Volume 33, Issue 2

The reduction of FeO-containing slag by blends of metallurgical coke and waste polypropylene (PP) has been investigated through experiments conducted in a laboratory scale horizontal tube furnace. Composite pellets of EAF slag (47.1% FeO) with coke, PP and blends of coke/PP (in three different proportions) were rapidly heated at 1500 °C under high purity argon gas and the off gas was continuously analysed for CO and CO 2 using an online infrared gas analyser (IR). The extent of reduction after fifteen minutes, level of carburisation and desulphurization were determined for each carbonaceous reductant. The results show that FeO can be effectively reduced from EAF slag to produce metallic iron using waste PP and its blends with coke as reductants; improvements in the extent of reduction and levels of carburisation and desulphurisation of the reduced metal were observed when coke was blended with PP.

The effects of lanthanum and boron on the inclusion size distribution, microstructure, texture and magnetic properties of three non-oriented electrical steels have been studied. After final annealing, lanthanum effectively inhibited the precipitation of MnS precipitates and promoted the growth of grains, an addition of 0.0041 wt.% boron led to the precipitation of Fe 2 B particles and inhibited grain growth. On the other hand, steel containing 0.0055 wt.% lanthanum had the strongest {100} and {111} fiber texture and the weakest {112}〈110〉 texture among the steels. Compared to steel without lanthanum and boron, steel with 0.0050 wt.% lanthanum and 0.0041 wt.% boron obtained slightly stronger intensities of {100} and {111} fiber texture, and a little weaker intensity of {112}〈110〉 texture. Steel containing 0.0055 wt.% lanthanum achieved the best magnetic properties, whose core loss and magnetic flux density were 4.268 W/kg and 1.768 T, respectively.

The aim of the project is to investigate new material as a reductant in nickel extraction and purification processes. The analyzed reductants were coke, pig iron, ferrosilicon and two copper-silicon alloys. The mixture with the slag and reductant was poured into a cylindrical alumina crucible and kept in a furnace for one hour at 1573 K (1300 °C). After settling, the solidified sample consisted of the matte settled at the bottom of the sample separated from the slag at the top. Ferrosilicon was found to be the most effective reductant for cobalt recovery while 70wt%Cu-30wt%Si alloy facilitated 72% copper and 87% nickel recovery. The highest copper recovery is achieved with 90wt%Cu-10wt%Si reductant. Due to low melting point, high exothermicity and suitable density, Cu-Si alloys could be an ideal choice for the pyrometallurgical converting processes.

By means of solution treatment, microstructure observation and mechanical property measurement, the microstructure and tensile deformation features of tandem hot rolling GH4169 alloy have been investigated. Results shown that, after solution treatment and aging, large numbers of the spherical γ′ phase and the flat-ellipsoidal γ″ phase dispersedly precipitate in the matrix, and acicular or short rod-like δ-phase discontinuously distribute along grain boundaries. As the tensile temperatures increases, the tensile strength and yield strength of the alloy gradually decrease. The tensile deformation features of the alloy are that the twinning and slipping dislocations with double orientations are activated in the matrix. In the later tension, the deformed dislocations pile up near the grain boundary to induce initiation and propagation of cracks due to stress concentration.

Intergranular corrosion and intergranular stress corrosion cracking is influenced by precipitation of chromium carbides at grain boundaries and formation of chromium depletion regions. The present study focuses on understanding the carbide precipitation and subsequent sensitization in the weldments of Alloy 600 using two different welding techniques. The effect of heat input on microstructure and IGC susceptibility was measured using electrochemical reactivation test. The SEM studies were done to evaluate the presence of chromium depleted regions. The carbide was indentified to be Cr 7 C 3 using TEM. The laser beam weldments showed an increased resistance to IGC as compared to TIG weldments.

The surface of the polyetheretherketone (PEEK) samples was modified by the plasma enhanced chemical vapor deposition (PECVD) in the mixture of He and N 2 as well as in the N 2 O atmosphere. Morphological characterization of the PEEK as well as its surface roughness, chemical structure, and surface free energy were investigated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and sessile drop technique, respectively. The highest increase in the polar component of the total surface energy was observed for PEEK modified by He+N 2 plasma, which correlated with significant increase in the concentration of oxygen and nitrogen-containing chemical functionalities as revealed by XPS. For PEEK submitted to N 2 O plasma treatment significant changes in surface topography and increase in roughness were observed, but changes in surface chemistry and surface free energy were mild.

