JPS6254056A - Brake shoe of cast iron for rolling stock - Google Patents

Abstract

PURPOSE:To reduce wear loss and to make a brake shoe fit for use under heavy pressure conditions by making a brake shoe out of cast iron containing specific amounts of C, Si, Mn, P, S, Cu, Cr and Mo. CONSTITUTION:The brake shoe for rolling stock is composed of cast iron consisting of, by weight, 2.7-3.3% C, 1.2-2.2% Si, 0.5-1.0% Mn, 0.1-0.4% P, 0.05-0.15% S, 0.5-1.5% Cu, 1.0-2.0% Cr, 0.2-0.6% Mo and the balance Fe. If necessary, 0.2-0.8% Ti and 0.1-0.7% Ni are added to the cast iron with the above composition. The brake shoe having this composition is capable of reducing wear rate to one-half or less while maintaining wear properties at a level equal to or higher than those of the one now in use and, moreover, heat checks of brake shoe as well as influences upon the wheel tread of rolling stock are minimized to such an extent as to cause practically no problem, so that it is fit for use under heavy load condition.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a control system mainly designed to be used in railway vehicles under high pressing pressure conditions (hereinafter referred to as high load conditions) such as locomotives. It is about the wheel.

[Conventional technology and its problems]

Conventionally, ordinary cast iron made of pearlite and flake graphite has been used as a brake shoe material for railway vehicles.

After the 1950s, synthetic brake shoes using phenol resin as a binding material became widely used in high-speed vehicles such as limited express trains and national electric vehicles.Furthermore, in the 1975s, synthetic brake shoes that used phenol resin as a binding material became widely used in high-speed vehicles such as limited express trains and national electric vehicles. Sintered alloy brake shoes have been put into practical use, mainly for express vehicles.On the other hand, special cast iron brake shoes with improved friction and wear performance are gradually being used in cast iron brake shoes as well. , sintered alloy, and special cast iron brake shoes have higher friction performance and considerably less wear compared to ordinary cast iron brake shoes, but each of them still has aspects that need to be improved. In particular, when used under high load conditions such as locomotives, the following points are cited as disadvantages.

Since synthetic brake shoes inherently have low thermal conductivity, much of the heat generated by friction is borne by the opposing wheel, resulting in a large temperature rise. Under high load conditions such as on a locomotive, there is a high possibility that the temperature of the wheels will exceed the allowable value due to the temperature rise. This allowable value is a value that is considered to prevent wheel breakage, etc. d Sintered alloy brake shoes are considered to have a stronger effect of scraping the wheel than before under high load conditions, and are also expensive, making them economical. Its use is limited for several reasons.

On the other hand, special cast iron brake shoes have hard phases such as cementite and steadite dispersed in pearlite in order to increase friction performance and reduce wear.

Since these hard phases are brittle, they tend to generate thermal cracks on the brake shoe surface due to frictional heat. Under the conditions of use in diesel cars, passenger cars, freight cars, etc., a mild steel plate is currently cast into the back of the brake shoe to prevent breakage due to thermal cracking. However, when used under high load conditions, thermal cracks are more likely to occur, and appropriate countermeasures are required.

[Means to solve the problem]

Based on the above-mentioned current situation, we conducted a study on the particle quality of brake shoes based on cast iron, with a particular focus on reducing the amount of wear, and found that C: 2.7 to 3.3% by weight. Si; 1.
2-0.15%, Mn; 0.5-1.0%, P
; 0.1-0.4%.

S: 0.05~0.15%, Cu: 0.5~
1. F1%, Cr; 1.0-2.0%.

Based on cast iron brake shoes for vehicles and the same composition system containing Mo; 0.2 to 0.6%, the balance being Fe, and Ti; 0.2 to 0.8%, Ni; 0.1 to 0. .7
We have developed cast iron brake shoes for vehicles that contain some or all of %.

The amounts of each element in the component system that characterizes the present invention will be explained below.

Cr is produced by precipitating cementite in cast iron.
Achieve reduced wear. This cementite is Hv12
00-1400, which is harder than cementite, a conventional special cast iron for brake shoes, which has a Hv of about 1000. It is also believed that Cr contributes to improving mechanical properties and stabilizing the structure at high temperatures. Considering the aggressiveness towards the other wheel and the degree of thermal cracking of the brake shoe, the Cr content should be set at 1.0 to 2.
．． It was set to 0%.

