JP2003247014A - Method of producing rotor for disk brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a rotor for a disk brake which has an improved thermal conductivity while securing strength, and has improved thermal cracking resistance. <P>SOLUTION: An Fe-Si based or Fe-Si-C based inoculant containing 1.0 to 3.0 wt.% Sr in 0.3 to 0.6 pts.wt. is added to 100 pts.wt. of the molten metal of flake graphite cast iron. After that, the inoculated molten metal of flake graphite cast iron is cast into the cavities of a mold, and a molding flask is removed before the completion of A<SB>1</SB>transformation. Thus, the rotor for a disk brake formed of flake graphite cast iron having a componential composition containing, by weight, 3.75 to 3.95% C, 1.80 to 2.20% Si, 0.5 to 0.8% Mn, ≤0.10% P, 0.08 to 0.15% S, 0.35 to 0.55% Mo, 0.35 to 0.55% V and 0.05 to 0.15% Cu, and in which the total of carbide forming elements other than Mo and V is ≤0.2%, and the balance Fe with inevitable impurities is produced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a disc brake rotor used for a vehicle disc brake device. In particular, it is suitable for a disc brake rotor mounted on a disc brake device such as a truck on which a high load acts.

[0002]

2. Description of the Related Art Conventionally, disk brake rotors have been strongly required to have high strength and excellent heat crack resistance. In particular, a disc brake rotor used in a disc brake device of a truck where a high load frequently acts is often used under severe conditions.
There is a strong demand for high strength and excellent heat crack resistance.

For this reason, cast steel products have generally been used as the material for the disc brake rotor. However, disc brake rotors made of cast steel are very expensive. Therefore, a low-cost flake graphite cast iron is being studied for development of a material having high strength and excellent thermal crack resistance.

Japanese Patent Publication No. 8-32944 discloses a disc brake rotor made of flake graphite cast iron. This disc brake rotor has a weight ratio of C: 3.5 to 3.7% and Si: 1.40 to 1.72.
%, Mn: 0.5 to 0.8%, Mo: 0.4 to 1.2
%, Ti: 0.05 to 0.10%, V: 0.02 to 0.
35%, Ce: 0.01 to 0.05%, Cu: 0.20
~ 2.0%, Cr: 0.05-1.0% included, balance F
It is made of flake graphite cast iron having a composition of e and unavoidable impurities, and is excellent in heat crack resistance, vibration damping, wear resistance, and strength. The disc brake rotor according to the above-mentioned publication is formed of flake graphite cast iron, not cast steel, and therefore has good castability, low cost, and excellent strength, and the flake graphite has a structure. Since they are dispersed, even if they are repeatedly braked from high speed running, they have excellent vibration damping and wear resistance. Furthermore, since it has high thermal conductivity, it is also excellent in thermal crack resistance.

[0005]

By the way, in recent years, further improvement in heat crack resistance has been demanded for disk brake rotors due to improvement in running performance of vehicles. Especially, in a disc brake rotor used for a disc brake device of a truck where a high load is frequently applied, the demand is very large. However, according to the above-mentioned publication technology, although it can be applied to a disc brake rotor of a passenger car, in a disc brake rotor used in a disc brake device of a truck where a high load frequently acts, improvement in heat crack resistance is achieved. There was a limit to what I could do.

In order to improve the heat crack resistance, it is considered effective to improve the thermal conductivity. However, the disk brake rotor according to the above-mentioned publication technique does not always provide satisfactory thermal conductivity. Specifically, according to the product of the present invention (No. 1) shown in Table 2 of the above publication, the thermal conductivity is 0.096.
calm / sec.degree. C. (.apprxeq.40.14 W / mK), and the thermal conductivity was not always sufficient to further improve the heat crack resistance of the disc brake rotor. By the way, according to the product of the present invention (No. 1) shown in Table 2 of the above publication, Mo: 0.80%, Cu: 1.
80%, Cr: 0.71%, and the contents of Mo, Cu, and Cr are considerably high.

The present invention has been made in view of the above-mentioned circumstances, and manufactures a disc brake rotor capable of improving the thermal conductivity while ensuring the strength, thereby improving the thermal crack resistance. The challenge is to provide a method.

