Preface
Compared with conventional welding technology, laser welding (see Figure 1) has the following benefits:
- Adjustable and central energy density.
- No contact with the welded workpiece.
- High welding effectiveness.
- Narrow joint and high strength after welding.
It is actively used in equipment manufacturing fields such as automobiles, ships, aerospace, and continues to broaden to more product processing terminal fields.
The world’s major manufacturing nations have successively proposed national techniques for updating and upgrading their production industries to respond much better to future manufacturing competitors.
The more popular ones are the German Industrial Manufacturing 4.0 and the American Industrial Web, which actively presented brand-new policies for updating the production market, encouraging technological innovation in the manufacturing market, and providing crucial financing.
Amongst them, laser welding has brought in much attention as a vital part of high-end equipment innovation.
According to the real welding needs, laser welding has proposed different brand-new technologies by solving practical problems. For example, Teacher W. Steen of Imperial College London proposed the idea of laser-arc hybrid welding.
The advancement of laser-arc hybrid welding innovation has offset the imperfections of single laser welding and expanded the application variety of laser welding.
The interaction between the arc and the laser puts in the advantages of both, decreases the requirements for the size of the welding gap, minimizes the cracks and pores that appear during welding, and improves the efficiency of the welding part.
Up until now, laser welding innovation has become numerous types, such as:
- Heat conduction laser welding.
- Laser deep penetration welding.
- Laser wire filler welding.
- Laser-arc hybrid welding.
- Remote laser scanning welding.
- Laser brazing.
Intermediate process control such as laser welding seam tracking and high-speed camera real-time tracking of the joint welding process and laser welding problem processing has been established to jointly solve the related limitations and deficiencies of laser welding.
Research Development In The House And Abroad
Recently, domestic and foreign research groups have continuously checked out and studied the most suitable process specifications from the perspective of laser motion and heat source combination and improved the innovation of numerous laser welding approaches, including laser deep penetration welding and laser-arc hybrid welding.
The research of laser welding is about appearance and investigating the process attributes of welding through modern characterization methods such as high-speed electronic cameras and spectral analysis, attempting to check out the development system of weld problems.
On the other hand, the internal changes of laser welding are more made complex.
Each research study group attempted to use external energy such as magnetic field, multi-arc and electric field in the laser welding procedure, concentrating on improving weld problems, mechanical properties, and welding quality.
1. Research Study On Laser Welding Innovation
Laser welding can acquire top-quality joint strength and a big depth ratio.
Compared to conventional welding technology, it has a bigger power density, has a better welding effect on hard products, and bonds products with various properties.
Foreign and domestic scholars have carried out a lot of research on it.
The research on laser technology in China generally focuses on the welding speed, laser power, defocusing quantity, laser pulse waveform and protecting gas flow, and other parameters of each welding process, and further the mechanical residential or commercial properties, structure evolution, and regulation of welded joints. In-depth research.
Laser pressure welding is a unique laser welding technology.
This innovation integrates laser-induced heating with traditional flat seam welding.
The working principle of laser pressure welding is: the workpiece to be bonded partly melted with a laser beam and after that rolled under high pressure to produce a bonded joint.
Because the melting zone is relatively narrow, welding flaws such as shrinking and gas cavities are avoided, and this technology can also be utilized to connect thin plates.
The research study team studied the development of the structure during laser pressure welding of pure aluminum, as displayed in Figure 2.
The team studied the basic elements of microstructure evolution during pure aluminum welding.
Through extensive analysis of the specimen’s microstructure during the laser pressure welding procedure, it is presumed that the solidification procedure began before the rolling, so the freshly crystallized material experienced plastic pressure.
Laser-arc hybrid welding (see Figure 3), as a promising processing method in the 21st century, has been deeply studied by many scholars.
The researcher studied the welding procedure of 50CrV/SPHE dissimilar steel by adjusting the procedure criteria and analyzed the influence on weld formation and droplet transfer.
