JPS6117793B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating agent for protecting metal melting crucibles or furnaces. More specifically, by applying this to a metal melting crucible or furnace, specifically a cast iron crucible, a reverberatory furnace, or a low frequency induction furnace, it is possible to create a flexible and stable gap between the molten metal and the crucible or furnace at the melting temperature of the metal. By forming a highly durable protective film, it can withstand the pressure of molten metal and the thermal expansion and contraction of the crucible or furnace, and prevent the intrusion of molten metal and flux gas, making it possible to significantly extend the life of the crucible or furnace. It relates to a seasoned protective coating. Conventionally, cast iron crucibles, firebrick reverberatory furnaces, low-frequency induction furnaces, and the like have been used for melting metals. Cast iron crucibles mainly melt aluminum, zinc, etc., but they also melt molten metal and fluxes used to remove impurities in the molten metal, such as highly reactive gaseous substances such as NaC, KC, BaF, and _AF3 . Cast iron crucibles have been coated with protective coatings in order to prevent corrosion of cast iron crucibles due to corrosion and to prevent contamination of molten metal by cast iron crucibles. These coating agents generally consist of heat-resistant materials such as earthy graphite, chromium oxide, titanium oxide, aluminum oxide, and zirconium oxide, and clay-based materials such as kaolins (Kibushi clay, etc.) and montmorillons (talc, bentonite, etc.). It is composed of a binder and an adhesion improver made of metal salts such as nitric acid, sulfuric acid, phosphoric acid, etc., and is strong enough to withstand the pressure of molten metal without decomposing or sublimating and disappearing at the metal melting temperature. , the main purpose is to obtain stability. Since the effects of these mold coating agents vary considerably depending on the proportions of their components, users must carefully consider the proportions of their ingredients. Generally, the blending ratios of these materials are approximately 30 to 50% by weight of the heat-resistant material, 53 to 42% by weight of the binder, and 8 to 12% by weight of the adhesion improver. After application of these conventional mold coating agents, as the temperature of the cast iron crucible is increased, the clay-based material used as a binder undergoes a dehydration reaction, resulting in an amorphous material with an irregular shape and a tendency to react. In addition, dehydration causes shrinkage and cracks in the mold coating. This cracking phenomenon also occurs due to the expansion and contraction of the cast iron crucible due to heating and cooling.As a result, the coating agent disappears into the molten metal, or the molten metal and flux gas enter the crucible, causing significant deterioration of the cast iron crucible. It is becoming. Therefore, it is highly desired to improve the above-mentioned drawbacks of conventional mold coating agents. In addition, reverberatory furnaces and low-frequency induction furnaces made of refractory bricks generally do not use coating agents like those used for cast iron crucibles, but when metal is melted, refractory bricks contain molten metal. and flux gases penetrate, making the refractory bricks extremely susceptible to damage. In addition, molten metal accumulates on the surface of the refractory brick, and together with the molten metal that has penetrated, this deposit adheres firmly to the surface of the refractory brick, and from the viewpoint of thermal efficiency and other reasons, when cleaning the furnace, etc. The damage to the refractory bricks caused by the removal of materials was significant. There is a strong demand for a coating agent that can prevent corrosion of refractory bricks from such molten metal and flux gas, and can also avoid deposition on the surface of refractory bricks. In view of these circumstances, the inventors of the present invention have made extensive efforts to solve the above-mentioned drawbacks, and as a result, have arrived at the present invention. The present invention provides a coating agent for metal melting crucibles that has a melting temperature.
Add a fritting agent adjusted to 400 to 900℃ to the mold coating agent.
This relates to a mold coating agent containing 10 to 180 parts by weight per 100 parts by weight, and by applying this to the crucible or furnace described above, it creates a viscous coating between the molten metal and the crucible or furnace during metal melting. A liquid coating film is formed, which can withstand the pressure of molten metal and the thermal expansion and contraction of the crucible or furnace, and can also prevent the intrusion of molten metal and flux gas, which satisfies the above requirements. The present invention provides a mold coating agent. As the coating agent to which the fritting agent used in the present invention should be added, it is possible to use the conventionally known coating agent for metal melting crucibles as described above to achieve the effect. Special Public Service proposed in 1982
The effect can be further improved by using the coating agent according to No. 6395, and the effect can be further improved by using the coating agent proposed in JP-A-53-34607. The fritting agent used in the present invention includes all those that exhibit a viscous liquid state at the melting temperature of the metal, but it is preferable to use one whose melting temperature is adjusted to 400 to 900°C. A fritting agent with a melting temperature exceeding 900°C cannot become a viscous liquid when melting metal, and cannot satisfactorily achieve the intended purpose of the present invention.
Furthermore, it is difficult to adjust the fritting agent with a melting temperature below 400℃, and even if it were possible to adjust it, the liquid viscosity would be lower than necessary at the metal melting temperature, and it would decompose or degrade at high temperatures. Many of these substances sublimate easily, making it difficult to achieve the intended purpose. The necessary amount of the fritting agent added is 10 to 180 parts by weight, preferably 30 to 150 parts by weight, per 100 parts by weight of the coating agent, but the optimum amount to be added depends on the material of the coating agent used and the crucible to which it is applied. Or it varies depending on the material of the furnace. The fritting agent can be added to the coating agent at any step up to coating as long as it is mixed uniformly, but it is usually preferable to add water to the coating agent in the form of a slurry. . It is possible to add to the mold coating agent of the present invention a melting agent capable of lowering the melting point of the mold coating agent in addition to those described above, and examples of the melting agent suitable for this purpose include potassium silicofluoride, borosilicate, Examples include fluorides such as potassium chloride. When applied to cast iron crucibles, reverberatory furnaces, low-frequency induction furnaces, etc., the coating agent of the present invention sublimates or thermally decomposes at the metal melting temperature, forming a viscous liquid film that does not disappear, and can withstand the pressure of molten metal. It also prevents the intrusion of molten metal and flux gas, and also prevents cracks from forming in cast iron crucibles due to thermal expansion and contraction.
This can significantly extend the life of the furnace. Next, the present invention will be explained with reference to Examples, but the present invention is not limited thereto. First, the test method performed on the mold coating agent of the present invention and the mold coating agent for comparison, and the mold coating agent used in the test will be explained. Molten metal deposition test: 1 using a crucible or furnace coated with a coating agent.
The metal is melted once a day and the same operation is repeated for 7 days, and the state of deposition on the crucible or furnace surface is observed and judged. 〇 Almost no accumulation is observed. △ Slight accumulation is visible. × The deposited layer is 2 cm or more. Test for cracks in crucible and furnace After repeated melting for 7 days under the same conditions as above and use, cracks were evaluated based on the degree of remaining coating agent and the degree of corrosion of the crucible (corrosion depth). In the case of a furnace, the evaluation was made based only on the extent to which the mold coating agent remained.

