JP2000220667A - Aluminum-made integrated caliper body and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fatigue of a bridge part by using Na, Sr, or Ca having a high refining effect of eutectic Si as refining treatment agent in a caliper body. SOLUTION: The aluminum alloy constituting a caliper body 2 contains at least one or two or more of 5-11 wt.% of Si, 0.25-0.7 wt.% of Mg, 0.002-0.02 wt.% of Na, 0.003-0.04 wt.% of Sr, and 0.003-0.04 wt.% of Ca. The remainder has the composition of Al, and the elements contained as impurities are regulated to 0.02 wt.% or less of P, 0.01 wt.% or less of Sb, 0.3 wt.% or less of Fe, and 0.5 wt.% or less in total of other impurity elements. The average length of eutectic Si of the casting composition is set to 10 μm or less, the arm spacing of dendrite is set to 50 μm or less, and the average number of interpositions is 0.02 piece/cm2 by K10 value. According to this, the fatigue cracking resistance of a bridge part 7 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caliper body for an opposed-piston disc brake having pistons disposed opposite to both side surfaces of a rotor, and a method of manufacturing the same.

An opposed-piston disc brake has a structure in which one or more pairs of pistons are opposed to a rotor fixed to an axle from both sides. Specifically, as shown in a plan sectional view of FIG. 1 showing the piston use state, the head of the rotor 1 faces the space near the center of the caliper body 2 and is attached to the tip of the piston 3. The brake pads 4 are opposed to both side surfaces of the rotor 1. When the piston 3 is pushed toward the rotor 1 by the hydraulic pressure sent from the pipe 5, the brake pad 4
Pressed on both sides of. The pressing force of the brake pad 4 acts as a braking force on the axle, and reduces the rotation speed of the axle. For the caliper body 2 supporting the piston 3, a cast iron casting is conventionally used. Since the hydraulic pressure supply pipe 5 is disposed in a cast iron casting, the steel pipe is cast into a cast iron and incorporated into the caliper body 2.

[0003]

The caliper body made of cast iron is heavy in weight, and it is not possible to reduce the weight, which is strongly required for equipment mounted on a vehicle. If an aluminum caliper body is used instead of cast iron, significant weight reduction is possible. However, due to the structure and function of the caliper body, cast iron cannot be simply replaced with aluminum. That is, oil is sent from the pipe 5 to the cylinder 6 and hydraulic pressure is applied to the piston 3 to apply a brake to the axle. At this time, a reaction force is generated in the direction in which the bridge portion 7 of the caliper body 2 opens.

[0004] Aluminum integrated caliper body 2
In this case, there is a possibility that the bridge portion 7 may be cracked due to metal fatigue due to the reaction force, and the safety problem remains unsolved. It is known that the caliper body is assembled by manufacturing the outer caliper and the inner caliper by dividing the bridge portion 7 into two parts along the line AA in order to avoid metal fatigue of the bridge portion 7, and fastening both with bolts. (Japanese Unexamined Patent Publication No. 9-177843). However, in the case of the split caliper body, the number of manufacturing steps is increased, and as a result, the cost is increased. In addition, accurate alignment between the outer caliper and the inner caliper is required, and strict control is required for the casting of the outer caliper and the inner caliper. Further, during the operation of the disc brake, stress concentrates on a bolt for fastening the outer caliper and the inner caliper, and the bolt may be damaged. Therefore, the present inventors have proposed in Japanese Patent Application No. 10-269425 that by improving the aluminum alloy used for the caliper body and the casting method, fatigue cracks that tend to occur in the bridge portion are suppressed. . In this method, eutectic Si is refined into an elongated shape by adding Sb, and elongation, fatigue strength, and wear resistance are improved.

[0005]

According to the present invention, eutectic Si can also be produced by using one or more of Na, Sr, and Ca as a refining agent instead of Sb proposed in the prior application. The present invention has been completed based on the knowledge of miniaturization, and has an object to provide an integrated caliper body which improves fatigue crack resistance of a bridge portion and is easy to manufacture and assemble. In order to achieve the object, the aluminum integrated caliper body of the present invention has an aluminum pipe that feeds hydraulic pressure to a piston pressed against a rotor via a brake pad, which is cast around the caliper body, and Constituting aluminum alloy is S
i: 5 to 11% by weight, Mg: 0.25 to 0.7% by weight, Na: 0.002 to 0.02% by weight, Sr: 0.00
3 to 0.04% by weight and Ca: 0.003 to 0.04% by weight, the balance being substantially Al, and the element contained as impurities being P: 0. 002
Wt% or less, Sb: 0.01 wt% or less, Fe: 0.3
% By weight, other impurity elements: regulated to a total of 0.5% by weight or less, and the average length of eutectic Si in the cast structure is 10 μm.
m or less, dendrite arm spacing is 50μm or less, the average number of inclusions is characterized in that 0.02 / cm ² or less at K ₁₀ value. The aluminum alloy used can further comprise 0.05 to 0.25% by weight of Ti and / or 0.0001 to 0.01% by weight of B.