[0008]

The inventor of the present invention is eagerly developing on the basis of the above problems. Then, the present inventor intended to further increase the amount of C to enhance the thermal conductivity and improve the thermal crack resistance. However, if the amount of C is increased, the strength tends to decrease. Therefore, it was decided to increase the strength by adding Mo and V. In addition, the combination of alloy elements and the addition amount that suppresses the decrease in thermal conductivity as much as possible while maintaining high strength were reviewed. Since Ti (graphite refining / eutectic graphitizing element) and Ce (spheroidizing element), which are elements that influence the graphite shape as alloying elements, have an effect on the graphite shape even if added in a small amount, and it becomes difficult to manage the components. I decided to avoid blending. Furthermore, although addition of Mo and V is effective for increasing strength, it promotes chilling, so an Fe-Si-based or Fe-Si-C-based inoculant containing Sr effective for suppressing chilling is added. By doing so, chilling of the flake graphite cast iron was suppressed. It has been decided to manufacture a disc brake rotor from flake graphite cast iron that achieves both such high thermal conductivity and high strength, and to improve the heat crack resistance and strength of the disc brake rotor. Based on such a design concept, the present inventor has developed a method for manufacturing a disc brake rotor according to the present invention.

That is, in the method for manufacturing a disc brake rotor according to the present invention, Fe-containing 1.0 to 3.0% by weight of Sr with respect to 100 parts by weight of molten flake graphite cast iron.
Si-based or Fe-Si-C-based inoculant 0.3-0.6
After adding 1 part by weight, the inoculated flake graphite cast iron melt is cast into a cavity of the mold, and the mold is unframed before the completion of A ₁ transformation, whereby the weight ratio of C: 3.75-
3.95%, Si: 1.80 to 2.20%, Mn: 0.
5 to 0.8%, P: 0.10% or less, S: 0.08 to
0.15%, Mo: 0.35-0.55%, V: 0.3
5 to 0.55%, Cu: 0.05 to 0.15%, a total of carbide forming elements other than Mo and V is 0.2% or less, and a flake graphite cast iron having a composition composition of balance Fe and unavoidable impurities. The disc brake rotor thus formed is manufactured. In this specification,% means% by weight unless otherwise specified.

The reasons for limiting the composition of the flake graphite cast iron forming the disk derailleur rotor will be described.

C has a great influence on the formation of flake graphite. When the amount of C is low, flake graphite is not sufficiently formed,
The thermal conductivity is low. When the amount of C is excessive, the thermal conductivity is high, but the strength is low. Therefore, set the C amount to 3.
It was set to 75 to 3.95%. Considering increasing the thermal conductivity while ensuring the strength, the C content is 3.78 to 3.9.
It can be 2%, 3.80 to 3.90%. The lower limit of the C content is 3.76 depending on the required characteristics.
%, 3.77% can be exemplified, and the upper limit of the amount of C that can be combined with the lower limit thereof can be 3.94%, 3.93%.

The amount of Si is a graphitization promoting element and is useful for depositing good flake graphite and ensuring good castability. However, if the amount of Si becomes excessive, the strength decreases. Therefore, the amount of Si is set to 1.80 to 2.20%. Above all, the amount of Si is 1.81 to 2.18%, 1.82 to 2.
It can be 15%.

The amount of Mn must be 0.5% or more in order to maintain the required strength of flake graphite cast iron. However, if it exceeds 0.8%, an effective strength improving effect is not recognized, and in addition,
MnS is likely to precipitate, so the content was made 0.5 to 0.8%.

The amount of P is set to 0.10% or less is 0.1
This is because if it exceeds 0%, chill tends to occur. Further, the amount of S is set to 0.08 to 0.15% because if it is less than 0.08%, flake graphite is less likely to precipitate, and if it exceeds 0.15%, chill is likely to occur.

Mo is a carbide forming element. If the amount of Mo is relatively low, the strength will be low, and if the amount of Mo is excessive, the thermal conductivity will be reduced, and chill will be more likely to occur. So Mo
The amount was 0.35 to 0.55%. Considering that chilling is suppressed, strength is secured, and thermal conductivity is increased, the Mo content is 0.36 to 0.55%, 0.40 to 0.5.
It can be 0%. Depending on the required characteristics, the lower limit of the Mo amount can be 0.36% and 0.37%, and the upper limit of the Mo amount that can be combined with the lower limit is 0.54% and 0.53. % Can be illustrated.

