Showing papers on "Austenite published in 1969"

Fe−Mn−Al precipitation-hardening austenitic alloys

Abstract: 1. To obtain an austenitic structure and good physicochemical properties Fe−Mn−Al alloys should contain 8–10% Al, 25–30% Mn, and ∼1% C. An increase of the aluminum content and decrease of the manganese and carbon content results in α-phase in the structure, which impairs the magnetic and plastic characteristics of the alloys. 2. After quenching from 1150°C and aging 16 h at 550°C the alloys of the optimal composition have the following mechanical properties: σb=90–95 kg/mm2; σ0.2=80–85 kg/mm2; δ=10–20%; ψ=15–30%. 3. Alloys of the optimal composition have a density of 6.7–6.8 g/cm3 and a substantially higher strength than the widely used Cr−Ni steel 10Kh2N24 or the Mn−Al steel 45G17Yu3. 4. Alloys with 8–10% Al have the same oxidation resistance as stainless steel 1Kh17N2.

Lattice Parameters of Martensite and Austenite in Fe–Ni Alloys

Abstract: The lattice parameters of the body‐centered cubic phase (martensite) and the face‐centered cubic phase (austenite) were determined for a series of Fe–Ni alloys. Compositions ranged from pure Fe to Fe‐35 at.% Ni. Careful film and diffractometer Debye‐Scherrer techniques on powder and bulk samples and computerized calculations and error analyses were employed. Results indicate that the martensite lattice parameter reaches a maximum between 10 and 20 at.% Ni and the room‐temperature lattice parameter of the face‐centered cubic phase has a maximum in alloys having greater than 35 at.% Ni.

Thermal expansivities, thermal conductivities, and densities of vanadium, titanium, chromium and some vanadium-base alloys: A comparison with austenitic stainless steel

Abstract: Computer-fitted polynomial expressions are presented that define the linear thermal-expansion behavior of vanadium, titanium, chromium, certain VTi and VTiCr alloys, and AISI Types 304 and 316 stainless steels between 0 ° and 1000 °C. The mean expansion coefficients for the vanadium-base alloys differ only slightly from those for unalloyed vanadium (plus or minus 6%), and are 65% to 80% lower than the mean expansion coefficients for the austenitic stainless steels. Densities of the vanadium-base alloys and the austenitic stainless steels were determined at 25 °C by liquid displacement. The VTi alloys show a non-linear decrease in density with increasing titanium for titanium contents greater than 30 wt.%. The VTiCr alloys also exhibit a non-linear change in density for compositions containing greater than 15 wt.% titanium, and greater than 5 wt.% chromium. A comparison of the mechanical and thermal properties of two vanadium-base alloys and two austenitic stainless steels was made to determine their relative usefulness as reactor fuel jackets for service between 500 ° and 700 °C. This comparison shows that vanadium alloy fuel jackets would be subjected to only one-third the thermal stresses generated in austenitic stainless steel jackets during reactor excursions between 500 ° and 700 °C under conditions where the fuel is not in intimate contact with the jacket. This difference in thermal stresses in the two jacket materials is the result of the 37% higher tensile strength, 40% higher thermal conductivity, and 70% lower thermal expansivity exhibited by the vanadium alloys as compared with austenitic stainless steel.

The role of nickel in the high-temperature oxidation of Fe-Cr-Ni alloys in oxygen

Abstract: The oxidation of several largely austenitic Fe-Cr-Ni alloys in 1 atm oxygen at 800–1200°C has been studied thermogravimetrically, metallographically, and in detail by electron probe micro analysis. Fe-Cr-Ni alloys of this type are protected by Cr2O3-healed scale, which thickens slower than on the corresponding binary Fe-Cr and Ni-Cr alloys, presumably because nickel and iron ions dope the Cr2O3 more effectively together than singly and/or because the alloy composition and ability to absorb cation vacancies are such as to produce a smaller vacancy activity gradient or level in the scale, or voids within it. The scale adhesion, as on Ni-Cr alloys, is generally good after long times, at least partly due to the convoluted alloy-oxide interface, in some cases to large intergranular Cr2O3-rich stringers, and possibly to the general specimen mechanical properties. Nonprotective stratified scale development is relatively unusual and often produces nickel-rich, alloy-particle-containing nodules, as on Fe-Ni alloys. Careful selection of ternary and more complex alloys with appropriate alloy interdiffusion coefficients and oxygen solubilities and diffusivities should permit development of materials with the best compromise between ease of Cr2O3 establishment, avoidance of breakaway, and readiness of scale healing.

Influence of Alloying Elements on the Stress Corrosion Behavior of Austenitic Stainless Steel

Abstract: In certain applications, stress corrosion cracking of austenitic stainless steels has occurred when these steels are subjected to tension stresses (residual and applied) and are exposed to...

