Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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T~E: DE~CEFORTREATINGTHESURFACES OFWORKPECES WITHLIGHT
BFAMS
This invention concerns a device for hardening, remelting,
coating, alloying and dispersing large areas of workpieces,
especially metals, by means of beams of light. For reasons o~
simplicity, hardening, remelting, coating, alloying and dispersing
workpieces are referred to below as surface treatment of
workpieces.
For surface treatment (hardening, remelting, alloying,
coating, etc.) of metals, methods using radiation have already been
employed in isolated cases. Electron beam installations have been
used and to an increasing extent, lasers are also used. The high
cost is a disadvantage and the limited beam power is a special
problem o~ lasers.
British Patent 2;083,728 describes a calcining oven with a
long-arc lamp which is mounted in a closed space. Static operation
is intended. The known device operates at relatively low
,
temperatures, namely calcination temperatures, in order to heal
lattice defects and thus dissipate internal stresses. An
aspherical reflector is used and the lamp is operated in pulsed
operation in order to achieve a high energy for healing the lattice
defects. A uniform energy distribution is provided and the
irradiated surface should not excee~ 12 times the light emitting
area of the lamp. The lamp and/or workpiece is mounted outside the
beam center of the reflector in this prior art document in order to
obtain uniform lighting of the workpiece. The ind vidual beams are
imaged in individual points so there is no bundling, i.e., no
focusing of the rays from the lamp.
German Patent (ALS) 2,257,739 describes a device for welding,
remelting or heating a workpiece with light eneryy. This device
includes an elliptical mirror with an arc lamp mounted as a
practically point-shaped radiation source for high temperature
radiation in or near the focal point that is close to the mirror
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and the workpiece is mounted in or near the other focal point that
is remote from the mirror. Due to such an arrangement, practically
only a point treatment of the surface of the workpiece can be
achieved, so large area treatments are tedious to perform and
` cannot be complete.
Japanese Patent A 59/181,528 and Japanese Patent A 56/80,138
describe the usP of a long-arc lamp of a low power for calcination
of single crystals of silicon. The lamp and silicon single crystal
are designed so they can be moved in two dimensions relative to
each other. Such silicon single crystals have a wall thickness of
less than 1 mm and have a relatively poor thermal conductivity.
This calcination treatment should eliminate lattice defects but the
lattice structure should be completely preserved. In order to
accomplish this goal, the temperature must be low and the treatment
time must be short. These known devices and this known equipment
for treatment of silicon single crystals are not suitable for
hardening and remelting, i.e., for solid and liquid phase
conversion, nor are they suitable for coating workpieces by means
of rays of light.
- The problem on which the present invention is based is to
develop a device of the type describecl~initially that permits
large-area surface treatment of workpieces easily with a high beam
power.
This problem is solved by the embodiment according to Claim 1.
With the help of the solution to the problem according to this
invention, it is possible to perform a large-area surface treatment
with high power lamps.
Advantageous and expedient embodiments of the solution to the
problem according to this invention are characterized in the
subclaims.
This invention will be illustrated in greater ~etail below on
~;; the basis of the accompanying figures which show the ~ollowing:
Figure 1 shows a schematic perspective view of a device
according to this invention with a reflector and a long-arc lamp
for surface treatment of a workpiece.
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Figure 2 shows a schematic diagram of the device according to
this invention according to Figure 1 in an inclined position for
adjusting the working track width.
Figures 3 and 4 show the device according to Figure 1 or 2
with additional use of apertures for limiting the radiation.
Figures 5 to 9 show the device according to Figures 1 or 2
with additional use of mirrors for limiting irradiation.
Figure 10 shows the device according to this invention in an
angular position where the reflector normal is at an angle between
the workpiece and the device, where the slope is to the
longitudinal axis of the long-arc lamp.
Figure 11 shows a device according to this invention with the
reflector inclined to the [longitudinal axis~1 between the
reflector and workpiece, where the slope is across the longitudinal
axis.
Figures 12 and 13 show the device according to this invention
with the additional use of a water spray for cooling and for
shielding the radiation with a relative movement in the direction
of and across the longitudinal axis of the line focus.
Figures 14 to 16 show the device according to this invention
with a device for supplying a processing gas stream.
In the figures shown here, the same parts are provided with
the same reference numbers.
The figure shows a device for surface treatment of workpieces.
The device includes a reflector 1 with an elliptical cylindrical
surface 11 and side walls 12 that hold a high power arc lamp 2
arranged in the focus near the reflector whose beams of light 30
are focused on a line focus 4 that is remote from the reflector
(see Figure 1).
The surface of a workpiece 3 to be treated is in or near this
line focus 4. Workpiece 3 is arranged so it can be moved in three
dimensions with the help of a device (not shown3 as indicated by
1Translator's Note: The term in brackets has been added to
correct an apparent omission in the original text.
~ 3
the coordinate intersection XYZ and the arrows 5. Instead of the
workpiece or in addition to the workpiece, the reflector 1 may also
be arranged so it can be moved in three dimensions. The relative
movement between the workpiece and reflector 1 or the lamp beam of
the reflector can be controlled by means of a CNC control system
whereby either the workpiece or the reflector or both are moved.