V is a carbide forming element. If the V content is low, the strength is low, and if the V content is excessive, the thermal conductivity is lowered and chilling is likely to occur. Therefore, the V amount is 0.35
Was set to 0.55%. Considering that chill is suppressed, strength is secured, and thermal conductivity is increased, the V amount can be set to 0.36 to 0.55% and 0.37 to 0.50%. Depending on the required characteristics, the lower limit of the V amount can be 0.36% and 0.37%, and the upper limit of the V amount that can be combined with the lower limit is 0.54.
% And 0.53% can be exemplified. The total amount of Mo and V can be 0.70 to 1.10%,
In particular, it can be 0.75-1.00%.

Cu supplements the strength improving effect of Mo and V. If Cu is too small, high strength cannot be obtained. Therefore, the amount of Cu is added at 0.05 to 0.15%. Among them, the Cu content is 0.06 to 0.14%,
It can be set to 07 to 0.13%. Depending on the characteristics required, the lower limit of the Cu content is 0.06%,
0.07% can be exemplified, and C that can be combined with the lower limit value
The upper limit of the u amount may be 0.14% and 0.13%.

Examples of carbide forming elements other than Mo and V include Cr, Sn and Nb. These promote redeburite formation, that is, chilling, and adversely affect the thermal conductivity.
Therefore, the total sum is set to 0.2% or less. In order to suppress redevelitization, it can be made 0.18% or less and 0.15% or less. Since it is not easy to control the composition of Ti and Ce, it is preferable not to contain Ti and Ce as active elements.

According to the method for manufacturing a disc brake rotor according to the present invention, F containing Sr: 1.0 to 3.0% is contained.
An e-Si-based or Fe-Si-C-based inoculant is used.
Assuming that the inoculant is 100%, Sr is contained in 1.0 to 3.0% of 100%. Sr is effective in suppressing chilling, but easily evaporates, so Sr is added as an Fe-Si-based or Fe-Si-C-based inoculant. Fe-Si system or Fe-Si containing Sr
By inoculating the -C type inoculant, chilling of flake graphite cast iron is suppressed. The inoculant is added in an amount of 0.3 to 0.6% (parts by weight) with respect to the melt of the flake graphite cast iron when the melt of the flake graphite cast iron is 100% (parts by weight). 0.3 ~
Addition of 0.6% (parts by weight) means externally added to the melt of flake graphite cast iron, and the addition of the inoculant makes the total 1%.
It becomes 00.3 to 100.6% (parts by weight). If the addition ratio of the inoculant is less than 0.3% (parts by weight), the improvement effect by inoculation is small, and if it exceeds 0.6% (parts by weight), inoculation unevenness is easily induced. The temperature of the molten metal at the time of inoculation is preferably 1480 to 1550 ° C.

After inoculation, the inoculated melt of flake graphite cast iron is cast into the molding cavity of the mold. After the molten metal is solidified, the mold is unframed before the A ₁ transformation is completed. If the mold is unframed before the A ₁ transformation is completed, it becomes possible to precipitate a dense pearlite matrix and increase the strength. As the mold, it is possible to use a mold made of raw sand, furan sand or the like.

The disc brake rotor manufactured by the above manufacturing method can have a thermal conductivity of 50 W / mK or more. In particular, since the structure is strengthened by adding Mo and V, the tensile strength can be 190 MPa or more and the thermal conductivity can be 50 W / mK or more. If the amount of C is large, the thermal conductivity can be 60 W / mK or more and the thermal conductivity can be 70 W / mK or more. By improving the thermal conductivity in this way, the thermal crack resistance of the disc brake rotor can be improved. Despite the large amount of C, the tensile strength is 190MP because the structure is strengthened by the addition of alloying elements such as Mo, V and Cu.
It is as high as a or more and has excellent wear resistance.

According to the above-mentioned manufacturing method, the composition of the molten metal is appropriate, even though Mo, V and the like are contained, and the Fe-Si system or Fe-Si containing Sr is contained.
Since it is inoculated with -C type inoculant, chilling is also suppressed.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. The present embodiment is a case where the present invention is applied to a disc brake rotor for a truck mounted in a brake device for a truck under a high load. Using a high frequency induction melting furnace, a melt of flake graphite cast iron compounded to have a target composition was melted in an air atmosphere. While pouring the molten metal into a pouring ladle (melting temperature 1480 ° C.), a Fe—Si inoculum containing Sr: 2% was inoculated. The ratio of the inoculant to be added is as follows: flake graphite cast iron melt 1
It was 0.5 parts by weight with respect to 00 parts by weight. The Fe-Si inoculant containing Sr is effective in preventing chilling, and contains 70 to 80% of Si.

