CN107008985B - Molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing - Google Patents
Molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing Download PDFInfo
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- CN107008985B CN107008985B CN201710284251.0A CN201710284251A CN107008985B CN 107008985 B CN107008985 B CN 107008985B CN 201710284251 A CN201710284251 A CN 201710284251A CN 107008985 B CN107008985 B CN 107008985B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/0008—Soldering, e.g. brazing, or unsoldering specially adapted for particular articles or work
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- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
Abstract
The invention discloses a molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing, which comprises the following steps of: 1) preprocessing a to-be-welded combination area of a to-be-welded workpiece, wherein the to-be-welded workpiece is made of molybdenum or molybdenum alloy; 2) filling intermediate layer metal at the to-be-welded joint surface of the to-be-welded workpiece, and then finishing the butt joint of the to-be-welded workpiece; 3) placing a workpiece to be welded in an atmosphere or vacuum environment protected by inert gas, and preheating a region to be welded of the workpiece to be welded; 4) completing fusion welding of the workpieces to be welded to obtain the welded workpieces; 5) and (3) preserving the heat of the welding joint of the welded workpiece, and then placing the welding joint of the welded workpiece in an inert gas protective atmosphere or a vacuum environment to cool to room temperature to complete molybdenum alloy fusion welding based on microalloying and synchronous parasitic brazing.
Description
Technical Field
The invention belongs to the technical field of welding, and relates to a molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing.
Background
The melting point of the molybdenum is as high as 2610 ℃, the neutron absorption cross section is small, the thermal expansion coefficient is low, the heat conduction performance is excellent, the high-temperature mechanical property is good, the machinability is good, and when the temperature is lower than 500 ℃, the molybdenum has good stability in air or water. The advantages lead the molybdenum and the molybdenum alloy, especially the high-performance molybdenum alloy to have important application in the fields of metallurgy, aviation, aerospace, nuclear energy, military and the like. The high-performance molybdenum alloy itself has excellent toughness, but once fusion welded, the excellent toughness is completely lost. Moreover, because the melting point of molybdenum is too high, the molybdenum is generally processed and prepared by adopting a powder metallurgy mode, on one hand, the compactness of the material cannot be compared with that of a fusion casting metallurgical material, the gas content is higher, and the welding pore defect is serious; on the other hand, impurities such as O, N and the like are easily introduced into the material, but the solubility of impurity elements such as O, N and the like in molybdenum is extremely low at room temperature, the impurity elements such as O, N and the like are easily segregated at the grain boundary when a molten pool is solidified, so that the grain boundary is seriously weakened, and the mechanical property of a welding seam is extremely poor, so that the problem that the molybdenum and the molybdenum alloy are used as structural materials in the key occasions such as nuclear power and the like is seriously restricted.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing, which can effectively improve the mechanical property of a welded joint of a welded workpiece.
In order to achieve the aim, the molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing comprises the following steps:
1) preprocessing a to-be-welded combination area of a to-be-welded workpiece, wherein the to-be-welded workpiece is made of molybdenum or molybdenum alloy;
2) filling intermediate layer metal at a to-be-welded joint surface of a to-be-welded workpiece, and then completing butt joint of the to-be-welded workpiece, wherein the melting point of the intermediate layer metal is lower than that of the to-be-welded workpiece, and the filling area range of the intermediate layer metal covers a fusion welding area and a heat affected area of fusion welding of the to-be-welded workpiece in the welding process;
3) placing a workpiece to be welded in an atmosphere or vacuum environment protected by inert gas, and preheating a region to be welded of the workpiece to be welded;
4) finishing the fusion welding of the workpieces to be welded, wherein in the fusion welding process, the joint position of the workpieces to be welded and the interlayer metal in the area nearby the joint position are melted, so that the interlayer metal and the joint position of the workpieces to be welded form fusion brazing metallurgical bonding;
5) and (3) preserving the heat of the welding joint of the welded workpiece, and then placing the welding joint of the welded workpiece in an inert gas protective atmosphere or a vacuum environment to cool to room temperature, thereby completing the molybdenum alloy fusion welding based on micro-alloying and synchronous parasitic brazing.
The specific operation of preprocessing the to-be-welded bonding area of the workpiece to be welded in the step 1) is as follows: sequentially polishing, alkali washing, acetone cleaning and drying the to-be-welded combination area of the to-be-welded workpiece;
the material of the workpiece to be welded is pure molybdenum, molybdenum alloy with the content of alloying elements less than or equal to 2 wt% or molybdenum alloy with the content of second phase dopants less than or equal to 2 wt%.
