DE1139983B - Use of a binary nickel-cobalt alloy for the production of magnetostrictive elements - Google Patents

Description

Use of a binary nickel-cobalt alloy for the production of magnetostrictive elements Magnetostrictive elements are used to convert electrical into mechanical vibrations and are used for this purpose, for example, in echo sounders and ultrasonic drilling devices. The square of the electromechanical coupling coefficient is decisive for the effectiveness of a magnetostrictive element. K, which in turn is a measure of the effectiveness of the magnetic material used in converting magnetic into mechanical energy. The said coefficient is defined by It can be determined through experiments. Originally, pure nickel was used as the material for magnetostrictive elements. However, the use of nickel steel, alloys of nickel and copper, nickel and cobalt, chromium-nickel, chromium steel and other metals has also been suggested. For example, studies carried out at field strengths of 60 to 1100 Örsted have shown that magnetostriction is particularly pronounced in cobalt-nickel alloys with a high cobalt content, i.e. more than 50% cobalt.

The invention relates to the case that a magnetostrictive Element at relatively low field strengths, i.e. those below 30 Örsted; has to work, a condition that e.g. B. in the converters mentioned above given is. It is based on the knowledge that at such low field strengths, in which the magnetic core still remains unsaturated, the coupling coefficient K a Maximum passes through at significantly lower cobalt contents. She proposes accordingly the use of a binary nickel-cobalt alloy with 15.0 to 20.5% cobalt for the manufacture of magnetostrictive elements for transducers that work at field strengths work under of 30 Örsted. It is particularly useful to @the alloy to choose from the narrower range, which is between 16.8 and 18.8% cobalt.

The dependence of the electromechanical coupling coefficient in front The cobalt content of a binary nickel-cobalt alloy is shown in the diagram. For each alloy examined, the magnetization field was adjusted so that K reached its maximum. Pure nickel gave a K of 31% and commercial nickel Nickel with 1% cobalt content; a K of 33%; at 15% cobalt, K was 41% and at 18% cobalt increased to 46%. With a further increase in the cobalt content began K then to fall again. At 20% cobalt it was 410/0.

It should be mentioned that the coefficient K has a further maximum at essential lower cobalt contents, namely in the range of 2 to 6% cobalt passes through. The use of binary alloys of nickel and cobalt in this area is the subject of an older patent.

It should also be mentioned that the percentages given here for K not necessarily comparable with K values that are not given in the above Way, but have been measured at remanence.

In the production of the alloys proposed according to the invention Normally commercially pure nickel is used, which contains the usual impurities and therefore often also contains small amounts of cobalt, which are taken into account during production Need to become.

With certain high power converters, such as those for Ultrasonic drill, must be provided by a constant flow of water for cooling. One of the reasons for this is that ferromagnetic alloys have their ferromagnetic Losing properties above the Curie temperature and therefore an excessive increase in temperature prevented are measured. It is an advantage of those used in the present invention Alloys that the Curie temperature increases by adding cobalt to nickel. Therefore, transducers for whose magnetostrictive elements one of the specified Range selected alloy is used, relatively high temperatures without severe deterioration in magnetic properties. For example the Curie temperature of a cobalt-nickel alloy with 18% cobalt is about 580 ° C compared to the Curie temperature of 355 ° C of commercially available nickel.

It has also been shown that an improvement in the dynamic Magnetostriction will cause a slight drop in the resonance frequency for a given transducer result [has. In the case of a converter operating with optimal magnetization, for example the mechanical resonance frequency for nickel fins is 34.2 kHz, while for fins made of an alloy of 18% cobalt and 82% nickel is 33.6 kHz. On that measured when designing a transducer and determining its excitation frequency To be taken into account.

Claims (2)

PATENT CLAIMS: 1. The use of a binary nickel-cobalt alloy with 15.0 to 20.5% cobalt to manufacture magnetostrictive elements for transducers that operate at field strengths below 30 Örsted. 2. The use of an alloy according to spoke 1 with 16.8 to 18.8% cobalt for the purpose specified in claim 1. References considered: U.S. Patent No. 2,063,946; R. M. B o z o r t h, Ferromagnetism, 1951, pp. 672, 673.