A method of welding powder metallurgical molybdenum-rhenium alloys

Abstract

The application discloses a kind of powder metallurgy molybdenum rhenium alloy welding method, first in the target weld of powder metallurgy molybdenum rhenium alloy Place metal foil material, then carry out electron beam welding.The application is by adding metal foil material to the target weld position of powder metallurgy molybdenum rhenium alloy substrate electron beam welding, utilize the higher chemical activity of high-temperature melting of metal foil material, with the volatile impurities generated after high-temperature melting of powder metallurgy molybdenum rhenium alloy substrate reaction compound, reduce even eliminate the bubble defect of weld, improve the performance of weld, and the element of metal foil material is in the weld fusion zone with substrate fusion homogenization and mixed solid solution form solid solution, the structure of fusion region is refined, further improve the performance of weld, suitable for the welding preparation of nuclear reactor structural material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of refractory metal processing, and particularly relates to a welding method of powder metallurgy molybdenum-rhenium alloy. BACKGROUND

[0002] The fast neutron reactor is the first selected reactor type of the fourth generation advanced nuclear energy system, and represents the development direction of the fourth generation nuclear energy system. Since the nuclear fuel in the reactor type is in a closed cycle, the utilization rate of uranium resources can be increased to more than 60%, and the amount of nuclear waste can be maximally reduced to achieve the minimization of radioactive waste. The molybdenum-rhenium alloy has excellent high-temperature performance and neutron radiation resistance, and is the first selected material of the fast neutron reactor.

[0003] In the nuclear reactor, the molybdenum-rhenium alloy is mainly applied in the form of pipe material, plate material and rod material. At present, the molybdenum alloy material is mainly prepared by the powder metallurgy method. However, since the powder metallurgy prepared molybdenum-rhenium alloy has high impurity content, welding bubbles and other defects are prone to occur, which seriously affects the performance of the weld. SUMMARY

[0004] The technical problem to be solved by the application is to provide a welding method of powder metallurgy molybdenum-rhenium alloy in view of the above-mentioned deficiencies of the prior art. In the application, the metal foil is added to the target weld position of the powder metallurgy molybdenum-rhenium alloy base body for electron beam welding. The high-activity metal foil element can absorb the volatile impurities generated at the weld during the electron beam welding process in the high-temperature molten state, reduce or even eliminate the bubble defects of the weld, and the added metal foil element can be melted and homogenized with the base body to refine the weld structure and improve the weld performance.

[0005] To solve the above technical problems, the application adopts the technical scheme of a welding method of powder metallurgy molybdenum-rhenium alloy, characterized in that a metal foil is placed at the target weld of the powder metallurgy molybdenum-rhenium alloy, and then electron beam welding is performed.

[0006] The welding method of powder metallurgy molybdenum-rhenium alloy is characterized in that the metal foil is a titanium foil or a zirconium foil. The titanium foil or the zirconium foil can form a solid solution with the molybdenum-rhenium alloy base body after melting, which can effectively strengthen the base body.

[0007] The welding method of the powder metallurgy molybdenum-rhenium alloy has the characteristics that, before the electron beam welding, a pre-test of the electron beam welding is carried out on a material with the same material and thickness as the powder metallurgy molybdenum-rhenium alloy, the welding parameters of the pre-test of the electron beam welding are selected and determined as the welding parameters of the electron beam welding of the powder metallurgy molybdenum-rhenium alloy, and the width and depth of the weld formed by the pre-test of the electron beam welding are measured.

[0008] The welding method of the powder metallurgy molybdenum-rhenium alloy has the characteristics that, the length of the metal foil is the same as the length of the weld formed by the pre-test of the electron beam welding, the thickness of the metal foil is 0.8% to 1.2% of the average width of the fusion zone of the weld formed by the pre-test of the electron beam welding, and the width of the metal foil is 0.5 mm to 1 mm larger than the depth of the weld formed by the pre-test of the electron beam welding.

[0009] The welding method of the powder metallurgy molybdenum-rhenium alloy has the characteristics that, the length of the metal foil is the same as the length of the weld formed by the pre-test of the electron beam welding, the thickness of the metal foil is 0.8% to 1.2% of the average width of the fusion zone of the weld formed by the pre-test of the electron beam welding, and the width of the metal foil is 0.5 mm to 1 mm larger than the depth of the weld formed by the pre-test of the electron beam welding.

[0010] Compared with the prior art, the present application has the following advantages:

[0011] 1. In the present application, the metal foil is added to the target weld position of the powder metallurgy molybdenum-rhenium alloy base body for electron beam welding. During the welding process, the metal foil is melted in the weld, and the melted metal foil forms a solid solution with the base body. After high-temperature melting, the metal foil has higher chemical activity, reacts with volatile impurities (mainly carbon, oxygen, and nitrogen) generated during welding with the base body to form compounds, reduces or even eliminates the bubble defects of the weld, and improves the performance of the weld.

