RU2644221C1 - Aluminium-titanium-boron master alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: aluminium-titanium-boron master alloy for modification of aluminium and its alloys contains at least 90 wt % of titanium diboride particles and not more than 10 wt % of particles of titanium aluminide or aluminium boride, at that, the ratio of titanium to boron in the master alloy is (1.918-2.356): 1.

EFFECT: reduced consumption of titanium-containing alloying additive, increased modifying ability of the master alloy and physical and mechanical properties of modified aluminium.

1 ex, 5 tbl, 2 dwg

Description

The invention relates to the metallurgy of aluminum and can be used to obtain modifying ligatures based on aluminum, used to grind the structure of semi-finished products and products from aluminum and its alloys. The receipt of a triple Al-Ti-B ligature was first announced by specialists of the Dutch company Cavecchi in patents No. 802701 (England), 1957 and No. 395549, No. 395550 (Switzerland), 1965. In accordance with these patents, the Al-Ti ligature -B is prepared by aluminothermic reduction of tetrafluoroborate and alkali metal hexafluorotitanate with vigorous stirring of the melt.

In the scientific and patent literature there is a large amount of information on the composition of the Al-Ti-B ligature and methods for its preparation. Several typical Al-Ti-B ligature formulations are known.

GOST 53777-2010, Aluminum ligatures, Technical conditions, M., Standartinform, 2012 [1], provides for the production and use of 4 types of Al-Ti-B alloys, the content of boron and titanium in which are given in table 1.

Some manufacturers of aluminum alloys expand the range of products. In particular, the SAS Engineering Company, in addition to the ligatures listed in GOST 53777-2010, produces the Al-3Ti-0,2B ligature (E-mail: info@sasua.com.ua; http://sasua.com.ua [ 2]). This ligature is applied "when using return or charge with a high titanium content." According to the technical nature and the presence of similar features to the claimed solution, these Al-Ti-B alloys compositions are selected as the closest analogue.

In the known compositions of Al-Ti-B alloys, there are two types of intermetallic compounds: titanium aluminide Al ₃ Ti and titanium diboride TiB ₂ . In FIG. 1 is a photograph of a typical Al-Ti-B ligature microstructure. Lighter and larger crystals of titanium aluminide Al ₃ Ti have a size of 10 ÷ 50 μm, in some cases up to 100 μm. The size of dark and small crystals of titanium diboride is 1 ÷ 3 microns. According to literature data (V.I. Napalkov, B.I. Bondarev, V.I. Tararyshkin, Chukhrov M.V. Ligatures for the production of aluminum and magnesium alloys. M: Metallurgy, 1983, 160 pp. [3]) maximum The effect of grinding the structure of aluminum and its alloys is provided by crystals of titanium diboride TiB ₂ . Titanium diboride practically does not dissolve in liquid aluminum, and the small size of the crystals creates a large number of crystallization centers. Titanium aluminide Al ₃ Ti dissolves in liquid aluminum. The speed and completeness of dissolution of titanium aluminide depends on the temperature of aluminum, the size of Al ₃ Ti crystals and the time from the moment the ligature is introduced into the melt to the crystallization of the metal.

The main disadvantage of the known Al-Ti-B alloys is that large crystals of titanium aluminide make an insignificant contribution to the grinding efficiency of the structure of aluminum and its alloys. Increased requirements for the content of impurities in the commodity metal have led to the fact that in most cases at the aluminum and metallurgical plants, Al-Ti-B ligature was introduced into the melt before inert gas refining plants with inert gases and ceramic foam filters. This is done in order to increase the ligature residence time in the metal being modified and to dissolve large crystals of titanium aluminide as much as possible. As a result, titanium aluminide crystals participate to a limited extent during the modification process, because they either float and pass to slag in metal refining inert gases, or are retained in ceramic foam filters. When refining a metal by blowing with inert gases and cleaning in ceramic foam filters, along with crystals of titanium aluminide, they partially pass into slag and small crystals of titanium diboride are captured.

The Al-Ti-B modifying ligature is fed into the melt to metal refining units in order to prevent large titanium aluminide crystals of several tens of microns in size, as well as oxide films from the surface of the ligature rod, getting into the marketable products. Large crystals of titanium aluminide with a size of 10 ÷ 50 μm during subsequent processing of modified ingots, for example, onto aluminum foil with a thickness of 5-7 μm, increase the yield of defective products. As a result, the Al-Ti-B alloy is used inefficiently. This is the main disadvantage of the known Al-Ti-B master alloy compositions.

