., “Interrelations
between aluminium grain refining by means of alumi
nium titanium boron alloys and the number of growth
centers ”, Internationale Leichtmetalltagung, Leobe
n-Wien 1987, 22-26 June, 1987]]. Conventional operating conditions were applied to the molten alloy incorporating the grain refiner. The results are shown in Table 1.

[0026]

[Table 1]

Examples 4-6 Using the same method as described in Examples 1-3, different products with different titanium and boron contents were produced. The results are shown in Table 2.

[0028]

[Table 2]

Example 7 Granules of the reaction product of titanium and aluminum contained in an aluminum matrix containing approximately 3.4% (m / m) titanium in the form of Al ₃ Ti and a boron content of 1.4% (m / m). )
A mixture of granules of the reaction product of boron and aluminum contained in an aluminum matrix having Subsequently, the mixture is extruded into a wire,
Annealed at 640 ° C. The results of the crystal refinement response are shown in Table 3.

[0030]

[Table 3]

Example 8 Granules of the reaction product of titanium and aluminum contained in an aluminum matrix containing about 3.4% titanium (m / m) in the form of Al ₃ Ti, and a boron content of 1.4% (m / m). A mixture of boron and a reaction product powder of aluminum contained in an aluminum matrix having Subsequently, the mixture was compressed, extruded into multiple wires and annealed at 640 ° C. In particular, the compressed material was extruded 5 times (after extrusion, the wire was cut into small pieces and again extruded to obtain the wire of the grain refiner). The results of the crystal refinement response are shown in Table 4.

[0032]

[Table 4]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Cornelis Jacobs Robert Fruunenberg 6827 Athe Arnhem, Netherlands, Westerforth Sedijk 67 D (72) Inventor Kristian Järn Hendrix Juan Clef Netherlands, 6827 Arte Arnhem, Westerfört Sedek 67 Day (72) Inventor Wim Albert Juan Ravenswii Netherlands, 6827 Arte Arne U, Westerford Cedeique 67 Day

Claims (17)

[Claims] 1. A reaction product obtained by homogeneously mixing at least one reaction product of titanium and aluminum contained in an aluminum matrix and at least one reaction product of boron and aluminum contained in an aluminum matrix. A method for producing a crystal-refining agent contained in an aluminum matrix, which comprises obtaining a solid-phase reaction product by solid-phase reaction of. 2. A process according to claim 1, characterized in that Al ₃ Ti is used as the reaction product of titanium and aluminum. 3. The method according to claim 1, wherein AlB ₂ and / or AlB ₁₂ is used as a reaction product of boron and aluminum. 4. The reaction product of titanium and aluminum and the reaction product of boron and aluminum, each contained in one aluminum matrix, are mixed. The method according to any one of items. 5. A mixture of particles of a reaction product of titanium and aluminum contained in an aluminum matrix and particles of a reaction product of boron and aluminum contained in an aluminum matrix is prepared, and then a solid phase reaction occurs. The method according to claim 4, which comprises heating under the following conditions. 6. The particles are powder particles, flakes,
Method according to claim 5, characterized in that it is selected from the group of granules and needles. 7. A reaction product of titanium and aluminum and a reaction product of boron and aluminum, each contained in an aluminum matrix, are extruded together and mixed homogeneously, and then to achieve said solid phase reaction. The method according to claim 1, wherein heating is performed. 8. A reaction product of titanium and aluminum and a reaction product of boron and aluminum, each contained in an aluminum matrix, are extruded and mixed together and heated during the extrusion. The method according to any one of claims 1 to 6. 9. The amount of titanium in the grain refiner is 0.2 to 15.
The method according to claim 1, wherein the method is wt%. 10. The amount of boron in the grain refiner is 0.02 to
The method according to any one of claims 1 to 9, which is 10% by weight. 11. A titanium to boron ratio (m / m) of 1-80.
The method according to any one of claims 1 to 10, wherein 12. The solid phase reaction product comprises at least Al ₃ Ti and TiB ₂ having a particle size of 15 to 30 μm and 1 to 5 μm, respectively. The method described in. 13. The method according to claim 1, wherein the grain refiner is produced in the form of a wire. 14. A process for the preparation of a grain refining agent contained in an aluminum matrix substantially as hereinbefore described with particular reference to the examples. 15. A crystal refining agent produced by the method according to any one of claims 1 to 14. 16. The particle size of Al ₃ Ti and TiB ₂ is 15 to ₃ respectively.
0 μm and 1-5 μm, and the ratio of titanium to boron (m /
m) is 1 to 80, and the amounts of Ti and B are each 0.2 to 15% by weight.
And 0.02 to 10% by weight of Al ₃ Ti and TiB ₂ in the aluminum matrix. 17. A method for producing a semi-finished aluminum product and a cast product, which uses the crystal refining agent according to claim 15 or 16.