RU2085611C1 - Method of manufacturing stock materials for rigid magnet disk of aluminium alloy - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: method includes operations executed in the following sequence: hot deformation of ingot with summary deformation degree higher than 80%, hot rolling at 340-500 C, diffusion, homogenizing annealing at 480-520 C for 2-4 h followed by cooling with rate 30-60 C/s, and cold rolling of sheet to required thickness. Method can be utilized in electronic engineering. EFFECT: improved quality of stock materials. 2 tbl

Description

 The invention relates to the field of electronic engineering and can be used in the manufacture of blanks for the basics of hard magnetic disks (hereinafter simply disks) from aluminum alloys.

 For the production of disks from aluminum alloys, there are many methods for their manufacture, where one of the main operations is the homogenization (diffusion annealing) of the preforms in the molded state in order to dissolve and reduce intermetallic particles inevitably present in the metal. Subsequent processing operations practically do not affect the size of the particles of intermetallic compounds in the finished discs.

A known method of manufacturing flat semi-finished products from Al alloys for the base of plate magnetic drives (see GDR patent N 276305 from 10.19.88), in which a cylindrical billet is cast, which is then cut into press blocks, the latter are heated for 4-6 hours at a temperature of 450-500 ^o C and press from them strips with a thickness of 6-7 mm, and then cold rolling is brought to a final thickness of 2-2.5 mm. The disadvantage of this method is that the structure of the workpiece is heterogeneous.

A known method of manufacturing blanks OZHMD from aluminum alloys (see patent GDR N 257648, C 22 C 21/06, 1988), which the authors took as a prototype. The method involves casting in a semicontinuous method of ingots from an aluminum alloy containing (wt.): Mg 2.8-3.2; Zn - 0.01-0.03; Be - 0.02-0.004; Fe <0.1; Si <0.05; Mn <0.005, homogenization at a temperature of 500-540 ^o C with holding for 8 hours, subsequent hot rolling with a total degree of deformation of 97-98% and cold rolling to the required sheet thickness.

 However, such a technological process does not guarantee to obtain individual particles of intermetallic compounds with a size of less than 7 microns.

 The main technical objective of the proposed method is to obtain a structure with uniformly distributed particles of intermetallic compounds with a size of 1-3 microns (single to 5 microns).

The problem is solved in that according to the known method, including casting ingots, their homogenization, hot deformation, hot and cold rolling of sheets to obtain a given thickness, after hot rolling of the sheet at temperatures of 340-500 ^o C conduct diffusion annealing at a temperature of 480-520 ^o C for 2-4 hours, followed by cooling at a speed of 30-60 ^o C / s.

 Upon receipt of the alloy, crystallization rates are quite high, and therefore crystallization itself proceeds under nonequilibrium conditions, which leads to the phenomena of dendritic and zonal segregation of the alloy components. In this case, the alloying components and impurities are distributed unevenly over the volume of the cast grains, and nonequilibrium particles of intermetallic compounds appear at the boundaries.

 Homogenization of ingots reduces dendritic segregation, but does not affect zonal. In addition to nonequilibrium eutectics and intermetallic particles formed as a result of dendritic segregation, the content of excess phases or complex equilibrium eutectics does not dissolve during homogenization of the cast material.

 Hot plastic deformation increases the density of defects, upsets the balance of complex eutectics, breaks up the molded structure, and breaks up intermetallic particles into smaller particles, which, with subsequent homogenization of hot-deformed sheets, facilitates their dissolution in the alloy matrix.

 The high cooling rate after homogenization prevents the precipitation of aluminum compounds from the solid solution with components having high diffusion rates, magnesium, copper, zinc and silicon.

 The joint use in the proposed method of the aforementioned known and distinguishing features will allow to obtain a new technical result, which consists in the manufacture of disks of aluminum alloy with a uniform distribution of dispersed particles of intermetallic compounds.

 The method is as follows: from an aluminum alloy with a chemical composition (wt.): Mg 3.8; Be 0.001; Zn 0.03; Mn <0.01; Cr <0.05; Ti <0.01; Fe <0.01; Si <0.01; Cu <0.01 (AMC1 according to TU 001.351-92), three lots of disks were made. One according to the known technological scheme and two according to the proposed technology.

 Methods of manufacturing disks are given in table 1.

 We present the data of metallographic control of three batches of manufactured disks presented in Table 2.

As can be seen from the table, the homogenization of cast billets at a temperature of 520 ^o C with exposure for 8 h leads to the presence of particles of intermetallic compounds up to 7 μm in an amount of up to four pieces on an area of 1 mm ² in the finished disks.

 Homogenization of hot-deformed sheets by the proposed method allows to obtain disks with uniformly distributed particles of intermetallic compounds with a size of 1-3 microns with a single not more than 5 microns.

Claims (1)

A method of obtaining a base blank of a hard magnetic disk made of aluminum alloy, including diffusion annealing, hot deformation of an ingot with a degree of total deformation of more than 80%, followed by hot and cold rolling of the sheet to the required thickness, characterized in that hot rolling is carried out at 340 500 ^o C, and diffusion annealing is carried out after hot rolling at 480 520 ^o C for 2 4 hours, followed by cooling at a speed of 30 60 ^o C / s

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