CS257222B1 - Alloy for core magnetic heads - Google Patents

Abstract

The alloy is intended for the cores of miniature magnetic heads, containing 76 to 80 wt. % nickel, 3 to 5 wt. % copper, 1.5 to 4 wt. % niobium, 0.2 to 1 wt. % titanium, the rest iron. The combination of additives meets all the requirements for a material for this purpose, as it is characterized by a large saturation magnetic induction, a large initial permeability, a suitable resistivity value and increased hardness and abrasion resistance.

Description

The invention relates to an alloy for cores of miniature magnetic heads.

With the development of magnetic recording of acoustic and other low-frequency signals on a moving carrier, there has been a demand to extend the life of magnetic heads. This is achieved by improving the abrasion resistance of the material for the core of the magnetic head while maintaining all the necessary and necessary properties of the material. The starting material is nickel-iron alloys with a content of 75 to 80% by weight. % nickel with 5 to 10 wt. non-magnetic metal such as molybdenum, copper, niobium and the like. By adding a small amount of element that forms fine hard precipitates, the hardness and abrasion resistance of the material can be substantially increased. For example, titanium is used, which forms a fine precipitate of the TiNi ^ type, or niobium, which together with titanium forms complex compounds (TiNb) Ni ₃ ·

The non-magnetic additives must be added to the nickel-iron base alloy in an amount such that the saturation rheostation coefficient is zero and the magnetic crystal anisotropy constant can be set to zero by suitable heat treatment. These are necessary conditions for achieving a large initial permeability. However, the high content of non-magnetic additives reduces the magnetic induction of saturation, which is not a malfunction in most cases.

However, for miniature magnetic heads used in cassette recorders and miniature apparatuses, the requirement for a sufficiently large induction of saturation is crucial. Otherwise, non-linear distortion would occur when recording the signal. Also, the resistivity of the head core material must be sufficiently low to achieve a balanced attenuation in the region of the bias frequencies.

An alloy of 77 wt. % nickel, 4.5 wt.%, copper, 3.5 wt. molybdenum, the remainder iron, which has a very high initial permeability but low abrasion resistance and is deteriorated considerably by mechanical machining of the head. Furthermore, an alloy of 80 wt. % nickel, 7 wt. niobium, the remainder iron, which has good abrasion resistance, but due to its high niobium content, it is difficult to form hot. Another known alloy contains 79 wt. % nickel, wt. % molybdenum, 3 wt. niobium, 2.5 wt. titanium, the rest iron. It has a very high initial permeability and good abrasion resistance, but due to the large content of non-magnetic components it has a magnetic saturation induction of only 0.45 T.

Table 1 shows the results of testing various alloy additives with a content of 77% by weight. nickel, the remainder iron, for its magnetic saturation induction B _g and hardness HV 0.1.

Table 1. Magnetic induction of saturation B _g and hardness HV 0.1. nickel, the rest iron.

Content of ingredients wt ^ J B s t ^raT ] HV 0,1 0 1 080 98 2 Mo 975 109 2 Cu 1 030 105 2 Nb 960 127 1 Ti 1 000 113 2 Ti 930 158

According to these measurement results, a combination of additives to the nickel-iron base alloy was found.

These disadvantages are overcome by the alloy for the cores of the miniature magnetic heads according to the invention, which comprises, by weight, 76 to 80% nickel, 3 to 5% copper, 1.5 to 4% niobium, 0.2 to 1% titanium and the remainder iron.

The alloy according to the invention fulfills the conditions imposed on the material for the cores of miniature magnetic heads. The addition of niobium improves initial permeability and increases hardness. At this niobium content, the hot forming conditions do not deteriorate considerably due to the high affinity of niobium for oxygen. Addition of molybdenum or copper has approximately the same effect on initial permeability, but molybdenum increases significantly the resistivity, which is not desirable. The addition of titanium increases the hardness, but at the same time rapidly reduces the magnetic induction of saturation. Therefore, the titanium additive was limited to below 1 wt. The combination of niobium, copper and titanium additives to the nickel-iron base alloy found meets all the material requirements for miniature recording or combined head cores, such as cassette recorders. This alloy has a large megnetic saturation induction, a large initial permeability, a suitable resistivity and an increased hardness and abrasion resistance.

Example

An alloy having a chemical composition of 77% by weight was cast. % nickel, 4 wt. copper, 2.5 wt. % niobium, 0.5 wt. titanium, the rest iron. After hot rolling to a thickness of 5 mm and subsequent cold rolling to a thickness of 0.1 mm, the following properties were achieved after the final heat treatment: initial permeability / 1 ^ = 18 000, magnetic saturation induction B _g = 0.76 T, coercivity H _c = 3.2 Am resistivity = 0.51 yuhm, hardness HV 0.1 = 115.

Claims (1)

An alloy for the cores of miniature magnetic heads, characterized in that it contains 76 to 80 wt. % nickel, 3 to 5 wt. % copper, 1.5 to 4 wt. % niobium, 0.2 to 1 wt. titanium, the rest iron.