WELDABILITY AND FRACTURE TOUGHNESS OF 5% NI STEEL – PART 1: WELD SIMULATION TESTING ; WELDABILITY AND FRACTURE TOUGHNESS OF 5% NI STEEL – PART 2: WIDE PLATE TESTING (To Purchase Call 1-800-854-7179 USA/Canada or 303-397-7956 Worldwide)
This paper describes an investigation on the weldability of a double normalized and tempered 5% Ni steel@ using weld simulation to estimate the heat-affected zone (HAZ) ductility at cryogenic temperatures. A series of large scale tensile tests have also been carried out on 5% Ni butt welds@ the results of which are reported in Part 2 of this WRC Bulletin. Charpy-V specimens were subjected to various weld simulation cycles and heat treatments and subsequently broken at a range of cryogenic temperatures. Very high peak temperatures result in a sharp drop in impact strength@ especially if high heat input welding is simulated. Very low base metal and HAZ ductilities can result from artificial aging@ such as a plastic deformation followed by heating in the 200-400C temperature range; this suggests that care must be taken when cold deformation is applied or distortions are corrected in structures made of 5% Ni steel. The ductility can be restored by heat treating the specimens for instance for 1 hr in a very narrow temperature range at around 650C.