Read the text: An important feature of hot working is that it provides the improvement of mechanical
properties of metals. Hot-working (hot-rolling or hot-forging) eliminates porosity,
directionality, and segregation that are usually present and toughness than the unworked
casting. During the forging of a bar, the grains of the metal become greatly elongated in the
direction of flow. As a result, the toughness of the metal is greatly improved in this direction
and weakened in directions transverse to the flow. Good forging makes the flow lines in the
finished part oriented so as to lie in the direction of maximum stress when the part is placed in
service.
The ability of a metal to resist thinning and fracture during cold-working operations plays an
important role in alloy selection. In operations that involve stretching, the best alloys are those
which grow stronger with strain (strain hardening) – for example, the copper-zinc alloy, brass,
used for cartridges and the aluminium-magnesium alloys in beverage cans, which exhibit
greater strain hardening.
Fracture of the workpiece during forming can result from inner flaws in the metal. These
flaws often consist of nonmetallic inclusions such as oxides or sulfides that are trapped in the
metal during refining. Such inclusions can be avoided by proper manufacturing procedures.
The ability of different metals to undergo strain varies. The change of the shape after one
forming operation is often limited by the tensile ductility of the metal. Metals such as copper
and aluminium are more ductile in such operations than other metals.
3. Find the following phrases in the text:
1. Важная особенность горячей обработки;
2. улучшение механических свойств металла;
3. необработанная отливка;
4. направление максимального напряжения;
сопротивляться утончению и разрушению;
6. проявлять большее деформационное упрочнение;
7. разрушение детали при штамповке;
металлов подвергаться деформации;
9. ограничивается пластичностью металла при растяжении.
