US2027997A - Permanent magnet containing copper - Google Patents

Description

Patented Jan. 14, 1936 UNITED STATES PATENT OFFICE PERMANENT MAGNET CONTAINING COPPER Tokushichi Mishima, Yodobashi-ku, Tokyo, Japan Japan March 9, 1931 4 Claims.

This constitutes a division from the co-pending application Serial No. 587,822 filed January 20, 1932.

This invention relates to a strong permanent magnet comprising 5 to 40% nickel, 7 to aluminium, copper from a trace to 20% and the remainder substantially iron. It has for its object to economically obtain a permanent magnet which possesses an extremely high coercive force and a strong residual magnetism without being quenched after casting and preserves these qualities without being influenced by thermal changes and mechanical shocks and having small specific gravity and non-corrosive property.

Nickel is a ferromagnetic substance while aluminium is a paramagnetic one, and it has long been known that these metals give no beneficial effects upon the coercive force and residual magnetism of steels when they are added to the latter individually.

Now nickel steels containing 5 to nickel are called irreversible steel by which is meant that they become transformed at appreciably higher temperatures on heating than on cooling. That is the A62 point (the temperature at which magnetism is lost on heating) is considerably higher than the An; point (the temperature at which magnetism begins to obtain on cooling), and the difference amounts to over 400 C. For 3 this reason, when cooling high-nickel steels from high temperature above the Ace point, the Ar: transformation points are suppressed and the steels become non-magnetic at room temperature due to the retention of 7-1101'1. This is the reason why scientists insist upon, and metallurgists give assent, to the fact that the nickel steels can not be used for magnet steels.

According to the invention economically obtain magnet steels which possess an extremely high coercive force and a strong residual magnetism without being quenched, and preserve these qualities permanently withoutbeing influenced by thermal changes and mechanical shocks. For this purpose the invention provides for a permanent magnet containing iron as its chief component, with the addition of 5 to 40% nickel, '7 to 20% aluminium and copper from trace to 20%.

As described above, according to the invention the nickel steel, formerly entirely disregarded as a, magnet steel, can now be easily changed into a' strong magnet steel by an addition of a proper amount of aluminium, which is a cheap material.

it is possible to ,The steel will be furnished with an'extremely high coercive force and a strong residual magnetism without being quenched. By this means, therefore, the defect that the known magnetic steel must necessarily be subjected to deformation and quenching-crack when quenched, is completely eliminated. The alloy according to the invention will be applied for general uses, and in particular forpermanent magnets of precise measuring apparatus and generators, and other various kinds of measuring devices.

According to the invention it has further been found that one portion of the nickel contained in the new permanent magnet above mentioned, will be substituted by copper, which is a very cheap material. The proportion for substitution is 20% and downwards to trace of the alloy. By this means the above mentioned magnetic properties of the alloy will be preserved and its forging property is never spoiled. The cost of manufacture for this alloy is very low.

Actual examples for this case are shown below:

In this case also it is noted that the presence of carbon of below 1.5% and/or a small amount of impurities does not materially affect the magnetic properties of the alloy.

I claim:

1. A permanent magnet comprising 5 to 40% nickel, '7 to 20% aluminum, from trace to 20% copper and the remainder iron.

2. A permanent magnet comprising 5 to 40% nickel, 7 to 20% aluminum, from trace to 20% copper and the remainder substantially iron.

3. A permanent magnet comprising 5 to 40% nickel, 7 to 20% aluminum, from trace to 20% copper, from trace to 1.5% carbon and the remainder iron.

4. A permanent magnet comprising 5 to 40% nickel, 7 to 20% aluminum, from trace to 20% copper, from trace to 1.5% carbon and the remainder substantially iron.

TOKUSHICHI MISHIMA,