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Steen W.M. Laser Material Processing (Springer, 1991)(K)(600dpi)(T)(275s)(ISBN 3540196706)_EO_.djvu |
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necessity working in a high vacuum and
hence enjoys the high penetration...
Table 4.7 is a summary of some of the laser welding
characteristics for the main alloy systems...
At very high speeds there may be some problems with the
weld bead profile since the weld pool is larger than with the laser alone...
Most experimental and theoretical results are likely to be reported using
such groups because of the ecomony of expression achieved this way...
From equation 5.11 an asymptotic solutioh for the rate of cooling can
be derived for the centreline location: x > 0, y=0 and the Peclet number
vx/2ct» 1 (i.e...
This is clearly the strength of this technique as a tool for
questioning process mechanisms...
The theoretical fit for this parameter, as
calculated by Sharp G) using a finite difference model, is shown in Fig...
This time dependent process does
not take long but is sufficient to necessitate some superheat above the
austenitising temperature, Acl, to allow it to proceed to any extent
during laser treatment...
TIG Limited section thickness, electromagnetic stirring, weld bead
may be rough, large thermal penetration and medium heat
input...
There are three metallurgical areas of considerable interest; cast irons,
tool steels and certain deep eutectics which can form metallic glasses at
high quench rates...
Laser Material Processing
Tool and special steels: These materials are usually hardened by a fairly
long process of solution treatment to dissolve the carbides followed by
a controlled quench to give a fine dispersion of carbides...
Materialjlow within the melt pool: There are many forces acting
on the melt pool as shown in Fig...
Cast iron: Surface alloying with Cr, Si or C are all possible methods to
make relatively cheap cast irons into superficially exotic irons...
The variation of typical laser cladding rates with power, clad thickness, and
powder particle size using the blown powder process with the reflective dome C8)...
Sheets passed
through the mill will be surface dulled to aid paint adhesion and flow as
well as improving press formability and work handling, Fig...
If there is any bend in the rod the inside of the bend will strike the laser
beam, become heated and expand thus straightening the rod...
Model Design
The first step in creating a model by stereolithography is to perform the
design function on a 3D CAD system...
Important applications which have been proposed or demonstrated
include:
* Three-dimensional topographic maps from satellite data...
In the future there is the
prospect of "adaptive control" or "intelligent" machines - in which the
machine can be set a task and it teaches itself to do the task better and
better according to some preset criteria...
It is quite
surprising how much power vibration and beam dilation there is
in the beam from some lasers...
These back reflections are strongly
fluctuating signals and on the whole
they cover the whole mirror surface,
so their thermal stress variations
are very large compared to the
relatively stable, but far more
powerful, laser beam...
All lasers of interest to material processing will be
classified as class 4 except some which are totally built into a machine
in which there is no human access possible without the machine being
switched off; so the list is somewhat academic for this book...
Fume Hazards
The very high temperatures associated with laser processing are able to
volatilise most materials and thus form a fine fume, some of which can
be poisonous...
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