P precipitates steadite, which has the effect of improving friction performance and reducing the amount of wear, but it also has the effect of making it easier to generate cracks, and as the pressing force increases, the improvement of friction and wear characteristics decreases. Since the effect is also reduced, the amount added is lower than that of conventional high phosphorus cast iron brake shoes. However, since it is thought that steadite is welded to the wheel tread under medium pressure by friction and has a kind of protective effect, the amount added was set at 0.1 to 0.4%.

Mo was added in an amount of 0.2 to 0.6% to uniformly distribute graphite in the cast iron and to increase the stability of the structure at high temperatures.

Cu was added in an amount of 0.5 to 1.5% in order to densify the pearlite and at the same time make the graphite smaller and disperse it uniformly.

Ni is used for the purpose of refining the graphite structure and making the structure uniform, and T
i was added for the purpose of finely dispersing graphite and improving heat resistance.

The respective amounts of Fe, C, St, Mn, and S were determined in order to make use of the characteristics of each of the above-mentioned elements and to obtain a well-balanced material for the brake shoe.

Table 1 shows the chemical composition of the brake shoes used in the test, and FC was a conventionally used ordinary cast iron brake shoe for comparison. D6 is of the present invention, and its metal structure consists of flaky graphite and pearlite, as well as cementite and a small amount of steadite, as shown in Figure 1, and the hardness of pearlite is Hv.
(0,1) 280-350.

The hardness of cementite is Hy (0,1) 1250~14
It was 00.

These brake shoes were subjected to a stopping brake test using a full-scale inertial type pre-ki tester. Real number condition is wheel diameter
860 rrrn Inertial weight 6.7, Brake pressing force 2.5 t, 5.21 Brake initial speed 3F), 65.9 Fl, 110 km/h Test number 5 times at each speed.

Figure 2 shows the relationship between the initial brake speed and the average friction coefficient.

In contrast to FC, in D6, when the pressing force is low, the average friction coefficient increases or decreases depending on the initial brake speed, but as the pressing force increases, it generally shows a slightly higher value. Furthermore, the degree of decrease in the average coefficient of friction caused by increasing the pressing pressure is small for D6 except when the initial brake speed is 65 km/h, and stability against changes in pressing force is high.

Figure 2 shows the relationship between brake initial speed and wear rate. When the pressing force is 2, 5t, or 5.2t, the wear rate of D6 is 1/3 or 175 compared to FC, and the wear rate is almost constant regardless of the initial brake speed. It's there. Furthermore, no particularly significant difference was found regarding the shadow 9 on the wheel tread.

It was also confirmed that thermal cracking of the brake shoe could be suppressed to a level that does not hinder use.

〔Effect of the invention〕

゛As described above, the brake shoe according to the present invention maintains friction performance equal to or higher than that of the current product, and has a wear rate of 17%.
In addition, the impact on the wheel tread and the thermal cracking of the brake shoes are at a level that poses no practical problem. Therefore, it is a brake shoe suitable for use in high-load steel applications.

[Brief explanation of the drawing]

Fig. 1 is a micrograph showing the metal structure of the present invention, Fig. 2 is a curve diagram showing the relationship between the initial brake speed and the average coefficient of friction,
FIG. 3 is a curve diagram showing the relationship between brake initial speed and wear rate. Designated Substitute Shioiri Kuchimoto National Railway President's Office Legal Affairs Division Chief Tatsuni Honma

Claims (2)

[Claims] (1) C as the chemical component (weight%) of the product: 2.7-3
．． 3%, Si; 1.2-2.2%, Mn; 0.5-1.
0%, P; 0.1-0.4%, S; 0.05-0.15
%, Cu; 0.5-1.5%, Cr; 1.0-2.0%
, Mo; 0.2 to 0.6%, and the balance is Fe. (2) C as the chemical component (weight%) of the product: 2.7 to 3
．． 3%, Si; 1.2-2.2%, Mn; 0.5-1.
0%, P; 0.1-0.4%, S; 0.05-0.15
%, Cu; 0.5-1.5%, Cr; 1.0-2.0%
, Mo; 0.2 to 0.6%, and Ti; 0.6%.
A cast iron brake shoe for a vehicle consisting of 2% to 0.8% Ni; 0.1% to 0.7%, part or all of which is added, with the balance being Fe.