WO2018196524A1

WO2018196524A1 - Molybdenum alloy fusion welding method based on micro-alloying and synchronized parasitic brazing

Info

Publication number: WO2018196524A1
Application number: PCT/CN2018/080433
Authority: WO
Inventors: 张林杰; 白清林; 宁杰; 杨健楠; 孙院军; 安耿; 朱琦; 李思功; 龚星; 李锐; 任啟森; 刘彤
Original assignee: 西安交通大学
Priority date: 2017-04-26
Filing date: 2018-03-26
Publication date: 2018-11-01
Also published as: CN107008985A; CN107008985B

Abstract

Disclosed is a molybdenum alloy fusion welding method based on micro-alloying and synchronized parasitic brazing, the method comprising the following steps: 1) pre-processing a bonding area to be welded of a workpiece to be welded, wherein the material of the workpiece to be welded is molybdenum or a molybdenum alloy; 2) a bonding surface to be welded of the workpiece to be welded being filled with an intermediate metal, and then completing the abutting of the workpiece to-be-welded; 3) placing the workpiece to be welded in an atmosphere protected by inert gases or in a vacuum environment, and then preheating the bonding area to be welded of the workpiece to be welded; 4) completing the fusion welding of the workpiece to be welded, and obtaining a welded workpiece; and 5) maintaining the temperature of a welded joint of the welded workpiece, and then placing the welded joint of the welded workpiece in the atmosphere protected by inert gases or in the vacuum environment where same is cooled to the room temperature, and thus finishing the molybdenum alloy fusion welding based on micro-alloying and synchronized parasitic brazing. The fusion welding method can effectively improve the mechanical properties of the welded joint of the welded workpiece.

Description

Molybdenum alloy welding method based on microalloying and synchronous parasitic brazing

Technical field

The invention belongs to the technical field of welding and relates to a method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing.

Background technique

Molybdenum, melting point up to 2610 ° C, small neutron absorption cross section, low thermal expansion coefficient, excellent thermal conductivity, good mechanical properties at high temperature, good processability, when the temperature is lower than 500 ° C, molybdenum has good stability in air or water. The above advantages make molybdenum and molybdenum alloys, especially high-performance molybdenum alloys, have important applications in metallurgy, aerospace, aerospace, nuclear energy, military and other fields. The high-performance molybdenum alloy itself has excellent toughness, but once it is welded, its toughness advantage will be completely lost. Not only that, because the melting point of molybdenum is too high, it must be processed by powder metallurgy. On the one hand, the density of the material cannot be compared with the molten metallurgy material, the gas content is high, and the weld porosity defects are serious; on the other hand, it is easy to Impurities such as O and N are introduced into the material, and the solubility of impurity elements such as O and N in molybdenum is extremely low at room temperature. When the molten pool is solidified, impurity elements such as O and N are easily segregated at the grain boundary, and the grain boundary is severely weakened. The mechanical properties of the joint are extremely poor. The above problems severely restrict the application of molybdenum and molybdenum alloys as structural materials in critical applications such as nuclear power.

Summary of the invention

The object of the present invention is to overcome the above disadvantages of the prior art, and to provide a method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing, which can effectively improve the mechanical properties of a welded joint of a workpiece after welding.

To achieve the above object, the molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing according to the present invention comprises the following steps:

1) pre-treating the joint to be welded of the workpiece to be welded, wherein the material to be welded is made of molybdenum or molybdenum alloy;

2) filling the intermediate layer metal at the joint surface to be welded of the workpiece to be welded, and then completing the butting of the workpiece to be welded, wherein the melting point of the intermediate layer metal is lower than the melting point of the workpiece to be welded, and the filling area of the intermediate layer metal covers the welding process The weld seam area of the workpiece to be welded and the heat affected zone of the fusion welding;

3) placing the workpiece to be welded in an atmosphere protected by an inert gas or in a vacuum environment, and preheating the joint to be welded of the workpiece to be welded;

4) Finishing the fusion welding of the workpiece to be welded, in the welding and welding process, the joint metal of the workpiece to be welded and the intermediate layer metal in the vicinity thereof are melted, so that the intermediate layer metal and the joint position of the workpiece to be welded are welded and brazed. Metallurgical combination;

5) Insulating the welded joint of the workpiece after welding, and then placing the welded joint of the welded workpiece in an inert gas protective atmosphere or cooling to room temperature in a vacuum environment to complete the molybdenum alloy welding based on microalloying and synchronous parasitic brazing .

