JP2001287018A - Al-BASED ALLOY-MADE COMPLEX BRAKE DISK AND ITS MANUFACTURING METHOD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To economically manufacture a brake disk satisfying both of the improvement of wear resistance and the maintenance of heat shock resistance by intensively and dispersively strengthening SiC limited to suitable grain size only on a sliding surface. SOLUTION: The Al-Si alloy-made brake disk is fully integrated by melt- sticking the sliding surface 1 which strengthens the wear resistance by dispersing 5-30 wt.% SiC having 3-50 μm grain diameter, and a heat radiation surface 2 composed of only Al-Si alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake disk made of an Al-based alloy for use in railway vehicles and the like.

[0002]

2. Description of the Related Art As a brake disk for railway vehicles, cast iron material is used from the beginning of the operation of the Shinkansen, and the precipitated graphite reduces the thermal shock caused by rapid heating and quenching during brake control. Abrasion resistance due to action has also been highly evaluated. However, as the speed of the vehicle increases, the characteristics required for brake discs, especially the thermal shock resistance, can be raised to a higher level.On the other hand, as the prerequisite for speeding up the vehicle body, weight reduction of individual components has become increasingly important. The commercialization of brake discs based on alloys has been developed and studied.

[0003] After the prior art such as JP-A-2-25538 and JP-A-3-47945, in which ceramics such as Al ₂ O ₃ and SiC are dispersed and strengthened in an Al-Mg alloy, the applicant of the present invention has previously published the Japanese Patent Application Laid-Open No. No. 2,797,770 has proposed a brake disk in which SiC is uniformly dispersed and strengthened. This prior application relates to an Al—Si alloy containing 6 to 13% by weight of Si,
SiC having a particle size of 3 to 50 μm is added to the matrix alloy in an amount of 5 to 30 μm.
The gist of the present invention is a brake disc formed by casting a material uniformly dispersed and strengthened in the range of weight%.

Conventionally, when the molten metal has an Al-Mg base phase, the added SiC undergoes a decomposition reaction to C and Si, and the generated C and molten Al form Al carbide to significantly impair the fluidity of the molten metal. This makes it more difficult to cast a complicated shape having a large number of complicated heat dissipation fans, but this earlier application claims that the generation of the Al carbide was prevented and the stall of the molten metal flow was prevented.

[0005]

The greatest object of the present invention is to improve the abrasion resistance of the sliding surface, not to mention the dispersion and mixing of SiC particles. Therefore, if only the wear resistance is considered, the wear resistance is improved by increasing the addition amount of the SiC particles, but the sliding surface is caused by rapid heat and rapid cooling during brake control in addition to the wear resistance. Since direct impact of thermal shock is unavoidable, simply increasing the amount of SiC unnecessarily causes loss of elongation, leading to deterioration of thermal shock. Also, the focus of the Al-based alloy brake discs was originally aimed at one blade that responded to the absolute proposition of reducing the weight of the entire vehicle, and it was based on this premise that a large amount of SiC with a large specific gravity was blended. It will go backwards.

In order to enhance the wear resistance by dispersing SiC, it is considered that the purpose can be achieved by intensively mixing SiC only on the target sliding surface. In fact, if the grain size of SiC is selected to be large and added to the molten metal and poured into a mold having a lower sliding surface, it is certain that Si having a large specific gravity during solidification in the mold.
Although C naturally sediments and a sliding surface with a high density of SiC is obtained, the sedimentation of SiC is already severe in the ladle before pouring, and the uneven distribution of SiC in the molten metal already occurs in the ladle and smooth. Casting becomes impossible, and if SiC particles large enough to produce such a result are interposed in the matrix, the strength, the thermal shock resistance, the machinability and the like are significantly reduced, and the original mission of the brake disk is maintained. Can be a serious flaw in the above.

Japanese Patent Application Laid-Open No. Hei 5-196071 discloses that the wear resistance of the sliding surface of a disk rotor made of Al or an Al-based alloy for light-load automobiles and the like and the high-temperature strength of parts other than the sliding surface are high. This is a conventional technique that aims to achieve improvement at the same time. Al-alloy powder is mixed with coarse-grained reinforcing particles (for example, iron powder, metal such as SiC or ceramics) to form a preformed body that is pressure-formed, and a disk rotor-shaped rough material is separately cast with the Al-alloy. I do. In order to adapt to the characteristics required for each part of a different disk rotor, several types of preforms are produced with different mixing ratios of reinforcing particles of different particle sizes, and the preforms are respectively formed at predetermined locations of the coarse material. Is heated until the temperature reaches the half-melting temperature of the Al-based alloy, the high-heated rough material is set in a preheated mold, and a step of further press-forming is performed.

