JPS60248864A - Brake drum made of cv graphite cast iron - Google Patents

Abstract

PURPOSE:To provide the titled brake drum having high performance by incorporating a specific compsn. amt. each of C, Si, Mn, P, S, etc. into a CV graphite cast iron thereby providing good heat conductivity, strength, ductility and attenuating power and providing stable base structure and low modulus of elasticity thereto. CONSTITUTION:The brake drum is made of the CV graphite cast iron contg. 3.0-4.0% C, 1.8-2.4% Si, <=0.8% Mn, <=0.08% P and <=0.03% S, contg. >=1 elements among 0.1-0.2% Cu, 0.01-0.02% Sn and 0.1-0.2% Cr according to need and contains further 0.05-0.15% (residual value) Ti. Said drum is thus made of the optimum brake drum material. The CV graphite cast iron consisting of the above-mentioned compsn. is usable as cast but the above-mentioned drum is preferably used after said drum is subjected to a heat treatment at about 850- 950 deg.C to stabilize the base structure to the uniform and fine structure and to improve additionally the physical and mechanical properties.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Cv graphite cast iron brake drum.

The brake drum is subjected to thermal cycles of heating and cooling during operation, and is subjected to severe thermal fatigue at locations where it is subjected to strong strain stress during brake operation. Therefore, the optimal brake drum material should have good thermal conductivity, a low coefficient of expansion, a low Poisson's ratio, some ductility, and a thermally stable matrix structure. .

Pearlitic flake graphite cast iron (F
(equivalent to C25) has good wear resistance and high thermal conductivity, but as the performance of automobiles improves, stronger materials are desired.

Spheroidal graphite cast iron, which is strong and ductile, has excellent fatigue resistance, but has poor thermal conductivity and is subject to large thermal stress, resulting in deformation, seizure, etc. Furthermore, since the damping capacity is low, so-called brake wear is large, making it unsuitable as a brake drum material.

CV graphite cast iron brake drums, which have physical and mechanical properties intermediate between those of flaky graphite cast iron and spheroidal graphite cast iron, have appropriate thermal conductivity, strength, ductility, and damping capacity, but in addition, The present invention, which has a stable base structure and a low elastic modulus, is optimal as a brake drum material.

The Cv graphite cast iron brake drum of the present invention has a C:3.
0-4.0%, Si: 1.8-2.4%, Mn:
It is characterized by having chemical components of ≦0.8%, P:≦0.08%, and S:≦0.03%. moreover,
For the purpose of stabilizing the pearlite base during heating and cooling,
Cu (copper): 0.1-0.2%, Sn (tin):
0.01-0.02%, Cr (chromium): 0.1
~0.2%, and in some cases, Ti (titanium): 0.05 to 0.15% is contained in order to increase the Cv of graphite as much as possible for the purpose of improving thermal conductivity. .

C (carbon) content 3.0 to 4.0%, Si (silicon)
The reason why the content is 1.8 to 2.4%, which is high in carbon and low in silicon, is that the higher the carbon content, the lower the thermal stress.

The reason why the upper limit of carbon content was set at 4.0% was to avoid the generation of quiche graphite and floating graphite, and the lower limit was set at 3.0%.
This is because good results cannot be obtained if the content is lower than 3.0%.

Since the thermal conductivity of silicon decreases as its content increases, the upper limit of the content was set at 2.4%, and the lower limit was set at 1.8% due to the risk of chill generation.

Setting the Mn (manganese) content to 0.8% or less is
This is to reduce the mechanical properties due to segregation of manganese at the eutectic cell boundary and to maintain the uniformity of the matrix structure.

The reason why the P (phosphorus) content is set to 0.08% or less is to avoid the generation of shrinkage cavities and the generation of steadite, which is a ternary eutectic of phosphorus and carbon monoiron.

The S (sulfur) content is desirably 0.03% or less when converting graphite to CV.
This is also because it is economical.

To produce general CV graphite cast iron, magnesium,
It is manufactured by adding rare earth elements, calcium, titanium, etc. singly or in combination, and titanium is a particularly useful element in preventing chills in thin-walled items such as brake drums and suppressing the generation of spheroidal graphite. .

