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