CN-121988887-A - Laser welding strength cooperative processing method and tool for stranded conductor

CN121988887ACN 121988887 ACN121988887 ACN 121988887ACN-121988887-A

Abstract

The invention discloses a laser welding strength cooperative processing method and a tooling for stranded conductors, wherein five working procedures are sequentially carried out, namely, radial compression force and axial pretension are applied to the stranded conductors to construct quasi-materialized constraint and preheat, laser welding is carried out under a local inert gas microenvironment and the temperature of a molten pool is monitored, a sacrificial absorption layer is arranged, a deionized water constraint layer is injected, a flexible anvil loaded with liquid metal-based magnetorheological fluid is positioned at the back of the conductors, the magnetic field strength is dynamically adjusted according to the material of a processing area, acoustic impedance matching of a carrier fluid is utilized to inhibit reflection in a low-impedance metal section, the backing is enabled to be in a quasi-solidification state through magnetic particle chaining in a high-impedance metal section, laser shock reinforcement is carried out, and after reinforcement, the compression force is unloaded to recover microscopic pores among the stranded wires, so that stranded gap layer penetration drying is realized. The invention realizes the cooperation of multiple physical fields of machinery, fluid, acoustics and thermodynamics, and is beneficial to improving the process stability and service reliability of the joint.

Inventors

LI WEI
SU BOYONG
LI MENGJIAO
ZHANG JIAYU
LU XINYI
LI XINYU
JIANG ZHIBO
FU RUIRUI

Assignees

南通大学

Dates

Publication Date: 20260508
Application Date: 20260330

Claims (10)

