Issue 30

A. Martín-Meizoso et alii, Frattura ed Integrità Strutturale, 30 (2014) 14-22; DOI: 10.3221/IGF-ESIS.30.03 14 Focussed on: Fracture and Structural Integrity related Issues Resilience and ductility of Oxy-fuel HAZ cut A. Martín-Meizoso, J. Aldazabal, J.L. Pedrejón CEIT and Tecnun (University of Navarra) ameizoso@ceit.es S. Moreno Tecnun (University of Navarra) s.moreno@alumni.tecnun.es A BSTRACT . Cutting processes affect the material to a deeper or shallower attached-to-the-cut zone. Its microstructure, its hardness and mechanical properties are changed. Also the cutting process introduces surface roughness and residual stresses. In most cases it is recommended to remove this region by grinding, in order to keep a smoother surface, free from the above mentioned effects. This work presents the characterization results of the Heat Affected Zone (HAZ) of a steel plate of grade S460M, with a thickness of 25 mm, cut by flame oxy- fuel gas cutting. The HAZ microstructure is observed (and the depth of the HAZ measured), the hardness profile and the stress vs. strain curves until fracture are measured by testing micro-tensile samples, instrumented with strain gauges. Micro-Tensile specimens are 200 microns in thickness and were obtained from layers of the HAZ at different distances from the oxy-fuel cut. The obtained stress-strain curves are compared with the hardness measurements and the observed metallography. K EYWORDS . Cutting; HAZ; Oxy-fuel; steel; Cut Affected Zone (CAZ). I NTRODUCTION he use of plates as part of constructions, structures, machinery… requires the cutting of large plates into smaller parts that eventually will be shaped and arranged together by means of mechanical joining techniques or welds. There are many available techniques for cuttings: shear cutting, oxy-fuel gas or flame cut, laser cut, plasma, water jet… all these techniques will affect the cut material to a swallower or deeper extent, modifying its microstructure, surface roughness and finishing and might also introduce residual stresses in the neighbour underlying parent material [1-5]. To optimize the use of cutting, particularly with respect to fatigue performances [6-11], the question of to what extent is a good idea to remove cut affected zones (for example, by grinding -what also introduces additional modifications on cut substrates-) is most relevant. This is the objective of a European Project (HIPERCUT) what deals with plate cutting techniques, ranging from 8 mm to 25 mm plate thickness and grades between S355M and S890Q. Different cutting techniques are studied: plasma, laser and oxy-fuel gas cuttings within this project. This paper is focused on the results obtained for a single grade (S355M), thickness (25 mm) and cutting technique (oxy-fuel gas). T