JPH0598371A - Production of nitride dispersion strengthened alloy - Google Patents

Abstract

PURPOSE:To produce a nitride dispersion strengthened alloy where fine nitrides can be dispersed in a matrix metal easily and uniformly. CONSTITUTION:A molten alloy 12 where a matrix metal difficult to form nitride and a nitride-forming element capable of forming nitride more easily than the matrix metal are melted is prepared. This molten alloy is heated in a heating atmosphere containing nitrogen gas by means of a high temp. arc 10. The nitride-forming element in the molten alloy 12 is nitrided by means of the nitrogen dissociated and activated by the arc 10, and the molten alloy where the resulting fine nitrides are uniformly dispersed and suspended is solidified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for producing a nitride dispersion strengthened alloy by a melting method.

[0002]

2. Description of the Related Art Dispersion strengthened composite materials in which fine particles of ceramics such as oxides and carbides are dispersed in a metal matrix are excellent in wear resistance, heat resistance, and oxidation resistance. Moreover, since the fine particles hinder the movement of the transition accompanying the deformation of the matrix, not only the wear resistance and heat resistance but also the mechanical strength are excellent.

Of the above ceramics, nitrides of transition elements such as Ti and Zr that are easily nitrided have excellent heat resistance,
Since it is stable and tough even at high temperatures, it is suitable as a dispersant for various base metals. In particular, a composite material in which a nitride is dispersed in copper or a copper alloy is suitable as an electrode tip material for resistance welding and a contact material in combination with high conductivity and high thermal conductivity of a base metal.

These nitride dispersion strengthened alloys are mainly manufactured by the powder metallurgy method and the melting method. In the powder metallurgy method, a metal material such as metallic titanium is nitrided to produce its nitride, then this nitride is crushed, the obtained powder is mixed with the base metal powder, and the mixed powder is molded. And then sinter. On the other hand, the melting method is, as disclosed in JP-A-64-36744, cast a molten metal obtained by adding and dispersing a powder of a nitride in a molten base metal using an appropriate mold. , A method of solidifying.

[0005]

The above-mentioned powder metallurgy method has a problem that the manufacturing cost of the raw material powder of the nitride and the base metal is high, and the molding and sintering process takes a long time, resulting in poor productivity. The melting method does not have these drawbacks and is economical. However, the weight segregation of dispersed particles and the tendency of coarsening due to particle aggregation are unavoidable, and there is a problem in the wettability of the dispersed particles with the base metal melt, making it difficult to add fine powder to the melt or evenly disperse it. There is a problem that is.

The present invention has been made in view of the above problems, and provides a method for producing a nitride dispersion strengthened alloy, which is capable of improving the conventional melting method and easily and uniformly dispersing fine nitrides in a base metal. The purpose is to do.

[0007]

In the method for producing a nitride dispersion strengthened alloy of the present invention, a base metal that hardly forms a nitride and a nitride forming element that easily forms a nitride than the base metal are melted. The alloy is melted, the molten alloy is heated by a high temperature arc in a heating atmosphere containing nitrogen gas, and the nitride forming element in the molten alloy is nitrided by the nitrogen dissociated or ionized by the arc to generate a nitride. Suspending in the molten alloy and solidifying the molten alloy. In the melting of the molten alloy, the matrix base metal, which is a main component of the base metal, and the nitriding master alloy containing the nitride-forming element may be melted. The heating atmosphere containing the nitrogen gas,
Atmosphere (air) can be used. As the high temperature arc, a plasma arc using a thermal plasma as a heat source may be used. Further, by using copper or a copper alloy as a base metal and zirconium as a nitride-forming element, a composite material suitable as a material for an electrode tip for resistance welding or the like can be easily obtained.

