Metallurgy

Preliminary treatment. Usually, an ore must first be treated in some way to concentrate its metal-containing portion. Ores are usually mixtures of a mineral containing the metal along with economically worthless rock material that must be discarded. During the preliminary treatment, the metal-containing mineral is separated from these less desirable parts of the ore. It may also be necessary to transform the metal-containing mineral by chemical reaction to a metal compound that is more easily reduced to the free metal. 

Reduction. Unless the metal occurs free, the metal compound obtained from preliminary treatment has to be reduced. Electrolysis or chemical reduction may be used, depending on the metal. 

Refining. Once the free metal is obtained, it may have to be purified before it can be used. This purification process is refored to as metal refining. 

The action of a flotation agent has some similarity to detergent action see Section 12.9. 

The ore attaches to bubbles of air and is carried off in the froth.The gangue settles to the bottom of the tank, where it is withdrawn. 

The cell is operated at about 600°C to keep the electrolyte molten calcium chloride is added to lower the melting point. About 14 kj of electrical energy is required to produce one gram of sodium, which is drawn off as a liquid (mp of Na = 98°C). The chlorine gas produced at the anode is a valuable byproduct. 

This icon introduces an opportunity for self-study and to explore interactive modules by signing in atacademicxengagexoin/now. 

An ore is a natural source from which a metal can be extracted profitably. 

It s cheaper to electrolyze NaCI(crqr), but you don t get sodium metal that way. 

Metals and the periodic table. The periodic table groups discussed in this chapter are Groups 1 and 2, the alkali and alkaline earth metals (shaded in blue), and the transition metals (shaded in yellow). Symbols are shown for the more common metals. 

In the solid state, metals are crystalline, i.e. the atoms are arranged in a regular three-dimensional pattern with cubic structures being the most common. This accounts for the excellent mechanical properties of metals such as ductility and toughness. Ceramics and glasses have extremely complicated crystal shapes and, as a result, are very hard and brittle at room temperature. Due to their crystal structure, it is possible to form alloys of two or more metals and this can result in a considerable improvement in certain mechanical properties such as strength and hardness. 

Metals and alloys that were shaped by mechanical means were called wrought alloys, with wrought iron and wrought brass being good examples of this class of materials. 

If the two metals that form the alloy are insoluble in one another, then they will exist as two separate phases, often in alternate layers such as observed in tin-lead alloys or cast irons, where the carbon is often found as minute tadpole like shape (flakes) adjacent to the pure iron. These types of two-phase alloys are extremely difficult if not impossible to shape by hot or cold working. Fortunately, these alloys have a melting point well below that of the parent metals and are very suitable to shape by casting into moulds. This is the reason why iron 4.5% carbon alloys were called cast irons. These alloys have two important limitations in that first, they are very brittle when subjected to impact loads, and second, their corrosion resistance is inferior to pure metals or single-phase alloys. 

Metals and alloys are commonly divided into two major types, Ferrous or Non-Ferrous. The former are alloys of iron while the latter includes the remainder of the metals including copper, lead, tin, silver, gold and aluminium and alloys of these metals. Ferrous materials can be divided into three types as follows  

Steels are alloys of iron and up to 1.7% carbon, although steels are not usually found with more than 1.2% carbon. The importance of steels is that their mechanical properties are greatly influenced by their carbon content. As the carbon increases in the steel, the ductility goes down while the hardness and tensile strength go up. A further important consideration is that the hardness of steels can be dramatically increased to even higher levels by a process of heating to above 800°C and quenching in water or some other fluid such as urine 

The rotary furnace has been used in non-ferrous melting for many years. In this application traditional oil-air burners can provide the relatively low melting temperatures. The development of oxygen-air burners has enabled the introduction of cast iron production, using a higher relative amount of steel scrap and applying graphite for carburisation. 

That is providing the energy for oxygen production is not taken into account. With ojqfgen production, the efficiency will be 10 to 15 % less. 

A significant disadvantage of the rotary furnace is that it also bums Fe, C, Si, Mn and S. These losses have to be compensated for by the addition of alloying elements before or after melting. The efficiency of uptake of these elements is usually rather low. Concentration gradients may occur between the front and the back of the metal bath due to the absence of axial motion and due to inhomogeneities in radiation and the atmosphere above the wide bath surface. 

Due to its batch character, the rotary furnace provides an equal flexibility as the coreless induction furnace in the cast iron foundry. The investment costs however are lower. A 5 tonne furnace costs EUR 500000 - 600000, of which 30 % are for the exhaust system and dedusting. The rotary furnace is also a good alternative for the small-scale cold blast cupola, due to its higher flexibility and lower environmental costs. Rotary furnaces are used for melting volumes of 2 to 20 tonnes, with production capacities of 1 to 6 tonnes per hour. 

Sign in to OVi/L at www.cengage.com/owl to view tutorials and simulations, develop problem-solving skills, and complete online homework assigned by your professor. 

Download mini lecture videos for key concept review and exam prep from OWL or purchase them from www.ceng %ebrain.com 

---

The flaw detector can be used in machine-building, metallurgy, mining extractive and other industries, also in public service and sities infrastructure. 

Approximately 200 large enterprises are operating in ferrous and non-ferrous metallurgy, pipe and rolling industry. These include the world largest complexes for the production of cast iron, steel, rolled stock and pipes in Dniepropetrovsk, Zaporozhje, Donetsk, Makeevka, Mariupol and other cities. 

The Ukrainian Research Institute of Pipes and Metallurgy Automation Research Institute have effective developments in the field of NDT in metallurgy (pipes and rolled stock). Other organisations were experts are working with success in the NDT field are ... 

K. L. Sutherland and I. W. Wark, Principles of Flotation, Australasian Institute of Mining and Metallurgy, Melbourne, 1935. 

Herring C 1949 Surface tension as a motivation for sintering The Physics of Powder Metallurgy ed W E Kingston (New York McGraw-Hiii) pp 143-79... 

The metal is isolated commercially by a complex chemical process, the final stage of which is the hydrogen reduction of ammonium ruthenium chloride, which yields a powder. The powder is consolidated by powder metallurgy techniques or by argon-arc welding. 

Young, R. S. Chemical Analysis in Extractive Metallurgy, Griffen London, 1971, pp. 302-304. 

---