CA1265209A - Process to remove contaminants, particularly rust/from metallic surfaces - Google Patents
Process to remove contaminants, particularly rust/from metallic surfacesInfo
- Publication number
- CA1265209A CA1265209A CA000474363A CA474363A CA1265209A CA 1265209 A CA1265209 A CA 1265209A CA 000474363 A CA000474363 A CA 000474363A CA 474363 A CA474363 A CA 474363A CA 1265209 A CA1265209 A CA 1265209A
- Authority
- CA
- Canada
- Prior art keywords
- impinging
- reflected
- path
- reflected beam
- regulating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
- B08B7/0035—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like
- B08B7/0042—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like by laser
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/03—Observing, e.g. monitoring, the workpiece
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K7/00—Cutting, scarfing, or desurfacing by applying flames
- B23K7/06—Machines, apparatus, or equipment specially designed for scarfing or desurfacing
Abstract
ABSTRACT
In a process for removing rust and other contaminants from a metallic surface by vapourizing the rust or the other contaminants by means of laser radiation, the laser radiation is controlled on the basis of the laser radiation that is reflected from the surface of the metal that become exposed.
In a process for removing rust and other contaminants from a metallic surface by vapourizing the rust or the other contaminants by means of laser radiation, the laser radiation is controlled on the basis of the laser radiation that is reflected from the surface of the metal that become exposed.
Description
~L26S~
23937~53 Process ~.o ~emove Contaminant.s, particularly Rust./
Erom Metallic Surfaces/
The present invention relat.es to a process for removing contarllinants, in particular the products of oxidation, and more particularly rust, from the surfaces of metals, especially of iron or steel, by vapourinzing the contaminanats by means of laser radiation./
The removal o~ rust from the surface of steel by vapourizing t.he rust using laser radiation, as is known from D~-O~ 29 43 lO7 is, most surprisingly, basically selective, which i9 tC) Scly tllat .it can be carriecl ou~. Wi~}lOUt vapour:iz:Lng the s~.eel or damag.Lng ~.he surface Oe tlle sl:eel by cau-.ing ~I:;rucl:ural chancJes. When the rust is vapourized the laser rad:iat:iotl i.s in part re~lec~.ecl from I:he sur~ace oE
~.he ~tee:L. ~i'or Ihe rema:incler, the heat ~.hat is generated within the s-teel as a resulk oE the laser radiatiorl on ~.he surface of the sl:eel is conducted away relatively rapidly, in all directions. A brief and high-level supply of energy to a relatively restricted spot thus does not cause any great heating, and can be accepted. The intensity and duration of the laser radiation required to vapourize ~he remaining rust once the loose rust has been removed mechanically can be so adjusted, even with a small excess, that the steel remains preserved./
~2~iS2~
I~. is t.he ~.ask of the present inven~.ion-~.o speed up the removal of rust from steel alld the cleaning of metal by vapourizing contanlinan-ts by the use of laser radiation and to do this such as-to cause the smallest losses and as safely as possible./
According to the present invention, this is done in that the laser radiation is controlled on the basis of the reflected laser radiation on t~he exposed surface of the metal/
Of particular siganificance in this regard is the possible aut-omatic control oE ~.he manner in which the laser radiat.ion is advanced along t.he surface of the metal and aut.omatic control of t~.'he lnt.ensit.y oE t'he laser radiation./
I, for exclmp:Le, t.he metaL surface is complet.ely exposed .in t-.'he lrrad:ia~.ed clrea oE ~ x ~ mm, or :LO x lO mm, kh.Ls w.tll r~fl~cl:;l sp~c:L~Eic port.:Lon Oe t.'he racli.a~.:ion; this is t~hen picJced up by a radLat.iorl det:ect.or and can th~n be processed in a ~ult.ab'Le control syst.em as a t.hreshold value for the advance Oe the irrad:iated area t.o l:he next s~uare or equivalent. A surplus of energy, that is a Eorm of loss on the one hand and on the other could damage the structure of the metal, can only occur on parts of t'he irradiated area, as long as other parts remain covered by rust or other dirt.
This excess radiation can be reduced by reducing the size of the irradiated area, and this is permitted by t'he control system proposed by the present invention the more so since ~s~
it permits an lmmediate and thus, on the whole, rapid and automatic advance; Eurthermore, a smalle.r irradiated area cuts down on irradiation -time as a whole, since it contacts areas that require a protracted period of irradiation less frequently.
Depending on conditions, intensity control is i.nvolved both as set out above, and as set out below.
