Welding Electrode Classification It increases the arc stability by introducing materials readily ionized (i.e.

, changed
The American Welding Society’s classification number series for welding into small particles with an electric charge) into the arc stream.
electrodes has been adopted by the welding industry. The electrode Some of the light coatings may produce a slag. The slag is quite thin and does
identification system for steel arc welding is set up as follows: not act in the same manner as the shielded arc electrode type slag.
E indicates electrode for arc welding. Light Coated Electrode
The first two (or three) digits indicate tensile strength (the resistance of the
material to forces trying to pull it apart) in thousands of pounds per square inch
of the deposited metal.
The third (or fourth) digit indicates the position of the weld. 0 indicates the
classification is not used; 1 is for all positions; 2 is for flat and horizontal positions
only; 3 is for flat position only. Figure 5-30: Arc Action Obtained With a Light Coated Electrode
The fourth (or fifth) digit indicates the type of electrode coating and the type of
power supply used; alternating or direct current, straight or reverse polarity. 3. Shielded Arc or Heavy Coated Electrodes
The types of coating, welding current, and polarity position designated by the Shielded arc or heavy coated welding electrodes have a definite composition on
fourth (or fifth) identifying digit of the electrode classification are as listed in table which a coating has been applied by dipping or extrusion. The electrodes are
5-4. manufactured in three general types: those with cellulose coatings; those with
6) The number E6010 indicates an arc welding electrode with a minimum stress mineral coatings; and those whose coatings are combinations of mineral and
relieved tensile strength of 60,000 psi; is used in all positions; and reverse cellulose. The cellulose coatings are composed of soluble cotton or other forms
polarity direct current is required. of cellulose with small amounts of potassium, sodium, or titanium, and in some
Coating, Current and Polarity Types Designated By the Fourth Digit in the cases added minerals. The mineral coatings consist of sodium silicate, metallic
Electrode Classification Number oxides clay, and other inorganic substances or combinations thereof. Cellulose
Digit Coating Weld Current coated electrodes protect the molten metal with a gaseous zone around the arc
as well as the weld zone. The mineral coated electrode forms a slag deposit. The
0 * * shielded arc or heavy coated electrodes are used for welding steels, cast iron,
and hard surfacing. See figure 5-31 below.
1 Cellulose Potassium ac, dcrp, dcsp Shielded Arc Electrode
Figure 5-31: Arc Action Obtained With A Shielded Arc Electrode
2 Titania sodium ac, dcsp
3 Titania potassium ac, dcsp, dcrp
4 Iron Powder Titania ac, dcsp, dcrp
5 Low hydrogen sodium dcrp
6 Low hydrogen potassium ac, dcrp
7 Iron powder iron oxide ac, dcsp Functions of Shielded Arc or Heavy Coated Electrodes
8 Iron powder low hydrogen ac, dcrp, dcsp  These welding electrodes produce a reducing gas shield around the arc. This
prevents atmospheric oxygen or nitrogen from contaminating the weld metal.
When the fourth (or last) digit is 0, the type of coating and current to be used are The oxygen readily combines with the molten metal, removing alloying
determined by the third digit. elements and causing porosity. Nitrogen causes brittleness, low ductility, and
in Some cases low strength and poor resistance to corrosion.
The Types of Electrodes  They reduce impurities such as oxides, sulfur, and phosphorus so that these
impurities will not impair the weld deposit.
1. Bare Electrodes  They provide substances to the arc which increase its stability. This eliminates
Bare welding electrodes are made of wire compositions required for specific wide fluctuations in the voltage so that the arc can be maintained without
applications. These electrodes have no coatings other than those required in wire excessive spattering.
drawing. These wire drawing coatings have some slight stabilizing effect on the  By reducing the attractive force between the molten metal and the end of the
arc but are otherwise of no consequence. Bare electrodes are used for welding electrodes, or by reducing the surface tension of the molten metal, the
manganese steel and other purposes where a coated electrode is not required vaporized and melted coating causes the molten metal at the end of the
or is undesirable. A diagram of the transfer of metal across the arc of a bare electrode to break up into fine, small particles.
electrode is shown in figure 5-29.  The coatings contain silicates which will form a slag over the molten weld and
Molten metal transfer with a bare electrode. base metal. Since the slag solidifies at a relatively slow rate, it holds the heat
and allows the underlying metal to cool and solidify slowly. This slow
solidification of the metal eliminates the entrapment of gases within the weld
and permits solid impurities to float to the surface. Slow cooling also has an
annealing effect on the weld deposit.
