RU2725498C1 - Sintered ligature from powder materials for alloying aluminum alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy of metals and alloys, namely, to production of aluminum alloys for alloying aluminum-based alloys containing refractory metals. Sintered ligature of powder materials for alloying aluminum alloys contains, wt%: molybdenum 40–50; copper 4.0–4.5; aluminum – balance.

EFFECT: invention is aimed at expansion of operational capabilities of ligature for melting of aluminum alloys due to improved distribution and increase rate of dissolution of alloying components in melt, improving stability of compositions of melted alloys with obtaining more accurate and homogeneous content thereof in the entire volume of the melt and the finished ingot.

1 cl, 4 tbl, 3 ex

Description

The invention relates to the field of powder metallurgy of metals and alloys, and in particular to the production of aluminum-based alloys for alloying aluminum-based alloys containing refractory metals, as well as to obtain the exact content of components in castings.

One of the effective directions of creating antifriction aluminum cast alloys for monometallic plain bearings is their alloying with refractory metals (elements of transition groups: molybdenum, tungsten, scandium, titanium, copper, zirconium, etc.) (N.A. Belov, E.I. Gershman , I.S. Gershman, I.T. Goryacheva, D.L. Zagorsky, E.G. Kotova, Yu.Yu. Makhovskaya, AM Mezrin, A.E. Mironov, T.I. Muravyova, B.Ya. Sachek, OO Stolyarova, EV Torskaya "Aluminum alloys of antifriction purpose" Monograph. Edited by AE Mironov, NA Belova, OO Stolyarova. Publishing House MISiS, 2016. - 223 from.).

The alloying process is designed to facilitate the introduction of various components into the melt and provide the necessary chemical composition of the alloy. But alloying aluminum with refractory metals is complicated by the low solubility of alloying elements, their high melting points and relatively low boiling point of aluminum. For this reason, alloying aluminum with more refractory metals, such as molybdenum, tungsten and chromium, seems to be problematic, and cast ligatures with the inclusion of chemical compounds of refractory metals are usually used for its implementation. Ligature is an auxiliary alloy of two or more components, designed to introduce refractory elements into the molten metals and alloys. The use of ligatures is due to the fact that the process of assimilation of an alloying element from a ligature is more reliable and efficient than when it is introduced in its pure form. In addition, the use of ligatures provides a more uniform distribution of the alloying element in the volume of the melt. However, the preparation of cast aluminum-refractory alloy ligatures is characterized by a high superheat temperature and volatility, low solubility and uneven distribution of alloying elements, which has a significant negative effect on the structure and properties of ingots and products obtained from them.

Known cast aluminum alloy Al-2% Mo for the smelting of cast aluminum alloys alloyed with molybdenum, and to obtain precision castings from them (patent RU 2232827, publ. 20.07. 2004).

The disadvantage of this ligature is the low content of molybdenum, which leads to its high consumption to achieve the required content of the alloying element in the melt. In turn, this leads to a long alloy smelting process and high energy costs.

The closest in technical essence to the invention is the Al-ETM-LTM-TE ligature selected as a prototype for producing amorphous aluminum alloys containing the following components with an atomic percentage: 85-94% Al, 0-8% ETM, 0-8% LTM and 0-1% TE, where the ETM is Ti, V, Cr, Zr, Nb, Mo, Hf, Ta or W; LTM is Mn, Fe, Co, Ni, Cu or Zn; TE refers to trace elements, such as B, Si, Ga, Ge, As, Se, Sb, Te or the like (patent CN 104532072, publ. 04/22/2015).

The disadvantages of the known solutions, including technical problems, are the limited content of molybdenum to about 22 wt. % in the ligature, the difficulty in its production, as well as the limitation of its use in aluminum antifriction alloys due to the presence of iron, the level of which cannot be reduced to zero, since its introduction occurs involuntarily in the manufacture of the melt. In addition, the use of this cast ligature does not guarantee the uniform distribution of alloying components in the finished ingot and the stability of the compositions of melted alloys in different melts, which creates certain technical problems when alloying aluminum alloys.

The proposed technical solution aims at eliminating the specified technical problems and allows to obtain a technical result - the technical expansion of the operational capabilities of the ligature for use in aluminum alloys, including antifriction aluminum alloys by improving the distribution and increasing the dissolution rate of alloying components in the melt, increasing stability compositions of smelted alloys in different melts in order to obtain a more accurate and homogeneous content in the entire volume of the melt and the finished ingot by increasing the molybdenum content in the ligature, completely eliminating or significantly reducing the amount of iron in the ligature, and using spark plasma sintering technology to consolidate the ligature component powders with the addition of copper.