In the step 4), fusion welding of the workpieces to be welded is completed by adopting a laser welding method, an electron beam welding method, a plasma beam welding method or an argon arc welding method;
the welded joints of the welded workpieces are in the form of pipe/rod sleeve joints, lap joints, butt joints with backing plates, back-cover butt joints, incompletely welded T-joints or incompletely welded cross joints.
The material of the intermediate layer metal is Ti, Ni, Zr or Al.
And 2) filling intermediate layer metal at the to-be-welded joint surface of the to-be-welded workpiece in a mode of directly filling metal foil, sputtering coating, electroplating, cold spraying or laser cladding.
The purity of the intermediate layer metal is more than or equal to 99.99 percent.
The preheating temperature in the step 3) is 400-500 ℃.
After the butt joint of the workpieces to be welded in the step 2) is finished, the butt joint gap of the workpieces to be welded is less than or equal to 0.1mm, the misalignment amount of the joint of the workpieces to be welded is less than or equal to 10% of the thickness of the workpieces to be welded, and the misalignment amount of the joint of the workpieces to be welded is less than 0.5 mm;
the gap of the lap joint area of the workpieces to be welded filled with the intermediate layer metal is less than or equal to 0.05 mm.
The invention has the following beneficial effects:
according to the molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing, during specific operation, the middle layer metal is filled at the surface to be welded of the workpiece to be welded, wherein the melting point of the middle layer metal is lower than that of the workpiece to be welded, so that part of the middle layer metal enters a molten pool in the fusion welding process to realize micro-alloying of a fusion welding seam, and meanwhile, because the heat conductivity of molybdenum and molybdenum alloy is higher, the middle layer metal within a certain distance range from the fusion welding seam of the welding seam is melted to form a brazing interface parasitic on a heat affected zone of the fusion welding, metallurgical bonding between the workpieces to be welded is realized through the brazing interface, and the molybdenum alloy fusion welding method has an obvious auxiliary bearing effect. It should be noted that, on one hand, the mechanical property of the fusion welding seam is effectively improved through micro-alloying, on the other hand, the auxiliary bearing of the welding joint is realized through synchronous parasitic brazing, and under the combined action of the two mechanisms, the overall mechanical property of the fusion welding joint of molybdenum and molybdenum alloy is obviously improved.
Drawings
FIG. 1 is a Ti-Mo binary equilibrium phase diagram;
FIG. 2a is a schematic structural view of the first embodiment without Ti foil;
FIG. 2b is a schematic structural diagram of the first embodiment when only Ti is added at the butt joint;
FIG. 2c is a schematic structural view of the first embodiment when Ti foils are added to both the butt joint and the lap joint;
FIG. 3a is a dimension view of the molybdenum tube 1 according to the first embodiment;
fig. 3b is a dimensional view of a molybdenum alloy end plug 2 according to a first embodiment;
FIG. 3c is a dimension chart of the interlayer metal 3 when only Ti is added at the butt joint in the first embodiment;
FIG. 3d is a graph showing the dimensions of the interlayer metal 3 when Ti foil is added to both the butt joint and the lap joint in the first embodiment;
FIG. 4 is a cross-sectional profile of a weld joint and an analysis of the composition of the braze interface in accordance with one embodiment;
FIG. 5a is a graph showing the microhardness distribution of a weld joint without the addition of Ti foil in the first example;
FIG. 5b is a graph showing the microhardness distribution of the welded joint when Ti foil is added to both the butt joint and the lap joint in the first embodiment;
FIG. 6 is a drawing diagram of a first embodiment of the present invention;
FIG. 7a is a graph showing the tensile failure of a weld joint without the addition of Ti foil in accordance with one embodiment;
FIG. 7b is a graph showing the welded joint after tensile fracture when Ti foils are added to both the butt joint and the lap joint in the first embodiment;
FIG. 8a is a micrograph of weld joint tensile fracture without the addition of Ti foil according to example one;
FIG. 8b is a micrograph of weld joint tensile fracture when Ti foil is added at both the butt joint and the lap joint in example I;
FIG. 9 is a cross-sectional view of a weld joint according to the second embodiment;
FIG. 10 is a graph showing the stretching curves in the second embodiment;
FIG. 11 is a cross-sectional view of a weld joint according to the third embodiment;
FIG. 12 is a graph showing the stretching of the third embodiment;
FIG. 13 is a graph showing the stretching of the fourth embodiment;
FIG. 14 is a micrograph of tensile fracture of the weld joint of example four.
