RU2486269C2 - Method for ladle modification of aluminium alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes supply of a molten metal from a mixer into a crystalliser via a casting box, comprising at least one source of ultrasound and a casting chute, besides, after filling of the casting box with the melt, a source or sources of ultrasound are lowered into the melt so that the depth of the melt underneath under the source of ultrasound submerged into the melt makes ≤ λ/20, where λ - wave length at the frequency of the ultrasound source, and a modifying bar is introduced into the melt under the source of ultrasound, and the bar comprises transition metals or their compounds.

EFFECT: grinding of grain, which results in increased manufacturability of bars, mechanical properties of deformed semi-finished products and more efficient use of a modifying bar.

3 cl, 2 ex, 3 tbl, 2 dwg

Description

The present invention relates to the field of metallurgy of light alloys and can be used to produce ingots and castings from aluminum alloys for the manufacture of nuclear, aerospace and automotive products. The use of this invention relates to the technology of after-furnace modification.

A known method of producing ingots of aluminum alloys, selected as an analogue, including the introduction into the melt of modifying rods in the arrival box. (Bondarev B.I., Napalkov V.I., Tararyshkin V.I. Modification of aluminum wrought alloys. - M .; Metallurgy, 1979, p. 224).

The disadvantage of this method is the presence in the structure of the bar of a large number of agglomerates of intermetallic compounds that are poorly soluble in the melt stream and subsequently deposited on refining devices, which leads to a significant decrease in the efficiency of modification.

There is also known a method that can be considered as a prototype, the production of ingots from aluminum alloys, including cavitation treatment of liquid metal directly in the mold or in front of it. (Eskin G.I. Ultrasonic processing of molten aluminum. - M .; Metallurgy, 1988, p. 232).

The disadvantage of this method is that technologically the method does not allow the implementation of multi-crystalline casting, because requires an increase in the number of ultrasound sources for cavitation treatment of each ingot.

The technical result of the proposed method is grinding grain up to non-dendritic, which leads to an increase in the manufacturability of ingots, an increase in the mechanical properties of deformed semi-finished products and a more efficient use of a modifying bar.

The proposed method for out-of-furnace modification of aluminum alloys involves the supply of molten metal through a casting trough from a mixer into the mold through a casting box containing an ultrasound source. After filling the box with the melt, the ultrasound source is lowered into the melt so that the melt depth in the box under the ultrasound source immersed in the melt is ≤ λ / 20, where λ is the wavelength at the frequency of the ultrasound source. Then, a modifying rod containing transition metals (PM) or their compounds is introduced into the melt under the ultrasound source.

To increase the efficiency of out-of-furnace modification of the melt, as well as to enable multi-crystallization casting in the chute, one or more ultrasound sources can be installed after the casting box.

For more efficient dissolution of the modifying rod, at least two ultrasound sources are placed in the casting box, tilted towards each other, and the modifying rod is introduced into the epicenter formed in the cavitation region.

The proposed method for producing ingots from aluminum alloys differs from the prototype in that due to cavitation treatment, when a modifying rod is introduced into the melt in front of the melt refining and filtering devices, agglomerates of active inoculators located in the structure of the rod are intensively destroyed. Such complex melt processing allows increasing the number of crystallization nuclei and increasing the efficiency of modification. An increase in the modification efficiency leads to a substantial refinement of the grain structure of the ingots, up to the formation of an extremely finely ground non-dendritic structure.

Thus, with the same amount of the modifying rod introduced into the melt, to a much greater extent than in the case of the analogue, the technological plasticity of ingots and the level of mechanical properties of deformable semi-finished products from aluminum alloys increase.

Example No. 1. Casting with a vertically mounted source (or sources) of ultrasound in a casting box.

When casting aluminum alloys (Fig. 1), the molten metal after the mixer (1) enters the casting box with the source (or sources) of ultrasound installed in it (2). After filling the box with the melt, the ultrasound source (s) is lowered into the melt and at the melt depth ≤ λ / 20 (≤ 17 mm), where λ is the ultrasound wavelength at the frequency of the ultrasound source (18 ÷ 22 · 10 ³ Hz), a ligature is introduced under the emitter bar.

λ = c / f,

where c is the speed of sound of 6000 m / s for aluminum;

f is the frequency, Hz.

The bar is fed at a given speed, determined from the calculation of introducing the required number of active PM inoculators or their compounds. Further, the melt, passing before this through the degassing and filtering devices of the melt (3), enters the mold (4).

