SU1127321A1 - Method of thermal treating of aluminium alloys - Google Patents

Abstract

METHOD TEP ^ MCHECKO

Description

The invention relates to the field of metallurgy of non-ferrous alloys, namely to heat treatment of aluminum alloys of the Al-Mg-Li system, and can be used in metallurgical plants to increase the technological plasticity of alloys, simplify technological schemes for hot deformation of ingots and improve the quality of semi-finished products.

It is known that the feature of the cast structure of aluminum alloys is the presence of brittle intermetallic rims along the boundaries of the dendritic branches, which cause a reduced plasticity of the cast slips. In the technological process of the production of wrought aluminum alloys, an ingot with a heterogeneous structure is subjected to homogenization annealing, in

1.2

h, and cooling from the second stage

up to 200 C - with a speed of 10-60 C / h.

WITH

The result of which its structure becomes more homogeneous, the plasticity increases, which allows to intensify the subsequent pressure treatment.

To improve the plasticity, ingots from aluminum alloy 01420 (Al-Mg-Li systems) are subjected to heat treatment (homogenization), which consists in loading the ingots into a furnace with an air atmosphere, heating to a temperature of 440-465 ° C, holding at this temperature for 12 hours subsequent cooling in the furnace to 200c, then, in the air. At the same time, the optimum temperature range of hot deformation of the alloy is 380-400 s, which is extremely narrow and makes it almost impossible to build a technological scheme for processing the material under production conditions. However, with the specified method of heat treatment (homogenization), sgshav 01420 has a low technological plasticity. The closest way to the proposed technical essence and the achieved result is the method of heat treatment of aluminum alloys, including loading into the furnace, AByxcTyneH4aT.TO homogenization with the temperature of the first stage 380-415 С, exposure 2-20 hours, the temperature of the second stage 490-540 ° A booster of 1.84, 2 hours and a heating rate between the steps of 20-100 ° C / h. The disadvantages of the known method are low technological plasticity, low quality of ingots and semi-finished products, as well as low technological plasticity. The aim of the present invention is to improve the quality and improve the technological plasticity of ingots. Delivered Del is achieved by the fact that B is the method of heat treatment of aluminum alloys, mainly aluminum-magnesium-lithium systems, including loading into the furnace, two-stage gomegenization with an exposure at the first 6-12H stage, a second stage temperature of 485-515 ° C and a heating rate between according to the invention, charging into an oven with an air or inert atmosphere is carried out at 180-200 ° C, the first step is carried out at 430-445 ° C, the second stage is carried out for 6-12 hours, and cooling from the second stage to 200 C with speed. Alloy 01420 is a high alloy material, therefore cast ingots have large internal residual stresses. In order to avoid stress cracking, ingots during homogenization should be loaded into wells (furnaces) at a temperature of 180,200 ° C. Loading at a lower temperature leads to an increase in the oxidation of the ingot surface as a result of an increase in the duration of exposure during heating. In aluminum alloys of the A1 llg-Li system, one of the permanently associated impurities is sodium, which adversely affects technology. The plasticity of the material, x.-1 + t, its content in reduced-reduction alloys is due to the use of more pure starting charge materials (lithium, aluminum) and yshyusov. In aluminum alloys, sodium may be present at the boundaries. free-flowing grains or components of low-melting plastics that can melt during heating. In order to dissolve low-melting eutectic containing sodium, the heating temperature of the ingots in the first stage of homogenization should correspond to 430445 ° C. The lower temperature of the first stage of homogenization (less than 430 s) does not lead to full dissolution of sodium and low-melting sodium-containing eutectics, on the contrary, a higher temperature of the first stage (more than 445 C) leads to partial melting of the grain boundaries and eutectics. The heating rates of ingots of alloys of the Al-Mg-Li system between the first and second stages of homogenizing annealing should be chosen from the conditions that at low values (less than 10 C / h) the material is intensively oxidized, and at high values (more bO S / h) they may crack due to the presence of large internal stresses. The