Laser Welding Technique Research Articles

A Reliable Nd:YAG Laser Welded Stainless Steel 304 for Photonics Device Packaging Application

An ultra compact pulsed Nd:YAG laser with laser beam peak power of 3.5kW and 6.5ms pulse duration is employed to produce a butt joint and lap joint for both spot and seam welding on a stainless steel 304 specimen. The strength test of the weld joints is conducted by pulling the joint materials using INSTRON Series IX/s Automated Materials Tester System. From the experimental results, it is found that a butt joint produces much stronger attachment than a lap joint. The stronger attachment is contributed by a larger volume of welded stainless steel 304 at the joint interfaces. However, the strength of a lap joint can be increased by producing a deeper weld penetration depth. It is done by controlling the laser beam parameters such as laser peak power and pulse duration. It is inferred that the commercial welding material, InvarTM, provides more robust joint than stainless steel 304. It is also concluded that the welded stainless steel 304 cannot attain the strength and elastic modulus of the stainless steel 304 itself. However, the stainless steel 304 is a good welding material for photonics device packaging by using pulsed Nd:YAG laser welding technique.

Various laser welding techniques – test results and possible applications

Laser welding technologies are part of those production techniques which have allowed many companies to modernize their technological processes as well as to initiate production of new-generation, ...

Corneal Tissue Welding With Infrared Laser Irradiation After Clear Corneal Incision

The aim of this study was to investigate the potential of infrared lasers for corneal welding to seal corneal cuts done in an experimental animal model. Full-thickness corneal cuts on freshly enucleated bovine eyes were irradiated with infrared (809-nm diode, 980-nm diode, 1070-nm YLF, and 1980-nm Tm:YAP) lasers to get immediate laser welding. An 809-nm laser was used with the topical application of indocyanine green to enhance the photothermal interaction at the weld site. In total, 60 bovine eyes were used in this study; 40 eyes were used in the first part of the study for the determination of optimal welding parameters (15 eyes were excluded because of macroscopic carbonization, opacification, or corneal shrinkage; 2 eyes were used for control), and 20 eyes were used for further investigation of more promising lasers (YLF and Tm:YAP). Laser wavelength, irradiating power, exposure time, and spot size were the dose parameters, and optimal dose for immediate closure with minimal thermal damage was estimated through histological examination of welded samples. In the first part of the study, results showed that none of the applications was satisfactory. Full-thickness success rates were 28% (2 of 7) for 809-nm and for 980-nm diode lasers and 67% (2 of 3) for 1070-nm YLF and (4 of 6) for 1980-nm Tm:YAP lasers. In the second part of the study, YLF and Tm:YAP lasers were investigated with bigger sample size. Results were not conclusive but promising again. Five corneal incisions were full-thickness welded out of 10 corneas with 1070-nm laser, and 4 corneal incisions were partially welded out of 10 corneas with 1980-nm laser in the second part of the study. Results showed that noteworthy corneal welding could be obtained with 1070-nm YLF laser and 1980-nm Tm:YAP laser wavelengths. Furthermore, in vitro and in vivo studies will shed light on the potential usage of corneal laser welding technique.

The Effect of Irradiance Level in 980-nm Diode Laser Skin Welding

Current research aimed to investigate the role of irradiance in skin laser welding. Optical and thermal responses of tissue to infrared irradiation are highly dependent on both wavelength and tissue type. The desired effect on tissue is created by proper selection of laser power, application time, and spot size. Full-thickness skin incisions on Wistar rat dorsum were welded with 980-nm diode laser application. Two irradiance levels (200 and 16.6 W/cm(2)) were applied with high (6 W, 400 ms) and low (0.5 W, 5 s) powers of laser with the same spot size (0.03 cm(2)). Subjects were monitored throughout a 21-day recovery period; incisions were sampled for histology and mechanical tests on particular control days (1, 4, 7, 14, and 21). Closure index, thermally altered areas, epidermal thickness, and granulation areas of H&E (eosin) stained samples were calculated. The breaking point during a mechanical tensile test that ran at 5-mm/min crosshead speed was recorded. In the suture group, there was no closure 24 h postoperation. For laser groups, immediate closure at the surface layers of the incisions was observed: Almost half-thickness (from surface to deep dermis) welding was achieved. Granulation tissue level and epidermal thickness level for all groups were similar on postoperative day 21. The laser welding technique was found reliable in terms of immediate and mechanically strong closure compared with suture. Low irradiance of a 980-nm laser (16.6 W/cm(2)) yielded noticeably stronger bonds at the end of 21 days of recovery, as well as minimal thermal damage.

