JPH09122882A - Coating material for aluminum alloy casting parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the erosion by a molten aluminum alloy. SOLUTION: At least either of calcium oxide and magnesium oxide component are added at prescribed ratios to the coating agent applied on the casting parts with which the molten aluminum alloy comes into contact. The amt. of the addition in the case the calcium oxide component is added alone is 2 to 30wt.% and the amt. of the addition in the case the magnesium oxide is added alone is 3 to 40wt.%. The total amt. of the addition in the case both are added is 3 to 50wt.%. The advance of the molten aluminum alloy into the microspacings of the coating material is prevented if the calcium oxide and/or the magnesium oxide component is included in the coating material. The erosion of the aluminum alloy is thus prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating agent for cast aluminum alloy parts, and more particularly to cast parts which come into contact with molten aluminum alloy, such as stalks and intermediate stalks for low pressure casting, and ladles and pots for die casting. The present invention relates to a coating agent applied to the surface of these parts in order to protect the above from the molten aluminum alloy.

[0002]

2. Description of the Related Art In casting aluminum alloys, cast iron is the mainstream for parts that come into contact with the molten aluminum alloy, such as intermediate stalks for low pressure casting. Cast iron is easily eroded by molten aluminum alloy. Therefore, conventionally, a commercially available coating agent has been applied to the surface of the intermediate stalk or the like to prevent adhesion of the molten aluminum alloy or prevent melting of the intermediate stalk due to the molten aluminum alloy. .

The above-mentioned commercially available coating agents are mainly composed of the following heat resistant aggregates, plasticizers and binders. Heat-resistant aggregate: Alumina, graphite, titanium oxide Plasticizer: Iron oxide, Kaolin clay Binder: Colloidal silicic acid, sodium silicate, boric acid, clay-based material

[0004]

However, even when the above-mentioned conventional coating agent is applied to the surface of a cast part, adhesion and erosion of the aluminum alloy occur during repeated casting, and the durability of the cast part is improved. We couldn't secure enough. In addition, due to the melting loss of cast iron, the iron content may be mixed as an impurity in the aluminum alloy, and the iron content contained in the aluminum alloy may fall outside the range of the impurity specifications.
Therefore, when using a conventional commercially available coating agent, it is necessary to increase the frequency of recoating the coating agent in order to sufficiently prevent adhesion and erosion of the aluminum alloy. Was in decline.

For example, when the above-mentioned conventional commercially available coating agent is applied to an intermediate stalk and cast for 8 hours, the coating agent film that comes into contact with a relatively low temperature part is discolored to gray.
The film of the coating agent that was in contact with the middle temperature part turned black, and the solidified aluminum alloy was adhered to the surface in a skin-like form with a thickness of about 5 to 8 mm. In addition, most of the coating film that comes into contact with the high temperature part is peeled off to expose the black cast iron, and the aluminum alloy is partially eroded to cause the alloy part of the aluminum alloy and the cast iron (size of about 30 mm). Was formed in several places. Further, the iron content in the aluminum alloy was 0.11% at the start of casting, but increased to 0.15% at the end of casting. Therefore, when a conventional commercially available coating agent is used, it is necessary to repeat the repair work of interrupting the casting and repainting the coating agent after about 6 hours have passed from the start of casting. Even when such repair work is repeated, the erosion of the aluminum alloy cannot be completely prevented, the life of the intermediate stalk is about 36 hours, and the aluminum alloy AC4C is also used.
In some cases, it was out of the range of the impurity iron standard.

The erosion by the molten aluminum alloy also occurs when the commercially available coating agent is applied to an intermediate stalk made of ceramics such as silicon carbide, silicon nitride and zircon having a high melting point and a high heat resistance. The present invention has been made in view of the above circumstances, and it is a technical problem to be solved to provide a coating agent for an aluminum alloy casting part that can effectively prevent erosion by the molten aluminum alloy. is there.

[0007]

A coating agent for an aluminum alloy casting part according to claim 1, which solves the above-mentioned problems, comprises:
A coating agent that is applied to cast parts that come into contact with molten aluminum alloy, and has a calcium oxide content of 2 to 30 wt%
It is characterized by being added. The coating agent for an aluminum alloy cast part according to claim 2 which solves the above-mentioned problems, is a coating agent applied to a cast part in contact with an aluminum alloy melt, wherein the magnesium oxide content is 3 to 40.
It is characterized in that wt% is added.

A coating agent for cast aluminum alloy parts according to claim 3 which solves the above problems is a coating agent applied to cast parts which are in contact with a molten aluminum alloy, wherein the calcium oxide content is 2 to 30 wt%. At the same time, magnesium oxide content of 3 to 40 wt% is added,
It is characterized in that the total amount of calcium oxide and magnesium oxide added is 3 to 50 wt%.

