JPS61153256A - Cast iron for brake shoe - Google Patents

Abstract

PURPOSE:To provide cast iron for a brake shoe preventing squeaking by specifying the contents of C, Si, Mn, P and S, restricting the carbon equiv., and forming a bainite matrix structure. CONSTITUTION:This cast iron for a brake shoe consists of, by weight, 3.7-4.5% C, 1.0-3.0% Si, 0.2-1.5% Mn, <=0.1% P, <=0.15% S and the balance essentially Fe and has >=4.3% carbon equiv. and a structure contg. flake graphite crystallized in the bainite matrix. A brake shoe made of the cast iron has large damping capacity and small amplitude at the beginning of vibration, so it has significant damping and vibration absorbing effects and hardly causes squeaking. The cast iron has strength sufficient to subject the brake shoe to practical use.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to cast iron for cast brake shoes, and is mainly used for drum brakes of automobiles.

(Prior art) As shown in Fig. 1, a brake shoe has a rim 1 curved in the shape of an arc and a crescent-shaped web 2 integrally formed of cast iron, and a lining on the outer peripheral surface of the rim 1. 3 is fixed to form a T-shaped cross section (for example, Japanese Utility Model Publication No. 58-32025).

(Problems to be Solved by the Invention) Conventionally, ordinary cast iron FC25 has been used as a cast iron material (for example, JP-A-57-171128), but although it has sufficient strength as a cast iron for brake shoes, it has poor damping ability. The problem is that it's small. Therefore, the problem to be solved by the present invention is to have a strength equivalent to ordinary cast iron FC25 and to increase the damping capacity.

(Means for solving the problem) The means for solving the above problem is to use a C:3 ratio by weight of 1.
．． 7-4.5%, Si: 1.0-3.0%, Mn: 0
．． 2 to 1.5%, P: 0.1% or less, S: 0.15% or less, the balance substantially consisting of Fe, carbon equivalent = 4.3% or more, and the structure is The purpose is to create a bainite base in which flaky graphite crystallizes.

The reasons for limiting the amount of each component added, carbon equivalent, and structure in the cast iron of the present invention will be explained.

Carbon generates flake graphite and contributes to improving the damping ability. If the carbon content is less than 3.7%, sufficient damping ability cannot be obtained;
Silicon is an element that promotes flake graphitization, and if it exceeds 1.0%, sufficient damping ability cannot be obtained, and if it exceeds 3.0%, the material becomes brittle and its strength decreases.

If manganese is less than 0.2%, the hardenability is reduced and bainite formation is insufficient, and if it exceeds 1.5%, chill is likely to be generated and machinability is reduced.

When phosphorus exceeds 0.1%, a eutectic of phosphorus is generated, and the material becomes brittle.

If the sulfur content exceeds 0.15%, sulfur will segregate at grain boundaries and the material will become brittle.

The reason why the carbon equivalent (C+1/3Si) is limited to 4.3% or more is that when the carbon equivalent exceeds 4.3%, the attenuation ability increases rapidly.

The reason for using bainite as the base structure is that in addition to increasing the attenuation capacity due to the carbon equivalent, the attenuation capacity can be further increased, and the strength equivalent to ordinary cast iron FC25 can be obtained.

(effect) The above means works as follows.

The vibration energy generated in the brake shoes during braking is absorbed by the cast iron rim and web made of bainite structure, suppressing the vibrations of the brake shoes, making it difficult for the brake shoes to vibrate and reducing noise (
The noise (squeal) may not occur, or even if it does occur, it will be difficult to hear and will cause no problem in practice.

(Example) Hereinafter, an example showing a specific example of the above means will be described.

The rim 1 and the web 2 are integrally formed using the test materials shown in the table below, and the lining 3 is bonded to the outer peripheral surface of the rim 1 to form a brake shoe as shown in FIG.
A comparison test was conducted on the sound. Figure 2 shows the damping state (A) of the brake shoe using the present invention material and the comparative material (normal cast iron FC).
Fig. 3 shows the evaluation results of the squeal susceptibility of the brake shoes using the present invention material and the comparative material.

The results of this example show that the damping capacity of the brake shoe made of the material of the present invention is greater than that of the brake shoe made of the comparative material, and the amplitude at the starting point of vibration is also small, so the damping effect and vibration suppression effect are high, and the noise is reduced. Hard to occur. Furthermore, it was confirmed that the material of the present invention has sufficient strength to be put to practical use as a brake shoe.

(Effect of the invention) The present invention produces the following effects.

The present invention provides a cast iron for brake shoes that is excellent in preventing brake squeal.1 If the cast iron of the present invention is used, squeal can be significantly reduced, so it has great industrial value as a material for brake shoes. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a brake shoe, FIG. 2 is a graph showing damping characteristics, and FIG. 3 is a graph showing squeal test results. 1... Rim 2... Web 3... Lining

Claims (1)

[Claims] In terms of weight ratio, C: 3.7-4.5%, Si: 1.0-3.
0%, Mn: 0.2-1.5%, P: 0.1% or less, S
: 0.15% or less, the remainder substantially consists of Fe, carbon equivalent: 4.3% or more, and the structure is characterized by crystallizing flaky graphite on a bainite base. cast iron.