Q.1 Who are Non ferrous metals write its advantage?
Ans. Non-ferrous metals are those which do not contain iron as the base material. The most commonly used non-ferrous metals in workshop are aluminium, copper, lead, tin, nickel and zinc. They also form very useful alloys amongst themselves, known as non-ferrous alloys, which posses very significant characteristic like high resistance to corrosion, conductivity of heat and electricity, lightness in weight and of being non-magnetic. These properties enable these metals and alloys to be preferred over iron, steel and their alloys where these characteristics stand as the primary considerations. Non-ferrous metal and alloys can also be cast and machined without any appreciable amount of difficulty, but they are more expensive as compared to the ferrous products. However, apart from the cost factor, there are some inherent disadvantages associated with non-ferrous metals, when compared with ferrous metals, such as high shrinkage, hot shortness and lower strength at elevated temperatures.
Use of non-ferrous metals in engineering offers the following advantages:Ans. Non-ferrous metals are those which do not contain iron as the base material. The most commonly used non-ferrous metals in workshop are aluminium, copper, lead, tin, nickel and zinc. They also form very useful alloys amongst themselves, known as non-ferrous alloys, which posses very significant characteristic like high resistance to corrosion, conductivity of heat and electricity, lightness in weight and of being non-magnetic. These properties enable these metals and alloys to be preferred over iron, steel and their alloys where these characteristics stand as the primary considerations. Non-ferrous metal and alloys can also be cast and machined without any appreciable amount of difficulty, but they are more expensive as compared to the ferrous products. However, apart from the cost factor, there are some inherent disadvantages associated with non-ferrous metals, when compared with ferrous metals, such as high shrinkage, hot shortness and lower strength at elevated temperatures.
(i) Very good electrical and magnetic properties.
(ii) Good castability. (iii) Good formability.
(iv) Ability to be easily cold worked. (v) High resistance to corrosion.
(vi) Attractive appearance. (vii) Lower density.
Q.2 Write short notes on:
(i) Aluminium, (ii) Magnesium, (iii) Zinc, (iv) Lead, (v) Tin, (vi) Nickel.
Ans. (i) Aluminium: -
Aluminium ore is found as a hydrated aluminium oxide, called bauxite. The impurities present in it are oxides of iron, silicon and titanium. The first process, therefore, is to separate aluminium oxide form these impurities. For this purpose, bauxite is fused in an electric furnace and carbon is added to reduce the impurities, which form a sludge and can be removed. As a result of this refining , pure aluminium oxide is separated from the impurities. Then an electrolytic bath is used to reduce aluminium from its oxide. As the electrolytic process proceeds the oxygen escapes through the bath and molten aluminium collects at the bottom (cathode), from where it is periodically tapped off. This mineral is mainly available in our country in Bihar, Maharashtra, Madhya Pradesh, Karnataka and Tamil Nadu.
Properties and Uses: -
(a) High electrical conductivity: Used for heavy conductors and busbar work.
(b) High heat conductivity: Used in various domestic utensils and other heat conducting appliances.
(c) Good resistance to corrosion: Used in manufacture of containers for chemical industry and window frames etc.
(d) It can be readily worked, extruded, rolled, drawn and forged.
(e) It has high ductility and is extremely light in weight. Widely used in aircraft industry.
(f) Its corrosion resistance can be considerably increased by anodizing.
(g) It becomes hard by cold working and, therefore, needs frequent annealing.
(h) Its low tensile strength can be sufficiently improved by adding 3 to 4 percent copper.
(ii) Magnesium: -
Principal sources for obtaining magnesium are natural salt brines, sea water, water liquors obtained from potash industry and ores. The principal ores are magnesite, dolomite and carnallite. Various processes have been developed for its extraction, but the most popular and widely used one is the electrolytic process.
Properties and Uses: -
(a) It is the lightest of all metals, weighting about two-third of aluminium.
(b) It may be sand, gravity and pressure die-cast.
