RU2622199C1 - Method for production of bars of high-strength aluminium alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method for production of bars made of aluminium alloys from aluminium-zinc-magnesium-nickel-iron-zirconium system includes preparation of an aluminium-based melt obtained by electrolysis with an inert anode and containing iron, adding zinc, magnesium, nickel, copper and zirconium into it, production of a cylindrical ingot, its heat treatment and deformation processing by radial displacement rolling at a temperature of 270 to 300°C with a total reduction of 65 to 85% and a roll speed of 40 to 60 rpm and hardening heat treatment of the resulting rod, including quenching and artificial aging.

EFFECT: production of high-strength calibrated bars with the following mechanical properties: a temporary resistance of at least 600 MPa, a yield strength of at least 550 MPa, an elongation of at least 5 percent.

2 cl, 1 ex, 2 tbl, 3 dwg

Description

Technical field

The present invention relates to the field of metallurgy of light alloys, in particular aluminum-based alloys, intended for the manufacture of products operating under high loads: parts of aircraft (aircraft, helicopters, rockets), automobiles and other vehicles (including: bicycles, scooters, trolleys), parts of sports equipment, etc.

State of the art

The most durable deformable aluminum alloys belong to the Al-Zn-Mg-Cu system (Belov N.A. Phase composition of industrial and promising aluminum alloys - M .: Publishing House MISiS, 2010, 511 pp.). The maximum level of strength properties of the alloys of this group is achieved in the bars obtained by pressing (Shcherba VN. Pressing of aluminum alloys (technology and equipment). M., Intermet Engineering, 2001, 868 pp.). In particular, B95 alloy (GOST 4784-97) in the form of extruded rod has the following tensile properties: σ _in = 530 MPa, σ _0,2 = 420 MPa, (GOST 21488-97). However, to obtain the highest quality pressed semi-finished products from alloys of type B95, it is necessary to strictly control the content of iron impurity, which usually does not exceed 0.1%. In this case, pressing is carried out at elevated temperatures (over 400 ° C) and in a narrow temperature range, in several stages and at low flow rates. All this leads to a complication of the process and the cost of the finished semi-finished product.

A known method for the production of calibrated rods from alloys of the Al-Mg-Si system, which is disclosed in the patent of the Russian Federation 2241781 (publ. 10.12.2004). The proposed method includes the production of ingots containing transition metals, deformation, hardening, drawing and aging, while before deformation, the ingots are homogenized, subsequent deformation is carried out first by warm pressing at 200-300 ° C, then drawing in two stages: the first drawing step is carried out after pressing, and the second after hardening, while drawing after pressing is carried out with a degree of deformation of 30-40%, and after hardening with a degree of deformation of 12-15%. The technical result of the invention is to obtain calibrated rods with a recrystallized structure and a regulated grain size of 25-60 microns with values of tensile strength, yield strength and elongation: 350 MPa, 300 MPa and 14.2%, respectively. One of the disadvantages of this method is that the alloying system of an aluminum alloy (type AD31, GOST 4784-97) does not allow to obtain a strength above 350 MPa in deformed semi-finished products. Another disadvantage lies in the complexity of the proposed multi-stage process of heat and deformation processing to obtain bars.

Closest to the claimed invention is a method for hot pressing of bars of high strength aluminum alloy, which is disclosed in the patent of the Russian Federation 2419663 (publ. May 27, 2011, Bull. No. 15). The method includes preparing a melt, introducing zinc, magnesium, nickel, copper, zirconium and iron into it, producing a cylindrical ingot, homogenizing annealing, hot pressing with a degree of reduction of about 90%, quenching heating, quenching in cold water and aging. This method can ensure the production of deformed semi-finished products with the following tensile properties: tensile strength σ _in - at least 640 MPa, yield strength σ _0.2 - at least 550 MPa, elongation δ - at least 5%.

High mechanical properties of the alloy are achieved due to the implementation of the structure, which is a deformed matrix formed by a solid solution of aluminum with uniformly distributed dispersed particles of secondary precipitates and relatively globular particles of the Al ₉ FeNi phase of eutectic origin uniformly distributed in the matrix.

A disadvantage of the known invention is the need for the introduction of iron from the Al-Fe ligature. In this case, the melt is prepared on the basis of vintage primary aluminum (in particular, the A5E brand), which leads to a relatively high cost of the alloy. Another disadvantage is the deformation processing method used - hot pressing. This method, as noted above, imposes serious restrictions on the processing of high-strength aluminum alloys.

Disclosure of invention

The technical result achieved in the invention is to obtain high-strength calibrated rods from an aluminum-based alloy, using a more productive and economical technology of deformation processing of high-strength aluminum alloys - radial shear rolling (CSP). The following mechanical tensile properties are justified: temporary resistance (σ _in ) - not less than 600 MPa, yield strength (σ _0.2 ) - not less than 550 MPa, elongation (δ) - not less than 5%.

The technical result is achieved in that iron from aluminum produced by an inert anode electrolysis technology is introduced into an aluminum-based melt containing zinc, magnesium, nickel, copper and zirconium. Next, the cylindrical ingot obtained by melting and casting the alloy is subjected to deformation processing by the radial-shear rolling method at a temperature of from 270 to 300 ° C with a total reduction of 65 to 85% and a roll rotation speed of 40 to 60 rpm.

In a private embodiment of the claimed method, the aging of the obtained rods is carried out at a temperature of from 140 to 160 ° C for a time of 3 to 8 hours, providing the following level of properties: temporary resistance (σ _in ) - not less than 600 MPa, yield strength (σ _0.2 ) - not less than 550 MPa, elongation (δ) - not less than 5%.