The research results program that the laser power remains in the series of 2800 ～ 3400W, the welding wire is heated consistently, and the welding process is stable.
Combine oscillating scanning with laser-arc hybrid welding to offset the defects of the weld.
Weld aluminum alloy materials with horizontal, vertical, and circular oscillation scanning methods and use high-speed electronic cameras and spectroscopy to evaluate the changes of the beads.
The outcomes show that the enhanced criterion range of the circular scanning method is much bigger than that of the horizontal and vertical instructions. It can promote the interaction with the plasma to form beads with a smaller sized diameter, which is beneficial to grain improvement.
The energy of plasma arc is more concentrated in contrast, and it is found that laser-plasma arc welding has excellent adaptability to spaces and incorrect edges in flat welding.
Research on welding technology abroad has focused on improving welding conditions and presenting external energy.
To explore the potential of this procedure to link big, safety-critical nuclear components, such as steam generators or pressurized water reactors (PWR) boosters.
Using vacuum laser welding technology, at a speed of 150mm/min, using a 16kW laser to produce 80mm thick welds of SA5083 grade steel in 2 weld passes.
And presented the benefits of vacuum laser welding and compared it with electron beam welding in procedure physics.
It is concluded that vacuum laser welding deserves further development since it offers essential expected future atomic energy building and construction plans.
Bunaziv I et al. thought about the cold metal transfer pulse (CMT+P) arc mode while utilizing fiber laser-MAG hybrid welding. They used metal-cored wire to weld 45mm thick high-strength steel (butt double-sided welding), and compared different pulses. The impact of the technique and the front and rear pilot arc on the weld.
Compared to conventional pulse arc welding, it is found that both can provide high-quality welding.
But CMT+P mode can provide more steady droplet transfer within a restricted series of feed speeds.
2. Laser Welding Process Control
Laser welding technology is a kind of welding technology that does not require contact. It has a faster speed and higher welding performance. The intermediate procedure treatment plays a crucial role in the efficiency of the bonded joint.
The domestic laser welding procedure control (see Figure 4) primarily focuses on monitoring the welding process with the assistance of optical gadgets, such as laser welding seam tracking and high-speed electronic cameras to keep track of the weld joint in real time.
For example, through a high-speed electronic camera monitoring system, real-time online monitoring of the formation procedure of pores and splashes of laser welding DP780 galvanized high-strength steel, and the escape path of pores was studied from the perspective of dynamics.
The laser welding head is incorporated with the CCD video tracking module, and a method of automatic welding seam detection using a line laser is proposed.
This technique utilizes laser triangulation to acquire shape information such as the height and width of the weld.
The principle of straight-line laser detection is displayed in Figure 5.
Throughout laser welding, a straight-line laser beam hits the welding joint vertically. The image is imaged on the CCD image airplane by the scattered reflection of the upper surface of the workpiece to be welded.
Each weld feature point on the image plane will distinctively determine a point on the surface of the workpiece to be bonded.
In terms of tracking algorithm, a fast-speed and high-precision nuclear-related filter target tracking algorithm are utilized to track the positions of typical straight and curved welds, respectively.
The error between the data fitting curve and the weld shape acquired in the experiment is within 5%, the arrangement is high, and the real-time tracking impact is good.
Foreign research study generally carried out comprehensive research on including external energy in the welding procedure and using expert system models to replicate and anticipate welding.
Utilizing extra specifications, oscillation frequency, and amplitude, integrated with the spatial power modulation approach of direct feed with superimposed circular movement, the welding of copper materials used in the interconnection of lithium-ion batteries, and high-power electronic devices has been studied.
The results show that not just can the connection area be increased, but likewise, the stability of the laser welding procedure and the quality attributes of the weld can be increased.
When welding some special metals, the solder can not be fully blended in the molten swimming pool, leading to the uneven circulation of aspects in the weld.
