Standing at the center of the Quwwatul Mosque the Iron Pillar is one of Delhi's most curious structures. Dating back to 4th century A.D., the pillar bears an inscription which states that it was erected as a flagstaff in honour of the Hindu god, Vishnu, and in the memory of the Gupta King Chandragupta II (375-413). How the pillar moved to its present location remains a mystery. The pillar also highlights ancient India's achievements in metallurgy. The pillar is made of 98 per cent wrought iron and has stood 1,600 years without rusting or decomposing.
Some physical facts about the pillar are reasonably well-established: it is 7.3 metres tall, with one metre below the ground; the diameter is 48 centimetres at the foot, tapering to 29 cm at the top, just below the base of the wonderfully crafted capital; it weighs approximately 6.5 tonnes. Made up of 98% pure wrought iron the pillar was manufactured by forge welding. The temperatures required to form such a pillar by forge welding could only have been achieved by the combustion of coal. The pillar is a testament to the high level of skill achieved by ancient Indian blacksmiths in the extraction and processing of iron.
In a report published in the journal Current Science, R. Balasubramaniam explains how the pillar's resistance to corrosion is due to a passive protective film at the iron-rust interface. The presence of second phase particles (slag and unreduced iron oxides) in the microstructure of the iron, that of high amounts of phosphorus in the metal, and the alternate wetting and drying existing under atmospheric conditions, are the three main factors in the three-stages formation of that protective passive film.
But, this said, nearly everything else about the pillar is surrounded by acute controversy: 1) For whom was it made? 2) Exactly when? 3)Where did it originally stand before it was moved to Delhi? 4) What is the true import of the long inscription in Brahmi characters engraved upon it? 5)Who placed the later inscriptions on it, and when? 6) Who had the pillar moved to its present location, and why? 7) What exact processes were followed in forging it into shape at that time, the 4th/5th century AD?
Above all, from the scientists' point of view, what is the secret, the great mystery, behind the fact of its being virtually non-rusting? There seems to be no end to the questions.
I. What interesting facts do you know about the Indian Pillar?
II. Find the answers to the questions stated in the text. Use the Internet resources.
III. Make a short presentation (write an abstract) on the basic components of the protective passive film.
IV. Make a review of metals that rust (corrode) and present it in the form of a bar chart or a diagram.
V. Write an abstract in Russian for the text The Iron Pillar from Delhi
VI. Write a summary for the text Iron and Steels
What is welding?
|1. Basic Level Text 1. The world of welding 2. Basic Level Text 2.WELDING 3. Grammar: Passive Voice, either....or; both....and 4. Text 3. HISTORY OF WELDING 5. Text 4. HISTORY OF WELDING - IN THE BEGINNING|
Exercise 1. Discuss the questions in your group:
1) Where is welding used?
2) What welding processes are widely used in our country?
3) What role will welding play in the future world?
4) Have you read anything about welding?
5) What do you know about your future specialty?
6) Is there welding equipment in the laboratory of your institute?
Text1. The world of welding
The technology of welding has contributed greatly toward making the world better, more productive and a more wonderful place in which to live. Welding is used in the manufacture of almost everything made of metal - ships, locomotive, railroad rails and care, automobiles, pipelines, tanks, aircraft, and household appliances.
Welding used today in so many important industries of our national economy, that if welding disappeared, we might say: «Without welding the world would fall apart». It keeps railroads, truck fleets, steel mills, power plants. Nuclear power plants and spaceships, translators and vacuum tubes, gas-turbine wheels and diaphragms require modern welding technology and quite unusual welding processes.
No present-day technological process has developed at such a rapid race as that of welding. Just a few years ago the ordinary manual arc welding processes was the basic method used in industry. Arc welding, resistance welding, gas welding, shielded inert-gas metal-arc welding, electro-slag welding, atomic hydrogen welding, ultrasonic welding and other commercial processes of manual and automatic welding are widely used in our country.
The scientific and technical aspects of electronic welding are studied by many research establishments, departments of higher schools and factory laboratories. The science and technology of welding have an important part to play in the future world. Without welding interplanetary liners cannot be built, welding is necessary for building launching sites on other planets and in outer space.
Among the means that would be used in the future to join refractory metals and other materials are high frequency current ultrasonic, plasma, controlled fusion and electron beam. The very term «Welding» would become old-fashioned and welding would be replaced by a kind of «gluing» or «cold welding», with which the metal was not heated to melting point but was joined by means of tremendous compression and the uniting of atoms.
1. no process - никакой процесс
2. as that of - «that» заменяет существительное
3. in the field - in the field of welding
4. the very term - сам термин
Дата: 2019-07-24, просмотров: 120.