On the physics and chemical thermodynamics of laser cutting

University dissertation from Luleå : Luleå tekniska universitet

Abstract: Over the past two decades C02 laser cutting has grown from an obscure laboratory technique into an important branch of manufacturing engineering. Industrial application of the process has been extremely successful even though the cutting process is not thoroughly understood in detail. This thesis presents the results of a number of theoretical and experimental investigations aimed at increasing our understanding of the interactions which are responsible for the cutting process. The thesis is equally divided between experimental and theoretical work and involves chemical as wen as physical analysis of the cutting mechanisms. Although many of the conclusions reached are valid for a wide range of materials the main thrust of the work is concerned with the cutting of steels. The reasons for this are twofold: Steel cutting is the prime source of the industrial growth of the subject The chemical and physical interactions involved in steel cutting are the most complex and the least understood. This work has helped to clarify a number of features of the laser cutting process including the following: The effects of process parameters on the efficiency of the cutting process. The nature and rate of oxidation reactions in the cut zone (and therefore the level of thermal input from such reactions). The source of cyclic variations in oxidation rate which lead to the generation of striations on the cut edge when cutting mild steel. The levels of reflection, conduction, convection and radiation of heat away from the cut zone. The theoretical development and experimental verification of an energy balance for the cutting process.

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