 The physical characteristics of the weld deposit are modified by incorporating
alloying materials in the electrode coating. The fluxing action of the slag will
also produce weld metal of better quality and permit welding at higher speeds.
2. Light Coated Electrodes
Light coated welding electrodes have a definite composition. A light coating has 4. Tungsten Electrodes
been applied on the surface by washing, dipping, brushing, spraying, tumbling, Non-consumable welding electrodes for gas tungsten-arc (TIG) welding are of
or wiping. The coatings improve the characteristics of the arc stream. They are three types: pure tungsten, tungsten containing 1 or 2 percent thorium, and
listed under the E45 series in the electrode identification system. tungsten containing 0.3 to 0.5 percent zirconium.
The coating generally serves the functions described below: Tungsten electrodes can be identified as to type by painted end marks as follows.
It dissolves or reduces impurities such as oxides, sulfur, and phosphorus. Green -- pure tungsten.
It changes the surface tension of the molten metal so that the globules of metal Yellow -- 1 percent thorium.
leaving the end of the electrode are smaller and more frequent. This helps make Red -- 2 percent thorium.
flow of molten metal more uniform. Brown -- 0.3 to 0.5 percent zirconium.
Pure tungsten (99. 5 percent tungsten) electrodes are generally used on less Aluminum or aluminum oxide (even when present in 0.01 percent), silicon, silicon
critical welding operations than the tungstens which are alloyed. This type of dioxide, and iron sulphate unstable. Iron oxide, manganese oxide, calcium oxide,
electrode has a relatively low current-carrying capacity and a low resistance to and stabilize the arc.
contamination. When phosphorus or sulfur are present in the electrode in excess of 0.04
Thoriated tungsten electrodes (1 or 2 percent thorium) are superior to pure percent, they will impair the weld metal because they are transferred from the
tungsten electrodes because of their higher electron output, better arc-starting electrode to the molten metal with very little loss. Phosphorus causes grain
and arc stability, high current-carrying capacity, longer life, and greater growth, brittleness, and "cold shortness" (i. e., brittle when below red heat) in the
resistance to contamination. weld. These defects increase in magnitude as the carbon content of the steel
Tungsten welding electrodes containing 0.3 to 0.5 percent zirconium generally increases. Sulfur acts as a slag, breaks up the soundness of the weld metal, and
fall between pure tungsten electrodes and thoriated tungsten electrodes in terms causes "hot shortness" (i. e., brittle when above red heat). Sulfur is particularly
of performance. There is, however, some indication of better performance in harmful to bare, low-carbon steel electrodes with a low manganese content.
certain types of welding using ac power. Manganese promotes the formation of sound welds.
Finer arc control can be obtained if the tungsten alloyed electrode is ground to a If the heat treatment, given the wire core of an electrode, is not uniform, the
point (see figure 5-33). When electrodes are not grounded, they must be electrode will produce welds inferior to those produced with an electrode of the
operated at maximum current density to obtain reasonable arc stability. Tungsten same composition that has been properly heat treated.
electrode points are difficult to maintain if standard direct current equipment is 7. Non-consumable Electrodes
used as a power source and touch-starting of the arc is standard practice. Types
Maintenance of electrode shape and the reduction of tungsten inclusions in the There are two types of non-consumable welding electrodes.
weld can best be accomplished by superimposing a high-frequency current on The carbon electrode is a non-filler metal electrode used in arc welding or cutting,
the regular welding current. Tungsten electrodes alloyed with thorium and consisting of a carbon graphite rod which may or may not be coated with copper
zirconium retain their shape longer when touch-starting is used. or other coatings.
