Method for improving mechanical property of molybdenum-rhenium alloy wire

Abstract

The invention discloses a method for improving the mechanical property of a molybdenum-rhenium alloy wire. The method comprises the steps that firstly, molybdenum powder and rhenium powder are mixed and then pressed and sintered in sequence, and a molybdenum-rhenium alloy blank is obtained; secondly, the molybdenum-rhenium alloy blank is sequentially subjected to electric arc melting and electron beam melting, and a molybdenum-rhenium alloy cast ingot is obtained; thirdly, the molybdenum-rhenium alloy cast ingot is subjected to hot extrusion and forging in sequence, and a molybdenum-rhenium alloy forged rod in the forging state is obtained; 4, drawing the molybdenum-rhenium alloy forging rod in the forging state for multiple times to obtain a molybdenum-rhenium alloy wire blank; and fifthly, the molybdenum-rhenium alloy wire blank is subjected to vacuum heat treatment, and the molybdenum-rhenium alloy wire is obtained. According to the method, pressing sintering, smelting, hot extrusion, forging and drawing processes are sequentially adopted, and a vacuum heat treatment annealing system is regulated and controlled, so that high strength is kept as far as possible on the premise of improving the room-temperature plasticity of the molybdenum-rhenium alloy wire, the purpose of optimizing the mechanical property of the molybdenum-rhenium alloy wire is achieved, the comprehensive mechanical property of the molybdenum-rhenium alloy wire is effectively improved, and the production cost is reduced. The process is simple, easy to operate and suitable for popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of molybdenum-rhenium alloy microstructure and mechanical property design and optimization, and specifically relates to a method for improving the mechanical properties of molybdenum-rhenium alloy wire. Background Art

[0002] Molybdenum-rhenium alloy is an ideal nuclear reactor core material with good comprehensive mechanical properties. In order to improve the purity and welding performance of the alloy, nuclear molybdenum-rhenium alloys are mostly prepared by vacuum melting, among which electron beam melting is a necessary process for preparing high-purity molybdenum-rhenium alloy ingots. The grains in the ingot after electron beam melting are very coarse, even at the centimeter level, resulting in poor mechanical properties. Therefore, it is necessary to use thermomechanical processing to break the grains to achieve the required shape and grain size of the product. After thermomechanical processing, the coarse equiaxed grains in the cast state are elongated into slender columnar crystals, and the grain size is greatly reduced. The disadvantage brought about by this is poor room temperature ductility, so subsequent heat treatment must be performed to achieve the purpose of toughening. However, with the increase of annealing temperature or the extension of annealing time, the room temperature yield strength of the alloy shows a significant decrease. Therefore, while improving ductility, maintaining the strength of molybdenum-rhenium alloy as much as possible has become a hot topic of research. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for improving the mechanical properties of molybdenum-rhenium alloy wire in view of the deficiencies of the above-mentioned prior art. The method sequentially adopts pressing sintering, smelting, hot extrusion, forging and drawing processes, and designs each process, combined with the regulation of vacuum heat treatment annealing system, effectively guarantees the grain size in the molybdenum-rhenium alloy, thereby inhibiting the reduction of the strength of the molybdenum-rhenium alloy, and increasing the room temperature deformation capacity of the molybdenum-rhenium alloy, effectively improving the comprehensive mechanical properties of the molybdenum-rhenium alloy, and solving the problem of reduced strength of the molybdenum-rhenium alloy wire after conventional heat treatment.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for improving the mechanical properties of molybdenum-rhenium alloy wire, characterized in that the method comprises the following steps:

[0005] Step 1: mixing molybdenum powder and rhenium powder, pressing and sintering them in sequence to obtain a molybdenum-rhenium alloy billet;

[0006] Step 2: arc melting and electron beam melting are performed on the molybdenum-rhenium alloy billet obtained in step 1 to obtain a molybdenum-rhenium alloy ingot;

[0007] Step 3: hot extruding and forging the molybdenum-rhenium alloy ingot obtained in step 2 in sequence to obtain a forged molybdenum-rhenium alloy forged rod;

[0008] Step 4: Drawing the molybdenum-rhenium alloy forged rod obtained in step 3 for multiple times to obtain a molybdenum-rhenium alloy wire blank;

[0009] Step 5: subjecting the molybdenum-rhenium alloy wire blank obtained in step 4 to vacuum heat treatment to obtain a molybdenum-rhenium alloy wire material.

