Lasline – gases forlaser welding andbrazing ,Expertise that gets right to the point

One of the keys to the optimal application oflaser technology is the selection of the operatingand process gases. With the Lasline® productline, Messer provides all of the gases and gasmixtures you need in order to successfullyprocess materials using lasers. 

Flexibility for many applicationsThrough its special characteristics, laser weldingperforms welding tasks like no other process. Itsmost distinctive feature is the highly concentra-ted heat input.Laser welding ensures:

• high welding speed• narrow HAZ• low heat input into the component• low distortion

And the types of joints are also somewhatspecial as compared with other weldingprocesses: the laser is capable of penetratingstraight through a component. This makes itpossible to weld in areas that would otherwisebe inaccessible. The automotive industry, inparticular, takes full advantage of this – on carbodies, where weld points are often very wellhidden, for example. In addition, the laseraddresses the need for high welding speeds andlow distortion. And laser welding is also ideallysuited for medical technology and micro-electronics.

Remote weldingRemote welding is used to weld complexcomponents from distances of up to two metresaway, for example. The principal advantage of theprocess is the very rapid positioning of the laserbeam. It is carried out by means of multi-axisadjustable mirrors from a central unit. Additionaladvantages of this approach include time savingsand elimination of the need for sophisticatedmechanical assemblies for beam guidance.

Increasing demands on productivity, cost-effectiveness and quality require new solutions.One such solution – laser technology – hasbecome indispensable in many areas ofproduction, research and medicine. The numberof applications and process technology solutionshere is growing continuously. The use of lasersto process materials offers a whole range ofadvantages over conventional processingtechniques: high product flexibility, excellentquality and reliability, and low unit costs.

Gear wheel/shaft connection, CO2 slab laser

Fuel filter made of aluminum, CO2 slab laser

Laser soldering, automobile body

Laserwelding-compatible designs

Laser technology – high-tech that has made its mark

The requirements of laser beams vary just aswidely as the range of processes and applicationsthat make use of them as a tool. Suppliers oflaser equipment respond to those requirementswith different configurations and power classes.Most systems can be classified into one of threemain groups: CO2 lasers, diode lasers and solid-state lasers – depending on the medium inwhich the laser light is generated.

CO2 lasers – the dominant solutionThe most commonly used type of laser by far isthe CO2 laser. The laser beam is generally produ-ced using a three-component gas consisting ofhelium, nitrogen and the component that givesthe system its name, CO2. The wavelength of theCO2 laser light is 10.6 µm and invisible to thehuman eye. Mirrors and lenses are used to directand shape it. One of the special configurationsused is the particularly efficient, diffusion-cooledCO2 laser.

Depending on the equipment configuration,either the laser gas is produced from the threecomponents in an internal mixer or else a pre-mixed product is used. The better reproducibilityof the latter approach has made it the preferredoption. The Lasline® product range offers asuitable selection here.

Solid-state lasers – rod, disk or fibre?For their laser-active medium, solid-state lasersuse synthetic YAG crystals (YAG = yttrium-aluminium-garnet). Besides the rod configurationwhich has been in use for a long time already,the disk configuration is also now starting to beused.

The laser beam is generated without the need foroperating gases. Process gases such as shieldinggases have a significant effect on the weldingprocess. Due to the short wavelength of just 1.06µm, the laser light can be transmitted throughfibre optic cables. This makes it easier toimplement automation solutions using articulatedrobots, for example. Fibre lasers that haverecently been expanded into the kilowatt rangehave a significantly smaller beam diameter thanCO2 or Nd:YAG lasers. This permits them toachieve greater precision when cutting materials.Fibre lasers are also the perfect solution for micro-welding operations. When processing a materialwith a fibre laser, the heat input is very low.That’s why it is preferred for welding with ahigher power beam.Diode lasers – the economical alternative

This type of laser is based on high-power diodes.The diode laser achieves its high power outputthrough the arrangement of many electroniccomponents in a block. Due to theircomparatively poor beamquality, high-performancediode lasers are lesssuitable for cutting –but they are perfectlyacceptable for welding,brazing or hardeningapplications.

Carbon dioxide 4.5Nitrogen 5.0

Helium 4.6

orPre-mix

(Laser gas mixture)

CO2 laser

Laser resonator

Diode laser Fibre laser

Rod laser

Individual diodesDiodepackages

Laser beam

Laser beam

EnergyLaser gasmixing unit

Laser gas

Fibres

Laser rod Laser beam

Disk laser

Diodepackages

Nd:YVO4

disk

Diode

Laser beam

Types of lasers – no universal solution

As has already been the case in cuttingtechnology, the use of lasers is also becomingincreasingly prevalent in welding and brazingapplications. Four variants are possible: heatconduction welding, deep penetration welding,

laser brazing and hybrid welding. The weldingprocess can be carried out with or without fillermaterial. It is also possible to weld dissimilartypes of metals and alloys, such as aluminum/steel or black/white.

