JPS6288830A - Disc rotor - Google Patents

Abstract

PURPOSE:To restrain a lowering of the coefficient of friction, to decrease thermal deformation and defective beads, and to improve durability by forming a re-fused layer having no pore 30-200mum thick on the surface of a thermal spraying layer. CONSTITUTION:A disc rotor body 1 is moulded by casting by using gray cast iron, and mixed powder composed of 36wt% Fe, 50wt% Cr, 4wt% C and 10wt% Mo is plasma-sprayed 0.3mm thick on a sliding surface of the disc rotor body to form a thermal spraying layer 2. Subsequently, high-density energy is applied to the thermal spraying layer 2 by using pulse TIG arc to re-fuse the surface. The surface is re-fused by using argon gas as sealed gas, and the re-fused layer 3 is finished. Accordingly, a lowering of the coefficient of friction can be restrained, and thermal deformation and defective beads can be reduced to improve the durability.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a disc rotor (brake disc) used in a disc brake, and more specifically, a metal disc rotor in which at least the sliding surface is made of wear-resistant and heat-resistant material. The present invention relates to a disc rotor on which a thermal sprayed layer is formed.

[Conventional technology]

Disc brakes are widely used as brakes for automobiles and the like. One of the components of this disc brake is the disc rotor, which is a disc-shaped part against which pads are pressed to perform a braking action on the disc brake.

This disc rotor is a relatively large component, and conventionally the main body is made of metal such as aluminum alloy, cast iron, steel, etc., and the sliding surface where the pads come into contact is plasma-sprayed with a ferrous material etc. to resist wear. It had properties such as heat resistance and heat resistance (
For example, Idgstrial Heating:
(February 1985, P45).

[Problem that the invention seeks to solve]

By the way, the thermal spray layer has 4% to 8% pores due to its manufacturing process. Due to the pores formed on the surface of this sprayed layer,
The surface of the disk pad (hereinafter simply referred to as a pad) that comes into sliding contact is likely to be scraped, and the scraped or chipped part of the pad will enter the pores of the sprayed layer. Then,
Organic components such as resin and rubber dust contained in the pad components are melted by frictional heat, etc., and an organic component-based lubricating film is formed on the surface of the disc rotor. As a result, there was a problem in that the coefficient of friction decreased.

Further, during braking, frictional heat generated by pressure contact between the disc rotor and the pad is released to the outside via the sprayed layer and the disc rotor body, but the presence of pores impairs thermal conductivity. As a result, the surface temperature of the disc rotor may rise excessively, causing thermal deformation of the disc rotor or hair cracks.

Therefore, there has been a desire for a method to prevent a decrease in the coefficient of friction and improve thermal conductivity by eliminating pores on the surface of the sprayed layer.

[Means for solving problems]

The L problem is solved by the disc rotor of the present invention, which will be described below.

That is, the disc rotor of the present invention is a disc rotor in which a sprayed layer made of a wear-resistant and heat-resistant material is formed on at least the sliding surface, and a remelted layer without pores is formed on the surface of the sprayed layer. 30μm
It is characterized by being formed with a thickness of ~200 μm.

In the present invention, metals such as aluminum alloy, cast iron, and steel can be used as the material for the disc rotor body, and the disc rotor is formed using these metals by appropriate means such as casting, pressing, and machining.

A sprayed layer made of a material with excellent wear resistance and heat resistance is formed on at least the sliding surface of this metal disc rotor. Here, materials with excellent wear resistance and heat resistance include:
For example, Fe--Cr alloy, Nj-based alloy, CO-based alloy, etc. can be used.

As this Fe-Cr alloy, chromium: 10% by weight
% to 40%, carbon: 1% to 8%, one or two of molybdenum, nickel, tungsten, boron, silicon
It is preferable to have a composition consisting of 5% to 20% of the total amount of elements or more, and the balance being iron.

Here, chromium is added in order to combine with carbon to form hard chromium carbide and improve wear resistance. The reason why this chromium content is set to 10% to 40% is because if it is less than 10%, the desired wear resistance cannot be sufficiently obtained, whereas if it exceeds 40%, the thermal shock resistance decreases and it is not economically preferable.

Further, carbon is added to form a carbide by combining with tungsten, molybdenum, etc., and to improve wear resistance.

The reason why this carbon content is set to 1% to 8% is that if it is less than 1%, the desired wear resistance cannot be obtained, whereas if it exceeds 8%, the impact resistance will decrease.

Molybdenum, nickel, tungsten, boron, and silicon are added to improve wear resistance and heat resistance.

Here, the total of these is 5% to 20%, which means 5%
If it is less than 20, the desired wear resistance and heat resistance cannot be obtained.
%, it is economically unfavorable.

This Fe-Cr alloy or the like is deposited on the sliding surface of the disc rotor by thermal spraying, but plasma spraying is particularly desirable in terms of adhesion.

The sprayed layer deposited on the sliding surface of the disc rotor typically has pores of 4% to 8% as a characteristic of the sprayed layer. In order to prevent the damage caused by pores, a remelted layer is formed on the sprayed layer.

This remelted layer is created by irradiating the surface of the sprayed layer with high-density energy using a high-density energy source.
It is formed by remelting a range of 0 μm to 200 μm.