Utilization of CO2 Laser for Temporal Fascia Graft Welding in Myringoplasty: An Experimental Study on Guinea Pigs

An experimental study was undertaken to investigate the use of a CO₂ laser welding technique in myringoplasty. Albumin solder was used to fix a temporal fascia graft via an overlay transcanal approach. The results of the operative procedure were assessed by microscopic and histopathologic examination over an interval of 1, 2, 3 and 4 weeks postoperatively. Materials and Methods: Forty-eight adult guinea pigs were divided into two groups after permanent perforation of the tympanic membrane was created: laser-assisted myringoplasty group and surgical myringoplasty group. Laser beam power was 0.4 W, pulse duration 0.75 s, pulse interval 0.1 s and spot size 250 µm. Each experimental group was further subdivided into four subgroups of 6 animals each. Histological and microscopic findings of the tympanic membrane for both groups after 1, 2, 3, and 4 weeks were compared. Results: Microscopic examination of the tympanic membrane showed high success rate in the laser-assisted myringoplasty group compared to the control group. Histological evaluation for the tympanic membrane showed complete repair of the tympanic membrane in the laser-assisted myringoplasty group. Conclusion: Laser-assisted myringoplasty using CO₂ might be a promising new method in surgical myringoplasty.

Progress in the development of reduced activation ferritic-martensitic steels and fabrication technologies in India

The Indian reduced activation ferritic-martensitic (RAFM) steel, meeting the stringent chemical composition requirements with respect to radiologically undesirable elements as well as trace and tramp elements, has been produced by vacuum induction melting followed by vacuum are refining. Also, the optimum combination of normalising and tempering heat treatments was determined. Detailed investigations on the microstructure, including thermodynamic and kinetic features of phase transformations, and tensile, creep and ductile–brittle transition behaviour of this steel indicate that the Indian RAFM steel has the required microstructure, phase stability, creep rupture strength, elevated temperature tensile strength as well as low ductile-to-brittle transition temperature. Systematic investigations have been conducted to optimise the welding parameters to produce crack-free welds using laser and electron beam welding techniques. Salient features associated with materials development, fabrication technologies and characterization of Indian RAFM steels are highlighted.

Packing experiment of breeder pebbles into water cooled solid breeder test blanket module for ITER

This paper describes an experiment in which Li 2TiO 3 tritium breeder pebbles were packed into a full-scale breeder pebble container (BPC) mockup. The BPC mockup, part of the Japanese water cooled solid breeder (WCSB) – Test Blanket Module (TBM) project, has been successfully developed using a reduced activation ferritic/martensitic steel, F82H. The BPC mockup was fabricated using a fiber laser welding technique, selected for its high focusing capability. Membrane panels, tube plates and side walls were joined by fiber laser welding to form the BPC. Its dimensions are 74 mm × 112 mm × 990 mm. It was confirmed to be gastight under pressurized helium up to 0.5 MPa. Packing tests were performed with real breeder material Li 2TiO 3 pebbles of 1 mm diameter. X-ray tomography revealed that dense packing was uniformly achieved throughout the BPC mockup.

Increase in the Alpha to Gamma Transformation Temperature of Pure Iron upon Very Rapid Heating

In recent years, laser and electron beam welding techniques have been developed with heating rates reaching 1 million K/s, and nonequilibrium microstructures sometimes result. In the present study, the alpha (bcc) to gamma (fcc) transformation in pure iron is studied using a bank of storage batteries for heating and a high speed data acquisition system to monitor the temperature determined from a thermocouple spot welded to the specimen. Heating rates up to 300,000 K/s were obtained with the transformation temperature increasing from the equilibrium value of 1185 K (912 °C) to over 2200 K (1927 °C). The results are presented in terms of continuous heating and isothermal transformation curves.