The specific operation of pretreating the joint to be welded of the workpiece to be welded in step 1) is: grinding the combined area of the workpiece to be welded, alkali washing, acetone washing and drying;

The material to be welded is made of pure molybdenum, a molybdenum alloy having an alloy element content of 2 wt% or less, or a molybdenum alloy having a second phase dopant content of 2 wt% or less.

In step 4), laser welding, electron beam welding, plasma beam welding or argon arc welding is used to complete the welding of the workpiece to be welded;

The welded joints of the workpiece after welding are in the form of pipe/bar casing joints, lap joints, butt joints with backing plates, backing joints, incompletely welded T-joints or incompletely welded cross joints.

The material of the intermediate layer metal is Ti, Ni, Zr or Al.

In step 2), the intermediate layer metal is filled at the joint surface to be welded of the workpiece to be welded by directly filling the metal foil, sputter coating, electroplating, cold spraying or laser cladding.

The purity of the intermediate layer metal is greater than or equal to 99.99%.

The temperature for preheating in step 3) is from 400 ° C to 500 ° C.

After the docking of the workpiece to be welded in step 2), the mating gap of the workpiece to be welded is less than or equal to 0.1 mm, the amount of misalignment of the joint of the workpiece to be welded is less than or equal to 10% of the thickness of the workpiece to be welded, and the joint of the workpiece to be welded is wrong. The side amount is less than 0.5mm;

The gap of the overlap region of the workpiece to be welded filled with the intermediate layer metal is 0.05 mm or less.

The invention has the following beneficial effects:

The molybdenum alloy welding method based on microalloying and synchronous parasitic brazing according to the present invention fills the intermediate layer metal at the joint surface to be welded of the workpiece to be welded in a specific operation, wherein the melting point of the intermediate layer metal is lower than Welding the melting point of the workpiece, so that part of the intermediate layer metal enters the molten pool during the welding process, realizing the microalloying of the welded weld, and at the same time, the weld line is welded due to the high thermal conductivity of the molybdenum and molybdenum alloy. The intermediate layer metal in a certain distance range is melted, thereby forming a brazing interface parasitic in the heat affected zone of the fusion welding, and the metallurgical bonding between the workpieces to be welded is realized through the brazing interface, and has obvious auxiliary bearing effect. It should be noted that, on the one hand, the micro-alloying effectively improves the mechanical properties of the welded weld, and on the other hand, the auxiliary bearing of the welded joint is realized by synchronous parasitic brazing, and under the joint action of the two mechanisms, significant Improve the overall mechanical properties of the welded joints of molybdenum and molybdenum alloys.

DRAWINGS

Figure 1 is a binary equilibrium phase diagram of Ti-Mo;

2a is a schematic view showing the structure of the first embodiment without adding a Ti foil;

2b is a schematic structural view of the first embodiment when Ti is added only at the butt joint;

2c is a schematic structural view of the first embodiment when Ti is added to the butt joint and the lap joint;

Figure 3a is a dimensional view of the molybdenum tube 1 of the first embodiment;

Figure 3b is a dimensional view of the molybdenum alloy end plug 2 of the first embodiment;

Figure 3c is a dimensional view of the intermediate layer metal 3 when only Ti is added at the butt joint in the first embodiment;

Figure 3d is a dimensional view of the intermediate layer metal 3 when the Ti foil is applied to both the butt joint and the lap joint in the first embodiment;