Wherein, 1 is a molybdenum tube, 2 is an end plug, and 3 is middle layer metal.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
the molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing comprises the following steps:
1) preprocessing a to-be-welded combination area of a to-be-welded workpiece, wherein the to-be-welded workpiece is made of molybdenum or molybdenum alloy;
2) filling an intermediate layer metal 3 at a to-be-welded joint surface of a to-be-welded workpiece, and then completing butt joint of the to-be-welded workpiece, wherein the melting point of the intermediate layer metal 3 is lower than that of the to-be-welded workpiece, and the filling area range of the intermediate layer metal 3 covers a fusion welding seam area and a heat affected area of fusion welding of the to-be-welded workpiece in the welding process;
3) placing a workpiece to be welded in an atmosphere or vacuum environment protected by inert gas, and preheating a region to be welded of the workpiece to be welded;
4) completing fusion welding of the workpieces to be welded, wherein in the fusion welding process, the joint position of the workpieces to be welded and the interlayer metal 3 in the area nearby the joint position are melted, so that fusion brazing metallurgical bonding is formed between the interlayer metal 3 and the joint position of the workpieces to be welded;
5) and (3) preserving the heat of the welding joint of the welded workpiece, and then placing the welding joint of the welded workpiece in an inert gas protective atmosphere or a vacuum environment to cool to room temperature, thereby completing the molybdenum alloy fusion welding based on micro-alloying and synchronous parasitic brazing.
The specific operation of preprocessing the to-be-welded bonding area of the workpiece to be welded in the step 1) is as follows: and sequentially polishing, alkali washing, acetone cleaning and drying the to-be-welded bonding area of the to-be-welded workpiece.
The material of the workpiece to be welded is pure molybdenum, molybdenum alloy with the content of alloying elements less than or equal to 2 wt% or molybdenum alloy with the content of second phase dopants less than or equal to 2 wt%.
And 4) finishing fusion welding of the workpieces to be welded by adopting a laser welding method, an electron beam welding method, a plasma beam welding method or an argon arc welding method in the step 4).
The welded joints of the welded workpieces are in the form of pipe/rod sleeve joints, lap joints, butt joints with backing plates, back-cover butt joints, incompletely welded T-joints or incompletely welded cross joints.
The material of the interlayer metal 3 is Ti, Ni, Zr or Al.
And in the step 2), the middle layer metal 3 is filled at the surface to be welded of the workpiece to be welded in a mode of directly filling metal foil, sputtering coating, electroplating, cold spraying or laser cladding.
The purity of the interlayer metal 3 is 99.99% or more.
The preheating temperature in the step 3) is 400-500 ℃.
After the butt joint of the workpieces to be welded in the step 2) is finished, the butt joint gap of the workpieces to be welded is less than or equal to 0.1mm, the misalignment amount of the joint of the workpieces to be welded is less than or equal to 10% of the thickness of the workpieces to be welded, and the misalignment amount of the joint of the workpieces to be welded is less than 0.5 mm;
the gap of the lap area of the to-be-welded workpiece filled with the interlayer metal 3 is 0.05mm or less.
Example one
Titanium is selected as the material of the interlayer metal 3, because the Ti and the Mo have a uniform crystal reaction in the process of converting from a liquid phase to a solid phase, as shown in figure 1, the Ti and the Mo are infinitely mutually soluble, and a brittle phase cannot be generated; the Mo-Ti solid solution has higher melting point and good high-temperature mechanical property; ti has strong affinity to elements such as O and the like at high temperature, and trace Ti in a welding pool reacts with O and Mo to generate MoxTiyOzThe second phase particles of the composite oxide can eliminate the grain boundary segregation of impurity elements and simultaneously play a role in strengthening the second phase particles to the welding seam metal.
