JP2001286978A - Core for casting and its facing material, and method for coating this core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the protection power of a core against molten iron. SOLUTION: The surface of the sand core is coated with a three-layer structure composed of an undercoating agent containing TiO2 applied as the lowermost layer, an ceramic base coating agent consisting essentially of SiO2 and MgO applied as the second layer and a flake-shaped graphite coating agent applied as the third layer. The undercoating agent is composed of 30g of TiO2, 5 cc of alumina sol and 50 cc of alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core for casting, for example, a ventilated brake disk rotor, a mold-coating agent therefor, and a method for coating the core.

[0002]

2. Description of the Related Art When a brake disk rotor, which is one of the automotive parts, becomes large in size, if the rotor is to be manufactured by a high-pressure casting method, it is necessary to secure the molten metal-running property. Since the temperature of the molten metal in contact with the surface is increased, burrs are likely to occur due to insertion of the molten metal into the core. In order to prevent the insertion of the molten metal, the core is coated with a mold wash to increase the strength against the pressure of the molten metal.

[0003] As this kind of technology, Japanese Patent Laid-Open No. 6-2347 is disclosed.
Japanese Patent Application Publication No. 6-204, discloses a method in which a coating agent in which a filler and an additive are dispersed in an organic resin binder composed of a linear organopolysiloxane is applied to a sand core to improve pressure resistance and improve coating workability. An approach has been proposed.

[0004]

However, the organic resin binder is insufficient in the pressure resistance, and has a problem that heat is generated from the molten metal to generate gas and cause a cavity.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an inexpensive core for casting, a mold-coating agent for the core, and a method of coating the core, which enhances the hiding power of the core against the molten metal. That is.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the object, a mold wash agent of the present invention is a mold wash agent used for a pressure-resistant coat of a casting core, and comprises a titanium oxide. Contains particles and an inorganic binder solution.

[0007] Preferably, the inorganic binder solution is mixed with the titanium oxide particles 10 in 50 cc of a solvent.
~ 35 g, and 1 to 10 cc of the inorganic binder.

Preferably, the inorganic binder solution is further mixed with whiskers.

Further, the casting core of the present invention is coated with a mold wash containing titanium oxide particles and an inorganic binder solution.

[0010] Preferably, the inorganic binder solution is mixed with the titanium oxide particles 10 in 50 cc of a solvent.
~ 35 g, and 1 to 10 cc of the inorganic binder.

[0011] Preferably, the inorganic binder solution is further mixed with whiskers.

Further, the method of coating a casting core of the present invention comprises:
Coating agent containing titanium oxide particles and inorganic binder solution, titanium oxide particles 10 to 35 with respect to 50 cc of solvent
g and an inorganic binder mixed with 1 to 10 cc, or a coating agent obtained by mixing a whisker with the inorganic binder solution, and then applied to a casting core, followed by a ceramic coating agent. The flaky graphite coating agent is applied in this order.

[0013]

As described above, according to the first and fourth aspects of the present invention, since the mold wash applied to the casting core contains titanium oxide particles and an inorganic binder solution, the particle size is reduced. Titanium oxide, which is extremely small, has high hiding power, is inexpensive, and is easily soluble in a solvent, can be firmly bonded with an inorganic binder to increase the pressure resistance. In addition, the amount of the titanium oxide particles is reduced to reduce dripping, and the core having a small thickness can be uniformly coated.

Further, the thickness of the coating layer can be reduced, cracks can be prevented, and titanium oxide can be saved.

According to the second and fifth aspects of the present invention, the inorganic binder solution is prepared by adding titanium oxide particles 1 to 50 cc of the solvent.
By mixing 0 to 35 g with an inorganic binder of 1 to 10 cc, the pressure resistance can be increased while preventing exposure of the core skin and cracking of the coat layer.

According to the third and sixth aspects of the present invention, the inorganic binder solution is obtained by further mixing whiskers.
Further, the pressure resistance of the coat layer can be improved, and the coat layer has elasticity, so that the mold and the core are in close contact with each other, so that it is difficult to insert the molten metal.

According to the seventh aspect of the present invention, a coating agent containing titanium oxide particles and an inorganic binder solution, and a solvent 50c
A casting agent obtained by mixing 10 to 35 g of titanium oxide particles and 1 to 10 cc of an inorganic binder with respect to c, or a coating agent obtained by mixing whiskers with an inorganic binder solution is used as a casting core. After applying, ceramic coating agent,
By applying the flaky graphite coating agent in this order, the ceramic coating agent layer and the flaky graphite coating agent layer can be reinforced as a base, and the pressure resistance can be increased.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a partial sectional view of a ventilated brake disk rotor casting mold in which a casting core and a composite porous member according to the present embodiment are arranged. FIG.
FIG. 2 is a front view of a casting core. FIG. 3 is a perspective view of a product after finishing processing, which is formed by the casting mold of the present embodiment.

