JPH037884A - Protective tube for measuring temperature of molten metal of nonferrous metal - Google Patents

Abstract

PURPOSE:To improve the resistance against the melting damage and the shock resistance by forming a composite material comprising titanium or titanium alloy, ceramic particles and unavoidable impurities, and specifying the volume content of the ceramic particles. CONSTITUTION:At least that part of the present protective tube for measuring temperature of molten metal of nonferrous metal which comes in contact with the molten metal is made of a composite metal comprising titanium or titanium alloy, ceramic particles and unavoidable impurities, and the volume content of ceramic particles is specified to be 0.1 to 50%. If the volume content is less than 0.1%, the hardness and the wear resistance become very low, and, if it is greater than 50%, the composite material becomes brittle, resulting in the degraded shock resistance and the susceptibility to crack. Further, the average size of ceramic particles is made 0.01 to 500mum. If the average particle size is less than 0.01mum, it becomes difficult to uniformly distribute ceramic particles in titanium or titanium alloy, and, if it exceeds 500mum, ceramic particles are separated too widely, resulting in the low hardness and poor wear resistance of the composite material. Nonferrous metals for which the present device can be used includes pure metals such as pure Al and pure Zn as well as their alloys.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a protection tube for measuring the temperature of molten nonferrous metals that protects thermocouples that measure the temperature of molten nonferrous metals such as aluminum, zinc, tin, and lead from the molten metal. .

[Prior Art] Conventionally, cast iron such as JIS FCD50 is generally used for protection tubes for temperature measurement of molten nonferrous metals (hereinafter referred to as protection tubes). However, since non-ferrous metals used in boat fishing tend to react easily with iron, significant erosion occurs in the protective tubes at the portions that come into contact with molten non-ferrous metals. Therefore, the protection tube must be replaced frequently, and its lifespan is short. For this reason, a ceramic layer is usually provided on the surface of the protective tube to suppress melting and damage of the protective tube. For example, for alumina of 325 mesh or less, which is a ceramic particle,
After coating the surface of the JTs FCD50 cast iron protective tube with a brush, a slurry made by blending 30% by weight of water glass and 30% by weight of water or a binder such as PVA (polyvinyl alcohol) was coated with a brush, and then thoroughly dried. In this way, a ceramic layer having a thickness of approximately 21 mm is formed. The ceramic-coated protective tube thus obtained has excellent erosion resistance. Furthermore, in recent years, protective tubes made of silicon nitride, which is a ceramic material that is stable against molten nonferrous metals, have also been used.

[Problems to be Solved by the Invention] However, the conventional protection tube for measuring and mixing non-ferrous metal molten metal described above has the following drawbacks. First, in a protective tube provided with a ceramic coating layer, the ceramic layer is likely to peel off during the course of use. When the ceramic layer peels off, there is a problem in that the cast iron protective tube is exposed and significant melt damage occurs in the protective tube.

Furthermore, although a protection tube made of silicon nitride has excellent corrosion resistance, it has the disadvantage of being brittle because its substrate is ceramic. For this reason, the silicon nitride protection tube is easily damaged when the metal ingot or the stirring blade collides with the protection tube when pouring the metal into the molten metal or stirring the molten metal. In this case, it becomes impossible to measure the temperature of the molten metal, and it becomes necessary to interrupt work such as casting, which reduces work efficiency.
>There is a problem.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a protective tube for temperature measurement of molten nonferrous metal that has excellent resistance to melting and damage to molten nonferrous metal, has excellent impact resistance, and has a long life and can improve workability.

[Means for Solving the Problems] The protection tube for measuring the temperature of molten nonferrous metal according to the present invention has at least the portion that comes into contact with the molten metal formed of a composite material consisting of titanium or a titanium alloy, ceramic particles, and inevitable impurities. and the volume content of the ceramic particles is 0.
．． It is characterized by being 1 to 50%.

[Function] In the present invention, at least the portion that comes into contact with the molten metal is formed of a composite material of titanium or a titanium alloy and predetermined ceramic particles. This composite material is made by adding high-strength and hard ceramic particles to titanium or titanium alloy, which has excellent corrosion resistance against molten nonferrous metals and also has excellent impact resistance. damage,
It has both impact resistance and abrasion resistance. Therefore, by forming the molten metal contact portion with this composite material, a protective tube for measuring the temperature of molten nonferrous metal can be obtained that has a long life and is excellent in workability.

Next, the reason for limiting the volume content and average particle size of the ceramic components constituting this composite material will be explained.

The volume content of ceramic particles in the composite material is 0.1%
If no grooves are formed, the hardness and wear resistance of the composite material will be extremely low. On the other hand, if the volume content of the ceramic particles exceeds 50%, the composite material becomes brittle, resulting in poor impact resistance and becoming susceptible to cracking. For this reason, the volume content of ceramic particles in the composite material is set to 0.1 to 50%.

