JPH0770693A - Corrosion resistant cast iron having high heat conductive - Google Patents

Abstract

PURPOSE:To provide corrosion resistant cast iron capable of swiftly releasing frictional heat and having a long service life. CONSTITUTION:The one constituted of a compsn. contg., by weight, 3.0 to 4.5% C in the range of 4.0 to 5.0% carbon equivalent and 1.5 to 3.0% Si, contg. 0.5 to 1.5% Mn, <=0.2% P, 0.06 to 0.25% S, 0.15 to 3.5% Cu and increased 0.2 to 2.0% Cr, and the balance Fe with impurities is furthermore added with 0.02 to 0.1%. Ca and 0.02 to 0.1% Al. Thus, by the improvement of the carbon equivalent and the addition of Ca, the growth of graphite is promoted, and by the growth of graphite, its heat conductivity is improved. Then, by the increase of the amt. of Cr, the strength of the material is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion-resistant cast iron suitable for sliding members of vehicles such as passenger cars and industrial machines, especially for brake rotors.

[0002]

2. Description of the Related Art Sliding members and brake members which generate frictional heat are required to have heat resistance and high thermal conductivity. The applicant is
Previously, Japanese Patent Publication No. 61-17900 proposed a corrosion-resistant cast iron with good characteristics. That is, in the range of carbon equivalent 3.8 to 4.5% by weight, C 2.8 to 4.0% by weight and Si 1.5
.About.3.0 wt%, Mn 0.3 to 1.2 wt%, P 0.2 wt% or less, S0.06 to 0.25 wt%, Cu 0.15 to 3.5 wt%, Cr0. 05-0.
A corrosion-resistant cast iron with improved delamination resistance of a rust layer, characterized by containing 5% by weight, 0.05 to 0.5% by weight Ni, and Fe and impurities as the balance.

[0003]

However, with the recent trend toward higher performance and higher grades of vehicles, the weight of the sliding members and the brake rotor is becoming more and more severe, and the braking performance is better. , Durable materials are required. In order to meet this demand, even if the carbon equivalent is simply increased to promote the growth of graphite, another problem occurs that the braking effect (friction coefficient) is reduced this time.

In addition, it is necessary to further reduce the squeal of the brake due to the demand for higher quality and improvement of the commercial property.

As described above, there is no end to the demand for improving the performance of sliding materials, especially brake members. Therefore, an object of the present invention is to provide a corrosion-resistant cast iron which has a thermal conductivity that can quickly release frictional heat and a long life.

[0006]

Means and Actions for Solving the Problems The present inventor diligently continued the research based on Japanese Patent Publication No. 61-17900 and found that the addition of Ca and Al and the increase of Cr were effective. succeeded in.

More specifically, C and Si in the components are basic elements constituting cast iron, and the combination thereof changes the morphology of graphite, which in turn affects the thermal conductivity. Therefore, the value of carbon equivalent defined by C weight% + 1 / 3Si weight% is used as an index of the cast iron structure. If this carbon equivalent exceeds 5.0% by weight, the amount of ferrite in the cast iron matrix increases and it becomes difficult to secure sufficient strength. Further, if it is less than 4.0% by weight, the graphite does not grow sufficiently and sufficient thermal conductivity cannot be secured. Therefore, the carbon equivalent is 4.0 to
Within the range of 5.0% by weight, C is set to 3.0 to 4.5% by weight and Si is set to 1.5 to 3.0% by weight.

[0008] Cr has the effect of suppressing the corrosion of cast iron, improving the matrix strength, and improving the material strength. However,
If it is less than 0.2%, its effect is small, and on the contrary, if it exceeds 2.0%, the matrix structure is deteriorated and other performances are deteriorated. Therefore, Cr is set in the range of 0.2 to 2.0% by weight. .

The added Ca acts as a promoting element for graphite growth. If the addition amount of Ca is less than 0.02% by weight, the effect is very small. On the contrary, if it exceeds 0.1% by weight, the action of spheroidizing the graphite is strengthened, so that preferable acicular graphite is sufficiently obtained. Disappear. Therefore, the addition amount of Ca is set in the range of 0.02 to 0.1% by weight.

Further, the added Al acts as an adjusting element for the ferrite precipitated in the cast iron matrix. If the added amount of Al is less than 0.02% by weight, oxidation proceeds in the dissolution process, and a sufficient effect cannot be expected. On the other hand, if it exceeds 0.1% by weight, the effect of spheroidizing the graphite is strengthened, so that preferable acicular graphite cannot be sufficiently obtained. Therefore, the amount of Al added is set in the range of 0.02 to 0.1% by weight.