The differences in the characteristics between the metal and the contamination can be such that it is better to irradiate a section of the surface with particularly stubborn dirt more intensely, for a brief period, or else, with regard to the metal, to reduce the :intensity oE the radiatlon, even though the irradi-ation will be .requi.red Eor a longer period. Thus the optimum adjustment oE the :radiation :intens.ity can be e:E:Eected as a Eunctlon oE the va:rious types o:E contamination. I:E, for example, va:r.ious contam.illclnt mate:r:i.a:Ls a:re spread over the surface to be cleal1c-~cl, and l.E the.re :L~ some ove.rlap, and i:E some can be removed more rapiclly th~n oth~:rs, once onc t~pe has been .removed, if the sur:Eace of the metal on the i.rradiated a:rea displays a speci:Eic degree oE reElection, one can switch Erom one radiation intensity that is best suited Eor one particular type of material to another intensity better suited to the other material.
~s~
Constarl~ con~rol of -the in~ensity, even down to zero in -the form of temporary swi~.ch-off can eliminate -the need for feed control in that., for a constant feed, the quantity of radiation can be matched to -the requirements of the loca-tion acted upon by the beam by radiation eon-trol.
According to the above, a device ~or carrying out the process according to the present invention has a laser irradiation system that incorporates a feed (advance) system that is eontrollad by the reflection of the laser radiation from the surfaee oE t}le metal and/or an intensity-eontrol system and/or other systems or deviees./
~ system otller-than the advance~ or feed system and the int.ensity contro:l syste~ ttlat::is controllecl'by the reeleet:ion oE the :laser radicltloll on t'he exposed surface of t'he m~.al eou'l.d, Eor exampLe/ be for proeessing small wor'k p.i~eea or smalLQr surEae~ seet.iorls, t'hes~ be:ing approximately t'he 6iZ~ oE l:he :irradia~.ed area, and eould be a simple Einal shut-of~ system. A'Lso eonsidered were a system that, for example, records and st.ores information eonearning residual amounts of eontaminants and then, during a subsequent pass by the same or an additional radiating device only irradiates t.hose areas where such residues remain. Further to this, an image processing system for the refleeted radiation is eoneeivable in that the laser beam after irradiating a basie area, as already indicated, for example, a square, is focussed even more and then provides a comparltively small, for example, circular, irradiat.ed area that: is direc-~ed against. residual amounts oE
contamination remaining within t.lle area tha~ was irradiated originally./
However, numerous other variations are possible to control the laser radiation on the basis of its own reflection./
Various me-thods can be used to capture ~he reflected radiation./
Thus, for example, the laser beam can be passed through a mirror for -the reflected radiation that i9 located above t.he surface of ~ e me~.al, preferably at an anyle of 40 - 50 to it, sclid mirror being to a large extent t.ransparent to ~.'he rad.ia~.:loll, and a laser raclLat:Lon clc~!~.ector beiny installed in t'h~ pat'h oE t'lle re~Elec~.ion com.ing Erom ~aid mirror. In t'his sense, a mirror is anything t'hat reflects a measurable portLon of t'he~ rad:Lal:Lon reElec~.e~ Erom the surface oE t'he metal, :L.e., independerltly of t'he remaining port:Lon that eventually pas~es l:hrough t'he mirror. It is also possible that mirror, preferably narrower, for the reElected radiation be moved on a preferably circular pa-th, that passes through the laser beam, laser radiation detector being installed in the or in one direction of reflection of the mirror. Both of these solutions make it possible to di:rect the laser beam perpendicularly onto the surface of the metal./
However, it is also possible to direct the laser beam obliquely onto -the surface oE the metal and arrange a laser radia-tion de-tector for -the laser beam in the direction of reflection from the surface of the metal.
Deflection of the reElected radiation in place of reflec-tion is also conceivable, this being done by an ultrasonic emitter in those locations such that -the laser beam that is directed onto the surface o:E the metal, and the re~lected radiation, a change in the density o:E tht-~ atmosphere in the pa-th of -the laser beam 1 n dive.rts some oE the reElected radiation onto a laser radiation detector.
:[n o:rder -to ensure that the lase.r radlation that is reflected on -the s~.r:Eace o:E the metal is captured ln the above clescr:i.bt.~d o:r a sim:i..l.a:r manne.r ant.l that th:is is done w.~th suE.Eicient ac1cu:racy, it :is also ~?oss:ib:l.e to ar.rancJe :Eo:r a supply o:E an inert o.r cleoxydl~i.n(J p:rotoct:ivt3 CJaS to the :i.rrad.iatet~ arecl to be a wash-:ing system.
The d:raw:incJs show an exemplary version of the present inventlon, this being a device to remove rust from sections of pipe.
