Showing papers on "Austenitic stainless steel published in 1973"

Tracer diffusion of59Fe and51Cr in Fe-17 Wt Pet Cr-12 Wt Pet Ni austenitic alloy

Abstract: The volume and grain-boundary diffusion of59Fe and51Cr have been studied in an austenitic iron alloy containing 17 wt pct Cr and 12 wt pct Ni. The diffusivities in this alloy of these two tracers and63Ni are compared with their diffusivities in pure iron and in other austenitic stainless steels. For volume diffusion at any particular temperature in the present alloy, Cr is the most rapid while Ni is the slowest, and all three tracers diffuse slower than that reported for pure iron or for other austenitic stainless steels. For grain-boundary transport, Fe diffuses most rapidly above 850°C and Ni diffuses most rapidly below that temperature. The activation energies for both volume and grain-bounary diffusion obey the relationshipQ Ni

Intergranular Corrosion of Iron-Nickel-Chromium Alloys

Abstract: Almost since their commercial inception about one-half century ago, it has been recognized that stainless steels and related iron-nickel-chromium alloys are susceptible to a particularly insidious mode of corrosive attack, namely intergranular corrosion. Indeed, in their classic paper, Bain et al.1 stated, “One of the few shortcomings of the austenitic stainless steels … [is that] … the metal, after exposure to moderately elevated temperature in the general vicinity of 1000-1500oF, has frequently been found to be subject to a very characteristic· form of intergranular corrosion, even in environments which ordinarily have no effect upon the normal alloy.”

Stress relaxation and mechanical equation of state in austenitic stainless steels

Abstract: Stress relaxation experiments have been performed on types 304 and 316 stainless steel at room temperature. The stress-strain rate data show that these materials exhibit the behavior of mechanical equation of state. The experimental results are discussed using the concept of internal stress.

Gas-phase hydrogen permeation through alpha iron, 4130 steel, and 304 stainless steel from less than 100 C to near 600 C

Abstract: Gas phase hydrogen permeation studies were conducted on hollow, cylindrical membranes of triply zone-refined alpha iron, AISI 304 austenitic stainless steel, and AISI-SAE 4130 steel in both the normalized (ferrite and carbide) and quenched and tempered (martensite) conditions. Membrane temperature was varied from less than 100 C to near 600 C and hydrogen pressure was varied. For one membrane material, normalized 4130 steel, gas phase hydrogen transport under both steady state and nonsteady state conditions was demonstrated to be controlled by lattice diffusion. Additionally, Sievert's law was shown to be applicable. For all membrane materials, expressions for the coefficients for hydrogen permeation were determined by analysis of steady state transport; the coefficients for diffusion were determined by the lag time technique applied to nonsteady state transport; and through a knowledge of the Sievert's constants, the subsurface equilibrium lattice hydrogen concentrations were determined.

Tracer diffusion of63Ni in Fe-17 wt pct Cr-12 wt pct Ni

Abstract: The tracer diffusion of63Ni in Fe-17 Cr-12 Ni by both volume and grain boundary transport has been studied from 600° to 1250°C. The use of an RF sputtering technique for serial sectioning allowed the determination of very small volume diffusion coefficients at the lower temperatures. Volume diffusion of nickel in this alloy was observed to be much slower than in pure iron or austenitic stainless steel at comparable temperatures. The volume diffusion coefficient is described byDv=8.8 exp (−60,000/RT) cm2/s and grain boundary diffusion is described by σDgb=3.7×10−9 exp (−32,000/RT) cm3/s.