As shown in fig. 2a, 2b and 2c, three sets of molybdenum alloy thin-wall tube-end plug 2 sleeve joints are welded by laser welding, wherein the first set is formed by directly assembling a molybdenum tube 1 and an end plug 2, the second set is formed by filling titanium foils at the butt joint of the molybdenum tube 1 and the end plug 2, and the third set is formed by filling titanium foils at the butt joint and the lap joint of the molybdenum tube 1 and the end plug 2. The test material was doped with 0.25 wt% La2O3High-performance molybdenum alloy of dispersion strengthening phase, high-performance molybdenum alloy thin-wall pipe and end plug 2 used for testAnd the dimensions of the titanium foil are shown in fig. 3a, 3b, 3c and 3 d; the specific operation is as follows: firstly, polishing the contact parts of the molybdenum tube 1 and the end plug 2 by using sand paper, then performing alkali washing by using a dilute sodium hydroxide aqueous solution, and then sequentially cleaning by using clear water and acetone and then drying by blowing; TA1 titanium foil having a thickness of 0.05mm was processed to the size shown in FIG. 3d using a 12mL HNO36mL of HF and 82mL of H2Pickling the solution prepared by O, sequentially washing with clear water and acetone, and drying; assembling the three groups of samples, then sequentially welding, placing the samples in a high-purity argon protective atmosphere during welding, preheating the joint, completing laser welding girth welding of the molybdenum tube 1 and the end plug 2 by using an IPG-4000 type optical fiber laser with welding parameters of 1200W of welding power P, +1mm of defocusing amount f and 0.2m/min of rotational linear velocity v when the temperature of the joint reaches 500 ℃, preserving heat of the welded joint for 30s at the temperature of more than 500 ℃ after welding, and then slowly cooling to the room temperature.
The welded joint cross section of the sample filled with titanium foil at both 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, parasitic braze metallurgical bonds are formed between the titanium foil and the molybdenum tube 1, and between the titanium foil and the end plug 2, and Mo and Ti are mutually dissolved at the braze interface.
Selecting a test sample without titanium foil and a test sample filled with titanium foil at the butt joint part and the lap joint part, and respectively measuring the microhardness of the weld joint melting area and the microhardness of the weld joint melting area, wherein the measurement results are shown in fig. 5a and 5 b. The measured microhardness of the molybdenum alloy base material used in the test is about 235HV, and as can be seen from fig. 5a and 5b, the microhardness of the weld melting zone of the test sample without the titanium foil is obviously reduced compared with the base material, and the reduction amplitude is about 30 HV; the micro-hardness of the sample weld filled with titanium foil at both the butt joint and the lap joint was reduced by only about 15HV compared to the parent metal, thus demonstrating that the weld strength can be improved by incorporating Ti as an alloying element into the weld.
Respectively measuring the tensile mechanical properties of the base metal of the molybdenum tube 1 and the three groups of welded joint samples, wherein the tensile curve is shown in figure 6, the tensile strength of the base metal of the molybdenum tube 1 is 720MPa, and the elongation at break reaches 10.6 mm; the tensile strength of the welding joint without the titanium foil is only 124MPa, and the elongation at break is only 0.6 mm; the tensile strength of a welding joint with titanium foil added at the butt joint of the molybdenum tube 1 and the end plug 2 is 606MPa, reaches 84.2% of the tensile strength of a base material, and the elongation at break is 3.1mm, which indicates that the tensile strength of a welding line can be obviously improved by doping Ti into the welding line as a microalloying element; meanwhile, the tensile strength of the welding joint with the titanium foil added at the butt joint part and the lap joint part of the molybdenum tube 1 and the end plug 2 reaches 688MPa, which is as high as 95.6 percent of the tensile strength of the base metal, and the elongation at break reaches 9.8mm, which shows that when Ti is added to microalloy the welding seam, the fusion brazing bonding area parasitizing on the heat affected area of the fusion welding joint plays an auxiliary bearing role, and the tensile strength of the welding joint is further improved, and the elongation of the welding joint is obviously improved.
As can be seen from fig. 7a and 7b, the former is broken at the weld, while the latter molybdenum tube 1 necks down significantly and starts to break from the molybdenum tube 1; as can be seen from fig. 8a and 8b, the welded joint is completely broken at the welded joint when the titanium foil is not added, and the fracture mode is mainly shown as intergranular fracture; the welded joint filled with titanium foil at the butt joint part and the lap joint part is mainly broken at the base metal, only a small part of fracture is in the welding line, and the fracture morphology on the welded fracture is mainly expressed as the crystal-through cleavage fracture.
