JPS58104149A - High magnetic permeability alloy - Google Patents

Abstract

PURPOSE:To obtain a high magnetic permeability alloy for a magnetic shield with imoroved corrosion resistance and hot workability by substituting Si and Mg for part of Fe in an Ni-Cu-Fe alloy. CONSTITUTION:This high magnetic permeability alloy consists of, by weight, 57-74% Ni, 12% Cu, 0.3-3.5% Si, 0.001-0.02% Mg and the balance Fe. Si is added to reduce the magnetostriction and magnetic anisotropy of the alloy as well as to improve the corrosion resistance. Mg is added to improve the hot workability of the alloy. By the alloy composition the high magnetic permeability alloy with superior initial permeability and maximum permeability as well as improved hot workability and corrosion resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic shield that has good magnetic properties when applied to magnetic shield members that require high magnetic permeability, and that also has improved corrosion resistance and hot workability without losing magnetic properties. The present invention relates to high magnetic permeability alloys for use.

Magnetic shielding members using Ni--Fe based high magnetic permeability alloys are widely used, for example, as shield cases for magnetic heads in magnetic recording devices such as tape recorders.

Among them, high Ni permalloy (JI) containing Mo, Cu, etc.
S-PC material) and low Ni permalloy (JIS-PB material) are often used.

The former has high magnetic permeability and high corrosion resistance, but it uses expensive Ni.
This is because it contains a large amount of 6% by weight (hereinafter simply referred to as %) or more, and also contains MO, which is more expensive.

Among magnetic alloys, it has the disadvantage of being expensive.

In addition, the latter has a Ni content of about 45%, so it is inexpensive and 1
Although the magnetic flux density B at 0 oersted is as high as 14,000 Gauss, the corrosion resistance is extremely poor and the initial permeability μ
The disadvantage is that i is 5000, which is lower than the former. For example, in order to use inexpensive 45% Ni-Fe permalloy as a head case for a magnetic shield, it is necessary to perform a plating treatment as a rust prevention treatment because of its poor corrosion resistance, which makes it rather expensive.

Therefore, conventional JIS-PC materials have excellent magnetic properties.

It has been difficult to obtain magnetic alloy materials that have high corrosion resistance and are inexpensive. However, from an industrial perspective, there is a strong demand for a magnetic alloy that is inexpensive and has excellent magnetic properties, corrosion resistance, and hot workability.

The present invention has been made in response to the above needs.

While maintaining the various properties of JIS-PC material, expensive Ni
The present invention provides a new high magnetic permeability alloy which is suitable for magnetic shielding members, which reduces the amount of Mo by several percent to about 20%, and which does not contain any expensive Mo.

By the way, Ni - which is obtained by adding O to Ni-Fe alloy
Research on Fe-Cu alloys has been conducted for a long time, and it is well known that they have excellent magnetic properties (μ1 = 14,000) (for example, in "Fe-Cu" by Boxorth).
rromagnetism” D, No5trand
Company, 1951).

However, in the above alloy system, if the Cu content is 10% or more, it has been difficult to put it into practical use because it has the disadvantage of significantly deteriorating hot workability.

The present inventors have improved the above-mentioned drawbacks and further improved Ni-Fe-C.
Has better magnetic permeability than u-ternary alloys.

We have been researching high magnetic permeability alloys with excellent hot workability and corrosion resistance. As a result, Ni was 57 to 74%.

By using an alloy consisting of 0u12 to 62% and the balance Fe, and replacing a part of the Fe with Si and Mg, the magnetic permeability is improved by several steps compared to the ternary alloy.

Initial permeability μi = 170000, maximum permeability μm =
220,000 was obtained, the hot workability was significantly improved, and the corrosion resistance was found to be superior to that of JIS-PC material.

The present invention was made based on the above results.

The magnetic alloy of the present invention contains 57 to 74% Ni, Cu1
2-32%, Si0.3-6.0%, Mg0.00
It is characterized by consisting of 1 to 0.02% and the balance Fe.

Here, Ni has high magnetic permeability in the range of 57 to 74%, but when Ni is less than 57%, the magnetic permeability decreases.

Corrosion resistance is also significantly inferior, and if it exceeds 74%, the Cu content is 12%.
% or more, the magnetic permeability decreases significantly.

Further, those containing more than 74% Ni are industrially disadvantageous in terms of saving resources and lowering prices.

Cu has a high magnetic permeability in the range of 12 to 32%.Ou has a high magnetic permeability in the range of 12%.In Migo, high magnetic permeability cannot be obtained unless the Ni amount exceeds 74%, and when Cu exceeds 32%, it becomes difficult to obtain high magnetic permeability. Magnetic permeability μi decreases and hot workability also deteriorates.

Si is added to improve the corrosion resistance of the nine alloy and to reduce magnetostriction and magnetic anisotropy. Si
By adding , a thin 8i oxide film is formed on the alloy surface layer during magnetic annealing, and this acts as a kind of passive film and improves corrosion resistance. In order to form a Si oxide film, it is necessary to add 0.3% or more of Si.