The task of the invention is to optimize the composition of the Al-Ti-B ligature.

The technical result when implementing the invention:

- reducing the consumption of titanium-containing dopant (K ₂ TiF ₆ , titanium sponge, briquettes of titanium sponge with flux) to obtain Al-Ti-B alloys;

- reduction of Al-Ti-B ligature consumption for modification due to reduction of intermetallic losses in refining plants;

- a possible change in the Al-Ti-B ligature supply scheme to the melt being modified: introduction of the ligature after metal refining plants;

- reduction in the number of defects due to the exclusion of large crystals of titanium aluminide in commercial products.

The technical result is achieved in that the Al-Ti-B alloy contains at least 90% by weight. particles of titanium diboride TiB ₂ and not more than 10% weight. particles of titanium aluminide Al ₃ Ti or aluminum boride AlB ₂ .

The technical nature of the proposed technical solution is as follows.

The claimed composition of the Al-Ti-B ligature is characterized by a maximum content of small crystals of titanium diboride and a minimum concentration of coarse crystals of titanium aluminide and aluminum boride (Fig. 2). The maximum (not less than 90%) content of finely dispersed crystals of titanium diboride and the minimum (not more than 10%) content of the claimed Al-Ti-B ligature composition of large crystals of titanium aluminide or aluminum boride increases the number of crystallization centers during metal modification and reduces the loss of large aluminide crystals titanium or aluminum boride.

The stated limits on the content in the proposed Al-Ti-B alloy ligature of titanium diboride, titanium aluminide or aluminum boride correspond to the weight ratio of titanium to boron in the ligature Ti: B = (1.918 ÷ 2.356): 1. For example: when the boron content in the ligature is 1% weight. the concentration of titanium in it will be from 1.918% by weight. up to 2,356% weight. None of the known Al-Ti-B master alloy compositions have such a ratio of titanium to boron.

It should be noted that in the Al-Ti-B ligature melt, if the solubility limit of titanium and boron in aluminum is exceeded, titanium diboride is primarily formed. This is confirmed by comparing the standard enthalpies of formation of intermetallic compounds: for TiB ₂ ΔH ₂₉₈ = -279.9 kJ / mol; for Al ₃ Ti, ΔH ₂₉₈ = -144 kJ / mol; for AlB ₂ ΔH ⁰ ₂₉₈ = -67 kJ / mol [3, 4]. If after the formation of titanium diboride, titanium remains in excess, titanium aluminide is synthesized in the melt, if there is an excess of boron, then aluminum boride is formed.

The stoichiometric composition of the Al-Ti-B ligature, in which only titanium diboride crystals are present (100% by weight of TiB ₂ ), corresponds to the weight ratio of titanium to boron in the Ti: B = 2.222: 1 ligature. When the content in the ligature 90% weight. titanium diboride and 10% weight. titanium aluminide, the weight ratio of titanium to boron in the ligature is 2.356: 1. When the content in the ligature is 90% by weight. titanium diboride and 10% weight. aluminum boride, the weight ratio of titanium to boron in the ligature is 1.918: 1.

The presence of limits on the content of intermetallic compounds is due to the fact that it is rather difficult to obtain an Al-Ti-B ligature in which only titanium diboride crystals are present (100% by weight. TiB ₂ ). In practice, as a rule, there is an overdose or insufficient amount of titanium or boron introduced into the ligature. Therefore, depending on which element (titanium or boron) is in excess, along with titanium diboride, either titanium aluminide (excess titanium) or aluminum boride (excess boron) is formed. The presence of limits on the content in the ligature of titanium diboride crystals (not less than 90%) and Al ₃ Ti or AlB ₂ crystals (not more than 10%) is associated with the technological features of the preparation of the ligature (temperature, duration, mixing ...), at which titanium and boron extraction from different alloying agents to the ligature may vary.

The declared limits on the content in the ligature is not less than 90% by weight. particles of titanium diboride TiB ₂ and not more than 10% weight. particles of titanium aluminide Al ₃ Ti or aluminum boride AlB ₂ - provide guaranteed production of Al-Ti-B alloys with a maximum concentration of titanium diboride using various types of alloying additives and various technological methods for producing ligatures.

The presence of Al-Ti-B in the ligature, along with crystals of titanium diboride, titanium aluminide or aluminum boride, is due to the conditions for the preparation of the ligature. In the case where the weight ratio of titanium to boron in the ligature is more than 2.222, there is an excess of titanium, therefore, along with TiB ₂ , Al ₃ Ti is present in the ligature. In the case where the weight ratio of titanium to boron in the ligature is less than 2.222, boron is abundant, therefore, along with TiB ₂ , AlB ₂ is present in the ligature.