The drawings are as follows:
Figure 1 shows the mechanical arrangement of the system as viewed from the end of the pipe section.
Figure 2 is a block diagram of the laser device used in the system.
Figure 3 shows the details of Figure 2 (the head) in greater detail and in axial cross-section.
6a 23937-53 Referring Eirst to Flgure 1, the beam that is produced by a laser 21 passes laterally from the laser section through the arm 22 and is deflected downwards. It passes through the head 7 directly over the surface of a pipe 24 that is to be derusted, said pipe being of a diameter of approximately 20 cm. The pipe 24 rests on a roller table 25 that causes it to rotate constantly and advances it such that the impact area of the laser beam on the surface of the pipe extends along an unbroken helical pat.h. T~le impact. area is of a diame~er of 5 mm, for example, and t}lUS ~.he pipe advances axially some 5 mm per revolution./
Roller tables of-this sort are known and used for examing pipe sections by means of ul-trasonic met:hods./
Such table consist of a row of supporting stands 28, each of which has two rows of rollers 26 and 27, this being arranged at intervals from each other and being in alignment. The pipe section 24 lies between these rollers
23937~53 Process ~.o ~emove Contaminant.s, particularly Rust./
Erom Metallic Surfaces/
The present invention relat.es to a process for removing contarllinants, in particular the products of oxidation, and more particularly rust, from the surfaces of metals, especially of iron or steel, by vapourinzing the contaminanats by means of laser radiation./
The removal o~ rust from the surface of steel by vapourizing t.he rust using laser radiation, as is known from D~-O~ 29 43 lO7 is, most surprisingly, basically selective, which i9 tC) Scly tllat .it can be carriecl ou~. Wi~}lOUt vapour:iz:Lng the s~.eel or damag.Lng ~.he surface Oe tlle sl:eel by cau-.ing ~I:;rucl:ural chancJes. When the rust is vapourized the laser rad:iat:iotl i.s in part re~lec~.ecl from I:he sur~ace oE
~.he ~tee:L. ~i'or Ihe rema:incler, the heat ~.hat is generated within the s-teel as a resulk oE the laser radiatiorl on ~.he surface of the sl:eel is conducted away relatively rapidly, in all directions. A brief and high-level supply of energy to a relatively restricted spot thus does not cause any great heating, and can be accepted. The intensity and duration of the laser radiation required to vapourize ~he remaining rust once the loose rust has been removed mechanically can be so adjusted, even with a small excess, that the steel remains preserved./
~2~iS2~
I~. is t.he ~.ask of the present inven~.ion-~.o speed up the removal of rust from steel alld the cleaning of metal by vapourizing contanlinan-ts by the use of laser radiation and to do this such as-to cause the smallest losses and as safely as possible./
According to the present invention, this is done in that the laser radiation is controlled on the basis of the reflected laser radiation on t~he exposed surface of the metal/
Of particular siganificance in this regard is the possible aut-omatic control oE ~.he manner in which the laser radiat.ion is advanced along t.he surface of the metal and aut.omatic control of t~.'he lnt.ensit.y oE t'he laser radiation./
I, for exclmp:Le, t.he metaL surface is complet.ely exposed .in t-.'he lrrad:ia~.ed clrea oE ~ x ~ mm, or :LO x lO mm, kh.Ls w.tll r~fl~cl:;l sp~c:L~Eic port.:Lon Oe t.'he racli.a~.:ion; this is t~hen picJced up by a radLat.iorl det:ect.or and can th~n be processed in a ~ult.ab'Le control syst.em as a t.hreshold value for the advance Oe the irrad:iated area t.o l:he next s~uare or equivalent. A surplus of energy, that is a Eorm of loss on the one hand and on the other could damage the structure of the metal, can only occur on parts of t'he irradiated area, as long as other parts remain covered by rust or other dirt.
This excess radiation can be reduced by reducing the size of the irradiated area, and this is permitted by t'he control system proposed by the present invention the more so since ~s~
it permits an lmmediate and thus, on the whole, rapid and automatic advance; Eurthermore, a smalle.r irradiated area cuts down on irradiation -time as a whole, since it contacts areas that require a protracted period of irradiation less frequently.
Depending on conditions, intensity control is i.nvolved both as set out above, and as set out below.