Example two
The method is characterized in that nickel is selected as a material of the middle layer metal 3, and two sets of molybdenum alloy thin-wall tube-end plug 2 sleeve joints are the same as those in the first embodiment, wherein the first set is formed by directly assembling a molybdenum tube 1 and an end plug 2, and the second set is formed by filling nickel foil on the joint surface of the molybdenum tube 1 and the end plug 2. The test material was doped with 0.25 wt% La2O3A dispersion strengthened phase of high performance molybdenum alloy; the specific fusion welding process comprises the following steps: firstly, polishing the contact part of the molybdenum tube 1 and the end plug 2 by using sand paper, then carrying out alkali washing by using a dilute sodium hydroxide aqueous solution, then sequentially washing by using clear water and acetone and drying by blowing; processing nickel foil with thickness of 0.05mm into the size shown in figure 3d, using HF: HNO3:H2Acid washing with mixed acid liquor with the ratio of O to O being 2:1:4.5, cleaning with clear water and acetone in sequence, and drying; and assembling the two groups of samples, and then sequentially carrying out fusion welding. During welding, the sample is placed in a high-purity argon protective atmosphere and then is weldedPreheating a joint, when the temperature of the joint reaches 500 ℃, using an IPG-4000 type optical fiber laser to complete laser welding girth welding of a molybdenum tube 1 and an end plug 2 by using welding parameters of which the welding power P is 1200W, the defocusing amount f is +1mm and the rotational linear speed v is 0.2m/min, preserving the temperature of the welded joint for more than 500 ℃ for 30s after welding, and then slowly cooling to room temperature.
The cross section of the welded joint of the sample filled with the nickel foil is shown in fig. 9, and it can be seen from fig. 9 that in the heat affected zone of the laser welded joint, the nickel foil filled between the molybdenum tube 1 and the end plug 2 is melted and welded, and parasitic brazed metallurgical bonds are formed between the nickel foil and the molybdenum tube 1 and between the nickel foil and the end plug 2.
Comparing the tensile mechanical properties of the two groups of welding joints without nickel foil and with nickel foil, the tensile curve is shown in FIG. 10, the tensile strength of the welding joint without nickel foil is only 124MPa, and the elongation at break is only 0.6 mm; the tensile strength of the welded joint filled with the nickel foil at the joint of the molybdenum tube 1 and the end plug 2 was 624MPa, which was 86.7% of the tensile strength of the base material (about 720MPa), and the elongation at break was 2.55mm, indicating that 0.25 wt% La was doped in the case of welding by laser welding2O3When the high-performance molybdenum alloy of the dispersion strengthening phase is adopted, the nickel foil is filled, and the strength and the elongation of a welding joint can be obviously improved under the combined action of two mechanisms of micro-alloying of weld metal and formation of synchronous parasitic brazing.
EXAMPLE III
Zirconium is selected as a filling metal material of the middle layer, the size of the molybdenum alloy thin-wall tube-end plug 2 sleeve joint is the same as that of the first embodiment, wherein the first group is that a molybdenum tube 1 and an end plug 2 are directly assembled, the second group is that a joint surface of the molybdenum tube 1 and the end plug 2 is filled with zirconium foil, and the test material is that the test material is doped with 0.25 wt% of La2O3The dimensions of the high-performance molybdenum alloy thin-wall tube and the end plug 2 used in the test are shown in fig. 3a and 3b, and the specific welding process is as follows: polishing the contact part of the molybdenum tube 1 and the end plug 2 by using sand paper, then performing alkali washing by using a dilute sodium hydroxide aqueous solution, and then sequentially cleaning by using clear water and acetone and drying by blowing; processing zirconium foil with thickness of 0.05mm to size shown in figure 3d, and mixing with HF and HNO3:H2Acid washing with mixed acid liquor of O3: 45:52, then washing with clean water and acetone in sequence, and drying; assembling two groups of samples, sequentially welding, placing the samples in a high-purity argon protective atmosphere during welding, preheating a joint, completing laser welding girth welding of a molybdenum tube 1 and an end plug 2 by using an IPG-4000 type optical fiber laser with welding parameters of 1200W of welding power P, +1mm of defocusing amount f and 0.2m/min of rotational linear velocity v when the temperature of the joint reaches 500 ℃, preserving heat of the welded joint for 30s at the temperature of more than 500 ℃ after welding, and then slowly cooling to the room temperature.
As shown in fig. 11, the welded joint cross section of the zirconium foil-filled test piece was observed; as can be seen from fig. 11, in the heat affected zone of the laser welding head, the zirconium foil filled between the molybdenum tube 1 and the end plug 2 melts, Zr and Mo diffuse into each other to form an intermetallic compound, and metallurgical bonds are formed between the zirconium foil and the molybdenum tube 1 and between the zirconium foil and the end plug 2.
