JPH021220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to melting of metal or flowing or transferring of molten metal in smelting or casting of non-ferrous metals.
Also used in equipment used in processes such as casting, such as melting furnace pots, ladles, runners, weirs, injection nozzles, stoppers, gas bubbling lances, porous plugs, thermometer tubes, molds, etc. (hereinafter simply referred to as "tools for smelting or casting non-ferrous metals").

(Prior Art and Problems to be Solved by the Invention) Fireproof materials are used as materials for equipment used in processes such as metal smelting, casting, pouring, transferring, and casting of molten metal. Things have always played an important role.

However, in the non-ferrous metal industry such as aluminum and copper alloys, there are naturally differences in melting temperature, so ``non-ferrous metal smelting or casting tools'' made of metal materials are increasingly being used instead of these refractories. ing. For example, pot furnace pots of low melting point alloys are made from riveted cast iron or steel sheets.

In addition, as the process becomes more mechanized and automated, such as by attaching a nozzle to the bottom and using a stopper to enable direct casting, or by pumping out the molten metal, conventional refractories can no longer be used for materials that come into contact with the molten metal. The current situation is that it is getting overwhelming.

Die casting (mold casting) is a typical example, and the cast product not only has excellent appearance and quality, but also
There are said to be hundreds of types of die-casting machines, ranging from manual to automatic, and the equipment that comes into contact with the molten metal is almost 100% made of metal.

Taking a die as an example, when considering the material conditions for these devices, first of all, the most important thing is the service life because they are used repeatedly. That is, it is important to satisfy the following conditions (a) to (d).

(a) It can withstand repeated thermal stress, (b) It does not deteriorate due to chemical reactions with molten metal, (c) It can withstand high temperatures and has excellent wear resistance, (d) It has high hardness. Regarding the hardness listed in (d), it is natural that the higher the hardness of the mold, the longer the lifespan, but since it is sometimes used for complex engraving (cutting), it may not be too hard. This also makes it difficult to work as a mold.

An appropriate hardness is Brinell hardness. 170 to 220 for tin and lead alloys 200-400 for zinc alloys Around 400 for magnesium alloy 400-500 for aluminum and copper alloys It is said that.

In particular, since aluminum corrodes iron and steel, Cr-V steel, W steel, etc. are deliberately used, even though they are poor in workability and are expensive.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned points, and is an object of the present invention to provide a method for scouring or casting non-ferrous metals that is easy to obtain, process, and therefore low-cost and has a long service life. The aim is to provide "tools and tools,"
Its constituent elements are 10 to 40 parts by weight of silicon nitride, and 90 to 60 parts by weight of an oxide of a nonferrous metal selected from the group consisting of aluminum, magnesium, silicon, and zirconium, or a composite oxide of these nonferrous metals. By spraying a granular composite thermal spray material, the silicon nitride and non-ferrous metal oxides or composite oxides of these non-ferrous metals are uniformly dispersed and mixed, resulting in heat resistance, corrosion resistance, wear resistance, and hardness. This is a tool for scouring or casting non-ferrous metals, characterized in that the surface of the main material that comes into contact with the molten metal is coated with an excellent composite sprayed coating.

That is, the tool for scouring or casting non-ferrous metals according to the present invention is first made of a material that is easily available and processed, and that the surface of the main material that comes into contact with the molten metal is made of silicon nitride, aluminum, magnesium, A granular composite thermal sprayed material prepared from an oxide of a non-ferrous metal selected from the group consisting of silicon and zirconium or a composite oxide of these non-ferrous metals is thermally sprayed and has excellent heat resistance, corrosion resistance, abrasion resistance, and hardness. It consists of two parts: it is coated with a composite thermally sprayed coating. Furthermore, the third point is that the silicon nitride in the form of silicon nitride whiskers exhibits the greatest effect of the invention.

In the present invention, the main material from which non-ferrous metal smelting or casting tools are formed is expressed as a material that is easily available and processed.As mentioned above, at present, Cr-V steel is used for aluminum alloys. ,
Instead of using special steel such as W steel,
This means that materials that are easy to work with, such as cast iron, are sufficient for the purpose. Of course, ceramics, cermets, etc. may be used as long as they satisfy the desired thermal and mechanical strength.

This is very important. For example, when comparing the content of the present invention with the invention of the corrosion-resistant and fire-resistant heat insulating material for non-ferrous metals disclosed in Japanese Patent Laid-Open No. 60-215566 by the applicant, it is clear that the present invention is superior to the present invention. It is clear that the price is significantly lower.