The differences in the characteristics between the metal and the contamination can be such that it is better to irradiate a section of the surface with particularly stubborn dirt more intensely, for a brief period, or else, with regard to the metal, to reduce the :intensity oE the radiatlon, even though the irradi-ation will be .requi.red Eor a longer period. Thus the optimum adjustment oE the :radiation :intens.ity can be e:E:Eected as a Eunctlon oE the va:rious types o:E contamination. I:E, for example, va:r.ious contam.illclnt mate:r:i.a:Ls a:re spread over the surface to be cleal1c-~cl, and l.E the.re :L~ some ove.rlap, and i:E some can be removed more rapiclly th~n oth~:rs, once onc t~pe has been .removed, if the sur:Eace of the metal on the i.rradiated a:rea displays a speci:Eic degree oE reElection, one can switch Erom one radiation intensity that is best suited Eor one particular type of material to another intensity better suited to the other material.
~s~
Constarl~ con~rol of -the in~ensity, even down to zero in -the form of temporary swi~.ch-off can eliminate -the need for feed control in that., for a constant feed, the quantity of radiation can be matched to -the requirements of the loca-tion acted upon by the beam by radiation eon-trol.
According to the above, a device ~or carrying out the process according to the present invention has a laser irradiation system that incorporates a feed (advance) system that is eontrollad by the reflection of the laser radiation from the surfaee oE t}le metal and/or an intensity-eontrol system and/or other systems or deviees./
~ system otller-than the advance~ or feed system and the int.ensity contro:l syste~ ttlat::is controllecl'by the reeleet:ion oE the :laser radicltloll on t'he exposed surface of t'he m~.al eou'l.d, Eor exampLe/ be for proeessing small wor'k p.i~eea or smalLQr surEae~ seet.iorls, t'hes~ be:ing approximately t'he 6iZ~ oE l:he :irradia~.ed area, and eould be a simple Einal shut-of~ system. A'Lso eonsidered were a system that, for example, records and st.ores information eonearning residual amounts of eontaminants and then, during a subsequent pass by the same or an additional radiating device only irradiates t.hose areas where such residues remain. Further to this, an image processing system for the refleeted radiation is eoneeivable in that the laser beam after irradiating a basie area, as already indicated, for example, a square, is focussed even more and then provides a comparltively small, for example, circular, irradiat.ed area that: is direc-~ed against. residual amounts oE
contamination remaining within t.lle area tha~ was irradiated originally./
However, numerous other variations are possible to control the laser radiation on the basis of its own reflection./
Various me-thods can be used to capture ~he reflected radiation./
Thus, for example, the laser beam can be passed through a mirror for -the reflected radiation that i9 located above t.he surface of ~ e me~.al, preferably at an anyle of 40 - 50 to it, sclid mirror being to a large extent t.ransparent to ~.'he rad.ia~.:loll, and a laser raclLat:Lon clc~!~.ector beiny installed in t'h~ pat'h oE t'lle re~Elec~.ion com.ing Erom ~aid mirror. In t'his sense, a mirror is anything t'hat reflects a measurable portLon of t'he~ rad:Lal:Lon reElec~.e~ Erom the surface oE t'he metal, :L.e., independerltly of t'he remaining port:Lon that eventually pas~es l:hrough t'he mirror. It is also possible that mirror, preferably narrower, for the reElected radiation be moved on a preferably circular pa-th, that passes through the laser beam, laser radiation detector being installed in the or in one direction of reflection of the mirror. Both of these solutions make it possible to di:rect the laser beam perpendicularly onto the surface of the metal./
However, it is also possible to direct the laser beam obliquely onto -the surface oE the metal and arrange a laser radia-tion de-tector for -the laser beam in the direction of reflection from the surface of the metal.
Deflection of the reElected radiation in place of reflec-tion is also conceivable, this being done by an ultrasonic emitter in those locations such that -the laser beam that is directed onto the surface o:E the metal, and the re~lected radiation, a change in the density o:E tht-~ atmosphere in the pa-th of -the laser beam 1 n dive.rts some oE the reElected radiation onto a laser radiation detector.
:[n o:rder -to ensure that the lase.r radlation that is reflected on -the s~.r:Eace o:E the metal is captured ln the above clescr:i.bt.~d o:r a sim:i..l.a:r manne.r ant.l that th:is is done w.~th suE.Eicient ac1cu:racy, it :is also ~?oss:ib:l.e to ar.rancJe :Eo:r a supply o:E an inert o.r cleoxydl~i.n(J p:rotoct:ivt3 CJaS to the :i.rrad.iatet~ arecl to be a wash-:ing system.
The d:raw:incJs show an exemplary version of the present inventlon, this being a device to remove rust from sections of pipe.
The drawings are as follows:
Figure 1 shows the mechanical arrangement of the system as viewed from the end of the pipe section.
Figure 2 is a block diagram of the laser device used in the system.
Figure 3 shows the details of Figure 2 (the head) in greater detail and in axial cross-section.
