Non-ferrous material

Introduction:

Unlike mild steel, non-ferrous Mattel do not in general display the discontinuity of yield point in the stress-strain curve. Appealed alloys may pass through a period of more rapid extension but cold worked metals pass imperceptibly from the proportional relationship to the condition where plastic flow has occurred, and the whole curves is smooth. For such material the yield strength is usually found by determining the load necessary to produce a specified total elongation.

An important method of increasing the strength and hardness of non-ferrous metals is by cold working in which the grains flow by a process involving the slip of blocks of blocks of atoms over each other, along definite crystallographic planes.  Many alloys can be hardened and strengthened by heat - treatment consisting of two-step process. First the alloy is given a solution heat-treatment followed by rapid quenching, and then a precipitation or ageing treatment is given to cause separation of second phase from solid solution and hardening. These alloys after a solution treatment are comparatively soft and consist of homogeneous grains of solid solution generally indistinguishable microscopically from a pure metal. Rapid cooling after solution treatment retains the supersaturated solution at room temperature, and if the alloy be subsequently reheated to a suitable temperature, fine particle of a new phase are formed and in time will grow to a microscopically resolvable size. At some stage in this precipitation process, the hardness, the tensile strength, and particularly the yield strength will be considerably increased.

Copper:

Copper is a very important metal in industry as has great corrosion resistance property. It has got good strength which is maintain at moderate temperature. It is very ductile and can be worked in to complex shapes. It can be very easily welded, soldered and riveted. It has got very high heat conductivity and electrical conductivity.

Material Properties:

	Annealed	Cold worked
Tensile strength kg/cm2	2000 - 2250	3000 - 4500
Hardness brinell	45 - 55	80-100
Elongation percent on 50mm	50-60	5-20
Modulus of Elasticity	0.95 to 1.2 x 106 kg/cm2	0.95 to 1.2 x 106kg/cm2

Copper and its alloys can be easily joined by soldering, brazing and welding.

Refining of copper:

           Blister copper, as obtained after roasting and converting the copper ore, contains about 98.5% copper and the rest 1.5% is made up of nickel, iron, selenium, lead, arsenic, antimony, bismuth, sulphur, precious metals, etc. Such a copper cannot be used in industry. So it is further refined by the processes in the sequence given below:

(1) Fire Refining: in order to produce purer and homogeneous anodes.

(2) Electrolytic Refining: For refining precious metals and removing the impurities.

(3) Second Firing: For adjusting the physical properties of electrolytic copper for use in industry.

After electrolytic refining operation, cathodes may be used directly for making alloys, but if copper is to be rolled to fabricated forms, it is melted and cast into wires, bars, billets. After the second firing operation, the correctly refined castings solidify with an approximately - level surface, the gas evolved during solidification balancing the shrinkage that would otherwise occur. This is known as though-pitch copper and has a density of  8.4 to 8.7 g/cc when cast, 8.89 to 8.92 when worked and annealed.

Types of Copper:

(1) High conductivity copper.

(2) Best select copper.

(3) Arsenical copper.

(4) Deoxidised copper.

Uses of copper:

Copper is used in huge quantity for making copper wire. It is used for making alloys such as brass. On account of its high resistance to corrosion, it is used in the form of copper sheets in chemical work, and food and brewing plants.

Copper can be cold rolled extensively up to 870ºC and beyond it hot-worked. Cold rolling increases the hardness and strength. Copper wire above 0.10mm diameter is commonly made by drawing from a hot-rolled rod without annealing but smaller size involve intermediate anneals. Copper shapes for electrical switch parts are made by extrusion, brushes and commutator sections by rolling and drawing.

Copper containing small amounts of silver or antimony retains the properties attained by cold working to a higher temperature than pure copper. This is useful where comparatively high temperature are to be withstood, as in soldering or enamelling operations.

Lead:

Lead is obtained from its ores, by concentration, floatation, and reduction in blast furnaces. The crude lead is purified by washing with molten zinc, and the resulting lead is cast into pigs.

Properties of lead:

Lead is a soft and weak metal. its tensile strength is about 150 kg/cm². It is very malleable and ductile. It is very heavy and resists corrosion. It has high density, low melting point and high boiling point. It can be easily melted(melting point 327ºC), cast, rolled and extruded. It is highly malleable and pliable. So it is easily melted during fabrication and installation. It has low strength and due to that its ductility is also low. It has got low elastic limit, high coefficient of thermal expansion and got very high anti-frictional properties. It is a good insulator against nuclear radiation. Impurities present in lead are very small but have profound effect chemically. Based on the content of impurities lead can be classified in to the following groups:

(1) Corroding lead.

(2) Chemical lead.

(3) Tellurium lead.

(4) Antimonial lead.

