JPH04120225A - Manufacture of ti-al series alloy - Google Patents

Abstract

PURPOSE:To reduce the content of oxygen as impurities in an alloy by adding Ca or a Ca-contg. allay to a melted Ti-Al series allay and executing deoxidizing treatment. CONSTITUTION:A Ti-Al allay is melted in a lime crucible in vacuum or in an inert atmosphere. To this melted alloy, metallic Ca or a Ca-contg. allay such as Ca-Al, Ti-Ca or the like is added, and deoxidizing treatment is executed to reduce the content of oxygen in the Ti-Al series allay to be manufactured. The temp. of the molten metal at the time of adding the Ca additive is preferably regulated to a one higher than the liquidus temp. of the Ti-Al series allay to be melted by >=10 deg.C as well as to <=1650 deg.C. The ingot obtd. by casting the molten metal after the deoxidization is subjected to plasma melting, vacuum melting or electron beam melting, by which the Ti-Al series allay in which the content of Ca is reduced and having high purity can be obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a Ti-Al alloy, and more specifically, it relates to a method for producing a Ti-Al alloy.
The present invention relates to a method for producing high-purity Ti-Al alloys such as -Al alloys and Ti-Al intermetallic compounds.

[Prior Art] Recently, in various industrial fields such as aircraft, automobiles, and chemical plants, there have been increasing demands for improvements in performance such as engine efficiency, cost reduction, and longer service life. As a measure to achieve this, there is a strong demand for high-performance and highly functional materials with characteristics such as high strength, high modulus of elasticity, high heat resistance, and high corrosion resistance.

Materials that are attracting attention as materials that meet this demand include alloys (intermetallic compounds) such as Ni-Al, Fe-Al, and TiAl. However, in particular, TiAl-based alloys (intermetallic compounds) have excellent properties such as light weight, high elastic modulus, and high heat resistance, so there are high expectations for their practical use.

When producing a Ti-Al alloy (intermetallic compound) with such excellent properties by a melting method, Ti-A
Since l-based alloys are mainly composed of active Ti and Al, they can be melted using crucibles made of refractories such as alumina and magnesia, which have traditionally been used for metals such as Fe and Ah Cu. Vacuum arc remelting, V
Currently, they must be manufactured by melting methods such as AR), plasma arc melting, and electron beam melting.

Furthermore, as a result of recent research, it has been proposed to use a lime crucible (Cab) for melting Ti--Al alloys, and the use is coming into use.

There are various methods such as those mentioned above for manufacturing active Ti-Al alloys (intermetallic compounds) by melting.
There are problems that will be explained below.

When melting a Ti-Al alloy using the vacuum arc melting method, granular or lumpy Ti and AI raw materials are compression-molded to create a rod-shaped compact, and then this compact is used as a consumable electrode. Ti-Al alloy ingots are produced by arc melting under vacuum, but the process of compression molding granular and lumpy Ti and A1 raw materials into rod-shaped electrodes is an extremely complicated process. , because it requires a lot of effort,
It is unavoidable that productivity is poor and costs are too high.Also, since the melting points of Ti and Al, which are the raw materials, are greatly different, the melting speeds of Ti and Al are different during arc melting, resulting in the melting of Ti only. There is a problem that unmelted Ti is mixed into the ingot, making it impossible to produce a homogeneous ingot.Furthermore, since stirring in the molten metal boule during melting is insufficient, pure Ti There is not enough time to uniformly mix the aluminum and pure Al, and the constituent elements constituting the ingot are likely to segregate, making it difficult to produce a homogeneous ingot. In this way, melting is sometimes performed twice to alleviate the problem of undissolved and segregation, but it is an undeniable fact that the process of dissolving requires complicated work and labor, which increases costs. .

In addition, in the plasma arc melting method and electron beam melting method, the raw material, granular or lumpy Ti5Al, is melted in a cold hearth and then poured into a water-cooled mold, or without using a cold hearth (directly melting Ti5Al). It is common to perform a melting method such as melting raw materials while charging them into a mold to produce an ingot.

In the case of the plasma arc melting method and the electron beam melting method, as in the vacuum arc melting method explained above, stirring in the molten metal boule is insufficient, so segregation and unmelting due to differences in melting points are likely to occur, resulting in a homogeneous product. There are problems in that it is not possible to produce ingots, and the cost of equipment is high.

Furthermore, the induction melting method using a lime crucible, which has recently been put into practical use, does not require any extra expense for the equipment because the induction melting equipment that has been used in the past can be used as is. In addition, it has the advantage that the raw materials Ti and AI in the crucible can be completely melted, and a homogeneous molten metal can be produced by the stirring effect, and a homogeneous ingot without segregation can be obtained. There is a problem that during melting, the lime (Cab) of the melting crucible material reacts and the amount of oxygen in the molten metal increases.

In order to bring out the original properties of this Ti-Al alloy (intermetallic compound), it is required that the amount of impurities be extremely small, and in particular, there is a strong demand for melting technology for high-purity materials with reduced oxygen content. Therefore, the conventionally used dissolution method using a lime crucible has not been able to sufficiently meet such requirements.