The casting mold illustrated in FIG. 1 is used for high-pressure casting of a ventilated disc brake rotor made of an aluminum alloy.

The casting mold has a cavity 3 formed therein by closing a pair of an upper mold 1 and a lower mold 2. The lower mold 2 has a sprue 4 for filling a molten metal, and a sprue 4. The apparatus includes a sleeve 5 forming a communicating molten metal passage, and a movable plunger 6 for slidingly contacting an inner wall of the sleeve 5 to press-fit the molten metal to the gate 4. The molten metal is pushed up by the movable plunger 6 and introduced into the cavity 3 from the gate 4 at a high pressure.

The cavity 3 extends downward and is inclined (tapered) toward the center in the radial direction while lowering. The lower mold outer peripheral surface 2a, a lower mold flat surface portion 2b extending from the lower end of the lower mold outer peripheral surface 2a to the radial center side, An upper die flat portion 1a extending radially from the upper end of the lower die outer peripheral surface 2a to a radial center, and a lower die projecting surface 2c extending downward from the inner end of the lower die flat portion 2b and inclined (tapered) toward the radial center. A lower die protruding surface 2d extending radially from the lower end of the lower die protruding surface 2c, and an upper die protruding surface 1b extending downward from the inner end of the upper die flat portion 1a and inclined (tapered) toward the radial center. And an upper mold projecting surface 1c extending from the lower end of the upper mold projecting surface 1b to the center in the radial direction. Lower die outer peripheral surface 2
a and the upper mold projecting surface 1b are inclined so as to be substantially parallel to each other.

In the cavity 3, the lower die flat portion 2b and the upper die flat portion 1a form a rotor sliding surface forming space 3a, and the lower die projecting surface 2c, the lower die projecting flat surface 2d, and the upper die projecting surface 1d.
b and the upper mold protruding surface 1c form a hub mounting surface forming space 3b and also form a gate 4.

In the cavity 3, a sand core 7 for forming a cooling ventilation hole in the pressure portion of the rotor is disposed.

The sand core 7 is disposed in the cavity 3 so that the axis of rotation of the rotor and the axis of the sleeve 5 coincide with the line R. The outer ring portion 8, the inner ring portion 9, the outer ring portion 8, and the inner ring portion 9 are provided. Are formed in a disk shape concentric with a line R having a connecting portion 10 that connects the two. The connecting portions 10 are formed at equal intervals radially around the line R in the circumferential direction.

The sand core 7 is formed in a tapered shape so that the outer peripheral surface 8a of the outer ring portion 8 abuts on the outer peripheral surface 2a of the lower die when the sand core 7 is disposed in the cavity 3. The child inner peripheral surface 9a is formed in a tapered shape so as to contact the upper die projecting surface 1b. As a result, the sand core 7 is placed in the cavity 3
Can be positioned accurately within Also, since the lower die outer peripheral surface 2a and the upper die projecting surface 1b are inclined so as to be substantially parallel to each other, it is easy to remove the die from the product.

On the side surface of the inner ring portion 9 facing the gate 4,
For example, four portions are connected at equal intervals in the circumferential direction.
A deleted portion 9b is formed so as to be flush with the side surface portion 9c of the inner ring portion 9 opposite to the gate 4.
The upper die 1 comes into contact with the vicinity of the inner end of the upper die flat portion 1a substantially perpendicular to the inflow direction S of the molten metal. The sand core 7 has a cantilever structure with the outer ring portion 8 as a fulcrum in the cavity 3.

In the present embodiment, the deleted portion 9b is formed so as to be flush with the connecting portion 10 in a straight line.
It becomes easy for the molten metal to penetrate, so that the porous members 11 and 12 can be easily impregnated into the outer ring portion 8 remote from the gate 4.
Sanding out from the mold is also easy. In addition, since the unevenness of the surface of the sand core 7 is reduced, there is an advantage that a pressure-resistant coat layer for suppressing insertion of the molten metal can be easily formed.

The side surface 9c of the inner ring portion 9 opposite to the gate 4 comes into contact with the vicinity of the inner end of the upper die flat portion 1a substantially perpendicular to the flow direction S of the molten metal in the upper die 1, so that the pressure of the molten metal is reduced. As a result, the sand core 7 can be pressed against and adhered to the upper mold flat portion 1a, so that the sand core 7 can be reliably positioned in the cavity 3, and the insertion of the molten metal can be suppressed to suppress burrs.

