RU2215058C1 - Method of manufacturing pressware from thermally strengthening aluminum alloys - Google Patents

Abstract

FIELD: nonferrous metallurgy. SUBSTANCE: invention relates to plastic working of thermally strengthening aluminum alloys accompanied by changing their physical structure, which can be utilized in pressware manufacture. Method comprises casting ingot, homogenizing it, and mechanically treating it to form blanks followed by compacting the latter in two steps: in the first step with constant metal outflow velocity and, in the second step, with smoothly reducing velocity, second step being started after pressing-out of at least 10% of blank. Then tempering and correcting of pressware are carried out by means of stretching with degree of deformation 0.5 to 2.5%. In particular embodiments of invention, the second compaction step is performed without delay after the first step, tempering is followed by natural aging during 48-96 h, and correction is made with degree of deformation 1.5-2.5%; or correction is made with degree of deformation 0.5-0.9% and then resulting ware are subjected to dragging followed by correction and aging. EFFECT: improved mechanical properties and precision of pressware. 7 cl, 2 ex

Description

 The invention relates to the field of metallurgy, in particular to the pressure treatment of thermally hardened aluminum alloys with a change in their physical structure, and can be used in the manufacture of extruded products.

 A known method of manufacturing extruded products from heat-hardenable aluminum alloys by casting an ingot, pressing products, hardening, finishing operations (G. Ya. Gun, V.I. Yakovlev, B.A. Prudkovsky and others. "Pressing aluminum alloys", publisher " Metallurgy "1974, pp. 9-20).

A known method for the production of extruded products from heat-hardenable aluminum alloys (aluminum-magnesium-silicon systems), including casting an ingot, homogenizing the ingot (560 ^o C, 4 h), machining it to produce billets, subsequent pressing at 480-500 ^o C from product blanks, hardening in the press and dressing by stretching, as well as artificial or natural aging (Z. N. Archakova et al. "Structure and properties of semi-finished products from aluminum alloys", reference book "Aluminum alloys", M .: Metallurgy, 1984, p. . 207-219). This method is the closest to the proposed.

 However, the accuracy of the pressed products and the level (guaranteed) of their mechanical properties of products made in accordance with known methods often do not satisfy the requirements of consumers of pressed products.

 Both press quality parameters are particularly influenced by both the pressing conditions and the technology of operations after hardening.

 During pressing, as the ingot is extruded, a change in temperature (heating) occurs in the deformation zone, which leads to a change in size along the length of the pressed product.

 In addition, a change in temperature during the pressing process has a significant effect on the structure of the products, which, upon subsequent quenching, leads to various degrees of recrystallization along the length of the pressing.

 In aluminum alloys, the degree of recrystallization has a significant effect both on the level of mechanical properties and on the conditions for finishing operations (tensile strains with a degree of 1-4%, and for especially precise drawing products after quenching).

 The objective of the invention is to increase the guaranteed level of mechanical properties and accuracy of extruded products from aluminum alloys.

 The problem is achieved in that in the known method for the production of pressed semi-finished products from heat-hardenable aluminum alloys, including casting an ingot, homogenizing the ingot, machining it to produce blanks, subsequent pressing from the blanks of the products, quenching and dressing of the products by tension, pressing is carried out in two stages - at the first stage with a constant flow rate of the metal, at the second stage with a monotonously reduced speed, and the second stage begins after extrusion in m nshey least 10% of the preform. The speed in the second stage, it is desirable to reduce by the end of the second stage at least twice.

 In private embodiments of the method, the second stage of pressing is carried out continuously after the first stage. Editing is carried out with a degree of deformation of 0.5-2.5%.

 After drawing carry out additional editing and aging.

 After hardening, in some cases, natural aging is carried out for 48-96 hours, and dressing is carried out with a degree of deformation of 1.5-2.5%.

 It is also possible to make corrections with a degree of deformation of 0.5-0.9%, and then the resulting products are subjected to drawing. After drawing carry out additional editing and aging.

 The essence of the method is as follows.

 Pressing is carried out in two stages - with a constant speed in the first and with a decreasing speed in the second, the pressing process is brought closer to isothermal, ensuring dimensional and structural stability along the length of the pressed product.

 It is important that the second stage of pressing begins after extrusion of at least 10% of the workpiece. Under such pressing conditions, an optimal design of the structure is achieved, which at the subsequent stages of processing (quenching and dressing by stretching with degrees of 0.5-2.5%) allows you to achieve the declared level of properties.

 Pre-natural aging before tensile deformation also reduces the spread of mechanical properties along the length of the press of the product, because the greater the recrystallization of the structure, the faster the process of natural aging. As a result, tensile deformation during dressing proceeds more evenly along the length of the product, which in turn allows more accurate products to be obtained in terms of cross-sectional dimensions.

