CN107790882B - Molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation - Google Patents
Molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation Download PDFInfo
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- CN107790882B CN107790882B CN201710909722.2A CN201710909722A CN107790882B CN 107790882 B CN107790882 B CN 107790882B CN 201710909722 A CN201710909722 A CN 201710909722A CN 107790882 B CN107790882 B CN 107790882B
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- 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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- 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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The invention discloses a molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation, which comprises the following steps: 1) pretreating a molybdenum and molybdenum alloy workpiece to be welded; 2) clamping the molybdenum and molybdenum alloy workpieces to be welded through a clamp, placing the molybdenum and molybdenum alloy workpieces to be welded in an inert gas atmosphere, and then adjusting a laser welding head to enable the included angle between the axis of a laser beam emitted by the laser welding head and the vertical direction to be 0-10 degrees; 3) the welding method comprises the steps of preheating a to-be-welded area of a to-be-welded molybdenum and molybdenum alloy workpiece step by step through laser beams emitted by a laser welding head, welding the to-be-welded molybdenum and molybdenum alloy workpiece through the laser beams emitted by the laser welding head, and then preserving heat of the to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through the laser beams emitted by the laser welding head to obtain the welded workpiece.
Description
Technical Field
The invention belongs to the technical field of welding, and particularly relates to a molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation.
Background
Molybdenum and molybdenum alloy are refractory metal materials with good application prospect, and are important raw materials and strategic materials for national development, and have the advantages of good high-temperature performance, good heat conduction and electric conductivity, good thermal shock resistance, strong abrasion resistance and corrosion resistance and the like. The pure molybdenum is widely used for heating elements, heat shields and high-temperature structural parts of high-temperature furnaces and electrodes in the industries of glass and glass fiber; the molybdenum-copper alloy can be used for installing and sealing integrated circuits and high-power semiconductor devices, such as ultrahigh frequency metal ceramic tubes, high-power transistors, substrates, embedded blocks, connecting pieces, heat dissipation elements and the like in high-power microwave devices; the molybdenum titanium zirconium alloy is widely applied to the fields of aerospace and the like, such as rocket nozzles, nozzle throat liners, gas distribution valve bodies, gas pipelines, electron tube grid materials, X-ray rotating anode parts, die casting molds, heating bodies in high-temperature furnaces, heat shields and the like; the molybdenum-rhenium alloy can be used as a structural sheathing material for a heat-ion exchanger of a space nuclear reactor.
For molybdenum and molybdenum alloy structural members to be used in engineering, a stable and feasible welding technology needs to be developed. Research results at home and abroad show that the great hot cracking tendency is a great problem faced by molybdenum and molybdenum alloy welding, and the main reasons are as follows: the intrinsic brittleness of molybdenum, and coarse grains under high temperature fusion welding conditions. In one aspect, molybdenum has low temperature brittleness and is a brittle material at room temperature. After the welding seam of molybdenum and molybdenum alloy is subjected to a welding cooling process from high temperature to room temperature, the welding seam is changed from a toughness state to a brittleness state, and the welding seam is easy to crack under the action of the shrinkage stress and the thermal stress of the welding seam. On the other hand, under the high-temperature condition of the melt brazing, the molybdenum and the molybdenum alloy cause coarse weld grains due to the recrystallization process and no solid phase transformation. The coarse grains further increase the crack tendency of the molybdenum and the molybdenum alloy under the action of thermal stress, and the mechanical property is not ideal. Therefore, reducing or eliminating thermal stress during welding is a key to solving the problem of welding cracks of molybdenum and molybdenum alloys.
As a precise and efficient high-energy beam welding method, laser welding has advantages for welding molybdenum and molybdenum alloy, and mainly comprises the following steps: the heat damage is small, the tissue structure of the parent metal is not easy to damage and the mechanical property of the parent metal is not easy to influence; the energy density is high, the heat affected zone is narrow, and the welding with a large depth-to-width ratio of a welding seam can be realized; the heat input is small, and compared with traditional welding methods such as argon arc welding and the like, the grain size of the welding seam of the molybdenum and the molybdenum alloy can be refined. However, due to the fast cooling speed of laser welding, large thermal stress is easily generated when welding molybdenum and molybdenum alloy.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation, which can effectively reduce the thermal stress generated when welding molybdenum and molybdenum alloy.