Comparison of the proposed solution with the closest analogue shows the following. The proposed solution and the closest analogue are characterized by similar features, according to which both Al-Ti-B alloys contain intermetallic compounds based on aluminum, titanium and boron.

The difference of the proposed solution from the closest analogue is as follows. Table 2 shows the compositions of Al-Ti-B ligatures according to the closest analogue and according to the proposed technical solution. The claimed composition of the ligature contains from 90% by weight. up to 100% weight. particles of titanium diboride TiB ₂ , up to 10% weight. particles of titanium aluminide Al ₃ Ti or up to 10% weight. particles of aluminum boride AlB ₂ .

In the known compositions of the Al-Ti-B ligature, the average content of particles of titanium diboride TiB ₂ varies from 5.0% to 60.7% by weight, and the average concentration of particles of titanium aluminide Al ₃ Ti from 39.3% to 95.0% the weight.

In the proposed composition of the Al-Ti-B ligature, the average content of particles of titanium diboride TiB ₂ varies from 90% to 100% by weight, the average concentration of particles of titanium aluminide Al ₃ Ti - from 0% to 10% by weight, the average concentration of particles of aluminum boride AlB ₂ - from 0% to 10% weight.

The proposed technical solution is characterized by features similar to those of the closest analogue, and distinctive features, which allows us to conclude that it meets the patentability condition of "novelty."

A comparative analysis of the proposed technical solutions with known solutions in this technical field, carried out according to the search results in the patent and scientific literature, revealed the following:

The Orion Spetsplav company (188304, Leningrad Region, Gatchina, Solodukhina St., 2, E-mail: orion_gatchina@mail.ru [5]) produces various types of alloying additives, including Al-Ti-B ligature according to GOST 53777-2010 with a titanium content of 3.0% to 5.0% by weight. and boron from 0.2% to 1.0% by weight. The compositions of the produced Al-Ti-B alloys correspond to the compositions according to the closest analogue (table 2).

A known method of producing aluminum-titanium-boron alloys for the modification of aluminum alloys, comprising introducing into the aluminum melt a component forming a eutectic with it, subsequent loading of sponge titanium and potassium fluoroborate in a mixture with potassium chloride at a ratio of (4.3 ÷ 4.9: 1) ) by mass (Patent No. 1774964, С22С 1/02, 1/06, publ. 07.11.1992. [6]). In examples of the method, the preparation of Al-Ti-B alloys with a titanium content of 3.8 ÷ 4.7% and boron of 0.6 ÷ 0.7% is described.

A known method of preparing the aluminum-titanium-boron alloys (Patent No. 2215810, C22C, publ. 10.11.2003. [7]), comprising melting aluminum, portioned introduction of a mixture of titanium with a boron-containing component into the aluminum melt, mixing the melt and pouring it, characterized in that preliminarily titanium in the form of a titanium sponge is crushed to a size of 10-15 mm, mixed with a boron-containing component in the form of potassium tetrafluoroborate, the mixture is placed in a metal container and heated to a temperature of 515-530 ° C, then compacted with pressure until the liquid phase disappears and After removal of pressure the resulting mixture was taken out of the container. In the examples explaining the technical essence of the invention, the composition of the obtained ligatures is represented by titanium (4.5 ÷ 5.2%) and boron (1.06 ÷ 1.20%). With an average titanium content of 4.85% and boron 1.13%, the concentration of intermetallic compounds in the ligature will be: TiB ₂ = 3.64%; Al ₃ Ti = 6.29% or in terms of 100% of the total content of intermetallic compounds: 36.7% TiB ₂ and 63.3% Al ₃ Ti.

The analysis carried out by the authors showed that at the time of filing the application for the invention, technical solutions were not identified that are characterized by a combination of known and unknown features similar to the proposed solution, which indicates the compliance of the proposed technical solution with the condition of patentability of the invention “inventive step”.

Compliance with the patentability condition “industrial applicability” is proved by experimental data obtained during laboratory research and testing.

Example

In a resistance furnace, 5 kg of aluminum of grade A8 is melted, the melt is heated to 800 ± 5 ° C and, after removing the slag from the metal surface, 650 g of potassium tetrafluoroborate KBF _{4 of} grade ChDA are introduced into the melt level in several stages using a titanium bell. The melt is maintained with periodic stirring for 30 minutes, after which slag is removed from the metal surface. The resulting aluminum-boron ligature is thoroughly mixed before casting, a sample is taken for analysis for boron content and poured into steel molds. The weight of the obtained Al-B ligature is 4890 g. According to the analysis of three samples, the boron content in the Al-B ligature was 0.92 ± 0.04%. Extraction of boron in the ligature - 80.6%.