[Problems to be Solved by the Invention] In view of the various problems of the conventional melting method for Ti-Al alloys (intermetallic compounds) explained above, the present inventor has conducted extensive research and studies. As a result of repeated efforts, they developed a method for producing high-purity Ti-Al ingots that minimizes the amount of impurity oxygen compared to the conventional melting method using a lime crucible.

[Means for solving the problems] The method for producing a Ti-Al alloy according to the present invention includes (1) T
A Ti-Al alloy is melted in a lime crucible in vacuum or in an inert atmosphere, and Ca or a Ca-containing alloy is added to the molten Ti-Al alloy for deoxidation treatment. - The first invention is a method for producing an Al-based alloy, (2) melting a Tf-Al-based alloy in a lime crucible in vacuum or an inert atmosphere, and adding carbon to the molten Ti-Al-based alloy.
A or a Ca-containing alloy is added and deoxidation treatment is performed at a temperature of 10°C or higher and 1650°C or lower than the liquidus temperature of the molten Ti-Al alloy.
- A second invention provides a method for producing an Al-based alloy, (3) Melting a Ti-Al-based alloy in a lime crucible in a vacuum or inert atmosphere, and adding carbon to the molten Ti-Al-based alloy.
A or a Ca-containing alloy was added and an ingot was cast from a molten metal that was deoxidized at a temperature of 10°C or higher than the liquidus temperature of the molten Ti-Al alloy and 1650°C or lower. Ti-A characterized by reducing Ca content by melting, vacuum melting or electron beam melting
This invention consists of three inventions, with the third invention being a method for producing an l-based alloy.

The method for manufacturing a Ti-Al alloy according to the present invention will be described in detail below.

When melting a Ti-Al alloy using a conventional lime crucible, the oxygen concentration in the molten metal depends on the melting time and melting temperature due to contamination from the lime crucible, but the oxygen content is usually 0.
It will be about 1 to 0.2vt%, but in extreme cases it will be about 03 to 0.2vt%.
Q: It can reach up to 5wt%.

Therefore, even if high-purity Ti and A1 were used as raw materials, it was unavoidable that the oxygen concentration would increase during melting.
It has been very difficult to produce l-based alloys.

In the method for producing a Ti-Al alloy according to the present invention, as a result of research on a method for preventing an increase in oxygen concentration in the molten metal during melting of the Ti-Al alloy in the conventional lime crucible described above, it was found that It was discovered that an equilibrium relationship of Ca-0 is established in the molten metal as shown in Figure 2, and by adding Ca to the molten metal using this equilibrium relationship, the deoxidation reaction progresses, and oxygen is removed. The purpose is to reduce the concentration. In addition, in Figure 2, ○ marks are 1550 to 1570°C, ・ marks are 1600 to 1620°C.
It is.

That is, in the method for producing a Ti-Al alloy according to the present invention, by adding Ca (including Ca-containing alloys) to the molten metal, a deoxidation reaction of Ca + O- + CaO is caused in the molten metal. , by floating and separating the generated CaO, or by adhering and absorbing it to the lime crucible wall,
It lowers oxygen concentration.

Ca added to this molten metal includes metal Ca, Ca-
It is preferable to use A1 alloy, Ti-Ca alloy, etc., and in addition to these, use a material alloyed with Ca and an element that does not have a negative effect on the properties of Ti-Al alloy (intermetallic compound). It is also possible to do so.

The Ca additive can be added by any method such as pouring it onto the surface of the molten metal, pushing it into the molten metal, or blowing powder into it, and the most suitable method should be selected taking into account equipment, workability, etc. In view of reaction efficiency, addition yield, etc., the preferred method is the method of pushing or blowing into the molten metal.

Further, the amount of the Ca additive may be determined based on the oxygen concentration in the molten metal before addition, the target oxygen concentration, and the above reaction and addition yield.

In the method for producing a Ti-Al alloy according to the present invention, C
The temperature of the molten metal and the timing of the addition of the additive a are important.The molten metal temperature at the time of addition depends on the composition of the Ti-Al alloy, but it depends on the liquidus temperature of the Ti-Al alloy to be melted. 10
The temperature shall be above ℃ and below 1650 ℃.

If the molten metal temperature is lower than the liquidus temperature + 10°C, the viscosity of the molten metal is high (CaO, which is a deoxidation product, is difficult to float and separate easily, and stable operation is difficult due to a drop in the temperature of the molten metal). Furthermore, although the above deoxidation reaction progresses at temperatures exceeding 1650°C, the rate of oxygen penetration from the lime crucible into the molten metal becomes significant, and the amount of oxygen increases rapidly after deoxidation, resulting in a decrease in the deoxidation effect. This is because it will be lost.

Furthermore, it is best to add the Ca additive 1 to 5 minutes immediately before tapping; if it is less than 1 minute before tapping, the flotation separation of CaO in the deoxidized product will be incomplete;
This is because if the temperature exceeds 10 minutes, the intrusion of oxygen from the lime crucible will progress and the deoxidizing effect will be lost.