In order to achieve the purpose, the molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation comprises the following steps:
1) pretreating a molybdenum and molybdenum alloy workpiece to be welded;
2) clamping the molybdenum and molybdenum alloy workpieces to be welded through a clamp, placing the molybdenum and molybdenum alloy workpieces to be welded in an inert gas atmosphere, and then adjusting a laser welding head to enable the included angle between the axis of a laser beam emitted by the laser welding head and the vertical direction to be 0-10 degrees;
3) preheating a to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through a laser beam emitted by a laser welding head, welding the to-be-welded molybdenum and molybdenum alloy workpiece through the laser beam emitted by the laser welding head, and then preserving heat of the to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through the laser beam emitted by the laser welding head to obtain a welded workpiece;
4) and closing the laser, and maintaining the inert atmosphere until the welded workpiece is cooled to room temperature, thereby completing the molybdenum and molybdenum alloy laser welding based on thermal cycle regulation.
The molybdenum alloy is a molybdenum-tungsten alloy, a molybdenum alloy with alloying element content not more than 2wt% or a molybdenum alloy with second-phase dopant content not more than 2 wt%.
The molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 1mm-4mm or pipes with the wall thickness of 0.5mm-3 mm.
The inert gas is argon with the purity of 99.999 percent, and the flow rate of the inert gas is 25L/min-40L/min.
When the molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 1-2mm,
the step-by-step preheating in the step 3) adopts a five-step preheating mode, wherein in the five-step preheating process, the laser power of a laser beam emitted by a laser welding head is respectively 400W, 400+ n 200W, 400+ n 300W and 400+ n 300W, wherein n is the thickness of the molybdenum and the molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage is scanned from one end of the area to be welded to the other end of the area to be welded at the speed of 2-3m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.5-0.8 mm;
in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head in the step 3), the laser power of the laser beams emitted by the laser welding head is 1700+ n 300W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.3-0.5mm, and the welding speed is 2.5-3.5 m/min;
and 3) performing heat preservation step by step in a five-stage heat preservation mode, wherein the laser power of laser beams emitted by the laser welding head in the five-stage heat preservation process is respectively 400+ n 300W, 400+ n 200W and 400W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan from one end of the areas to be welded to the other end of the areas to be welded at the speed of 2-3m/min in the heat preservation process of each stage.
When the molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 2-4mm,
the step-by-step preheating in the step 3) adopts a six-step preheating mode, wherein in the six-step preheating process, the laser power of a laser beam emitted by a laser welding head is respectively 500W, 500+ n 100W, 500+ n 150W, 500+ n 200W, 500+ n 250W and 500+ n 300W, wherein n is the thickness of the molybdenum and the molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage is scanned from one end of the area to be welded to the other end of the area to be welded at the speed of 1.5-3m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.4-0.8 mm;
in the step 3), in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head, the laser power of the laser beams emitted by the laser welding head is 2000+ n × 400W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.2-0.4mm, and the welding speed is 1.5-2.5 m/min;
and 3) performing gradual heat preservation in the step 3) by adopting a six-stage heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the six-stage heat preservation process is respectively 500+ n 300W, 500+ n 250W, 500+ n 200W, 500+ n 150W, 500+ n 100W and 500W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan from one end of the areas to be welded to the other end of the areas to be welded at the speed of 1.5-3m/min in the heat preservation process of each stage.
When the molybdenum and molybdenum alloy workpieces to be welded are pipes with the wall thickness of 0.5mm-1.5mm,
the step-by-step preheating in the step 3) adopts a four-stage preheating mode, wherein in the four-stage preheating process, the laser power of laser beams emitted by the laser welding head is respectively 600W, 600+ n 100W, 600+ n 200W and 600+ n 300W, wherein n is the wall thickness of the molybdenum and the molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage scans the area to be welded for one circle at the speed of 1-2.5m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.5-0.7 mm;
in the step 3), in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head, the laser power of the laser beams emitted by the laser welding head is 1500+ n × 200W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.3-0.5mm, and the welding speed is 1.5-2.5 m/min;
and 3) performing the step-by-step heat preservation in a four-stage heat preservation mode, wherein the laser power of laser beams emitted by the laser welding head in the four-stage heat preservation process is respectively 600+ n 300W, 600+ n 200W, 600+ n 100W and 600W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan the areas to be welded for one circle at the speed of 1.5m/min in the heat preservation process of each stage.
