4. Translate into English:

1. При волочении проволоки диаметр отверстия волочильной доски каждый раз уменьшается.

2. Штамповка листового металла включает в себя ковку, изгиб и обрезку.

3. Небольшая деформация листа при растяжении помогает сохранить новую форму детали.

4. Изменение формы при штамповке производится путем сжатия между двумя штампами.

5. Края листа при штамповке отрезаются для получения конечных размеров.

6. При проковке деталь должна быть горячей для уменьшения необходимых усилий и увеличения пластичности металла.

7. После ковки в закрытых штампах детали не требуют большой механической обработки. 8. При чеканке деформация металла невелика и отпечаток формируется на поверхности металла.

8. Высадка используется для изготовления головок гвоздей и болтов.

Cold and Hot Forging: An Overview

Among all manufacturing processes, forging technology has a special place because it can be used to produce parts of superior mechanical properties with minimum waste of material.

Forging can be produced at multiple temperature levels. Room temperature (or heat added process) forging is commonly called cold forging. This process is less costly, less heat energy consuming, provides greater dimensional accuracy, and can be very efficient for mass production of small parts (less than 50lbs). The downfall is that it requires much larger pressures to form the metal requiring large machinery and more frequent tool wear.

At the other end of the temperature spectrum is hot forging, where the work piece is heated up to about 75% of its melting temperature. As the temperature of the work piece, prior to forging approaches the melting temperature, the flow stress and energy required to form the material is decreased. Therefore, the strain rate or rate of production can be increased. This is a more expensive approach to metal forging and can be detrimental, leading to die failure by thermal stresses.

Generally, forging is a metal shaping process in which a malleable metal part, known as a blank, billet or work-piece, is worked to a predetermined shape by one or more processes such as hammering, upsetting, pressing, rolling and so forth. Cold forming is a precision category of forging which does the same thing without heating of the material (room temperature), or removal of material.

Forging results in metal that is stronger than cast or machined metal parts. This stems from the grain flow caused through forging. As the metal is pounded the grains deform to follow the shape of the part, thus the grains are unbroken throughout the part. Some modern parts take advantage of this for a high strength-to-weight ratio.

Many metals are forged cold, but iron and its alloys are almost always forged hot. This is for two reasons: first, if work hardening were allowed to progress, hard materials such as iron and steel would become extremely difficult to work with; secondly, steel can be strengthened by other means than cold-working, thus it is more economical to hot forge and then heat treat. Alloys that are amenable to precipitation hardening, such as most alloys of aluminum and titanium, can also be hot forged and then hardened. Other materials must be strengthened by the forging process itself.