The technical result is achieved by a sintered alloy of powder materials for alloying aluminum alloys, including molybdenum, copper and aluminum in the following ratio, wt. %: molybdenum 40-50; copper 4.0-4.5; aluminum - the rest.

The invention is characterized as follows.

Sintered alloy of powder materials for alloying aluminum alloys includes, by weight. %:

molybdenum 40-50;

copper 4.0-4.5;

aluminum - the rest.

The use of molybdenum, copper and aluminum powders as starting materials makes it possible to produce sintered ligature with the exact content of components, as well as to eliminate or reduce the presence of a significant amount of iron in it. Since iron is a harmful impurity for aluminum antifriction alloys, its elimination from the ligature allows us to expand its operational capabilities for use in antifriction alloys.

The consolidation of the powdered components of the ligature is carried out using spark plasma sintering technology (Spark Plasma Sintering). This technology allows you to control the grain size during sintering, to preserve the structure of the initial powders, to obtain uniform microstructures in the ligature, to apply low values of pressure during sintering in comparison with other similar methods, which significantly increases the porosity and surface area of the ligature. Thus, the use of this sintering technology to consolidate the initial powders makes it possible to obtain a sintered ligature with a homogeneous distribution of components in its entire volume and with a large contact surface with the melt, accelerating the dissolution of the ligature in the melt, which, in turn, reduces the alloy smelting process , increasing the stability of the chemical compositions of the alloy in different melts and reducing energy costs.

The addition to the main components (molybdenum and aluminum) of copper powder in an amount of 4.0-4.5 wt. % increases the mechanical strength of sintered ligatures due to improved adhesion between particles of copper, aluminum and molybdenum while maintaining increased porosity. In addition, the indicated mass of copper will complement the required amount of this element, which is present in most anti-friction aluminum alloys.

The combined use of the powder components of the ligature and the technology of spark plasma sintering makes it possible to produce sintered ligature that does not have a restriction on the content of molybdenum in aluminum, as is the case with cast ligatures. Due to this, it is possible to produce a ligature sintered from powder materials containing a large amount of molybdenum (40-50 wt.%) In an aluminum matrix, which increases the efficiency of using the ligature by reducing its consumption to achieve the required molybdenum content in the melt. In addition, the use of one Al-Mo-Cu ligature allows replacing the use of two double cast Al-Cu and Al-Mo ligatures.

The industrial applicability of the invention is confirmed by the following examples of specific performance.

As an example, we consider the manufacture of two sintered powder ligatures and the use of cast ligatures made according to the description of the prototype for casting cylindrical ingots with a diameter of 100 mm and a height of 500 mm from Al-1Mo alloy. To obtain these ingots, it is required to melt 12 kg of the alloy containing 120 g of Mo in an open high-frequency induction furnace.

The following alloys were used: 1 - sintered AlMo40Cu4 ligature; 2 - sintered AlMo50Cu4.5 ligature; 3 - cast ligature (prototype) AlMo23Cu2.

In order to determine the stability of alloying for each example, three ingots were cast, differing in the melt holding time after dissolution of the ligature: two of them were aged for 10 minutes, and the third - 22 minutes.

Example 1

To prepare the sintered AlMo40Cu4 alloy, the following powder materials were used in the following ratio of components, wt. %: molybdenum 40, copper 4.0 and aluminum - the rest.

The powders of the components are mixed in a ball mill in isopropyl alcohol together with hard alloy balls until they are completely mechanically activated, followed by drying in a vacuum oven at a temperature of 90 ° C to obtain a powder mass - a mixture. Next, the resulting mixture is sieved through a 100 μm sieve, then 20 g of the resulting mass are loaded into a graphite matrix for spark plasma sintering in order to obtain a disk with a diameter of 40 mm and a height of ~ 4 mm. The sintering process is carried out at a temperature of 400 ° C without exposure and a pressure of 48 MPa.

The results of determining the chemical composition of the obtained sintered alloys are shown in table 1, and the porosity and tensile strength of the sintered discs are given in table 2.

Then, the obtained disks from sintered alloys were used in casting cylindrical ingots from Al-1Mo alloy. For casting one ingot, 300 grams of sintered AlMo40Cu4 ligature per 11.7 kg of molten aluminum will be required.

Tests have shown that the dissolution of the required mass of A1Mo40Ci4 ligature occurs 8 minutes after it is introduced into the melt, table 3. After that, the melt was poured into the mold.

After hardening, a chemical analysis was carried out in three places of the ingot at a distance of 50, 250 and 450 mm from its bottom. The results on the distribution of molybdenum in cross sections of the ingot are given in table 4. The distribution of iron over the ingot was relatively uniform and is in the range of 0.07-0.1 wt. %

Example 2

By analogy with example 1, a mixture was prepared for the preparation of sintered AlMo50Cu4.5 ligature. For this, the following powder materials were used in the following ratio of components, wt. %: molybdenum 50, copper 4.5 and aluminum - the rest.