This caliper body is subjected to degassing, deslagging and fine processing in a batch type holding furnace (hand-held furnace) after a predetermined amount of molten aluminum alloy melted and adjusted in a melting furnace. 680-7 molten aluminum alloy
After maintaining the temperature at 50 ° C, the required amount of molten metal for one casting was transferred to a basin, the temperature of the molten metal in the basin was adjusted to 640 to 700 ° C, and then an aluminum pipe as a material to be cast was set. It is manufactured by pouring the molten metal into the finished mold.
At the time of casting, an amount of molten metal necessary for one casting is pumped out of a holding furnace, transferred to a cooling gutter connected to a pool of a mold, and supplied to the pool via the cooling gutter. As the cooling gutter, a cooling gutter having a weir for adjusting the flow rate of the molten metal flowing into the pool and having a heat radiation structure is used. On the other hand, the basin is lined with a heat insulating material in order to suppress the temperature drop of the contained molten metal and to achieve a uniform temperature distribution. A flow path from the pool to the cavity of the mold is provided with a weir whose bottom is open. The molten metal sent from the pool is
The dam is gently dipped and injected into the mold. When the molten metal goes under the weir, inclusions such as oxides floating in the molten metal are captured by the weir, and the purified molten metal is injected into the mold.

[0007] The flow rate of the molten metal injected into the mold is such that the surface of the molten metal fed into the mold cavity from the pool is prevented in order to prevent the molten metal sent from the pool from directly contacting the aluminum pipe. After ascending and covering the aluminum pipe, it is adjusted to rapidly supply the remaining molten metal to the cavity to increase productivity. Specifically, until the surface of the molten metal rising in the cavity covers the aluminum pipe, the molten metal fed from the pool does not directly contact the aluminum pipe, so that a mold in which the pool is integrated or A tilt casting method in which molten metal is fed from a mold to a cavity while gradually rotating a rotatable pool is adopted. After the cavity is filled with the molten metal, defects such as cavities are prevented when the pouring gate is operated by raising the gate. During the injection of the molten metal, one end of the aluminum pipe is connected to a vacuum system as required, and the outside air is sucked from the other end. This cools the aluminum pipe and prevents erosion. When a solution treatment at 520 to 545 ° C. × 1 to 15 hours, a water quenching, and an aging treatment at 150 to 170 ° C. × 2 to 10 hours are performed after casting, mechanical properties necessary for a caliper body are imparted.

[0008]

The present inventors have investigated the cause of the occurrence of fatigue cracks in the bridge portion 7 and examined the effects of alloy composition, casting method, etc. on the occurrence of fatigue cracks. as a result,
It has been found that fatigue cracks are generated starting from inclusions such as oxides contained in the aluminum alloy of the caliper body and coarse intermetallic compounds. Therefore, an alloy design and a casting method for suppressing inclusions and coarse intermetallic compounds were elucidated. The aluminum alloy used for the caliper body according to the present invention is designed as follows.

Si: Improves the flow of molten metal poured into a mold of 5 to 11% by weight ,
g ₂ Si is precipitated to improve the mechanical strength of the alloy. Further, by adjusting the Si content to 5 to 11% by weight, the melting point is lower than that of the aluminum pipe which is a material to be cast and the aluminum pipe is prevented from being melted by the molten metal poured into the mold. I do. Si content 5-1
The range of 1% by weight is a hypoeutectic composition, which is advantageous in improving machinability during machining. In the hypereutectic region where the Si content exceeds 11% by weight, the primary crystal S
i becomes a crack generation source due to the stress and lowers the fatigue strength. Further, in the hypereutectic region, since there is almost no α-Al crystal, the elongation of the material becomes extremely small, and when a fatigue crack occurs, the propagation speed of the crack increases and the fatigue strength decreases. On the other hand, when the Si content is less than 5% by weight, the flow of the molten metal becomes poor, and the occurrence of casting defects, the machinability and the strength tend to be reduced. Further, when the melting point increases with a decrease in the Si content, there is a possibility that the aluminum pipe, which is the material to be cast, is melted and damaged.

[0010] Mg: 0.25 to 0.7 to form a Mg ₂ Si by wt% the heat treatment, to improve the mechanical strength of the alloy. However, a large amount of Mg exceeding 0.7% by weight
Is contained, the Mg-based oxide increases. When the Mg-based oxide is mixed into the product, it becomes a crack generation source and lowers the fatigue strength. Further, it also causes a reduction in elongation and a reduction in fatigue strength. Conversely, less than 0.25 wt% Mg
With the content, Mg ₂ Si is not sufficiently precipitated, and the required strength cannot be obtained. Na: 0.002 to 0.02% by weight, Sr: 0.003
To 0.04% by weight, Ca: 0.003 to 0.04% by weight
One or two or more of the above eutectic Si have the effect of refining and increasing elongation and fatigue strength. Na: 0.002% by weight or more, Sr: 0.00
The effect becomes significant with at least one of 3% by weight or more and Ca: 0.003% by weight or more. However, more than 0.02% by weight of Na, more than 0.04% by weight of Sr or 0.1%.
If Ca exceeds 0.4% by weight, not only the effect of addition is saturated, but also the generation of oxides and the absorption of hydrogen gas become remarkable, and the fatigue strength is reduced.

Ti: 0.05-0.25% by weight and / or
B: 0.0001 to 0.01% by weight The anisotropy of the elongation and fatigue strength of the material by refining the cast crystal grains of α-Al crystal and improving the dendrite to a small and non-directional dendrite structure. And an effect of improving the values of elongation and fatigue strength. But,
If the amount of Ti exceeds 0.25% by weight or the amount of B exceeds 0.01% by weight, coarse AlB ₂ , which is a crack generation source,
TiB ₂ , TiAl _3, etc. are generated, and cause a reduction in fatigue strength. Conversely, if the Ti content is less than 0.05% by weight or the B content is less than 0.0001% by weight, the refining effect is reduced. The cast crystal grains can be refined by adding Ti or B alone, but the refining effect becomes more remarkable by the combined use of Ti and B. P: 0.002 wt% or less P is an element used as a refiner of primary crystal Si.
Since the l-P-based compound functions as a crystal nucleus of Si, it causes coarsening of eutectic Si and crystallization of primary Si. Coarse eutectic Si or primary crystal Si becomes a crack generation source and lowers fatigue strength. Further, when the eutectic Si is coarsened, the elongation is reduced. For this reason, the P content is preferably as small as possible, but it is unavoidable that the P content is mixed as an impurity during the compounding of the alloy. Therefore, in the present invention, the upper limit of the P content is set to 0.002% by weight.