When the molybdenum and molybdenum alloy workpieces to be welded are pipes with the wall thickness of 1.5mm-3mm,
the step-by-step preheating in the step 3) adopts a six-step preheating mode, wherein in the six-step preheating process, the laser power of a laser beam emitted by a laser welding head is respectively 600W, 600+ n 100W, 600+ n 200W and 600+ n 300W, wherein n is the wall thickness of the molybdenum and molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage scans the area to be welded for one circle at the speed of 1-2.5m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.4-0.7 mm;
in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head in the step 3), the laser power of the laser beams emitted by the laser welding head is 2200+ n × 400W, wherein the diameter of a light spot of the laser beams on the area to be welded is 0.2-0.4mm, and the welding speed is 1-2 m/min;
and 3) performing gradual heat preservation in the step 3) by adopting a six-stage heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the six-stage heat preservation process is respectively 600+ n 300W, 600+ n 200W, 600+ n 100W and 600W, the diameter of light spots of the laser beams on the areas to be welded is 0.4-0.7mm, and the laser beams scan one circle on the areas to be welded at the speed of 1-2.5m/min in the heat preservation process of each stage.
The specific operation of the step 1) is as follows: and (3) polishing the molybdenum and molybdenum alloy workpieces to be welded by using abrasive paper, removing oxides and impurities on the surfaces of the molybdenum and molybdenum alloy workpieces to be welded, and scrubbing the molybdenum and molybdenum alloy workpieces to be welded by using acetone.
The invention has the following beneficial effects:
the laser welding method of molybdenum and molybdenum alloy based on thermal cycle regulation and control comprises the steps of preheating the to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through laser beams emitted by a laser welding head, welding the to-be-welded molybdenum and molybdenum alloy workpiece through the laser beams emitted by the laser welding head, then carrying out step by step heat preservation on the to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece through the laser beams emitted by the laser welding head to obtain the welded workpiece so as to reduce the thermal stress generated during welding of molybdenum and molybdenum alloy, specifically, carrying out step by step quick preheating on the to-be-welded area so as to preheat the to-be-welded area to be higher than ductile-brittle transition temperature, and carrying out step by step heat preservation on the to-be-welded area after welding, thereby relieving the thermal stress, realizing regulation and control on the thermal cycle curve of molybdenum and molybdenum alloy, and further effectively solving the problem of thermal crack welding, the method improves the quality of the welding seam of the molybdenum and molybdenum alloy laser welding, leads the surface of the welding seam to be smooth and regular, and can lead the strength of the welding seam to reach 70 percent of the tensile strength of the molybdenum and molybdenum alloy parent metal.
Drawings
FIG. 1a is a graph of the surface topography of a laser weld of molybdenum and molybdenum alloy obtained in the first example;
FIG. 1b is a cross-sectional profile of a laser weld of molybdenum and molybdenum alloy obtained in accordance with the first example;
FIG. 2a is a surface topography of a laser weld of molybdenum and molybdenum alloy obtained in example two;
FIG. 2b is a cross-sectional profile of a laser weld of molybdenum and molybdenum alloy obtained in example two;
FIG. 3a is a surface topography of a laser weld of molybdenum and molybdenum alloy obtained in example III;
FIG. 3b is a cross-sectional profile of the laser weld of Mo and Mo alloys obtained in example III.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
the invention relates to a molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation, which comprises the following steps:
1) pretreating a molybdenum and molybdenum alloy workpiece to be welded;
wherein the molybdenum alloy is molybdenum-tungsten alloy, molybdenum alloy with alloying element content not more than 2wt% or molybdenum alloy with second phase dopant content not more than 2wt%, and the molybdenum and molybdenum alloy workpiece to be welded is a plate with thickness of 1mm-4mm or a pipe with wall thickness of 0.5mm-3 mm. The specific operation of the step 1) is as follows: and (3) polishing the molybdenum and molybdenum alloy workpieces to be welded by using abrasive paper, removing oxides and impurities on the surfaces of the molybdenum and molybdenum alloy workpieces to be welded, and scrubbing the molybdenum and molybdenum alloy workpieces to be welded by using acetone.
