Английский для сварщиков. Гричин С.В. - 58 стр.

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58
every zero crossing, has been addressed with the invention of special power
units that produce a square wave pattern instead of the normal sine wave,
making rapid zero crossings possible and minimizing the effects of the
problem.
Consumable electrode methods
One of the most common types of arc
welding is shielded metal arc welding
(SMAW), which is also known as
manual metal arc welding (MMA) or
stick welding. Electric current is used to
strike an arc between the base material
and consumable electrode rod, which is
made of steel and is covered with a flux
that protects the weld area from
oxidation and contamination by
producing CO
2
gas during the welding process. The electrode core itself acts
as filler material, making a separate filler unnecessary. The process is very
versatile, requiring little operator training and inexpensive equipment.
However, weld times are rather slow, since the consumable electrodes must
be frequently replaced and because slag, the residue from the flux, must be
chipped away after welding. Furthermore, the process is generally limited to
welding ferrous materials, though special electrodes have made possible the
welding of cast iron, nickel, aluminum, copper, and other metals. The
versatility of the method makes it popular in a number of applications,
including repair work and construction.
Gas metal arc welding (GMAW), also known as metal inert gas (MIG)
welding, is a semi-automatic or automatic welding process that uses a
continuous wire feed as an electrode and an inert or semi-inert gas mixture to
protect the weld from contamination. Since the electrode is continuous,
welding speeds are greater for GMAW than for SMAW. However, because
of the additional equipment, the process is less portable and versatile, but still
useful for industrial applications. The process can be applied to a wide
variety of metals, both ferrous and non-ferrous. A related process, flux-cored
arc welding (FCAW), uses similar equipment but uses wire consisting of a
steel electrode surrounding a powder fill material. This cored wire is more
expensive than the standard solid wire and can generate fumes and/or slag,
but it permits higher welding speed and greater metal penetration.
Shielded metal arc welding a pipe

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