Welding electrodes classification for Shielded Metal Arc Welding  (SMAW) by American Welding Society (AWS) is as follows.

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Mild Steel Coated Electrodes

Example Electrode Designation :

E7018-X

E –  Indicates that this is an Electrode.
70 – Indicates tensile strength. Measured in thousands of pounds per square inch.
1  – Indicates welding position.
8  – Indicates the coating, penetration, and current type used. (See Classification Table below)
X – Indicates that there are more requirements. (See Additional Requirements below)

WELDING POSITIONS

1	All positions (Flat, Horizontal, Vertical (up), Overhead)
2	Flat, Horizontal
4	Flat, Horizontal, Overhead, Vertical (down)

CLASSIFICATION TABLE

Class	Electrode Coating	Penetration	Current Type
Exxx0	Cellulose, Sodium	Deep	DCEP
Exxx1	Cellulose, Potassium	Deep	AC, DCEP
Exxx2	Rutile, Sodium	Medium	AC, DCEN
Exxx3	Rutile, Potassium	Light	AC, DCEP, DCEN
Exxx4	Rutile, Iron Powder	Medium	AC, DCEP, DCEN
Exxx5	Basic, Low Hydrogen, Sodium	Medium	DCEP
Exxx6	Basic, Low Hydrogen, Potassium	Medium	AC, DCEP
Exxx7	Basic, Iron Powder, Iron Oxide	Medium	AC, DCEN
Exxx8	Basic, Low Hydrogen, Iron Powder	Medium	AC, DCEP
Exxx9	Basic, Iron Oxide, Rutile, Potassium	Medium	AC, DCEP, DCEN

ADDITIONAL REQUIREMENTS

Suffix	Additional Requirement
-1	Increased toughness (impact strength).
-M	Meets most military requirements – greater toughness,  lower moisture content as received after exposure, diffusible hydrogen limits for weld metal.
-H4, -H8, -H16	Indicates the maximum diffusible hydrogen limit measured in millimeters per 100 grams (mL/100g). The 4, 8, and 16 indicates what the limit is. Example: -H4 = 4mL per 100 grams

LOW ALLOY STEEL COATED ELECTRODES

SUFFIX TABLE

Suffix	Steel Alloy Type	Suffix Number Description
-A1	Carbon-Molybdenum	0.40 – 0.65 Mo
-B1	Chromium-Molybdenum	0.40 – 0.65 Cr 0.40 – 0.65 Mo
-B2	Chromium-Molybdenum	1.00 – 1.50 Cr 0.40 – 0.65 Mo
-B2L	Chromium-Molybdenum	Lower Carbon B2
-B3	Chromium-Molybdenum	2.00 – 2.50 Cr 0.90 – 1.20 Mo
-B3L	Chromium-Molybdenum	Lower Carbon B3
-B4L	Chromium-Molybdenum	1.75 – 2.25 Cr 0.40 – 0.65 Mo
-B5	Chromium-Molybdenum	0.40 – 0.60 Cr 1.00 – 1.25 Mo
-B6		4.6 – 6.0 Cr 0.45 – 0.65 Mo
-B8		8.0 – 10.5 Cr 0.8 – 1.2 Mo
-C1	Nickel Steel	2.00 – 2.75 Ni
-C1L	Nickel Steel	Lower Carbon C1
-C2	Nickel Steel	3.00 – 3.75 Ni
-C2L	Nickel Steel	Lower Carbon C2
-C3	Nickel Steel	0.80 – 1.10 Ni
-NM	Nickel-Molybdenum	0.80 – 1.10 Ni 0.40 – 0.65 Mo
-D1	Manganese-Molybdenum	1.00 – 1.75 Mn 0.25 – 0.45 Mo
-D2	Manganese-Molybdenum	1.65 – 2.00 Mn 0.25 – 0.45 Mo
-D3	Manganese-Molybdenum	1.00 – 1.80 Mn 0.40 – 0.65 Mo
-W	Weathering Steel	Ni, Cr, Mo, Cu
-G	No required chemistry
-M	Military grade May have more requirements

CHEMICAL SYMBOLS FOR THE ELEMENTS

C	Carbon Most effective hardening element in steel
Mn	Manganese Hardening element second to carbon
Si	Silicon Deoxidizer, moderate strengthener
P	Phosphorus Causes cracking if too high
S	Sulfur Aids in machining – Cracking problems like P
Cr	Chromium Hardness (low) – corrosion resistance (high)
Ni	Nickel Hardening element – better cold toughness
Mo	Molybdenum Hardenability – high temp tensile – creep strength
B	Boron Very small amounts increase hardness
Cu	Copper Corrosion resistance (low) – cracking (high)
Al	Aluminum Deoxidizer – improves mechanical properties
Ti	Titanium Removes: Oxygen, S, N, and C
N	Nitrogen Improves strength – lowers toughness
Cb	Columbium Hardness – Improves mechanical properties
V	Vanadium Hardness – Improves mechanical properties