JP3487553B2 - Powder release lubricant for mold casting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder mold release lubricant for die casting, which uses a gas generated by thermal decomposition of an inorganic substance as a heat insulating boundary layer.

[0002]

2. Description of the Related Art As a powder release lubricant used in a mold casting process, an inorganic powder excellent in heat insulation and heat retention is mainly used in order to reduce a heat flow rate from a molten metal to a mold. Is used for. When utilizing the properties of the inorganic powder itself such as heat insulation and heat retention, it is often the case that natural mineral products such as talc must be selected.As it is a natural mineral product, asbestos may be an impurity depending on the place of origin. There is concern about the inclusion of crystallin silica or crystalline silica. As described above, in the case of utilizing the heat insulating property and heat retaining property of the inorganic powder itself, there are great restrictions in selecting raw materials, and in some cases, the release lubricant is extremely expensive.

On the other hand, organic powders such as polyethylene wax and metal soap are not only high in initial cost of raw materials, but when they are often used, decomposition gas such as methane, ethane and hydrogen is cast when they come into contact with molten metal. It may enter the product and become a factor that deteriorates the quality of the product.

[0004]

SUMMARY OF THE INVENTION The present invention was developed in view of the above-mentioned circumstances. Instead of utilizing the heat insulating property of the inorganic powder itself, the inorganic material constituting the powder comes into contact with the molten metal. By utilizing the gas generated by thermal decomposition at that time as an adiabatic boundary layer between the molten metal and the mold, heat transfer from the molten metal to the mold can be effectively reduced, and at a low cost. It is an object of the present invention to propose a powder release lubricant for mold casting that uses an inorganic powder.

[0005]

That is, the gist of the present invention is as follows. 1. Aluminum hydroxide, calcium hydroxide, and hydroxide that generate gas by thermal decomposition when they come into contact with molten metal .
Gnesium, calcium carbonate, magnesium carbonate and
At least one selected from basic magnesium carbonate
Powder separation for die casting, characterized by comprising a mixed powder of inorganic powder of one kind, boron nitride as a improver of lubricity, and organic powder as an improver of adhesion and lubricity. Type lubricant.

[0006]

2 . The powder mold release lubricant for die casting according to the above 1 , wherein the compounding amount of boron nitride as a lubricity improver is 50 mass% or less of the whole inorganic material including the inorganic powder.

[0008] 3 . The amount of the above organic powder is 50 mass% or less of the whole mixed powder, or the above 1 or
2. A powder release lubricant for die casting according to 2 .

[0009] 4 . The powder release lubricant for mold casting according to the above 1, 2 or 3 , wherein the organic powder is at least one selected from synthetic polymer compounds and fatty acid metal salts.

[0010]

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The present invention, by the contact between the inorganic powder and the molten metal,
The gas generated by thermal decomposition is used as an adiabatic boundary layer.
Because the gas generated as described above penetrates seamlessly between the molten metal flowing in the casting process and the mold, it is effective to use such a gas film as a boundary layer. This is because excellent heat insulation and heat retention can be obtained.

[0012] Also, as the inorganic powder as described above, it is necessary to pyrolysis temperature is in the range of 100 to 1000 ° C. in an air atmosphere. Because the thermal decomposition temperature is 100
Below ℃, the mold surface is usually kept at 200 to 300 ℃, so there is a risk of decomposition at the same time as adhesion.
On the other hand, if it exceeds 1000 ° C, decomposition is unlikely to occur even if it comes into contact with molten metal, and gas generation may not occur. Examples of such inorganic powder include aluminum hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, and basic magnesium carbonate.

Further, as such an inorganic powder, a powder that produces inorganic particles as a decomposed product or a product even after thermally decomposing to generate a gas is particularly suitable. The reason is that if inorganic particles are generated as decomposition products or products even after the gas is generated by thermal decomposition, the generated gas is pinned by the generated inorganic powder, so a more uniform heat insulation layer is formed. As a result, the heat flow rate from the molten metal to the mold is remarkably reduced, and good release lubrication performance is exhibited. Examples of the inorganic powder include aluminum hydroxide, magnesium hydroxide, magnesium carbonate, calcium carbonate, and basic magnesium carbonate among the above-mentioned powders.