Creep of austenitic 20% Cr/35% Ni stainless steels at low stresses

Abstract: The present work comprises measurements of the secondary creep-rate at different stress levels with rates between about 2×10−5 %/h and 10%/h and the grain-boundary sliding at 700° C in two austenitic 20 wt % Cr/35 wt % Ni stainless steels. One alloy was a pure 20 wt % Cr/35 wt % Ni steel, whereas the other contained about 0.5 wt % Ti and 0.5 wt % Al so that it precipitated γ′ during creep at 700° C. Special care was taken to assure equivalent microstructure in the specimens and precise creep conditions so as to obtain accurate and reproducible creep-rates. Both materials exhibited decreasing stress-dependence of the creep-rate at low stresses. Neither the stress-dependence of the creep-rate, nor the absolute creep-rate was consistent with diffusion-creep. The amount of grain-boundary sliding was measured separately by means of scribed grid lines on the creep specimens for the pure material at stresses above the “creep yield”. The values for the component of the creep-rate due to grain-boundary sliding coincide very well with the extrapolated line of the low-stress branch of the creep-rate/stress curve. All these results taken together suggest that the most likely explanation of the creep yield in 20 wt % Cr/35 wt % Ni steels is the one based upon grain-boundary sliding.

Austenitic steel combining strength and resistance to intergranular corrosion

Abstract: Austenitic stainless steel characterized by a combination of good hot-rolling and good cold-rolling properties, good strength and ductility, and good welding properties, with resistance to intergranular corrosion in the as-welded condition. The steel contains about 17.5 to 22.5 percent chromium, about 5 to 9.5 percent nickel, at least 2.5 percent but less than 7 percent manganese, with a nitrogen content of about 0.2 to 0.4 percent, carbon not exceeding 0.040 percent, and remainder substantially iron. Where desired, there may be employed columbium in amounts up to about 1 percent and/or molybdenum up to about 3 percent. The steel is made available in the form of hot and cold flat-rolled products, as well as wire. It is suited to a wide variety of applications in the arts.

Temper resistant chromium-containing titanium carbide tool steel

Abstract: A heat treatable, temper resistant, chromium-containing, carbidic tool steel having a total carbon content of at least about 6 percent by weight is provided comprising about 25 to 75 percent by volume of primary carbide grains of essentially titanium carbide distributed through a heat treatable steel matrix containing by weight about 6 to 12% chromium, about 0.6 to 1.2% carbon, about 0.5 to 5% molybdenum, 0 to 5% tungsten, the total tungsten and molybdenum content not exceeding about 5%, 0 to 2% vanadium, 0 to 3% nickel, 0 to 5% cobalt, 0 to 1.5% silicon, 0 to 2% manganese and the balance essentially iron, the ratio by weight of chromium to carbon in the steel matrix ranging from about 7:1 to 25:1, the steel matrix surrounding the primary carbide grains being characterized by a microstructure comprising an austenitic decomposition product.

Intergranular Stress-Corrosion Resistance of Austenitic Stainless Steels in Water/Oxygen Environment: Accelerated Test Procedure

Abstract: A system for studying the stress-corrosion behaviour of materials loaded in uni-axial tension in water at 289° is described. Using this system,the stress-corrosion of austenitic stainless steels has been investigated in water containing 100 ppm dissolved oxygen. The experimental variables studied included heat-treatment, carbon content, and alloy composition.Annealed Type-304 stainless steel when stressed in uni-axial tension did not show any evidence of cracking even in the presence of high concentrations of hexavalent chromium ions. Sensitised Type-304 stainless steel (24 h at 595°) developed intergranular fracture in 17 hours. The time-to-failure in the sensitised condition was found to be a function of the carbon content of the alloy. Data obtained on carbon-containing alloys indicate that, below 0·03 wt.-% carbon, no stress-corrosion cracking occurs over a test period of 300 hours.Duplex alloys (austenite+ferrite) show no tendency to stress-corrosion cracking even at high carbon levels and a...

Ferritic, austenitic, martensitic stainless steel

Abstract: Rollable and weldable stainless steel with a high degree of tension and toughness within a wide range of temperatures both in a hardened and a tough-hardened condition comprising 5-15 percent by weight of ferrite, 10-40 percent by weight of austenite and the remainder tempered martensite.

