Investigation On The Mechanism And Application Of Pulsed Laser Coloring Of 316L Stainless Steel

316L stainless steel has the advantages of high appearance gloss,high temperature resistance and corrosion resistance,and is widely used in pipelines,heat exchangers,food industry and watch industry.However,with the continuous improvement of people's quality of life requirements,new requirements have been put forward for the appearance of 316 L stainless steel.The appearance of stainless steel coloring technology has endowed 316 L stainless steel with new value.Among them,laser coloring technology has become a stainless steel coloring technology with the greatest application potential by virtue of its high efficiency,environmental protection and flexible processing.At present,the large-scale application of laser coloring technology still has the problem that it is difficult to accurately control the coloring color.Based on the mutual coupling effect of different laser coloring process parameters on the coloring effect,this thesis investigates the mechanism and application of pulsed laser coloring of 316 L stainless stee.The main contents are as follows:(1)Through the dual-variable combination test method,the laser coloring test was carried out on 316 L stainless steel by using different laser coloring process parameter combinations to study the influence of different process parameter combinations on the pulsed laser coloring effect of 316 L stainless steel.The study found that under the combination of laser pulse width ? = 8ns,scanning line spacing d = 0.001 mm and scanning speed v = 1200 mm / s,adjusting the laser power P and frequency f can achieve a slow transition of 2 to 3 colors,which shows that within the same gradient,the laser power and pulse frequency have a similar effect on the 316 L stainless steel laser coloring effect;While in the laser power P = 7W,pulse frequency f = 450 kHz,scan line spacing d = 0.001 mm and scanning speed v =1500mm / s parameter combination,adjusting the pulse width ? can quickly achieve 6 to 7 color transitions,which shows that the pulse width has much more influence on the coloring effect than the laser power and pulse frequency;The scanning speed v and line spacing d mainly pass the pulse laser spot The lap rate controls the laser coloring effect of 316 L stainless steel.The greater the lap rate,the more heat the material surface absorbs,and the more obvious the coloring effect.(2)Through ANSYS finite element analysis software,the variation rule of temperature field of laser colored 316 L stainless steel under different technological parameter combinations was analyzed,and the influence mechanism of temperature on the thickness of oxide film on colored surface was explored.The study found that the increase of the single pulse energy Ep can cause the temperature of the entire temperature field to increase,while the increase of the pulse width ? will reduce the temperature of the entire temperature field;At the same time,in the case of continuous pulses,the surface temperature of the material rises rapidly in a single pulse processing cycle,then naturally cools,and has cooled to room temperature before the next pulse.This indicates that the mechanism of continuous pulses is the superposition of multiple single-shot heating effects.This indicates that the mechanism of continuous pulses is the superposition of multiple single-shot heating effects.This heating effect,which is determined by the laser power P,pulse frequency f and pulse width ?,affects the microscopic thickness of the surface oxide film layer after a single pulse;The scanning speed v and the line spacing d directly determine the number n of this stacking.The final stacking number n and the single heating effect together determine the thickness of the oxide film layer after multiple stacking.(3)The microscopic morphology observation,element content measurement and chromatic characterization of the colored 316 L stainless steel surface were used to verify the mechanism of laser coloring,and the quality of the 316 L stainless steel pulse laser coloring effect was evaluated according to the chromaticity value.The study found that when the laser power P was continuously increased from 4W to 12 W,the oxygen content of the surface area of 316 L stainless steel increased continuously from 9.49% to 12.35%,indicating that the surface area of 316 L stainless steel after laser coloring is mainly oxide film,and with the increase of the laser power P,the greater the thickness of the oxide film,which is consistent with the effect of the laser parameters on the thickness of the oxide layer;The chromatic aberration ranges of single laser coloring and multiple laser coloring are 0~0.5 and 0~0.6 respectively,indicating that the pulsed laser coloring of 316 L stainless steel process can meet most application requirements in terms of color uniformity and stability,and is completely practical.(4)BP neural network was used to simulate the coloring test data,and a laser coloring model was constructed.The software model was used to verify and predict the coloring effect of 316 L stainless steel pulse laser,which provided guidance for the parameter selection of the laser coloring test.The study found that the color prediction value of the test sample of the laser coloring color prediction model of the 316 L stainless steel surface based on the BP neural network is basically consistent with the actual value,and the average color difference does not exceed 2.This shows that it is completely feasible to predict the stainless steel coloring effect by means of the BP neural network.It can achieve the prediction of the laser coloring effect under the continuous change of the laser process parameters within a small parameter range,which can provide powerful support for the further application and development of the plused laser coloring of the 316 L stainless steel.