temperature of the ingots at the second stage is chosen to be 485-515 s, taking into account ensuring the maximum dissolution of fragile AI terms and rims and non-equilibrium inclusions. The temperature rise of the second stage of homogenization (more than 515 ° C) is impossible, t, k. this will lead to the temperature of the non-equilibrium solidus of the alloy and cause the melting of the grain boundaries. The cooling of the alloy ingots after homogenizing annealing should be carried out at a rate in the range of 10 bO / h. The rate of cooling of the drift too slow (less than 10 ° C / h) gives the productivity of the thermal equipment. An excessively high (more than 60 ° C / h) of coins lead to ingot rejects in cracks due to the occurrence of large internal residual stresses of 1-1x. Example. Under the conditions of the metallurgical plant, and under the jja6opaTop conditions, ingots were otpty, respectively, 225x950 mm in size and 70 mm in diameter from alloy 01420, which were subjected to homogenization ozhi 1 PG according to the serial and proposed methods. Modes are presented in Table. 1 From the obtained material, samples were made for determining the relative elongation of the compared alloy variants and samples with a diameter of 15 mm and a height of 20 mm to determine the allowable degree of deformation during the upsetting transformation. The determination of the relative elongation was carried out in accordance with GOST 1497-61. Tests of samples with a diameter of 15 mm and a height of 20 mm were carried out on a hydraulic press. The characteristics of the tests of these samples were determined at different temperatures in the range of 20-450 C; These results are shown in Table. 2, 3. From the data table. 2 that the ingots processed in the ranges indicated in the application (alloys 1-3) have 10–200% (1.5–2 times) higher than the relative values of their extensions compared to ingots processed in ranges of values apply. The properties of ingots of alloy b, processed according to a known regime, are 50–300% (2-3 times) lower than the properties of ingots treated at the intervals indicated in the application. Properties of ingots of alloy 7 ,. It was not possible to obtain the treatment according to the well-known regime, because of the firing during the homogenization of the ingots. From the data table. 3 it can be seen that the values of the limiting deformation of the ingots processed in the claimed intervals of values (alloys 1-3) are 10-250% (1.5-2.5 times) higher than the values of the limiting deformation compared to the ingots processed in the ranges of values outside (alloys 4, 5). The limiting strain values for 1 ingots processed by a known method (alloy 6) are 10–300% lower (1.53 times) than for ingots processed at the stated intervals of values (alloys 1–3). Limit deformatschsh ingots of alloy 7, processed by a known method, could not be obtained because of the burnout of the material during the homogenization of ingots. From the data table. 4, it can be seen that the state of the surface of the ingots processed in the claimed value ranges (alloys 1-3) is satisfactory, ingots without cracks, the yield is 100%. The ingots processed in the range of values outside the limits specified in the application have cracks, the yield is 80%. The ingots processed by a known method have an unsatisfactory surface condition, tertiary, the yield of the alloy ingots is 6-20%, and the alloy is 7-0%. From the data table. 5, it can be seen that the highest yields are given by sheets made from; ingots prepared by the proposed method (alloys 1-3). The yields of suitable sheets made of ingots processed in the ranges of values by the claimed limits (alloys 4, 5) are much lower. The yields of suitable sheets made from ingots processed by a known method (alloy 6) are also low, and the sheets of glory 7 were not made, since the yield of ingots was 0%, the ingots were all cracked and burned out. As follows from the foregoing, the technical and economic effect of the proposed salvage before the known is achieved by obtaining high-quality ingots with high technological plasticity.

Modes of thermal processing ingots from alloy 01420

Table 1

Average values of relative elongation Table of alloy ingots 01420 Average, values

The state of the ingots and the yield after homogenization

Table 4 nation

Ingots without trepshn

Uncracked ingots

Uncracked ingots

Uncracked ingots

One ingot with a crack

Four ingots with a crack

Three bars with treshinanami, burned out

Table 5 .112732110 of the limiting formation of ingots of alloy 01420 T a l and c a - 3

- -25-30

Sheets were not made, because ingots were burned with homogenization