Post-heating Process Research Articles

LJ707-Crnimo Flux Cored Wire of Basic Slag System Be Applied to Non-Preheating Welding Technology of HSLA

This article investigates the welded joints of HSLA Q550 without preheating and post-heating treatment process. Tensile test, bending test, low temperature impact test, and the impact fractures and joint microstructure observation and analysis are used.The test result shows that the welded joins achieves equal strength with base metal. The average values of the welded joints impact absorbed energy at-20 °C are greater than 40J and at-40 °C its average values are greater than 27J, thus the low-temperature impact energy joint can meet the service requirements of hydraulic support. It shows that choosing proper welding material, developing reasonable welding and post-heating treatment process can cancel the preheating process of Q550 steel welding.

Differences in crystallisation behaviours during cooling and post-heating processes of Ti based metallic powders

The different crystallisation behaviours of Ti based metallic powders were systematically investigated. Governed by a higher transition temperature (a lower supercooling degree), the composition of the microsized precipitations (Sn and Ti rich) of cooling significantly varies from that of the glassy matrix (Cu and Zr rich). On the other hand, a kinetics limited condition (a lower transition temperature) results in nanocrystals and various compositional regions between small atoms (Ti, Ni and Cu) and large atoms (Sn and Zr) for the post-heating. The different crystallisation mechanisms are considered to be determined by the synergetic effect of thermodynamics (supercooling degree) and kinetics (transition temperature).

스테인리스강의 마찰교반접합 기술 개발 동향

Stainless steels is widely used in various industries due to its high strength and excellent corrosion resistance. However, in the case of fusion welding for stainless steel, chromium deficiency layer produced by chromium carbide precipitation during welding process causes corrosion-resistance to be lower and formation of intergranular corrosion. It requires a inevitable complex procedure such as pre-heating and post-heating process etc. to prevent such weld defects. From this viewpoint, the new welding process such as a solid state welding method is suited for welding of stainless steels due to its advantages over the fusion welding. Therefore this paper intends to investigate the research trend on friction stir welding, one of solid state welding processes for stainless steels.

Composite produced from rice husk and chopped carbon fiber without using any binders

A composite was fabricated from agricultural waste and industrial waste, namely rice husk (RH) and carbon fiber (CF) ends. A mixture of powdered RH and chopped CFs was molded into a slab by means of hot pressing without the use of any binders, after which some samples were subjected to a post-heating process. The physical properties of bulk density, Shore hardness, bending strength, and compressive strength of composites produced at different heating temperatures and various CF fractions were subsequently evaluated. The coefficient of kinetic friction and specific wear rate at the surfaces of these composites in contact with a SUS304 stainless steel ball were also ascertained. Unfilled (CF-free) composites heated to 1000°C displayed the greatest mechanical strength and optimal sliding properties, superior to the CF filled samples, resulting from the densification of the molded lignocellulosic elements in RH. However, this densification was accompanied by a large thermal shrinkage, causing a large molding error. The composite that contained 20% (by mass) CF and which was not subjected to a post-heating process turned out to be subject to only a minor molding error (∼1%), but was characterized by satisfactory mechanical and sliding properties: bulk density 1.19g/cm3, Shore hardness 76.1HS, bending strength 41.2MPa, compressive strength 150.2MPa, kinetic friction coefficient 0.19, and specific wear rate of 2.6×10−9mm2/N. Filling CFs into composites that were then treated with a post-heating process at 800–1200°C reduced their mechanical and sliding properties, which is associated with a difference in the thermo-mechanical properties between CFs and the RH matrix.

Nanosphere assembled mesoporous titanium dioxide with advanced photocatalystic activity using absorbent cotton as template

Nanosphere assembled mesoporous TiO2 products with large specific surface area and high crystallinity were prepared by a combined hydrothermal and post-heating process, where absorbent cotton was used as a template. The as-synthesized samples were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption/desorption, Fourier transform infrared spectroscopy, and UV–Vis diffuse reflectance spectroscopy. Results indicate that the obtained products exhibit a unique 3D mesoporous structure and demonstrate a significantly improved photocatalytic performance, which can be attributed to concurrent effects of high surface area, the presence of accessible mesopores channels and high crystallinity.