Galling resistant austenitic stainless steel

Abstract: An austenitic stainless steel having excellent galling resistance by reason of a silicon-containing surface oxide film and a high work hardening rate, good wear resistance, good corrosion resistance in chloride-containing environments, and excellent oxidation resistance, containing 10 to 25 percent chromium, 3 to 15 percent nickel, 6 to 16 percent manganese, 2 to 7 percent silicon, 0.001 to 0.25 percent carbon, 0.001 to 0.4 percent nitrogen, and balance iron except for incidental impurities. Up to 4 percent molybdenum, up to 4 percent copper, 0.09 percent maximum phosphorus, up to 0.25 percent maximum sulfur and up to 0.50 percent maximum selenium may be present. The steel is readily workable on ordinary equipment into plate, sheet, strip, bar, rod and like wrought products.

Transmission electron microscopy at 2.5 MeV

Abstract: SUMMARY Measurements of penetration on silicon and austenitic stainless steel have been continued using the same criteria as previously reported (Thomas, 1968) up to 2.5 MeV using the 3 MeV Toulouse electron microscope. The results show that penetration increases to about 14 μm at 2.5 MeV for silicon although the curve starts to flatten out above 1.5 MeV, but no significant gain was found for stainless steel ≃2μm at 2.5 MeV). Primary knock-on damage occurs readily in both materials. The critical voltages for 440 silicon and 422 tantalum were measured, and both found to be 1.4 MeV (± 10 kV). Attempts to measure the variation of radiation damage with beam voltage in crystalline amino acids as indicated by the fading of diffraction patterns indicated that the damage rates apparently decrease as the voltage is raised to 2.5 MeV. However, it was not possible to determine this variation quantitatively because of difficulties in measuring the absolute values of the critical exposures.

Corrosion resistant austenitic steel

Abstract: A substantially non-porous, austenitic stainless steel that is resistant to dilute sulfuric acid and to chloride pitting, and a method of making it, are disclosed. The steel includes from 21-45 percent manganese, from 10-30 percent chromium, from 1-5 percent molybdenum, from 0.85-3 percent nitrogen, up to 2 percent silicon, up to 1 percent carbon and the balance iron and residuals. In addition to containing elements within the abovenoted composition ranges, the alloys must be such that: 1. %Cr+ %Mo + 0.8(%Mn) - 11.8(%N - 0.1) > OR = 28.5 2. 30(%C + %N) + 0.5 (%Mn)/%Cr + %Mo + 1.5 (%Si) > OR = 1.5 The steels are cast and worked to avoid a dwell period in the temperature range 1,000*-1,600*F.

Microstructural stability of thermal-mechanically pretreated type 316 austenitic stainless steel

Abstract: Studies of the microstructural stability of Type 316 austenitic stainless steel were performed for a wide range of thermal-mechanical pretreatments in the limited aging temperature range of 550° to 760°C. The pretreatments were selected in order to investigate the effects of varying solution treatment temperature, amount of cold reduction by rolling, initial grain size, and initial precipitate distribution. Large variations in both phase stability and recrystallization behavior can be effected by appropriate pretreatments. Cold work accelerates precipitation of M23C6 carbide and the intermetallic compounds (Laves, χ, and σ phases). Both the amount and kinetics of σ phase formation are especially enhanced by recrystallization occurring in the aging temperature range. It is suggested that this occurs due to ready σ nucleation at slowly moving (recrystallizing) grain boundaries together with enhanced growth rates due to diffusion along the boundary. Fine grain size enhances phase instability by providing additional nucleating sites and decreased diffusion paths for precipitate forming elements, but in the grain size range studied (ASTM No. 3.5 to No. 13) the effect is not as significant as the effect of cold work, particularly when recrystallization occurs during the aging treatment. Fine grain size and pretreatments which precipitate the carbides prior to the final cold working step enhance recrystallization kinetics relative to solution treated and cold-worked materials. This is apparently due to stabilization of the cold-worked substructure in the solution treated samples by precipitation of carbide and Laves phases on the dislocations and stacking faults.