Further, in the present invention, at least one selected from the above-mentioned hydroxides or carbonates as the inorganic powder which generates gas by thermal decomposition, and boron nitride as the lubricity improver. A mixed inorganic mixed powder is used. According to the present invention, it becomes possible to supply an inexpensive mold release lubricant for die casting by using a hydroxide or a carbonate as the inorganic powder. Further, by additionally using a solid lubricant having a hexagonal crystal structure such as boron nitride and having a self-lubricating property, it is possible to further improve lubricity and releasability. Here, the blending ratio of the boron nitride described above is too large, or of products surface on factors darkening poor appearance, not only the cost, because there is a possibility that gas generation amount is suppressed, boron nitride The compounding ratio is preferably 50 mass% or less of the whole inorganic material including the inorganic powder.

Furthermore, the present invention improves the adhesion to the mold inorganic powder, yet in order to ensure the lubrication performance during inorganic powder, it is assumed that compounding organic powder
It was That is, in the powder release lubricant of the present invention, even if the inorganic powder alone lacks the adhesive force, the adhesive force can be expected by using the organic powder together, and the lubricating performance can be improved at the same time. . The upper limit of the amount of the organic powder blended is preferably 50 mass% or less of the total mixed powder.
Yes. The reason is that if the content exceeds 50 mass%, the amount of decomposed gas generated from organic substances becomes too large, and the product may be caught in a cast product, resulting in deterioration of quality.

As such organic substances, synthetic polymer compounds such as polyethylene wax and polypropylene wax and fatty acid metal salts such as lithium stearate, calcium stearate and zinc stearate are preferable. Such a high molecular compound or a fatty acid metal salt has a low melting point and exerts a wetting effect on the mold surface when the temperature of the mold surface changes to change from a solid to a liquid, thereby increasing the adhesive force. It also has the effect of intervening between the solidified metal and the mold to improve the mold release lubricity.

Next, the experimental results which are the basis of the present invention will be described. In the present invention, the heat insulating / heat retaining effect of the powder release lubricant was evaluated by the flow length L when the molten metal was poured. The flow length shall be measured by the flow length measuring device shown in FIG. 1, and in the figure, numeral 1 is a crucible, 2 is a stopper, 3
Is a thermometer, and 4 is a molten metal (Al alloy). Further, 5 is a flow path of the molten metal 4, 6 is a heater, 7 is a viewing window, 8 is a zoom microscope, and 9 is a high speed VTR.

Now, a powder release lubricant is uniformly applied in advance to the flow path 5 of the flow length measuring die as shown in FIG. 1 at a rate of ² g / m ² . In addition, as a comparative example, a commonly used aqueous lubricant was diluted under normal use conditions and similarly applied to a mold. After applying the mold release lubricant, apply the flow length measurement mold to 200
Raise the temperature to ℃. The temperature was controlled by PID control to have an error of ± 1 ° C.

Next, the crucible 1 made of stainless steel preheated to 600 ° C. is set at a predetermined position of the mold (upper mold), and the stopper 2 made of stainless is used to plug the crucible 1. Note that the inner surface of the crucible 1 and the outer peripheral surface of the stopper 2 are coated with so-called "grate". Then, a molten aluminum alloy (ADC 12) molten metal 4 at 700 ° C. is poured into the crucible 1. At that time, in order to keep the hydrostatic pressure of the molten metal constant, the molten metal is always poured to a constant height. After pouring the molten metal 4 into the crucible 1, a CA thermocouple is inserted into the molten metal and the temperature is measured. When the stopper 2 is pulled up when the molten metal temperature reaches 630 ° C., the molten metal 4 flows into the flow path 5 engraved in the flow length measuring die (lower die). After solidification, by measuring the length of the casting, the flow length L
To measure.