Figure 4 is a cross-sectional view of the welded joint of the first embodiment and a composition analysis diagram of the brazing interface;

Figure 5a is a microhardness distribution diagram of a welded joint in the first embodiment without a Ti foil;

Figure 5b is a microhardness distribution diagram of the welded joint when the Ti foil is added at the butt joint and the lap joint in the first embodiment;

Figure 6 is a tensile diagram of the first embodiment of the present invention;

7a is a topographical view of the welded joint after tensile fracture in the first embodiment without the Ti foil;

Figure 7b is a top view showing the tensile fracture of the welded joint when the Ti foil is added at the butt joint and the lap joint in the first embodiment;

Figure 8a is a microscopic top view of the tensile fracture of the welded joint without the Ti foil in the first embodiment;

Figure 8b is a microscopic top view of the tensile fracture of the welded joint when the Ti foil is added at the butt joint and the lap joint in the first embodiment;

Figure 9 is a cross-sectional top view of the welded joint of the second embodiment;

Figure 10 is a tensile diagram of the second embodiment;

Figure 11 is a cross-sectional top view of the welded joint of the third embodiment;

Figure 12 is a tensile diagram of the third embodiment;

Figure 13 is a tensile diagram of the fourth embodiment;

Figure 14 is a microscopic topographical view of a tensile fracture of a welded joint in the fourth embodiment.

Among them, 1 is a molybdenum tube, 2 is an end plug, and 3 is an intermediate layer metal.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings:

The molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing according to the present invention comprises the following steps:

2) filling the intermediate layer metal 3 at the joint surface to be welded of the workpiece to be welded, and then completing the butting of the workpiece to be welded, wherein the melting point of the intermediate layer metal 3 is lower than the melting point of the workpiece to be welded, and the filling area of the intermediate layer metal 3 Covering the weld zone of the workpiece to be welded and the heat affected zone of the fusion welding during the welding process;

4) Finishing the welding and welding of the workpiece to be welded, in the welding and welding process, the joint layer of the workpiece to be welded and the intermediate layer metal 3 in the vicinity thereof are melted, so that the intermediate layer metal 3 and the joint position of the workpiece to be welded are melted. Brazing metallurgical bonding;

The specific operation of pretreating the joint to be welded of the workpiece to be welded in step 1) is: grinding the combined area of the workpiece to be welded, alkali washing, acetone washing and drying.

In step 4), the welding of the workpiece to be welded is completed by laser welding, electron beam welding, plasma beam welding or argon arc welding.

The welded joints of the workpiece after welding are in the form of tube/bar sleeve joints, lap joints, butt joints with backing plates, backing joints, incompletely welded T-joints or incompletely welded cross joints.

The material of the intermediate layer metal 3 is Ti, Ni, Zr or Al.

In step 2), the intermediate layer metal 3 is filled at the joint surface to be welded of the workpiece to be welded by directly filling the metal foil, sputter coating, electroplating, cold spraying or laser cladding.

The intermediate layer metal 3 has a purity of 99.99% or more.

The temperature for preheating in step 3) is from 400 ° C to 500 ° C.

The gap of the overlap region of the workpiece to be welded filled with the intermediate layer metal 3 is 0.05 mm or less.

Embodiment 1

Titanium is selected as the material of the intermediate layer metal 3, because Ti and Mo undergo a homogenization reaction during the transition from the liquid phase to the solid phase, as shown in Fig. 1, so that Ti and Mo are infinitely miscible with each other, and no brittle phase is formed. Mo-Ti solid solution has a high melting point and good high temperature mechanical properties; Ti has a strong affinity for elements such as O at high temperature, and a trace amount of Ti in the weld pool reacts with O and Mo to form Mo _x Ti The second phase particles of the _y O _z composite oxide can eliminate the segregation of the impurity element grain boundaries and can enhance the second phase particles of the weld metal.