In summary of the above, the present invention has a carbon equivalent of 4.0.
To 5.0 wt%, C3.0 to 4.5 wt% and Si1.5 to 3.0 wt% are contained, and Mn0.5 to
1.5 wt%, P 0.2 wt% or less, S0.06-0.
25% by weight, 0.15 to 3.5% by weight of Cu and 0.2 to 2.0% by weight of Cr, with the balance being Fe and impurities, and 0.02 to 0.1% by weight of Ca. , Al 0.02 to 0.1% by weight is added.

[0012]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. Examples 1 to 8 and Comparative Example; Table 1 is a list of component compositions of Examples 1 to 8 and Comparative Example. In the table, iron Fe
And impurities were omitted.

[0013]

[Table 1]

Ventilated brake discs having a diameter of 280 mm, a plate thickness of 9 mm and a bench width of 10 mm were manufactured using cast iron having the material composition shown in Table 1. In addition, the raw materials are melted in cupola, and electrode graphite, FeCa (Fe30% C
a alloy) and Al (purity 99.7%) were used to adjust the components. The main mold in casting was a green sand mold, and the core was a shell core. The component compositions of Examples 1 to 8 and Comparative Example will be described in detail below.

Example 1 Carbon C 3.9% by weight Silicon Si 2.05% by weight Manganese Mn 1.0% by weight Phosphorus P less than 0.6% by weight Sulfur S 0.15% by weight Copper Cu 1.0% by weight Impurity Minor amount Fe Fe Residual amount Calcium Ca 0.02 wt% addition Aluminum Al 0.06 wt% addition

Example 2; Compared with Example 1, the amount of calcium Ca added was increased. That is, carbon C 3.9% by weight silicon Si 2.05% by weight manganese Mn 1.0% by weight phosphorus P less than 0.6% by weight sulfur S 0.15% by weight copper Cu 1.0% by weight impurities minute amount iron Fe Residual amount Calcium Ca 0.03% by weight added Aluminum Al 0.06% by weight added

Example 3 Compared to Example 2, the amount of calcium Ca added was increased. That is, carbon C 3.9% by weight silicon Si 2.05% by weight manganese Mn 1.0% by weight phosphorus P less than 0.6% by weight sulfur S 0.15% by weight copper Cu 1.0% by weight impurities minute amount iron Fe Residual amount Calcium Ca 0.04 wt% added Aluminum Al 0.06 wt% added

Example 4 The amount of calcium Ca added was increased as compared with Example 3. That is, carbon C 3.9% by weight silicon Si 2.05% by weight manganese Mn 1.0% by weight phosphorus P less than 0.6% by weight sulfur S 0.15% by weight copper Cu 1.0% by weight impurities minute amount iron Fe Residual amount Calcium Ca 0.05% by weight added Aluminum Al 0.06% by weight added

Example 5: Compared to Example 1, the components and the addition amount were changed over the entire surface. That is, carbon C 3.6% by weight silicon Si 2.7% by weight manganese Mn 1.0% by weight phosphorus P less than 0.6% by weight sulfur S 0.15% by weight copper Cu 1.0% by weight impurities minute amount iron Fe Residual amount Addition of calcium 0.04% by weight Addition of aluminum 0.04% by weight

Example 6: 0.3 compared with Example 3
Weight% Cr was added. That is, carbon C 3.9% by weight silicon Si 2.05% by weight manganese Mn 1.0% by weight phosphorus P less than 0.6% by weight sulfur S 0.15% by weight copper Cu 1.0% by weight chromium Cr 0.3 Weight% Impurity Minor amount Fe Fe Residual amount Calcium Ca 0.04 wt% addition Aluminum Al 0.06 wt% addition

Embodiment 7: Similarly to Embodiment 3,
0.5 wt% Cr was added. That is, carbon C 3.9% by weight silicon Si 2.05% by weight manganese Mn 1.0% by weight phosphorus P less than 0.6% by weight sulfur S 0.15% by weight copper Cu 1.0% by weight chromium Cr 0.5 Weight% Impurity Minor amount Fe Fe Residual amount Calcium Ca 0.04 wt% addition Aluminum Al 0.06 wt% addition

Example 8: Similarly to the above Example 3,
1.0 wt% Cr was added. That is, carbon C 3.9% by weight silicon Si 2.05% by weight manganese Mn 1.0% by weight phosphorus P less than 0.6% by weight sulfur S 0.15% by weight copper Cu 1.0% by weight chromium Cr 1.0 Weight% Impurity Minor amount Fe Fe Residual amount Calcium Ca 0.04 wt% addition Aluminum Al 0.06 wt% addition

Comparative Example: Carbon C 3.3 wt% Silicon Si 2.0 wt% Manganese Mn 0.6 wt% Phosphorus P less than 0.6 wt% Sulfur S less than 0.2 wt% Copper Cu 0.4 wt% Impurity Minor amount Iron Fe Residual amount

Life of the brake disc having the above-mentioned composition,
The evaluation results of the cooling performance and the braking effect will be specifically described with reference to FIGS. Fig. 1 is a correlation diagram between the amount of calcium added and the length of graphite. The microstructure of the brake disk was observed,
The length of graphite was measured, and it was confirmed that the graphite lengthened in almost direct proportion to the amount of calcium Ca.