If it is less than 0.3%, no oxide film will be formed and corrosion resistance will deteriorate. Furthermore, even if Si exceeds 3.0%, an oxide film is formed and corrosion resistance is improved.

At the same time, the magnetic flux densities B and IO decrease significantly, and the magnetostriction and magnetic anisotropy increase. From the above, it is preferable that the amount of Si added be in the range of 0.6 to 3.0% in order to improve corrosion resistance and further reduce magnetostriction and magnetic anisotropy.

Mg is added to improve the hot workability of this alloy, and if it is less than 0.001%, no effect will be seen.
If it exceeds 0.02%, the initial magnetic permeability decreases and it cannot be put to practical use. (Details will be described in Example 1.) In addition, A1°C, Ca was added to the alloy of the present invention as a deoxidizing agent and a desulfurizing agent.
, Mn, etc. may be added in a total amount of 1% or less.

Next, the present invention will be explained with reference to examples.

<Example-1> A total amount of 3 Ky of Ni, Cu, Si, Mg, and Fe having the composition shown in Table 1 was melted in a magnesia crucible in a vacuum high-frequency induction furnace, and then cast into an iron mold, so that no segregation of O would occur. An ingot was obtained by cooling to room temperature at an appropriate cooling rate. This ingot was subjected to homogenization annealing at 1300°C for 5 hours, and then a JIS-13 test piece with a thickness of 10111 (JIS
Z2201) was cut out.

A tensile test was conducted at 1200° C. in an argon atmosphere using the specimens cut out from sample numbers No. 71 to No. 006. The strain rate at this time is 4.2×1
0-1 was used. FIG. 1 shows the relationship between the Mg content, the initial magnetic permeability μi, and the cross-sectional shrinkage rate. Here, the larger the cross-sectional shrinkage rate, the better the workability. From this figure, the initial magnetic permeability μi decreases as the Mg amount increases,
It can be seen that when the Mg content exceeds 0.02%, μi<10000, making it difficult to put the alloy to practical use as a high magnetic permeability alloy. In addition, the cross-sectional shrinkage rate increases as the Mg content increases,
When the amount of Mg is 0.02% or more, a saturated state is exhibited.

Next, a tensile test was conducted using specimens cut from sample numbers No. 1 and No. 3 at an appropriate temperature of 800 to 1300°C. The atmosphere and strain rate were the same as above.

Figure 2 shows the relationship between the test temperature and cross-sectional shrinkage rate at this time. From this figure, the Mg-added specimen (No. 3) is Mg-added.
It can be seen that the cross-sectional shrinkage rate is higher than that of the additive-free specimen (No. 1).

From the above, it can be seen that the influence of Mg on the cross-sectional shrinkage rate is extremely large. That is, Mg is 0.001 to 0.02
When added in the range of %, hot workability is improved.

<Example-2> In the same manner as in Example-1, an ingot having the composition shown in Table 2 was obtained. 1. A plate thickness of 0.5 m111 was obtained by normal hot working and cold working.
A plate material was prepared. Here during hot processing.

In the material of the present invention, no corner cracks or edge cracks occurred and the hot workability was good, but comparative sample No.
In case 1, many ear cracks occurred.

Hot workability was extremely poor. From these plate materials, samples for magnetic measurement (ring with outer diameter 45× and inner diameter 33III+) and corrosion resistance test sample (5C11IX50mm) were prepared.
were prepared, and these samples were subjected to magnetic annealing. Magnetic measurements include initial magnetic permeability iμi, maximum magnetic permeability μm, and coercive force HC.
l and magnetic flux density B...1::,,...! 1'&) and the results are shown in Table 2. In addition, a salt spray test (65°C, 5% salt water) was used for the corrosion resistance test. The results at this time are shown in Table 2.

From the results shown in the margin below, the alloy of the present invention has superior magnetic properties and corrosion resistance compared to JIS-PB material (sample number No. 14), and JI 5-PC material (sample number No. 12゜13).
), and has the same magnetic properties as JIS-P in terms of corrosion resistance.
C! It is superior to other materials, and does not rust even after a 96-hour salt spray test.

As mentioned above, the alloy of the present invention has properties equivalent to or superior to JIS-PC materials conventionally used as a high magnetic permeability alloy, has excellent hot workability, and is inexpensive. It is suitable for use in a shield case for a magnetic head.

[Brief explanation of the drawing]

Figure 1 shows the M of the alloy of the present invention when subjected to a tensile test at 1200°C.
The relationship between the g amount, the initial magnetic permeability μi, and the cross-sectional shrinkage rate is shown, and FIG. 2 shows the relationship between the test temperature and the cross-sectional shrinkage rate when the alloy of the present invention and a comparative material were subjected to a tensile test. Figure 2 M bus station Reido ('C)

Claims (1)

[Claims] 1.Ni57-74%, 0u12-32% by weight
, SiO, 3-5.0%, Mg 0.001-
High permeability alloy consisting of 0.02% and the balance re.