Laser cleaning as a new type of surface cleaning technology, with no mechanical contact, no base damage, selective cleaning, green and other advantages, in the cultural relics protection, optoelectronic components preparation, tire mold cleaning and other fields widely used, the cleaning mechanism Research and development of finished products by domestic and foreign researchers in the field of concern. This paper introduces the application of laser rust cleaning of steel, mainly carried out three aspects of work: the experimental side, relying on the laboratory has the conditions to carry out the corresponding experimental study, put forward the floating layer of the simultaneous cleaning passivation conditions And the two-beam wet-cleaning and dehumidification passivation method. On the theoretical side, the ANSYS finite element method is used to simulate the process of interaction between laser and rust, and a layered model of rust cleaning below material gasification threshold is proposed. As a result, two different types of low-power laser cleaning equipment were assembled by team members, and the application of industrial paint removal and rust removal was carried out.
details as follows:
(1) laser cleaning of the object can be divided into two kinds of particles and film, for the removal of particles have three effects in the inside, one is thermo-elastic expansion, the second is laser ablation, the third is the gap liquid film explosive boiling, etc. Thermoelastic expansion mechanism. There are many specific embodiments, from the point of view of incidence, can be divided into positive incidence, angular incidence, grazing incidence and back incidence of four, by analyzing the laser heating caused by the temperature distribution and displacement distribution, the establishment of laser-induced detachment stress And the relationship between the adhesion force, or the relationship between the thermal elastic properties and the bond potential, and then determine the cleaning conditions, and finally get the laser parameters, material parameters and environmental parameters and cleaning effects, the relationship between the decision.
(2) A double-beam wet cleaning and dehumidification cleaning method and cleaning device are proposed. In the double beam, one beam is pulsed CO2 laser, and one beam is quasi-continuous Nd: YAG laser. Pulsed CO2 laser can improve the cleaning efficiency of laser rust in liquid film assisted condition. Quasi-continuous Nd: YAG laser removes the residual liquid film by heating the steel base, avoids secondary corrosion, and then controls the substrate by controlling the number of pulses Of the surface temperature rise, to achieve active oxidation of steel passivation.
(3) the use of quasi-continuous laser line scan mode to remove the floating rust, synchronized to achieve passivation pass. The pulse width of the quasi-continuous laser is 150 ns at a fixed repetition frequency of 3 kHz and a pump current of 20 A, which is in the medium pulse width range and has a cleaning characteristic different from that of the short pulse laser. The use of the medium pulse width laser on the floating layer of laser removal, laser energy density in the appropriate choice, through the laser heating to the substrate to the melting point, the use of metal bath on the temperature and oxygen content of the uniform effect, can make the activated steel The oxidation of the substrate is more uniform, thus achieving passivation while cleaning. When the laser energy density is only to remove the surface rust layer, the corrosion of the steel surface after the corrosion resistance is only partially improved, can not provide passivation effect; and laser energy density is too high, making the rust surface temperature exceeds its decomposition temperature, The rust layer will decompose, and the deep pool will lead to the deep diffusion of oxygen content, the formation of multi-layer structure, but also the loss of the passivation effect; through the experimental results and ANSYS simulation results, the final determination of the cleaning passivation condition.
(4) proposed a stratified model of laser rust below gasification threshold. Laser irradiation to the surface of the corroded sample, due to the absorption of the surface of the laser layer attenuation effect, the surface temperature can reach the decomposition temperature of iron oxide, through the decomposition of melting to achieve removal, and deeper laser energy can not directly break the rust layer , But by heating the rust layer to loose the internal structure of the air, the use of air pressure expansion can also play a role in the rust layer, that is, phase explosion mechanism. Melt decomposition and phase explosion through the accumulation of multi-pulse, gradually reduce the thickness of the rust layer, when the rust layer thickness is reduced to less than the thermal diffusion depth, part of the laser energy
1000W laser metal rust removal machine
