CN-121972809-A - Laser welding method for dissimilar metals of titanium alloy and niobium alloy

CN121972809ACN 121972809 ACN121972809 ACN 121972809ACN-121972809-A

Abstract

The invention discloses a titanium alloy and niobium alloy dissimilar metal laser welding method, which belongs to the technical field of dissimilar metal welding and comprises the steps of processing a surface to be welded of titanium alloy and niobium alloy, assembling the processed titanium alloy and niobium alloy by adopting an asymmetric thinning lock bottom structure to form a closed bottom cavity, arranging a back protection gas circuit right below a to-be-welded position, arranging a front protection cover above the back protection gas circuit to form a double-sided gas protection device, clamping a workpiece in a self-adaptive clamp, applying pretightening force to position the workpiece, presetting a scanning path of a laser beam, adopting a continuous fiber laser to enable the laser beam to execute welding operation along the preset scanning path to complete main welding and execute targeted remelting treatment along the surface of a welding seam, continuously introducing protection gas to cool to room temperature after the welding is completed, and carrying out destressing heat treatment on a welding joint.

Inventors

LI HAIQING
LI ZHAOJIE
XU FANGTAO
LI PENGFEI
YIN HONGBIN
WANG JIE
HAN XU
ZHANG YUYANG

Assignees

北京神箭空天科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260401

Claims (9)

1. The laser welding method for the dissimilar metals of the titanium alloy and the niobium alloy is characterized by comprising the following steps of: The method comprises the steps of S1, polishing, descaling and degreasing cleaning the surface to be welded of the titanium alloy and the niobium alloy, assembling the treated titanium alloy and the treated niobium alloy by adopting an asymmetric thinning lock bottom structure, carrying out multiple thinning on the low-melting-point titanium alloy side, carrying out less thinning on the high-melting-point niobium alloy side, and bonding the thinning surfaces on the two sides to form a closed lock bottom cavity; S2, arranging a back protection gas circuit right below a to-be-welded part formed after the assembly of the S1, arranging a front protection cover above the to-be-welded part, forming a double-sided gas protection device by the back protection gas circuit and the front protection cover, integrating an annular gas circuit conduit assembly in the front protection cover, and respectively introducing protection gas into the back protection gas circuit and the front protection cover; s3, clamping the workpiece processed by the S2 in the self-adaptive clamp, and applying pre-tightening force to the self-adaptive clamp for positioning; s4, presetting a scanning path of a laser beam according to the thermophysical difference of the titanium alloy and the niobium alloy, wherein the scanning path is a spiral track or a sine wave track; S5, adopting a continuous fiber laser to emit laser beams, and enabling the laser beams to execute welding operation on the to-be-welded part along a scanning path preset in S4 to finish main welding so as to form a welding joint; S6, continuously introducing protective gas after welding is finished, and slowly cooling the workpiece to room temperature along with the double-sided gas protection device; and S7, carrying out stress relief heat treatment on the welded joint after the slow cooling in the step S6.
2. The method for welding the dissimilar metals of the titanium alloy and the niobium alloy is characterized in that in the step S1, the thinning amount of the titanium alloy side is 80-90% of the thickness of the titanium alloy, the thinning amount of the niobium alloy side is 10-20% of the thickness of the niobium alloy, the width of a closed lock bottom cavity is 0.4-0.6 times of the preset welding line width, the butt joint gap between the titanium alloy and the niobium alloy is less than or equal to 0.1mm, and the slope edge of the closed lock bottom cavity is rounded by 0.1-0.2 mm.
3. The method for laser welding of dissimilar metals of titanium alloy and niobium alloy according to claim 2, wherein in the step S2, the back protection gas path is a copper U-shaped groove, back gas outlets are uniformly distributed on the side surface of the inner wall of the back protection gas path, and the back gas outlets are obliquely upwards arranged.
4. The method for welding dissimilar metals of titanium alloy and niobium alloy according to claim 1, wherein in the step S2, a front protective cover covers a to-be-welded part and a peripheral area of at least 10cm, a flexible sealing edge is arranged at the bottom of the front protective cover, laser transmission holes are reserved at the top of the front protective cover, an annular gas path duct assembly is provided with array type front gas outlet holes along the circumferential direction and the axial direction, the front gas outlet holes face to the center of the to-be-welded part, and an included angle between the axis of the front gas outlet holes and the axis of a preset laser beam is 15-25 degrees.
5. The method for welding dissimilar metals of titanium alloy and niobium alloy according to claim 1, wherein in the step S2, the protective gas is high-purity argon with purity of more than or equal to 99.999%, the back protective gas path and the front protective cover adopt independent gas supply, the pressure and flow of the gas supply of the back protective gas path and the gas supply of the front protective cover are respectively and independently regulated, the gas supply is started 30-60S before the laser welding starts, the gas supply is continuously carried out in the welding process, and the gas supply is continuously carried out 30-60S after the welding is finished.
6. The method for laser welding of dissimilar metals of titanium alloy and niobium alloy according to claim 1, wherein in the step S4, a spiral line scanning track is circular swing superposition linear feeding, and a sine wave scanning track is reciprocating swing superposition linear feeding along the width direction of a welding line.
7. The method for laser welding of dissimilar metals of titanium alloy and niobium alloy according to claim 6, wherein in step S4, in a spiral line scanning track or a sine wave scanning track, the coverage time of the niobium alloy side is 55-65%, the coverage time of the titanium alloy side is 35-45%, and the coverage area of the niobium alloy side is 15-25% larger than that of the titanium alloy side.
8. The method for welding dissimilar metals of titanium alloy and niobium alloy according to claim 1 is characterized in that in the step S5, the main welding process parameters are that laser power is 2200-2800W, welding speed is 1.5-2.0 m/min, defocusing amount is 0- +5mm, the targeted remelting process parameters are that laser power is 1400-1800W, scanning speed is 1.8-2.4 m/min, and defocusing amount is 0- +5mm.
9. The method for laser welding of dissimilar metals of titanium alloy and niobium alloy according to claim 1, wherein in step S7, the technological parameters of the stress relief heat treatment are that the vacuum degree is not lower than 10 -3 Pa, the heating temperature is 500-800 ℃, the heat preservation is carried out for 30-60 minutes, and the annealing is carried out.