Microstructures in a resistance spot welded high strength dual phase steel

The microstructure of a high strength dual phase steel resistance spot welded with tempering-pulse technology is characterized in this paper. In the fusion zone, there is a needle-like microstructure identified as acicular or side plate ferrite that has a cube-on-cube orientation relationship with respect to the surrounding martensite. In contrast to the microstructures produced by the lower cooling rate arc or laser welding techniques, the nucleation of this fine intragranular ferrite takes place independent of inclusions. Further, a leaf-like microstructure within the martensitic matrix is found to contain primitive orthorhombic Cr 3C 2 and face-centered cubic CrC chromium carbides, rather than Cr 23C 6 or Cr 7C 3 as is commonly observed in steel alloys. The formation histories of both the ferrite phase and the chromium carbides are analyzed.

In vivo comparison of near infrared lasers for skin welding

The skin closure abilities of near infrared lasers and suturing were compared by histological examination and mechanical tensile tests during a 21-day healing period. One-centimeter incisions on the dorsal skin of Wistar rats were treated by one of the closing techniques: (a) soldering, using an 809 nm diode laser (0.5 W, 5 s) with 25% bovine serum albumin (BSA) and 2.5 mg/ml indocyanine green (ICG); (b) direct welding with a 980 nm diode laser (0.5 W, 5 s); (c) direct welding with a 1,070 nm fiber laser (0.5 W, 5 s); (d) suturing. Six spots (79.61 J/cm(2) for each spot) were applied through the incisions. Healing was inspected on the 1st, 4th, 7th, 14th, and 21st post-operative days. The closure index (CI), thermally altered area (TAA), granulation area (GA) and epidermal thickness (ET) were determined by histological examination. Tensile tests were performed at a 5 mm/min crosshead speed up to the first opening along the incision. Immediate superficial closure with high CI values was found for the laser-irradiated incisions at the early phase of recovery. Clear welds without thermal damage were observed for the group irradiated at 1,070 nm. For the sutured group, the incisions remained unclosed for the first day, and openings through the incision were observed. At the end of the 21-day recovery period, no differences between experimental groups were observed in terms of the CI, GA and ET values. However, the tensile strength of the groups irradiated at 980 nm and 1,070 nm was found to be higher than that of the sutured incisions. The laser welding techniques were found to be reliable in terms of immediate and mechanically strong closure compared with suturing. Of them, 1,070 nm laser welding yielded noticeably stronger bonds, with minimal scarring at the end of the 21-days of recovery.

Practical Design of Lensed Fibers for Semiconductor Laser Packaging Using Laser Welding Technique

We propose a set of guidelines for the practical design of lensed fiber for the optical coupling of semiconductor lasers in butterfly packages using laser welding. These guidelines have optimized the tradeoff between coupling efficiency and alignment tolerance. Moreover, a radius of curvature of 11 mum is shown to be optimal for semiconductor lasers whose divergence angles range from 5deg to 30deg. To experimentally evaluate the design, lensed fibers were assembled by a Nd:YAG laser welding technique in conventional butterfly packages and their coupling efficiencies were 28%-72% without horizontal misalignment compensation.

Development of Remote Laser Welding Method Using Long Focal-Distance Lens for Automobile Galvannealed Steel

The purpose of this study was to develop the remote laser welding technique for galvannealed steel sheets using the pre-deforming process by laser heating and to develop in-line inspection system for remote laser welding system using visible images. It was concluded that the weldabillity of lap welding joint of galvannealed steel sheets could be improved by making the sheet gap of more than 0.04mm using the laser pre-deforming process before laser welding and moreover the quality of lap joints could be evaluated by using the proposed in-situ monitoring system.

