WELDABILITY OF HSLA-65 STEEL FOR SHIP STRUCTURES

HSLA-65 steel (ASTM A945) is being considered to replace higher streng th steels (HSS) such as DH-36. However, the 70-series consumables (70 ksi [482 MPa] minimum transverse weld tensile strength) used to join H SS (71 ksi [489 MPa] tensile strength) could produce a welded joint in HSLA-65 (78 ksi [537 MPa] tensile strength) with under-matched streng th. The objective of this study was to determine the procedure limits for welding HSLA-65 with 70-series consumables. Multipass weldments we re made and evaluated in 1/2- to 11/4-in. (13 to 32 mm) thick HSLA-65 and 5/8-in. (16 mm) thick DH-36 steel plates by shielded metal are (SM A), flux cored are (FCA), gas metal are (GMA) and submerged are weldin g (SAW) at weld cooling rates from 3 to 75 degrees F/s (1.7-42 degrees C/s). Additional one-sided, high-energy-input, single-pass, multiwire submerged are weldments were made with weld cooling rates less than 1 degrees F/s (0.55 degrees C/s). The results showed that there was no cracking in the weld metal or heat-affected zone (HAZ) and that HSLA-6 5 did not exhibit excessive hardness or softness in the HAZ. Transvers e weld tensile strengths were above the 78 ksi minimum specified. The measured HAZ CVN toughness in multipass welds was influenced by the to ughness of the adjacent weld metal, but was capable of meeting base me tal requirements. The single-pass, high-energy-input submerged are wel dments exhibited reduced HAZ CVN toughness; however, the degradation w as not as severe when compared to the DH-36 HAZ toughness. The CVN tou ghness values of the weld metals at low weld cooling rates were lower than values obtained in electrode conformance testing. Weld metal toug hness criteria need to be established for the intended applications. R esults from this study indicate that HSLA-65 can be welded using 70-se ries consumables over the range of procedures and cooling rates common ly used in shipyard fabrication while exhibiting adequate soundness an d meeting specified minimum transverse weld tensile strength.