1. The laser welding strength cooperative treatment method for the stranded conductor is characterized by comprising the following steps of: S1, workpiece clamping and preheating constraint construction, wherein radial centripetal compression force is applied to a stranded conductor to be processed through the same iris clamping mechanism, axial pretension is matched, strand gaps are compressed to enable the stranded conductor to tend to be quasi-solid, and the stranded conductor is preheated; S2, carrying out local microenvironment laser welding and monitoring, and carrying out circumferential multi-channel laser fusion connection on the joint peripheral region of the stranded conductor under the protection of local closed inert gas so as to form a continuous metallurgical bonding belt on the joint periphery; S3, setting an absorption layer and reconstructing an underwater sound liquid boundary, setting a sacrificial absorption layer on the surface to be reinforced, injecting deionized water to the laser incidence side to establish an external constraint water layer, and positioning a flexible anvil block loaded with liquid metal-based magnetorheological fluid at the back of the stranded conductor, wherein the magnetorheological fluid is prepared by dispersing magnetic particles in liquid metal carrier liquid at room temperature and is sealed in a flexible sound-transmitting film, and the flexible sound-transmitting film can realize conformal lamination along with the surface profile deformation of the conductor; S4, self-adaptive acoustic regulation and laser shock reinforcement are carried out, laser shock reinforcement is carried out, the magnetic field intensity applied to the magnetorheological fluid is dynamically regulated according to the material of the current processing area so as to regulate the state of a backing medium, when the backing medium is positioned in a metal section with low acoustic impedance, the first magnetic field intensity is applied to enable the magnetic particles to keep a dispersion state, the acoustic mismatch of a conductor and a backing interface is reduced by utilizing the acoustic impedance of the liquid metal carrier fluid close to the metal section, and reflection is inhibited; S5, unloading and penetrating layer drying, namely removing the external constraint water layer and the flexible anvil after strengthening, unloading the radial centripetal compression force to a micro-supporting state which reduces the radial clamping pressure to 0.5-1 MPa through the iris clamping mechanism, recovering microscopic pores among stranded conductor strands, and finally cooling and unloading the part through the synergistic effects of radially injecting hot gas into the periphery of the conductor, applying vacuum negative pressure to the outside of the conductor, applying induction auxiliary heating to the conductor and carrying out high-speed gas blowing on the outer surface of the conductor.
2. The method of claim 1, wherein in S4, the magnetic field strength continuously varies between the first magnetic field strength and the second magnetic field strength as the transition region between the low acoustic impedance metal segment and the high acoustic impedance metal segment is processed, so that the rheological state and the power consumption capability of the backing medium smoothly transition, and local secondary stress concentration caused by abrupt backing response is avoided.
3. The method of claim 1, wherein the liquid metal-based magnetorheological fluid has an equivalent acoustic impedance of 15-20 MRayl, the flexible acoustically transparent film has a thickness of no more than 0.15 mm, and the flexible acoustically transparent film is capable of being tightly adhered to the curved surface of the conductor under the action of shock wave pressure to reduce an air gap between the conductor and the backing.
4. The method of claim 1, wherein the radial centripetal compression force in S1 and the radial centripetal compression force in S5 are applied by the same iris clamp, wherein in S1 the iris clamp performs high pressure compaction constraints to inhibit stranding during the reinforcement phase, and wherein in S5 the iris clamp is unloaded to a micro-support state to restore microscopic channels of available gas seepage between strands during the drying phase.
5. The method of claim 4, wherein said iris clamping mechanism is comprised of a staggered overlapping of a plurality of non-magnetic high strength alloy blades with synchronized centripetal motion achieved by cam disk drive, said blades having heating elements integrated therein for uniform heat transfer to said stranded conductor during said S1 preheat phase.
6. The method according to claim 1, wherein the penetrating layer drying process in S5 is to radially inject a preheating gas into the periphery of the stranded conductor through an annular porous nozzle, wherein the preheating gas is nitrogen or inert protective gas, the preheating gas permeates into the conductor through an outer layer strand gap and forms continuous penetrating layer flow along the strand gap under the action of external vacuum negative pressure to take out water vapor generated by evaporating residual water, and simultaneously, the stranded conductor is subjected to low-frequency induction heating through an induction auxiliary heating coil to promote the evaporation of the residual water in the strand gap.
7. The method according to claim 1, wherein the dew point temperature of the exhaust gas is monitored in real time by a dew point sensor during the strike-through drying of S5, and the drying is judged to be completed when the dew point temperature is stabilized below-40 ℃ for more than a preset time.
8. The method according to claim 1, wherein the preset threshold in S2 is 60 ℃, the shrinkage is stopped when the radial clamping pressure in S1 reaches 25-35 MPa, the axial pretension is set according to conductor material segments, the first magnetic field strength is 0.2-0.3T, the second magnetic field strength is 0.5-0.8T, and the radial clamping pressure after unloading in S5 is reduced to 0.5-1 MPa.
9. A self-adaptation rotatory constraint frock for strong collaborative processing of transposition conductor laser welding, its characterized in that includes: The iris clamping mechanism (5) is formed by overlapping a plurality of blades in a staggered manner to form an annular array, realizes synchronous centripetal movement through the driving mechanism, is used for applying adjustable radial centripetal compression force to the stranded conductor (7), and has two switchable working modes of high-pressure compaction constraint and micro-support unloading; An annular environment microcavity (9) which adopts a split structure and is provided with an optical window for forming a sealable space outside a processing area of the stranded conductor, and can selectively establish an inert gas protection environment or a water confinement layer environment in the cavity; A water nozzle (1) arranged on the microcavity and used for injecting deionized water into the microcavity to establish an external constraint water layer (4); A laser head (2) for outputting a welding laser beam and/or an impact strengthening pulse laser beam to a processing region through the optical window; The magnetorheological anvil comprises a cavity for containing a liquid metal-based magnetorheological liquid layer (301), a flexible sound-transmitting film (302) sealed at an opening of the cavity and an electromagnetic coil (303) for generating a magnetic field with adjustable strength, wherein the flexible sound-transmitting film can be conformally attached along with the surface profile deformation of a conductor, and the whole magnetorheological anvil can move forward and backward relative to the stranded conductor to realize positioning and evacuation; An annular porous gas injection nozzle (10) disposed around the stranded conductor for injecting gas radially into the outer periphery of the conductor; a vacuum suction channel (11) for communicating the space outside the stranded conductor with an external vacuum system; an induction-assisted heating coil (12) disposed around the stranded conductor for applying induction heating to the conductor; The controller is used for controlling the electromagnetic coil (303) to output different magnetic field intensities according to the preset material-position mapping relation of the processing area and the current position information output by the position feedback unit so as to realize the self-adaptive acoustic regulation and control of the low-acoustic-impedance metal section, the high-acoustic-impedance metal section and the transition area.
10. The tool according to claim 9, wherein a honeycomb-shaped fluid rectifying grid is integrated in the annular environment microcavity (9) and is used for eliminating turbulent bubbles in a water injection stage, a miniature energy accumulator is integrated in a fluid loop of the microcavity and is used for absorbing water hammer shock waves at the moment of water injection termination to protect the optical window, the tool further comprises a dew point sensor (13) for monitoring the dew point temperature of exhaust gas in a layer penetrating drying process in real time, and blades of the iris clamping mechanism (5) are made of non-magnetic high-strength alloy.