6a 23937-53 Referring Eirst to Flgure 1, the beam that is produced by a laser 21 passes laterally from the laser section through the arm 22 and is deflected downwards. It passes through the head 7 directly over the surface of a pipe 24 that is to be derusted, said pipe being of a diameter of approximately 20 cm. The pipe 24 rests on a roller table 25 that causes it to rotate constantly and advances it such that the impact area of the laser beam on the surface of the pipe extends along an unbroken helical pat.h. T~le impact. area is of a diame~er of 5 mm, for example, and t}lUS ~.he pipe advances axially some 5 mm per revolution./
Roller tables of-this sort are known and used for examing pipe sections by means of ul-trasonic met:hods./
Such table consist of a row of supporting stands 28, each of which has two rows of rollers 26 and 27, this being arranged at intervals from each other and being in alignment. The pipe section 24 lies between these rollers
2~ and 27. ~ne section oE the supporting stand has a pressure roller 29 that rests on t.op Oe ~.he pipe section bet.weerl the rollers 26 and 27./
~ ome part oL t'he suppork arld/or pressure rollers 26, 27, and 29, is provided W:ittl a rol:-.ltional drive system oE a knowrl k:incl, w'hictl ts nol: s'howll irl ttle clraw:Lrlgs. ~t. least.
tlle3e drLven rol.'Lers o t:h~3 roL'Ler bench arc arrangecl oblique'Ly t.o t'he axis oE t.tle pipe SO as to produce t'he axia:L
aclvarlcirlg motion o t'tle sectiorl, i.e., the axis oE t'he rollers is skewed by a small angle within the tangential plane 3~ on the point of contac-t on the pipe. The oblique arrangement shown in E'igure 2, in which the t.wo supportiny rollers 26 and 27 and also the pressure roller 29 are to be driven, is exaggerated Eor reasons of clarit.y./
The driven rollers can be provided with a coating having a large coefficient of friction in comparison to the surface of the pipe in order to ensure a more reliable drive ~L~6~2~
effect. lf the non-driven rollers are not adjusted to an angle ~.hat does no-t conform exactly or at all to the feed, the pipe will slip on -~.his in ~he direction of the feed./
In order -to ensure an unbroken helical coverage of the surface of the pipe by the impact area it is possible to arrange for a posit.ive feed such that the axial advance caused by the driven rollers is slightly too great, a mechanical restraining device engaging the pipe section, t.his releasing the pipe for the precise amount of advance as a result of being controlled synchronously with the rotation and/or such that a-threaded rod is clamped rigidly to one side axially aloncJ the p:ipe, this passing through a fixed nut, such that l:he pitCIl iS equal to tlle pitch of the helical path o~ ~:h~ lltlpclcl: area on t:h~ surEace oE ~.he pipe./
rrhe sy~l:ems nulllbered :L in tll~ c~raw.irlcJ are shown in cletail .in F.iCJUre` ~- The :Lager 3~ ln ~.his exarnple is a C02 laser w.ith a h:ic~h Erequerlcy exciter of L3.5 or 27 MHz that del.ivers an output power oE ~5~CW. This emit~ a laser beam 9 that. is, for example, 50 mm in diameter. This passes through the arm 22 and is cdeflected downwards by the deflection mirror and passes into the head 7b through a lens 8 (Figure 3) that focusses it to the above-describecl impact area diameter of 5 mm. This results of a radiation intensity of 107 Watt/cm2 on the surface 11 of the pipe section 24 from which the rust is to be removed./
~, !
; 8 ~;~6S2~
The laser radiat,ion t.ha~, is reflect.ed from the exposed surface of ~he metal is deElect.ed from the cross-section of the laser bearn 9 by a rota-ting reflector 32 and passed to a detector 33./
The rotat.ing reflector consists, for example, of a 2-mm thick copper rod that passes at high speed along a circular path that cuts through the laser beam 9. Various versions of such a system are known./
The detector 33 is, for example, a pyrodetector of the sort familiar to the expert and designated "Molectron P 3."/
The signal from this is passed through a signal ampl:ifier and processor 34t:o a power supply Ullit 35 to excite and control the laser cl:ischarcJe./
T'he elemen~.s 32 ~.o 35 are suc'h ~.ha~. t.'he laser 31 :Ls cut down to low in~.en~ or swLtc'h~d o comple~.ely as soon as the reElec~.ecl la~r rldi~.iorl reactles an in~.ens.ity generated b,y the surEace oE l:~e m~l:al ln the impact area being completely expos~d; kh~ laser is t'hen brought I:o full cont.inuous power as soon as t'he intenqity of the reflected laser radiation falls below the threshold value./
This intensity cont.rol of t.he laser radition is completed within a few milliseconds. In comparison to this, t.he impact area is advanced very slowly along t,he surface of the pipe. The circumference speed Oe the pipe rotation may amount to ~0 to 50 m/min in the above example./
The size of the 5-mm diameter impact area is selected ~i;5260~ `
with regard to the structure o:E the rust. Typically, rust centres are from 1 ~o 5 mm diamet:er./
With regard to -l:he highest possible power of the contact. on the one hand, and pro-tection of the material on the other the selected intensity of 107 Watt/cm2 appears best suited with regard to the other factors in the example~ In general, a range of 106 to 10~ Watt/cm2 is considered./
It is underskood thak-the above details cannot apply to every application for khe removal of rus-t or cleaning.