2) Clamping the molybdenum and molybdenum alloy workpieces to be welded through a clamp, placing the molybdenum and molybdenum alloy workpieces to be welded in an inert gas atmosphere, and adjusting a laser welding head to enable an included angle between the axis of a laser beam emitted by the laser welding head and the vertical direction to be 0-10 degrees, wherein the inert gas is argon with the purity of 99.999 percent, and the flow of the inert gas is 25-40L/min;
3) preheating a to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through a laser beam emitted by a laser welding head, welding the to-be-welded molybdenum and molybdenum alloy workpiece through the laser beam emitted by the laser welding head, and then preserving heat of the to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through the laser beam emitted by the laser welding head to obtain a welded workpiece;
4) and closing the laser, and maintaining the inert atmosphere until the welded workpiece is cooled to room temperature, thereby completing the molybdenum and molybdenum alloy laser welding based on thermal cycle regulation.
When the molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 1-2mm, the step-by-step preheating in the step 3) adopts a five-step preheating mode, wherein in the five-step preheating process, the laser power of laser beams emitted by a laser welding head is respectively 400W, 400+ n 200W, 400+ n 300W and 400+ n 300W, wherein n is the thickness of the molybdenum and molybdenum alloy workpieces to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage is scanned from one end of the area to be welded to the other end of the area to be welded at the speed of 2-3m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.5-0.8 mm;
in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head in the step 3), the laser power of the laser beams emitted by the laser welding head is 1700+ n 300W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.3-0.5mm, and the welding speed is 2.5-3.5 m/min;
and 3) performing heat preservation step by step in a five-stage heat preservation mode, wherein the laser power of laser beams emitted by the laser welding head in the five-stage heat preservation process is respectively 400+ n 300W, 400+ n 200W and 400W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan from one end of the areas to be welded to the other end of the areas to be welded at the speed of 2-3m/min in the heat preservation process of each stage.
When the molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 2-4mm, the step-by-step preheating in the step 3) adopts a six-step preheating mode, wherein in the six-step preheating process, the laser power of laser beams emitted by a laser welding head is respectively 500W, 500+ n 100W, 500+ n 150W, 500+ n 200W, 500+ n 250W and 500+ n 300W, and n is the thickness of the molybdenum and molybdenum alloy workpieces to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage is scanned from one end of the area to be welded to the other end of the area to be welded at the speed of 1.5-3m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.4-0.8 mm; in the step 3), in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head, the laser power of the laser beams emitted by the laser welding head is 2000+ n × 400W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.2-0.4mm, and the welding speed is 1.5-2.5 m/min; and 3) performing gradual heat preservation in the step 3) by adopting a six-stage heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the six-stage heat preservation process is respectively 500+ n 300W, 500+ n 250W, 500+ n 200W, 500+ n 150W, 500+ n 100W and 500W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan from one end of the areas to be welded to the other end of the areas to be welded at the speed of 1.5-3m/min in the heat preservation process of each stage.
When the molybdenum and molybdenum alloy workpieces to be welded are pipes with the wall thickness of 0.5mm-1.5mm, the step-by-step preheating in the step 3) adopts a four-stage preheating mode, wherein in the four-stage preheating process, the laser power of laser beams emitted by a laser welding head is 600W, 600+ n 100W, 600+ n 200W and 600+ n 300W respectively, wherein n is the wall thickness of the molybdenum and molybdenum alloy workpieces to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage scans the area to be welded for one circle at the speed of 1-2.5m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.5-0.7 mm; in the step 3), in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head, the laser power of the laser beams emitted by the laser welding head is 1500+ n × 200W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.3-0.5mm, and the welding speed is 1.5-2.5 m/min; and 3) performing the step-by-step heat preservation in a four-stage heat preservation mode, wherein the laser power of laser beams emitted by the laser welding head in the four-stage heat preservation process is respectively 600+ n 300W, 600+ n 200W, 600+ n 100W and 600W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan the areas to be welded for one circle at the speed of 1.5m/min in the heat preservation process of each stage.
