Shielded Metal Arc Welding Electrodes: Chapter Objectives
Shielded Metal Arc Welding Electrodes: Chapter Objectives
Shielded Metal Arc Welding Electrodes: Chapter Objectives
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It is, of course, your objective to be able to deposit A composite filler metal electrode consisting of a core of a
welds that have the most desirable physical and chemical bare electrode or metal cored electrode to which a covering
properties, soundness, and appearance that the electrodes sufficient to provide a slag layer on the weld metal has been
are capable of giving. Study Fig. 12-1 carefully. Learn to applied. The covering may contain materials providing such
recognize good and bad welds and to understand the fac- functions as shielding from the atmosphere, deoxidation,
and arc stabilization, and can serve as a source of metallic
tors involved in good and bad welding. After you are thor-
additions to the weld.
oughly familiar with the characteristics of the electrodes
discussed in this chapter, you should consult the catalogs Introduction to Covered Electrodes
of electrode suppliers and the materials available from the
American Welding Society for information on other types The type of covering influences the degree of penetration
of electrodes, such as those for high tensile steel, alloy of the arc and the crater depth. The proper electrode selec-
steels, nonferrous materials, and surfacing materials. tion, therefore, makes it possible to obtain sound welds in
close-fitting joints and to avoid burning through poorly fitted
joints. Since the covering influences the extent of penetra-
Shielded Metal Arc WeldingElectrodes tion, it affects the extent of recrystallization and annealing of
The general definition of a shielded metal arc welding previously deposited layers. This characteristic improves the
covered electrode, as given in the American National internal (radiographic) quality of the weld. The low electrical
Standard and the American Welding Societys Standard conductivity of the covering permits the use of electrodes in
Welding Terms and Definitions, A3.0 is as follows: narrow grooves. The covering also reduces weld spatter.
A B C D E F
Welding Current Welding Current Arc Too Long Welding Speed Welding Speed Proper Current
Too Low Too High (Voltage Too High) Too Fast Too Slow Voltage & Speed
Excessive piling up Excessive spatter to Bead very irregular Bead too small, with Excessive piling up A smooth, regular,
of weld metal. be cleaned off. with poor penetration. contour irregular. of weld metal. well-formed bead.
Overlapping bead Undercutting along Weld metal not Not enough weld Overlapped without No undercutting,
has poor penetration. edges weakens joint. properly shielded. metal in the cross penetration at edges. overlapping, or
section. piling up.
Slows up progress. Irregular deposit. An inefficient weld. Weld not strong Too much time Uniform in cross
enough. consumed. section.
Wasted electrodes Wasted electrodes Wasted electrodes Wasted electrodes Wasted electrodes Excellent weld at
and production time. and production time. and production time. and production time. and production time. minimum material
and labor cost.
Fig. 12-1 Plan and elevation views of welds made with shielded arc electrodes under various conditions. Hobart Brothers, Co.
Minimum
Tensile Yield Minimum
Type of Position of Type of Rate of Appearance Slag Strength Point Elongation
Coating Welding Current1 Penetration Deposition of Bead Spatter Removal (p.s.i.) (p.s.i.) in 2 in. (%)
E6010 High cellulose All positions DCEP Deep Average rate Rippled and Moderate Moderately 62,000 50,000 22
sodium flat easy
E6011 High cellulose All positions DCEP, a.c. Deep Average rate Rippled and Moderate Moderately 62,000 50,000 22
potassium flat easy
E6012 High titania All positions DCEN, a.c. Medium Good rate Smooth and Slight Easy 67,000 55,000 17
sodium convex
E6013 High titania All positions DCEP, DCEN, a.c. Mild Good rate Smooth and Slight Easy 67,000 55,000 17
potassium flat to convex
E7014 Iron powder All positions DCEP, DCEN, a.c. Medium High rate Smooth and Slight Easy 70,000 60,000 17
titania flat to convex
E7015 Low hydrogen All positions DCEP Mild to Good rate Smooth and Slight Moderately 70,000 60,000 22
sodium medium convex easy
E7016 Low hydrogen All positions DCEP, a.c. Mild to Good rate Smooth and Slight Very easy 70,000 60,000 22
potassium medium convex
E6020 High iron oxide Flat hor. fillets Flat: d.c., a.c. hor. Deep High rate Smooth Slight Very easy 62,000 50,000 25
fillets: DCEN, a.c. and flat to
concave
E7024 Iron powder Flat hor. fillets DCEN, DCEP, a.c. Mild Very high Smooth Slight Easy 72,000 60,000 17
titania rate and slightly
convex
E6027 Iron powder Flat hor. fillets Flat: d.c., a.c. hor. Medium Very high Flat to Slight Easy 62,000 50,000 25
iron oxide fillets: DCEN, a.c. rate concave
E7018 Iron powder All positions DCEP, a.c. Mild High rate Smooth and Slight Very easy 72,000 60,000 22
low hydrogen flat to convex
E7028 Iron powder Flat hor. fillets DCEP, a.c. Mild Very high Smooth Slight Very easy 72,000 60,000 22
low hydrogen rate and slightly
convex
E7048 Iron powder All positions DCEP, a.c. Mild High rate Smooth Slight Easy 72,000 58,000 22
low hydrogen vertical and slightly
down convex
1
DCEP means direct current, electrode positive (reverse polarity).
DCEN means direct current, electrode negative (straight polarity).
Source: National Cylinder Gas Division, Chemetron Corp.
Table 12-5 Current Range for Mild and Low Alloy Steel Electrodes
11018 11018
Fig. 12-3A Location of electrode classification
number for covered end-grip welding electrodes.
Identifying Electrodes
Must be used as an electrode.
The identifying system for covered arc welding elec- Minimum tensile strength in 1,000 p.s.i.
trodes requires that the electrode classification number be increments. May be two or three digits.
imprinted or stamped on the electrode covering, within Welding position.
212 inches of the grip and of the electrode. (See Fig. 12-3A
and B.) Type of covering and type of welding
current.
Table 12-7 Interpretation of the Last Digit in the AWS Electrode Classification System
F-No Classification Current Arc Penetration Covering & Slag Iron Powder (%)
F-3 EXX10 DCEP Digging Deep Cellulose-sodium 010
F-3 EXXX1 AC & DCEP Digging Deep Cellulose-potassium 0
F-2 EXXX2 AC & DCEN Medium Medium Rutile-sodium 010
F-2 EXXX3 AC & DC Light Light Rutile-potassium 010
F-2 EXXX4 AC & DC Light Light Rutile-iron powder 2540
F-4 EXXX5 DCEP Medium Medium Low hydrogen-sodium 0
F-4 EXXX6 AC or DCEP Medium Medium Low hydrogen-potassium 0
F-4 EXXX8 AC or DCEP Medium Medium Low hydrogen-iron powder 2545
F-l EXX20 AC or DC Medium Medium Iron oxide-sodium 0
F-l EXX24 AC or DC Light Light Rutile-iron powder 50
F-l EXX27 AC or DC Medium Medium Iron oxide-iron powder 50
F-l EXX28 AC or DCEP Medium Medium Low hydrogen-iron powder 50
Note: Iron powder percentage is based on weight of the covering.