Next, the surface in contact with the main molten metal is made of a granular composite prepared from silicon nitride and an oxide of a nonferrous metal selected from the group consisting of aluminum, magnesium, silicon, and zirconium or a composite oxide of these nonferrous metals. By thermally spraying a thermal spraying material, silicon nitride and oxides of nonferrous metals or composite oxides of these nonferrous metals are uniformly dispersed and mixed, resulting in composite thermal spraying with excellent heat resistance, corrosion resistance, wear resistance, and hardness. Coating with a coating is another structural requirement.

This is GAYasinskaya (Ornoupory,
Vol. 30, pp. 20, 1965) and JFColns, R.W.
As reported by Gerdy et al. (J.Metals, Vol. 7, pp. 612, 1955), nitrides and carbides have better corrosion resistance than oxides, especially for non-ferrous metals. This is recognized, and the present inventor has repeatedly conducted many experiments, and as the technical basis of the above-mentioned application and the present application, silicon nitride is composited with non-ferrous alloys as the most effective material in terms of corrosion resistance.

In addition, the present applicant has obtained a composite thermal sprayed coating by thermally spraying the above-mentioned composite thermal sprayed material manufactured according to the method of JP-A-60-174862 filed by the present applicant (see Examples below). Silicon nitride and oxides of non-ferrous metals or composite oxides of these non-ferrous metals are uniformly dispersed and mixed, thereby achieving the above (a) to (d).
conditions, namely heat resistance, corrosion resistance, abrasion resistance,
The present invention has been completed based on the discovery that a composite sprayed coating with excellent hardness can be formed.

Next, the point that it is more desirable that silicon nitride be included in the composite sprayed coating in the form of whiskers will be explained.

The present applicant previously applied for Japanese Patent Publication No. 61-56312, Japanese Patent Publication No.
No. 61-56313 and Japanese Patent Application Laid-open No. 60-174862 disclose that whiskers are contained in a thermal spray material by plasma and gas spraying, and that by thermal spraying the whiskers, the thermal spray coating contains whiskers and is reinforced with so-called fibers. It has been demonstrated that this results in extremely strong adhesion, increased hardness, improved wear resistance, and resistance to thermal shock.

Exhibition of these characteristics completely coincides with the conditions (a) to (d) described above as conditions for ensuring a long mold life, and the third aspect of the present invention is, so to speak, , the application of the above-mentioned Japanese Patent Publication No. 61-56312, Japanese Patent Publication No. 61-56313, and Japanese Patent Application Publication No. 60-174862,
Its effectiveness as a tool for smelting and casting non-ferrous metals has become even clearer.

In addition, silicon nitride whiskers are made from α-Si ₃ , such as those made by the manufacturing method disclosed in JP-A-57-196711, JP-A-57-200299, and JP-A-58-172298 by the present applicant. _N4 98% or more, diameter 0.5-1μm, length
It is desirable to use a material with a diameter of 100 to 200 μm.

(Example) Next, the effects of the present invention will be explained with reference to Examples.

The thermal spray material used in this case was manufactured in accordance with the method disclosed in Japanese Patent Application Laid-open No. 174862/1986 filed by the present applicant.

That is, to put it simply, silicon nitride in powdered or granular or whisker form and an oxide of a non-ferrous metal selected from the group consisting of aluminum, magnesium, silicon and zirconium in powdered or granular form or a composite of these non-ferrous metals. The oxides are mixed uniformly, and the mixture is heated at a temperature and for a period of time such that substantially no reaction occurs between the silicon nitride and the oxide of a non-ferrous metal or a composite oxide of these non-ferrous metals. Baked under the following conditions,
It is further ground to 150 meshes or less (preferably 200 meshes or less) and 5μm or less (preferably
A thermal spray material was prepared by removing fine particles (10 μm or less) by classification.

In addition, in the various examples below, examples of silicon nitride, aluminum, magnesium oxides, and composite oxides of these are described for convenience, but those skilled in the art will be able to understand this from the description of these examples. It will be easily understood that the present invention is applicable to non-ferrous metals other than silicon, for example, silicon and zirconium.

Example 1 A composite thermal spraying material containing 90 parts by weight of alumina powder (300 mesh) and 10 parts by weight of silicon nitride powder (200 mesh) was prepared, and a thermal spray coating was applied to the inner surface of a cast iron mold using a plasma spraying device manufactured by Plasma Dyne. thick contract
It was sprayed to a thickness of 100 μm.

