JPH0321618B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial field] This invention is a lightweight titanium (Ti) alloy with excellent corrosion resistance and heat resistance, such as Ti-6Al-2Sn-4zr-
The present invention relates to aluminum (Al) and molybdenum (Mo) master alloys for producing titanium alloys suitable for melting 6Mo alloys, Ti-6Al-2Sn-4zr-2Mo alloys, etc. The master alloys conventionally used for Ti alloy melting are:
Al-V (vanadium) master alloy is known from Japanese Patent Publication No. 53-7368 or Japanese Patent Publication No. 53-8642. -I don't know about the existence of Mo master alloy. The basic phase diagram of pure metal Al-Mo is as shown in the figure, based on experiments carried out by the applicant's company. In the figure, curves CDE and FE indicate liquidus lines, and when Mo is 57% by weight or less, it is an envelope. Because it is a crystalline system, when it is cooled from a liquid phase state, Al 8 Mo ₃ is precipitated as a primary crystal in the curve DC, and after that, Al ₈ Mo 3 is precipitated as a primary crystal at 1130℃.
Although Al ₈ Mo ₃ continues to precipitate until the temperature reaches 735°C, solidification is not completed and the welding state continues up to 735°C, resulting in the formation of voids and shrinkage pores due to released gas and segregation of ingredients, resulting in Al -Applies to the cleanliness and homogeneity required of the Mo master alloy. In addition, since the alloy has coarse crystals, when adjusting the grain size to the required grain size as a master alloy for Ti alloys, the processing yield is significantly reduced due to the generation of fine powder, making it impossible to put it to practical use. Therefore, the inventor decided to
Focusing on the eutectic part containing 57 to 67% by weight of Mo, we found that a master alloy can be obtained from the eutectic reaction line GEH in which the solidification in the low-temperature solid part has a eutectic structure. There are three possible melting methods for Al-Mo: induction melting, welding in a vacuum arc furnace, and aluminothermite melting, but the induction melting method is extremely complicated and the equipment is expensive. Segregation inside the alloy due to the difference in specific gravity of Mo is also large. Also, in the melting method in a vacuum arc furnace, the master alloy is contaminated by the melting of the arc pole, and it is difficult to produce a homogeneous master alloy. The aluminothermite melting method has the characteristics of simple equipment and short reaction time;
Due to its characteristics, conventional compositions of 50% by weight Mo and the balance Al caused a violent reaction, almost explosive, and the composition was violently blown out and volatilized outside the crucible, resulting in a significant decrease in yield (approximately 50%). , Al−Mo
Conventionally, the composition ratio that can be melted using the aluminothermite method was set to be less than 50% by weight of Mo, but as described above, this composition ratio is in the peritectic range and cannot be put to practical use. Therefore, the inventors developed a practical method for the aluminothermite method in the eutectic region, which had been considered extremely difficult in the past. [Purpose] The purpose of this invention is to develop a method for obtaining a new material of Al-Mo master alloy with a eutectic structure, which does not cause intense reaction and does not cause evaporation of Al or MoO ₃ The objective is to obtain a clean Al--Mo mother alloy with little loss due to volatilization, a significantly high circumferential ratio, and a clean Al--Mo mother alloy. Another objective is that this new substance
The purpose is to obtain a new material that is a master alloy that is relatively close to the melting point of Ti, does not become pulverized when crushed, and whose particle size can be easily adjusted. [Structure] The present invention relates to an aluminum-molybdenum alloy whose alloy composition is aluminum 33 to 43.
This is an aluminum-molybdenum master alloy for producing titanium alloys, which is characterized by having a eutectic structure containing 57 to 67% by weight of molybdenum. In another invention, when aluminum powder and molybdenum oxide powder are mixed and reacted using the thermite method, the mother alloy structure is changed to aluminum 33.
The molybdenum oxide powder and aluminum powder are mixed so that the molybdenum is 57 to 67% by weight, and the weight ratio is about 30 to 50%, preferably 42 to 43% based on the weight of the mixture. Aluminum, which is characterized by containing a slag-forming agent.
This is a method for producing molybdenum master alloy. [Effect] By adopting the above method, even if the aluminothermite method is used, the internal composition can be changed by the reaction in the crucible by using the slag forming agent in the above ratio. The slag caused by these slag-forming agents covers the surface of the liquid water, prevents volatilization of Al, and volatilization in the MoO ₃ state, and reduces the Al-Mo weight ratio. is in the eutectic region within the above range, so the melted alloy has a eutectic structure. Furthermore, since the upper limit of the weight percentage of Mo is 67 weight percent, the following drawbacks are not present. That is, if the temperature is too close to the eutectic point E, the solidification temperature range from the precipitation of AlsMo ₃ primary crystals to the eutectic precipitation will be too narrow, entrainment of specific metal inclusions will occur, and gas release will be incomplete. It becomes difficult to obtain a clean alloy and a material without pores, which are necessary conditions for the master alloy.
In addition, in the conventional thermite method, a complicated process is performed in which the molten metal is extracted, degassed, and then cast into a mold, but in this invention, the molten metal is simply poured into a mold in a reactor, and then cooled and solidified. A very good alloy is obtained by a simple method. Furthermore, the particle size of the master alloy obtained by this method can be easily adjusted when it is crushed. This invention will now be explained in detail with reference to the following experimental examples.