Molten graphite cast iron, which had been inoculated as described above, was poured from a pouring ladle into the cavity of the mold for casting (casting temperature: 1360 to 1420 ° C.). The mold is made of green sand. Then, before the cast product completed the A ₁ transformation, the mold surrounding the cast product was opened, the cast product was exposed to the atmosphere, and the cast product was air-cooled. Thus, if the mold is unframed before completing the A ₁ transformation, it becomes possible to precipitate a dense pearlite matrix and increase the strength.

As shown in FIGS. 1 and 2, a cast disc brake rotor casting 10 has a cylindrical portion 12 having a central hole 11 and a coaxial extension at one end portion of the cylindrical portion 12 in the axial direction. It has the sliding parts 13 and 14 provided, and the flange part 15 extended coaxially at the other end of the tubular part 12 in the axial direction. The textures of the sliding portions 13 and 14 and the flange portion 15 were formed of a matrix mainly composed of pearlite and a large number of flake graphite dispersed in the matrix. No chills were found.

Cast product 10 of the disc brake rotor.
From the flange portion 15 of the tensile test piece (JIS Z 220
No. 14 test piece The parallel part is machined out) and the sliding part 13 of the casting 10 of the disc brake rotor is cut out.
Kara thermal diffusion test piece (disk with a diameter of 10 mm and a thickness of 2 mm)
Was cut out and subjected to a tensile test and a thermal diffusivity measurement test. In the thermal diffusivity measurement test, a thermal diffusivity (α) of the thermal diffusive test piece was determined by a laser flash method using a thermal constant measuring device TC-3000 manufactured by Vacuum Riko Co., Ltd. based on the following formula. Further, the thermal conductivity was calculated from the thermal diffusivity (α), specific heat and density. Specifically, the surface of the thermal diffusion test piece was irradiated with a pulse laser to rapidly heat the surface, and the temperature increase on the back surface opposite to the thermal diffusion test piece was recorded.
The thermal conductivity λ of the thermal diffusion test piece was calculated based on the following equation.

Thermal conductivity λ = α · Cp · ρ (Cp: specific heat of thermal diffusion test piece, ρ: density of thermal diffusion test piece) α = 1.37 × L / (π · t _0.5 ) where L is The thickness of the thermal diffusion test piece, t _0.5 , indicates the time for the temperature to rise to half the maximum temperature rise Tmax on the back surface of the thermal diffusion test piece.

[0028]

[Table 1]

Table 1 shows the test results together with the component composition (analytical value) of the test piece. In Table 1, Test Example No. 1 to N
o. 9 indicates an invention product. In the invention product, the total sum of carbide forming elements (Cr, Sn, Nb, etc.) other than Mo and V is 0.2.
% Or less. Test example No. 10-No. 14 is a comparative product.

As shown in Table 1, Test Example N which is an invention product
o. 1-No. In No. 9, the tensile strength is 190 MPa or more, the thermal conductivity is 50 W / mK or more, high strength,
It was compatible with high thermal conductivity. In addition, the occurrence of chill was not recognized. In particular, the test example No. 1, the tensile strength was 190 MPa or more and the thermal conductivity was 7
It was 4 W / mK, which was quite high. Further, test example No. 3,
No. 5, No. In No. 9, the tensile strength was 195 MPa or more, and the thermal conductivity was 64 W / mK, which was considerably high. Inventive test example No. 1-No. Even when the disc brake rotor according to No. 9 was mounted on an actual machine and tested, the heat crack resistance was good.

Test example No. which is a comparative product. In No. 10, although the amount of C is excessive and the thermal conductivity is as high as 76 W / mK,
The tensile strength was low at 188 MPa. In addition, test example No. In No. 11, although the Cu content was low and the thermal conductivity was high at 72 W / mK, the tensile strength was 187 MPa.
Was low. Furthermore, the test example No. which is a comparative product. In 12,
The C content was as low as 3.72% and the tensile strength was good, but the thermal conductivity was low at 48 W / mK. Test example No. which is a comparative product. In No. 12, the V content was 0.57%, which was excessive and the tensile strength was good, but the thermal conductivity was 48 W.
As low as / mK, chills were also generated. Furthermore, the test example No. which is a comparative product. No. 13, the Mo content was 0.57%, which was excessive, and although the tensile strength was good, the thermal conductivity was 47 W /
As low as mK, chills were generated. In addition, test example No. In No. 14, since the inoculum containing Sr was not inoculated, the thermal conductivity was low at 48 W / mK, and chills were generated.