As shown in Fig. 2a, Fig. 2b and Fig. 2c, three sets of molybdenum alloy thin-walled tube-end plug 2 casing joints are welded by laser welding, wherein the first group is directly assembled with the molybdenum tube 1 and the end plug 2, and the second group In order to fill the titanium foil at the abutment of the molybdenum tube 1 and the end plug 2, the third group is filled with titanium foil at the abutment and the lap joint of the molybdenum tube 1 and the end plug 2. The test material is a high-performance molybdenum alloy doped with 0.25 wt% La ₂ O ₃ dispersion strengthening phase. The dimensions of the high-performance molybdenum alloy thin-walled tube, end plug 2 and titanium foil used in the test are shown in Figures 3a, 3b, 3c and 3d; the specific operation is as follows: firstly, the contact parts of the molybdenum tube 1 and the end plug 2 are sanded with a sandpaper, then washed with a dilute aqueous solution of sodium hydroxide, then washed with water and acetone, and then dried; The 0.05 mm TA1 titanium foil was processed into a size as shown in Fig. 3d, and pickled with a solution prepared from 12 mL of HNO ₃ , 6 mL of HF and 82 mL of H ₂ O, and then washed with water and acetone in turn. Dry; assemble three sets of samples, and then weld them in sequence. Place the sample in a high-purity argon protective atmosphere during welding, and then preheat the joint. When the joint temperature reaches 500 °C, use IPG-4000. The fiber laser completes the laser welding ring welding of the molybdenum tube 1 and the end plug 2 with the welding parameters of the welding power P of 1200 W, the defocusing amount f of +1 mm, and the rotating linear velocity v of 0.2 m/min. Keep at 500 ° C for 30 s, then slowly cool to room temperature.

A cross section of the welded joint of the sample filled with the titanium foil at the butt joint and the lap joint was observed (as shown in Fig. 4). As can be seen from FIG. 4, in the heat affected zone of the laser welding head, the titanium foil filled between the molybdenum tube 1 and the end plug 2 is melted and brazed, and the titanium foil and the molybdenum tube 1, the titanium foil and the end plug 2 are A parasitic brazing metallurgical bond is formed between them, and Mo and Ti are mutually soluble at the brazing interface.

The sample without titanium foil and the sample filled with titanium foil at the butt joint and the joint were respectively measured for the microhardness of the weld zone of the weld, and the measurement results are shown in Fig. 5a and Fig. 5b. After measurement, the microhardness of the molybdenum alloy base material used in the test is about 235 HV. It can be seen from Fig. 5a and Fig. 5b that the microhardness of the weld zone of the weld without the titanium foil is significantly lower than that of the base metal. It is about 30 HV; the microhardness of the sample weld filled with titanium foil at the butt joint and the lap joint is only about 15 HV lower than that of the base metal, so it is indicated that by incorporating Ti into the weld as an alloying element. Can improve the weld strength.

The tensile mechanical properties of the parent material of the molybdenum tube 1 and the three sets of welded joints were measured respectively. The tensile curve is shown in Fig. 6. The tensile strength of the parent material of the molybdenum tube 1 is 720 MPa, and the elongation at break is 10.6 mm. The tensile strength of welded joints without titanium foil is only 124 MPa, and the elongation at break is only 0.6 mm; the tensile strength of welded joints with titanium foil at the joint of molybdenum tube 1 and end plug 2 is 606 MPa, reaching the mother The tensile strength of the material is 84.2%, and the elongation at break is 3.1mm, which indicates that the incorporation of Ti into the weld as a microalloying element can significantly improve the tensile strength of the weld; at the same time, the joint between the molybdenum tube 1 and the end plug 2 The tensile strength of the welded joint with titanium foil at the joint and the lap joint reaches 688 MPa, which is as high as 95.6% of the tensile strength of the base metal, and the elongation at break reaches 9.8 mm, indicating that the weld is microalloyed while Ti is added. The fusion-welding joint region parasitic in the heat-affected zone of the welded joint serves as an auxiliary load-bearing function, and the tensile strength of the welded joint is further improved, and the elongation of the welded joint is remarkably improved.

