RU2722950C1 - Aluminum-based alloy and method of producing article therefrom - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to non-ferrous metallurgy, particularly, to heat-strengthened aluminum alloys based on aluminum-magnesium-silicon system used in various industries. Aluminum-based alloy contains, wt%: magnesium 0.80–1.10, silicon 0.85–1.20, manganese 0.20–0.40, copper up to 0.05, iron up to 0.20, zinc up to 0.10, chrome 0.10–0.30, titanium 0.06–0.10, indium 0.001–0.01, aluminum and unavoidable impurities making the rest. Disclosed method of producing pressed articles includes ingot casting from alloy of said alloy, ingot homogenisation at temperature below solidus temperature by 20–40 °C for 4–10 hours, pressing at billet heating temperature 420–490 °C with quenching and profile straightening with stretching with value of permanent deformation of not more than 1 %, subsequent artificial aging at temperature of 160–175 °C and holding time of 8–12 hours with a pause between quenching and aging of not more than 24 hours.EFFECT: obtaining pressed articles with high corrosion resistance.6 cl, 2 dwg, 2 tbl, 4 ex

Description

Technical field

The invention relates to the field of non-ferrous metallurgy, in particular to thermally hardened aluminum alloys based on the aluminum-magnesium-silicon system used in various industries, including as elements of building and decorative structures obtained by pressing.

State of the art

Among the thermally hardenable aluminum alloys based on the aluminum-magnesium-silicon system, the alloy AD35 / 6082 (GOST 4784), which has the following composition, wt. %:

magnesium 0.6-1.2 silicon 0.7-1.3 aluminum the basis iron up to 0.5 manganese 0.4-1.0 copper up to 0.1 zinc up to 0.2 chromium up to 0.25 titanium to 0.10.

This alloy is used in various industries, including in building and decorative structures obtained by pressing.

The disadvantage of this alloy is the tendency to delaminating and intergranular corrosion.

Known aluminum alloy 6XXX series (patent RU No. 2385359, C22C21 / 18, publ. 03/27/2010), designed for pressed semi-finished products as structural materials, obtained by casting into billets with further extrusion of profiles, including pipes for the oil and gas industry. The technical result of the present invention is to increase the strength, corrosion resistance and improved processability of the proposed alloys. The proposed alloy has the following composition, wt. %:

magnesium 0.9-1.3 silicon 0.7-1.1 copper 0.8-1.7 manganese 0.2-0.6 chromium 0.18 - 0.3 zinc 0.4-0.8 titanium 0.01-0.03 molybdenum 0.0007 - 0.012 calcium 0.05 - 0.15 beryllium 0.00005 - 0.00015 aluminum and unavoidable impurities rest

The disadvantage of this alloy is the tendency to delaminating and intergranular corrosion due to the high copper content.

Closest to the proposed alloy according to the characteristics and adopted for the prototype is an aluminum alloy 6xxx series (patent RU No. 2163939, C22C21 / 08, publ. 10.03.2001) and a method for the production of semi-finished products from it. The technical result of this invention is to improve the operational characteristics of the product, which is achieved by increasing the corrosion resistance of the alloy. The specified aluminum-based alloy contains, by weight. %:

magnesium 0.3-1.2 silicon 0.3-1.7 copper 0.02-0.9 manganese 0.15-1.1 chromium 0.02-0.9 zinc up to 0.3 titanium up to 0.2 zirconium 0.02-0.9 calcium 0.002 - 0.1 iron up to 1.0 aluminum and unavoidable impurities rest

The proposed method for the preparation of semi-finished products includes the preparation of the above alloy, casting of ingots, annealing of ingots at 350 - 610 ° С for 1 - 20 h, deformation, heat treatment for solid solution is carried out at 500 - 550 ° С for 20 - 12000 s. Depending on the geometric dimensions and surface quality of the final semi-finished product, deformation is carried out either only in hot, or in hot and cold.

The disadvantage of this composition is its tendency to intergranular corrosion in an artificially aged state. In addition, the presence of a high content of manganese, chromium and zirconium leads to the release of large unfavorable intermetallic compounds during crystallization, which, in turn, reduces the manufacturability of alloy ingots during pressing. Also, this leads to a decrease in the level of mechanical, fatigue and corrosion properties in deformed semi-finished products.

Disclosure of invention

The objective of the invention is to develop a heat-hardenable alloy based on aluminum of the 6XXX series for use in structural and decorative structures and to obtain extruded products from it with increased rates of resistance to intergranular and delaminating corrosion while maintaining the level of mechanical properties relative to the analogue alloy.

The technical result is to obtain extruded products in the form of profiles with increased corrosion resistance with mechanical properties at the level of aluminum alloy AD35 / 6082 due to the use of the optimal alloy composition with the addition of elements that increase corrosion resistance and the exclusion of elements that reduce it. As a result, the obtained profiles are not prone to intergranular corrosion, and the tendency to delaminating corrosion is 1 point.

