Cast Stainless Steel Research Articles

Effects of Alveolar Bone Loss and Post-Core Design on Stress Distribution of Severely Damaged Canine

To investigate the influence of alveolar bone loss and post design on stress distribution of a severely damaged canine. The residual canal dentin wall in the cervical region was standardized at 0.5mm in thickness. Twelve two-dimensional finite element models were created. The models were varied in their alveolar bone loss. The post systems include computer-aided design/computer-aided manufacturing zirconium post, prefabricated glass fiber post, cast stainless steel post, and cast gold post. The numerical models were considered to be restored with an all-ceramic crown. A load of 100N was applied to the crown at an angle of 45 degree on the lingual surface, and Mises stresses were calculated. Finite element analysis revealed that cast stainless steel post system showed the lowest maximum Mises stress in the dentine at 86.46 MPa, while, glass fiber post resulted in the highest stress concentration in the dentin at 174.3 MPa. Stresses were reduced by increasing alveolar height. Loss of alveolar bone loss may lead to an increased risk of failure.

Characterisation of ASTM A747-grade CB7Cu-1 precipitation hardening cast stainless steel

This paper reports on a microstructural characterisation of standard ASTM A747/A747M grade CB7Cu-1 precipitation hardening cast stainless steel with a martensitic matrix, a material widely applied today in rotary and static components subject to wear, although the majority of publications about this family of stainless steels focus on wrought and rolled stainless steels. An optical microscopy analysis was performed to clearly identify the constituents of the microstructure in the as cast state and in the solution annealed condition at 1140°C for 2 h, followed by water quenching. In the as cast state, the microstructure was composed of splinter shaped martensitic dendrites constituting the matrix and delta ferrite precipitated in the interdendritic regions. The same phases were found in the solution annealed state, but the dendritic structure was ‘broken’ by the heat treatment. Quantitative metallography using image analysis software showed that the volumetric concentrations of delta ferrite in the as cast and solution annealed states were 15·22 and 12·44% respectively. The results of the energy dispersive spectroscopy microanalysis revealed higher concentrations of chromium and silicon in the delta ferrite and of nickel and copper in the martensite, which is a product of transformation of the previous austenite. A comparison between two different chemical analysis methods: optical emission spectroscopy and microanalysis indicated a slight difference (<2%) in the elements chromium, nickel and silicon, while the difference for the element copper was close to 12%. Aging heat treatments at various temperatures showed that the maximum hardness was obtained in the range of 400–500°C, with 2 h for soaking time.

Effects of phosphate addition on biofilm bacterial communities and water quality in annular reactors equipped with stainless steel and ductile cast iron pipes

The impact of orthophosphate addition on biofilm formation and water quality was studied in corrosion-resistant stainless steel (STS) pipe and corrosion-susceptible ductile cast iron (DCI) pipe using cultivation and culture-independent approaches. Sample coupons of DCI pipe and STS pipe were installed in annular reactors, which were operated for 9 months under hydraulic conditions similar to a domestic plumbing system. Addition of 5 mg/L of phosphate to the plumbing systems, under low residual chlorine conditions, promoted a more significant growth of biofilm and led to a greater rate reduction of disinfection by-products in DCI pipe than in STS pipe. While the level of THMs (trihalomethanes) increased under conditions of low biofilm concentration, the levels of HAAs (halo acetic acids) and CH (chloral hydrate) decreased in all cases in proportion to the amount of biofilm. It was also observed that chloroform, the main species of THM, was not readily decomposed biologically and decomposition was not proportional to the biofilm concentration; however, it was easily biodegraded after the addition of phosphate. Analysis of the 16S rDNA sequences of 102 biofilm isolates revealed that Proteobacteria (50%) was the most frequently detected phylum, followed by Firmicutes (10%) and Actinobacteria (2%), with 37% of the bacteria unclassified. Bradyrhizobium was the dominant genus on corroded DCI pipe, while Sphingomonas was predominant on non-corroded STS pipe. Methylobacterium and Afipia were detected only in the reactor without added phosphate. PCR-DGGE analysis showed that the diversity of species in biofilm tended to increase when phosphate was added regardless of the pipe material, indicating that phosphate addition upset the biological stability in the plumbing systems.