[0010] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that the atomic ratio of molybdenum in the molybdenum-rhenium alloy billet in step 1 is 67% to 70%, and the remainder is rhenium, recorded as Mo 70 Re 30 .

[0011] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that the mass purity of the molybdenum powder and the rhenium powder in step one is both above 99.97%, and the Fisher particle size is 2.5μm to 5.0μm; the rotation speed used for the mixing is 80r / min to 90r / min, and the time is 6h.

[0012] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that the pressing in step one adopts cold isostatic pressing processing, the pressure is 180MPa~200MPa, and the holding time is 60min~70min.

[0013] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that the sintering in step one is protected by a hydrogen atmosphere, and the sintering temperature is 2100° C. to 2250° C., and the insulation time is 5 hours.

[0014] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that during the arc melting process in step 2, the vacuum degree in the melting furnace is 1.2×10 -2 Pa~1.6×10 -2 Pa, the current of the DC arc is 3900A-3980A, the voltage is 35V-40V, an external magnetic field is applied for stirring, and the diameter of the ingot obtained by arc melting is 80mm-82mm; during the electron beam melting process, the vacuum degree of the molten pool area is 6.0×10 -3 Pa~7.6×10 -3 Pa, the electron beam current is 6A-6.5A, the acceleration voltage is 23kV-24kV, the electron beam power is 138kW-156kW, and the diameter of the molybdenum-rhenium alloy ingot is 78mm-80mm.

[0015] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that the heating temperature of the hot extrusion in step three is 1450°C to 1550°C, the holding time is 10min to 15min, and the extrusion ratio is 4; the heating temperature of the forging is 1450°C to 1550°C, the holding time is 10min to 15min, and the single deformation rate is 10% to 15%, and finally a forged molybdenum-rhenium alloy rod with a diameter of 5.5mm to 6.0mm is obtained.

[0016] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that flame heating is used during the multiple drawing in step 4, the heating temperature is 1000°C ± 15°C, and the multiple drawing process is: when the drawing starts, the diameter reduction after a single drawing is 0.9mm-1mm; when the diameter of the drawing object is less than 2mm, the diameter reduction after a single drawing is 0.4mm-0.5mm; when the diameter of the drawing object is less than 1mm, the diameter reduction after a single drawing is 0.1mm-0.2mm; the final diameter of the molybdenum-rhenium alloy wire blank is 0.5mm ± 0.05mm. By controlling the process of multiple drawing, it is ensured that the wire is deformed as evenly as possible during the drawing process to avoid cracking.

[0017] The above-mentioned method for improving the mechanical properties of molybdenum-rhenium alloy wire is characterized in that the temperature of the vacuum heat treatment in step 5 is 800℃±10℃, 1150℃±10℃, 1400℃±15℃, 1500℃±15℃ or 1600℃±15℃, the heating rate is 30℃ / min, the holding time is 2h, and the furnace is cooled after the holding is completed. Compared with the prior art, the temperature range of the vacuum heat treatment of the present invention is significantly broadened and consistent with the structural evolution of the wire at high temperature. At the same time, the holding time is increased to ensure that the wire obtains a more stable structure at high temperature.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention sequentially adopts pressing and sintering, smelting, hot extrusion, forging and drawing processes, and designs each process to obtain a molybdenum-rhenium alloy wire blank, and then performs vacuum heat treatment and selects a suitable vacuum heat treatment annealing system to obtain a fine and uniform molybdenum-rhenium alloy wire, which effectively guarantees the grain size in the molybdenum-rhenium alloy, thereby inhibiting the reduction of the strength of the molybdenum-rhenium alloy, and increasing the room temperature deformation ability of the molybdenum-rhenium alloy. Under the premise of improving the room temperature plasticity of the molybdenum-rhenium alloy wire, the high strength is maintained as much as possible, the mechanical properties of the molybdenum-rhenium alloy are optimized, and the comprehensive mechanical properties of the molybdenum-rhenium alloy are effectively improved.

