High Purity Ferritic Stainless Steel Research Articles

Effect of Titanium on Oxidation Behavior of High-Purity Ferritic Stainless Steel

Effect of Titanium on Oxidation Behavior of High-Purity Ferritic Stainless Steel

Effect of Nb Addition on Dendrite Growth and Equiaxed Grain Ratio of Fe-20 Pct Cr High-Purity Ferritic Stainless Steel

The acquisition of a high equiaxed zone ratio (EZR) is crucial for ferritic stainless steel (FSS). The main method of achieving this is to use effective particles to promote heterogeneous nucleation. In this study, an increased EZR was obtained owing to dendritic growth kinetics influenced by Nb addition. The EZR increased from 12 to 44 pct when 0.7 wt pct Nb was added to the FSS. The mechanism of increase of the EZR was analyzed by modified dendritic growth kinetics using the Kurz–Giovanola–Trivedi model coupled with thermodynamic data from ThermoCalc. The dendritic growth kinetics for Fe-20 pct Cr and Fe-20 pct Cr-0.7 pct Nb can be expressed as $$ V = 2.258 \times 10^{ - 5} \cdot \Delta T^{3.617} $$ and $$ V = 5.755 \times 10^{ - 7} \cdot \Delta T^{3.248} $$ , respectively, which means that undercooling (ΔT) of Fe-20 pct Cr-0.7 pct Nb was larger than that of Fe-20 pct Cr under the same solidification velocity (V). The undercooling enlarged at the dendrite tip then provided favorable nucleation conditions for FSS and increased the EZR. The as-cast structure, simulated by the cellular automaton–finite element model combined with modified dendritic growth kinetics, compared well with an actual ingot.

Effect of Ti Addition on Oxidation Behavior of High-Purity Ferritic Stainless Steel

Effect of Ti Addition on Oxidation Behavior of High-Purity Ferritic Stainless Steel

強い{111}〈112〉集合組織をもった高純度フェライト系ステンレス鋼の深絞り成形時の肌荒れ発生機構

強い{111}〈112〉集合組織をもった高純度フェライト系ステンレス鋼の深絞り成形時の肌荒れ発生機構

フェライト系ステンレス鋼のマクロ組織微細化

Effect of Mg and Ti addition on the solidification macrostructure of high purity ferritic stainless steel was evaluated in order to obtain the fine grains. In this work, columnar to equiaxed transition could not be obtained by the addition of Mg and Ti. This is due to the small constitutional undercooling in this alloy system. However, fine columnar grains were obtained by adding Mg and Ti. It is thought that the larger number of inclusion particles for heterogeneous nucleation is related to obtain the finer grain structure at the initial stage of solidification with large undercooling. Moreover, grain selection behavior of columnar grains has been also analyzed in this work.

The Effect of Si on the Precipitates for Nb Bearing High Purity Ferritic Stainless Steel

Abstract The effect of Si on the precipitation of the Laves phase in high purity 17Cr–0.5Nb ferritic stainless steel was investigated. Precipitation was observed using a scanning electron microscope and transmission electron microscope. Quantitative analysis of the amount of precipitates as Laves phase was performed. The precipitation rate of the Laves phase and the equilibrium amount of precipitates of the Laves phase increased with the amount of Si. A Si peak was detected in the Laves phase in 0.5Si steel by energy dispersive X-ray spectrometer analysis. It was revealed that precipitation of the Laves phase was promoted and the chemical composition of the Laves phase was changed by the addition of Si.

Microstructure, Texture, and Formability of Nb+Ti Stabilized High Purity Ferritic Stainless Steel

The microstructure, texture, and formability of Nb+Ti stabilized high purity ferritic stainless steel were investigated. The interstitial element carbon and nitrogen could be fully stabilized with niobium and titanium, and the precipitates were mainly composed of TiN and NbC. By analyzing the texture in various thermomechanical processes, the intensity of α-fiber obtained during hot rolling was reduced greatly after annealing and non-uniform γ-fiber was obtained. The favorable γ-fiber was observed in cold rolled and annealed sheet, whereas the maximum value of texture is located in (554)<225>. The formation of this shifted texture was mainly attributed to the influence of “Zener” drag and selective growth. Finally, the high purity steel showed an excellent formability, which was reflected in a marked increase in average plastic strain ratio (average of 1. 70) compared with the traditional steel sheet (average of 1.06).