It can be seen from Fig. 7a and Fig. 7b that the former is broken in the weld seam, and the latter molybdenum tube 1 is necked significantly and starts to break from the molybdenum tube 1; as can be seen from Fig. 8a and Fig. 8b, the welded joint is not added when the titanium foil is added. Breaking in the weld, the fracture mode is mainly characterized by intergranular fracture; the welded joint filled with titanium foil at the joint and the joint is mainly broken in the base metal, only a small part of the fracture is in the weld and is located on the fracture of the weld. The fracture morphology is mainly characterized by transgranular cleavage fracture.

Embodiment 2

Nickel is selected as the material of the intermediate layer metal 3, and the two sets of molybdenum alloy thin-walled tube-end plug 2 casing joints are the same as in the first embodiment, wherein the first group is the direct assembly of the molybdenum tube 1 and the end plug 2, and the second group is The joint surface of the molybdenum tube 1 and the end plug 2 is filled with a nickel foil. The test material is a high-performance molybdenum alloy doped with 0.25wt% La ₂ O ₃ dispersion strengthening phase; the specific welding process is: sanding the contact part of molybdenum tube 1 and end plug 2 with sandpaper, then dilute sodium hydroxide The aqueous solution was washed with alkali, washed successively with water and acetone, and dried; the nickel foil having a thickness of 0.05 mm was processed into a size as shown in Fig. 3d, and the ratio was HF: HNO ₃ : H ₂ O = 2: The mixed acid of 1:4.5 was pickled, then washed with water and acetone, and then dried; the two sets of samples were assembled, and then welded and welded. When welding, the sample is placed in a high-purity argon protective atmosphere, and then the joint is preheated. When the joint temperature reaches 500 °C, the IPG-4000 fiber laser is used to weld the power P to 1200 W, and the defocus amount f The laser welding ring welding of the molybdenum tube 1 and the end plug 2 is completed for the welding parameters of +1 mm and the rotating linear velocity v of 0.2 m/min. After welding, the welded joint is kept at 500 ° C for 30 s, and then slowly cooled to room temperature.

The cross section of the welded joint of the sample filled with nickel foil is shown in Fig. 9. As can be seen from Fig. 9, in the heat affected zone of the laser welded joint, the nickel foil filled between the molybdenum tube 1 and the end plug 2 melts and melts. Brazing, nickel foil and molybdenum tube 1, nickel foil and end plug 2 form a parasitic brazing metallurgical bond.

Compared with the tensile mechanical properties of the welded joints without nickel foil and nickel foil, the tensile curve is shown in Fig. 10. The tensile strength of the welded joint without nickel foil is only 124 MPa, and the elongation at break is only 0.6mm; the tensile strength of the welded joint filled with nickel foil at the joint surface of the molybdenum tube 1 and the end plug 2 is 624 MPa, reaching 86.7% of the tensile strength of the base material (about 720 MPa), and the elongation at break is 2.55. Mm, indicating that when laser welding is used to weld high performance molybdenum alloy doped with 0.25 wt% La ₂ O ₃ dispersion strengthening phase, the two mechanisms of microalloying of weld metal and simultaneous parasitic brazing are formed by filling nickel foil. The strength and elongation of the welded joint can be significantly improved by the action.

