The present work is concerned with the determination of boron activation energy in theC35 steel and an estimation of the mass gain generated by the boriding treatment. Theboride layers are produced by the pack-boriding method on the C35 steel in the temperaturerange of 800−1000 °C for atreatment time ranging from 0.5 to 8 h. The presence of both FeB and Fe2B phases was confirmed by theX-ray diffraction technique and by a microscopic examination of the cross-sections ofborided samples. The boron activation energy was evaluated as 153.1 kJ mol-1 in the temperature range of800−1000 °C. This value ofenergy is in agreement with the literature data. The mass gain was measured by weighingthe samples before and after the boriding treatment by the weighing technique. Theevolution of mass gain as a function of temperature and time can be described by aparabolic law. Finally, an iso-thickness diagram was established to be used as a tool tooptimize the boride layers thicknesses according to the industrial application.

The accuracy of the parameters is of great importance in the calculation and simulationof the COREX process. Therefore, it is necessary to measure some parameters, especiallythe heat loss and its distribution, which have not been reported before. Based on thecharacteristics of the two sets of the Baosteel COREX-3000 process, a method and standardare established for the heat loss and its distribution. Then the heat loss anddistribution are calculated based on the measured parameters. The results show that thetotal heat loss of the two COREX processes is 495.4 MJ/tHM and 413.7 MJ/tHM. The heat losscaused by cooling water accounts for more than 93% of the total heat loss while the heatloss of furnace shells is less than 7%. The main heat loss caused by cooling water takesplace at the tap hole zone, which is also the part of the COREX system with the most heatloss Its heat loss is about 30% of the heat loss caused by cooling water and 28% of thetotal heat loss of the COREX system. The main heat loss of furnace shells takes place atthe dome of the melter-gasifier and the reducing gas entrance position of the shaftfurnace, where the heat loss accounts for nearly 90% of the heat loss of furnace shells.It is also found that the energy utilization efficiency of the 1# COREX system is muchlower than that of the 2# COREX system after comparison.

Brass-graphite composites were fabricated by adding graphite/Cu/Zn compact powderusingthe stir-casting technique and their tribological behavior against a brass disk wasstudied under simulated actual conditions, in comparison with the common graphite/brasscomposite The tribological properties of the brass-graphite composite were compared withdifferent percentages of graphite in the structure using the pin-on-disk method. Theexperimental results showed that the 7−9 wt.% graphite creates a better wear resistance in high-pressureapplications. Continuous Zn layers successfully covered the surface of the graphiteparticles, which could contribute to the improvement of interfacial wettability betweengraphite and brass. In this study, brass-graphite composites containing 8.4 ~ 15 wt.% of Ni-coated graphitewere fabricated. The friction coefficient of composites decreased with increasing graphitecontent. The wear resistance was improved by the addition of Ni-coated graphite butdegraded at high graphite content. The results indicated this composite showed much bettermechanical properties and tribological properties in comparison with brass. The compositewith 11.7 wt.% nickel-coated graphite showed the best tribological properties.

Study of the acid bake-leach process has shown potential advantages for the treatment ofenargite (Cu3AsS4) concentrates. Among the most important advantages of theprocess is the transformation of enargite to water-soluble copper sulfate and highlysoluble arsenic trioxide (arsenolite). Because arsenic is retained in the condensed phaseduring the baking, the vapor pressure of arsenic trioxide should be estimated at typicalbaking temperatures (e.g. 473 K). To that end, the vapor pressure of As4O6 (g) was estimated under thebaking conditions based on published thermodynamic values. The vapor pressure ofarsenolite at 473 K was found to be approximately 9.03 × 10-4 atm. Based on thelinear regression analysis of the published vapor pressure values for arsenolite in thetemperature range 366−579 K,the equation for the best fit line was found to be as follows, with a correlationcoefficient of 0.9973:

logPArsenolite(atm) = (-5780.7)/(T (K))+9.16.

Available information on arsenic trioxide does not allow a definite conclusion regardingthe arsenolite/claudetite transformation temperature and their exact melting points.However, the transition temperature has been reported to be in the wide range of240−506 K in differentreferences. Furthermore, the thermodynamic information concerning arsenolite/claudetite issparse and at times not consistent. An effort has been made in this paper to compile themost reliable thermodynamic information for arsenic trioxide (arsenolite and claudetite).

Les boulets de broyage ou de concassage sont des éléments de broyeurs utilisés dans lescimenteries; ils exigent une résistance à l’usure élevée sous l’action de produitsabrasifs lors de la transformation de la roche en fines particules de taille inférieure aumillimètre. Les traitements thermiques constituent une étape essentielle pourl’élaboration du boulet. Ils permettent d’obtenir des duretés et une résistance à l’usureconvenables. Les analyses structurales et microstructurales par diffraction X etmicroscopie électronique à balayage permettent de comprendre leurs corrélations. Dans cetobjectif, nous avons étudié l’influence de quelques facteurs déterminants dans cestraitements. Les facteurs considérés dans le présent travail sont : la températured’austénitisation (950 °C et1050 °C), la sévérité dumilieu de trempe (refroidissement à l’air ventilé et à l’huile) et le diamètre des boulets(boulets de diamètre 50 et 70 mm). Les résultats obtenus ont révélé la présence decarbures de type Cr7C3 répartis dans une matrice martensitique ou ferritique etque le taux de l’austénite présent dans les boulets trempés à l’air ventilé est inférieurà celui des boulets trempés à l’huile. La température d’austénitisation et la taille desboulets influent sur la trempabilité. En effet, l’écart de dureté entre la surface et lecœur des boulets de diamètre 50 et 70 mm chauffés à 1050 °C, refroidis à l’air ventilé et à l’huile,est plus important que celui des boulets correspondants chauffés à 950 °C. Une augmentation de la taille desboulets conduit à la diminution de la trempabilité notamment les boulets de diamètre 70 mmchauffés à 1050 °C.

Steam ejector vacuum pumps (SVPs) are mainly used on larger melt sizes up to 350 t inintegrated steel plants because of the availability of steam. The use of dry operatingmechanical vacuum pumps (MVPs) for steel degassing has made a tremendous step forward inthe past 10 years but is still confined to melts below 150 t while its progress towardslarger melt sizes is not completed. Besides the consideration of investment and operatingcosts there is no restriction in using any type of modern vacuum pump system for allvacuum processes and plant designs. Both systems fulfil all metallurgical requirements.Considering the significant savings in operating cost offered by MVP systems it is worthreconsidering the efforts for reducing air leaks, the use of protective gases and pressurelosses between the pump set and the metallurgical reaction vessel. Both systems have madeprogress in energy optimising but the MVPs have a striking energy advantage. Only theoverall costs should be considered, including those necessary to meet emission constraintsand safety standards, and only the pressure prevailing at the reaction vessel is to beconsidered when comparing vacuum pump systems. Also, the means and use of dust abatementsystems should be reconsidered since they offer cost savings by reducing the frequency ofcleaning, less wear, little sludge handling and the significantly lower design suctioncapacity of SVP systems. The SVP mass flow need is to be corrected by a specialcoefficient before being applied to the volume conveying MVPs. Depending on theoperational pressure required for the pump design, MVP systems can reach the sameperformance at the reaction vessel with much less mass flow capacity than that needed by aSVP system.