Unit 13 non-ferrous metals. Magnesium

Magnesium has long been known as the lightest of all engineering metals. This metal, silvery white in color, has a specific gravity of only 1.74. Aluminum, the next lightest structural metal, is 11 times heavier; zinc is 4 times heavier; iron and steel are 41 times heavier; and copper and nickel are 5 times heavier. Magnesium does not occur in the free state but is very abundant in nature, constituting 2.5 per cent of the earth's crust in the form of various ores. It is the third most abundant structural metal, being exceeded only by iron and aluminum.

Magnesium is unique, however, it also exists in the form of magnesium chloride in the oceans. Sea water is the source most widely used for production in the United States but magnesium is also commercially produced from magnesite, dolomite, and other ores as well as from certain inland brines.

Not only is magnesium potentially very abundant but it is in addition a very versatile metal and can be shaped and worked by practically all methods known to the art of metal working. It can be cast by sand, die, and the various permanent-mold methods; extruded into an endless variety of shapes and rolled into sheet, plate, and strip. Magnesium is readily forged and can be formed into useful shapes by drawing, bending, spinning, impact extrusion, and other standard methods.

The joining of magnesium is accomplished by gas, arc and electric-resistance welding methods and by brazing, bolting, and riveting. The machinability of magnesium is unsurpassed by that of any other structural metal and magnesium is often selected for an application because of this characteristic. The chemical and electrochemical properties of magnesium also provide the bases for important commercial uses that will be discussed later.

Because of the two outstanding characteristics, availability and workability, magnesium is now considered to be destined to become one of the world's common structural metals. This is in contrast to conditions existing only about a decade ago, before sea-water plants had been developed and before common metal-working techniques had been sufficiently adapted to magnesium fabrication.

Task 1. Give Ukrainian equivalents to the following words and word combinations.

specific gravity, fabrication, to occur, outstanding characteristics, abundant, availability, to exist, workability, ore, to accomplish, versatile, brazing, permanent-mold methods, riveting, bending, to provide, spinning, to forge, impact extrusion, inland brines.

Task 2. Fill in the correct words and word combinations from the list below. Use each word only once.

welding methods, form, crust, commercial, endless variety of, useful, methods , joining, metal-working, to occur.

1. … techniques 6. the … of magnesium

2. … in the free state 7. important … uses

3. electric-resistance … 8. by all …

4. … shapes 9. in the … of various ores

5. …shapes 10. earth's …

Task 3. Fill in the gaps with the verbs from the list below used in the proper tense form.

To select, to develop, not to occur, to be, to know, to consider, to exist, to be, to adapt, to be, to accomplish.

1. Magnesium … unique, however, it also … in the form of magnesium chloride in the oceans.

2. The joining of magnesium … by gas, arc and electric-resistance welding methods and by brazing, bolting, and riveting.

3. This is in contrast to conditions existing only about a decade ago, before sea-water plants … and before common metal-working techniques sufficiently … to magnesium fabrication.

4. Magnesium … in the free state but is very abundant in nature, constituting 2.5 per cent of the earth's crust in the form of various ores.

5. Magnesium … as the lightest of all engineering metals.

6. Magnesium often … for an application because of this characteristic.

7. Magnesium now … to be destined to become one of the world's common structural metals.

8. Sea water … the source most widely used for production in the United States but magnesium … also commercially produced from magnesite, dolomite, and other ores as well as from certain inland brines.

UNIT 14 NON-FERROUS METALS. NICKEL

NICKEL is known to be a chemical element of 8-th group of periodic system of elements by D.I.Mendeleev. It consists of 5 stable isotopes, 7 radioactive isotopes. For the first time nickel was received in 1751 by I.Kronstadt. In nature nickel is found in combination with sulfur, oxygen, arsenic etc. Nickel is not oxidized under usual conditions in the air, it has high resistance to the influence of atmospheric gases, sulfur, halogens etc. In compounds it shows valency +2 and +3 and easily forms complex compounds.

In the XIXth century Russia had no the nickel industry and imports nickel from abroad. This industry was created in the former USSR only in the XXth century. The first nickel producing plant started its work at Ural in 1934.

Metal nickel has silvery color with a yellowish shade, it is very hard, well polished, drawn by a magnet. It is characterized by high corrosion resistance - is resistant in an atmosphere, in water, in alkalis and a number of acids. Nickel is actively dissolved in nitric acid. Chemical stability of nickel is presupposed by it's ability to "passivating" – i.e., forming the oxide films on a surface, which have a strong protective action.

The main part of nickel is used in manufacture of various alloys with iron, copper, zinc and other metals. The additive of nickel to steel raises its viscosity and corrosion resistance. Nickel-based alloys can be divided into heat resistant alloys, magnetic alloys and alloys with special properties. Heat resistant nickel alloys are used in modern turbines and jet engines where the temperature achieves 850-900 °C. Alloys on the basis of iron do not withstand such temperatures. The major heat resistant alloys are nimonic, inconel, etc. Their structure consists of over 60 % of nickel, 15-20 % chromium and 20-25% of some other metals. The ceramic-metal heat resistant alloys containing nickel as binding metal are also produced. These alloys can withstand heating up to 1100° C. Alloys of nimonic type are widely applied for manufacturing elements of electrical heating devices, elementary of which contain 80 of nickel and 20 % of chromium.

Nickel alloys with special properties include nickeline, constantan, invar, platinite. Nickeline and constantan are also the alloys of nickel with copper. They have high electric resistance which almost does not vary with temperature changes, and are used in the electric equipment. Invar (the alloy of 36 % of nickel and 64 % of iron) practically does not extend at heating up to 100 °C and applies in an electric and radio engineering and in chemical mechanical engineering. The alloy of nickel with iron - platinite - has the same coefficient of expansion as that for the glass and it is used for soldering the metal lead-in contacts into glass.

Rather small amounts of nickel are spent for plating of other metals. Finely crashed nickel is applied as the catalyst in many chemical processes. Pure nickel is used for the production of laboratory utensils.

Nickel plating - a covering of metal products with a layer of nickel approximately 20-30 micron thickness for protection from corrosion and in the decorative purposes. Nickel is widely applied for protection and decorative processing of automobile parts, bicycle components, various devices, surgical tools etc.

Nickeline - the alloy of copper with nickel (25-35% Ni), contains additions of manganese, iron, zinc. It is characterized by the high electric resistance and is applied for manufacture of rheostats and other electric devices.