Experimental and numerical study of static and fatigue properties of titanium alloy welded joints

Titanium and its alloys have high specific strength, good mechanical properties at high temperature, high resistance to corrosion and to attack by most acid solutions. Such characteristics make this material attractive for numerous applications because of recent improvements in welding techniques that allow to realize high quality welded joints. For example, new utilizations of titanium alloys are currently being studied in naval industry, where resistance to corrosion is a basic requirement in the choice of materials. Although fatigue strength of titanium alloys is the basic information required for designing navy structures, no official standard similar to Eurocode exists. Furthermore, data available in literature are still insufficient for reliably designing structure under fatigue loads. This paper aims to study static and fatigue behavior of butt welded joints made of titanium grade 2 and grade 5, all realized by laser welding technique. Experimental results of fatigue tests are presented both in terms of nominal stress amplitude σ a and local strain amplitude ε a. A finite element model is set on the basis of experimental results in order to assess the stress/strain concentration at the weld seam. Experimental tests show that fatigue failures in the titanium grade 2 and grade 5 specimens occur inside the base materials, but not at the weld location. Good correlation between experimental and numerical results is observed.

Determination of Optimum LASER Welding Parameters and the Development of a LASER Welding Technique to Enhance the Lateral Impact Strength of a Spacer Grid Assembly for a PWR Fuel Assembly

A spacer grid assembly, which is an interconnected array of slotted grid straps welded at the intersections to form an egg crate structure, is one of the core structural components of the nuclear fuel assemblies of a Pressurized light Water Reactor (PWR). The spacer grid assembly is structurally required to have enough buckling strength under lateral loads so that the nuclear fuel rods are maintained in a coolable geometry, and that control rods are able to be inserted. The ability of a spacer grid assembly to resist lateral loads is usually characterized in terms of its dynamic and static crush strengths. Since the crush strengths of a spacer grid assembly are known to depend on the weld qualities at the intersections of the slotted grid straps, high-tech welding methods, such as a TIG welding, LASER beam welding or Electron beam welding method, have been used recently in the nuclear fuel manufacturing fields. In this study, to meet the above requirements, two kinds of researches were carried out. First, by adjusting the LASER beam welding parameters, an optimum welding combination of the LASER beam welding parameters was obtained for welding a spacer grid assembly. Second, a new LASER beam welding technique was proposed to obtain a longer weld line and a smaller weld bead size by tilting the LASER beam. The buckling strength of the spacer grid welded by the new LASER beam welding technique was enhanced by up to 30 % when compared to that by the conventional LASER beam welding method.

Passive fit of frameworks in titanium and palladium–silver alloy submitted the laser welding

This study evaluated the precision of fit of implant frameworks cast in titanium (cp Ti) and palladium-silver alloy (Pd-Ag), made by the one-piece cast and laser welding techniques. From a metal matrix with five implants, 20 master casts were obtained, to which replicas of implants were incorporated. On these masters 10 frameworks were made for each type of material (cp Ti and Pd-Ag alloy). Half of these were made by the one-piece cast technique and the other half by the laser welding technique. The implant/prosthesis interface was analysed and measured in the vestibular and lingual regions of the central and distal implants with the help of a measuring microscope. The results indicated that in the central cylinders, the Tukey test (P<0.0005) showed a significant difference in the passive fit between the laser-welded frameworks (34.73 microm) and those one-piece cast frameworks (151.39 microm), and as regards materials, the palladium-silver alloy (66.30 microm) showed better results than the titanium (119.83 microm). In the distal cylinders there was no significant difference between the frameworks cast in titanium and palladium-silver by the one-piece technique. However, after laser welding, there was a significant difference for the frameworks cast in titanium (31.37 microm) and palladium-silver (106.59 microm).

The infrared thermography control of the laser welding of amorphous polymers

In laser welding technique, a real-time control of temperature distribution inside the irradiated materials is essential when attempting to optimize the process. For all laser welding methods that operate by the transmission principle, the difficulty of recording the developed temperature at the interface derives from the fact that materials to be welded are in contact throughout the entire process. In the present study, in order to overcome this issue, a contact-free method such the infrared thermography is used for surface temperature measurement. Corroborating this data with a numerical simulation of the temperature field evolution inside the components, an assessment of optimal process parameters is possible. The experimental investigations are made on amorphous polymers, in a typical configuration for through-transmission laser welding. The fine agreement obtained between the experimentally and calculated data, validate the infrared thermography as a non-destructive method for real-time monitoring of the welding process.

