JPH071077A - Die treated with heat insulating film for longer life - Google Patents

Abstract

PURPOSE:To dispense with the repairing/executing process, to omit the set-up process, and to remarkably improve the dimensional precision by using the plating film having the heat insulating property, the heat resistance and the functionality to the die in the low pressure casting and the die casting. CONSTITUTION:The surface roughness of the die is rough in the range of 30-400mum, the adhering surface of the plating is increased, and the stresses associated with the thermal expansion/contraction are dispersed to prevent the peeling of the film. The eutectoid dispersion of the particles and fibers such as the organic resin and ceramics is realized on the plating film. This allows the relaxation and dispersion of the stresses in the plating film and provides the effect of the peelability. The heat treatment is executed to release the excessive gasified contents in the plating layer and the adhesivity is improved. The eutectoid-dispersed particles and fibers of organic resin are eluted by the heat in the heat treatment to form the porous plating film to keep the heat insulation. The eutectoid-dispersed particles and fibers of ceramics improves the heat resistance and the heat insulation. In addition, the eutectoid dispersion of the high thermal conductive substance in the plating film can manufacture the casting of aluminum of fine equi-axed crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a functional plating film on the surface of a mold to be used as a coating agent for low-pressure casting / mold casting and at the same time prolongs the life of the mold, thereby making a leap in productivity. The present invention relates to a plating film that is improved.

[0002]

2. Description of the Related Art Conventionally, in low-pressure casting / die casting, a heat-retaining coating agent for casting is coated and used as a coating agent. The composition of the mold wash was (binder) + (plasticizer) + (pigment). In the binder
Inorganic materials such as colloidal silica, sodium silicate, and aluminum monophosphate were used. Various clay-based materials have been used as plasticizers that facilitate spray coating. For the pigment, oxide ceramics, porous vermiculite / isolite powder for heat retention, and graphite / boron nitride for lubricity were used. The coating composition constituted as described above is diluted with water to give 18
The surface of the mold preheated to 0 to 250 ° C. was spray-coated with air to form a coating film. Depending on the material composition of this mold coating agent and its construction method, it was difficult to form a uniform coating film in which the strength, film thickness, surface roughness of the coating film and the adhesion to the mold varied. . This variation makes casting quality and productivity unstable and shortens the life of the coating film.
There was frequent interruption of production due to the correction work. or,
The thickness of the coating film required for casting was not constant at 0.05 to 0.4 mm, the dimensional accuracy was poor, and the coating film became unstable due to repair. When the coating film reached the end of its life (4 to 60 hours), there was a step of stopping the casting machine, lowering the mold, peeling the coating film by shots or sandblasting, and forming the coating film again. The film properties of the coating material made it difficult to cast a thick wall having a thickness of 20 mm or more and a thin wall having a thickness of 3 mm or less, causing many defects in the drawing core. The deterioration of casting quality due to the aging of the coating film always requires a human check, and even if it is automated, it does not lead to labor saving.

[0003]