Predicting Delta Ferrite Content in Stainless Steel Castings

The distribution of delta ferrite fraction was measured with the magnetic method in specimens of different stainless steel compositions cast by the investment casting (lost wax) process. Ferrite fraction measurements published in the literature for stainless steel cast samples were added to the present work data, enabling an extensive analysis about practical methods to calculate delta ferrite fractions in stainless steel castings. Nineteen different versions of practical methods were formed using Schaeffler, DeLong, and Siewert diagrams and the nickel and chromium equivalent indexes suggested by several authors. These methods were evaluated by a detailed statistical analysis, showing that the Siewert diagram, including its equivalent indexes and iso-ferrite lines, gives the lowest relative errors between calculated and measured delta ferrite fractions. Although originally created for stainless steel welds, this diagram gives relative errors lower than those for the current ASTM standard method (800/A 800M-01), developed to predict ferrite fractions in stainless steel castings. Practical methods originated from a combination of different chromium/nickel equivalent indexes and the iso-ferrite lines from Schaeffler diagram give the lowest relative errors when compared with combinations using other iso-ferrite line diagrams. For the samples cast in the present work, an increase in cooling rate from 0.78 to 2.7 K/s caused a decrease in the delta ferrite fraction, but a statistical hypothesis test revealed that this effect is significant in only 50% of the samples that have ferrite in their microstructures.

G040034 発電水車用ステンレス鋳鋼SCS6の平面ひずみ状態における変動荷重下疲労き裂進展挙動

G040034 発電水車用ステンレス鋳鋼SCS6の平面ひずみ状態における変動荷重下疲労き裂進展挙動

603 2相鋼の低温脆性破壊における第二相粒子の影響(OS4-1 オーガナイズドセッション《材料・組織と加工》)

Ferrite steels exhibits ductile-brittle transition in general even in cases bearing the second phase. Low temperature brittle fracture mechanism in two cases of two-phase steels; one is two-phase stainless cast steel bearing ductile austenite grains and the other is pearlite steel bearing brittle cementite plates. Two-plane observations consisting of SEM fracture surface observation and Optical/SEM/EBSD observation on the sectioned and polished plane to reveal microstructure and crystallographic feature was performed. The role of the second phase particle for cleavage fracture of bcc grains is discussed.

OS2110 発電水車用ステンレス鋳鋼SCS6の疲労き裂発生・進展挙動に及ぼす超音波ショットピーニングの影響

OS2110 発電水車用ステンレス鋳鋼SCS6の疲労き裂発生・進展挙動に及ぼす超音波ショットピーニングの影響

Effect of Surface Damage by Cavitation Erosion on Fatigue Strength of Stainless Cast Steel SCS5 for Hydraulic Turbine Runner

Effect of Surface Damage by Cavitation Erosion on Fatigue Strength of Stainless Cast Steel SCS5 for Hydraulic Turbine Runner

Evaluation of Cavitation Erosion and Fatigue Properties in High Cr-Ni Based Alloy INCONEL625 for Welding Material of Hydraulic Turbine Runner