Comparative results of changes in the grain structure depending on the concentration of the transition metal introduced into the aluminum alloy of the 1960 type, which does not contain PM in the charge composition, and the number of ultrasound sources are presented in Table 1.

The effect of complex processing of the melt flow on the grain size and structure type of the ingot of the 1960 alloy containing PM in the charge composition are presented in Table 2.

Along with this, we note that the proposed scheme of complex out-of-furnace modification (Fig. 1) also allows casting aluminum alloys (Fig. 2) to the crystallizer block (5) (multicrystallization casting) to carry out effective modification by introducing a ligature rod in front of the degassing and filtering device melt (3) into the casting box (2) with the ultrasound source (or sources) installed in it.

Example No. 2. Casting with two sources of ultrasound tilted to each other in a casting box of alloys.

When casting aluminum alloys according to the proposed scheme (Fig. 1) with out-of-furnace modification of the melt flow, two sources of ultrasound tilted towards each other were used in the casting box to increase the efficiency of the modification, and the modifying rod was introduced into the epicenter formed in the cavitation region.

The effect of complex processing of the melt flow on grinding grain size of a 1960 type alloy containing PM in the charge composition, with one ultrasound source mounted vertically and two tilted, is presented in Table 3. The modification efficiency was increased by a factor of ~ 2.

Thus, the proposed method for out-of-furnace modification of aluminum alloys allows to obtain a greater effect of structural modification in comparison with previously known, as well as at a more economical consumption of ligature rods. For example, for alloys of the Al-Mg-Sc-Zr system, as a rule, to obtain ingots of a non-dendritic structure, an increased content of PM, such as scandium (≈0.3 wt%), is required. The proposed method of out-of-furnace modification of aluminum alloys allows to obtain a non-dendritic structure at reduced scandium content by increasing the efficiency of using scandium ligature. In this case, maximum grinding of the grain structure of the ingots is achieved, up to the formation of an extremely finely ground non-dendritic structure with the economical use of expensive scandium.

Table 1. Comparative results of the change in the grain structure depending on the concentration of the transition metal introduced by the ligature bar into an aluminum alloy of type 1960 that does not contain PM in the charge composition, and on the number of ultrasound sources The concentration of PM introduced by the bar,% Grain size, microns Without RCD 1 source of RCD 2 sources of RCD - ≥ 800 ** 420 ** 360 ** 0.013 - - 110 ** 0,03 - one hundred** - 0.08 - 60 ** 42 * 0.09 120 ** fifty* 40 * 0.11 115 ** 45 * - 0.12 122 ** 40 * - 0.19 one hundred** - - * - non-dendritic structure; ** - dendritic structure Table 2. The effect of complex processing of the melt flow on the grain size and structure type of an ingot of an 1960 alloy containing PM in the charge composition. The concentration of PM in the base alloy,% RCD melt flow Additional introduction of PM,% Grain size, microns Zr Ti 0.15 0.03 - - 500 ** 0.15 0.03 + 0.01 35-40 * * - non-dendritic structure; ** - dendritic structure

Table 3. The effect of complex processing of the melt flow depending on the location of ultrasound sources on the efficiency of grinding the structure of an alloy of type 1960 (an additional 0.03% PM). Number of cavitation sources The concentration of PM in the base alloy,% Position of sources Grain size, microns Modification Efficiency Zr Ti one 0.05 0.01 vertical 80-100 ** - 2 0.05 0.01 tilted 40-45 * ~ 2 times * - non-dendritic structure; ** - dendritic structure

Claims (3)

1. A method for out-of-furnace modification of aluminum alloys, comprising supplying molten metal from a mixer to a crystallizer through a casting box containing at least one ultrasound source, and a casting chute, and after filling the casting box with the melt, the ultrasound source or sources are lowered in this way, so that the depth of the melt in it under the source of ultrasound immersed in the melt is ≤λ / 20, where λ is the wavelength at the frequency of the source of ultrasound, and m is introduced into the melt under the source of ultrasound difitsiruyuschy rod containing transition metals or compounds thereof. 2. The method according to claim 1, characterized in that the casting box contains at least two sources of ultrasound, tilted towards each other, and the modifying rod is introduced into the epicenter of the resulting cavitation region. 3. The method according to claim 1, characterized in that in order to increase the efficiency of out-of-furnace modification of the melt after the casting box, one or more ultrasound sources are additionally installed in the trough.

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