Sb: 0.01% by weight or less Sb is a component exhibiting an effect of refining eutectic Si.
When coexisting with a, Ca, Sr, etc., the action of Na, Ca, Sr, etc. is hindered. In the present invention, since the eutectic Si is refined with Na, Ca, and Sr, the upper limit of the Sb content is set to 0.1.
It was set to 01% by weight. Fe: 0.3% by weight or less Fe is an element that forms an Al-Fe-Si-based compound serving as a crack generation source, so that a smaller amount is more preferable. But F
Extremely lowering the e content restricts the raw materials used at the time of compounding the alloy, thereby increasing the cost of the alloy. Therefore, in the present invention, the upper limit of the Fe content is set to 0.3% by weight. Other impurity elements: 0.5% by weight or less in total The aluminum alloy used in the present invention employs an alloy design that prevents entrapment of oxides that cause fatigue cracks and crystallization of intermetallic compounds. . Therefore, it is necessary to reduce other impurity elements as much as possible. From such a viewpoint, in the present invention, the total amount of other impurity elements is regulated to 0.5% by weight or less.

Average length of eutectic Si: 10 μm or less The smaller the eutectic Si, the more effective it is in elongating the alloy material and improving the fatigue strength. The size of eutectic Si is N
It is adjusted by the addition amount of a, Ca, Sr and the like. Eutectic S
When i exceeds 10 μm in average length, it tends to be a source of fatigue cracks. In addition, since abrasion resistance is required in the cylinder portion where the piston slides, excessively fine eutectic Si is not preferable. Dendrite arm spacing (DAS): 50 μm
Hereinafter, the smaller the DAS of the α-Al crystal is, the more the alloy material elongates and the fatigue strength is improved. Therefore, in the present invention,
The upper limit of DAS was set to 50 μm. When the DAS exceeds 50 μm, coarse intermetallic compounds are generated and aggregated at boundaries between dendrites and crystal grain boundaries, and are likely to become fatigue crack generation sources. In order to reduce the DAS, it is necessary to rapidly cool the molten metal poured into the mold. However, in the casting method according to the present invention, a cooling mechanism is set at a necessary position inside the mold and supplied to the cooling mechanism. It is also possible to cool the mold with cooling water.

[0014] The average number of inclusions: 0.02 at K ₁₀ value /
Coarse inclusions having a length of 0.1 mm or more, which are observed with the naked eye or a 10-fold loupe or the like with a size of ² cm or less , are a source of fatigue cracks. Such coarse inclusions include oxides and oxide films such as Al, Na, Ca, Sr, and Mg, Al-Si-Fe, Al-Ti,
It is derived from a crystallized intermetallic compound such as Ti-B or Mg-Sb or a foreign material mixed from a furnace material, a tool or the like. It is important to suppress coarse inclusions to 0.02 / cm ² or less in the observation visual field.
No fatigue cracks are generated in the bridge portion 7, and an integrated caliper body excellent in fatigue strength and safety is obtained. The average number of inclusions, the fracture surfaces of the cast alloy material was observed with a 10-fold loupe, it displayed the counted number in the K ₁₀ value in terms of per unit area. In the measurement of the average number, the two fractured surfaces on the left and right are evaluated as one piece, and 5 to 6 pieces are evaluated as one sample. In the present invention, the area 2
The average number of inclusions was calculated as data of one sample at 5 cm ² , and the average of the data of seven samples. With such the K ₁₀ value obtained is 0.02 / cm ² or less, excellent elongation characteristics and fatigue strength are imparted to the alloy material. On the other hand, if the K ₁₀ value of more than 0.02 / cm ^2, not obtained fatigue strength in need.

[0015] 0.02 / cm ² or less of K ₁₀ value can be achieved by the following method. By rotating and degassing the molten metal contained in the holding furnace, oxides, oxide films and the like derived from added Na, Ca, Sr, etc. are floated and separated from the molten metal. When the floating slag is removed from the molten metal, it becomes an aluminum alloy molten metal having extremely small amounts of oxides, oxide films, and the like.
Mg, Al and the like also float as oxide films on the surface of the molten metal, and these oxide films are also separated from the molten metal at the time of removing the slag.
When the molten metal is transferred from the holding furnace to the pool, a method is adopted in which oxides and oxide films are not entangled in the molten metal.
Further, by adjusting the manufacturing conditions, Fe, Ti,
Prevent other elements from growing into coarse crystals. Inclusions derived from furnace materials and tools are separated from the molten metal by holding the molten metal at a high temperature.

For example, in the Na treatment, a Na-based flux is added simultaneously with or before rotation degassing to reduce the amount of hydrogen gas and to remove Na-based oxides. S
When treated with r, Ca, etc., Al-80% Sr, Al-
After or simultaneously with the addition of a master alloy such as 10% Sr and Al-10% Ca, the molten metal is subjected to rotary degassing to reduce the amount of hydrogen gas and remove inclusions. At the time of rotational degassing, processing conditions are set so that oxides such as Al, Mg, Sr, and Ca and oxide films are not involved. Eutectic S by adding Sb proposed in Japanese Patent Application No. 10-269425.
Although Sb is not easily oxidized in the miniaturization treatment of i, in the present invention using Na, Ca, Sr, or the like, which is easily oxidized, as a refining agent, care must be taken in removing inclusions.

