KR101113668B1 - Brake drum for a vehicle and method for manufacturing the same - Google Patents

Abstract

A brake drum for a vehicle that has excellent wear resistance and provides a stable braking force, in weight percent, carbon (C) 3.2-4.2%, silicon (Si) 1.5-2.8%, manganese (Mn) 0.6-0.9%, sulfur (S) 0.1 A brake drum with a composition comprising less than%, chromium (Cr) 0.1-0.3%, molybdenum (Mo) 0.2-0.5%, graphene (5-10%), remaining iron and other unavoidable impurities is introduced.

Brake drum, heat resistant, wear-resistant

Description

BRAKE DRUM FOR A VEHICLE AND METHOD FOR MANUFACTURING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake drum for a vehicle and a method of manufacturing the same, which have excellent wear resistance and provide a stable braking force.

The drum brake system uses a method of stopping the vehicle by hydraulically pushing a shoe, which is called a lining, with a drum inside the rotating drum together with the wheels. The main components are drum, back plate, brake shoe, wheel cylinder, adjusting screw, return spring, parking brake strut strut).

The brake drum is installed on the drive shaft or wheel spindle together with the wheel. Therefore, when the wheel rotates, the structure rotates together. The brake shoes and the parts generating the expansion force are installed on the back plate. And the back plate is installed and fixed to the axle housing (axle housing). That is, the shoe is installed so that it can be expanded but not rotated.

When the brake shoe is depressed, the brake shoe is pressed onto the inner wall of the drum by an expansion mechanism, that is, a brake shoe actuating pin or a cam. At this time, through the lining (lining) attached to the brake shoe generates a friction force necessary for braking. The force required to extend the shoe is generated by the hydraulic pressure of the wheel cylinder in the main brake and by the cable or lever in the parking brake.

The brake drum is bolted to the wheel hub between the hub and the wheel to rotate together with the wheel to generate a braking force by friction with the shoe. The drum requires the following conditions. First, static and dynamic equilibrium, second, sufficient stiffness not to deform when the brake is extended, third, sufficient wear resistance to the friction surface of the shoe, fourth, heat dissipation It will work out well, fifth, and farewell.

As the material of the brake drum, cast iron, steel, aluminum, and the like are used. Cast iron is hard but brittle and brittle. However, the wear is not good, there is less torsion and the resistance to a large amount of heat. Nowadays, most cars have cast iron rims and drums with steel plate cores, which include carbon mixtures, chromium, magnesium, silicon and phosphorous.

In order to improve heat dissipation, there are drums with fins in the direction perpendicular to the circumferential direction. In particular, aluminum has the effect of improving heat transfer on the friction surface. Some drums have a high tension spring on the outside, which reduces the vibration of the drum during brake operation. Mounting of drums includes rear-drive axle flange mounting, rear wheel hub mounting (front wheel drive vehicles), front wheel hub mounting (spherical wheel hub mounting vehicles), etc. There is this.

The hottest part of the brake drum is the friction surface, which is not well cooled because it is not exposed to the atmosphere. The brake drum expands due to overheating, which results in a greater distance between the shoe and the drum, resulting in longer brake pedal travel. During extreme braking, the heat can cause the drum to twist or become elliptical because the outward pressure from the shoe is not evenly distributed inside the drum. When the oval drum cools, it retains its shape, which causes pedal vibration during operation and decreases efficiency. Overheating can also cause bell-mouthed (harder outer diameters than larger inner diameters), hard spots, checks, and cracks.

The present invention has been proposed to solve the problems described above, and an object thereof is to provide a brake drum for a vehicle and a method of manufacturing the same, which exhibit excellent wear resistance even after long-term use.

Vehicle brake drum according to the present invention for achieving the above object, by weight, carbon (C) 3.2 ~ 4.2%, silicon (Si) 1.5 ~ 2.8%, manganese (Mn) 0.6 ~ 0.9%, sulfur (S ) 0.1% or less, chromium (Cr) 0.1-0.3%, molybdenum (Mo) 0.2-0.5%, 5-10% of graphene (graphene), the remaining iron and other unavoidable impurities.