At this time, the remelted layer is instantly cooled by the remaining sprayed layer and the disc rotor body. The thickness of the remelted layer is 30
The reason why it is set to 200 μm is because if it is thinner than 30 μm, sufficient durability to satisfy the vehicle life cannot be obtained.
If the thickness is greater than 200 μm, not only will no further improvement in durability be obtained, but it will also require an increase in the power of the high-density energy source during remelting, and cracks will occur in the remelted layer. This is because bead defects such as dents and dents occur. Note that a laser, TIG arc, plasma arc, etc. can be used as the high-density energy source.

After the surface of the sprayed layer of the disc rotor is remelted, it is polished to a predetermined shape and size.

[Effect]

According to the present invention, the surface of the sprayed layer formed on the disc rotor body is remelted. Since the remelted layer obtained as a result has no pores, a decrease in the coefficient of friction due to the presence of pores can be significantly suppressed.

Furthermore, since the number of pores is reduced, a decrease in thermal conductivity is suppressed, and thermal deformation and cranking of the disc rotor are prevented.

Furthermore, the remelted layer on the surface has a more dense structure than the sprayed layer, improving durability.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Here, FIG. 1 is a schematic configuration diagram of a disc rotor according to an example of the present invention, FIG. 2 is an enlarged view of the Z section of FIG. 1, and FIG. 3 is a diagram of a disc rotor obtained in the present invention and a comparative example. It is a graph showing the relationship between deceleration and friction coefficient.

First, a disc rotor main body 1 having an outer diameter of 250+n was cast using gray cast iron (JIS Fe12). The sliding surface of the obtained disc rotor body 1 was coated with Fe:
A mixed powder of 36% Cr, 50% C, 4% C, and 10% Mo was plasma sprayed to a thickness of 0.3 m. Next, the sprayed layer 2 was irradiated with high-density energy using a pulsed TIG arc to remelt the surface of the sprayed layer. At this time, the remelting process is performed by flowing argon gas at 251/min as a shield gas into the processing section, and rotating the disc rotor at 1/min.
While rotating at /8 rotations, the torch was moved back and forth in the radial direction at 6 rotations per second, base current: 30A, peak current: 5
I went at 0A. After remelting, finishing was performed. As a result, a disc rotor A shown in FIG. 1 was obtained. In FIGS. 1 and 2, 3 is a remelted layer. In addition,
As shown in FIG.
However, no pores 4 were observed in the remelted layer 3.

(First Comparative Example) The difference from the example is that the finished product was made at the stage where a sprayed layer was formed on the sliding surface of the disc rotor without remelting, and the other points were substantially the same as the example. Disc rotor B was manufactured in the same manner.

(Second Comparative Example) The difference from the example is that the disc rotor was cast and finished as a finished product without thermal spraying or remelting treatment, and the other points were substantially the same as the example. Disc rotor C was manufactured in the same manner.

(Comparative Test) An evaluation test was conducted under the following conditions using disc rotors A, B, and C obtained in Examples and Comparative Examples.

In other words, a semi-metallic pad is used as the mating material, the speed is 5Qkm/H, and the deceleration is 0.3G.
After repeated braking, the coefficient of friction during the effectiveness test was measured. At this time, the efficacy test was performed at a speed of 1) 00k/H.
Deceleration 0.1G, 0.3G.

This was done by braking at 0.45G, 0.6G, and 0.8G. The results are shown in FIG.

As is clear from Fig. 3, the friction coefficient of the disc rotor A of this example (indicated by A in the figure, the same applies hereinafter) is much larger than that in the case of only thermal spraying, and is much larger than that of the cast iron material without thermal spraying. It can be seen that the value is almost the same as that of .

Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes various embodiments within the scope of the claims.

For example, in the embodiment, pulsed TI is used as a heat source for remelting treatment.
Although an example using a G-arc has been shown, other high-density energy sources such as a laser or a plasma arc may be used.

Furthermore, the thinner the sprayed layer is, the more the thermal conductivity can be improved.

〔Effect of the invention〕

As described above, the disc rotor of the present invention provides the following effects.

(a) Compared to disc rotors that have undergone conventional thermal spraying treatment,
Decrease in friction coefficient is significantly suppressed.

(b) Since the number of pores in the sprayed layer is reduced, thermal conductivity is improved and thermal deformation and bead defects are reduced.

(c) Since the remelted layer is denser than the sprayed layer, durability is improved.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a disc rotor according to an embodiment of the present invention, Fig. 2 is an enlarged view of the Z section of Fig. 1, and Fig. 3 is a reduction in the disc rotor obtained in the present invention and a comparative example. It is a graph showing the relationship between speed and friction coefficient. l-・--Disc rotor body 2--Thermal spray layer 3--Remelting layer 4--1--Pore A---Disc rotor applicant Toyota Motor Corporation No. Figure 1 Figure 2

Claims (1)

[Claims] (1) A disc rotor in which a sprayed layer made of a wear-resistant and heat-resistant material is formed on at least the sliding surface, and the surface of the sprayed layer has a remelted layer with a thickness of 30 μm without pores.
A disc rotor characterized by having a thickness of ~200 μm.