Unit7 (Total Score – 21 points)

I. Прочитайте наступний текст и намагайтеся запам`ятати методи нагріву сталі электричним струмом. (Score – 6 points)

Heating by Electric Current

The following two main methods of heating steel by electricity for forging and stamping are employed: contact and induction electric heating.

The forge stock is held between contact holders of a secondary low-voltage mains. The current, flowing through the stock, heats it to the required temperature as the result of the conversion of electric energy into heat energy. Alternating current of industrial frequency is mainly used for contact heating.

Stock is heated by this method uniformly throughout its entire cross-section; along its length, however, its temperature will vary; the temperature of required forging temperature. Contact heating is employed for heating stock from 18 to 70mm in diameter; it cannot be employed for heating of stepped cross-section. Contact and induction steel heating methods are steadily displacing furnaces in serving high-productive units such as forging machines and forge-stamping presses. Reduced heating time cuts down losses of steel due to scale, and results in finer grain structure. This permits a higher forging temperature interval (deformation temperature) which, in its turn, increases the productivity of forge units.

The most progressive heating method in use to-day is the induction heating method. This method results in high speeds of heating and permits heating stock of stepped cross-section by electric current. Cylindrical stock is inserted into the inductor along guides. Alternating current of high or super-high frequency is passed through coil. As a result of electro magnetic induction, eddy currents are generated in the stock thereby heating it. For heating a piece of stock from 30 to 80mm in diameter, an alternating current of 2,500 cycles per second is passed through the coil; and stock up to mm in diameter is heated by an alternating current of 500-1,00 cycles per second.

The current must be of still lower frequency for heating stock of greater diameter, when ordinary alternating current of so-called commercial frequency is used.

II. Складіть план тексту. (Score – 6 points)

III. Дайте короткий переказ тексту українською мовою. (Score – 6 points)

IV. Перекладіть 3-й абзац. (Score – 3 points)

(Total Score – 21 points)

Unit8 (Total Score – 17 points)

I. Прочитайте наступний текст, намагайтесь зрозуміти його зміст, приготуйтесь відповідати на запитання до тексту (Score – 6 points)

Drop-Forging Methods

Two methods of drop-forging are practiced: drop-forging in single-impression, and multiple-impression drop-forging. Single-impression drop-forging consists, in forging the work in one (finished) forging impression. Here the preliminary operations(edging, bending reducing, etc.) are carried out on other equipments forge hammers, forging rolls etc.

In multiple-impression drop-forging, all the impressions, from the preliminary to the finished impression, are contained in one set of dies, and the forging process is carried out on one hammer only. Drop-forging by steps (passes) is only a variety of the multiple-impression process, this process entails several sets of dies for forging the work. In this method, the forging is conducted on several hammers, each of which is equipped with a different set of dies designed for one definite operation. Usually the stock is heated only once and then transferred from hammer to hammer without reheating. This process of multiple-impression drop-forging is widely practiсed in the mass or large-scale production of forgings, as it is more productive and permits the organization of flow lines for the production of duplicate forgings. The connecting rod will be forged from a round stock in the following, sequence; it is first drawn in a fullering-impression so as to leave a definite volume of metal at its ends for forming head of the rod; in impression the stock is given the approximate shape of the forging, having a sufficient volume of metal at the ends for forming the heads of the connecting rod| in blocking impression the forging is given its rough shape, while its final shape is given in finish impression. Blocking impression is designed for transforming the stock, which until then had only a simple shape, into a more intricate shape approximating that of the finished forging. The use of shaped rolled sections for stock obviates the necessity for these preliminary impressions. The rough impression facilitates drop-forging in the finish impres­sion, reduces the amount of metal wasted as the flash and prolongs the life of the finished impression, which is more susceptible to wear than the others.

П. Дайте відповіді на наступні питання: (Score – 5 points)

1. What are two methods of drop-forging?

2. What is single-impression drop-forging?

3. What is multiple-impression drop-forging?

4. What is drop forging by steps?

5. Give the example of the process of drop-forging?

Ш. Складіть анотацію. (Score – 6 points)

(Total Score – 17 points)