On the other hand, the brake drum manufacturing method according to the invention, the process of mixing the alloy powder; And thermoforming the mixed alloy powder at a temperature of 130 ° C. to 160 ° C. and a pressure of 100 ° C. to 160 kgf / cm 2, wherein the alloy powder is, in weight%, 3.2% to 4.2% of carbon (C). Si) 1.5 ~ 2.8%, Manganese (Mn) 0.6 ~ 0.9%, Sulfur (S) 0.1% or less, Chromium (Cr) 0.1 ~ 0.3%, Molybdenum (Mo) 0.2 ~ 0.5%, Graphene 5 ~ 10 %, Remaining iron and other unavoidable impurities.

Preferably, after the thermoforming, the molding is heat treated at 130 ~ 160 ℃.

According to the present invention as described above, it is possible to obtain a brake drum exhibiting excellent wear resistance and stable braking force even after long-term use.

In addition, as graphene is added to the drum material in the composition as described above, the thermal conductivity is high, the coefficient of thermal expansion is low, the melting point is high, the density is low, the heat capacity is high, the abrasion resistance and the heat resistance as compared with the prior art A brake drum can be obtained that maintains strength and hardness over a high, wide temperature range.

First, look at the reason for limiting the composition of the brake drum according to the present invention.

The brake drum contains 3.2 to 4.2% by weight of carbon (C). When the carbon content is less than 3.2% by weight, it is difficult to improve abrasion resistance and crack resistance, and when the carbon content exceeds 4.2% by weight, more specifically, 3.7% by weight, abnormal graphite is excessively generated to increase the rate of casting bonds. It is controlled at 3.2 to 4.2 wt%.

Silicon (Si) is used to prevent ringworming and excessive precipitation of ferrite, and its content is controlled to 1.5 to 2.8% by weight. If the silicon content is less than 1.5% by weight, the tendency of chilling of the matrix structure becomes large, so that the deformation resistance decreases. If the content exceeds 2.8% by weight, the strength decreases due to coarsening of graphite.

Manganese (Mn) is an element that promotes a matrix of matrix structure and contributes to the improvement of abrasion resistance by strengthening the matrix structure, and its content is controlled to 0.6 to 0.9% by weight. If the manganese content is less than 0.6% by weight, deoxidation and dehydration of the molten metal are insufficient, and if it is more than 1.0% by weight, more specifically, 0.9% by weight, the tendency of chilling increases.

Sulfur (S) is brittle in the presence of 0.1% by weight or more, so it is better to be managed as low as possible, preferably limited to 0.1% by weight or less.

Molybdenum (Mo) is an element that improves the hot strength, when less than 0.2% by weight can not have a sufficient effect, when it exceeds 0.5%, it causes segregation within the cell boundary of the matrix, 0.2 to 0.5% by weight It is desirable to limit to%.

Chromium (Cr) is a strong graphite inhibiting element, and when 0.3% or more is added, it inhibits the growth of graphite by the formation of complex carbide in cast iron along with the formation of reddeburite. Therefore, it is preferable that chromium is contained in 0.1 weight% or more and 0.3 weight% or less contained from raw materials, such as a scrap.

Graphene is contained 5 to 10% by weight. When the graphene is contained in less than 5% by weight, the effect of the addition of graphene, such as improved wear resistance is insignificant, and when it exceeds 10% by weight, the increase in effect despite the increase in the graphene content is insignificant, The content of is preferably 5 to 10% by weight.

The graphene is a two-dimensional carbon atomic layer material having electrons moving at about one million meters per second and behaving like relativistic particles without a static mass. These graphenes are very thin in thickness and structurally and chemically very stable and exhibit excellent properties, which are added to the production of drums as described above to improve the wear resistance of the drums.

The composition range of the brake drum as described above is shown in Table 1 below.

ingredient C Si Mn S Cr Mo Graphene Fe weight% 3.2 ~ 4.2 1.5-2.8 0.6 ~ 0.9 0.1 or less 0.1 to 0.3 0.2-0.5 5 to 10 Remainder

Next, look at the manufacturing method of the brake drum according to the present invention.