High temperature holding: maintained at 680-750 ° C. in a holding furnace.
The raw material mixed so as to have a predetermined composition is prepared into a molten aluminum alloy through steps such as degassing, miniaturization, and slag after melting. The molten metal is 680 in a holding furnace.
The temperature is maintained at ７750 ° C., and a stable high-quality molten metal can be obtained. As the holding furnace, a small hand-held furnace of about 500 to 1000 kg is preferable in order to stably control the quality of the molten metal by properly managing the molten metal. By the high-temperature holding treatment, inclusions such as oxides generated in the smelting stage and foreign matters derived from furnace materials and tools are separated from the molten metal and float on the surface of the molten metal as furnace slag. Therefore, when the furnace slag is removed, furnace slag such as oxide is prevented from being introduced into the product, and an alloy melt in which the number of inclusions that cause fatigue cracks is reduced as much as possible can be obtained.

The holding temperature is set at 680 to
It is set to a temperature range of 750 ° C. However, Na, C
Since a, Sr, and the like are consumed by holding for a long time and the amount effective for miniaturization of eutectic Si decreases, the holding time is preferably set within 3 hours. At a holding temperature exceeding 750 ° C., the depletion of Na, Sr, Ca, etc. is large, and the consumption of heat energy becomes too large. Conversely, at a holding temperature not reaching 680 ° C., the viscosity of the molten metal increases, and Insufficient flotation separation. When the molten metal is held at a temperature lower than 680 ° C. for a long time, Ti added as a refiner of the cast crystal grains becomes coarse TiAl ₃ and crystallizes in the molten metal.
When TiAl ₃ crystallization is mixed into a product, it becomes a source of fatigue cracks. Also in this respect, the molten metal holding temperature is set to 680 to 680.
It is important to set the temperature in the range of 750 ° C. Even at the stage of transferring the molten metal from the holding furnace to the basin, there is a possibility that oxides may be mixed into the molten metal when the amount of molten metal required for one casting is pumped with a ladle. Therefore, it is necessary to take care that no oxide is involved in the pumping.

Casting The molten aluminum alloy prepared as described above is cast by gravity casting, low pressure casting, or the like. An aluminum pipe for supplying hydraulic pressure is set in the mold in advance, but the DAS of the cast structure can be reduced by water-cooling the core and the inside of the mold. The temperature of the molten metal injected into the mold is preferably adjusted so that the temperature of the molten metal in the mold becomes 585 to 640 ° C. in order to prevent the aluminum pipe set in the mold from being melted. . Therefore, how to lower the temperature of the molten metal at a temperature of 680 to 750 ° C. contained in the holding furnace and cast it is an important problem. In the present invention, the holding temperature is from 680 to 750 ° C to the pouring temperature 585 to 6
In order to industrially lower the temperature to 40 ° C., the following method is adopted.

(Method 1) In the vicinity of the gate 11 of the mold 10,
A basin 12 capable of accommodating a single casting amount of molten metal M is provided integrally with the mold 10. When the temperature of the molten metal M stored in the basin 12 is controlled at 640 to 700 ° C., the mold 10
Is cooled by the mold 10 and cooled to a temperature of 585-640 ° C. The molten metal M pumped out from the holding furnace (not shown) by the ladle 13 is 680 to 750
It is possible to transfer the molten metal M directly to the basin 12 and maintain the molten metal M in the basin 12 until the temperature falls to 640 to 680 ° C. However, the pool 12
Is the molten metal of one casting amount.
It is not productive to wait for the temperature to drop after every casting. Therefore, it is preferable to transfer the molten metal M from the holding furnace to the cooling gutter 14. The cooling gutter 14 has a heat radiation structure for lowering the temperature of the transferred molten metal M. Specifically, thickness 1-20
mm of steel with a thin coating of release agent on the inside.

A weir 15 is provided on the outlet side of the cooling gutter 14, and an outlet 16 is provided below the weir 15. The weir 15 prevents the slag carried from the holding furnace via the ladle 13 to the pool 12 and the oxide film generated on the surface of the molten metal M while being stored in the cooling gutter 14 from flowing into the pool 12. I do. The cooling gutter 14 further regulates the amount of the molten metal M flowing out from the outlet 16, and is also effective for the residence time of the molten metal M in the cooling gutter 14, and also for lowering the temperature and temperature of the molten metal M. In addition,
In order to more positively adjust the flow rate, it is preferable to provide the weir 15 with respect to the cooling gutter 14 so as to be able to move up and down, and to make the flow passage cross-sectional area of the outlet 16 variable. The molten metal M is sent through the weir 15 from the outlet 16 to the pool 12 along the supply gutter 17. The molten metal M transferred to the cooling gutter 14 at 680 to 750 ° C. is cooled to 640 to 700 ° C. when it flows into the pool 12 via the cooling gutter 14 and the supply gutter 17. Ladle 1
The time required for the molten metal M to move from 3 to the pool 12 via the cooling gutter 14 is about ten and several seconds, and the molten metal M falls to 640 to 700 ° C., which is effective for pouring, in a short time. Implemented with productivity.

