Exceed the impact with chromatic to stainless steel surface parameter of fast laser technology

Laser of 1 skin second is chromatic the working principle with chromatic to laser mechanism, have two kinds of different point of views domestic and internationally. The first kind of viewpoint is oxidation film view, because laser pulse serves as local heat source,thinking laser can make metallic surface presents colour is, make in the process of irradiation metallic surface produced oxidation reaction, the surface formed a transparent or translucent oxidation film, oxidation film interferes effect in the generation below Bai Guang, the oxidation film of different ply produces different color. The oxidation film that chromatic law thinks shows this one theory and traditional metal be identical of lubricious academic photograph. Domestic and international researcher undertakes with accept second laser metallic surface makes bid chromatic, the basis is oxidation film the theory that show scene. But appear as what exceed fast laser to be like leather second and flying second laser and apply stage by stage, people offerred the 2nd kind of point of view, namely the surface is periodic phenomenon of stripe small structure. Researcher discovery exceeds short pulse laser, fly especially second laser is chromatic and OK the laser that forms accept rice to measure level in metallic surface is revulsive small structure of periodic surface stripe (NC G LIPSS) . Small structure of this kind of stripe has the characteristic of reflex bar and quality, white smooth illuminate produces diffraction to make the light of different stripe diffraction is interfered each other between each other when metallic surface, the way that the great value of the smooth interference with different wavelengh appears is different, consequently white smooth course reflexes the chromatic dispersion after grating and become spectrum, formed chromatic design. This one theory basically applies Yu Chao metal of short pulse laser is chromatic. Surface of metal of irradiation of accept second laser forms oxidation film is the main basis that produces color. In process of surface of stuff of metal of irradiation of accept second laser, can form as chromatic as chemical oxidation law, electrochemistry to oxidize the same chromatic appearance such as chromatic law oxidizes layer, the hot influence area that arises to metallic surface as a result of accept second laser is too large, metallic surface is easy form again the problem such as casting layer and micro-crack, acquire good exterior stripe small structure hard. Surface of metal of irradiation of flying second laser forms periodic stripe small structure is the main reason that produces color. Pulse of flying second laser has cutty pulse width and extremely high peak value power, with material appear when interaction intense nonlinear effect, effect time is extremely short, fuel factor is minor, to be being machined material oxidizes, be out of shape, hot influence area all lesser, treatment precision is very tall, can acquire all sorts of good exterior stripe small structures. Be in the leather second laser between accept second laser and flying second laser, can resemble accept second laser already same, heat in metallic surface irradiation form the oxidation film that presents different color, also can pass scanning means to achieve metallic appearance like flying second laser periodic stripe small structure, thereby modulation spectral reflectivity, caused the change of metallic surface color. Its difference basically depends on parameter of leather second laser if energy of span of speed of facula size, scanning, line, pulse and collaboration uses the several put together that wait. In pulse width the pulse energy with shorter, appropriate span of slower, line mixes speed of small, scanning a several conditions below, leather second laser can be in the small structure of periodic surface stripe with good performance of metallic surface preparation (LIPSS) . Graph １ is in for accept second laser and leather second laser the structure after stainless steel surface is chromatic. Accept second laser is chromatic use the lamp to smoke laser of YAG of carry Nd ∶ , laser power is 70W, scanning speed is 80mm/s, repeat frequency 2kHz, scanning span 0.

01mm, slant on workbench anxious 2.

0mm, stimulate smooth wavelengh 1064nm, stimulate ＝ of M2 of factor of quality of beam of light 1.

5, diameter of stain of the laser after focusing is 15 μ M about. Energy of odd pulse of leather second laser is 120mJ/cm2, scanning speed 150 μ M/s, scanning span 0.

005mm, 1064nm of laser center wavelengh, stimulate ≤ of M2 of factor of quality of beam of light 1.

8, repeat frequency 30kHz, pulse width 10ps, facula diameter makes an appointment with 10 μ M. From the graph 1 can see, the metallic surface after irradiation of accept second laser is layer of one thin oxidation (end panel) , and the metallic surface after irradiation of leather second laser is a kind of relatively clear stripe small structure. 2.