They are merely reference points Eor arriving ak more suitable specific parameters./
~ c~laniccll con9~.:r~1c~ on Oe ~.h~ s~s~.~m i9 s'tlown in great.er dcka:il in F:Lgure ~, which SllOWS ~ e head 7 ~.ha~. is mo~lnted at ~ end o~ th~ arm 22 .in ~real:er detail./
The'head 7 conkains t'he previously men~.ioned lens 8 or focussing the Laser beam, so tllak immediat.eLy behind the conical outlek 10 of khe head khe laser beam has the desired size o impact, area on the surEace 11 of the pipe section from which the rust is to be removed. A protective gas inlet 12 and suction outlet 13 lead through the head 7.
The first opens out more or less level with the head and within this. The inlet for the latter is somewhat further back on the outside of the head at the rear of a cowl 14 that is in the form of a bellows and encloses the head.
~2~.~2~3 This cowl can be held a~.-the Eron~ by strut.s shown at 15.
~n a specific case it is held on rod-like distance pieces 16 that.can be adjust.ed in holders 17 mounted rigidly on the head 7 and which, when the slides 36 are in contact with t.he surface 11 from which the rust is to be removed hold the head 7 including the cowl 14 at the desired distance from the surface./
Were a swinging mirror used, it would also be possible to move the laser beam back and forth such that the impact area described a zig-zag or serpentine path on the surface to be cleaned. ~uch a solution is useful in part.icular for large areas such as the sides o~ shi~s./
~ ome part oL t'he suppork arld/or pressure rollers 26, 27, and 29, is provided W:ittl a rol:-.ltional drive system oE a knowrl k:incl, w'hictl ts nol: s'howll irl ttle clraw:Lrlgs. ~t. least.
tlle3e drLven rol.'Lers o t:h~3 roL'Ler bench arc arrangecl oblique'Ly t.o t'he axis oE t.tle pipe SO as to produce t'he axia:L
aclvarlcirlg motion o t'tle sectiorl, i.e., the axis oE t'he rollers is skewed by a small angle within the tangential plane 3~ on the point of contac-t on the pipe. The oblique arrangement shown in E'igure 2, in which the t.wo supportiny rollers 26 and 27 and also the pressure roller 29 are to be driven, is exaggerated Eor reasons of clarit.y./
The driven rollers can be provided with a coating having a large coefficient of friction in comparison to the surface of the pipe in order to ensure a more reliable drive ~L~6~2~
effect. lf the non-driven rollers are not adjusted to an angle ~.hat does no-t conform exactly or at all to the feed, the pipe will slip on -~.his in ~he direction of the feed./
In order -to ensure an unbroken helical coverage of the surface of the pipe by the impact area it is possible to arrange for a posit.ive feed such that the axial advance caused by the driven rollers is slightly too great, a mechanical restraining device engaging the pipe section, t.his releasing the pipe for the precise amount of advance as a result of being controlled synchronously with the rotation and/or such that a-threaded rod is clamped rigidly to one side axially aloncJ the p:ipe, this passing through a fixed nut, such that l:he pitCIl iS equal to tlle pitch of the helical path o~ ~:h~ lltlpclcl: area on t:h~ surEace oE ~.he pipe./
rrhe sy~l:ems nulllbered :L in tll~ c~raw.irlcJ are shown in cletail .in F.iCJUre` ~- The :Lager 3~ ln ~.his exarnple is a C02 laser w.ith a h:ic~h Erequerlcy exciter of L3.5 or 27 MHz that del.ivers an output power oE ~5~CW. This emit~ a laser beam 9 that. is, for example, 50 mm in diameter. This passes through the arm 22 and is cdeflected downwards by the deflection mirror and passes into the head 7b through a lens 8 (Figure 3) that focusses it to the above-describecl impact area diameter of 5 mm. This results of a radiation intensity of 107 Watt/cm2 on the surface 11 of the pipe section 24 from which the rust is to be removed./
~, !
