Influence of friction stir welding conditions on joinability of oxide dispersion strengthened steel / F82H ferritic/martensitic steel joint

AbstractAs one of the joining methods for the reduced activation materials to realize the fusion reactors with high efficiency in the future, friction stir welding (FSW) is selected for fabricating the dissimilar butt joint between oxide-dispersion strengthened (ODS) alloy and F82H, and the effect of FSW conditions on joinability of this dissimilar joint was examined. The sound dissimilar joint can be produced under the condition that ODS plate is set on the advancing side and the FSW tool is plunged into F82H. As for the mild steel backside plate, the sound joint can be fabricated in the case of 150rpm rotational speed and 50mm/min traveling speed. On the other hand, by employing the silicon nitride backside plate, the total heat input should be decreased to obtain the sound joint, where the traveling speed is 100 or 150mm/min and rotational speed is 150rpm. In addition, the finite element heat conduction analyses indicate that the influence of traveling speed on the joinability with the mild steel backside plate seems to be smaller than that with the silicon nitride plate and the allowable range of the appropriate traveling speed for the joint becomes to be wider by employing the silicon nitride backside plate

Control of the Morphology and Porosity of Hematite Particles through the Use of Tannic Acids

The shape and porosity of hematite particles formed from the forced hydrolysis of acidic FeCl 3 solutions could be controlled by the use of two types of tannic acid (hydrolysable and non-hydrolysable) within the concentration range 0–2 × 10 −2 wt%. The system with hydrolysable tannic acid (AL) initially provided quite small spherical particles at concentrations up to 10 −2 wt% and finally irregular small hematite particles at 2 × 10 −2 wt%. In the system with condensed non-hydrolysable tannic acid (KT), on the other hand, the hematite particles became ellipsoidal in shape at concentrations above10 −2 wt%. The formation of ellipsoidal particles was explained by the adsorption of KT molecules onto the growing polynuclear primary particles. TEM and XRD measurements revealed that all the hematite particles produced from FeCl 3 /HCl solutions with tannic acids are polycrystalline. The rate of phase transformation from β-FeOOH to hematite was accelerated as the concentration of AL increased, whereas no significant change was observed for the KT system. Analysis by t-plots revealed that the porosity of the hematite particles changed from mesoporous to microporous when the concentration of AL increased. In contrast, the presence of very low amounts of KT molecules (10 −5 and 10 −4 wt%) produced non-porous hematite particles via strong aggregation of polynuclear (PN) particles by hydrogen bonding between hydroxy and carboxy groups. Not only the morphology but also the pore size of hematite particles was controlled from non-porous to mesoporous by using different kinds of tannic acids