JPS5940210B2 - Melting method of titanium alloy for hydrogenation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydrogenation alloys containing titanium.

Recently, the use of metal hydrides has been considered as a hydrogen storage method instead of liquid hydrogen.

Titanium-based hydrogenation alloys are highly practical, and magnesium-based and rare earth-based alloys are also known.

Titanium type contains 36-47% Ti, T1Co, Ti
Mn.

FeTi, T1CoO3Mn0.5, T1Co0.
Research has been conducted on the composition of 5Fe□, 5, etc.

Such titanium alloys for hydrogenation have a high melting point and are active (have a high affinity for oxygen and nitrogen), so
Manufactured using special melting technology.

That is, in general, the arc melting method involves applying a voltage between a compression-molded titanium sponge electrode and a water-cooled copper mold in a vacuum or an inert gas atmosphere to generate an arc and melting the electrode, or A plasma melting method is used, in which a plasma flame is irradiated onto a titanium sponge placed on a water-cooled copper mold.In addition to this, melting methods using tungsten or graphite as a cathode are also available in the laboratory.

In the case of forming the above alloy, segregation is likely to occur because the difference in specific gravity between the alloy components is large and the solidification temperature range is wide, and to prevent this, two-stage melting is also performed.

However, all of these melting methods are disadvantageous in that they require a large amount of electricity and are expensive.

A melting method using a high frequency furnace or a low frequency furnace can be considered as an economically advantageous method, but in this case, problems arise from the viewpoint of the purity of the alloy.

In other words, in titanium alloys for hydrogenation, in order to maintain hydrogen storage properties, the target concentration range of titanium must be narrow and the concentration of impurities such as oxygen, aluminum, and silicon must be kept sufficiently low. When melting titanium alloys, contamination by refractory furnace materials that come into contact with the molten metal becomes a particular problem.

For example, magnesia and graphite refractory materials have been considered as high-frequency furnace materials for melting titanium alloys for hydrogenation, but such materials do not absorb oxygen or oxygen in titanium alloys, as shown by the formula below. This is not desirable because it causes an increase in carbon concentration.

Mg0 (furnace material) = Mg (gas) + 0 (in molten metal)...(
1) C (furnace material) = C (in molten metal) ・・・・・・・・・
・・・・・・・・・(2)C+Ti=TiC=・・・・・・
・・・・・・・・・・・・・・・・・・(3) Reaction (1) proceeds quickly at temperatures above 1250°C, and a large amount of oxygen dissolves into the alloy during melting, producing magnesium. .

This dissolved oxygen becomes an intermetallic compound upon solidification, causing a decrease in hydrogen storage capacity.

Furthermore, as the melting temperature increases, the wear and tear on the furnace material increases.

Although the solubility of carbon in titanium alloys is small, it increases as the melting temperature rises, making it impossible to obtain alloys with a constant composition.

In addition, reaction 3 generates carbide and floats, increasing the loss of titanium.
).

Due to the situation described above, most of the conventional research and development of titanium alloys for hydrogen storage has been carried out only by arc melting method, despite the economic disadvantage.

Therefore, the purpose of the present invention is to solve the problem of contamination caused by refractory furnace materials when melting a titanium alloy for hydrogenation using a high-frequency induction furnace, and thus to economically produce a titanium alloy with high hydrogen storage capacity. To provide a method for melting.

The present inventors conducted various studies on refractory materials and melting methods for melting titanium hydride alloys using high-frequency induction furnaces, and found that CaO was used as the raw material for at least the parts of the melting furnace that come into contact with the molten metal. The present inventors have discovered that when a refractory material is used and melted in an inert gas atmosphere such as Ar, contamination by the refractory material hardly occurs, leading to the present invention.

Thus, according to the present invention, by lining the parts of the melting furnace that come into contact with the molten metal with clinker (mixture of powder and granules) or molded products (brick, etc.) of CaO-based refractory material,
Alternatively, by using a melting furnace entirely made of such a CaO-based refractory material, a titanium alloy whose hydrogenation properties are not impaired can be melted.

