Stainless Pipe Research Articles

OS0820 軸力と曲げを受ける切欠付ステンレス配管の塑性崩壊強度および最大荷重評価

OS0820 軸力と曲げを受ける切欠付ステンレス配管の塑性崩壊強度および最大荷重評価

Effect of Electrode Coatings on Diffusible Hydrogen Content, Hardness and Microstructures of the Ferritic Heat Affected Zones in Bimetallic Welds

Bimetallic welds (BMWs) have been a necessity within the steam generators of nuclear power plants, where the heavy section low alloy steel components are usually connected to stainless steel primary piping systems. These welds represent zones with metallurgical discontinuities, which tend to localize the strains and cause failures. The other critical issues which must be taken care of while welding of bimetallic joints include solidification cracking, thermal fatigue and residual stresses in welds. The occurrence and severity of all these problems associated with bimetallic welds depend upon the type of welding process used along with the other variables like welding consumables, heat input etc. In shielded metal arc welding (SMAW), welding electrode consumables/coatings play an important role in deciding the weld metal quality. The development of welding electrode coatings is quite difficult due to very rapid complex reactions taking place during welding and the involvement of many controlled process variables. The present paper is an effort to highlight the general issues and challenges for the systematic and scientific development of welding electrode coatings for bimetallic welds. The experimental procedure contains three sets of coated electrodes having varying ferro-alloys, silica and carbon content. In the first set of electrodes, non-ferrous elements are also introduced into the weld metal through flux addition. Further, the welded joints are subjected to various tests and then evaluated to ascertain their mechanical as well as metallurgical behaviour.

A-53 地震等に配慮したステンレス配管の高耐久性の確保に関する研究 : (第1報)E-ディフェンスによる高層建物用配管の耐震性評価実験

A-53 地震等に配慮したステンレス配管の高耐久性の確保に関する研究 : (第1報)E-ディフェンスによる高層建物用配管の耐震性評価実験

Improvement of Local Decrease in Material Thickness of Fuel Supply Pipe

Growing demand for lightweight products has been increased by the rapid development of automobiles since the global environment conservation meeting at Kyoto. Lighter products have been necessary when considering in taking action to reduce fuel consumption. One of the key is the utilization of high strength and light materials, such as stainless, high-tensile strength steels and magnesium alloys, which are difficult to be formed due to their high strength compared to normal steel pipes. This paper is concerned with the development of pressing technology that copes with forming relatively high strength stainless pipe with screw threads on the surface of pipes. Our new press-forming process in order to obtain accurate screw threads on the stainless pipe was tested. A 3-D digitizer was used for the measurement of the accuracy of manufactured pipes by the proposed pressing method. It is found that the proposed our press-forming was effective to improve decrease of pipe thickness compared to conventional roll forming technology. The maximum decrease in material thickness was 20% using our press-forming process for screw threads in the formed pipe.

Ultrasonic defect localization in pipes using time reversal.

Time reversal mirrors have been shown to effectively focus acoustic waves for structural health monitoring in thin plates. This approach achieves a high degree of accuracy, despite the complex propagation environment inherent to thin plates. We consider ultrasonic defect localization via time reversal in thin‐walled pipes. The different boundary conditions in pipes give rise to new wave modes and dispersive effects. We use an array of six transducers arranged around the circumference of a 10‐cm‐diameter steel pipe to excite guided ultrasonic wave modes, and apply iterative time reversal to focus these waves on a defect. We apply maximum likelihood to detect the presence of a defect, and then correlate the response from the defect with a library of known signatures to locate the defect. Results are provided from a simulation based on experimental data collected from a stainless steel laboratory pipe specimen 11.5 cm in diameter and 1.5 m in length. We simulated our defect with a grease‐coupled commercial t...