2 colour model and space of evaluation CIEL*a*b* color are international Commission on Illumination (a kind of when CIE) makes even color system, a kind of any color can express in CIEL*a*b* lubricious space, among them L* is brightness, limits extraction a cost is 0 (black) ~ 100 (white) ;a* and B* express lubricious coordinate (among them A* represents red green axis, b* represents) of yellow blue axis, their extraction is worth limits to be - 128 ~ 127. The premise that gets value of L* , A* , B* is to be measured so that the 3 stimulation of sample are worth (X, y, z) and chroma coordinate (X, y, z) . In changing what color changes CIEL*a*b* system from XYZ system the relation to be type, xn ＝ 95.

047, yn ＝ 100.

0, zn ＝ 108.

883. And 3 stimulate value and coordinate of CIEL*a*b* colour space to change more complex, its calculation method and measure are: 1) use photometric undertake to sample spectrum measures;2) to be in Matlab software, guide with Load function the spectral power of standard illuminant data, sample distributings the 3 stimulation of data and CIE standard illuminant are worth;3) to write functional function, get;4) of sample chroma coordinate to write a space to change function H(x, y, z, l* , a* , b* ) , the L* of computational sample, A* , B* is worth. The difference of two kinds of different colors can discern with off color, e computation type is off color Δ to think usually, value of E of two kinds of colorific Δ is less, explain these two kinds of colour are more adjacent. If Δ E ＜ 2, even if is professional is distinguished very hard also with naked eye. Concerned research is worth off color Δ E ≤ the 4 evaluation level that stabilizes as color. 3 experiments method and test result are analysed 3.

1 test facilities and place of experiment means test are PSHE300-06A skin second with laser fiber-optic laser, 1064nm of laser center wavelengh, stimulate ≤ of M2 of factor of quality of beam of light 1.

8, repeat frequency 30kHz, odd pulse energy is 200mJ/cm2, pulse width 30ps, facula diameter makes an appointment with 15 μ M. Laser chooses the focusing field lens of 163mm, effective mark engraves 112mm of area 112mm × . Test data chooses 1mm the 304 stainless steel that thick, dimension is 100mm × 100mm board, material surface passes polishing processing, the surface is slick level off. The element with influence metal chromatic laser is very much, include energy of quality of light beam of laser wavelengh, laser, pulse and pulse wide, pulse repeats number, arteries and veins the physical property of span of speed of frequency, scanning, line, metal, wait for an element from anxious quantity. Color technology combines referenced domestic and international laser practical test condition, study energy of speed of fill line span, scanning, pulse and workbench wait for an element to be opposite from anxious quantity chromatic influence. Consult accept second and flying second laser are chromatic experience, primary election space is apart from 0.

005mm, the pulse energy of 50 ％ (namely 100mJ/cm2) , 150 μ M/s is speed the experiment is initiative and fiducial parameter. 3.

The circle that the area of influence laser scanning with 2 scanning speed and line chromatic to laser span is diametical 2mm is lubricious piece, below different parameter array becomes 10 × color piece forms the circle of 10; fill limits 0.

001~0.

01mm, removed 0.

μ M/s of 30~300 of 001mm; speed limits, removed limits of energy of odd pulse of 30 μ M/s; ％ of 10 ％ ~100, removed 10 ％ . Laser repeats frequency 20kHz; Zhen Jing to leave anxious 2mm up. Test data and result are shown 2 times like the graph. Can see from inside graph 2(a) , change speed and line span can are opposite chromatic effect produces distinct effect, and but preparation a variety of colour. When speed is less than 90 μ M/s, color is deeper, the specification is slow the laser below fast circumstance already heavier; becomes ablation when speed is more than 90 μ M/s, colour distributings have symmetry. The place on put together is narrated, can get particular case issues pulse energy, reasonable range is 90~300 μ M/s, space is apart from 0.

001~0.

01mm. Reasonable rate can receive the facial expression with bright-coloured colour and lustre below parameter limits. The metabolic case that the average of the L* that graph 2(b) is corresponding CIEL*a*b* colour system, A* , B* follows scanning beam span. From the graph 2(b) can see, as the accretion of speed, l* , A* , B* increases first, reduce quickly after that. Span of the scanning beam when this shows leather second laser is chromatic cannot pass big. 3.

3 space are apart from and the influence with pulse chromatic to laser energy uses same method to analyse space to be apart from change and pulse energy change to be opposite the influence of chromatic effect, the test result that gets 3 are shown pursueing. From the graph 3(a) can see, be more than when line span 0.

01mm and pulse energy are less than 30 ％ time base to cannot see originally colored appear, and line span is less than 0.