The basin 12 has a heat insulation structure lined with a heat insulating material 18 having a thickness of 1 to 5 cm, for example.
The surface of No. 8 is coated with a release agent. Therefore, when the molten metal M is poured into the mold 10 from the pool 12, the temperature of the molten metal M is not excessively lowered, and the flow of the molten metal in the mold 10 is guaranteed. Molten metal M stored in basin 12
The temperature distribution is made uniform by the heat retaining structure of the basin 12, and is poured and cast into the mold 10 under stable conditions. In the molten metal flow path from the pool 12 to the cavity 19 of the mold 10, a weir 22 whose lower part is opened is provided. Molten metal
Flows into the cavity 19 through the weir 22 with the molten metal surface in contact with the weir 22. As the weir 22, for example, a steel member coated with a release agent is used. Molten M is weir 22
When diving, the oxide M and the oxide film floating on the surface of the melt M are captured by the weir 22 and separated from the melt M, so that the melt M flowing into the cavity 19 is formed of oxide, oxide film, etc. Not a clean melt. In particular, since Na, Ca, Sr, and the like, which are easily oxidized as compared with Sb, are used as a refiner, separation and removal of oxides, oxide films, and the like by the weir 22 are effective in improving the quality of a cast product. . After confirming that the temperature of the molten metal M in the basin 12 is in the range of 640 to 700 ° C., the molten metal M is injected into the mold 10 from the basin 12 through the weir 22. The core 20 and the aluminum pipe 21 are set in the mold 10 in advance, and the mold 10 is arranged so that the gate 11 faces in the horizontal direction.

When the molten metal M is injected into the mold 10, the mold 10 is gradually rotated with the end corner of the mold 10 on the ground level GL as the rotation center O as shown in FIG. With the rotation of the mold 10, the pool 12 integrated with the mold 10 tilts, and the molten metal M is turned into the pool 12.
Through the gate 11 and slowly into the cavity 19 in the mold 10. If the flow of the molten metal M toward the cavity 19 comes into direct contact with the aluminum pipe 21, the aluminum pipe 21 may be melted and damaged. Therefore, when the rotation speed of the mold 10 is adjusted so that the melt M flows into the cavity 19 along the inner wall of the mold 10, direct contact between the melt M and the aluminum pipe 21 is prevented, and the aluminum pipe 21 is removed. Protected from erosion.
The direct contact between the molten metal M and the aluminum pipe 21 can also be prevented by devising the bottom surface from the basin 12 to the gate 11 and the inclined surface of the gate 11.

The molten metal M that has flowed in accumulates from the bottom of the cavity 19 and gradually raises the molten metal surface S. Then, the molten metal M cooled by the mold 10 and the core 20 gradually fills the aluminum pipe 21. In addition, a mold 10 and a core 20 each having a water cooling mechanism for cooling required portions with cooling water are used so that cooling of the molten metal M is promoted in order to prevent a casting cavity which may cause fatigue cracks. It is preferable to inject the molten metal M while cooling it. During casting, one end of the aluminum pipe 21 is connected to a vacuum system, and the other end is cooled by sucking outside air from the other end.
Is reliably prevented from being melted. Cooling by vacuum suction is also effective in ensuring the safety of the casting operation. what if,
Even if the aluminum pipe 21 melts and the internal space of the pipe comes into contact with the molten metal M, the molten metal M sent into the aluminum pipe 21 by vacuum suction solidifies as it is and closes the pipe. The work safety is improved. On the other hand, in a system in which pressurized air or cooling water is sent to the aluminum pipe 21 for cooling, the pressurized air or water is melted when the aluminum pipe 21 is melted.
Danger of blowing inside is dangerous.

When the mold 10 is further rotated, the inclination angle becomes θ ₁ →
At the stage of θ ₂ (FIG. 4), the molten metal surface S completely covers the aluminum pipe 21. In this state, the molten metal M flowing into the cavity 19 from the pool 12 does not directly hit the aluminum pipe 21. Therefore, in order to increase the productivity, the rotation speed of the mold 10 is increased, and the mold 10 is simultaneously rotated to an upright state (FIG. 5). In the upright state, the gate 11 faces vertically upward and the cavity 1
The molten metal M injected into 9 is pressurized by the pusher H, and the occurrence of a cavity is suppressed.

(Method 2) Die 1 in which water pool 12 is integrated
By rotating the pool 12 separated from the mold 10 instead of the rotation of 0, the molten metal M flowing from the pool 12 can be prevented from directly contacting the aluminum pipe 21. For example, as shown in FIG. 6, the mold 10 is disposed obliquely at a predetermined inclination angle θ ₃ , and the rotatable basin 12 is extended from the mold 10 to the gate 1 extending obliquely upward.
Face 1 The gate 11 is provided in a positional relationship in which the molten metal M that has flowed in accumulates from the bottom of the cavity 19 so that the molten metal M flowing into the cavity 19 does not directly contact the aluminum pipe 21. In the initial stage of the injection of the molten metal M, the rotation speed of the pool 12 is reduced so that the molten metal M is gradually stored in the cavity 19. Then, when the injected molten metal M completely covers the aluminum pipe 21, the rotation speed of the pool 12 is increased, and the remaining molten metal M is injected into the cavity 19 at once. After the amount of the molten metal M for one time has been injected, the mold 10 is rotated to exert the pusher effect. Alternatively, as shown in FIG.
Is provided, the gate 11 can be rotated without rotating the mold 10.
The molten metal M accumulated in the cavity becomes the hot water H and the cavity 1
The molten metal in 9 is pressurized.

The aluminum pipe 21 which is preset to an aluminum pipe molds 10
Is held by the core 20 and secured at a predetermined position in the cavity 19. The aluminum pipe 21 is cast with the molten metal M, and the inside becomes a hydraulic supply path. There is also a method of manufacturing a caliper body by directly machining a solid casting to make a hole, but machining after casting increases the manufacturing cost. In this regard, in the present invention, since the aluminum pipe 21 is made of an aluminum casting alloy constituting the caliper body, machining after casting can be omitted, and manufacturing costs can be reduced. The aluminum pipe 21 has an outer diameter of 5 to 7 mm and an inner diameter of 2 to 4 mm in a normal specification, and is generally formed of a complicated three-dimensional shape, and is generally a material which is easy to process and has little springback after the process. Required. Therefore, 1000 series, 3000 series, 6
000 series etc. (specifically, A1050, A3003, A
6063) aluminum alloy is used.