Further, the average particle size of the ceramic particles in the composite material is 0.
If it is less than 0.01 μm, it becomes difficult to uniformly disperse the ceramic particles in the titanium or titanium alloy matrix, making it difficult to obtain a composite material with stable characteristics. On the other hand, when the average particle size of the ceramic particles exceeds 500 μm, the distance between the ceramic particles becomes large, so that the hardness of the composite material tends to decrease. This also reduces the wear resistance of the composite material. Therefore, the average particle size of the ceramic particles in the composite material is 0. It is preferable to set the thickness to 01 to 500 μm.

In addition, in the present invention, the non-ferrous metal to be used is pure A! Of course, in addition to pure metals such as pure Zn, alloys of these metals are also included.

[Example] Next, an example of the present invention will be described in comparison with a comparative example.

First, titanium alloy powder having an average particle size of 35 μm and containing 5% by weight of CO and silicon carbide (SiC) powder having an average particle size of 15 μm were uniformly mixed in the proportions shown in Table 1 below. Used as raw material.

This raw material was charged into a rubber mold, a core metal was placed in the center, and cold isostatic press (
CI P) processing was performed. As a result, a powder compact in the form of a Tamman tube was obtained. Then, the degree of vacuum of this powder compact is 10-5.
A protective tube made of a composite material having the composition shown in Table 1 was manufactured by sintering it in a vacuum furnace at a temperature of 1300°C. These protective tubes were designated as Examples 1 to 4 and Comparative Examples 1 to 3.

Table 1 A protective tube made of a composite material was manufactured by melting a steel mold. These protective tubes were designated as Examples 5 to 9 and Comparative Example 4.

Table 2 Next, titanium powder with an average particle size of 20 μm and a purity of 99.7% by weight or more and A1 with the average particle size shown in Table 2 below.
□03 powder was mixed at a volume ratio of 80:20 (volume content of ceramics: 20%) to prepare a raw material.

This raw material is sealed in a mold made of JIS 5S41 steel plate with a thickness of 1 dragon, and the pressure is 1 ton/c11 temperature is 1
Sintering was performed by hot isostatic pressing (HIP) at 250°C. Next, the entire sintered body and steel mold were immersed in a concentrated hydrochloric acid solution, and then cast iron (FC
After coating the surface of the D50 type protection tube with a slurry made by mixing alumina particles of 325 mesh or less (69% by weight), 1% by weight of water glass, and 30% by weight of water with a brush, apply thoroughly. It was dried to form a ceramic layer about 2 inches thick. This ceramic layer-coated cast iron protective tube was designated as Conventional Example 1. Further, a protection tube made of silicon nitride was used as Conventional Example 2.

For each protection tube of the above-mentioned example, comparative example, and conventional example,
The following tests were conducted to examine its performance.

(2) Hardness Test The micro-Vickers hardness of each protection tube of the Example, Comparative Example, and Conventional Example was measured.

■Tensile test Elongation was measured using a tensile tester.

(4) Practical Test The protective tubes of Examples, Comparative Examples, and Conventional Examples were immersed in an aluminum alloy melting furnace (capacity: 1 ton), and the state of melting damage after 1000 hours was investigated.

The results of these tests are summarized in Table 3 below.

However, regarding the erosion condition, the maximum amount of erosion on the surface of the protection tube is 0.
．． ◎ if it is less than 1■, 0. if it is more than 0.1mm and less than 0.3m■. Cases exceeding 0.3 mm are indicated by Δ.

Table 3 (Part 1) Table 3 (Part 2) As is clear from Table 3, in Examples 1 to 8, the amount of erosion was less than 0.1 m, and no cracking occurred. On the other hand, in Comparative Example 3 and Conventional Example 2, the elongation was extremely low at 0.2% or less, and cracks occurred due to contact when the metal was introduced. The other Comparative Examples, 2°4, and Conventional Example 1 all had an amount of erosion exceeding 0.1■■, and had poor erosion resistance.

Note that the ceramics that can be used in the present invention are not limited to the above-mentioned SiC and A1□03, but include Cr
Oxide ceramics such as 2O3, TiO2, ZrO2, MgO1Y203, S13N4, TiNs
Nitride ceramics such as B N and AlN, WCzT
Carbide ceramics such as tCsBaC and CrC2,
Various materials can be used, such as boride ceramics such as ZrB2 and TiB2, and sialon.

Moreover, two or more types of these ceramics can be mixed and used.

[Effects of the Invention] As explained above, according to the present invention, at least the portion of the nonferrous metal molten metal temperature measuring protection tube that comes into contact with the molten metal is formed of a composite material of titanium or a titanium alloy and ceramic particles. A protective tube excellent in both erosion resistance and impact resistance can be obtained.

Therefore, if this protection tube is used, melting damage is suppressed and the service life is extended, and cracking is also suppressed even when subjected to impact such as when inserting ingots, and workability can be significantly improved.

Claims (2)

[Claims] (1) At least the part that comes into contact with the molten metal is made of a composite material consisting of titanium or titanium alloy, ceramic particles, and unavoidable impurities, and the volume content of the ceramic particles is 0.1 to 50%. A protective tube for temperature measurement of molten non-ferrous metals. (2) The protective tube for measuring the temperature of molten nonferrous metal according to claim 1, wherein the ceramic particles have an average particle size of 0.01 to 500 μm.