The refractory material used as the CaO raw material in the present invention includes:
Various refractory materials obtained by firing lime, limestone, calcium carbonate, chalk, calcium hydroxide, etc. as raw materials at high temperatures can be used.

Particularly preferred is fused calcia, i.e., the above-mentioned CaO raw material, heated at 2500 to 3000°C in an electric furnace because it is easy to construct a furnace and has high chemical stability.
It is a refractory material consisting essentially of CaO obtained by heating and melting it.

Even if some other calcia, such as quicklime, is used in combination with fused calcia, the same effect as in the case of fused calcia alone can be obtained.

The reason why the problem of contamination due to the furnace material is drastically reduced by using a furnace made of CaO-based refractory material according to the present invention is understood to be that CaO is more stable than MgO or the like.

That is, the dissociation oxygen pressure according to the formula Cab (furnace material) - Ca (gas) + 9 (in the molten metal) (4) is extremely small (6.3
100-25at for CaO2. IX
10-0-29at, the amount of dissolved oxygen that forms intermetallic compounds also decreases.

Furthermore, since CaO has a property of being difficult to wet with molten metal, the rate of the reaction expressed by the above equation (4) is slowed down, and therefore, the amount of CaO dissolved into the titanium alloy is also reduced.

Furthermore, the boiling point of the calcium produced is high (1440°C).
Therefore, wear and tear on the furnace material is reduced compared to magnesia whose product is magnesium (boiling point 1110°C).

As is clear from the above description, according to the method of the present invention, the amount of inclusions and dissolved oxygen due to consumption of the furnace material is small, and therefore a titanium alloy with high hydrogen storage capacity can be melted economically.

Thus, the present invention provides T1Co, TiMn, FeTi
, T1Co□, 5Mng, 5, T iCo□, 5Fe
It is extremely useful industrially in that it has enabled mass production of titanium alloys for hydrogenation such as O,5.

Next, the present invention will be explained along with examples.

Example 1 A mixture of powder and grains obtained by crushing electrified calcia was placed in a crucible shape and solidified into a melting furnace using a high frequency induction vacuum melting furnace.

The melting base materials are sponge titanium, electrolytic iron, metallic cobalt,
Metallic manganese was used, mixed to a target composition, and placed into the above-mentioned crucible in which fused calcia was compacted.

After the inside of the furnace was evacuated to a vacuum of 10 mmHg or less, it was filled with Ar gas and the metal was melted at 1350°C.

In addition, similar melting was performed for electrofused magnesia lining and compared with calcia lining.

When magnesia is used as a lining material, fumes are generated from the time of melting and become more intense as the temperature rises.

When the lining was examined after melting, the parts that came in contact with the hot water turned completely black, and some metal penetration was observed.

In melting using calcia lining, the generation of fume during both burn-through and melting is significantly less.

Parts of the lining that come into contact with hot water have turned black, but no metal has penetrated.

When the hydrogen storage properties of this sample were investigated, alloy (1) melted with calcia lining absorbed up to 2.6% by weight of hydrogen, which was higher than the 1.1% by weight of the arc-melted product.

Alloy (2) melted with calcia lining absorbs up to 26% by weight of hydrogen, which is higher than the 1.7% by weight of the arc-melted product.

Example 2 70% by weight of crushed fused calcia and 30% by weight of crushed industrial quicklime were mixed and compacted to form a lining for a high-frequency induction vacuum melting furnace.

When Alloys I and II were melted in the same manner as in Example 1, a complete melt was obtained with little burn-through and fume generation during melting, and a blackened lining thickness of approximately 5 mm.

When the hydrogen storage properties of the obtained alloys I and II were investigated,
It was found that both alloys ① and ② had a hydrogen content of 2.6% by weight and were not significantly different from those in which only fused calcia was used as the lining.

Claims (1)

[Claims] 1. When melting a titanium alloy for hydrogenation in a high-frequency induction furnace in an inert gas atmosphere, 03-width raw material is used as the furnace material for at least the part in contact with the molten metal in the melting furnace.
A method for producing a titanium alloy for hydrogenation, characterized by using a refractory material whose main component is fused calcia obtained by heating and melting at 000°C.