JPH05179408A - High strength soft-magnetic material for torque sensor - Google Patents

Abstract

PURPOSE:To obtain an alloy steel material having high strength and low coercive force and suitable as material for torque sensor by adding specific amounts of Ni, Mo, and Al to an Fe-Cu alloy steel and then applying heat treatment to this alloy steel under specific conditions. CONSTITUTION:A sensor for detecting torque from the change in magnetostriction of a rotary driving shaft of machinery is produced by using, as a material, a low carbon alloy steel having a composition containing, by weight, <0.03% C, <0.10% Si, <0.10% Mn, 3.0-8.0% Ni, 0.2-5.0% Mo, 3.0-7.0% Cu, and 1.5-3.5% Al. A torque sensor prepared by using this alloy steel as a stock is subjected to solution heat treatment at 1000 deg.C for about 1hr and further to aging treatment at 500 deg.C for 5hr. By this method, the soft-magnetic material having high sensitivity and low coercive force and also having superior characteristics required of magnetostriction type torque sensor can be obtained.

Description

Detailed Description of the Invention

[0010]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type magnetostrictive torque sensor material, and more particularly to a magnetic material having high strength and low coercive force.

[0020]

2. Description of the Related Art In recent years, with respect to system control having a rotary drive shaft in industrial equipment such as machine tools and construction machines and automobiles, a technique of directly detecting and controlling torque from a magnetostriction change of the shaft has been put into practical use. As a material for detecting this torque, magnetic properties such as ferromagnetism and magnetostriction as well as high-strength mechanical properties as a rotary drive shaft are required. Examples of the above-mentioned torque detection material include ordinary machine structural steel (JIS SCM, SNCM, etc.) and 18Ni maraging steel.

[0030]

However, the mechanical properties and the coercive force are proportional to each other as a general property of the steel for machine structural use and the 18Ni maraging steel used. In other words, the coercive force increases as the mechanical properties become higher. Therefore, when attempting to increase the mechanical strength, the coercive force increases proportionally, and the soft magnetism deteriorates. Therefore, a magnetic material that solves this problem has been demanded. The present invention provides a high strength and low coercive force high strength soft magnetic material for a torque sensor.

[0040]

As a result of intensive studies conducted by the present inventors to improve the contradictory relationship between strength and soft magnetism, the general relationship is that the coercive force is proportional to the increase in strength. Then, the inventors found an Fe-Cu alloy system that suppresses the increase in coercive force to the low coercive force side. This Fe-
High strength and low coercive force that can increase the strength of the Cu alloy steel by precipitation hardening by heat treatment by adding Ni, Mo, Al and suppress the increase of coercive force by suppressing the addition amount of all alloying elements. The inventors have found a magnetic material having magnetic force and completed the present invention. That is, in the present invention, the weight ratio is C
0.03% or less, Si 0.10% or less, Mn 0.10%
Below, Ni3.0-8.0%, Mo0.2-5.0%,
A high-strength soft magnetic material for a torque sensor, characterized by containing Cu 3.0 to 7.0% and Al 1.5 to 3.5%, and the balance being iron.

Next, the reasons for limiting the components in the present invention will be described in detail. C: 0.03% or less C is mixed as an impurity, but if it exceeds 0.03%, the coercive force deteriorates.

Si: 0.10% or less Si is used as a deoxidizing agent. Addition in a large amount lowers the strength and increases the coercive force, so 0.10% is sufficient to obtain a deoxidizing effect. Mn: 0.10% or less Mn is used as a deoxidizing agent. Addition in a large amount lowers the strength and increases the coercive force, so 0.10% is sufficient to obtain a deoxidizing effect.

Ni: 3.0 to 8.0% Ni is an essential element for improving the strength of the Fe-Cu alloy. If it is less than 3.0%, sufficient strength cannot be obtained. Although the strength increases as the amount of addition increases, even if the content exceeds 8.0%, the strength is gradually saturated, so that no significant strength can be obtained and the cost becomes high.

Mo: 0.2 to 5.0% Mo is a precipitation hardening element, but if it is less than 0.2%, it is less effective in improving strength. On the other hand, if it exceeds 5%, the coercive force increases. Also, the cost is high.

Cu: 3.0 to 7.0% Cu is a basic element of the present invention and is a precipitation strengthening element. Reinforcement by Cu is not sufficient if it is less than 3.0%, and the coercive force increases if it exceeds 7.0%. Furthermore, if added in excess of 7.0%, the hot workability will deteriorate.

Al: 1.5 to 3.5% Al is a main element as a precipitation hardening element. 1.5
If it is less than%, there is little effect on the strength improvement. On the other hand, 3.5%
If it exceeds, the coercive force will increase.

【Example】

The present invention will be described in detail below with reference to examples. Table 1 shows the chemical components of various high-strength soft magnetic materials for torque sensors according to the present invention, and Table 2 shows the results of measuring the tensile strength and coercive force of each high-strength soft magnetic material for torque sensors. In Tables 1 and 2, No.
A to E are invention steels, Nos. F to J are comparative steels, and Nos. K to M are conventional steels. Also, the above tensile strength (N / mm ² ) is
A JIS No. 4 test piece having a diameter of 5 mm in the parallel portion and a length of 25 mm was prepared, subjected to solution treatment at 1000 ° C. for 1 hour, then subjected to aging treatment at 500 ° C. for 5 hours, and then measured.
Coercive force (Oe) has an outer diameter of 24 mm, an inner diameter of 16 mm, and a thickness of 12
The coercive force Hc was measured using a ring-shaped test piece of mm.

[0120]

[Table 1]

[0130]

[Table 2]

It can be seen from Tables 1 and 2 that the invention steels A to E have a high tensile strength of 1,000 N / mm ² or more and a low coercive force of 10 Oe or less. Comparative Steel F has a small amount of Ni and therefore has a coercive force of 7.4 O.
Although it is as low as e, the tensile strength is lowered. Comparative steel G is M
The tensile strength is as high as 1,481 N / mm ² due to the large amount of o,
The coercive force is as high as 13.5 Oe. Comparative Steel H has a low coercive force of 7.0 Oe due to the small amount of Cu, but the tensile strength is lowered. Comparative Steel I has a high tensile strength due to the large amount of Cu, and also has a high coercive force of 13.8 Oe. Comparative Steel J has a high tensile strength and a high coercive force because it contains a large amount of Al.

Next, the conventional steel K and the conventional steel L have a coercive force of about 10 Oe but a tensile strength of 1,000 N / mm ²
However, only low strength was obtained. In addition, conventional steel M
Has a high tensile strength of 1,884 N / mm ² but a coercive force of 19.2 Oe.

INDUSTRIAL APPLICABILITY In the Fe-Cu alloy system of the present invention, for a torque sensor having a high strength of 1,000 N / mm ² or more due to precipitation hardening and a low coercive force of 10 Oe or less by suppressing the addition amount of all alloying elements. A high strength soft magnetic material can be obtained.

Claims (1)

[Claims] 1. A weight ratio of C0.03% or less, Si0.
10% or less, Mn 0.10% or less, Ni 3.0 to 8.0
%, Mo 0.2 to 5.0%, Cu 3.0 to 7.0%, A
High strength soft magnetic material for torque sensor, characterized by containing 1.5 to 3.5% and the balance being iron.