; 8 ~;~6S2~
The laser radiat,ion t.ha~, is reflect.ed from the exposed surface of ~he metal is deElect.ed from the cross-section of the laser bearn 9 by a rota-ting reflector 32 and passed to a detector 33./
The rotat.ing reflector consists, for example, of a 2-mm thick copper rod that passes at high speed along a circular path that cuts through the laser beam 9. Various versions of such a system are known./
The detector 33 is, for example, a pyrodetector of the sort familiar to the expert and designated "Molectron P 3."/
The signal from this is passed through a signal ampl:ifier and processor 34t:o a power supply Ullit 35 to excite and control the laser cl:ischarcJe./
T'he elemen~.s 32 ~.o 35 are suc'h ~.ha~. t.'he laser 31 :Ls cut down to low in~.en~ or swLtc'h~d o comple~.ely as soon as the reElec~.ecl la~r rldi~.iorl reactles an in~.ens.ity generated b,y the surEace oE l:~e m~l:al ln the impact area being completely expos~d; kh~ laser is t'hen brought I:o full cont.inuous power as soon as t'he intenqity of the reflected laser radiation falls below the threshold value./
This intensity cont.rol of t.he laser radition is completed within a few milliseconds. In comparison to this, t.he impact area is advanced very slowly along t,he surface of the pipe. The circumference speed Oe the pipe rotation may amount to ~0 to 50 m/min in the above example./
The size of the 5-mm diameter impact area is selected ~i;5260~ `
with regard to the structure o:E the rust. Typically, rust centres are from 1 ~o 5 mm diamet:er./
With regard to -l:he highest possible power of the contact. on the one hand, and pro-tection of the material on the other the selected intensity of 107 Watt/cm2 appears best suited with regard to the other factors in the example~ In general, a range of 106 to 10~ Watt/cm2 is considered./
It is underskood thak-the above details cannot apply to every application for khe removal of rus-t or cleaning.
They are merely reference points Eor arriving ak more suitable specific parameters./
~ c~laniccll con9~.:r~1c~ on Oe ~.h~ s~s~.~m i9 s'tlown in great.er dcka:il in F:Lgure ~, which SllOWS ~ e head 7 ~.ha~. is mo~lnted at ~ end o~ th~ arm 22 .in ~real:er detail./
The'head 7 conkains t'he previously men~.ioned lens 8 or focussing the Laser beam, so tllak immediat.eLy behind the conical outlek 10 of khe head khe laser beam has the desired size o impact, area on the surEace 11 of the pipe section from which the rust is to be removed. A protective gas inlet 12 and suction outlet 13 lead through the head 7.
The first opens out more or less level with the head and within this. The inlet for the latter is somewhat further back on the outside of the head at the rear of a cowl 14 that is in the form of a bellows and encloses the head.
~2~.~2~3 This cowl can be held a~.-the Eron~ by strut.s shown at 15.
~n a specific case it is held on rod-like distance pieces 16 that.can be adjust.ed in holders 17 mounted rigidly on the head 7 and which, when the slides 36 are in contact with t.he surface 11 from which the rust is to be removed hold the head 7 including the cowl 14 at the desired distance from the surface./
Were a swinging mirror used, it would also be possible to move the laser beam back and forth such that the impact area described a zig-zag or serpentine path on the surface to be cleaned. ~uch a solution is useful in part.icular for large areas such as the sides o~ shi~s./
Claims (24)
PROPERTY OF PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of removing impurities from the surface of a metallic object, including removing rust and/or other oxidation products from the surface of an object which contains iron or steel, comprising the steps of directing a beam of coherent radiation upon the object to impinge upon and heat the impurities on the surface of the object to evaporation temperature and to thereby effect evaporation of impurities as well as the exposure of the thus cleaned surface to the impinging beam whereby the cleaned surface reflects the beam; and regulating the action of the impinging beam upon the object in dependency on changes in the characteristics of the reflected beam,
2. The method of claim 1, wherein the beam is a laser beam.
3. The method of claim 1, wherein said regulating step includes varying the intensity of the impinging beam in response to variations in intensity of the reflected beam.
4. The method of claim 1, wherein said regulating step includes changing the positions of the impinging beam and the object relative to each other in response to variations in intensity of the reflected beam.
5. The method of claim 4, wherein said position changing step includes moving the object relative to the impinging beam.
6. The method of claim 1, further comprising the step of effecting a movement of the object and the impinging beam relative to each other so that the impinging beam is at least intermittently directed against different portions of the object.
