Preparation of Ceramic Composite Pipes Through Paste Extrusion

An experimental investigation was carried out in order to prepare ceramic composite pipes used for tubular solid oxide fuel cells by using a multi-billet extrusion technique. Particular emphasis was given to the forming possibility and extrusion behavior of a two-layer pipe consisting of NiO-YSZ(PSZ) (anode) and YSZ (electrolyte). It is shown that the extrusion pressure and binder content required decrease with increasing the fraction of nickel oxide in the anode layers. The porosity in the anode layers depends on the binder content in pastes. It is feasible to prepare anode/electrolyte composite pipes by means of co-extrusion of different pastes.Furthermore, it is possible to obtain sound sintered pipes even under pressureless sintering conditions.     

Rheological Behaviour of Steel ZG15CrMoV and Carbon Steel 35 at High Temperatures

1.IntroductionModeling of metallic materials pro-cesses has been developed rapidly during thelast quarter century to meet the needs forbetter components to provide higher stand-ards of performance and reliability inservice.But,up to now,design and mod-     

Cracking Mechanism of Medium-High Carbon Steel during Hardfacing and Effect of Electrode Composition

In this paper,the temperature and stress fields during hardfacing and the crack mor-phology in welded specimens were studied by using a medium-high carbon steel 60CrMnMo, and a RE-doped electrode for cracking resistance has been developed.The temperature fields on the upper surface of simulated specimens during the hardfacing and the following colding were measured by a thermovision analyzer and the residual stress fields were determined by an X-ray stress analyzer. Both these fields have been simulated by usmg the FEM. The calculated re-sults of the temperature and the residual stress fields talhed with the measured ones quite well. The calcu-lations for establishing the influence of martensite transformation temperatures of the hardfacing metal on the stress distribution m simulated specimens show that,with their lowering,the peaks of tensile residual stress at dangerous positions reduce which is considered to be benefit to avoid the occurence of hardfacing cracks.It is shown that,by adding the RE-oxi     

A Dynamics Study of a Magnetic Flux Leakage （MFL） Signal and its Application to Defect Location Discrimination in Steel Pipes MFL Testing Equipment

Difference processing was used to the direct current magnetic flux leakage(DC-MFL) signal,emanating from the defects machined artificially on the internal and external surfaces of a steel pipe.Consequently,the location discriminating index δ was provided to identify the defect whether it is on the internal surface or the external one.Three characteristics,shape,depth and orientation of the defect,were discussed through a series of experiments on the artificial defects,such as transverse notches,oblique notc...     

Prediction of Austenitization and Homogenization of Q235 Plain Carbon Steel during Reheating Process

In this paper,the austenitization and homogenization process of Q235 plain carbon steel during reheating is predicted using a two-dimensional model which has been developed for the prediction of diffusive phase transformation(e,g.αto γ).The diffusion equations are solved within each phase(αand γ) and an explicit finite volume technique formulated for a regular hexagonal grid are used.The discrete interface is represented by special volume elements α/γ,an volume element α undergoes a transition to an interface state before it becomes γ.The procedure allows us to handle the displacement of theinterface while respecting the flux condition at the interface.The simulated microstructure shows the dissolution of ferrite particles in the austenite matrix is presented at different stages of the phase transflrmation.Specifically,the influence of the microstructure scale and the hwating rate on the phase transformation kinetics has been investigated.The experimental results agree well with the simulated ones.     

Effects of Carbon on the CG HAZ Toughness and Transformation of X80 Pipeline Steel

X80 pipeline steel produced by TMCP has high strength and high toughness with ultrafine grain microstructure. The microstructure coarsens and the toughness worsens at the coarse grained (CG) HAZ apparently after weld simulation. The experimental results indicated that the bainitic ferrite and the second phases formed at cooling are differently as the variation of carbon in base metal. In low carbon steels, the bainitic ferrite laths are long and narrow, the second phases are complex including residual austenite, martensite, the M-A constituent and the Fe3C carbide. The formation of Fe3C carbide is the main reason of the poor toughness in CG HAZ. The ultralow carbon in base metal, however, can improve the CG HAZ toughness through restraining the formation of carbides, decreasing the M-A constituent, increasing the residual austenite content, which are beneficial to the CG HAZ toughness.     