Effects of Carbon and Nitrogen Contents on Recrystallization Behavior in Ti added High Purity 11Cr Stainless Steels

The effects of (C+N) contents on the recrystallization behaviors of Ti added high purity ferritic stainless steels were investigated. Recrystallization and grain growth of Ti added ferritic stainless steels retarded as Ti and (C+N) contents increased. It is considered that the retardation of recrystallization and grain growth in Ti added steels became more significant through the increase in the Ti and C contents accompanied by the increase in the amount of Ti(C, N), which pinned dislocations and grain boundaries.

Thermodynamic Analysis of Steels by Incorporating First-Principles Calculations into the CALPHAD Approach

A thermodynamic analysis of the Fe−M−P (M = Nb, Ti) ternary system has been performed by combining first-principles calculations with the CALPHAD approach. Because of the lack of experimental information available, thermodynamic properties of orthorhombic anti-PbCl2-type FeMP were evaluated using the Full Potential Linearized Augmented Plane Wave method, and the estimated values were introduced into a CALPHAD-type thermodynamic analysis. Applying this procedure, the phase diagrams of the Fe−M−P ternary phase diagrams whose contents are uncertain so far were calculated with a high degree of probability. Phase diagrams for high-purity ferritic stainless steels obtained following the same procedure are also presented.

Ti添加高純フェライト系ステンレス鋼の熱間再結晶挙動に及ぼす加熱温度及び巻取り温度の影響

Ti添加高純フェライト系ステンレス鋼の熱間再結晶挙動に及ぼす加熱温度及び巻取り温度の影響

Effects of molybdenum on the pitting of ferritic- and austenitic-stainless steels in bromide and chloride solutions

The effect of Mo on the pitting potential, dissolution kinetics, and repassivation behavior of high purity ferritic stainless steels, Fe–18%Cr– x%Mo, and austenitic stainless steels, Fe–18%Cr–12–15%Ni– x%Mo, was studied in solutions of bromide and of chloride. Large increases in the pitting potential of Fe–18%Cr– x%Mo in chloride solution were found with increasing Mo content, compared with the distinctly smaller increases in bromide solution. There was an excellent correlation between the increase in pitting potentials of ferritic alloys between Fe–18%Cr–2% and 5%Mo in the chloride and bromide solutions with the increased dissolution overvoltages in the saturated solution of dissolved products within artificial pits. Austenitic stainless steels also showed larger increases in pitting potential in chloride solution than in bromide solution. Higher pitting potentials were recorded for the austenitic than the ferrite steels with the same Mo content. For austenitic steels, the pitting potentials in bromide and chloride solutions were not attributable solely to the difference in dissolution rates or repassivation characteristics in saturated solution of the dissolved products. It was concluded that initiation processes play an important role in the pitting of austenitic stainless steels.

高温濃厚臭化リチウム水溶液中におけるステンレス鋼用の腐食抑制剤

The new inhibitor for stainles steel (mainly high purity ferritic stainless steel) in the high temperature concentrated aqueous solution of lithium bromide was investigated. According to the results of the electrochemical measurements, and the immersion tests using autoclaves, the mixture of three chemicals, LiOH+Na2SO3+SbCl3, is effective as an inhibitor for stainles steel to prevent hydrogen generation, pitting corrosion and macro-cell corrosion with copper.The reasons of this result are assumed that the sodium sulfite in this inhibitor remains the free-corrosion potential of stainless steel lower, and antimony in this inhibitor prevents hydrogen generation. This inhibitor also prevents stress corrosion cracking of austenitic stainless steel in the high temperature concentrated aqueous solution of lithium bromide.

腐食防食小特集 高純度フェライト系ステンレス鋼単結晶の水素ぜい化に及ぼす引張軸方位の影響

The tensile properties of single crystals of high purity ferritic stainless steel were investigated under cathodic charging. The susceptibility to hydrogen embrittlement (HE) and the fracture morphology were influenced prominently by the tensile axis orientation. In the [001]-oriented specimen, the susceptibility to HE had a maximum and the fracture surface was characterized by the cleavage growth along (001) plane which was perpendicular to the tensile axis. On the other hand, the susceptibility of the [101]-oriented specimen had a minimum and the fracture surface with some small cleavage facets was observed. From the results of stereographic analysis, these facets were composed of two equivalent {100} planes in schmid factor.