中性子回折法による大口径配管溶接部の残留応力測定

The RESA-1 neutron engineering diffractometer in the JRR-3 (Japan Research Reactor No.3) at the Japan Atomic Energy Agency, which is used for stress measurements, was upgraded to realize residual stress measurements of large scaled mechanical components. A series of residual stress measurements was made to obtain through-thickness residual stress distributions in a Type 304 stainless steel butt-welded pipe of 500A-sch.80 using the upgraded RESA-1 diffractometer. We evaluated effects of crack propagation such as stress corrosion cracking (SCC) and a part-circumference repair weld on the residual stress distributions induced by girth welding. Measured residual stress distributions near original girth weld revealed good agreement with typical results shown in some previous works using finite element method, deep hole drilling as well as neutron diffraction. After introducing a mock crack with 10 mm depth in the heat affected zone on the inside wall of the pipe by electro discharge machining, the axial residual stresses were found to be released in the part of the mock crack. However, changes in the through-wall bending stress component and the self-equilibrated stress component were negligible and hence the axial residual stress distribution in the ligament was remained in the original residual stresses near girth weld without the mock crack. Furthermore, changes in hoop and radial residual stress were also small. The residual stress distributions after a part repair welding on the outer circumference of the girth weld were significantly different from residual stress distributions near the original girth weld. The through-thickness average axial residual stress was increased due to increase of the tensile membrane stress and mitigation of the bending stress after repair welding. Throughout above studies, we evidenced that the neutron diffraction technique is useful and powerful tool for measuring residual stress distributions in large as well as thick mechanical components.

G030034 固有ひずみ法を用いた大口径原子力配管溶接継手の残留応力測定([G03003]材料力学部門一般セッション(3):残留応力)

Three-dimensional distribution of weld residual stress in a large-bore and heavy-walled stainless pipe with butt-welded joint was evaluated by inherent strain method with distribution function. The weld joint was made by TIG welding with single-U shape groove and its size is used in the primary coolant system in nuclear power facilities. The residual stress distribution in the circumferential direction as well as in the through-thickness direction of the joint was estimated using the measurement values obtained in the multiple positions. It was clarified that the three-dimensional stress distribution in the weld end was different from that in the other region.

Thermomechanical and isothermal fatigue behavior of 347 and 316L austenitic stainless tube and pipe steels

Many components of nuclear power plant piping systems are made of austenitic stainless steels. These structures undergo degradation by thermomechanical loading caused by thermal transients and stratifications. In scientific literature, most of the studies deal with this problem under isothermal fatigue conditions, which is different from the typical service conditions. In addition, less attention has been paid to thermo-mechanical fatigue ( TMF). This work aims to understand and compare the cyclic deformation behavior during TMF and isothermal fatigue ( IF) testing in air for two of the most commonly used grades of austenitic stainless tube and pipe ( TP) steel, the non-stabilized TP 316L and the niobium-stabilized TP 347, under light water reactor relevant temperature conditions. Three types of tests, i.e. in-phase, out-of-phase TMF in the 100–340 °C temperature range, and IF tests at the maximum temperature T max of TMF were performed. All the tests were carried out under total strain control, for two different mechanical strain amplitudes (Δ ε mech /2 = 0.3% and 0.5%). Results revealed that irrespective of the tested strain amplitude and material, in-phase TMF showed a higher lifetime over out-of-phase TMF and IF at T max . A crossover in fatigue lifetime was observed in TP 316L between out-of-phase TMF and IF test at T max with decreasing strain amplitude. In TP 347, out-of-phase TMF and IF test at T max showed similar fatigue lifetimes for both strain amplitudes. Finally, three lifetime prediction models were selected and compared to evaluate the possibility of estimating TMF lifetime by using IF data. Satisfactory predictions were obtained from all the prediction approaches.

Flow regime determination in horizontal hydrotransport using non‐intrusive acoustic probes

AbstractA variety of flow regimes may be observed in the hydrotransport of solids. Maintaining a consistent operation requires rapid detection of any change in flow regime. The objective of this study was to develop reliable, non‐intrusive, and on‐line methods for flow regime detection in a hydrotransport pipe based on acoustic measurements.Slurries were transported in a 0.05 m diameter stainless steel hydrotransport pipe. Acoustic measurements were recorded by microphones along the length of the horizontal pipe. Two flow regimes were observed: suspended solids flow and flow over settled solids. Cycle and frequency analyses of the acoustic signals provided reliable identification of these flow regimes.