7. The method of claim 6, wherein said movement effecting step includes simultaneously moving the impinging beam and/or the object in a plurality of different directions.
8. The method of claim 1, further comprising the step of focusing the impinging beam upon the object so that the maximum dimension of the focused beam at the locus of impingement upon the object is less than 10 mm.
9. The method of claim 1, wherein said directing step includes guiding the beam along a fixed first portion of a path which terminates at the object and guiding the beam along a continuously moving second portion of the path so that the beam continuously impinges upon different parts of the object.
10. The method of claim 1, further comprising the step of gathering the evaporated impurities.
11. Apparatus for removing impurities from the surface of a metallic object, including removing rust and/or other oxidation products from an object which contains iron or steel, comprising a source of coherent radiation; means for directing a beam of coherent radiation against the object to impinge upon and heat the impurities on the surface of the object to evaporation temperature and to thereby effect evaporation of impurities as well as the exposure of the thus cleaned surface to the impinging beam whereby the cleaned surface reflects the beam; means for monitoring the characteristics of the reflected beam; and means for regulating the action of the impinging beam upon the object in dependency on monitored changes in the characteristics of the reflected beam.
12. The apparatus of claim 11, wherein said regulating means includes means for varying the intensity of the beam which impinges upon the object as a function of changes in the intensity of the reflected beam.
13. The apparatus of claim 11, wherein said regulating means includes means for effecting a relative movement between the impinging beam and the object in response to changes in the intensity of the reflected beam.
14. The apparatus of claim 11, further comprising means for diverting at least a portion of the reflected beam, said monitoring means including detector means located in the path of propagation of the diverted beam.
15. The apparatus of claim 14, wherein said diverting means includes a mirror having a diverting portion making an angle of between about 40 to 50 degrees with the path of the reflected beam.
16. The apparatus of claim 14, wherein said diverting means comprises a mobile mirror which is located in and moves relative to the path of propagation of the reflected beam.
17. The apparatus of claim 11, wherein said directing means comprises means for directing the beam at an oblique angle to the surface of the object so that the path of the reflected beam deviates from the path of the impinging beam.
18. The apparatus of claim 11, further comprising a source of protective gas and means for directing such gas from the respective source to the location of impingement of the beam upon the object.
19. The apparatus of claim 11, further comprising means for diverting at least a portion of the reflected beam against said monitoring means including ultrasonic transducer means disposed adjacent to the beam and arranged to effect density changes in the atmosphere of the path of the beam.
20. The apparatus of claim 11, wherein said source includes a laser.
21. The method of claim 1, wherein said regulating step includes varying the dimensions of the impinging beam in response to a change in the characteristics of the reflected beam.
22. The method of claim 1, wherein the directing step is performed in such a manner that the impinging beam impinges upon the surface of the object substantially at a right angle; and further comprising the step of diverting at least a portion of the reflected beam from the path of the impinging beam.
23. The apparatus of claim 11, wherein said regulating means includes means for varying the dimension of the impinging beam in response to a change in the characteristics of the reflected beam.
24. The apparatus of claim 11, further comprising means for effecting movement of the object and the impinging beam relative to each other so that the impinging beam is at least intermittently directed against different portions of the object.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3405700 | 1984-02-17 | ||
| DEP3405700.5 | 1984-02-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1265209A true CA1265209A (en) | 1990-01-30 |
Family
ID=6228003
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000474363A Expired - Lifetime CA1265209A (en) | 1984-02-17 | 1985-02-15 | Process to remove contaminants, particularly rust/from metallic surfaces |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4720621A (en) |
| AU (1) | AU589353B2 (en) |
| CA (1) | CA1265209A (en) |
| ZA (1) | ZA851227B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109590148B (en) * | 2019-01-23 | 2023-08-22 | 山东交通学院 | Robot for rust removal and maintenance of track fasteners and working method |
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-
1985
- 1985-02-15 CA CA000474363A patent/CA1265209A/en not_active Expired - Lifetime
- 1985-02-15 AU AU38770/85A patent/AU589353B2/en not_active Ceased
- 1985-02-18 ZA ZA851227A patent/ZA851227B/en unknown
- 1985-02-19 US US06/702,529 patent/US4720621A/en not_active Expired - Fee Related
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109590148B (en) * | 2019-01-23 | 2023-08-22 | 山东交通学院 | Robot for rust removal and maintenance of track fasteners and working method |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA851227B (en) | 1985-10-30 |
| AU589353B2 (en) | 1989-10-12 |
| US4720621A (en) | 1988-01-19 |
| AU3877085A (en) | 1985-08-22 |
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