Instrucciones para la preparación de los trabajos a presentar en el XV congreso Nacional de Ingeniería Mecánica

ABSTRACT 
This article presents the optimum cutting conditions for Advanced High 
Strength Steel (AHSS) laser cutting. Different series of AHSS, used in 
automotive industry at date, have been tested with different laser cutting 
parameters.
The influence of laser cutting in the material and the changes on metallurgic 
characteristics has been studied. The results, as expected, demonstrate very 
different behaviour as a function of sheet thickness, whilst the variation of 
cutting parameters due to the influence of the material is less important. The 
results have been divided into two large groups with thicknesses of more 
and less than 1 mm. Parameter variation inside each group mainly depends 
on sheet material coating. 
The optimum cutting areas and the quality of the cut evaluated with 
different criteria are presented. Finally, the best position for the laser beam 
has been observed to be underneath the sheet. 
KEYWORDS:, AHSS, CO
2
Laser cutting, Laser cutting parameter optimization.
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1. INTRODUCTION 
Advanced high strength steel (AHSS) has spread in car bodywork in recent years. These 
types of steels allow a weight reduction and a higher impact resistance of the bodywork, 
resulting in a lighter and safer car. The main disadvantage is that shaping of these steels 
is very difficult given their high springback and the need to use very hard dies. Other 
operations, such as welding or thermal cutting, are more challenging because of their 
higher carbon content. Some welding studies [1] describe that these steels have very 
different behaviour to mild steels. 
Regarding to laser cutting process, there are few data on high strength steel cutting [2]. 
For this reason, a study has been developed to define its cutting parameters. It is 
difficult to predict the quality of the cut [3], due to the coupling of thermal effect of the 
laser and the oxidation of the material by the oxygen used as assisting gas. The 
exothermal reactions of iron and other alloy elements are complex [4], and AHSS steels 
have a high content of alloy elements, which can lead to differences with regard to the 
cutting of common steels. 
Laser cutting is a consolidated industrial process, used mainly in boiler works and sheet 
metal trimming [4, 5]. It is the process that implies the least material wastage, lessens 
the distortion of parts for medium and low thickness sheets and prevents tools from 
wear and tear [6]. Although laser cutting has been used traditionally, together with 
punching, for cutting mild steel (with a carbon content less than 0.13%), the automotive 
industry has incorporated the laser cutting process to trim the sheets that will later on be 
shaped. Thus, laser cutting is becoming more and more widespread in other materials, 
such as composites or high strength steels [2, 7]. 
Some works have focused in laser cutting modelling [3]. This works establish a relation 
between laser cutting parameters and material properties, usually a power balance 
between laser beam power and heat and melt required power. Other authors works have 
developed finite element models of laser cutting process. These works have been 
applied for 2D models, but recently some 3D models have been developed [9]. These 
models used to introduce material properties such as specific heat, thermal conductivity, 
density, etc. However, thermal characteristics of AHSS are almost equal as mild steel 
but the optimum cutting parameters are significantly different due to metallurgical 
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transitions and oxidation. These effects are not considered in the presented models and 
can only be evaluated using an experimental study.