JP3294685B2 - High thermal conductive corrosion resistant cast iron - Google Patents

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, in particular, brake rotors.

[0002]

2. Description of the Related Art Sliding members and brake members that generate frictional heat are required to have heat resistance and high thermal conductivity. The applicant has
Previously, Japanese Patent Publication No. 17900/1986 proposed a corrosion-resistant cast iron having good characteristics. That is, when the carbon equivalent is in the range of 3.8 to 4.5% by weight, C 2.8 to 4.0% by weight and Si 1.5
To 3.0 wt%, Mn 0.3 to 1.2 wt%, P 0.2 wt% or less, S 0.06 to 0.25 wt%, Cu 0.15 to 3.5 wt%, Cr0. 05 to 0.
Corrosion resistant cast iron having improved rust layer delamination resistance, characterized by containing 5% by weight, 0.05 to 0.5% by weight of Ni and the balance of Fe and impurities.

[0003]

However, with the recent increase in the weight of vehicles due to their high performance and high quality, the load on the sliding members and the brake rotor has become increasingly severe, and the better braking performance has been achieved. There is a need for a material with good durability. To meet this demand, simply increasing the carbon equivalent to promote the growth of graphite causes another problem that the braking effect (friction coefficient) is reduced.

[0004]

[0005] As described above, there is no end to the demand for improving the performance of sliding members, particularly brake members. Accordingly, an object of the present invention is to provide a corrosion-resistant cast iron having a thermal conductivity capable of rapidly releasing frictional heat and a long life.

[0006]

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

More specifically, C and Si in the components are the basic elements constituting cast iron, and the combination changes the form of graphite, which in turn affects the thermal conductivity. Therefore, the value of the carbon equivalent defined by C weight% + ／ Si weight% is used as an index of the cast iron structure. If the carbon equivalent exceeds 5.0% by weight, the amount of ferrite in the cast iron matrix increases, making it difficult to secure sufficient strength. If the content is less than 4.0% by weight, the graphite does not grow sufficiently and sufficient thermal conductivity cannot be secured. Therefore, the carbon equivalent of 4.0 to 4.0
5.0% by weight, C-3.6 to 4.5% by weight and Si
It is set to 1.5-3.0% by weight.

[0008] Cr has the effect of suppressing corrosion of cast iron, improving matrix strength, and improving material strength. However,
When the content is less than 0.2%, the effect is small. On the contrary, when the content exceeds 2.0%, the base structure is deteriorated and other performances are reduced. Therefore, Cr is set in the range of 0.2 to 2.0% by weight. .

The added Ca acts as an element promoting graphite growth. If the amount of Ca is less than 0.02% by weight, the effect is very small, and if it exceeds 0.1% by weight, the effect of spheroidizing graphite is enhanced, so that preferable needle-like graphite is sufficiently obtained. Disappears. Therefore, the addition amount of Ca is set in the range of 0.02 to 0.1% by weight.

[0010] The added Al acts as an adjusting element for the ferrite precipitated in the cast iron matrix. If the amount of Al added is less than 0.02% by weight, oxidation proceeds during the dissolution process, and a sufficient effect cannot be expected. Conversely, if the content exceeds 0.1% by weight, the spheroidizing action of graphite becomes stronger, so that satisfactory needle-like graphite cannot be sufficiently obtained. Therefore, the addition amount of Al is set in the range of 0.02 to 0.1% by weight.

In summary , the high heat conductive corrosion-resistant cast iron for a sliding member of the present invention has a carbon equivalent of 4.0 to 5.0% by weight, a C equivalent of 3.6 to 4.5 % by weight and a Si of 1.5 to 1.5% by weight. 3.0
Wt%, Mn 0.5-1.5 wt%, P0.2
% By weight, S 0.06 to 0.25% by weight, Cu 0.1
5 to 3.5% by weight and 0.2 to 2.0% by weight of Cr, with the balance being Fe and impurities,
0.02-0.1% by weight, Al 0.02-0.1% by weight
Is characterized in that acicular graphite is generated in the tissue by adding.

