TWI Industrial Member Report Summary 314/1986
By A Duncan
A major consideration in the selection of structural steels, particularly those to be used for offshore fabrications, is the attainment of good toughness in both weld metal and heat affected zone (HAZ). Recent trends in the development of these steels have centred on two areas, namely, the use of additions to the steel which can control inclusion shape and distribution, and controlled thermomechanical processing to achieve adequate strength in parent plate with a reduced C content. A programme of work has been undertaken to evaluate the welding characteristics of such new steels. This report details tests carried out to assess the toughness of weldments made by the submerged-arc (SA) process in three steels of this type, employing boron-containing and conventional consumables, and arc energies of 2.7 and 4.9kJ/mm. The steels investigated included both calcium-treated (Ca-treated) and rare earth metal treated (REM-treated) types, produced using different thermomechanical treatments, but all intended to meet requirements of BS 4360 Grade 50D. A further recently produced normalised steel was included for comparative purposes. Each was subjected to Charpy testing of weld metal and HAZ, crack tip opening displacement (CTOD) testing of HAZ, determination of tensile properties and metallurgical evaluation.