When the molybdenum and molybdenum alloy workpieces to be welded are pipes with the wall thickness of 1.5mm-3mm, the step-by-step preheating in the step 3) adopts a six-step preheating mode, wherein in the six-step preheating process, the laser power of laser beams emitted by a laser welding head is 600W, 600+ n 100W, 600+ n 200W and 600+ n 300W respectively, wherein n is the wall thickness of the molybdenum and molybdenum alloy workpieces to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage scans the area to be welded for one circle at the speed of 1-2.5m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.4-0.7 mm; in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head in the step 3), the laser power of the laser beams emitted by the laser welding head is 2200+ n × 400W, wherein the diameter of a light spot of the laser beams on the area to be welded is 0.2-0.4mm, and the welding speed is 1-2 m/min; and 3) performing gradual heat preservation in the step 3) by adopting a six-stage heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the six-stage heat preservation process is respectively 600+ n 300W, 600+ n 200W, 600+ n 100W and 600W, the diameter of light spots of the laser beams on the areas to be welded is 0.4-0.7mm, and the laser beams scan one circle on the areas to be welded at the speed of 1-2.5m/min in the heat preservation process of each stage.
Example one
In this embodiment, a molybdenum-rhenium alloy plate is welded, the size of the molybdenum-rhenium alloy plate is 100x50 x3mm, specifically, the molybdenum-rhenium alloy plate is firstly polished by abrasive paper, oxides and impurities on the surface of the molybdenum-rhenium alloy plate are removed, metallic luster is exposed, and then the molybdenum-rhenium alloy plate is scrubbed by acetone; clamping a molybdenum-rhenium alloy plate by using a clamp, introducing argon with the purity of 99.9 percent into a welding gas protection device before welding, wherein the gas flow is 30L/min; adjusting the laser welding head to enable the included angle between the axis of the laser beam emitted by the laser welding head and the vertical direction to be 5 degrees; starting a laser, and welding along the welding direction, wherein the laser power is 3200W, the spot diameter is 0.2mm, and the welding speed is 2 m/min; and cutting off laser output after the welding process is finished, and maintaining argon protection until the workpiece is cooled to room temperature to obtain the molybdenum alloy welding seam with obvious crack defects. Wherein, the surface appearance and the cross section microscopic appearance of the welding seam are shown in figure 1a and figure 1 b.
Example two
In this embodiment, a molybdenum-rhenium alloy plate is welded, the size of the molybdenum-rhenium alloy plate is 100x50 x3mm, specifically, the molybdenum-rhenium alloy plate is firstly polished by sand paper, oxides and impurities on the surface of the molybdenum-rhenium alloy plate are removed, a metallic luster is exposed, and then the molybdenum plate is scrubbed by acetone. Clamping the molybdenum-rhenium alloy plate by using a clamp; argon with the purity of 99.9 percent is introduced into a welding gas protection device before welding, and the gas flow is 30L/min. Adjusting the laser welding head to enable the included angle between the axis of the laser beam emitted by the laser welding head and the vertical direction to be 5 degrees; starting a laser, wherein six stages of preheating are adopted in the preheating stage, each stage adopts large-spot-diameter laser beams with laser power of 500W, 800W, 950W, 1100W, 1250W and 1400W to scan from one end to the other end, the spot diameter is 0.6mm, and the scanning speed is 2 m/min; in the welding stage, a small-spot-diameter laser beam with the laser power of 3200W is adopted for welding, the spot diameter is 0.2mm, and the welding speed is 2 m/min; in the heat preservation stage, six stages of heat preservation are adopted, and each stage adopts large-spot-diameter laser beams with laser power of 1400W, 1250W, 1100W, 950W, 800W and 500W to perform reciprocating scanning, wherein the spot diameter is 0.6mm, and the scanning speed is 2 m/min; and cutting off laser output after the welding process is finished, and maintaining argon protection until the workpiece is cooled to room temperature to obtain the molybdenum alloy welding seam with a regular and flat surface and no crack defects, wherein the surface appearance and the cross section microscopic appearance of the welding seam are shown in fig. 2a and 2 b.