Next, the resulting mixture is sieved through a 100 μm sieve, then 23 g of the resulting mass is loaded into a graphite matrix for spark plasma sintering to obtain a disk with a diameter of 40 mm and a height of ~ 4 mm. The sintering process is carried out at a temperature of 400 ° C without exposure and a pressure of 48 MPa.

The results of determining the chemical composition of the obtained sintered alloys are shown in table 1, and the porosity and tensile strength of the sintered discs are given in table 2.

Then, the obtained disks from sintered alloys were used in casting cylindrical ingots from Al-1Mo alloy. For casting one ingot, 240 grams of sintered AlMo50Cu4.5 ligature per 11.76 kg of molten aluminum will be required. Tests have shown that the dissolution of the required mass of AlMo50Cu4.5 ligature occurs 11 minutes after it is introduced into the melt, table 3. After that, the melt was poured into the mold.

After hardening, a chemical analysis was carried out in three places of the ingot at a distance of 50, 250 and 450 mm from its bottom. The results on the distribution of molybdenum in cross sections of the ingot are given in table 4. The distribution of iron over the ingot was relatively uniform and is in the range of 0.07-0.1 wt. %

Example 3

To compare the obtained sintered ligatures, it was necessary to produce castings of cylindrical ingots from Al-1Mo alloy using cast ligatures. To implement this example, a cast alloy AlMo23Cu2 was used, made according to the description of the prototype. For its manufacture, powder materials were used in the following ratio of components, wt. %: molybdenum 23, copper 2 and aluminum - the rest, which corresponds to the following atomic percentages: 7.86% molybdenum, 1.03% copper and 91.11% aluminum. The results of determining the chemical composition of this ligature are shown in table 1.

For casting one ingot, 522 grams of AlMo23Cu2 ligature per 11.35 kg of molten aluminum will be required. Tests have shown that the dissolution of the required mass of AlMo23Cu2 ligature occurs 36 minutes after it is introduced into the melt, table 3. After that, the melt was poured into the mold.

After hardening, a chemical analysis was carried out in three places of the ingot at a distance of 50, 250 and 450 mm from its bottom. The results on the distribution of molybdenum in cross sections of the ingot are given in table 4. The distribution of iron over the ingot was relatively uniform, and is in the range of 0.14-0.17 wt. %

The results of the study of ligatures and ingots showed that the use of the invention allows to increase the molybdenum content in the ligature to 40-50 wt. %, increase the dissolution rate and improve the distribution of alloying components in the melt, increase the stability of the compositions of the alloyed alloys in different melts, obtain a more accurate and homogeneous content of the alloying component in the entire volume of the finished ingot, completely eliminate the amount of iron in the ligature and, thereby, significantly reduce the amount iron ingots up to 0.07-0.1 wt. %

Thus, the claimed combination of essential features, reflected in the independent claim, ensures the achievement of the claimed technical result - technical expansion of the operational capabilities of the ligature for use in aluminum alloys, including for antifriction aluminum alloys due to improved distribution and increased dissolution rate of alloying components in the melt, to increase the stability of the compositions of melted alloys in different melts in order to obtain a more accurate and homogeneous content in the entire volume of the melt and the finished ingot by increasing the molybdenum content in the ligature, completely eliminating or significantly reducing the amount of iron in the ligature, and using spark plasma sintering technology for the consolidation of powders of ligature components with the addition of copper.

The analysis of the claimed technical solution for compliance with the conditions of patentability showed that the characteristics indicated in the formula are essential and interconnected with the formation of a stable set of necessary characteristics, unknown at the priority date from the prior art and sufficient to obtain the required synergistic (super-total) technical result.

Thus, the above information indicates the fulfillment of the following set of conditions when using the claimed technical solution:

- the object embodying the claimed technical solution in its implementation is intended for the production of aluminum-based alloys for alloying aluminum-based alloys containing refractory metals, as well as to obtain the exact content of components in castings;

- for the claimed object in the form described in the formula, the possibility of its implementation using the methods and methods described above or known from the prior art on the priority date is confirmed;

- the object embodying the claimed technical solution, when implemented, is able to ensure the achievement of the technical result perceived by the applicant.

Therefore, the claimed subject matter meets the patentability criteria of “novelty”, “inventive step” and “industrial applicability” under applicable law.

Claims (1)

Sintered alloy of powder materials for alloying aluminum alloys, including molybdenum, copper and aluminum, characterized in that it contains components in the following ratio, wt. %: molybdenum 40-50; copper 4.0-4.5; aluminum - the rest.