Tungsten Electrode Taper The tungsten electrode is defined as a non-filler metal electrode used in arc
welding or cutting, made principally of tungsten.

Carbon Electrodes
The American Welding Society does not provide specification for carbon welding
electrodes but there is a military specification, no. MIL-E-17777C, entitled,
"Electrodes Cutting and Welding Carbon-Graphite Uncoated and Copper
Figure 5-33: Correct Electrode Taper in Tungsten Electrode Coated".
The welding electrode extension beyond the gas cup is determined by the type This specification provides a classification system based on three grades: plain,
of joint being welded. For example, an extension beyond the gas cup of 1/8 in. uncoated, and copper coated. It provides diameter information, length
(3.2 mm) might be used for butt joints in light gage material, while an extension information, and requirements for size tolerances, quality assurance, sampling,
of approximately 1/4 to 1/2 in. (6.4 to 12.7 mm) might be necessary on some fillet and various tests. Applications include carbon arc welding, twin carbon arc
welds. The tungsten electrode of torch should be inclined slightly and the filler welding, carbon cutting, and air carbon arc cutting and gouging.
metal added carefully to avoid contact with the tungsten. This will prevent
contamination of the electrode. If contamination does occur, the electrode must Stick Electrodes
be removed, reground, and replaced in the torch. Stick welding electrodes vary by:
size: common sizes are 1⁄16, 5⁄64, 3⁄32 (most common), 1⁄8, 3⁄16, 7⁄32, 1⁄4, and
5. Direct Current Arc Welding Electrodes 5⁄16 inch. Core wire used with electrodes needs to be narrower than the
The manufacturer’s recommendations should be followed when a specific type materials that are welded.
of welding electrode is being used. In general, direct current shielded arc material: stick welding electrodes come in cast iron, high carbon steel, mild steel,
electrodes are designed either for reverse polarity (electrode positive) or for iron-free (nonferrous) and special alloys.)
straight polarity (electrode negative), or both. Many, but not all, of the direct strength: referred to as tensile strength. Each weld needs to be stronger than the
current electrodes can be used with alternating current. Direct current is metal being welded. This means that the materials in the electrode need to be
preferred for many types of covered, nonferrous, bare and alloy steel electrodes. stronger as well.
Recommendations from the manufacturer also include the type of base metal for welding position (horizontal, flat etc): different electrodes are used for each
which given electrodes are suited, corrections for poor fit-ups, and other specific welding position.
conditions. iron powder mix (up to 60% in flux): iron powder in the flux increases the amount
In most cases, straight polarity electrodes will provide less penetration than of molten metal available for the weld (heat turns powder into steel).
reverse polarity electrodes, and for this reason will permit greater welding speed. soft arc designation: for thinner metals or for metals that don't have a perfect fit
Good penetration can be obtained from either type with proper welding or gap.
conditions and arc manipulation. SMAW Welding Electrode Diagram
As described above there are many kinds of electrodes. Here are the most
6. Alternating Current Arc Welding Electrodes popular stick welding (SMAW) electrodes:
Coated electrodes which can be used with either direct or alternating current are E6013 and E6012: For thin metals and joints that do not easily fit together.
available. Alternating current is more desirable while welding in restricted areas E6011: Good for working on surfaces that are oily, rusted or has dirt. Versatile in
or when using the high currents required for thick sections because it reduces that it works with DC or AC polarity. Creates little slag, another big plus. Note
arc blow. Arc blow causes blowholes, slag inclusions, and lack of fusion in the that this electrode should not be placed into an electrode oven.
weld. E6010: Similar to the E6011 but only works with direct current (DC). Note that
Alternating current is used in atomic hydrogen welding and in those carbon arc this electrode should not be placed into an electrode oven.
processes that require the use of two carbon electrodes. It permits a uniform rate E76018 and E7016: Manufactured with iron powder in the flux. Creates strong
of welding and electrode consumption. In carbon-arc processes where one welds, but has a puddle that might present some control issues for beginners.
carbon electrode is used, direct current straight polarity is recommended,
because the electrode will be consumed at a lower rate.

Electrode Defects and Their Effects