[0020] 2. The present invention can achieve organizational control of the molybdenum-rhenium alloy wire by regulating the temperature and time of vacuum heat treatment, effectively improving the microstructure and room temperature mechanical properties of the molybdenum-rhenium alloy wire. The process is simple and easy to operate, and is suitable for promotion.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a longitudinal cross-sectional metallographic image of the molybdenum-rhenium alloy wire blank prepared in Example 1 of the present invention.

[0023] Figure 2 This is the room temperature tensile curve of the molybdenum-rhenium alloy wire blank prepared in Example 1 of the present invention.

[0024] Figure 3 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in Example 1 of the present invention.

[0025] Figure 4 This is the room temperature tensile curve of the rhenium alloy wire prepared in Example 1 of the present invention.

[0026] Figure 5 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in Example 2 of the present invention.

[0027] Figure 6 This is the room temperature tensile curve of the rhenium alloy wire prepared in Example 2 of the present invention.

[0028] Figure 7 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in Example 3 of the present invention.

[0029] Figure 8 This is the room temperature tensile curve of the rhenium alloy wire prepared in Example 3 of the present invention.

[0030] Fig. 9 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in Example 4 of the present invention.

[0031] Fig.10 This is the room temperature tensile curve of the rhenium alloy wire prepared in Example 4 of the present invention.

[0032] Fig.11 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in Example 5 of the present invention.

[0033] Fig.12 This is the room temperature tensile curve of the rhenium alloy wire prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0034] Example 1

[0035] This embodiment includes the following steps:

[0036] Step 1: Mix molybdenum powder and rhenium powder, press and sinter them in sequence to obtain a molybdenum-rhenium alloy billet; the atomic ratio of molybdenum in the molybdenum-rhenium alloy billet is 70%, and the remainder is rhenium, recorded as Mo70 Re 30 The purity of the molybdenum powder and the rhenium powder is above 99.97%, and the Fisher particle size is 2.5 μm to 5.0 μm; the mixing speed is 80 r / min to 90 r / min, and the time is 6 hours; the pressing adopts cold isostatic pressing, the pressure is 180 MPa to 200 MPa, and the holding time is 60 minutes; the sintering adopts hydrogen atmosphere protection, and the sintering temperature is 2100°C to 2250°C, and the holding time is 5 hours;

[0037] Step 2: arc melting and electron beam melting are performed on the molybdenum-rhenium alloy billet obtained in step 1 to obtain a molybdenum-rhenium alloy ingot; during the arc melting process, the vacuum degree in the melting furnace is 1.2×10 -2 Pa~1.6×10 -2 Pa, the current of the DC arc is 3900A-3980A, the voltage is 35V-40V, an external magnetic field is applied for stirring, and the diameter of the ingot obtained by arc melting is 80mm-82mm; during the electron beam melting process, the vacuum degree of the molten pool area is 6.0×10 -3 Pa~7.6×10 -3 Pa, the electron beam current is 6A-6.5A, the acceleration voltage is 23kV-24kV, the electron beam power is 138kW-156kW, and the diameter of the molybdenum-rhenium alloy ingot is 78mm-80mm, wherein the head diameter is 80mm and the tail diameter is 78mm;

[0038] Step 3: hot extrude and forge the molybdenum-rhenium alloy ingot obtained in step 2 in sequence to obtain a forged molybdenum-rhenium alloy forged rod; the heating temperature of the hot extrusion is 1450°C to 1550°C, the holding time is 10 minutes, and the extrusion ratio is 4; the heating temperature of the forging is 1450°C to 1550°C, the holding time is 10 minutes, and the single deformation rate is 10% to 15%, and finally a forged molybdenum-rhenium alloy rod with a diameter of 5.5 mm to 6.0 mm is obtained.

[0039] Step 4: Drawing the forged molybdenum-rhenium alloy forged rod obtained in step 3 for multiple times to obtain a molybdenum-rhenium alloy wire blank; flame heating is used during the multiple drawing, and the heating temperature is 1000°C ± 15°C, and the multiple drawing process is as follows: when the drawing starts, the diameter reduction after a single drawing is 0.9mm-1mm; when the diameter of the drawing object is less than 2mm, the diameter reduction after a single drawing is 0.4mm-0.5mm; when the diameter of the drawing object is less than 1mm, the diameter reduction after a single drawing is 0.1mm-0.2mm; the final diameter of the molybdenum-rhenium alloy wire blank is 0.5mm±0.05mm;

[0040] Step 5: subjecting the molybdenum-rhenium alloy wire blank obtained in step 4 to vacuum heat treatment to obtain molybdenum-rhenium alloy wire; the temperature of the vacuum heat treatment is 800°C ± 10°C, the heating rate is 30°C / min, the insulation time is 2h, and the wire is cooled with the furnace after the insulation is completed.

