JPH03247742A - Rotor material for eddy current type reduction gear and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a rotor material for an eddy current type reduction gear excellent in durability by subjecting a steel having a specified compsn. constituted of C, Si, Mn, P, Ni, Nb, V, N and Fe to hot forging and thereafter executing specified hardening and tempering. CONSTITUTION:A steel contg., by weight, 0.05 to 0.15% C, 0.13 to 3.0% Si, 1.0 to 6.0% Mn, <=0.3% P, 0.5 to 5.0% Ni, 0.005 to 0.020% Nb, 0.03 to 0.07% V and <=0.01% N, furthermore contg., at need, <=1.0% Mo and the balance substantial Fe is hot-forged. After that, this forged part is hardened at 850 to 900 deg.C and is then tempered at 600 to 700 deg.C. In this way, a rotor material for an eddy current type reduction gear excellent in strength and toughness as well as electromagnetic characteristics and in which the remarkable improvement of durability is realizable without deteriorating its damping capacity can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a row member suitable for use in eddy current speed reducers for large vehicles such as lotuses and trucks.

<Prior art and its problems> The main brake, which is the foot brake, and the auxiliary brake, which is the exhaust brake, are indispensable as braking devices for large vehicles such as lotus cars and trucks. An eddy current speed reduction device is also an important auxiliary device in order to provide stable deceleration and prevent burnout of the foot brake.

This eddy current type speed reduction device is disclosed in Japanese Patent Application Laid-Open No. 5061574, for example.
As shown in the publication, the magnetic pole is an electromagnet with an electromagnetic coil wound around an iron core, and a large number of the magnetic poles are arranged facing each other on both sides of the disk, and a magnetic field is generated when energized from the battery power source. The eddy current phenomenon that occurs when the brake is applied functions to generate 1.rook in the direction of decelerating the disk, thereby making it possible to obtain the desired braking force.

However, since this eddy current reduction gear uses an electromagnet with an electromagnetic coil wrapped around an iron core as the magnetic pole, it is heavy and large in external dimensions, making it difficult to install it on vehicles with limited space and total weight. I had to say it was a disadvantage. Moreover, during braking, it is necessary to keep the deceleration device energized at all times, and this consumes a lot of battery power, so it is also necessary to increase the battery capacity and power generation function.

Therefore, in order to solve the above problem, the present applicant and others first used a permanent magnet instead of an electromagnet as the magnetic pole, and attached the permanent magnet (1) to a support ring, as shown in cross section in Fig. 1, for example. In (2), a plurality of them are installed side by side so that the polarities of adjacent ones are opposite to each other, and these are supported on a rotating shaft (4) having a rotor (3) fitted to the end thereof,
The pole face of the permanent magnet (1) is opposed to the cylindrical part of the rotor (3) with a required gap, and the eddy current generated in the rotor is turned on and off by the magnetic circuit of the permanent magnet. We proposed an eddy current speed reduction device that requires only short energization during braking (Japanese Patent Application No. 61631/1983,
No. 61.633, Japanese Patent Application No. 127696/1983). In FIG. 1, reference numeral 5 indicates a support portion +4, 6 indicates a pole piece, 7 indicates a cooling fin, 8 indicates a bearing box cylinder, and 9 indicates a metal fitting.

By the way, regardless of the type, the rotor of these eddy current reduction gears (herein, the general term for rotor members including "disc") generates braking torque due to eddy current phenomenon during braking, and at the same time Since it is heated by Joule heat and cooled by air when not braking, a significant thermal cycle is imposed by repeating braking and non-braking. Moreover, in recent years, the required braking performance for eddy current reduction gears has been increasing, and in fact, the operating conditions for eddy current reduction gears have become even more severe, and the thermal load applied to the rotor is also increasing. .

On the other hand, cast steel having the compositions shown in Table 1 has been generally used as a material for such low heating.

