Comprehension assignments

1. Find in the text English equivalents to the following Ukrainian words and word combinations:

• нержавіюча сталь;

• числовим програмним керуванням;

• високий виробіток механізму;

• використовувати розтягувальне кування;

• винятковий допуск на розмір;

• ударяти з частотою;

• точний метод кування;

• одночасна робота чотирьох молотів;

• запобігати утворенню тріщин;

• при єдиному ступені нагрівання;

• висока точність розмірів;

• патрон;

• обертати;

• зворотно-поступальний рух;

• вал;

• кінцеве положення;

• ручний режим роботи.

2. Put questions to the words in bold type:

1. Automatic program control ensures uniform quality in spite of the high output of the machine.

2. This machine produces forging with exceptional dimensional tolerances and improved structure.

3. This feature precludes the formation of cracks in the core of the bar.

4. The bars forged on the numerically controlled machine have better and more uniform structure than bars forged under a hammer.

5. Dimensional accuracy is particularly important in the case of square bars.

6. The first chuck rotates the workpiece.

7. The reciprocating movement of the hammers is effected by four rotating eccentric shafts.

3. Match the words to make up the combinations traced in the text:

1. stainless	A. structure
2. uniform	B. presses
3. high	C. output
4. improved	D. advantage
5. important	E. modes
6. simultaneous	F. steel bars
7. conventional	G. action
8..operation	H. quality

4. Using your plan give an oral summary of the text. Text 6 forging methods

1. Flash Forging. Full three-dimensional control (width, length and height) involves the use of impressions in the dies. In open die forging the workpiece is placed between the upper and lower dies and squeezed so that the metal flows to take up the form in the dies. As the dies come together, the workpiece is deformed plastically until its enlarged sides touch the walls of the die impression. “Flash” material begins to flow outside the die impressions. During further die approach, the flash is thinned and cools rapidly to give increased resistance to deformation of material.

In effect, the flash helps to contain and build up pressure inside the workpiece, and so helps material to flow into the die impressions. When removing the flash by trimming, the loss of material takes place.

2. Flashless Forging. In truly closed-die forging, metal is deformed in a cavity that allows little or no escape of material. The workpiece is compressed but barreling is restricted by the dies, so that pressure rises and the workpiece is caused to fill all parts of the impression.

Flashless forging has considerably more demands than impression or closed-die forging in die design and quality of forging production. For example, with a typical impression-die forging on a hammer, certain stock distribution problems can be corrected by using additional blows. In closed-die forging it is seldom possible, since the work is usually performed on presses and upsetters, and is often completed in a single workstroke.

This process requires accurate workpiece sizing to ensure that the die cavity is being filled, but not overfilled.

3. Typical Hammer Forging. It is usually necessary to preform the stock in one or more preliminary operations. A moulding impression may be used to bring the part to its approximate shape ready for final forging in the finishing impression. Possibly one or two preparatory impressions prior to the moulding impression will be desirable.

A typical design of dies for a hammer forging contains impressions for several operations. The first impression draws out and reduces the cross-sectional area of the stock so that after four blows filling is completed.

The second roller impression further shapes the forging in three or more hammer blows. Next, impression moulding gives the forging its approximate contour, after three blows the forging being in recognizable form, surrounded by flash, and with a tongs hold. The finish impression – three blows – gives final shape; a gutter provides for the flash and allows the upper and lower dies to be brought together.

4. Press Forging. While in hammer forging repeated blows are often used in the same die impression to bring the forging to shape, mechanical forging presses use just one blow for impression, and preliminary impressions in press dies are designed with this in mind. The skill of the operator is generally less important on presses and upsetters than on hammers.