“keyhole” phenomenon and its aplicability for welding with laser of the diamond segments/parts
DESCRIPTION
“KEYHOLE” PHENOMENON AND ITS APLICABILITY FOR WELDING WITH LASER OF THE DIAMOND SEGMENTS/PARTS. Ing. Cristina Marinescu Dr.ing. Paul Beca INCDMF- Bucharest, Romania Dr. Ing. Ioan Farcas INFLPR – Bucharest, Romania. Introduction. - PowerPoint PPT PresentationTRANSCRIPT
Ing. Cristina MarinescuDr.ing. Paul Beca
INCDMF- Bucharest, Romania
Dr. Ing. Ioan FarcasINFLPR – Bucharest, Romania
Introduction
presents the “keyhole” phenomenon applied to welding with high power laser of the diamonded segments on the disks surface
with the apparition of the high power lasers were realized studies on “keyhole” – deep laser welding, characterized by narrow and deep fusion, limited by parallel surfaces
Deep laser weldingelectromagnetic radiation absorption study of the polarization status dependency in the case of
oblique incidence and of the incidence angle
Absorption variation with the incidence angle
Deep laser weldingWhen the laser fascicle touches the surface of the part, a part of it is
reflected and another one is absorbedThe absorbed power is transformed in heat: photons from the laser
fascicle excite the electrons from the metal superficial layers on the superior energy levels
The excited electrons come back to the initial status providing energy to the metal atomic net as heat
This phenomenon is produced in an interval of about 10-12 sThe fascicle absorption in the part material is made according to Beer
law I(z) = I0 e-αz α is the absorption factor The absorption length in the material is defined as the distance
towards which the intensity is reduced with a factor of 1/e the absorption length is very small and the laser fascicle is absorbed and transformed in heat in a very thin layer at the surface of the very surface
Deep laser weldingThe balance between the absorbed power and the incident
power is named coupling factor and is expressed in percentagesIt depends of physical parameters such as: complex
permittivity, electric resistance and the refraction index and by other parameters with practical value, such as: the nature of the part material and the level of the surface finish; the laser fascicle wave length; the part temperature depending on the fascicle power and its intensity
In the welding with laser processes not all the incidental intensity I will be coupled within the processed part but only the fraction I0 = AI, determines the absorption A
Characteristics of the welding with laser
high energy density – keyhole weldinghigh processing speedrapid switch on/offwelding at atmosphere pressure X rays are not generatedwithout additional materialnarrow weldingreduced influenced thermal ariavery precise weldinggood profile of the welding marginthe fascicle is mot moving in the magnetic fieldsmall contamination or not contaminated small loose of volatile parts sometimes can be welded “not welded” materials
Experiments
Macro laser Centre having the ROFIN SINAR RS 2000 equipment and needed to adapt the parts modules in order to achieve the optimal values of the process parameters
ROFIN SINAR RS 2000 have been made tests for welding the diamonded parts on disks made by steel for constructions
As a result of this tests were necessary adjustments, constructive and functional modifications of the substances entering in the MACROLASER Center structure
ExperimentsLaser fascicle supplying system – emits a high quality laser
fascicle (spot) previously adjusted for the following parameters:absorbed power P- 17600 W argon flow – 6l/mindisc rotation 4,17 rot/min
for the mentioned parameters have been obtained at present the welding belt according to requests
LASER FASCICLE TRANSPORT SYSTEM - realizes the laser fascicle orientation from the laser source being improved to:cables/wires for transport was realized by aluminum bar, telescopic
fixed realizing the horizontal and vertical transport of the laser fascicle,parts for laser fascicle defluxion – changes the laser fascicle direction
by the help of deflectors, supporting frame
ExperimentsACTIVE SYSTEM FOR PROCESSING – realizes the laser fascicle
motion over the processed materials Head for fascicle focalization – drives the fascicle in the active aria and
passes it through the fascicle concentrate mirrors.MODULE FOR FASCICLE ADJUSTMENT – focalizes the
fascicle energy by pressing the4 max. aria intensity fascicle in the active aria.
MODULE FOR PROTECTION GAZES – directions/drives the protection gaze in the working aria
POSITIONING AND FIXING MODULE – drives the diamonded segment and the metallic disk towards the laser fascicle
UNIT FOR ORDER AND CONTROL – orders the port components (segments/disk) module displacement and rotation by the specific SOFTWARE PROGRAM. The equipment uses “an using interface” choused from more options of the LabVIEW VI Express program, realizes applications and measure the specific application parameters.
Laser fascicle focalizing head
The main characteristics: positions correctly the two components during processingpositions the diamonded segments between two positioning stiffs and between two windows from the supporting plate, necessary for spot passing provides the segments pressing on the disk steel bodydisplays the sub ensemble port components to the focalizing head “ready for welding”provides the speed of the rotating disk according to the welding regime choused
Results
As results of the tests has been noted the necessity of doing some constructive modifications of the nozzle from the let out of the laser computer, for reorientation of the compressed air jet so that it stops the deposits penetration from the (scanteie) on the deflection prism Glass
CEEX 1 project – “The national research facility with laser fascicle” high power MACROLASER Center – 2200 W, functioning with gas CO2, and wave length: 10,6µm