In one preferred embodiment of the invention, the achievement of the technical result is ensured by the fact that in an aluminum-based alloy containing magnesium, silicon, manganese, copper, iron, chromium and titanium, it is new that it additionally contains indium in the following ratio of components, wt. %:

magnesium 0.80-1.10 silicon 0.85-1.20 manganese 0.20-0.40 copper up to 0.05 iron up to 0.20 zinc up to 0.10 chromium 0.10-0.30 titanium 0.06-0.10 indium 0.001 - 0.01 aluminum and unavoidable impurities rest.

In accordance with another aspect, the claimed invention relates to a method for producing an aluminum-based alloy product, including casting an alloy ingot, homogenizing the ingot at a temperature T _{solidus of} -20 to 40 ° C for 4 to 10 hours, pressing at a heating temperature of the workpiece 420 to 490 ° C with quenching and straightening the profile by stretching with a residual strain of not more than 1%, followed by artificial aging at a temperature of 160 - 175 ° C with a holding time of 8 to 12 hours with a break between hardening and aging of no more than 24 hours.

In particular embodiments of the claimed process, quenching is carried out on press table for profiles with a wall thickness of 8 mm or vertical hardening furnaces for profiles with a wall thickness greater than 8 mm, the quenching temperature is 520 - 540 ° ^C.

In accordance with another aspect, the claimed invention relates to an aluminum-based alloy product made in the manner described above.

Brief Description of the Drawings

In FIG. 1 shows profile 1.

In FIG. 2 shows profile 2.

The implementation of the invention

The magnesium content at the level of 0.80 - 1.10 wt. % and silicon at the level of 0.85 - 1.20 wt. % provides the necessary level of strength during heat treatment. When the content of magnesium and silicon is lower than stated, the mechanical properties of the alloy are at a low level. When the silicon content is above 1.20 wt. % significantly reduced corrosion resistance. The excess of magnesium over 1.10 wt. % reduces the manufacturability of alloys, and also reduces the susceptibility to heat treatment of the alloy.

The presence in the alloy of manganese at the level of 0.20 - 0.40 wt. % promotes the binding of iron to the Al ₈ (Mn, Fe) ₂ Si phase, which, to a much lesser extent compared to Al ₅ FeSi, leads to the formation of defects during the pressing process and, together with chromium, provides the necessary level of mechanical properties.

The copper content at a concentration of up to 0.05 wt. % and iron at a concentration of up to 0.20 wt. % provides a high level of corrosion resistance and eliminates the formation of defects in the form of undesirable for pressing intermetallic compounds.

The presence of titanium in an amount of 0.06 - 0.10 wt. %, as a grain modifier, guarantees a uniform fine-grained structure in products, subject to heat treatment.

The indium content in the alloy increases corrosion resistance due to the inhibition of the cathodic reaction of hydrogen evolution, through which corrosion develops in aluminum and its alloys. When the indium content is below the specified limit, the effect is not manifested. When the indium content is higher than 0.01 wt. % pure indium appears in the structure, causing hot cracking during compaction.

In the proposed method for producing pressed products, homogenization is carried out at a temperature T of _{solidus of} -20 - 40 ° C for 4 to 10 hours, which ensures sufficient transformation and spheroidization of the glandular phases without negative changes in the metal structure in the form of grain enlargement. Homogenization up to 4 hours does not eliminate the effects of nonequilibrium crystallization of the ingot and transformation of the glandular phases, and more than 10 hours of exposure is not economical.

Pressing is carried out at a workpiece heating temperature of 420 - 490 ° C to ensure the temperature of the metal at the exit from the die point 520 - 540 ° C. When the metal temperature exceeds 540 ° C and when the metal temperature is below 520 ° C, the mechanical properties of the pressed products decrease. The indicated temperature range guarantees the optimal degree of supersaturation of the solid solution, which in turn allows to obtain higher mechanical properties of the profile.

Hardening in the process of artificial aging of this alloy is ensured by the maximum enrichment of the solid solution and the optimal cooling rate during quenching on the press table for profiles with wall thicknesses up to 8 mm or in a vertical quenching furnace for profiles more than 8 mm and the optimal aging mode.

Hardening occurs due to the release of dissolved components into phases that are located in the grains in the form of small formations and increase the resistance of the material to shear deformation. The optimal aging regime is 160 - 175 ° C with a shutter speed of 8 - 12 hours. At an aging temperature of less than 160 ° C, the concentration of precipitates is insufficient to obtain the required level of properties of pressed products and is not optimal due to the low rate of strength growth, and at an aging temperature above 175 ° C due to overcooking, the level of properties decreases, and the temperature is also not optimal. At the same time, the interval between hardening and aging should not exceed more than 24 hours, since this leads to a decrease up to 20% in the increase in strength during artificial aging due to the allocation of coarser phases.

Various extruded articles in the form of profiles, for example, elements of building and decorative structures, can be made of the proposed alloy.

Examples of carrying out the invention

Example 1. In an industrial furnace with a capacity of 7.5 tons were made melting of the following chemical composition, wt. %, Table 1:

Table 1.