Problems to be Solved by the Invention Problems that occur only with the conventional material composition and construction method are: (1) Short life of the coating film. When the surface roughness of the coating film is worn away, defects such as scratches and chamfering frequently occur. (2) Repair the coating film during production. In order to correct the above-mentioned worn roughness, the production is interrupted by spray coating, and the temperature of the mold which can be produced is raised. (3) The dimensional accuracy is poor and does not become constant. The applied coatings are of different thickness and are constantly changing due to wear during production. (4) It is necessary to repeat the process of applying the coating film. Four
The coating film has reached the end of its life in about 40 hours, and it is necessary to peel off the coating film each time and form a coating film again. In this construction process, it is necessary to take down the die from the casting machine for 2 to 12 hours. In addition, sand blasting is applied to remove the coating film, which also wears the die and shortens the life of the die. (5) Coating life is shortened due to improved productivity. When the shot cycle is shortened and the productivity is improved, the mold temperature rises, the heat load of the coating film increases, and the life is shortened. Moreover, in order to cool the overheated part of the mold, holes are drilled in the mold and water cooling is performed. Due to the heat cycle, the coating film is peeled off. (6) Casting hole by die. The drawing core for making the casting hole has high mold release resistance, high temperature, boundary air between the mold and aluminum, etc., which easily causes defects such as scratches and seizures, and the coating film wears quickly. Even if you have it well, it is 6 hours or less. (7) Prevent full automation. As the coating ages,
Since the casting quality also deteriorates from moment to moment, it is not possible to omit human checks and repair processes to maintain the quality. (8) Variations in coating film construction. The conditions for applying the coating are
Even with a work standard that is set very finely and quantified as much as possible, the performance of the coating film has largely fluctuated due to the subtle feeling of the construction worker. For example, the life of the coating film easily changes 5 to 10 times. (9) There is a non-castable area due to coating film performance. As the functional requirements for parts become stricter, casting products with higher soundness are required. However, with the conventional coating film, a sound casting product having a wall thickness of 20 mm or more and a sound casting product having a thickness of 3 mm or less have not been obtained. This is due to the gradual cooling due to the heat retaining property of the coating film and the forming force using low gravity due to insufficient strength of the coating film. The present invention has been invented in order to solve these drawbacks and problems and to expand the possibilities of casting.

[0004]

[Means for solving the problem]

(B) Use plating instead of the binder. Problems (1) to (9) are the limits of the material composition of the coating film and the construction method itself, and there is room for improvement, but it is not possible to solve it. Therefore, the binding force of the plating, which has a completely different material composition and construction method, was used instead of the binder of the coating film. As a result, the process of applying the coating film becomes unnecessary, and the binding force as a binder increases dramatically. However, the mold is 3
Since the temperature is raised to about 50 to 430 ° C., the peeling of the plating film due to its thermal expansion and oxidation becomes a problem. This measure was absorbed by the following to prevent peeling. (A-1) The roughness of the die surface was roughened in the range of 30 to 400 μm, the adhesion area of plating was increased, and the stress due to thermal expansion / contraction was dispersed in the roughness of the die. In the manufacturing method for making the surface of the mold rough, the order in which the effect is high with respect to peeling was shot peening> chemical polishing> electrical discharge machining> sandblasting of steel balls. On the other hand, when the thickness is 30 μm or less, the effect of dispersing the stress due to the roughness of the mold is not exerted, and the peeling is performed similarly to the flat surface. When the thickness is 400 μm or more, there is no problem in peelability, but the unevenness marks the cast product. (A-2) Raise the temperature slowly (350 ° C x 30m