Melt

Welding depth

Plasma cloud

Melt

Vapour channel

Weldingdepth

Heat conduction weldingHeat conduction welding does not require high power levels.The energy of the laser is converted to heat at the surface ofthe component, so that a melt pool forms, which passesalong the heat energy through convection. As with arcwelding, this convection can be influenced by shielding gasesand the penetration profile can be adapted to the specificwelding requirements.

Deep penetration weldingDeep penetration welding requires higher power levels, asthe metal is not merely melted but also vaporised. In thisway, the laser penetrates deep into the workpiece and formsa so-called “keyhole”. A column of plasma is created in thiskeyhole, which absorbs the energy of the laser and transfersit to the material. The result is a continuous welding process.The plasma cloud emerging from the vapour channel has tobe blown away with a shielding gas, otherwise it wouldabsorb the laser energy and disable it from contributing to thewelding process.

Laser brazingLaser brazing is similar to heat conduction welding. Theenergy required by the solder here must be taken intoconsideration. Laser brazing is now widely used, particularlyin the automotive industry. Along with advantages such aslow heat input and distortion, the corrosion resistance of thesolder and the easier processability are also major factorshere. The reliability of joints and long service life also makelaser brazing a good alternative.

Hybrid weldingThe hybrid process is a combination of multiple methods. Inthe case of laser welding, the combination with MAG weldingis especially useful. This pairing combines the cost-effectiveness of laser welding with the high deposition rateof the MAG process and is suitable for use on thicker platesand sheets.

Laser welding and soldering – four efficient options

Gases are needed at several points in theprocess. Depending on the system, they performthe following functions:

Gases used as operating gases to generatethe laser beam (CO2 laser)

•

Cross jet•Purge gas•Shielding gas•

Laser (operating and) process gasesLaser or operating gases are required in order tooperate the resonator. Process gases are fed intothe laser beam in the workspace, e.g.as shielding gas or cutting gas. The purity, qualityand mixing consistency of the operating gasesfor CO2 lasers are subject to the higheststandards – and for good reason:

Even traces of moisture or hydrocarbons canimpair operation.

•

Hydrocarbons can damage sensitive andexpensive optical components.

•

Moisture disturbs the excitation discharge anddisables the laser from achieving its fullefficiency.

•

The formation of acid molecules can lead tocorrosion damage.

•

Dust particles can scatter the laser light,thereby disrupting the process.

•

For perfect laser operation, therefore, it isabsolutely essential that the gases used areextremely pure and free of disruptive contami-nants. These gases are either supplied in pre-mixed form or their separate components aremixed in the laser unit. And the gas supplysystem must also satisfy the purity requirementsas well.

Shielding gasesIn welding, the shielding gas performs severalfunctions. One of the main roles is to protect thehot material, as contact with the atmosphere cancause surfaces to absorb nitrogen or moisture orto oxidize.

Totally reflectingmirror

Partially reflecting mirror

Deflecting mirror

Energy

Gases and gas supply – reliable and application-based

Laser gas(CO2 N2 He)

Focusing lens

Laser welding: principle of operation

Shielding gas Feed direction

cross jet

Purge gas(N2)

Laser beam

Gases and gas supply – reliable and application-based

Laser beam

Shielding gasnozzle

Shielding gas

Component

Lens

Weld

Welding without shielding gasParticularly in applications using solid-state lasers,welding is often performed without shielding gas.It creates a welded joint with a correctappearance – but that alone is not the decidingfactor. Without shielding gas, the weld metal canabsorb nitrogen, oxygen and moisture, which caneventually lead to pore formation and hydrogencracking. Especially in plain and low-alloy steels,nitrogen causes premature ageing andembrittlement. In most cases, the effectsbecome visible only after the component hasbeen subjected to the relevant stresses forseveral years.

Gas injection and shielding gas supplyWhen applying gas to the weld or solder point,laminar flow is a prerequisite for proper shieldinggas coverage. High shielding gas velocity causesturbulence which entrains atmospheric air withthe gas flow.

Shielding gas supply in laser welding: coaxial or lateral

The shielding gas also continuously removes theplasma cloud over the workpiece. The addition ofCO2, oxygen, helium, nitrogen or hydrogen makesit possible to affect the welding process thermallyor metallurgically.

Originally, pure helium was used for welding.Today the shielding gases used in laser weldingtend to be more like those used in gas metal arcwelding. The reasons for this are different lasersources with different wave lengths, as wellas the metallurgical effect of CO2 and oxygen, thethermal effect of helium and hydrogen and thecost-reducing effect of argon. This led to the useof typical gas mixture combinations such asargon/helium, argon/oxygen and argon/hydrogen.Messer has developed its own product rangeunder the name Lasline®. It is based on extensivewelding tests and reflects both experience in themarket and the results of research anddevelopment work.