Corrosion Behavior of Types 304 and 316 Stainless Steel in Hot 85% Phosphoric Acid

Abstract: Polarization experiments and immersion tests were performed with Types 304 and 316 austenitic stainless steels in reagent grade 85% phosphoric acid The immersion tests were performed at 80, 100, 113, and 130 C (176, 212, 236, and 266 F) and the potentiodynamic polarization experiments at 80, 113, and 130 C Type 304 steel showed a critical corrosion behavior within a temperature range of 105 to 107 C (221 to 224 F); activation could be obtained only within or above this temperature range Type 316 steel did not exhibit any critical corrosion behavior up to 130 C The potentiodynamic polarization diagrams for the Type 304 steel were characterized by two anodic current peaks in the active-passive transition region These peaks became progressively more prominent as the temperature of the test medium was increased For Type 316 steel, only one current peak was present up to 130 C The position of this peak on the polarization diagram closely corresponded to the position of the second peak on the po

Production of metal resistant to neutron irradiation

Abstract: A PROCESS IS DISCLOSED FOR PRODUCING A METAL WHICH IS HIGHLY RESISTANT TO DAMAGE BY NEUTRON IRRADIATION. AUSTENITIC STAINLESS STEELS OR NICKEL-BASE ALLOYS, WHICH ALSO CONTAIN SUITABLE CARBIDE-FORMERS SUCH AS NIOBIUM (COLUMBIUM), TITANIUM, TANTALUM, OR ZIRCONIUM, ARE SUBJECTED TO A SERIES OF THERMAL AND MECHANICAL TREATMENTS, NAMELY: (1) SOLUTION HEAT TREATMENT AT A TEMPERATURE SUFFICIENTLY HIGH TO PLACE IN SOLID SOLUTION SUBSTANTIALLY ALL THE DISSOLVABLE CARBIDES, (2) QUENCHING AT A CONTROLLED RATE, (3) PLASTIC DEFORMATION AT OR NEAR ROOM TEMPERATURE, AND (4) PLASTIC DEFORMATION AT HIGH TEMPERATURE.

Ferritic stainless steel

Abstract: A hot rolled ferritic stainless steel having up to 0.07% carbon, 10-12.5% chromium, traces to 0.75% silicon, traces to 3% manganese, traces to 2% copper, 0.5 to 1.5% nickel, 0.1 to 0.5% titanium and which may contain as small alloying additions aluminum, vanadium, zirconium, columbium or combinations thereof. The elements of the steel are also balanced with respect to each other so that it is capable of being softened to RB80 hardness or lower in less than about 24 hours of subcritical box annealing and develops at least 50% austenite during hot rolling so as to exhibit a charpy V-notch impact strength of at least 20 ft.-lb. at 0* F.

The Mechanism of Formation of a Periodic Eutectoid Structure at Low Temperatures in Plain Chromium Steel

Abstract: Especially at low temperatures, the decomposition of austenite in plain chromium steel results in a periodic structure consisting of walls of carbide embedded in a ferrite matrix, with the walls parallel to the ferrite/austenite interface. It has been shown that this periodic eutectoid structure forms through the growth of steps at the interface in a direction parallel to it. The mechanism is assumed to be a general one in phase transformations in various alloys.

Method of processing steel sheet or strip

Abstract: A METHOD OF PRODUCING FULLY-HARD, STRESS-RELIEVED PLAIN CARBON STEEL STRIP SUITABLE FOR USE AS CAN END-STOCK WHEREIN A LOW CARBON STEEL IS HOT ROLLED TO HOT BAND GAUGE AT TEMPERATURES WITHIN THE AUSTENITIC RANGE AND THEREAFTER RAPIDLY COOLED TO A TEMPERATURE BELOW THE AUSTENTIC RANGE PRODUCTING SMALL DISPERSED CARBIDES. THE STEEL IS COLD REDUCED TO FINAL GAUGE AND CONTINUOUS ANNEALED AT A TEMPERATURE BELOW ABOUT 1050*F. TO RELIEVE ROLLING STRESSES BUT AVOID SUBSTANTIAL RECRYSTALLIZATION. ON THE OTHER HAND, A STEEL STRIP SUITABLE FOR USE AS CAN BODY STOCK, I.E. HAVING LESS STRENGTH BUT GREATER FORMABILITY IF PRODUCED IF THE STEEL COOLED SLOWLY AFTER HOT ROLLING TO CAUSE LARGE AGGLOMERATED CARBIDES, AND IT THE FINAL CONTINUOUS ANNEAL IS AT A TEMPERATIVE BELOW ABOUT 1025*F., AGAIN TO RELEIVE ROLLING STRESSES BUT AVOID SUBSTANTIAL RECRYSTALLIZATION.

Properties of austenitic steel with nickel and nitrogen at low temperatures

Abstract: 1. Nickel increases the ductility and fracture toughness of austenitic steel at low temperatures due to the higher stability with respect to the martensitic transformation. 2. The addition of 0.22–0.26% N raises the strength of the steel, the ductility and fracture toughness remaining fairly high.