Strength of Joining Seams in Glass Welded by Ultra-fast Lasers Depending on Focus Height

Glass welding by ultra short laser pulses allows joining without the need of an absorber or a preand post-heating process. However, in order to achieve high joining strength the processing parameters such as feed speed, repetition rate, laser power and focal height must be chosen correctly. We show in this work that albeit the shear force of the joining seam depends on the displacement between the focal position and the joining interface the focal height can be chosen in a relatively wide range to provide welding seams with good quality. Furthermore, two different ways are examined in order how to measure the shear strength of a welding seam inside optically contacted area.

Effect of Curing Procedures on the Electrical Properties of Epoxy-Based Isotropic Conductive Adhesives

The effects of different curing and post-heating treatment procedures on the electrical properties of isotropic conductive adhesives (ICAs) were investigated in this work. The results showed that the bulk resistivity of ICAs cured by multi-step method was lower than that cured by the one-step method, even though they were cured for the same periods. It was also found that the electrical resistance of ICAs continued to decrease during the subsequent post-heating treatment processes. The in situ monitoring the variations in electrical resistance was studied during the curing and post-heating treatment process, and it was found that the cooling process continued to decrease the electrical resistivity of ICAs. The trend of the evidence has been consistent and indicated that the internal stress of ICAs, which depended on the curing and post-heating treatment temperatures, had a significant effect on the electrical resistivity of ICAs. Meanwhile, it was proved that the bulk resistivity of ICAs increased as the internal stress of ICAs weakened by the addition of PEG.

Localized CO2 laser treatment and post-heating process to reduce the growth coef f icient of fused silica surface damage

The lifetime of optical components in high-fluence ultraviolet (UV) laser applications is typically limited by laser-initiated damage and its subsequent growth. Using 10.6-μm CO2 laser pulses, we successfully mitigate 355-nm laser induced damage sites on fused silica surface with dimensions less than 200 μm. The damage threshold increases and the damage growth mitigates. However, the growth coefficients of new damage on the CO2 laser processed area are higher than those of the original sample. The damage grows with crack propagation for residual stress after CO2 laser irradiation. Furthermore, post-heating is beneficial to the release of residual stress and slows down the damage growth.

Microstructural Evolution and Weldability of AISI 4042 Steel

High carbon content and addition of other elements, such as Mn in steel, causes some difficulties in the weldability of these materials. In this study, pre and post heating processes were applied for the multipass welded specimens. Tensile test, notch impact test and hardness measurements were carried out, and microstructural features were examined. The weldability of these steels can be improved with the pre and post heat treatments. Maximum hardness values were obtained for the non-heat treated specimens due to large grain structure and high volume percentage of the pearlite content. Although applied heat treatments caused decrease in hardness values, an increase in tensile properties and toughness values at all temperatures occurred. Changes in these properties were explained in the light of the microstructure of the AISI 4042 steel specimens.

Synthesis of LiMPO4 (M=Fe, Mn, Co) nanocrystals in polyol medium and their electrochemical properties

Olivine-structured LiMPO4 (M=Fe, Mn, Co) nanocrystals were synthesized by the solvothermal process in a polyol medium of diethylene glycol (DEG) at low temperature without any further post-heating process. The x-ray diffraction (XRD) patterns of LiMPO4 (M=Fe, Mn, Co) revealed highly crystalline and pure olivine structure (space group: Pnma) based on the Rietveld refinement method. The synthesized LiMPO4 (M=Fe, Mn, Co) nanocrystals with morphologies of plates and rods exhibited average particle sizes of 325, 487 and 581 nm, respectively. Among them, LiFePO4 nanocrystals showed an excellent reversible capacity of 167 mA h g−1 that corresponds to 98% utilization of its theoretical capacity and with a good extended cyclability rate of 50 C.