Description

Laser welding strength cooperative processing method and tool for stranded conductor Technical Field The invention relates to the technical field of laser precision machining and ocean engineering equipment manufacturing, in particular to a laser welding strength cooperative treatment method and a tool for stranded conductors. Background As ocean engineering and offshore wind power develop into deep open sea, the demand for large-section high-voltage submarine cables continues to increase. In the manufacture of deep sea flexible joints, the connection of dissimilar metal stranded conductors such as copper, aluminum and the like is a core process link. The traditional welding mode is easy to generate residual tensile stress and microscopic defects at the welding seam, and the laser shock strengthening is used as an advanced surface modification technology, so that deep residual compressive stress can be induced to improve the fatigue service capacity of the joint. However, when the laser shock peening technique is directly applied to a stranded conductor, the recoil force of the GPa-level high-voltage shock wave tends to cause radial birdcage-like bulging of loose strands lacking full circumferential restraint, i.e., the stranding effect, severely affecting the geometric integrity and forming quality of the joint. The existing clamping scheme is mainly designed for solid conductors, and is difficult to adapt to discrete geometric characteristics and impact load working conditions of stranded cables. Meanwhile, the acoustic impedance difference of the copper metal and the aluminum metal is remarkable, and the conductor cylindrical curved surface and the back air medium have extreme acoustic mismatch. In the laser shock strengthening process, shock waves transmitted to the back of the conductor are strongly reflected at the interface between the conductor and air and converted into tensile waves, so that brittle copper-aluminum welding interfaces are easy to generate spalling or stripping damage. The traditional elastic body or liquid backing can be bonded with the curved surface, but the acoustic impedance is fixed and generally low, the acoustic coupling requirements of two metals with distinct acoustic impedance of a copper section and an aluminum section cannot be simultaneously met, and the capability of carrying out real-time self-adaptive regulation and control according to the material change of a processing area is lacking. In addition, the water-binding layer required for the laser shock peening process can penetrate into the deep gaps between the stranded conductor strands by capillary action. The traditional surface air knife can only remove the liquid drops on the outer surface, and residual moisture deeply hidden in the gaps of the multi-layer folded yarns can not be effectively removed. If the moisture is not sufficiently removed, it may evaporate to form air hole defects during subsequent processes or cause corrosion during long-term service, severely affecting the reliability of the joint. The existing open processing environment lacks an effective dehumidification means for deep gaps of stranded conductors, and a system scheme capable of realizing penetrating layer drying from inside to outside is needed. Disclosure of Invention The invention aims at solving the technical problems that in the manufacturing process of a copper-aluminum dissimilar metal soft joint of a deep sea cable, a stranded conductor is easy to generate scattered strand and birdcage deformation under the action of high-energy shock wave recoil force generated by laser shock reinforcement, an effective water layer constraint and flexible acoustic coupling backing are lacked in the processing of a cylindrical curved surface, so that shock wave energy dissipation is insufficient and secondary damage caused by reflected waves is caused, residual moisture in stranded gaps is difficult to effectively remove in the existing open environment, and further welding pores are induced. In order to achieve the aim, the invention provides the technical scheme that the laser welding strength cooperative processing method for the stranded conductor comprises the following steps of: S1, workpiece clamping and preheating constraint construction, wherein radial centripetal compression force is applied to a stranded conductor to be processed through the same iris clamping mechanism, axial pretension is matched, strand gaps are compressed to enable the stranded conductor to tend to be quasi-solid, and the stranded conductor is preheated; S2, carrying out local microenvironment laser welding and monitoring, and carrying out circumferential multi-channel laser fusion connection on the joint peripheral region of the stranded conductor under the protection of local closed inert gas so as to form a continuous metallurgical bonding belt on the joint periphery; S3, arranging an absorption layer and reconstructing an underwater sound liquid boundary, a