Austenitic cast steel of high strength and excellent ductility at high temperatures

Abstract: An austenitic cast steel having high strength and excellent ductility at temperatures higher than, for example, 700 DEG C. consisting essentially of C in the range from 0.30 to 0.55 percent, Si in the range from 0.2 to 2.0 percent, Mn in the range from 0.5 to 3.0 percent, Ni in the range from 15 to 40 percent, Cr in the range from 20 to 30 percent, Ti in the range from 0.05 to 0.6 percent, a rare earth metal alloy containing Ce and La as the main components in the range from 0.05 to 0.5 percent (as the additive amount) and the balance substantially iron. The steel may further contain from 0.07 to 0.7 percent by weight of Nb.

Effect of deoxidation on the fracture of high-manganese steel

Abstract: 1. The toughness of low-carbon (C<0.10%) high-manganese (6–9%) steel depends not only on the heat treatment but also the melting and deoxidizing conditions. 2. The optimal heat treatment, ensuring the highest impact toughness, is tempering in the intercritical range, which results in a structure consisting of a fine mixture of ferrite and austenite highly alloyed with manganese as well as a small amount of ɛ-phase. 3. To obtain a high impact toughness, and particularly a low cold brittleness threshold, it is necessary to neutralize the harmful effect of the elevated nitrogen concentration (up to 0.018%) in such steels by adding nitride-forming elements — aluminum (0.04–0.07%) or titanium (0.04–0.07%). 4. To obtain a high impact toughness it is important not only to combine the nitrogen into stable nitrides but also to use melting and crystallizing procedures ensuring finely dispersed and evenly distributed nitrides. This can be achieved by electroslag remelting.

Alloying austenitic steels with nitrogen

Abstract: 1. A structural diagram was constructed for 25% Cr steel that allows one to determine the minimum concentrations of nickel and nitrogen guaranteeing a stable austenitic structure. 2. Alloying the steels with nitrogen is accompanied by a linear increase of the strength characteristics in short-term and long-term tests at room and elevated temperatures. The nitrogen-containing steels have the best combination of properties when microalloyed with boron. 3. Increasing the nickel concentration in nitrogen-containing steels to the upper limit required to obtain a \gg solid solution has no effect on the mechanical or heat-resisting characteristics.

Increasing the ductility of martensitic steels by heat treatment

Abstract: 1. The toughness of nickel, stainless, and complex alloyed martensitic steels at room and cryogenic temperatures can be increased by stabilizing 10\2-25% austenite in a dispersed state. 2. A large amount of stable austenite can be obtained in Fe\t-Ni, Fe\t-Cr\t-Ni, and other martensitic steels by heating them 30\2-80\dg above the beginning temperature of the reverse transformation for long periods (2\2-3 h). With increasing nickel concentrations the amount of stable austenite fixed in the reverse transformation (while retaining the martensitic struture) increases, thus increasing the toughness at cryogenic temperatures. 3. Multiple heating at reverse transformation temperatures increases the amount of stable austenite by comparison with single heating, but only in those cases where the direct martensitic transformation occurs during intermediate cooling. 4. The lower impact toughness at cryogenic temperatures in stainless martensitic steels as compared with Fe\t-Ni steels with the same amount of stable austenite is due to the lower toughness of the martensitic matrix itself and to a considerably extent to the formation, of a carbide network in the grain boundaries during heating 5. The highest mechanical properties of stainless martensitic steels at room and cryogenic temperatures can be obtained by stabilizing 15\2-25% austenite in the direct transformation without the formation of a carbide network. This process consists of austenitizing, quenching in a medium with a temperature between Ms and Mf, and immediate heating to a temperature below the temperature of aging or intensive carbide formation. This method of austenite stabilization is applicable to a large number of martensitic steels with fairly low Ms (\<-250\dgC).

Method for producing a stainless steel resistive to high temperature and neutron irradiation

Abstract: BY SUBJECTING A STAINLESS STEEL OF AISI 300 SERIES TO COLD WORKING OF AT LEAST 10 PERCENT, AND A STRAIN AGING AT 500*C-800*C, AND THEN TO RECRYSTALLIZATION TREATMENT AT 540*C-950*C, A STAINLESS STEEL HAS BEEN OBTAINED THAT HAS HIGH-TEMPERATURE YIELD STRENGTH APPROXIMATELY TWICE THAT OF THE CONVENTIONAL AUSTENITE STEEL OF THE SAME COMPOSITION, IS RESISTANT TO EMBRITTLEMENT DUE TO HIGH TEMPERATURE REACTOR IRRADIATION, AND YET RETAINS DUCTILITY AND MICROSTRUCTURE STABILITY