Essentials of Welding
5 Essentials of Arc Welding
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CURRENT SETTING
LENGTH OF ARC
ANGLE OF ELECTRODE
SPEED OF TRAVEL
SELECTION OF ELECTRODE
1.CURRENT SETTING
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The welding current or amperage is essential to producing welds with good appearance and the required strength
characteristics. The welder controls the amperage variable by setting the amperage on the welding machine prior to
welding.
The amperage is set from recommended ranges according to the size of the electrode, the type of electrode, and the
type current AC, DCEN or DCEP you are using.
The correct current setting will determine with the kind of electrode to be used, kinds and thickness of plates and the
welding position.
The chart below shows typical amperage ranges
CURRENT RANGES
SIZE
3/32
1/8
5/32
E6013/ E6011
60-90
90-120
110-170
E7018
70-100
120-160
130-170
Amperage may be referred to as the heat by some welders
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In a example A, the E-6010 weld made with the correct amperage appears properly formed with the appropriate width
and consistency.
In example B the weld made with amperage setting too low appears thin and stringy.
In example C the weld made with amperage setting too high appears wide and flat with excessive spatter and
evidence of undercut.
A. NORMAL WELD
B. CURRENT TOO LOW
C. CURRENT TOO HIGH
D. SPEED TOO FAST
E. SPEED TOO SLOW
F. ARC TOO LONG
Note:
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If you are welding multiple passes in the vertical position and using a weave technique you may need to increase the
amperage when weaving over a prior weld bead.
You may want to use higher setting for setting for welding flat and horizontal than for welding in other positions.
A setting used on one machine may need to be adjusted when using another machine, if the machines are not
calibrated the same.
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One welder (operator) ray prefers to use a slightly higher setting and travel faster than you, so set the amperage for
your technique.
The correct amperage is one that provides a good weld and is not based on a specific number on the machine.
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LENGTH OF ARC
The correct arc length is one of essential factor in obtaining a good weld. An arc length should be equal to the
diameter of the welding rod being used.
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The Arc is the term used to describe the distance from the tip of the electrode to the base metal and can be varied
from lightly touching the metal at an angle sufficient to maintain an ac to a distance far enough from the base
metal to extinguish the arc.
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It contacts with the base metal is made too quickly however, the electrode will stick or freeze to the metal.
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Another method to employ is to allow slight gap between the electrode tip and the base metal.
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The length of the arc gap affects the appearance of the weld.
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One way of checking if the arc length is proper is to listen to the sound of the arc.
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Proper arc length will produce a crackling or hissing sound.
2.
Too short arc length may short out while welding. The beads also will become high with poor penetration and
overlap.
3.
Too long arc length will cause a great deal of filler metal spattering, small- solidified metal drops or the base
metal surface. It causes also that the bead will be too low with poor penetration and undercut. The welding
machines used in Shielded Metal Arc Welding are known as Constant Current machines which mean that the
current stays relatively constant through changes in the voltage. The machine increases the voltage as the arc
length increased to maintain current flow at the amperage level set on the machine If the voltage is increased too
much the arc may become unstable and result in a poor quality weld.is proper is to listen to the sound of the arc.
EFFECT OF ARC LENGTH
The correct arc length may vary according to the type of electrode and the position of welding.
When production welding flat or
horizontal the drag method is often
used for ease in welding and faster
travel speeds. When a slight gap is
maintained the force of the are provides
a weld bead with a slighuy flatter
appearance with less chance of slag
inclusions and better joint penetration.
Note: Make sure you are maintaining a proper arc length before adjusting the amperage on the welding machine.
If the arc length is too long and the voltage increases, it may seem as though the amperage is too high, or the
sticking caused by too low an arc length with some electrodes may seem as though the amperage is too low.
3.ANGLE OF ELECTRODE The variation of electrode angle is depending upon the position of welding to be performed.
Therefore, the correct electrode angle should be considered by the one who is performing the welding. There are two
electrode angles that the welder must control in Shielded Metal Arc Welding; The first angle is the one formed between
the electrode and the base metal, called the work angle. The second angle is the angle the electrode is held at relative to
the relative to the direction of travel, called the travel angle. The travel
angle for the flat, horizontal and overhead can be either pulled or
pushed and the travel angle for the vertical can be either upward or
downward.
Travel Angle
4 SPEED OF TRAVEL
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The correct travel speed will be determined by the width of the bead and the bullet nose shaped appearance of
the ripples at the rear of the molten pool in the arc crater.
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The rate of travel across the joint is controlled by the welder during welding and greatly strength and appearance
affects the characteristics of the weld.
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The amount of weld metal deposited (weld deposition rate) and the travel speed may vary with the type and size
of electrode being used. The correct weld speed will result in a well-formed weld bead that shows good fusion,
penetration and a gradual transition of weld metal into the corners of the joint.
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Since the travel speed is not timed in
stick welding. the welder must be able to
read the molten weld pool as the
electrode is manipulated across the joint.
A weld speed that is too fast results in a
thin stringy weld with poor strength. A
weld bead that is too slow a speed will
result in a heavy weld that has too much
convexity.
Some of the mast widely used Electrodes are those used for
welding carbon Steel. The following is a brief description of the
most commonly used electrodes for welding Carbon Steel. The
electrodes are classified by a letter and numbering system as
follows:
The tensile strength is defined as the ability of the weld metal to withstand forces acting to pull it apart. The last digit indicates
the type of flux or electrode covering and in turn determines the type of current, penetration and appearance of the weld.