JPS58133338A - Method for melting titanium group metal or alloy thereof - Google Patents

Abstract

PURPOSE:To obtain a product ingot free from segregation and having a uniform composition, by melting a Ti-group metal under vacuum or an argon atmosphere in a dielectric heating furnace lined with a calcareous refractory material. CONSTITUTION:The inner surface of the furnace main body 16 of a dielectric heating furnace 15 used in melting a Ti-group metal or an alloy thereof is lined with a calcareous refractory material 18 such as calsis. A stock material as the Ti-group metal or the alloy thereof is charged into the furnace main body 16 from a stock material charging chamber 30 and, after an opening and closing door 27 is closed, a container 22 and the stock material charging chamber 30 are evacuated to form a vacuum atmosphere or, according to necessity, filled with an argon gas to form an argon atmosphere. In the next step, the stock material in the furnace main body 16 is subjected to dielectric heating in said atmosphere to be melted. By this method, the segregation of a product ingot is reduced and the uniformity of components in the ingot is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for melting titanium group metals or their alloys.

The most common methods for melting titanium or titanium alloys include the following two methods.

One method uses a consumable electrode type vacuum arc furnace shown in FIG. 1, and the other method uses a non-consumable electrode type melting/filling method shown in FIG. 2, which is an explanatory diagram of the mechanism.

First, to explain the former, raw materials consisting of titanium sponge, titanium scrap, alloy components, etc. are pressed in advance with a breather culm (1) to form a crimped product called a compact (3), and a large number of these pieces are then welded in the next welding process. In step (2), they are connected using a welding torch to form a rod-shaped electrode (5), and this is used to perform melting. That is, such a compact is used as an electrode (5) in a primary vacuum arc furnace (4), an arc is generated between the electrode (5) and the molten metal (6) in the mold (7), and the arc heat is released. The electrode (5) is melted and cast into a mold (7) to form an ingot. Next, the electrode (9) is used as an electrode (9) in the ingot internal vacuum arc furnace (8), and the electrode (9) is similarly melted by arc heat and cast into the mold 00 to form an ingot product.

This method requires processes such as compact molding and electrode assembly prior to melting, and the proportion of titanium nuclear wrap used is limited in order to maintain the strength of the compact at the stage of compacting the raw material. However, since the removal of impurities is not sufficient with only secondary melting, and the alloy components are not distributed uniformly within the ingot, melting is required at least twice, making the process complicated and time-consuming. There is.

The latter method, which uses a non-consumable electrode type vacuum arc furnace, is a method that improves the above-mentioned drawbacks, and uses granular or small pieces of titanium sponge, titanium scrap, alloy components, etc. as raw materials, as shown in Figure 2. This raw material is charged into a water-cooled copper crucible (01) in a vacuum atmosphere, where it is placed in a non-consumable electrode (2).
), the raw material is melted by the arc heat to obtain a molten metal α, and this molten metal Q3 is appropriately cast into a mold 041 to form an ingot product.

In this method, steps such as compact molding and electrode assembly prior to melting are not required, so the steps are simplified and the restriction on the proportion of titanium scrubs 1 to be used is also eliminated. However, since an arc is used as a heating source, it is not only necessary to make the raw material into granules or small pieces;
Since the amount of molten metal that can be pooled in the crucible (0) is extremely small compared to the practical size of the ingot product, it is necessary to inject the molten metal intermittently or semi-continuously as the raw materials are melted during casting. Therefore, segregation of components within the mold is unavoidable, and there is a risk that the uniformity of the components of the ingot as a whole may be impaired.

Other melting methods of this type include those that use electron beam or plasma beam heating as a substitute for the arc heating described above, but no matter which of these methods is used,
Although an increase in the amount of molten metal pool in the crucible may be desired, the above-mentioned problem of ingot composition non-uniformity is still unavoidable.

The present invention improves the latter method and makes it possible to avoid component segregation in the finished ingot and obtain uniformity of the components as a whole ingot, and also to avoid crushing coarse scraps into small pieces as a raw material. Another object of the present invention is to provide a method for melting titanium group metals such as titanium, zirconium, and hafnium and their alloys so that they can be used as they are.

That is, the method for melting a titanium group metal or its alloy according to the present invention is characterized by melting the titanium group metal or its alloy in a vacuum or an argon gas atmosphere using an induction heating melt having a calcareous refractory lining on its inner surface. shall be.

As in the case of using the non-consumable a-electrode vacuum arc furnace,
In melting methods in which raw materials are stored in a crucible, melted, and then cast into a mold, in order to avoid component segregation in the finished ingot, the amount of molten metal boule in the crucible must be increased to accommodate one ingot. The entire amount of molten metal may be stored in the crucible and then poured. However, if conventional heating methods such as arc, electron beam, or plasma beam are used, as mentioned above, only a very small amount of molten metal pool can be secured for a practical size ingot, and it is completely impossible to take the above measures. It's impossible.

Now, if an induction heating furnace is used to heat and melt the raw materials, its high heating capacity will produce enough molten metal to cast a practical-sized ingot.