[0008]

[Function] When a molten alloy of a base metal that hardly forms a nitride and a nitride-forming metal element that easily forms a nitride is heated on the surface of the molten metal by a high temperature arc in a heating atmosphere containing nitrogen gas, the molten alloy is easily formed. The nitrogen gas in the heating atmosphere is dissociated or ionized into an atomic state by the arc discharge. The activity of this atomic nitrogen increases as the temperature of the arc increases. Therefore, even nitrogen, which is inert to the base metal at the normal melting temperature, is easily absorbed in the molten alloy and preferentially combines with the nitride-forming element to form a fine nitride. In this way, the particles of the nitride produced by reaction in the molten alloy are extremely fine and have good wettability with the molten metal, so compared with the case where a crushed nitride is simply added and mixed in the molten metal, It is unlikely to cause specific gravity separation or aggregation, has excellent adhesion to the matrix, and is superior in strengthening function by preventing crystal dislocation. Further, since the density of the nitride particles is higher than that of oxides, carbides, and boride particles, the difference in specific gravity between the molten base metal is small, and the particles float in suspension in the molten metal for a long time. Until then, weight segregation (specific gravity separation) is unlikely to occur.

A plasma arc is preferably used as the high temperature arc. The plasma arc has a mechanically and electrically focused thermal plasma, and is in the thousands to tens of thousands of degrees K
It can be used as an extremely high temperature heat source. Atmosphere can be used as the heating atmosphere containing the nitrogen gas. When arc discharge occurs in the atmosphere, when the temperature in the arc atmosphere reaches about 6730 ° C, nitrogen in the air is reduced to 33%.
% Decomposes and 1% ionizes, 100% at about 11730 ° C
It is said that it decomposes and 14% is ionized. Plasma arcs easily raise above 8000 ° C and thus produce significant atomic nitrogen. On the other hand, since the molten alloy is easily heated to 2000 ° C. or higher by the irradiation of the plasma arc, the activated nitrogen is easily absorbed in the molten alloy and the nitride forming element is preferentially nitrided.

By using pure copper or a copper alloy having good conductivity as the base metal and zirconium as the nitride forming element, a composite material having excellent conductivity, heat conductivity, heat resistance and strength can be easily obtained. Can be obtained. Zirconium is easy to nitride and zirconium nitride has a melting point of 25.
It is extremely high at about 00 ° C or higher, and part of the zirconium is used as a constituent component of the base metal without nitriding the whole zirconium, so that the conductivity and thermal conductivity of copper and its alloys are not significantly damaged, This is because it is possible to strengthen (solid solution strengthening). In addition, since the specific gravity of zirconium nitride and the specific gravity of copper or its alloy are very close to each other, it is possible to suspend and suspend the nitride particles for a long time in combination with the fineness of the generated nitride particles. Even in this case, there is no fear of specific gravity separation, and the excellent uniform dispersibility. still,
The decrease in conductivity due to the dispersion of nitride particles is almost proportional to the volume ratio of dispersed particles, but since the volume ratio is usually within a few percent,
The decrease in electrical conductivity and thermal conductivity is negligible and causes almost no problem.

[0011]

EXAMPLES The base metal which is hard to form a nitride used in the present invention is not limited to iron and steel materials such as cast iron and steel, but may be non-ferrous metals such as copper or aluminum or alloys thereof. On the other hand, the element that easily forms a nitride may be any element that is more likely to form a nitride than the base metal, such as Zr, Ti, Hf, V, Nb, Ta, and Sc. One or more elements of the IIa, IIIa, IVa, Va and IIIb groups of the periodic table can be used. However, as described above, as the electrode tip material for resistance welding and the material for contacts, copper or its alloy (for example, Ag-Cu, Cr-C) is used.
A combination of u, Be-Cu) and Zr is preferable.

In order to produce a molten alloy in which a base metal and a nitride-forming element are melted, a base composed of a nitriding mother alloy containing the nitride-forming element and a main component of the base metal is used rather than a simple substance of the nitride-forming element. It is better to dissolve the base metal. This is because many of the above elements are active and the surface of the simple metal is easily nitrided. However, depending on the type of element, there are some that can be used as a simple metal. The melting means is not limited to the high-temperature arc described later, but may be melted using a normal melting furnace such as a crucible furnace. Incidentally, of the mother alloy for nitriding,
Components other than the nitride-forming element form the base metal of the composite together with the base metal.

