Nickel-free Stainless Steel Research Articles

Torsion and Tensile Properties of Thin Wires of Nickel-Free Stainless Steel with Nitrogen Absorption Treatment

A new manufacturing process for nickel-free austenitic stainless steel has been developed by authors. In combination with machining and a nitrogen absorption treatment, this process makes it possible to form small precise devices with a maximum thickness or diameter of 4 mm. The refinement of grains of Fe-24Cr-2Mo in mass% was attempted by thermo-mechanical treatment before nitrogen absorption treatment in order to increase the mechanical properties after nitrogen absorption treatment. Torsion and tensile properties and microstructures of Fe-24Cr-2Mo before and after nitrogen absorption treatment were evaluated to understand the effects of grain refinement on nitrogen absorption. The thin wire of the alloy is completely austenitized with nitrogen absorption at 1473 K for over 7.2 ks. The mean grain size of the alloy with nitrogen absorption decrease with the grain refinement process attempted in this study. The values of ultimate tensile strength and elongation in the alloy with and without nitrogen absorption increase with the grain refinement process. The torsional stress and rotation angle to fracture of the alloy increase with the grain refinement process and nitrogen absorption. According to the results of the torsion and tensile tests, the thin wire of the alloy with nitrogen absorption is expected to have good mechanical properties than conventional austenitic stainless steels.

窒素吸収処理により作製したニッケルフリーステンレス鋼の破面形態

窒素吸収処理により作製したニッケルフリーステンレス鋼の破面形態

Dowpharma offers chiral hydroformylation catalysts

Various catalysts based on rhodium, palladium and platinum on γ-alumina were wash-coated into micro structured reactors. The catalysts were applied in the partial oxidation of propane aiming for synthesis gas. Best results were achieved with pure rhodium and bimetallic rhodium/platinum catalysts having at least a rhodium concentration exceeding 0.5 wt.%. With rhodium-based catalysts complete propane conversion was observed. Selectivities of hydrogen and carbon monoxide were close to the thermodynamic equilibrium. During long-term operation, coke formation was observed resulting in an increase of the pressure drop over the reactors. Upon inspection of the reactors it turned out that the micro channels were marginally covered with coke depositions but the outlet tube of the reactor was found to be fully plugged. With the help of a simulated reformate it was found that coke formation was only little dependent on the operating temperature. In contrast, coke formation was significantly reduced by the employment of reaction plates made of a nickel-free stainless steel and by a protective coating consisting of α-alumina.

Mechanical Properties and Microstructures of a Thin Plate of Nickel-Free Stainless Steel with Nitrogen Absorption Treatment

We have developed a new manufacturing process for nickel-free austenitic stainless steel. In combination with machining and a nitrogen absorption treatment, this process makes it possible to form small precise devices. However, the temperature for the nitrogen absorption, 1473 K, was sufficiently high for grain growth, and coarsening was observed after nitrogen absorption. Therefore, a nitrogen absorption treatment which allows the retention of strength and ductility was performed with a grain refinement process before nitrogen absorption. In this study, we attempted the refinement of grains by thermo-mechanical treatment before nitrogen absorption treatment. The mechanical properties and microstructures of Fe–24Cr and Fe–24Cr–2Mo with fine grains before and after nitrogen absorption treatment were evaluated to understand the effects of grain refinement on nitrogen absorption. The austenintic phase was only obtained from the surface to a 0.1-mm depth in Fe–24Cr and Fe–24Cr–2Mo with nitrogen absorption at 1473 K for 2.7 ks. The balance between strength and elongation in Fe–24Cr and Fe–24Cr–2Mo with nitrogen absorption at 1473 K for 2.7 ks was better than that in conventional austenitic stainless steel. The values of ultimate tensile strength in both alloys with nitrogen absorption increased with the grain refinement process attempted in this study. The balance between strength and elongation in both alloys with nitrogen absorption over 2.7 ks decreased because of grain growth. Therefore, the process described in this study can be used to manufacture small devices with a great deal of precision and parts with a maximum thickness or diameter of 0.2 mm in a short time. Grain refinement in a nickel-free austenitic stainless steel can increase the balance between the strength and elongation.

Stainless steel in bone surgery

Today, stainless is one of the most frequently used biomaterials for internal fixation devices because of a favorable combination of mechanical properties, corrosion resistance and cost effectiveness when compared to other metallic implant materials. The biocompatibility of implant quality stainless steel has seen been proven by successful human for decades. Composition, microstructure and tensile properties of stainless steel used for internal fixation is standardized in ISO and ASTM material specifications. Metallurgical requirements are stringent to ensure sufficient corrosion resistance, nonmagnetic response, and satisfactory mechanical properties. Torsional properties of stainless steel screws are different from titanium screws. Stainless steel bone screws are easier to handle because the surgeon can feel the onset of plastic deformation and this provides adequate prewarning to avoid overtorquing the screw. New nickel-free stainless steels have been recently developed primarily to address the issue of nickel sensitivity. These stainless steels also have superior mechanical properties and better corrosion resistance. The Ni-free compositions appear to possess an extraordinary combination of attributes for potential implant applications in the future.

Aging Behaviour of 25Cr-17Mn High Nitrogen Duplex Stainless Steel.