The coating agent for cast aluminum alloy parts of the present invention contains at least one of a calcium oxide component and a magnesium oxide component, which can sufficiently prevent adhesion and erosion of molten aluminum alloy. it can. The erosion of the molten aluminum alloy occurs because the molten aluminum alloy enters the minute gaps in the film of the coating agent, but if the coating agent contains calcium oxide or magnesium oxide, the molten aluminum alloy is It is possible to effectively prevent entry into the minute gaps of the membrane. It is considered that this is because the addition of the calcium oxide component and the magnesium oxide component increases the surface wettability, that is, the surface contact angle of the aluminum alloy.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The coating agent for cast aluminum alloy parts of the present invention can contain a heat resistant aggregate, a plasticizer and a binder as shown below in a preferred embodiment. Heat-resistant aggregate ： Alumina, zircon Plasticizer ： Clay-based materials such as kibushi clay and kaolin clay Binder ： Clay-based materials such as colloidal silicic acid, sodium silicate, aluminum phosphate, kibushi clay and kaolin clay The blending amounts of the heat-resistant aggregate, the plasticizer and the binder are not particularly limited, but the following blending amounts can be mentioned as preferred embodiments. The blending amount shown in parentheses is more preferable.

Heat-resistant aggregate: 20-80 wt% (40-60 wt%) Plasticizer: 1-20 wt% (3-15 wt%) Binder: 3-30 wt% (5-20 wt%) The above heat-resistant aggregate If the blending amount is less than 20 wt%, the heat resistance will be insufficient and the coating will be easily cracked, while if it exceeds 80 wt%, the coating strength will be insufficient and the coating will be rough and easily broken. On the other hand, if the compounding amount of the plasticizer is less than 1 wt%, the film becomes rough and uneven during application, while if it exceeds 20 wt%, the film may be cracked due to the large drying shrinkage of the viscous material. Further, if the amount of the binder added is less than 3 wt%, the coating strength is low and it tends to be broken, while if it exceeds 30 wt%, foaming may occur due to evaporation of water during heating. When a clay-based material such as kaolin clay or Kibushi clay is used as a binder, this clay-based material also serves as a plasticizer, so it is not necessary to add another clay-based material as a plasticizer. .

The coating agent according to the present invention contains at least one of a calcium oxide component and a magnesium oxide component in a predetermined amount. When the calcium oxide component is added alone, the addition amount is 2 to 30 wt%. This calcium oxide component may be added either as a single oxide or as a complex oxide containing calcium oxide.

When the magnesium oxide component is added alone, the addition amount is 3-40 wt%. This magnesium oxide component may be added as a single oxide or may be added as a composite oxide containing magnesium oxide. Furthermore, when both the calcium oxide content and the magnesium oxide content are added, the addition amount of the calcium oxide content is set to 2 to 30 wt% and the addition amount of the magnesium oxide content is set to 3 to 40 wt%.
%, And the total amount of calcium oxide and magnesium oxide added is 3 to 50 wt%. The calcium oxide content and the magnesium oxide content may each be added as a single oxide or may be added as a composite oxide containing at least one of calcium oxide and magnesium oxide.

When the amount of calcium oxide or magnesium oxide added is less than the above range, it becomes difficult to sufficiently prevent erosion by the aluminum alloy, while the amount of calcium oxide or magnesium oxide added is in the above range. If the amount is larger than the range shown in (1), the film strength of the coating agent may be lowered and the coating agent may be peeled off during casting. The coating agent according to the present invention is applied to the surface of a cast component with which the molten aluminum alloy comes into contact. The coating method is not particularly limited. For example, after adding 10 to 30% of water to 70 to 90 wt% of the coating agent of the present invention and stirring well, 40 to 40
It is possible to coat the surface of the cast component heated to about 70 ° C. with a brush so as to evaporate the water content to a film thickness of about 50 to 500 μm. Alternatively, the coating agent 15 of the present invention
Water of 60 to 85 wt% is added to -40 wt% and well stirred, and this is sprayed onto the surface of a cast part preheated to about 180 to 250 ° C. with a spray gun to obtain 50 to 500 μm.
It can be applied to a film thickness of the order.

The coating agent according to the present invention can be applied to a cast part in contact with a molten aluminum alloy, and is particularly suitable for application to a high temperature part (about 740 to 780 ° C.). For example, it can be applied to the surfaces of stalks and intermediate stalks for low pressure casting, and ladles and pots for die casting.

[0016]

[First Embodiment]

(Example 1) 60 wt% alumina, 5 wt% sodium silicate
%, Kaolin clay 15 wt%, and calcium oxide 20
A coating agent having a composition of wt% was prepared by kneading with a mill.