Since the aluminum pipe 21 is set in the mold 10 and the molten metal M is injected into the cavity 19, it is required that the heat of the molten metal M does not damage the aluminum pipe 21. Since the melting point of aluminum alloys such as 1000 series and 3000 series is 640 to 660 ° C, a casting alloy having a melting point of 630 ° C or less is used as the molten metal M. The melting point of the casting alloy can be adjusted by the Si content. Preferably, a casting alloy having a melting point near 615 ° C. is used,
The casting conditions are selected so that the temperature of the molten metal M in the mold 10 becomes 585 to 645 ° C. It is also preferable to cover the aluminum pipe 21 with a heat insulating material such as an anodic oxide film and a release agent in order to prevent the aluminum pipe 21 from being melted.

An aluminum pipe 21 is cast in a caliper body (hereinafter, referred to as a cast material) cast by heat treatment . The shaped material is subjected to solution treatment after cutting and separating the hot water H or the like. By the solution treatment, alloy components such as Si and Mg are dissolved in the matrix, and the corners of the crystallized eutectic Si are rounded and elongation is improved. The average length of eutectic Si is shorter than that during casting. After the solution treatment, an aging treatment for improving the strength by precipitation of Mg ₂ Si or the like is performed. As the heat treatment applied to the shaped material, a solution treatment (520 to 545) is performed.
℃ × 1-15 hours) → water quenching → artificial aging (150-1)
(70 ° C. × 2 to 10 hours) → Air-cooled T6 treatment is preferred.
If the solution treatment temperature is lower than 520 ° C., solid solution of Si, Mg, etc. does not sufficiently proceed. Conversely, if the solution treatment temperature exceeds 545 ° C., an effect commensurate with the temperature increase cannot be obtained, which is not economical, and also causes dissolution in a part. In order to obtain uniform hardenability, 5%
It is quenched in water maintained at about 0 to 80 ° C. Next, Mg ₂ Si is precipitated by heating at 150 to 170 ° C., and the strength and elongation are secured. At an aging temperature lower than 150 ° C., the precipitation of Mg ₂ Si is insufficient,
At an aging treatment temperature exceeding ℃, the precipitated particles become large and the strength tends to be rather lowered.

The heat-treated shaped material is machined and subjected to hard alumite treatment as required. In the hard alumite treatment, a film thickness 30 to 40 effective for improving abrasion resistance
An anodized film of about μm is formed on the cylinder surface. The caliper body obtained in this manner is assembled with a disc brake in combination with other parts. Since the caliper body has no inclusions that cause fatigue cracks and the crystal grain size is appropriately adjusted, cracks occur in the bridge portion 7 even under the condition where the reaction force of the piston 3 is repeatedly applied. Nothing. In addition, since it is an integral type, steel tightening bolts and nuts are not required as compared with the split caliper body, and the product is lightened accordingly. Further, since the number of man-hours for machining is reduced, it can be provided at low cost.

[0031]

EXAMPLE A molten aluminum alloy whose composition was adjusted was transferred to a holding furnace, subjected to ordinary molten metal processing such as rotary degassing, finer treatment, and deslagging, and kept at 725 ° C. for 40 minutes in the holding furnace. Alloy 1 according to the present invention was refined by Na treatment using a mixed flux of NaF + NaCl. As the molten metal of the comparative alloy 2, the same composition as that of the alloy 1 of the present invention and the same molten metal treatment was used, but the molten metal was poured from the pool 12 into the cavity 19 of the mold 10 through the molten metal flow path without the weir 22. did. The molten metal of the comparative alloy 3 was injected into the cavity 19 through the molten metal flow path having the weir 22, but was not subjected to the miniaturization treatment. The composition (% by weight) of each alloy is as follows.

Inventive Alloy 1 and Comparative Alloy 2: Si: 7.20%, Mg: 0.51%, Ti: 0.20%, B: 0.001%, P: 0.0006%, Ca: 0 0.001%, Na: 0.006%, Sr: 0.0000%, Fe: 0.13%, Cu: 0.01%, Mn: 0.00%, Cr: 0.00%, Zn: 0. 01%, Sn: 0.00%, Ni: 0.00%, Pb: 0.00%, Sb: 0.0002% Comparative alloy 3: Si: 6.9%, Mg: 0.50%, Ti: 0.18%, B: 0.001%, P: 0.0005%, Ca: 0.001%, Na: 0.0005%, Sr: 0.00000%, Fe: 0.15%, Cu: 0 0.00%, Mn: 0.00%, Cr: 0.00%, Zn: 0.00%, Sn: 0.00%, Ni: 0.0 0%, Pb: 0.00% Sb: 0.0002%