− It becomes possible to do. Moreover, in this case, there is an advantage that even if coarse titanium scrap is used as a raw material, it can be sufficiently melted.

However, there are major problems that cannot be avoided with the use of induction heating furnaces. In the case of an induction heating furnace, due to the heating method, the kettle itself, which serves as the melting vessel corresponding to the crucible, must be made of refractory material rather than copper like the crucible, but generally used as this refractory material. These refractories are made of magnesia, magnesia chromite, etc. When these refractories come into contact with molten titanium, titanium alloys, etc., they are easily immersed in a short period of time, and they also react with the components in titanium and titanium alloys. There is a high risk of it happening. Therefore, it is impossible to obtain a furnace that can be used to melt titanium or titanium alloys simply by forming the furnace using the above-mentioned general refractories.

The present inventors conducted experiments and research on various materials in order to find (4) large materials suitable for melting titanium, etc., and found that calcareous refractories (calcia) such as Ca oxides are not suitable for melting titanium, etc. It is not easily attacked by contact with
It was discovered that there is no reactivity with titanium or its alloy components. In order to take advantage of the effectiveness of the calcareous refractory as a furnace property, it is sufficient to line the inner surface of the furnace that comes into contact with the molten metal with this calcareous refractory. The calcareous refractory lining is poured like regular castable,
Alternatively, it can be easily accomplished by spraying. Note that in the present invention, the material is mainly limited to a calcareous refractory, which means that a small amount of a binder or the like may be included in addition to the calcareous refractory.

The present invention will be described in detail below based on the drawings listed as examples. FIG. 8 is a longitudinal sectional view of an apparatus suitable for carrying out the method of the invention.

In the figure, αO is an induction heating melting furnace, which is composed of a furnace body serving as a melting vessel and a coil α wound around it. The furnace body QO has a calcia lining α on the inner surface of the container made of general refractory material as described above.
A barrel is provided, and this is placed on a pedestal a0. The coil α power is a water-cooled coil to which high-frequency alternating current is supplied via a cable (not shown) to induction heat the raw material in the furnace body.

(1) is an armor type, and in the illustrated example, a water-cooled copper mold is used, and it is movably provided on the top of the mold.

The furnace body α and the mold have approximately the same capacity.

(A) is a vacuum container that houses the above-mentioned induction heating melting furnace OF5, and (E) is a vacuum vessel that houses the above-mentioned tower-shaped hood, and each is evacuated by exhaust ports (C) and (C), which are not shown. connected to the system. The vacuum container (to) is connected to the vacuum container (to) via an airtight sliding door (a) that fits into the sleeve M and moves up and down.
b). In addition, on the opposite side of the opening/closing door (A), there is provided an exit door for transporting the mold out of the container, and the exit (to) has a vertical sliding type that can be opened and closed with excellent airtightness, similar to the opening/closing door mentioned above. It is equipped with a door.

(To) is a raw material charging chamber with an airtight structure provided above the vacuum container (A), connected to a vacuum exhaust system (not shown) through an exhaust port 0), and equipped with rock pulp (A). It communicates with the vacuum vessel (A) via a connecting ramp (To). Inside this connecting slope (), there is a diagonal conveyance gutter (2) whose rear end protrudes from the slope (to) into the vacuum vessel (A) and whose tip faces the mouth of the melting furnace main body 0Q. The raw material in the chamber (7) slides down the diagonal gutter (2) and is charged into the furnace body (α).

In addition, ")" is a sample collector for collecting a sample of the molten metal inside the door body aQ, and (g) is a thermocouple that measures the temperature of the molten metal inside the crucible 0→.

The procedure for melting titanium or titanium alloy based on the method of the present invention using the apparatus configured as described above is as follows.

First, the required amount of titanium or titanium alloy raw material whose composition has been adjusted is slid down from the raw material charging chamber (G) over the diagonal gutter (2) and charged into the furnace main body QQ. Next, the opening/closing door (A) is closed, and the inside of the container (A) and the raw material-charging chamber (To) are evacuated from the exhaust port (F) and 01) to create a vacuum atmosphere. Further, if necessary, the vacuum atmosphere is filled with argon gas to create an argon gas atmosphere.

Thereafter, the raw material in the furnace body Ql is heated by induction in a vacuum or an argon gas atmosphere to melt the raw material. During this melting, analysis of various components of the molten metal as necessary,
Measurement of temperature, etc. is carried out as usual.

While performing the above melting, in the container C that stores the mold, close the opening/closing door at the outlet and exhaust the air from the exhaust port (C) to create a vacuum atmosphere inside, and as necessary, as above. Create an argon gas atmosphere.

After the above melting is completed, the opening/closing door is fully opened and the mold is opened.
is carried into a position close to the furnace main body a0 in the container sonai,
Lift and tilt the furnace body using a lifting tilter (not shown)□
Then, pour the molten metal into the mold. The above is one cycle of dissolution.

Next, an example in which a titanium alloy was melted and refined by the method of the present invention will be described.