Table 1 Although this material has the advantage of being inexpensive because it is cast steel, it does not have very high strength and toughness, and if used for a long time under harsh conditions, it will generate heat on the rotor surface. There are problems in that cracks occur and the service life is shortened, and in recent years, as usage conditions have become more severe, the need for improved performance has been strongly recognized and recognized.

However, taking these circumstances into consideration, C, Si.

The tensile strength is 100 kgf, which is made by controlled rolling of steel with reduced Mn and N and added Ti and B.
A method for manufacturing high-tensile hot-rolled steel sheets with high magnetic flux density has also been proposed (Japanese Patent Application Laid-Open No. 166931/1983), but since this hot-rolled steel sheet has an elongation at break of 15% or less at room temperature, As can be seen, it has low toughness, which makes it unsuitable for use in parts that bear a large mechanical load and require high safety, such as the rotor material of an eddy current reduction device.

Therefore, an object of the present invention is to provide a material for a rotor of an eddy current speed reduction device that has high strength and toughness, is excellent in durability, and can eliminate the above-mentioned problems that have been pointed out in the past. was placed in

Means for Solving the Problems> The inventors of the present invention have conducted intensive research to achieve the above object, and as a result, have reached the following conclusion.

That is, in addition to the above-mentioned high strength and toughness, the rotor material of the eddy current reduction gear must have predetermined electromagnetic properties. In other words, in order to generate braking l-lux as efficiently as possible and reduce Joule heat, electromagnetic characteristics such as (al) high electrical resistance ρ (bl) low coercive force Hc are required.However, Said first
Conventional rotor material, which is cast steel with the composition shown in the table, contains approximately 0.20% C and 0.3% Cr to obtain strength, but C and Cr are As shown in FIG. 3, it is an element that has an adverse effect on the electromagnetic properties (coercive force).

Therefore, if we design the composition of steel to reduce the C content, do not add Cr, and especially adjust the strength by solid solution strengthening with P 1Mn + N + and precipitation strengthening with V, after hot forging, By simply performing heat treatments such as quenching and tempering, it is possible to create a steel material that has sufficient strength and toughness required for the rotor material of an eddy current reduction gear, and also has superior electromagnetic properties compared to conventional materials.

The present invention has been made based on the above research results and the like.
(% by weight).

Si: 0.10-3.0%, Mn: 1.
0-6.0% p: 0.3% or less, Ni: 0
．． 5-5.0%Nb: 0.005-0.020%,
V: 0.03-0.07%.

N:O,O]% or less, or if necessary, Mo: 1.0% or less, with the remainder substantially consisting of Fe, Furthermore, ``After hot forging the steel with the above composition,
By quenching at 600 to 700°C and then tempering at 600 to 700°C, rotor material for eddy current reduction gears with high durability and excellent strength, toughness, and electromagnetic properties can be produced industrially and stably. It is also characterized by the fact that

Next, the reason why the component composition and heat treatment conditions of the rotor material are numerically limited as described above in the present invention will be explained in detail together with their effects.

Effects> A) Component content ratio C is the most basic element that determines strength, but if its content is less than 0.05%, the strength level required for the rotor material cannot be secured. On the other hand, coercive force (Hc)
It increases as the C content increases, and when the content is 0.1
If it exceeds 5%, the braking performance of the eddy current reduction device will not be adversely affected. Therefore, the C content is 0.05~0
．． It was set at 15%, but preferably 0.09 to 0.12%.
It is best to adjust it to

tSi acts as a deoxidizing agent for steel and also has the effect of improving hardenability, but its content is 0.10%.
If the amount is less than that, the effect of the above action cannot be expected sufficiently, and on the other hand, it is not preferable to contain a large amount of Si from the viewpoint of grain boundary and matrix toughness.

Therefore, the Si content was set at 0.10 to 3.0%, but
Preferably, it is adjusted to 0.2 to 2.0%.