[Table] Durability test: 1 time using a crucible or furnace coated with a coating agent.
The metal was melted and the coating agent was renewed once a week, and the durability of the crucible and furnace was expressed in days. The mold coating agents of Examples and Comparative Examples of the present invention were prepared as follows. Gradually add a specified amount of tap water to a mixture of heat-resistant material, binder, and adhesion improver to form a uniform slurry, then add a fritting agent, halogen-containing organic phosphorus polymer, fiber, etc. to make it uniform. did. Example 1 Zircon flour 45 (same parts by weight) Kibushi clay 22.5 Talc 22.5 Boric acid 10 Fritting agent A 50 Tap water 150 Example 2 Zircon flour 25 Aluminum oxide (A ₂ O ₃ ) 20 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Fritting agent B 40 Tap water 140 Example 3 Zircon flour 45 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Halogen-containing organic phosphorus polymer A 10 Fritting agent A 150 Tap water 250 Example 4 Zircon flour 45 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Halogen-containing organic phosphorus polymer A 10 Fritting agent B 50 Tap water 150 Example 5 Zircon flour 25 Aluminum oxide 20 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Halogen-containing organic phosphorus polymer A 5 Cellulose fiber A 3 Fritting agent AB 25 Tap water 128 Example 6 Zircon flour 45 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Halogen-containing organic phosphorus polymer A 10 Fritting agent B 40 Potassium borofluoride 10 Tap water 150 Comparative example 1 Zircon flour 45 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Tap water Water 100 Comparative example 2 Earthy graphite 45 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Tap water 100 Comparative example 3 Earthy graphite 45 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Fritting agent C 50 Tap water 150 Comparative example 4 Zircon flour 25 Aluminum oxide 20 Kibushi clay 22.5 Talc 22.5 Boric acid 10 Heat resistant agent A 25 Tap water 125 Note) Fritting agent A (PbO, Na ₂ O, K ₂ O,
ZnO, CaO, A ₂ O ₃ ,
Melting temperature, consisting of SiO ₂
Fritz at 500℃) Fritz agent B (SL made by Nippon Fritz Co., Ltd.)
1500 melting temperature 820℃) Fritz agent C (lead-free Fritz 251 (manufactured by Nippon Fritz Co., Ltd.) melting temperature
1000℃) Halogen-containing organic phosphorus polymer A

[Formula] 20 parts of xylene and an alkyl phenyl ether type nonionic activator (Takemoto Yushi Pionin D-6120/P-
15) Add 10 parts to make emulsion. Fiber A (Viscose fiber cut into short lengths of 2 mm) Heat resistant agent A (K ₂ SiF ₆ melting point 1000°C) Test example 1 Coating agent on the inner surface of a 350 kg metal melting cast iron crucible
1000 g of the crucible was applied uniformly with a brush, and then each lined crucible was placed in a heating furnace for preheating, after which the aluminum ingot and flux were placed in the crucible and heated with a heavy oil burner to melt. At this time, the temperature of the melted aluminum was 700-800°C. The test results are shown in Table 1, and it is clear that the mold coating agent of the present invention exhibits remarkable effects compared to conventional mold coating agents.

[Table] Test Example 2 After uniformly applying 1800 g of coating agent to the inner surface of a 500Kg low-frequency induction furnace in the same manner as in Test Example 1, aluminum ingots and flux were placed in the furnace, and then heated and melted. The test was conducted in the same manner as in Example 1. The test results are shown in Table 2, and the effects of the mold coating agent of the present invention are extremely excellent.

[Table] Test Example 3 After uniformly applying 1800 g of coating agent to the inner surface of a 500 kg reverberatory furnace as in Test Example 1, aluminum base metal,
The flux was put into a furnace, then heated and melted, and tested in the same manner as in Test Example 1. The test results are shown in Table 3, and the effects of the present invention are outstanding.

【table】

Claims (1)

[Claims] 1 The coating agent for metal melting crucibles has a melting temperature of 400~
A mold coating agent for protecting a crucible or furnace for metal melting, characterized in that 10 to 180 parts by weight of a fritting agent adjusted to 900° C. is added to 100 parts by weight of the coating agent.