Fracture toughness of laser welds in ship steel

Abstract

Shipbuilders are showing increasing interest in laser welding as a means of reducing fabrication costs. The nature of the weld zone is very different to that in an arc weld. Careful research is needed to establish the safety of laser welded structures against a range of risk scenarios. This report deals with fracture toughness and defect tolerance. The laser weld is shown to exhibit very unusual behaviour. The lowest toughness is obtained when a crack is located at the heat affected zone (HAZ), but there is no apparent microstructural embrittlement at this location. It is proposed that the effect arises from an elevation of crack tip tensile stresses induced by the strength overmatch of the adjacent weld zone.

Hybrid laser arc welding of X80 and X120 steel grade

“…Thus, sufficiently high notch impact toughness of the laser hybrid welds on steel grades up to X70 with maximal wall thickness of 16 mm could already be demonstrated. [6][7][8][9] Laser hybrid welding trials on X80 grade steel have also demonstrated acceptable notch impact toughness of welds with a maximum root face depth of 9 mm. 10 Some promising results regarding weldability aspects of X100 grade steel in the high power fibre laser welding process have already been achieved.…”

“…The achievable mechanical and technological properties of laser hybrid welds are currently being investigated intensively by , № 1( 22) 2017 international research groups. Thus, sufficiently high notch impact toughness of the laser hybrid welds on steel grades up to X70 with maximal wall thickness of 16 mm could already be demonstrated [6][7][8][9]. Laser hybrid welding trials on X80 grade steel have also demonstrated acceptable notch impact toughness of welds with a maximum root face depth of 9 mm [10].…”

Investigations on the Fracture Toughness of Electron Beam Welded Steels

“…CPD can be observed during fracture mechanic test as well, especially when tests are performed at temperatures where ductile failure is common. [3] Testing at lower temperatures (e.g. ductile-brittle transition region) can lead to crack propagation in the weld line when the crack starter notch was already placed in the weld line, as shown in [4,5].…”