JPH0432528A - Method for melting carbide dispersing type titanium base alloy - Google Patents

Abstract

PURPOSE:To reduce unit consumptions of a crucible and electric power by melting raw material for melting containing carbide in an induction heating melting method using the graphite crucible. CONSTITUTION:The main raw material, auxiliary raw material and carbide are charged into the graphite crucible 4 at inside from a raw material charging chamber 7, and the melting furnace 1 is kept to under vacuum or inert gas atmosphere of Ar, etc., and the raw material is melted with high frequency current induced from the high frequency induction coil 6. The carbide is TiC, ZrC, SiC, WC, etc. By this method, carbon is infiltrated from interface between inner surface of the graphite crucible and the molten metal, and interface between the carbide surface and the molten metal, but the quantity from the latter is by far more than that from the former. Therefore, compared with the conventional melting method, which titanium carbide is developed with the carbon infiltrated only from the graphite crucible, this can be melted for shorter time and erosion of the graphite crucible is a little with this method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for melting a carbide-dispersed titanium-based alloy having high ductility and excellent wear resistance.

(Prior Art) Titanium or titanium alloy (hereinafter collectively referred to as "titanium base metal" in this specification) has high specific strength and excellent corrosion resistance and heat resistance, so it is used as a metal material for aircraft. Although its use is expanding as a metal material for the chemical industry, it does not have sufficient wear resistance, and there are problems with its use in sliding parts of mechanical parts.

Therefore, in recent years, new titanium-based alloys with improved wear resistance have been developed. For example, JP-A-6468437 discloses a carbide-dispersed titanium base metal in which titanium carbide is uniformly dispersed and crystallized in a titanium or titanium alloy matrix. This carbide-dispersed titanium base metal has excellent wear resistance due to the coexistence of carbides, but
The carbide-dispersed alloy described in No. 4, No. 68437 is manufactured by a tungsten arc melting method, and therefore has problems in melting efficiency and manufacturing cost.

In consumable electrode arc melting methods such as tungsten arc melting, consumable electrodes are produced by compact pressing raw materials such as titanium sponge and alloy elements to create compacts, which are then welded into large numbers by electron beam welding. In addition, the amount of scrap titanium or titanium alloy used must be limited in order to ensure the strength of the molded body. Furthermore, since the alloy components are not uniformly distributed within the ingot with only the first melting, at least two meltings are required. For these reasons, the consumable electrode arc melting method is industrially and economically disadvantageous.

On the other hand, as a low-cost and highly productive melting method, it is possible to melt steel materials and
There is an induction heating melting method using a graphite crucible that is used for melting I-based alloys and Co-based alloys, and is disclosed in JP-A-1-2220.
Publication No. 26 discloses a method of dissolving a carbide-dispersed titanium base metal using this melting method. This Unexamined Publication No. 1-22
The invention described in Publication No. 2026 is not aimed at improving wear resistance, but in order to increase the ductility of titanium-based alloy.
Using a graphite crucible, high-frequency melting is performed while containing carbon in an amount exceeding the solid solubility limit in the alpha phase, and the solute carbon is precipitated as titanium carbide during the cooling process. In the melting method of the present invention, carbon in an amount exceeding the solid solubility limit infiltrates from the graphite crucible, but in melting a carbide-dispersed titanium-based alloy, all of the carbon necessary for precipitation of titanium carbide is removed from the graphite crucible. If the infiltrated carbon is used to secure the melt, the crucible will be severely eroded, the life of the crucible will be shortened, and the crucible consumption rate of the melting cost will increase. Furthermore, when producing a material with a high carbon content and a large amount of titanium carbide dispersed, the melting time becomes longer and the melting power consumption becomes higher.

(Problems to be Solved by the Invention) An object of the present invention is to solve the problems in conventional melting methods. That is, an object of the present invention is to provide a method that can efficiently and economically melt a carbide-dispersed titanium-based alloy in which titanium carbide is uniformly dispersed in a titanium or titanium alloy matrix.

(Means for solving the problem) The induction heating melting method using a graphite-based crucible is inexpensive and has excellent melting efficiency, but in the case of the melting method described in JP-A-1-222026, the life of the crucible is short and the melting The disadvantage is that it takes a long time. This is because the carbon necessary for the precipitation of titanium carbide is secured by the carbon that enters from the graphite crucible. However, the present inventors have found that if the carbon that enters from the graphite crucible is used as an auxiliary, and if carbide is used separately as a carbon source, most of the carbon required for the precipitation of titanium carbide can be obtained from the carbide. As a result, the melting time is shortened and erosion of the crucible is reduced, resulting in a longer crucible life.