heat treatment (in), the excess gasification component in the plating layer was generated and the adhesion was improved. (A-3) Since the pigments of (claim 3) to (claim 6) are eutectically dispersed in the plating layer, the stress in the plating layer is relaxed and dispersed. If the eutectoid dispersion is at least 5% by volume, sufficient peeling effect can be obtained. However, below 5% by volume
No effect on casting is recognized, and the bonding strength of the plating becomes weak at 80% by volume or more. (B) Make the plating film heat-retaining. In low pressure casting / die casting, a heat insulating layer such as a coating film is required on the die surface. In order to impart heat retention to the plated layer, a porous plated layer may be formed. For this reason, organic resin particles and fibers are co-eutectically dispersed during plating, and during heat treatment for increasing adhesion, the heat is used to elute and form a porous plating film. If it is 5% by volume or less, the elution of the organic resin is small, and if it is 80% by volume or more, the strength of the coating is lowered. The material of the organic resin is not limited to polyethylene, vinyl, nylon, etc. as it is eluted by heat treatment. Further, the surface oxidation by heat treatment has a characteristic that the thermal conductivity is lowered and returned to have a heat retaining effect. (C) Make the plating film heat resistant. Ceramic particles and fibers are eutectoidally dispersed in the plating film to improve heat resistance and heat retention. Ceramic materials include aluminum, which is a casting material, and carbides such as SiC and TiC, which have wettability, and Ti and Al. An oxide such as Mg is preferable. The eutectoid dispersion amount of ceramic particles and fibers is preferably 5 to 90% by volume. 5
Below volume%, the heat resistance and non-wetting effects are low,
If it is more than the volume%, the bonding strength of the plating will decrease. (D) A highly heat-conductive substance is codeposited and dispersed in the plating film. The finer the equiaxed crystal in the cast aluminum product, the higher the soundness and strength, and the superior quality. The formation of the fine equiaxed crystal was achieved by solidifying the casting material by the heat capacity of the spotted portion when the high thermal conductive material was spotted, while the casting material was not solidified early by the heat insulation plating film. The same casting is cast with a coating and plating film, and the same 38mm
When 10 thick portions were cut out and the macrostructures were compared, the number of crystal grains per 25 mm square was 8 to 22 for the coating film.
The number of grains / plated film was 160 to 420, which was about 1/10 of the size of crystal grains. (E) The coating film is coated on the plating film. If pressure is higher than gravity, or if mold release is difficult due to thick and complicated shape and it is more difficult to cast, reduce the eutectoid dispersion amount in the plating film to increase the film strength. Therefore, in order to secure the insufficient heat retaining property, the castability is improved by forming the coating film into two thin layers. The plating film composed of (a) to (e) above has a high film strength and thus has permanent durability, and the life of the plating film is the life of the die. This long service life eliminates the need for (2) coating repair during production and (4) repeated coating application steps, so there are no variations in installation and dimensional accuracy is constant. Problems due to the high strength of the plating film (5) (6)
It is possible to sufficiently cope with the mold part under the condition that the film strength is required such as (9). Once the plating film is formed, it can be used for the life of the mold, so there is no factor of variation in casting, and automation can save labor.