Electrolytic separation of metals

Abstract: A process for separating silver, gold or a silver/gold alloy from a composite metal body in which the silver, gold or alloy is adhered as an external layer over a ferritic or austenitic stainless steel substrate. Separation is effected by controlled potential electrolysis in which the metal composite serves as the anode and in which the electrolytic solution used contains between about 1% and about 10% by weight of an alkali metal cyanide and up to about 10% by weight of an alkali metal hydroxide. During electrolysis the anode voltage is controlled by reference to a standard electrode at a voltage at which the degree of dissolution of the stainless steel in the half cell comprising stainless steel and the solution is substantially less than the degree of dissolution of the silver, gold or silver/gold alloy in the half cell comprising silver, gold or silver/gold alloy and the solution thereby causing selective removal from the substrate of the silver, gold, or alloy thereof.

Grain-boundary corrosion of Type 304 stainless steel by cesium oxides.

Abstract: When austenitic stainless steel (300 series) is exposed to cesium oxides in the tempera-ture range from 450° to 700°C the grain boundaries are attacked preferentially. The penetration of cesium oxides into the grain boundaries of AISI Type 304 stainless steel has been studied as a function of time and temperature. These investigations have established that the penetration kinetics are linear in time, the activation energy for the process is 19 kcal/mole, and the rate of penetration is fairly insensitive to carbide precipitation and precipitate composition and morphology. The kinetics of the process are approximately an order of magnitude faster than those observed for some reactor (U, Pu) oxide fuel elements clad with Type 304 stainless steel under fast-flux irradiations, and the results are discussed qualitatively.

Void Volume Swelling dependent on Grain Size in an Austenitic Stainless Steel

Abstract: THE phenomenon in which the formation of voids in metals and alloys is induced by irradiation is now well documented. Void formation and the concomitant swelling in volume is undesirable in fast breeder reactors, so a great effort is being made to understand the phenomenon in detail. The process of void formation is, however, a complex function of several variables to do with the irradiation (flux, energy, temperature and so on) and material (dislocations, impurities, grain boundaries, particles and so on). The influence of only a few of these parameters on the void characteristics of metals and alloys has been studied theoretically and/or determined experimentally. As grain boundaries act as neutral and unsaturable sinks for both vacancies and self-interstitials, grain refinement is expected to reduce the void volume swelling. Here I describe some of the main findings of a systematic study of the effect of grain size on the void volume swelling.

The Effects of Yttrium Ion Implantation Upon the Oxidation Behaviour of an Austenitic Stainless Steel

Abstract: Studies have been carried out on the effect of yttrium ion implantation into 20% Cr — 25% Ni — niobium stabilised stainless steel upon the long term oxidation behaviour of the steel in carbon dioxide at 700° C, 800° and 850° C. The maximum depth of penetration of yttrium ions was 0.25 μm and the initial yttrium concentration was 0.2%. The oxidation resistance of the steel was improved by the implantation by up to a factor of 2–3 at the higher temperatures. The extent of oxidation of the implanted steel were similar to those of 20/25/Nb steels containing alloy additions of 0.11–0.41% yttrium. The oxide adherence was also increased by the implantation at 800° and 850° C, although not to the same extent as with the alloy additions of yttrium.

Weldable, age hardenable, austenitic stainless steel

Abstract: An age hardenable, austenitic stainless steel having superior weldability properties as well as resistance to degradation of properties in a hydrogen atmosphere has a composition of from about 24.0 to about 34.0 weight percent (w/o) nickel, from about 13.5 to about 16.0 w/o chromium, from about 1.9 to about 2.3 w/o titanium, from about 1.0 to about 1.5 w/o molybdenum, from about 0.01 to about 0.05 w/o carbon, from about 0 to about 0.25 w/o manganese, from about 0 to about 0.01 w/o phosphorous and preferably about 0.005 w/o maximum, from about 0 to about 0.010 w/o sulfur and preferably about 0.005 w/o maximum, from about 0 to about 0.25 w/o silicon, from about 0.1 to about 0.35 w/o aluminum, from about 0.10 to about 0.50 w/o vanadium, from about 0 to about 0.0015 w/o boron, and the balance essentially iron.