[0041] Figure 1 This is a longitudinal cross-sectional metallographic image of the molybdenum-rhenium alloy wire blank prepared in this embodiment. Figure 1 It can be seen that the grains of the molybdenum-rhenium alloy wire blank are very fine, the grains are elongated into columnar crystals along the drawing direction, and the average grain size is 0.3 μm.

[0042] Figure 2 This is the room temperature tensile curve of the molybdenum-rhenium alloy wire blank prepared in this embodiment. Figure 2 It can be seen that the breaking strength of the molybdenum-rhenium alloy wire blank is as high as 2.4 GPa, and the room temperature plasticity is less than 1%.

[0043] Figure 3 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in this embodiment. Figure 3 It can be seen that Figure 1 The grains of the rhenium alloy wire material are still columnar in shape, and the average grain size increases slightly to 1.5 μm.

[0044] Figure 4 is the room temperature tensile curve of the rhenium alloy wire prepared in this example. Figure 4 It can be seen that Figure 2 Compared with the molybdenum-rhenium alloy wire blank that has not been vacuum heat treated, the tensile strength of the molybdenum-rhenium alloy wire is reduced to 1.9 GPa, and the room temperature plasticity is not much different.

[0045] Example 2

[0046] The difference between this embodiment and embodiment 1 is that the temperature of the vacuum heat treatment in step 5 is 1150°C±10°C.

[0047] Figure 5 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in this embodiment. Figure 5 It can be seen that the grains of the rhenium alloy wire are still columnar grains, but partial recrystallization has begun to occur, the aspect ratio of the columnar grains has decreased, and the average grain size is 2.8 μm.

[0048] Figure 6 is the room temperature tensile curve of the rhenium alloy wire prepared in this example. Figure 6 It can be seen that the yield strength of the rhenium alloy wire drops to 1.3 GPa, the tensile strength is 1.5 GPa, and the room temperature ductility is 19%, which is significantly increased compared with Example 1.

[0049] Example 3

[0050] The difference between this embodiment and embodiment 1 is that the temperature of the vacuum heat treatment in step 5 is 1400°C±15°C.

[0051] Figure 7 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in this embodiment. Figure 7 It can be seen that the grains of the rhenium alloy wire are close to equiaxed grains, and the average grain size is 5.8 μm.

[0052] Figure 8 is the room temperature tensile curve of the rhenium alloy wire prepared in this example. Figure 8 It can be seen that the yield strength of the rhenium alloy wire material drops to 0.9 GPa, the tensile strength is 1.2 GPa, and the room temperature ductility is 17%. Compared with Example 2 and Example 3, the ductility is not much different, but the strength is significantly reduced.

[0053] Example 4

[0054] The difference between this embodiment and embodiment 1 is that the temperature of the vacuum heat treatment in step 5 is 1500°C±15°C.

[0055] Fig. 9 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in this embodiment. Fig. 9 It can be seen that the grains of the rhenium alloy wire are equiaxed, and the grain size in the center of the wire is larger than that at the edge.

[0056] Fig.10 is the room temperature tensile curve of the rhenium alloy wire prepared in this example. Fig.10 It can be seen that the yield strength of the rhenium alloy wire is about 0.9 GPa, the tensile strength is 1.1 GPa, and the room temperature ductility is 19%. Compared with Examples 2 and 3, the ductility is not much different, but the strength is gradually reduced.

[0057] Example 5

[0058] The difference between this embodiment and embodiment 1 is that the temperature of the vacuum heat treatment in step 5 is 1600°C±15°C.

[0059] Fig.11 This is a longitudinal cross-sectional metallographic image of the rhenium alloy wire prepared in this embodiment. Fig.11 It can be seen that the grains of the rhenium alloy wire have grown dramatically, showing equiaxed crystals, and only a few grains penetrate the cross section perpendicular to the drawing direction, with the grain size reaching hundreds of microns.