[0012]

The present invention will now be described by way of examples, which should not be construed as limiting the invention. Example 1 to Example 8 and Comparative Example; Table 1 is a list of the component compositions of Examples 1 to 8 and Comparative Example. In the table, iron Fe
And impurities were omitted.

[0013]

[Table 1]

Using cast iron having the material composition shown in Table 1, a ventilated brake disk having a diameter of 280 mm, a plate thickness of 9 mm, and a bench width of 10 mm was manufactured. The raw materials were dissolved in cupola, electrode graphite, FeCa (Fe30% C
a) and Al (purity: 99.7%). The main mold used in the casting was a green sand mold, and the core used was a shell core. The component compositions of Examples 1 to 8 and Comparative Examples are described in detail below.

Example 1: 3.9% by weight of carbon C 2.0% by weight of silicon Si 1.0% by weight of manganese Mn 1.0% by weight of phosphorus P 0.15% by weight of sulfur S 0.15% by weight of copper Cu 1.0% by weight Impurity minute amount Iron Fe remaining amount Calcium Ca 0.02% by weight addition Aluminum Al 0.06% by weight addition

Example 2 The amount of calcium Ca added was increased in comparison with Example 1. Carbon 3.9 wt% Silicon Si 2.05 wt% Manganese Mn 1.0 wt% Phosphorus P Less than 0.6 wt% Sulfur S 0.15 wt% Copper Cu 1.0 wt% Impurity Fine iron Fe Residual Calcium Ca 0.03% by weight added Aluminum Al 0.06% by weight added

Example 3 In comparison with Example 2, the amount of calcium Ca added was increased. Carbon 3.9 wt% Silicon Si 2.05 wt% Manganese Mn 1.0 wt% Phosphorus P Less than 0.6 wt% Sulfur S 0.15 wt% Copper Cu 1.0 wt% Impurity Fine iron Fe Residual Calcium Ca 0.04% by weight added Aluminum Al 0.06% by weight added

Example 4 The amount of calcium Ca added was increased in comparison with Example 3. Carbon 3.9 wt% Silicon Si 2.05 wt% Manganese Mn 1.0 wt% Phosphorus P Less than 0.6 wt% Sulfur S 0.15 wt% Copper Cu 1.0 wt% Impurity Fine iron Fe Residual Calcium Ca 0.05% by weight added Aluminum Al 0.06% by weight added

Example 5: The components and the amounts added were changed from those of Example 1. 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 Impurity Fine iron Fe Residual amount Calcium added 0.04% by weight Aluminum added 0.04% by weight

Embodiment 6;
Weight percent Cr was added. That is, carbon C 3.9 wt% silicon Si 2.05 wt% manganese Mn 1.0 wt% phosphorus P less than 0.6 wt% sulfur S 0.15 wt% copper Cu 1.0 wt% chromium Cr 0.3 % By weight Impurity minute amount Iron Fe remaining amount Calcium Ca 0.04% by weight addition Aluminum Al 0.06% by weight addition

Embodiment 7: Similarly to Embodiment 3,
0.5% by weight of Cr was added. 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 % By weight Impurity minute amount Iron Fe remaining amount Calcium Ca 0.04% by weight addition Aluminum Al 0.06% by weight addition

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

Comparative Example: Carbon C 3.3% by weight Silicon Si 2.0% by weight Manganese Mn 0.6% by weight Phosphorus P Less than 0.6% by weight Sulfur S less than 0.2% by weight Copper Cu 0.4% by weight Impurity minute amount Iron Fe remaining amount

The life of the brake disk 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 added calcium and the graphite length, and the microstructure of the brake disc was observed.
The length of the graphite was measured, and it was recognized that the length of the graphite was increased almost directly in proportion to the amount of calcium Ca.

FIG. 2 (a) is a micrograph (magnification: 100) showing the metal structure of the cast iron for brake according to the present invention, and FIG. 2 (b) is a micrograph (magnification) showing the metal structure of the conventional cast iron for brake. 100). The conventional graphite shown in dark color in FIG. 2 (b) is short. In contrast, the graphite of the present invention shown in FIG. 2A is sufficiently long.