In order to obtain the vanadium pentoxide, the process of vanadium pentoxide preparation by calcination from industrial ammonium metavanadate was further investigated. The effects of calcination temperature and calcination time were studied. The conditions of technique to prepare vanadium pentoxide in flakes by calcination from industrial ammonium metavanadate were optimized using a central composite design of response surface methodology. A quadratic equation model for field was built and effects of main factors and their corresponding relationships were obtained. The statistical analysis of the results showed that in the range studied, the rate of weight loss of the industrial ammonium metavanadate was significantly affected by the calcination temperature and calcination time. The results showed that the optimum conditions of ammonium metavanadate calcination were as follows: sample mass 15 g, calcination temperature 900 °C, calcination time 2.4 h, the rate of weight loss 85.1%. In addition, the sample was characterized by XRD and SEM. The SEM analysis and XRD showed the product was layer structure. According to results from analysis of variance, the value of the determination coefficient (R 2  = 0.9417) indicates that the model was a good fit that 94.17% of the variation could be explained well by the model.

This study has arisen from the necessity to manufacture an impeller and a shaft pair of a water pump from two different types of steels. The impeller has to have resistant to corrosion and the shaft has to have magnetic permeability property. It is deemed suitable to use the AISI 316 austenitic stainless steel performing high resistance corrosion for the impeller and Ck 45 carbon steel with magnetic permeability property for the shaft. The joining of AISI 316 and Ck 45 steels has been achieved by using the friction welding method. After welding process, the tests of tensile and micro hardness were applied, the microstructures were observed, and composition of elements was found in the welding zone. As optimum welding parameters, 100 MPa of friction pressure, 10 s of friction time, 200 MPa of upset pressure and 20 s of upset time were determined in 3000 rev/min rotation speed.

This communication presents thermal diffusivity measurements of fourteen layered insulating composite materials. Composite materials that were taken under investigation contained matrixes based on epoxy and phenol-formaldehyde resins and reinforcements, such as glass, basalt fiber and wrapping or ceramic paper. They were all prepared by the Rocket Section of the Students Space Association (RS-SSA). Manufacturing process of samples is described. Additional objective of this research was to obtain the quality of such prepared materials and if they are reliable enough to be used in solid-fuel rocket motors. Use of composite materials to build combustion chamber walls of solid fuel rocket engines, rather than metal, leads to weight reduction and increases amount of fuel that rocket can carry. That improves performances and gives new possibilities for rocket applications. To apply new high performance solid fuels, development of new composite materials was required. Analysis of thermal properties gives the answer, which material should be used for new solid-fuel rockets designed by RS-SSA.

The hot ductility and high-temperature oxidation behavior of 20CrMnTi steel with 0.02% Cu and x % Sn (0.004 ⩽  x  ⩽ 0.049) were investigated. The results show that tin has no significant effect on tensile strength of sample with less than 0.049% Sn. The critical temperature where the hot ductility reduces dramatically rises with the increase of tin content while the hot ductility decreases with its increase. The average tin content at austenite grain boundaries (GB) and substrate is 0.108% and 0.045% respectively in the specimen containing 0.049% tin quenched after heated to 1223 K and held for 600 s. Sn-segregation at the GB deteriorates the hot ductility. There is no direct relationship between the cause of the ductility trough and tin. However, Sn-segregation at the GB causes it to deepen a lot. The tin content should be controlled below 0.021%, which would not deteriorate the hot ductility significantly. There is no tin-enrichment at the scale/substrate interface when tin content is less than 0.049%. Moreover, although Sn is enriched under the steel surface, any liquid Sn-enrichment wasn't observed at the oxide/steel interface even in as high as 0.45% Sn-bearing steel with 0.02% Cu.

Solubility of bismuth in liquid Bi-S based free cutting steel was measured using a vapor-liquid equilibration method at 1540–1600 °C, and the recovery rate of bismuth in the steel with different temperatures under an atmospheric pressure was also measured. The results showed that the solubility of bismuth in liquid Bi-S based free cutting steel from experiment under a constant volume at 1540, 1560, 1580, and 1600 °C were 0.174, 0.181, 0.205, and 0.220 mass%, respectively, and the relationship of bismuth solubility vs. temperature could be expressed as lg[%Bi] = −6049/T + 2.572. Meanwhile, the solubility of bismuth increased with the increase of Mn content, but decreased with the increase of C content. The recovery of bismuth in this experiment reached a maximum when the temperature was at bismuth boiling point or so, and then it was decreased with the increase of temperature when the temperature was above 1560 °C, which might be attributed to the accelerating of bismuth evaporation that were caused by the increase of bismuth equilibrium partial pressure above the surface of the molten steel with increasing temperature.