Dual-phase Stainless Steel Research Articles

X-ray Mesurement of Macro- and Microstresses Using Imaging Plate and Its Application to Ferritic and Austenitic Dualphase Stainless Steel.

X-ray stress measurement of a composite material using a diffraction ring detected by a two dimensional detector was studied. The merit of the method is the reduction of time required for the X-ray measurement. A theoretical background of the method for determining phase stresses, macro- and microstresses from one diffraction ring was given in the first section of the paper. An experiment on the applicability of the method to a damaged layer of ferritic and austenitic dualphase stainless steel after grinding was also described. The depth profiles of residual macro- and microstresses were obtained from phase stresses. Plastic strains, which can be measured using the Eshelby/Mori-Tanaka model, were also shown which results of the residual phase stresses were discussed. It was found that residual stresses in the surface layer which built up after grinding are mainly under the control of plastic strain rather than macrostress.

Evaluation of the corrosion and mechanical properties of a range of experimental CrMn stainless steels

In this resumed investigation, the effectiveness of manganese as an austenite-forming element in 17% and 20% chromium stainless steels has been investigated. The effect of manganese on the corrosion and mechanical properties of a range of experimental, low-cost, manganese-containing, dual-phase stainless steels is evaluated and reported.Metallographic examination and image analysis of the alloys revealed that manganese contents of up to 9%, in both 17% and 20% chromium alloys, are effective in producing a dual-phase structure comprising ferrite and austenite/martensite. It was found that manganese acts as an austenite-forming element under the conditions of the investigation.Mechanical testing of the alloys included hardness, tensile and Charpy impact testing. The results of the hardness testing showed that a 1050 °C normalizing treatment, followed by a 600 °C heat treatment and water quenching, resulted in alloys in their softest condition. It was found that manganese additions increased the toughness of the stainless steels, while tensile testing revealed that manganese additions increased the ultimate tensile strength of the alloys, but had little effect on the yield strength.The addition of manganese was found to reduce both the general and pitting corrosion resistances. Under reducing conditions, manganese additions resulted in a dramatic deterioration of the corrosion properties of the alloys.

フロッピーディスクセンターコア用フェライト‐マルテンサイト複合組織ステンレス鋼板の開発

フロッピーディスクセンターコア用フェライト‐マルテンサイト複合組織ステンレス鋼板の開発

Influence of ageing on the texture development of tensile-deformed duplex steel

Remanit dual-phase stainless steel in the annealed state was studied after 20% tensile deformation in 0, 45 and 90 ° with respect to the rolling direction and subsequent ageing at 475 and 850 °C for 3 h, and water quenched for texture development in ferrite and austenite phases by ODF analysis. It is concluded that 20% tensile deformation leads to deformation of both ferrite and austenite phases. The degree of deformation of the respective phases is dependent upon the deformation direction. Furthermore, the texture for the ferrite phase changes distinctly after ageing at 475 or 850 °C, but the texture for the austenite phase remains unaffected. Thus it may be concluded that ageing treatment leads to change predominantly of the ferrite phase.

Hydrogen Embrittlement and Permeation in Multi-layered Dual Phase Stainless Steel

Hydrogen Embrittlement and Permeation in Multi-layered Dual Phase Stainless Steel

Growth characteristics of large and small fatigue cracks in dual-phase stainless steel.

Growth characteristics of large and small fatigue cracks in dual-phase stainless steel.

The overall elastoplastic stress-strain relations of dual-phase metals

T wo simple, albeit approximate, theories are developed to estimate the stress-strain relations of dual-phase metals of the inclusion-matrix type, where both phases are capable of undergoing plastic flow. The first one is based upon Hill's recognition of a weakening constraint power in a plastically deforming matrix, whereas the second one is based on Kröner's elastic constraint in the treatment of the single inclusion-matrix interaction. The inclusion-inclusion interaction at finite concentration is accounted for by the Mori-Tanaka method in both cases. Consistent with the known elastic behavior, the first theory discloses that the geometrical arrangement of the constituents has a significant influence on the overall elastoplastic response. When the harder phase takes the position of the matrix the composite is far Stiffer than that when it takes the position of inclusions. The strong elastic constraint associated with the second theory tends to provide an upper-bound type of estimate regardless of whether the matrix is the harder phase or the softer, and, therefore, it is suggested that this theory be used only for the class of composites whose matrix is the harder phase. Both theories are finally applied to predict the stress-strain relations of dual-phase stainless steels, and the results are found to be in satisfactory agreement with the test data.

人工海水中における耐海水２相ステンレス鋼の腐食疲労き裂進展挙動

The corrosion fatigue crack growth rate of dual-phase stainless steel SUS329J1 has been measured in synthetic sea water at various stress ratios and stress cycle frequencies under free corrosion and a cathodic potential. In air the roughness-induced wedge effect enlarges the region II in the load-strain hysteresis loop. In synthetic sea water, the corrosion products-induced wedge effect under free corrosion and the Ca and Mg deposites-induced wedge effect under a cathodic potential are conspicuous, thereby enlarging the region II and raising Kop. Under free corrosion the stress assisted dissolution accerelates the crack growth rate at a low ΔKeff. In addition, at a high ΔKeff at R=0.1 and f=0.17Hz the crack growth rate is much more accerelated due to hydrogen embrittlement. Under a cathodic potential, ΔKth is remarkably high. But the crack growth rate is much accerelated due to hydrogen embrittlement in terms of ΔKeff.

Microstructure and mechanical properties of α-particle irradiated stainless steels

The effect of helium injected in stainless steels on the mechanical properties are investigated. The materials used are 100 μm thick foils of type 316 austenitic stainless steel, dual phase (9Cr-2Mo, ferritic and martensitic phase) stainless steel and duplex (22Cr-5Ni, ferritic and austenitic phase) stainless steel. The tensile strength (0.2% proof strength and ultimate strength in room temperature tensile test) of these materials increased slightly with the amount of injected alpha particles, but the elongation of these steels decreased with the alpha particle dose. Intergranular type fracture was observed only on the 316 stainless steel in which alpha particles had been injected in amounts up to 1.3 × 10 17 cm −2 at the depth of range. Transgranular fracture occurred on a post-injection annealed 316 stainless steel and on the other materials. The transmission electron microscope observation of helium bubble distribution established that the intergranular fracture is caused by a highly dense distribution of small helium bubbles at grain boundaries.

Void swelling and microstructure evolution of a dual phase (ferritic and austenitic) stainless steel

In-situ HVEM irradiation experiments have been performed on both 50% austenitic and ferritic phases of dual phase stainless steel (Fe-22Cr-5Ni-3Mo-0.02C-0.1N). Voids occurred in the austenitic phase at irradiation temperatures of and higher than 673 K, The observed void swelling at a dose of 20 dpa was 0.5%, 0.7% and 1.4% at 673 K, 773 K and 873 K, respectively. In the ferritic phase, up to 20 dpa voids are not formed at irradiation temperatures of 573 K, 673 K and 773 K, while swelling occurs at 623 K at this dose, amounting to 1.4%. The void swelling behaviour is discussed and compared with the results of a previous investigation on 316 austenitic stainless steel using the HVEM.