According to one example, the brake drum is produced by uniformly mixing the alloy powder satisfying the composition ranges shown in Table 1, and thermoforming under conditions of temperature 130 ~ 160 ℃ and pressure 100 ~ 160Kgf / ㎠. The thermoformed molding is preferably heat treated at a temperature of 130 to 160 ° C., which is of high quality and least scattered at this heat treatment temperature. Naturally, the brake disc may be manufactured by dissolving the alloying component.

In the thermoforming process, when graphene adheres to the base material, it provides the drum with additional mechanical strength and friction properties. Since graphene particles are quite small and the base material has a relatively large surface area, the graphene particles are well adhered to the gaps or gaps between the base material, ie, particles other than graphene. In addition, the size of the graphene particles is considerably smaller than that of the base material, so that the friction deformation material of the graphene particle size is dispersed evenly throughout the base material.

Look at the experimental example for the performance evaluation of the brake drum according to the present invention. As an example, after producing the brake drums (Examples 1 and 2, Comparative Examples 1 and 2) having the composition shown in Table 2 below, the heat dissipation performance and the amount of wear were measured.

ingredient C Si Mn S Cr Mo Graphene iron Example 1 4.0 2.5 0.6 0.1 0.3 0.2 10 Remainder Example 2 4.0 2.0 0.9 0.1 0.2 0.4 5 Remainder Comparative Example 1 4.0 2.5 0.6 0.1 0.3 0.5 - Remainder Comparative Example 2 4.0 2.5 0.6 0.1 0.3 0.4 - Remainder

The experiment was conducted by measuring the heat dissipation performance and the amount of wear while varying the braking speed, deceleration, and braking frequency for each brake drum. Experimental conditions are as described in Table 3 below.

Braking speed Deceleration Braking Temperature (Pad Temperature) Braking frequency 80 → 0 KPH 0.4g FR: 80 ℃ 1,000 50 → 0 KPH 0.25g FR: 200 ℃ 4,000 50 → 10 KPH 0.2 g FR: 180 ℃ 1,600

After the above experiment, the heat dissipation performance and the amount of wear of each of the brake drums according to Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 4 below. In Table 4, the heat dissipation performance represents the cooling time after braking until the drum temperature reaches 20 ° C. The heat dissipation performance of the brake drum according to the embodiment was improved by about 22 to 30%, and the amount of wear was reduced by about 43 to 50%.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Heat dissipation performance (second) 395 415 532 563 Abrasion amount (mm) 2.42 2.54 4.34 4.81

While specific embodiments of the present invention have been illustrated and described, those of ordinary skill in the art may vary the present invention without departing from the spirit of the invention as set forth in the following claims. It is to be understood that modifications and variations are possible.

Claims (3)

By weight%, carbon (C) 3.2-4.2%, silicon (Si) 1.5-2.8%, manganese (Mn) 0.6-0.9%, sulfur (S) 0.1% or less, chromium (Cr) 0.1-0.3%, molybdenum ( Mo) vehicle brake drum, characterized in that it has a composition containing 0.2 to 0.5%, graphene (5 to 10%), the remaining iron and inevitable impurities. Mixing the alloy powder; And It includes a process of thermoforming the mixed alloy powder at a temperature of 130 ~ 160 ℃, pressure 100 ~ 160Kgf / ㎠; The alloy powder is, in weight percent, carbon (C) 3.2-4.2%, silicon (Si) 1.5-2.8%, manganese (Mn) 0.6-0.9%, sulfur (S) 0.1% or less, chromium (Cr) 0.1- 0.3%, molybdenum (Mo) 0.2 ~ 0.5%, graphene (graphene) 5 ~ 10%, the remaining iron and other inevitable impurities manufacturing method for a vehicle brake drum. The method of claim 2, wherein the molded product after the thermoforming is heat treated at 130 ~ 160 ℃.