ESAB Miniarc 150, Инструкция по эксплуатации, Страница: 22 / 48

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Figure 3.12 Arc Initiation - Scratch Start
When the electrode touches the work, the welding starts. If held in this position, the electrode would freeze or weld itself to
the work. To overcome this, the electrode should be slightly withdrawn from the work immediately after contact has been
made. The distance that the electrode is withdrawn is small and depends upon the diameter of the electrode; this distance
is known as the arc length. If in striking an arc, the electrode freezes, it may be freed by a quick twist of the wrist. Practice
striking the arc until the knack of arc starting has become second nature.
Determination of the correct arc length is difficult since there is no ready means of measuring it. As a preliminary guide, use
about 1/16” arc length on 1/16” and 3/32” electrode; for 1/8” electrodes use about 1/8” arc length. As skill is acquired, the
sound of the arc will be a good guide. A short arc with correct current will give a sharp, cracking sound.
A portion of the electrode coating forms a protective coating called slag over the deposited weld metal. To examine the
weld, remove the slag from the weld with a chipping hammer.
Figure 3.13 - Electrode Position
Once the knack of establishing and holding an arc has been learned, the next step is learning to run a good weld bead. In
the beginning it is best to run beads of weld metal on flat plates using a full electrode. Practice moving from left to right
and from right to left. The electrode should be held less than perpendicular to the work, tilting it in the direction of travel.
The correct position is shown in Figure 3.13.
A proper weld bead is illustrated in Figure 3.1. This shows a cross section through the bead and identifies the various terms
used in describing a weld. To produce these results it is necessary to hold a short arc, travel at a uniform speed, and feed the
electrode downward at a constant rate as it melts.
SECTION 3 OPERATION