The present invention relates to [a method for melting a carbide-dispersed titanium-based alloy, characterized in that a melting raw material containing carbides is melted in a vacuum or an inert atmosphere by an induction heating melting method using a graphite crucible; do.

In the present invention, a carbide-dispersed titanium-based alloy refers to a titanium-based alloy in which titanium carbide is crystallized or precipitated and dispersed in a titanium or titanium alloy matrix, and the titanium alloy matrix has a β titanium phase, an α titanium phase, It is either α+β titanium phase.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic explanatory diagram showing an example of an apparatus from melting to casting that implements the method of the present invention.

In FIG. 1, ``■'' is a melting furnace, and a crucible 2 and a mold 3 are placed in this melting furnace P1. The illustrated crucible 2 is composed of an inner graphite crucible 4 and an outer calcia crucible 5. The outer calcia-based crucible 5 is for keeping the inner graphite-based crucible, which has good thermal conductivity, warm, and is not necessarily necessary in the zero-start melting method. 6
is a high-frequency induction coil, 7 is a raw material charging chamber, 8 is a melted raw material,
9 is a sampling rod.

The melted raw material 8 is a main raw material, an auxiliary raw material, and a carbide of a carbon source, where the main raw material is titanium sponge or titanium scrap, and the sublayer #4 is V-AI master alloy, Mo-1
Mother alloy, pure AI, pure Mo, pure v1 pure W, pure Fe, pure Cr
, pure Sn, pure Zr, etc. Carbides include TiC1ZrC,
SiC, MO2C1vc, w2c,, wc, Kano v C
2. It is NbC. These carbides are one or two types.
Among them, hO□C1VC, which is a carbide in which a β-stabilizing element and carbon are combined, can be used.
In the case of W2C, WC, Cr=Ct and ~bc, it can be used as a carbon source for producing titanium carbide and at the same time as an auxiliary raw material for β-stabilizing elements such as Mo, V, W, Cr, Nb, etc. can also be used.

Further, although carbides in which these β-stabilizing elements and carbon are combined have a high specific gravity, when used as an auxiliary raw material, the specific gravity is lower than that of pure metals, so it is effective in reducing segregation. Furthermore, W2C and WC have a melting point of 500~500% higher than that of pure W.
Since it is as low as 600'C, if it is used in place of pure W, which has a high melting point of 3400°C, the residual melting can be reduced.

In the method of the present invention, these main raw materials, auxiliary raw materials, and carbide are charged into the inner graphite crucible 4 from the raw material charging chamber 7 and melted by high frequency current flowing from the high frequency induction coil 6. At this time, the main raw material, auxiliary raw material, and carbide may be simultaneously charged and melted in the graphite crucible 4, but only the main raw material, titanium sponge or titanium scrap, may be charged, and after this is melted, the molten metal Auxiliary raw materials and carbide may be charged and dissolved therein. This way, it can be understood in a shorter time.

Melting is carried out in a melting furnace kept in vacuum or in an inert gas atmosphere such as Ar or He. When dissolved in the atmosphere, the viscosity becomes too high due to significant oxidation of the titanium-based alloy, making it difficult to dissolve. If melting under vacuum, the degree of vacuum should be 10-”
If it is better than toll, it can be dissolved without any problem. As long as it is dissolved under an inert gas atmosphere, the pressure of the inert gas atmosphere may be reduced pressure, normal pressure, or increased pressure.

Carbon infiltrates into the molten metal due to melting. In the melting method of the present invention, carbon enters from the interface between the inner surface of the graphite crucible and the molten metal and the interface between the carbide surface and the molten metal, but the amount of carbon is larger in the latter because it is warmer. The contact area between the carbide surface and the molten metal is significantly larger than the contact area between the crucible and the molten metal, and the intrusion of carbon into the molten metal is dominated by the carbide, while the intrusion of carbon from the graphite crucible is significantly smaller. For this reason, compared to the conventional melting method that generates titanium carbide using carbon that enters only from a graphite-based crucible, it can be melted in a shorter time, and the graphite-based crucible suffers less erosion, resulting in a longer crucible life. be.

After melting, the ingot is cast into a mold 3 placed in the same atmosphere as the crucible, as shown in FIG. 1, to form an ingot of a carbide-dispersed titanium-based alloy in which titanium carbide is dispersed.

