KR930003108B1 - Tungsten alloys and its production method - Google Patents

Abstract

A high toughened tungsten based heavy alloy is composed of (1) mixing the basic W-Ni-Fe system, which contains 90-95 wt.% tungsten (W), 2-9 wt.% nickel (Ni) and 1-3 wt.% iron (Fe), with 0.1-1.0 wt.% lanthanium (La) or 0.01-0.3 wt.% calcium (Ca); (2) drying; (3) crushing; (4) premolding; (5) heating the premolded body at 1475 deg.C under hydrogen gas atmosphere for 60-100 minutes; (6) heat treating the obtained alloy at 1,150 deg.C under inert gas atmosphere for 1 hour; (7) cooling by water; and (8) aging treating the resulting alloy at 500-600 deg.C under inert gas atmosphere for 1 hour. Then the high toughened tungsten based alloy is manufactured.

Description

High toughness tungsten polymer alloy and its manufacturing method

1 is a scanning electron micrograph of the impact wave surface of the W-Ni-Fe-based polymer alloy specimens, a is a wavefront for a conventional polymer gold specimen, b is a wavefront for the polymer gold specimen of the present invention.

Figure 2 is a graph showing a comparison of the change in impact energy according to the cooling rate at the heat treatment temperature (1150 ℃) of the conventional polymerized gold and the present invention.

The present invention relates to a tungsten-based polymer alloy containing tungsten (W) as a main component, and in particular, trace amounts of lanthanum (La) or calcium (Ca) are added to the tungsten (W) -nickel (Ni) -iron (Fe) -based basic composition. The present invention relates to a high toughness tungsten-based polymer alloy and a method for producing the same, which prevents grain boundary segregation of impurities and exhibits high toughness regardless of the content of phosphorus or sulfur as impurities, cooling rate after sintering, and reheat treatment conditions.

In general, tungsten-based polymerized gold is an alloy composed of 90 wt% tungsten and the remaining nickel and iron (or copper). As tungsten, which is a main component, is a high melting point metal, it is usually produced through liquid sintering, which is one of powder metallurgy processes.

Tungsten-based polymer alloys are widely used in various industries such as weight of gyroscopes, balance supports of aircraft, storage containers of radioactive materials, vibration damping devices and armored warheads.

Tungsten-based polymer alloys are superior in strength and elongation to other alloys in terms of mechanical properties, but toughness varies greatly depending on the manufacturing process and the powder used. Polymerized gold produced using powders that have not been sufficiently removed with the same impurity has a drawback that cannot be used for applications requiring high mechanical properties such as armored warhead warheads because mechanical properties including toughness are greatly reduced.

The reason why the mechanical properties of the polymer gold are degraded by impurities is known to be due to the interfacial segregation of the contained impurities. Accordingly, the study is intended to prevent the mechanical properties of the polymer gold from degrading by inhibiting the interfacial segregation of impurities present in the polymer gold. Has been done.

At present, as a known method of interfacial segregation of impurities, the interfacial segregation of impurities is essentially reduced with increasing temperature, so that water is cooled at a high temperature of 1000 ° C. to 1350 ° C. when the amount of impurities is not as high as several hundred ppm. There is a method for preventing interfacial segregation of impurities and subsequent deterioration of brittleness.

On the other hand, the water-cooled polymer gold is known to improve the mechanical properties by the aging treatment at a relatively low temperature of 500-600 ℃ as a subsequent heat treatment process, but is dispersed in the tissue through such an aging treatment process As impurities migrate to grain boundaries and cause interfacial segregation, the problem of interfacial segregation reemerges, thus increasing the mechanical properties of polymerized gold by water cooling and low temperature aging.

Therefore, for the production of polymer alloys having high toughness, a new type of polymer alloys having a composition capable of maintaining high mechanical properties regardless of a certain amount of impurities or heat treatment conditions is required.

The present invention was devised in view of the problems of the conventional tungsten-based polymerized gold, and has high toughness without being affected by the amount of impurities such as phosphorus or sulfur contained in the polymerized gold or by the cooling rate and reheating treatment. An object of the present invention is to provide a high toughness tungsten-based polymer gold having a new composition and a method for producing the same.

The high toughness tungsten polymer alloy of the present invention is composed of W-Ni-Fe based on tungsten (W) of 90 wt% or more and the remaining 10 wt% or less of nickel (Ni) and iron (Fe) as a basic element. Lanthanum (La) is added or calcium (Ca) is added.

More specifically, the composition of the present invention is expressed in weight percent by weight of 90-95wt%, 2-9% of Ni and 1-3% of Fe based on W-Ni-Fe based composition based on La 0.01-1% is included or Ca is added 0.01-0.3%.