The outer ring portion 8, the inner ring portion 9, and the connecting portion 10 are formed with a step in the opening direction R of the rotor shaft and the upper die 1, and both sides of the connecting portion 10 are combined with the molten metal. Member 1 such as a ceramic porous body preformed in advance
Numerals 1 and 12 are respectively disposed and partially combined with the brake disk rotor sliding surface. In other words, the porous member can be reliably positioned via the sand core using this step.

The porous members 11 and 12 are formed in an annular shape concentric with the line R.

As shown in FIG. 3, the ventilated brake disk rotor 20 cast at a high pressure using the casting mold has sliding surfaces 21 and 22 of the brake disk rotor.
The porous members 11 and 12 are formed into a composite, and the surface layer is cut by about 1 mm by finishing, and a plurality of cooling ventilation holes are radially provided between the rotor sliding surfaces 21 and 22 (rotor pressure portions). 25 are formed. Also, a convex hub mounting portion 2 protruding from the brake disk rotor sliding surface 21.
3, three screw mounting holes 24 are formed.

Brake disk rotor sliding surfaces 21, 22
Is formed by arranging a pre-formed body composed of porous ceramic particles / fibrous formed body in a mold, impregnating with an aluminum alloy melt, and solidifying.

As the porous member, other than a ceramic porous body, a metal fiber material made of stainless steel or the like can be used. Tungsten, molybdenum, carbon steel, and the like may be used as the metal fiber material in addition to stainless steel, but the stainless fiber material is practical since it has the highest strength and is inexpensive. [Example] The casting conditions of the present embodiment are, as an example, a molten metal forging method in which pressure is applied at about 60 MPa and filling is performed at a filling speed of 50 mm / sec. .

The sand core of the present embodiment has a resin amount of 2.1 to 2.1.
2.3% by weight, bending strength about 6.5 MPa, particle size index (AF
S) The resin-coated shell core having an average particle diameter of 65 to 75 and an average particle diameter of 0.15 mm is formed as an example, and is formed by baking at 573 to 593K, blowing for 3 seconds, and curing for 40 seconds. [Pressure-Resistant Coating Layer] In casting of an aluminum alloy by a high-pressure casting method, such as a ventilated brake disk rotor exemplified in the present embodiment, in order to form cooling ventilation holes, insertion of molten metal into a sand core is prevented. It is necessary to form a pressure-resistant coating layer.

For this reason, the surface of the sand core 7 is coated with an undercoating agent as a coating agent containing TiO ₂ (average particle diameter 0.3 μm) applied on the lowermost layer, and a SiO ₂ applied as a second layer. ₂ and a ceramic coating agent containing MgO as a main component, and a flaky graphite coating agent applied as a third layer.

The undercoat agent is, for example, TiO ₂ 30
g, alumina sol 5cc, alcohol (ethanol) 5
0 cc. The alumina sol contains 20 to 21% of alumina (Al ₂ O ₃ ) as an inorganic binder and has a colloidal size of 5 to 200 μm as shown in any of the following chemical formulas (i) to (iii). Hydrate is a viscous colloidal liquid in which polymer particles are dispersed with anions in water as a stabilizer. The alumina particles are positively charged.

Al ₂ O ₃ .H ₂ O. (H ⁺ , NO ₃ ⁻ ) ... (i) Al ₂ O ₃ .H ₂ O. (H ⁺ , Cl ⁻ )... (Ii) Al ₂ O ₃ .H ₂ O · (H ⁺ , CH ₃ COO ⁻ ) (iii) The alumina of (i) is granular or rod-shaped, (ii) and (ii)
i) is present in the liquid in the form of feathers.

[0039] After the sand core 7 was immersed in the undercoat coating agent, alumina sol alcohol and dried contains TiO ₂ particles by evaporation to solidify (gel), TiO ₂
Since the bonding between the TiO ₂ particles is stronger than in the case of only the particles, the pressure resistance is improved and the undercoat layer can be made thinner.

The undercoating agent is composed of 10 g of TiO ₂ particles.
Coating is difficult to sand core 7 in the following, since prone to clumping and TiO ₂ particles is too much at least 35 g, the alcohol 50 cc, TiO ₂ particles 10 to 35
g, 1 to 10 cc of alumina sol.

According to the undercoating agent, alumina
TiO compared to the case without _TwoFewer particles
As a result, when dripping decreases
However, it becomes easier to remove after drying. In addition, medium thickness
The child can be evenly coated.

Further, the ceramic coating agent layer and the flaky graphite coating agent layer can be reinforced as a base, and the pressure resistance can be increased.