However, this conventional technique has many manufacturing steps,
The number and types of materials (preforms) to be assembled are large and extremely complicated. In addition, since the solid-state bonding is performed while the oxidation reaction is activated at a high temperature, atmosphere adjustment is indispensable. Isn't it necessary to impose a heavy burden on equipment costs such as pressing, work efficiency, and daily maintenance?

In order to solve the above problems, the present invention intensively disperses and strengthens SiC having an appropriate grain size only on the sliding surface to achieve both improvement of abrasion resistance and maintenance of thermal shock resistance. An object of the present invention is to provide a technology for economically manufacturing a brake disc.

[0010]

The Al-Si according to the present invention
An alloy brake disk is made of an Al-Si alloy containing 6 to 13% by weight of Si and containing 5 to 50 μm of SiC having a particle size of 3 to 50 μm.
The sliding surface 1 in which abrasion resistance is enhanced by dispersing 30% by weight and the heat radiating surface 2 made of only the Al-Si alloy are welded and completely integrated.

[0011] As a method of manufacturing the Si, 6-1 to Si
A molten metal A in which 5 to 30% by weight of SiC particles are uniformly dispersed in a molten metal of an Al-Si alloy containing 3% by weight;
Melt B consisting of Al-Si alloy containing up to 13% by weight
Are individually melted, and the molten metal A received in the ladle is first cast into the gate 11 of the mold 10 of the brake disk to form a molten layer having a desired thickness on the sliding surface portion 12 in the mold 10. The molten metal B received in another ladle while the molten metal A stayed in the gate 11 was continuously cast to fill the remaining mold, and the molten layer was almost fixed to the sliding surface portion 12. It is characterized by a procedure in which liquid phase bonding is performed on the upper surface of the molten layer and solidification is integrally performed. More specifically, the casting temperature of the molten metal A is adjusted to be lower than the temperature at which the SiC particles and the Al-Si alloy start reacting, and to be higher than the solidification temperature by 50 ° C. or more,
The casting temperature of the melt B is the same as the casting temperature of the melt A,
It is a desirable embodiment to adjust the temperature higher than 0 ° C., and it is also desirable that the volume ratio of the molten metal A is more than 20% and less than 50% of the molten metal B.

[0012]

1 (A) to 1 (C) are a plan view (A), a front view (B), and a rear view (C) of a composite brake disc according to an embodiment of the present invention. In the figure, a sliding surface 1 corresponds to an operating surface which, when controlled, is pressed against both sides of a rotating wheel to rapidly stop rotation, and a large number of radiating fins 21 are radially provided on a heat radiating surface 2 on the back side. The frictional heat generated by the sliding is rapidly dissipated into the atmosphere to suppress overheating of the brake disk and the wheels, thereby reducing thermal shock. The sliding surface 1 shown in the figure is made of an Al-Si alloy layer containing a desired thickness of SiC, and the portion other than the sliding surface 1 is made of only a normal Al-Si alloy. The boundary 3 with the surface 2 forms a composite which is integrally welded during the solidification stage after casting. In the embodiment of this figure, the layer thickness on the sliding surface 1 side is set to 20 mm, and the overall thickness is set to 50 mm.
The reason why the layer thickness is set to 20 mm is a value which is set in consideration of factors which determine a service life such as a use limit due to progress of thermal shock and a use limit due to progress of wear, in consideration of weight reduction of the entire brake disc. Therefore, if the conditions of use change, the ratio is appropriately changed to the optimum ratio. When the layer thickness is 20 mm, the volume ratio between the sliding surface side and the heat radiating surface side in the entire brake disk is approximately 4: 6. At least 20% is required because the particle dispersion of the particles may become non-uniform and the strengthening effect may be significantly reduced.

