KR930008549B1 - Fe-friction material - Google Patents

Abstract

The sintered friction material being useful for a brake system of the high weight transporter comprises 7-10 wt.% graphite with 0.1- 0.9 mm particle size, 2-4 wt.% MoS2, 1-5 wt.% feldspar, 0.5-3 wt.% SiO2 and the balance Fe. Pref. the particle size of feldspar and SiO2 is in a range of 0.1 to 1 mm. Specially, an inclusion of the feldspar enhances a friction performance of the friction material to increase a friction coefficient and to decrease a variation of friction coefficient according to a temperature difference, and to lengthen a life of friction material.

Description

Iron-based Sintered Friction Material

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used in a brake system of a transport mechanism for high speed, high weight, and more particularly, to a method of manufacturing iron (Fe) -based sintered friction material produced by powder metallurgy.

Friction materials are used in brake systems of transport mechanisms such as automobiles, heavy equipment, and airplanes, and the braking force is exerted by converting and absorbing the kinetic energy of the transport mechanism into thermal energy and releasing them to the surroundings.

Initially, as the friction material, an organic friction material made by combining asbestos and resin was used, but this material has a small absorbable energy and the braking force is significantly reduced when the temperature rises. Semimetallic friction material is used as the material.

This material is made by combining metal powder with organic binder, which eliminates the pollution problem caused by organic friction material and absorbs more energy, improving braking performance. However, this material also has a lot of problems in use because the braking force is lowered and the life is shortened when the temperature of the friction material rises due to heat generated during friction.

As such, when the conventional friction material is braked in a high kinetic energy state, the temperature rises due to the frictional heat generated during braking, and the strength of the friction material decreases due to the high temperature and thermal stress. The phenomenon appears.

In order to solve the above problems, metal-based friction materials using metal powders have been developed a lot, and are classified into copper and iron-based friction materials according to the type of metal powder for injection.

Metal-based sintered friction materials are produced by mixing, forming, and sintering various metal and nonmetal powders by a powder metallurgy method.

In the production of such sintered friction material, the type and amount of powder used in the sintered friction material are classified into matrix power, lubricant, and friction modifier according to the function in friction of the friction material.

The base powder is a main component of the friction material, which affects the strength of the friction material and the degree of deterioration of the friction material due to temperature change, and serves to maintain friction performance by fixing the lubricant and the friction control agent in the friction material.

The lubricant helps to achieve a smooth draft with low transfer strength of the lubricant at the interface with the material facing the friction. Graphite, MoS ₂ , MnS and the like are used as such lubricants, and graphite is mainly used at low temperatures, and sulfides (MoS ₂ and MnS) serve as lubricants at high temperatures of 400 ° C. or higher.

In addition, the friction modifier increases the coefficient of friction of the friction material to increase the braking performance.At high temperatures, it provides stability to the braking performance of the friction material and prevents adhesion between the friction material and the facing material (the surface of the two materials melts at high temperatures). give.

In order to act as a friction modifier, the melting point must be higher than that of the base structure, and there must be no reaction with the base structure. And have adequate mechanical strength and hardness.

In the conventional metallic friction material, nonmetal powders such as SiO ₁ , Al ₁ O ₃ , and Mullite (Al ₂ O ₃ : SiO ₂ ) have been used.

An object of the present invention is to produce an iron-based friction material having excellent energy absorption ability and excellent braking ability as a metal-based sintered friction material, less deterioration of friction material due to heat, and exhibiting stable braking performance even at high temperatures.

In the present invention, the powder used and the composition range of the sintered friction material are shown in Table 1.

TABLE 1

* Composition of feldspar: K ₂ O · Al ₂ O ₃ · 6SiO ₂

Here, graphite is coarse than the known powder iron using a powder having a particle size of 0.1-0.9mm and the density is only about one fourth.

If the content of graphite is too small, it is difficult to obtain an even distribution in the friction material, and thus, it is difficult to function as a lubricant. If the content of graphite is too high, the strength of the sintered body is reduced and the coefficient of friction is low. Therefore, the graphite content is preferably 7-10 wt%. .

MoS ₂ can obtain an even distribution by using fine particles as a high temperature lubricant, and 2-4 wt% is preferable to obtain an appropriate friction coefficient.