By substituting a part of TiO ₂ with fine and thin fibrous whiskers such as aluminum borate whiskers and potassium titanate whiskers, the pressure resistance of the undercoating layer can be further improved, and the coating layer has elasticity. Therefore, the mold and the core are in close contact with each other, and the molten metal is difficult to insert. In this case, it is preferable that about 20% of the weight of the TiO ₂ particles be replaced with whiskers. If the number of whiskers is too large, the denseness of the undercoat coat layer is lost, and the insertion of the molten metal cannot be prevented.

As a method of coating the core with the undercoating agent, the core is sufficiently stirred and mixed, and then the sand core 7 is immersed for about 10 seconds and air-dried for 2 to 3 hours.
Thus, an undercoat layer having a thickness of about 40 μm is formed.

For the ceramic coating agent as the second layer, an alcohol that can be easily dried is used as a solvent, and the weight ratio between the stock solution of the ceramic coating agent and the alcohol solvent is 1:
As a method for coating the core, the core is sufficiently stirred and mixed, and then the sand core 7 coated with the undercoat is soaked for about 10 seconds and naturally dried for 2 to 3 hours.
As a result, a ceramic coating layer having a thickness of about 200 μm is formed.

As shown in FIG. 4, the composition of the ceramic coating agent is mainly composed of SiO ₂ and MgO, and as shown in FIG. 5, has a fine particle size of 40 μm or less.

The flaky graphite coating agent as the third layer is prepared by using water as a solvent in a flaky graphite having an average particle size of about 5 to 10 μm, and the weight ratio of the water-soluble graphite coating agent stock solution to water is 1:
The method for coating the core is as follows. The core is sufficiently stirred and mixed, and then the sand core 7 coated with the undercoating agent and the ceramic coating agent is dipped for about 10 seconds to form
Allow to air dry for 10 hours. Thereby, the film thickness is 30 μm
A grade of flaky graphite coat layer is formed.

The above is a description of the embodiments and examples of the present invention. However, the aluminum alloy casting manufactured by the present invention is not limited to the ventilated brake disk rotor formed by the high-pressure casting method as in the above-described embodiments. However, the present invention can be applied to other parts requiring wear resistance and weight reduction. According to the present invention, in addition to the aluminum alloy,
For example, it can be applied to other light alloy castings such as a magnesium alloy.

Further, a silica sol may be used in place of the alumina sol.

As shown in the following chemical formula (iv), the silica sol has a negatively charged amorphous silica (SiO ₂ ) particle dispersed as a stabilizer in water to form a colloid, and the particle has a fine spherical shape. ing.

SiO ₂ .H ₂ O. (Na ⁺ , O ⁻ )... (I
v)

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a ventilated brake disk rotor casting mold in which a casting core and a composite porous member of the present embodiment are arranged.

FIG. 2 is a front view of a casting core.

FIG. 3 is a perspective view of a product after a finishing process formed by a casting mold according to the embodiment.

FIG. 4 is a view showing a chemical composition of a ceramic coating agent.

FIG. 5 is a diagram showing a particle size distribution of a ceramic coating agent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Upper mold 2 ... Lower mold 3 ... Cavity 4 ... Gate 5 ... Sleeve 6 ... Plunger 7 ... Sand core 8 ... Outer ring part 9 ... Inner ring part 10 ... Connection part 11, 12 ... Porous member 20 ... Ventilated disc Brake rotor 23: Hub mounting surface 25: Cooling vent

Claims (7)

[Claims] 1. A coating composition used for pressure-resistant coating of a casting core, comprising titanium oxide particles and an inorganic binder solution. 2. The method according to claim 1, wherein the inorganic binder solution contains 50 cc of a solvent.
2. The coating composition according to claim 1, wherein 10 to 35 g of the titanium oxide particles and 1 to 10 cc of the inorganic binder are mixed. 3. The coating composition according to claim 1, wherein the inorganic binder solution is further mixed with whiskers. 4. A casting core, which is coated with a mold wash containing titanium oxide particles and an inorganic binder solution. 5. The method according to claim 1, wherein the inorganic binder solution comprises 50 cc of a solvent.
5. The casting core according to claim 4, wherein 10 to 35 g of the titanium oxide particles and 1 to 10 cc of the inorganic binder are mixed. 6. The casting core according to claim 4, wherein the inorganic binder solution is further mixed with whiskers. 7. A coating agent containing titanium oxide particles and an inorganic binder solution, a coating agent obtained by mixing 10 to 35 g of titanium oxide particles and 1 to 10 cc of an inorganic binder with respect to 50 cc of a solvent, or After applying to the casting core any one of the coating agents obtained by mixing whiskers with the inorganic binder solution, a ceramic coating agent and a flake graphite coating agent are applied in that order. Coating method.