Composite Ring Beam Generation Method And Its Characteristics In Spot Welding

Compared with other welding methods,laser welding has unique advantages such as non-contact,high welding quality,high productivity.It is gradually replacing traditional welding methods such as resistance welding,arc welding,and gas welding,and has a broad market prospect.However,the pollution damage of the optical lens of the welding head is a common problem in laser welding.How to reduce the plume produced by the interaction between the laser and the welding material and ensure the high welding quality is the main problem studied in this thesis.This thesis proposes methods for generating dynamic and static composite ring beams,and conducts experimental research on spot welding of thin stainless steel plates.The innovation results are as follows:（1）Using a dual-core fiber,the two beams are respectively coupled to the first circular core and the second ring core,and the composite circular beam is obtained by transmitting in the dual-core fiber.（2）The method of generating two beams is to divide the incident beam into two0^th and+1^st diffracted beams through an acousto-optic modulator,and the diffraction efficiency is changed by adjusting the external signal of the driving power source to achieve the continuous adjustment of the light splitting ratio of the high-power laser beam.(The range of 0^th beam energy to total energy is 24%～90%)（3）This method can achieve a static composite ring beam and a dynamic composite ring beam.Under the condition that the total energy of the composite ring beam remains unchanged,static refers to the energy distribution between the first core and the second ring core unchanged;dynamic refers to the energy distribution between the first core and the second ring core changes periodically,and the frequency range is1～150k Hz.（4）Using a 1500W single-mode fiber laser and the single-factor control variable method,the static and dynamic composite ring beam and single-core（the same diameter as the first core in the dual-core）circular beam laser spot welding experiment were carried out respectively.The experimental results show that:In the static composite ring beam spot welding,when the center beam energy ratioη_core1is greater 50%,the weld penetration is deeper than the single-core circular beam spot welding penetration depth,and the depression phenomenon in the middle of the molten pool surface is significantly improved;When the center beam energy ratioη_core1 is 50%,not only the weld penetration is deeper than the single-core circular beam spot welding,but also the plume height is lower.In the dynamic composite ring beam,when the center beam energy ratioη_core1 is 50%and the repetition frequency is 15k Hz,the weld penetration is greater than the single-core circular beam welding and the plume height is lower.Under different composite ring beam energy distributions,79%of the dynamic composite ring beam spot welding penetration depth is greater than the static composite ring beam spot welding penetration depth.In this thesis,the composite ring beam is applied to laser spot welding,and it is concluded that its effective to deepen penetration while reducing plume.The research results have reference value for the subsequent promotion of dynamic composite ring beam to thin plate seam welding and thick plate deep penetration welding.