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The effects of power beam (laser and electron beam (EB)) welding on the mechanical properties of both commercially produced steels and selected laboratory melts have been assessed with a view to establishing what changes or improvements in steel quality are necessary to introduce this technology for structural steel applications. In order to compare the mechanical behaviour with conventional welding techniques both crack tip opening displacement (CTOD) and Charpy tests were performed. In nearly all of the steels considered, the intercritically reheated zone showed poorer toughness than that of the fused zone. The intercritical heat affected zone (ICHAZ) toughness was directly related to the parent plate ferrite grain size and extent of precipitation hardening. A study of steels of constant composition rolled to different parent plate microstructures confirmed this effect of microstructure. Two distinct types of microstructures have been associated with good toughness. One consisting largely of fine intragranularly nucleated upper bainite (Type III bainite) is favoured by low C (less than 0.07% C) Nb-Ti composition. The other, acicular ferrite, is promoted by deliberate O additions to low Al (less than 0.006%) steels. In both cases the types of oxide inclusions present in the weld metals have a decisive influence on the development of the fused zone microstructures.

Additional information

Authors: COCHRANE R C, British Steel plc, London (GB);SENOFLES D J, British Steel plc, London (GB);LLOYD L J, British Steel plc, London (GB)
Bibliographic Reference: EUR 17996 EN (1998) 71pp., ECU 13.50
Availability: Available from the (2)
ISBN: ISBN 92-828-4135-9
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