Wear resistant low-alloy valve steel

Abstract: A wear resistant nickel-free austenitic stainless steel alloy, with relatively low alloy content, and particularly adapted for the manufacture of valves for internal combustion engines operating on low-lead or lead-free gasoline. The alloy consists essentially of, in weight percent, 0.25 to 0.55 carbon, 0.05 to 0.45 nitrogen, with carbon plus nitrogen within the range of 0.65 to 0.95, 10 to 14 manganese, 0.20 to 1.5 silicon, 15 to 20 chromium, 1 max. aluminum, up to 1.0 of elements from a group consisting of the strong carbide forming elements columbium, tantalum, titanium, zirconium and hafnium, 0.0008 to 0.005 boron and balance iron.

Protection of stainless steel parts - by spraying with more electronegative metal

Abstract: Austenitic stainless steel parts are protected against stress corrosion cracking by coating the surface to be protected with a metal of more electronegative potential than the part. The coating method, pref. spraying, must ensure electrical contact between coating and substrate. The coating metal claimed is either Al or Mg.

Effects of electrode coverings on elevated temperature properties of austenitic stainless steel weld metal

Abstract: 306-s I JULY 197 3 ABSTRACT. The creep-rupture properties at 1200 F of deposits made with the flux-covered E308 electrode depend on the type of covering used. Batches of electrodes with lime, limetitania (approx 25% Ti02), and titania (approx 50% T i0 2 ) f lux coverings were produced from a single heat of Type 308 stainless steel core wire by a commercial producer. The covering formulas were adjusted to produce weld deposits of essentially identical composition. Oneinch thick, Type 304 stainless steel plates were joined with each batch under identical conditions of current, voltage and travel speed. The three different weld deposits exhibited essentially identical deposit composition, ferrite number, and ferrite morphology. However, the three weldments had significantly different creep-rupture characteristics at 1200 F. The limecovered electrode deposit exhibited comparatively short rupture times and high ductility. The lime-titania and the titania-covered electrode deposits had significantly longer rupture times at a given stress level, but strained less than 1% before failing at rupture times approaching 1000 h. The lime-covered electrode deposit also demonstrated low fracture ductility at low stresses when tested to rupture.

Notch toughness of austenitic stainless steel weldments with nuclear irradiation

Abstract: The preand postirradiation notch toughness of austenitic stainless steel plates and weld deposits was explored to aid materials selection and application for liquid metal fast breeder (LMFBR) reactors. The study encompassed six plates (AISI Types 304, 316, 304L, 316LF . two submerged arc weld deposits (Types 308 and 316), and one shielded metal-arc weld deposit (Type 308). Dynamic tear (DT) and Charpy-V (C v) test methods were employed to determine notch toughness trends. Specimen irradiations were conducted in the EBR-II reactor in sodium at temperatures from 700 F (371 C) to 840 F (449 C). Neutron fluences ranged from 1 to 12 x 10' n/cm >0.1 MeV. Significant radiation reductions in notch toughness were observed for both weld deposit and plate materials. Postirradiation toughness of weld deposits in general appeared to be inferior to that of base metals. A J. R. HAWTHORNE and H. E. WATSON are associated with the Reactor Materials Branch, Metallurgy Division, Naval Research Laboratory, Washington, D.C. postirradiation C v energy level of less than 20 ft-lb and a postirradiation DT energy level of approximately 250 ftlb were observed for one Type 308 weld deposit. Comparisons indicate significantly greater DT notch toughness for welds produced by the shielded metal-arc method than by the submerged arc method. Delta ferrite content as well as composit ion are viewed as critical factors in postirradiation behavior. The DT and Cv performance of plate and weld deposits were found relatively independent of postirradiation test temperature for the range 75 F (24 C) to 900 F (482 C) but were noticeably higher at 1100 F (593 C). All weldments gave evidence of notch toughness degradation with 1000 hr thermal aging at 900 F (482 C).