STP679: Influence of Small Amounts of Niobium on Mechanical and Corrosion Properties of Type 304 Stainless Steel

    Sikka, VK
    Metallurgist, Mechanical Properties Group, metallurgist, Welding and Brazing Group, and group leader, Mechanical Properties Group, Oak Ridge National Laboratory, Oak Ridge, Tenn.

    Moorhead, AJ
    Metallurgist, Mechanical Properties Group, metallurgist, Welding and Brazing Group, and group leader, Mechanical Properties Group, Oak Ridge National Laboratory, Oak Ridge, Tenn.

    Brinkman, CR
    Metallurgist, Mechanical Properties Group, metallurgist, Welding and Brazing Group, and group leader, Mechanical Properties Group, Oak Ridge National Laboratory, Oak Ridge, Tenn.

    Pages: 34    Published: Jan 1979


    Abstract

    Creep and creep-rupture properties of several experimental heats of Type 304 stainless steel containing 20, 50, 100, 200, 500, 700, and 1000 ppm (by weight) of niobium were investigated in the temperature range of 482 to 649°C. Resistance to intergranular corrosion of these heats was also studied. Results of tests on the experimental heats were compared with the creep properties of 20 commercial heats of Type 304 stainless steel and data from the literature on several heats of Type 347 (4000 to 3000 ppm niobium) stainless steel.

    Results on experimental heats were used to check that heat-to-heat variations in creep properties of 20 commercial heats of Type 304 stainless steel are caused by variations in carbon, nitrogen, grain size, and for the most part by residual niobium (10 to 200 ppm). The time to rupture increased and minimum creep rate decreased with increasing niobium content until a saturation level was attained at about 500 to 1000 ppm.

    Type 304 stainless steel containing 500-ppm niobium offers superior creep and creep-rupture properties with improved creep ductility and a factor of approximately 5 better intergranular corrosion resistance [in boiling copper sulfate (CuSO4) solution] than Type 304 stainless steel (20-ppm niobium). In their welding work on the same heats, Moorhead et al have observed that Type 304 containing 500 to 1000 ppm niobium exhibits a weldability similar to that of Type 304 stainless steel.

    Keywords:

    niobium, austenitic stainless steel, tensile properties, creep properties, yield, ultimate tensile strength, corrosion resistance, heat-to-heat variations, mechanical properties


    Paper ID: STP38354S

    Committee/Subcommittee: A01.13

    DOI: 10.1520/STP38354S


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