The basic composition of the W-Ni-Fe-based polymer in the present invention is a known composition of a high toughness tungsten-based polymer alloy, and lanthanum (La) or calcium (Ca) added as a trace element acts as a toughness determinant of the polymer gold. An element that reacts well with phosphorus or sulfur, which is an impurity, added, lanthanum or calcium forms La or Ca compounds containing phosphorus or sulfur in the matrix and inhibits impurities from moving to grain boundaries, thereby preventing interfacial segregation and improving toughness. To improve.

Representative compositions of the present invention in the present invention is a weight ratio of 93W-4.9Ni-2.1Fe in the basic composition of a portion of the tungsten (W) is replaced by lanthanum or calcium, and the range of lanthanum and calcium is replaced Is preferably 0.1-0.3wt% and 0.01-0.05wt%, respectively. The reason for limiting the composition of such lanthanum or calcium is as follows.

First, in the case of lanthanum, when the content is less than 0.1wt%, it does not sufficiently inhibit the interfacial segregation of phosphorus or sulfur as impurities, and on the contrary, when the content exceeds 0.3wt%, the amount of inclusions is excessively formed, resulting in deterioration of tensile properties. Done.

In addition, when the addition amount of calcium is also 0.01 wt% or less like the above lanthanum, the amount of calcium compounds for preventing interfacial segregation of sulfur or phosphorus is insufficient, so that the interfacial segregation of these impurities is not sufficiently suppressed, while the addition amount is 0.05wt. Exceeding the% will result in a decrease in tensile properties due to excessive formation of inclusions.

On the other hand, when the amount of nickel and iron in the tungsten-based basic composition is changed within the range of the alloying gold (about 10% by weight) or the amount of impurities is different, the amount of lanthanum or calcium added as a trace element in the present invention is a general alloy. As with additives, some variation is possible.

Polymeric gold of the present invention is produced through the following manufacturing method.

First, lanthanum or calcium is added to the W-Ni-Fe powder mixture weighed in the range of tungsten-based polymer alloy and wet-mixed, and then presintered in a tubular furnace of a hydrogen atmosphere through a drying and molding process. After pre-sintering, sintering in a hydrogen atmosphere at 1475 ° C. for 60 to 100 minutes, heat treatment in an inert atmosphere at 1150 ° C., water cooling, and heat treatment in an inert atmosphere at 500-600 ° C., thereby obtaining a high toughness tungsten polymer alloy of the present invention. .

Such polymerized gold of the present invention is used in reheating treatment, including the amount of impurities contained in the raw powder or the cooling rate during the manufacturing process, as lanthanum or calcium added as a trace element prevents grain boundary segregation of impurities such as phosphorus and sulfur. Irrespective of uniformity and high toughness.

The present invention will be more clearly understood through the following examples.

Example 1

LaCl so that the amount of lanthanum in the W-Ni-Fe powder mixture containing about 200 ppm of phosphorus and about 200 ppm of sulfur and weighed in the composition range of tungsten-based alloying gold remain in the range of the present invention. After dissolving in distilled water in the form of ₃ , 7H ₂ 0, the mixture was wet mixed.

In order to prepare another sample of the present invention, sulfur is dissolved by adding Ca (NO ₃ ) ₂ 4HO (calcium nitrate) to ethyl alcohol so that the amount of calcium remains in a W-Ni-Fe powder mixture containing 50 to 200 ppm, and then wetted. Mixed.

Next, the mixed powder mixture was pulverized sufficiently after distilled water was evaporated over 4 hours in an oven heated to 70 ℃. The pulverized powder was pressurized at a pressure of 100 MPa using a compression separation mold to form a impact test piece or a tensile test piece. Thereafter, the pre-sintering of the green compact was carried out at a constant rate of 45-50 ° C./minute to 950 ° C. in a tubular furnace of a hydrogen atmosphere, followed by 1 hour and 30 minutes, and was performed at 1200 ° C. for 30 minutes.

The presintered specimens were sintered in a hydrogen atmosphere at 1475 ° C. for 60-100 minutes. The cooling time at the sintering temperature was about 60 minutes. After sintering, the specimens were heat-treated for 1 hour in an inert atmosphere such as nitrogen or argon at 1150 ° C. and then water cooled. The impact test specimen thus obtained was processed to 7.5 mm x 7.5 mm x 32 mm without a notch, and the Charpy impact test was performed.

The wavefront was observed after the tensile test and the impact test, and the composition of the interface was analyzed by Auger electron spectroscopy.

Tensile and impact properties of the specimens obtained through the method are shown in Tables 1 and 2 below.

TABLE 1

TABLE 2

In Table 1 and Table 2 above, the specimen A1-A5 is a specimen of the present invention gold and the specimen B1-B3 is a comparison specimen for comparison with the present invention gold is a conventional gold alloy.