The invention is illustrated by drawings, where in FIG. 1 shows a diagram of the CPD for determining rational deformation conditions (β ₀ is the angle of elevation of the helical path in the deformation zone; β ₁ is the angle of elevation of the helical path at the exit of the rolls, 1 is the roll, 2 is the workpiece, 3 is the path), FIG. 2 - obtained cylindrical ingots for CPN and in FIG. 3 - the appearance of the rods obtained by the developed method.

The invention consists in the following.

The preparation of a melt based on aluminum, produced by inert anode electrolysis (EIA) technology, eliminates the operation of introducing Al-Fe alloys into the melt, since the required amount of iron is already contained in EIA aluminum. In addition, the use of EIA aluminum instead of branded primary aluminum reduces the cost of castings. The introduction of the optimal amount of zinc and magnesium ensures the achievement of the required level of strength properties of the alloy after hardening heat treatment. The introduction of nickel leads to the formation of compact particles in the alloy structure (either immediately after crystallization of the alloy or after high-temperature annealing) of the Al ₉ FeNi phase of eutectic origin, the crystallization of which prevents the formation of coarse glandular phases that reduce the workability of the alloy pressure. Radial-shear rolling provides deformed semi-finished products of circular cross section with a high level of service properties. In this case, the deformation temperature does not exceed 300 ° C. A schematic diagram of the stress-strain state of a metal during radial shear rolling is shown in FIG. 1. RSP is a method of powerful plastic deformation for deep structuring of metal in long products such as rods and pipes. The trajectory-speed conditions for the deformation of the CSP provide a deep study of the metal structure at all levels of the metal-physical structure, including the nanoscale. The helicoidal outflow of metal along predetermined paths with a slowdown of the outer layers of the workpiece and acceleration of the inner (see Fig. 1) creates intense macro-shear movements in the deformation zone. The decrease in the particle velocity of the outer layer is due to the formation of expanding current tubes (diffusers). The advantages of this method are due to the presence of this particular zone, which is absent in other stationary processes for producing long rods, such as longitudinal rolling or pressing. There is no such metal flow pattern in methods for testing metals for mechanical properties. There is a deep compaction and study of metal at all levels of the metal-physical structure. Elements of the alloy structure take the form of isotropic isolated particles of high dispersion. In its morphological structure, metal after CPD becomes a material of new quality. A comprehensive increase and stabilization of the physicomechanical and service properties of the alloy occurs. The greatest increase is achieved in plastic and viscous, as well as in the correlation-related operational properties. The development of initial surface defects is reduced. The maximum deviation in diameter is not more than ± 0.5% of the nominal value. The curvature of the rods does not exceed 0.75 mm per linear meter. The influence of the negative features of the structural structure of continuously cast metal on the quality of the final product and the technological costs of production is almost completely eliminated.

EXAMPLE

Were obtained cylindrical ingots of high strength aluminum alloy with the following chemical composition, mass. %: 7.0% Zn; 2.8% Mg, 0.6% Ni, 0.5% Fe, 0.15% Cu, 0.15% Zr, Al base.

The alloy (in the amount of 2 kg per ingot with a diameter of 60 mm and a length of 210 mm) was prepared from aluminum grade A85 (GOST 11069-2001) and aluminum produced by the electrolysis technology with an inert anode in an induction furnace in graphite chamotte crucibles. Alloying elements were introduced in pure form (zinc, magnesium, copper) and in the form of ligatures (Al-Ni).

Casting ingots (Fig. 2) was made in a metal mold. To obtain a deformed semi-finished product (Fig. 3), the following sequence of technological operations was used:

1 - Two-stage homstenic annealing of the ingot;

2 - Deformation processing by radial shear rolling;

3 - Hardening heat treatment of the obtained rod (hardening and artificial aging).

Table 1 shows five modes of deformation processing, differing in temperature, total compression and speed of rolls rotation, according to which deformed semi-finished products in the form of rods were obtained, and their mechanical properties after artificial aging at a temperature of 150 ° C and a holding time of 5 h. The first mode, characterized by the lowest temperature of deformation processing, but low total compression and low speed of rotation of the rolls, does not provide the required level of mechanical properties. The second mode is also characterized by a relatively low temperature, but a large total reduction at a higher speed of rotation of the rolls ensures the achievement of the required level of mechanical properties. Despite the higher temperature of the third mode, a large total reduction and a high speed of rotation of the wolves will also achieve the required level of mechanical properties. Modes four and five, characterized by relatively high compression and the highest speed of rotation of the rolls, do not provide the required level of mechanical properties due to elevated temperature.

For the bar obtained according to regime 3 (table. 1), studies have been conducted of the effect of various aging conditions on the mechanical properties (table. 2). From the presented data it can be seen that in order to achieve the required level of mechanical properties, it is necessary to apply aging in the temperature range of 140-160 ° C, at shutter speeds of 3-8 hours.

Claims (2)

1. A method of producing rods from aluminum alloys of the aluminum-zinc-magnesium-nickel-iron-zirconium system, comprising the preparation of a melt based on aluminum obtained by an inert anode electrolysis technology and containing iron, introducing zinc, magnesium, nickel, copper and zirconium, obtaining a cylindrical ingot, its heat and deformation processing by the method of radial-shear rolling at a temperature of from 270 to 300 ° C with a total compression of 65 to 85% and a roll speed of 40 to 60 rpm and hardening heat treatment obtained bar, including hardening and artificial aging. 2. The method of producing rods according to claim 1, in which aging is carried out at a temperature of from 140 to 160 ° C for a time of 3 to 8 hours to obtain a bar having a temporary resistance (σ _in ) of at least 600 MPa, yield strength ( σ _0.2 ) - not less than 550 MPa, elongation (δ) - not less than 5%.

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