(c) Its castings are pressure tight and obtain good surface finish. A few examples of magnesium castings include motor car gear box and differential housing and portable tools.
(d) It may be easily formed, spun, drawn, forged and machined with high accuracy.
(e) Additions of 10% aluminium and small amounts of zinc and manganese improve its strength and casting characteristics.
(f) Addition of 2% Mn help in its easy forming into plates and sheets and extrusion work.
(g) In finely divided from it is likely to burn, and adequate fire protection measures should be strictly observed.
(iii) Zinc: -
The zinc ore is first concentrated through a suitable process. This concentrate is fed into a retort with a suitable amount of carbonaceous material ( say coal). Several retorts are housed in one furnace and their temperature raised to 1100°C. Zinc emerges as vapour and is passed through a condenser, where it is collected as a liquid. The impurities are given out as gases and burn at the mouth of the condenser. By rapid cooling the zinc vapour may be quickly converted into powdered zinc.
Properties and Uses: -
(a) High corrosion resistance: Widely used as protective coating on iron and steel. It may be coated either by dip glavanising, electroplating or sheradising.
(b) Low melting point and high fluidity: Make it the most suitable metal for pressure die-casting, generally in the alloy form.
(iv) Lead: -
Lead ores are generally found as oxides or sulphides. Other impurities present in the ores are iron, copper and zinc etc. The prepared ore concentrate, together with the flux ( lime and silica), is fed into a small blast furnace where the temperature is raised to about 1010°C. The lead is melted and a liquid slag formed of the impurities. Both slag and molten lead are tapped at intervals. Further refining is carried out in a reverberatory furnace, where an oxidizing atmosphere is maintained to burn out the impurities.
Properties and Uses: -
(a) Good corrosion resistance: Used for water pipes and roof protection.
(b) Good resistance to chemical action: Used for acid baths and containers in chemical industry.
(c) It is soft, heavy and malleable, can be easily worked and shaped.
(d) It is used as an alloying element in making soft solders and plumber’s solders.
(e) It is also alloyed with brass and steel to impart them free cutting properties.
(v) Tin: -
The most prominent tin ore is cassiterite. It also carries compounds of copper, iron, lead antimony, bismuth and zinc etc. As usual an ore concentrate is prepared. This concentrate is roasted to drive off excess arsenic and sulphur. The roasted ore is transferred to a reverberatory furnace, where it is heated. Anthracite is added to the charge which reacts chemically to separate tin, the latter sinking to the bottom of the furnace. From there it is tapped at intervals. This crude tin is remelted and refined further. For obtaining high purity tin the electro-deposition method is used.
Properties and Uses: -
(a) Good resistance to acid corrosion: Used as coating on steel containers for food.
(b) It is soft, has good plasticity and can be easily worked.
(c) It can be easily rolled into thin foils, but cannot be drawn due to low strength.
(d) It is used as an alloying element in soft solders, bronzes bearing metals.
(vi) Nickel: -
Its extraction process consists of first roasting the ore, followed by smelting in a small blast furnace. Limestone and quartz are added as flux. They form slag with impurities. Coke is used as fuel. Crude molten nickel is tapped off periodically from the bottom of the furnace. This crude metal is further refined in a bessemer converter followed by treating with sulphuric acid to extract pure nickel. Copper is separated as copper sulphate.
Properties and Uses: -
(a) It has a good resistance to both acid and alkali corrosion. It is, therefore, widely used in food processing equipment.
(b) It has high tensile strength and can be easily worked cold and hot.
(c) It is plated on steel to provide a corrosion-resistant surface.
(d) It is an important alloying element with steel. Its higher proportions are advantageously used in the production of stainless steel like monel and inconel.
Q.3 What are the major use of copper. (AKTU - 2008-09)
Ans. Application: -
Electrical applications: -
· Copper wire.
· Electromagnets.
· Printed circuit boards.