The alloy base of the ingot may be either a β titanium phase, an α titanium phase, or a β+α titanium phase, but when the alloy base is a β titanium phase, it has significantly better wear resistance than other ingots. It is. When β titanium phase is used as the alloy base, carbides include Mo2C1VC1W2C, WC, Cr+Cz, NbC, in which β stabilizing elements and carbon are combined.
It is better to use

Using these carbides, Mo, W, ■, Cr, F
If the contents of e and Nb are added so as to satisfy the following formula, the alloy matrix can be made into a β titanium phase.

Mo +0.6W+0.8V+1.5(1:r+3.O
Fe 〇, 2Nb≧12 (wt%) The present invention will be further explained below with reference to Examples.

(Example 1) A graphite crucible having a calcia crucible on the outside as shown in FIG. 1 was set in a high frequency induction heating furnace having a capacity of Nt 17 kg, and a graphite mold was also prepared. The inner graphite crucible has an inner diameter of 110mm, an outer diameter of 260a+m, and a thickness of 25m.
m, width: 275 mm.

Raw materials include sponge titanium and Ti-6 as main raw materials.
Prepare AI-4V scrap and use it as an auxiliary raw material
I master alloy, V-AI master alloy, pure gate 〇 powder, pure ■ flake, pure W powder, AI bronc, electrolytic Cr, electrolytic Fe, T
Prepare Sn, sponge zirconium and pure Nb1 powder and treat it as a carbide. 2C1vc, w, c, WC,
Cr: +Cz, NbC, ZrC and TiC! # Prepared.

After weighing these into the amounts shown in Table 1, titanium sponge or Ti 6Al 4V scrap was charged into a graphite crucible, melted and cast in the following steps, and an ingot with a target carbon content of 1.1% by weight was produced. was manufactured.

A graphite crucible was used for each material shown in Table 1, and the melting was repeated until the graphite crucible became eroded and a hole appeared.

(a) After performing evacuation and Ar substitution once, and evacuation again, Ar gas is introduced up to 500 Lorr, and energization is started.

(b) Apply current to the maximum output of 25 and a frequency of 4 kHz for 1 hour.

(C1 After melting at the above output and confirming that the melt has dropped, charge the auxiliary raw materials and carbide into the molten metal from the raw material charging chamber, and perform sampling every 10 minutes until the carbon content is 1.0% by weight.) At the point beyond which the molten metal is cast into a graphite mold, 1201 diameter x 2
An ingot with a length of 90 mm is produced.

As a comparative example, an ingot of the same size was produced by melting without adding carbide.

After casting, the central part of the ingot (total length 172, radius 1
) 2 A test piece was taken from the surface (entered from the surface) and analyzed for its components. Also, from the same position, 20mm square x 311
A block with a thickness of 11 mm was cut out, and the constituent phases were examined by X-ray analysis. Table 2 shows the component analysis results, constituent phases, and number of dissolutions. In addition, the component analysis results showed the average value of total dissolution.

(Hereinafter, blank space) From Table 2, it can be seen that in all of the examples of the present invention, Nα1 to No. 17, the target carbon content was almost reached after 10 minutes of melting, and the number of times of melting was as many as 50 or more. On the other hand, N(
118~No, 20, N (122~No, 24 and N
In the comparative example of U26, it took 50 to 6 to reach the target carbon content.
It requires a dissolution time of 0 minutes and the number of times of dissolution is extremely small. In addition, No. 21 and No. 25 are comparative examples that were dissolved in 10 minutes, but after 10 minutes of dissolution, the carbon content was low and did not reach the target of 1.1% by weight at all, resulting in titanium carbide. is not precipitated.

(Effects of the Invention) As shown in the examples, the method of the present invention, which uses carbide as a carbon source and melts it by induction heating in a graphite crucible, has a small amount of erosion of the graphite crucible, and can produce desired carbide-dispersed titanium in a short time. Base alloys can be melted.

For this reason, the crucible consumption rate and power consumption rate do not become excessively high unlike in the past, so the manufacturing cost is low.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an example of an apparatus from melting to casting that implements the method of the present invention. 1: Melting furnace, 2: Crucible, 3: Mold, 4: Graphite Y crucible,
5: Calcia crucible, 6. High frequency induction coil, 7. Raw material charging chamber, 8: Dissolved raw material, 9: Sampling rod.

Claims (1)

[Claims] A method for melting a carbide-dispersed titanium-based alloy, which comprises melting a melting raw material containing carbides in a vacuum or an inert atmosphere by an induction heating melting method using a graphite crucible.