Uses of lead :

(1) Lead is used in the manufacture of a number of chemicals. (ex) it is used for lining in the tank, when ground bauxite is treated with sulphuric acid for manufacturing alum, etc. The heating Coil is also made of lead.

(2) It is used Battery plates.

(3) Lead can be safely used in various processes where it comes in contact with the following  chemical:

    (a) Solvents such as alcohols, acetone, trichloroethylene, etc.

    (b) Acids such as sulphuric acid, chromic acid, hydrofluoric acid, etc.

    (c) Alkalise such as ammonium hydroxide, sodium hydroxide, etc.

(4) It is introduced into alloys to produced free-cutting characteristics.

(5) In paint industry lead is used as oxide of basic carbonate as pigment. 

Aluminium:

 

   

 First stage in the production of aluminium is the production of alumina by chemical refinement of bauxite. Aluminium is then produced by the electrolysis of alumina dissolved in a bath of molten cryolite. It is available in the market as wrought and cast products in the form of ingots or notched bars for remelting. It is possible to obtain over 99.97% pure aluminium commercially.

Properties of Aluminium:

Physical properties: Aluminium is a silver white metal. Its outstanding properties are lightness good electrical and thermal conductivity. It is a good reflector of light and a good radiator of energy. It is non-magnetic. It is resistant to atmospheric attack. Oxide film that is set up upon exposure to air insulates it against continued attack. It has good tensile strength in the form of alloys. Due to its ductility it can be easily worked. By itself it is very weak and ductile and metals at 660ºC. It's tensile strength is 600kg/cm² but it can be increased by cold working.

Aluminium is generally 99.9% pure as obtain by hall-heroult process and impurities of iron and silicon present from alloy with aluminium. Pure aluminium is silvery white in colour but commercial aluminium due to impurities has got a bluish tinge.  

Chemical Properties:

It is resistant to atmosphere due to the formation of a protective oxide film. This oxide film is very thin, less than 0.02micron (µm) in thickness but is impervious and highly protective. On heating, this film increase in thickness. Heat of combination of aluminium with oxygen is very high. Finely divided powered aluminium burn in air.

 Uses and Engineering Application:

(1) Chemical and Food Industry:

           Aluminium is resistant to many mineral and organic acids, salt solutions, organic compounds, sulphur and many other substances. Aluminium is available in different fabricated forms and it can be assembled and finished by different processes. Due to all these reasons it is used for fabricating equipment for chemical and food processing industries.

(2) Metallurgical Industries:

           Aluminium is used in the metallurgy of iron and steel as it is a powerful deoxidizer and reduces the dissolved and combined oxygen content of molten steel.

(3) Structural Application:

          Due to its light weight and high tensile strength it is used for the construction of aeroplanes, Buses, Tracks, Trains and ships.  

(4) Aluminium also used in Electrical industry, Brewery industry.

Nickel:

Properties of Nickel:

Nickel is a hard, lustrous, white metal. It fuses at 1484ºC. It can take up high polish and is stable in dry air. However, when exposed to dampness, it tarnishes. It is not attacked by alkalis. Cast nickel contains carbon which makes it non-malleable. Its electrical conductivity is less than iron. It is magnetic and is more resistant to corrosion and to loss of strength due to heating in comparison to iron.

The ease with nickel can be cast, machined, spun, drawn into wire, forged, welded, brazed soft and silver-soldered, makes it as good as mild steel. Nickel is used in large quantities due to its higher resistance to even highly corrosive solutions.

Physical properties:

Specific gravity	8.9
Melting point	1458ºC
Tensile strength	3700 kg/cm2
Thermal conductivity at 100ºC	0.145
Thermal conductivity at 290ºC	0.128
Specific heat mean 0 to 100ºC	0.1147
Coefficient of linear expansion between 25 to 100ºC	1.33x10-6

Zinc:

Zinc is a weak metal . Zinc tensile strength is 1550kg/cm². It resists corrosion due to formation of a dense layer of corrosion product which insulates it against continued corrosion.

Uses of Zinc:

Zinc is used as a protective coating for steel. Zinc is applied on steel by hot dipping or by electroplating . It is used in the form of rolled sheets for rooting and battery containers, and as a lining for transportation cases, because it can be made water and air-tight and is proof against insects, etc.

Tin:

Properties of tin:

Specific gravity	7.285
Melting point	232ºC
Tensile strength	130kg/cm2

   It is soft metal having very low tensile strength. When cold it is quite brittle and it cracks when it is bent. It is malleable at about 100ºC.At this temperature it can be rolled into sheets or drawn into pipes.

Uses of Tin:

(1) As it is not corroded by water and organic acid, it is used for lining  copper and iron tanks and also cooking vessels. it is plated on iron sheets.

(2) it is used to form very useful alloys such as solder, bell metal, bearing alloys etc.