JPH0636664B2 - Non-magnetic shaft for motor - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a non-magnetic shaft for a motor.

[Technical background of the invention and its problems]

Among various motors, especially the magnetic recording related equipment such as video tape recorders, floppy disk drives, hard disk drives, etc., the shafts of micromotors require a non-magnetic material to prevent the magnetic field of the motor from leaking to the outside. However, conventionally, copper, brass, stainless steel, etc. have been used.

By the way, with the recent strong demand for miniaturization and weight reduction of the magnetic recording-related equipment, for example, in the case of a video tape recorder, if one unit weight of a motor shaft is reduced by 1 g, other peripheral parts are Since the size of the motor shaft is greatly reduced and the cost is reduced by several thousand yen, it has a large ripple effect, which makes it possible to reduce the size and weight of the motor shaft. It is non-magnetic and has excellent corrosion resistance and deflection resistance. At times, there is a demand for a motor shaft made of a hard material that is not easily scratched during assembly. Also, non-magnetic and lightweight microshafts such as VTRs, FDDs and HDDs are desired.

[Object of the Invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a small-sized, lightweight non-magnetic shaft for a motor, which is excellent in corrosion resistance and flexure resistance and has high hardness.

[Outline of Invention]

According to the present invention, as a result of extensively experimenting and studying the composition of various alloys, processing, etc., it was found that a non-magnetic shaft for motors, which is excellent in corrosion resistance and flexure resistance, and has high hardness, can be obtained. .

That is, in the present invention, at least 0.05% to 1.5% of carbon or nitrogen and 10% of manganese are used by weight.
A non-magnetic shaft for a motor, characterized by being composed of an alloy of -30%, chromium 10-30%, balance iron and incidental impurities.

Here, the reasons for limiting the chemical composition of the non-magnetic shaft for a motor according to the present invention will be described.

Carbon and nitrogen are elements that improve the flexural resistance while reducing the magnetic permeability by using the structure of the non-magnetic shaft for a motor according to the present invention as an austenite phase, and at least 0.
05% or more is necessary. However, a large amount of Ni deteriorates workability, and a large amount of nitrogen causes generation of pinholes and blowholes.
Desirably, 0.3 to 1.0% is preferable, and when corrosion resistance is required, carbon is 0.3% or less, preferably 0.2% or less.

Chromium is an element necessary for improving corrosion resistance, securing flight magnetism by stabilizing flexural properties and stabilizing the structure, and further reducing the specific gravity of the alloy for weight reduction, and at least 10% or more is necessary. However, the inclusion of a large amount impairs the workability and promotes the formation of the ferrite phase to increase the magnetic permeability, so the content is set to 30%. 16 to 25 is desirable.
% Is good.

Manganese suppresses the formation of martensite phase and ferrite phase to ensure non-magnetism, improves the flexural resistance by work hardening, and further lowers the specific gravity of the alloy like chromium to reduce the non-magnetic properties for motors according to the present invention. At least 10% of the elements necessary to reduce the weight of the shaft are necessary.
However, if a large amount is contained, workability deteriorates, so 30%
Up to In addition, 15-25% is desirable.

It should be noted that it is possible to add a small amount of Si as a deoxidizing agent when smelting the steel constituting the non-magnetic shaft for a motor according to the present invention, and also Cu or Ni for the purpose of stabilizing the austenite phase. It is permissible to add a small amount of Mo and to add Mo in a range in which a ferrite phase does not appear for the purpose of improving corrosion resistance.

The non-magnetic shaft for a motor according to the present invention, which is excellent in bending resistance, lightweight and high in hardness, is manufactured as follows, for example.

That is, the raw materials are mixed so as to have the composition of the alloy according to the present invention and melted, and then an ingot is obtained by casting.

Next, this ingot is heated to 1100 to 1200 ° C. and hot forged, and then hot rolled into a rod shape by groove roll processing. After that, the wire is cold drawn to form a shaft material, and this material is cut and cut into a shaft. It should be noted that strain relief annealing may be performed during the cold wire drawing process,
Heating at 900 ℃ or higher is preferable, but especially before the final cold working, 1000 ℃ or more is good as solution treatment, 1050 to 1100 ℃
Is desirable. However, since the non-magnetic shaft for a motor according to the present invention has a higher hardness than the conventional non-magnetic shaft for a motor, it may be in a state of being strain-taken up or solution-treated not at the time of cold working.

Example of Invention

Alloys having the chemical compositions shown in Table 1 were melted in a high frequency vacuum induction melting furnace and cast into a mold to obtain an ingot. Nitrogen was added as an iron-chromium-nitrogen master alloy.

Next, after heating this ingot to 1150 ° C., casting,
A non-magnetic shaft material for motors was obtained by rolling.

When the test pieces were taken from these ingots and the specific gravity was measured, the specific gravity was 7.61 to 7.64, which was much smaller than copper 8.9 and brass 8.2, and austenitic stainless steel SUS316 7.8. It can be seen that the specific gravity is small and it is suitable for weight reduction.

Next, the shaft for motors was measured for the important bending resistance. In addition, the measurement was made by rolling a material to 0.3 mm and by heating it at 1050 ° C. for 1 hour and then rapidly cooling it and subjecting it to solution treatment, a plate with a width of 10 mm and a length of 100 mm was sampled, and a cantilever support burr was taken. The measurement was performed with a measuring length of 30 mm and a load of 15 g, and the amount of deflection at the tip of the sample was measured. Further, the observation of the metal structure, the hardness measurement, the magnetic permeability measurement, and the corrosion resistance measurement were also performed. The corrosion resistance was evaluated after leaving it in artificial seawater for 2 months.

The test results are shown in Table 2 with copper and brass used conventionally.
Shown together with SUS316.

As is clear from Table 2, the flexure amount of the present invention is 0.29 to 0.34, which is 36 to 54% smaller than the flexural amount of conventional copper or brass of 0.53 to 0.63 which is a comparative example. Considering the difference in specific gravity, it is possible to greatly reduce the size of the motor by the effect of reducing the weight caused by the fact that the core diameter of the motor shaft can be made thinner and the weight reduction caused by the decrease in the specific gravity. It is also clear that the hardness is much higher, so that it is possible to manufacture a motor with high accuracy that is hard to be scratched, easy to transport and assemble.

In addition, compared with the conventional SUS316, the specific gravity and the amount of deflection are small as mentioned above, so the weight of the motor shaft can be reduced, the motor can be downsized, and the hardness is about 120 HV. From the above high values, it is understood that the motor shaft can be manufactured with high accuracy in which the motor shaft is not easily scratched during manufacturing, transportation, or assembly of the motor.

By the way, in order to further reduce the weight of the motor shaft, the shape of the shaft may be cylindrical, and the effect can be achieved by the second moment of area.

Since the non-magnetic shaft for a motor according to the present invention has excellent wear resistance, wear of the bearing portion is small and stable rotation can be secured for a long period of time.

As described above, the non-magnetic shaft for a motor according to the present invention enables miniaturization of the motor, and further the miniaturization and weight reduction of magnetic recording-related equipment due to the ripple effect of miniaturization of peripheral parts, and motor shaft hardness. It is easy to manufacture shafts, transport and assemble motors because it is high in quality and is not easily scratched.
It is industrially useful.

Claims (1)

[Claims] 1. A weight percentage of at least one of carbon and nitrogen of 0.05% to 1.5% and manganese of 10 to 30.
%, Chromium 10 to 30%, balance iron, and an additional impurity alloy.