In hydraulic turbine runners, accidents due to cyclic loading often occur. In this study, cyclic tension-compression loading tests and fatigue crack growth tests using compact tension specimens under the stress ratio R-constant and repeated two-step load sequences were carried out for welding material INCONEL625, in order to clarify fatigue properties, fracture mechanisms, fatigue crack growth and closure properties. The test results are summarized as follows : (1)The volume loss rate of INCONEL625 improves 30% than that of SUS309 by using a test apparatus an ultrasonic vibratory cavitation device. (2)The S-N curve of welding material INCONEL625 used in this study has narrow scatter and the tension-compression fatigue strength was higher than the test data of the stainless cast steel SCS5 used as hydraulic turbine runner material. (3)From SEM observation of the fracture surfaces, there were two types of fracture origin ,that indicate fatigue crack initiation by slip deformation at surface and from the casting defects. (4) Fatigue crack growth rates of the specimens which are the vertical and the parallel to welded direction under the stress ratio R-constant could be correlated with the effective stress intensity factor range ΔKeff. And ΔKeff under varying loading was the same as that under the stress ratio R-constant. Crack propagation rate under varying loading could be predicted by fatigue crack growth data under constant amplitude loading.

セラミック・シェルモールド・ステンレス鋳鋼の健全域に及ぼす種々の要因

セラミック・シェルモールド・ステンレス鋳鋼の健全域に及ぼす種々の要因

KUBOTA ALLOY HD

Abstract Kubota Alloy HD (UNS J93005) is a heat-resisting stainless steel casting alloy suitable for long-term service at temperatures up to 1095 deg C (2000 deg F). The nearest wrought equivalent is type 327. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as creep. It also includes information on corrosion resistance as well as casting and joining. Filing Code: SS-1110. Producer or source: Kubota Metal Corporation, Fahramet Division.

Effects of working temperature and carbon diffusion on the microstructure of high pressure heat-resistant stainless steel tubes used in pyrolysis furnaces during service condition

In the present study, high pressure heat-resistant cast stainless steels (HP steels) modified with niobium and titanium were investigated in as-cast conditions and after being used in pyrolysis furnaces. Life span of the studied specimens obtained from pyrolysis furnace was 5 years. Microstructural changes were studied via scanning electron microscopy (SEM) equipped with energy dispersive spectrum (EDS), optical microscopy (OM), and X-ray diffraction (XRD). The effect of temperature and carbon diffusion on the microstructure, chromium-rich carbides, the NbC transformation to G-phase and other precipitates formed during service condition were discussed. The results showed that two major phases, namely chromium and niobium carbides, existed in the as-cast specimens. Temperature and carbon diffusion influenced the composition and volume fraction of secondary precipitates. Chromium and niobium carbides were transformed to M 23C 6 and G-phase respectively during service. Higher working temperatures do not always cause coarsening of precipitates. However, factors such as decarburization and carbon diffusion have important roles, too.

X-ray photoelectron investigation of nanostructures in modified cast irons and steels

A comparative study of industrial samples of classic cast iron, stainless steel, and nanomodified samples was performed. It was shown that the high strength of the obtained materials could be explained by the formation of strong hybridized 3d(Fe) and 3p(Al) bonds, and by the presence of C-C complexes with diamond-like sp 3 hybridization of electrons.

Biaxial Low Cycle Fatigue Behavior and Martensite Formation of a Metastable Austenitic Cast TRIP Steel Under Proportional Loading

In this paper the biaxial low cycle fatigue behavior under proportional loading of a recently developed metastable austenitic stainless cast steel is presented. Total strain controlled tests were carried out on a 250 kN biaxial servohydraulic tension-compression testing machine equipped with a biaxial orthogonal extensometer to measure the principal strains in the gauge area of the used cruciform specimens. The principal stresses were determined based on the compliance after the load reversals. The low cycle fatigue behavior under biaxial synchronous loading is compared to the uniaxial behavior. Therefore, biaxial single step tests and a biaxial multiple step load increase test were carried out. The dependence of the stress state on the cyclic deformation curves, cyclic stress-strain curves and the formation of martensite are described. Finally, the fatigue life relationship according to Basquin and Manson-Coffin was determined and compared to the Smith, Watson and Topper damage parameter, which provides a satisfactory fatigue life prediction.