As is clear from the above-mentioned test example, according to this embodiment, the thermal conductivity can be improved while ensuring the strength of the disc brake rotor. This can improve the heat crack resistance. Therefore, it is suitable for a disc brake rotor for a truck, in which a high load frequently acts.

From the above description, the following technical idea can be understood. (Appendix 1) In claim 1, the flake graphite cast iron forming the disc brake rotor has a thermal conductivity of 60 W / mK.
The above is a method for manufacturing a disc brake rotor. (Appendix 2) In claim 1, the flake graphite cast iron forming the disc brake rotor has a thermal conductivity of 65 W / mK.
The above is a method for manufacturing a disc brake rotor. (Additional Item 3) In claim 1, the flake graphite cast iron forming the disc brake rotor has a thermal conductivity of 70 W / mK.
The above is a method for manufacturing a disc brake rotor. (Appendix 4) In claim 1, the flake graphite cast iron forming the disc brake rotor has a tensile strength of 200 MPa.
The above is a method for manufacturing a disc brake rotor. (Appendix 5) In claim 1, the flake graphite cast iron forming the disc brake rotor has a tensile strength of 220 MPa.
The above is a method for manufacturing a disc brake rotor. (Appendix 6) In claim 1, the flake graphite cast iron forming the disc brake rotor has a tensile strength of 200 MPa.
As described above, the method for manufacturing a disc brake rotor, wherein the flake graphite cast iron forming the disc brake rotor has a thermal conductivity of 55 W / mK or more. (Appendix 7) In claim 1, the flake graphite cast iron forming the disc brake rotor has a tensile strength of 200 MPa.
As described above, the method for producing a disc brake rotor, wherein the flake graphite cast iron forming the disc brake rotor has a thermal conductivity of 60 W / mK or more. (Appendix 8) A method for manufacturing a rotor for a disc brake used in a large vehicle such as a truck according to claim 1.

[0034]

As described above, according to the method for manufacturing a disc brake rotor of the present invention, it is possible to manufacture a disc brake rotor having improved thermal conductivity while ensuring strength. Also, chilling can be suppressed. According to such a disc brake rotor,
The heat crack resistance can be improved.

Further, according to the method for manufacturing a disc brake rotor according to the present invention, compared with the above-mentioned prior art, the trace additive elements (Ti, Ce) having a narrower composition range are not contained as positive elements. In addition, it is easy to manage the components during smelting, and to manufacture disc brake rotors such as disc brake rotors for trucks, which were cast steel products in the past, at low cost with good productivity using flake graphite cast iron with good productivity. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a manufactured cast disc brake rotor.

FIG. 2 is a plan view of a manufactured cast disc brake rotor.

[Explanation of symbols]

In the figure, 10 is a cast product of a disc brake rotor, 1
Reference numerals 3 and 14 denote sliding portions.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16D 65/12 F16D 65/12 EU

Claims (3)

[Claims] 1. Fe-Si containing 1.0 to 3.0% by weight of Sr with respect to 100 parts by weight of a melt of flake graphite cast iron.
System or Fe-Si-C inoculant 0.3 to 0.6 parts by weight is added, and the inoculated flake graphite cast iron melt is cast into the cavity of the mold, and before the completion of A ₁ transformation, By unraveling the mold, the weight ratio of C: 3.75-3.
95%, Si: 1.80 to 2.20%, Mn: 0.5 to
0.8%, P: 0.10% or less, S: 0.08 to 0.1
5%, Mo: 0.35-0.55%, V: 0.35-
0.55%, Cu: 0.05 to 0.15%, Mo and V
Other than carbide-forming elements other than 0.2%, balance Fe
And a method for manufacturing a disc brake rotor, which comprises manufacturing a disc brake rotor formed of flake graphite cast iron having a composition of inevitable impurities. 2. The thermal conductivity of the flake graphite cast iron forming the disc brake rotor according to claim 1, which is 50 W / mK.
The above is a method for manufacturing a disc brake rotor. 3. The tensile strength of the flake graphite cast iron forming the disc brake rotor according to claim 1, is 190 MPa.
The above is the method of manufacturing a disc brake rotor, wherein the flake graphite cast iron forming the disc brake rotor has a thermal conductivity of 50 W / mK or more.