The ability when 01mm and pulse energy are more than 30 ％ sees clearer color changes. Explain right now pulse energy is too small, cannot produce effect to stainless steel surface. When pulse energy is more than 70 ％ , because pulse energy is exorbitant, metallic surface is excessive destroy, also cannot appear color, present the black when giving a metal to be scorched however. Analyse by above knowable, reasonable line span and pulse energy parameter are respectively 0.

001~0.

01mm and ％ of 30 ％ ~70. Graph 3(b) is the average of the L* of corresponding CIEL*a*b* colour system, A* , B* . From the graph 3 (B) can see, l* is reduced as the accretion of pulse energy, the accretion of A* , B* as pulse energy, reduce first increase after that. 3.

The influence with 4 speed and pulse energy chromatic to laser power takes line span 0.

005 Mm is calm value, change speed and pulse energy. Speed span takes 30~300mm/s, interval is 30mm/s. Pulse energy limits ％ of 10 ％ ~100, interval is 10 ％ . Test result is shown 4 times like the graph. From graph 4(a) knowable, better color range basically is centrally inside the area that place of ％ of 40 ％ ~70 forms speed 150~300mm/s and pulse energy. Can see from inside the graph colour distributings to have apparent symmetry along diagonal, explain speed and pulse energy all can affect chromatic result apparently, and effect effect comparatives. Graph 4(b) is the average of the L* of corresponding CIEL*a*b* colour system, A* , B* . From the graph 4(b) can see, as the accretion of speed, l* shows close linear direction to increase a current, a* , B* appears to fluctuate certainly. 3.

5 chromatic to laser from anxious quantity influences are installed respectively from anxious quantity parameter is 2, 1, 0mm has a test, through 3 kinds chromatic graph contrasts, the color hue that discovers chromatic extent is basic and changeless, produced the little change of colour lightness and purity only, color of chromatic from anxious generous graph is lighter, reduced the color after leaving anxious amount to deepen. This indirect also confirm the energy that the focus is in most concentration. 3.

6 results analysis and discuss the research that passes chromatic to laser of stainless steel surface test, it is certain to discover periodic stripe small structure is in exterior color and corresponding surface the phenomenal existence connection such as the scattering of light that produces below the condition, reflection, diffraction. Small structure of this kind of periodic stripe has the function of reflex bar structure, when incident nature smooth illuminate arrives when the face that has periodic stripe small structure, as a result of the diffractive action of grating, light passes the chromatic dispersion after grating and become spectrum, present a chromatic result consequently. Domestic and international scholar been flyinging respect of structure of rice of small accept of second laser preparation did many experiment and research, the absorption of successful change metal to spectrum and reflection function. Use laser of leather second pulse to undertake scanning handling to stainless steel surface, also can form small structure of accept rice or surface of cycle of close accept rice in stainless steel surface. In the experiment, after passing irradiation of leather second laser, surface of sample of major stainless steel appeared apparent diffractive effect. Use scanning electron microscope (SEM) undertakes scanning to stainless steel surface, discover its surface formed one sort to be like the periodic small structure of grating, cycle is 300nm~20 μ M about, be this phyletic and periodic stripe small structure brought about light to produce diffractive effect in its surface, cause the surface to present the appearance of color. The graph shows the SEM picture of surface of sample of the green after be irradiation of laser of second of skin of classics of stainless steel surface 5 times. If the graph is shown 6 times,the green sample reflex that uses spectrometer of AURORA4000 high resolution to be measured interferes spectrum, the reflex of green sample interferes spectral existence an overt peak value, peak wavelength is 580nm, with the green conform to that appear, demonstrative theory and test result are main be identical, the parameter that carries laser of control skin second namely can realize stainless steel effectively the preparation of all sorts of color inside limits of visible light chart. Accordingly, the surface of small structure of different periodic stripe can present different color, affect the size of the L* of color, A* and B* . From the graph 2(b) can see, increase as what scanning speed and space are apart from, l* is reduced quickly, show stripe small structure fails to form. Speed of the scanning when this explained leather second laser is chromatic and line span cannot cross big; to be able to see from graph 3(b) , l* increases as pulse energy and reduce, after as pulse the accretion of energy is reduced first, A* , B* increases. When this explains energy is too big, ablation of stainless steel surface is serious, not only did not form small stripe, still make exterior darkly lubricious, absorbed each wavelengh paragraph Bai Guang. Stainless steel of chromatic aging behavior passes laser of 4 second of stainless steel skin after laser is chromatic not only colourful, return the physico-chemical performance that can improve data and mechanical function, if be able to bear or endure,ultraviolet illuminate, wear-resisting, heat-resisting is mixed be able to bear or endure the function such as corrode, among them the color ageing problem of chromatic stainless steel is all in all. For the color aging behavior after laser of check stainless steel is chromatic, undertook ageing tests to the chromatic sample after laser irradiation. Choose laser of second of 3 seed coat chromatic sample (Sample1, Sample1, Sample3) and laser of second of a kind of accept are chromatic sample (Sample1) consults standard of plastic ageing tests undertakes fluorescence ultraviolet the lamp quickens imitate ageing tests artificially (smooth ageing) . Use CI65/DMC quicken climate box artificially, luminous intensity is set for (2100 ± 300)lux, irradiation intensity value is set for (5.