No. Mg Si Mn Cu Zn Ca Fe Cr Ti Zr In Al 1 0.80 1.20 0.40 0.01 0,025 - 0.10 0.17 0.09 - 0.01 main 2 1.10 0.90 0.30 0.04 0.05 - 0.15 0.30 0.10 - 0.008 main 3 0.95 0.85 0.40 0.05 0,028 - 0.13 0.20 0.06 - 0.001 main 4 0.87 0.98 0.20 0.015 0.10 - 0.20 0.10 0.10 - 0.01 main Prototype 0.3-1.2 0.3-1.7 0.02-0.9 0.15-0.1 up to 0.3 0.002 - 0.1 up to 1.0 0.02-0.9 up to 0.2 0.02-0.9 - main

The method of semi-continuous casting was cast cylindrical ingots with a diameter of 125 mm and a length of 840 mm. The obtained ingots were homogenized at a temperature T _solidus -20 - 40 ° C for 4 hours.

The ingots were pressed into profiles, the drawing of which is shown in FIG. 1. The profile wall thickness is 6 mm. The ingots were heated before pressing to a temperature of 420 - 490 ° C. The resulting profiles were hardened on a press table. Next, the profile was straightened by stretching with a residual strain of not more than 1%. Artificial aging of the profiles was carried out at a temperature of 160 ° C with a holding time of 8 hours with a break between hardening and aging of 10 hours.

Example 2. The melting and casting of the ingots was carried out as in example 1. The resulting ingots were homogenized at a temperature T _solidus -20 - 40 ° C for 10 hours. The ingots were pressed into profiles, the drawing of which is shown in FIG. 2. The wall thickness of the profile is 12 mm. The ingots were heated before pressing to a temperature of 420 - 490 ° C. The resulting profiles were hardened in vertical quenching furnaces. Tempering temperature in the tempering furnace is vertical temperature profile at the outlet from the die - 520 - 540 ^C. Changes were performed according to Example 1. The profiles Artificial aging was carried out at a temperature of 175 ° C with 12 hours delay interval between quenching and aging for 24 hours.

Example 3. Melting and casting of the ingots was carried out as in example 1. The resulting ingots were homogenized at a temperature T _{solidus of} -20 - 40 ° C for 6 hours. The ingots were pressed into profiles, the drawing of which is shown in FIG. 1. The wall thickness of the profile is 6 mm. The ingots were heated before pressing to a temperature of 420 - 490 ° C. The resulting profiles were hardened on a press table. Editing was carried out according to example 1. Artificial aging of the profiles was carried out at a temperature of 165 ° C with a holding time of 10 hours with a break between hardening and aging 24 hours.

Example 4. Melting and casting of ingots, homogenization, pressing, hardening and dressing was carried out as in example 2. Artificial aging of the profiles was carried out at a temperature of 170 ° C for 12 hours with a break between hardening and aging of 20 hours.

The mechanical properties of extruded profiles after artificial aging obtained in example 1, 2, 3 and 4 are shown in table 2.

table 2 Alloy Tensile strength, MPa Yield Strength, MPa Relation elongation,% MKK / RSK 1 320 280 thirteen Missing / 1 point 2 330 290 12 Missing / 1 point 3 325 285 12 Missing / 1 point 4 325 285 12 Missing / 1 point Prototype 335 275 thirteen 0.05 mm / -

As can be seen from table 2, the achieved level of mechanical properties of products in the form of profiles obtained by the claimed method is at the level of the prototype, however, the proposed compositions do not have intergranular corrosion, while the value of intergranular corrosion of the prototype is 0.05 mm In addition, the proposed composition also has the minimum values of DSC - 1 point out of 10.

Claims (7)

1. An aluminum-based alloy containing magnesium, silicon, manganese, copper, iron, zinc, chromium and titanium, characterized in that it additionally contains indium in the following ratio of components, wt.%: magnesium 0.80-1.10 silicon 0.85-1.20 manganese 0.20-0.40 copper up to 0.05 iron up to 0.20 zinc up to 0.10 chromium 0.10-0.30 titanium 0.06-0.10 indium 0.001-0.01 aluminum and unavoidable impurities rest 2. A method of producing an aluminum-based alloy product, including casting an alloy ingot according to claim 1, homogenizing the ingot at a temperature below the solidus temperature of 20-40 ° C for 4-10 hours, pressing at a heating temperature of the workpiece 420-490 ° C with quenching and straightening the profile by stretching with a residual strain of not more than 1%, subsequent artificial aging at a temperature of 160-175 ° C and holding time of 8-12 hours with a break between hardening and aging of no more than 24 hours. 3. The method according to claim 2, characterized in that the hardening is carried out on a press table for profiles with a wall thickness of up to 8 mm. 4. The method according to claim 2, characterized in that the hardening is carried out in vertical quenching furnaces for profiles with a wall thickness of more than 8 mm. 5. The method according to claim 2, characterized in that the hardening temperature is 520-540 ° C. 6. The product is made of an alloy based on aluminum, characterized in that it is made by the method according to any one of paragraphs. 2-5.