After the base metal and the nitriding element are melted, the molten alloy is heated by a high temperature arc in a heating atmosphere containing nitrogen gas. Air (air) can be used as the heating atmosphere containing nitrogen gas, but of course,
You may heat in a nitrogen gas atmosphere. As the high-temperature arc, it is sufficient that the molten alloy can be heated to a high temperature and nitrogen is dissociated and activated, and an arc discharge may be generated between the molten alloy and the electrode, but a thermal plasma using nitrogen gas as a plasma forming gas. It is preferable to use a torch or a plasma arc generated by a multi-phase multi-electrode plasma arc generator described later because an ultrahigh temperature of about 10,000 ° C. can be easily obtained. Particularly, according to the multi-phase multi-electrode plasma arc generator, a non-transition type ultra-high temperature plasma arc can be easily and continuously generated. Is rapidly heated to a high temperature and nitrogen in the heating atmosphere can be rapidly dissociated and activated, and carbon monoxide generated by the oxidation of the graphite electrode is (CO) ⁺ , C ⁺
As a result, a plasma arc that is extremely rich in reducing properties is formed, so that hydrogen and oxygen in the molten alloy can also be expelled, and a sound composite material can be obtained.

Next, a multi-phase multi-electrode plasma arc generator for carrying out the present invention will be described. FIG. 1 shows a layout of a plasma arc generator 100. The generator 100 is installed on a pedestal 101, and a lower part of the pedestal 101 is for cooling and solidifying the molten alloy flowing down from the generator 100. A mold device 120 is attached. The generator 100
Are disclosed in Japanese Examined Patent Publication No. 56-31188 and Japanese Unexamined Patent Publication No. 63-130269, and as shown in FIG.
1, 2, 3, 1A, 2A, 3A, each electrode has an inverted conical shape and is radially arranged at an equal angle (60 °) when viewed from above so as to focus at the electrode tip 9. .. Each electrode is movable back and forth by an electrode feeding mechanism (not shown), and is adjusted according to the wear of the electrode. Reference numerals 4, 5 and 6 are current phase adjusting devices for three-phase AC output, which are for adjusting the intensity of the arc. Each electrode 1,2,3,1A, 2A, 3A
When an AC voltage having a phase difference of 120 ° with respect to the adjacent electrodes is applied from the three-phase AC power source 7 through the current phase adjusting devices 4, 5 and 6, the electrode tip 9 is not shifted downward. Plasma arc 10 is generated. Below the electrode tip 9,
A graphite crucible 11 for accommodating an irradiation object 12 is installed. The number of electrodes and the number of alternating current phases are not limited to those in the above example, and can be increased in multiples of 3, respectively. In addition, a neutral electrode may be provided at the center of the plurality of radially arranged electrodes.

The casting mold apparatus 120 is provided with an inner container 122 for accommodating the molten alloy flowing out from the crucible 11 through a refractory funnel 13 and an outer container 121 for accommodating the inner container. Is configured so that cooling water is injected from a water supply port 121A mounted near the bottom part and discharged from a drain port 121B mounted on the upper end part of the side wall, so that a constant level of cooling water is always filled. ing. Reference numeral 123 is a support frame that supports the inner container 122 with a slight gap from the bottom surface of the outer container 121.

The multi-phase multi-electrode plasma arc generator 100
The method of implementing the present invention will be described with reference to. First, the cover
From the raw material charging chute 102 attached to the raw material metal 103 (for example, pure copper and Zr-Cu alloy or Ti-Cu alloy)
A predetermined amount of the lump of is put into the crucible 11. In this state, the three-phase AC power supply 7 is turned on, and the plasma arc 10 is generated at the tips of the six graphite electrodes in the atmosphere. Then, the metal mass in the crucible 11 is heated and melted by the irradiation of the plasma arc 10, and the nitride-forming element in the molten metal 12 is combined with nitrogen in the atmosphere dissociated and activated by the plasma arc 10 to form fine nitride particles. The fine particles are uniformly dispersed in the molten alloy. Then, replenish the lumps of raw metal, and crucible 11
When the molten alloy therein is full, it overflows and flows through the funnel 13 below it into the inner container 122 of the mold apparatus 120.