50 wt% of the above coating agent and 50 wt% of water
%, And after stirring well, this was applied to the surface of a cast iron intermediate stalk preheated to 70 ° C. by brush coating to a film thickness of 100 μm. Thus, using the intermediate stalk coated with the coating agent according to the first embodiment, the aluminum alloy (AC
4C) was low pressure cast. The casting conditions were such that the melting and holding temperature of the aluminum alloy was 700 ± 10 ° C.

Then, 8 hours after the start of casting, the casting was interrupted, and after observing the film of the coating agent applied on the surface of the intermediate stalk, casting was performed again for 8 hours, and the film of the coating agent was observed. As a result, the coating film was not changed at all after 8 hours. Further, after 16 hours, the film of the coating agent, which was in contact with the high temperature part (about 700 ° C.), was discolored to a slight gray color, but no other change was observed in the film of the coating agent.

The iron content in the aluminum alloy was 0.12% before the start of casting and 0.15% after 16 hours of casting. (Example 2) The composition of the coating agent was 60 wt% zircon,
Kaolin clay 20 wt% and magnesium oxide 20 w
A coating agent was applied to the surface of the intermediate stalk in the same manner as in Example 1 except that t% was set. Then, low pressure casting was performed under the same casting conditions as in Example 1, the casting was interrupted after 8 hours, and the film of the coating agent applied to the surface of the intermediate stalk was observed 6 times.

As a result, even in the final stage after 48 hours of casting time, there was no blackened portion on the surface of the coating agent film that was in contact with the aluminum alloy. Further, although the aluminum alloy was adhered to the coating agent in contact with the high temperature part (about 700 ° C.) in a skin-like shape, the aluminum alloy could be peeled off by hand. Further, the iron content contained in the aluminum alloy is 0.12% before the start of casting,
It was 0.13% after 48 hours of casting.

(Example 3) As in Example 1, except that the composition of the coating agent was 60 wt% zircon, 5 wt% aluminum phosphate, 15 wt% kaolin clay, and 20 wt% magnesium oxide, an intermediate stalk was formed. The coating agent was applied to the surface. Then, low pressure casting was performed under the same casting conditions as in Example 1, the casting was interrupted after 8 hours, and the film of the coating agent applied to the surface of the intermediate stalk was observed 12 times.

As a result, even in the final stage after 96 hours of casting time, there was no blackened portion on the film surface of the coating agent that was in contact with the aluminum alloy. Further, the aluminum alloy did not adhere to the film of the coating agent in a skin form. Further, the iron content contained in the aluminum alloy is
It was 0.12% before the start of casting and 0.12% after 96 hours of casting.

In Example 3, although the casting time was longer than that in Example 2, the aluminum alloy did not adhere to the coating film even at the final stage. This is presumably because aluminum phosphate was used as the binder in Example 3, and the film of the coating agent became a denser and more uniform film due to the reaction between magnesium oxide and aluminum phosphate.

(Example 4) As in Example 1, except that the composition of the coating agent was 55 wt% zircon, 15 wt% kaolin clay, 15 wt% calcium oxide and 15 wt% magnesium oxide, the surface of the intermediate stalk was coated. The coating agent was applied. Then, low pressure casting was performed under the same casting conditions as in Example 1, the casting was interrupted after 8 hours, and the film of the coating agent applied to the surface of the intermediate stalk was observed.
Repeated times.

As a result, even in the final stage after 96 hours of casting time, there was no blackened portion on the surface of the coating film of the coating agent which was in contact with the aluminum alloy. Further, the aluminum alloy did not adhere to the film of the coating agent in a skin form. Further, the iron content contained in the aluminum alloy is
It was 0.12% before the start of casting and 0.12% after 96 hours of casting.

Further, even in the final stage after the casting time of 96 hours, no damage was found in the intermediate stalk. In addition, in the present Example 4 in which both the calcium oxide content and the magnesium oxide content were added, compared with the above-mentioned Example 1 and Example 2 in which either one of the calcium oxide content and the magnesium oxide content was added, Despite the long casting time, the aluminum alloy did not adhere to the coating film even at the final stage.

(Example 5) As in Example 1, except that the composition of the coating agent was zircon 55 wt%, kaolin clay 15 wt%, calcium oxide 15 wt% and magnesium oxide 15 wt%, the surface of the intermediate stalk was coated. The coating agent was applied. Then, low-pressure casting was performed under the same casting conditions as in Example 1, after 8 hours × 15 times of 120 hours of casting, the casting was interrupted after 8 hours, and the film of the coating agent applied to the intermediate stalk surface was observed. Was repeated 10 times.

As a result, even at the final stage after 200 hours of casting time, the film of the coating agent in contact with the high temperature part (about 700 ° C.) turned a little gray, but no erosion of the aluminum alloy was observed. It was The iron content contained in the aluminum alloy was 0.12% before the start of casting, 0.14% after 120 hours elapsed, and 0.15% after 200 hours casting.