EXAMPLE III
In this embodiment, a molybdenum-tungsten alloy tube is welded, the thickness of the molybdenum-tungsten alloy tube is 1mm, specifically, the molybdenum-tungsten alloy tube is firstly polished by abrasive paper, oxides and impurities on the surface of the molybdenum-tungsten alloy tube are removed, metallic luster is exposed, and then the molybdenum-tungsten alloy tube is scrubbed by using acetone. Clamping the molybdenum-tungsten alloy tube by using a clamp; argon with the purity of 99.999 percent is introduced into the welding gas protection device before welding, and the gas flow is 40L/min; adjusting the laser welding head to enable the included angle between the axis of the laser beam emitted by the laser welding head and the vertical direction to be 0 degree; in the preheating stage, four stages of preheating are adopted, each stage adopts large-spot-diameter laser beams with laser power of 600W, 700W, 800W and 900W to scan for one circle, the spot diameter is 0.5mm, and the scanning speed is 1.5 m/min; in the welding stage, a small-spot-diameter laser beam with the laser power of 1700W is adopted for welding, the spot diameter is 0.3mm, and the welding speed is 2.5 m/min; the heat preservation stage adopts four-stage heat preservation, each stage respectively adopts large-spot diameter laser beams with laser power of 900W, 800W, 700W and 600W to scan for one circle, the spot diameter is 0.5mm, and the scanning speed is 1.5 m/min; and cutting off laser output after the welding process is finished, maintaining argon protection until the workpiece is cooled to room temperature, and obtaining the molybdenum alloy welding seam with a regular and flat surface and no crack defects, wherein the surface appearance and the cross section microscopic appearance of the welding seam are shown in fig. 3a and 3 b.
Claims (1)
1. A molybdenum and molybdenum alloy laser welding method based on thermal cycle regulation is characterized by comprising the following steps:
1) pretreating a molybdenum and molybdenum alloy workpiece to be welded;
2) clamping the molybdenum and molybdenum alloy workpieces to be welded through a clamp, placing the molybdenum and molybdenum alloy workpieces to be welded in an inert gas atmosphere, and then adjusting a laser welding head to enable the included angle between the axis of a laser beam emitted by the laser welding head and the vertical direction to be 0-10 degrees;
3) preheating a to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through a laser beam emitted by a laser welding head, welding the to-be-welded molybdenum and molybdenum alloy workpiece through the laser beam emitted by the laser welding head, and then preserving heat of the to-be-welded area of the to-be-welded molybdenum and molybdenum alloy workpiece step by step through the laser beam emitted by the laser welding head to obtain a welded workpiece;
4) closing the laser, maintaining the inert atmosphere until the welded workpiece is cooled to room temperature, and completing the laser welding of molybdenum and molybdenum alloy based on thermal cycle regulation;
the molybdenum alloy is molybdenum-tungsten alloy, molybdenum alloy with alloying element content not more than 2wt% or molybdenum alloy with second-phase dopant content not more than 2 wt%;
the inert gas is argon with the purity of 99.999 percent, and the flow rate of the inert gas is 25L/min-40L/min;
the molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 1mm-4mm or pipes with the wall thickness of 0.5mm-3 mm;
when the molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 1-2mm,
the step-by-step preheating in the step 3) adopts a five-step preheating mode, wherein in the five-step preheating process, the laser power of a laser beam emitted by a laser welding head is respectively 400W, 400+ n 200W, 400+ n 300W and 400+ n 300W, wherein n is the thickness of the molybdenum and the molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage is scanned from one end of the area to be welded to the other end of the area to be welded at the speed of 2-3m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.5-0.8 mm;
in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head in the step 3), the laser power of the laser beams emitted by the laser welding head is 1700+ n 300W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.3-0.5mm, and the welding speed is 2.5-3.5 m/min;
the step-by-step heat preservation in the step 3) adopts a five-step heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the five-step heat preservation process is respectively 400+ n 300W, 400+ n 200W and 400W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan from one end of the areas to be welded to the other end of the areas to be welded at the speed of 2-3m/min in the heat preservation process of each step;
