Effects of residual niobium on Type 304 stainless steel. [900 to 1200/sup 0/F]

Journal Article · Sat Sep 01 04:00:00 EDT 1979 · Weld. J. (Miami); (United States)

OSTI ID:5922320

Moorhead, A J; Sikka, V K

Some heats of Type 304 SS are stronger than can be explained by carbon and nitrogen content or grain size; this is attributed to the strengthening effect of residual niobium. Time to rupture increased and minimum creep rate decreased with increasing niobium until a saturation level was attained at about 500 to 1000 ppM. To systematically study the effect of niobium on the behavior of Type 304 stainless steel, a low-niobium commercial heat with varying additions was remelted. An experimental heat containing 500 ppM niobium exhibited improved creep and creep rupture properties with high ductility in the range 482 to 649 C (900 to 1200 F). Additionally, use of the Spot Varestraint weldability test led to the finding that the fusion and heat-affected zone (HAZ) cracking behavior of the experimental heats was similar to that of a heat of commercial Type 304 stainless steel and much superior to that of a heat of Type 347. This superior resistance to fusion zone cracking in the commercial and experimental Type 304 materials is attributed to a small amount of delta-ferrite in the weld microstructure. The outstanding HAZ cracking behavior in both the experimental heats and the commercial Type 304 is at least partly attributed to backfilling of grain boundary separations. It is hypothesized that a relatively wide partially melted zone prevents backfilling of HAZ cracks in Type 347 stainless steels.

• Research Organization: Oak Ridge National Lab., TN
• OSTI ID: 5922320
• Journal Information: Weld. J. (Miami); (United States), Journal Name: Weld. J. (Miami); (United States) Vol. 59:9; ISSN WEJUA
• Country of Publication: United States
• Language: English

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ALLOYS
BREEDER REACTORS
CHEMICAL COMPOSITION
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-NICKEL STEELS
CORROSION RESISTANT ALLOYS
CRACKS
CREEP
CRYSTAL STRUCTURE
DUCTILITY
ELEMENTS
FAILURES
GRAIN BOUNDARIES
GRAIN SIZE
HEAT AFFECTED ZONE
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HIGH TEMPERATURE
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
METALS
MICROSTRUCTURE
NICKEL ALLOYS
NIOBIUM
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
REACTORS
REFRACTORY METALS
RUPTURES
SIZE
STAINLESS STEEL-304
STAINLESS STEEL-347
STAINLESS STEELS
STEELS
TENSILE PROPERTIES
TRANSITION ELEMENTS
WELDABILITY