In the method for melting a Ti-Al alloy according to the present invention, as a method for further improving the purity of the ingot produced by the method described above, the molten metal after deoxidation is cast into a rod shape, and the molten metal is cast into a rod shape for vacuum arc melting. As a consumable electrode, 10"~10-'To
By dissolving in a vacuum atmosphere of about rr,
By evaporating and removing Ca remaining during deoxidation, it is possible to produce a high purity ingot with low concentrations of both Ca and oxygen. Ti-A
The vapor pressure of Ca in the l-based alloy melt is high, and a high-purity TiAl-based alloy ingot can be easily produced.

In addition, the method for producing Ti-Al alloys according to the present invention can solve the problems of the conventional vacuum arc melting method, that is, the compression molding process of raw materials for manufacturing consumable electrodes can be omitted. Since the consumable electrode itself is homogeneous, there are no problems such as segregation of the ingot or the remaining of unmelted parts, and it is excellent in terms of quality and cost.

Furthermore, similar effects can be expected by electron beam melting and plasma arc melting instead of vacuum arc melting.

The alloy that can be used in the method for producing a Ti-At alloy according to the present invention includes T containing 25 to 60 vt% of Al.
Of course, the binary alloy of i may contain other alloying elements such as Mn, Cr, V, Ni, Nb, and W.

Examples include multi-component alloys containing Ag, Zr, B, etc., but other alloys can also be used as long as a high purity ingot can be obtained.

[Example] An example of the method for manufacturing a Ti-Al alloy according to the present invention will be described.

Example 1 Using pure Ti and pure A1 as raw materials, 5 kg of Ti-Al alloy with various AI contents was melted in a vacuum induction melting furnace using a lime crucible, and after melting, various conditions were applied. After processing the molten metal, it was cast into an iron mold.

Table 1 shows the results.

The atmosphere during melting was Ar, and the components of the molten metal were analyzed using a sample taken with an immersion sampler.

In addition, deoxidation treatment is performed by adding Al-Ca alloy.1.
After being held for 3 minutes after deoxidizing treatment, a sample for molten metal analysis was taken.

It is clear from the No. 1 to No. 10 of the Ti-Al alloy manufacturing method according to the present invention in Table 1 that the molten metal subjected to deoxidation treatment has a higher The oxygen concentration has decreased significantly, and the Ti according to the present invention
- It can be seen that the method for producing Al-based alloys is excellent. In addition, when the temperature during deoxidation treatment is high, No. 11 and N
As is clear from No. 0 and No. 12, no deoxidizing effect was observed.

Example 2 Using pure Ti and pure A1 as raw materials, a Ti-Al alloy was subjected to vacuum induction melting in a lime crucible, and Example 1 was prepared before tapping.
Similarly, deoxidizing treatment was performed using Al-Ca alloy, and the diameter was 20 mm.
An ingot with a diameter of 0 mm and a length of 1000 m+a was produced.

Vacuum arc melting was performed using this ingot as a primary consumable electrode to produce an ingot with a diameter of 2601 ml and a length of 500 mm.

Table 2 shows the component analysis values of the primary electrode material and the ingot after vacuum arc melting.

It is clear from Table 2 that by further performing vacuum arc melting on an ingot produced from deoxidized molten metal, a high purity ingot with reduced Ca and O content can be produced. It turns out that it is possible.

Table [Effects of the Invention] As explained above, since the method for producing a Ti-Al alloy according to the present invention has the above configuration, the Ti-Al alloy is melted by induction melting using a lime crucible. By this,
The content of oxygen as an impurity in the produced Ti-Al alloy can be significantly reduced, and high purity Ti-A
It is possible to produce l-based alloy ingots, and has the excellent effect of reducing not only the oxygen content (but also the Ca content).

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between dissolution time and oxygen content, Figure 2 is a diagram showing the relationship between dissolution time and oxygen content.
The figure shows the relationship between Ca and O in the molten metal during melting. Patent applicant: Kobe Steel, Ltd. Membership concentration (y?%)

Claims (3)

[Claims] (1) A Ti-Al alloy is melted in a lime crucible in vacuum or in an inert atmosphere, and carbon is added to the molten Ti-Al alloy.
A method for producing a Ti-Al alloy, characterized by adding a or a Ca-containing alloy and performing deoxidation treatment. (2) A Ti-Al alloy is melted in a lime crucible in vacuum or in an inert atmosphere, and carbon is added to the molten Ti-Al alloy.
A or a Ca-containing alloy is added and deoxidation treatment is performed at a temperature of 10°C or higher and 1650°C or lower than the liquidus temperature of the molten Ti-Al alloy.
-A method for producing an Al-based alloy. (3) A Ti-Al alloy is melted in a lime crucible in vacuum or in an inert atmosphere, and carbon is added to the molten Ti-Al alloy.
A or a Ca-containing alloy was added and an ingot was cast from a molten metal that was deoxidized at a temperature of 10°C or higher than the liquidus temperature of the molten Ti-Al alloy and 1650°C or lower. Ti-A characterized by reducing Ca content by melting, vacuum melting or electron beam melting
Method for producing l-based alloy.