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Heavy section laser beam welding of fine-grained structural steels


Kohler, H.:
Laser : Technologie und Anwendungen. Jahrbuch 1993
Essen: Vulkan-Verlag, 1993 (Laser-Jahrbuch 3.1993)
ISBN: 3-8027-2168-3
Book Article
Fraunhofer ILT ()
carbon; ductility; influence; laser beam welding; weldability; weldment

The fusion zone of laser beam welded steels is very small due to the low heat input. Typical cooling rates amount between 1s and 10s. Thus, shrinkage and deformation are quite low. On the other hand, high carbon steels with a content of about (C)=0.18% tend to form a hardened fusion zone. The maximum hardness can be reduced by means of an appropriate choice of the welding parameters or a suitable modification of the chemical composition of steel. It has been shown that the reduction of carbon from 0.18% to 0.10% for steels of the same strength level (two different kinds of StE 355 steels) causes a lower hardness combined with enhanced impact energy values. The increasing application of modern steels with a lower carbon content but with solid solution hardening elements or micro-alloying elements promotes the use of the laser welding technique. Thermomechanically treated steels are more and more applied in e.g. steels structures and in the shipbuilding industry. Their carbon content is about 0.10% or less and the tolerance in their properties is very limited compared to normalized steels. One specific problem with ordinary welding techniques is the softening in the HAZ due to the relatively high heat input. The advantage of the low heat input with lasers is the absence of that softened zone. It is feasible to attain weld properties which are close to those of the base material.