Based on this research, the oscillating electromagnetic field is utilized to form a non-conservative Lorentz force part in the molten pool to enhance the aspect distribution throughout the density of the material.
Spectroscopy (EDS) evaluated the circulation of the two tracking elements (Ni, Cr) was evaluated by spectroscopy (EDS). The results revealed that the solder circulation was essentially enhanced when the magnetic field was rotated 30 ° to the welding instructions.
This research study provides data support for making use of magnetic fields in welding.
Belitzki proposed an approach that can minimize the deformation of the complex frame structure with several welds. The meta-model established by the artificial neural network is applied to the laser welding process to predict the city based on the welding criteria in the sub-area. Warped.
The genetic algorithm is utilized to effectively find the welding specifications appropriate for the international structure.
The results show that the technique can effectively and dependably identify the least distortion parameter among more than 1 billion potential criterion combinations.
3. Laser Welding Problem Treatment
The application of laser welding is really broad, but the welding process is frequently accompanied by welding defects such as fractures, welding pores, and spatter.
A great deal of research study has been done on it at home and abroad. They use oscillation, pulse, and other approaches to combine with laser welding.
While studying the principle, it also attaches value to incorporating industrial devices, actively utilizing new items to promote its research study, and its research has high usefulness.
Domestic research is primarily concentrated on how to resolve the welding joint problems of laser welding, and the development mechanism of welding defects has also been studied in information.
Numerous research teams utilize simulation analysis, scanning electron microscopy, and other techniques to study molten swimming pool splash and Fresnel absorption impact.
The high-power laser is irradiated on the work surface to quickly vaporize the product and produce a keyhole. The Fresnel absorption impact of the molten pool and the keyhole figure out the welding quality.
Welding flaws are produced throughout the laser welding procedure. Figure 6 reveals the porosity problems triggered by laser welding of galvanized DP780 high-strength steel.
Research study on the keyhole and Fresnel absorption of laser deep penetration welding discovered that the several reflections of the laser in the keyhole triggered the overall power density of Fresnel absorption to be unequal, and the density near the bottom of the keyhole was higher than the upper hole. And the essential element affecting the density circulation is the reflection of the laser.
The single-focus laser welding technique still has certain restrictions.
For example, the temperature cycle throughout welding can not be controlled, and when welding products with a high thermal level of sensitivity, cracks are vulnerable to appear inside the weld.
To stabilize the welding process, lots of scholars have studied dual-focus laser welding.
Some scholars have studied the stability of the keyhole and the circulation in the molten pool of aluminum alloys in the serial arrangement of the laser double focus.
It established a coupling design for the welding transient molten swimming pool and the internal circulation of the molten swimming pool for dual-focus laser welding of aluminum alloy. It used the ray-tracing method to establish the heat source model, considering the Fresnel absorption impact, steam recoil force, and internal flow of the molten pool influences.
Research study results program that dual-focus laser welding is more steady and manageable, and the fluctuation of the keyhole is considerably weaker than that of single laser welding.
Compared with foreign countries, domestic research focuses on the modification of the laser beam’s beam morphology. Most of them concentrate on the research of laser welding flaws by changing the number of laser beams.
Foreign research teams attempted to use new optical elements to explore the formation system of keyhole collapse and molten swimming pool splash.
Some foreign scholars have likewise attempted new techniques to enhance the shortages of laser welding, such as beam oscillation or laser power modulation, to minimize problems.
Utilized a recently established multifocal beam shaping optical component.
This component can produce a multi-beam laser in the axial instructions, which can modify the energy input in the keyhole in the extra location to describe the system of spatter development and evaluate the capacity of axial beamforming to suppress defects during laser deep penetration welding.
The results show that the variety of splashes can be effectively decreased under high-intensity light irradiation. The keyhole collapse is prevented, the upper keyhole area has sufficient energy input, and the liquid splash can be decreased.