A Study on Mechanical Damage of Tumor Microvasculature Induced by Alternate Cooling and Heating

Tumor microvascular damage caused by the alternate cooling and heating treatment was found much more severe than that of cooling or heating alone from our previous experimental studies. The induced stresses on the vessel wall are expected to play an important role in vascular damage. Both thermal and mechanical stresses are involved due to the rapid changes in temperature and blood reperfusion during the treatment. To investigate the stress effect, theoretical modeling and numerical simulations have been performed in the present study. Thermal stresses on the tumor microvessel wall during the freezing process are analyzed using the elastic models through the coupled field method. To simulate mechanical stresses induced by blood reperfusion, the fluid and structural mechanics are coupled on the interface between the blood flow domain and the vessel wall. Numerical results show that the thermal stress on the vessel wall is negative in the tumor center, indicating the compression effect during the freezing process. The magnitude of the radial stress reaches 2.5×107 dyn/cm2. During the postheating process, the nonuniform stress distribution exists in the tortuous periphery vessel wall owing to the irregular structures, and higher stresses normally appear at the vessel bifurcations. Synergy of the thermal and mechanical stresses on the vessel wall play critical roles in damaging of the heterogeneous tumor vasculature during the alternate cooling and heating treatment. Results obtained in the present study are expected to help better understand the vascular injury process, and to develop a more effective thermal treatment protocol for tumor therapy.

Microstructure transformations of laser-surface-melted near-alpha titanium alloy

Microstructural transformations of near-alpha titanium alloy under laser-surface -melted and post-heat treated conditions were systematically investigated. The results show that, after laser surface melting treatment, a melted zone and a heat-affected zone are formed in the titanium alloy. The melted zone consists of columnar grains, which are characterized by fine a″ phase, distributed dispersively in acicular martensite phase α′. Martensite transformation occurs at a lower temperature in post-heating process. The α phase in the laser-surface-melted zone is further refined during the recrystallization, and a fine dispersive α + β microstructure is formed when experienced post-heat treatment at an elevated temperature.

Preparation and characteristics of crosslinked sulfonated poly(phthalazinone ether sulfone ketone) with poly(vinyl alcohol) for proton exchange membrane

In order to further overcome the trade-off between high conductivity and good mechanical property of proton exchange membrane (PEM), direct covalent crosslinking of sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) and poly(vinyl alcohol) (PVA) was prepared through post-heating process. Polymer PVA has attractive advantages to be a crosslinker with SPPESK, since the crosslinking of SPPESK with PVA requires relatively lower crosslinking temperature and has much higher stability in water, compared with small molecule crosslinker of glycol and glycerol. The crosslinking is confirmed by solubility change and analysis of ion exchange capacity (IEC) and sulfur content ( C S) of uncrosslinked and crosslinked SPPESK with PVA (Un S-P and Cr S-P). Calculation of degree of crosslinking (DC) of sulfonic group shows that most –SO 3Hs of SPPESK are not involved in the crosslinking, which can maintain the ion exchange and proton transport function. ATR-FTIR spectra analysis manifests the PVA in Cr S-P are oxidized and dehydrated during the crosslinking process with SPPESK. Cr S-P membrane still has higher thermal stability, despite T d (252–273 °C) is less than that (306 °C) of pristine SPPESK. SEM images and XRD patterns show that the Cr S-P is a homogenous and amorphous material. Water uptake of Cr S-P membrane decreases with increasing PVA content, and Cr S-P membrane with lower PVA content (e.g. 15% and 20%) has high water uptake (111.1% and 98.0%) at 80 °C. All the swelling ratio values of Cr S-P (15–35% of PVA content) are at a lower level (≤36%) even at 80 °C. Some Cr S-P membranes (with lower PVA content) have much higher conductivity than that of stable pristine SPPESK, e.g. conductivity of S-P 85/15 reaches 2.00 × 10 −2 S cm −1 which is almost twice as that (1.03 × 10 −2 S cm −1) of SPPESK DS 81% membrane. All above properties of Cr S-P membrane (especially PVA content: 15–20%) indicate the kind of crosslinked sulfonated polymer with PVA is another alternative or prospective approach to prepare PEM.

