Английский язык для инженеров сварочного производства. Гричин С.В - 52 стр.

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52
электродом, дуговая сварка металлическим электродом в среде
инертного газа и дуговая сварка под флюсом. Подробное описание
каждой из данных разновидностей сопровождается перечислением их
преимуществ и недостатков, пригодности использования в зависимости
от типа свариваемого материала, требований к квалификации сварщика,
экономичности, скорости и других параметров.
Skim the English texts (1-4)(Power Supplies, Consumable Electrode
Method, Non-consumable Electrode Method, Safety Issues), and match
them and Russian texts (A-D) in the previous activity.
1 Power Supplies
To supply the electrical energy
necessary for arc welding processes, a
number of different power supplies can be
used. The most common classification is
constant current power supplies and
constant voltage power supplies. In arc
welding, the voltage is directly related to
the length of the arc, and the current is
related to the amount of heat input.
Constant current power supplies are most
often used for manual welding processes
such as gas tungsten arc welding and shielded metal arc welding, because
they maintain a relatively constant current even as the voltage varies. This is
important because in manual welding, it can be difficult to hold the electrode
perfectly steady, and as a result, the arc length and thus voltage tend to
fluctuate. Constant voltage power supplies hold the voltage constant and vary
the current, and as a result, are most often used for automated welding
processes such as gas metal arc welding, flux cored arc welding, and
submerged arc welding. In these processes, arc length is kept constant, since
any fluctuation in the distance between the wire and the base material is
quickly rectified by a large change in current. For example, if the wire and
the base material get too close, the current will rapidly increase, which in turn
causes the heat to increase and the tip of the wire to melt, returning it to its
original separation distance.
The type of current used in arc welding also plays an important role in
welding. Consumable electrode processes such as shielded metal arc welding
and gas metal arc welding generally use direct current, but the electrode can
be charged either positively or negatively. In welding, the positively charged
Fig. 1 A constant current welding
power supply capable of AC and DC

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