FIG. 2 is a half sectional plan view (A) and a vertical sectional front view (B) showing a mold 10 for carrying out the present invention. The mold 10 is divided into an upper mold and a lower mold at a sliding surface portion 12, and a heat radiation surface portion 13 and a gate 11 are formed on the upper mold. Since the Al-based alloy has an extremely high affinity for oxygen, the oxide (Al
Special attention must be paid to the possibility that ₂ O ₃ ) may be entrained, and if entrained, defects such as voids will occur. In the example of this figure, a gate 11 is set up at the center of a brake disk mold which is an annular plate, and a ceramic filter 1 is provided near the bottom of the gate.
4 crosses. The ceramic filter 14 filters the molten metal, blocks foreign substances such as oxides mixed therein, and passes only the clean molten metal. A burr 15 is provided below the ceramic filter 14 to squeeze the molten metal and uniformly feed the molten metal from the entire circumference to the mold body. In addition, other gate shoot 1
At 6, the molten metal from the ladle (not shown) is guided to the gate 11,
It is also a desirable embodiment to take measures such as preventing the temperature of the cast molten metal from being lowered by surrounding the outer periphery of the gate 11 with the heat insulating sleeve 17.

The molten metal A and the molten B are separately melted in a melting furnace. In the embodiment, the melt B is made of Al— containing 9% by weight of Si.
Melt A is the same Al-Si alloy as particle size 1
It is made of an alloy to which 20% by weight of SiC particles having a size of 0 to 15 μm is added and uniformly dispersed in a furnace. The particle size of SiC is desirably in the range of 5 to 30 μm. If the particle size is out of this range, it is difficult to uniformly disperse or the mechanical properties of the sliding surface after casting deteriorate, This is not preferred because it is likely to cause the property to be significantly reduced. The mixing ratio of SiC particles in the melt A is 5 to 30%.
If it is less than 5%, the coefficient of friction and the abrasion resistance decrease, so that it cannot withstand sudden sliding friction from a high speed such as emergency braking, and if it exceeds 30%, castability is poor and machining is difficult. All are unsuitable as brake disc materials, for example, the brittleness increases.

The pouring begins with the melt A first. The casting temperature of the melt A is preferably 750 ° C. or less, at which the SiC particles and the Al—Si alloy start reacting in a molten state, and 650 ° C. or more, which is 50 ° C. or more higher than the solidification temperature, and preferably around 700 ° C. Becomes The temperature of the molten metal B to be poured later is preferably the same as this temperature or a high temperature in the range up to about 50 ° C., and the temperature in the range of 700 to 750 ° C. is appropriate. It goes without saying that the casting temperature is appropriately selected depending on the compounding ratio of the SiC particles, the particle size of the particles, the size of the brake disk to be cast, particularly the surface area of the sliding surface.

As described above, the volume ratio of the molten example and the molten B is determined in view of the demand for reducing the overall weight and preventing the heat shock resistance from being reduced. If it is cut off, the function of strengthening the sliding surface cannot be sufficiently achieved, which is not appropriate for achieving the purpose.

The most important requirements in casting are:
The molten metal at the gate 11 continues to stay without interruption,
The point is that casting is continuously performed while always keeping the stagnant state. That is, it is necessary to add the molten metal B from another ladle while the molten metal A previously poured into the gate 11 is accumulated in the molten metal gate and continuously feed the molten metal into the mold without interruption. is there. Since this mold solution is formed so as to uniformly enter the main mold through the burr 15 from the entire periphery of the central gate 11, the molten metal A that has entered first has a substantially uniform layer thickness. The molten surface B filled on the sliding surface side with the layer and subsequently poured is evenly fed from the entire circumference into the remaining hollow above the molten layer. Since the specific gravity of the molten metal B is 2.3, the molten metal A having a specific gravity of 2.5 is hardly mixed by being pushed up, and the molten metal on the heavy sliding surface side is slightly melted on the heavy sliding surface side. The layers spontaneously overlap and begin to solidify as separate layers. However, at the boundary surface between the two molten layers, active exchange is performed with each other and solidified together by solidification, so that a composite casting is firmly connected. In this case, when the cooling is locally promoted by applying a cooling metal to the lower mold surface forming the sliding surface, the crystal grains of the base material are further refined, the material strength is improved, and the dispersion of SiC particles is also reduced. It is well recognized that this has a good effect on prevention of thermal shock cracking.

FIG. 3 shows a magnification of 10 in the embodiment of the present invention.
Microscopic structure of 0x, the lower part is the sliding surface side made of Al-Si alloy dispersion-strengthened with SiC, and the upper part is the heat radiation surface side made of only Al-Si alloy. No sound bubbles, no pinholes, no blowholes, and no cracks or peeled surfaces.