Further, even in the final stage after the casting time of 200 hours, no damage was found in the intermediate stalk. (Comparative Example 1) A commercially available coating agent (trade name: Topcoat SP-1000) having the composition shown below was prepared.

Ferric oxide (Fe ₂ O ₃ ): 5 to 8 wt% Alumina: 35 to 45 wt% Titanium oxide: 5 to 10 wt% Silica (colloidal silica, SiO ₂ · xH ₂ O): 5 to 10 wt% Water: 18 to 20 wt% Similar to Example 1, this coating agent was applied to the surface of the intermediate stalk and low pressure casting was performed under the same casting conditions as in Example 1, 8
The casting was stopped at a certain time, and the film of the coating agent applied to the surface of the intermediate stalk was observed.

As a result, about 60% of the surface area of the coating film contacting the aluminum alloy was discolored black. The coating film was peeled off in about 45% of the black discolored portion, and erosion by the aluminum alloy was observed in about 20% of the black discolored portion. And the attached aluminum alloy could not be removed without hitting with a chisel.

The iron content contained in the aluminum alloy was 0.14% before the start of casting and increased to 0.22% after 8 hours of casting. Further, the average stalk life was 36 hours on average. (Comparative Example 2) The composition of the coating agent was 20 wt% alumina,
A coating agent was applied to the surface of the intermediate stalk in the same manner as in Example 1 except that 5 wt% of sodium silicate, 15 wt% of kaolin clay, and 60 wt% of silicon carbide were used. Then, low pressure casting was performed under the same casting conditions as in Example 1, the coating agent film was observed after casting for 8 hours, and then 4 castings were performed again to observe the coating agent film.

As a result, after casting for 8 hours, the surface area of the coating film contacting with the aluminum alloy was about 50%.
% Was discolored black. Further, the aluminum alloy adhered to a part of the coating agent film that was in contact with the high temperature portion, and when the adhered alumina alloy was peeled off, the coating agent film was also peeled off together. At the final stage after 12 hours of casting, the result was almost the same as that of Comparative Example 1.

The iron content contained in the aluminum alloy was 0.12% before the start of casting and increased to 0.21% after 12 hours of casting. [Second Example] (Examples 6 to 21) A coating agent having the composition shown in Table 1 was prepared, and the coating agent was applied to the surface of the intermediate stalk and low-pressure casting was performed in the same manner as in Example 1 above. Casting for 8 hours × 10 times a day was continued for 1 week. Then, after continuously casting for one week, the film of the coating agent was visually observed. The number of points at which the aluminum alloy was eroded in the intermediate stalk is also shown in Table 1, and is also shown by the number in ○ in FIG.

[0035]

[Table 1] (Comparative Examples 3 to 10) A coating agent having the composition shown in Table 2 was prepared, the coating agent was applied to the surface of the intermediate stalk and low-pressure casting was performed, and 8 hours × 10 times a day, as in Example 1 above. Casting continued for a week. Then, after continuously casting for one week, the film of the coating agent was visually observed. The number of points at which the aluminum alloy was eroded in the intermediate stalk is also shown in Table 2, and is also shown by the numbers in the circles in FIG.

[0036]

[Table 2] As is clear from Tables 1 and 2 and FIG. 1, it is understood that the addition of calcium oxide or magnesium oxide within the scope of the present invention can effectively prevent the corrosion of the aluminum alloy.

[0037]

As described in detail above, since the coating agent for cast aluminum alloy parts of the present invention contains a predetermined amount of calcium oxide or magnesium oxide, it effectively prevents the adhesion or erosion of the aluminum alloy. Can be prevented. Therefore, the durability of the cast part can be improved, and the coating agent can be repainted less frequently to improve the productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amounts of calcium oxide and magnesium oxide added and the number of erosion points.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Baba 1 Toyota-cho, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Yoshiyuki Ito 1-cho, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. ( 72) Inventor Yuji Sengoku 57-1, Hashime-cho, Okazaki-shi, Aichi

Claims (3)

[Claims] 1. A coating agent applied to a cast part which is in contact with a molten aluminum alloy, wherein the content of calcium oxide is 2%.
A coating agent for cast aluminum alloy parts, characterized by being added in an amount of ˜30 wt%. 2. A coating agent applied to a cast part which is in contact with a molten aluminum alloy, wherein the magnesium oxide content is added in an amount of 3 to 40 wt%. 3. A coating agent applied to a cast part that is in contact with a molten aluminum alloy, the calcium oxide content being 2%.
-30% by weight, magnesium oxide content of 3-40% by weight, and total addition amount of calcium oxide content and magnesium oxide content of 3-50% by weight. Agent.