Application Status Of Laser Welding
After years of research and advancement, laser welding technology has been used in equipment production industries such as cars, oil and gas pipelines, and tram equipment.
This short article primarily presents the application of the core parts of the laser welding system and its engineering application in product processing.
1. The Core Components Of The Laser Welding System
1.1 Laser generator
In the laser welding system, the core element is the laser generator used to create laser light.
There are many kinds of lasers. However, their structure is the same. They are made up of three parts: excitation system, laser active medium, an optical resonant cavity.
After years of development, the performance of lasers has been significantly improved.
There are numerous kinds of lasers, such as fiber lasers, semiconductor lasers, CO2 lasers, etc., as displayed in Figure 7.
Foreign outstanding laser companies consist of Coherent, Trumpf, and so on, whose lasers have inherent advantages.
After years of research and advancement and improvement, its beam quality is high, the photoelectric conversion performance is high, and stability is great.
The spot of a semiconductor laser is more focused than that of a fiber laser, the power distribution is more consistent, and the energy consumption is lower.
For example, the TruDiode series of high-efficiency semiconductor lasers have won the favor of users with the best application outcomes, incredibly low investment expenses, and operating expenses.
The laser offers steady laser power of up to several kilowatts.
Typical applications are deep penetration welding, heat conduction welding, laser metal cladding, brazing, and plastic welding, with a high performance of up to 40% to lower production operating costs.
Considering that there is no need for an additional resonant cavity structure, the TruDiode laser is extremely delicate.
CO2 lasers prevail with gas lasers, which can use the energy level structure of CO2 particles to acquire the spectral output of different wavelength bands.
It transcends to solid-state lasers in thermal efficiency, can build up a big amount of heat depending on gas circulation, and is ideal for use as high-power lasers.
The advancement of domestic lasers has the benefit of backward movement. After years of technical research study, many exceptional laser businesses have emerged in China, such as Raycus Laser, Chuangxin Laser, and other impressive domestic laser brands.
With excellent laser products, economic costs, and product localization strategy, it rapidly acquired a large domestic laser market share.
Figure 7b reveals the quasi-continuous fiber laser produced by Raycus. Its power is small, covering 75 ~ 300W, with much better compatibility, greater electro-optical conversion effectiveness, better beam quality, and less upkeep cost. Suitable for commercial applications needing long pulse width and high peak values such as laser area welding and laser seam welding.
1.2 Laser welding head
With the development of laser welding technology, laser welding heads have also presented various kinds of laser welding heads according to their needs and functions, as displayed in Figure 8.
From delegated right, welding head, laser galvanometer scanning head, welding swing head double area & beam shaping head, which can stand up to approximately 50kW power.
According to the real welding requirements, the welding head is developed and applied to the actual welding processing place, which offers services for various welding requirements.
The laser requires to split numerous beams to enhance welding performance. At this time, using a scanning galvanometer welding head can effectively solve the requirement of high efficiency.
As shown in Figure 8, the swing welding joint can effectively enhance the internal and look quality of the weld and enhance the weldability of products vulnerable to problems.
2. Engineering Application Of Laser Welding Innovation
From the start, laser welding has been applied in automobile (see Figure 9) production and other fields and has slowly broadened to shipbuilding, aerospace, semiconductor, electronic industries, and consumer products, from standard fields to more diverse and thorough product processing terminal applications.
In the car manufacturing procedure, laser welding innovation is generally utilized to tailor the welding of body plates with different thicknesses, body welding, and welding of auto parts.
Through using laser welding technology, the weight of the car body can be decreased. The result of energy-saving and emission decrease can be attained, the marking and assembly costs in the vehicle production process can be reduced, the assembly accuracy of the vehicle body, the rigidness of the cars and truck body, and the degree of integration of the vehicle body can be enhanced, thereby enhancing the automobile The convenience and security.
Laser welding is extensively utilized in the automotive industry.