CV graphite cast iron having the above components may be used as-cast, but heat treatment not only stabilizes the base structure uniformly and finely but also improves the elastic modulus and damping ability as a material for brake drums. It provides optimum physical and mechanical properties. This heat treatment ranges from 850°C to 9°C.
Perform at about 50°C.

The present invention will be explained in detail below.

Example-1 C: 3.9%, Si in a high frequency furnace with a capacity of 300 kg
: 1°6%, Mn: 0.4%, P: 0.
05%, S: Make a molten metal of 0.03%, Mg
: 4.8%, Ti: 9.1%, RE: 1.0%
, Ca: 4.0%, Si: 48%, Fe
: bal, c7) C■ 150 kg of graphitized alloy was processed by sandwich method with addition of 1.0%, and Y was heated at 1380°C.
It was cast into a shape test piece. On the other hand, the remaining 150Kg is Mg:
3.2%, RE: 1°2%, Ca: 1.0%, Si
: 45% alloy was spheroidized by the sandwich method with 1.6% addition and cast into Y-shaped specimens at 1380'0. The final Si content of each was adjusted to 2.4% and 2.7%.

The CV graphite cast iron products were prepared not only as-cast but also subjected to a standard treatment of holding at 900° C. for 1 hour and then forced air cooling.

The mechanical and physical properties of these specimens are shown in Table 1.

It can be seen that the combination of mechanical and physical properties of the product of the present invention is optimal as a brake drum material.

Example-2 C: 3.1%, Si: '2.1%, Mn: 0
．． Chemical composition of 3% IP = 0.03%, S: 0.021% (7) CV graphite cast iron is made, and as-cast products and 850
Table 2 shows the physical and mechanical properties of the heat-treated material that was held at ℃ for 1 hour and then cooled with forced air.

Example-3 C: 3.5%, Si: 1.8%, Mn: 0.8%
, P: 0.03%, S: 0.025%, Cu
: 0.15%, Sn: 0.012%, Cr:
Make 0.18% molten metal, Mg: 5.2%, RE
: 4.8%, Ca: 3.0%, Si:
Cv graphitized alloy of 45%, Fe: bal, 0.7
% addition, followed by 75% S
Inoculated with i-containing inoculant, JIS, No. A Y-B 1o
Table 3 shows the physical and mechanical properties of the as-cast product and the tempered product.

The product of the present invention, which has the above-mentioned characteristic physical and mechanical properties, has higher strength and ductility than conventional flake graphite cast iron products, and generates less thermal stress and is resistant to severe thermal fatigue. It was confirmed that the product was durable and its lifespan was twice that of conventional products.

Patent applicant Kusaka Rare Metals Research Institute Co., Ltd. Agent
Patent attorney Mitsuo Takahashi F': Zui-'j-1: + Seal of procedural amendment) 1 Indication of the case 1982 Patent Application No. 103809 2 Title of the invention Cv Graphite cast iron brake drum 3 Person making the amendment Relationship to the incident Patent applicant address (residence) 2-3-15 Shiba Daimon, Minato-ku, Tokyo Name (
Name) Current Rare Metal Research Institute 4 Limited Company Address (Residency) 7-3-10-6 Nishi-Shinjuku, Shinjuku-ku, Tokyo
Number of inventions increased by amendment 7 Target of amendment Description (second column of detailed description of invention)
Table and Table 3)

Claims (1)

[Claims] 1. A CV graphite cast iron brake drum having the following chemical components. C: 3.0~4.0% Si: 1.8~2.4%
Mn: ≦0.8% P: ≦0.08% S: ≦0.03 2, C: u: 0.1-0.2%, Sn: 0.0
The CV graphite cast iron brake drum according to claim 1, which contains one or more elements among 1 to 0.02% of Cr and 0.1 to 0.2% of Cr. 3.7i: The C■ graphite cast iron brake drum according to claim 1 or 2, containing 0.05 to 0.15% (residual value). 4. A heat-treated CV graphite cast iron brachitram according to claim 1, 2, or 3.