Then, when the molten alloy is accumulated in the inner container 122 to some extent, the supply of the raw material metal is temporarily stopped. Where the outflow of molten alloy from the crucible 11 has stopped,
The solidified material X is taken out by observing the solidified state of the casting mold device 120.
The solidified product X is a high-quality nitride dispersion strengthened composite material in which nitride particles are uniformly dispersed in the base metal. In the above implementation method, the plasma arc 10 was generated in the atmosphere,
The cover 103 of the generator 100 may have a structure capable of being sealed from the outside air, the inside of the device may be shielded from the outside air and filled with nitrogen gas, and a plasma arc may be generated as a nitrogen gas atmosphere. Further, in the above method, the raw metal ingot was supplied to the crucible 11, and this was melted in the plasma arc 10 and heated to nitride the nitride-forming element, but in the crucible 11, the molten alloy melted in a separate melting furnace was used. It may be supplied.

If there is a base metal alloy (raw material alloy) containing a predetermined amount of the nitride-forming element in the base metal, it is sufficient to supply this alloy lump to the crucible 11, and the base mother metal and nitride It is convenient because it is not necessary to supply the elemental metal of the forming element or the nitriding mother alloy. Such a raw material alloy can be easily manufactured by providing the sealable cover 100A. That is, the inside of the apparatus is made to be an atmosphere of an inert gas other than nitrogen (for example, argon gas), and a lump of the base mother metal and the nitriding mother alloy (for example, copper and Cu-Zr alloy) is mixed in the crucible 11 with a predetermined composition. It may be supplied and dissolved.

FIG. 3 shows another example 100A of the multi-phase multi-electrode plasma arc generator, which is a continuous supply mechanism for continuously supplying powdery raw material metal to the center of the plasma arc with respect to the apparatus 100 of FIG. 81 is attached, the other configurations are the same, and the same reference numerals are given. This continuous feeding mechanism 81
Is a charging port for charging powdered raw metal into the mechanism.
13, a fixed amount supply device 14 which is disposed at the base of the charging port 13 and sends out a powder of the raw material metal in constant amounts, and the fixed amount supply device 14
It is composed of a charging grate 15 and a charging pipe 16 for guiding the raw material metal from the above to the center of the electrode tip 9.

According to this plasma arc generator 100A, when a powdery raw material metal is supplied to the central portion where a large number of electrodes are concentrated in the atmosphere, the powder metal is heated while passing through the maximum heating portion of the plasma arc. Since the nitride forming element is nitrided as it is melted, it is possible to rapidly melt the molten metal in which the fine nitride is uniformly dispersed. By continuously supplying the raw material metal powder, the molten alloy overflowing from the crucible 11 can be continuously supplied to the casting mold device 120 via the funnel 13.

Next, specific examples will be given. Pure copper 900g
Was dissolved in a graphite crucible of a kerosene burner crucible furnace, and 50 g of a Zr-Cu mother alloy (Zr content 30 wt%) was added and dissolved. After that, the molten alloy was supplied to the graphite crucible of the multi-phase multi-electrode (graphite electrode) plasma arc generator shown in FIG. 1, and the surface of the molten alloy was irradiated with a non-transfer type plasma arc in the atmosphere. Zr in the molten alloy was nitrided while being heated to ℃ or more. The plasma arc irradiation conditions were 63 KVA for 2 minutes.