The precipitation behaviour of a nickel free stainless steel containing 25% chromium, 17% manganese and 0.54% nitrogen, with duplex ferritic‐austenitic microstructure, was studied using several complementary techniques of microstructural analysis after aging heat treatments between 600 and 1 000°C for periods of time between 15 and 6 000 min. During aging heat treatments, ferrite was decomposed into sigma phase and austenite by a eutectoid reaction, like in the Fe‐Cr‐Ni duplex stainless steel. Chromium nitride precipitation occurred in austenite, which had a high nitrogen supersaturation. Some peculiar aspects were observed in this austenite during its phase transformations. Chromium nitride precipitation occurred discontinuously in a lamellar morphology, such as pearlite in carbon steels. This kind of precipitation is not an ordinary observation in duplex stainless steels and the high levels of nitrogen in austenite can induce this type of precipitation, which has not been previously reported in duplex stainless steels. After chromium nitride precipitation in austenite, it was also observed sigma phase formation near the cells or colonies of discontinuously precipitated chromium nitride. Sigma phase formation was made possible by the depletion of nitrogen in those regions. Time‐temperature‐transformation (precipitation) diagrams were determined.

Nickel-Free High Nitrogen Austenitic Stainless Steels Produced by Metal Injection Moulding

Nickel can cause allergic reactions to human beings. In the last several years the need of nickel free stainless steels for applications at and in the human body has become more and more urgent. Such Ni-free steels have recently been developed at ETH Zurich. They are characterized by a full replacement of nickel by nitrogen. The production of Ni-free HNS through ingot metallurgy requires special high pressure facilities, while no special equipment is necessary when powder metallurgy routes are applied. The paper describes the P/M-processing of the new biocompatible Ni-free stainless steel Catamold®P.A.N.A.C.E.A. by using the metal injection moulding technique (MIM). With this process the desired nitrogen content can be added easily during consolidation. It is shown that with well balanced processing parameters (chemical composition, sintering atmosphere and temperature) a fully austenitic structure with low porosity can be achieved. The MIM components are nonmagnetic and exhibit a high corrosion resistance as well as excellent mechanical properties.

Injection moulding of nickel-free stainless steels: M.O.Speidel et al. (Swiss Federal Inst. of Technology, Zurich, Switzerland.)

Aging at 700 °C results in grain boundary nitride precipitation only, while aging at 900 °C results in grain boundary and cellular precipitation (40 vol%). These thermal treatments have a small but positive effect on YS, no effect on the UTS, but dramatically reduce the ability of the material to deform under localized plastic deformation (necking), leading to reduced tensile ductility. The plastic flow behavior of all annealed and aged high-nitrogen samples were modeled using the modified Ludwik relation (equation 2). Below the UTS, grain boundary nitride precipitation at 700 °C has no measurable effect on the plastic flow behavior of the material, and the modeling parameters n1, K1, n2, and K2 have values which do not deviate significantly from the behavior of the un-aged material. Cellular precipitation, caused by aging at 900 °C, does significantly affect the plastic flow behavior of the material at both low and high strains. Cellular precipitation causes both increased strengthening of the matrix in the low strain regime (0.001 < ε < 0.03) and systematic decreases in the strain hardening exponent (n1) and strength coefficient (K1) with increased aging. The rate of strain hardening (dσdε) measured from the σ-ε plots is unaffected by isothermal aging and nitride formation.

Advanced nickel-free stainless steel for wide application

Advanced nickel-free stainless steel for wide application

Manganese as an austenite stabilizer in FeCrMnC steels

As part of an alloy development program for a nickel-free stainless steel, five FeMn, 13 FeCrMn and 15 FeCrMnC alloys were examined to determine the austenite-stable region in the FeCrMnC system. After various heat treatments, optical and electron microscopy studies and magnetic measurements were used to assess the microstructural constituents present. The results indicate that the Schaeffler diagram, which was developed to predict the phases present in FeCrNiC stainless steels, cannot be directly applied to FeCrMnC steels. Manganese has a lower austenite-stabilizing capability against δ-ferrite formation than the Schaeffler diagram predicts by simply considering it half as effective as nickel. However, its stabilizing capability against martensite formation is higher than predicted by the diagram on the same basis. The new results can be used to establish the austenite-stable composition region that should be suitable for alloying to develop a manganese-stabilized stainless steel.

２０Ｃｒ‐１３Ｍｎ‐Ｎ‐Ｂ無ニッケルステンレス鋼の特性に及ぼす二相組織の影響

２０Ｃｒ‐１３Ｍｎ‐Ｎ‐Ｂ無ニッケルステンレス鋼の特性に及ぼす二相組織の影響

Structure and properties of the corrosion-resistant sheet steel 06Kh18Ch alloyed with rare-earth metals and calcium

1. Introduction of rare-earth metals and calcium into chromium stainless steels considerably increases their ductility and resistance to intercrystalline corrosion, at the same time preserving their polishing properties. 2. A new economically alloyed, nickel-free stainless steel 06Kh18Ch, containing, as calculated, 0.3–0.4% rare-earth metals and 0.2% Ca, was developed. 3. Industrial tests on chromium steel 06Kh18Ch proved that this steel is suitable for manufacturing car components with decorative surfaces, and is in no way inferior to chromiumnickel steels of the 12Kh18N9 type.

Corrosion resistance of low-cost stainless steel alloys in softened water

Corrosion-electrochemical characteristics and analytical data on the transition of iron into softened water have been investigated for low-cost nickel-containing and nickel-free stainless steels and type 12Kh18N10T steel.

USS TENELON

Abstract USS TENELON is a completely austenitic, nickel-free stainless steel with exceptionally high strength which is retained at elevated temperatures. It has excellent corrosion resistance in atmospheric and mild acid exposures and maintains nonmagnetic characteristics even when 60% cold reduced. It also has good stress-rupture and creep properties in the range 1200-1500 F. It has a wide range of applications. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness, creep, and fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-311. Producer or source: United States Steel Corporation.