As shown in the specimen B1 of Table 1, when the phosphorus is contained as much as 150ppm, even though the water is cooled at the heat treatment temperature of the conventional segregation prevention method, the impact energy is very low, but lanthanum is added 0.1wt% and 0.3wt%, respectively. In the case of the present invention, the tensile properties slightly decreased, but the impact energy rapidly increased.

1 is a scanning electron micrograph of the shock wave surface of the specimen, where a is the wavefront of specimen B1 and b is the wavefront of specimen A2.

Even when water is cooled at a high temperature when 150 ppm of phosphorus is present inside, specimen B1 undergoes interfacial bleeding as shown in a of FIG. 1, thereby deteriorating impact properties, which causes phosphorus to be present at the interface between tungsten and tungsten or the interface between tungsten and base. This is because segregation caused interfacial embrittlement.

This is evident in the photographs, where the points marked C and D are the grain boundary fractures between tungsten and tungsten and the grain boundary fractures between tungsten and the base, respectively.

On the contrary, when 0.3 wt% of lanthanum is added to the specimen having 150 ppm of phosphorus as shown in the wavefront photograph b of the specimen A2 of the present invention, the tungsten interior has a typical soft fracture form along the matrix, resulting in impact resistance. Increased. This is because segregation of phosphorus was suppressed by the production of a lanthanum compound containing a phosphorus (parts indicated by arrows), and parts indicated by A and B were broken into known (soft) fractures and tungsten mouths containing nickel as a main component, respectively.

In addition, as shown in Table 2, when the sulfur is contained 50-200ppm, similar to the effect of phosphorus, the conventional alloy gold specimens B2 and B3 have a significantly reduced impact properties, but 0.01 to 0.04wt% calcium or 0.3wt% lanthanum is added. The added specimens A3 to A5 of the present invention exhibited high impact properties by forming calcium compounds or lanthanum compounds in the tissues and suppressing sulfur unbalance.

Example 2

In order to investigate the effect of the addition of lanthanum or calcium to the powder mixture in which the raw material powder is carefully prepared and the phosphorus is present in a very small amount of only about 20 ppm, the specimen is sintered by the same method as in Example 1 to obtain an activity of 1150 ° C. After annealing in an atmosphere for 1 hour, the samples were cooled at different cooling rates. In addition, after the heat treatment and water cooling and then aged for 1 hour in an inert atmosphere of 500-600 ℃ to measure the impact energy change, the results are shown in Figure 2, the measured impact energy values are shown in Table 3 below Same as

TABLE 3

In Table 3 above, specimens A6 and A7 are the present invention gold alloy specimens and specimen B4 is a comparative specimen having a conventional polymer gold composition for comparison with the present invention gold alloy.

As shown in Table 3, in the case of heat treatment at 600 ° C. for 1 hour after water cooling, the conventional polymerized gold (ie, specimen B4) had a sharp drop in impact property. In the present invention in which A6) and calcium were added, specimen A7 maintained high impact properties.

As shown in the graph showing the relationship between the cooling time and the impact energy of FIG. 2, when the phosphorus is contained as little as 20 ppm, the conventional polymerized alloy (Sample B4) increases the amount of segregation of phosphorus as the cooling time increases from the heat treatment temperature. Although the properties are rapidly reduced, it can be seen that the present invention gold (Sample A6) to which the lanthanum is added in an amount of 0.1-0.3 wt% has almost no impact property.

Meanwhile, the present invention gold alloy (Sample A7) to which 0.04-0.05 wt% of calcium was added was 38 (± 6) joules and 33 (± 6) under the condition that the impact energy value was cooled at 1150 ° C. and cooled for 1 hour. ) joules.

However, these values are much higher than 28.5 (± 8) joules in water cooling conditions and 5.4 (± 3) joules in water cooling conditions shown in FIG. .

Claims (3)

W-Ni-Fe, which is 90-95% in weight, 2-9% in Ni and 1-3% in Fe, is 0.01-1.0% by weight of La and contains inevitable impurities when manufacturing other alloys. High toughness tungsten-based polymer gold is included. W-Ni-Fe, which is 90-95% by weight, 2-9% by Ni, and 1-3% by Fe, contains Ca by 0.01-0.3% by weight and contains unavoidable impurities when manufacturing other alloys. High toughness tungsten-based polymer gold is included. W-Ni-Fe powder mixture consisting of 90-95% W, 2-9% Ni and 1-3% Fe by weight, dried and ground by mixing La 0.01-0.1% or Ca 0.01-0.3% After preforming through a molding process, the alloy obtained by heating for 60 to 100 minutes in a hydrogen atmosphere at 1475 ℃ for 1 hour heat treatment in an inert atmosphere of 1150 ℃, water cooled and then aged for 1 hour in an inert atmosphere of 500-600 ℃ Method for producing a high toughness tungsten-based polymer gold, characterized in that.