[0005]

[Operation] Due to the long durability of the plating film, production was not interrupted at all, and there was no need to remove the mold from the casting machine, enabling extremely stable production. As a result, the casting quality and dimensional accuracy were constant, the production was improved by 34.2% in the cylinder head, and the mold life was 50,000 to 60,000 shots, but it was damaged even after reaching 220,000 shots. I didn't. Therefore, it was possible to make dramatic improvements in all aspects of productivity, quality, manageability, and price.

[0006]

EXAMPLES Examples of the present invention will be described below. (Comparative Example-1) Product name Manifold (4 wheels 1800
cc) Coating film The product with the longest life out of the commercial products Setup process: Mold maintenance-mold preheating-Coating film coating-set mold on casting machine Total time: 3.5 hrs Production process: Mold preheating -Production cycle-Film coating repair-Film life Total time: 120 hr Production time: 98 hr Production number: 1176 pieces 9.8 pieces / hr (Example-1) Product name Same as (Comparative example-1) Plating film Organic resin Particles (particle size 50 μm) 30
Volume% Ceramic particles (particle diameter 25 μm) 15% by volume Plating film Chromium plating Film thickness 100 μm Setup process: Set the mold on the casting machine Total time; 0.3 hr Production process: Mold preheating-Production cycle-stop for one month Total time 504 hr Production time; 498 hr Production number; 6474 pieces 12.8 pieces / hr (Example-2) Product name Same as (Comparative Example-1) Plating film Organic resin fiber (fiber diameter 20 μm × fiber length 6)
0 μm) 20% by volume Ceramic fiber (fiber diameter 15 μm x fiber length 100 μm)
20% by volume Setup process: Set mold in casting machine Total time: 0.3 hr Production process; Mold preheating-Production cycle-Stop in 1 month Total time: 504 hr Production time; 496 hr Production number: 6448 pieces 12.8 pieces / hr (Comparative Example-2) Product name Cylinder head (4 wheels 18
00cc) Coating film The product with the longest life in the commercial products Setup process: Mold maintenance-mold preheating-Coating film coating-mold setting on casting machine Total time: 12.5 hrs Production process: Mold preheating one Production cycle-coating repair-one coating life Total time: 120 hr Production time: 94 hr Production number: 1253 10.4 / hr (Example-3) Product name Same as (Comparative-2) Plating film Organic resin fiber ( Fiber diameter 15 μm x fiber length 5
0 μm) 25% by volume Ceramic particles (particle size 30 μm) 30% by volume Plating film Electroless Ni-P plating Thickness 150 μm Setup process: Set mold on casting machine Total time: 0.6 hr Production process: Mold preheating-Production Cycle-Stop for one month Total time: 504 hr Production time: 493 hr Production number: 6545 pieces 13.0 pieces / hr (Example-4) Product name (Comparative Example-2) Same as plating film Organic resin particles (particle diameter 25 μm) 40% by volume Ceramic fiber (fiber diameter μm × fiber length 60 μm) 30% by volume Plating film Electroless Ni-B plating Setup process: Set mold in casting machine Total time: 0.6 hr Production process: Mold preheating-Production cycle -Stop in 1 month Total time: 504 hr Production time: 493 hr Production number: 6567 pieces 13.0 pieces / hr (Comparative example- ) Product Name Piston product shape maximum thickness portion for car cooler (30 × 40 × 40mm ²⁾ product quality on higher graphite mainly of cooling performance in the coating film commercially available test results productivity 10.2 pieces / hr Macro Texture 9 to 36 pieces / 25 mm square (number of crystal grains / unit area) Microstructure When observed at 800 times, fine shrinkage cavities are recognized between crystal grains. Tensile strength 22.4 kg / mm ² Elongation rate 4.2
% He gas pressure resistance 6.3 kg / cm ² (helium gas leakage pressure) (Example-5) Product name and product shape are the same as (Comparative example-3) Plating film Organic resin particles (particle diameter 20 μm / 10% by volume) ) High thermal conductive atoms (tungsten 20% by volume) Plating film Ni-P electroless plating Film thickness 50 μm Product quality inspection results Productivity 13.9 / hr Macro structure 243 to 456/25 mm square (number of crystal grains / unit Area) Microstructure: No defects are observed in the range of 800 times. Tensile strength 30.1 kg / mm ² Elongation 7.6
% He gas pressure resistance 9.4 kg / cm ² (helium gas leakage pressure) (Example-6) Product name Manifold (wall thickness 2.5 m
(For trial production of m) The coating film does not come off easily because the bathing area is poor and there are holes. Plated film Organic resin particles (particle size 20 μm, 55% by volume) Colloidal silica (film thickness 30 μm) Plated film Ni-B electroless plating film thickness 75 μm) Product passing rate In case of film 5/105 (pieces) 4.
8% In case of plating film 62/70 (pieces) 88.6% (margin below)

[0007]

[Effects of the Invention] Permanent coating is made possible by making the plating coating heat-retaining, heat-resistant, and functional in low-pressure casting / die casting with a coating. As a result, there is no need for the repair and construction process of the coating film that exists because of the coating film, and the setup process can be omitted and the dimensional accuracy is dramatically improved. In addition, as a result of adding functionality to the plating film, the range of soundness of castings and possibilities of casting can be greatly expanded. Since the die is protected by the plating film, the die life is extended by 2 to 4 times, and the abrasion is very little, so that stable production which cannot be obtained by the coating film can be performed. The effects of all four production factors of quality, productivity, controllability, and price are recognized.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C23C 26/00 A C25D 7/00 F

Claims (8)

[Claims] 1. A mold surface coating which is used for low-pressure casting / die casting by forming a coating on the die surface using electroless plating / electroplating as a binder. 2. A plating film according to claim 1, which is plated with nickel, chromium, chromate, Ni-P, and Ni-B. 3. A plating film formed on the surface of a mold having a surface roughness roughened in the range of 30 to 400 μm (claim 1). 4. A heat-retaining plating film in which particles and fibers of an organic resin are eutectically dispersed in the film of (claim 1) and heated to elute organic substances. 5. A heat-resistant plating film in which ceramic particles and fibers are eutectically dispersed in the film according to claim 1. 6. W.Mo.S in the film of (claim 1)
Local high thermal conductivity plating film in which rO / BaO / Be etc. are codeposited and dispersed. 7. 3-100 on the film of (claim 1)
In the range of μm, coating agent, sodium silicate, aluminum phosphate,
A two-layer film with a film of colloidal silica, alumina, titanium, gallium, and Teflon. 8. A plating film, characterized by using (claims 2 to 7) in combination to satisfy various functions required for casting.