[Table] Mix the raw materials with the above composition, and
Thermite is reacted in a magnesia-lined furnace (crucible) with a 200mm top, an inner diameter of 400mm, and a depth of 300mm, and the slag layer and alloy layer are separated by the difference in specific gravity. After cooling sufficiently, the solidified alloy is taken out of the furnace and slag, shrinkage cavities, etc. are removed to obtain a finished Al--Mo alloy.

[Table] The raw materials having the above composition were mixed and an alloy was recovered in the same manner as in Experimental Example 1.

[Table] The raw materials having the above composition were mixed and an alloy was recovered in the same manner as in Experimental Example 1.

[Table] The raw materials with the above composition were mixed, melted in the same manner as in Experimental Example 1, and after degassing the molten metal with chlorine gas, the bottom inner diameter was 150 mm, the upper inner diameter was 300 mm, and the depth was
It was poured into a 300mm copper mold and allowed to cool and solidify.

[Table] Alloys were recovered using the same method as in other experimental examples using raw materials with the above-mentioned composition. The results of these experiments are shown in the table below.

【table】

[Table] As is clear from the above result table, the alloy obtained by the method of the present invention has excellent requirements as a Ti master alloy, especially in high yield and cleanliness. The content of inclusions is about 1/10 of that of conventional examples, especially for materials such as Ti alloys whose properties change greatly depending on the inclusion rate of impurities.
The cleanliness of this master alloy is a noteworthy effect. Furthermore, when the alloys of Experimental Examples 1, 2, 3, and 4 are crushed, they do not become fine powders and the particle size can be easily adjusted. The melting point of this Al-Mo master alloy is 1760℃, and the Ti
Its melting point is relatively close to 1665℃, making it easy to melt into a ternary alloy. In the methods shown in Experimental Examples 1 to 3, in a crucible for carrying out a thermite reaction,
Since the method involves cooling and solidifying the molten metal, no mold is required, making the operation simple. In the method shown in Experimental Example 4, the metal that has become molten in the crucible is poured into the mold by thermite reaction, so gas can be removed during this process and the rate of porosity can be further reduced. This increases crucible usage efficiency since the empty crucible can be used for the next reaction.

[Brief explanation of the drawing]

The figure is a phase diagram of an Al-Mo alloy.

Claims (1)

[Claims] 1. In aluminum-molybdenum alloys, these alloy compositions include 33 to 43% by weight of aluminum;
An aluminum-molybdenum master alloy for producing titanium alloys, characterized by having a eutectic structure containing 57 to 67% by weight of molybdenum. 2. When aluminum powder and molybdenum oxide powder are mixed and reacted using the thermite method, the molybdenum oxide powder and aluminum powder are mixed so that the mother alloy structure is 33 to 43% by weight of aluminum and 57 to 67% by weight of molybdenum. and the weight ratio of about 30 to the weight of these mixtures.
A method for producing an aluminum-molybdenum master alloy, which comprises adding a sludge forming agent of 50% to 50%, preferably 42 to 43%. 3. The method for producing an aluminum-molybdenum master alloy according to claim 2, wherein the slag-forming agent is one of calcium oxide, calcium fluoride, and a mixture thereof.