1. Answer the following questions

1. What melting equipment is the most economical ?

2. What is the most popular melting equipment ?

3. When is the direct-arc electric used for producing steel at a lower cost ?

4. What furnaces are maintenance costs considerably lower for ?

5. Does an electric furnace have any advantages over an open-hearth?

6. What sort of castings require extremely critical degree and quality control ?

7. What are the advantages of electric furnace ?

8. What ensures very precise specifications ?

9. Why does the user of steel castings need to investigate fully the aspect of a foundry's competence ?

2. Match the words on the left with their definitions on the right

1. melting, fusion

2. scrap

3) open-hearth furnace

4. direct-arc furnace

5. electric furnace

6) induction furnace

1. a furnace, in which heat is gener­ated by electricity

2. a reverberatory furnace used for melting steel heated with gas, which is usually preheated together with the blast in generators

3. an electric furnace, in which the charge is heated by the flow of a secondary current induced in the charge

4. the passing of a solid body into the liquid state

5. waste metal and otherwise useless metal, objects , suitable for remelt-ing in the foundry or processing in the chemical industry

6. an electric furnace in which the heat is generated by an electric arc between the metal charge and electrodes

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3. Render the following

Reverberatory furnaces are made in many sizes and are em­ployed in a large number of metallurgical processes .

The reverbertory is essentially a melting furnace. The open-hearth furnace is a reverbertory furnace used for melting steel heated with gas, which is usually preheated together with the blast in generators.

The name «open-hearth» is given to it because the hearth of the furnace is exposed to the sweep of the flames, which melt the steel. The capacity of the open-hearth furnace varies, at an average, from 50 to 400 tons of metals.

The electric furnace generates extremely high temperatures (up to 3000 c) very rapidly. The temperature is, at all times, under pre­cise control and is easily regulated. The electric furnace is used for the production of the highest quality of steel.Many grades of steel are now made by this method.

4. Translate at sight

Основными методами получения жидкой стали являются процесс плавки на открытом поду, мартеновский процесс, дуго­вая печь прямого нагрева (с зависимыми электродами), индук­ционная печь.

Мартеновская печь представляет собой развитие отража­тельной печи, которая применялась для производства сварочного железа. Первая отражательная печь была построена Генри Кортом в 1784 году.

В некоторых случаях мартеновский процесс является наи­более экономичным. Однако там, где мартеновские печи не могут быть использованы из-за низкой производительной скорости и обилия скрапа, дуговые печи прямого нагрева могут производить сталь меньшей стоимости.

Эксплуатационные расходы значительно ниже при исполь­зовании электрических печей, которые имеют ряд преимуществ перед мартеновскими. В электрических печах достигают чрезвы­чайно высокой температуры очень быстро. Температура находит-

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ся всегда под точным контролем. Электрические печи производят многие сорта высококачественной стали.

Unit 6

MELTING AND POURING

The properties of the finished casting are influ­enced greatly by the melting unit which is used. It makes a great deal of differences whether steel is made in a converter, an open-hearth fur­nace, a direct-arc furnace, or an induction furnace. Grey iron made in an acid-lined cupola is not the same as iron made in a neutral-lined or basic-lined cupola. AH melting processes have two characteristics in common; namely,

• the metal is melted inside a refractory container of some kind,

• heat is applied to the metal from heat source of some type. Within these two characteristics there are many variations, from

which a foundry-man can choose to produce optimum result for any given metal.

Refractory linings are generally classified as follows: acid, neu­tral, basic.

Each of these linings produces different effects on the chemistry of the metal and the slag formations. Each refractory has such applica­tions where it produces optimum results. For example, grey-iron foun­dries normally practise economy in melting grey-iron. However, a ba­sic-lined or a neutral-lined cupola is usually found superior for melting ductile iron, where the sulphur content or the iron is important.

Similar differences exist in melting certain types of steel. The choice of a refractory is determined by^the-economy, as well as, by the quality requirements of foundry customers.

The fuel, which is used for producing heat, has important effects on the chemistry of the metal, the temperature attainable in the melt, Wd the degree of control possible. Fuels used are coal, coke, oil, gas, or electric power. Melting units include the cupola, air furnace, cruci-

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Ые furnace, open-hearth, indirect-arc (electric), direct arc (electric), an

induction (electric) and consumable-arc-electrode (electric).

Exercises