In a resistance furnace, 1 kg of the obtained Al-B alloy is melted in four crucibles. The molten ligature is heated to 900 ± 10 ° C and the calculated amount of titanium sponge grade ТГ-100 GOST 17746-79, pre-impregnated with carnallite melt KCl⋅MgCl _{2, is} loaded into each crucible. Impregnation of a titanium sponge with carnallite flux ensures spontaneous immersion of the sponge on the bottom of the crucible and its rapid dissolution in Al-B ligature with minimal losses. The alloys are maintained at 900 ± 20 ° C with periodic stirring for 30 minutes, the slag is removed from the metal surface and poured into massive iron molds. The result is 4 ligatures Al-Ti-B. The first three ligatures No. 1–3 correspond to the claimed composition, the fourth composition of the ligature is with a known ratio of titanium to boron equal to ~ 5: 1.

The initial data and the results of the experiments are shown in tables 3, 4.

The Al-Ti-B alloys obtained in experiments Nos. 1-4 are used to modify A7 grade aluminum. To do this, 5 kg of aluminum are successively melted in four crucibles and the metal temperature is adjusted to 720 ± 5 ° C. After removing slag from the surface of the aluminum melt, 8 grams of Al-Ti-B alloys obtained in experiments Nos. 1-4 are introduced into each of the four crucibles. The melt in each crucible is thoroughly mixed for 5 minutes, after which it is poured into a cast-iron cylindrical mold with a diameter of 80 mm through a funnel. A foam ceramic filter with a porosity of 40 ppi (pore size 1250-1500 μm) is installed in a funnel, simulating aluminum filtration in an industrial environment. The conditions for the modification, casting and crystallization of aluminum are the same in all four experiments.

Three transverse templates are cut from each of the obtained modified aluminum ingots: 1st — 50 mm from the top of the ingot, 2nd — 50 mm from the bottom of the ingot, and 3rd — in the middle of the ingot. The surface of the templates is treated on a grinding wheel and etched in a solution of caustic soda NaOH until a granular macrostructure of aluminum.

The macrostructure of the samples was studied using a scanner and a stereoscopic microscope Stemi 2000-C, Carl Zeiss. Grain size was determined by linear analysis (secant method).

The mechanical characteristics of aluminum samples were determined by the results of static tensile tests of cylindrical samples (Type 3) with a diameter of the working part of 5 mm and a length of the working part of 25 mm in accordance with GOST 1497-84 “Metals. Tensile test methods. "

The averaged results of experiments on grinding the macrostructure of technical aluminum and the physicomechanical characteristics of the samples are presented in table 5.

Using the proposed technical solution reduces the consumption of a titanium-containing alloying additive (in this example, a titanium sponge, and in the general case of any titanium-containing raw material: K ₂ TiF ₆ , briquettes of a titanium sponge with flux ...) to obtain an Al-Ti-B alloy without reducing the modifying ability of the ligature and physico-mechanical characteristics of the modified aluminum.

Information

1. GOST 53777-2010. Ligatures are aluminum. Technical conditions M., Standartinform. 2012.

2. Engineering company SAS. Products E-mail: info@sasua.com.ua; http://sasua.com.ua.

3. Napalkov V.I., Bondarev B.I., Tararyshkin V.I., Chukhrov M.V. Ligatures for the production of aluminum and magnesium alloys. // M .: Metallurgy. - 1983 .-- 160 s.

4. Thermal constants of substances. / Ed. V.P. Glushko et al. M .: ed. VINITI AN USSR Issue. 7, part 1, 2.

5. The company "Orion Spetsplav", 188304, Leningrad region, Gatchina, st. Solodukhina, house 2. E-mail: orion_gatchina@mail.ru.

6. Patent No. 1774964, C22C 1/02, 1/06, publ. 11/07/1992.

7. Patent No. 2138572, C22C, publ. 09/27/1999.

Claims (1)

An aluminum-titanium-boron master alloy for modifying aluminum and its alloys containing intermetallic compounds, characterized in that it contains at least 90 wt.% Particles of titanium diboride and not more than 10 wt.% Particles of titanium aluminide or aluminum boride, wherein the ratio of titanium to boron in the ligature is (1,918-2,356): 1.

Images