FIG. 3 is a correlation diagram between the carbon content and the hot fatigue life. The braking from the maximum speed to the stop on the inertia dynamo was repeated until cracks occurred. That is, a life test at high temperature and high load was performed. 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 a rise in the temperature of the brake fluid. A test corresponding to a continuous downhill was performed on the inertia dynamo, and the temperature of the brake fluid was measured as an index of the generated heat. The temperature of the conventional example reached 135 ° C., whereas the temperature of Example 3 was 120 ° C., indicating a temperature decrease of about 15 ° C.

FIG. 5 is a comparison diagram of the braking effect. A braking effect test based on JASOC 406 was performed on the inertia dynamo, and the average value of the braking effect was obtained. The average braking effect of Example 3 was 0.4 or more in terms of the coefficient of friction μ, and the comparative example was less than 0.4.

FIG. 6 is a correlation diagram between Cr content and tensile strength. Example 7 containing 0.5% by weight of Cr has a tensile strength of 16 kg / mm ² , and Example 7 containing 0.5% by weight of Cr has a tensile strength. In Example 8 containing more than 16 kg / mm ² and 1.0% by weight of Cr, the tensile strength was more than 19 kg / mm ² ,
The one containing no Cr is 15 kg / mm ² . That is,
In comparison with Examples 1 to 5 which do not contain Cr, Example 7 is about 1
kg / mm ² , and Example 8 can improve the strength by about 4 kg / mm ² . In addition, when Cr is added, chromium carbide is easily precipitated. 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 high heat conductive corrosion-resistant cast iron for a sliding member of the present invention has a carbon equivalent of 4.0 to 5.0% by weight.
3.6-4.5% by weight of C and 1.5-3.
0% by weight, Mn 0.5-1.5% by weight, P0.
2% by weight or less, S 0.06 to 0.25% by weight, Cu0.
15 to 3.5% by weight and 0.2 to 2.0% by weight of Cr, with the balance being Fe and impurities,
a , characterized in that acicular graphite was formed in the tissue by adding 0.02 to 0.1% by weight of Al and 0.02 to 0.1% by weight of Al , and the needle was improved by increasing the carbon equivalent and adding Ca. Promotes the growth of dendritic graphite, improves the thermal conductivity by the growth of acicular graphite, and at the same time, by adding Al, it is possible to precipitate an appropriate amount of ferrite in the matrix structure, thereby improving the braking performance. It can be achieved. The tensile strength of the material can be improved by increasing the amount of Cr.

[Brief description of the drawings]

FIG. 1 is a correlation diagram between the amount of added calcium and the length of graphite.

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

FIG. 3 is a correlation diagram between carbon content and hot fatigue life.

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

FIG. 5 is a comparison diagram of braking effectiveness.

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

Continuation of the front page (56) References JP-A-61-153256 (JP, A) JP-A-61-26754 (JP, A) JP-A-3-107442 (JP, A) JP-A-61-143554 (JP) JP-A-62-240746 (JP, A) JP-A-63-140064 (JP, A) JP-A-1-247553 (JP, A) JP-A-1-205058 (JP, A) 7-3380 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 37/00 C22C 37/06 C22C 37/08

Claims (1)

(57) [Claims] Claims: 1. A carbon equivalent of 4.0 to 5.0% by weight,
3.6-4.5% by weight and 1.5-3.0% by weight of Si
And Mn 0.5 to 1.5% by weight, P 0.2% by weight
Hereinafter, S 0.06 to 0.25% by weight, Cu 0.15 to
Containing 3.5% by weight and 0.2 to 2.0% by weight of Cr, with the balance being Fe and impurities,
0.02-0.1% by weight, Al 0.02-0.1% by weight
A highly heat-conductive corrosion-resistant cast iron for sliding members, characterized in that needle-like graphite is generated in the structure by adding Cu.