Microstructure of Laser Processed T10 Carbon Tool Steel

The microstructure of the laser melted 1.0%C tool steel have been investigated.The region affectedby the laser can be subdivided into 3 zones,which consist of a melted region at the surface,a zonewith solid state transformation and the area adjacent to the unaffected substrate where cementite isslightly dissolved.The melted zone possessed a cellular growth morphology consisting of austeniteand martensite.The carbon content of the austenite was measured to be over 1 wt-%.A great deal ofretained austenite and twinned martensite were found in the first two zones(the melted and solidtransformed).     

Investigation on Initial Stage of Electroless Deposition on Low Carbon Steel and Pure Iron

Initial process is influenced by substrate microstructure according to the study of initial stage of electroless plating on low carbon steel and pure iron. For low carbon steels, depositing on cementite is prior to that on ferrite, and for pure iron, the grain boundaries and some favourable grains are deposited more easily. The initial reactions of electroless depositing of Ni-P alloy have been tentatively proposed     

Dynamic Alignment of Single-Walled Carbon Nanotubes in Pulsed Magnetic Fields

We have used linear dichroism spectroscopy to measure the dynamic alignment of single-walled carbon nanotubes (SWNT) in pulsed magnetic fields up to 55 T. We make use of the fact that SWNTs absorb light only when the electric-field vector is oriented parallel to the tube axis. SWNTs thus produce a polarization dependent change of the optical transmission, that permits precise measurements of their orientation. In order to distinguish the influence of different mechanisms governing the alignment such as the external magnetic field, Brownian motion or the tube length, we have systematically varied parameters such as the viscosity of the aqueous solution and the sample temperature.     

Initial Studies Concerning the Current Status and Problems on the Formulation and Revision of the National Standards for Electric Insulation Materials

IntroductionAfteritsaccessiontotheWTO,Chinamustestab-lishanoperationalmechanismforthestandardizationworktomeetthedemandsofdomesticandforeignmarkets,andgraduallyperfectastandardsystemthatmeettheneedsofnationaleconomyandsocialdevel-opment.AmongChina'sstandardsystems,thecurrentnationalstandardsforelectricalinsulationmaterialsonlyaccountforasmallpart,yettheyarewidelyusedinthefieldsofelectricalappliances,electricalengines,transformers,condensers,switches,powergeneration,powertransmission,power-tr…     

Monitoring of Martensitic Transformation in Austenitic Stainless Steel 304 L by Eddy Currents

A nondestructive eddy current technique has been applied to cyclic-strain induced martensitic transformation (MT) monitoring in austenitic stainless steel 304 L. During plastic deformation, the austenite transforms locally in martensite. Transformed martensite distribution depends on the geometry of the specimen under test (rectangular section in this work): transformation occurs first in the corners, later close to the flat free surfaces, and finally in the bulk. The obtained value is then representative of a small volume of the sample. Local measurements with an eddy current probe proved to be sensitive to this kind of transformation and even quantitatively after calibration. This article proposes a procedure to calibrate the eddy current response in order to determine the fraction of martensite formed under the probe without the need of X-ray measurements.     

Analysis on Microstructure and Misorientation of Ultrathin Hot Strip of Low Carbon Steel Produced by Compact Strip Production

The microstructure and misorientation of ultrathin hot strip were analyzed by CSP technology using electron back scattered diffraction(EBSD)method and Autoforge finite element program.The experimental results showed that the finishing hot rolling microstructures were the mixture of recrystallized and deformed austenite.After phase transformation,ferrite grains embody substructures and dislocations,leading to the high strength and relatively low elongation rate of the ultrathin hot strip.The FEM simulation of strain mode and distribution in deformation area has been fulfilled.The simulation results are in good agreement with the theoretical analysis and experimental results.     