 The time range of preliminary natural aging is due to the fact that when aging for up to 48 hours the aging process is not active enough, and when aging for more than 96 hours, the products gain strength that prevents tensile deformation.

 During tensile deformation in a freshly quenched state, dislocations accumulate along the grain boundaries, and upon deformation after preliminary natural aging, dislocations are delayed by the Guinje-Preston zones, evenly distributed in the grain volume, which also affects the increase in the level of mechanical properties.

 Preliminary tensile deformation in the production of drawing products allows to obtain products with reduced curvature, because such deformation significantly reduces the level of thermal stresses caused by quenching.

 The range of tensile deformation (in this case, 0.5-0.9%) is due to the fact that a deformation of less than 0.5% does not effectively reduce the level of thermal stresses, and a deformation of more than 0.9% leads to the heating of the products, which complicates the process of subsequent drawing.

The essence of the method can be carried out according to the following technological schemes:
ingot casting
homogenization
cutting ingots into billets
billet heating
constant speed pressing
pressing with a change in the rate of metal flow as the workpiece is extruded
hardening -
a) natural aging - stretching correction
b) editing by stretching - drawing - editing on a roller straightening machine.

Example 1
Ingots ⌀ 320 • 6000 mm were cast from alloy 2017 (D1), homogenized at a temperature of 500 ± 10 ^o С for 12 h, grinded and cut into blanks ⌀ 295 • 600 mm, heated blanks to 420 ^o С, pressed bar ⌀ 41 mm with an initial flow rate of metal 2 m / min, and after extruding 200 mm of the workpiece, the flow rates were monotonically reduced to 0.5 m / min by the end of pressing, the rods were quenched from a temperature of 495 ± 5 ^o С in water, the rods were kept for 60 hours air, ruled by stretching with a degree of deformation of 2%.

As a result of the tests, the mechanical properties were obtained: σ _in = 46-49 kg / mm ² ; σ ₀₂ = 35-37 kg / mm ² , δ - 14-18%.

According to the known method, σ _in = 37-44 kg / mm ² , σ ₀₂ = 28-34 kg / mm ² , δ = 12-20%.

 The spread of size 41 mm along the length of the bar was ± 0.08 mm. In a known manner ± 0.3 mm

Example 2
⌀ 162 • 6000 mm ingots were cast from 6061 alloy (ADZZ), homogenized at a temperature of 560 ± 10 ^o С for 24 h, cut into blanks размером 162 • 450 mm in size, billets were heated to 500 ^o С, a bar ⌀ 25 mm s was pressed the initial flow rate of the metal was 8 m / min, and after extruding 150 mm of the workpiece, the flow rate was monotonically reduced to 2 m / min at the end of pressing, the rods were tempered from a temperature of 520 ^o C into water, the rods were deformed by tension with a degree of 0.7%, dragged, ruled on a roller straightening machine and artificially aged.

As a result of tests, it was found that the obtained rods have the following strength characteristics: σ _in = 32-33 kgf / mm ² , σ ₀₂ = 27-30 kgf / mm ² , and δ = 12-14% (characteristics of the bar obtained in a known manner σ _c = 28-30 kgf / mm ² , σ ₀₂ = 24-26 kgf / mm ² , and δ = 12-14%). The curvature of these rods does not exceed 0.5 mm per meter of length (the curvature of the rods according to the known method was 2 mm per meter of length).

 Thus, the proposed method will increase the level of strength characteristics and accuracy of products.

Claims (7)

 1. A method of manufacturing pressed semi-finished products from heat-hardenable aluminum alloys, including casting an ingot, homogenizing the ingot, machining it to produce blanks, subsequent pressing from the blanks of the products, hardening and dressing of the products by tension, characterized in that the pressing is carried out in two stages - at the first stages with a constant rate of metal outflow, in the second stage with a monotonously decreasing speed, and the second stage begins after extruding at least 10% of the workpiece.  2. The method according to p. 1, characterized in that the second stage of pressing is carried out continuously after the first stage.  3. The method according to p. 1 or 2, characterized in that the speed in the second stage is reduced by the end of the second stage at least twice.  4. The method according to any one of paragraphs. 1-3, characterized in that the dressing is carried out with a degree of deformation of 0.5-2.5%.  5. The method according to any one of paragraphs. 1-4 formulas, characterized in that after quenching, natural aging is carried out for 48-96 hours, and dressing is carried out with a degree of deformation of 1.5-2.5%.  6. The method according to any one of paragraphs. 1-4, characterized in that the dressing is carried out with a degree of deformation of 0.5-0.9%, and then the resulting product is subjected to drawing.  7. The method according to p. 6, characterized in that after drawing carry out additional dressing and aging.