Reflector 1 with the high power long-arc lamp 2 is adjustable
at the side at an angle ~ between O and 90 orthogonally to the
relative movement indicated by arrows S in order to be able to
adjust the working track width 6 (see Figure 2).
In order to reduce the irradiation area on the surface of
workpiece 3, coolable apertures 7, 7' arranged in the path of the
beam 30 are provided to limit the beam (see Figures 3 and 4),
whereby the apertures 7 serve to limit the width of the radiation
area (Figure 3) and the apertures 7' serve to limit the length of
the radiation area (Figure 4) of workpiece 3.
The width of the radiation area can also be limited by mirror
8 (Figure 5) and mirror 18 (Figure 7) and mirror 28 (Figure 9) and
the length of the radiation surface can be limited by mirror 8'
(Figure 6) and 18' (Figure 8).
In order to improve the heating ancl cooling processes in the
edge layer of the workpiece, reflector 1 can be pivoted about the
longitudinal axis of long-arc lamp 2 in such a way that the
workpiece surface normal and the reflector normal are at an angle
B about the longitudinal axis of the long-arc lamp to each other as
illustrated in Figure 10. Furthermore, reflector 1 can be inclined
with the longitudinal axis of the long-arc lamp 2 approximately in
the focus near the reflector at an angle J across the longitudinal
axis of the long-arc lamp (see Figure 11).
In this way a controlled influence on heating in the radiation
line focus is possible, especially to avoid overheating of
workpiece areas with a reduced thermal conduction, e.g., edges and
corners.
A cooling device 25, e.g., in the form of a tube or a plate-
shaped hollow body with nozzles 26 pointing toward workpiece 3 can -~
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~e moved into the path of the beam 30 between the reflector 1 a
workpiece 3 in order to cool the heated edge layer or the heat~
surface as rapidly as possible (see Figures 12, 13). At the san
time, this device can serve as an aperture to limit the path of t~
beam. Cooling device 25 can be arranged in such a way tha
quenching of the workpiece is achieved with a relative movement i
the direction of the line focus longitudinal axis (see Figure 13
or quenching of the workpiece is achieved with a relative movemen
across the line focus longitudinal axis (see Figure 12). It may b~
advantageous for the cooling device to be a type of water sprinkle
in order to be able to better quench the edge layer of th~
workpiece with water especially with long beam treatment times.
In order to prevent soiling of the reflector due to the gasec
and vapors ascending from the workpiece surface, a processing gac
stream 31 may be directed across or especially against the
direction of forward movement between the reflector and the
workpiece when the workpiece is moved or in the direction of
movement when the reflector is moved. ~or this purpose, a device
27 with a processing gas nozzle 2g may be arranged beneath or to
the side of the reflected beam bundle 30 (see Figures 14 and 15).
The processing nozzle 29 may also be integrated into the reflector
as illustrated in Figure 16, mainly at locations in the reflector
that make little or no contribution to the beam intensity in the
line focus. These locations include, for example, the zenith of
the reflector or the side walls of the reflector. This arrangement
of the processing nozzles has the advantage that when using water
for quenching, the resulting water vapor is blown away from the
reflector.
In order to eliminate a warmup area where the thermal
conductivity conditions are not steady state at the start of the
surface treatment or when starting up the treatment over a
workpiece edge for a short period of time, especially more than 3
seconds, the relative movement between the workpiece and reflector
is omitted and the workpiece surface is exposed to the radiation
under stationary conditions.
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To avoid overheating o~ the workpiece edge area when passing
over the edge of the workpiece or an area of the workpiece where
dissipation of heat is reduced, the lamp power may be reduced in
accordance with the thermal conductivity conditions or the
preheating of the workpiece.
The device described above may be used for large area surface
treatment of workpieces. For this surface treatment, the light of
the high power long-arc lamp ~ is focused on the surface of
workpiece 3 with the help of reflector 1 whereby there is either a
relative movement between the workpiece and the reflector for
heating over the surface or there is stationary heating of the edge
layer in order to heat the edge layer and melt it at a high
intensity in the focus and/or with a long beam treatment time and
then cool it by self-quenching or by quenching with a medium such
as water. In the case of rapid heating, i.e., high intensities in
the line focus and short beam trea-tment times, cooling of
workpieces with a large wall thickness mainly greater than 20 mm
can be accomplished by means of self-quenching. With long beam
treatment times, the quenching is preferably performed with water
as mentioned above. In order to harden the surface of a workpiece,
the intensity in the line focus, i.e., the lamp power and/or the
beam treatment time selected will be so small that the melting
temperature of the workpiece edge layer is not reached.
For remelting, coating, dispersing and alloying with lamps, it
is preferable to work with high intensities in the line focus of
the reflector, i.e., with high lamp powers and/or long beam
treatment times in order in this way to reach the melting point of
the workpiece and also that of the second material in coating and
alloying.
It should be pointed out that no absorption increasing agents
need be applied to the surface of the workpiece for eneryy input of
the radiation of the device according to this invention into the
workpiece surface of steel and cast iron or a number of other
materials.
The workpSece can also be subjected to another heat treatment
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before the lamp treatment or after the lamp treatment.
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