The influence of strain amplitude on the transient current behaviour in corrosion fatigue of Fe‐26Cr‐1Mo

Corrosion fatigue damage and its electrochemical characteristics of high purity ferritic stainless steel (Fe‐26Cr‐1Mo) under symmetrical tension and compression strain control have been investigated in 1M H2SO4 and 3.5 % NaCl solution by using three‐electrode technique at imposed passive potential. The tests were carried out at the total strain amplitudes of 4 × 10−3, 8 × 10−3, 1.0 × 10−2 and 1.2 × 10−2. The effects of the strain amplitude on the electrochemical dissolution and plastic deformation on the surface were studied particularly. At low strain amplitude (Δεt = 4 × 10−3), the passivity‐maintaining current was small and stable because of the small slip activity. The maximum current at the tensile half cycle, ltp, was always bigger than lcp, or sometimes equal to lcp, the maximum current at the compressive half cycle in 3.5 % NaCl. At high strain amplitude (Δεt = 1.2 × 10−2), the enhanced deformation on the surface induced the increasing dissolution. The increasing anodic current reflects the breakdown of the surface film, and only one current peak occurs within one cycle. At intermediate strain amplitude (Δεt = 8 × 10−3), the current behaviour was very stable after cyclic hardening in 3.5%, NaCl, but periodical jumpings of current during cycling were observed in the saturation region in 1 M H2SO4.

Transient current behaviour in corrosion fatigue of a ferritic stainless steel

Push-pull fatigue under plastic strain control was carried out with a high-purity ferritic stainless steel Fe-26Cr-1Mo in both 1M H2SO4 and 1M NaCl solutions. The current transient behaviour during corrosion fatigue was studied. Sharp current peaks corresponding to the points of maximum tensile and compressive strains were observed in 1M H2SO4, but only one current peak, which occurred at approximately 50% of the applied tensile strain, was observed in one strain period in NaCl solution. The evolution of the currents with successive cycles was different from each other in both solutions. A sudden current drop or dump occurred as the test started with tension in H2SO4 solution. The experimental results were explained in terms of the depassivation-repassivation process induced by strain cycling with taking account of the effect of chloride ions.

２相系および高純度フェライト系ステンレス鋼の接合技術

２相系および高純度フェライト系ステンレス鋼の接合技術

ALLEGHENY LUDLUM AL 29-4-2

Abstract ALLEGHENY LUDLUM AL 29-4-2 alloy is a high-purity ferritic stainless steel designated to provide superior resistance to corrosion by aggressive environments. It also offers fabrication characteristics that (along with E-BRITE Alloy) are unique among highly alloyed ferritic materials. The combination of properties available in AL 29-4-2 alloy makes it an attractive, cost-effective alternative to titanium, high-nickel and nickel-base alloys for many harsh environments. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-480. Producer or source: Allegheny Ludlum Corporation.

The effects of strain rate on the corrosion fatigue behaviour of B.C.C. Fe26Cr1Mo stainless steels

The corrosion fatigue damage mechanisms leading to crack initiation were studied in high purity ferritic stainless steels (Fe26Cr1Mo where the composition is given in approximate weight per cent) in a 3.5% NaCl solution at 300 K and at the imposed corrosion potential. Particular attention was paid to the influence of strain rate on both the plastic deformation mechanisms and the dissolution characteristics which govern the crack initiation process. At high strain rates (about 10 −2s −1), pencil glide occurs because of the behaviour of screw dislocations and induces strain localization at grain boundaries; dissolution is then principally localized at grain boundaries, crack initiation is intergranular and lifetimes are reduced in comparison with those in air. The influence of the pH and the strain amplitude is also of great importance. At intermediate strain rates (about 10 −3s −1), dissolution is entirely localized at grain boundaries because of pencil glide; crack initiation is intergranular and fatigue lifetimes are shorter than at high strain rates. At low strain rates (less than 10 −4s −1), the amount of dissolution is lower than the critical value for corrosion fatigue damage. Crack initiation which is induced by the mechanical damage (persistent slip bands due to wavy slip) is transgranular and fatigue lifetimes are similar in air and in the corrosive solution.

The low cycle fatigue behavior of spinodally decomposed Fe26Cr1Mo alloys

The low cycle fatigue of spinodally decomposed Fe-26Cr-1 Mo high purity ferritic stainless steel was studied in comparison with the solution treated homogeneous state under constant plastic strains and strain rates at room temperature. Correlation between cyclic softening and the demodulation of composition waves was examined by small angle neutron scattering (SANS). Surface and dislocation microstructures were investigated by optical microscopy and TEM. The cyclic stress response was quite different between as-quenched and aged materials. Aged materials showed hardening for the first few cycles followed by softening, reaching a minimum point and hardening again, whereas as-quenched materials showed only hardening throughout the test. SANS and TEM observation suggest that the cyclic softening mechanism observed is similar to that seen in f.c.c. spinodal alloys.

8.高純度フェライト系ステンレス鋼の溶接

8.高純度フェライト系ステンレス鋼の溶接