Structural investigation of Ni–Nb–Ti–Zr–Co–Cu glassy samples prepared by different welding techniques

Although, bulk metallic glasses exhibit remarkable mechanical, physical and chemical properties, their critical size (the largest size of fully glassy sample produced by casting) is limited. The utilization of a welding technique enables producing larger glassy samples. Ni 53Nb 20Ti 10Zr 8Co 6Cu 3 glassy alloy ribbon samples prepared by melt spinning of the pre-alloyed arc-melted ingots were welded by the electron-beam and fiber laser-beam welding techniques. The detailed structural investigations of the welded bead and thermally affected zone were performed by micro-area X-ray diffractometry, scanning and transmission electron microscopy. At certain optimized welding conditions the amorphous structure can be retained after melting. The obtained data are promising for future applications of the laser and electron-beam welding techniques to glassy alloys.

Application of the standard options of the FITNET procedure to the structural integrity assessment of welded specimens containing cracks

In this paper, the structural integrity of welded specimens is assessed. The specimens were welded using a conventional technique, MAG, and an unconventional one, laser technology. Welded specimens were of the central crack under tension (CCT) type. The elements were loaded, the maximum load was recorded, and the second and the third options of the FITNET procedure were utilized to estimate the critical loading. Estimated and recorded loads were compared to verify the conservatism of the estimated results. For comparison, the results obtained using Option 1 of the FITNET procedure (not recommended in the case analysed) are also presented. Results of the mechanical properties, hardness, fracture toughness for the base and the weld material and residual stress distributions are reported for both MAG and laser welding techniques. The results obtained confirm that the FITNET procedures were properly deigned. The higher the level of analysis, the smaller the conservatism of predictions observed. The overconservative conclusions, following from the lower level of analysis, suggest that the structural element is endangered, do not have to exclude it from exploitation. The higher level of analysis can, in some cases, confirm that the structural element containing a crack can still be exploited.

DIODE LASER-ASSISTED CAROTID BYPASS SURGERY

Conventional suturing methods of microvascular anastomosis are associated with various degrees of vascular wall damage that can lead to thrombosis and bypass occlusion. An experimental model of double end-to-side venous graft anastomosis on the common carotid artery was set up to compare conventional suturing methods with a low-power diode laser vascular welding technique. The experiments were performed on 40 rabbits that underwent implantation of a 15-mm segment of jugular vein on the common carotid artery. The proximal end-to-side suture was performed by eight interrupted stitches; the distal suture, which was done using a laser welding technique, was supported by four stay sutures. The animals were evaluated after 2 days (n = 15), 9 days (n = 15), and 30 days (n = 10). The vascular segments were excised and subjected to histological, immunohistochemical, and ultrastructural evaluation. The average clamping time to perform both anastomoses was 35 minutes. At the end of the follow-up period, one case of complete occlusion was observed after 9 days and one case was observed after 30 days. Surgical observations and pathological evaluation indicated that adoption of the laser welding technique reduced operative time and bleeding. Histologically, a reduction of thrombosis, inflammation, myointimal hyperplasia, and dystrophic calcification was observed in laser-assisted anastomoses. A better preservation of the endothelium was also evident in laser-treated anastomoses. The observed differences were deemed statistically significant (P < 0.05). Our study demonstrated the efficacy of diode laser welding in improving surgical techniques of high-flow bypass and in reducing the vascular wall damage observed with conventional methods.

Clinical observation on treatment of gastric cancer with Zhijing Granules: a report of 148 cases

This study was intended to design a kind of resisting part dint of device in order to preventing the base plate break while being subjected to the dint when partial base plate dint concentrates because of the increase of the magnetic attachment to the original movable artificial teeth.Ten patients who should increase magnetic attachment was adopted in the study, and we increased a kind of new designed partial cast base plate on the original base plate using laser welding technique, then designed magnetic attachment and artificial teeth.None of ten sufferers appeared the phenomenon of the break of the base plate.The application of the laser welding technique can prevent the break of the base plate when partial dint increase because of the increase of the magnetic attachments.