Embodiment 3

Zirconium is selected as the intermediate layer filling metal material, and the size of the molybdenum alloy thin-walled tube-end plug 2 casing joint is the same as that of the first embodiment, wherein the first group is to directly assemble the molybdenum tube 1 and the end plug 2, and the second group is The joint surface of the molybdenum tube 1 and the end plug 2 is filled with zirconium foil. The test material is a high performance molybdenum alloy doped with 0.25 wt% La ₂ O ₃ dispersion strengthening phase. The high performance molybdenum alloy thin wall tube and end plug 2 size used in the test. As shown in Fig. 3a and Fig. 3b, the specific welding process is as follows: the contact parts of the molybdenum tube 1 and the end plug 2 are sanded with a sandpaper, then washed with a dilute aqueous solution of sodium hydroxide, and then washed and blown with water and acetone. Dry; a zirconium foil having a thickness of 0.05 mm is processed into a size as shown in Fig. 3d, and then pickled with a mixed acid solution having a ratio of HF:HNO ₃ :H ₂ O=3:45:52, and then sequentially After washing with water and acetone, dry it; assemble the two sets of samples and weld them in sequence. Place the sample in a high-purity argon atmosphere and then preheat the joint. When the joint temperature reaches 500 °C. After that, the IPG-4000 fiber laser was used to have a welding power P of 1200 W, a defocus amount f of +1 mm, and a rotational linear velocity v. 0.2m / min to complete the welding parameters for laser welding a molybdenum tube 1 and the end plug weld ring 2, after the welded joint heat above 500 ℃ 30s, and then slowly cooled to room temperature.

As shown in Fig. 11, the cross section of the welded joint of the sample filled with the zirconium foil was observed; as can be seen from Fig. 11, in the heat affected zone of the laser welded joint, the zirconium foil filled between the molybdenum tube 1 and the end plug 2 was melted. Zr and Mo interdiffused to form an intermetallic compound, and a metallurgical bond was formed between the zirconium foil and the molybdenum tube 1, the zirconium foil and the end plug 2.

Comparing the tensile mechanical properties of the two welded joints without zirconium foil and zirconium foil, the tensile curve is shown in Fig. 12. The tensile strength of the welded joint without zirconium foil is 124 MPa, which is only the tensile strength of the base metal. 17.2% of about 720 MPa), the elongation at break is only 0.6 mm; the tensile strength of the welded joint filled with zirconium foil at the joint surface of the molybdenum tube 1 and the end plug 2 is 480 MPa, and the tensile strength of the base material is 66.7. %, the elongation at break is 1.55mm, indicating that when laser welding is used to weld high-performance molybdenum alloy doped with 0.25wt% La ₂ O ₃ dispersion strengthening phase, micro-alloying and formation of weld metal is performed by filling zirconium foil The strength and elongation of the welded joint can be significantly improved by the combination of two mechanisms of simultaneous parasitic brazing.

Embodiment 4

The material of aluminum is the material of the intermediate layer metal 3, and the size of the sleeve of the molybdenum alloy thin-wall tube-end plug 2 is the same as that of the first embodiment, wherein the first group is to directly assemble the molybdenum tube 1 and the end plug 2, and the second group is The aluminum foil is filled at the joint surface of the molybdenum tube 1 and the end plug 2; the test material is a high-performance molybdenum alloy doped with 0.25 wt% La ₂ O ₃ dispersion strengthening phase, and the high-performance molybdenum alloy thin-walled tube and the end plug 2 are used for the test. As shown in Fig. 3a and Fig. 3b, the specific welding process is as follows: first, the contact portion of the molybdenum tube 1 and the end plug 2 is sanded with a sandpaper, then alkali washed with a dilute aqueous solution of sodium hydroxide, and then washed with water and acetone in turn. Drying; processing the aluminum foil with a thickness of 0.05 mm into the size shown in Figure 3d, washing it with a dilute aqueous solution of sodium hydroxide, washing it with water and acetone, then drying it; assembling the two sets of samples Then, the welding is carried out in turn, the sample is placed in a high-purity argon protective atmosphere, and the joint is preheated. When the joint temperature reaches 500 ° C, the IPG-4000 fiber laser is used to have a welding power P of 1200 W. The welding parameters of the defocusing amount f is +1 mm and the rotating linear velocity v is 0.2 m/min. Laser welding of the molybdenum tube 1 and the end plug 2; after welding, the welded joint is kept at 500 ° C for 30 s, and then slowly cooled to room temperature.