As the casting apparatus, an apparatus having the equipment configuration shown in FIG. 2 was used, and an A300 having an outer diameter of 6 mm and an inner diameter of 4 mm was used.
The 3 aluminum alloy pipe 21 was set in the mold 10 in advance. 10 kg each of the inventive alloy 1 and the comparative alloy 2
Was pumped into a ladle and transferred to a cooling gutter 14. The molten metal M cooled by the cooling gutter 14 passed through the weir 15 and was stored in the pool 12. The temperature of the molten metal M in the basin 12 is 67
When the temperature reaches 2 ° C., the mold 10 is rotated to obtain the alloy 1 of the present invention.
In addition, in the molten metal of the comparative alloy 3, the molten metal M was injected into the cavity 19 through the weir 22 provided at the entrance of the mold 10 so that the molten metal M did not directly hit the aluminum pipe 21.
The melt of the comparative alloy 2 was injected into the cavity 19 in the same manner except that the mold 10 having no weir 22 at the inlet was used. The surface S of the molten metal M injected into the mold 10 gradually rises from the bottom of the cavity 19 and
1 was completely covered. Specifically, the mold 10 is rotated at a rotation speed of about 2 degrees / second, and when the inclination angle becomes 50 degrees after 25 seconds from the start of rotation, the aluminum pipe 21 is rotated.
All dived below the surface S. Then, the rotational speed of the mold 10 is increased to 8 degrees / second to erect the mold 10 (FIG. 5),
The molten metal M in the mold 10 was pressurized by the hot water H. The casting was completed 30 seconds after the start of rotation of the mold 10.

Next, the cooling of the mold 10 was continued, and the product was taken out of the mold 10 when 145 seconds had elapsed from the start of casting.

In this embodiment, the aluminum pipe 21 was cast into the molten metal M injected into the cavity 19 without being cooled by the vacuum suction method. In order to investigate the thermal effect of the molten metal M on the aluminum pipe 21, a thermometer T was installed at a position 1 mm near the aluminum pipe 21, and the temperature of the molten metal M near the aluminum pipe 21 was detected. The temperature of the molten metal M indicated by the thermometer T was only 617 ° C. at the maximum, and was sufficiently lower than the melting point of about 655 ° C. of the A3003 aluminum alloy used for the aluminum pipe 21. Therefore, even when the molded body obtained after casting was cut and cast into an aluminum pipe 21, no damage caused by erosion was detected, and it was found that the aluminum pipe 21 could be sufficiently used as a hydraulic circuit.

The above casting was repeated seven times using the alloy 1 of the present invention and the comparative alloys 2 and 3. A test piece was cut out from the center of each of the obtained shaped members, and the microstructure, mechanical properties and inclusion distribution were investigated. In microstructure observation, DA
S was measured, and the observation results were image-processed to obtain eutectic Si
The average length was determined. In the investigation of the distribution of inclusions, a notch was cut into a long thick plate having a height of 0.5 cm and a length of 5 cm cut out from the molded body, and the plate was broken with a naked eye and a 10-fold loupe to obtain a sample of 0.5 cm × 5 cm. observing the fracture surface (second surface) counts the number of inclusions was calculated K ₁₀ value from the count. Most of the inclusions are oxide-based,
The inclusions of about 3 mm had a blackish color tone.

As can be seen from the investigation results in Table 1, the eutectic Si in the alloy 1 of the present invention and the comparative alloy 2 has an average length of 10 μm or less, but has a mean length of 10 μm or less, but the comparative alloy 3 without Na treatment
It is a small value compared to. The difference in the average length of the eutectic Si is caused by the fact that the alloy 1 of the present invention and the comparative alloy 2 are refined with Na, whereas the comparative example 3 is not treated. The inclusions were included in Comparative Alloy 2 in large amounts. A large amount of inclusions are generated by the oxidation of the refining agent Na during the process of transferring the molten metal cleaned by the rotary degassing process and the slag removing process from the holding furnace to the basin 12, and the oxides floating on the surface of the molten metal. This is because the oxide film or the like flows into the cavity 19 without being separated from the molten metal M and is taken into the casting. On the other hand, in the alloy 1 of the present invention, oxides, oxide films, and the like are captured by the weir 22 and separated from the molten metal M, so that the obtained casting has high cleanliness. The trapping action of oxides, oxide films, and the like by the weir 22 is also observed in the comparative alloy 3, but the casting of the comparative alloy 3 has a cast structure in which the size of eutectic Si is large. DAS is a value determined by the alloy system and the cooling rate.
Since the same conditions are adopted in all of the above, almost the same value of 50 μm or less is shown.

[0038]

Next, T6 treatment (solution solution 53) was applied to each cast material.
(5 ° C. × 6 hours → water quenching → Left at room temperature for 6 hours → artificial aging 155 ° C. × 5 hours). A sample was cut out from the cast material after the heat treatment, and the tensile strength, 0.2% proof stress, elongation, and fatigue strength of a Clause type rotary bending fatigue tester were measured.
In the Clause-type rotating bending fatigue test, the test piece was 120 N /
The number of revolutions before breaking was determined by applying a stress of mm ² .
As can be seen from the survey results in Table 3, the elongation of Comparative Example 2 is about 6.0% on average, whereas the Example 1 of the present invention has Table 2
As shown in the figure, the average growth was as high as about 9.9%. This shows that the product 1 of the present invention is excellent in toughness and impact load. As for the fatigue properties, the product 1 of the present invention shows a higher fatigue strength than that of the comparative example 2 because the number of impurities is small, and can be said to be a material suitable for the caliper body. The cause of such a large difference in fatigue strength is due to the dispersion state of inclusions and the size of eutectic Si. That is, Comparative Alloy 2 shows low fatigue strength because the inclusions that cause the occurrence of fatigue cracks are dispersed in a large amount. On the other hand, in the product 1 of the present invention, 25 cm
0.28 pieces ² of the area (in terms the 0.0112 cells / c
Only inclusions of m ² ) were observed, and less inclusions appeared as excellent fatigue strength.