Metallurgical and Corrosion Properties of Explosively Welded Ti6A14V/Low Carbon Steel Clad

1.IntroductionIn order to join metals preserving their propertiesand to join metals having different properties,solid-statewelding methods are used[1].Explosive welding is a solid-state process in which controlled explosion forces to jointwo or more materials together under high pressures[2~5].It is used to joint directly a wide variety of similar or dis-similar metals that cannot be joined by any other weld-ing or bonding technique[6~8].The parameters of thesystem include:(1)the explosive cha…     

Ductile-to-Brittle Transition and Impact Fracture Behavior of 3Mn–Si–Ni Low Carbon Martensitic Steel

Strength of Materials - Impact behavior related to crack initiation and growth of low carbon martensitic 3Mn–Si–Ni steel was investigated by instrumented impact Charpy V-notch tests....     

Characterization and Properties of Nanostructured Surface Layer in a Low Carbon Steel Subjected to Surface Mechnaical Attrition

A nanostructured surface layer was synthesized on a low carbon steel by using surface mechanical attrition (SMA) technique,The refined microstructure of the surface layer was characterized by means of different techniques, and the hardness variation along the depth was examined,Experimental results show that the microstructure is inhomogeneous along the depth ,In the region from top surface to about 40 μm depth,the grain size increases from about 100 nm to 1000 nm ,The grain refinement can be associated with the activity of dislocations After the SMA treatment, the hardness of the surface layer is enhanced significantly compared with that of the original sample ,which cam primarily be attributed to the grain refinement.     

Characterization and Properties of Nanostructured Surface Layer in a Low Carbon Steel Subjected to Surface Mechanical Attrition

A nanostructured surface layer was synthesized on a low carbon steel by using surface mechanical attrition (SMA)technique. The refined microstructure of the surface layer was characterized by means of different techniques,and the hardness variation along the depth was examined. Experimental results show that the microstructure is in homogeneous along the depth. In the region from top surface to about 40 /zm deep, the grain size increases fromabout 10 nm to 100 nm. In the adjacent region of about 40~80 /zm depth, the grain size increases from about 100nm to 1000 nm. The grain refinement can be associated with the activity of dislocations. After the SMA treatment,the hardness of the surface layer is enhanced significantly compared with that of the original sample, which canprimarily be attributed to the grain refinement.     

Acoustic Emission Monitoring and Microscopic Investigation of Cracks in ERCuNi Cladding

A corrosion resistant CuNi cladding was deposited on SM45C (equivalent to AISI1045) substrate by DC inverse arc welding. During the welding process, a three channel acoustic emission (AE) monitoring system was applied to detect the crack signals generating from both the cladding process and after cladding. Characteristics of the welding crack signal and noise signal had been analyzed systematically. Based on the record time of the signal, the solidification crack and delayed crack were distinguished. By two-dimensional AE source location, the crack position was located,and then investigated by scanning electron microscopy (SEM). Results showed that the AE system could detect the welding crack with high sensitivity and the two-dimensional source location could accurately determine the crack position. Microstructures of the cladding and heat affected zone (HAZ) were examined. Dendrites in the cladding and coarse grains in the HAZ were found.     

Through Thickness Variation of Cross Shear Rolling Texture in Grain Oriented Silicon Steel

The texture inhomogeneity in cross shear rolled grain oriented Si steel was investigated by means of the through thickness texture analysis. For the chosen rolling reductions (55%, 66.5%) and mismatch speed ratios (1.0, 1.1, 1.3), the deformation textures in various thickness layers consist of three major components, i.e. strong γ-fiber, medium α-fiber and weak η-fiber, and they show an asymmetrical distribution throughout the thickness. The effect of reduction on the texture gradient is found to be more significant at and near the center layer; however, the effect of mismatch speed ratio is less important. In most cases, a strong {111}<112> texture component appears in the subsurface layers, that may favour the formation of a sharp Goss texture during the subsequent annealing.