· Electrical machines, especially electromagnetic motors, generators and transformers.
· Electrical relays, electrical busbars and electrical switches.
· Vacuum tubes, cathode ray tubes, and the magnetrons in microwave ovens.
· Wave guides for microwave radiation.
· Integrated circuits, increasingly replacing aluminium because of its superior electrical conductivity.
Architecture And Industry: -
· Copper has been used as water-proof roofing material since ancient times, giving many old buildings their greenish roofs and domes. Initially copper oxide forms, replaced by cuprous and cupric sulfide, and finally by copper carbonate. The final carbonate patina (termed verdigris) is highly resistant to corrosion.
· Statuary: The Statue of Liberty, for example, contains 179,220 pounds (81.3 tonnes) of copper.
· Alloyed with nickel, e.g. cupronickel and Monel, used as corrosive resistant materials in shipbuilding.
· Watt’s steam engine firebox due to superior heat dissipation.
· Copper compounds in liquid form are used as a wood preservative,
Household Products: -
· Copper plumbing fittings and compression tubes.
· Doorknobs and other fixtures in houses.
· Roofing, guttering, and rainspouts on buildings.
· In cookware, such as frying pans.
· Copper Sinks
· Copper slug tape
Coinage: -
· As a component of coins, often as cupronickel alloy, or some form of brass or bronze.
· Coins in the following countries all contain copper: European Union (Euro), United States, United Kingdom (sterling), Australia and New Zealand.
· U.S. Nickels are 75.0% copper by weight and only 25.0% nickel.
Biomedical Applications: -
· As a biostatic surface in hospitals, and to line parts of ships to protect against barnacles and mussels, originally used pure, but superseded by Muntz metal. Bacteria will not grow on a copper surface because it is biostatic. Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaires’ disease is suppressed by copper tubing in air-conditioning systems.
· Copper(II) sulfate is used as a fungicide and as algae control in domestic lakes and ponds. It is used in gardening powders and sprays to kill mildew.
Chemical applications: -
· Compounds, such as Fehling’s solution, have applications in chemistry.
· As a component in ceramic glazes, and to color glass.
Weaponry: -
Small arms ammunition commonly uses copper as a jacketing material around the bullet core.
Q.4 Explain aluminium alloys?
Related Questions -
Q. Name two alloys of aluminum with compositions. (AKTU - 2011 - 12)
Ans. Aluminium Alloys: -
Duralumin: -
It contains 4% Cu, 0.5% Mg, 0.5% Mn and the rest aluminium. It has high tensile strength, comparable with mild steel, combined with the characteristic lightness of aluminium. It, however, possesses a low corrosion resistance. To improve upon the same, a thin film of Al is rolled on the duralumin sheets. These sheets are known by their trade name Alclad, and are widely used in aircraft industry. It is available in various forms like bars, tubes and sheets. In its wrought form it can be cast, forged and stamped easily. It can also be age hardened.Duralumin: -
Aluminium Casting Alloys: -
A general purpose casting alloy contains 90% Al, 8% Cu, 1% iron and 1% Si. It has good strength, hardness and machinability. It may be sand, gravity or pressure die cast.
Another general purpose aluminium casting alloy consists of 13.5% Zn, 3% Cu and the remainder Al. Similarly, a large number of aluminium casting and forging alloys have been developed in the recent past which possess fairly high strengths.
Al-Si alloys contain 5 to 15% Si and the rest Al. They have good castability, low shrinkage, and the castings made from them are quite sound. A more refined structure of casting is obtained by adding a small amount of sodium.
Y-alloy: -
It contains 93% Al, 4% Cu, 2% Ni and 1% Mg. Its principal use is as a casting alloy. It maintains its strength at elevated temperatures, and is used for pistons of I.C. engines. A heat treatment of Y-alloy castings, consisting of quenching in boiling water from a temperature of 510°C and then again for 5 days, develops very good mechanical properties in them. It is also used in strip and sheet forms.
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