Electrical and flexural anisotropy in freeze tape cast stainless steel porous substrates

Engineered metal foams have strong potential in applications such as fuel cell electrodes, sensors, variable springs, filtering media, and compositionally graded composite structures. In this study, the variation in mechanical and electrical properties was characterized in engineered porous metal foams with aligned porosity to ascertain the degree of anisotropy that can be induced in these substrates. Porous substrates were prepared by freeze tape casting of powdered ferritic stainless steel. After directional solidification of the slurry, the solvent was sublimed from ~ 1 mm thick tapes, yielding porous green metal compacts which were sintered in a protective atmosphere. The resulting disks exhibit long range ordered acicular pores with substantial anisotropy in the mechanical and electrical properties that is related to the cross sectional pore morphology and connectivity. DC conductivity testing revealed up to 61% variation depending on direction of measurement relative to the alignment of pores. Also, an 89% variation in flexural rigidity in relation to pore orientation was observed in identical disks.

Fe-Mn-Al 系低比重ステンレス鋳鋼の高温引張変形と破壊特性

Fe-Mn-Al 系低比重ステンレス鋳鋼の高温引張変形と破壊特性

Investigation of weldability and property changes of high pressure heat-resistant cast stainless steel tubes used in pyrolysis furnaces after a five-year service

High pressure heat-resistant cast stainless steel (HP steel) tubes produced by centrifugal casting are used in petrochemical industries for pyrolysis furnaces. They have appropriate ductility and weldability in as-cast conditions. These steels lose their ductility and weldability after being used in service and, hence, require repair. In the present study, the effect of metallurgical changes on weldability and ductility was investigated. The life span of the studied tubes was 5 years. Using electrodes with a chemical composition close to the base metal analysis, welding was done by gas-tungsten arc welding (GTAW) process. Solution treatment was used to recover the properties of tubes which can be useful, depending on metallurgical changes.

Influence of Heat Treatment Time and Temperature on the Microstructure and Corrosion Resistance of Cast Superaustenitic Stainless Steels

Abstract The influence of heat treatment time and temperature on the microstructure and corrosion resistance of cast stainless steel alloys CN3MN (UNS J94651) and CK3MCuN (UNS J93254) were investig...

Characterization of stress–strain behavior of a cast TRIP steel under different biaxial planar load ratios

This paper investigates the stress–strain curves of different load paths and the initial yield surface of a metastable austenitic stainless cast steel under biaxial planar loading using cruciform specimens. These tests were carried out on a 250 kN biaxial servohydraulic tension-compression testing machine. The laborious stress determination was undertaken with a new testing method by using global elastic unloading to measure the local stiffness. Isotropic yielding and mainly isotropic strain hardening were found. To evaluate the microstructure, the martensite formation was detected by use of a ferrite sensor and scanning electron microscopy and electron backscatter diffraction were applied.

STRAIN RATE CHANGE FROM 0.04 TO 0.004%/S IN AN ENVIRONMENTAL FATIGUE TEST OF CF8M CAST STAINLESS STEEL

To define the effect of strain rate variation from 0.04% to 0.004%/s on environmental fatigue of CF8M cast stainless steel, which is used as a primary piping material in nuclear power plants, low-cycle fatigue tests were conducted at operating pressure and temperature condition of a pressurized water reactor, 15 MPa and <TEX>$315^{\circ}C$</TEX>, respectively. A high-pressure and high-temperature autoclave and cylindrical solid fatigue specimens were used for the strain-controlled low-cycle environmental fatigue tests. It was observed that the fatigue life of CF8M stainless steel is shortened as the strain rate decreases. Due to the effect of test temperature, the fatigue data of NUREG-6909 appears a slightly shorter than that obtained by KEPRI at the same stress amplitude of <TEX>$1{\times}10^3$</TEX> MPa. The environmental fatigue correction factor <TEX>$F_{en}$</TEX>'s calculated with inputs of the test data increases with high strain amplitude, while the <TEX>$F_{en}$</TEX>'s of NUREG-6909 remain constant regardless of strain amplitude.