The flow length L was measured for various releasing lubricants in the above manner, but as an inorganic substance which satisfies the requirements of the present invention and which is thermally decomposed by contact with molten metal (molten metal) to generate gas. , Aluminum hydroxide [Al (OH) ₃ ], calcium hydroxide [Ca (OH) ₂ ] and calcium carbonate [CaCO
₃ ] was used. The average particle size of these inorganic powders was about 0.5 to 30 μm.

First, the thermal balance was used to measure how many times these inorganic powders were thermally decomposed and how much gas was generated. The result is shown in FIG. The experiment was conducted in an Ar atmosphere and the temperature rising rate was 10 ° C / min. As shown in the figure, it was found from the change in weight that aluminum hydroxide was thermally decomposed at around 300 ° C. and about 370 ml of water vapor was generated as thermally decomposed gas per 1 g. Here, the gas generation amount is an amount converted into a so-called standard state (0 ° C., 1 atmospheric pressure). Similarly, it was found that calcium hydroxide was thermally decomposed at around 450 ° C. and about 250 ml of water vapor was generated as thermally decomposed gas per 1 g. Also, calcium carbonate is 7
It was found that thermal decomposition occurred at around 00 ° C. and about 100 ml of carbon dioxide was generated as thermal decomposition gas per 1 g. In this way, these inorganic powders can be used in the sleeve (inside the injection cylinder) or inside the die during die casting for 600
When it contacts with molten aluminum above ℃, it is thermally decomposed and gas is generated.

Next, the results of measurement of the flow length L in the case of using each inorganic powder alone, and in the case of using graphite or organic powder as a subcomponent were used,
FIG. 3 shows a comparison with that of a conventional release lubricant. Conventionally,
In powder release lubricants, talc has been mainly used as an inorganic substance, but in this case, the low heat transfer characteristics of talc itself are used to reduce heat transfer between the molten metal and the mold. It was a thing. On the other hand, when the powder release lubricant of the present invention is used, compared with talc, the flow length L is about 30% with calcium hydroxide and about 40% with aluminum hydroxide.
Has been improved.

Further, as compared with the water-soluble mold release agent which has been conventionally used, a powder mold release lubricant in which calcium hydroxide (represented by a symbol C), graphite (the same G) and wax (the same W) are mixed. 2.2 times for (CGW (54,36,10) in the figure),
The powder release lubricant (AGW (50, 25, 25) in the figure) using aluminum hydroxide instead of calcium hydroxide showed a flow length of 3.4 times. It should be noted that the powder mold release lubricant that uses talc instead of calcium hydroxide or aluminum hydroxide (TGW (50, 25, 25) in the figure) is 1.8 times as much as the conventional water-soluble mold release agent. The flow length was obtained,
The effect was inferior to the case where calcium hydroxide or aluminum hydroxide was used as the inorganic powder according to the present invention.

As described above, the reason why excellent fluidity is obtained when the powder release lubricant according to the present invention is used is that the inorganic powder contained as a component in the powder release lubricant is molten metal. This is because when they come into contact with each other, they are heated to generate gas, and a vapor phase film is effectively formed between the molten metal and the mold, which acts as a heat insulating boundary layer.

Further, a water-soluble release agent, TGW (50, 25, 2
5) and AGW (50, 25, 25) were respectively applied to the mold at 2 g / m ² and the heat transfer coefficient from the molten metal to the mold was 14, 3, 2 kW / M ² K respectively. Yes, from this value
It can be seen that GW (50, 25, 25) has excellent heat insulating properties.

[0026]

[0027]

[0028]

[0029]

[0030]

As described above, according to the present invention, as the constituents of the powder release lubricant, "an inorganic substance which thermally decomposes to generate a gas when heated and heated, and a boron nitride as an agent for improving lubricity are provided.
And organic powders as adhesion and lubricity improvers "
By mixing and using, the heat retention of the molten metal inside the sleeve and the heat retention / fluidity of the molten metal inside the cavity in die casting can be significantly improved.