[0060] Fig.12 is the room temperature tensile curve of the rhenium alloy wire prepared in this example. Fig.12It can be seen that the yield strength of the rhenium alloy wire drops to 0.7 GPa, the tensile strength is 0.9 GPa, and the room temperature ductility is 11%. Compared with Examples 2, 3 and 4, both the strength and plasticity are significantly reduced.

[0061] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for improving the mechanical properties of molybdenum-rhenium alloy wire, characterized in that: The method comprises the following steps: Step 1: mixing molybdenum powder and rhenium powder, pressing and sintering them in sequence to obtain a molybdenum-rhenium alloy billet; Step 2: arc melting and electron beam melting are performed on the molybdenum-rhenium alloy billet obtained in step 1 to obtain a molybdenum-rhenium alloy ingot; Step 3: hot extruding and forging the molybdenum-rhenium alloy ingot obtained in step 2 in sequence to obtain a forged molybdenum-rhenium alloy forged rod; Step 4: Drawing the molybdenum-rhenium alloy forged rod obtained in step 3 for multiple times to obtain a molybdenum-rhenium alloy wire blank; Step 5: subjecting the molybdenum-rhenium alloy wire blank obtained in step 4 to vacuum heat treatment to obtain a molybdenum-rhenium alloy wire material.

2. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: The atomic ratio of molybdenum in the molybdenum-rhenium alloy billet in step 1 is 67% to 70%, and the remainder is rhenium, which is recorded as Mo. 70 Re 30 .

3. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: The mass purity of the molybdenum powder and the rhenium powder in step 1 are both above 99.97%, and the Fisher particle size is 2.5μm to 5.0μm; the rotation speed used for mixing is 80r / min to 90r / min, and the time is 6h.

4. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: The pressing in step 1 is performed by cold isostatic pressing, the pressure is 180 MPa to 200 MPa, and the holding time is 60 min to 70 min.

5. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: The sintering in step 1 is protected by a hydrogen atmosphere, and the sintering temperature is 2100° C. to 2250° C., and the holding time is 5 hours.

6. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: During the arc melting process in step 2, the vacuum degree in the melting furnace is 1.2×10 -2 Pa~1.6×10 -2 Pa, the current of the DC arc is 3900A-3980A, the voltage is 35V-40V, an external magnetic field is applied for stirring, and the diameter of the ingot obtained by arc melting is 80mm-82mm; during the electron beam melting process, the vacuum degree of the molten pool area is 6.0×10 -3 Pa~7.6×10 -3 Pa, the electron beam current is 6A-6.5A, the acceleration voltage is 23kV-24kV, the electron beam power is 138kW-156kW, and the diameter of the molybdenum-rhenium alloy ingot is 78mm-80mm.

7. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: The heating temperature of the hot extrusion in step three is 1450°C to 1550°C, the holding time is 10min to 15min, and the extrusion ratio is 4; the heating temperature of the forging is 1450°C to 1550°C, the holding time is 10min to 15min, and the single deformation rate is 10% to 15%, and finally a forged molybdenum-rhenium alloy rod with a diameter of 5.5mm to 6.0mm is obtained.

8. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: The multiple drawing described in step 4 uses flame heating, the heating temperature is 1000°C ± 15°C, and the multiple drawing process is: when starting to draw, the diameter reduction after a single drawing is 0.9mm~1mm; when the diameter of the drawing object is less than 2mm, the diameter reduction after a single drawing is 0.4mm~0.5mm; when the diameter of the drawing object is less than 1mm, the diameter reduction after a single drawing is 0.1mm~0.2mm; the final diameter of the molybdenum-rhenium alloy wire blank is 0.5mm±0.05mm.

9. A method for improving the mechanical properties of molybdenum-rhenium alloy wire according to claim 1, characterized in that: The temperature of the vacuum heat treatment in step five is 800℃±10℃, 1150℃±10℃, 1400℃±15℃, 1500℃±15℃ or 1600℃±15℃, the heating rate is 30℃ / min, the holding time is 2h, and the furnace is cooled after the holding is completed.

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