FIG. 2 (a) is a photomicrograph (magnification 100) showing the metallographic structure of the cast iron for brakes according to the present invention, and FIG. 2 (b) is a photomicrograph (magnification) showing the metallographic structure of the conventional cast iron for brakes. 100). The conventional graphite shown in dark color in FIG. 2B is short. On the other hand, the graphite of the present invention shown in FIG. 2 (a) is sufficiently long.

FIG. 3 is a correlation diagram of carbon content and hot fatigue life. Braking from the maximum speed to the stop was repeated on an inertia dynamo until a crack was generated. That is, a life test was performed at high temperature and high load. In Example 3 having a large amount of carbon, the life was extended to 4 to 5 times that of the conventional example.

FIG. 4 is a comparison diagram of the temperature rise of the brake fluid. A test corresponding to continuous downhill was carried out on the inertia dynamo, and the temperature of the brake fluid was measured as an index of the heat generated. In the conventional example, the temperature reached 135 ° C, whereas in Example 3, the temperature was 120 ° C, and a temperature decrease of about 15 ° C was observed.

FIG. 5 is a comparative view of the braking effectiveness. A braking effectiveness test according to JASOC 406 was carried out on an inertia dynamo, and an average value of the braking effectiveness was obtained. The average braking effectiveness of Example 3 was 0.4 or more in terms of the friction coefficient μ, and it was less than 0.4 in the comparative example.

FIG. 6 is a correlation diagram of the amount of Cr and the tensile strength. Example 7 containing 0.5% by weight of Cr had a tensile strength of 16 kg / mm ² , and Example 7 containing% by weight of Cr had a tensile strength. Of 16 kg / mm ² and 1.0% Cr by weight in Example 8 has a tensile strength of 19 kg / mm ^{2 or} more,
The content not containing Cr is 15 kg / mm ² . That is,
In comparison with Examples 1 to 5 containing no Cr, Example 7 has about 1
kg / mm ² and Example 8 can improve the strength by about 4 kg / mm ² . When Cr is added, chromium carbide is likely to precipitate. Chromium carbide reduces braking performance. Therefore, the present invention is characterized in that the precipitation of chromium carbide is suppressed by increasing the carbon equivalent, and the amount of Cr can be increased.

[0030]

As described above, the present invention contains C3.0-4.5% by weight and Si1.5-3.0% by weight in the carbon equivalent range of 4.0-5.0% by weight. And Mn0.
5 to 1.5% by weight, P 0.2% by weight or less, S0.06 to
0.25% by weight, 0.15 to 3.5% by weight of Cu, and 0.2 to 2.0% by weight of Cr, with the balance being Fe and impurities, and 0.02 to 0.1% by weight of Ca. %, Al 0.02 to 0.1% by weight is added, the growth of graphite is promoted by the improvement of carbon equivalent and the addition of Ca, and the thermal conductivity is improved by the growth of graphite. By adding Al, it is possible to precipitate a proper amount of ferrite in the matrix structure, and thereby improve the braking performance. In addition, there is an effect that sliding characteristics are improved by the growth of graphite, and further, generation of brake noise can be suppressed by changing the resonance frequency. The tensile strength of the material can be improved by increasing the amount of Cr.

[Brief description of drawings]

[Figure 1] Correlation diagram between the amount of calcium added and the length of graphite

FIG. 2A is a micrograph showing a metal structure of cast iron for brakes according to the present invention (magnification 100), and FIG. 2B is a micrograph showing a metal structure of conventional cast iron for brakes (magnification 10).
0)

[Fig. 3] Correlation diagram of carbon content and hot fatigue life

FIG. 4 is a comparison diagram of temperature rise of brake fluid.

[Figure 5] Comparison of braking effectiveness

FIG. 6 is a correlation diagram of Cr content and tensile strength.

Claims (1)

[Claims] 1. C3.0-4.5% by weight and Si1.5-3.0 in the range of carbon equivalent 4.0-5.0% by weight.
% By weight, Mn 0.5-1.5% by weight, P0.2
Wt% or less, S0.06-0.25 wt%, Cu0.1
5 to 3.5% by weight and 0.2 to 2.0% by weight of Cr, and the balance of Fe and impurities, and 0.02 to 0.1% by weight of Ca and 0.02 to 0% of Al. .1
High thermal conductivity corrosion-resistant cast iron characterized by having added wt%.