Top Gun 351 SWF, Руководство пользователя

Страница: 15 / 32

13
The securing of an arc length necessary to produce a neat weld, soon becomes almost automatic.
You will find that a long arc produces more heat. A very long arc produces a crackling or spluttering noise and the weld metal comes across
in large, irregular blobs. The weld bead is flattened and spatter will increase. A short arc is essential if a high quality weld is to be obtained
although if it is too short, there is the danger of it being blanketed by slag and the electrode tip being solidified in.
If this should happen, give the electrode a quick twist back over the weld to detach it. Contact or “touch-weld” electrodes do not stick in
this way, and make welding much easier.
Arc Length
Rate of Travel
After the arc is struck, your next concern is to maintain it, and this requires moving the electrode tip towards the molten pool at the same
rate as it is melting away. At the same time, the electrode has to move along the plate to form a bead. The electrode is directed at the pool
at about 20’ from the vertical plane.
The rate of travel has to be adjusted so that a well-formed bead is produced. If the travel is too fast, the bead will be narrow and strung out
and may even be broken up into individual globules. If the travel is too slow, the weld metal piles up and the bead will be too large.
Joint Preparation
In many cases, It will be possible to weld steel sections without any special preparation. For heavier sections and for repair work on castings,
etc, it will be necessary to cut or grind an angle between the pieces being joined to ensure proper penetration of the weld metal and to
produce structurally sound joints.
In general, surfaces being welded should be clean and free of rust, scale, dirt, grease, etc. Slag should be removed from oxy-cut surfaces.
Typical joint designs are shown in Figure 6-10.