In addition to acting as a deoxidizing and desulfurizing agent for steel, Mn also has the effect of improving hardenability and increasing strength through solid solution strengthening, but if its content is less than 1.0%, the above effects will not be achieved. On the other hand, if the content exceeds 6.0%, nonmetallic inclusions may remain and the toughness will also decrease. Therefore, the Mn content was set at 1.0-6.0%,
It is preferably adjusted to 1.3 to 4.0%.

Note that the influence of Mn content on electromagnetic properties is small.

P increases the strength of the rope through solid solution strengthening, and also increases the electrical resistance [
It is an effective element for increasing ρ]. However, on the other hand, it is not preferable to contain a large amount of P from the viewpoint of hot forgeability, and therefore the upper limit of the P content is set at 0.30%.

Ni Ni has the effect of increasing the strength of steel through hardenability and solid solution strengthening, but if its content is less than 0.5%, the effects of the above effects are insufficient, and on the other hand, the balance between economic efficiency and effectiveness is Considering this, it is disadvantageous to contain more than 5.0%. Therefore, although the Ni content was determined to be 0.5 to 5.0%, it is preferably adjusted to 0.8 to 3.0%.

Note that the Ni content also has a small effect on the electromagnetic properties.

Nb Nb has the effect of strengthening the grain boundaries in addition to the effect of refining the crystal grains of steel, but when its content is 0.005
If it is less than 0%, the effect of the above action will not be sufficient;
．． If the Nb content exceeds 0.020%, the toughness decreases, so the Nb content is set at 0.005% to 0.020%, but it is preferably adjusted to 0.010% to 0.015%.

■■ has the effect of improving the strength of steel by precipitation strengthening of vanadium carbides, but if its content is less than 0.03%, the effect of the above effect is not sufficient;
If the content exceeds 0.07%, it will not only lead to a decrease in toughness (but also
Because it also deteriorates electromagnetic properties, the content is 0.03 to 0.
．． It is set at 0.07%, but preferably 0.04 to 0.06%.
It is best to adjust it to

When the N content in the steel material increases, carbonitrides of V and Nb are generated, which adversely affects electromagnetic properties. Therefore, the upper limit of the N content was set at 0.01%.

O Mo has the effect of improving the toughness and strength of the steel, so it is an element that is added as necessary, but even if it is added in excess of 1.0%, not only will the effect of improving the toughness and strength be saturated.
Since this would cause an economic disadvantage, the Mo content was set at 1.0% or less.

In addition to the above-mentioned components, the content of S contained as an impurity was set to 0. It is desirable to keep it below 4%.

1 B) Heat treatment conditions Regarding the thorny degree quenching temperature, the austenitization transformation temperature (A
3 transformation point), the lower limit temperature is set at 8
The temperature was set at 50°C. On the other hand, if the quenching temperature exceeds 900°C, the crystal grains will become coarser, so the upper limit temperature should be set at 900°C.
The temperature was set at 00°C.

If the tempering temperature is less than 600°C, the strength of the steel material will be high, but sufficient toughness will not be obtained. On the other hand, tempering at a temperature exceeding 700°C improves toughness but fails to ensure sufficient strength. Therefore, the tempering temperature is 600~
The temperature was set at 700°C.

Next, the effects of the present invention will be explained in more detail with reference to Examples.

<Example> First, steel having the composition shown in Table 2 was melted using a normal method to prepare test materials.

Note that "conventional steel" in Table 2 is cast steel having the same composition as shown in Table 1, and inventive materials 1 to 3 and comparative materials 1 to 6 are hot forged steels.

FIG. 4 compares and compares the results of an investigation of the tempering temperature and tensile strength of conventional materials and materials 1 to 3 of the present invention, which were hardened at 900°C.

As is clear from the results shown in Figure 4, the tensile strength of the material of the present invention is higher than that of the conventional material, and the tempering temperature is 6.
At 50℃, the tensile strength of conventional material is approximately 50kgf/
mnl, whereas all the materials of the present invention have a weight of 70 kgf.
/mJ or more.