Feldspar and SiO ₂ use a powder with a particle size of 0.1-1mm, which significantly reduces the friction effect when the particles of feldspar and SiO ₂ are less than 0.1mm. It not only lowers the strength of the metal but also adversely affects the bonding with the iron plate, and therefore, it is preferable to apply the optimum particle size of 0.1-1 mm in consideration of the friction effect and the sinterability of the material. In addition, due to the low density, the volume of the friction material is large.

Of the feldspar and SiO ₂ when the content is excessively large, and the sintering of the sintered body becomes difficult to reduce the intensity, it is too small, preventing its role as a friction material, so the coefficient of friction falls, feldspar 1-5wt% are preferred, and SiO ₂ is feldspar 0.5-3 wt% is preferable because a smaller amount may be added.

In addition, the feature of the present invention is that feldspar is used as a main raw material of the friction regulator.

SiO _{2, which} is mainly used, does not provide sufficient coefficient of friction required for iron-based friction material and shows high wear rate. When feldspar is used together with SiO ₂ , the friction coefficient is increased as the friction material, the wear rate is decreased, and the friction material is improved.

The overall manufacturing process of the sintered friction material is in order of sieving → weighing → mixing → molding → sintering, looking at the embodiment within the composition range of Table 1

EXAMPLE

A sintered friction material was prepared by selecting a composition ratio as shown in Composition Example 1 in Table 2 below in the composition range of Table 1. And also for the influence of feldspar was produced to the value of Composition Example 2.

TABLE 2

Molding was performed at 2.5-5 ton / cm 2, and sintering was performed at 900-1000 ° C. for 2 hours. In this process, a sintering pressure of 10-20 Kgf / cm 2 was applied to promote sintering, and the sintering atmosphere was maintained in an anoxic atmosphere.

Table 3 below is a graph showing the friction test results for the sintered friction materials produced for each composition, the friction test is a friction test at constant speed and the test conditions are shown in Table 3.

In this test, the test was carried out at intervals of 100 ° C. from 150 ° C. to 550 ° C. in order to measure the change in friction characteristics with temperature.

As a result of the test, it can be seen that the composition example 1 shows a stable friction performance with respect to temperature due to the small change of the friction coefficient even with increasing temperature. In the case of abrasion rate, as the temperature increases, the abrasion rate gradually increases, and the wear of the friction material proceeds slowly even at high temperatures.

In addition, in the case of the composition example 2, the friction coefficient with the temperature change is severe, the friction coefficient value is low at high temperature, the friction performance at high temperature is reduced. In the case of abrasion, as the temperature increases, the abrasion rate rapidly increases, and the wear of the friction material proceeds rapidly, thus shortening the life of the friction material.

As shown in the above results, feldspar increases the friction coefficient of the friction material and improves the friction performance of the friction material by reducing the change of the friction coefficient according to the temperature change, and also reduces the wear rate of the friction material to extend the life of the friction material. give.

TABLE 3

Table 4 below shows Danamo test results for the actual product.

This test evaluates the change in the kinetic energy absorption of the friction material and the change in braking performance according to the temperature increase while reproducing the conditions of use of the product with the DANAMO tester.

Here, the braking pressure is the pressure applied to the friction material of the brake brake, and the braking torque is a value appearing at this time, indicating the braking characteristic of the friction material. At this time, the braking torque × braking time represents the amount of energy absorbed by the friction material during the braking time.

As shown in Table 4, which is the test result, in the case of the composition example 1, the braking performance was maintained even when the friction material progressed and the temperature of the friction material increased while the frictional pressure was applied. However, in the case of the composition example 2, even if a braking pressure similar to that of the composition example 1 is applied, it can be seen that the braking torque decreases as the temperature increases and the braking performance is lowered. Therefore, in the case of the composition example 2, energy absorption amount also becomes small.

In this test, the temperature of the friction material is also raised to 600-700 ° C.

As described above, the sintered friction material produced according to the present invention has excellent absorption ability and excellent braking performance, and the change in braking performance according to temperature increase is small, so that it can be used as a friction material of a brake system of a high speed and heavy weight transportation mechanism. It can be effective.

TABLE 4

Claims (2)

Designed sintered friction material manufactured through sieving, weighing, mixing, forming and sintering process, 7-10wt% graphite, 2-4wt% MoS ₂ , 1-5wt% and SiO ₂ with a pressure of 0.1-0.9mm An iron-based sintered friction material, characterized in that the 0.5-3wt%, manufactured in a composition with the remaining amount of Fe. The iron-based sintered friction material according to claim 1, wherein the feldspar and SiO _{2 have} a particle size of 0.1-1 mm.