Compared with the tensile mechanical properties of the welded joints without aluminum foil and aluminum foil, the tensile curve is shown in Fig. 13. The tensile strength of the welded joint without aluminum foil is 124 MPa, which is only the tensile strength of the base material (about 720 MPa). 17.2%, the elongation at break is only 0.6mm; the tensile strength of the welded joint filled with aluminum foil at the joint surface of the molybdenum tube 1 and the end plug 2 is 557 MPa, reaching 77.4% of the tensile strength of the base material, and elongation at break The amount is 1.8mm. Figure 14 shows the tensile fracture morphology of the aluminum foil sample. The fracture mode of the fracture is dominated by transgranular fracture, which indicates that the laser is used to weld high-performance molybdenum alloy doped with 0.25 wt% La ₂ O ₃ dispersion strengthening phase. Filled with aluminum foil, the strength and elongation of the welded joint can be significantly improved by the combined action of weld metal microalloying and simultaneous parasitic brazing.

Claims

A method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing, comprising the steps of:

1) pre-treating the joint to be welded of the workpiece to be welded, wherein the material to be welded is made of molybdenum or molybdenum alloy;

2) filling the intermediate layer metal (3) at the joint surface to be welded of the workpiece to be welded, and then completing the butting of the workpiece to be welded, wherein the melting point of the intermediate layer metal (3) is lower than the melting point of the workpiece to be welded, and the intermediate layer metal ( 3) The filling area covers the welding seam area of the workpiece to be welded and the heat affected zone of the welding during the welding process;

3) placing the workpiece to be welded in an atmosphere protected by an inert gas or in a vacuum environment, and preheating the joint to be welded of the workpiece to be welded;

4) Finishing the fusion welding of the workpiece to be welded, in the welding and welding process, the joint position of the workpiece to be welded and the intermediate layer metal (3) of the vicinity of the workpiece are melted, so that the intermediate layer metal (3) and the workpiece to be welded The joint position forms a fusion brazing metallurgical bond;

5) Insulating the welded joint of the workpiece after welding, and then placing the welded joint of the welded workpiece in an inert gas protective atmosphere or cooling to room temperature in a vacuum environment to complete the molybdenum alloy welding based on microalloying and synchronous parasitic brazing .
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein the specific operation of pretreating the joint region to be welded of the workpiece to be welded in step 1) is: to be welded The joint area to be welded of the workpiece is sequentially ground, alkali washed, acetone washed and dried.
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein the material to be welded is made of pure molybdenum, a molybdenum alloy having an alloying element content of 2 wt% or less or a second phase. A molybdenum alloy having a dopant content of 2% by weight or less.
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein the step 4) is completed by laser welding, electron beam welding, plasma beam welding or argon arc welding. Welding and welding of welded workpieces.
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein the welded joint of the workpiece after welding is in the form of a tube/bar sleeve joint, a lap joint, and a backing plate. Butt joints, back cover butt joints, T-joints that are not fully penetrated, or cross joints that are not fully penetrated.
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein the material of the intermediate layer metal (3) is Ti, Ni, Zr or Al.
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein the step 2) is directly filled with a metal foil, sputter coating, electroplating, cold spraying or laser cladding. In the manner of filling the intermediate layer metal (3) at the joint to be welded of the workpiece to be welded.
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein the intermediate layer metal (3) has a purity of 99.99% or more.
The method of claim 1, wherein the preheating temperature in the step 3) is from 400 ° C to 500 ° C.
The method for welding a molybdenum alloy based on microalloying and synchronous parasitic brazing according to claim 1, wherein after the butting of the workpiece to be welded in step 2) is completed, the butt joint gap of the workpiece to be welded is less than or equal to 0.1 mm. The amount of misalignment at the joint of the workpiece to be welded is less than or equal to 10% of the thickness of the workpiece to be welded, and the amount of misalignment at the joint of the workpiece to be welded is less than 0.5 mm.