Comparing the tensile mechanical properties of the two groups of welded joints without and with zirconium foils, the tensile curve is shown in FIG. 12, the tensile strength of the welded joint without zirconium foil is 124MPa, which is only 17.2% of the tensile strength of the parent metal (about 720MPa), and the elongation at break is only 0.6 mm; the tensile strength of the welding joint filled with the zirconium foil at the joint of the molybdenum tube 1 and the end plug 2 is 480MPa, reaches 66.7 percent of the tensile strength of a base material, and the elongation at break is 1.55mm, which indicates that 0.25wt percent of La is doped in the welding process of laser welding2O3When the dispersion strengthening phase is high-performance molybdenum alloy, the strength and the elongation of a welding joint can be obviously improved under the combined action of two mechanisms of micro-alloying of weld metal and formation of synchronous parasitic brazing by filling zirconium foil.
Example four
The method is characterized in that aluminum is selected as a material of the middle layer metal 3, the size of the molybdenum alloy thin-wall tube-end plug 2 sleeve joint is the same as that of the first embodiment, wherein the first group is that a molybdenum tube 1 and an end plug 2 are directly assembled, and the second group is that aluminum foil is filled at the joint surface of the molybdenum tube 1 and the end plug 2; the test material was doped with 0.25 wt% La2O3The dimensions of the dispersion strengthening phase high-performance molybdenum alloy, the high-performance molybdenum alloy thin-wall pipe used in the test and the end plug 2 are shown in figure 3a and figure 3b, and the specific welding processComprises the following steps: firstly, polishing the contact part of the molybdenum tube 1 and the end plug 2 by using sand paper, then carrying out alkali washing by using a dilute sodium hydroxide aqueous solution, then sequentially washing by using clear water and acetone and then drying by blowing; processing an aluminum foil with the thickness of 0.05mm into the size shown in figure 3d, washing the aluminum foil with alkali by using a dilute sodium hydroxide aqueous solution, washing the aluminum foil with clean water and acetone in sequence, and drying the aluminum foil; assembling two groups of samples, sequentially welding, placing the samples in a high-purity argon protective atmosphere during welding, preheating a joint, and completing laser welding girth welding of a molybdenum tube 1 and an end plug 2 by using an IPG-4000 type optical fiber laser according to welding parameters of a welding power P of 1200W, a defocusing amount f of +1mm and a rotation linear speed v of 0.2m/min after the temperature of the joint reaches 500 ℃; after welding, the welded joint is kept at the temperature of more than 500 ℃ for 30s, and then is slowly cooled to the room temperature.
Comparing the tensile mechanical properties of the two groups of welded joints without aluminum foil and with aluminum foil, the tensile curve is shown in FIG. 13, the tensile strength of the welded joint without aluminum foil is 124MPa, which is only 17.2% of the tensile strength of the base material (about 720MPa), and the elongation at break is only 0.6 mm; the tensile strength of the welded joint in which the aluminum foil was filled at the joint between the molybdenum tube 1 and the end plug 2 was 557MPa, which was 77.4% of the tensile strength of the base material, and the elongation at break was 1.8 mm. FIG. 14 is a graph of tensile fracture morphology of an aluminum foil specimen, with the overall fracture mode dominated by transgranular fracture, illustrating incorporation of 0.25 wt% La in laser welding2O3When the high-performance molybdenum alloy of the dispersion strengthening phase is adopted, the aluminum foil is filled, and the strength and the elongation of a welding joint can be obviously improved under the combined action of two mechanisms of micro-alloying of weld metal and formation of synchronous parasitic brazing.