[0012] 2. In the electron beam welding process of the present application, the metal foil elements are melted and mixed with the base body in the weld fusion zone, and form a solid solution. The impurity elements react to form compounds, refine the structure of the fusion zone, and further improve the performance of the weld.

[0013] 3. In the present application, the target weld is preheated before the formal electron beam welding, so that most of the low-melting-point volatile impurities in the region are absorbed by the reaction, reducing the evaporation of impurities in the weld region during the electron beam welding process, which helps to reduce the defects in the weld region.

[0014] 4. The present invention determines the thickness and height of the metal foil based on the weld width and depth formed in the electron beam welding pre-test, and keeps the length of the metal foil consistent with the weld length, thereby quickly determining the size specifications of the metal foil, standardizing the addition amount of high-activity metal, effectively controlling the content of metal elements in the molten area of ​​the weld, and improving the mechanical property stability of the weld.

[0015] 5. The present invention limits the width of the metal foil to 0.5mm to 1mm greater than the weld depth formed in the electron beam welding pre-test, that is, the metal foil at the welding surface is 0.5mm to 1mm higher than the base material, thereby avoiding the large impact kinetic energy of the electron beam bombardment that causes the metal foil to be melted and carried to the deeper position of the weld, and the phenomenon that the element content of the metal foil in the surface layer of the weld surface is low due to the wider weld surface, which helps to increase the element content of the metal foil in the upper layer of the weld and ensure the uniformity of the element distribution of the metal foil at the weld.

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a metallographic cross-sectional view of the weld of the powder metallurgy Mo-14Re plate after electron beam welding in Example 1 of the present invention.

[0018] Figure 2 This is a metallographic cross-sectional view of the weld of powder metallurgy Mo-14Re after electron beam welding in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0019] Example 1

[0020] This embodiment includes the following steps:

[0021] Step 1: Select a powder metallurgy Mo-14Re plate material with a thickness of 3 mm for an electron beam welding pre-test. Check that the weld is welded on one side and the double-sided forming quality is good. Select and determine the corresponding electron beam welding pre-test welding parameters as the welding parameters for electron beam welding of powder metallurgy molybdenum-rhenium alloy: high voltage 80 kV, current 25 mA, welding speed 0.05 m / s. At the same time, the average width of the weld formed by the electron beam welding pre-test is measured to be 1.2 mm, 3 mm in depth, and 100 mm in length.

[0022] Step 2: According to the weld size formed in the electron beam welding pre-test in step 1, prepare a titanium foil with a length of 100 mm, a thickness of 0.012 mm, and a width of 3.5 mm as the metal foil;

[0023] Step 3: The titanium foil prepared in step 2 is sandwiched between a 3 mm thick powder metallurgy Mo-14Re plate material substrate, and the length end and the back side of the titanium foil are kept flush with the target weld, and the titanium foil is higher than the substrate at the weld surface. Then, electron beam welding is performed: first, the electron beam focus diameter is enlarged to 6 mm, and a welding power of 10% is used to preheat the area within 5 mm to 10 mm around the target weld for 1 minute. After the vacuum is stabilized, electron beam welding is performed according to the welding parameters selected and determined in step 1, namely, a high voltage of 80 kV, a current of 25 mA, and a welding speed of 0.05 m / s.

[0024] Figure 1 This is a metallographic cross-sectional view of the weld of the powder metallurgy Mo-14Re plate after electron beam welding in this embodiment. Figure 1 It can be seen that the molten area, heat-affected zone and original metallographic state can be clearly distinguished at the weld, and the pores in the molten area have basically disappeared.

[0025] Comparative Example 1

[0026] The difference between this comparative example and Example 1 is that no titanium foil is used and electron beam welding is directly performed.

[0027] Figure 2 The metallographic cross-section of the weld of powder metallurgy Mo-14Re after electron beam welding in this comparative example is shown in FIG. Figure 2 It can be seen that there is a string of black spherical substances distributed along the depth of the weld at the edge of the molten area. This is because the low-melting-point substances produced by welding form a gas under the high temperature of welding melting, and form porosity defects after cooling.

[0028] Will Figure 1 and Figure 2 By comparison, it can be seen that the present invention adds metal foil to the target weld position of the powder metallurgy molybdenum-rhenium alloy matrix for electron beam welding, so that the molten metal foil with higher chemical activity reacts with the volatile gas impurities generated after the high-temperature melting of the powder metallurgy molybdenum-rhenium alloy matrix to form compounds, thereby reducing or even eliminating bubble defects in the weld and improving weld performance.