Furthermore, FIG. 5 shows a comparison of the results of an investigation of the tempering temperature and fracture toughness values for conventional materials and materials 1 to 3 of the present invention that were quenched at 900°C. From the results shown in FIG. 5, it can be confirmed that the fracture toughness of the material of the present invention greatly exceeds that of the conventional material at any tempering temperature.

On the other hand, Table 3 shows the mechanical properties (yield stress, tensile strength, , fracture elongation), fracture toughness, electrical resistance, and coercive force.

From the results shown in Table 3, it can be confirmed that the material of the present invention not only has improved strength and toughness compared to the conventional material, but also has improved electromagnetic properties.

In addition, since Comparative Materials 1 to 3 all have high P, V, or Mn contents, they have even higher strength than the present invention materials, but their fracture toughness values are significantly lower, and Comparative Materials 4. It is also clear that samples 6 to 6 have low V, Mn, or Ni contents and therefore do not have sufficient strength.

Next, a rotor for an eddy current reduction gear of the type shown in Figure 1 was created using each of the test materials shown in Table 2, and an eddy current reduction gear to which this rotor was applied was applied to the propeller of a large truck. A "repeated braking test" was carried out by installing it in the middle of the shaft.

During the test, the propeller shaft rotation speed was set to 3000
With the rotation/rotation constant, braking was repeated for 2 minutes and non-braking for 3 minutes, and the number of repetitions until thermal cracks were generated on the surface of the rotor was measured. Note that the maximum temperature reached on the rotor surface at this time was approximately 600°C.

The test results are shown in Table 4.

From the results shown in Table 4, thermal cracks occurred in the conventional and comparative materials after 3,500 to 7,000 repetitions, whereas in the present invention, thermal cracks occurred even after 10,000 repetitions. No cracks were observed, confirming that it had excellent durability.

Summary of Effects> As explained above, according to the present invention, it is possible to provide a rotor for an eddy current speed reduction device that has sufficiently superior strength, toughness and electromagnetic properties compared to conventional materials, and Industrially, extremely useful effects are brought about, such as a significant improvement in durability without reducing the braking performance of the type reduction gear.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of the eddy current speed reduction device proposed earlier. FIG. 2 is a graph showing the relationship between the Cr content of the preparation and the coercive force. FIG. 3 is a graph showing the relationship between C content and coercive force of steel materials. FIG. 4 is a graph comparing the tensile strength of the present invention material and the conventional material depending on the tempering temperature. FIG. 5 is a graph comparing the fracture toughness values of the present invention material and the conventional material depending on the tempering temperature. In the drawing, ■...Permanent magnet, 2...Support ring 3.
...Rotor, 4...Rotating shaft 5...Supporting member, 6...Pole piece. 7...Cooling fan, 8...Bearing box tube. 9...Mounting with metal fittings.

Claims (3)

[Claims] (1) C: 0.05-0.15%, Si: 0.10-3.0% by weight
, Mn: 1.0 to 6.0%, P: 0.3% or less, Ni:
0.5-5.0%, Nb: 0.005-0.020%,
A rotor material for an eddy current speed reduction device, characterized in that it contains V: 0.03 to 0.07%, N: 0.01% or less, and the remainder essentially consists of Fe. (2) C: 0.05-0.15%, Si: 0.10-3.0% in weight percentage
, Mn: 1.0 to 6.0%, P: 0.3% or less, Ni:
0.5-5.0%, Nb: 0.005-0.020%,
V: 0.03 to 0.07%, N: 0.01% or less, Mo
: A rotor material for an eddy current reduction device, characterized in that it contains 1.0% or less, and the remainder consists essentially of Fe. (3) An eddy current reduction method, characterized in that the steel having the composition according to claim 1 or 2 is hot forged, then quenched at 850 to 900°C, and then tempered at 600 to 700°C. Method for manufacturing rotor material for equipment.