[0040]

[0041]

[0042]

As described above, in the caliper body of the present invention, N has a high effect of miniaturizing eutectic Si.
By using a, Sr, Ca, etc. as a refining agent, producing a clean molten metal by appropriate molten metal treatment and holding, and separating oxides generated in the molten metal transfer process from the molten metal before the mold. In addition, generation of oxides and removal of the generated oxides are performed to inject a clean molten metal into a mold to reduce inclusions that cause fatigue cracks and control the form of eutectic Si. The cast body thus obtained exhibits excellent fatigue characteristics and mechanical properties, and is therefore used as an integrated caliper body having no fatigue cracks in the bridge portion.

[Brief description of the drawings]

FIG. 1 is a sectional view of an integrated caliper body.

FIG. 2 illustrates a casting method according to the present invention.

FIG. 3 is a diagram showing a state in which a mold is being rotated.

FIG. 4 is a view showing a state in which an aluminum pipe is covered with molten metal.

FIG. 5 is a diagram in which a mold is upright.

FIG. 6 is a view showing an apparatus in which a mold is fixed and a pool is rotatable;

[Explanation of symbols]

1: Rotor 2: Caliper body 3: Piston
4: Brake pad 5: Pipe 6: Cylinder 7: Bridge part 10: Die 11: Gate 12: Pool 13:
Ladle 14: Cooling gutter 15: Weir 16: Outlet 17: Supply gutter 18: Insulation material 19: Cavity 20: Core 21: Aluminum pipe
22: Weir M: Molten molten metal 0: Center of rotation S: Hot surface H: Hot water T: Thermometer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C22F 1/00 601 C22F 1/00 601 602 602 627 627 627 631 631A 691 691B 691C (72) Inventor Hamano Yasuhiko 43-3 Harumi-cho, Tomakomai-shi, Hokkaido Nippon Light Metal Co., Ltd. Tomakomai Factory (72) Inventor Kaoru Sugita 2-2-2 Higashishinagawa, Shinagawa-ku, Tokyo Japan Light Metal Co., Ltd. (72) Inventor Akio Hashimoto Shizuoka 1-334-1, Kambara, Kambara-cho, Anbara-gun, Nippon Light Metal Co., Ltd. Group Technical Center F-term (reference) 3J058 AA43 AA48 AA53 AA66 AA69 AA73 AA77 AA84 AA87 BA46 BA61 CC03 CC22 CC36 DD11 EA08 FA01

Claims (12)

[Claims] An aluminum pipe for supplying hydraulic pressure to a piston pressed against a rotor via a brake pad is cast in a caliper body, and an aluminum alloy constituting the caliper body is made of Si: 5 to 11% by weight, Mg: 0.25 to 0.7% by weight, and Na: 0.0
02 or 0.02% by weight, Sr: 0.003 to 0.04% by weight, Ca: 0.003 to 0.04% by weight.
At least P, 0.002% by weight or less of the elements contained as impurities.
b: 0.01% by weight or less, Fe: 0.3% by weight or less, other impurity elements: regulated to 0.5% by weight or less,
Average length of eutectic Si of the cast structure is 10μm or less, dendrite arm spacing is 50μm or less, an aluminum integral caliper body average number of inclusions is 0.02 / cm ² or less at K ₁₀ value. 2. The aluminum alloy according to claim 1, further comprising: 0.05 to 0.25% by weight of Ti and / or B: 0.0% by weight.
An integrated caliper body made of aluminum containing 001 to 0.01% by weight. 3. The molten aluminum alloy adjusted to the composition according to claim 1 or 2 is transferred from the melting furnace to a batch-type holding furnace, degassed, de-slagged, and refined.
The temperature is maintained at 80 to 750 ° C., and the amount of molten metal necessary for one casting is transferred to a pool, and the temperature of the molten metal in the pool is set at 640 to 70.
A method for manufacturing an integrated caliper body, comprising: adjusting a temperature to 0 ° C .; and pouring molten metal into a mold in which an aluminum pipe as a material to be cast is set. 4. An amount of molten metal required for one casting is pumped out of a holding furnace, transferred to a cooling gutter connected to a pool of a mold, and supplied to the pool via the cooling gutter. Item 4. The method for producing an integrated caliper body according to Item 3. 5. The method for manufacturing an integrated caliper body according to claim 3, wherein a cooling gutter having a weir for adjusting a flow rate of the molten metal flowing into the basin and having a heat radiation structure is used. 6. The method for manufacturing an integrated caliper body according to claim 3, wherein a basin in which a heat insulating material is lined is used. 7. The method for manufacturing an integrated caliper body according to claim 3, wherein a weir is provided in a flow path of the molten metal from the pool to the mold. 8. The molten metal fed from the basin into the cavity of the mold rises and covers the aluminum pipe, and then the remaining molten metal is rapidly supplied to the cavity to be fed from the basin. The method for manufacturing an integrated caliper body according to any one of claims 3 to 7, wherein the molten metal is prevented from directly contacting the aluminum pipe. 9. A mold or a mold in which a pool is integrated so that molten metal fed from the pool does not directly contact the aluminum pipe until the surface of the molten metal rising inside the cavity covers the aluminum pipe. 9. The method for manufacturing an integrated caliper body according to claim 8, wherein the molten metal is fed into the cavity from the mold while gradually rotating the rotatable pool. 10. The molten metal is poured into the cavity, and then the gate is positioned upward to exert a pusher effect.
The method for producing an integrated caliper body according to any one of the above. 11. The integrated caliper body according to claim 3, wherein one end of the aluminum pipe is connected to a vacuum system during the injection of the molten metal, and the aluminum pipe is cooled by outside air sucked from the other end. Manufacturing method. 12. 520-545 ° C. × 1-15 after casting
Time solution treatment, water quenching, 150 ~ 170 ℃ × 2
The method for manufacturing an integrated caliper body according to any one of claims 3 to 11, wherein the aging treatment is performed for 10 hours.