Leak testing of cryogenic components — problems and solutions

A prototype of Cold Neutron Source (CNS) for Dhruva Reactor is being manufactured at Centre for Design and Manufacture (CDM), BARC, Mumbai for validating the mechanical and thermal engineering design aspects, besides checking the integrity of all joints and components at low temperature, 77K. Task of a Cold Neutron Source is to generate cold neutrons by cooling down the thermal neutrons, which are originally produced in a nuclear research reactor. The complete Cold Neutron Source system comprises a complex arrangement of moderator pot, transfer line (piping), pumps, refrigerators, storage tanks, a heat exchanger and associated controls and instrumentation. The heart of the system is moderator pot in which water (moderator) is cooled down by Liquid Nitrogen (LN2) being circulated through an annular cavity machined on the walls of the pot. Transfer lines for LN2 basically consist of two concentric Stainless Steel flexible pipes, which are joined to the inlet and outlet Aluminium tubes of the moderator pot through transition joints. Leak in any component may result in loss of liquid Nitrogen, degradation of vacuum, which in turn may affect the heat removal efficiency of the source. Hence, leak testing was considered a very important quality control tool and all joints and components were subjected to helium leak test using mass spectrometer leak detector (MSLD) at cryogenic temperature. During one of the earlier experiments, flow of LN2 through inner flexible pipe of the transfer line resulted in rise of pressure in the vacuum annulus and sweating on the outer flexible pipe. After investigations it was found that large thermal stress compounded with mechanical stress resulted in cracks in the inner pipe. Accordingly design was modified to get leak proof transfer line assembly. Further, during leak testing of thin wall moderator pot, gross leak was observed on the outer jacket welded joint. Leak was so large that even a small amount of Helium gas in the vicinity of the moderator pot was driving the MSLD out of range. Since it was very difficult to locate the leak by Tracer Probe Method, some other technique was ventured to solve the problem of leak location. Finally, it was possible to locate the leak by observing the change in Helium background reading of MSLD during masking/unmasking of the welded joints. This paper, in general describes the design and leak testing aspects of cryogenic components of Cold Neutron Source and in particular, the problems and solutions for leak testing of transfer lines and moderator pot.

Sensitivity of the magnetization curves of different austenitic stainless tube and pipe steels to mechanical fatigue

In meta-stable austenitic stainless steels, fatigue is accompanied by a partial strain-induced transformation of paramagnetic austenite to ferromagnetic martensite [G.B. Olsen, M. Cohen, Kinetics of strain induced martensite nucleation, Metall. Trans. 6 (1975) 791–795]. The associated changes of magnetic properties as the eddy current impedance, magnetic permeability or the remanence field may serve as an indication for the degree of fatigue and therefore the remaining lifetime of a component, even though the exact causal relationship between martensite formation and fatigue is not fully understood. However, measuring these properties by magnetic methods may be limited by the low affinity for strain-induced martensite formation. Thus other methods have to be found which are able to detect very small changes of ferromagnetic contents. With this aim the influence of cyclic strain loading on the magnetization curves of the austenitic stainless tube and pipe steels TP 321, 347, 304L and 316L is analysed in the present paper. The measured characteristic magnetic properties, which are the saturation magnetization, residual magnetization, coercive field and the field dependent permeability (AC-magnetization), are sensitive to fatigue and the corresponding material changes (martensitic transformation). In particular, the AC-magnetization was found to be very sensitive to small changes of the amount of strain induced martensite and therefore also to the degree of fatigue. Hence we conclude that applying magnetic minor loops are promising for the non-destructive evaluation of fatigue in austenitic stainless steel, even if a very small amount of strain induced martensite is formed.

Joint for connecting stainless steel water pipes

Joint for connecting stainless steel water pipes

Numerical and experimental investigations on welding residual stress in multi-pass butt-welded austenitic stainless steel pipe

During the course of the welding, high residual stress and distortion often occur. This causes the problem in nuclear power plant components especially where the danger of stress corrosion cracking (SCC) exists. In this study, both the experiment and the finite element method (FEM) are utilized to investigate the welding residual stress distribution in medium thick-walled austenitic stainless steel pipe. Firstly, the experiments are carried out to examine the characteristics of the temperature cycle and the welding residual stress in SUS304 stainless pipe, which is performed using a multi-pass welding process. Secondly, 2-D axi-symmetric FEM models are developed to simulate the welding temperature field and the residual stress field. In the finite element models, the temperature-dependent material properties, work hardening behavior, and annealing of historical plastic strain are taken into account. Finally, the influence of the yield strength of the weld metal on the welding residual stress is clarified by means of numerical simulation.

Microstructural aspects of low cycle fatigued austenitic stainless tube and pipe steels

Material degradation of thermomechanically strained reactor coolant piping made of austenitic stainless steels is accompanied by the strain-induced martensitic transformation of the metastable austenite to varying extents. Besides the accumulated plastic strain, the volume fraction of the α′ martensite also depends on the chemical composition, processing and final heat treatment or cold work condition of the individual heat. The objective of our study was to investigate the microstructural changes in isothermally low cycle fatigued specimens made out of industrially processed tube and pipe steels and tested in air. The volume fractions of martensite, determined by optimized magnetic nondestructive test methods, were globally small but could be large in the vicinity of the crack tip where higher plastic strains are present. The martensite was found at the intersections of slip bands. It was shown that the Schaeffler diagram and M d30 temperature provide only qualitative information for the susceptibility to the transformation.

