20w UV Laser Marking Source for cleaning steel surface paint

Achievement introduction: Scholars from Harbin Institute of Technology used an environmentally friendly nano-ultraviolet (UV) laser to innovatively apply laser cleaning to the paint on the surface of AH36 steel. The possibility of using this UV laser for cleaning was innovatively proposed and experimentally verified, and further verification was carried out using a theoretical model. The surface quality after laser cleaning was characterized. Its mechanical properties, such as surface microhardness, tensile strength and flexural strength, were characterized. The results show that laser cleaning has very significant advantages as a means of replacing traditional paint removal in marine engineering.

1. Background introduction

Surface cleaning has received much attention over the past few decades, especially in the fields of aerospace, marine engineering, microelectronics, and medicine. The pollutants on the surface of living organisms are nothing more than the presence of oxides, paints, polymers, coatings, microorganisms and particulates on the surface. Ships cruising in the sea are of great concern because they are mainly subject to severe corrosion caused by seawater. For this reason, ships often have to remove the surface paint layer after a period of service, and at the same time carry out the maintenance process of new paint. In particular, it is important to note that each of the above process operations consumes billions of dollars in annual budgets. Therefore, the removal of paint from the surface of the substrate for re-coating and thereby extending the life of the vessel is critical. Looking at previous studies, traditional surface cleaning methods, including mechanical and chemical cleaning methods, are currently the most common methods. However, the problem with these means is that they either pollute the air and water, or generate secondary polluting waste. Based on this consideration, laser cleaning technology, as an emerging surface cleaning technology, is considered to be the most advanced technology to replace traditional cleaning technology, because laser cleaning technology is considered to be more environmentally friendly and does not require contact the surface of the object being cleaned. Depending on the (including but not limited to) excellent plasticity and strength, high mechanical properties and accompanying light weight of AH36 steel, AH36 steel is widely used in marine engineering. However, it should be emphasized that the service life of this steel is strongly affected by the marine environment in which it is used, and a large number of highly corrosive ions and microorganisms existing in the marine environment will act synergistically to accelerate the surface degradation of the steel substrate. Peeling of the coating. Immediately afterwards, the inner layer of the steel matrix surface will also begin to continue to fail when exposed to the harsh ocean. Therefore, surface cleaning becomes necessary as it allows the removal of surface damaged paint and contaminated substrate surfaces. There has been a lot of work on laser cleaning paint. Back in 1974, J.A. Fox pioneered the use of Q-switched lasers for paint removal. It has been reported that the paint layer on the surface can be effectively removed under intense laser photon-induced stress. In addition, K.Liu and F.Garmire et al. used different types of lasers and different pulse widths for depainting. It has been reported that Nd:YAG lasers with Q-switched mode are more effective in removing paint than other lasers, such as CO2 lasers, excimer lasers, and CW lasers. Chen et al.'s study also pointed out that the use of laser cleaning, compared with the traditional cleaning technology, overcomes the main shortcomings, such as secondary pollution.

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However, current laser cleaning, mainly nanosecond lasers in the infrared band, usually exploits thermally induced defects, which means that recast layers and heat-affected zones are formed on the surface of the object. On the other hand, UV lasers may avoid these problems because UV lasers rely on photon energy and the corresponding breakdown of molecular bonds. To the authors' knowledge, there have been no studies using UV lasers to remove paint layers. More importantly, the influence of the corresponding process parameters on the cleaning effect is also unclear. In this study, scholars from Harbin Institute of Technology used UV lasers for the first time to carry out research on removing paint, and changed the laser energy to carry out research. Further, the cleaned samples were tested in metallography, scanning electron microscope and optical profile measurement, as well as mechanical properties.

2. Laser cleaning mechanism

In this experiment, the ultraviolet laser produced by Huari, a unit of Jiangsu Laser Alliance, was used. The mechanism of action is: it is generally believed that in the process of laser cleaning, the photochemical interaction, that is, the energy of the photons emitted by the UV laser, is much greater than the energy of the molecular bonding inside the material, which in turn further destroys the molecules. bonding.

3. Experimental results

Основан на инновационном использовании наносекундного УФ-лазера для лазерного отслаивания слоя краски на подложке AH36. Этот инновационный эксперимент теоретически и практически продемонстрировал осуществимость и эффективность УФ-лазерной очистки лакокрасочного покрытия стали AH36, а также основной механизм взаимодействия УФ-лазера, такой как фототермические и фотохимические взаимодействия. Была создана термодинамическая модель для описания взаимосвязи между температурой и энергией лазера, и результаты показали, что пороговое значение для лазерной очистки составляет 4,65 Дж/см exp(2), что очень близко к теоретическому значению (теоретическое значение составляло 5 Дж). /см эксп( 2)). В то же время обсуждается существование этой разницы. Морфология поверхности, химический состав и механические свойства до и после лазерной очистки также были подробно оценены с помощью СЭМ. EDS, оптический профилограф и методы испытаний механических свойств. После тестирования с помощью СЭМ на поверхности появляются типичные морщинистые формы, ямки и круглые микроструктуры при различных условиях подвода лазерной энергии. Относительно механических свойств следует отметить, что удаление краски УФ-лазером позволяет значительно улучшить микротвердость поверхности, прочность на растяжение и прочность на изгиб. Это связано с быстрым плавлением и затвердеванием во время очистки поверхности с помощью УФ-лазеров, что приводит к микроструктуре круглой и морщинистой морфологии, а также к высокой плотности дислокаций. Таким образом, эта передовая технология УФ-наносекундной лазерной очистки не только безвредна для окружающей среды, но и позволяет значительно улучшить механические свойства деталей после лазерной очистки.