[0029] Example 2

[0030] This embodiment includes the following steps:

[0031] Step 1: Select a powder metallurgy Mo-14Re plate material with a thickness of 3 mm for an electron beam welding pre-test. Check that the weld is welded on one side and the double-sided forming quality is good. Select and determine the corresponding electron beam welding pre-test welding parameters as the welding parameters for electron beam welding of powder metallurgy molybdenum-rhenium alloy: high voltage 80 kV, current 25 mA, welding speed 0.05 m / s. At the same time, the average width of the weld formed by the electron beam welding pre-test is measured to be 1.2 mm, 3 mm in depth, and 100 mm in length.

[0032] Step two, according to the weld size formed by the electron beam welding pretest in step one, prepare zirconium foil material with a length of 100 mm, a thickness of 0.0096 mm and a width of 4 mm as the metal foil material;

[0033] Step three, sandwich the zirconium foil material prepared in step two in the middle of the powder metallurgy Mo-14Re plate material substrate with a thickness of 3 mm, and the length end and the welding back of the zirconium foil material are flush with the target weld, and the zirconium foil material is higher than the substrate at the welding surface, then electron beam welding is carried out: first enlarge the electron beam focal point diameter to 3 mm, preheat the range of 5 mm to 10 mm around the target weld with 15% welding power for 2 min, and after the vacuum is stable, electron beam welding is carried out according to the welding parameters selected and determined in step one, i.e. high voltage 80 kV, current 25 mA and welding speed 0.05 m / s.

[0034] Example 3

[0035] This example includes the following steps:

[0036] Step one, select powder metallurgy Mo-14Re plate material with a thickness of 3 mm for electron beam welding pretest, check the single-sided welding of the weld, and the double-sided forming quality is good, select and determine the corresponding electron beam welding pretest welding parameters as the welding parameters of powder metallurgy molybdenum-rhenium alloy electron beam welding: high voltage 80 kV, current 25 mA, welding speed 0.05 m / s, and at the same time, measure the average width of the weld formed by the electron beam welding pretest, which is 1.2 mm, the depth is 3 mm, and the length is 100 mm;

[0037] Step two, according to the weld size formed by the electron beam welding pretest in step one, prepare zirconium foil material with a length of 100 mm, a thickness of 0.0096 mm and a width of 4 mm as the metal foil material;

[0038] Step three, sandwich the zirconium foil material prepared in step two in the middle of the powder metallurgy Mo-14Re plate material substrate with a thickness of 3 mm, and the length end and the welding back of the zirconium foil material are flush with the target weld, and the zirconium foil material is higher than the substrate at the welding surface, then electron beam welding is carried out: first enlarge the electron beam focal point diameter to 3 mm, preheat the range of 5 mm to 10 mm around the target weld with 15% welding power for 2 min, and after the vacuum is stable, electron beam welding is carried out according to the welding parameters selected and determined in step one, i.e. high voltage 80 kV, current 25 mA and welding speed 0.05 m / s.

[0039] The above is only a preferred embodiment of the present application, and does not limit the present application in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the present application still falls within the protection scope of the technical solution of the present application.

Claims

1. A method for welding powder metallurgy molybdenum-rhenium alloy, characterized in that: Place metal foil, titanium foil or zirconium foil at the target weld of powder metallurgy molybdenum-rhenium alloy, clamp the metal foil between the powder metallurgy molybdenum-rhenium alloy substrate, and keep the length end and the back of the weld flush with the target weld. The metal foil is higher than the substrate at the weld surface, and then electron beam welding is performed: first enlarge the electron beam focus diameter to 3mm~6mm, use 10%~15% welding power to preheat the range of 5mm~10mm around the target weld for 1min~3min, and after the vacuum is stable, perform electron beam welding according to the selected welding parameters.

2. The method for welding a powder metallurgy molybdenum-rhenium alloy according to claim 1, wherein: Before the electron beam welding, a material with the same material and thickness as the powder metallurgy molybdenum-rhenium alloy is selected in advance for an electron beam welding pre-test, and the weld forming quality of the electron beam welding pre-test is used as an indicator to select and determine the electron beam welding pre-test welding parameters as the welding parameters for the powder metallurgy molybdenum-rhenium alloy electron beam welding, and at the same time, the weld width and depth formed in the electron beam welding pre-test are measured.

3. The method for welding a powder metallurgy molybdenum-rhenium alloy according to claim 2, wherein: The length of the metal foil is the same as the length of the weld formed in the electron beam welding pre-test, the thickness of the metal foil is 0.8% to 1.2% of the average width of the molten zone of the weld formed in the electron beam welding pre-test, and the width of the metal foil is 0.5 mm to 1 mm greater than the depth of the weld formed in the electron beam welding pre-test.

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