Further, since the temperature decrease rate of the molten metal inside the sleeve is small, the molten metal temperature until the completion of injection can be kept higher than in the case where the conventional sleeve lubricant is used. Similarly, since the heat retention of the molten metal inside the cavity is high, the molten metal filling time can be extended.
As a result, the injection speed of the molten metal into the mold cavity (plunger tip speed and gate speed) is up to 1/1 compared with the case of using conventional oil-based or other lubricants.
It can be reduced to about 0, and so-called low-speed filling becomes possible. As a result, it is possible to reduce the defects of the cast product due to the air entrainment during the filling of the molten metal into the cavity to 1/10 or less.

Further, there is an effect that the heat retaining property of the molten metal in the sleeve is improved, and casting defects called fracture chill layer can be reduced. That is, as the casting becomes thinner, it is known that the solidification rate of the molten metal is significantly affected by the presence or absence of a fracture chill layer, but according to the present invention, the fracture chill layer decreases, Compared with conventional water-soluble mold release lubricants, it is possible to manufacture thinner and larger cast products.

[Brief description of drawings]

FIG. 1 is a view showing a flow length measuring device.

FIG. 2 is a diagram showing a thermal decomposition temperature of an inorganic powder.

FIG. 3 is a diagram showing a comparison of flow lengths of various release lubricants.

[Explanation of symbols]

1 crucible 2 stopper 3 thermometer 4 Molten metal 5 channels 6 heater 7 peep windows 8 zoom microscope 9 High speed VTR

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification FI C10M 103: 00 C10M 103: 06 A 103: 06 105: 24 105: 24) C10M 107: 02 (C10M 111/04 C10N 10:02) 103: 00 10:04 103: 06 10:06 107: 02) 20:00 AC 10N 10:02 30:00 Z 10:04 30:06 10:06 40:36 20:00 50:06 30:00 50 : 08 30:06 40:36 50:06 50:08 (72) Inventor Makoto Yoshida 2-360 Kagamiyama, Higashihiroshima City, Hiroshima Prefecture 2-406 Second dormitory 2-406 (72) Inventor Hideyuki Yoshimatsu Yoshiga, Okayama City, Okayama Prefecture 5301 Okayama Prefecture Industrial Technology Center (72) Inventor Satoru Ueno 5301 Haga, Okayama City, Okayama Prefecture 5301 Okayama Prefecture Industrial Technology Center (72) Inventor, Keiki Sawai 3-2 Takazukadai, Nishi-ku, Kobe City, Hyogo Prefecture 45 Hanano Trading Co., Ltd. (56) References JP-A-5-92232 (JP, A) JP-A-6-346075 (JP, A) JP-A-6-32 8190 (JP, A) JP 2001-198649 (JP, A) JP 2001-353550 (JP, A) JP 2-242897 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C10M 111/02-111/04 C10M 103/00-103/06 C10M 105/24-105/26 C10M 107/00-107/54 C10M 129/28-129/46 C10M 143/00-157 / 10 C10M 169/04 C10N 10:02-10:06 C10N 20:00 C10N 30:00 C10N 30:06 C10N 40:36 C10N 50:06-50:08 B22C 3/00-3/02 B22D 17/20

Claims (4)

(57) [Claims] 1. Aluminum hydroxide, calcium hydroxide, which thermally decomposes to generate gas when contacted with molten metal ,
Magnesium hydroxide, calcium carbonate, magnesium carbonate
A small amount selected from aluminum and basic magnesium carbonate
Powder for die casting, comprising at least one kind of inorganic powder, boron nitride as a lubricity improver, and organic powder as an adhesion and lubricity improver Body release lubricant. Wherein the amount of boron nitride as a lubricity improving agent, a powder for die casting according to claim 1, wherein a is not more than 50 mass% of the total inorganics including the inorganic powder Release lubricant. 3. The compounding amount of the organic powder is 50 mass% or less of the total mixed powder, or
2. A powder release lubricant for die casting according to 2 . 4. The organic powder, synthetic polymer compound or fatty acid powdery mold release lubricants for die casting according to claim 1, wherein is at least one selected from among metal salts.