Manufacturing of the coil support structure for W7-X

Equipos Nucleares S.A. as one of the contractors for the Wendelstein 7-X Stellarator project is currently manufacturing the coil support structure (CSS), which is a stainless steel ring-shaped structure formed by five equal sectors (modules), each of them made up from two symmetric half-modules, everything joined together by way of bolts and super-bolts. This CSS works as the central support for both planar and non-planar coils. The complicate shape of the CSS allows the ports to pass through the structure and reach their place into the vacuum vessel. Furthermore, all the structure is cooled down by way of a copper coated stainless steel long pipe going through the entire structure. Liquid helium at 4 K will be used as coolant to refrigerate the entire structure. Temperature and stresses on the structure will be controlled by means of advanced temperature sensors and strain gauges glued to the structure. Equipos Nucleares collaborates both in the design and the manufacturing of the CSS with the highest and newest technologies such as 3D CAD systems, laser trackers for dimensional controls, tools, machines, non-destructives tests, etc.

Stainless piping can be coupled with style

Victaulic has introduced the Style W89 AGS Rigid Coupling for use with stainless steel pipe Schedule S10 or higher.

Transition between stratified and non-stratified horizontal oil–water flows. Part I: Stability analysis

The characteristics of waves at the interface of oil–water stratified flow and at the onset of entrainment, where drops of one phase appear into the other, were studied. Theoretically a model was developed based on Kelvin–Helmholtz instability to predict the critical wave amplitude at which the waves become unstable for a specific wavelength. According to the model, waves become unstable in stratified flow when at a particular wavelength they exceed a critical amplitude, which decreases with increasing wavelength until it acquires an almost constant value. The model predictions showed that for low-viscosity oils the maximum critical amplitude appears at slip velocity close to zero, while for high-viscosity oils, the maximum amplitude appears for water velocity higher than that of the oil. Also the required entrainment wavelength over the pipe diameter, calculated using literature experimental onset conditions, was found to decrease as the viscosity of the oil increased. Experimentally, wave characteristics before and at the onset of entrainment were investigated by measuring the instantaneous fluctuations of the interface between oil (5.5 mPa s, 828 kg / m 3 ) and water in a 0.038 m ID stainless steel horizontal pipe using a conductivity probe. The formation of drops and the onset of entrainment were identified using a high-speed video camera. At the onset of entrainment, wave characteristics were above the stability lines predicted by the model. Using a semi-empirical characteristic amplitude and wavelength in the model, it was possible to predict the onset of entrainment and transition from stratified to other mixed flow patterns reported in a number of studies.

137 ステンレス鋼管ろう付圧接部の組織と強度および耐食性(溶接・接合の動向とその展開2)

The braze pressure welding (BPW) of the austenitic stainless pipe is conducted under the various joining condition with various filler metal; two Fe-based filler metals, four Ni-based filler metals and their mixture are used. With CR3B Fe-based filler metal, the metallographic observation and the elemental analysis reveal the formation of sound joint. This joint has the enough tensile strength demanded for the commercial standard. The distribution of Cr around the joint interface is not uniform, which might lower the corrosion resistance. The mixture of filler metals forms the residual layer in the joint interface which weakens the joint. The higher joining pressure and the uniformity of the temperature distribution around the joint interface contribute to the formation of sound joint. The usage of Fe-based filler metal with richer Cr and Mo as minor element and the higher joining pressure is considered to provide the better condition.

Fabrication of thin-walled 316L stainless steel seamless pipes by extrusion technology

Thin-walled 316L stainless steel seamless pipes with different diameters are fabricated by extrusion technology. An aqueous solution of water-soluble hydroxypropyl methylcellulose (HPMC) is used as binder. The effect of the binder content on the extrusion behavior of the pipe is discussed. The green products are debound and pressureless sintered at vacuum atmosphere. Good thin-walled pipes have been obtained after sintering at 1100 °C, and at that temperature, a microstructure with the battle-necks forming between the round particles has formed that guarantees the thin-walled pipes having the pores with homogeneous size distribution. Scanning electron microscope is used to observe the microstructure.

Full-wave analysis and design of microstrip antenna in-pipe for rectenna using FDTD method

The circular polarized microstrip antenna in the stainless pipe is analyzed by the finite-difference time-domain (FDTD) method with PML absorbing boundary condition. The microstrip antenna is used as a microwave energy supply element for the in-pipe micromachine inspecting. The numerical results agree well with the measured ones.