Description

Laser welding method for dissimilar metals of titanium alloy and niobium alloy Technical Field The invention relates to the technical field of dissimilar metal welding, in particular to a laser welding method for dissimilar metals of titanium alloy and niobium alloy. Background The titanium alloy has the characteristics of low density, high specific strength, excellent corrosion resistance and the like, the niobium alloy has excellent high-temperature mechanical property and thermal stability, and the dissimilar connection structure of the two has irreplaceable application value in the fields of aerospace (such as rocket engine thrust chambers, jet pipe extension sections), high-end equipment manufacturing and the like, namely the dual targets of low cost and light weight and high-temperature performance guarantee can be realized, and the weight and manufacturing cost of the whole structure are obviously reduced. However, the difference of the thermal physical characteristics of the titanium alloy and the niobium alloy is extremely large, the titanium alloy has low thermal conductivity and strong molten pool mobility, the niobium alloy has high thermal conductivity and weak molten pool mobility, the difference of the melting points of the titanium alloy and the niobium alloy is about 1000 ℃, the essential difference causes three major core problems of difficult balance of heat input, easy overfusion and spreading of the titanium alloy side and insufficient fusion and penetration of the niobium alloy side, and the two metals are high-activity metals which are easy to react with elements such as oxygen, nitrogen, hydrogen and the like in the welding process to generate brittle compounds (such as TiO 2、Nb2O5) to cause embrittlement and mechanical property reduction of a welding seam, and the welding seam surface is easy to generate undercut defects due to uneven flow of the molten pool to influence the structural integrity and corrosion resistance. In the prior art, the dissimilar connection of the titanium alloy and the niobium alloy is mainly realized by adopting an electron beam welding process, but has obvious limitations that 1) the electron beam welding is needed to be carried out in a vacuum cabin, the equipment purchase and operation cost is extremely high, 2) the process flexibility is poor, and the welding of large or complex structural members is difficult to adapt to the parts with the length exceeding the size of the vacuum cabin or the special-shaped structures; Therefore, developing a welding method for dissimilar metals of titanium alloy and niobium alloy which does not need a vacuum environment, has accurate heat input regulation and control, reliable oxidation prevention effect and can effectively optimize surface defects becomes a technical problem to be solved in the field. Disclosure of Invention The invention aims to provide a laser welding method for dissimilar metals of titanium alloy and niobium alloy, which aims to solve the problems of high equipment cost, complex process, unbalanced heat input and outstanding oxidation and surface defects in the conventional welding technology for the dissimilar metals of titanium alloy and niobium alloy. In order to achieve the above purpose, the invention provides a laser welding method for dissimilar metals of titanium alloy and niobium alloy, comprising the following steps: The method comprises the steps of S1, polishing, descaling and degreasing cleaning the surface to be welded of the titanium alloy and the niobium alloy, assembling the treated titanium alloy and the treated niobium alloy by adopting an asymmetric thinning lock bottom structure, carrying out multiple thinning on the low-melting-point titanium alloy side, carrying out less thinning on the high-melting-point niobium alloy side, and bonding the thinning surfaces on the two sides to form a closed lock bottom cavity; S2, arranging a back protection gas circuit right below a to-be-welded part formed after the assembly of the S1, arranging a front protection cover above the to-be-welded part, forming a double-sided gas protection device by the back protection gas circuit and the front protection cover, integrating an annular gas circuit conduit assembly in the front protection cover, and respectively introducing protection gas into the back protection gas circuit and the front protection cover; s3, clamping the workpiece processed by the S2 in the self-adaptive clamp, and applying pre-tightening force to the self-adaptive clamp for positioning; s4, presetting a scanning path of a laser beam according to the thermophysical difference of the titanium alloy and the niobium alloy, wherein the scanning path is a spiral track or a sine wave track; S5, adopting a continuous fiber laser to emit laser beams, and enabling the laser beams to execute welding operation on the to-be-welded part along a scanning path preset in S4 to finish main welding so as to form a welding joint; S6, continuousl