High-frequency induction heating furnace α with a capacity of 100 kq shown in Figure 3
Using a mold (1) of the same capacity as that of the sponge titanium V
-A7 alloy, pure Aj, etc., with a blending ratio aiming at Ti-6Az 4y, were melted and cast to obtain an ingot product.

Table 1 shows representative components other than titanium sponge as the raw material and Ti in the ingot product.

Table 1 The above ingot product has a target alloy composition of T1-6A.
It almost satisfies z--caV. Furthermore, impurity components such as H, Mg, and Ct are also extremely low.

This is because the heating furnace body IN has a larger capacity and a larger free surface than a conventional crucible, and the degassing reaction of the components described above proceeds effectively.

Next, in order to investigate the segregation state of At among the above components, as shown in the explanatory diagram of FIG. Divide horizontally into specimens of 1 fin thickness (
6) horizontal direction 2 centered on the ingot of each specimen.
The At content at each position was measured, and the average value at the same position from each ingot of each specimen was shown in the diagram of FIG. 5 as a characteristic curve ('P).

As a comparative example, a sample was taken from an ingot obtained by melting and casting the same raw material as above in the conventional consumable electrode-type vacuum arc furnace shown in Figure 1, and the same method was used. The measured At values every 2 MI in the horizontal direction from the center of the ingot are also shown in FIG. 5 as a characteristic curve (Q,).

As shown in FIG. 5, in the comparative example, there is extremely large segregation in the At value ranging from 6.6% to 5.3% in the width direction of the ingot, whereas in the example of the present invention, the At value is 6.0%.
The segregation remained at a slight level of around 4%, indicating that the uniformity of the At component within the ingot was maintained at a high level.

Furthermore, using the same titanium alloy raw material as above in the non-consumable electrode type vacuum arc furnace shown in FIG.
An ingot of Ti-5At-4V titanium alloy was melted and cast, and the obtained ingot product was investigated for the segregation of At in the ingot using the same procedure as above. At compared to the invention example
The segregation was extremely large.

The method for melting titanium group metals or alloys thereof according to the present invention described in detail above has the following advantages.

- There is no need for the processes of compact molding and electrode assembly shown in Figure 1 prior to melting, and furthermore, the limitations on the scrap utilization rate that were necessary for compact molding can be eliminated.

■ It has the same characteristics as the method shown in Figure 2 (method using non-consumable electrodes) in that all the raw materials used can be scrapped, and in addition, it uses induction heating with a large heating capacity for melting. Restrictions regarding size are eliminated, and even large scraps can be used as is.

■ In addition, by using induction heating, it is possible to pool the entire amount of molten metal required for casting a finished ingot of practical size prior to casting, so the segregation of the finished ingot is reduced as much as possible, and the The uniformity of the ingredients is significantly improved.

■ In addition, since a large molten metal pool can be created before pouring, Mg, Ct, H,
It becomes possible to achieve effective promotion of degassing of N and the like. In addition, impurity components such as WC mixed in from the scrap raw material can be separated by settling at the bottom of the ingot during melting, so the problem of ingot contamination due to the use of scrap can be solved.

Therefore, it can be said that the present invention greatly contributes to reducing the melting cost of titanium group metals or their alloys and improving the quality of finished ingots.

[Brief explanation of drawings]

Figure 1 is a diagram of a conventional melting process for titanium or titanium alloy using a consumable electrode type vacuum arc furnace, Figure 2 is a longitudinal cross-sectional view to explain the melting method using a non-consumable electrode type vacuum arc furnace, and Figure 3 4 is a longitudinal cross-sectional view of an apparatus suitable for carrying out the method of the present invention, FIG. 4 is an explanatory diagram regarding a sample taken from an ingot, and FIG. 5 is a chart showing changes in At content in a titanium alloy ingot. 1: Pressing process, 2: Welding process, 8: Compact, 4-2 primary vacuum arc furnace, 5, 9: Electrode, 6, 18: Molten metal, 7
．． 10.14,20: Mold, 8: Secondary vacuum arc furnace,
ll: water-cooled copper crucible, 12: non-consumable electrode, 15: induction heating device, 16: crucible, 17: coil, 18: calcia, 19: pedestal, 21: rail, 22.28: vacuum container,
24.25,81: Exhaust port, 26: Nuritsuto, 27.
29: Opening/closing door, 28: Exit, 30: Raw material charging chamber, 82:
Rock pulp, 88: Connection slope, 84: Diagonal conveyance gutter, 85
: Sample collector, 86: Thermocouple, 40: Ingot, 41
: Sample, 42: Sample Applicant Sumitomo Metal Industries Co., Ltd. No. 1 No. 2 Mi14 F) (V's CD rrs-1 like!l
'l+me←<182-

Claims (1)

[Claims] (1) A method for melting titanium group metals or their alloys, which comprises melting the titanium group metals or their alloys in a vacuum or argon atmosphere using an induction heating melting furnace whose inner surface is mainly lined with calcareous refractories.