JPS5856017B2 - Protection tube for temperature measuring equipment made of molybdenum-zirconia composite alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protective tube for a temperature measuring device made of a molybdenum-zirconia composite alloy, which is a new alloy with excellent oxidation resistance and molten metal corrosion resistance.

Although molybdenum Mo has a high melting point and high strength at high temperatures, it has the disadvantage that it is easily oxidized by air at temperatures above 500° C., so no alloy with a high Mo content that takes advantage of the above-mentioned properties of Mo is known.

In view of this, the present inventor conducted research on zirconia (Zr), which has good oxidation resistance at high temperatures and poor wettability with molten metal.
It was discovered that a dispersed molybdenum-zirconia composite alloy made by blending Mo with O2) has excellent oxidation resistance and molten metal corrosion resistance without loss of mechanical strength.Based on this, the present invention was developed. succeeded in doing so.

The alloy of the present invention is composed of Mo 55-90% by weight □, the same hereinafter, ZrO2 45-10%, and if the blending ratio of ZrO2 is less than 10%, the oxidation resistance is insufficient;
If the ZrO2 content exceeds 5%, the transverse rupture strength will drop significantly and the mechanical strength will be poor, whereas those with a ZrO2 content of 10 to 45% will have the characteristics of a pure Mo sintered body and will have good oxidation resistance and resistance. Excellent erodibility against molten metal.

Porcelain materials are used for protective tubes of temperature measuring devices for molten metal, and the materials are metal oxides such as aluminum oxide (A1203), silicon oxide (Si02), and magnesium oxide (MgO).

Protective tubes made of these metal oxides have good heat resistance, but
All of them have the drawbacks of low mechanical strength and poor impact resistance, and some have poor molten metal erosion resistance and short service life.

On the other hand, the protective tube for high-temperature temperature measuring equipment made of the MO-ZrO2 composite alloy in the above blending range of the present invention does not have the drawbacks of the above-mentioned porcelain material, and has excellent mechanical strength, molten metal corrosion resistance, and thermal shock resistance. It has the advantage of being able to be used repeatedly because of its properties.

The protective tube of the alloy of the present invention can be made by mixing Mo powder and ZrO2 powder at a predetermined mixing ratio, filling a rubber mold with a predetermined shape, and sintering the mixture under hydrostatic pressure in a compression wave furnace.

Because the alloy of the present invention has the above-mentioned excellent properties, it can be used as protection tubes for high-temperature temperature measuring instruments and crucibles for molten metal, as well as having a high degree of oxidation resistance under high temperatures, resistance to molten metal corrosion, and resistance to thermal shock. It is suitable for materials for machines or equipment that require

Example 1 Mo powder (fineness: average 3μ, maximum 30μ) produced by reduction method and Kasumi Zr 02 powder (fineness: average 3μ,
(up to 30μ) in the ratio shown in Table 1, mixed in a ball mill for 40 hours, filled into a rubber mold, compression molded with 1.7ttIrL/-, and heated in an electric current in a hydrogen stream. The product was sintered in a furnace at 1800°C for 4 hours to obtain a product having the specific gravity shown in Table 1.

Tensile strength and oxidation resistance tests were conducted on each product, and the results are shown in Figure 1.

The oxidation resistance test was conducted using a pipe-type electric furnace with an inner diameter of 40 mrIL.
A 101m x 10m meter was kept at 200℃ and weighed in it.
A sample of 10 mm x 10 mm was placed in this electric furnace.
After supplying hot air at a temperature of 51° C. for 2 hours, the sample was taken out of the furnace, left to cool, and then weighed to determine the percentage loss.

Figure 2 shows the transverse rupture strength and molten metal corrosion resistance test results.

Molten metal corrosion resistance test: Fe: 98.7%, C: 0.3
%, Mn 1.0% in a molten steel at 1650° C. for 3 hours.

It can be seen from the above figures that the MO-ZrO2 alloy of the present invention has excellent mechanical strength, oxidation resistance, and molten metal corrosion resistance.

Example 2 A rubber mold for molding with an inner diameter of 8 mm, an outer diameter of 12 mm, and a length of 40 mm.
Protective tubes for three types of thermometers having different composition ratios of Mo and ZrO2 were manufactured in the same manner as in Example 1, except that the tubes having a diameter of mm were used.

These protection tubes and commercially available Al203i, A1203S
Protective tubes made of three types of porcelain materials, i02 series and MgO series, and M
The protective tube made only of O was tested for thermal shock resistance, transverse rupture strength, coefficient of thermal expansion, and resistance to molten metal erosion, and the results are shown in both Figures 3 and 4.

Thermal shock resistance was indicated by the processing temperature at which the sample was held in an electric furnace at a predetermined temperature for 15 minutes, then taken out of the furnace and allowed to cool in the atmosphere, after which it was repeated 5 times without any damage.

It can be seen from FIG. 3 that the protective tube made of the Mo-Z r 02 alloy of the present invention is far superior in thermal shock resistance and transverse rupture strength as compared to the protective tube made of porcelain material.

From FIG. 4, it can be seen that the protection tube made of the MO-ZrO2 alloy of the present invention has no significant difference in coefficient of thermal expansion and is far superior in resistance to molten metal erosion compared to the protection tube made of porcelain material.

[Brief explanation of drawings]

Fig. 1 is a graph showing the tensile strength and oxidation resistance of the Mo-ZrO2 alloy, Fig. 2 is a graph showing the transverse rupture strength and molten metal erosion resistance of the MO-ZrO2 alloy, and Fig. 3 is a graph showing the tensile strength and oxidation resistance of the MO-ZrO2 alloy.
A graph showing the thermal shock resistance and transverse rupture strength of a thermometer protective tube made of an O2 alloy and a protective tube made of a porcelain material, respectively.
FIG. 4 is a graph showing the thermal expansion coefficient and molten metal corrosion resistance of a protection tube of a temperature measuring device made of a MoZrO2 alloy and a protection tube made of a porcelain material, respectively.

Claims (1)

[Claims] 1. A protective tube for a temperature measuring device, characterized in that the material is a molybdenum-zirconia composite alloy consisting of 55-90% molybdenum, 45-10% zirconia and inevitable impurities by weight.