Material Products

Un- and low-alloyed steels Lasline X4

High-alloyed, austenitic steels Lasline H7

Duplex steels Lasline He30 X1Lasline He68 H2

Aluminum and its alloys Lasline He70 N

Un- and low-alloyed steels Lasline He50

Different shielding gas mixtures also affect thelaser beam. Different nozzle arrangements canbe used to provide shielding gas coverage inlaser beam welding: coaxial, lateral or peripheraland annular nozzles.

In coaxial shielding gas supply, the entire beamarea between the nozzle outlet and the lens isblanketed with shielding gas. In this case, aplasma column can cause damage. The lateralsupply of shielding gases often forms an injectorwhich causes air to be drawn into the weldingarea. As a result, the welding process takes placeunder a shielding gas/air mixture, which leads topores, annealing colors and other weldingdefects. With annular nozzles, it is helpful to usean additional assist gas for purging (e.g. nitrogen).This prevents the shielding gas from reaching thelaser optics. The annular nozzle ensures that themelt pool is uniformly covered by shielding gas.

Gas supplyDepending on the quantity needed and on theintended use, Messer offers various supplyconcepts which have proven themselves inpractice. Smaller quantities such as in the supplyof laser gases (operating gases) are handled withgas cylinders. Individual 10-litre or 50-litrecylinders are most commonly used. For welding,all shielding gases and gas mixtures can besupplied in separate cylinders or in bundles.

For the supply lines in the fixed part of theequipment, pipes made of copper or CrNi steelare ideal. Hoses always carry the risk thatnitrogen, oxygen and especially moisture willdiffuse into them. The use of special materialscan minimise this problem.

Safety – without compromiseEquipment used in the laser processing ofmaterials requires consideration of severalspecial work safety aspects which are typical oflasers-based processes. First and foremost, thereis the laser beam itself: its potential risks differdepending on the type of laser, and so theprotective measures also differ accordingly.Moreover, emissions generated during weldingor cutting must be appropriately extracted andfiltered. For the safe use of laser systems andtheir peripheral equipment, the applicableguidelines and regulations have to be followed.

2.5 = 99,5 %

3.5 = 99,95 %

4.6 = 99,996 %

5.0 = 99,9990 %

InstallationFor optimal gas supply, gases have to betransported to their destination without becomingcontaminated. This requires proper installation ofthe hardware, appropriate selection of gas fittingsand a need-based supply of gases in the purityneeded. The installation of a particle filterprovides additional security. The supply of gas tothe resonator also demands extremely highpurity, both in the resonator gases themselvesand also for the pipes and hoses used as supplylines.

The degree of purity of the gases is indicated inpercent – a figure given to several decimalplaces. In order to simplify labelling, aninternational index system has been established.The indices consist of a digit, a point and asecond digit. The first digit indicates the numberof nines, and the digit to the right of the pointrepresents the last digit of the complete value.Example:

Technical centres – sources for innovationFor the development of new technologies in thefield of welding and cutting, Messer operatestechnical centres in Germany, Switzerland,Hungary and China. These facilities provide idealconditions for innovative projects as well ascustomer presentations and training courses.

Portfolio of gases – comprehensive and clearMesser offers a spectrum of gases that extendswell beyond the standard fare: it ranges from justthe right gas for each application, and clear,application-oriented product designations to thecontinuous introduction of new gas mixturesdesigned to address current trends.

Specialised on-site consulting – right whereyou need itSpecifically in the context of your particularapplication, we can show you how to optimisethe efficiency and quality of your processes.Along with process development, we supportyou with troubleshooting and processdevelopment.

Cost analyses – fast and efficientWe will be glad to analyze your existingprocesses, develop optimisation proposals,

Good for you and the environmentThis brochure not only contains interesting information – it is also kind to the environmentas it is printed on 100% recycled paper. We would kindly ask you to dispose of any brochuresthat you have “finished reading” or no longer require as waste paper for recycling.

© Messer Group GmbH

Messer Group GmbHGahlingspfad 31

47803 KrefeldTel. +49 2151 7811-0

Fax +49 2151 7811-503welding-technology@messergroup.com

www.messergroup.com

support process modifications and compare theresults with the original conditions – becauseyour success is also our success.

Training courses – always up to dateFor the optimal handling of our gases, we cantrain you on processes and how to use them.Our training courses illustrate the use of variousshielding gases for welding and explain how tohandle them safely. This also includes thestorage of the gases and the safe transport ofsmall quantities. Information and trainingmaterials for your plant are also part of theservice, of course.

You can also download this brochure andmany others from the Internet as a PDF file:www.messergroup.com

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