Figure 9b reveals the workshop of a domestic car parts business. Its automobile door is laser brazed and bonded. It uses a bigger laser area (2 ~ 4mm), the laser power is 2 ~ 4kW, and the contact tracking is utilized to check the edge nodes. After calibration, it was discovered that the weld seam was narrower than other welding techniques, which efficiently improved the general appearance of the car body.
After testing, it is concluded that compared with regular welding, its strength has been greatly enhanced.
Laser welding needs to pick the matching shielding gas according to the nature of the actual connection product. The laser welding speed is much faster, the welding effectiveness is higher, the working location is little, and the contortion of the processed workpiece is small.
In many cases, heat treatment to remove residual tension is not required. Using laser welding technology in mechanical manufacturing can significantly improve the quality of bonded products and improve the work efficiency of the production market.
Laser welding technology fulfills the requirements of high cleanliness in the production process of medical gadgets. There is no need to add any adhesive during the welding process, and practically no welding slag and debris is created. Therefore, the emergence of laser welding technology has considerably promoted the development of medical gadgets.
There is a big distinction between the plates used in ships and the plate choice of regular mechanical items. Making use of laser welding technology can efficiently fix longer weld joints and warpage of ship plates.
The engineering application coverage of laser welding process processing is relatively broad. It can be used for welding joint positioning, cross-sectional scanning, and online monitoring of surface area formation.
Figure 10 shows the brand-new welding whole-process tracking system LDD-700 based upon coherent interference imaging technology. Its 3D imaging mode makes it possible for LDD-700 to adapt to the changes in keyhole geometry of different procedures, which is a fundamental ability for accurate depth measurement.
Powerful software supports tailored keeping an eye on options to meet different procedure requirements.
Laser welding is likewise widely used in the connection of petroleum pipelines.
Using robot laser welding can improve welding efficiency and dependability and improve the quality of bonded joints.
As an advanced high-energy beam welding technology, laser welding has the attributes of no need for a vacuum environment, focused heat input, little thermal deformation, the big aspect ratio of the weld, high accuracy, and easy awareness of automated welding. It was finally figured out as the most ideal for CC. The finest way to seal the coil box.
Summary and Outlook
Laser welding has obtained great development from the research and engineering application of procedure processing, welding procedure treatment, and welding defect resolution.
From the current research study and engineering practice, domestic and foreign scholars generally deepen the research of laser welding and fix commercial application issues from the following two elements.
Based on actual industrial needs, study the causes of defects in the laser welding process and constantly improve and optimize the processing parameters to improve or remove laser welding defects.
Second, try to combine external energy such as magnetic field and oscillation with laser energy to check out new processing techniques to enhance welding stability, resolve laser welding problems, and improve the efficiency of welded joints.
From the preliminary heat conduction laser welding to the present multi-field coupling laser welding research study, laser welding has constantly broadened the application field of laser.
Laser equipment. Laser development is also constantly being brought out. For instance, semiconductor lasers have improved their photoelectric conversion efficiency, with lower energy intake and more focused light areas, which have gradually become the advancement pattern of new lasers. Scholars at the house and abroad are also continuously studying new ones.
With the constant breakthrough and development of brand-new laser devices, it is foreseeable that soon, the application fields of laser welding innovation will continue to be applied to more material processing terminal fields, helping the commercial upgrading of manufacturing.
Laser welding innovation is a kind of welding technology that does not need contact. The meta-model established by the synthetic neural network is used in the laser welding procedure to anticipate the regional area based on the welding parameters in the sub-area. Perfect for commercial applications needing long pulse width and high peak worths, such as laser area welding and laser joint welding.
There is no requirement to include any adhesive throughout the welding process, and almost no welding slag and particles are generated. As a sophisticated high-energy beam welding technology, laser welding has the characteristics of no requirement for a vacuum environment, focused heat input, small thermal contortion, the big element ratio of the weld, high precision, and easy realization of automatic welding.