Scratch behavior of multi-layered metallic thin films on Al 2O 3 substrates

Au/NiCr/Ta and Au/NiCr multi-layered metallic films were deposited on hard Al 2O 3 substrates by magnetron sputtering and a scratch test method was applied with both friction and acoustic emission modes to monitor changes of scratched response of the films. The characteristic curve in the scratch and the morphology of the films were compared with those of a TiN film. It is evident that both modes can eventually be used for conventionally critical load determination, but the friction mode can additionally reflect the changes at different metallic film layers. The critical characteristic load at each point corresponding to abrupt change of the coefficient of friction was not sensitive to deposition temperature and post-heating process, but sensitive to the number of layers and the thickness of films. It increases approximately linear with increasing the thickness of metallic films.

The tubular conical helix of graphitic boron nitride

We employed a novel synthetic route for the generation of a boron nitride (BN) filamentarynanostructure. A pre-formed filamentary microstructure was used as a template insteadof a conventional metal catalyst. BN nanotubes exhibiting the geometry of anArchimedes spiral were obtained via a post-heating process at temperatures above1750 °C on the intermediate BN microstructures pre-formed under heating to1700 °C.An enthalpy was found to primarily determine the structures of the resultanthelical–conical nanotubes (HCNTs). Therefore, the structural parameters, particularly theapex angles of the cones, can be easily varied via simple annealing. This unique structuralproperty is favourable to interlayer sliding in the HCNT structure, as was documentedduring electron beam induced deformation. HCNTs can be bent by an angle as high as180° at room temperature and, then, fully recover the starting morphology after the release ofan external stress, exhibiting a spring-like behaviour. The striking elasticity and flexibilityof these nanotubes stem from both the high stiffness and the extraordinary flexibility ofthe BN filaments, and the ease of interlayer sliding in a graphitic structure. Thenovel BN tubular geometry broadens the range of known helical cone structures.Structural models were developed taking into account the disclination angles or apexangles, wrapping modes, coincidence site lattices and packing patterns of the BNHCNTs.

SiO 2/TiO 2 double-layer antireflective coating deposited at room temperature for metal/insulator/n-Si/p-Si solar cells

Double-layer antireflective coatings for metal/insulator/n-Si/p-Si solar cells were deposited by the reactive evaporation of Ti 2O 3. Both the outer layer (SiO 2) and the inner layer (TiO 2) were formed at room temperature to prevent metal atoms of the ytterbium electrode from diffusing into the bulk silicon. The refractive indices and transmittance of the films were measured and proved to be in a reasonable range. The reflectance was less than 3% in the wavelength range 570–632 nm. After deposition of the antireflective coating, the short-circuit current increment of 44% at air mass 1 and 46% at air mass 0 illumination were obtained without reducing the open-circuit voltage or the fill factor. This represents a low temperature technique which may provide a two-layer antireflective coating on those photovoltaic devices for which the post-heating processes are not suitable, and which gives superior performance in the UV region.

ガス局部定温加熱法による高張力鋼溶接部の後熱

From the viewpoint of the prevention from being cracked by welding, it is greatly significant to adopt a post heating process in order to bring down the hardness of the hardened part in the welding heat-affected zone. Though there may be various kinds of post heating process, it seems the easiest to make use of gas flames. It was, however, not easy to heat exactly the part containing weld metal and heat-affected zone below the Al transformation point or above the As transformation point or at any other desired temperature. But A process for local heating at constant maximum temperature with gas flames, which was published before by one of the authors, has made it quite easy. In this work, the outline of this post heating process was described first, and secondly the result of the experiment in which post heating of welded Dart of high tensile steel was done by using the equipment for this process was clearly shown.The experiment has confirmed that the hardened part in the welding heat-affected zone was surely softened by this process. Besides it was clarified that the hydrogen removal before immersion of welded part in glycerin was increased remarkably, if post heating is done just after completion of welding. But it goes without saying that the degrees of softening and hydrogen removal differ with the height of the maximum temperature and the proceeding rate of heating torch.