In this case, the mold was first sandblasted, then a nickel-chromium (Ni80, Cr20) undercoat was applied, followed by a thermal spray coating. For a test piece (60 x 60 x 1.2 mm) made of the same material and method, diameter 17
When an alumina ball weighing 10.5 g was dropped from a height of 300 mm and the test was repeated to check for cracks and peeling, local cracks of about 5 mm began to appear after 45 drops, and peeling occurred after 55 drops.

When this test piece was subjected to a repeated thermal shock test at 900°C for 30 minutes and then dropped into water, peeling occurred after 27 times.

In a test in which molten aluminum was actually cast using a mold, the release from the mold and the appearance of the product were good, and no change was observed in the mold after 50 or more repeated castings, so it is safe to continue continuous work as is. I found out that it doesn't happen.

Incidentally, the cast iron mold requires spraying a mold coating agent each time it is cast, and the surface of the product is much rougher and more rough than the one made using the thermal spray mold in this example.

Example 2 90 parts by weight of alumina powder (>300 mesh) and silicon nitride whiskers (0.5 to 1 μm in diameter, 100 to 200 μm in length)
A composite thermal sprayed material containing 10 parts by weight of α-Si ₃ N ₄ (98% or more) was prepared, and molds and test pieces were made in the same manner as in Example 1.

In this case, the undercoat of Example 1 was omitted. No abnormalities were observed in 100 ball drop tests, and no cracks or peeling was observed in 50 thermal shock tests. Casting with the mold did not change even after 200 repetitions, and its durability as a continuous mold for continuous casting was confirmed.

Example 3 33 parts by weight of fine alumina powder, basic aluminum lactate (trade name Taxeram, analytical value Al ₂ O ₃ 36%:
A thermal spray material was prepared using 61 parts by weight of lactic acid (51%) and 6 parts by weight of silicon nitride whiskers so that Al ₂ O ₃ :Si ₃ N ₄ =90:10, and a 1/2 inch pipe of low carbon steel _SS was prepared.
The external surface of a length of 65 cm was sprayed according to Example 1 (with undercoat).

When used as a gas bubbling lance for molten aluminum, it was immersed in molten metal for 1 hour and nitrogen gas was blown into it to bubble the molten metal. Even after using it 50 times, there was almost no corrosion due to the molten metal.

For comparison purposes, when a pipe without thermal spraying is used as a lance, corrosion is observed after two uses, that is, two hours, to the extent that it cannot withstand further use.

Example 4 A thermal spraying material containing 85 parts by weight of spinel (MgO・Al ₂ O ₃ ) and 15 parts by weight of silicon nitride whiskers was prepared and applied to a SUS304 1/2 inch pipe (length 1 m) with a closed tip as in Example 1. Thermal spraying was carried out accordingly. in this
A platinum-platinum-rhodium thermocouple insulated with an MgO insulator tube was loaded and immersed in molten copper alloy at 1200°C to repeatedly measure the temperature.
Even after 500 temperature measurements, there was almost no corrosion on the surface, and it was confirmed that it is useful as a protection tube.

Example 5 13 parts by weight of silicon nitride powder, 20 parts by weight of silicon nitride whiskers
Weight part, alumina short fiber (product name: Safil)
_{Si 3 N 4} : _{Al 2} O ₃ =
50:50 and 50wt% of the total is short fibers,
A thermal spraying material containing 30 wt% of silicon nitride whiskers was prepared and sprayed onto the inner surface of a cast iron mold according to Example 1 so that the sprayed film had a thickness of approximately 300 μm (without an undercoat). .

In an actual repeated casting test of copper alloy, there were no abnormalities after 200 castings.

Claims (1)

[Scope of Claims] 1. Granules consisting of 10 to 40 parts by weight of silicon nitride and 90 to 60 parts by weight of an oxide of a nonferrous metal selected from the group consisting of aluminum, magnesium, silicon, and zirconium or a composite oxide of these nonferrous metals. By thermal spraying a composite thermal spray material, the silicon nitride and non-ferrous metal oxides or composite oxides of these non-ferrous metals are uniformly dispersed and mixed, resulting in excellent heat resistance, corrosion resistance, wear resistance, and hardness. A tool for scouring or casting non-ferrous metals, characterized in that the surface of the main material that comes into contact with the molten metal is coated with a composite thermally sprayed coating. 2. A tool for scouring or casting non-ferrous metals according to claim 1, characterized in that the silicon nitride is in the form of silicon nitride whiskers.