4 ± 0.

27)kW/m2, irradiation time is 1 day respectively, 1 week, 2 weeks, 3 weeks mix 4 weeks. If test result expresses 1 to show. From the metabolic process that expresses color of surface of the 1 sample in can watching smooth ageing process. Show each color of chromatic sample with CIEL*a*b* value, computational hind gets the chromatism between each ageing tests and primitive sample is worth Δ E. From ageing tests data can see, chromatic ageing sample and primitive sample compare laser of second of stainless steel skin, each time paragraph the E of Δ of off color value of ageing sample and primitive sample is smaller, be in in ageing 504h less than and primitive sample chromatism 4.

0 the following, belong to not apparent but oversight color changes, the stainless steel that explains leather second laser is chromatic is able to bear or endure smooth aging behavior is exceedingly good, can reach the technical target in 504h of ultraviolet illuminate ageing at least. Surface of laser of second of skin of test result proof is chromatic processing effect is good, fade slow, chromatic effect has better endurance. Chromatic ageing sample and primitive sample compare accept second laser, each time paragraph off color is worth Δ E all bigger, be more than with primitive sample chromatism later in ageing 336h 4.

0, the NC G LIPSS after the oxidation film after the result explains accept second laser is chromatic is colorrer than leather second laser fades should fast, colorific endurance is more chromatic than leather second laser low. Oxidize as to the surface after accept second laser is chromatic the other property of the metallic stuff surface of the LIPSS of exterior NC G after film and leather second laser are chromatic is like wearability, still need further experiment research. 5 conclusion use laser of fiber-optic skin second to take travel laser chromatic test on 304 stainless steel, the experiment shows in pulse width slow, space is apart from speed of small, scanning shorter fall with appropriate pulse energy condition, leather second laser can be in the small structure of periodic surface stripe with good performance of metallic surface preparation. Studied the impact between parameter of leather second laser and colour space, emphasize analysed the main parameter such as energy of speed of fill line span, scanning, pulse to be opposite the influence of chromatic effect, gave out appropriate parameter size range of pipe bent, conclude as follows: 1) change speed and line span all can are opposite chromatic effect produces distinct effect. When increasing speed and line span, color edge diagonal shows approximate semmetry to distributing, the specification changes speed and line span to have same effect effect to color. It is 60~140mJ/cm2 when pulse energy, speed is 90~300 μ M/s, line span is 0.

003~0.

It is better to can get when 01mm, rich surface colour color. The change also can change colour effect from anxious quantity, but without energy of scanning beam span, pulse and scanning speed 3 person affect remarkable;2) to use CIEL*a*b* colour model, can acquire the metabolic concern between parameter of leather second laser and CIEL*a*b* colour space. As the accretion of scanning speed, ;L* is reduced as the accretion of pulse energy quickly after L* , A* , B* increases first, after as pulse the accretion of energy is reduced first, A* , B* increases the; accretion as scanning speed, l* shows close linear direction to increase a current, a* , B* appears trial of fair sex of fluctuant;3) smooth ageing makes clear, chromatic sample is in laser the E of off color Δ of ageing 504h less than and primitive sample is in 4.

0 the following, belong to not apparent but the color of oversight changes, the chromatic stainless steel that explains parameter of technology of laser of this skin second falls is able to bear or endure smooth aging behavior is exceedingly good, can achieve at least in 504h of ultraviolet illuminate ageing chromatic colour does not degrade, and chromatic sample is in accept second laser E of off color Δ appears to greaten apparently namely after 336h ageing, colour and lustre appeared difference. Surface of laser of proof skin second is chromatic processing effect is good, fade slow, chromatic effect has better endurance. CNC Milling