Next, the molten alloy heated by the plasma arc was cast into a graphite mold of φ200 × 200 mm for sample casting. The cast sample was subjected to solution treatment at 1000 ° C to prevent oxidation, then 50% cold working, and tempered at 500 ° C. Microscopic observation of the cross section of this sample revealed that extremely fine nitrides were uniformly distributed. The amount of zirconium nitride dispersed was 1.8 vol%. Moreover, when the hardness was measured, it was 145 Hv and the hardness was high, and the conductivity was 88 (I
ACS%) was a good value. The results of analyzing the composition of this sample are shown below. The unit is wt% and Zr% is the value of free Zr.

Si: 0.02%, Fe: 0.01% Zr: 0.23%, balance substantially Cu After heating the sample at 800 ° C. for 1 hour, the hardness was measured and found to be 120 Hv. The decrease was slight. In addition, the same component without particle dispersion, Cu-Z after the same solution treatment and aging treatment
The hardness of the r alloy was 148 HV, but the hardness after heating at 800 ° C. × 1 Hr was greatly reduced to about Hv60. Further, when the sample of the example was redissolved in a crucible furnace and solidified, an alloy having good particle dispersibility was obtained.

[0024]

As described above, according to the method for producing a nitride dispersion strengthened alloy of the present invention, a base metal that hardly forms a nitride and a nitride forming element that easily forms a nitride than the base metal. Since the molten alloy that has melted is heated by a high-temperature arc in a heating atmosphere containing nitrogen gas, nitride formation in the molten alloy heated to a high temperature by nitrogen activated by dissociating or ionizing the nitrogen gas in the heating atmosphere The element can be easily nitrided, and the fine nitride particles generated by this can be uniformly suspended and dispersed in the molten alloy.By solidifying the molten alloy, the fine nitride particles can be made uniform. A dispersed strengthening alloy can be easily obtained. Further, when the atmosphere is used as the heating atmosphere, nitrogen in the air can be used, so that the present invention can be implemented very easily. Further, when a plasma arc is used as the high temperature arc, the molten metal can be rapidly heated by the ultrahigh temperature thermal plasma, and nitrogen can be dissociated and activated, which is highly efficient. Further, by using copper or copper alloy as the base metal, and by using zirconium as the nitride forming element, wear resistance and strength at high temperature, conductivity,
A nitride dispersion strengthened alloy having excellent thermal conductivity can be easily obtained.

[Brief description of drawings]

FIG. 1 is a layout view of a multi-phase multi-electrode plasma arc generator for implementing the present invention.

FIG. 2 is an explanatory diagram showing an outline of a configuration of the same generator.

FIG. 3 is an explanatory diagram showing an outline of a configuration of another example of the same generator.

[Explanation of symbols]

 1 Graphite Electrode 1A Graphite Electrode 2 Graphite Electrode 2A Graphite Electrode 3 Graphite Electrode 3A Graphite Electrode 4 Current Phase Adjuster 5 Current Phase Adjuster 6 Current Phase Adjuster 7 3-Phase AC Power Supply 9 Electrode Tip 10 Non-Transitional Plasma Arc 11 Crucible 12 Molten alloy 100 Multi-phase multi-electrode plasma arc generator 100A Multi-phase multi-electrode plasma arc generator 120 Mold equipment

Claims (4)

[Claims] 1. A method for producing a nitride dispersion strengthened alloy for solidifying a molten alloy in which nitride is suspended in a molten base metal, wherein a base metal which hardly forms nitride and a nitride more than the base metal are formed. An alloy in which a nitride-forming element that is easily formed is melted, the molten alloy is heated by a high-temperature arc in a heating atmosphere containing nitrogen gas, and nitride in the molten alloy is generated by nitrogen dissociated or ionized by the arc. A method for producing a nitride dispersion strengthened alloy, which comprises nitriding a forming element and suspending the generated nitride in a molten alloy. 2. The method for producing a nitride dispersion strengthened composite material according to claim 1, wherein the molten alloy is heated in the atmosphere. 3. The heating with a plasma arc.
A method for producing a nitride dispersion strengthened alloy according to 1. 4. The method for producing a nitride dispersion strengthened alloy according to claim 1, wherein the base metal is copper or a copper alloy and the nitride forming element is zirconium.