From the cross section of the embodiment of the present invention, test pieces of the sliding surface 1 and the heat radiating surface 2 were cut out, and their mechanical properties were examined.
N / mm ² , elongation was 0.7%, whereas heat dissipation surface 2
The tensile strength on the side was 220 N / mm ² and the elongation was 4%.

Further, apart from the embodiment of the present invention, a comparative example in which the entire mold was poured using only an Al—Si alloy containing SiC particles under the same conditions was manufactured and the two were compared. The weight of the brake disc was 50 kg, whereas the weight of the brake disc was 49 kg in the embodiment of the present invention.
A weight reduction of 2% corresponding to the difference in specific gravity between the two was observed, as compared with the case where the C particles were dispersed and strengthened. Since the sliding surfaces of both brake discs are considered to be the same, the same abrasion resistance is expected, but from the result of the material test, the heat dissipating surface side of the comparative example is considered to be the same as the sliding surface side. Thus, the prediction that the elongation is significantly reduced and the thermal shock resistance is largely lost is established.

[0021]

As described above, according to the present invention, in a brake disk based on an Al-based alloy, the wear resistance of a sliding surface on which a braking force acts is greatly improved, and the improvement of the wear resistance is achieved. Maintain brake disc characteristics exceeding conventional technologies, such as minimizing the inevitable increase in weight to obtain and maintaining the same mechanical properties of the brake disc itself except for the sliding surface to ensure thermal shock resistance. There is a combined effect. Moreover, the production of this composite brake disc does not require much complicated processes and expensive equipment if casting technology is used, and the advantage of mass production of high quality at relatively low cost is far superior to the conventional technology. The effect is.

[Brief description of the drawings]

FIG. 1 is a plan view (A), a front view (B), and a rear view (C) of an embodiment of the present invention.

FIG. 2 is a half plan view (A) of a mold used for carrying out the present invention.
And a vertical sectional front view (B).

FIG. 3 shows a metallographic structure (magnification: 10) of the embodiment of the present invention.
0).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sliding surface 2 Heat radiating surface 10 Mold 11 Gate 12 Sliding surface 13 Heat radiating surface

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F16D 65/12 F16D 65/12 M (72) Inventor Ichizo Sakurai 1-112-19 Kitahorie, Nishi-ku, Osaka Co., Ltd. F-term in Kurimoto Works (reference) 3J058 AA41 AA48 AA58 BA32 BA41 BA44 BA61 BA68 CA44 CA47 DD11 DD26 EA08 EA12 FA21 GA22 GA49 GA62 GA63 GA82 GA92 GA95 4E014 NA08 4K020 AA22 AC01 BA08 BB22

Claims (4)

[Claims] 1. A sliding surface 1 having abrasion resistance enhanced by dispersing 5 to 30% by weight of SiC having a particle size of 3 to 50 μm in an Al—Si alloy containing 6 to 13% by weight of Si; Al-Si
A composite brake disc made of an Al-based alloy, wherein the heat-dissipating surface 2 made of only an alloy is welded and completely integrated. 2. A molten metal A in which 5 to 30% by weight of SiC particles are uniformly dispersed in a molten metal of an Al—Si alloy containing 6 to 13% by weight of Si, and an Al— containing 6 to 13% by weight of Si.
The molten metal B made of only Si alloy is individually melted, and the molten metal A received in the ladle is first cast into the gate 11 of the mold 10 of the brake disc, and the molten metal A having a desired thickness is formed on the sliding surface 12 in the mold 10. While forming the molten layer, the molten metal A received in another ladle is continuously cast while the molten metal A is staying in the sprue 11 to fill the remaining mold and slide the molten layer. Face part 12
A method of manufacturing a composite brake disc made of an Al-based alloy, wherein the two layers are liquid-phase bonded to each other on the upper surface of the molten layer and solidified integrally. 3. The casting of the molten metal B according to claim 2, wherein the casting temperature of the molten metal A is adjusted to be lower than the temperature at which the SiC particles and the Al—Si alloy start to react and higher than the solidification temperature by 50 ° C. or more. The pouring temperature is the same as the pouring temperature of the molten metal A, or 50
A method of manufacturing a composite brake disc made of an Al-based alloy, characterized in that the temperature is adjusted to a high temperature within the range of ° C. 4. The method for manufacturing a composite brake disc made of an Al-based alloy according to claim 2, wherein the volume ratio of the molten metal A is more than 20% and less than 50% of the molten metal B.