when the molybdenum and molybdenum alloy workpieces to be welded are plates with the thickness of 2-4mm,
the step-by-step preheating in the step 3) adopts a six-step preheating mode, wherein in the six-step preheating process, the laser power of a laser beam emitted by a laser welding head is respectively 500W, 500+ n 100W, 500+ n 150W, 500+ n 200W, 500+ n 250W and 500+ n 300W, wherein n is the thickness of the molybdenum and the molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage is scanned from one end of the area to be welded to the other end of the area to be welded at the speed of 1.5-3m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.4-0.8 mm;
in the step 3), in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head, the laser power of the laser beams emitted by the laser welding head is 2000+ n × 400W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.2-0.4mm, and the welding speed is 1.5-2.5 m/min;
the step-by-step heat preservation in the step 3) adopts a six-step heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the six-step heat preservation process is respectively 500+ n 300W, 500+ n 250W, 500+ n 200W, 500+ n 150W, 500+ n 100W and 500W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan from one end of the areas to be welded to the other end of the areas to be welded at the speed of 1.5-3m/min in the heat preservation process of each step;
when the molybdenum and molybdenum alloy workpieces to be welded are pipes with the wall thickness of 0.5mm-1.5mm,
the step-by-step preheating in the step 3) adopts a four-stage preheating mode, wherein in the four-stage preheating process, the laser power of laser beams emitted by the laser welding head is respectively 600W, 600+ n 100W, 600+ n 200W and 600+ n 300W, wherein n is the wall thickness of the molybdenum and the molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage scans the area to be welded for one circle at the speed of 1-2.5m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.5-0.7 mm;
in the step 3), in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head, the laser power of the laser beams emitted by the laser welding head is 1500+ n × 200W, wherein the diameter of light spots of the laser beams on the areas to be welded is 0.3-0.5mm, and the welding speed is 1.5-2.5 m/min;
the step-by-step heat preservation in the step 3) adopts a four-stage heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the four-stage heat preservation process is respectively 600+ n 300W, 600+ n 200W, 600+ n 100W and 600W, the diameter of light spots of the laser beams on the areas to be welded is 0.5-0.8mm, and the laser beams scan the areas to be welded for one circle at the speed of 1.5m/min in the heat preservation process of each stage;
when the molybdenum and molybdenum alloy workpieces to be welded are pipes with the wall thickness of 1.5mm-3mm,
the step-by-step preheating in the step 3) adopts a six-step preheating mode, wherein in the six-step preheating process, the laser power of a laser beam emitted by a laser welding head is respectively 600W, 600+ n 100W, 600+ n 200W and 600+ n 300W, wherein n is the wall thickness of the molybdenum and molybdenum alloy workpiece to be welded; and the laser beam emitted by the laser welding head in the preheating process of each stage scans the area to be welded for one circle at the speed of 1-2.5m/min, and the diameter of the laser beam emitted by the laser welding head on the area to be welded is 0.4-0.7 mm;
in the process of welding the molybdenum and molybdenum alloy workpieces to be welded through the laser beams emitted by the laser welding head in the step 3), the laser power of the laser beams emitted by the laser welding head is 2200+ n × 400W, wherein the diameter of a light spot of the laser beams on the area to be welded is 0.2-0.4mm, and the welding speed is 1-2 m/min;
the step-by-step heat preservation in the step 3) adopts a six-step heat preservation mode, wherein the laser power of laser beams emitted by a laser welding head in the six-step heat preservation process is respectively 600+ n 300W, 600+ n 200W, 600+ n 100W and 600W, the diameter of light spots of the laser beams on the areas to be welded is 0.4-0.7mm, and the laser beams scan one circle on the areas to be welded at the speed of 1-2.5m/min in the heat preservation process of each step;
the specific operation of the step 1) is as follows: and (3) polishing the molybdenum and molybdenum alloy workpieces to be welded by using abrasive paper, removing oxides and impurities on the surfaces of the molybdenum and molybdenum alloy workpieces to be welded, and scrubbing the molybdenum and molybdenum alloy workpieces to be welded by using acetone.
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