Scarcity Of Metals Research Articles

Nouveaux développements dans les outils de coupe en cárbure fritte

Economic and strategic considerations due to the scarcity and cost of metals (tantalum, tungsten, cobalt etc.) together with technological requirements (improved machining properties to increase toughness and wear resistance) require the development of new sintered hard metals. Such materials can be produced by the total or partial replacement of cobalt by iron, nickel or ruthenium, of tungsten by molybdenum or titanium and of tantalum by niobium or hafnium. They can also be produced by optimal control of composition and microstructure, the development of specific substrates for coating and the development of new coatings.

Removal of Heavy Metals from Industrial Effluents

Increasingly stringent effluent discharge requirements have spurred an interest in more effective and economical methods of removing heavy metals from industrial wastes. Increasing scarcity and prices of metals also hasten efforts to achieve metal removal and recovery. Neutralization and chemical precipitation have been utilized for years. Operating data indicate metal removals are possible beyond those indicated by metal hydroxide solubilities, apparently as a result of coprecipitation. Reported costs of neutralization are given as a function of waste character. Metal sulfides exhibit lower solubilities than do metal hydroxides. This fact is used to advantage in sulfide-precipitation systems, utilizing a variety of sources of sulfide ion. Other treatment systems, such as cementation, ion exchange, sorption, or reverse osmosis are utilized in special cases, and are examined.

Ferro-Concrete Ships

THE heavy demand for steel and iron for munitions has enforced economy in the use of these materials for other purposes, and led to the substitution of other materials wherever possible. The shortage of shipping and the necessity of making good war losses have produced recently a considerable development in the building of ferro-concrete vessels of a sea-going type, especially in the Scandinavian countries, where the losses have been great and the scarcity of metals has been much felt. Reference has already been made in our Notes columns to articles in Engineering giving interesting information as to what has been done in Norway in the building of such vessels, and most of the experience available at present has been obtained in Norwegian yards. The production of concrete and ferro-concrete vessels such as barges, intended for quiet waters, is by no means novel, but the problem becomes complicated when the vessel is to undertake sea voyages under her own propulsive power. This is principally owing to the uncertainty of the loads imposed on the vessel, especially when in turbulent waters. Of course, the same difficulty occurs in the design of steel vessels, but the strength of these is determined almost entirely by experience, and there is plenty of experience available and embodied in the rules of the various registration societies. Until experience has accumulated of the actual behaviour of ferro-concrete sea-going vessels no rules will be formulated. The leading societies, however, are taking an active interest in the development, and Lloyd's Register has approved of plans up to 500 tons. The maximum weight of vessel projected so far appears to be 1000 tons.