Claims (7)
1. A molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing is characterized by comprising the following steps:
1) preprocessing a to-be-welded combination area of a to-be-welded workpiece, wherein the to-be-welded workpiece is made of molybdenum or molybdenum alloy;
2) filling an intermediate layer metal (3) at a to-be-welded joint surface of a to-be-welded workpiece, and then completing butt joint of the to-be-welded workpiece, wherein the melting point of the intermediate layer metal (3) is lower than that of the to-be-welded workpiece, and the filling area range of the intermediate layer metal (3) covers a fusion welding seam area and a heat affected zone of fusion welding of the to-be-welded workpiece in the welding process;
3) placing a workpiece to be welded in an atmosphere or vacuum environment protected by inert gas, and preheating a region to be welded of the workpiece to be welded;
4) finishing the fusion welding of the workpieces to be welded, wherein in the fusion welding process, the joint position of the workpieces to be welded and the interlayer metal (3) in the area nearby the joint position are melted, so that the interlayer metal (3) and the joint position of the workpieces to be welded form fusion-brazing metallurgical bonding;
5) preserving the heat of the welding joint of the welded workpiece, and then placing the welding joint of the welded workpiece in an inert gas protective atmosphere or a vacuum environment to cool to room temperature to complete molybdenum alloy fusion welding based on micro-alloying and synchronous parasitic brazing;
the material of the interlayer metal (3) is Ti, Ni, Zr or Al;
the purity of the interlayer metal (3) is more than or equal to 99.99 percent;
the preheating temperature in the step 3) is 400-500 ℃.
2. A molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing according to claim 1, characterized in that the specific operation of preprocessing the to-be-welded bonding area of the workpiece to be welded in the step 1) is as follows: and sequentially polishing, alkali washing, acetone cleaning and drying the to-be-welded bonding area of the to-be-welded workpiece.
3. A molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing as claimed in claim 1 characterized in that the material of the work piece to be welded is pure molybdenum, molybdenum alloy with alloying element content less than or equal to 2 wt% or molybdenum alloy with second phase dopant content less than or equal to 2 wt%.
4. A molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing according to claim 1, characterized in that the fusion welding of the workpieces to be welded is completed in step 4) by laser welding, electron beam welding, plasma beam welding or argon arc welding.
5. A molybdenum alloy fusion welding method based on microalloying and simultaneous parasitic brazing according to claim 1, characterized in that the welded joints of the welded workpieces are in the form of pipe/rod sleeve joints, lap joints, butt joints with backing plates, butt joints at the back, T-joints with incomplete penetration or cross joints with incomplete penetration.
6. A molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing according to claim 1, characterized in that in step 2) the interface surfaces to be welded of the workpieces to be welded are filled with interlayer metal (3) by means of direct filling of metal foil, sputter coating, electroplating, cold spraying or laser cladding.
7. A molybdenum alloy fusion welding method based on microalloying and synchronous parasitic brazing according to claim 1, characterized in that after the butt joint of the workpieces to be welded in the step 2) is completed, the butt joint gap of the workpieces to be welded is less than or equal to 0.1mm, the misalignment amount of the joint of the workpieces to be welded is less than or equal to 10% of the thickness of the workpieces to be welded, and the misalignment amount of the joint of the workpieces to be welded is less than 0.5 mm.
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| PCT/CN2018/080433 WO2018196524A1 (en) | 2017-04-26 | 2018-03-26 | Molybdenum alloy fusion welding method based on micro-alloying and synchronized parasitic brazing |
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| CN107008985B (en) * | 2017-04-26 | 2020-03-31 | 西安交通大学 | Molybdenum alloy fusion welding method based on micro-alloying and synchronous parasitic brazing |
| CN109943802A (en) * | 2019-04-22 | 2019-06-28 | 西安交通大学 | The method for improving molybdenum and molybdenum alloy fusion welding seam intensity by pack carburizing mode |
| CN110340505A (en) * | 2019-06-25 | 2019-10-18 | 西安交通大学 | A kind of Mo alloy lap joint electric resistance welding method adding titanium foil |
| CN112222614B (en) * | 2020-08-27 | 2022-02-11 | 西安交通大学 | Method for improving molybdenum and molybdenum alloy laser welding head in nitrogen alloying mode |
| CN113732504B (en) * | 2021-09-18 | 2022-10-25 | 西安交通大学 | Method for strengthening welding performance of tungsten/molybdenum and tungsten/molybdenum alloy by ODS (oxide dispersion strengthened) |
| CN113894420A (en) * | 2021-10-27 | 2022-01-07 | 西安交通大学 | Local vacuum laser welding method for tungsten/molybdenum and alloy component thereof |
| CN115415623B (en) * | 2022-08-05 | 2023-08-22 | 西安交通大学 | Method for assembling and welding molybdenum alloy heat pipe sleeve joint |
| CN117655530A (en) * | 2024-02-02 | 2024-03-08 | 安徽瑞控信光电技术股份有限公司 | Quick reflection mirror, cross flexible supporting structure of quick reflection mirror and forming process method of cross flexible supporting structure |
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